KR20080040952A - Liquid crystal display and method for driving the same - Google Patents

Abstract

An LCD device and a driving method thereof are provided to display gray scales constantly by compensating for the ripple characteristics of common voltages due to parasite capacitance. An LCD(Liquid Crystal Display) device includes a liquid crystal panel(110), a timing controller(210), a data driver(230), a common voltage generator(240), a common voltage compensator(250), and a gamma voltage compensator(260). The liquid crystal panel includes gate and data lines across each other. The timing controller outputs gate and data control signals and pixel data. The data driver receives the pixel data and the data control signal, and drives data lines of the liquid crystal panel according to the data control signal. The voltage generator generates common voltages to be supplied to the liquid crystal panel and gamma voltages to be supplied to the data driver. The common voltage compensator receives the common voltages, compensates for the variation of the common voltages, and supplies the compensated common voltages to the liquid crystal panel. The gamma voltage compensator receives the gamma voltages, compensates for the received gamma voltages according to the variation of the common voltages, and supplies the compensated gamma voltages to the data driver.

Description

Liquid crystal display and method for driving the same {Liquid crystal display and method for driving the same}

1 is a configuration diagram of a liquid crystal display according to the prior art.

FIG. 2 is a detailed configuration diagram of the gamma voltage generator shown in FIG. 1.

FIG. 3 is a view illustrating variation of a common voltage by a parasitic capacitor in the liquid crystal display according to the related art.

4 is a configuration diagram of a liquid crystal display according to the present invention.

FIG. 5 is a circuit diagram illustrating a detailed configuration of a common voltage compensator shown in FIG. 4.

6 is a circuit diagram illustrating a detailed configuration of a gamma voltage compensator shown in FIG. 4.

7 is a diagram illustrating in detail a configuration of a liquid crystal display according to the present invention.

8 is a diagram illustrating a mounting structure of a common voltage compensator and a gamma voltage compensator of a liquid crystal display according to the present invention.

9 is a flowchart illustrating a method of driving a liquid crystal display according to the present invention.

10 and 11 are flowcharts showing the driving method of FIG. 9 in detail.

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

110, 110 ': liquid crystal panel 210: timing controller

220: gate driver 230, 230 ': data driver

240: voltage providing unit 241: gamma voltage generating unit

242: gate voltage generator 243: common voltage generator

250: common voltage compensator 260: gamma voltage compensator

270, 270 ': printed circuit board SIC_1-8: data driver chips

TCP: Tape Carrier Package

OP-AMP10, OP-AMP20: first and second comparators

R11, R12, and R13: first resistive elements

R21, R22, R23: second resistive elements

C1, C2: first and second capacitors

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof for optimizing a common voltage and a gamma voltage for driving a liquid crystal panel to prevent deterioration of image quality.

In general, the liquid crystal display device displays an image by adjusting the light transmittance of the liquid crystal according to an image signal. The liquid crystal display suppresses the deterioration of the image due to flickering or afterimage, and at the same time, the image information has a positive (+) and negative (-) configuration for a constant voltage level in order to lower the driving voltage of the liquid crystal display. To control.

In this case, in the liquid crystal display, a gamma characteristic in which the gray level of the image does not change linearly but varies linearly according to the voltage level of the video signal appears.

The cause of the gamma characteristic is that the light transmittance of the liquid crystal does not change linearly according to the voltage level of the image signal, and the gray scale of the image does not change linearly according to the light transmittance of the liquid crystal.

Therefore, in the conventional liquid crystal display device, a gamma characteristic is added to the voltage level of the image information by an offset voltage so that the gray level of the image may be linearly changed according to the voltage level of the image information. This deterioration is prevented.

Hereinafter, the configuration of the liquid crystal display according to the related art will be described.

1 is a configuration diagram of a liquid crystal display according to the prior art, FIG. 2 is a detailed configuration diagram of the gamma voltage generator shown in FIG. 1, and FIG. 3 is a ripple of a common voltage in the liquid crystal display according to the prior art. It is a figure for demonstrating a characteristic.

First, referring to FIG. 1, a liquid crystal display according to the related art includes a liquid crystal panel 10 in which liquid crystal cells are arranged in a matrix form, and a gate driver for driving gate lines G1 to Gn of the liquid crystal panel 10. 20, a data driver 30 for driving the data lines D1 to Dm of the liquid crystal panel 10, a timing controller 40 for controlling the gate driver 20 and the data driver 30, and gamma And a voltage supply unit 50 for supplying the voltage Vgma, the gate voltage Vg, and the common voltage Vcom.

In detail, the liquid crystal panel 10 includes liquid crystal cells arranged in a matrix and thin film transistors TFT formed at intersections of the plurality of gate lines G1 to Gn and the data lines D1 to Dm, respectively. do.

