JPH11307296A - Low-pressure discharge lamp lighting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To modulate light in a wide modulating range even though an electrode having a structure equipped with a large electrode and a small electrode is used. SOLUTION: This low-pressure discharge lamp La is equipped with a series circuit of a large electrode 1 and a small electrode having different heat capacities. An inverter circuit INV can adjust a power supplied to the low voltage discharge lamp La, and is connected to the large electrode 1 side. A lamp current of the low voltage discharge lamp La is detected as a terminal voltage of a resistance R, and a detecting circuit SN controls switch elements S1, S2 connected in parallel with the large electrode 1 and the small electrode respectively. When the lamp current is small, the switch element S1 is turned on, and when it is big, the switch element S2 is turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a low-pressure discharge lamp lighting device suitable for lighting a low-pressure discharge lamp provided with two types of filaments having different heat capacities at each pole.

[0002]

2. Description of the Related Art Conventionally, there has been provided a low-pressure discharge lamp in which two types of filaments having different heat capacities are provided for each pole. Hereinafter, the filament having the larger heat capacity is referred to as a large electrode, and the filament having a smaller heat capacity is referred to as a small electrode.

For example, in Japanese Patent Application Laid-Open No. Hei 8-298096, as shown in FIG. 10, two introduction wires 5a and one support wire 5b are erected on a stem 4 provided at an end of a valve 3. An electrode is disclosed in which one end of a large electrode 1 and a small electrode 2 are coupled to different introduction lines 5a, respectively, and the other end of the large electrode 1 and the small electrode 2 is commonly coupled to a support line 5b. The large electrode 1 mainly functions as a lighting electrode that forms a discharge arc at the time of steady lighting, and its specifications are defined according to the rating of the low-pressure discharge lamp. The small electrode 2 mainly functions as a starting electrode through which current flows at the time of starting, and has a smaller wire diameter than the large electrode 1 and a smaller heat capacity than the large electrode 1. Large electrode 1 and small electrode 2
All carry an electron-emitting substance.

[0004] The operation of the electrode having this configuration will be described below. Now, it is assumed that the low-pressure discharge lamp is turned on with the large electrode 1 as the power supply side and the small electrode 2 as the non-power supply side. Immediately after the series circuit of the large electrode 1 and the small electrode 2 is energized, the temperature of the small electrode 2 having a small heat capacity rises before the large electrode 1. , Discharge starts from the small electrode 2. That is, as shown in FIG.
A bright spot B is formed on the small electrode 2, and a current flows through the path shown in FIG. That is, when the discharge by the small electrode 2 is started, a current flows through the large electrode 1. Here, if the cathode drop voltage of the large electrode 1 immediately after the start of lighting is Vlc, the cathode drop voltage of the small electrode 2 immediately after the start of lighting is Vsc, and the voltage drop due to the current flowing through the large electrode 1 immediately after the start of lighting is Vf,
In the state shown in FIG. 11A, the following relationship is established. Vsc + Vf <Vlc (1) On the other hand, when a certain time has elapsed since the low-pressure discharge lamp started lighting, the temperature of the large electrode 1 rises due to Joule heat, so that thermionic electrons are also emitted from the large electrode 1, As the cathode drop voltage of the large electrode 1 decreases, the resistance value of the large electrode 1 increases, and the voltage drop due to the current flowing through the large electrode 1 increases. In addition, the cathode drop voltage of the small electrode 2 hardly changes from immediately after lighting even after a lapse of time from the start of lighting. That is, the following relationship holds. Vsc ≒ Vsc ′ Vlc> Vlc ′ Vf <Vf ′ where Vlc ′ is the cathode drop voltage of the large electrode 1 after a lapse of time from the start of lighting, and Vsc ′ is the cathode drop voltage of the small electrode 2 after a lapse of time from the start of lighting. The cathode drop voltage, Vf ', is a voltage drop due to a current flowing through the large electrode 1 after a lapse of time from the start of lighting. When an appropriate time (several seconds) elapses and a steady lighting state is reached, the magnitude relationship between the left side and the right side of equation (1) is reversed, and the following equation is established. Vsc ′ + Vf ′> Vlc ′ In short, compared to the state where the bright spot B is formed on the small electrode 2,
Since the applied voltage is lower when the bright spot B is formed on the large electrode 1 (that is, because the energy is lower), FIG.
A current flows through the path (b), and a bright spot B is formed on the large electrode 1.

