JP2001337640A - Drive circuit and drive method for capacitive load - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a drive circuit which has a simplified and inexpensive circuitry with an electric power recovery function. SOLUTION: The power supply voltage V is applied to a series resonant circuit consisting of the coil 26 and the capacitive current 25 when the switch SW31 is turned to ON status. The voltage Vc of capacitive current 25 is clamped by the power supply voltage V and a resonance stops since the diode DI31 is conducted when voltage Vc of capacitive current 25 exceeds power supply voltage V A flywheel current flows on a loop of coil 26 → diode DI31 → switch SW31 on 'ON' status. When switch SW31 is turned 'OFF', the flywheel current i keeps up its current because the loop is disrupted and a voltage at point A drops rapidly below a ground electric potential, and the diode DI33 is conducted. Then, the flywheel current i is regenerated to the power supply 27 through a path of diode DI33 → coil 26 → diode DI31, electric current energy accumulated on coil 26 is returned to the power supply 27.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit and a driving method for a capacitive load, and more particularly, to a constituent electrode of a dot matrix type display panel, particularly a constituent electrode of a plasma display panel or an EL (Electro Luminescence) display panel. The present invention relates to a driving circuit and a driving method for a capacitive load suitable for driving a load exhibiting such a capacitance.

[0002]

2. Description of the Related Art As a natural process of the development of display devices, in recent years, there has been an increasing need for large-screen display devices of 40-inch (102 cm diagonal) or more. In this class, CRT (Cathode-
Ray-Tube) is difficult to achieve, so projection and reflection type projectors are widely used. However, there are fundamental problems such as display brightness, viewing angle, color reproducibility, and depth. It is difficult to respond to the recent trend of panelization and weight reduction. In order to meet the needs of this market, development and products of a large-screen plasma display device that is flat, lightweight, thin and has a self-luminous type, and has excellent visibility such as viewing angle and color reproducibility. Is noticed,
Early dissemination is expected.

[0003] A plasma display device includes a panel unit (hereinafter, simply referred to as a panel or a plasma display panel in detail) for displaying an image using a light emission discharge phenomenon, and a drive circuit unit for driving the panel unit. DC discharge type and AC discharge type,
The electrodes are classified into a surface discharge type, a counter discharge type, a two-electrode type, a three-electrode type, and the like according to a difference in electrode structure. In the DC discharge type, the electrodes are directly exposed to the discharge space, and once the discharge occurs, the DC current continues to flow. Further, in the AC discharge type, since an insulating layer is interposed between the electrode and the discharge gas,
The current is limited to the capacitance of the insulating layer, and after a voltage is applied, the current flows in a pulse for a short time of about 1 μs and ends. Since the insulating layer functions as a capacitor, in the AC discharge type, by applying an AC pulse voltage of both polarities to one electrode or by applying a pulse alternately to both electrodes,
Light emission is repeated and display is performed.

[0004] Although the DC type has a simple structure, it has a drawback that the electrodes are directly exposed to electric discharge, so that the electrodes are greatly consumed and it is difficult to obtain a long life. On the other hand, the AC type has an advantage that the life is long because the electrode is covered with the insulating layer. After all, among the various plasma display methods proposed so far, the one in which a three-electrode surface-discharge type panel is AC-driven by a scan-maintenance separation type has excellent durability, a simple structure, and a high structure. It is relatively easy to cope with the definition and the enlargement of the screen, and it is possible to easily realize a light emission maintaining function called a memory that enables high luminance light emission. Therefore, at present, this method is mainly adopted.

[0005] In any type of plasma display panel, two substrates (ie, a front transparent substrate and a rear substrate) are disposed opposite to each other, and display cells are arranged in a matrix in a gap between these substrates. He-Xe or N
a discharge gas space filled with a discharge gas such as e-Xe, and various stripe-shaped electrodes arranged in a manner orthogonal to each other on the inner surfaces of the front transparent substrate and the rear substrate,
The electrodes on the front transparent substrate side and the electrodes on the rear substrate side are aligned so as to intersect via each display cell.

Next, a three-electrode surface discharge type panel structure will be described as a representative of an AC-driven plasma display panel. 17 is an exploded perspective view showing the configuration of a three-electrode surface discharge type plasma display panel in an exploded state, FIG. 18 is a sectional view of the panel, and FIG. 19 is an enlarged sectional view showing a part of the panel in a further enlarged manner. FIG. 20 is a plan view showing the electrode structure of the panel, and FIG. 21 is a plan view showing the display cell structure of the panel. In the three-electrode surface-discharge type panel 1, as shown in FIGS. 17 to 21, the display cells Cr, Cg, Cb,...
The scanning electrodes S1, S2,...
A large number of surface discharge electrode pairs composed of pairs of Su2,... Are formed. Scan electrodes S1, S2,... And sustain electrodes Su1, S
u2,... are made of a transparent conductive thin film such as ITO (Indium Tin Oxide) or SnO ₂ , and these scan electrodes S1, S
, And the sustain electrodes Su1, Su2,..., And the scan electrodes S1, S2,.
Bus electrodes B, B,... Made of a thick silver film or the like are provided on one side end of the surface of 1, Su,. Bus electrode B,
, And sustain electrodes Su, S1, S2,.
Are covered with a transparent dielectric layer 3, and an MgO protective layer 4 for protecting the dielectric layer 3 from ion bombardment during discharge is provided on the transparent dielectric layer 3.
Are stacked on top of each other.

[0007] On the inner surface of the back substrate 6, striped partition walls 7, 7, ... that define a striped discharge gas space extending in the column direction, and each display cell Cr, in the discharge gas space.
Are provided with data electrodes (that is, column electrodes) D1, D2,... Made of a silver film or the like that communicate Cg, Cb,. A dielectric layer 8 is formed on the data electrodes D1, D2,.
Is formed, and the dielectric layer 8, the partition 7 and the adjacent partition 7 are formed.
The three types of phosphors 9r, 9g, 9b,... That convert the ultraviolet light generated by the discharge in the discharge gas into visible light of each color of R, G, and B are provided on the wall surface of the groove of the discharge gas space composed of
Are stacked in a stripe pattern.

As described above, in the three-electrode surface discharge type plasma display panel 1, as shown in FIG.
r, Cg, Cb,..., scan electrodes S1, S2,
, And sustain electrodes Su1, Su2,... And data electrodes D1, D2,. The repetition unit of the display cells Cr, Cg, Cb,... Of R, G, B colors is one pixel. In the column direction, display cells Cr, Cg, Cb of the same color are arranged side by side. As a large-screen three-electrode surface discharge panel, for example,
480 scanning electrodes S1, S2,...
.. And 80 in the column direction.
A 42-inch (diagonal 106 cm) panel 1 in which 559 data electrodes D1, D2,... Are arranged is obtained. This panel has 480 pixels in the row direction and 85 pixels in the column direction.
3. The pitch of each pixel is about 1 mm in both the row and column directions.

Next, a driving circuit for driving the plasma display panel 1 will be described. FIG. 22 is a block diagram showing an electrical configuration of a three-electrode surface discharge type AC drive plasma display panel and a drive circuit thereof. The drive circuit section is configured to perform display driving by a combination of a write operation and a sustain discharge operation. In the write operation, the data electrode D
, D2,... And the scanning electrodes S1, S2,..., A write pulse is generated as shown in FIG. 25 (f), and the scanning electrodes of the display cells Cr, Cg, Cb,. Lighting display data is written by forming wall charges on S1, S2,. In the sustain discharge operation, after the end of the write operation, the scan electrodes S as shown in FIGS.
, S2,... And the sustain electrodes Su1, Su2,... Are alternately applied to sustain the luminescence discharge only in the display cells Cr, Cg, Cb,.

In order to realize the two-stage driving (scanning sustain separation driving), a driving circuit section includes a driving timing control circuit 10 and a data electrode driving circuit 11 as shown in FIG.
, Display data control circuit 12 and data electrode driving element 1
3, scan electrode drive circuit 14, scan electrode drive element 15
, A sustain electrode drive circuit 16 and a drive power supply 17. The drive timing control circuit 10 generates various timing pulses necessary for driving the panel unit 1 based on a vertical synchronization signal included in an input signal transferred from the display data control circuit 12, and controls the entire panel unit 1. In the plasma display device, one field period is constituted by a plurality of periods (i.e., subfields) with different numbers of pulses applied in the sustain operation period for gray scale display. , And is controlled by the drive timing control circuit 10. The data electrode drive circuit 11 generates a data pulse train based on the clock signal supplied from the drive timing control circuit 10 and supplies the data pulse train to the data electrode drive element 13. The display data control circuit 12 is configured to include a frame memory, processes input display data, and performs processing on all display cells C.
Generates write data (ie, lighting display data) for each subfield for r, Cg, Cb,... and serially transfers the write data to the data electrode driving element 13 at high speed.

The data electrode driving element 13 converts the write data supplied from the display data control circuit 12 into a serial /
It is composed of a shift register for parallel conversion, and a high-voltage switch element group having a CMOS configuration connected one-to-one to the data electrodes D1, D2,... Upon receiving the signal, the display cells Cr, Cg,
Cb,... Simultaneously drive the data electrodes D1, D2,. 24. That is, for all data electrodes D1, D2,... Passing through the display cells Cr, Cg, Cb,. , Rdn are applied at the same time.

When the scan electrode drive circuit 14 receives the supply of various ON / OFF signals that make one cycle per subfield from the drive timing control circuit 10, the scan electrode drive circuit 14 shown in FIGS. The pre-discharge pulse Pp, pre-discharge erase pulse Pd, base pulse Pb1,
Pb2,..., Pbn and the sustain pulse train Pm are sequentially generated and supplied to the scan electrode driving element 15. Scan electrode drive element 1
When receiving various collective synchronization signals supplied from the drive timing control circuit 10, the pre-discharge pulse P sequentially supplied from the scan electrode drive circuit 14 according to the type.
p, the preliminary discharge erasing pulse Pd, and the sustain pulse train Pm are simultaneously applied to all the scan electrodes S1, S2,.
, S2,... Are driven collectively, and during the writing period of the lighting display data, the scanning electrodes S1, S2,. Then, scanning (row selection) pulses Ps1, Ps2,..., P are applied to the selected scanning electrode Sn.
Apply sn.

When the sustain electrode drive circuit 16 receives various ON / OFF signals from the drive timing control circuit 10 that make one cycle per subfield, the sustain electrode drive circuit 16
A pre-discharge pulse Qp, a sustain pulse Qm, and a sustain erase pulse Qd as shown in FIG. 24A are sequentially generated, and the generated various pulses are simultaneously applied to all the sustain electrodes Su1, Su2,. , Su2,... Are driven collectively. The drive power supply 17 supplies necessary drive power to the data electrode drive circuit 11, the scan electrode drive circuit 14, and the sustain electrode drive circuit 16.

Next, a method of performing gradation display using such a plasma display panel will be described. In a plasma display panel, the relationship between the applied voltage and the luminance is not linear, and it is difficult to perform high-luminance gradation display by changing the applied voltage. Therefore, gradation display is performed by controlling the number of times of light emission. . In particular, a subfield method is used to perform high-luminance gradation display. FIG. 23 is an explanatory diagram for explaining a driving sequence by the subfield method. The horizontal axis represents time, and the vertical axis represents scanning electrodes S1 and S1.
2,..., Sn are taken. One image is sent during one field. The time of one field varies depending on each computer or broadcasting system, but is generally about 1/5
It is often set in the range of 0 seconds to 1/75 seconds.
In the gradation image display by the plasma display panel, one field is divided into k subfields (six subfields SF1, SF2,..., SF6 in the same figure) as shown in FIG.

Each subfield SF1, SF2,..., S
F6 is a writing period for writing the lighting display data into the display cells Cr, Cg, Cb,... With the scanning pulse and the data pulse, and the display cells Cr and Cg where the lighting display data is written, as shown in FIG. , Cb,... For sustaining a light emission display. In this writing period, as shown in the figure, after erasing discharge or forcible preliminary discharge of the lighting display data written in the previous subfield is performed, the data electrodes D1, D2,. A voltage pulse is applied to S2,... To generate a write discharge. Wall charges are formed on the scanning electrodes S1, S2,... Of the display cells Cr, Cg, Cb,. In the sustain discharge period following the write period, the scan electrodes S
By applying an AC sustaining pulse between the sustain electrodes Su1, Su2,... And the sustain electrodes Su1, Su2,. The light emission luminance of each display cell Cr, Cg, Cb,... Is obtained by weighting the number of light emission times of the sustain discharge of each display cell Cr, Cg, Cb,.
Is controlled based on the

[0016]

(Equation 1)

Here, n is the number of the subfield, and the subfield having the lowest luminance is "1" and the subfield having the highest luminance is "k". L1 is the luminance (the number of times of light emission) of the sub-field having the lowest luminance, and an is a variable having a value of “1” or “0”.
When b,... emit light, it is "1", and when it is not emitted, it is "0". As described above, since the emission luminance differs between subfields, the display cell C
By selecting lighting / non-lighting of r, Cg, Cb,..., the luminance is controlled. For color display, use R,
Since the repetition unit of the display cells Cr, Cg, Cb,... Of each color of G and B is one pixel, when k = 6, 2 ^{k is used for} each color.
(= 2 ⁶ = 64) stages of gradation expression. As the pigment, 64 ³ = 262144 colors (including black) can be displayed. If k = 1, 1 field = 1 subfield, and two gradations (on or off) can be displayed for each color. As the number of colors, 2 ³ = 8 colors (including black) can be displayed.

