KR20040073703A - Driving Methode for Liquid Crystal Display device and Driving Circuit at the same - Google Patents

Abstract

PURPOSE: A method for driving a liquid crystal display and a driver circuit thereof are provided to increase a response speed of a liquid crystal. CONSTITUTION: According to the method for driving a liquid crystal display, a control part receives an image control signal and then outputs an inversion signal and a data signal and a gate signal to a data driver and a gate driver. The gate driver receives the gate signal of the control part and then outputs a gate driving pulse to a liquid crystal. The data driver outputs a plurality of data voltages to the liquid crystal by being synchronized to the gate driving pulse of the gate driver. And a common voltage is output to the liquid crystal so that the common voltage is varied to have an opposite polarity to the data voltage.

Description

Driving method for a liquid crystal display device and a driving circuit thereof {Driving Methode for Liquid Crystal Display device and Driving Circuit at the same}

The present invention relates to a method of driving a liquid crystal display device and a driving circuit thereof, and more particularly, to a method of driving a liquid crystal display device capable of increasing a liquid crystal response speed by outputting a common voltage having a different polarity from a data signal that is inverted and output. It relates to a drive circuit thereof.

Recently, due to the rapid development of the information and communication field, the importance of the display industry for displaying desired information is increasing day by day, and to date, CRT (cathod ray tube) among information display devices can display various colors and display brightness It has also enjoyed steady popularity so far because of its superiority.

However, there is an urgent need for the development of flat panel displays instead of CRTs that are bulky and bulky due to the desire for large, portable and high resolution displays. These flat panel displays have a wide range of applications from computer monitors to displays used in aircraft and spacecraft.

Currently produced or developed flat panel displays include liquid crystal display (LCD), electro luminescent display (ELD), field emission display (FED), plasma display panel (PDP) Light weight, high brightness, high efficiency, high resolution, high speed response characteristics, low driving voltage, low power consumption, low cost, and color display characteristics are required for an ideal flat panel display. Among such flat panel displays, the liquid crystal display device is in the spotlight because of its durability as well as its desire.

In addition, a thin film transistor-liquid crystal display (hereinafter referred to as TFT-LCD) having excellent color reproducibility and thinness has been developed. In particular, the above-described thin film transistor and pixels connected to the thin film transistor have been developed. Active matrix LCDs (AM-LCDs), in which electrodes are arranged in a matrix manner, are attracting the most attention due to their excellent resolution and ability to implement video.

Such a liquid crystal display device is an image display device using optical anisotropy characteristics of liquid crystals. When light is irradiated onto a liquid crystal having polarization characteristics according to a voltage application state, the liquid crystal display device may pass light depending on the alignment state of the liquid crystals according to the voltage application. It is a device that can express the image by adjusting the amount.

In order to configure the liquid crystal display device, a liquid crystal panel including the liquid crystal layer and a circuit disposed around the liquid crystal panel to apply a signal to the liquid crystal panel and control the signal are further required.

Hereinafter, a TN mode liquid crystal display device will be described with reference to the accompanying drawings.

1 is a schematic perspective view of a TN mode liquid crystal display device, wherein a TN mode liquid crystal display device includes an upper substrate 11 and a lower substrate 12 and a liquid crystal layer 13 formed between the two substrates to express colors. The panel 10 and the first and second polarizers 14 and 15 are disposed to intersect the polarizers 19 above and below the liquid crystal panel 10.

Although not shown, a backlight for irradiating transmitted light from the rear surface of the liquid crystal panel 10 is formed, and a plurality of alignment films rubbed to cross on the two substrates for alignment of the liquid crystal layer 13 are further formed. have.

Here, the first and second polarizing plates 14 and 15 have a characteristic in which the polarization direction is vertical.

The lower substrate 12 may also be referred to as an array substrate, and a thin film transistor (not shown), which is a switching element, and a pixel electrode (not shown) for displaying an image are located in a matrix type. In order to operate the thin film transistor, the gate wiring 16 and the data wiring 17 are formed to be orthogonal to each other. In addition, a common electrode (not shown) is formed on the upper substrate 11.