As described above, the large electrode 1 and the small electrode 2
If the large electrode 1 is connected to the power supply side using a series-connected electrode, the temperature of the small electrode 2 having a small heat capacity is higher than that of the large electrode 1 even when a lighting device having no function of preheating the electrode is used. Also rises first and thermionic electrons are emitted from the small electrode 2, so that a so-called hot cathode start is performed. That is,
Ion bombardment of the electrode during startup is greatly reduced, preventing the emission of electron-emitting substances from the electrode, and consequently the number of times the lamp can be started (lighting life) is short even when used in a lighting device without a preheating function. It doesn't. In addition, since a bright spot is formed on the large electrode 1 during lighting, the small electrode 2 is not overheated and the life of the small electrode 2 is not shortened. Is determined.

Incidentally, in the above-described conventional configuration, the large electrode 1
Is connected to the power supply side, and the connection relationship with the lighting device is limited. However, Japanese Patent Application Laid-Open No. 7-17373 discloses that the small electrode 2 is connected between the pair of large electrodes 1. An arrangement is described that obviates certain restrictions.
This publication also describes conditions for the wire diameter and wire length of the large electrode 1 and the small electrode 2.

The electrodes shown in FIG. 10 are a large electrode 1 and a small electrode 2.
Are connected in series, as shown in FIG.
There is also an electrode in which a large electrode 1 and a small electrode 2 are connected in parallel as in the configuration described in JP 9-20120. In this electrode, starting is started by the small electrode 2 by arranging the large electrode 1 near the positive electrode with respect to the small electrode 2, and the bright spot moves to the large electrode 1 having a small inter-electrode distance in a steady lighting state. There is a configuration. In other words, even with this configuration, it functions similarly to an electrode having a configuration in which the large electrode 1 and the small electrode 2 are connected in series.

However, in any of the electrodes,
Since the current continues to flow not only in the large electrode 1 but also in the small electrode 2 during steady lighting after an appropriate time has elapsed since the start,
A current that hardly contributes to maintaining the discharge arc continues to flow through the small electrode 2 and Joule loss occurs.

In addition, during dimming lighting, the current flowing through the electrode is smaller than during rated lighting, and it is difficult to establish the relationship during steady-state lighting as shown in the above equation. 2 is heated, and the small electrode 2 is overheated. In other words, the small electrode 2 is
May be heated by the large electrode 1 and the life of the small electrode 2 may be shortened by overheating.

In order to avoid this kind of problem, Japanese Patent Laid-Open No.
JP-A-147807 describes a configuration in which a large electrode 1 and a small electrode 2 are connected in series, and a switch is connected between both ends of the small electrode 2 in the configuration of FIG. In this configuration, the switch is turned on so that no current flows through the small electrode 2 after an appropriate time has elapsed from the start or at the time of dimming, so that the Joule loss due to the small electrode 2 and the deterioration due to overheating of the small electrode 2 can be achieved. Has been prevented.

[0011]

However, in the above-described configuration in which a switch is connected between both ends of the small electrode 2, a bright spot is formed only on the large electrode 1 during dimming. If the output is reduced to about several percent of the rated output, it is difficult to stabilize the position of the luminescent spot, and there is a problem that flicker tends to occur. In short, it cannot be used in applications where the light output is reduced to about 10% or less of the rated value.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a low-voltage control apparatus capable of performing dimming with a wide dimming range while using an electrode having a large electrode and a small electrode. An object of the present invention is to provide a discharge lamp lighting device.

[0013]

According to a first aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having two filaments having different heat capacities, a large electrode and a small electrode. At the time of starting, the discharge is started from the small electrode, and the lamp is lit using the small electrode in a low output region where the lamp current is equal to or less than a specified value.

According to a second aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, on one electrode. , And the lamp is turned on using a large electrode in a steady output region where the lamp current is equal to or higher than a specified value and equal to or lower than the rated value.

According to a third aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, on one electrode. The discharge is started from the beginning, and in the high output region exceeding the rated output, the lighting is performed using the large electrode and the small electrode.

