KR20070080952A - Data modulation device, liquid crystal display device having the same and method for driving the same - Google Patents

Abstract

A data modulator, a liquid crystal display device having the same, and a method for driving the LCD(Liquid Crystal Display) device are provided to improve image quality by reducing a response time of the LCD device. A data modulator sequentially modulates first to third frames of data and includes first and second look-up tables and a controller. The first LUT(Look-Up Table)(116) compares a first data signal from the first frame with a second data signal from the second frame during the second frame, and outputs a first compensation data signal according to the comparison result. The second LUT(118) compares a second data signal from the second frame with a third data signal from the third frame during the second frame, and outputs a second compensation data signal according to the comparison result. The controller(109) controls the first and second LUTs during the respective frames.

Description

 Data modulation device, liquid crystal display device having same and driving method thereof {Data modulation device, liquid crystal display device having the same and method for driving the same}

1 is a view showing a liquid crystal display device having a conventional overdriving circuit.

FIG. 2 is a detailed view of the ODC driver of FIG. 1. FIG.

3 is a view showing a liquid crystal display device according to the present invention.

4 illustrates the timing controller of FIG. 3 in detail.

5 is a view showing a driving voltage of a liquid crystal display according to the present invention.

<Brief description of the main parts of the drawing>

102: liquid crystal panel 104: gate driver

106: data driver 108: timing controller

109: ODC control unit 110: ODC drive unit

114: frame memory 116: first lookup table

118: Second lookup table

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a data modulation device, a liquid crystal display device, and a driving method thereof capable of improving image quality even at high speed by applying overvoltage for two frames.

A liquid crystal display device displays an image using the optical anisotropy and polarization property of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

In general, the liquid crystal display may be classified into a liquid crystal panel displaying an image and a driving unit applying a driving signal to the liquid crystal panel.

Although not shown in the figure, the liquid crystal panel is composed of two substrates bonded with a constant cell gap and a liquid crystal layer formed between the two substrates.

One of the two substrates includes a plurality of gate lines arranged at regular intervals, a plurality of data lines arranged in a direction perpendicular to the gate lines to define a pixel region, and a plurality of gate lines arranged in each pixel region. A thin film transistor is formed at a portion where the pixel electrode, the gate line, and the data line cross each other.

The thin film transistor transfers the data signal of the data line to each pixel electrode according to the scan signal of the gate line. Accordingly, when a scan signal is sequentially applied to the plurality of gate lines, a data signal is applied to the pixel electrode of the corresponding pixel region so that an image is displayed.

When the image displayed on the liquid crystal panel is a still image, it is composed of one frame. When the plurality of sequential still images are continuously displayed, the image is composed of a plurality of frames. When the image is a video, the liquid crystal layer is continuously driven by the size of the data signal corresponding to each frame.

On the other hand, the magnitude of the data signal of each frame is represented by the magnitude of the gray scale voltage in the liquid crystal layer to change the direction of the liquid crystal molecules of the liquid crystal layer. Since the liquid crystal molecules have dielectric anisotropy, This change causes the dielectric constant to change. The gradation voltage applied to the liquid crystal layer is changed by the change of the dielectric constant, and the response speed of the liquid crystal molecules of the liquid crystal layer is significantly decreased by the change of the gradation voltage.

That is, when the gray voltage applied to the liquid crystal is changed from a low gray voltage to a high gray voltage, the gray voltage of the current frame data signal is not affected by the gray voltage of the previous frame data signal and thus does not reach the desired gray voltage. Only after the data signal has passed a few frames does the normal gray voltage be reached.

For example, if a single video composed of two consecutive frames is represented, the liquid crystal maintains the state of being changed to the magnitude of the gradation voltage corresponding to the image of the first frame, and then corresponds to the image of the second frame. When the response speed of the liquid crystal molecules decreases due to the above factors, the liquid crystal cannot prevent the image of the second frame from expressing the corresponding gray voltage in one frame.

Such a phenomenon may be expressed as an afterimage in which the image of the first frame of the previous time is blurred on the image of the second frame on the liquid crystal panel. Therefore, a method of improving the response speed of the liquid crystal molecules by overdriving the data signal for setting the gray scale voltage to a higher value than the normal value has been studied.

Hereinafter, a liquid crystal display device having a conventional over driving circuit will be described in detail with reference to the accompanying drawings.

1 is a view showing a liquid crystal display device having a conventional overdriving circuit.

