JP2002100496A - Dimming device of plane lamp - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a dimming device of a plane lamp for expanding a dimming range of the plane lamp for a backlight, reducing electric power consumption and capable of dimming the light, without impairing stability of lighting of the plane lamp. SOLUTION: In this dimming device 1 of the plane lamp, for supplying source voltage 8 supplied from a power source part 5 to a plane lamp part 3 via an inverter unit part 2, a duty control circuit 4 is arranged for supplying a duty pulse lighting signal 10, for turning on and off the source voltage 8 to the inverter unit part 2, by taking the logical product of a pulse lighting signal 6 and a duty signal 7 outputted from a duty signal generating circuit 9, and the plane lamp is driven by plane lamp driving voltage 11 outputted from the inverter unit part 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming device for a flat lamp, and more particularly to a small liquid crystal display (LCD).
The present invention relates to a flat lamp dimmer suitable for use as a backlight of a crystal display panel.

[0002]

2. Description of the Related Art In a conventional flat lamp, a driving circuit or a lighting circuit of the flat lamp only turns on a fluorescent lamp at a constant brightness, and a so-called control for changing the brightness of the fluorescent lamp. Driving devices for flat lamps that do not emit light have been common.

[0003] For example, as a device relating to a flat driving device for a backlight of a liquid crystal display panel, there is a technology described in Japanese Patent Application Laid-Open No. 5-307945.

FIG. 5 is a block diagram showing a driving circuit connected to a flat fluorescent lamp described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 5-307945.

As shown in FIG. 5, a method of supplying a voltage to a flat fluorescent lamp 51 for backlight of a liquid crystal display panel is such that a power supply + B is supplied via a lighting drive circuit including a transformer 53 and a transistor 54. Connected to a flat fluorescent lamp 51, and the transistor 54 of the lighting drive circuit is driven by a pulse signal from a pulse generation circuit 52. As a result, the transistor 54 is turned on while the pulse signal is at the high level, and the
The voltage boosted in step 3 is applied between the two poles of the flat fluorescent lamp 51. On the other hand, when the pulse signal is in a low level period, the transistor 54 is turned off, and LC oscillation occurs on the secondary side of the transformer 53, 50 between both poles of the flat fluorescent lamp 51
A high voltage of about 0 V is applied to obtain high luminance. The cycle of the pulse voltage is set to about 15 KHz.

Japanese Patent Application Laid-Open No. H11-122937 discloses a backlight control circuit for a liquid crystal display device using a fluorescent lamp other than a flat lamp. The technology is known.

FIG. 6 is a circuit diagram of a backlight control circuit of a liquid crystal display device using a fluorescent lamp described in Japanese Patent Application Laid-Open No. H11-122937. In FIG. 6, 6
1 is a dimming control circuit, 62 is an input voltage control circuit, 63 is a logic circuit, 64 is a fluorescent lamp, Q61 is a transistor, L
61 to L65 are coils, C61, C62 and C63 are capacitors, D61 is a diode, R61 to R66 are resistors,
Vcon is a dimming voltage, and Vin is an input voltage.

FIGS. 7A and 7B are waveform diagrams for explaining the operations of the dimming control circuit 61 and the input voltage control circuit 62. FIG. 7A shows the dimming control for controlling the inverter oscillation waveform of the dimming control circuit 61. The circuit output signal, (b) is the inverter oscillation waveform of the input voltage control circuit 62 and the input voltage control circuit output signal.

In the backlight control circuit shown in FIG. 6, a current flowing through the fluorescent lamp 64 is converted into a voltage by a resistor R64, and rectified by a diode D61 and a capacitor C63 to extract an average voltage. This average voltage and the dimming voltage Vcon
Is divided by resistors R61 and R62, and a dimming control circuit 61
Give to.