According to a fourth aspect of the present invention, in the third aspect of the present invention, in the high output region, the operating frequency of the lamp voltage applied between the electrodes of the low-pressure discharge lamp and the voltage between both ends of the series circuit of the large electrode and the small electrode. And the electrode heating frequency of the heating voltage applied to the electrodes is made different from each other.

According to a fifth aspect of the present invention, in the first aspect of the present invention, the low output region is a region where the lamp current is 30% or less of the rated current of the large electrode.

According to a sixth aspect of the present invention, in the first aspect of the invention, the steady output region is a region where the lamp current is 30 to 100% of the rated current of the large electrode.

According to a seventh aspect of the present invention, in the third aspect of the invention, the lamp current is set to 100% or more of the rated current of the large electrode in the high output region.

The invention according to claim 8 is provided with a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, in one electrode. And means for selecting between a state in which the large electrode is energized and a state in which the small electrode is energized so that the electrode temperature is kept within a predetermined range during dimming lighting.

In a ninth aspect of the present invention, in the invention of the eighth aspect, the upper limit of the temperature range is a state in which an end glow occurs in the electrode, and the lower limit is a state in which the luminescent spot moves in an unstable manner.

According to a tenth aspect, in the eighth aspect, the means maintains the electrode temperature at 800 to 1200 ° C.

According to an eleventh aspect, in the first to tenth aspects, the large electrode and the small electrode are connected in series.

According to a twelfth aspect of the present invention, in the first to tenth aspects, the large electrode and the small electrode are connected in parallel.

According to a thirteenth aspect of the present invention, in the first to twelfth aspects, the dimming range is set to 0.1 to 1 of a rated value.
00% and 130%.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) In this embodiment, as shown in FIG. 1, a low-pressure discharge lamp La having a large electrode 1 and a small electrode 2 is used as each electrode. The large electrode 1 and the small electrode 2 are connected in series, and lead-in lines 5a are connected to both ends of a series circuit of the large electrode 1 and the small electrode 2 and to a connection point between the large electrode 1 and the small electrode 2, respectively. Auxiliary anodes 6 made of metal rods project from both ends of a series circuit of the large electrode 1 and the small electrode 2 to the positive column.

A series circuit of the large electrode 1 and the small electrode 2 is connected between both ends of a secondary winding of the transformer T1, and a heating voltage is applied by an electrode heating circuit (not shown) connected to the primary winding of the transformer T1. Is done. Further, switch elements S1 and S2 are connected in parallel to the large electrode 1 and the small electrode 2, respectively. As the lighting circuit, an inverter INV that outputs a high-frequency AC voltage and applies a lamp voltage using an AC power supply Vs such as a commercial power supply as an input power supply is used, and a resistor R is connected between output terminals of the inverter INV. The low-pressure discharge lamp La is connected. This inverter device INV has a variable power supply to the low-pressure discharge lamp La, and is used as a dimming ballast. Here, one end of the large electrode 1 in each pole of the low-pressure discharge lamp La is set as a power supply side.

The resistor R detects a lamp current. By detecting the voltage across the resistor R, a voltage proportional to the lamp current flowing through the low-pressure discharge lamp La can be obtained. The voltage across the resistor R is input to the detection circuit SN. The detection circuit SN has, for example, the configuration shown in FIG. 2 and controls the switch elements S1 and S2 based on the voltage across the resistor R. A capacitor C1 is connected between both ends of the resistor R via a diode D1 and the resistor R1, and a voltage across the resistor R is rectified by the diode D1 and smoothed by the capacitor C1. The voltage across the capacitor C1 is 3
The voltage is divided by a series circuit of the resistors R2 to R4. The light emitting diode LD1 is connected in parallel to the series circuit of the resistors R2 to R4, the light emitting diode LD2 is connected in parallel to the series circuit of the resistors R3 and R4, and the light emitting diode LD3 is connected in parallel to the series circuit of the resistors R4. That is, if the average value of the voltage across the resistor R is divided into four voltage sections,
In the first voltage section where the voltage is the lowest, the light emitting diode L
None of D1 to LD3 is turned on, only the light emitting diode LD1 is turned on in the second second voltage section, the light emitting diodes LD1 and LD2 are turned on in the third third voltage section, and the fourth fourth voltage section is turned on. Then, all the light emitting diodes LD1 to LD3 are turned on.

