KR20090007165A - Apparatus and method for improving response speed of liquid crystal display - Google Patents

Abstract

An apparatus for improving response speed of LCD capable of preventing image blur and method thereof are provided to improve response speed by using ODC(Over Drive Circuit) gray voltage having permeability like gray voltage. A timing controller(41) generates a data control signal(DDC) and a gate control signal(GDC) with vertical/horizontal synchronization signal and clock signal. A data driver converts digital video data(RGB) into analog image signal voltage in response to the data control signal. A gate driver(44) successively supplies a scan pulse to a gate line(GL1-GLn) in response to the gate control signal. The timing controller performs a control function for over driving in IPS(IN Plane Switching) mode with an over driving part(41A). A multiplexer(42A) of a gamma voltage supply part(42) selectively sends a first gamma voltage(VG1) or a second gamma voltage(VG2) to a data driver(43) according to switching control signal of the over driving part.

Description

Apparatus and method for improving response speed of liquid crystal display device {APPARATUS AND METHOD FOR IMPROVING RESPONSE SPEED OF LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving technology of a liquid crystal display device. In particular, the response speed of a liquid crystal display device suitable for improving a motion picture response time (MPRT) and a moving picture blurring phenomenon by using an extended gamma voltage. The present invention relates to an improvement apparatus and a method.

In general, a liquid crystal display device may be classified into a liquid crystal display panel displaying a video signal and a driving circuit unit applying a driving signal to the liquid crystal display panel. The liquid crystal display panel includes two transparent substrates (glass substrates) bonded to each other with a predetermined space, and a liquid crystal layer formed between the two transparent substrates.

Here, one of the two transparent 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 formed in each pixel region. And a plurality of thin film transistors formed at the intersections of the plurality of pixel electrodes and the gate lines and the data lines to transfer the data signals of the data lines to the pixel electrodes according to the gate signals of the gate lines.

Therefore, when the turn-on signal is sequentially applied to the gate line, a data signal is applied to the pixel electrode of the corresponding line to display an image.

Here, the image displayed on the liquid crystal display panel is composed of one frame in the case of a still image, but a plurality of frames in the case of a moving image in which a plurality of sequential still images are continuously displayed.

When the image is a video, the liquid crystal continuously changes by the size of the data signal corresponding to each frame.

For example, in order to display a moving picture of five frames on a liquid crystal display, since each data signal of each frame has a different size, each liquid crystal continuously changes by the size of the data signal corresponding to each frame. Done.

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, When the change is made, the dielectric constant is changed, and the gray 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 remarkably decreased by the change of the gray voltage.

For example, when the gray voltage applied to the liquid crystal is changed from a low gray voltage to a high gray voltage (or from a high gray voltage to a low gray voltage), the gray voltage of the current frame data signal is equal to the gray voltage of the previous frame data signal. Because it is affected, it does not reach the desired gray scale voltage immediately, and reaches the normal gray scale voltage only after several frames have elapsed.

In other words, if a single video composed of two consecutive frames is represented, the liquid crystal maintains a state in which the gray level voltage corresponding to the image of the first frame is changed and then the gray level corresponding 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 express the magnitude of the gray scale voltage corresponding to the image of the second frame within one frame time.

Due to this phenomenon, the image of the second frame on the liquid crystal display panel may be represented as an afterimage in which the image of the first frame of the previous time is blurred.

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, overdriving in the conventional LCD will be described with reference to the accompanying drawings.

FIG. 1A is a graph showing a relationship between transmittance and supply voltage in a method of applying an extended voltage of 255 gray voltage or more to improve response characteristics. As shown in the figure, the transmittance does not increase continuously with the voltage, but increases to the center of the 255 gray voltage and then decreases again.

1 (b) and (c) show an overdriving method according to the prior art. FIG. 1 (b) shows that when an arbitrary voltage of 255 gray voltage or more is set as the overdriving voltage, the luminance is changed in two stages due to the characteristics of gray voltages having the same transmittance and different levels. In addition, (c) of FIG. 1 shows a case in which a voltage is applied by a pre-twist voltage application method, and it can be seen that the luminance is changed step by step over two times.

