KR20060028904A - Liquid crystal display device and method for driving the same - Google Patents

Abstract

A liquid crystal display device having improved image quality is disclosed.

Liquid crystal display device of the present invention; Control means for generating a 2-dot control signal; And a data driver for driving the liquid crystal panel in a horizontal 2-dot inversion method and a vertical 2-dot inversion method according to the 2-dot control signal.

Horizontal 2-dot Inversion, Vertical 2-dot Inversion, Vertical Sync Signal (Vsync)

Description

Liquid crystal display device and method for driving the same

1 is a block diagram showing a conventional liquid crystal display device.

Figures 2a and 2b is a view showing a state driven by the horizontal two-dot inversion method.

3A and 3B are views showing a state driven by the vertical two-dot inversion method.

Fig. 4A is a waveform diagram showing a relationship between a polarity signal and a dot control signal of the vertical 2-dot inversion method.

Fig. 4B is a waveform diagram showing the relationship between the polarity signal and the dot control signal of the horizontal 2-dot inversion method.

Fig. 5A is a block diagram showing a data driver of a conventional liquid crystal display device in the case of a vertical two-dot inversion driving method.

Fig. 5B is a block diagram showing a data driver of a conventional liquid crystal display device in the case of a horizontal 2-dot inversion driving method.

6 is a block diagram showing a liquid crystal display device according to the present invention.

7 is a block diagram showing a data driver of a liquid crystal display according to the present invention.                 

8A, 8B, 8C, and 8D are views illustrating a state in which a liquid crystal display according to the present invention is driven for each frame.

9 is a waveform diagram showing the relationship between the dot control signal, the polarity signal, and the vertical synchronization signal of the liquid crystal display according to the present invention;

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof having improved image quality.

As shown in FIG. 1, a conventional liquid crystal display device includes a liquid crystal panel 2 in which liquid crystal cells are arranged in a matrix, and a gate driver for driving gate lines GL1 to GLn of the liquid crystal panel 2. (4), a data driver 6 for driving the data lines DL1 to DLm of the liquid crystal panel 2, a timing controller for controlling the gate driver 4 and the data driver 6; (10) is provided.

The liquid crystal panel 2 is formed at each intersection of the liquid crystal cells arranged in a matrix form and the gate lines GL1 to GLn and the data lines DL1 to DLm, and is connected to each of the liquid crystal cells. TFT).

The gate driver 4 sequentially supplies a gate high voltage VGH to the gate lines GL1 to GLn in response to gate control signals GSP, GSC, and GOE from the timing controller 10. . Accordingly, the gate driver 4 causes the thin film transistor TFT connected to the gate lines GL1 to GLn to be driven in units of the gate line GL.

The data driver 6 outputs a pixel signal of one line for each horizontal period H1, H2,... In response to the data control signals SSP, SSC, SOE, and POL from the timing controller 10. In particular, the data driver 6 supplies the digital pixel data R, G, and B from the timing controller 10 to the gamma voltage generator (not shown). The voltage is converted into an analog pixel signal and supplied.

The timing controller 10 generates gate control signals GSP, GSC, and GOE to control the gate driver 4, and generates data control signals SSP, SSC, SOE, and POL to generate the data driver. (6) will be controlled. In addition, the timing controller 10 arranges the pixel data R, G, and B and supplies the same to the data driver 6. As such, the liquid crystal display uses an inversion method to prevent degradation of the liquid crystal cells and to improve image quality. In order to reduce power consumption, the dot inversion method causes flicker when the frame frequency is lowered from a typical 60 Hz to 50 to 30 Hz, and as illustrated in FIGS. 2A and 2B and 3A and 3B to compensate for this. The same horizontal two-dot inversion method and vertical two-dot inversion method are used.

2A and 2B illustrate a pixel signal polarity supplied to liquid crystal cells in a horizontal 2-dot inversion scheme divided into odd frames and even frames.