On the other hand, each of the switch elements S1 and S2 includes two MOSFETs Qa1, Qb1, Qa2,
Qb2 and two MOSFETs Qa1, Qb1,
In Qa2 and Qb2, sources are commonly connected and gates are commonly connected. The figure shows diodes connected in anti-series, but the MOSFETs Qa1, Qb1, Qa2, Q
If a body diode of b2 is used, there is no need to separately connect a diode. MOSFET Qa1, Q
The transistor Qc1 is connected between the gate and source of b1, and the collector and emitter of the transistor Qc2 are connected between the gate and source of the MOSFETs Qa2 and Qb2.

MOSFET constituting switch element S1
A series circuit of a phototransistor PT1, a resistor Ra1, and a DC power supply Ea1 is connected between the gates and sources of Qa1 and Qb1. The phototransistor PT21 and the resistor Rb1 are connected between the base and the emitter of the transistor Qc1.
And a DC power supply Eb1 are connected in series. On the other hand, MOSFETs Qa2 and Qb2
, A series circuit of a phototransistor PT22, a resistor Ra2, and a DC power supply Ea2 is connected between
A series circuit of a phototransistor PT3, a resistor Rb2, and a DC power supply Eb2 is connected between the base and the emitter of the transistor Qc2. The phototransistor PT1 forms a photocoupler together with the light emitting diode LD1, and the phototransistors PT21 and PT22 include the light emitting diode L1.
D2 forms a photocoupler, and the phototransistor PT3 forms a photocoupler together with the light emitting diode LD3.

In the above configuration, when the average value of the voltage across the resistor R is in the first voltage section, both switch elements S1 and S2 are turned off. In the second voltage section, the switch element S1 is on and the switch element S2 is off. In the third voltage section, the switch element S1 is off and the switch element S2 is on. S2 turns off.

The voltage V1 applied between both ends of the series circuit of the resistors R2, R3 and R4 is expressed by the following equation, where the peak value of the voltage across the resistor R is Vp. V1 = V
p [1-exp {-(R1 + Rx) t / C1.R1.R
x}] / R1, where Rx = R2 + R3 + R4.
Therefore, the phototransistor PT1 is turned on after a predetermined start-up period (for example, set to 0.5 seconds) after the power supply of the inverter INV is turned on (that is, when the above-mentioned t is 0.5). Light emitting diode LD
1 so that the phototransistor PT1 is turned on), the resistors R1 and Rx, and the capacitor C1 are set. If the power supply of the inverter INV is turned on, the first voltage section is set during the startup period. And both switch elements S1,
Both S2 are turned off.

When the startup period ends, the light emitting diode L
Since D1 is turned on and only the switch element S1 is turned on, the large electrode 1 is short-circuited, and current can flow only to the small electrode 2. When the current flowing through the resistor R increases and the light emitting diode LD2 also lights up,
Since the switch element S1 is turned off but the switch element S2 is turned on, the small electrode 2 is short-circuited, so that current can flow only to the large electrode 1. When the current further increases and the current also flows through the light emitting diode LD3, the switch elements S1 and S2 are both turned off, so that the current can flow through the series circuit of the large electrode 1 and the small electrode 2. .

By the way, it is known that a low-pressure discharge lamp using a general electrode can stably control light up to about 0.5% of the rated current. On the other hand, when a large electrode 1 and a small electrode 2 are connected in series as electrodes, the blinking life becomes the longest when the current rating of the small electrode 2 is set to about 30% of the current rating of the large electrode 1. It is
It is known by the description in US Pat.
Therefore, if the small electrode 2 having a current rating of 30% of the current rating of the large electrode 1 is used, and only the small electrode 2 is used for dimming, the dimming can be stably performed to around 0.1%. Become. Hereinafter, 0.1 to 30% of the rated current of the large electrode 1 is defined as a low output region, and 30 to 100% is defined as a steady output region.

Based on such findings, the filament and the tube diameter of the current 30 W fluorescent lamp (core wire diameter of about 9
It is assumed that a low-pressure discharge lamp La using a current 10 W fluorescent lamp filament (having a core wire diameter of about 50 μm) as the small electrode 2 is configured. This low-pressure discharge lamp La
If only the large electrode 1 is used at the time of rated lighting, the rated current is 0.6 A, and 30% of the rated current is 0.2 A. Therefore, the resistors R2 to R4 are set so that the light emitting diode LD2 is turned on when the lamp current becomes 0.2A or more, and the light emitting diode LD3 is turned on when the lamp current becomes 0.6A or more.

