KR100915356B1 - An inverter apparatus for a liquid crystal display - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for a liquid crystal display device which controls the brightness of a lamp provided on the rear surface of a liquid crystal panel according to the lighting duty ratio of the lamp.

Inverter device according to the invention, triangular wave generating means for generating a triangular wave signal by periodically repeating the charging and discharging; Triangular wave resetting means for resetting the triangular wave generation of the triangular wave generating means each time a vertical start signal is input; And comparison means for generating a pulse width modulated signal having a predetermined on / off duty ratio by comparing the triangle wave signal generated by the triangle wave generator and the dimming signal.

In the above-described inverter device for liquid crystal display device of the present invention, the triangle wave reset means resets the generation time of the triangle wave whenever the vertical start signal is input, so that the comparison means is applied to the vertical start signal whenever a pulse of the vertical start signal is generated. By synchronizing to generate a pulse width modulated signal having a predetermined on / off duty ratio, as a result, the drive frequency of the ramp drive signal produced using the pulse width modulated signal can be synchronized to the timing of the vertical start signal. Therefore, the beat phenomenon due to the difference between the frequency of the vertical start signal and the driving frequency of the ramp can be eliminated.

Description

Inverter device for liquid crystal display device {AN INVERTER APPARATUS FOR A LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an inverter device for a liquid crystal display device, and more particularly, to an inverter device for controlling the brightness of a lamp installed on a rear surface of a liquid crystal panel according to a lighting duty ratio of a lamp. The present invention relates to an inverter device that generates a pulse width modulation (PWM) signal by synchronizing with the timing of the signal and causes the lamp to be turned on in accordance with the pulse width modulation signal.

Recently, in the field of display devices such as personal computers and televisions, large screens, light weights, and thinners are required. In order to satisfy such demands, a liquid crystal display (LCD) is used instead of a cathode-ray tube (CRT). Flat panel displays, such as liquid crystal displays, have been developed and put into practical use in fields such as desktop computers, liquid crystal televisions, and the like.

The panel of the liquid crystal display device includes a substrate on which a pixel pattern is formed in a matrix form and a substrate opposite thereto. A liquid crystal material having an anisotropic dielectric constant is injected between the two substrates. An electric field is applied between the two substrates, and by adjusting the intensity of the electric field, the amount of light passing through the substrate is controlled to display a desired image.

Such a liquid crystal display device is not a self-luminous display device, and is configured such that a lamp provided on the rear surface of the liquid crystal panel operates as a light source.

As a high display quality is required in a liquid crystal display, a dimming function for adjusting the brightness of the lamp is required as needed. This dimming function is particularly useful for displaying movies. In order to adjust the brightness of the lamp, a method of changing the intensity of the current flowing through the lamp and a method of changing the on / off duty ratio of the current while keeping the magnitude of the lamp current constant are possible. Do. The former method has a problem in that when the luminance is required for the lamp, the magnitude of the current supplied to the lamp becomes small, so that the lighting of the lamp is very unstable and the lamp is easily turned off. On the other hand, the latter method can easily control the amount of light, that is, the brightness of the lamp by adjusting the duty ratio of the on / off period.

However, in the latter method, when the on / off duty ratio does not exactly match an integer multiple of the frame frequency, which is the display driving frequency of the liquid crystal panel, a "water fall" in which the splatter slowly rises or falls in the vertical direction of the screen. Phenomenon occurs. For example, if the frame frequency is 60 Hz and the on / off duty ratio of the lamp current is 65 Hz, horizontal smears moving on the screen occur at 5 Hz, the difference between these two frequencies. In very extreme cases, horizontal smearing occurs even if the difference is 0.1 Hz. Although the horizontal smear moves on the screen at 0.1Hz, it can be identified by the human eye.

Therefore, in the conventional liquid crystal display device, there is a problem in that a horizontal spot is generated because the phase between the frame frequency of the screen and the on / off lighting frequency of the lamp does not exactly match.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described technical problem, and provides an inverter device for a liquid crystal display device which controls brightness of a lamp by adjusting an on / off frequency of a lamp driving current, and in particular, a timing controller. An object of the present invention is to provide an inverter device for a liquid crystal display device in which a pulse width modulated signal for deciding on / off of a lamp is synchronized according to a vertical start signal outputted from the.