Next, FIGS. 24 (a), (b), (c),
Various drive waveforms in one subfield will be described with reference to (d) and (e). FIG.
As shown in (c) and (d), the scan electrodes S1, S2,
, Sn, a pre-discharge pulse (positive pulse) Pp, a pre-discharge erase pulse Pd, and a sustain pulse Pm common to these electrodes are applied.
Scan pulses Ps1, Ps2,..., Psn are applied line-sequentially at timings independent of 1, S2,. When one scan electrode is selected, scan base pulses Pb1, Pb2,..., Pbn are applied to the remaining non-selected scan electrodes. The sustain electrodes Su1, Su2,..., As shown in FIG.
2,..., Pre-discharge pulse (positive pulse) applied to Sn
A pre-discharge pulse (negative pulse) Qp is applied in synchronization with Pp, and at the time of sustain discharge, sustain pulse Qm is applied alternately with the timing at which sustain pulse Pm is applied to scan electrodes S1, S2,. Is applied, and when ending the sustain discharge, a sustain erase pulse Qd is applied. As shown in FIG. 3E, when there is lighting display data to be written at the data electrodes D1, D2,..., Data pulses Rd1, Rd2,.
Rdn is applied in synchronization with the scanning pulses Ps1, Ps2,..., Psn.

Next, FIGS. 25 (a), (b), (c),
The steps (1) to (5) of the subfield operation in the three-electrode surface discharge type plasma display device will be described with reference to (d), (e), and (f). (1) Sustain discharge erasing As shown in FIG. 1C, the sustain electrode driving circuit 16 applies the sustain erasing pulse Qd to the sustain electrodes Su1, Su2,... At the timing specified by the drive timing control circuit 10, Display cell C emitting light in the immediately preceding subfield
Erase the discharge of r, Cg, Cb, .... As a result, extra wall charges that cause noise are eliminated. (2) Pre-discharge Next, as shown in FIG.
And the sustain electrode drive circuit 16 controls all the scan electrodes S at the timing specified by the drive timing control circuit 10 simultaneously.
, S2,... And sustain electrodes Su1, Su2,... Are applied with positive and negative pre-discharge pulses Pp, Qp to generate a voltage between the two electrodes, and all display cells Cr, Cg, Cb,.
... is forcibly discharged once. (3) Pre-discharge erasure After that, as shown in FIG.
5 applies a predischarge erasing pulse Pd to all the scan electrodes S1, S2,... At a timing designated by the drive timing control circuit 10 to erase the predischarge. This allows
Active particles are injected into the discharge space, and writing discharge by the next applied scanning pulses Ps1, Ps2,..., Psn is likely to occur. (4) Write discharge After the preliminary discharge and erasure, the data electrode 13 and the scan electrode driving element 15 are connected to the scan electrodes S1, S2,... D2,..., And scanning pulses Ps1, Ps2,.
When d2,..., Rdn are applied, the display cells Cr, Cg, Cb,.
As shown in FIG. 7F, the display cell C which has been selectively discharged is used.
Wall charges are formed on the scan electrodes S1, S2,... of r, Cg, Cb,. Thus, the lighting display data is written in such a manner that wall charges are formed. Note that only the scanning pulses Ps1, Ps2,..., Psn or the data pulses Rd1, Rd1
When only d2,..., Rdn are applied, no write discharge occurs, and no sustain discharge thereafter occurs. (5) Sustain discharge After the write discharge, the scan electrode drive element 15 and the sustain electrode drive circuit 16 are applied at alternately supplied timings by the drive timing control circuit 1 as shown in FIGS. , Scan electrodes S1, S2,... And sustain electrode Su.
, Su2,..., And sustain pulses Pm, Qm are alternately applied to display cells Cr, Cg, C on which wall charges are formed.
b,... only in adjacent sustain electrodes Su1, Su
, And sustain electrodes (emission discharges) between scan electrodes S1, S2,.

One subfield operation is completed in the above steps (1) to (5), and the process proceeds to the next subfield operation to repeat the above steps (1) to (5). Note that the light emission luminance of each subfield is controlled based on the number of repetitions of the sustain discharge.

Generally, in a dot matrix type display panel, a large number of row electrodes and column electrodes are formed, and display pixels or display cells are formed at intersections of these electrodes.
Therefore, the sum of the capacitances existing between the counter electrodes and between the parallel electrodes is enormous. Therefore, when driving a dot matrix type display panel, the required operating voltage cannot be applied to each display element unless the charging of these capacitances is completed. The power used for charging these capacitances is different from the power actually consumed, and can be recovered and reused by an appropriate method, so that it becomes reactive power. In particular, in plasma display panels,
Since the light emission discharge phenomenon is used, the applied driving voltage is high and the reactive power is increased. Also corresponds to the reusable reactive power of the same quality as the charging power for the capacitance.

To overcome this difficulty, attempts have been made to reduce the power consumption by collecting and reusing (ie, regenerating) the charging power for the capacitive load. For example, Japanese Patent Publication No. 5-81912 discloses a technique of collecting electric charge accumulated in a capacitance to an original power supply and reusing the same (hereinafter, referred to as a first conventional technique). Also, Japanese Patent No. 2801908 discloses a technique for collecting and reusing an electric charge accumulated in a capacitance in a dedicated collecting capacitor (hereinafter referred to as a second technique).
Of the prior art).

First, the basic circuit in the first prior art and
The operation will be described. FIG. 26 shows this first prior art.
Technology of sustain pulse generation circuit with power recovery function
FIG. 27 is a circuit diagram showing the basic configuration, and FIG.
It is a time chart for clarification. This sustain pulse
The raw circuit generates a sustain pulse to generate a sustain electrode or scan electrode.
Circuit for supplying power to the
Voltage switch SW₁₁, SW ₁₂, SW₁₃, SW₁₄And da
Iod DI₁₁, DI₁₂, DI₁₃, DI₁₄And power recovery
Coil L for₁₁And external capacitance including stray capacitance in the circuit
C₁₂It is composed of It should be noted that in FIG.
Sensor C₁₁Is the capacitor of DC power output, capacitor C₁₃
Is a heterogeneous electrode of plasma display panel (various panel
Pole), capacitive load, terminal TP₁ Is a sustain pulse
Output terminal of the circuit and terminal TP_Two Gives the voltage VS
This is a terminal for connecting a power supply.

Next, the operation of the sustain pulse generating circuit having the above configuration will be described with reference to FIGS. At time T _11, to provide the sustain pulse voltage, as shown in FIG. 27 (d), to indicate the switch SW ₁₄ off state, and in FIG. 6 (a), the switch SW ₁₁ in the ON state to charge the external capacitor C ₁₂ and the capacitive load C ₁₃ through coil L _11. At the time T _12, the terminal TP
₁ voltage becomes conductive diode DI ₁₃ is higher than the voltage VS of the terminal TP ₂ of the DC power source, as shown in FIG. (E), the voltage at the terminal TP ₁ is clamped to the voltage VS of the terminal TP ₂ . Then, as shown in FIG. 6 (a), when the switch SW ₁₁ in synchronism exactly the time T ₁₂ to the OFF state, the energy stored in the coil L ₁₁ is the coil L
₁₁ , the diode DI ₁₃ , and the diode DI ₁₂ are collected in the capacitor C ₁₁ . Also, at time T _12, as shown in FIG. (C), the switch SW ₁₃ in the ON state, connects the terminals TP ₁ to the DC power supply, to fix the voltage of the terminal TP ₁ to sustain pulse voltage VS.

Next, when removing the sustain pulse voltage VS,
Is the time T, as shown in FIG. ₁₃At the switch
Switch₁₃As shown in FIG.
Like switch SW₁₂Is turned on. Then,
Il L₁₁Through terminal TP₁ Voltage drops to zero voltage
go. Time T₁₄At the terminal TP₁ Voltage is zero voltage
Diode DI when lower₁₄Is conducted, and FIG.
As shown in FIG. ₁ Is clamped to zero voltage
You. And this time T₁₄Switch S in exact synchronization with
W₁₂Is turned off, the coil L₁₁Energy stored in
Lugi is the same coil L ₁₁, Diode DI₁₁,diode
DI₁₄Through capacitor C₁₁Will be collected. Also when
Time T₁₄At the terminal TP as shown in FIG.₁ 
When the voltage of the switch becomes lower than zero voltage, the switch SW₁₄
Is turned on, and the terminal TP₁ To the ground
Child TP₁ Is fixed to zero voltage.

Next, the basic circuit of the second prior art and its operation will be described.
The work will be described. FIG. 28 shows the second prior art.
The basic structure of the sustain pulse generating circuit having the power recovery function
And FIG. 29 illustrates the operation of the circuit.
Diagram of the output voltage and the current due to the electromotive force of the coil
is there. This sustain pulse generating circuit is configured as shown in FIG.
And a capacitor C for energy recovery_{twenty one}And coil L_{twenty one},
Charge recovery unit 1 that is connected in series with switch means 18
9 and switch SW_{twenty one}And constitute a capacitive load Cp.
A panel electrode 20 such as a sustain electrode or a scanning electrode is supplied with a power supply voltage.
A first clamping means 21 for clamping to Vcc;
Switch_{twenty two}And clamps panel electrode 20 to ground
And the coil L_{twenty one}Electricity flowing through
When the backflow is detected, the clamp means 21 or the
First and second driving means 23 for driving the pump means 22;
24. The switch means 18 is
As shown in FIG._{twenty three}And diode DI_{twenty one}When
Connected in series and a switch SW_{twenty four}And diode
DI _{twenty one}Diode DI in the opposite direction_{twenty two}And are connected in series
Are connected in parallel with each other, the coil L_{twenty one}Flow
The off state when the current flowing to zero becomes zero.
ing. Note that, as shown in FIG.
The raw circuit is connected to the scan electrode and to the sustain electrode.
Used in pairs with those that follow.

Next, the operations (1) to (4) of the sustain pulse generating circuit having the above configuration will be described with reference to FIGS. Now, the terminal voltage Vss Vcc / 2 of the capacitor C ₂₁ for energy recovery, the capacitive load Cp terminal voltage Vp is zero, the switch SW _21, SW ₂₃ is turned off, and the switch SW _22, SW ₂₄ is turned on And This is referred to as state [0], and the process proceeds to state [1].

(1) Operation in State [1] First, the switch SW ₂₁ is turned on, the switch SW ₂₂ is turned off, and the switch SW ₂₄ is turned off. When the switch SW ₂₁ is turned on, the series resonant circuit is formed by the coil L ₂₁ and the capacitive load Cp, this time, the terminal voltage Vss of the capacitor C ₂₁ has a forcing voltage of Vcc / 2. Next, the inter-terminal voltage Vp of the capacitive load Cp is raised up to the power supply voltage Vcc, the current IL by the electromotive force of the coil L ₂₁ at this time is zero, further, the diode DI ₂₁ is reverse biased. (2) by the operation switch SW ₂₃ in the ON state in the state [2] to clamp the terminal voltage Vp of the capacitive load Cp to the power supply voltage Vcc, and a discharge current path for the display cell should be all in the ON state Bring. (3) Operation switch SW ₂₂ in the state [3] is turned on, the switch SW ₂₁ is turned off, and the switch SW ₂₃ is turned off. Switch S
When W ₂₂ is turned on, the coil L ₂₁ and the capacitive load Cp
Series resonance circuit is formed again by the, at this time, the terminal voltage Vss of the capacitor C ₂₁ has a forcing voltage of Vcc / 2. Then, the terminal voltage Vp of the capacitive load Cp lowered to ground level, at this point, the current IL by the electromotive force of the coil L ₂₁ is zero, further, the diode DI ₂₂ is reverse biased. (4) by the operation switch SW ₂₄ in the ON state in the state [4] to clamp the terminal voltage Vp of the capacitive load Cp to ground. At this time, another sustain pulse generating circuit forming a pair is a capacitive load Cp
The opposite side of the panel electrodes constituting driven to the supply voltage Vcc, and when there is a display cell to be a "on", the discharge current flows through the switch SW _24.

As described above, in the first and second prior arts, the reactive power is reduced by collecting and reusing the charge / discharge power of the capacitance.

[0030]

However, the first and second prior arts have the following problems. That is, in the first and second prior arts, in order to efficiently recover power, the on / off of each switch is accurately adjusted in accordance with the timing at which the voltage of the capacitive load is clamped to the power supply voltage and the ground potential. There is a problem that control must be performed (first prior art) or on / off control of a clamp switch must be performed with accurate timing (second prior art). if,
If this timing is inaccurate, a large gas discharge current also flows through a drive circuit such as a sustain pulse generation circuit, so that the power loss inside the drive circuit increases and the charge / discharge power recovery efficiency deteriorates significantly. In the worst case, the diode and the switch may be burned.