The thin film transistor TFT supplies the video data signal from the data lines D1 to Dm to the liquid crystal cells in response to the gate signal from the gate lines G1 to Gn.

The liquid crystal cells may be equivalently represented by a liquid crystal capacitor Clc including a common electrode Vcom facing the liquid crystal and a pixel electrode connected to the thin film transistor TFT.

In the liquid crystal cells, a storage capacitor Cst is formed to maintain the data voltage charged in the liquid crystal capacitor Clc until the next data voltage is charged. The storage capacitor Cst is formed between the previous gate electrode and the pixel electrode.

In addition, a plurality of parasitic capacitors may be formed in the thin film transistor TFT and the liquid crystal cell such as parasitic capacitance between the pixel electrode and the next storage capacitor Cst. These parasitic capacitors vary the data voltage charged in the liquid crystal capacitor Clc by a predetermined amount.

The illustrated voltage supply unit 50 includes a gate voltage generator 51, a gamma voltage generator 52, and a common voltage generator 53.

The gate voltage generator 51 is a gate voltage Vg for turning on / off the thin film transistor TFT of the liquid crystal panel 10. The gate voltage generator 51 generates a gate high voltage and a gate low voltage to generate the gate driver 20. To serve as

The common voltage generator 53 generates a common voltage Vcom, which is a center potential of pixel driving, and supplies the generated common voltage Vcom to the liquid crystal panel 10.

The gamma voltage generator 52 compensates the gamma characteristics of the liquid crystal panel 10. The gamma voltage generator 52 generates a gamma voltage Vgma necessary for the digital / analog conversion of the data driver 30 within the grayscale range for each gray level, and thereby the data driver. Supply to (30).

As shown in FIG. 2, the gamma voltage generator 52 includes a positive gamma part 52a and a negative gamma part 52b connected in parallel between the power supply voltage terminal VDD and the base voltage terminal VSS. And a buffer section 53c.

The positive gamma portion 52a and the negative gamma portion 52b include a plurality of positive resistance groups RP1 to RPK or a plurality of negative polarities connected in series between the power supply voltage terminal VDD and the ground voltage terminal VSS. Resistance groups RN1 to RNK. With this configuration, in the positive gamma part 52a and the negative gamma part 52b, the power supply voltage VDD is divided by the resistances of the positive resistance groups RP1 to RPK or the negative resistance groups RN1 to RNK. K positive gamma voltages VP1 to VPK or K negative gamma voltages VN1 to VNK are generated, respectively. Accordingly, gamma voltages having a low potential difference based on the common voltage Vcom correspond to gray (gradation) close to white, and gamma voltages having a high potential based on the common voltage Vcom correspond to gray close to black.

The buffer unit 52c outputs the positive gamma voltages VP1 to VPK and the negative gamma voltages VN1 to VNK generated by the positive gamma part 52a and the negative gamma part 52b.

In the conventional liquid crystal display configured as described above, as illustrated in FIG. 1, the timing controller 40 or the voltage supply unit 50 may be mounted on a separate printed circuit board (PCB) 60. have. More specifically, it may be provided on a source printed circuit board (source PCB) connected to the liquid crystal panel 10 through the data driver 30.

Accordingly, the conventional liquid crystal display displays an image by adjusting light transmittance by an electric field applied between the pixel electrode and the common electrode according to a video data signal applied for each liquid crystal cell.

That is, an electric field generated by the difference between the data voltage and the common voltage applied to each pixel is supplied to the liquid crystal capacitor Clc, so that light transmits at a transmittance corresponding to the intensity of the electric field. In this case, the storage capacitor Cst maintains the data voltage applied to the pixel for a predetermined period of time.

In this case, the data voltage (gamma voltage) applied through the data lines is generally applied while switching the positive voltage and the negative voltage around the common voltage Vom.

In addition, since the common voltage Vcom becomes the center potential of the pixel when driving the pixel unit, the common voltage having the same level should be applied to all the pixels regardless of the position of the liquid crystal panel 10 to improve the image quality.

However, when the common voltage Vom is input from one side of the liquid crystal panel 10 and output to the other side, such as the line 70 shown in bold in FIG. 1, as shown in FIG. Ripple phenomenon in which the common voltage Vcom is shaken due to a difference in the capacitor coupling effect due to parasitic capacitances Cgd, Cgs, and Cg-p existing between the electrode terminal of the TFT and the liquid crystal cell electrode. Appears.

This ripple phenomenon causes poor afterimages, flicker, crosstalk, and greenish of the screen, thereby degrading the picture quality.

Accordingly, although the conventional liquid crystal display device includes a common voltage compensation circuit separately to compensate for the above-described fluctuation of the common voltage Vcom, the liquid crystal panel 10 is not made in detail, and the common voltage (for the data voltage) is used. Vcom) has a problem that image quality defects such as afterimages, flicker, and crosstalk are generated by inputting a constant gamma voltage without considering the ripple component of Vcom.