In the dimming control circuit 61, the transistor Q61 is turned on / off by the input voltage by turning on / off the fluorescent lamp with the output signal of the dimming control circuit having a frequency of a fraction to one-tenth of the oscillation frequency of the inverter circuit. A signal is output to control the voltage input to the inverter circuit in transistor Q61 (see FIG. 7A).

That is, when the dimming voltage Vcon is reduced, the voltage input to the dimming control circuit 61 decreases, and the dimming control circuit 61 lengthens the period during which the transistor Q61 is on, and the current flows through the fluorescent lamp 64. It works to increase the duration.

Conversely, when the dimming voltage Vcon is increased, the voltage input to the dimming control circuit 61 increases, and the dimming control circuit 61 shortens the period during which the transistor Q61 is on, and causes the fluorescent lamp 64 to supply a current to the fluorescent lamp 64. Operates to reduce the period during which the current flows.

At this time, the ratio between the period in which the fluorescent lamp 64 is turned on and the period in which the fluorescent lamp 64 is turned off is changed between the high level period and the low level period of the dimming control circuit output signal shown in FIG. This makes it possible to adjust the ratio between the period in which the fluorescent lamp 64 is turned on and the period in which the fluorescent lamp 64 is turned off, to change the brightness of the backlight of the liquid crystal, and to widen the dimming range.

In the circuit shown in FIG. 6, a voltage input to the inverter circuit is extracted as a voltage divided by resistors R65 and R66, and the detected voltage is input to an input voltage control circuit 62. As shown in FIG. 7B, the input voltage control circuit 62 outputs an on / off signal for controlling the duty of the transistor Q61 at twice the oscillation frequency of the inverter circuit by this voltage, and outputs the on / off signal of the transistor Q61. By controlling the ratio between the period and the off period, the voltage input to the inverter circuit is limited to a preset value.

As described above, in the circuit shown in FIG. 6, two signals output from the dimming control circuit 61 and the input voltage control circuit 62 are logically ORed by the logic circuit 63 to provide two different control signals. Can be controlled only by the transistor Q61.

[0016]

In a digital camera or the like, it is important to extend the use time of a battery, and a flat lamp dimming used as a backlight of a small liquid crystal display panel mounted on the battery is important. It is required to reduce power consumption. In addition, there is a demand for dimming a flat lamp, such as adjusting the brightness of a backlight when the ambient brightness is different, such as when the weather is fine and at night.

However, the above-mentioned Japanese Patent Application Laid-Open No. 11-122
The dimming method disclosed in Japanese Patent No. 937 is a dimming method in which a fluorescent lamp other than a flat lamp is strengthened against power supply voltage fluctuations, and cannot be used for a flat lamp for a backlight.

Further, a dimming method in which the brightness of the flat lamp is changed by raising and lowering the voltage value of the power supply voltage, and changing the brightness of the flat lamp by changing the high level period of the pulse of the pulse lighting signal of the flat lamp. In particular, the use of a flat lamp for a backlight used in a small (about 1.8 to 2.0 inch) liquid crystal display panel mounted on a digital still camera or the like is considered. The power could not be reduced to about 0.4 W or less by the above two dimming methods.

The reason for this is that the above two dimming schemes are not effective.
This is because if the power consumption is reduced to about 4 W or less, the lighting performance of the flat lamp is deteriorated, and the four corners of the light emitting surface of the flat lamp are darkened, and the uniformity as a backlight is reduced.

In addition, the brightness adjustment range which can be achieved by the above two methods is limited to only a small range of 50% to 100%, and is 50% or less while maintaining the lighting stability of the flat lamp. Could not be achieved.

The present invention has been made in view of the above-mentioned problems, and is particularly directed to a small (about 1.8 to 2.0 inch) liquid crystal display panel mounted on a digital still camera or the like. Provided is a flat lamp dimming device capable of expanding the dimming range of a flat lamp used for a backlight, reducing power consumption, and performing dimming without impairing lighting stability of the flat lamp. With the goal.

