JPH10301535A - Display device and fluorescent tube drive method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a display device capable of being in service for a long time using an incorporated power source (e.g. battery power source) and a drive method of a fluorescent tube in this display device. SOLUTION: This display device is provided with at least the incorporated power source 1 and an external input power source 2 such as an AC adapter, a backlight 10, an FL driver (fluorescent tube drive circuit) 9 and a liquid crystal display panel 5 operated by the battery power source 1 or the external input power source 2. And further, the display device is provided with a detection circuit 7 judging from which a power source is supplied, the battery power source 1 or the external input power source 2 and an FL controller 8 changing a pulse width of a drive source signal inputted to the FL driver 9 according to a detection signal from the detection circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention uses an internal power supply built in a display device such as a battery power supply or an external input power supply which is supplied with power from outside the display device such as a car adapter or an AC adapter. The present invention relates to a display device and a fluorescent tube driving method in the display device.

[0002]

2. Description of the Related Art In a conventional display device of this type, as shown in FIG. 4, a horizontal synchronizing signal A obtained by separating a video signal B output from an IF 31 via a tuner 30 by a synchronizing separation circuit 32 is used as a waveform shaping circuit. 38, a predetermined pulse width, a waveform-shaped signal is sent to the FL driver 36, and the backlight 33 is
The image controller 34 outputs an image control signal C and sends it to a liquid crystal driver 35, which drives a liquid crystal panel 37.

[0003]

However, in the above-mentioned conventional liquid crystal display device, the ratio of the power consumption of the illumination to the total power consumption of the liquid crystal display device is large, and the built-in power supply of the display device using a battery power supply or the like is required. When the display is operated with the lighting turned on brightly, there is a problem that the usable time is short.

An object of the present invention is to solve the above-mentioned conventional problems, and a first object of the present invention is to provide a liquid crystal display device which can be used for a long time with a built-in power supply.

It is a second object of the present invention to provide a fluorescent tube driving method which can be used for a long time with a built-in power supply.

[0006]

In order to achieve the above object, at least a power supply is provided for a built-in power supply built in the display device and an external input power supply inputted from outside the display device. In a display device comprising a flat fluorescent tube, a flat fluorescent tube driving circuit, and a display panel, a determination circuit for determining whether power is supplied from the internal power supply or the external input power supply, and a determination signal from the determination circuit. And a control circuit for changing a pulse width of a drive source signal input to the fluorescent tube drive circuit.

A flat fluorescent tube, a flat fluorescent tube driving circuit, and a display panel, which are provided with at least a power source of a built-in power source built in the display device and an external input power source input from the outside of the display device, operate by the power source. A display circuit for determining whether power is supplied from the internal power supply or the external input power supply, and a frequency of a drive source signal input to the fluorescent tube drive circuit based on a determination signal from the determination circuit. And a control circuit for changing the value.

A flat fluorescent tube, a flat fluorescent tube driving circuit, a liquid crystal display panel, and a flat fluorescent tube which are provided with at least a power source of a built-in power source built in the display device and an external input power source input from the outside of the display device. A display circuit comprising: a determination circuit that determines whether power is supplied from the internal power supply or the external input power supply; and a drive source signal input to the fluorescent tube drive circuit based on a determination signal from the determination circuit. A display device having a control circuit for changing a pulse width and a frequency.

[0009] At least a power supply of a built-in power supply built in the display device and an external input power supply input from the outside of the display device, further comprising a flat fluorescent tube and a flat fluorescent tube driving circuit operated by the power supply, In the fluorescent tube driving method for driving the fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to the fluorescent tube driving circuit, power is supplied from either the built-in power supply or the external input power supply. A fluorescent tube driving method characterized in that the driving power of the fluorescent tube is controlled by changing the pulse width of the fluorescent tube driving source signal in accordance with a determination signal for determining whether the fluorescent tube has been operated.

The apparatus has at least a power source of a built-in power source built in the display device and an external input power source input from outside of the display device, and further comprises a flat fluorescent tube operated by the power source and a fluorescent tube driving circuit. In the fluorescent tube driving method for driving the fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to the fluorescent tube driving circuit, power is supplied from either the built-in power supply or the external input power supply. A driving signal of the fluorescent tube is controlled by changing a frequency of the fluorescent tube driving source signal in accordance with a determination signal for determining whether or not the fluorescent lamp is driven.