The operation will be described with this setting example. As described above, the light emitting diodes LD1 to LD1 are activated from the power-on to the startup period.
None of the LDs 3 is turned on, and the light emitting diode LD1 is turned on after the elapse of the activation period. Thereafter, the lamp current Il
The relationship between a and the on / off of the switch elements S1 and S2 is as follows.

Ila ≦ 0.2A S1 = ON S2 = OFF 0.2A <Ila ≦ 0.6A S1 = OFF S2 = ON 0.6A <Ila S1 = OFF S2 = OFF The above switch elements S1 and S2 By action
When the lamp current is 0.2 A or less, current flows only to the small electrode 2. When the lamp current is 0.2 to 0.6 A, current flows only to the large electrode 1. When the lamp current exceeds 0.6 A, the large electrode 1 flows.
A current flows through a series circuit of the electrode and the small electrode 2. That is, immediately after the power is turned on, a bright spot is formed on the small electrode 2 to facilitate start-up. After that, when the lamp current increases, the operation is shifted to steady lighting using the large electrode 1. Further, at the time of dimming, only the large electrode 1 is used in a range where the lamp current is 0.6 A or less and 0.2 A or more (steady output region), and a small electrode 2 is used in a range where the lamp current is 0.2 A or less (low output region). Dimming is performed using only the light. As a result, only the large electrode 1 is 0.5% of the rated current.
Although the dimming can be stably performed only to the extent, the dimming can be stably performed to about 0.1%. Here, the ratio of the rated current between the large electrode 1 and the small electrode 2 is not limited to 100: 30, but this ratio is a desirable value.

By the way, when the lamp current exceeds the rated current,
When a predetermined high output area is reached, a heating voltage of the electrode heating frequency is applied across both electrodes of the low-pressure discharge lamp La, and a lamp voltage of the lighting frequency is applied between both electrodes. The lighting frequency and the electrode heating frequency are set to be different from each other. Here, either the lighting frequency or the electrode heating frequency may be higher, but the case where the lighting frequency is higher than the electrode heating frequency will be described below. Here, when the above-mentioned ones are used for the large electrode 1 and the small electrode 2, the high output region is desirably 130% of the rated current.

Here, in general, the operation of the electrode includes an anode cycle and a cathode cycle. In the anode cycle, electrons flow into the electrode. Therefore, during this period, a bright spot is basically unnecessary. However, in practice, the electrons flow into the location where the flow is most likely to occur, so that the temperature of the electrode is locally high. Therefore, the auxiliary anode 6 is provided. In the anode cycle, electrons flow into the auxiliary electrode 6 to prevent local overheating of the electrode and extend the life of the electrode. That is, since the auxiliary electrode 6 is provided, only the cathode cycle needs to be considered for the bright spot. As described above, since no problem occurs in practical use only by considering the cathode cycle, only the bright spot in the cathode cycle will be described.

Now, it is assumed that the lamp voltage Vla having the polarity shown by the arrow in FIG. 3 is applied to the power supply side ends a1 and a2 of the respective electrodes 7, and the lamp current Ila flows in the direction shown by the arrow.
Assuming that the lighting frequency is set to be twice the electrode heating frequency, the lamp voltage Vla is applied between both ends of each electrode 7 (a1-b1
Heating voltage Vf1, Vf applied between
The relationship with 2 can be divided into four cases A to D (see FIG. 4). In short, the case where the heating voltages Vf1 and Vf2 are positive and the lamp voltage Vla is positive is A, and the heating voltages Vf1 and Vf2 are positive and the lamp voltage Vl
B when a is negative, C when the heating voltages Vf1 and Vf2 are negative and the lamp voltage Vla is positive, and C when the heating voltages Vf1 and Vf2 are negative and the lamp voltage Vla.
Is D when the polarity is negative. Considering the positions of the bright spots in consideration of only the cathode cycle, the positions of the bright spots corresponding to each of the cases A to D are A → a1, B → a2, C → b
1, D → b2.