Inverter device for a liquid crystal display device of the present invention for achieving the above object,

Triangular wave generating means for generating a triangular wave signal by periodically repeating charging and discharging;

Triangular wave resetting means for resetting the triangular wave generation of the triangular wave generating means each time a vertical start signal is input; And,

And comparison means for generating a pulse width modulated signal having a predetermined on / off duty ratio by comparing the triangular wave signal generated by the triangular wave generating means with a dimming signal.

In the above-described inverter device for liquid crystal display device of the present invention, the triangle wave reset means resets the generation time of the triangle wave whenever the vertical start signal is input, so that the comparison means is applied to the vertical start signal whenever a pulse of the vertical start signal is generated. By synchronizing to generate a pulse width modulated signal having a predetermined on / off duty ratio, as a result, the drive frequency of the ramp drive signal produced using the pulse width modulated signal can be synchronized to the timing of the vertical start signal. Therefore, the beat phenomenon due to the difference between the frequency of the vertical start signal and the driving frequency of the ramp can be eliminated.

The objects, technical configurations, and effects thereof of the present invention described above will become more apparent from the following description of the embodiments.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.

Before explaining this invention, the panel structure of the liquid crystal display device to which the inverter device of this invention is applied is demonstrated. 1 is a view schematically showing a panel structure of a liquid crystal display device to which an inverter device of the present invention is applied, and an edge light emitting method in which a lamp is installed at an edge of a panel is used in the panel structure.

Referring to FIG. 1, the liquid crystal display device 900 to which the present invention is applied includes a liquid crystal display module 700 for displaying an image on a screen according to an applied image signal, and a housing of the liquid crystal display module 700. It consists of a front case 810 and a rear case 820. The liquid crystal display module 700 includes a display unit 710 including a screen for displaying an image.

The display unit 710 includes a liquid crystal display panel 712, a data side printed circuit board 714, a gate side printed circuit board 719, and a data side tape carrier package (TCP). 716 and gate-side TCP 718.

The liquid crystal display panel 712 includes a thin film transistor substrate 712a, a color filter substrate 712b, and a liquid crystal (not shown), and displays an image on a screen according to an image signal.

More specifically, the thin film transistor substrate 712a is a transparent glass substrate on which a thin film transistor in a matrix form is formed. The data line is connected to the source terminal of the thin film transistor, and the gate line is connected to the gate terminal. In addition, a pixel electrode made of indium tin oxide (ITO), which is a transparent conductive material, is formed in the drain terminal. When an electrical signal is input to the data line and the gate line, an electrical signal is input to a source terminal and a gate terminal of each thin film transistor, and the thin film transistor is turned on or turned off according to the input of the electrical signal, thereby draining the drain terminal. The furnace outputs an electrical signal for the display operation of the pixel.

The color filter substrate 712b is provided to face the thin film transistor substrate 712a. The color filter substrate 712b is a substrate in which an RGB pixel, which is a color pixel for displaying a predetermined color as light passes, is formed by a thin film process. The front surface of the color filter substrate 712b is coated with a common electrode made of ITO.

When power is applied to the gate terminal and the source terminal of the thin film transistor formed on the thin film transistor substrate 712a and the thin film transistor is turned on, an electric field is formed between the pixel electrode and the common electrode of the color filter substrate. By the electric field, the arrangement angle of the liquid crystal injected between the thin film transistor substrate 712a and the color filter substrate 712b is changed, and the light transmittance is changed according to the changed arrangement angle to obtain a desired image and luminance.

In the liquid crystal display panel 712, a driving signal and a timing signal are applied to the gate line and the data line of the thin film transistor to control the arrangement angle of the liquid crystal and the timing of the liquid crystal. As shown in the figure, one side of the liquid crystal display panel 712 is attached with a data side TCP 716, which is a type of flexible circuit board that determines the timing of applying the data driving signal, and the other side of the liquid crystal display panel 712 has a timing of applying the gate driving signal. A gate side TCP 718 is attached, which is a type of flexible circuit board for determining.

The data side printed circuit board 714 and the gate side printed circuit board 719 receive an image signal from the outside of the liquid crystal display panel 712 and apply driving signals to the gate line and the data line, respectively, and the liquid crystal display panel 712. Are connected to data TCP 716 on the data line side and gate TCP 718 on the gate line side, respectively.