The fluorescent tube comprises at least a power source of a built-in power source built in the display device and an external input power source input from the outside of the display device, comprising a fluorescent tube operated by the power source and a fluorescent tube driving circuit. In a fluorescent tube driving method for driving a flat fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to a driving circuit, it is determined whether power is supplied from the internal power supply or the external input power supply. A fluorescent tube driving method, wherein the driving power of the fluorescent tube is controlled by changing a pulse width and a frequency of the fluorescent tube driving source signal according to a determination signal.

With this configuration, the determination circuit determines which power supply is selected, and when the built-in power supply is selected, the control circuit narrows the pulse width of the drive source signal to reduce the fluorescent lamp (back-up). By reducing the power consumption of the light, the operation time (battery life) of the display device using the built-in power supply can be extended, and the built-in power supply can be used continuously for a long time.

In the display device according to the present invention, the control circuit may change a frequency of a drive source signal input to the fluorescent tube drive circuit according to a determination signal from the determination circuit. Alternatively, the pulse width and frequency of the drive source signal may be changed. In these cases, the same operation as the above operation can be achieved.

A determination signal is used to determine whether a power supply of the internal power supply or the external input power supply is selected,
When the built-in power supply is selected, the driving power of the fluorescent tube is controlled by changing the pulse width of the fluorescent tube driving source signal, and the pulse width of the driving source signal is narrowed, so that the fluorescent tube (backlight) By reducing power consumption, battery life is extended, and long-term continuous use of the internal power source battery is enabled.

In the fluorescent tube driving method of the present invention, the driving power of the fluorescent tube may be controlled by changing the frequency of the fluorescent tube driving source signal according to the determination signal. The driving power of the fluorescent tube may be controlled by changing the pulse width and frequency of the fluorescent tube driving source signal according to the signal. In these cases, the same operation as the above operation can be achieved.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of a liquid crystal display device showing an embodiment of the present invention.

The liquid crystal display device shown in FIG. 1 includes a battery power source 1 as a built-in power source, an external input power source 2 such as an AC adapter or a car adapter, an image controller 3, a liquid crystal driver 4, a liquid crystal panel 5, , A sync separation circuit 6,
It has a detection circuit (judgment circuit) 7, an FL controller (control circuit) 8, an FL driver (fluorescent tube driving circuit) 9, and a backlight (fluorescent tube) 10. The battery power supply 1 and the external input power supply 2 are both power supplies for the liquid crystal display device, and either one is selectively used.

The image controller 3 separates the input composite video signal into primary colors to generate R, G, and B image data, separates a synchronizing signal from the composite video signal, and converts the synchronizing signal into the image data and the synchronizing signal. Based on this, an image control signal is generated and output.

The liquid crystal driver 4 drives the liquid crystal panel 5 according to the image control signal. Also, the sync separation circuit 6
Separates the horizontal synchronizing signal and the vertical synchronizing signal from the input composite video signal, and outputs this.

The detection circuit 7 detects whether the liquid crystal display device shown in FIG. 1 uses the battery power supply 1 or the external input power supply 2, and outputs a detection signal indicating the detection result. Also,
The FL controller 8 changes the pulse width of the input horizontal synchronization signal from the synchronization separation circuit 6 according to the detection signal,
The pulse width modulated horizontal synchronization signal is output as an FL control signal. The FL driver 9 also controls the backlight 1 composed of a flat fluorescent lamp according to the FL control signal.
Drive 0.

Next, the operation of the liquid crystal display device shown in FIG. 1 will be described. The image controller 3 generates R, G, and B image data from the input composite video signal, separates a synchronization signal, and generates an image control signal based on the image data and the synchronization signal.

The above-described image control signal is input to the liquid crystal driver 5, and the liquid crystal driver 5 drives the liquid crystal panel 6 according to the image control signal. Further, the sync separation circuit 6 separates a horizontal sync signal from the input composite video signal. The detection circuit 7 detects whether the liquid crystal display device shown in FIG. 1 uses the battery power supply 1 or the external input power supply 2 and outputs a detection signal. The FL controller 8 generates an FL control signal by changing the pulse width of the horizontal synchronization signal according to the detection signal.

The FL control signal is input to the FL driver 9, and the FL driver 9 drives the backlight 10 according to the FL control signal.

Here, the period of the horizontal synchronizing signal in the NTSC system is 64 [μs], the horizontal synchronizing pulse is usually a negative pulse, and the pulse width is 10.6 [μs].
It is. In the liquid crystal display device of FIG. 1, the FL control signal is a signal having a positive polarity pulse having the same cycle as the horizontal synchronizing signal, and its pulse width is maximum (when battery power source 1 is selected).
10.6 [μs]. The detection signal is the battery power 1
It is assumed that this signal is at the L level when is selected and at the H level when the external input power supply 2 is selected.

