KR20090086867A - Apparatus for driving liquid crystal display of 2 dot inversion type - Google Patents

Abstract

An apparatus for driving liquid crystal display of 2 dot inversion type is provided to prevent a horizontal line by compensating the difference charge of a pixel between a odd line and even line. In an apparatus for driving liquid crystal display of 2 dot inversion type, a gate driving unit(72) supplies a scan pulse to each gate line of a liquid crystal panel(75). A gamma voltage generation unit(73) generates two levels by compensating brightness difference between an odd horizontal line and even horizontal line. A data driving unit changes a pixel signal level of the odd horizontal line to be lower than the pixel signal of the even horizontal line and output it to the data lien of the liquid crystal display panel.

Description

A driving device of the 2-dot inversion liquid crystal display device {APPARATUS FOR DRIVING LIQUID CRYSTAL DISPLAY OF 2 DOT INVERSION TYPE}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving technology of a liquid crystal display device, and more particularly, to a driving device of a two-dot inversion liquid crystal display device suitable for preventing a horizontal line phenomenon generated in a two-dot inversion driving method.

Recently, with the development of information technology (IT), the importance of the flat panel display device as a visual information transmission medium has been further emphasized, and low power consumption, thinning, light weight, and high quality are required to secure improved competitiveness in the future.

A liquid crystal display (LCD), which is a typical display device of a flat panel display device, is an apparatus for displaying an image using optical anisotropy of liquid crystal, and has advantages such as thin, small size, low power consumption, and high quality.

Such a liquid crystal display device is a display device in which image information is individually supplied to pixels arranged in a matrix, and a desired image is displayed by adjusting light transmittance of the pixels. Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels, which are the smallest unit for implementing an image, are arranged in an active matrix form, and a driving unit for driving the liquid crystal panel. Since the LCD does not emit light by itself, a backlight unit is provided to supply light to the LCD. The driver includes a timing controller and a data driver and a gate driver.

FIG. 1 is a block diagram of a liquid crystal display according to the related art, and as shown therein, a gate control signal GDC and a data control signal DDC for controlling driving of the gate driver 12 and the data driver 14. A timing controller 11 for outputting the digital pixel data RGB and reordering the digital pixel data RGB; A gate driver 12 for supplying a gate signal to each gate line GL1 to GLn of the liquid crystal panel 15; A gamma voltage generator 13 for supplying a gamma voltage to the data driver 14; A data driver 14 for supplying a pixel signal to each of the data lines DL1 to DLm of the liquid crystal panel 15; It is composed of a liquid crystal panel 15 which displays an image by providing a liquid crystal cell driven by the gate signal and the pixel signal in a matrix form. The operation thereof will be described as follows.

The timing controller 11 may include a gate control signal GDC and a data driver 14 for controlling the gate driver 12 using the vertical / horizontal synchronization signals Vsync / Hsync and the clock signal CLK supplied from the system. Outputs a data control signal (DDC) for controlling. In addition, the timing controller 11 samples digital pixel data (hereinafter, referred to as 'data') RGB input from the system and rearranges the digital pixel data (hereinafter referred to as 'data') to the data driver 14.

Examples of the gate control signal GDC include a gate start pulse GSP, a gate shift clock GSC, a gate out enable signal GOE, and an example of the data control signal DDC, a source start pulse. SSP, source shift clock SSC, source out enable signal SOE, polarity signal POL, and the like.

The gate driver 12 sequentially supplies the gate signals to the gate lines GL1 to GLn under the control of the gate control signal GDC input from the timing controller 15, thereby supplying the gate signals to the gate lines GL1 to GLn. The connected thin film transistor TFT is turned on in the corresponding gate line unit.

The data driver 14 corresponds to the grayscale value of the pixel data RGB by using the gamma voltage supplied from the gamma voltage generator 13 under the control of the data control signal DDC input from the timing controller 11. An analog pixel signal (data signal or data voltage) is generated, and the generated pixel signal is supplied to the data lines DL1 to DLm on the liquid crystal panel 15.

FIG. 2 is a circuit diagram illustrating a gamma voltage generation principle in the gamma voltage generator 13. As shown in FIG. 2, a resistor in which a power supply voltage VDD supplied from a DC / DC converter (not shown) is connected in series. The voltage is divided by the resistance ratios of R1 and R2, and the corresponding gamma voltage Gamma1 is supplied to the data driver 14.

The liquid crystal panel 15 includes data lines (DL1~DLm) and a gate line, to the intersection of the (GL1~GLn) having a plurality of liquid crystal cells (C _LC) disposed in a matrix form a plurality of liquid crystal cells (C _LC Are driven by the pixel signal and the gate signal to display a desired image.