The data side printed circuit board 714 is provided with a source portion for receiving a video signal generated from an external information processing apparatus (not shown) such as a computer and providing a data driving signal to the liquid crystal display panel 712. A gate portion for providing a gate driving signal to a gate line of the liquid crystal display panel 712 is formed on the gate side printed circuit board 719.

That is, the data side printed circuit board 714 and the gate side printed circuit board 719 may include a gate driving signal, a signal for driving the liquid crystal display, a data signal, and a plurality of timing signals for applying these signals at an appropriate time. Generate. The gate driving signal is applied to the gate line of the liquid crystal display panel 712 through the gate side TCP 718, and the data signal is applied to the data line of the liquid crystal display panel 712 through the data TCP 716.

The backlight unit 720 is provided below the display unit 710 to provide uniform light to the display unit 710. The backlight assembly 720 includes first and second lamp parts 723 and 725 provided at both ends of the liquid crystal display module 700 to generate light. The first and second lamp parts 723 and 725 are composed of first and second lamps 723a and 723b and third and fourth lamps 725a and 725b, respectively. 722a and 722b, respectively.

The light guide plate 724 has a size corresponding to that of the liquid crystal display panel 712 of the display unit 710, and is disposed below the liquid crystal display panel 712 to be generated in the first and second lamp units 723 and 725. The light path is changed while guiding the light to the display unit 710.

The light guide plate 724 has an edge shape with a uniform thickness, and the first and second lamp parts 723 and 725 are installed at both ends of the light guide plate 724 to increase light efficiency. The number of lamps of the first and second lamp units 723 and 725 may be appropriately arranged in consideration of the overall balance of the liquid crystal display device 900.

A plurality of optical sheets 726 are provided on the light guide plate 724 to uniform the luminance of light emitted from the light guide plate 724 and directed toward the liquid crystal display panel 712. In addition, a light reflector 728 is provided under the light guide plate 724 to reflect light leaking from the light guide plate 724 to the light guide plate 724 to increase light efficiency.

The display unit 710 and the backlight assembly 720 are fixedly supported by a mold frame 730 that is a storage container. The mold frame 730 has a box shape of a rectangular parallelepiped, and an upper surface thereof is opened.

Further, the data side printed circuit board 714 and the gate side printed circuit board 719 of the display unit 710 are fixed to the bottom surface of the mold frame 730 while being bent to the outside of the mold frame 730. A chassis 740 is provided to prevent 710 from being dislodged. The chassis 740 is opened to expose the liquid crystal display panel 710, and the sidewall portion is bent in an inner vertical direction to cover a periphery of the upper surface of the liquid crystal display panel 710.

An inverter device for a liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings. An inverter device according to an embodiment of the present invention is characterized in that a pulse width modulated signal is generated by synchronizing with a vertical start signal.

Hereinafter, an inverter device for a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIGS. 2 to 5.

2 illustrates the overall configuration of a liquid crystal display device to which an inverter device according to an embodiment of the present invention is applied.

As shown in FIG. 2, a liquid crystal display device to which an inverter device according to an exemplary embodiment of the present invention is applied includes a liquid crystal panel 10, a gate driver 20, a data driver 30, a lamp 40, and an inverter device ( 50, a voltage generator 60, and a timing controller 70.

The liquid crystal panel 10 includes a substrate on which a pixel pattern is formed, and a plurality of gate lines and a plurality of data lines perpendicular to the gate lines are formed on the substrate. Pixels are formed at the intersections. Each pixel is arranged in a matrix form. Each pixel includes a thin film transistor having a gate electrode and a source electrode connected to a gate line and a data line, and a pixel capacitor and a storage capacitor connected to a drain electrode of the thin film transistor. In such a pixel structure, when a gate voltage for sequentially selecting each gate line is applied by the gate driver 20, a thin film transistor of a pixel connected to the corresponding gate line is turned on, and then each data driver 30 is turned on by the data driver 30. An image data voltage including pixel information is applied to the data line. This voltage is applied to the pixel capacitor and the sustain capacitor through the thin film transistor of the pixel, and these capacitors are driven to perform a predetermined display operation.