As described above, by controlling the two frequencies of the lighting frequency that defines the lamp voltage Vla and the electrode heating frequency that defines the heating voltages Vf1 and Vf2, the time during which a bright spot occurs can be controlled. As a result, it is possible to control the ratio of the current flowing to both ends of the electrode 7.
In the example of FIG. 4, the ends a1, a2 and the ends b1, b2 of the electrode 7
And 50% of bright spots are generated.

As shown in FIG. 5, the lamp voltage Vl
The lighting frequency corresponding to a is set to three times the electrode heating frequency corresponding to the heating voltages Vf1 and Vf2, and the heating voltage Vf
When Vf1 and Vf2 are set to mutually opposite phases, 6 shown in FIG.
Cases can be divided into AF. The positions of the bright spots corresponding to each of the cases A to F are A → a1, B → b2, C → a
1, D → a2, E → b1, F → a2. Thus, the position and time of the luminescent spot can be controlled.

In the above description, the electrode 7 composed of one filament is used to explain the basic operation.
In the present embodiment, an electrode in which the large electrode 1 and the small electrode 2 are connected in series is used. Therefore, the electrode heating frequency is controlled to match the rated values of the large electrode 1 and the small electrode 2. However, as described above, if the lighting frequency and the electrode heating frequency are set so that the current flowing through the large electrode 1 is set to 100% and the current of 30% flows through the small electrode 2,
It is necessary to modulate the electrode heating frequency.

For example, when the lamp voltage Vla is set so that two frequencies are alternately changed by one wavelength as shown in FIG. 6, electrons are emitted from the small electrode 2 in the shaded portion in FIG. Become. At other locations, the large electrode 1 emits electrons. Note that the polarities of the lamp voltage Vla and the electrode heating voltages Vf1 and Vf2 are the polarities shown in FIG.

Assuming that the two frequency components included in the lamp voltage Vla are ωt and ωt / n (where n is an integer), the ratio of the effective values of the currents flowing through the large electrode 1 and the small electrode 2 is , As follows. (Square of current of small electrode 2): (square of current of large electrode 1)
= 1: (1 + n) In other words, it can be seen that n = 10 should be set in order to make the current flowing through the small electrode 2 approximately 30% of the current flowing through the large electrode 1. By alternately applying two frequency voltages having a frequency ratio of 1:10 in this manner, a current of about 30% of that of the large electrode 1 can flow through the small electrode 2. By such control, the current ratio flowing between the large electrode 1 and the small electrode 2 in the high output region can be appropriately distributed,
Although the output is high, the lighting life of the large electrode 1 and the small electrode 2 is not impaired.

(Embodiment 2) In Embodiment 1, the lamp voltage V
Changing the frequency of la over time (that is, FM modulation)
In this embodiment, the frequency of the lamp voltage Vla is constant and the amplitude is changed with time, as shown in FIG. That is, the ratio of the current flowing through the large electrode 1 and the small electrode 2 is adjusted by AM modulation.

That is, in the ramp voltage Vla waveform shown in FIG. 7, electrons are emitted from the small electrode 2 in the hatched portion, and electrons are emitted from the large electrode 1 in other places. Therefore,
Assuming that the peak value of the lamp voltage Vla is changed to I0 and I1 without changing the frequency, the following relationship is established. (Square of current of small electrode 2): (square of current of large electrode 1)
= I0 ² : (I0 ² + I1 ² ) From this, in order to make the current flowing through the small electrode 2 about 30% of the current flowing through the large electrode 1, it is necessary to set I0: I1 = 1: 3. Recognize. Thus, the lamp voltage V
The current ratio flowing to the large electrode 1 and the small electrode 2 can be adjusted by AM-modulating la. If such control is performed in the high-power region, the current flowing to the electrodes is appropriately distributed. Therefore, the current can be appropriately distributed to the large electrode 1 and the small electrode 2 while the output is high, and the lighting life is not impaired. Other configurations and operations are the same as those of the first embodiment. (Embodiment 3) In the first embodiment, the on / off of the switch elements S1 and S2 is selected according to the lamp current. However, in the present embodiment, the switch elements S1 and S2 are selected according to the electrode temperature.
On and off. That is, when the electrode temperature is too high, the electron-emitting substance carried by the electrode evaporates and the life is shortened. When the electrode temperature is too low, the electron-emitting substance is scattered by ion bombardment and the life is shortened. The temperature needs to be maintained properly.