Accordingly, an aspect of the present invention is to provide a liquid crystal display device and a driving method thereof, which may improve image quality defects by optimally compensating a common voltage and a gamma voltage according to whether a common voltage for driving a liquid crystal panel changes. It is.

Further technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above are clearly understood by those skilled in the art from the following description. It can be understood.

According to an aspect of the present invention, there is provided a liquid crystal display device including: a liquid crystal panel in which horizontal gate lines and vertical data lines are arranged in a matrix; a gate control signal for controlling driving timing of the liquid crystal panel; A timing controller which outputs a data control signal and pixel data, a data driver which receives pixel data and a data control signal output from the timing controller and drives data lines of the liquid crystal panel according to the data control signal, and the liquid crystal panel A voltage generator for generating a common voltage to be provided to the data driver and a gamma voltage to be provided to the data driver, and receiving a common voltage from the voltage generator and receiving a feedback of a change in the common voltage provided to the liquid crystal panel. To compensate for the liquid crystal A gamma voltage compensated for the common voltage compensator for supplying the panel back to the panel, and a gamma voltage received from the voltage generator, and receiving the feedback of the common voltage provided to the liquid crystal panel while receiving the gamma voltage. And a gamma voltage voltage compensator for supplying the compensation gamma voltage to the data driver.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method including: (a) generating a gate control signal, a data control signal, and pixel data for controlling a driving timing of a liquid crystal panel; Generating a common voltage for driving the panel and a plurality of gamma voltages having different voltage levels according to the pixel data, and (c) receiving a common voltage provided to the liquid crystal panel and comparing the reference voltage with a reference common voltage. After compensating with the compensation common voltage of the level, providing the compensation common voltage to the liquid crystal panel; and (d) compensating the gamma voltage according to the change of the common voltage while receiving feedback of the common voltage provided to the liquid crystal panel. And outputting the signal to the gate lines of the liquid crystal panel according to the gate control signal. (F) supplying a data voltage to data lines of the liquid crystal panel according to the data control signal using the compensation gamma voltage, (g) the data voltage according to the scan signal on the liquid crystal panel And charging the difference voltage of the compensation common voltage to display an image.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

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

4 is a configuration diagram of a liquid crystal display according to the present invention.

Referring to FIG. 4, the liquid crystal display according to the exemplary embodiment of the present invention includes a liquid crystal panel 110, a timing controller 210, a gate driver 220, a gate driver 230, a voltage generator 240, and a voltage. Compensation units 250 and 260 are included.

In the liquid crystal panel 110, the gate lines GL1 to GLn in the horizontal direction and the data lines DL1 to DLm in the vertical direction are arranged in a matrix, and the gate lines GL1 to GLn and the data lines intersected with each other. It consists of a plurality of pixels separated by (DL1 to DLm). A thin film transistor TFT having a gate electrode, an active layer, a source electrode, and a drain electrode is disposed at the intersection of the gate lines GL1 to GLn and the data lines DL1 to DLm.

Each pixel is filled with a liquid crystal material equivalent to the liquid crystal cell Clc, and a storage capacitor Cst is formed to maintain a constant voltage charged in the liquid crystal cell Clc.

The liquid crystal panel 110 displays an image in each pixel according to a scan signal supplied through the gate lines GL1 through GLn and a data voltage supplied through the data lines DL1 through DLm. Here, the scan signal is a pulse signal in which the gate high voltage VGH supplied only for one horizontal time and the gate low voltage VGL supplied for the remaining time are alternated.

When the gate high voltage VGH is supplied from the gate lines GL1 to GLn, the thin film transistor TFT is turned on to supply the data voltages from the data lines DL1 to DLm to the liquid crystal cell Clc. do.

The liquid crystal cell Clc is formed between the pixel electrode to which the data voltages from the data lines DL1 to DLm are applied, and the common electrode to which the common voltage is applied.

Accordingly, in the liquid crystal display, when the thin film transistor TFT of each pixel is turned on and the data voltage is applied to the pixel electrode, the liquid crystal cell Clc is charged with the difference voltage between the data voltage and the common voltage to display an image. will be.

On the contrary, when the gate low voltage VGL is supplied from the gate lines GL1 to GLn, the thin film transistor TFT is turned off while the data voltage charged in the liquid crystal cell Clc is stored in the storage capacitor Cst. By doing so, one frame period is maintained.

As described above, the liquid crystal panel 110 repeats the above operation according to the scan signal supplied through the gate lines GL1 to GLn.

The timing controller 210 rearranges the digital pixel data R, G, and B data of red (R), green (G), and blue (B) input from the outside and supplies the rearranged digital pixel data (R, G, B DATA) to the data driver 230. The gate control signal GCS and the data driver 230 are driven to control the driving timing of the gate driver 220 using the vertical synchronization signal Vsync, the horizontal synchronization signal Hsync, the clock CLK, and the like. A data control signal DCS for controlling timing is generated.