As shown in FIG. 1, a conventional liquid crystal display device includes a liquid crystal panel 2 for displaying a predetermined image, a gate driver 4 and a data driver 6 for driving the liquid crystal panel 2, And a timing controller 8 for controlling the gate driver 4 and the data driver 6. The liquid crystal display is driven at a driving frequency of 60 Hz.

Conventional liquid crystal display device with over-driving circuit is a well known technique and will be described briefly.

The timing controller 8 sequentially receives R, G, and B data signals from frame to frame, not shown. In addition, the timing controller 8 includes an ODC driver 10, and the ODC driver 10 is a circuit part for overdriving driving.

As shown in FIG. 2, the ODC driver 10 includes a frame memory 14 in which R, G, and B data signals of a previous frame supplied from a system are stored for one frame, and a current frame supplied from the system. The comparison unit 16 for comparing the R, G, B data signals with the R, G, B data signals of the previous frame stored in the frame memory 14, and the current result according to the comparison result of the comparison unit 16. And a lookup table 18 for outputting the corrected R, G, B data signals during the frame. In this case, the corrected R, G, B data signals are different from the R, G, B data signals of the current frame input from the system.

The lookup table 18 arranges values corresponding to the R, G, and B data signals of the previous frame and the R, G, and B data signals of the current frame on the X and Y axes, respectively, where the X and Y axes meet. It is made by inputting the value corresponding to the corrected R, G, B data signal.

The frame memory 14 stores R, G, and B data signals supplied from the system during the previous frame. R, G, and B data signals supplied from the system during the current frame are supplied to the comparator 16, and the comparator 16 is at the same time R, G, and B of the previous frame stored in the frame memory 14. Loading a B data signal is compared with the R, G, and B data signals of the current frame.

The lookup table 18 finds values of portions where the R, G, and B data signals of the previous frame intersect the values of the R, G, and B data signals of the current frame, and corrects the corrected R, G, and B data signals. Will print.

The corrected R, G, and B data signals are supplied to the data driver 6 during the current frame and applied to each pixel electrode, thereby overdriving the liquid crystal formed on the liquid crystal panel 2 to a higher gray voltage.

On the other hand, when the LCD has a driving frequency of 120 Hz or more, overdriving is driven when a difference between the gray voltage of the previous frame and the gray voltage of the current frame occurs. When the liquid crystal display has a driving frequency of 120 Hz, one frame is shorter than that of the conventional 60 Hz.

When the overdriving operation is performed for one short frame, a response time of a desired liquid crystal is shortened, which may cause a problem in that the magnitude of the gray scale voltage corresponding to the current frame cannot be expressed within one frame time. As a result, afterimages in which the image of the previous frame overlaps with the image of the second frame may occur.

That is, in a liquid crystal display device having a driving frequency of 120 Hz or more, the response time of the liquid crystal is shortened, and if the conventional overdriving drive is applied, a phenomenon such as an afterimage may occur, and thus it may be applied to a liquid crystal display device for high speed driving. Overdriving drive must be developed.

It is an object of the present invention to provide a data modulation device having an overdriving circuit applicable to high speed driving, a liquid crystal display device having the same, and a driving method thereof.

A data modulation device according to the present invention for achieving the above object is a data modulation device for modulating data in the order of the first, second and third frames, the first data signal of the first frame during the second frame And a first lookup table for comparing the second data signal of the second frame and outputting a first correction data signal according to the comparison result, the second data signal of the second frame and the second frame during the third frame. A second lookup table for comparing the third data signals of the third frame and outputting a second correction data signal according to the comparison result, and a control unit controlling the output of the first and second lookup tables during each frame. do.

A liquid crystal display device according to the present invention for achieving the above object comprises a data modulation device for modulating data in the order of first, second and third frames, wherein the first frame during the second frame. A first lookup table for comparing a first data signal of a frame with a second data signal of the second frame and outputting a first correction data signal according to a result of the comparison; and the first frame of the second frame during the third frame. A second lookup table for comparing a second data signal with a third data signal of the third frame and outputting a second correction data signal according to the comparison result, and outputting the first and second lookup tables during each frame; A data modulator configured to control the control unit and displaying an image corresponding to the first and second correction data signals during the second and third frames. Include crystal panel.

According to an aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method including: storing a data signal supplied to a previous frame and comparing the data signal of the previous frame to a data signal supplied to the current frame; Outputting a first correction data signal to a current frame according to the comparison result; comparing a data signal of the previous frame with a data signal supplied to the current frame in a next frame; and according to the comparison result Outputting a second correction data signal to a next frame, and displaying an image corresponding to the first and second correction data signals during the current and next frames and two frames.