Hereinafter, the FL controller 8 and the FL driver 9 will be described in detail. FIG. 2 is a diagram showing an internal circuit of the FL controller 8. In FIG. 2, the FL controller 8 includes a NAND gate N1, an inverter I1,
Variable resistor VR1, capacitor C1, and AND gate A
1 and a buffer B1. Here, the frequency control signal is always at the H level.

When the external input power supply 2 is selected,
Since the detection signal is at the H level, the horizontal synchronization signal input from the synchronization separation circuit 7 is inverted by the NAND gate N1 (waveform A) and output as the FL control signal via the AND gate A1 and the buffer B1. You.

When the battery power source 1 is selected, the horizontal synchronizing signal A inverted by the AND gate N1 is:
The signal is inverted again by the inverter I1, and is input to an integration circuit including the variable resistor VR1 and the capacitor C1 to become an integration signal B. Since the detection signal is at the L level, the integration signal B is input to the AND gate A1 to generate an AND signal C with the inverted signal A. The AND signal C is output to the FL via the buffer B1.
It is output as a control signal. At this time, the pulse width of the FL control signal is 1 when the external input power supply 2 is selected.
It becomes smaller than 0.6 [μs]. This pulse width can be easily varied by adjusting the variable resistor VR1.

Next, the FL driver 9 controls the backlight 1
The backlight 10 is driven during the horizontal blanking period so that the discharge noise of 0 does not affect the liquid crystal screen. Furthermore, a high-voltage pulse with a very narrow pulse width is used so that the backlight 10 performs a uniform surface discharge.
The backlight 10 is driven.

FIG. 3 is a diagram showing an internal circuit of the FL driver 9. In FIG. 3, the FL driver 9 includes a complementary inverter Q2 using a complementary bipolar transistor, and n
It has a channel field effect transistor Q1 and a high voltage transformer T1.

When the FL control signal from the FL controller 8 goes high, the npn transistor of the complementary inverter Q2 turns on and the pnp transistor turns off, thereby turning off the transistor Q1.

When the transistor Q1 is turned off, a pulse width of 2 to 3 [μs] is applied to the secondary winding of the high-voltage transformer T1.
A high voltage pulse of the order is generated, and the backlight 10 is discharged by the high voltage pulse within the horizontal blanking period. At this time, the power consumption of the backlight 10 decreases as the pulse width of the FL control signal decreases.

As described above, according to the above-described embodiment, the detection circuit 7 detects which power supply is selected, and when the battery power supply 1 is selected, the FL controller 8 controls the pulse of the FL control signal. By narrowing the width and reducing the power consumption of the backlight 10,
The battery life is prolonged, and the battery can be used continuously for a long time when driven.

The power consumption of the backlight 10 can be reduced even if the frequency of the FL control signal is reduced (the cycle is lengthened). For example, the period of the FL control signal is twice as long as the horizontal synchronization signal, and one FL control pulse is output for two horizontal synchronization pulses. That is, in FIG. 2, the horizontal synchronization signal is frequency-divided by 2 and used as a frequency control signal, and the horizontal synchronization signal is supplied to the NAND gate N1.
When the frequency control signal is inverted each time the signal is input to the horizontal synchronization signal, the FL control signal can be used as the frequency-divided signal of the horizontal synchronization signal.

In the present invention, an embodiment using a liquid crystal panel as a display panel for displaying an image has been described. However, it is obvious that the present invention is not limited to a liquid crystal display device using a liquid crystal panel. .

[0035]

As described above, the judgment circuit for judging whether the power is supplied from the built-in power supply or the external input power supply, and the driving signal inputted to the fluorescent tube driving circuit based on the judgment signal from the judgment circuit. And a control circuit for changing the pulse width of the source signal, the determination circuit determines which power source is selected, and when the battery power source is selected, the control circuit changes the pulse width of the drive source signal. By reducing the power consumption, the operation time (battery life) of the display device using the built-in power supply can be prolonged, and long-term use in driving the built-in power supply can be achieved by reducing the power consumption of the fluorescent tube (backlight).

In the display device according to the present invention, the control circuit may change a frequency of a drive source signal input to the fluorescent tube drive circuit according to a determination signal from the determination circuit. Alternatively, the pulse width and frequency of the drive source signal may be changed. In these cases, the same effects as those described above can be obtained.

