KR20050065114A - Driving apparatus of liquid crystal display and driving method thereof - Google Patents

Abstract

The present invention relates to a driving apparatus of a liquid crystal display and a driving method thereof, wherein the driving apparatus of the liquid crystal display according to the present invention evenly divides the first group of image information applied through the first switching unit with the odd pixel line image information. A data processor for dividing the second pixel line image information and selectively outputting one of odd-numbered pixel line image information and even-numbered pixel line image information of the first group of image information; A first memory for storing odd-numbered pixel line image information or even-numbered pixel line image information selectively output from the data processor; A second memory configured to receive image information of a second group through a second switching unit and store the image information in a frame unit; The odd-numbered pixel line image information or the even-numbered pixel line image information of the first group of image information stored in the first memory is compared with the image information of the frame unit stored in the second memory, and image information modulated according to the variation is obtained. It includes a data comparison table that outputs an image signal to process the reduced image information compared to the prior art, thereby reducing the capacity of the memory to reduce the production cost, miniaturization and thinning of the liquid crystal display device, liquid crystal display The driving speed of the device can be improved.

Description

     DRIVING APPARATUS OF LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof, and more particularly, to over-driving a liquid crystal, thereby reducing production costs while improving a moving image realization characteristic of the liquid crystal panel, The present invention relates to a driving device of a liquid crystal display device and a driving method thereof to reduce the size and weight of the liquid crystal display device.

In general, a liquid crystal display (LCD) displays an image by using optical anisotropy of liquid crystal, and replaces a cathode ray tube (CRT) due to its thin, small size, low power consumption, and high image quality. It is being developed as a major product of flat panel display.

However, since the liquid crystal display device has lower moving picture realization characteristics than the cathode ray tube, research is being conducted to improve the liquid crystal display device.

1A and 1B are exemplary views schematically illustrating image quality degradation in a moving image implementation through a liquid crystal display device.

As shown in FIG. 1A, when the white object 20 displayed on a black background on the screen implements a moving image moving in the direction of the arrow, the outline of the white object 20 is blurred as shown in FIG. 1B. Attraction occurs.

The above-described problem in realizing a moving image is firstly due to the response time (RT) of the liquid crystal with respect to the image signal.

Generally, in a liquid crystal display device of a twisted nematic (TN) type or a super twisted nematic (STN) type, an electric field is applied to liquid crystal molecules, and then the arrangement of the liquid crystal molecules is changed so that desired light The electro-optic response time required to reach the transmittance is several times longer than that of 16.7 ms, which is the display period of a typical frame, due to characteristics such as liquid crystal viscosity and elastic restoring force.

Accordingly, as shown in FIGS. 1A and 1B, an image signal for white display is performed on a liquid crystal displaying black to implement a moving image in which a white object 20 displayed on a black background of a liquid crystal panel is moved in the direction of an arrow. Even if is applied, the electro-optic response time of the liquid crystal is required until the liquid crystal completely performs the white display. As described above, the electro-optic response time of the liquid crystal is not completed within one frame time.

Due to the delay of the electro-optic response time of the liquid crystal, motion blurring occurs.

Second, the display type of the liquid crystal display device, which is a hold type that maintains light emission until the image signal of the next frame is applied, is a cause of low display quality of the moving picture. Referring to FIG. As follows.

FIG. 2 is an exemplary view showing a luminance change according to an image display of a general liquid crystal display device. As shown in FIG. 2, a liquid crystal display device has a relatively high ratio of charge accumulated in liquid crystal molecules by an electric field until the next electric field is applied. It is driven by the hold type which is kept as.

Therefore, each pixel of the liquid crystal display maintains light emission until the image signal of the next frame is applied. At this time, the graph VD shown by a dotted line is a waveform of an image signal applied to the liquid crystal display device, and the graph BL shown by a solid line is a luminance waveform of an image displayed on the liquid crystal display device substantially corresponding to the image signal. to be.

The slow electro-optic response time of the liquid crystal is not a problem in a moving picture or a still picture in which the brightness of the image does not change much every frame. However, as shown in Fig. 2, when implementing a moving picture in which the brightness of the image changes every frame, the actual luminance of the pixel changes in response to the image signal of the next frame without sufficiently reaching the level of the image signal. Images displayed on the liquid crystal display are not displayed at the desired luminance in every frame, resulting in deterioration of image quality (e.g., contrast reduction).

In consideration of the problems described above, an over-driving method of a liquid crystal display device for compensating an electro-optic response time of a liquid crystal through modulation of an image signal has been proposed.

3 is a diagram illustrating a modulated image signal and a luminance waveform when a moving image is changed every frame according to an over-driving method of a liquid crystal display.

Referring to FIG. 3, in the over-driving method of a liquid crystal display, when a level of a next frame image signal is increased by comparing a current frame image signal with a next frame image signal, modulation is performed by increasing a predetermined level to the image signal of the next frame. The supplied image signal MVD is supplied to the liquid crystal.