Pixel electrodes (not shown) and common electrodes (not shown) respectively formed on the lower substrate 12 and the upper substrate 11 are indium-tin oxides for transmitting light emitted from the backlight. -oxide: It is composed of transparent conductive metal such as ITO).

The liquid crystal molecules 18 of the liquid crystal layer 13 formed between the upper substrate 11 and the lower substrate 12 are formed by the alignment layer (not shown) formed on the surfaces of the two substrates facing each other. The azimuth angles from 12) to the upper substrate 11 are twisted by 90 degrees.

That is, white light irradiated from the backlight is polarized in one direction by the second polarizing plate 15, and light polarized by the second polarizing plate 15 is refracted by the lower substrate 12 and the liquid crystal layer 13. do.

At this time, as shown, the light incident on the liquid crystal layer 13 is refracted to be orthogonal to the direction polarized by the second polarizing plate 15 by rotating the azimuth angle by 90 degrees by the twisting of the liquid crystal molecules 18. . As such, the intensity of transmitted light may be adjusted by adjusting the azimuth or polar angle of the liquid crystal molecules 18 in the liquid crystal layer 13.

In addition, the white light refracted by the liquid crystal layer 13 passes through the upper substrate 11 having a color filter (not shown) capable of displaying RGB color, and has a color by the upper substrate 11. Light passes through the first polarizing plate 14 and is represented as an image.

2 is a block diagram of a liquid crystal display according to the related art.

That is, as described above, the liquid crystal display device includes a liquid crystal panel 10 in which a plurality of pixel regions defined by a plurality of gate lines 16 and data lines 17 perpendicular to each other are arranged in a matrix form, and The driving circuit unit 22 and the liquid crystal module (LCM) driving system 27 for supplying a driving signal and a data signal to the liquid crystal panel 10 are divided.

Here, the LCM driving system 27 supplies power to the driving circuit unit 22, and the vertical synchronization signal (Vsync: frame discrimination signal), the horizontal synchronization signal (Hsync: line discrimination signal), and the data enable signal (DE: Enable signal only during the period in which the data voltage is output) and a clock signal.

In addition, the driving circuit unit 22 may include a data driver 21b for inputting a data signal to each data line 17 of the liquid crystal panel 10 and a gate line 16 of the liquid crystal panel 10. A timing controller for generating a gate signal 21a for applying a gate driving pulse, a driving pulse for driving the gate driver 21a, and a load signal and a data signal for driving the data driver 21b; 23, the power supply unit 24 for supplying the required voltage to the liquid crystal panel 10 and the respective portions, and the digital data input from the data driver 21b by receiving power from the power supply unit 24, and analog data. Gamma reference voltage unit 25 for supplying a reference voltage required for conversion to the constant voltage, constant voltage V _DD and gate high voltage used in the liquid crystal panel 10 using the voltage output from the power supply unit 24. And a DC / DC converter 26 for outputting V _GH , a gate low voltage V _GL , a reference voltage V _ref , a common voltage Vcom, and the like.

Here, the data driver 21b applies a data voltage to the data line 17 using the data signal output from the timing control unit 23, and the DC / DC converter is connected to the liquid crystal panel 10. The common voltage Vcom for inducing an electric field from the data voltage is output.

As described above, in the liquid crystal panel 10, a plurality of gate lines 16 arranged in a horizontal direction and a plurality of data lines 17 arranged in a vertical direction cross each other to form a matrix structure. The thin film transistor K is positioned at the intersection of the and the data line 17, and a pixel electrode to which the data voltage Vd is applied, electrically connected to the thin film transistor K, is positioned in the matrix structure.

In addition, the thin film transistor K is formed by stacking a gate electrode G made of a conductive metal, a source electrode S, a drain electrode D, and a semiconductor layer, and the gate electrode G includes a gate line 32 and The source electrode S is electrically connected to the data line 17, and the drain electrode D is electrically connected to the pixel electrode to which the data voltage Vd is applied.