As described above, in the overdriving technology of the conventional liquid crystal display device in which a method of applying 255 gray voltage or more is applied to improve the response characteristics of the liquid crystal, a moving picture blur occurs when the video response speed is measured. There was a problem of deterioration.

Accordingly, it is an object of the present invention to set an overdriving voltage so as not to cause a moving image blur in a method of applying a 255 gray voltage or more in order to improve a response characteristic.

In order to achieve the above object, the present invention outputs a switching control signal for selecting a basic gamma voltage or an extended gamma voltage and selects an overdriving voltage that does not cause moving image blur by using a lookup table. A timing controller having an overdriving unit for outputting a control signal; A gamma voltage supply unit which selects the basic gamma voltage or the extended gamma voltage according to the switching control signal and outputs the data to the data driver; According to the data control signal is characterized in that it comprises a data driver for generating an original gray voltage and transmittance of the same gray gray voltage and a high level to the data line on the liquid crystal panel.

 According to yet another aspect of the present invention, an overdriving voltage is selected that outputs a switching control signal for selecting a basic gamma voltage or an extended gamma voltage and does not cause a moving image blur by using a lookup table. Outputting a data control signal if possible; Selecting the basic gamma voltage or the extended gamma voltage according to the switching control signal and outputting the selected data to the data driver; According to the data control signal, the original gray voltage and transmittance are the same, and the level is generated, including the step of generating a high DC gray voltage and outputting the data line on the liquid crystal panel.

The present invention further provides a gray voltage of an extended area of 255 gray or more and selects an OCD gray voltage having the same transmittance with respect to the gray voltage as one overdriving voltage, thereby improving response speed and reducing luminance during overdriving. There is an effect that can prevent the appearance of a moving image blur phenomenon due to.

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

FIG. 2 is a block diagram illustrating an embodiment of an apparatus for improving a response speed of an LCD according to the present invention. As shown in FIG. 2, the gate control signal GDC and the data control signal DDC are output and input. The digital video data RGB is sampled and rearranged and output. The overdrive section 41A outputs a switching control signal CTL for selecting a basic gamma voltage or an extended gamma voltage and a lookup table. A timing controller 41 for outputting a data control signal DDC such that an overdriving voltage that does not cause a moving image blur is selected using the? A gamma voltage supply unit 42 which selects the basic gamma voltage or the extended gamma voltage and outputs the selected data to the data driver 43 according to the switching control signal CTL; According to the data control signal DDC inputted from the timing controller 41, an original gray voltage and transmittance are generated, and the level of the DC gray voltage is high and is output to the data lines DL1 to DLm on the liquid crystal panel 45. A data driver 43; A gate driver 44 for supplying a scan signal to the gate lines GL1 to GLn on the liquid crystal panel 45 under the control of the timing controller 41; The liquid crystal panel 45 in which m × n liquid crystal cells Clc are arranged in a matrix type, m data lines DL1 to DLm and n gate lines GL1 to GLn cross each other, and a thin film transistor is formed at an intersection thereof. It will be described in detail with reference to Figure 3 attached to the operation of the present invention configured as described above, which is configured as follows.

The timing controller 41 uses a vertical / horizontal synchronization signal and a clock signal supplied from the system to control the data control signal DDC for controlling the data driver 43 and the gate control signal for controlling the gate driver 44. GDC). In addition, the timing controller 41 samples the digital video data RGB input from the system, rearranges the digital video data RGB, and supplies the data to the data driver 43.

The data driver 43 converts the digital video data RGB into an analog image signal voltage (data voltage) corresponding to the gray scale value in response to the data control signal DDC from the timing controller 41. The converted image signal voltage is supplied to the data lines DL1 to DLm of the liquid crystal panel 45.