In the odd and even frames shown in Figs. 2A and 2B, the horizontal two-dot inversion scheme applies pixel voltages having the same phase to two adjacent pixels in the horizontal direction, that is, the gate line direction, and the two pixels. The other two pixels adjacent to are driven by applying a pixel voltage having an inverted phase. The horizontal 2-dot inversion method has an advantage of smaller power consumption than the 1-dot inversion method. However, since the pixel voltage of the same phase is applied to two adjacent pixels and the pixel voltage of the inverted phase is applied to the other two pixels adjacent to the two pixels, the vertical line phenomenon occurs in the data line direction.

3A and 3B illustrate the pixel signal polarity supplied to the liquid crystal cells in a vertical 2-dot inversion scheme divided into odd frames and even frames.

As shown in FIGS. 3A and 3B, in the odd frame and the even frame, the vertical two-dot inversion scheme changes the polarity of the pixel signal in the unit of dots in the horizontal direction, as in the conventional dot inversion scheme, but is vertical. The direction is driven so that the polarity is changed in units of 2 dots. The vertical two-dot inversion method has the advantage that the flicker phenomenon is reduced in comparison with the dot inversion method in a commercial screen driven at a frame frequency of 60 Hz. However, horizontal lines are generated according to the luminance difference every two scanning lines, and in particular, in the case of the twisted nematic (TN) mode liquid crystal display, since the normally white mode, Green, which has a low voltage, appears brighter than other colors. Greenish) phenomenon.

4A and 4B are waveform diagrams showing the relationship between the polarity signal POL and the dot control signal for each frame in the vertical two-dot inversion driving method and the horizontal two-dot inversion driving method.                         

As shown in Fig. 4A, in the vertical two dot inversion driving method, the dot control signal generated by the timing controller is supplied to the data driver. The dot control signal has a low value in the vertical two dot inversion driving method. Accordingly, when the dot control signal is supplied to the data driver (not shown) at a low value, the liquid crystal display device is driven by a vertical two-dot inversion driving method. Accordingly, the polarity signal POL including the negative signal (−) and the positive signal (+) is periodically changed and supplied every two gate lines.

As shown in FIG. 4B, in the horizontal two dot inversion driving method, a dot control signal generated by a timing controller is supplied to a data driver (not shown). Here, the dot control signal has a high value in the horizontal two dot inversion driving method. Accordingly, when a dot control signal is supplied to the data driver (not shown) at a high value, the liquid crystal display device is driven by a horizontal two-dot inversion driving method.

5A and 5B are detailed block diagrams of a data driver IC driven by a vertical two dot inversion driving method and a horizontal two dot inversion driving method.

As shown in Fig. 5A, the data driver 16 of the vertical two-dot inversion driving method has a digital-to-analog converter (hereinafter referred to as 'DAC') 18 for converting digital pixel data into an analog pixel signal and the timing. A vertical two-dot driving unit 17 is operated so as to be driven at two vertical dots in response to the dot control signal generated by the controller 10. Here, the dot control signal is set to have a low value. The data driver 16 subdivides the reference gamma voltage from the signal control unit 19 relaying the data control signals supplied from the timing controller 10 and the digital pixel data, and a reference gamma voltage unit (not shown). And a gamma voltage unit 20 to be supplied to the DAC converter 18.

As shown in Fig. 5B, the data driver 26 of the horizontal two dot inversion driving method has the same structure as the data driver 16 of the vertical two dot inversion driving method. The horizontal 2-dot inversion data driver 26 corresponds to a digital-to-analog converter (DAC) converter 28 for converting digital pixel data into an analog pixel signal and a dot control signal generated by the timing controller 10. It is provided with a horizontal two-dot drive unit 27 so that it can be driven by two horizontal dots. Here, the dot control signal is set to have a high value. In addition, the data driver 26 subdivides the reference gamma voltage from a signal control unit 29 relaying data control signals supplied from the timing controller 10 and digital pixel data, and a reference gamma voltage unit (not shown). A gamma voltage unit 30 is further provided to the DAC converter 28.

Therefore, when the dot control signal generated by the timing controller 10 has a low value, the data driver of the liquid crystal display device is driven in a vertical 2-dot inversion scheme. When the dot control signal generated by the timing controller 10 has a high value, the data driver of the liquid crystal display device is driven in a horizontal 2-dot inversion scheme.