In this case, between the pixel electrode to which the data voltage Vd is applied and the common electrode to which the common voltage Vcom corresponding thereto is applied, the liquid crystal cell Clc represented by a capacitor and preferably the liquid crystal cell Clc are provided. Storage capacitors Cst connected in parallel are formed.

The data driver 21b and the gator driver 21a are positioned at the edge of the liquid crystal panel 10 to apply the data voltage and the gate driving pulse to the data line 17 and the gate line 16.

Accordingly, in the conventional LCD, a plurality of thin film transistors are driven along the gate line 16 in one direction by selectively applying the gate driving pulse Vg to the gate line 16. The application method of the pulse Vg uses a line sequential driving method in which voltage is applied one line at a time by the gate driver 30 and continuously moved to the next adjacent gate line 16, and gates are applied to all gate lines. When the driving pulse Vg is applied, one frame is completed.

That is, when the gate driving pulse Vg is applied to the i-th gate line Gi, all the thin film transistors K connected to the i-th gate line Gi to which the gate driving pulse Vg is applied are simultaneously turned on. When the turned-on thin film transistor K is applied along the plurality of data lines 17, each data voltage Vd is applied to the corresponding pixel electrode, and the i-th gate line Gi is applied. The liquid crystal cell and the storage capacitor are accumulated in the plurality of pixel electrodes controlled by the pixel voltage by the pixel voltage Vp corresponding to the data voltage Vd.

Therefore, the liquid crystal molecules in the liquid crystal cell are rearranged according to the pixel voltage accumulated in the liquid crystal cell and display a desired image by optical anisotropy.

After the gate driving pulse is moved to the next i + 1 th gate line Gi + 1 and applied, the thin film transistors K connected to the i th gate line Gi are all turned off. The voltage accumulated in the storage capacitor Cst and the liquid crystal cell capacitor Clc electrically connected to the gate line Gi is maintained until the thin film transistor K is turned on again in the next frame.

Accordingly, in the conventional liquid crystal display, the data voltage Vd output through the plurality of data lines 17 is transmitted to each pixel electrode by the gate driving pulse Vg applied to the gate electrode G. The variable data voltage Vd gradually changes the polarization state of the liquid crystal so that the transmitted light can be controlled to express various gray levels in the liquid crystal display.

In this case, in a large area liquid crystal display device employing a thin film transistor (K) as a switching element, when a DC bias is applied to both ends of the liquid crystal, the liquid crystal molecules are easily deteriorated by the DC voltage, and the dielectric constant of the liquid crystal cell is changed according to the arrangement direction of the liquid crystal molecules. Since they have varying dielectric anisotropy, an AC voltage is generally used to change the polarity of the voltage applied to the liquid crystal for each frame.

As described above, the inversion method of changing the image signal applied to the liquid crystal includes four methods: a frame, a column, a line, and a dot inversion.

3A to 3D are plan views illustrating polarity inversion of the respective inversion schemes, respectively.

As shown in FIG. 3A, the frame inversion method is a method in which all pixels receive the same image signal and change the polarity of the entire pixel every time the frame is changed. The column inversion method is shown in FIG. 3B. Likewise, the polarity of neighboring column lines (vertical lines) is changed in one frame.

In addition, the line inversion method is a method in which the polarity of neighboring low lines (horizontal lines) is changed in one frame.

In the dot inversion scheme, as shown in FIG. 3D, polarities of peripheral pixels of one pixel are different from each other so that the polarity is changed every frame.

The reason for using this inversion method is to reduce cross-talk and flicker of screen flicker.

Therefore, the liquid crystal display of the prior art can prevent the degradation of the liquid crystal characteristics having dielectric anisotropy by using the frame, column, line, and dot inversion methods, and prevent cross talk and flicker from each other.

4 to 5 are waveforms showing the output voltage of the data driver according to the prior art.