The gate control signal GCS includes a gate start pulse (GSP), a gate shift clock (GSC), a gate output enable signal (GOE), and the like. The data control signal DCS includes a source start pulse (SSP), a source shift clock (SSC), a source output enable (SOE), and a polarity signal (POL). Etc. are included.

The gate driver 220 supplies a scan signal sequentially shifted to the gate lines GL1 to GLn according to the gate control signal GCS supplied from the timing controller 210.

The data driver 230 receives red, green, and blue digital pixel data (R, G, B DATA) input from the timing controller 210 in response to the data control signal DCS supplied from the timing controller 210. Is converted into a data voltage and supplied to the data lines DL1 through DLm.

Here, the digital pixel data (R, G, B DATA) is a digital signal representing a gradation, and is generally set to have a value between 0 and 255.

The data voltage is red, green, and blue pixel data R, G, and B DATA input from the outside of the gamma voltages Vgma supplied from the gamma voltage generator 241 of the voltage generator 240, which will be described later. Is a gamma voltage selected corresponding to

The gate driver 220 and the data driver 230 are typically formed of a plurality of driver chips and provided on a tapered carrier package (TCP) or a chip on film (COF).

The voltage generator 240 includes a gamma voltage generator 241, a gate voltage generator 242, and a common voltage generator 243. The voltage generator 240 has a common voltage Vcom to be provided to the common electrode for driving the pixel of the liquid crystal panel 110 and a gamma voltage having different voltage levels according to the pixel data R, G, and B DATA. Vgma and gate voltages VGH and VGL, respectively.

In detail by component, the gamma voltage generator 241 is required when the data driver 230 converts the digital pixel data R, G, and B data to be provided to the liquid crystal panel 110 into an analog signal. The gamma voltage Vgma is provided to generate and output gamma voltages Vgma necessary for the digital / analog conversion of the data driver 230 for each gray level within the gray scale range.

The gate voltage generator 242 generates a gate high voltage VGH and a gate low voltage VGL for turning the thin film transistor TFT of the liquid crystal panel 110 on and off and supplies the gate high voltage VGL to the gate driver 220.

The common voltage generator 243 generates and outputs a common voltage Vcom serving as the center potential of the pixel driving.

The common voltage compensator 250 receives the common voltage Vcom from the common voltage generator 243 and receives a feedback of a change in the common voltage Vcom F / B provided to the liquid crystal panel 110 to supply a constant voltage. After compensating for this, the liquid crystal panel 110 is supplied to the liquid crystal panel 110 again.

The gamma voltage compensator 260 receives the gamma voltage Vgma from the gamma voltage generator 241 and receives the feedback of the change in the common voltage Vcom F / B provided to the liquid crystal panel 110, thereby receiving the common voltage Vcom. The received gamma voltage Vgma is compensated with the compensation gamma voltage Vgma 'according to the change of F / B, and then the compensation gamma voltage Vgma' is supplied to the data driver 230.

In general, when the common voltage Vcom F / B provided to the liquid crystal panel 110 is input from one side of the liquid crystal panel 10 and output to the other side, the electrode terminal of the thin film transistor TFT and the liquid crystal cell in each pixel. Due to parasitic capacitances Cgd, Cgs and Cg-p existing between the electrodes, a ripple phenomenon in which the common voltage Vcom F / B is shaken occurs.

The ripple phenomenon here corresponds to the variation of the common voltage.

Due to the ripple of the common voltage Vcom F / B, the difference voltage between the pixel data applied from the data lines of the liquid crystal panel 110 and the common voltage is not kept constant, so that the same gray level is not displayed in each pixel. I can't.

Therefore, the common voltage compensator 250 and the gamma voltage compensator 260 are not only the common voltage Vcom but also the gamma voltage Vgma according to the variation of the common voltage Vcom F / B generated in the liquid crystal panel 110. ) Is simultaneously compensated so that the difference voltage between the pixel data applied from the data lines of the liquid crystal panel 110 and the common voltage is always maintained.

The common voltage compensator 250 and the gamma voltage compensator 260 are configured as follows.

5 is a circuit diagram illustrating a detailed configuration of the common voltage compensator illustrated in FIG. 4, and FIG. 6 is a circuit diagram illustrating a detailed configuration of the gamma voltage compensator illustrated in FIG. 4.

Referring to FIG. 5, the common voltage compensator 250 of the liquid crystal display according to the present invention may include a comparator OP-AMP10 (hereinafter, referred to as a “first comparator”) and resistors R11, R12, and R13 (hereinafter, referred to as “comparator”). , 'First resistor elements'), and capacitor C1 (hereinafter, 'first capacitor').

