KR101830610B1 - Driving circuit for liquid crystal display device and method for driving the same - Google Patents

Abstract

The present invention relates to a driving apparatus for a liquid crystal display device capable of improving the display quality by preventing a luminance difference from occurring between the upper and lower ends of a liquid crystal panel while reducing power consumption by inverting a common voltage level supplied to the liquid crystal panel, A liquid crystal display device comprising: a liquid crystal panel having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels; A gamma reference voltage generating unit for generating gamma reference voltages whose voltage levels are gradually changed for each frame by using a gradually increasing driving voltage for each frame; A data driver for driving the data lines of the liquid crystal panel using the gamma reference voltages whose voltage levels are variable; And a timing controller for aligning image data input from the outside and supplying the data to the data driver and generating a data control signal to control the data driver.

Description

TECHNICAL FIELD [0001] The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof. BACKGROUND OF THE INVENTION [0002]

The present invention relates to a liquid crystal display device, and more particularly to a liquid crystal display device capable of reducing a power consumption by inverting a common voltage level supplied to a liquid crystal panel and preventing a luminance difference between the upper and lower ends of the liquid crystal panel, To a driving apparatus for a liquid crystal display device and a driving method thereof.

A liquid crystal display device displays an image using electrical and optical characteristics of a liquid crystal. Liquid crystals can have different anisotropic properties depending on the molecular axis and minor axis direction, such as refractive index and dielectric constant, and can easily control the molecular arrangement and optical properties. A liquid crystal display device using the same displays an image by changing the alignment direction of liquid crystal molecules according to the electric field size and adjusting the light transmittance transmitted through the polarizing plate.

The liquid crystal display device includes a liquid crystal panel in which a plurality of pixels are arranged in a matrix form, a gate driver for driving gate lines of the liquid crystal panel, and a data driver for driving the data lines of the liquid crystal panel.

In the liquid crystal display, an inversion driving method such as a frame inversion system, a line inversion system, and a dot inversion system is used to drive pixels of a liquid crystal panel . Among such inversion driving methods, the frame and line inversion methods can further reduce the power consumption as compared with the dot inversion method, and in the case of the dot inversion method, the image with higher image quality .

In recent years, the common voltage level supplied to each pixel of the liquid crystal panel is also inverted while adopting the line inversion or the frame inversion method, thereby improving the image quality while increasing the power consumption reduction effect.

However, although the data voltage supplied to each pixel is sequentially supplied from the first line to the last line of each frame, since the polarity of the common voltage is inverted every frame, the brightness characteristic of the display image is distorted Defects will occur. That is, the polarity of the common voltage is inverted with the start of each frame, but the data voltage is sequentially supplied from the first line of every frame. Therefore, coupling phenomenon occurs due to the change in the polarity of the common voltage in the pixels that are charged with the data voltage of the previous frame. In this case, since the charged data voltage level changes, a luminance difference occurs between the upper and lower ends of the display panel, and image quality defects such as a crosstalk phenomenon occur.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and it is an object of the present invention to provide a liquid crystal display device capable of reducing the power consumption by inverting the common voltage level supplied to the liquid crystal panel and preventing a luminance difference between the upper and lower ends of the liquid crystal panel, And a method of driving the liquid crystal display device.

According to an aspect of the present invention, there is provided a driving apparatus for a liquid crystal display, including: a liquid crystal panel having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels; A gamma reference voltage generating unit for generating gamma reference voltages whose voltage levels are gradually changed for each frame by using a gradually increasing driving voltage for each frame; A data driver for driving the data lines of the liquid crystal panel using the gamma reference voltages whose voltage levels are variable; And a timing controller for aligning image data input from the outside and supplying the data to the data driver and generating a data control signal to control the data driver.

The gamma reference voltage generator includes at least one VDD generating and supplying unit for generating a driving voltage such that the voltage level gradually increases or decreases from the start to the end of each frame, And a plurality of resistance columns for generating the gamma reference voltages gradually increasing or decreasing in voltage level per frame by dividing the driving voltage gradually increasing or decreasing.

The VDD generating and supplying unit supplies a driving voltage source having a DC level and a square wave swinging at least one frame unit at a time from the start point to the end point of each frame according to the driving voltage source of the input DC level and the voltage level of the swinging square wave And an integrator for generating and outputting the driving voltage so that the voltage level gradually increases or decreases.