As described above, Greenish and vertical line phenomena occur while being driven for each frame in a vertical two-dot inversion scheme and a horizontal two-dot inversion scheme, respectively.

That is, in a liquid crystal display device in which the dot control signal generated by the timing controller is applied with a high value, when the liquid crystal panel is driven in a horizontal two-dot inversion method due to the dot control signal having a high value, the data line The vertical line phenomenon occurs in the direction. In a liquid crystal display device in which a dot control signal generated by the timing controller is applied at a low value, when the liquid crystal panel is driven in a vertical two-dot inversion manner due to the dot control signal having a low value, The horizontal line phenomenon and the greenish phenomenon appear, resulting in deterioration of image quality.

Accordingly, the present invention provides a liquid crystal display device and a driving method thereof capable of eliminating problems caused by driving a liquid crystal panel in a vertical two-dot inversion method and a horizontal two-dot inversion method for each odd frame and even frame. There is a purpose.

According to a preferred embodiment of the present invention for achieving the above object, a liquid crystal panel; Control means for generating a 2-dot control signal; And a data driver for driving the liquid crystal panel in a horizontal 2-dot inversion method and a vertical 2-dot inversion method according to the 2-dot control signal.

According to another preferred embodiment of the present invention, generating a two-dot control signal; And driving the liquid crystal panel in a horizontal two-dot inversion method and a vertical two-dot inversion method according to the two-dot control signal.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention.

6 is a circuit diagram of a liquid crystal display according to the present invention.

As shown in FIG. 6, in the liquid crystal display of the present invention, the vertical two-dot inversion method and the horizontal two-dot inversion method are driven alternately in every odd and even frames according to a dot control signal.

The liquid crystal display device includes a liquid crystal panel 102 in which liquid crystal cells are arranged in a matrix, a gate driver 104 for driving gate lines GL1 to GLn of the liquid crystal panel 102, and the liquid crystal panel ( A data driver 106 for driving the data lines DL1 to DLm of the 102 and a timing controller 110 including the data alignment unit 111 and the controller 112 are provided.

The liquid crystal panel 102 is a thin film transistor connected to each of the liquid crystal cells arranged in a matrix form and formed at each intersection of the gate lines GL1 to GLn and the data lines DL1 to DLm. TFT).

The thin film transistor TFT is turned on when the scan signal from the gate line GL, that is, the gate high voltage VGH is supplied, and supplies the data signal from the data line DL to the liquid crystal cell. The thin film transistor TFT is turned off when the gate low voltage VGL is supplied from the gate line GL to maintain the data signal charged in the liquid crystal cell.

The liquid crystal cell is equivalently represented by a liquid crystal capacitor Clc, and includes a common electrode sandwiching the liquid crystal and a pixel electrode connected to the thin film transistor TFT. The liquid crystal cell further includes a storage capacitor Cst to maintain the charged data signal in a stable state until the next data signal is charged. The liquid crystal cell realizes gradation (bright and dark degree of color) by adjusting the light transmittance by changing the arrangement state of the liquid crystal having dielectric anisotropy according to the data signal charged through the thin film transistor (TFT).

The gate driver 104 sequentially supplies the gate high voltage VGH to the gate lines GL1 to GLn in response to the gate signals GSP, GSC, and GOE provided from the timing controller 110. The thin film transistor TFT connected to the gate lines GL1 to GLn by the gate high voltage VGH is driven along the gate line.

The data driver 106 outputs a data line for one line for each horizontal period H1, H2 .. in response to the data control signals SSP, SSC, SOE, and POL provided from the timing controller 110. To DL1 to DLm. In particular, the data driver 106 converts and supplies the digital data R, G, and B provided from the data alignment unit 111 of the timing controller 110 into an analog data signal.

FIG. 7 is a detailed block diagram illustrating a data driver of the LCD shown in FIG. 6.