However, for a plasma display panel requiring a very high-speed operation (the rising or falling time of the sustain pulse is about 0.2 to 0.5 μsec),
There is no high-voltage and high-withstand-voltage switching device having a sufficiently fast operation speed (preferably, an operation delay time of 0.1 μs or less) capable of accurately turning on only during the rise or fall time, or Expensive.

Therefore, if a circuit with good timing characteristics is to be produced by using a low-priced switching device having inferior characteristics, the circuit configuration becomes extremely complicated, resulting in an expensive circuit, which is inconvenient. In addition, the gas discharge current flowing in the drive circuit is not constant, and the number of pixels to be lit for each subfield changes according to the input display data. Since the capacitance also changes, and the resonance frequency of the resonance circuit with the coil also changes, it is more difficult to accurately control the on / off timing of various switches. At the time of voltage clamping, a high-speed transient occurs,
Unwanted electromagnetic radiation is large.

The present invention has been made in view of the above circumstances, and has a simple circuit configuration, is capable of recovering reactive power sufficiently in practical use, and is capable of reducing unnecessary electromagnetic wave radiation. It is an object to provide a driving circuit and a driving method.

[0034]

According to a first aspect of the present invention, there is provided a driving circuit for supplying a pulse to a capacitive load which is a constituent electrode of a capacitive display panel. A coil connected directly or indirectly to a capacitive load to form a series resonance circuit together with the capacitive load; and a first power supply voltage output from a DC power supply when turned on, the series resonance circuit A first switch for applying a first resonance to start the first resonance, and a point at which the voltage of the capacitive load starts to exceed the first power supply voltage after the first resonance starts. A first clamping means for clamping the voltage of the first power supply voltage to the first power supply voltage to stop the first resonance, and when the first resonance is stopped,
First flywheel current holding means for holding the current flowing in the coil in a first flywheel operating state and holding the current in the first flywheel operating state to the DC power supply; By turning on the current regenerating means, the charging voltage of the capacitive load is turned on,
A second switch for starting a second resonance in a series resonance circuit with the coil, and a second power supply voltage for outputting the voltage of the capacitive load from the DC power supply after the second resonance starts At the time of starting to fall below, the second clamp means for clamping the voltage of the capacitive load to the second power supply voltage to stop the second resonance, and when the second resonance stops, The current flowing through the coil is
Second flywheel current holding means for holding the flywheel in the flywheel operating state, and second current regenerating means for regenerating the current in the second flywheel operating state to the DC power supply. It is characterized by.

According to a second aspect of the present invention, there is provided the driving circuit for a capacitive load according to the first aspect, wherein the first current regenerating means is configured to control the first current regenerating means in accordance with a regenerative pulse input timing.
After a part or most of the current in the (or second) flywheel operating state is regenerated to the DC power source, the remaining current for continuing the first (or second) flywheel operation is regenerated to the DC power source. It is characterized by doing.

According to a third aspect of the present invention, there is provided the driving circuit for a capacitive load according to the first aspect, wherein the first current regenerating means includes a third switch, and the third switch is turned on. Then, the current in the first flywheel operating state is regenerated to the DC power supply.

According to a fourth aspect of the present invention, there is provided the driving circuit for a capacitive load according to the first aspect, wherein the first clamp means includes a wiring connecting the coil and the capacitive load and a DC power supply. And a second diode is inserted between the wiring and the second power supply voltage in such a manner that a direction from the coil toward the DC power supply is a forward direction. A second diode is interposed between the second power supply voltage and the second power supply voltage so that a direction from the second power supply voltage toward the coil is a forward direction.

According to a fifth aspect of the present invention, there is provided a driving circuit for a capacitive load according to the first aspect, wherein the first flywheel current holding means includes the coil, a first diode,
The first switch in the ON state is connected in series in this order, and with respect to the first diode, in a mode in which the direction of this order is forward, the first switch is connected to the second switch, and The flywheel current holding means includes: the coil, the second switch in an ON state, and a second diode, which are connected in series in this order, and the direction of the second diode is set to a forward direction. And wherein the currents in the first and second flywheel operating states flow in opposite directions in the coil.

According to a sixth aspect of the present invention, there is provided the driving circuit of the capacitive load according to the first aspect, wherein the first current regenerating means is connected in parallel with the second switch in an off state. The diode, the coil, and the first diode are connected in series in this order, and the third and first diodes are connected in such a manner that the order of the order is forward. The power supply device is interposed between a DC power supply and a second power supply voltage.
, The coil, and a fourth diode connected in parallel with the first switch in an off state, in this order, and for the second and fourth diodes, in this order. In a mode in which the direction is forward, the first switch is connected and inserted between the DC power supply and a second power supply voltage, and when the second switch is in an off state, the first switch is also connected. When the first switch is in the off state, the first current regeneration unit is in the current regeneration state. On the other hand, when the first switch is in the off state, when the second switch is also in the off state, the second current regeneration unit is in the off state. It is characterized in that it enters a current regeneration state.

According to a seventh aspect of the present invention, there is provided a driving circuit for a capacitive load according to the first aspect, wherein the driving circuit is directly or indirectly connected to the capacitive load to form a series resonance circuit together with the capacitive load. A first coil inserted between the coil, a wire connecting one end of the coil and the capacitive load, and the DC power supply, and in a manner that a direction from the coil toward the DC power supply is a forward direction. And a second diode interposed between the wiring and a second power supply voltage in such a manner that a direction from the second power supply voltage toward the coil is forward. A third diode inserted between the coil and the DC power supply, and in such a manner that a direction from the coil toward the DC power supply is a forward direction, and a third diode interposed between the coil and the DC power supply. Inserted between the DC power supply, A first switch connected in parallel with the third diode, and at the other end of the coil, between the coil and a second power supply voltage, and from the second power supply voltage to the coil. The fourth diode is inserted between the coil and the second power supply voltage, and the fourth diode is inserted in such a manner that the direction toward
And a second switch connected in parallel with the diode.

According to an eighth aspect of the present invention, there is provided a driving circuit for a capacitive load according to the seventh aspect, wherein the third diode and the first switch are connected in parallel, and the fourth diode and the second switch are connected in parallel. In parallel connection with the switch is constituted by MOSFETs each having a built-in parasitic diode.

According to a ninth aspect of the present invention, there is provided the driving circuit for a capacitive load according to the first aspect, wherein the first power supply voltage is lower than the second power supply voltage when the first power supply voltage is lower than the second power supply voltage. Instead of the clamping means, after the first resonance starts, at the time when the voltage of the capacitive load starts to fall below the first power supply voltage, the voltage of the capacitive load is changed to the first power supply voltage. And a third clamping means for clamping to stop the first resonance, and in place of the second clamping means, after the second resonance is started, the voltage of the capacitive load is reduced to the second voltage. And a fourth clamping means for stopping the second resonance by clamping the voltage of the capacitive load to a second power supply voltage when the power supply voltage starts to exceed the power supply voltage.

According to a tenth aspect of the present invention, there is provided a driving method for supplying a pulse train to a capacitive load which is a constituent electrode of a capacitive display panel by using the driving circuit according to the first aspect. Then, after turning on the first switch, applying the first power supply voltage to the series resonance circuit to start the first resonance, and after the first resonance starts,
At a second point in time when the voltage of the capacitive load starts to exceed the first power supply voltage, the charging voltage of the capacitive load is changed to the first voltage.
The first resonance is stopped by clamping to the power supply voltage of the power supply, and at this time, the current flowing through the coil is maintained in the first flywheel operating state, and at the third time, the first flywheel is operated. To turn off the switch, to regenerate the current in the first flywheel operating state to the DC power supply, and to turn on the second switch at a fourth point in time to charge the capacitive load. Is applied to the series resonance circuit to start a second resonance. After the second resonance starts, at a fifth point in time when the voltage of the capacitive load starts to fall below the second power supply voltage, Clamping the voltage of the capacitive load to the second power supply voltage to stop the second resonance, and at this time, holding the current flowing through the coil in the second flywheel operating state; At a sixth point, the second Switch in the off state, by repeating a series of operations until the regenerative current of the second flywheel operation state to the DC power source, is characterized by supplying the pulse train to the capacitive load.

An eleventh aspect of the present invention relates to the driving method of the capacitive load according to the tenth aspect, wherein the third (or sixth) method is used.
At the point of time, the step of turning off the first (or second) switch to regenerate the current in the first (or second) flywheel operating state to the DC power supply includes a third 1 ( Alternatively, at the time of the sixth 1), the first (or the second) switch is turned off for a predetermined time, during which a part of the current in the first (or the second) flywheel operating state is set. Or, regenerate the majority to the DC power supply, and
At the time point 2 (or sixth 2), the first (or second) switch is turned off again, and the remaining current that continues the first (or second) flywheel operation is changed to the It is characterized in that it is a step of regenerating to a DC power supply.

According to a twelfth aspect of the present invention, there is provided the driving method of the capacitive load according to the eleventh aspect, wherein the third (or sixth) time point is determined according to the load capacity of the capacitive load. Is controlled.

According to a thirteenth aspect of the present invention, there is provided the driving method of the capacitive load according to the eleventh aspect, wherein the third time point (or the sixth time point) corresponds to the load capacity of the capacitive load. Wherein the time width of the off state of the first (or second) switch is controlled.

According to a fourteenth aspect of the present invention, there is provided the driving method of the capacitive load according to the tenth aspect, wherein the third (or sixth) method is used.
The step of turning off the first (or second) switch to regenerate the current in the first (or second) flywheel operating state to the DC power supply at the time of the third (or At the time of the sixth, a third (or fourth) switch is turned on to regenerate the current in the first (or second) flywheel operating state to the DC power supply. And

According to a fifteenth aspect of the present invention, in the driving method of the capacitive load according to the tenth aspect, when the first power supply voltage is lower than the second power supply voltage, the capacitive load is driven. At a second point in time when the load voltage begins to fall below the first power supply voltage, the charging voltage of the capacitive load is clamped to the first power supply voltage to stop the first resonance, and at this point in time, A current flowing through the coil is maintained in the first flywheel operating state, and the voltage of the capacitive load starts to exceed the second power supply voltage.
At this time, the voltage of the capacitive load is clamped to a second power supply voltage to stop the second resonance, and at this time, the current flowing through the coil is held in the second flywheel operating state. It is characterized by doing.

According to a sixteenth aspect of the present invention, in the drive circuit for a capacitive load according to the first aspect, a capacitor for suppressing a sudden change in the voltage of the capacitive load is provided.

According to a seventeenth aspect of the present invention, in the drive circuit for a capacitive load according to the first aspect, the capacitive load is charged when the voltage of the capacitive load is applied, and the voltage of the capacitive load is reduced. A capacitor is provided which suppresses a sudden change in the voltage of the capacitive load by supplying a voltage to the capacitive load by discharging sometimes.

[0051]

Embodiments of the present invention will be described below with reference to the drawings. First, the basic principle of the present invention will be described. FIG. 1 is a circuit diagram showing a basic configuration of a capacitive load drive circuit according to the present invention, and FIG. 2 is a time chart for explaining the operation of the circuit.
The driving circuit according to the present invention is largely different from the above-described first and second prior arts in that the two conventional clamping switches are eliminated, and the prior art is provided without newly providing components. It has a flywheel current holding function which is not provided in the art, and the flywheel current held by this function is regenerated to the power supply. In this flywheel current holding function, when the resonance state of the series resonance circuit composed of the capacitive load and the coil is forcibly stopped by the clamp means, the current flowing in the coil at that point in time remains in the flywheel even after the resonance stops. Maintained in the operating state, the energy stored in the coil is maintained.

In order to realize the above function, as shown in FIG. 1, the capacitive load driving circuit 11a according to the present invention comprises a capacitor such as a row electrode or a column electrode which is a constituent electrode of a plasma display panel or an EL display panel. Connected in series to the active load 25. The drive circuit 11a includes a coil 26 forming a series resonance circuit together with the capacitive load 25, and a coil 26 and a high-voltage power supply 27 at one end (capacitive load side) of the coil 26.
And a diode DI inserted in a manner such that the direction from the coil 26 to the power supply 27 is a forward direction.
₃₁ and a diode DI ₃₂ inserted between the coil 26 and the ground at one end side (capacitive load side) of the coil 26 in such a manner that the direction from the ground to the coil 26 is the forward direction. at the other end of the coil 26, between the coil 26 and the power source 27, and in a manner that a direction from the coil 26 to the power supply 27 is forward, and a diode DI ₃₄ interposed, a coil 26 and a power supply 27 and a switch SW ₃₁ connected in parallel with the diode DI ₃₄ to the other end of the coil 26.
And between the ground and in a manner that a direction from the ground to the coil 26 becomes forward, a diode DI ₃₃ interposed, is interposed between the coil 26 and the ground, and in parallel to the diode DI ₃₃ And a switch SW ₃₂ connected thereto.