The integrator receives the driving voltage source of the direct current level and the rectangular wave swinging at least one frame unit at the inverting and noninverting terminals, respectively, and outputs the positive or negative polarity An output section for selectively outputting the driving voltage of the positive or negative polarity level by using a plurality of switching elements and a non-inverting terminal of the operational amplifier and an output terminal of the operational amplifier in series with the output terminal of the output section, And a feedback controller for setting a waveform such that the driving voltage of the positive or negative polarity level output from the operational amplifier is gradually increased or decreased through a plurality of resistance elements formed in a parallel form.

Wherein the data driver divides gamma reference voltages whose voltage levels are gradually varied for each frame to generate positive or negative gamma voltages corresponding to all the gradation values of the image data, And selects the positive or negative gamma voltage corresponding to the gradation value of the data arranged according to the version signal, and supplies the selected gamma voltage to each of the data lines as a video signal.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device including a liquid crystal panel having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels, A method of driving a liquid crystal display (LCD) device for displaying an image, the method comprising: generating gamma reference voltages whose voltage levels are gradually varied for each frame using a driving voltage that gradually varies from frame to frame; Driving data lines of the liquid crystal panel using the gamma reference voltages whose voltage levels are variable; And arranging image data inputted from the outside and supplying the data to the data driver, and controlling the data driver by generating a data control signal.

Wherein the step of generating the gamma reference voltages comprises: generating a drive voltage such that the voltage level gradually increases or decreases from a start point to an end point of each frame; and generating the gamma reference voltages by gradually increasing or decreasing the drive voltage And generating the gamma reference voltages gradually increasing or decreasing in voltage level on a frame-by-frame basis.

The generating of the driving voltage may include receiving a driving voltage source of a DC level and a square wave swinging at least one frame unit using an integrator, receiving a driving voltage source of the input DC level and a voltage level of the swinging square wave, Generating and outputting the driving voltage so that the voltage level gradually increases or decreases from the starting point to the end point of the driving voltage.

Generating and outputting the driving voltage includes generating a driving voltage source having a direct current level and a square wave swinging at least one frame unit using the operational amplifier using an operational amplifier, Outputting a driving voltage having a positive or negative polarity according to a voltage level of a square wave to be applied to the operational amplifier; selectively outputting the driving voltage having the positive or negative polarity using a plurality of switching elements; The step of setting the waveform so that the driving voltage of the positive or negative polarity level outputted from the operational amplifier gradually increases or decreases through a plurality of resistance elements formed in series or in parallel with the non-inverting terminal and the output terminal of the output section .

The step of driving the data lines of the liquid crystal panel divides gamma reference voltages whose voltage levels are gradually changed for each frame to generate positive or negative gamma voltages respectively corresponding to all the gray levels of the image data And selects a positive or negative gamma voltage corresponding to a gradation value of data arranged according to an external inversion signal, and supplies the selected gamma voltage to each of the data lines as a video signal.

The driving apparatus and the driving method of the liquid crystal display according to the present invention having the above characteristics can reduce the power consumption by inverting the common voltage level supplied to the liquid crystal panel. In addition, it is possible to prevent defects such as a difference in brightness between the upper and lower ends of the liquid crystal panel and the occurrence of a crosstalk phenomenon, thereby further improving the display quality of the image.

BRIEF DESCRIPTION OF DRAWINGS FIG. 1 is a circuit diagram showing a driving apparatus of a liquid crystal display according to an embodiment of the present invention; FIG.
Fig. 2 is a waveform diagram showing a common voltage swing method supplied to the liquid crystal panel of Fig. 1; Fig.
FIG. 3 is a block diagram schematically showing the gamma reference voltage generator shown in FIG. 1. FIG.
4 is a diagram illustrating positive and negative gamma voltages that are variably generated in the data driver of FIG. 1;
5 is a configuration circuit diagram specifically showing the VDD generation supply unit of FIG.
FIG. 6 is an output waveform diagram of driving voltages output from the VDD generation and supply unit of FIG. 5;
FIG. 7 is a graph for explaining the luminance change effect for each display position of an image. FIG.
8 is a graph for explaining the luminance change effect of a black image for each display position of an image.