In this embodiment, the on / off of the switch elements S1 and S2 is controlled by detecting the temperature of the electrodes. That is, while the switch element S1 is turned on and the switch element S2 is turned off, when the temperature of the small electrode 2 exceeds the first specified value, the switch element S2 is turned on, the switch element S1 is turned off, and the large electrode 1 is turned off. When the large electrode 1 is used with the switch element S2 turned on and the switch element S1 turned off, when the temperature of the large electrode 1 becomes equal to or lower than the second specified value, the switch element S is switched.
1 is turned on, the switch element S2 is turned off, and the small electrode 2 is used. Even with this configuration, it is possible to stably control light. Here, the temperature of the electrode is 800-1200.
It is desirable to keep it at ° C.

By the way, in order to detect the temperature of the electrode, when the temperature of the electrode becomes high, an end glow is generated at both ends of the electrode, and the current flowing through the end glow suddenly increases. This is based on the fact that the voltage between both ends of the electrode becomes unstable due to the start of unstable movement. That is, the temperature of the electrode can be estimated by detecting the current and the voltage. Further, the temperature of the electrode may be estimated by detecting the terminal voltage of the electrode based on the relationship between the temperature of the electrode and the resistance value. Other configurations and operations are the same as those of the first embodiment.

Instead of using the transformer T1 as described above, it is possible to adopt a circuit configuration in which a capacitor C2 is provided between one ends of the small electrodes 2 as shown in FIG.

In each of the above-described embodiments, the large electrode 1
And the small electrode 2 are connected in series, but a configuration in which the large electrode 1 and the small electrode 2 are connected in parallel as shown in FIG. 9 and the large electrode 1 is arranged on the positive column side may be adopted. The low-pressure discharge lamp La having this configuration has the same configuration as that described in Japanese Patent Publication No. 39-20120, but by applying a low-pressure discharge lamp lighting device having the configuration shown in FIG. To achieve the object of the present invention.

The cathode drop voltages of the large electrode 1 and the small electrode 2 are Vlc and Vsc, respectively. Since the small electrode 2 has a smaller heat capacity than the large electrode 1, Vlc> Vsc, and the small electrode 2 starts discharging. The lamp voltage V at this time
la1 is represented by the following equation, where Vd is the voltage between the large electrode 1 and the small electrode, and VD is the voltage between the large electrodes 1. Vla1 = Vsc + 2 × Vd + VD Then, since the large electrode 1 is heated, Vlc <Vsc +
When the voltage becomes 2 × Vd, discharge starts between the two large electrodes 1. That is, the lamp voltage Vla2 is represented by the following equation. Vla2 = Vlc + VD When the discharge current is reduced from this state, Vlc rises, and when Vlc> Vsc + 2Vd, discharge is performed between both small electrodes 2. As described above, since the large electrode 1 and the small electrode 2 are automatically selected according to the lamp current, the life can be maintained without largely changing the electrode heating voltage.

[0053]

According to the first aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, in one electrode. The discharge is started from the small electrode, and the lamp is lit using the small electrode in a low output region where the lamp current is equal to or less than a specified value. Since the dimming is performed using the small electrode in the low output region, the light output is small. It is possible to stably light up to the area.

According to a second aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, on one electrode. In addition to starting discharge from the lamp, the lamp is lit using the large electrode in the steady output region where the lamp current is equal to or higher than the specified value and equal to or lower than the rating.In the steady output region, the large electrode is used. Unnecessary current does not flow, and the life of the small electrode can be maintained.

According to a third aspect of the present invention, there is provided a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, on one electrode. In addition to starting discharge from the high power region exceeding the rated output, the lighting is performed using the large electrode and the small electrode, and in the region exceeding the rated output of the large electrode, both the large electrode and the small electrode are used. It is possible to obtain a high output exceeding the rating of the large electrode without affecting the life.