When the switch SW ₃₁ is turned on, the power supply voltage is applied to a series resonance circuit including the coil 26 and the capacitive load 25 to start resonance during charging, while being turned off, Power supply for flywheel current 27
To regenerate. At the time of this charge, as shown in the figure, the coil 26 → diode DI ₃₁ → on-state switch SW ₃₁
Constitutes a flywheel current holding circuit, and a path of the diode DI ₃₃ → the coil 26 → the diode DI ₃₁ which is interposed between the ground and the power supply 27 and connected in series with each other forms a current regeneration circuit. Constitute. The diode DI ₃₁ inserted between the capacitive load 25 and the power supply 27 functions as a clamp for fixing the charging voltage of the capacitive load 25 to the power supply voltage.

On the other hand, switch SW₃₂Is turned on
As a result, the voltage of the capacitive load 25 is
To the series resonance circuit consisting of
On the other hand, the flywheel
A power supply current is regenerated to the power supply 27. At the time of this discharge,
As shown in FIG. ₃₂
→ Diode DI₃₂Loop consisting of flywheel
A current holding circuit, and between the ground and the power supply 27.
And a diode DI connected in series with each other₃₂
→ coil 26 → diode DI₃₄Path is the current regeneration circuit
Is composed. Also, between the ground and the capacitive load 25
Interposed diode DI₃₂Is the voltage of the capacitive load 25
Function as a clamp for fixing the
You. Note that the power supply smoothing capacitor 28 shown in FIG.
Changes in voltage due to regeneration of current flowing through coil 26
Not to be compared with the capacitance Ct of the capacitive load 25.
Therefore, a capacitor having a sufficiently large capacitance Cin is used.

Next, the operations (1) to (6) of the drive circuit 11a of FIG. 1 will be described with reference to FIGS. Now, the voltage of the capacitive load 25 is 0 [V], the current flowing through the coil 26 is 0 [A], and the switch SW _31, SW ₃₂ are both set to OFF state, and the state as [0]. Time A
At this point, the state proceeds from the state [0] to the state [1]. (1) Operation in State [1] As shown in FIG.
_{When the} switch ₃₁ is turned on, the power supply voltage V is applied to the point A of the series resonance circuit including the coil 26 and the capacitive load 25, and charging of the capacitive load 25 is started, as shown in FIG. You.

The resonance equation of this charging circuit is expressed by equation (2). From the equation (2), the natural oscillation frequency fo of the circuit shown in the equation (3) is derived. When the initial condition is applied to the equation (2), the current i flowing through the coil 26 at the time t is given by the equation (4).
The voltage Vc of 5 is given by equation (5). In these equations, L is the inductance of the coil 26 and C
t is the capacitance of the capacitive load 25.

(Equation 2)

(Equation 3)

(Equation 4)

(Equation 5)

Therefore, the current i flowing through the coil 26 is
Vibration starts at the natural vibration frequency fo, and rises as shown in FIG. On the other hand, the capacitive load 2
The voltage Vc of 5 also starts oscillating at the natural oscillation frequency fo,
In accordance with the equation (5), as shown in FIG.

(2) Operation in State [2] At time B, if the voltage Vc of the capacitive load 25 exceeds the power supply voltage V, the diode DI ₃₁ conducts.
As shown in (d), the voltage Vc of the capacitive load 25 is clamped at the power supply voltage V. As a result, the resonance stops at time B. The time B is a time when 1/4 of the natural oscillation period has elapsed from the time A, as derived from the equation (5). The current i flowing through the coil 26 is derived from Expression (4), and is a maximum current at the time of time B at the time of resonance as shown in FIG. 26 → loop composed of the diode DI ₃₁ → switch SW ₃₁ in the oN state (i.e., the flywheel current holding circuit) continues the flywheel operation by circumfluence a. Hereinafter, the current in the flywheel operating state is also referred to as flywheel current.

(3) Operation in State [3] As shown in FIG.
₃₁Is turned off, the flywheel current i
The voltage at point A to maintain the current.
Drops rapidly and drops below ground potential.
Code DI₃₃Is made conductive. Then the flywheel current
i is a diode DI as shown in FIG. ₃₃→ coil 2
6 → Diode DI₃₁Is regenerated by the power supply 27 in the path of
The current energy stored in the file 26 returns to the power source 27.
Is done. As shown in FIG. 2C, the current flows through the coil 26.
The flywheel current i decreases with regeneration. This
The slope of the current i at the time is expressed by -V / L [A / sec].
You.

[0060] (4) As shown in operation Figure 2 (b) in the state [4], at time D the current i flowing through the coil 26 becomes zero, when the switch SW ₃₂ in the ON state, the coils 26 The voltage Vc stored in the capacitive load 25 is applied to the series resonance circuit composed of the capacitive load 25 and the capacitive load 25, and the discharge of the capacitive load 25 is started as shown in FIG. The resonance equation of this discharge circuit is given by equation (6). From the equation (6), the natural oscillation frequency fo of the circuit shown in the equation (3) is derived. When the initial condition is applied to the equation (6), the current i flowing through the coil 26 at the time t is given by the equation (7), and the voltage Vc of the capacitive load 25 at the time t is calculated by the equation (8) ).

(Equation 6)

(Equation 7)

(Equation 8)

The current i flowing through the coil 26 starts oscillating at the natural oscillation frequency fo, and according to the equation (7), (c) in FIG.
Descend as shown. On the other hand, the voltage V of the capacitive load 25
c also starts to vibrate at the natural vibration frequency fo, and falls toward the negative value -V of the power supply voltage V according to the equation (8), as shown in FIG. The time that the switch SW ₃₂ to the ON state, may be earlier than the time D. However,
In order to prevent the short circuit of the power supply 27, the time cannot be set earlier than the time C.

(5) Operation in State [5] When the voltage Vc of the capacitive load 25 falls below the ground potential,
Since the diode DI ₃₂ conducts, the voltage Vc of the capacitive load 25 is clamped to the ground potential as shown in FIG. As a result, the resonance stops at time E. The time E is a time when 1/4 of the natural oscillation period has elapsed from the time D, as derived from the equation (8). The current i flowing through the coil 26 is derived from Expression (7), and is a negative maximum current at the time of time E at the time of resonance as shown in FIG. 2C. , The coil 26 → the switch SW _{32 in the} ON state → the diode DI ₃₂ circulates a loop (that is, a flywheel current holding circuit) to continue the flywheel operation.

(6) Operation in State [6] As shown in FIG.
_When the switch ₃₂ is turned off, the flywheel current breaks the loop. Therefore, to maintain the current, the voltage at the point A sharply rises, rises above the power supply voltage, and the diode DI
_{Make 34} conductive. Then, the flywheel current i is regenerated to the power supply 27 through the path of the diode DI ₃₂ → the coil 26 → the diode DI ₃₄ , and the current energy stored in the coil 26 is returned to the power supply 27. As shown in FIG. 2C, the flywheel current i flowing through the coil 26 decreases with regeneration. The slope of the current at this time is V /
It is indicated by L [A / sec].

By repeating the above operations (1) to (6),
A voltage pulse train is supplied to the capacitive load 25. As described above, the ineffective electric power only for charging and discharging the capacitive load 25 is retained in the form of the current energy of the coil 26 and then regenerated to the power supply 27, so that the power consumption can be reduced. it can. Further, although the conventional two switches for clamping, which are difficult to control the timing, are eliminated and the number of parts is reduced, the function of regenerating the flywheel current to the power supply is provided as described above. Therefore, it is possible to obtain practically sufficient power recovery efficiency with a simple and inexpensive circuit configuration. In addition, since a series resonance circuit is formed by the coil 26 and the capacitive load 25, a gentle transient pulse train can be obtained. If a gentle transient is used, the high frequency component of the pulse waveform is reduced, so that unnecessary electromagnetic wave radiation generated from the capacitive load can be reduced.

In addition, after the start of charging or discharging, one-fourth of the natural oscillation period of the series resonance circuit due to the coil and the capacitive load.
After the time elapses, the switch is automatically clamped without using a switch. Therefore, even when the value of the capacitive load fluctuates randomly and the voltage clamping time fluctuates randomly, it can be easily followed. For this reason, it is possible to avoid the conventional control difficulties in which the switch timing had to follow the clamp time that fluctuates randomly.
As a practical matter, when this type of driving device is applied to a driving device for a data column electrode, the value of the capacitive load fluctuates randomly and sometimes suddenly. This is because a driving element composed of a switching device row is interposed between the coil 26 and the capacitive load 25, and the number of data electrodes selected by these driving elements fluctuates according to input display data. It is.

Next, as a first embodiment of the present invention,
An example in which the drive circuit of FIG. 1 is applied to a data electrode drive circuit of a three-electrode surface discharge type plasma display panel will be described.

[0067]First embodiment  FIG. 3 shows a data electrode drive according to the first embodiment of the present invention.
FIG. 4 is a circuit diagram showing an electrical configuration of the driving circuit, and FIG.
Principal part of electrical configuration of plasma display device provided with drive circuit
And FIG. 5 illustrates the operation of the drive circuit.
It is a time chart for. Data electrode drive in this example
Circuit 11b is a realistic circuit embodying the basic circuit of FIG.
A switch SW shown in FIG.₃₁And Daio
Do DI₃₁And the switch SW₃₂And Daio
Code DI₃₂3 is connected in parallel as shown in FIG.
Built-in parasitic diodes 29a and 29b, respectively
N-type switching element (hereinafter referred to as MOSFE)
T switches 30a and 30b).
You. With a plasma display device incorporating this drive circuit 11b,
Are the coils 26, as evident in FIGS.
, And data electrodes D1, D2,...
A series resonance circuit is formed via the element 13.

In the row electrode driving of the sustain electrodes Su1, Su2,..., The entire surface of the panel 1 is driven by the same pulse during the sustain discharge period. Therefore, one power recovery circuit may be added. However, since the data (column) electrodes D1, D2,... Are driven according to the image to be displayed, they cannot be driven collectively. For this reason, a data electrode driving circuit 11b is provided outside as a driving pulse supply means, and the data electrode driving circuit 11b has a power recovery function, and the data electrode driving circuit 11b and each data electrode D1, D2 on the panel 1 are provided. , ..., for each line-sequential scan, and
A data electrode drive element 13 is provided for selecting whether to send or block a drive pulse for each data electrode. As shown in FIG. 2, the data electrode drive element 13 is composed of a CMOS-structured high breakdown voltage switch element group T1, T2,... Connected to the data electrodes D1, D2,.
The display data control circuit 12 is controlled at the timing of each line-sequential scan controlled by the drive timing control circuit 10 of FIG.
Are simultaneously supplied to only the data electrodes D1, D2,... Selected based on the write data for n data electrodes supplied from the data electrode driving circuit 11b.

At the time of write scanning, the data electrodes D1, D2,
.. Are not sent at all, the data electrode drive circuit 11b is configured to keep sending a pulse train to the data electrode drive element 13. In such a case, the load capacitance becomes extremely small, so that the data electrode drive circuit 11b operates at high speed. A transient occurs, and as a result, unnecessary electromagnetic waves are radiated. Therefore, even in such a case, in order to mitigate the transient and prevent generation of unnecessary electromagnetic waves, in this embodiment, a capacitor Cext is inserted between the output side of the data electrode drive circuit 11b and the ground. I have. This capacitor Cext can be omitted in an environment where radiation of unnecessary electromagnetic waves does not particularly matter.

In FIG. 3, the same components as those in FIG. 1 are denoted by the same reference numerals, and description thereof will be omitted. Similarly, in FIG. 4, the same components as those in FIG. 22 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 4, the scan electrode drive circuit 14, the scan electrode drive element 15, and the sustain electrode drive circuit 1 as shown in FIG.
6 is omitted because it is unnecessary for the description in this embodiment.

The data (column) electrodes D1, D2,... On the plasma display panel 1 are arranged between the scanning electrodes S1, S2,. Has a capacitance component called a counter capacitance. Furthermore, if there is a non-selected data electrode around the data electrode selected and written during the line sequential scanning period, the non-selected electrode is fixed to the ground potential, so that the selected data electrode and the non-selected data electrode are fixed. A data inter-electrode capacitance occurs between the electrodes. A capacitor Cex for transient mitigation is added to these opposed capacitance and capacitance between data electrodes.
The total capacitance including the capacitance t and the like constitutes a capacitive (total) load 25a connected to the data electrode driving circuit 11b of this example, and the capacitive load 25a is a display input for each line-sequential scan. Varies depending on the data. The data electrode driving element 13 updates the write data only at the timing when the voltage Vc of the capacitive load 25a is 0V. This update timing is supplied from the drive timing control circuit 10 in FIG. 22 to the data electrode drive element 13 as described above.