[0022]

In order to solve the above-mentioned problems, a dimming device for a flat lamp according to the present invention provides a power supply voltage supplied from a power supply unit to a flat lamp unit via an inverter unit. In the dimming device for a flat lamp to be supplied, a pulse lighting signal and a duty signal output from a duty signal generating circuit are ANDed to turn on / off a power supply voltage with respect to the inverter unit. A duty control circuit for supplying a duty pulse lighting signal is provided, and the flat lamp is driven by the flat lamp driving voltage output from the inverter unit.

With such a configuration, dimming can be performed without deteriorating the stability and uniformity of lighting of the flat lamp, and the dimming range of the flat lamp can be widened. Thus, low power consumption can be realized (claim 1).

Further, by controlling the frequency and / or duty ratio of the duty signal (the ratio of the high level in one cycle of the duty signal), dimming for changing the brightness of the flat lamp can be performed ( Claim 2).

Further, the frequency of the duty signal is 100 Hz to 1000 Hz, and the duty ratio (the ratio of the high level in one cycle of the duty signal) is 10%.
The light control range of the flat lamp is 10% to 100%, which is a practical light control range in which the luminance can be changed according to the surrounding brightness.
(Claim 3).

The flat lamp is used for a backlight of a liquid crystal display panel, and the pulse lighting signal is a signal synchronized with a horizontal synchronizing signal of a video signal for the liquid crystal display panel. When the dimming range for changing the luminance of the backlight is increased in accordance with the change in the brightness, it is possible to prevent the four corners of the liquid crystal display panel from becoming dark. Further, the lighting signal for the inverter unit can be shared with the video signal for the liquid crystal display, and switching noise or the like caused by turning on and off the inverter unit affects the operation of the liquid crystal drive circuit, causing the liquid crystal display panel to malfunction. Can be prevented (claim 4).

The frequency of a signal synchronized with the horizontal synchronizing signal of the liquid crystal display panel by the lighting pulse of the inverter unit is set to 15.7 KHz.

[0028] In addition, a duty pulse lighting signal is generated in which a pulse signal that is turned on / off at a predetermined cycle is continuously supplied by a first number and then is continuously stopped by a second number. By supplying a driving voltage to the flat lamp in response to the duty pulse lighting signal, by continuing a first number of pulses,
The flat lamp can be reliably turned on.
By stopping the supply of the number of pulses, the visibility does not decrease due to the afterglow of fluorescent light and the afterimage even when the flat lamp is turned off. Then, by repeating these operations, stable lighting and dimming of the flat lamp can be performed (claim 6).

When the first number is 10, the flat lamp can be reliably turned on.

When the frequency of the duty pulse lighting signal is 100 Hz or more, the flat lamp can be seen to be lighted constantly. In addition, when the frequency is 1000 Hz or less, the discharge in the flat lamp can be stabilized (claim 8).

The duty pulse lighting signal is obtained by taking the logical product of the pulse lighting signal of the predetermined cycle and the duty signal of a cycle longer than the predetermined cycle, so that the waveform after the logical product is obtained. Since the duty pulse lighting signal can be generated without disturbing the pulse waveform of the pulse lighting signal having a predetermined period, the discharge in the flat lamp can be stabilized (claim 9).

[0032]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A dimming device for a flat lamp according to an embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a block diagram of a dimming device for a flat lamp according to an embodiment of the present invention.

As shown in FIG. 1, a flat lamp dimming apparatus 1 according to the present embodiment supplies a power supply voltage 8 supplied from a power supply section 5 to an inverter unit section 2 and outputs the output plane voltage. The lamp driving voltage 11 is supplied to the flat lamp unit 3.

Further, a duty control circuit 4 for controlling the inverter unit 2 is provided. The duty control circuit 4 receives the pulse lighting signal 6 and the duty signal 7 output from the duty signal generating circuit 9, and sends a duty pulse lighting signal 10, which is the logical product of these signals, to the inverter unit 2. It is configured to output.