The first comparator OP_AMP10 uses an operational amplifier, and the (-) input terminal of the operational amplifier is a reference value from the common voltage generator (243 of FIG. 4) of the voltage generator (240 of FIG. 4) as a reference value. ) Is continuously received, and the positive input terminal of the operational amplifier is connected to the first capacitor C1 and the resistor R11.

In addition, a resistor R12 is connected between the positive input terminal and the output terminal of the operational amplifier, and the other side of the first capacitor C1 receives the common voltage Vcom F / B provided to the liquid crystal panel 110. Receive continuous feedback.

Accordingly, the common voltage compensator 250 configured as described above is an input terminal, the reference common voltage Vcom_ref from the common voltage generator 243 of FIG. 4, and the common voltage Vcom F / generated on the liquid crystal panel 110. Continuously receiving the change of B), and adjusts the compensation ratio (R11 / R12) and outputs the compensation common voltage (Vcom ') to the output terminal.

That is, when the common voltage Vcom F / B supplied to the liquid crystal panel 110 is fed back to the common voltage compensator 250, the common voltage compensator 250 receives the common voltage Vcom by the first capacitor C1. The direct current (DC) component of F / B) is removed and only the alternating current (AC) component is applied. The alternating current component of the common voltage Vcom F / B is a ripple component generated by parasitic capacitance existing between the electrode terminal of the thin film transistor and the liquid crystal cell electrode, and corresponds to a variation of the common voltage Vcom F / B. Yes.

Subsequently, the compensation value for the change in the common voltage Vcom F / B is compensated for by comparing the change in the common voltage Vcom F / B and the reference common voltage Vcom_ref in the first comparator OP-AMP10 at a later stage. Determined by (R11 / R12), and converts the reference common voltage Vcom_ref to the compensation common voltage Vcom 'according to the compensation value and outputs the converted common voltage. The output compensation common voltage Vcom 'is supplied to the liquid crystal panel 110 again.

Here, the compensation ratio R11 / R12 of the compensation common voltage Vcom 'may be set by the first resistance elements R11 and R12 using a variable resistor.

Referring to FIG. 6, the gamma voltage compensator 260 of the liquid crystal display according to the present invention includes a reference gamma voltage Vgam_ref from the gamma voltage generator 241 of FIG. 4, and a liquid crystal panel 110. By receiving the common voltage Vcom F / B supplied to the feedback, the gamma voltage Vgma corresponding to each digital pixel data input to the data lines of the liquid crystal panel 110 is converted into the common voltage Vcom F / B. Compensation according to the ripple component of As a result, the difference voltage between the compensated common voltage Vcom 'compensated by the common voltage compensator 243 and the pixel data output from the data driver 230 is maintained constant.

In this case, the common voltage Vcom F / B fed back from the gamma voltage compensator 260 is the same voltage as the common voltage Vcom F / B fed back to the input terminal of the common voltage compensator 250. By reflecting the ripple component of the common voltage (Vcom F / B) provided to the gamma voltage, the compensated gamma voltage (Vgma ') to maintain a constant level relative to the compensation common voltage (Vcom').

In particular, it is a feed-through voltage generated by the ripple component of the common voltage Vcom charged in the liquid crystal cell at a difference voltage between the data voltage supplied to the data lines and the liquid crystal cell voltage charged in the liquid crystal cell. This is to improve the image quality defect due to the feed through voltage ΔVp by reflecting the voltage and ΔVp in the gamma voltage Vgma.

As shown, the gamma voltage compensator 260 includes a comparator OP-AMP20 (hereinafter referred to as a 'second comparator') and resistance elements R21, R22, and R23 of a variable resistor (hereinafter, 2 resistor elements') and capacitor C2 (hereinafter referred to as' second capacitor ').

The negative input terminal of the second comparator OP_AMP20 continuously receives the reference gamma voltage Vgma_ref from the gamma voltage generator 241 of FIG. 4 as a reference value, and the operational amplifier. The second capacitor C2 and the resistor R22 are connected to the positive input terminal of the (+) input terminal.

In addition, a resistor R22 is connected between the positive input terminal and the output terminal of the second comparator OP_AMP20, and the other side of the second capacitor C1 is a common voltage Vcom F provided to the liquid crystal panel 110. / B) keep getting feedback.

Accordingly, the gamma voltage compensator 260 configured as described above is a reference gamma voltage Vgma_ref from the gamma voltage generator 241 of FIG. 4 and a common voltage Vcom F / fed back from the liquid crystal panel 110 as an input terminal. When each of B) is received, the feedback common voltage Vcom F / B is removed through the second capacitor C1, and the direct current (DC) component of the common voltage Vcom F / B is removed, and only the alternating current (AC) component is used. Will be authorized. The alternating current component of the common voltage Vcom F / B is a ripple component generated by parasitic capacitance existing between the electrode terminal of the thin film transistor and the liquid crystal cell electrode, and corresponds to a variation of the common voltage Vcom F / B. Yes.