The gate driver 44 sequentially supplies scan pulses (gate pulses) to the gate lines GL1 to GLn in response to the gate control signal GDC from the timing controller 41. On 45) horizontal lines from which data is supplied are selected.

The liquid crystal panel 45 includes a plurality of liquid crystal cells Clc arranged in a matrix at the intersection of the data lines DL1 to DLm and the gate lines GL1 to GLn. Each transistor TFT formed in the liquid crystal cell Clc transfers an image signal voltage input from the data lines DL1 to DLm to the liquid crystal cell Clc in response to a scan signal supplied from the gate lines GL1 to GLn. do. In addition, a storage capacitor Cst is formed in each of the liquid crystal cells Clc, which is formed between the pixel electrode of the liquid crystal cell Clc and the front gate line, or between the pixel electrode and the common electrode of the liquid crystal cell Clc. It is formed to maintain a constant voltage of the liquid crystal cell (Clc).

On the other hand, the timing controller 41 has an overdriving portion 41A and uses the same to form a common electrode and a pixel electrode on the same substrate in an in-plane switching (IPS) mode for driving liquid crystal molecules. Perform the control function for overdriving.

The multiplexer 42A of the gamma voltage supply unit 42 is configured to have a first gamma voltage (or a basic gamma voltage) VG1 or a second gamma voltage (or) according to the switching control signal CTL supplied from the overdriving unit 41A. The extended gamma voltage VG2 is selected and output to the data driver 43.

3A illustrates the entire range of gamma voltages output from the multiplexer 42A of the gamma voltage supply unit 42. That is, as shown in FIG. 3A, the first gamma voltage VG1 ranges from 0 to 255 of the normal gray voltage region. Also, the range of the second gamma voltage VG2 is an extended gray voltage region for overdriving around a relatively high gray, for example, 200 gray voltage, among the gray voltages of the first gamma voltage VG1. This corresponds to 127 ODC gray voltage at.

Of course, the ranges of the first and second gamma voltages VG1 and VG2 output from the multiplexer 42A of the gamma voltage supply unit 42 are not fixed as shown in FIG. I can adjust it.

For example, the overdriver 41A analyzes the digital video data RGB input from the system and determines that the overdriving unit 41A corresponds to a relatively low gray voltage (eg, 80 gray voltage) in the normal gray voltage region. The switching control signal CTL is output as 'low' so that the first gamma voltage VG1 is selected by the multiplexer 42A of the gamma voltage supply part 42.

In addition, the overdriving unit 41A generates an ADC gray voltage for the corresponding data among the digital video data RGB by using an internal lookup table so that the voltage is output from the data driver 43. Output a control signal DDC.

Accordingly, the multiplexer 42A selects the first gamma voltage VG1 and outputs the first gamma voltage VG1 to the data driver 43.

The data driver 43 generates an ADC gray voltage for the corresponding video data using the first gamma voltage VG1 according to the data control signal DDC. Output to the data line.

As another example, the overdriving unit 41A analyzes the digital video data RGB input from the system and determines that the overdriving unit 41A corresponds to a relatively high gray voltage (eg, 127 gray voltage). The switching control signal CTL is output as 'high' so that the second gamma voltage VG2 is selected by the multiplexer 42A.

In addition, the overdrive 41A generates an 127 BC gray voltage for the corresponding data among the digital video data RGB using an internal lookup table so that the voltage is output from the data driver 43. Output the data control signal DDC.

Accordingly, the multiplexer 42A selects the second gamma voltage VG2 and outputs the second gamma voltage VG2 to the data driver 43.

In addition, the data driver 43 generates a 127 BC gray voltage for the corresponding video data using the second gamma voltage VG2 according to the data control signal DDC, thereby generating data lines DL1 to DLm. Will be output to the corresponding data line.

3 (b) shows an example of overdriving by the above process. That is, when the overdriving unit 41A analyzes the digital video data RGB input from the system and determines that the overdriving unit 41A is 232 gray voltage, the overdriving unit 41A receives a second gamma voltage at the multiplexer 42A. The switching control signal CTL is output 'high' so that VG2 is selected.