By controlling the frequency and / or duty ratio (the ratio of the high level in one cycle of the duty signal) of the duty signal 7 input to the duty control circuit 4, for example, the pulse lighting signal 6
A duty pulse lighting signal 10 is output, which is turned on / off by a duty signal 7, and the power supplied to the inverter unit 2 is controlled, so that the brightness of the flat lamp unit 3 can be adjusted over a wide range. Can be done.

Next, the operation of the light control device for a flat lamp according to this embodiment will be described.

FIG. 2 is a waveform diagram for explaining the operation of the dimming device for a flat lamp according to one embodiment of the present invention, in which (a) a pulse lighting signal 6, (b) a duty signal 7, (b). c) Duty pulse lighting signal 10.

The waveform shown in FIG. 2A is a pulse lighting signal 6, which is a pulse signal that becomes a source of a lighting pulse of a flat lamp by repeating a pulse having the same width at a constant pulse cycle. This pulse signal is synchronized with the liquid crystal display panel, for example, at 15.7 KHz.

The waveform shown in FIG. 2B is the duty signal 7 which is the output of the duty signal generating circuit 9 shown in FIG. This signal repeats a level and a low level.

Further, the waveform shown in FIG. 2C is a duty pulse lighting signal 10, which is the pulse lighting signal 6 shown in FIG. 2A and the duty signal shown in FIG. This is a signal obtained by taking a logical product of the logical product of the logical product of FIG.

By adjusting the high-level period of the duty signal 7 as shown in FIG.
The generation period of the lighting pulse of the duty pulse lighting signal 10 which is the output signal of the duty control circuit 4 is adjusted as shown in FIG. 2 (c), and the duty pulse lighting signal 10 is input to the inverter unit 2 and A switching element such as a transistor constituting the unit unit 2 is turned on / off to control a period during which the flat lamp unit 3 is turned on, and power supplied to the flat lamp is adjusted.

Preferably, in the high-level period of the duty signal 7, at least ten or more pulses of the pulse lighting signal 6 continue, more preferably, about 10 to 30 pulses continue. , The duty signal 7 needs to be set.

Preferably, the duty signal 7 must be set so that, after 10 or more pulses continue during the high level period of the duty signal 7, 90 or less pulses are not output during the low level period. There is.

As described above, by making ten or more pulses continuous during the high level period of the duty signal 7, the flat lamp can be reliably turned on.
If the number of pulses not output during the low level period is 90 or less, even if the flat lamp is turned off, there is almost no reduction in visibility due to afterglow of fluorescent light and afterimage.

The duty signal 7 has a frequency of 100 Hz
A frequency of 1000 Hz is used.

This is because if the duty signal 7 is less than 100 Hz, the period during which the duty signal 7 is at the low level becomes longer, and as a result, the duty pulse lighting signal 10 for lighting the flat lamp has a low level with no pulse. Becomes longer, and the time during which the flat lamp is turned off becomes longer. Therefore, the light cannot be compensated for by the afterglow and the afterimage phenomenon. For this reason, the duty signal 7 is set to 100 Hz or more so that the flat lamp appears to be lit constantly.

On the other hand, if the frequency exceeds 1000 Hz, the frequency of the duty signal 7 and the pulse lighting signal 6 becomes close to each other. This is because the number of generated ON pulses of the pulse lighting signal 6 becomes less than ten, the waveform for driving the flat lamp when viewed microscopically is disturbed, and the discharge in the flat lamp becomes unstable. .

Therefore, the duty signal 7 is set to 1000 Hz or less in order to perform sufficient dimming of the flat lamp.

The duty ratio (the ratio of the high level in one cycle of the duty signal) is 10% to 1%.
Use in the range of 00%.