The timing controller 70 receives RGB image data (RGB data), vertical and horizontal sync signals (Vsync / Hsync), and a clock signal (CLK) input from an external graphic source (not shown). Basically, the timing controller 70 converts the format of the input RGB image data to match the data format required by the data driver 30, and controls the liquid crystal panel 10. In order to drive, a control signal to be used in the gate driver 20 and the data driver 30 is generated and output. In addition, the timing controller 70 outputs a vertical start signal (STV) to the inverter device 50.

The voltage generator 60 generates and outputs a gray voltage Vgray and a gate voltage Vgate, which are voltages that are actually applied to the data line and the gate line of the liquid crystal panel 10. Here, the gray voltage Vgray has a plurality of voltage levels and is transmitted to the data driver 30. The gate voltage Vgate includes a gate on voltage and a gate off voltage, and is transmitted to the gate driver 20.

The gate driver 20 includes a plurality of gate driver ICs (not shown) each responsible for a predetermined number of gate lines on the liquid crystal panel 10, and a control signal CONT provided from the timing controller 70. And gate lines on the liquid crystal panel 10 are sequentially scanned in units of one horizontal scanning period by using the gate voltage Vgate provided from the voltage generator 60. For example, the gate driver 20 applies a gate-on voltage to the gate line to be scanned and a gate-off voltage to the remaining gate lines, and the application time of the gate-on voltage is one horizontal scanning period. This scanning process is performed sequentially for all gate lines.

The data driver 30 includes a plurality of data driver ICs (not shown) each responsible for a predetermined number of data lines on the liquid crystal panel 10. The data driver 30 sequentially latches the RGB image data (RGB data) supplied from the timing controller 70 to change the data sequence of the point sequential method to a line sequential method, and to adjust the gradation for each image data. The voltage Vgray is selected, and the selected voltages are applied as image data voltages to each data line on the liquid crystal panel 10 in units of one horizontal scanning period. One screen, that is, a frame, is divided by a pulse of the vertical start signal STV, and the above-described operation in the data driver 30 is continuously performed for one frame in units of one horizontal scanning period. This operation is also repeated for every frame.

The inverter device 50 generates a lamp driving signal using a dimming signal Vdim and a vertical start signal STV output from the timing controller 70, and the lamp driving signal is a rear surface of the liquid crystal panel 10. It controls the light emission of the lamp 40 installed in. The dimming signal Vdim may be provided by the timing controller 70 or may be provided by an external display-related peripheral board. In the embodiment of the present invention, it is assumed that the dimming signal Vdim is provided from an external peripheral board, but the technical scope of the present invention is not limited thereto. The lamp driving signal has a turn-on and turn-off period, and in the inverter device of the present invention, the amount of light, that is, brightness, of the lamp 40 may be controlled by adjusting an on / off period duty ratio of the lamp driving signal. The on / off duty ratio of the ramp driving signal is determined by the pulse width modulation signal PWM generated using the dimming signal Vdim and the vertical start signal STV. In the inverter device 50 of the present invention described above, whenever a pulse of the vertical start signal STV indicating the start of one frame occurs, the generation of a triangular wave which is a reference signal for generating the pulse width modulated signal PWM is reset. In this way, a pulse width modulated signal synchronized with the timing of the vertical start signal is generated, and the driving of the lamp is controlled by the pulse width modulated signal so that the driving frequency of the lamp and the phase of the vertical start signal indicating the start of the frame are mutually different. It is characterized by the same thing.

Next, a more detailed configuration and operation of the inverter device 50 will be described with reference to FIGS. 3 to 5.

FIG. 3 is a block diagram showing the configuration of the inverter device according to the embodiment of the present invention shown in FIG. 2, and FIG. 4 is a circuit diagram showing the actual implementation of the PWM signal generator shown in FIG. FIG. 5 shows waveforms of signals used in the circuit of FIG. 4.

As shown in FIG. 3, the inverter device 50 according to the embodiment of the present invention includes a PWM signal generator 51, a power driver 52, and a booster 53. The PWM signal generator 51 receives a vertical start signal STV from the timing controller 70, receives a dimming signal Vdim from an external peripheral circuit, and has a PWM signal having a predetermined on / off duty ratio. Create More specifically, the PWM signal generating unit 51 generates a triangular wave signal, and compares the triangular wave signal with the dimming signal Vdim to generate an on level in a section in which the triangular wave signal is larger than the dimming signal Vdim and the triangular wave. In an interval where the signal is smaller than the dimming signal Vdim, an off level is generated to generate a PWM signal having a predetermined on / off duty ratio. At this time, whenever the pulse of the vertical start signal STV occurs, the generation of the triangular wave of the triangular wave signal is reset so that the PWM signal can be synchronized with the timing of the vertical start signal STV.