Here, the reason why the data drive is pulsed is only to cause the power recovery operation to be performed. However, in order to increase the power recovery efficiency, the variation in the characteristics between the electrodes and the load corresponding to the input display data are required. Since it is necessary to apply a predetermined voltage for as long as possible in consideration of the fluctuation of the capacitance Ct, the duty ratio is high. Further, when a parasitic diode exists inside the data electrode driving element 13, it can be used as a diode for clamping and current regeneration, so that it is used for clamping and current regeneration inserted between the coil 26 and the ground. The diode DI ₃₂ can be omitted.

Next, the operations (1) to (7) of this example will be described with reference to FIGS. 3, 4 and 5. Now, the voltage of the capacitive load 25a is 0 [V], the current flowing through the coil 26 is also 0 [A], and the MOSFET switches 30a, 3
0b are both turned off, and this state is referred to as state [0]. At time A, the state proceeds from state [0] to state [1].

(1) Operation in State [1] As shown in FIG.
When the switch 30a is turned on, the power supply voltage V is applied to the point A of the series resonance circuit including the coil 26 and the capacitive load 25a, as shown in FIG.
The charging of 5a is started. Current i flowing through coil 26
Starts oscillation at the natural oscillation frequency fo of the series resonance system determined by the inductance L and the load capacitance Ct.
As shown in FIG. On the other hand, the voltage Vc of the capacitive load 25a also starts oscillating at the natural oscillation frequency fo, and increases toward twice the value of the power supply voltage V as shown in FIG.

[0075] At the time of operation time B in (2) state [2], when the voltage Vc of the capacitive load 25a exceeding the power supply voltage V, the diode DI ₃₁ conducts, as shown in FIG. 5 (d) , The voltage Vc of the capacitive load 25a is clamped to the power supply voltage V. As a result, the resonance stops at time B. The time B is a time when 1/4 of the natural oscillation period has elapsed from the time A, as derived from the equation (5). When the load capacity is minimum, the natural oscillation cycle is the shortest, as indicated by the solid line in FIG. 3D, and therefore, time B (clamp time) arrives earlier. On the other hand, when the load capacity is the maximum, as indicated by the broken line in FIG. 3D, the load capacity is the longest, and therefore, time B (clamp time) arrives later. The current i flowing through the coil 26 is derived from Expression (4), and is the maximum current at the time of time B at the time of resonance, as shown in FIG. , Coil 26 → diode DI ₃₁ → on-state MOSFET switch 30 a
(That is, the flywheel current holding circuit) is circulated to continue the flywheel operation.

(3) Operation in State [3] As shown in FIG.
When the switch 30a is turned off, the flywheel current i breaks the loop, so that the current is maintained.
The voltage at the point A sharply drops, drops below the ground potential, and turns on the parasitic diode 29b. Then, the flywheel current i is changed from the parasitic diode 29b to the coil 26.
→ Regenerated by the power supply 27 through the path of the diode DI ₃₁ , and the current energy stored in the coil 26 is returned to the power supply 27. As shown in FIG. 5C, the flywheel current i flowing through the coil 26 decreases with regeneration. Here, the time at which the current i flowing through the coil 26 becomes 0 as a result of the regeneration depends on the natural oscillation period or the flywheel current value at the time point C, so that the load capacitance C
When the load capacitance Ct is the maximum, the delay is the longest as shown by the broken line in FIG. On the other hand, when the load capacitance Ct is the minimum, as shown by the solid line in FIG.

(4) Operation in State [4] Next, the MOSFET switch 30b is turned on.
The timing at which the MOSFET switch 30b is turned on is from the time when the current i flowing through the coil 26 becomes 0.
As a whole, the earlier the delay, the better the current recovery efficiency is. Therefore, in this example, as shown by the solid line in FIG. At the time D when the current i flowing through the coil 26 becomes 0, the timing for turning on the MOSFET switch 30b is adjusted. The reason why the earlier the current recovery efficiency is, the better the current recovery efficiency will be described in the second embodiment of the present invention.

As shown in FIG. 5B, when the MOSFET switch 30b is turned on at time D,
The charging voltage Vc of the capacitive load 25a is applied to the series resonance circuit including the coil 26 and the capacitive load 25a, and the discharge of the capacitive load 25a is started as shown in FIG. The current i flowing through the coil 26 is equal to the natural vibration frequency f
The vibration starts at o, and according to the equation (7), FIG.
Descend as shown. On the other hand, the voltage Vc of the capacitive load 25a also starts oscillating at the natural oscillation frequency fo, and the equation (8)
Therefore, as shown in FIG.
It descends toward V.

[0079] (5) When the voltage Vc of the operation the capacitive load 25a in the state [5] is below ground potential, the diode DI ₃₂ conducts, as shown in FIG. 5 (d), the voltage of the capacitive load 25a Vc is clamped to the ground potential. As a result, the resonance stops at time E. This time E is, as derived from equation (8),
This is when 1/4 of the natural oscillation period has elapsed from the time point D. The current i flowing through the coil 26 is given by equation (7)
As shown in FIG. 5 (c), at time E, the current is a negative maximum current at the time of resonance. Starting from time E, the current is the coil 26 → the on-state MOSFET switch 30b → The loop (ie, flywheel current holding circuit) formed by the diode DI ₃₂ is circulated to continue the flywheel operation.

(6) Operation in State [6] As shown in FIG.
When the switch 30b is turned off, the flywheel current breaks the loop, so that the current is maintained.
The voltage at point A rises sharply, rises above the power supply voltage, and turns on the parasitic diode 29a. Then, the flywheel current i is regenerated to the power supply 27 through the path of the diode DI ₃₂ → the coil 26 → the parasitic diode 29a, and the coil 2
The current energy stored in 6 is returned to the power supply 27. As shown in FIG. 5C, the flywheel current i flowing through the coil 26 decreases with regeneration.

(7) Operation in State [7] Next, the MOSFET switch 30a is turned on to be in the state [7] similar to the state [1]. For the same reason as described above in the description of the state [4], this timing is determined when the load capacitance Ct including the transient mitigation capacitor Cext is minimum, as shown by the solid line in FIG. When the current i flowing through the coil 26 becomes 0, M
The timing (ie, time A) for turning on the OSFET switch 30a is adjusted.

A series of operations (1) to (7) described above are repeated to supply a voltage pulse train to the capacitive load 25a. According to the configuration of this example, the reactive power of about 60% or more can be reduced under the operating conditions of a total load capacitance of 15 nF, a coil inductance of 2.7 μH, a power supply voltage of 70 V, and a pulse period of 2.6 μs. In particular, when the time of 1/4 of the natural oscillation period of the series resonance circuit due to the coil and the capacitive load elapses, the switch is automatically clamped without using a switch. Even if the voltage clamping time fluctuates randomly, it can be easily followed.
This is effective when applied to driving data electrodes having different load capacities. Also, between the output side of the coil 26 and the ground side,
Since the capacitor Cext is interposed, the transient can be alleviated even when the load capacity is minimum, and therefore, generation of unnecessary electromagnetic waves can be prevented.

[0083]Second embodiment  Next, a second embodiment of the present invention will be described. Up
In the first embodiment described above, as shown in FIG.
At time C, the MOSFET switch 30a is turned off
Later, a tie to turn on the MOSFET switch 30b
Flowing through the coil 26 when the load capacitance Ct is the minimum.
At the time D at which the current i becomes 0,
As shown in FIG. 5B, at time F, the MOSFET switch
After the switch 30b is turned off, the MOSFET switch
The timing at which 30a is turned on is determined by the load capacitance Ct.
Time when the current i flowing through the coil 26 at the minimum is 0
A is set at the time of A, but in the second embodiment
Then, after the time C and earlier than the time D, the MOSF
Set the timing to turn on the ET switch 30b
Similarly, after time F, at a time earlier than time A, M
Timing for turning on OSFET switch 30a
Is different from the first embodiment in that
You.

As described above, in this embodiment, FIG.
At the time C of (a), the MOSFET switch 30a
Is turned off, and earlier than time D, MO
When the SFET switch 30b is turned on, the flywheel current i is thereafter changed to the parasitic diode 29b →
The MOSFET switch 30 is turned on without being regenerated by the power supply 27 through the path from the coil 26 to the diode DI _31.
Since the power is regenerated to the power supply 27 through the path of b → coil 26 → diode DI ₃₁ , forward loss due to passing through the parasitic diode 29b can be reduced. Similarly, FIG.
At time F in (b), the MOSFET switch 30b
Is turned off, and at a time earlier than time A, MO
When the SFET switch 30a is turned on, thereafter, the flywheel current i is not regenerated to the power supply 27 through the path of the diode DI ₃₂ → the coil 26 → the parasitic diode 29a, but as shown in FIG. DI
₃₂ → coil 26 → MOSFET switch 30 in ON state
Since the power is regenerated to the power supply 27 through the path a, the forward loss caused by passing through the parasitic diode 29a can be reduced. Therefore, according to the configuration of this example, a much higher current regeneration efficiency can be achieved than in the case of the above-described first embodiment.

Here, the MOSFET switch 30b (3
As the timing of turning on 0a) becomes closer to time C (A), an improvement in current regeneration efficiency can be expected. In addition, at time C (time F) when the MOSFET switch 30a (30b) is turned off, the MOSFET 26 at point A in FIG.
Before the T switch 30b (30a) is turned on,
Since voltage inversion occurs, the MOSFET switch 30b
The switching loss when (30a) is turned on is greatly reduced. Therefore, it is preferable to shorten the time interval between the times C and D (the times F and A). However, in order to prevent a short circuit of the power supply 27, the same timing is set at time F
The time cannot be set earlier than (A).

[0086]Third embodiment  FIG. 6 shows a data electrode drive according to a third embodiment of the present invention.
FIG. 7 is a circuit diagram showing the electrical configuration of the driving circuit, and FIG.
It is a time chart for explaining operation of a road. this
The configuration of the data electrode driving circuit 11c of the example is the same as that of the first data electrode driving circuit 11c described above.
FIG. 7A shows a point that is significantly different from that of the embodiment.
As shown, the duration of the flywheel current (flywheel
Regeneration during MOSFET switch 30a
Pulse Kp is applied to accelerate flywheel current regeneration.
In addition, as shown in FIG.
Instead of the diode 29b, a high-speed die having a short reverse recovery time is used.
In that the current is regenerated via the Aether 31a
is there.

The flywheel current is not lossless,
In the flywheel current holding circuit, diodes DI ₃₁ ,
Forward voltage drop of DI ₃₂ , MOSFET switch 30
Since the power is gradually consumed by the on-resistances a and 30b and the DC resistance component of the coil 26, the improvement of the current regeneration efficiency is hindered accordingly. Therefore, in this embodiment,
During the positive current phase with a long flywheel period,
Immediately after the current i flowing through the coil 26 becomes maximum, the regenerative pulse (negative pulse) Kp is supplied to the MOSFET 30a.
Is applied to forcibly accelerate the current regeneration, thereby reducing the energy loss due to the decrease in the flywheel current. In this case, the voltage Vc of the capacitive load 25a is reduced by the application of the regenerative pulse Kp before the discharge of all the display cells selected for writing is not completed yet, which adversely affects the image quality. Therefore, in this embodiment, the width of the regenerative pulse is set to a length that does not cause commutation in the coil 26.

As shown in FIG. 6, the data electrode drive circuit 11c includes a MOSFET switch 30a,
A high-speed diode 31a having a short reverse recovery time with the direction from ground to point B being a forward direction between the common connection point (point B) of the MOSFET switch 30b and the coil 26 and the ground.
In order to prevent a regenerative current from flowing through the parasitic diode 29b, the point B and the MO
Point B → MOSFET between SFET switch 30b
Diode 31 with the direction of switch 30b as the forward direction
b is interposed.

The use of the parasitic diode 29b is abolished for the following reason. That is, the power MOSFE
The reverse recovery time of a parasitic diode of a T-switch is generally long. If current regeneration is performed using such a parasitic diode 29b, after application of the regeneration pulse Kp, the MOSF
When the ET switch 30a is turned on, the parasitic diode 29b is supplied with the power supply 27 → the on-state M
This is because a through current flows through the OSFET switch 30a → the diode 31b → the parasitic diode 29b → the ground, which causes deterioration of energy efficiency.

Next, the operations (1) to (8) of this example will be described with reference to FIGS. Now, the voltage of the capacitive load 25a is 0 [V], the current flowing through the coil 26 is also 0 [A], the MOSFET switches 30a and 30b are both turned off, and this state is referred to as state [0]. At time A, the state proceeds from state [0] to state [1].

(1) Operation in State [1] As shown in FIG.
When the T switch 30a is turned on, the power supply voltage V is applied to the series resonance circuit (point B) including the coil 26 and the capacitive load 25a, as shown in FIG. Charging is started. As shown in FIG. 3C, the current i flowing through the coil 26 is equal to the natural vibration frequency fo.
Vibration is started according to the vibration equation (1) and rises. As shown in FIG. 4D, the voltage Vc of the capacitive load 25a becomes
It increases toward twice the value of the power supply voltage V. In FIGS. 9C and 9D, the broken lines show the current-voltage waveform when the load capacitance Ct is the maximum, and the solid lines show the current-voltage waveform when the load capacitance Ct is the minimum.