When the line sequential driving method is used as the driving method of the liquid crystal display device, as described above, the data voltage Vd input to the source electrode S of the thin film transistor (K in FIG. 2) in an arbitrary frame is the thin film transistor K. Accumulate in the liquid crystal cell Clc and the storage capacitor Cst from the time when the gate driving pulse Vg for turning on is applied, and the accumulated voltage must be maintained until the next frame. .

However, the level shift phenomenon occurs because a certain amount of discharge is caused by the parasitic capacitor (Cgs in FIG. 2) generated by the overlap between the gate electrode G and the source electrode S of the thin film transistor K.

Here, the driving method of the liquid crystal panel (10 in FIG. 1) of the liquid crystal display device is dot or line inversion.

In addition, the pixel voltage Vp while the gate driving pulse Vg is applied appears to have a nonlinear characteristic due to the dielectric anisotropy of the liquid crystal.

At this time, the lower the pixel voltage Vp applied to the pixel electrode through the thin film transistor K, the more difficult it is to align the liquid crystal molecules.

That is, the common voltage Vcom applied to the common electrode is kept constant, and the capacitance Clc of the liquid crystal cell is stored and the pixel voltage Vp is increased by the data voltage applied to the pixel electrode.

In this case, the lower the data voltage Vd applied to the liquid crystal, the lower the pixel voltage Vp and the smaller the slope of the curve.

Accordingly, the liquid crystal display according to the related art may apply a data voltage Vd whose polarity is inverted on the basis of a fixed fixed common voltage Vcom to prevent deterioration of the characteristics of the liquid crystal. By applying the pixel voltage Vp induced in the liquid crystal cell, the molecular alignment of the liquid crystal may be destroyed.

However, the conventional liquid crystal display device driving method has the following problems.

The conventional driving method of the liquid crystal display device has a disadvantage in that it is not suitable to implement a moving image requiring a response speed of the liquid crystal because the data voltage applied to the liquid crystal panel cannot be applied high and the common voltage is fixed.

The present invention has been made to solve the above problems, a liquid crystal that can increase the response speed of the liquid crystal by outputting a common voltage having a polarity opposite to the data voltage to make a relatively high potential with the normal output data voltage It is an object of the present invention to provide a driving method of a display device and a driving circuit thereof.

1 is a schematic perspective view of a TN mode liquid crystal display device.

2 is a block diagram of a liquid crystal display according to the prior art.

3A to 3D are plan views showing polarity inversions of the respective inversion schemes, respectively.

4 to 5 are waveform diagrams showing data voltages and pixel electrodes of a data driver according to the related art.

6 is a data voltage waveform and a common voltage waveform diagram of a liquid crystal display according to a first embodiment of the present invention.

FIG. 7 is a diagram illustrating pixel voltages applied using a method of driving a liquid crystal display according to a first embodiment of the present invention; FIG.

8 is a data voltage waveform and a common voltage waveform diagram of a liquid crystal display according to a second exemplary embodiment of the present invention.

9 is a block diagram showing a driving circuit of the liquid crystal display device according to the present invention;

10 is a schematic plan view of a liquid crystal panel according to the present invention;

11 is a circuit diagram schematically showing a common voltage variable part according to the present invention.

12 is a view showing various waveforms input and output to the common voltage variable portion according to the present invention.

* Description of the main parts of the drawings *

51 liquid crystal panel 51a gate driver

51b: data driver 52: driver

53: timing controller 54: power supply

55: gamma reference voltage section 56: DC / DC conversion section

57: LCM drive system 58: common voltage variable part

59: common line 60: operational amplifier

61: multiplexer 62: common voltage variable signal

63: DAC 64: Control Signal

D: data line G: gate line

Vcom: Common Voltage Vp: Pixel Voltage

Vd: data voltage

According to an aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method comprising: receiving an image control signal and outputting an inversion signal, a data signal, and a gate signal to a data driver and a gate driver by a controller; Receiving a gate driver and outputting a gate driving pulse to the liquid crystal panel by the gate driver, outputting a plurality of data voltages to the liquid crystal panel by the data driver in synchronization with the gate driving pulse of the gate driver, And outputting a common voltage to the liquid crystal panel so that the initial voltage value has a polarity opposite to the data voltage at the time of output.