Hereinafter, with reference to the accompanying drawings will be described an embodiment according to the present invention.

3 is a view showing a liquid crystal display according to the present invention.

As shown in FIG. 3, the liquid crystal display according to the present invention includes a plurality of gate lines GL0 to GLn and data lines DL1 to DLm defining a plurality of pixel regions, to display a predetermined image. A gate driver 104 for supplying scan signals to the panel 102, the plurality of gate lines GL0 to GLn to drive the plurality of gate lines GL0 to GLn, and the plurality of data lines DL1 to And a data controller 106 for supplying a data signal to the pixel electrode formed in the pixel region through a DLm, and a timing controller 108 for controlling the gate driver 104 and the data driver 106.

The liquid crystal display is driven by a high speed drive of 120Hz or more.

The liquid crystal panel 102 is composed of two substrates (not shown) and a liquid crystal layer formed between the two substrates. A plurality of gate lines GL0 to GLn and data lines DL1 to DLm are arranged in the liquid crystal panel 102 to define a plurality of pixel regions, and the gate lines GL0 to GLn and data lines DL1 to DLm. Thin film transistors (TFTs), which are switching elements, are formed at intersections of. The thin film transistor TFT is electrically connected to the pixel electrode.

The gate driver 104 sequentially supplies a scan signal, that is, a gate high voltage VGH, to the plurality of gate lines GL1 to GLn according to the gate control signal supplied from the timing controller 108. When the gate high voltage VGH is supplied to the plurality of gate lines GL1 to GLn, the thin film transistor TFT connected to the plurality of gate lines GL1 to GLn is turned on.

In addition, when the gate high voltage VGL is supplied to the plurality of gate lines GL1 to GLn and the gate low voltage VGL is supplied, the thin film transistor TFT is turned off.

The data driver 106 supplies a data signal to the plurality of data lines DL1 to DLm according to a data control signal supplied from the timing controller 108 to correspond to the data signal on the liquid crystal panel 102. The image to be displayed is displayed.

The timing controller 108 generates the gate control signal and the data control signal using a vertical / horizontal synchronization signal (Vsync / Hsync), a data enable (DE) signal, and a predetermined clock signal supplied from a system (not shown). do. In addition, the timing controller 108 includes an ODC driver 110 for overdriving driving and an ODC controller 109 for controlling the ODC driver 110.

The ODC controller 109 supplies first and second control signals to the ODC driver 110 during overdriving driving. The first and second control signals mean a signal having a high or low level. The first and second control signals generated by the ODC control unit 109 serve to control the first and second lookup tables (not shown) included in the ODC driver 110.

This will be described in detail with reference to FIG. 4.

4 is a diagram illustrating the timing controller of FIG. 3 in detail.

As shown in FIG. 4, the ODC driver 110 stores a frame memory 114 that stores R, G, and B data signals input in units of frames from a system (not shown) for one frame, and the frame memory 114. First and second outputting first and second R, G, and B correction data signals according to the R, G, and B data signals of the previous frame stored in &lt; RTI ID = 0.0 &gt; and &lt; / RTI &gt; Two lookup tables 116, 118.

The frame memory 114 stores the R, G, and B data signals supplied from the system for one frame and supplies the R, G, and B data signals to the first and second lookup tables 116 and 118.

The first lookup table 116 includes first R, G, and B data signals supplied from the frame memory 114 and first R, G, and B data signals corresponding to R, G, and B data signals supplied from the system during the current frame. B correction data signals are stored.

That is, the first lookup table 116 arranges values corresponding to the previous frame R, G, and B data signals and the current frame R, G, and B data signals on the X and Y axes, respectively. The value corresponding to the first R, G, B correction data signal is stored in this encountering portion.

Therefore, when the previous frame R, G, B data signal and the R, G, B data signal of the current frame are supplied to the first lookup table 116, the first lookup table 116 may be configured to include the previous frame and the current frame. A first R, G, B correction data signal determined by the R, G, B data signals is supplied to the data driver 106 during the current frame.

In this case, the first lookup table 116 is controlled by the ODC controller 109. When the first control signal is supplied from the ODC controller 109, the first lookup table 116 performs the above operation. The first R, G, and B correction data signals are supplied to the data driver 106 during the current frame.

The first R, G, and B correction data signals output from the first lookup table 118 have a gray voltage greater than that of the current frame R, G, and B data signals supplied from the system.

The second lookup table 118 performs the same function as the first lookup table 118.

The second lookup table 118 uses a previous frame R, G, B data signal supplied from the frame memory 114 and a second R, G, B data signal supplied from the system to a current frame. G and B correction data signals are supplied to the data driver 106 for the next frame.