(2) Operation in State [2] As shown in FIG.
When the voltage Vc of 5a exceeds the power supply voltage V, the diode D
Since I ₃₁ becomes conductive, the voltage Vc of the capacitive load 25a is clamped to the power supply voltage V, the resonance is stopped. This time B
Is when 1/4 of the natural vibration period has elapsed from the time A. As shown in FIG. 7C, at time B, the current i flowing through the coil 26 is the maximum current at the time of resonance.
6 → Diode DI ₃₁ → Circuit the loop of the MOSFET switch 30a in the ON state (that is, flywheel current holding circuit) to continue flywheel operation.

(3) Operation in State [3] As shown in FIG. 7A, at the time K1, the MOSF
A negative regenerative pulse Kp is input to the gate of the ET switch 30a. This regenerative pulse Kp is supplied by a timing control circuit (not shown). The time K1 is set to a time immediately after the current i flowing through the coil 26 reaches the maximum value when the load capacitance Ct is the maximum. When the load capacitance Ct is the maximum, the current i of the coil 26 reaches the maximum value with the latest delay. Therefore, if the regenerative pulse application timing is adjusted at this time, no matter how the load capacitance changes,
This is because the regeneration pulse Kp can be applied during the flywheel period. The regenerative pulse K is applied to the MOSFET switch 30a.
When p is input, the MOSFET switch 30a is turned off, and the loop of the flywheel current i is cut off. Therefore, the voltage at the point B drops sharply to maintain the flywheel current, falls below the ground potential, and turns on the diode 31a.

[0094] Then, the flywheel current i is regenerated to the power source 27 in the path of the diode 31a → coil 26 → diode DI _31, current energy stored in the coil 26 is returned to the power source 27. As shown in FIG. 7C, the flywheel current i flowing through the coil 26 decreases with regeneration. However, as described above, in this example, the width of the regenerative pulse Kp must be set to a length that does not cause commutation of the coil 26 when the load capacity is minimum. That is, to prevent the coil current from reversing,
In order to suppress a decrease in output voltage, it is necessary to set the pulse to stop immediately before the coil current becomes 0 when the load capacity is minimum. This fixed-timing regenerative pulse K
At p, a corresponding flywheel current flows even after time K2 when the load capacity is at a maximum, as shown in FIG. As shown in FIG. 3D, the voltage Vc of the capacitive load 25a keeps the power supply voltage V necessary for driving the panel even during the application of the regenerative pulse Kp.

(4) Operation in State [4] As shown in FIG.
When the MOSFET switch 30a is turned on at the point of time 2, as shown in FIG.
The power supply voltage V is applied again to (point). However, since the voltage Vc of the capacitive load 25a remains clamped to the power supply voltage V, as shown in FIG. 3C, the slightly remaining current of the coil 26 is changed from the coil 26 → the diode DI ₃₁ → on. The flywheel operation is continued by circulating the loop of the MOSFET switch 30a in the state.

(5) Operation in State [5] As shown in FIG.
When the switch 30a is turned off, the flywheel current i breaks the loop, so that the current is maintained.
The voltage at point B drops sharply, drops below ground potential, and turns on parasitic diode 29a. Then, the flywheel current i is regenerated by the power supply 27 through the path of the diode 31a → the coil 26 → the diode DI ₃₁ and the coil 2
Current energy remaining in 6 is returned to power supply 27.

(6) Operation in State [6] As shown in FIG.
When the switch 30b is turned on, the capacitive load 25a
Is the oscillation equation of this resonant circuit (ie,
The vibration starts in accordance with the natural vibration frequency fo), and falls toward the negative value -V of the power supply voltage V as shown in FIG. The current i flowing through the coil 26 also oscillates according to the oscillation equation (natural oscillation frequency fo) of the resonance circuit, and falls as shown in FIG.

(7) Operation in State [7] When the voltage Vc of the capacitive load 25a falls below the ground potential, the diode DI ₃₂ conducts, and as shown in FIG. Vc is clamped to the ground potential. As a result, the resonance stops at time E. This current starts at time E,
6 → diode 31b → on-state MOSFET switch 30b → diode DI ₃₂ loop (that is, flywheel current holding circuit) to continue flywheel operation.

(8) Operation in State [8] As shown in FIG.
When the switch 30b is turned off, the flywheel current breaks the loop, so that the current is maintained.
The voltage at point B rises sharply, rises above the power supply voltage V, and turns on the parasitic diode 29a. Then, the flywheel current i is regenerated to the power supply 27 through the path of the diode DI ₃₂ → the coil 26 → the parasitic diode 29a, and the current energy stored in the coil 26 is returned to the power supply 27. As shown in FIG. 7C, the flywheel current i flowing through the coil 26 decreases with regeneration.

A series of operations (1) to (8) described above are repeated to supply a voltage pulse train to the capacitive load 25a. According to the configuration of this example, the current regeneration is forcibly accelerated by applying the regeneration pulse Kp, so that the energy loss of the flywheel current can be reduced, and the current recovery efficiency can be improved accordingly. . Further, since a high-speed diode having a short reverse recovery time is used instead of the parasitic diode 29b of the power MOSFET switch having a problem with the reverse recovery time, the adverse effect associated with the application of the regenerative pulse (that is, the through current Deterioration of power efficiency)
Can also be prevented.

[0101]Fourth embodiment  FIG. 8 shows a data electrode drive according to a fourth embodiment of the present invention.
5 is a time chart for explaining the operation of the driving circuit.
In this embodiment, as shown in FIG.
The number of selected electrodes is sequentially calculated for each writing scan, and the calculated
Suitable application timing of regenerative pulse Kp based on the number of selected electrodes
And the pulse width is controlled. In FIG.
As shown, at time B, the voltage Vc of the capacitive load 25a is
Generated flywheel current i clamped to source voltage V
However, this time point B depends on the natural oscillation period,
Therefore, it differs depending on the load capacity. Sand
That is, when the load capacity Ct is the maximum,
When the load capacity Ct is the minimum, the
Will be Further, the current flows to the coil 26 at the time point B of the clamp.
The flywheel current i is at the maximum load capacity Ct.
Is the maximum current amount and the minimum load capacitance Ct is
The amount of current is also minimal. Therefore, in this embodiment,
As the load capacity Ct increases, the application time of the regeneration pulse Kp increases.
There is no control that lags stepwise or continuously
On the other hand, the pulse width increases as the load capacitance Ct increases.
It is controlled to be longer.

In the third embodiment described above, since the regenerative pulse is fixed, the control is simple, but the drawback is that the efficiency of recovering the flywheel current at the maximum load is low. On the other hand, according to the configuration of the fourth embodiment, it is necessary to control the regenerative pulse, but it is possible to regenerate the flywheel current almost entirely irrespective of the load capacity. Loss can be reduced.

As a modification of the fourth embodiment, a change in the current flowing through the coil 26 may be detected, and the timing of the regenerative pulse Kp may be determined based on the detection result. In this case, in order to modulate the regenerative pulse by detecting only the change in the current of the coil, the voltage Vc of the capacitive load also needs to be taken into consideration, particularly, in order to detect the start timing of the regenerative pulse, because the differential value of the current must be considered. The method of monitoring and detecting is practically preferable.

[0104]Fifth embodiment  FIG. 9 shows a data electrode drive according to a fifth embodiment of the present invention.
FIG. 10 is a circuit diagram showing the electrical configuration of the driving circuit, and FIG.
5 is a time chart for explaining the operation of the circuit. This
In the embodiment, as shown in FIG.₃₁
In place of the MOSFET having the parasitic diode 29c
The T switch 30c is provided, and the regeneration pulse is omitted.
To turn on the MOSFET switch 30c
With the configuration that forcibly accelerates the regeneration of flywheel current
Has become.

The MOSFET switch 30a, MO
A high-speed diode 31c with a short reverse recovery time between the power supply 27 and the common connection point (point B) of the SFET switch 30b and the coil 26, with the direction from the point B to the power supply 27 being a forward direction.
In order to prevent a regenerative current from flowing through the parasitic diode 29a, the point B and the MO are connected.
A diode 31 having a forward direction from the MOSFET switch 30a to the point B between the SFET switch 30a and the SFET switch 30a.
d is inserted.

Next, the operations (1) to (7) of this example will be described with reference to FIGS. 9 and 10. Now, the voltage Vc of the capacitive load 25a is 0 [V], the current flowing through the coil 26 is also 0 [A], and the MOSFET switches 30a, 30
b and 30c are both turned off, and this state is referred to as state [0].
And At time A, the state proceeds from state [0] to state [1].

(1) Operation in State [1] As shown in FIG.
When the ET switch 30a is turned on, the power supply voltage V is applied to the series resonance circuit (point B) including the coil 26 and the capacitive load 25a, as shown in FIG. Charging is started. As shown in FIG. 3D, the current i flowing through the coil 26 is equal to the natural vibration frequency f.
Oscillation starts in accordance with the oscillation equation o and rises, and the voltage Vc of the capacitive load 25a rises toward twice the value of the power supply voltage V as shown in FIG.

(2) Operation in State [2] As shown in FIG. 10E, when the voltage Vc of the capacitive load 25a exceeds the power supply voltage V at the time B, the parasitic diode 29c becomes conductive. The voltage Vc of the capacitive load 25a is clamped to the power supply voltage V, and the resonance stops. The time B is a time when 1/4 of the natural vibration period has elapsed from the time A. As shown in FIG.
At the time point B, the current i flowing through the coil 26 is the maximum current at the time of resonance.
The loop composed of the OSFET switch 30a and the diode 31d (that is, the flywheel current holding circuit) is circulated to continue the flywheel operation.

(3) Operation in State [3] Next, at the time X1, as shown in FIG.
The MOSFET switch 30a is turned off, and FIG.
As shown in (c), the MOSFET switch 30c is turned on. The time X1 is set to a time immediately after the current i flowing through the coil 26 reaches the maximum value when the load capacitance Ct is the maximum. MOSFET switch 30a
Is turned off, the loop of the flywheel current i is broken, so that the voltage at the point B drops sharply to maintain the flywheel current, drops below the ground potential, and turns on the diode 31a.

Then, the flywheel current i is regenerated to the power supply 27 through the path of the diode 31a → the coil 26 → the MOSFET 30c, and the current energy stored in the coil 26 is returned to the power supply 27. As shown in FIG. 10D, the flywheel current i flowing through the coil 26 is
Decreases with regeneration. However, as shown in FIG. 5E, even when the current i of the coil 26 decreases to 0, the voltage Vc of the capacitive load 25a remains clamped at the power supply voltage V by the MOSFET 30c in the ON state. Becomes

(4) Operation in State [4] As shown in FIG.
When the current i at 6 becomes 0, the voltage at point B rises and is clamped to the power supply voltage V.

(5) Operation in State [5] Next, as shown in FIGS. 10B and 10C, at time D, the MOSFET switch 30c is turned off, and M
When the OSFET switch 30b is turned on, the charging voltage Vc of the capacitive load 25a is applied to the series resonance circuit including the coil 26 and the capacitive load 25a, and FIG.
As shown in (2), the discharge of the capacitive load 25a is started.
The current i flowing through the coil 26 starts oscillating at the natural oscillation frequency fo and falls as shown in FIG. On the other hand, the voltage Vc of the capacitive load 25a is also the natural oscillation frequency f
The vibration starts at o, and falls toward the negative value -V of the power supply voltage V as shown in FIG.

(6) Operation in State [6] When the voltage Vc of the capacitive load 25a falls below the ground potential, the diode DI ₃₂ conducts, so that the voltage of the capacitive load 25a is reduced as shown in FIG. Vc is clamped to the ground potential. As a result, the resonance stops at time E. When the load capacity Vc is the maximum, the latest time E
Then, the voltage Vc of the capacitive load 25a is clamped to the ground potential. This current, as a starting point the time E, the coil 26 → diode 31b → ON state of the loop composed of MOSFET switch 30b → diode DI ₃₂ (i.e., the flywheel current holding circuit) continues the flywheel operation by whirling the .

(7) Operation in State [7] As shown in FIG. 13 (b), when the load capacity is the maximum, at the time F after the latest clamp time E, the MO
When the SFET switch 30b is turned off, the flywheel current breaks the loop, so that the voltage at the point B rapidly rises to maintain the current, rises above the power supply voltage V, and turns on the parasitic diode 31c. . Then
Flywheel current i is diode DI ₃₂ → coil 2
6 → regenerated to the power supply 27 through the path of the diode 31c, and the current energy stored in the coil 26 is returned to the power supply 27. As shown in FIG. 10D, the flywheel current i flowing through the coil 26 decreases with regeneration.

A series of operations (1) to (7) described above are repeated to supply a voltage pulse train to the capacitive load 25a. According to the configuration of this example, since the optimization control of the regenerative pulse timing is not required, the loss of the flywheel current can be reduced with simple control.