The PWM signal is output to the power driver 52, and the power driver 52 switches a DC power on / off during the turn-on period of the PWM signal to generate a signal having an on / off level. The signal is output to the booster 53, and the booster 53 generates a sinusoidal signal according to the on / off signal. In addition, the booster 53 converts the voltage of the generated sinusoidal signal into a high voltage by a transformer included therein, and converts the converted high voltage sinusoidal signal as a lamp driving signal into the lamp 40. To apply.

Referring to FIG. 4, a circuit in which the PWM signal generator 51 is actually implemented is shown.

In Fig. 4, transistors Q1 and Q2 operate as switching elements and operational amplifiers OP1 and OP2 operate as comparators. The power supply voltage VCC is a positive voltage, and the power supply voltage VEE is a negative voltage. The capacitor C1 repeats charging and discharging, and a triangular wave signal is generated through the voltage Vcap of the output node by repeated charging and discharging. The vertical start signal STV is input to the base of the transistor Q2 via the resistors R6 and R5, the emitter of the transistor Q2 is connected to ground and the collector is passed through the resistors R3 and R2. It is connected to the base of transistor Q1. The emitter of the transistor Q1 is connected to the power supply voltage VCC and the collector is connected to the capacitor C1. In addition, a power supply voltage VEE is connected to the capacitor C1 via a resistor R7. The voltage Vcap of the output node of the capacitor C1 is input to the (+) terminal of the operational amplifier OP2, and the dimming signal Vdim is input to the (-) terminal of the operational amplifier OP2. The resistors R8, R9 and R10 connected to the operational amplifier OP1 are for providing bias conditions, and the capacitors C3 and C2 are for removing noise components. The output signal of the operational amplifier OP1 is input to the base of the transistor Q1 via a resistor R4. Here, the transistor Q1 is a pnp bipolar type and the transistor Q2 is an npn bipolar type, but the technical scope of the present invention is not limited thereto, and it is possible to easily change the design by those skilled in the art.

The circuit of FIG. 4 is a transistor Q1, an operational amplifier OP1 and a capacitor C1 for generating a triangular wave signal, and a transistor for resetting generation of the triangular wave signal according to the vertical start signal STV. Q2 and an operational amplifier OP2 for generating a PWM signal by comparing the triangular wave signal and the dimming signal Vdim.

When the transistor Q1 is turned on by the initial condition, the power supply voltage VCC is applied to the capacitor C1 to charge the capacitor C1. The voltage Vcap of the output node is rapidly increased by the charging of the capacitor C1, and the operational amplifier OP1 compares the voltage Vcap with the initially set bias voltage so that the voltage Vcap is greater than or equal to a predetermined value. Increasing it will output a high level. The transistor Q1 is turned off by the high level output of the operational amplifier OP1, and the power supply voltage VCC is not applied to the capacitor C1. Therefore, the capacitor C1 discharges the charged energy toward the power supply voltage VEE, which is a negative voltage. When the voltage Vcap of the output node drops below a predetermined value due to the discharge of the capacitor C1, the operational amplifier OP1 outputs a low level, and the transistor Q1 is output by the low level output of the operational amplifier OP1. ) Is turned on. Therefore, the power supply voltage VCC is supplied to the capacitor C1, so that the capacitor C1 periodically charges and discharges. The output node voltage Vcap of the capacitor C1 is shown in FIG. 5 and represents a triangular wave. In addition, since the charge path and the discharge path of the capacitor C1 are configured differently, the rising and falling angles of the triangular wave are different from each other.

Meanwhile, as shown in FIG. 5, the vertical start signal STV generates one pulse per frame. When the pulse of the vertical start signal STV is input to the transistor Q2, the transistor Q2 is turned on, and its K potential is applied to the bay of the transistor Q1. Thus, the transistor Q1 is turned on and a power supply voltage VCC is applied to the capacitor C1. That is, each time the pulse of the vertical start signal STV is input, the capacitor C1 starts charging, and thus, the voltage Vcap of the output node starts generating a triangular wave.