Hereinafter, a driving apparatus and a driving method of a liquid crystal display according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram showing a driving apparatus for a liquid crystal display according to an embodiment of the present invention. 2 is a waveform diagram showing a common voltage swing method supplied to the liquid crystal panel of FIG.

The driving apparatus of the liquid crystal display shown in FIG. 1 includes a liquid crystal panel 2 having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels; A gate driver 6 for driving the gate lines GL1 to GLn of the liquid crystal panel 2; A gamma reference voltage generator 10 for generating gamma reference voltages RGV whose voltage levels are gradually changed gradually every frame using a driving voltage VDD which is gradually changed for each frame; A data driver 4 for driving the data lines DL1 to DLm of the liquid crystal panel 2 using the gamma reference voltages RGV whose voltage levels are gradually changed; And the image data RGB inputted from outside are supplied to the data driver 4 and the gate and data control signals GCS and DCS are generated to control the gate and data drivers 6 and 4, And a controller 8.

The liquid crystal panel 2 includes a thin film transistor (TFT) formed in each pixel region defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm, And a capacitor Clc. The liquid crystal capacitor Clc is composed of a pixel electrode connected to the TFT, and a common electrode arranged between the pixel electrode and the liquid crystal. At this time, the common voltage Vcom of the first and second voltage levels is supplied to the common electrode of each pixel region by swinging every frame. On the other hand, the TFT supplies a video signal from each of the data lines DL1 to DLm to the pixel electrode in response to a scan pulse from each of the gate lines GL1 to GLn.

The liquid crystal capacitor Clc charges the difference voltage between the video signal supplied to the pixel electrode and the common voltage Vcom at the first or second voltage level and varies the arrangement of the liquid crystal molecules in accordance with the difference voltage to change the light transmittance Thereby realizing the gradation. At this time, the storage capacitor Cst may be formed by overlapping the pixel electrode with the storage line interposed therebetween, and a parasitic capacitor Cgs may be further formed between the source electrode of the TFT and the gate line GL.

Referring to FIG. 2, a common voltage supplier of a first level or a second level is alternately supplied to each pixel region of the liquid crystal panel 2 in units of frames. For example, a positive common voltage (+) of a first voltage level is supplied to each pixel region in an N frame period (N Frame), which is an odd frame period, and an N + 1 frame period N +1 frame), a negative common voltage (-) of the second voltage level may be supplied to each pixel region. At this time, the positive voltage (+) of the first voltage level is supplied at a positive voltage level of + 5V in the N frame period (N frame), and in the (N + The negative voltage (-) of the voltage level can be supplied to 0V.

The data driver 4 receives a data control signal DCS from the timing controller 8, for example, a source start signal SSP, a source shift clock SSC, a source output enable That is, a video signal, from the timing controller 8 using a source output enable (SOE) signal and an inversion signal (Pol Signal). Specifically, the data driver 4 latches the aligned data Data through the timing controller 8 in accordance with the SSC, and then, in response to the SOE signal, supplies the scan pulses to the gate lines GL1 to GLn And supplies video signals for one horizontal line to each of the data lines DL1 to DLm for each horizontal period.

At this time, the data driver 4 receives the gamma reference voltages RGV whose voltage levels have been gradually changed for each frame from the gamma reference voltage generator 10, and supplies the gamma reference voltages RGV corresponding to the total gray- Thereby generating positive or negative gamma voltages. And selects the positive or negative gamma voltage corresponding to the gradation value of the data Data arranged in accordance with the inversion signal from the timing controller 8 and supplies the selected gamma voltage to each of the data lines DL1 to DLm .

The positive and negative gamma voltages of the data driver 4 are generated by dividing the gamma reference voltages RGV input from the gamma reference voltage generator 10 corresponding to the total gray level values of the image data RGB . Therefore, the positive or negative gamma voltages corresponding to the gamma reference voltages RGV whose voltage levels are gradually changed also gradually change in voltage level. In particular, since the voltage level of the gamma reference voltages RGV may be gradually increased in order to prevent a luminance difference between the upper and lower sides of the liquid crystal panel 2, the positive and negative gamma voltages The voltage level may be generated so as to gradually increase.