According to a fourth aspect of the present invention, in the third aspect of the invention, in the high output region, the lighting frequency of the lamp voltage applied between the electrodes of the low-pressure discharge lamp and the voltage between both ends of the series circuit of the large electrode and the small electrode. When the electrode heating frequency and the lighting frequency are set appropriately, the power between the large electrode and the small electrode can be appropriately distributed at the time of high output. As a result, the large electrode and the small electrode can be used with an appropriate life. In addition, since the power supplied to the large electrode and the small electrode can be distributed by controlling the frequency, the control is relatively easy.

The invention according to claim 8 is provided with a dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, in one electrode. And a means for selecting between a state in which the large electrode is energized and a state in which the small electrode is energized so as to maintain the electrode temperature within a predetermined range during dimming lighting. The life can be maintained by controlling the temperature with the electrodes.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a main part circuit diagram of the same.

FIG. 3 is an operation explanatory diagram of the above.

FIG. 4 is an operation explanatory view of the above.

FIG. 5 is an operation explanatory view of the above.

FIG. 6 is an operation explanatory view of the above.

FIG. 7 is an operation explanatory diagram of Embodiment 2 of the present invention.

FIG. 8 is a circuit diagram showing another configuration example.

FIG. 9 is a circuit diagram showing still another configuration example.

FIG. 10 is a perspective view of a main part showing a conventional example.

FIG. 11 is an operation explanatory diagram of the above.

FIG. 12 is a perspective view of a main part showing another conventional example.

[Explanation of symbols]

 1 Large electrode 2 Small electrode INV Inverter device La Low pressure discharge lamp R Resistance S1, S2 Switch element SN detection circuit Vs AC power supply

Claims (13)

[Claims] 1. A dimming electronic ballast for supplying electric power to a low-pressure discharge lamp having a large electrode and a small electrode which are two filaments having different heat capacities on one electrode, and starting discharge from the small electrode at the time of starting. A low-pressure discharge lamp lighting device characterized in that a small electrode is used for lighting in a low output region where the lamp current is equal to or less than a specified value. 2. A dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, on one electrode. A low-pressure discharge lamp lighting device characterized in that the lamp is lit using a large electrode in a steady output region where the lamp current is equal to or more than a specified value and equal to or less than a rating. 3. A dimming electronic ballast for supplying power to a low-pressure discharge lamp having two electrodes, a large electrode and a small electrode having different heat capacities, on one electrode, and starting discharge from the small electrode at start-up. A low-pressure discharge lamp lighting device characterized in that a large electrode and a small electrode are used for lighting in a high output region exceeding a rated output. 4. In the high-power region, the operating frequency of the lamp voltage applied between the electrodes of the low-pressure discharge lamp and the electrode heating frequency of the heating voltage applied across the series circuit of the large electrode and the small electrode are mutually different. 4. The lighting device for a low-pressure discharge lamp according to claim 3, wherein the lighting device is different. 5. The low pressure discharge lamp lighting device according to claim 1, wherein the low output region is a region where the lamp current is 30% or less of the rated current of the large electrode. 6. The low pressure discharge lamp lighting device according to claim 2, wherein the steady output region is a region where the lamp current is 30 to 100% of the rated current of the large electrode. 7. The low-pressure discharge lamp lighting device according to claim 3, wherein a lamp current in the high output region is 100% or more of a rated current of the large electrode. 8. A dimming electronic ballast for supplying power to a low-pressure discharge lamp having a large electrode and a small electrode, which are two filaments having different heat capacities, in one electrode. And a means for selecting between a state in which the large electrode is energized and a state in which the small electrode is energized so that the electrode temperature is kept within a predetermined range during the dimming operation. 9. The low pressure discharge lamp lighting device according to claim 8, wherein the upper limit of the temperature range is a state in which an end glow occurs in the electrode, and the lower limit is a state in which the luminescent spot moves in an unstable manner. 10. The method according to claim 1, wherein the temperature of the electrode is from 800 to 120.
9. The low-pressure discharge lamp lighting device according to claim 8, wherein the temperature is maintained at 0 ° C. 11. The lighting device for a low-pressure discharge lamp according to claim 1, wherein the large electrode and the small electrode are connected in series. 12. The low-pressure discharge lamp lighting device according to claim 1, wherein the large electrode and the small electrode are connected in parallel. 13. The light control range is 0.1% to 100% of the rated value.
13. The low-pressure discharge lamp lighting device according to claim 1, wherein the ratio is 130%.