The operational amplifier OP2 compares the dimming signal Vdim and the voltage Vcap of the output node of the capacitor C1 generating the triangular wave. As shown in FIG. 5, the voltage Vcap is a dimming signal ( High level is output in the section larger than Vdim, and low level is output in the other case. Accordingly, in the operational amplifier OP2, a PWM signal having a predetermined on / off duty ratio is obtained according to the dimming signal Vdim, and the PWM signal is synchronized by the vertical start signal STV.

As a result, in the inverter device according to the embodiment of the present invention, since the PWM signal is synchronized by the vertical start signal, and the lamp drive signal is generated by the PWM signal, the lamp drive frequency is exactly equal to the phase of the vertical start signal. Can be synchronized.

As described above, in the inverter device for a liquid crystal display of the present invention, by generating a triangle wave by using a vertical start signal, a PWM signal is synchronized to it every time a pulse of the vertical start signal is generated, thereby turning on / off a period. As a result, the driving frequency of the ramp drive signal can be synchronized to the timing of the vertical start signal. Therefore, the beat phenomenon due to the difference between the frequency of the vertical start signal and the driving frequency of the ramp can be eliminated.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

1 is a view schematically showing a panel structure of a liquid crystal display device to which an inverter device of the present invention is applied.

2 is a view showing the configuration of a liquid crystal display device to which the inverter device of the present invention is applied.

3 is a view showing in more detail the inverter device of the present invention shown in FIG.

4 is a diagram illustrating a detailed circuit of the PWM signal generation unit illustrated in FIG. 3.

5 is a view showing the waveform of the main signal used in the PWM signal generation unit of FIG.

(Explanation of symbols for the main parts of the drawing)

10 liquid crystal panel 20 gate driver

30: data driver 40: lamp

50: inverter device 60: voltage generator

70: timing controller 51: PWM signal generator

52: power drive unit 53: boosting unit

Claims (8)

Triangular wave generating means for generating a triangular wave signal by periodically repeating charging and discharging; Triangular wave resetting means for resetting the triangular wave generation of the triangular wave generating means each time a vertical start signal is input; And, A comparison means for generating a pulse width modulated signal having a predetermined on and off duty ratio by comparing a triangular wave signal generated by the triangular wave generating means with a dimming signal, And the triangle wave reset means is a second transistor that is turned on every time the vertical start signal is input. The method of claim 1, The triangle wave generating means A capacitor connected with a negative power supply voltage as a discharge path and providing a voltage of an output node to the comparing means; A first transistor configured to apply a positive power supply voltage to said capacitor when it is turned on; And, And a first operational amplifier to turn off the first transistor when the voltage of the output node of the capacitor is greater than or equal to a predetermined value, and to turn on the first transistor when less than or equal to the predetermined value. Inverter device for liquid crystal display device. The method of claim 2, When the second transistor is turned on to turn on the first transistor Inverter device for liquid crystal display device. The method of claim 3, The first transistor is pnp bipolar type and the second transistor is npn bipolar type Inverter device for liquid crystal display device. The method of claim 2, The charge path and the discharge path of the capacitor are configured differently Inverter device for liquid crystal display device. The method of claim 2, The comparison means A second operational amplifier configured to compare an output node voltage of the capacitor with a dimming signal and output a high level when the output node voltage is large and a low level when the output node voltage is small. Inverter device for liquid crystal display device. The method of claim 1, The vertical start signal is provided by a timing controller of the liquid crystal display, and the dimming signal is provided by a timing controller of the liquid crystal display or an external peripheral board. Inverter device for liquid crystal display device. Triangular wave generating means for generating a triangular wave signal by periodically repeating charging and discharging; Triangular wave resetting means for resetting the triangular wave generation of the triangular wave generating means each time a vertical start signal is input; Comparison means for generating a pulse width modulated signal having a predetermined on and off duty ratio by comparing a triangular wave signal generated by the triangular wave generating means with a dimming signal; A power driver for controlling the output of the DC power on and off in accordance with the pulse width modulation signal; And, A booster for converting the on and off signals into a high voltage by a transformer and applying the converted high voltage signal to the lamp as a lamp driving signal; Inverter device for liquid crystal display device.