The gate driver 6 sequentially drives the gate lines GL1 to GLn in accordance with the gate control signal GCS from the timing controller 8. [ Specifically, the gate driver 4 outputs a gate start signal (GSP), a gate shift clock (GSC), a gate output enable (GOE) signal Or the like so that the scan pulses of the gate high voltage (VGH) level are sequentially supplied to the gate lines GL1 to GLn. And the gate-low voltage is supplied to the remaining period in which the scan pulse is not supplied.

The gamma reference voltage generator 10 generates the gamma reference voltages RGV whose voltage levels are gradually changed on a frame-by-frame basis through a driving voltage VDD which is gradual changed every frame. Specifically, the gamma reference voltage generator 10 generates a driving voltage VDD of a step-like waveform such that the voltage level gradually increases or decreases from the beginning to the end of each frame. Then, the gamma reference voltages RGV whose voltage levels are gradually increased or decreased in units of frames are divided by dividing the driving voltage VDD of the step-like waveform gradually increasing or decreasing in voltage level for each frame through a plurality of resistance arrays . Gamma reference voltages RGV whose voltage levels are gradually increased or decreased are supplied to the data driver 4 so as to generate positive or negative gamma voltages.

On the other hand, the timing controller 8 includes a common voltage supply unit (not shown) according to external video data RGB and a plurality of synchronization signals DCLK, Hsync, Vsync, (6). Specifically, the timing controller 8 arranges image data (RGB) input from the outside so as to be suitable for driving the liquid crystal panel 2, and supplies the image data to the data driver 4. A gate control signal GCS and a data control signal GCS are generated by using at least one of a synchronizing signal input from the outside, that is, a dot clock DCLK, a data enable signal DE, and horizontal and vertical synchronizing signals Hsync and Vsync DCS, and supplies them to the gate driver 6 and the data driver 4, respectively. At this time, the timing controller 8 supplies an inversion signal (Pol Signal) to the common voltage supply unit and the data driver 4, which are not shown. That is, the timing controller 8 controls the common voltage supply unit to invert the level of the common voltage Vcom every frame unit through the inversion signal, and controls each pixel region formed in the liquid crystal panel 2 to be connected to the line And controls the data driver 4 to be driven by at least one of an inversion method, a column inversion method, a frame inversion method, and a dot inversion method.

FIG. 3 is a schematic diagram illustrating the gamma reference voltage generator shown in FIG. 1. Referring to FIG.

The gamma reference voltage generator 10 of FIG. 3 includes at least one VDD generating and supplying unit 12 that generates a driving voltage VDD such that the voltage level gradually increases or decreases from the beginning to the end of each frame, The gamma reference voltages RGV whose voltage levels are gradually increased or decreased on a frame-by-frame basis by dividing the gradually increasing or decreasing driving voltage VDD are connected in series to the output terminals of the VDD generating and supplying unit 12, And a plurality of resistance arrays R1 to Rn to be generated.

Each VDD generating and supplying unit 12 receives a driving voltage source of a DC level and a square wave swinging at least one frame unit, and outputs a driving voltage from a starting point to an ending point of each frame in accordance with a voltage level of a square- And generates and outputs the driving voltage VDD of the stepped waveform so that the voltage level gradually increases or decreases. Each VDD generating supply 12 is configured in the form of an integrator. Therefore, each VDD generating and supplying unit 12 in the form of an integrator receives the driving voltage source of the DC level and the square wave swinging at the inverting and non-inverting terminals, and gradually increases the voltage level according to the voltage level difference between the driving voltage source and the square wave Or the driving voltage VDD of the decreasing stepped waveform.

For example, when a driving voltage source at a DC level and a square wave swinging at a lower level than a driving voltage source are input to a VDD generating and supplying unit 12, the VDD generating and supplying unit 12 generates a step waveform And generates and outputs the driving voltage VDD. When a driving voltage source at a DC level and a square wave swinging at a higher level than a driving voltage source are input to the other VDD generating and supplying unit 12, the VDD generating and supplying unit 12 supplies a driving voltage of a stepped waveform VDD).

The plurality of resistance arrays R1 to Rn are connected in series between the output terminal of each VDD generating and supplying section 12 and the low potential voltage source to divide the driving voltage VDD input to gradually increase or decrease, And outputs gamma reference voltages RGV whose voltage levels gradually increase or decrease gradually.

FIG. 4 is a diagram illustrating positive and negative gamma voltages that are variably generated in the data driver of FIG. 1. FIG.