Such a liquid crystal display uses an inversion method to prevent deterioration of the liquid crystal cells. In particular, the liquid crystal display device provides an excellent image quality compared to other inversion methods, but to compensate for the dot inversion method, which consumes a lot of power. The vertical two-dot inversion scheme as shown in 3b is mainly used.

3A and 3B illustrate polarities of pixel signals supplied to liquid crystal cells in a vertical two-dot inversion scheme divided into odd frames (previous frames) and even frames (current frames). In the odd and even frames shown in Figs. 3A and 3B, the vertical two-dot inversion scheme changes the polarity of the pixel signal in dots in the horizontal direction, as in the conventional dot inversion scheme, while in the vertical direction. It is characterized by a change of 2 dots.

4 is a waveform diagram of a pixel signal driven according to the vertical 2-dot inversion scheme.

However, in the vertical two-dot inversion method, a difference in charging amount appears between an even horizontal line and an odd horizontal line due to the load characteristic of the data driver 14, which is represented by a luminance difference. For example, FIG. 5 illustrates the charging charge amount of two pixels that are continuous in the vertical direction in FIG. 3A or FIG. 3B, and the charging charge amount Qo of the pixel positioned in the odd horizontal line is even. It can be seen that less than the charge amount Qe of the pixel located at.

The reason for this is that in the case of pixels on the odd horizontal line, the polarity is changed from the positive (+) to the negative (-) signal or vice versa, which requires a relatively long charging rise time or fall time. On the other hand, since the pixels located in the even horizontal line are changed in a signal of the same polarity, such a time is required less.

In this case, based on the TN mode, a pixel located in the odd horizontal line and having a small amount of charging charge Qo is positioned in the even horizontal line, and thus, is brighter than a pixel having a large amount of charged charge Qe. As a result, a luminance difference is generated between the odd horizontal line and the even horizontal line. As a result, a 2-line dim phenomenon occurs on the screen as shown in FIG. 6.

As described above, in the conventional liquid crystal display device to which the vertical two-dot inversion method is applied, a luminance difference is generated between the odd horizontal line and the even horizontal line due to the difference in the charge amount between the even horizontal line and the odd horizontal line. -Line Dim) phenomenon occurred.

Accordingly, an object of the present invention is to change the level of the gamma voltage supplied to the pixels located in the odd horizontal line and the pixel located in the even horizontal line in the liquid crystal panel to which the vertical two-dot inversion driving method is applied. The difference between the charge charge amount of the pixel and the charge charge amount of the pixel on the even horizontal line is compensated for.

The present invention for achieving the above object, the gate driver for supplying a scan pulse to each gate line of the liquid crystal panel; A gamma voltage generator configured to generate and output two levels of gamma voltages to compensate for a luminance difference between the even horizontal line and the odd horizontal line on the liquid crystal panel; And a data driver converting the pixel signal level of the pixel located in the even horizontal line to be slightly lower than the pixel signal level of the pixel located in the even horizontal line using the gamma voltages of the two levels, and outputting the pixel signal level to the data line of the liquid crystal panel. It is characterized by the configuration.

According to the present invention, in the liquid crystal panel to which the vertical two-dot inversion driving method is applied, the charging charge amount of the pixel located in the odd horizontal line is different from the gamma voltage level supplied to the pixel located in the odd horizontal line and the pixel located in the even horizontal line. It is possible to compensate for the difference in the charging charges of the pixels in the even horizontal line, so that the charge charges of the pixels in the odd horizontal line and the charging charge of the pixels in the even horizontal line are different from each other. There is an effect that can be prevented from occurring.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 7 is a block diagram showing an embodiment of a driving apparatus of a two-dot inversion liquid crystal display according to the present invention. As shown therein, the driving of the gate driver 72 and the data driver 74 is controlled. A timing controller 71 for outputting the gate control signal GDC and the data control signal DDC, and for realigning and sampling the digital video data RGB; A gate driver 72 supplying scan pulses to the gate lines GL1 to GLn of the liquid crystal panel 75 under the control of the gate control signal GDC; A gamma voltage generator for generating and outputting two levels of gamma voltage to compensate for the difference in luminance between the odd horizontal line and the even horizontal line due to the difference in the charge amount between the even horizontal line and the odd horizontal line. )Wow; In supplying the pixel signal to each of the data lines DL1 to DLm of the liquid crystal panel 75 under the control of the data control signal DDC, the analog of the pixel located in the even horizontal line using the two levels of gamma voltages. A data driver 74 for converting and supplying the level of the pixel signal to be slightly lower than the level of the analog pixel signal of the pixel located in the odd horizontal line; The liquid crystal panel driven by the scan pulse and the pixel signal is provided in a matrix form to form an LCD panel for displaying an image.