Subsequently, the compensation value for the variation of the common voltage Vcom F / B is compensated for by comparing the variation of the common voltage Vcom F / B and the reference gamma voltage Vgma_ref in the second comparator OP-AMP10 at a later stage. It determines according to (R21 / R22), converts the reference gamma voltage Vgma_ref to the compensation gamma voltage Vgma 'according to the compensation value, and outputs it.

The output compensation gamma voltage Vgma 'is supplied to the data driver 230 (in FIG. 4) again, and the digital image data R, G, and B DATA output from the timing controller unit 210 (in FIG. 4) are output in analog form. It is applied to convert and generate data voltage.

The compensation ratio R21 / R22 of the compensation gamma voltage Vgma 'may be set by the second resistance elements R21 and R22 using a variable resistor.

In addition, when the first and second capacitors C1 and C2 receive the common voltage Vcom F / B, the first and second capacitors C1 and C2 may remove the DC component of the common voltage Vcom F / B and adjust the value to receive only the AC component. have.

The common voltage compensator 250 and the gamma voltage compensator 260 configured as described above may be mounted on a printed circuit board (PCB) or a data driver (230 of FIG. 4) as described below. .

FIG. 7 is a diagram illustrating in detail a configuration of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 8 is a diagram illustrating a mounting structure of a common voltage compensator and a gamma voltage compensator of a liquid crystal display according to the present invention.

Referring to FIG. 7, in the liquid crystal display according to the present invention, the data driver 230 includes a plurality of data driver chips SIC_1 to SIC_8, and the plurality of data driver chips SIC_1 to SIC_8 are tape carrier packages TCP. It may be mounted on a Taped Carrier Package.

In addition, the data driver chips SIC_1 to SIC_8 may be mounted on a chip on film (COF).

The gate driver (not shown) may also include a plurality of gate driver chips (not shown), and the plurality of gate driver chips may be provided on a tapered carrier package (TCP) or a chip on film (COF). have.

One end of the liquid crystal panel 110 includes a printed circuit board 270 connected to data lines of the liquid crystal panel 110 through the data driver 230. More specifically, it is a source printed circuit board (source PCB).

On the printed circuit board 270, the timing controller (210 in FIG. 4) or the gamma voltage generator (241 in FIG. 4), the gate voltage generator (242 in FIG. 4), and the common voltage of the liquid crystal display according to the present invention. The voltage generator 240 (including the generator 443 of FIG. 4) may be mounted.

In addition, the common voltage compensator 250 of FIG. 4 and the gamma voltage generator 260 of FIG. 4 may be mounted.

Alternatively, the common voltage compensator 250 of FIG. 4 and the gamma voltage generator 260 of FIG. 4 may be mounted on the data driver 230 to simplify the circuit configuration of the printed circuit board 270 and reduce the size of the entire circuit. Can be reduced.

FIG. 8 is a view illustrating a mounting structure of a common voltage compensator and a gamma voltage compensator of a liquid crystal display according to an exemplary embodiment of the present invention, and a common voltage compensator (not shown) and a gamma voltage compensator of a liquid crystal display according to the present invention. Although not shown, all are mounted on the data driver 230 ', but a portion of the compensation circuit is mounted on the printed circuit board 270'.

In detail, as illustrated, a compensation circuit corresponding to the common voltage compensation unit and the gamma voltage compensation unit is mounted in the data driver 230 ′, and the capacitor C and the resistors R1 and R2 are respectively It is mounted on a printed circuit board 270 '.

Although not illustrated for convenience of description, the first capacitor (C1 of FIG. 5) and the first resistor elements (R11 and R12 of FIG. 5) of the common voltage compensator (not shown) and the gamma voltage compensator (not shown) are illustrated. The second capacitor C2 of FIG. 6 and the second resistor elements R21 and R22 of FIG. 6 may be mounted on the printed circuit board 270 ′.

Therefore, compensation ratios of the common voltage and the gamma voltage may be set according to the characteristics of the liquid crystal panel 110 ′ or the degree of variation of the common voltage Vcom.

According to the configuration of the present invention, even if a ripple component of the common voltage Vcom occurs due to the parasitic capacitance existing between the electrode terminal of the thin film transistor and the liquid crystal cell electrode in the liquid crystal panel, the variation in the common voltage Vcom is caused. Since the common voltage Vcom and the gamma voltage Vgma are simultaneously compensated, the difference voltage between the common voltage Vcom and the pixel data to be provided to the data lines is kept constant to display the same gray scale.

Furthermore, by setting the resistors R1 and R2 and the capacitors C to be tunable on the printed circuit board 270 'as shown in FIG. 8, the gamma voltage and the liquid crystal panel 110 having a plurality of levels are provided. The optimal compensation ratio for the common voltage and the gamma voltage can be set according to the characteristics of ').