As described above, the data driver 4 divides the gamma reference voltages RGV input from the gamma reference voltage generator 10 in accordance with the total gray level values of the image data RGB, thereby obtaining the positive and negative Lt; / RTI > Therefore, the positive or negative gamma voltages corresponding to the gamma reference voltages RGV whose voltage levels are gradually changed also gradually change in voltage level. In particular, in order to prevent a luminance difference between the upper and lower sides of the liquid crystal panel 2, the voltage level of the gamma reference voltages RGV is gradually increased in the case of positive polarity and gradually decreased in the case of negative polarity . Thus, the positive gamma voltages gradually increase as they approach the end of each frame, and the negative gamma voltages gradually decrease as they approach the end of each frame.

5 is a configuration circuit diagram specifically showing the VDD generation supply unit of FIG.

The VDD generation and supply unit 12 shown in FIG. 5 receives a driving voltage source of a DC level and a square wave swinging at least one frame unit at a start of each frame according to a voltage level of a square wave that swings with a driving voltage source And an integrator for generating and outputting the stepped waveform drive voltage VDD_EVEN so that the voltage level gradually increases or decreases from the time point to the end point.

Such an integrator has a driving voltage source of a DC level and a square wave swinging at least one frame unit at a reverse or a non-inverting terminal, respectively. The integrator has a positive or negative polarity level An operational amplifier for outputting the driving voltage VDD_EVEN,

An output section for selectively outputting the drive voltage (VDD_EVEN) at the positive or negative polarity level using a plurality of switching elements, and

A waveform is set so that the driving voltage of positive or negative polarity output from the operational amplifier is gradually increased or decreased through a plurality of resistance elements formed in series or in parallel with the non-inverting terminal of the operational amplifier and the output terminal of the output section. And a feedback control section.

The integrator thus constructed, as shown in the following equation,

The minimum voltage level and the maximum voltage level are set according to the driving voltage source of the DC level, the swing voltage level of the swinging square wave, and the resistance value of each resistance element. The slope of the driving voltage (VDD_EVEN) waveform which gradually increases or decreases according to the two resistance values connected in parallel and the capacitor capacity is adjusted. As such, each VDD generating and supplying unit 12 includes an integrator to generate and output a driving voltage VDD that gradually increases or decreases the voltage level by adjusting the RC time constant to be optimized.

In the case of FIG. 5, only the integrator structure for generating the driving voltage VDD_EVEN in the even-numbered frame is shown, but it is possible to output the driving voltage of the opposite polarity through the other integrator. In this case, the driving voltages (Even_VDD and Odd_VDD) of the positive polarity and the negative polarity can be generated so as to be inverted in units of at least one frame, and can be selectively used in units of at least one frame. As described above, when the positive and negative driving voltages are supplied to the VDD generating and supplying unit 12, the positive and negative driving voltages (Even_VDD and Odd_VDD), whose voltage levels are gradually changed, are divided into odd and even frame units Respectively.

As described above, the gamma reference voltage generating unit 10 uses the at least one VDD generating and supplying unit 12 and the resistance arrays R1 to Rn to generate the gamma reference voltage And the data driver 4 divides the gamma reference voltages RGV gradually increasing or decreasing in voltage level corresponding to the total gray level values of the image data RGB, And negative gamma voltages. Accordingly, the data driver 4 uses the gamma voltages gradually increasing as the frame approaches the end, and the gamma voltages gradually decreasing as the frame approaches the end of the frame, As shown in FIG. 7 and Table 1 below, it is possible to display an image such that a luminance difference does not occur between the upper and lower sides of the liquid crystal panel 2.

Also, even when displaying an experimental image of a black image, an image can be displayed so that a luminance difference does not occur between the top and bottom of the liquid crystal panel 2, as shown in FIG. 8 and Table 2 below.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention. Will be clear to those who have knowledge of.