In this case, the overdriver 41A generates a 232 BC gray voltage for the corresponding data among the digital video data RGB using an internal lookup table, and outputs the voltage from the data driver 43. Output a control signal DDC.

Accordingly, the multiplexer 42A selects the second gamma voltage VG2 and outputs the second gamma voltage VG2 to the data driver 43.

In addition, the data driver 43 generates a 232 BC gray voltage for the corresponding video data using the second gamma voltage VG2 according to the data control signal DDC, thereby generating data lines DL1 to DLm. Will be output to the corresponding data line.

However, it can be seen that the relationship between the 232 gray voltage and the 232 BC gray voltage has different transmittances although the voltage levels are different from each other as shown in FIG. As described above, when selecting and outputting the DC gray voltage having the same transmittance when outputting the DC gray voltage for a certain gray voltage, it can be seen that there is no change in the luminance level due to overdriving as shown in FIG. . As a result, a moving picture blur due to overdriving does not appear.

As a result, as described above, the second gamma voltage VG2 is further supplied to the multiplexer 42A of the gamma voltage supply part 42 so that the OCD gray voltage can be selected for the gray voltage, and the overdriving part 41A is provided. The data control signal DDC is outputted so as to select an DC gray voltage that does not cause a moving picture blur, that is, an DC gray voltage having the same transmittance, using the lookup table.

The overdriving unit 41A may output the data control signal DDC by using a single lookup table. However, the overdriving unit 41A may output the data control signal DDC, respectively, as necessary for each of the first and second gamma voltages VG1 and VG2. A lookup table may be provided and the data control signal DDC may be output using the lookup table.

1 (a) is a graph showing a relationship between transmittance and voltage in a method of applying an extended voltage of 255 gray voltage or more.

1 (b), (c) is a graph showing an overdriving method according to the prior art.

2 is a block diagram of an apparatus for improving a response speed of a liquid crystal display according to the present invention.

Figure 3 (a) is a graph of the relationship between the transmittance and the voltage showing the basic gamma voltage and the extended gamma voltage according to the present invention.

Figure 3 (b) is a graph showing the overdriving method according to the present invention.

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

41: timing controller 41A: overdriving section

42: gamma voltage supply 42A: multiplexer

43: data driver 44: gate driver

45 liquid crystal panel

Claims (6)

An overdriving unit for outputting a switching control signal for selecting a basic gamma voltage or an extended gamma voltage and for outputting a data control signal such that an overdriving voltage that does not cause a moving image blur is selected; A gamma voltage supply unit which selects the basic gamma voltage or the extended gamma voltage according to the switching control signal and outputs the data to the data driver; According to the data control signal, by using the extended gamma voltage, the original gray voltage and the transmittance of the same and the level of the higher than the gray gray voltage to generate an output to the data line on the liquid crystal panel, characterized in that it comprises a data driver The response speed improvement device of the liquid crystal display device. The apparatus of claim 1, wherein the overdriving unit is installed inside the timing controller. The apparatus of claim 1, wherein an overdriving unit is configured to output the data control signal using at least one lookup table. The apparatus of claim 1, wherein the Odyssey gray voltage is a voltage with respect to the gray voltage of the middle portion or more of the 0 to 255 gray voltages. Outputting a switching control signal for selecting a basic gamma voltage or an extended gamma voltage and outputting a data control signal such that an overdriving voltage is selected using a lookup table so as not to cause a moving image blur; Selecting the basic gamma voltage or the extended gamma voltage according to the switching control signal and outputting the selected data to the data driver; According to the data control signal, using the extended gamma voltage, the original gray voltage and the transmittance of the same and the level of the higher than the gray gray voltage to produce a step of outputting to the data line on the liquid crystal panel Method of improving response speed of liquid crystal display device. 6. The method of claim 5, wherein the lookup table is used separately or in common to output data control signals for the basic gamma voltage and the extended gamma voltage.

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