According to the fluorescent tube driving method of the present invention,
A fluorescent tube and a fluorescent tube driving circuit which are provided with at least a power supply of a built-in power supply and an external input power supply, and further operate by the power supply, and a fluorescent tube driving source signal input to the fluorescent tube driving circuit is used for driving the fluorescent tube. In the fluorescent tube driving method of driving the fluorescent tube by being input to the, the determination signal to determine whether power is supplied from the internal power supply or the external input power, by changing the pulse width of the fluorescent tube drive source signal, By controlling the driving power of the fluorescent tube, it is determined by the determination signal which power source is selected, and when the built-in power source is selected, the pulse width of the fluorescent tube driving source signal is changed. Alternatively, the driving power of the fluorescent tube is controlled, the pulse width of the driving source signal is narrowed, and the power consumption of the fluorescent tube (backlight) is reduced, so that the built-in power supply is used. Extending the time period to allow long-term use in internal power drive.

Further, in the fluorescent tube driving method of the present invention, the driving power of the fluorescent tube may be controlled by changing the frequency of the fluorescent tube driving source signal according to the determination signal. The driving power of the fluorescent tube may be controlled by changing the pulse width and frequency of the fluorescent tube driving source signal according to the signal. In these cases, the same effects as those described above can be obtained.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 shows F in the liquid crystal display device according to the embodiment of the present invention.
It is a circuit diagram of an L controller.

FIG. 3 shows F in the liquid crystal display device according to the embodiment of the present invention.
FIG. 3 is a circuit diagram of an L driver.

FIG. 4 is a block diagram showing a conventional liquid crystal display device.

[Explanation of symbols]

 Reference Signs List 1 battery power supply 2 commercial power supply (external power supply input terminal) 3 image controller 4 liquid crystal driver 5 liquid crystal panel 6 synchronization separation circuit 7 detection circuit (judgment circuit) 8 FL controller (control circuit) 9 FL driver (fluorescent tube drive circuit) 10 back Light (fluorescent tube)

Claims (6)

[Claims] 1. A flat fluorescent tube, a flat fluorescent tube driving circuit, and a display panel, which are provided with at least a power source of a built-in power source built in the display device and an external input power source input from the outside of the display device. A determination circuit for determining whether power is supplied from the built-in power supply or the external input power supply; and a drive source signal input to the fluorescent tube drive circuit based on a determination signal from the determination circuit. A control circuit for changing a pulse width of the display device. 2. A flat fluorescent tube, a flat fluorescent tube driving circuit, and a display panel having at least a power supply of a built-in power supply built in the display device and an external input power supply input from outside of the display device. A determination circuit for determining whether power is supplied from the internal power supply or the external input power supply, and a drive source signal input to the fluorescent tube drive circuit based on a determination signal from the determination circuit And a control circuit for changing the frequency of the display device. 3. A flat fluorescent tube, a flat fluorescent tube driving circuit, and a liquid crystal display, comprising a power source of at least a built-in power source built in the display device and an external input power source input from outside of the display device. A display device comprising a panel, a determination circuit for determining whether power is supplied from the built-in power supply or the external input power supply, and a drive source input to the fluorescent tube drive circuit based on a determination signal from the determination circuit A display device, comprising: a control circuit that changes a pulse width and a frequency of a signal. 4. A flat fluorescent tube and a flat fluorescent tube driving circuit which are provided with at least a power source of a built-in power source built in the display device and an external input power source input from the outside of the display device. A fluorescent tube driving method for driving the fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to the fluorescent tube driving circuit, wherein power is supplied from either the built-in power supply or the external input power supply. A driving signal of the fluorescent tube is controlled by changing a pulse width of the fluorescent tube driving source signal in accordance with a determination signal for determining whether or not the fluorescent tube is supplied. 5. A flat fluorescent tube and a fluorescent tube driving circuit which are provided with at least a power supply of a built-in power supply built in the display device and an external input power supply inputted from outside of the display device. A fluorescent tube driving method for driving the fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to the fluorescent tube driving circuit, wherein power is supplied from either the built-in power supply or the external input power supply. A fluorescent tube driving method, wherein the driving power of the fluorescent tube is controlled by changing the frequency of the fluorescent tube driving source signal according to a determination signal for determining whether the fluorescent tube is supplied. 6. A fluorescent tube and a fluorescent tube driving circuit, comprising at least a power source of a built-in power source built in the display device and an external input power source input from outside of the display device, wherein the fluorescent tube operates by the power source. In a fluorescent tube driving method for driving a flat fluorescent tube by an output of the fluorescent tube driving circuit based on a fluorescent tube driving source signal input to a fluorescent tube driving circuit, power is supplied from either the built-in power supply or the external input power supply. A driving signal of the fluorescent tube is controlled by changing a pulse width and a frequency of the fluorescent tube driving source signal in accordance with a determination signal for determining whether or not the fluorescent lamp is driven.