In this case, when the data voltage is sequentially changed in polarity due to dot inversion or line inversion, the common voltage may be output to have a polarity opposite to that of the data voltage.

Preferably, the common voltage is varied such that the data voltage is higher than the common voltage by n + 10 gray levels.

The time when the common voltage is variable is preferably before the pixel voltage reaches a target value.

When the data voltage is output in the same polarity for one frame due to column inversion or frame inversion, the common voltage is preferably output with the same polarity opposite to the data voltage.

In addition, another feature of the present invention is a data driver and a gate driver for outputting a data voltage and a gate driving pulse to each data line and gate line of the liquid crystal panel, and each driving signal and inversion to drive the data driver and the gate driver. A timing controller for generating a signal, a power supply unit for supplying a voltage required for the liquid crystal panel and each part, a gamma reference voltage unit for supplying a reference voltage to the data driver by receiving power from the power supply unit, and from the power supply unit A DC / DC converter for outputting a constant voltage, a gate high voltage, a gate low voltage, a reference voltage and a common voltage to the liquid crystal panel using the output voltage, and the common voltage according to the data voltage to have a polarity opposite to the data voltage. A liquid including a common voltage variable part that is variable and outputs It is the driving circuit of the display device.

The common electrode may be formed to be connected to each data line so that the common voltage is applied to a separate pixel.

When the data voltage is dot inversion, the common voltage applied to the liquid crystal panel is divided into Nth and N-1th so as to be opposite to the data voltages having different polarities, respectively, and the positive and negative common voltages are alternately output, and the line And in the case of frame inversion, it is preferable to output the common voltage applied to the Nth and the N-1th to have polarities opposite to the data voltages of the same polarity.

The common voltage variable part may include an operational amplifier and a multiplexer for varying a common voltage output from the DC / DC converter by a constant voltage value.

In order to make the common voltage output from the common voltage variable part into an analog voltage, it is preferable to further include a digital analog converter composed of ASIC.

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

6 is a data voltage waveform and a common voltage waveform diagram of the liquid crystal display according to the first embodiment of the present invention.

As shown in FIG. 6, in the liquid crystal display according to the first exemplary embodiment of the present invention, the common voltage is initially determined according to the data voltage Vd which is sequentially changed in polarity by dot inversion or line inversion in a data driver. The pixel voltage (not shown) is increased by changing Vcom so that the polarity is opposite to that of the data voltage Vd.

Here, the common voltage Vcom is variable and output so as to have the opposite polarity while the data voltage Vd is output to be equal to or greater than the gray level of the data voltage Vd.

For example, when a 128 full gray pattern is to be displayed, the response speed of the liquid crystal may be increased by outputting a common voltage Vcom having a variable n + 10 gray voltage compared to the conventional common voltage Vcom for a predetermined time. have.

In this case, the time at which the common voltage Vcom is varied is before the pixel voltage Vp reaches a target value.

Therefore, the driving method of the liquid crystal display according to the first exemplary embodiment of the present invention uses a common voltage having the opposite polarity to the data voltage Vd so as to make a high potential relative to the data voltage Vd having a constant gray level. The response speed can be increased by outputting Vcom).

That is, in the driving method of the liquid crystal display according to the first exemplary embodiment of the present invention, first, an image control signal is input, and a timing controller outputs an inversion signal, a data signal, and a gate signal to the data driver and the gate driver. The gate driver outputs a gate driving pulse.

The data driver outputs a plurality of inverted data voltages Vd in synchronization with the gate driving pulses, and has a polarity in which an initial voltage value is opposite to the data voltage Vd when the data voltages Vd are applied. It is possible to increase the response speed of the liquid crystal by outputting a common voltage (Vcom) variable to have.

FIG. 7 is a diagram illustrating pixel voltages applied using a method of driving a liquid crystal display according to a first exemplary embodiment of the present invention. When the data voltage (Vd of FIG. 6) is applied to the liquid crystal panel, the dielectric constant anisotropy of the liquid crystal is applied. As a result, the pixel voltage Vp does not rise vertically but increases with a delay time.