Hereinafter, the driving method of the liquid crystal display device according to the present invention will be described in detail.

9 is a flowchart illustrating a driving method of the liquid crystal display according to the present invention, and FIGS. 10 and 11 are flowcharts showing the driving method of FIG. 9 in detail with reference to FIG. 4.

First, referring to FIG. 9, in the driving method of the liquid crystal display according to the present invention, first, in step S100, the timing controller 210 may control driving timing of the gate driver 220 and the data driver 230, respectively. The gate control signal GCS, the data control signal DCS, and the digital pixel data R, G, and B DATA are generated.

Next, in operation S110, a common voltage Vcom for driving the pixels of the liquid crystal panel 110 and a plurality of gamma voltages Vgma having different voltage levels according to the pixel data are generated and output.

Next, in operation S120, the common voltage compensator 250 receives a common voltage Vcom F / B provided to the liquid crystal panel 110 while being fed back to the reference common voltage to compensate for a constant level of the common voltage Vcom ′. After compensation, the compensated compensation common voltage Vcom 'is supplied to the liquid crystal panel 110.

This step S120 may be subdivided into steps S121 to S124 as shown in FIG. 10.

Referring to FIG. 5, in operation S121, the reference common voltage Vcom_ref is continuously received from the common voltage generator 243 at an input terminal of the common voltage compensator 250.

Next, in step S122, the compensation ratios R11 and R12 are set by adjusting the values of the first resistance elements R11 and R12 of the common voltage compensator 250. The first resistance elements R11 and R12 are provided as variable resistors.

Next, in step S123, the common voltage Vcom F / B provided to the liquid crystal panel 110 is fed back to the input terminal of the common voltage compensator 250.

In the last step S124, the reference common voltage Vcom_ref and the fed back common voltage Vom F / B are compared through the first comparator OP-AMP10 to determine the change in the fed back common voltage Vom F / B. The compensation value is determined by the set compensation ratio, and the reference common voltage Vcom_ref is converted into the compensation common voltage Vcom 'according to the compensation value and then output.

Referring back to FIG. 9, in the next step S130, the common voltage Vom F / B provided to the liquid crystal panel 110 is fed back simultaneously with the common voltage compensator 250 and the common voltage Vom F / B The level of the gamma voltage Vgma is compensated for by the variation.

Next, in step S140, the gate driver 220 supplies the scan signals to the gate lines GL1 to GLn of the liquid crystal panel 110 according to the gate control signal GCS as shown in FIG. 4.

Next, in step S150, the data driver 230 supplies the data voltages to the data lines DL1 to DLn of the liquid crystal panel 110 according to the data control signal DCS.

Next, in step S160, the thin film transistor TFT of each pixel is turned on for one horizontal period according to the scan signal from the gate lines GL1 to GLn, and the thin film transistor TFT is turned on in the turn-on state of the thin film transistor TFT. An image is displayed for each pixel while the liquid crystal cell Clc of the pixel is charged with a difference voltage between the data voltage and the compensation common voltage Vcom '.

In the above steps, step S130 is composed of steps S131 to S134 as shown in FIG.

Referring to FIG. 6, in operation S131, the reference gamma voltage Vgma_ref is continuously received from the common voltage generator 250 at an input terminal of the gamma voltage compensator 260.

Next, in operation S132, the compensation ratios R21 and R22 are set by adjusting the values of the second resistance elements R21 and R22 of the gamma voltage compensator 260. The second resistors R21 and R22 may also be provided as variable resistors like the first resistors.

Next, in step S133, the common voltage Vom F / B provided to the liquid crystal panel 110 is fed back to the input terminal of the gamma voltage compensator 260.

In the last step S134, the reference gamma voltage Vgma_ref and the feedback common voltage Vom F / B are compared through the second comparator OP = AMP20, and thus the variation of the feedback common voltage Vom F / B is measured. The compensation value is determined by the set compensation ratio, and the reference gamma voltage Vgma_ref is converted into the compensation common voltage Vgma 'according to the compensation value and then output.

The liquid crystal display according to the exemplary embodiment of the present invention driven by such a process compensates for the common voltage Vcom and the gamma voltage Vgma at the same time according to the variation of the common voltage Vcom even when the common voltage changes in the liquid crystal panel. Therefore, the difference voltage between the common voltage Vcom and the pixel data to be provided to the data lines is constantly maintained to display the same gray scale.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

In the liquid crystal display according to the present invention, the ripple characteristic of the common voltage due to parasitic capacitance present in the liquid crystal panel is optimally compensated by reflecting not only the common voltage but also the gamma voltage. The difference voltage between the video data to be provided to the data lines is kept constant, so that the same gray level can be displayed.

As a result, image quality defects such as afterimages of the screen, flicker, crosstalk, and Greenish of the screen can be improved.