[0116]Sixth embodiment  FIG. 11 shows a three-electrode surface discharge type plasma table using the driving circuit of FIG.
Circuit diagram showing an example applied to a sustain electrode drive circuit of a display panel
It is. The sustain electrode drive circuit 40 is configured as shown in FIG.
In addition, an n-channel type MOSFET (hereinafter, “nMOS”)
41), nMOS 42, diode for clamping
43 and 44, and a coil 45. nMOS4
1, 42 are parasitic diodes 41d, 42d, respectively.
Have. Sustain electrode driving circuit 40 has a power supply smoothing circuit.
The capacitors 51 and 52 are connected. Also, sustain electrode
The drive circuit 40 includes a capacitive load having a panel capacitance Cp.
25a is connected.

FIG. 12 shows the sustain electrode driving circuit 40 of FIG.
4 is a time chart of signals of respective units for explaining the operation of FIG. Operations (1) to (9) of sustain electrode drive circuit 40 of this embodiment will be described with reference to FIG. (1) Operation in State [1] At time A, when the nMOS 41 is turned on, the series resonance circuit formed by the coil 45 and the panel capacitance Cp existing between the driving electrodes of the capacitive load 25a of the plasma display panel is: When the power supply voltage 2Vs is applied, resonance starts, and the panel capacitance Cp is charged while the coil current i and the voltage Vc of the capacitive load 25a increase. (2) Operation in State [2] At time B, when the voltage Vc of the capacitive load 25a exceeds the power supply voltage + Vs, the diode 43 conducts, and the voltage Vc of the capacitive load 25a is clamped to the power supply voltage + Vs. As a result, resonance stops, and the maximum current at the time of resonance flows through the coil 45. This current i circulates through a loop composed of the coil 45 → the diode 43 → the nMOS 41 → the coil 45 to continue the flywheel operation. (3) Operation in State [3] At time Td +, a large current is generated due to light emission discharge of the capacitive load 25a of the plasma display panel. Since this current has a steep transient, the power supply voltage +
In the path of Vs → nMOS 41 → coil 45, the coil 4
Due to the influence of the inductance of No. 5, it hardly contributes to the supply. For this reason, when the panel capacity Cp is small and a large current accompanying the light emission discharge cannot be supplied, the capacitive load 25a
Voltage Vc causes a remarkable voltage fluctuation. (4) Operation in State [4] At time C, when the nMOS 41 is turned off, the circulating route of the flywheel current i becomes the diode 42d
→ The coil 45 changes to the diode 43, and the current energy stored in the coil 45 is regenerated to the power supply. After the time C, when the nMOS 42 is turned on, the circulating route has the nMOS 42 → coil 4
5 → diode 43, and the regeneration efficiency is improved. (5) Operation in State [5] At time D, the coil current i becomes 0, and the regeneration to the power supply ends. Since the nMOS 42 is already in the ON state, the power supply voltage -2 Vs is applied to the series resonance circuit including the coil 45 and the panel capacitance Cp to start resonance, and the coil current i and the voltage of the capacitive load 25a are started. As Vc decreases, the panel capacitance Cp is charged to a negative potential. (6) Operation in State [6] At time E, when the voltage Vc of the capacitive load 25a falls below the power supply voltage -Vs, the diode 44 conducts, and the voltage Vc of the capacitive load 25a is clamped at the power supply voltage -Vs. You. As a result, resonance stops, and the maximum current in the negative direction at the time of resonance flows through the coil 45. This current i circulates through a loop composed of the coil 45 → the nMOS 42 → the diode 44 → the coil 45 to continue the flywheel operation. (7) Operation in State [7] At time Td-, a large current is generated again due to light emission discharge of the capacitive load 25a of the plasma display panel. Since this current has a steep transient, it hardly contributes to the supply of the current through the path of the coil 45 → the nMOS 42 → the power supply voltage−Vs due to the influence of the inductance of the coil 45. For this reason, when the panel capacity Cp is small and a large current accompanying the light emission discharge cannot be supplied, the capacitive load 2
A remarkable voltage fluctuation occurs in the voltage Vc of 5a. (8) Operation in State [8] At time F, when the nMOS 42 is turned off, the circulating route of the flywheel current i is changed from the diode 44 to
The state changes from the coil 45 to the diode 41d, and the current energy stored in the coil 45 is regenerated to the power supply. After the time F, when the nMOS 41 is turned on, the recirculation route changes from the diode 44, the coil 45, and the nMOS 41 in which the voltage drop becomes smaller, and the regeneration efficiency is improved. (9) Operation in State [9] At time A, the coil current i becomes 0, and the regeneration to the power supply ends. Since the nMOS 41 has already been turned on, the power supply voltage of 2 Vs is applied to the series resonance circuit again, and the panel capacitance Cp is charged while the coil current i and the voltage Vc of the capacitive load 25a rise. In the sustain drive cycle period, the above operations (1) to (9) are repeatedly performed.

As described above, sustain electrode driving circuit 40
In the operation of (3), when the panel capacitance Cp is small, the time Td
At + and Td-, a significant voltage fluctuation occurs in the voltage Vc of the capacitive load 25a. In addition, since this variation is modulated by the display data of the capacitive load 25a of the plasma display panel, it may be difficult to uniformly and stably maintain the light emission of the capacitive load 25a of the plasma display panel. Further, the voltage Vc of the capacitive load 25a
The remarkable voltage fluctuation generates a large amplitude in a fast transient, and unnecessary electromagnetic wave radiation may be generated therefrom. Therefore, the sixth embodiment provides a sustain electrode drive circuit that has a simple circuit configuration, can sufficiently collect reactive power in practical use, and can reduce unnecessary electromagnetic wave radiation.

FIG. 13 is a circuit diagram showing an electric configuration of a sustain electrode driving circuit according to a sixth embodiment of the present invention.
Elements common to those in FIG. 11 are denoted by common reference numerals. In the sustain electrode driving circuit 40A of this embodiment, FIG.
A capacitor CL11 is connected between the cathode of the middle diode 44 and the ground. Capacitor CL1
1 is charged when the voltage Vc of the capacitive load 25a is applied, and discharged when the voltage Vc of the capacitive load 25a decreases to supply a voltage to the capacitive load 25a. A sudden change in the voltage Vc of the load 25a is suppressed.

FIG. 14 is a circuit diagram of the sustain electrode driving circuit 40 shown in FIG.
6 is a time chart of signals of respective units for explaining the operation of A. The operation of sustain electrode drive circuit 40A of this embodiment will be described with reference to FIG. The operation of sustain electrode drive circuit 40A of this embodiment differs from the operation of sustain electrode drive circuit 40 of FIG. 11 in the following points. That is, the time T
At d +, the capacitive load 25a of the plasma display panel
A large current is generated due to the light emission discharge of the light emitting device. This current is
Because it has a steep transient, the power supply voltage + Vs →
In the path from the nMOS 41 to the coil 45, it hardly contributes to the supply due to the influence of the inductance of the coil 45. At this time, the capacitor CL11 and the panel capacitance Cp
, The current is quickly supplied, and as a result, the voltage fluctuation of the voltage Vc of the capacitive load 25a is suppressed to a small amount.

Further, at time Td-, a large current is generated again due to the light emission discharge of the capacitive load 25a of the plasma display panel. Since this current has a steep transient, the coil 45 → the nMOS 42 → the power supply voltage −V
In the path s, almost no contribution can be made to the supply due to the effect of the inductance of the coil 45. At this time, the current is quickly supplied by the negative charges charged in the capacitor CL11 and the panel capacitance Cp, and as a result, the voltage fluctuation of the voltage Vc of the capacitive load 25a is suppressed to a slight one.

Note that the addition of the capacitor CL11 increases the transient time of the sustain drive waveform.
14 than the time of the state [1] and the state [5] in FIG.
The times AB and DE of the middle states [1] and [5] become longer. However, if this increase in the transient time is not preferable in terms of the driving characteristics of the capacitive load 25a of the plasma display panel, the coil By reducing the inductance of 45, the transient time can be adjusted and accommodated.

As described above, in the sixth embodiment,
The voltage V of the capacitive load 25a is determined by the capacitor CL11.
Since the rapid change of c is suppressed, the times Td +, Td−
, The fluctuation of the voltage Vc of the capacitive load 25a becomes small, and a simple circuit configuration can sufficiently recover the reactive power in practical use, and also realizes a sustain electrode driving circuit that can reduce unnecessary electromagnetic wave radiation.

[0124]Seventh embodiment  FIG. 15 shows a sustain electrode drive according to a seventh embodiment of the present invention.
FIG. 16 is a circuit diagram showing an electrical configuration of a dynamic circuit, according to a sixth embodiment.
Elements common to the elements in FIG.
Is attached. In this form of sustain electrode drive circuit 40B,
Is the source of the nMOS switch 42 as shown in FIG.
And the anode of diode 44 are connected to ground
Therefore, the capacitor 52 in FIG. 13 is omitted. Sa
In addition, in sustain electrode driving circuit 40B, parasitic diode
NMOSs 61 and 6 each having a built-in
2, diode 63, 64, coil 65, capacitor
And a capacitor 5 for smoothing the power supply.
3 are connected. Other configurations are the same as those in FIG.
You.

FIG. 16 shows sustain electrode drive circuit 40 of FIG.
6 is a time chart of signals of each unit for explaining the operation of B. The operation of sustain electrode drive circuit 40B of this embodiment will be described with reference to FIG. In the operation of sustain electrode drive circuit 40B of this mode, as shown in FIGS. 16A and 16B, nMOS 41 and nMOS 62 and nM
The OS 42 and the nMOS 61 are controlled at the same timing. Therefore, as shown in FIGS. 16C and 16D, the drive voltage Vc1 and the drive voltage Vc2 of the capacitive load 25a are output in opposite phases. Therefore, FIG.
As shown in (e), the drive voltage Vc1 and the drive voltage Vc2
14D of the sixth embodiment is the same as the waveform of the drive voltage Vc in FIG. 14D, and the single power supply voltage Vs
A waveform of the same driving voltage Vc can be obtained only with the above.

As described above, in the seventh embodiment,
The drive voltage Vc shown in FIG.
Since the same waveform as that of the sixth embodiment can be obtained, in addition to the advantages of the sixth embodiment, components having a relatively low withstand voltage can be used for each component constituting the sustain electrode drive circuit 40B.

The embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and there is a change in design without departing from the gist of the present invention. Is also included in the present invention. For example, the switch is not limited to the nMOS, but may be a p-channel type MOSF.
It may be an ET or a bipolar transistor. Further, as long as the AC drive is used, the discharge is not limited to the surface discharge type, but may be the opposed discharge type. Also,
In each embodiment, the case where the driving circuit of the present invention is applied to a plasma display panel has been described. However, the present invention is not limited to this.
An EL display panel may be used as long as the display panel is a capacitive display panel. In addition, the power supply voltage may be higher or lower than the ground potential. Further, in each embodiment, the case where the present invention is applied to a drive circuit for supplying a pulse to a data (column) electrode has been described. However, the present invention may be applied to a drive circuit for driving a scan electrode and / or a sustain electrode. Of course it is good. In the sixth and seventh embodiments, instead of adding the capacitors CL11 and CL12, a design is made such that the panel capacitance Cp existing between the drive electrodes of the capacitive load 25a of the plasma display panel is intentionally increased. You may. Thereby, substantially the same operation and effect as those of the sixth and seventh embodiments can be obtained.

[0128]

As described above, according to the configuration of the present invention, of the power supplied to the capacitive load, the invalid power only for charging and discharging the capacitive load is, as described above, After being held in the form of coil current energy,
Since power is regenerated to the power supply, power consumption can be reduced. In addition, despite the elimination of the conventionally used two switches for clamping, which are difficult to control the timing, and a function to regenerate the flywheel current to the power supply despite the reduced number of components, the circuit configuration is reduced. Although simple and inexpensive, practically sufficient power recovery efficiency can be obtained. Also, since a series resonance circuit is formed by the coil and the capacitive load, a gentle transient pulse train can be obtained. If a gentle transient is used, the high frequency component of the pulse waveform is reduced, so that unnecessary electromagnetic wave radiation generated from the capacitive load can be reduced.

In addition, after the start of charging or discharging, one-fourth of the natural oscillation period of the series resonance circuit due to the coil and the capacitive load.
After the time elapses, the switch is automatically clamped without using a switch, so that the value of the capacitive load fluctuates randomly, so that even if the voltage clamping time fluctuates randomly, it can easily follow. (It is possible to avoid the conventional control difficulties in which the switch timing must follow the randomly varying clamp time.) In addition, since the sudden change in the voltage of the capacitive load is suppressed by the capacitor, the fluctuation of the voltage of the capacitive load is small, and the reactive power can be recovered practically sufficiently with a simple circuit configuration, and is unnecessary. A sustain electrode drive circuit that also reduces unnecessary electromagnetic wave radiation can be realized.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a basic configuration of a capacitive load drive circuit according to the present invention.

FIG. 2 is a time chart for explaining the operation of the circuit.

FIG. 3 is a circuit diagram showing an electrical configuration of a data electrode drive circuit according to the first embodiment of the present invention.