The second lookup table 118 arranges values corresponding to the previous frame R, G, and B data signals and the current frame R, G, and B data signals on the X and Y axes, respectively, where the X and Y axes meet. A value corresponding to the second R, G, B correction data signal is stored in the portion.

The second R, G, B correction data signal is different from the first R, G, B correction data signal. The gray voltage corresponding to the second R, G, B correction data signal may be equal to or smaller than the gray voltage corresponding to the first R, G, B correction data signal.

The ODC control unit 109 supplies a first control signal to the first lookup table 116 and a second control signal to the second lookup table 118 during the current frame. When the second control signal is supplied to the second lookup table 118, the second lookup table 118 does not operate during the current frame.

In addition, the ODC controller 109 supplies a first control signal to the second lookup table 118 and a second control signal to the first lookup table 116 in the next frame. When the second control signal is supplied to the first lookup table 116, the first lookup table 116 is not operated in the next frame.

As a result, a frame in which the first and second lookup tables 116 and 118 perform an operation is determined by the first and second control signals supplied from the ODC controller 109.

Alternatively, the ODC controller 109 may generate first and second control signals inverted from frame to frame and supply the first and second lookup tables 116 and 118 to each other. That is, the first control signal is supplied to the first lookup table 116 and the second control signal is supplied to the second lookup table 118 so that the first and second lookup tables 116 and 118 may be used. The presence or absence of driving can be determined.

Meanwhile, the ODC driver 110 does not drive when the R, G, B data signals of the previous frame and the R, G, B data signals of the current frame are the same. The driving is performed when the B data signal and the R, G, and B data signals of the current frame are different from each other.

As a result, the ODC driver 110 is driven and controlled by the ODC controller 109 only when the R, G, B data signals of the previous frame and the current frame supplied from the system are different from each other.

When the ODC driver 110 is driven, previous frame R, G, and B data signals are stored in the frame memory 114 and together with the first frame R, G, and B data signals supplied from the system. The lookup tables 116 and 118 are supplied.

At the same time, the ODC control unit 109 stores first and second control signals in the first and second lookup tables 116 and 118 by supplying first and second control signals to the first and second lookup tables 116 and 118. It is determined in which frame the first and second R, G, and B correction data signals are output.

The first R, G, and B correction data signals output from the first lookup table 116 during the current frame are converted into higher gradation voltages than the current frame R, G, and B data signals supplied from the system, and thus the liquid crystal panel ( A predetermined image is displayed on 102.

In the next frame, second R, G, and B correction data signals are output from the second lookup table 116 and displayed on the liquid crystal panel 102 through the data driver 106 as a predetermined image.

In this case, the second R, G, and B correction data signals output from the second lookup table 116 may include current frame R, G, and B data signals supplied from a system and a first output from the first lookup table 116. 1 is different from the R, G, and B correction data signals.

The second R, G, B correction data signal may be larger or smaller than the first R, G, B correction data signal.

As a result, the liquid crystal display according to the present invention supplies the first and second R, G, and B correction data signals to the data driver 106 over two frames during overdriving driving, so that the first, second R, G, An image corresponding to the B correction data signal is displayed on the liquid crystal panel 102.

As mentioned above, since the liquid crystal display according to the present invention is driven at a high speed of 120 Hz, the time of one frame is shorter than that of the 60 Hz. Therefore, the first R, G, and B correction data signals output from the first lookup table 118 for a short one frame during overdriving driving are supplied to the data driver 106 in the current frame.

The second R, G, and B correction data signals output from the second lookup table 118 are then supplied to the data driver 106 in the next frame.

When a difference between the gradation voltage of the previous frame and the gradation voltage of the current frame occurs, the liquid crystal display according to the present invention displays the first R, G, and B correction data signals output from the first lookup table 116 during the current frame. During the next frame, an overdriving operation for displaying the second R, G, and B correction data signals output from the second lookup table 118 is performed.

In the liquid crystal display device driven by the high speed drive, the response time of the liquid crystal is also shortened because the time of one frame is short. When the conventional overdriving driving method that outputs corrected R, G, and B data signals during one frame is applied to a liquid crystal display device driven at a high frequency, the response time of the liquid crystal is shortened and the desired gray scale voltage is not reached within one frame. After the first frame has elapsed, the normal gradation voltage is reached.

Therefore, in the case of the liquid crystal display device driven by high-speed driving, two overdrivings are performed for two frames to reach a desired gray scale voltage during the two frames.