On the contrary, when the current frame image signal is compared with the next frame image signal and the level of the next frame image signal is lowered, the modulated image signal MVD is reduced to a liquid crystal image. This drive method is called over-driving.

As described above, when the modulated image signal MVD is applied to the liquid crystal by increasing or decreasing a certain level compared to the original image signal, the response speed of the liquid crystal compared to the case where the original image signal is applied to the liquid crystal As shown in Fig. 3, when a moving picture in which the brightness of the image changes in units of frames is implemented as the speed increases, the luminance of the pixel changes in response to the image signal of the next frame in the state of reaching the level of the image signal. Therefore, the image displayed on the liquid crystal display device has a desired luminance in every frame, thereby preventing the deterioration of the image quality (for example, the decrease in contrast). At this time, the graph VD shown by a dotted line is a waveform of an image signal applied to the liquid crystal display device, and the modulated image signal MVD is a level of a predetermined level with the original image signal as indicated by an arrow in the waveform of the image signal. Is increased or decreased and applied. Further, the graph BL shown by the solid line is the luminance waveform of the image displayed on the liquid crystal display device corresponding to the waveform of the image signal, and the modulated luminance waveform MBL is applied to the waveform of the modulated image signal MVD. Correspondingly, the luminance waveform of the image displayed on the liquid crystal display device.

4 is an exemplary view showing a conventional over-driving apparatus for implementing the over-driving method of the liquid crystal display as described above.

As shown in FIG. 4, the over-driving apparatus of the conventional liquid crystal display includes a first frame memory 50 which receives and stores the image information DATA_ODD of the odd-numbered frame through the first switching unit 60; A second frame memory 51 which receives and stores the image information DATA_EVEN of even-numbered frames through the second switching unit 61; The image information DATA_EVEN of the even-numbered frame applied through the second switching unit 61 is compared with the image information DATA_ODD of the odd-numbered frame stored in the first frame memory 51 and according to the variation, Odd number of levels is increased or decreased from the image information DATA_ODD of the frame to output the modulated image information MVD as an image signal of an odd number of frames, and is also applied through the first switching unit 60. The image information DATA_ODD of the first frame and the image information DATA_EVEN of the even-numbered frame stored in the second frame memory 51 are compared and a predetermined level is increased from the image information DATA_EVEN of the even-numbered frame according to the variation. And a data comparison table 70 for outputting the increased or decreased modulated image information MVD as an image signal of even-numbered frames. In this case, a lookup table is generally applied to the data comparison table 70.

The driving method for the over-driving device of the conventional liquid crystal display device configured as described above will be described in detail as follows.

First, when the image information DATA_ODD of the first frame is supplied, the first switching unit 60 is turned on and the second switching unit 61 is cut off. Accordingly, the image information DATA_ODD of the first frame is applied to and stored in the first frame memory 50 through the first switching unit, and is simultaneously applied to the data comparison table 70.

Since there is no image information to compare because the image information of the previous frame is not applied to the data comparison table 70, the image information DATA_ODD of the first frame is output as it is as the image signal MVD of the first frame.

When the image information DATA_EVEN of the second frame is supplied, the first switching unit 60 is blocked, the second switching unit 61 is turned on, and the image information DATA_EVEN of the second frame is the second frame. The second frame memory 51 is applied to and stored in the second frame memory 51 through the switching unit 61 and is applied to the data comparison table 70.

In this case, the data comparison table 70 receives the image information DATA_ODD of the first frame stored in the first frame memory 50 and then receives the image information DATA_EVEN of the second frame applied through the second switching unit 61. ) And outputs the image signal MVD of the second frame in which the predetermined level is increased or decreased from the image information DATA_EVEN of the second frame according to the variation.

When the image information DATA_ODD of the third frame is supplied, the first switching unit 60 is turned on, and the second switching unit 61 is cut off so that the image information of the third frame is stored in the first frame memory 50. DATA_ODD) is stored and applied to the data comparison table 70.

The data comparison table 70 receives the image information DATA_EVEN of the second frame stored in the second frame memory 51, and the image information DATA_ODD of the third frame applied through the first switching unit 60. In comparison, the image information of which the predetermined level is increased or decreased from the image information DATA_ODD of the third frame according to the variation is output as the image signal MVD of the third frame.

As described above, in the over-driving apparatus of the conventional LCD, the image information DATA_ODD of the odd-numbered frame and the image information DATA_EVEN of the even-numbered frame are provided through the first switching unit 60 and the second switching unit 61. Are stored alternately in the first frame memory 50 and the second frame memory 51, and the data comparison table 70 and the image information DATA_ODD of the odd-numbered frame applied through the first switching unit 60 are stored. Compares the image information DATA_EVEN of the previous even frame stored in the second frame memory 61 and increases or decreases a certain level from the image information DATA_ODD of the odd frame according to the variation, and thereby increases the odd frame. The image information DATA_EVEN of the even-numbered frame applied through the second switching unit 61 and the image information DATA_ODD of the previous odd-numbered frame stored in the first frame memory 60. Compare that to According to the variation, a certain level is increased or decreased from the image information DATA_EVEN of the even-numbered frame and output as an image signal MVD of the even-numbered frame.