FIG. 4 is a circuit diagram showing a main part of an electrical configuration of a plasma display device including the data electrode drive circuit.

FIG. 5 is a time chart for explaining an operation of the driving circuit.

FIG. 6 is a circuit diagram showing an electrical configuration of a data electrode drive circuit according to a third embodiment of the present invention.

FIG. 7 is a time chart for explaining an operation of the driving circuit.

FIG. 8 is a time chart for explaining an operation of a data electrode drive circuit according to a fourth embodiment of the present invention.

FIG. 9 is a circuit diagram showing an electrical configuration of a data electrode drive circuit according to a fifth embodiment of the present invention.

FIG. 10 is a time chart for explaining the operation of the driving circuit.

FIG. 11 is a circuit diagram showing a modified example of the data electrode drive circuit of FIG. 3;

FIG. 12 is a time chart for explaining an operation of the data electrode drive circuit 11e of FIG. 11;

FIG. 13 is a circuit diagram showing an electrical configuration of a data electrode drive circuit according to a sixth embodiment of the present invention.

FIG. 14 is a time chart for explaining an operation of the data electrode drive circuit 11f of FIG. 13;

FIG. 15 is a circuit diagram showing an electrical configuration of a data electrode drive circuit according to a seventh embodiment of the present invention.

FIG. 16 is a time chart for explaining an operation of the data electrode drive circuit 11g of FIG. 15;

FIG. 17 is an exploded perspective view showing the configuration of a three-electrode surface discharge type plasma display panel in an exploded manner.

FIG. 18 is a sectional view of the panel.

FIG. 19 is an enlarged sectional view showing a part of the panel in a further enlarged manner.

FIG. 20 is a plan view showing an electrode structure of the panel.

FIG. 21 is a plan view showing a display cell structure of the panel.

FIG. 22 is a block diagram showing an electrical configuration of a three-electrode surface discharge type AC driven plasma display panel, and particularly showing an electrical configuration of a drive circuit unit.

FIG. 23 is an explanatory diagram for describing a driving sequence by a subfield method.

FIG. 24 is a waveform chart showing various drive waveforms in one subfield.

FIG. 25 is an explanatory diagram for explaining a subfield operation of the three-electrode surface discharge type plasma display device.

FIG. 26 is a circuit diagram showing a basic configuration of a sustain pulse generating circuit having a power recovery function according to a first related art.

FIG. 27 is a time chart for explaining the operation of the circuit.

FIG. 28 is a circuit diagram showing a basic configuration of a sustain pulse generating circuit having a power recovery function according to a second conventional technique.

FIG. 29 is a waveform diagram of an output voltage and a current due to an electromotive force of a coil for describing an operation of the circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Plasma display panel (capacitive display panel) 10 Drive timing control circuit 11a Capacitive load drive circuit 11b, 11c, 11d, 11e, 11f, 11g
Data electrode drive circuit 12 Display data control circuit 13 Data electrode drive element 14 Scan electrode drive circuit 15 Scan electrode drive element 16 Sustain electrode drive circuit 25, 25a Capacitive load S1, S2,..., Sn Scan electrode (constituting electrode, capacitance Su1, Su2,..., Sun Sustain electrode (constituent electrode, capacitive load) D1, D2,... Data electrode (constituent electrode, capacitive load) 26 Coil (part of series resonance circuit) 27 Power supply 28, 38 Power supply smoothing capacitors DI ₃₁ and DI ₄₁ diodes (first diode,
First clamping means, the first flywheel current holding means, the first current regeneration means) DI _32, DI ₄₂ diodes (second diode,
Second clamping means, second flywheel current holding means, second current regenerating means) DI ₃₃ diode (first current regenerating means, third diode) DI ₃₄ diode (second current regenerating means, 4 diodes) SW ₃₁ switches (first switch, the first flywheel current holding means) SW ₃₂ switches (second
Switch, second flywheel current holding means) 2
9a, 39a Parasitic diode (fourth diode) 29b, 39b Parasitic diode (third diode) 30a, 40a MOSFET switch (first switch) 30b, 40b MOSFET switch (second switch) 30c MOSFET switch (first switch) 31a Diode (first current regenerating means) Pp, Qp Predischarge pulse Pd Predischarge erasing pulse Pm Sustain pulse Qd Sustain erasure pulse Ps1, Ps2, ..., Psn Scan pulse Kp regeneration pulse CL11, CL12 Capacitor

Claims (17)

[Claims] 1. A drive circuit for supplying a pulse to a capacitive load which is a constituent electrode of a capacitive display panel, wherein the drive circuit is directly or indirectly connected to the capacitive load and connected in series with the capacitive load. A coil that forms a resonance circuit; a first switch that, when turned on, applies a first power supply voltage output from a DC power supply to the series resonance circuit to start first resonance; At the point when the voltage of the capacitive load starts to exceed the first power supply voltage after the start of the first resonance, the voltage of the capacitive load is clamped to the first power supply voltage and the first power supply voltage is clamped.
First clamp means for stopping the resonance of the first, and first flywheel current holding means for holding the current flowing through the coil in a first flywheel operating state when the first resonance is stopped, A first current regenerating means for regenerating the current in the first flywheel operating state to the DC power supply; and, when turned on, a charge voltage of the capacitive load as a source, and A second switch for causing the series resonance circuit to start a second resonance, and a point in time when the voltage of the capacitive load starts to drop below a second power supply voltage output from the DC power supply after the second resonance starts. And a second clamp means for clamping the voltage of the capacitive load to the second power supply voltage to stop the second resonance; and when the second resonance stops, a current flows through the coil. Electric telephone A second flywheel current holding means for holding a current in the second flywheel operating state, and a second current regenerating means for regenerating the current in the second flywheel operating state to the DC power supply. A drive circuit for a capacitive load, comprising: 2. The first current regenerating means regenerates a part or most of the current in the first (or second) flywheel operating state to the DC power supply in accordance with a regenerative pulse input timing. The drive circuit for a capacitive load according to claim 1, wherein the remaining current that continues the first (or second) flywheel operation is regenerated to the DC power supply. 3. The first current regenerating means includes a third switch, and when the third switch is turned on, regenerates the current in the first flywheel operating state to the DC power supply. The driving circuit for a capacitive load according to claim 1, wherein: 4. The first clamping means is arranged between a wiring connecting the coil and the capacitive load and the DC power supply, and a direction from the coil to the DC power supply is a forward direction. And a second diode interposed between the wiring and a second power supply voltage, and a direction from the second power supply voltage toward the coil is a forward direction. 2. The driving circuit for a capacitive load according to claim 1, wherein the driving circuit includes a second diode. 5. The first flywheel current holding means includes: a coil, a first diode, and an on-state first switch, which are connected in series in this order, and for the first diode. The second flywheel current holding means comprises: a coil; an on-state second switch; and a second flywheel current holding means.
And the second diode is connected in series in this order, and the second diode is connected in such a manner that the direction of the order is forward, and the first and second flywheels are connected to each other. The driving circuit for a capacitive load according to claim 1, wherein currents in an operating state are configured to flow in opposite directions in the coil. 6. The first current regenerative means includes a third current switch connected in parallel with the second switch in an off state.
The diode, the coil, and the first diode are connected in series in this order, and the third and first diodes are connected in such a manner that the order of the order is forward. The second current regeneration means is interposed between a DC power supply and a second power supply voltage, and is connected in parallel with a second diode, the coil, and the first switch in an off state. And a fourth diode connected in series in this order, and with respect to the second and fourth diodes, in such a manner that the order of the order is forward. When the first switch is also turned off when the second switch is turned off, the first current regenerating means is turned on in the current regenerating state. When the first switch is off Wherein the even turned off the second switch, the capacitive load driving circuit according to claim 1, wherein said second current regeneration means is characterized by comprising a current regeneration state. 7. A coil directly or indirectly connected to the capacitive load to form a series resonance circuit together with the capacitive load, a wire connecting one end of the coil to the capacitive load, and A first diode inserted between the wiring and a second power supply voltage, in a mode in which a direction from the coil to the DC power supply is a forward direction. And a second diode interposed between the coil and the DC power supply at the other end of the coil, in a mode in which the direction from the power supply voltage toward the coil toward the coil is forward. A third diode inserted between the coil and the DC power supply, and connected in parallel with the third diode, such that a direction from the coil to the DC power supply is a forward direction. And the first switch At Ku other end of the coil, between the coil and the second power supply voltage, and in a manner that said second direction from the power supply voltage to the coil in a forward direction, the interposed 4
And a second switch interposed between the coil and the second power supply voltage and connected in parallel to the fourth diode. Drive circuit for sexual load. 8. A parallel connection part between the third diode and the first switch and a parallel connection part between the fourth diode and the second switch are each formed by a MOSFET having a parasitic diode built therein. 8. The driving circuit for a capacitive load according to claim 7, wherein: 9. When the first power supply voltage is lower than the second power supply voltage, the first power supply voltage is replaced with the capacitive voltage after the first resonance starts, instead of the first clamp means. A third clamping unit that clamps the voltage of the capacitive load to the first power supply voltage to stop the first resonance when the voltage of the load starts to fall below the first power supply voltage; Instead of the second clamping means, after the second resonance starts, at the time when the voltage of the capacitive load starts to exceed the second power supply voltage, the voltage of the capacitive load is changed to the second power supply voltage. 2. The driving circuit for a capacitive load according to claim 1, further comprising fourth clamping means for stopping the second resonance by clamping to a voltage. 10. A driving method for supplying a pulse train to a capacitive load, which is a constituent electrode of a capacitive display panel, using the driving circuit according to claim 1, wherein at a first point in time, the first driving method is performed. Turn on the switch of
Applying the first power supply voltage to the series resonance circuit,
After the first resonance starts, at a second point in time when the voltage of the capacitive load starts to exceed the first power supply voltage, the charging voltage of the capacitive load is changed to the first voltage. The first resonance is stopped by clamping to the power supply voltage, and at this time, the current flowing through the coil is maintained in the first flywheel operating state, and at the third time, the first flywheel is operated. Turn off the switch,
Regenerating the current in the first flywheel operating state to the DC power supply; turning on the second switch at a fourth point in time;
Applying the charging voltage of the capacitive load to the series resonance circuit to start a second resonance, and after the second resonance starts, the voltage of the capacitive load starts to fall below the second power supply voltage At a fifth time, the voltage of the capacitive load is clamped to the second power supply voltage to stop the second resonance, and at this time, the current flowing in the coil is changed to a second flywheel. At the sixth time point, the second switch is turned off,
A method of driving a capacitive load, comprising: repeating a series of operations until the current in the second flywheel operating state is regenerated to the DC power supply to supply a pulse train to the capacitive load. 11. At the third (or sixth) time point, the first (or second) switch is turned off, and the current in the first (or second) flywheel operating state is reduced to In the step of regenerating to the DC power supply, at the time of the third 1 (or the sixth 1), the first (or the second) switch is turned off for a predetermined time, during which the first (or the sixth) is turned off. Part or most of the current in the second state of the flywheel operation is regenerated to the DC power supply, and thereafter, at the time of the third 2 (or the sixth 2), the first 2
(Or the second) switch is turned off, and the first switch is turned off.
The method of driving a capacitive load according to claim 10, further comprising a step of regenerating the remaining current that continues the (or second) flywheel operation to the DC power supply. 12. According to a load capacity of the capacitive load,
The method of driving a capacitive load according to claim 11, wherein a time point of the third one (or the sixth one) is controlled. 13. According to a load capacity of the capacitive load,
The driving of the capacitive load according to claim 11, wherein a time width of the off state of the first (or second) switch at the time of the third 1 (or sixth 1) is controlled. Method. 14. At the third (or sixth) time point, the first (or second) switch is turned off, and the current in the first (or second) flywheel operating state is supplied to the first (or second) flywheel operating state. The step of regenerating to the DC power supply includes, at the third (or sixth) time point, turning on a third (or fourth) switch to set the current in the first (or second) flywheel operating state. 11. The method of driving a capacitive load according to claim 10, further comprising the step of: 15. When the first power supply voltage is lower than the second power supply voltage, at a second point in time when the voltage of the capacitive load starts to fall below the first power supply voltage. The charging of the capacitive load is clamped to the first power supply voltage to stop the first resonance, and at this time, the current flowing in the coil is maintained in the first flywheel operating state. At a fifth point in time when the voltage of the capacitive load starts to exceed the second power supply voltage, the voltage of the capacitive load is clamped to a second power supply voltage to stop the second resonance,
11. The method of driving a capacitive load according to claim 10, wherein the current flowing through the coil is kept in the second flywheel operating state at this time. 16. The driving circuit for a capacitive load according to claim 1, further comprising a capacitor for suppressing a sudden change in the voltage of the capacitive load. 17. The capacitive load driving circuit according to claim 1, wherein the capacitor is charged when the voltage of the capacitive load is applied, and is discharged when the voltage of the capacitive load decreases. A drive circuit for a capacitive load, comprising: a capacitor for supplying a voltage to the capacitive load to suppress a sudden change in the voltage of the capacitive load.