The gamma voltage generator 73 includes a power supply voltage generator 73A for alternately selecting and outputting the first power supply voltage and the second power supply voltage at different levels in synchronization with the horizontal synchronization signal; And a gamma voltage generator 73B for generating and outputting first and second gamma voltages corresponding to the first and second power supply voltages input from the power supply voltage generator.

Referring to Figures 8 to 10 attached to the operation of the present invention configured as described above in detail as follows.

The timing controller 71 controls the gate driver 72 and the data driver 74 to control the gate driver 72 using the vertical / horizontal synchronization signal Hsync / Vsync and the clock signal CLK supplied from the system. Outputs a data control signal (DDC) for controlling. In addition, the timing controller 71 samples the digital pixel data RGB input from the system, rearranges the digital pixel data RGB, and supplies the same to the data driver 74.

Here, the gate control signal GDC means a gate start pulse GSP, a gate shift clock signal SC, and a gate out enable signal GOE, and the data control signal DDC is a source start pulse SSP, a source. The shift clock signal SSC, the source out enable signal SOE, and the polarity signal POL.

The gate driver 72 sequentially supplies the gate signal to the gate lines GL1 to GLn under the control of the gate control signal GDC input from the timing controller 71, thereby corresponding thin film transistor TFT on the horizontal line is provided. ) Are turned on. Accordingly, pixel signals supplied through the data lines DL1 to DLm are stored in the respective storage capacitors C _ST through the thin film transistors TFT.

In more detail, the gate driver 72 shifts the gate start pulse GSP according to the gate shift clock GSC to generate a shift pulse. The gate driver 72 supplies a gate signal consisting of gate on / off sections (signals) to the corresponding gate line GL in a horizontal period in response to the shift clock. In this case, the gate driver 72 supplies a gate-on signal only in an enable period in response to the gate-out enable signal GOE, and supplies a gate-off signal (gate low signal) in other periods.

When the gamma voltage generator 73 supplies the gamma voltage required by the data driver 74, the odd horizontal line and the even horizontal line are changed due to the difference in the charge amount between the even horizontal line and the odd horizontal line. In order to compensate for this, a gamma voltage of two levels is generated and supplied.

The data driver 74 corresponds to the grayscale value of the pixel data RGB by using the gamma voltage supplied from the gamma voltage generator 73 under the control of the data control signal DDC input from the timing controller 71. The pixel signal is converted into an analog pixel signal (data signal or data voltage), and the converted pixel signal is supplied to the data lines DL1 to DLm on the liquid crystal panel 75.

In more detail, the data driver 74 generates the sampling signal by shifting the source start pulse SSP according to a source shift clock. Subsequently, the data driver 74 sequentially inputs and latches the pixel data RGB by a predetermined unit in response to the sampling signal. The data driver 74 converts the latched pixel data RGB for one line into an analog pixel signal and supplies the same to the data lines DL1 to DLm.

The liquid crystal panel 75 is formed for each of intersections of the plurality of liquid crystal cells (C _LC) arranged in a matrix, a data line (DL1~DLm) and gate line (GL1~GLn) each of the liquid crystal cell (C _LC And a thin film transistor (TFT) connected to each of them.

The thin film transistor TFT is turned on when the gate signal is supplied from the gate line GL, and supplies the pixel signal supplied through the data line DL to the liquid crystal cell C _LC . The thin film transistor TFT is turned off when the gate off signal is supplied through the gate line GL to maintain the pixel signal charged in the liquid crystal cell C _LC . The liquid crystal cell C _LC includes a pixel electrode connected to a common electrode and a thin film transistor TFT with a liquid crystal interposed therebetween. The liquid crystal cell C _LC further includes a storage capacitor C _ST so that the charged pixel signal is stably maintained until the next pixel signal is charged. The storage capacitor C _ST is formed between the pixel electrode and the previous gate line. In the liquid crystal cell C _LC , an arrangement state of liquid crystals having dielectric anisotropy varies according to pixel signals charged through the thin film transistor TFT, and light transmittance is adjusted accordingly to implement gradation.

On the other hand, the gamma voltage generator 73 in the process of generating a gamma voltage of two different levels in consideration of the occurrence of the luminance difference between the odd horizontal line and even horizontal line in the vertical two-dot inversion method as described above The more detailed description is as follows.

The gamma voltage generator 73 is composed of a power supply voltage generator 73A and a gamma voltage generator 73B. FIG. 8 shows an embodiment of the power supply voltage issuing device 73A. The power supply voltage distribution unit 81 of the power supply voltage generator 73A uses predetermined resistors R1 and R2 connected in series with the first power supply voltage VDD1 supplied from a DC / DC converter or a power integrated device. The voltage is divided in proportion to generate a second power supply voltage VDD2 according to the voltage division. The switch 82 alternately selects and outputs the first power supply voltage VDD1 and the second power supply voltage VDD2 in synchronization with the horizontal synchronization signal Hsync. FIG. 9A shows waveform diagrams of the power supply voltages VDD1 and VDD2 output from the switch 82.