If the duty signal 7 is less than 10%, the low-level period of the duty signal 7 is longer than the high-level period during one cycle, and as a result, the duty signal 7 appears during the high-level period of the duty signal 7. This is because the number of lighting pulses of the duty pulse lighting signal 10 that is generated becomes extremely small, and the stability of the flat lamp deteriorates.

Therefore, in order to perform dimming while maintaining stable lighting of the flat lamp, the duty signal 7 is set to 10%.
Above.

As shown in FIG. 2C, the duty pulse lighting signal 10 formed as described above has more OFF periods than ON periods when viewed from the entire waveform. Since the power supplied to the flat lamp is extremely small, low power consumption is achieved, and the frequency of the duty signal is 100 Hz to 1000 Hz, the afterimage phenomenon occurs even if there are many off periods. Due to the effect of (1), the lighting state of the flat lamp seems to be kept constant to human eyes, so that the function as a backlight is sufficient.

As described above, the duty control circuit 4 is provided for controlling the inverter unit 2, and the switching elements constituting the inverter unit 2 are turned on and off in accordance with the duty ratio, thereby providing the flat lamp. Dimming range can be in the range of 10% to 100%,
Stable and uniform lighting is possible with low power consumption of about 0.1 W.

Next, a circuit example of the dimming device for a flat lamp according to this embodiment will be described with reference to FIGS.

FIG. 3 is a circuit example of a dimming device for a flat lamp according to an embodiment of the present invention.

FIG. 4 is a waveform diagram for explaining the cycle and width of the pulse of the pulse lighting signal.

As shown in FIG. 3, the flat lamp FL1 constituting the flat lamp unit 3 is composed of a transistor Q2, a FET Q1 and a transformer T1 in the inverter unit 2 for supplying power to the flat lamp FL1. It is lit by an inverter circuit (lighting circuit).

The duty pulse lighting signal 10 is inputted to the base terminal of the transistor Q2 via the capacitor C1 and the resistor R1. The duty pulse lighting signal 10 is an output of the AND gate AN1 in the duty control circuit 4. The input terminal of the AND gate AN1 has a pulse lighting signal 6 input from outside the dimming device of the flat lamp and the duty signal. The duty signal 7 output from the signal generation circuit 9 is input.

The duty signal generation circuit 9 includes the oscillation unit 1
2 and a duty section 13. The oscillating unit 13 adjusts the variable resistor R4 so that the frequency ranges from 100 Hz to 1 Hz.
It is an oscillator that oscillates a signal of 000 Hz.

The duty section 13 has a variable resistor R
5, the duty ratio (the ratio of the high level within one cycle of the duty signal 7) is 10% to 1%.
It is configured so that it can be adjusted to 00%. In the figure,
R2 and R3 are resistors, C2 to C5 are capacitors, N1 to N
4 is a NOT circuit, and FF1 is a flip-flop circuit.

FIG. 4 shows an example of a lighting pulse for one cycle of the pulse lighting signal 6 inputted from outside of the dimming device for a flat lamp. It will be described with reference to FIG.

As shown in FIG. 4, the lighting pulse is a rectangular pulse having a fixed period. Under a standard lighting condition, when the high level of the pulse is 5V and the low level is 0V, the pulse period is 63.5 μs, and the high level width of the pulse is given in 5.25 μs. The input voltage Vcc at this time is + 6V.

Generally, a lighting pulse for lighting a flat lamp is a pulse synchronized with a horizontal synchronization signal (frequency 15.7 KHz) of a liquid crystal display panel. Therefore, the cycle of the lighting pulse is 63.5 μs (frequency 15.7 KHz)
It is. The high level width of the pulse is about 4 to 10 μs.

In the dimming device for a flat lamp according to the embodiment of the present invention, the frequency of the duty signal ranges from 100 Hz to 1 Hz.
000 Hz, which is sufficiently lower than the above-mentioned lighting pulse frequency of the flat lamp of 15.7 KHz. Therefore, when the dimming device for a flat lamp according to the embodiment of the present invention is applied to the above-described flat lamp, the stability of the discharge in the flat lamp is not impaired.