At this time, by applying the data voltage Vd and the common voltage Vcom having the opposite polarity to the voltage, the pixel voltage Vp becomes relatively high and an operating voltage increases.

In general, it is well known that the alignment of liquid crystal molecules is easily broken down as the operating voltage is increased.

Therefore, in the driving method of the liquid crystal display according to the first embodiment of the present invention, since the operating voltage becomes high, the liquid crystal response speed is increased by reaching the target value within a short time.

8 is a data voltage waveform and a common voltage waveform diagram of a liquid crystal display according to a second exemplary embodiment of the present invention.

As shown in FIG. 8, in the driving method of the liquid crystal display according to the second exemplary embodiment of the present invention, when the positive data voltage Vd is outputted by column inversion or frame inversion, the data voltage Vd and the polarity are the same. The opposite voltage is changed to the negative common voltage Vcom to increase the pixel voltage (Vp of FIG. 7).

On the other hand, although not shown, when the data voltage is output with a negative polarity, the common voltage Vcom is output with a variable polarity.

At this time, the common voltage Vcom is varied so that the data voltage Vd is output to be equal to or greater than the gray level of the data voltage Vd (10 gray levels) and has the opposite polarity so that the pixel voltage Vp is relatively. As a result, the operating voltage is increased to increase the response speed of the liquid crystal.

Therefore, the driving method of the liquid crystal display according to the second exemplary embodiment of the present invention is applied to the data voltage Vd to make a potential relatively high to the data voltage Vd having the same polarity and a constant gray level for one frame. The response speed can be increased by outputting the common voltage Vcom having the opposite polarity.

Looking at the driving circuit of the liquid crystal display device of the present invention driven in this way as follows.

9 is a block diagram showing a driving circuit of the liquid crystal display according to the present invention.

As shown in FIG. 9, the data driver 51b and the gate driver 51a output the data voltage Vd and the gate driving pulse Vg to each data line D and gate line G of the liquid crystal panel. A timing controller 53 for generating driving signals and inversion signals for driving the data driver 51b and the gate driver 51a, and a power supply unit 54 for supplying voltages necessary for the liquid crystal panel and the respective parts. And a gamma reference voltage unit 55 which receives power from the power supply unit 54 and supplies a reference voltage to the data driver 51b, and a liquid crystal panel using the voltage output from the power supply unit 54. 51 is a DC / DC converter 56 for outputting a constant voltage, a gate high voltage, a gate low voltage, a reference voltage and a common voltage Vcom, and the common voltage Vcom according to the data voltage Vd. Reverse polarity with voltage (Vd) And a common voltage varying section 58 that is variable and outputs.

Reference numerals 52 and 57 are the driving unit and the LCM driving system, respectively.

Although not shown, the common electrode must be formed to be connected to each data line D so that the common voltage Vcom can be applied to a separate pixel.

The common voltage variable part 58 may output an initial common voltage Vcom having polarities opposite to each other from the data voltage Vd output from the data drive 51b.

10 is a schematic plan view of the liquid crystal panel according to the present invention, and the common line 59 is formed in the liquid crystal panel 51 according to the present invention so as to be parallel to the data line (D of FIG. 9).

That is, the driving circuit of the liquid crystal display according to the present invention divides the common line 59 applied to the liquid crystal panel 51 into Nth and N-1th in the case of dot and column inversion, respectively. The positive and negative common voltages Vcom are alternately outputted so as to be opposite, and in the case of line and frame inversion, the common voltages Vcom applied to the Nth and N-1th common lines 59 have the same polarity. Output

Although not shown, a gate line G of FIG. 9 is formed to be perpendicular to the common line 59 from which the common voltage Vcom is output.

11 is a circuit diagram schematically illustrating a common voltage variable part according to the present invention.