5 is a view showing a driving voltage of the liquid crystal display according to the present invention.

As shown in FIGS. 4 and 5, when the data voltage of the previous frame and the data voltage of the current frame are different from each other, that is, when the video is displayed, overdriving driving is performed for two frames.

If one moving picture is composed of two consecutive frames, the liquid crystal maintains the state changed by the gradation voltages of the R, G, and B data signals during the previous frame, and then the gradation of the R, G, and B data signals of the current frame. It must change with voltage.

As the liquid crystal display according to the present invention is driven at a high speed, the response time of the liquid crystal is shortened, thereby performing two overdriving driving for two frames in order to improve the liquid crystal response speed.

That is, the first R, G, B correction data signal output from the first lookup table 116 for one frame is supplied to the data driver 106 of FIG. 3 to provide the first R, G, B correction data signal. The gray scale voltage of is displayed on the liquid crystal panel (102 in FIG. 3).

The gradation voltages of the second R, G, B correction data signals output from the second lookup table 118 for the next frame in succession are displayed on the liquid crystal panel 102.

As mentioned above, in the case of a liquid crystal display device driven by high-speed driving, since the response time of the liquid crystal is short, two overdriving driving is performed for two frames in order to increase the liquid crystal response speed.

As a result, the gray scale voltages of the first and second R, G and B correction data signals having a level higher than the gray voltages of the R, G, and B data signals supplied from the actual system during two frames during the overdriving operation are displayed in the liquid crystal panel 102. By supplying the liquid crystal display, the liquid crystal response speed of the liquid crystal display device driven by the high speed drive can be improved to prevent unwanted afterimages from being displayed, thereby improving image quality.

The liquid crystal display according to the present invention is driven by a high-speed drive and when the gray scale voltage of the previous frame and the gray frame voltage of the current frame are different from each other, the liquid crystal response speed is improved by performing two overdrivings over two frames to prevent afterimages. Image quality can be improved.

As described above, the liquid crystal display according to the present invention has first and second R, G, and B correction data having a level higher than the gradation voltage of the R, G, and B data signals supplied from the system during overdriving driving. High speed driving (e.g., when driven from 60 Hz to 120 Hz) by including the first and second lookup tables for outputting signals and outputting the first and second R, G, and B correction data signals, respectively, for two frames. In the case of driving with, the response speed of the liquid crystal may be improved to prevent an afterimage or the like, in which an image displayed on a previous frame is overlapped with a current frame, to improve image quality.

Claims (12)

A data modulation apparatus for modulating data in the order of first, second and third frames, A first lookup table for comparing the first data signal of the first frame and the second data signal of the second frame during the second frame and outputting a first correction data signal according to the comparison result; A second lookup table for comparing the second data signal of the second frame and the third data signal of the third frame during the third frame and outputting a second correction data signal according to the comparison result; And And a controller for controlling the output of the first and second lookup tables during each frame. The method of claim 1, And the first and second correction data signals are different from each other. The method of claim 2, And the second correction data signal is larger or smaller than the first correction data signal. The method of claim 1, And a frame memory for storing the data signal of each frame for one frame. The method of claim 1, And the second lookup table is not driven while the first lookup table is driven by the controller. The method of claim 1, And the first lookup table is not driven while the second lookup table is driven by the controller. A liquid crystal display comprising a data modulator for modulating data in the order of first, second and third frames. A first lookup table for comparing the first data signal of the first frame and the second data signal of the second frame during the second frame and outputting a first correction data signal according to a result of the comparison; A second lookup table for comparing the second data signal of the second frame with the third data signal of the third frame during the frame, and outputting a second correction data signal according to the comparison result; A data modulation device including a control unit for controlling output of the first and second lookup tables; And And a liquid crystal panel displaying an image corresponding to the first and second correction data signals during the second and third frames. The method of claim 7, wherein And the first and second correction data signals are different from each other. The method of claim 8, And the second correction data signal is larger or smaller than the first correction data signal. The method of claim 7, wherein And the second lookup table is not driven while the first lookup table is driven by the controller. The method of claim 7, wherein And the first lookup table is not driven while the second lookup table is driven by the controller. Storing the data signal supplied in the previous frame; Comparing the data signal of the previous frame with the data signal supplied to the current frame in the current frame; Outputting a first correction data signal in a current frame according to the comparison result; Comparing the data signal of the previous frame with the data signal supplied to the current frame in a next frame; Outputting a second correction data signal in a next frame according to the comparison result; And And displaying an image corresponding to the first and second correction data signals during the current, next frame, and two frames.

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