Claims (10)

A liquid crystal panel having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels;
A driving voltage of a plurality of stepped waveforms whose voltage levels gradually change from a start point to an end point of a frame of each frame is generated and the driving voltage of the plurality of stepped waveforms is selectively transmitted to a circuit in which a plurality of resistors are connected in series A gamma reference voltage generating unit for generating gamma reference voltages whose voltage levels are gradually changed on a frame-by-frame basis;
Wherein the gamma reference voltages generated by the gamma reference voltage generator are divided into a plurality of gamma reference voltages corresponding to all the gradation values of the image data to gradually vary the voltage level corresponding to the gamma reference voltages varying in the voltage level A data driver for generating a positive or negative gamma voltage to drive data lines of the liquid crystal panel; And
And a timing controller for controlling the data driver by generating a data control signal including an inversion signal (POL signal) by supplying image data inputted from the outside to the data driver, . The method according to claim 1,
The gamma reference voltage generator
At least one VDD generating and supplying section for generating a driving voltage such that the voltage level gradually increases or decreases from the start point to the end point of each frame,
A plurality of resistance columns for generating the gamma reference voltages gradually increasing or decreasing in voltage level per frame by dividing the gradually increasing or decreasing driving voltage by being connected in series to the output terminals of the VDD generating and supplying sections, And a driving circuit for driving the liquid crystal display device. 3. The method of claim 2,
The VDD generation and supply unit
A driving voltage source of a DC level and a square wave swinging at least one frame unit are respectively supplied to the driving voltage source of the DC level and the voltage level of the swinging square wave to gradually increase the voltage level from the start point to the end point of each frame And an integrator for generating and outputting the driving voltage so as to increase or decrease the driving voltage of the liquid crystal display device. The method of claim 3,
The integrator
The drive voltage source of the direct current level and the square wave swinging at least one frame unit are respectively inputted to the inverting and noninverting terminals and driven at the positive or negative polarity according to the voltage level of the rectangular wave having the input voltage An operational amplifier for outputting a voltage,
An output section for selectively outputting the drive voltage at the positive or negative polarity level using a plurality of switching elements,
Wherein the operational amplifier outputs a waveform having a positive or negative polarity level gradually increased or decreased through a plurality of resistance elements formed in series or in parallel with the noninverting terminal of the operational amplifier and the output terminal of the output section, And a feedback control section for setting the control signal. delete A method of driving a liquid crystal display device for displaying an image through a liquid crystal panel having a plurality of pixel regions supplied with a common voltage swinging at first and second voltage levels,
Generating a driving voltage of a plurality of stepped waveforms whose voltage levels progressively vary from a start point to an ending point of each frame and selectively transmitting a driving voltage of the plurality of stepped waveforms to a circuit in which a plurality of resistors are connected in series, Generating gamma reference voltages whose voltage levels are gradually changed on a frame-by-frame basis;
A step of arranging image data inputted from outside and supplying the data to the data driver, and controlling the data driver by generating a data control signal including an inversion signal (Pol signal); And
Wherein the gamma reference voltages having the variable voltage levels are divided according to all the gradation values of the image data so that the positive or negative gamma voltages having the variable voltage levels gradually corresponding to the gamma reference voltages having the varying voltage levels And driving the data lines of the liquid crystal panel. The method according to claim 6,
The step of generating the gamma reference voltages
Generating a drive voltage such that the voltage level gradually increases or decreases from the start point to the end point of each frame; and
And generating the gamma reference voltages in which the voltage level is gradually increased or decreased for each frame by dividing the gradually increasing or decreasing driving voltage by using a plurality of resistance columns. Driving method. 8. The method of claim 7,
The step of generating the drive voltage
A driving voltage source having a direct current level and a square wave swinging at least one frame unit are supplied with a voltage from the starting point to the end point of each frame according to the driving voltage source of the inputted direct current level and the voltage level of the swinging rectangular wave, And generating and outputting the driving voltage so that the level gradually increases or decreases. 9. The method of claim 8,
The step of generating and outputting the driving voltage
The driving voltage source of the direct current level and the square wave swinging at least one frame unit are input to the inverting and noninverting terminals using an operational amplifier to generate a positive or negative voltage according to the voltage level of the driving voltage source and the square wave swinging Outputting a drive voltage of a negative polarity,
Selectively outputting the drive voltage of the positive or negative polarity level using a plurality of switching elements, and
A waveform is set so that the driving voltage of the positive or negative polarity level output from the operational amplifier gradually increases or decreases through a plurality of resistance elements formed in series or in parallel with the noninverting terminal of the operational amplifier and the output terminal of the output section And driving the liquid crystal display device. delete

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