As illustrated in FIG. 11, the common voltage variable unit 58 of the liquid crystal display device of the present invention is provided with an operational amplifier (PLC) outputted to a common voltage Vcom outputted from a DC / DC converter 56 (56 of FIG. 9) with a constant voltage value. The OPAMP 60 and the multiplexer MUX 61 may be used in combination with the common voltage variable signal 62 to output a common voltage Vcom having opposite polarities to the data voltage Vd.

At this time, since the data voltage Vd is an analog voltage, an analog voltage may be output to the common voltage variable signal 60, which is a square wave, by using a digital analog converter (DAC) 63.

In addition, the DAC 63 may be configured using an application specific integrated circuit (ASIC).

FIG. 12 shows various waveforms inputted and outputted to the common voltage variable part according to the present invention, and is fixed with the common voltage variable signal 62 made by the inverted data voltage Vd of the data driver 51b of FIG. The inverted common voltage V'com is generated using the operational amplifier 60 from the common voltage Vcom, and the variable common voltage Vcom is controlled using the multiplexer 61 controlled by the control signal 64. ) Can be printed.

Therefore, the liquid crystal display driving circuit of the present invention can increase the initial pixel voltage Vp by outputting the initial voltage value according to the data voltage Vd to have a polarity opposite to the data voltage Vd, and the initial pixel. As the voltage Vp increases, the response speed of the liquid crystal may be increased.

As described above, the driving method and the driving circuit thereof of the liquid crystal display device of the present invention have the following effects.

The driving method of the liquid crystal display device and the driving circuit thereof according to the present invention can improve the liquid crystal response speed because the pixel voltage can be increased by outputting a common voltage having an opposite polarity and a variable voltage to a data voltage having a constant gray level.

Claims (10)

Receiving an image control signal and outputting an inverted signal, a data signal, and a gate signal to a data driver and a gate driver by a controller; Receiving a gate signal from the controller and outputting a gate driving pulse to a liquid crystal panel by a gate driver; Outputting a plurality of data voltages to the liquid crystal panel by the data driver in synchronization with a gate driving pulse of the gate driver; And outputting a common voltage to the liquid crystal panel such that an initial voltage value of the data voltage is output to have a polarity opposite to the data voltage. The method of claim 1, And the common voltage is output to have a polarity opposite to that of the data voltage when the data voltage is sequentially changed in polarity due to dot inversion or line inversion. The method of claim 1, And varying the common voltage so that the data voltage is higher than the common voltage by n + 10 gray levels. The method of claim 1, And a time period during which the common voltage is varied is before the pixel voltage reaches a target value. The method of claim 1, And when the data voltage is output in the same polarity for one frame by column inversion or frame inversion, the common voltage is output with the same polarity opposite to the data voltage. A data driver and a gate driver for outputting a data voltage and a gate driving pulse to each data line and gate line of the liquid crystal panel; A timing controller for generating each driving signal and an inverting signal to drive the data driver and the gate driver; A power supply unit supplying a voltage required for the liquid crystal panel and each unit; A gamma reference voltage unit receiving power from the power supply unit and supplying a reference voltage to the data driver; A DC / DC converter for outputting a constant voltage, a gate high voltage, a gate low voltage, a reference voltage and a common voltage to the liquid crystal panel using the voltage output from the power supply unit; And a common voltage varying unit configured to vary and output the common voltage according to the data voltage to have a polarity opposite to that of the data voltage. The method of claim 6, And a common electrode connected to each data line such that the common voltage is applied to a separate pixel. The method of claim 6, When the data voltage is a dot version, the common voltage applied to the liquid crystal panel is divided into N-th and N-1-th so as to be opposite to the data voltages of different polarities, respectively, and outputs the positive or negative common voltages alternately, and the line and And a frame voltage for outputting the common voltage applied to the N th and N-1 th so as to have a polarity opposite to that of the data voltage having the same polarity. The method of claim 6, And the common voltage variable part comprises an operational amplifier and a multiplexer for varying a common voltage outputted from the DC / DC converter by a constant voltage value. The method of claim 6, And a digital analog converter (ASIC) configured to make the common voltage output from the common voltage variable part into an analog voltage.