The gamma voltage generator 73B corresponds to the power supply voltages VDD1 and VDD2 as shown in FIG. 9A input from the switch 82 and thus corresponds to the gamma voltage GA1 as shown in FIG. 9B. Outputs (GA2). That is, the gamma voltage generator 73B outputs two gamma voltages GA1 and GA2 having a predetermined level difference, instead of outputting one level of gamma voltage when generating the gamma voltage.

Here, the level difference between the power supply voltages VDD1, VDD2, and the gamma voltages GA1, GA2 is set to compensate for the luminance difference between the odd horizontal line and the even horizontal line in the vertical 2-dot inversion scheme.

The data driver 74 converts the pixel data RGB into an analog pixel signal (data signal or data voltage) corresponding to the gray scale value under the control of the data control signal DDC input from the timing controller 71. In this case, as shown in FIG. 10, the gamma voltages GA1 and GA2 supplied from the gamma voltage generator 73 are converted.

That is, the data driver 74 uses the gamma voltages GA1 and GA2 when converting the pixel data RGB input from the timing controller 71 into analog pixel signals corresponding to grayscale values. The level of the analog pixel signal of the pixel located in the even horizontal line is converted to be slightly lower than the level of the analog pixel signal of the pixel located in the even horizontal line.

By doing so, in the liquid crystal panel to which the vertical 2-dot inversion method is applied, the charging characteristic of the pixel positioned in the odd horizontal line is prevented from being less than the charging charge of the pixel positioned in the excellent horizontal line due to the load characteristic. The charging charge of the pixels between the excellent horizontal lines is balanced so that a 2-line dim phenomenon does not occur.

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

FIG. 2 is a circuit diagram illustrating a gamma voltage generation principle in the gamma voltage generator of FIG. 1. FIG.

3A and 3B are polarity arrangement diagrams of pixel signals showing a vertical two-dot inversion scheme in a conventional liquid crystal display.

4 is a waveform diagram of a conventional pixel signal driven according to a vertical two-dot inversion scheme in a conventional liquid crystal display.

FIG. 5 is a waveform diagram showing charging amounts of two pixels continuous in a vertical direction in a conventional liquid crystal display. FIG.

FIG. 6 is a screen illustrating a horizontal line phenomenon caused by a luminance difference between an odd horizontal line and an even horizontal line in a conventional liquid crystal display. FIG.

Fig. 7 is a block diagram of a drive device for a 2-dot inversion liquid crystal display device according to the present invention.

FIG. 8 is a detailed circuit diagram of a power supply voltage generator in FIG. 7. FIG.

9A and 9B are waveform diagrams of a power supply voltage and a gamma voltage in FIG.

10 is a waveform diagram of a pixel signal according to the present invention;

*** Description of the symbols for the main parts of the drawings ***

71: timing controller 72: gate driver

73: gamma voltage generator 73A: power supply voltage generator

73B: gamma voltage generator 74: data driver

75: liquid crystal panel

Claims (5)

A gate driver supplying a scan pulse to each gate line of the liquid crystal panel; A gamma voltage generator configured to generate and output two levels of gamma voltages to compensate for a luminance difference between the even horizontal line and the odd horizontal line on the liquid crystal panel; And a data driver converting the pixel signal level of the pixel located in the even horizontal line to be slightly lower than the pixel signal level of the pixel located in the even horizontal line using the gamma voltages of the two levels, and outputting the pixel signal level to the data line of the liquid crystal panel. A drive device for a 2-dot inversion liquid crystal display device, which is configured. The method of claim 1, wherein the gamma voltage generation unit A power supply voltage generator configured to alternately select and output first and second power supply voltages having different levels; And a gamma voltage generator configured to generate and output first and second gamma voltages corresponding to the first and second power supply voltages input from the power supply voltage generator. 3. The driving apparatus of claim 2, wherein the power supply voltage generator is configured to alternately select the first power supply voltage and the second power supply voltage in synchronization with a horizontal synchronization signal. The method of claim 2, wherein the power supply voltage generator A power supply voltage divider for dividing the first power supply voltage in series at a predetermined ratio using two resistors connected in series to generate a second power supply voltage; And a switch for alternately selecting and outputting the first power supply voltage and the second power supply voltage. The liquid crystal panel according to claim 1, wherein the data driver has a level enough to compensate that the charging charge of the pixels positioned on the odd horizontal lines is less than that of the pixels located on the even horizontal lines in the liquid crystal panel to which the vertical 2-dot inversion method is applied. And a pixel signal of a pixel positioned in the even and odd horizontal lines so as to have a difference.

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