In the above embodiment, an example in which the duty control circuit is connected in parallel with the power supply has been described. However, for example, the duty control circuit is connected in series between the power supply unit 5 and the inverter unit 2. Various embodiments may be employed within the technical scope of the present invention.

[0067]

According to the first aspect of the present invention, the power supply voltage supplied from the power supply unit is changed via the inverter unit.
In a dimming device for a flat lamp to be supplied to a flat lamp unit, a power supply voltage is turned on / off for the inverter unit by taking a logical product of a pulse lighting signal and a duty signal output from a duty signal generating circuit. By providing a duty control circuit for supplying a duty pulse lighting signal for turning off the flat lamp, the flat lamp is driven by the flat lamp driving voltage output from the inverter unit. Provided is a dimming device for a flat lamp which can perform dimming without deteriorating the stability and uniformity of the flat lamp, can widen the dimming range of the flat lamp, and can realize low power consumption. You can do it.

According to the second aspect of the present invention, by controlling the frequency and / or the duty ratio of the duty signal (the ratio of the high level in one cycle of the signal), the dimming for changing the luminance of the flat lamp is performed. The present invention can provide a dimming device for a flat lamp that can be used.

According to the third aspect of the present invention, the frequency of the duty signal is 100 Hz to 1000 Hz, and the duty ratio (the ratio of the high level in one cycle of the signal) is one.
By setting the range of 0% to 100%, the dimming range of the flat lamp is 10% to 10%, which is a practical dimming range in which the luminance can be changed according to the surrounding brightness.
It is possible to provide a dimming device for a flat lamp that can be extended to 0%, can achieve low power consumption of about 0.1 W, and can perform dimming while maintaining stable and uniform lighting. is there.

According to the fourth and fifth aspects of the present invention, the flat lamp is used for a backlight of a liquid crystal display panel, and the pulse lighting signal is a signal synchronized with a horizontal synchronizing signal of a video signal for the liquid crystal display panel. Preferably, by setting the frequency to 15.7 KHz, the four corners of the liquid crystal display panel become dark when the dimming range for changing the luminance of the backlight is widened according to the change in the brightness around the liquid crystal display panel. In addition, the lighting signal for the inverter unit can be shared with the video signal for the liquid crystal display, and the control pulse can be made to exist within the horizontal blanking period.
An object of the present invention is to provide a dimming device for a flat lamp, which can prevent a switching noise or the like caused by turning off from affecting the operation of a liquid crystal driving circuit and causing a malfunction of a liquid crystal display panel.

According to the sixth aspect of the present invention, a duty pulse which repeats a continuous supply of a pulse signal which is turned on / off at a predetermined cycle by a first number and then continuously stops the supply by a second number. By generating a lighting signal and supplying a driving voltage to the flat lamp according to the duty pulse lighting signal, the first number of pulses can be made continuous to reliably light the flat lamp. In addition, by stopping the supply of the second number of pulses, the visibility does not decrease due to the afterglow of fluorescent light and the afterimage even when the flat lamp is turned off. By repeating these operations, a flat lamp dimming device capable of performing stable lighting and dimming of the flat lamp can be provided.

By setting the first number to 10, it is possible to provide a dimming device for a flat lamp that can reliably light the lamp.

When the frequency of the duty pulse lighting signal is 100 Hz or more, the flat lamp can be seen to be lit constantly. Further, when the frequency is 1000 Hz or less, a dimming device for a flat lamp that can stabilize the discharge in the lamp can be provided.

The duty pulse lighting signal is obtained by taking the logical product of the pulse lighting signal of the predetermined cycle and the duty signal of a cycle longer than the predetermined cycle, so that the waveform after the logical product is obtained. Since the duty pulse lighting signal can be generated without disturbing the pulse waveform of the pulse lighting signal having a predetermined period, it is possible to provide a flat lamp dimming device capable of stabilizing the discharge in the flat lamp. .