Claims (21)

A liquid crystal panel in which horizontal gate lines and vertical data lines are arranged in a matrix; A timing controller for outputting a gate control signal, a data control signal, and pixel data for controlling driving timing of the liquid crystal panel; A data driver which receives pixel data and a data control signal output from the timing controller and drives data lines of the liquid crystal panel according to the data control signal; A voltage generator configured to generate common voltages to be provided to the liquid crystal panel and gamma voltages to be provided to the data driver; A common voltage compensator for receiving a common voltage from the voltage generator, compensating for a constant level of voltage while receiving feedback of a change in the common voltage provided to the liquid crystal panel, and then supplying the common voltage to the liquid crystal panel; And The gamma voltage is received from the voltage generator, and the gamma voltages are compensated with the compensation gamma voltage according to the change of the common voltage while receiving feedback of the change in the common voltage provided to the liquid crystal panel. Gamma Voltage Voltage Compensator for Data Driver Liquid crystal display comprising a. The method of claim 1, And a gate driver for driving gate lines of the liquid crystal panel according to the gate control signal output from the timing controller. The method of claim 1, The voltage generator, A common voltage generator configured to generate a reference common voltage to be provided to the liquid crystal panel; A gamma voltage generator configured to generate a plurality of gamma voltages having different voltage levels according to the video data Liquid crystal display comprising a. The method of claim 3, The voltage generator, And a gate voltage generator configured to generate gate voltages for turning on / off gate lines of the liquid crystal panel. The method of claim 1, The common voltage compensator, And compensating by comparing the common voltage provided to the liquid crystal panel with a reference common voltage output from the voltage generator. The method of claim 1, And a common voltage fed back to the common voltage compensator and a common voltage fed back to the gamma voltage compensator. The method of claim 1, The common voltage compensator A first comparator configured to receive and compare the common voltage fed back from the liquid crystal panel and the reference common voltage; First resistor elements for setting a compensation ratio of the first comparator Liquid crystal display comprising a. The method of claim 1, The gamma voltage compensator A second comparator configured to receive and compare a common voltage fed back from the liquid crystal panel and a reference gamma voltage; Second resistance elements for setting a compensation ratio of the second comparator Liquid crystal display comprising a. The method according to claim 7 or 8, The input terminals of the first and second comparators are connected to capacitors for removing direct current (DC) components of a common voltage fed back from the liquid crystal panel, respectively. The method according to claim 7 or 8, And the first and second resistor elements are variable resistors. The method of claim 1, The data driver And a data driver chip mounted on a tape carrier package (TCP) and connected to the liquid crystal panel. The method of claim 1, And the voltage generator is mounted on a printed circuit board. The method of claim 1, The common voltage compensator is mounted on a printed circuit board. The method of claim 1, The gamma voltage compensator is mounted on a printed circuit board. The method of claim 1, The common voltage compensator is mounted on the data driver. The method of claim 1, The gamma voltage compensator is mounted on the data driver. The method according to claim 15 or 16, And the first and second resistors are mounted on a printed circuit board to adjust the compensation ratio. The method according to claim 15 or 16, And the capacitors are mounted on a printed circuit board and are adjustable. (a) generating a gate control signal, a data control signal, and pixel data for controlling driving timing of the liquid crystal panel; (b) generating a plurality of gamma voltages having different voltage levels according to the common voltage for driving the liquid crystal panel and the pixel data; (c) compensating a common voltage provided to the liquid crystal panel with a compensation common voltage having a constant level compared with a reference common voltage while receiving feedback, and providing the compensation common voltage to the liquid crystal panel; (d) compensating the gamma voltage according to the change of the common voltage while receiving a common voltage provided to the liquid crystal panel and outputting the compensating gamma voltage; (e) supplying a scan signal to gate lines of the liquid crystal panel according to the gate control signal; (f) supplying data voltages to data lines of the liquid crystal panel according to the data control signal using the compensation gamma voltage; (g) displaying an image by charging the difference voltage between the data voltage and the compensation common voltage according to the scan signal on the liquid crystal panel; Method of driving a liquid crystal display comprising a. The method of claim 19, In step (c), Receiving the reference common voltage; Setting a compensation ratio by the plurality of resistance elements; Receiving a feedback of the common voltage provided to the liquid crystal panel; And Determining a compensation value for the variation of the feedback common voltage based on the set compensation ratio, converting the reference common voltage into a compensation common voltage according to the compensation value, and outputting the compensation value; Method of driving a liquid crystal display comprising a. The method of claim 19, In step (d), Receiving the reference gamma voltage; Setting a compensation ratio by the plurality of resistance elements; Receiving a feedback of the common voltage provided to the liquid crystal panel; And Determining a compensation value for the variation of the feedback common voltage based on the selected compensation ratio, and converting the reference gamma voltage into a compensation gamma voltage according to the compensation value and outputting the compensation value; Method of driving a liquid crystal display comprising a.

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