As shown in FIG. 7, the data driver 116 of the liquid crystal display according to the present invention includes a digital-analog converter (hereinafter referred to as 'DAC') 119 for converting digital pixel data into an analog pixel signal and the timing. In response to the 2-dot control signal generated by the controller 110, a vertical 2-dot driving unit 117 and a horizontal 2-dot driving unit 118 operable to be driven in a vertical 2-dot and horizontal 2-dot inversion scheme are provided. The data driver 116 divides the reference gamma voltage from the signal controller 120 relaying the data control signals supplied from the timing controller 110 and the digital pixel data, and a reference gamma voltage unit (not shown). A gamma voltage unit 121 is further provided to the DAC converter 119.

In the liquid crystal display, when the 2-dot control signal supplied from the timing controller 110 to the data driver 116 is low, the 2-dot control signal is input to the vertical 2-dot driving unit 117. Accordingly, the vertical 2-dot driving unit 117 is operated so that the liquid crystal panel 102 is driven by the vertical 2-dot inversion method.

When the two-dot control signal supplied from the timing controller 110 to the data driver IC 116 is high, the two-dot control signal is input to the horizontal two-dot driver 118. Accordingly, the horizontal 2-dot driving unit 118 is operated so that the liquid crystal panel 102 is driven in the horizontal 2-dot inversion method.

As illustrated in FIG. 6, the timing controller 110 enables driving in a vertical 2 dot inversion method and a horizontal 2 dot inversion method according to a dot control signal.

The timing controller 110 includes a data alignment unit 111 for aligning and supplying digital data R, G, and B to the data driver 106, and a controller 112 for generating a control signal. The control unit 112 includes a control signal generator 113 for generating a control signal for driving the gate driver 104 and the data driver 106, a vertical 2-dot inversion method, and a horizontal 2-dot inversion method. And a dot controller 114 for generating a dot control signal for controlling the liquid crystal display to be driven.

The control signal generator 113 controls a control signal capable of driving the gate driver 104 and the data driver 106 by using an external horizontal synchronization signal Hsync and a vertical synchronization signal Vsync. Create

Here, the control signal generated by the timing controller 110 and provided to the gate driver 104 is the first gate of the screen during a period of time when data of one frame is applied, that is, a period of time in which the vertical synchronization signal Vsync is applied. A gate start pulse (GSP) indicating a time point at which the line is turned on, and a gate shift clock (GSC) determining a time for turning on / off the gate of the thin film transistor TFT of the liquid crystal panel 102. A gate output clock (GOE) and a gate output enable (GOE) for controlling the output of the gate driver 104. In addition, a control signal provided to the data driver 106 generated by the timing controller 110 is a source indicating a start point of data, that is, a point in time at which the data is applied to the first data line in one horizontal synchronization signal Hsync. A source start pulse (SSP), a source shift clock (SSC) indicating a time for driving the data driver 106, and a source output for controlling an output of the data driver 106 Contains the Source Output Enable (SOE) signal.

The dot controller 114 generates a 2-dot control signal. As shown in FIG. 9, the two-dot control signal may be controlled using a vertical synchronization signal Vsync input from the outside. That is, the two-dot control signal is generated as a high level signal and a low level signal for each frame according to the vertical synchronization signal Vsync. That is, a low level signal is generated in the first frame, a high level signal is generated in the second frame, and a low level signal is generated in the third frame in synchronization with the vertical synchronization signal Vsync. Accordingly, the two-dot control signal is generated alternately with a low level signal and a high level signal for each frame. Therefore, when the two-dot control signal is generated as a low level signal, the two-dot control signal is driven by a vertical two-dot inversion driving method, and is high level. When generated as a signal, it is driven by a horizontal 2-dot inversion drive. As a result, as the two-dot control signal is alternately generated with the low level signal and the high level signal, the liquid crystal display is alternately driven by the vertical two-dot inversion driving method and the horizontal two-dot inversion driving method.

8A, 8B, 8C, and 8D illustrate polarities of pixel signals driven in a vertical 2-dot inversion scheme and a horizontal 2-dot inversion scheme for each frame.

As shown in FIG. 8A, since the 2-dot control signal is generated in the first frame by the low level signal from the timing controller and supplied to the data driver, the 2-dot control signal is driven by the vertical 2-dot inversion method. Therefore, the polarity of the pixel signal is inverted by 2 dots in the vertical direction.