As described above, according to the present invention, the dimming range of a flat lamp for a backlight used in a small (about 1.8 to 2.0 inch) liquid crystal display panel mounted on a digital still camera or the like. It is possible to provide a dimming device for a flat lamp which can reduce the power consumption, and can perform dimming without deteriorating the stability of lighting of the flat lamp.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a flat lamp dimming device according to an embodiment of the present invention.

FIG. 2 is a waveform chart for explaining the operation of FIG.

FIG. 3 is a circuit example of a dimmer of the flat lamp according to the embodiment of the present invention.

FIG. 4 is a waveform diagram illustrating a pulse cycle and width of a pulse lighting signal of the flat lamp dimming device according to the embodiment of the present invention.

FIG. 5 is a diagram showing a basic lighting circuit of a conventional flat lamp.

FIG. 6 is a backlight control circuit diagram of a liquid crystal display device using a fluorescent lamp other than the conventional flat lamp.

FIG. 7 is a waveform chart for explaining the operation of FIG. 6;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Dimming device of flat lamp 2 Inverter unit part 3 Flat lamp part 4 Duty control circuit 5 Power supply part 6 Pulse lighting signal 7 Duty signal 8 Power supply voltage 9 Duty signal generation circuit 10 Duty pulse lighting signal 11 Flat lamp driving voltage 12 (Duty Oscillator 13 of the signal generating circuit Duty section of the duty signal generating circuit

Claims (9)

[Claims] 1. A flat lamp dimmer for supplying a power supply voltage supplied from a power supply unit to a flat lamp unit via an inverter unit unit, wherein a pulse lighting signal and a duty output from a duty signal generating circuit are provided. By taking the logical product with the signal,
A duty control circuit for supplying a duty pulse lighting signal for turning on / off a power supply voltage is provided to the inverter unit, and the flat lamp is driven by the flat lamp driving voltage output from the inverter unit. A dimming device for a flat lamp, wherein the dimming device is configured as described above. 2. The frequency of the duty signal and / or
2. The dimming device for a flat lamp according to claim 1, wherein a duty ratio (a ratio of a high level in one cycle of the duty signal) is controlled. 3. The frequency of the duty signal is 100.
Hz to 1000 Hz, and the duty ratio (the ratio of the high level in one cycle of the duty signal) is 10% to 10%.
The dimming device for a flat lamp according to claim 2, wherein the range is 0%. 4. The liquid crystal display panel according to claim 3, wherein the flat lamp is used for a backlight of a liquid crystal display panel, and the pulse lighting signal is a signal synchronized with a horizontal synchronization signal of a video signal for the liquid crystal display panel. Dimming device for flat lamp. 5. The frequency of the pulse lighting signal is 15.7.
The dimmer of a flat lamp according to claim 4, wherein the frequency is KHz. 6. A dimming device for a flat lamp, which controls a driving voltage supplied to the flat lamp unit to control the brightness of the flat lamp, wherein a pulse signal which is turned on / off at a predetermined cycle is a first number. Generating a duty pulse lighting signal that repeats continuously stopping the supply with a second number after supplying continuously, and supplying a driving voltage to the flat lamp according to the duty pulse lighting signal. The dimming device for a flat lamp according to claim 7, wherein 7. The dimmer of a flat lamp according to claim 6, wherein the first number is ten. 8. The dimming device for a flat lamp according to claim 7, wherein a frequency of the duty pulse lighting signal is 100 Hz or more and 1000 Hz or less. 9. The duty pulse lighting signal according to claim 7, wherein the duty pulse lighting signal is obtained by taking a logical product of the pulse lighting signal having the predetermined cycle and a duty signal having a cycle longer than the predetermined cycle. Dimming device for flat lamp.