As shown in FIG. 8B, since the two-dot control signal is generated as a high level signal by the timing controller in the second frame and supplied to the data driver, the two-dot control signal is driven in the horizontal two-dot inversion method. Therefore, the polarity of the pixel signal is inverted by 2 dots in the horizontal direction.

As shown in FIG. 8C, the third frame is driven by a vertical two-dot inversion method because a two-dot control signal is generated as a low level signal from the timing controller and supplied to the data driver. At this time, the polarity of the pixel signal is inverted by 2 dots in the vertical direction as opposed to that shown in 8a.

As shown in FIG. 8D, the fourth frame is driven in a horizontal two-dot inversion manner because a two-dot control signal is generated as a high level signal by the timing controller and supplied to the data driver. In this case, the polarity of the pixel signal is inverted by 2 dots in the horizontal direction as opposed to that shown in FIG. 8B.

Accordingly, the liquid crystal display is driven in the vertical two-dot inversion method in the first frame, and the liquid crystal display is driven in the horizontal two-dot inversion method in the second frame. The liquid crystal display is driven in a vertical two-dot inversion method having a polarity opposite to that of the first frame in the third frame, and the liquid crystal is operated in a horizontal two-dot inversion method having a polarity opposite to that of the second frame in the fourth frame. The display device is driven. Therefore, the liquid crystal display is driven in the vertical two-dot inversion method in the odd frame, and the liquid crystal display is driven in the horizontal two-dot inversion method in the even frame. Accordingly, the greenish phenomenon that occurs when driving in the vertical 2-dot inversion method and the vertical line phenomenon that occurs when driving in the horizontal 2-dot inversion method do not appear continuously for each frame.

Therefore, when driven in the vertical 2-dot inversion method, the greenish phenomenon that occurs continuously for each frame occurs only in the odd frame in the liquid crystal display according to the present invention. When driven in the horizontal 2-dot inversion method, the vertical line phenomenon continuously occurring for each frame occurs only in the even-numbered frame in the liquid crystal display according to the present invention. Accordingly, the greenish phenomenon and the vertical line phenomenon can be eliminated in the liquid crystal display according to the present invention.

As described above, according to the liquid crystal display and the driving method thereof according to the present invention, the image quality is compensated by compensating the greenish phenomenon and the vertical line phenomenon by alternately driving the vertical two-dot inversion method and the horizontal two-dot inversion method for each frame. Can be improved.

Claims (12)

A liquid crystal panel; Control means for generating a 2-dot control signal; And And a data driver for driving the liquid crystal panel in a horizontal 2-dot inversion method and a vertical 2-dot inversion method according to the 2-dot control signal. The method of claim 1, And the second dot control signal is generated according to a vertical synchronization signal. The method of claim 1, The second dot control signal is a liquid crystal display, characterized in that the first and second signals are generated alternately for each frame. The method of claim 3, wherein And the second dot control signal is driven in a vertical two dot inversion method for every odd frame. The method of claim 3, wherein And the second dot control signal is driven in a horizontal two dot inversion method for every even-numbered frame when the second dot control signal is a second signal. The method of claim 1, And the data driver causes the polarity of the pixel signal to be inverted in units of 2 dots in the vertical direction for every odd frame. The method of claim 1, And the data driver causes the polarity of the pixel signal to be inverted in units of 2 dots in the horizontal direction for every even-numbered frame. Generating a 2-dot control signal; And And driving the liquid crystal panel in a horizontal two-dot inversion method and a vertical two-dot inversion method according to the two-dot control signal. The method of claim 8, And the second dot control signal is generated according to a vertical synchronization signal. The method according to claim 8 or 9, The second dot control signal is a driving method of the liquid crystal display, characterized in that the first and second signals are generated alternately for each frame. The method according to claim 8 or 9, And the second dot control signal is driven in a vertical two dot inversion method for every odd frame. The method according to claim 8 or 9, And the second dot control signal is driven in a horizontal 2-dot inversion method every every even-numbered frame when the second dot control signal is the second signal.

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