Recently, liquid crystal displays have tended to be larger in area, thinner, and lighter, and have been mass-produced to meet many demands. As such, in mass production of liquid crystal display devices, the reduction of some parts or devices leads to a significant reduction in production cost, and thus the price competitiveness is an important issue for the company and a great consideration for the consumer who purchases the product. to be.

However, the conventional over-driving device of the liquid crystal display device increases the production cost by using two large-capacity frame memories to store image information of odd-numbered frames and image information of even-numbered frames. There was a problem that adversely affects thinness and weight.

In addition, when over-driving using two frame memories, the image quality can be improved by storing, comparing, and modulating the image signal every frame, but the processing speed of the image signal is slowed.

The present invention has been made to solve the conventional problems as described above, an object of the present invention is to over-driving the liquid crystal, thereby improving the moving image realization characteristics of the liquid crystal panel, the amount of frame memory used compared to the conventional The present invention provides a driving device for a liquid crystal display device and a method of driving the same, which can reduce production costs and reduce the size and weight of a liquid crystal display device.

In order to achieve the object of the present invention as described above, the driving apparatus of the liquid crystal display device divides the first group of image information applied through the first switching unit into odd-numbered pixel line image information and even-numbered pixel line image information. A data processor for selectively outputting any one of odd-numbered pixel line image information and even-numbered pixel line image information of the first group of image information; A first memory for storing odd-numbered pixel line image information or even-numbered pixel line image information selectively output from the data processor; A second memory configured to receive image information of a second group through a second switching unit and store the image information in a frame unit; The odd-numbered pixel line image information or the even-numbered pixel line image information of the first group of image information stored in the first memory is compared with the image information of the frame unit stored in the second memory, and image information modulated according to the variation is obtained. And a data comparison table output as an image signal.

In addition, the driving method of the driving apparatus of the liquid crystal display device for achieving the object of the present invention includes a first step of storing the first group of image information in the first memory and output as an image signal; One of the odd-numbered pixel line image information and the even-numbered pixel line image information of the second group of image information is selectively stored in the second memory, and compared with the previous frame image information stored in the first memory, A second step of outputting, as an image signal, modulated image information of which the predetermined level is increased or decreased from odd-numbered pixel line image information or even-numbered pixel line image information among the second group of image information; The image information of the first group is stored in the first memory and compared with the previous frame image information stored in the second memory, and a predetermined level is increased or decreased from the first group of image information according to the variation. And a third step of outputting image information as an image signal, and repeating the second and third steps.

Features of the present invention as described above

Referring to the driving device of the present invention as described above in detail with reference to the accompanying drawings as follows.

5 is an exemplary view showing a block configuration of a driving device of the liquid crystal display device according to the first embodiment of the present invention.

Although not shown in the drawings, the liquid crystal display device includes a first substrate and a second substrate which are bonded to face each other, a liquid crystal layer formed by filling a liquid crystal between the first substrate and the second substrate, and on the first substrate. A plurality of data lines arranged to be vertically spaced apart from each other, a plurality of gate lines arranged to be uniformly spaced apart laterally on the first substrate, and a pixel formed in an area where the data lines and the gate lines intersect each other And an image display unit formed of a plurality of pixel lines.

Referring to FIG. 5, the driving apparatus of the liquid crystal display device includes a first memory 150 that receives image information of a first group through the first switching unit 160 and stores the image information in a frame unit, and image information of a second group. Is applied through the second switching unit 161 to divide the odd-numbered pixel line image information and the even-numbered pixel line image information, and selectively output the odd-numbered pixel line image information or even-numbered pixel line image information. 155; A second memory 151 for storing odd-numbered pixel line image information or even-numbered pixel line image information of the second group of image information selectively received from the data processor 155; A data comparison table for comparing the image information stored in the first memory 150 and the second memory 151, and outputting the modulated image information as an image signal by increasing or decreasing a predetermined level according to the change amount ( And 170).

In this case, the first group may represent an odd frame, the second group may represent an even frame, and conversely, the first group may be an even frame and the second group may be an odd frame.

Referring to the driving of the driving device of the liquid crystal display according to the present invention having the configuration as described above in detail as follows.

First, when the first group of image information is applied to the first memory 150 through the first switching unit 160 is stored. At this time, the second switching unit 161 is blocked so that the image information of the first group is not applied to the second memory. The image information of the first group is applied through the first switching unit 160, is stored in the first memory 150, and is applied to the data comparison table 170. The previous frame to be compared with the image information of the first group is provided. Since there is no image information, the first group of image information is output as an image signal and displayed on the screen.

When the image information of the second group is supplied, the first switching unit 160 is blocked, so that the image information of the second group is not applied to the first memory 150 and the second switching unit ( The data is applied to the data processor 155 through 161.

The data processor 155 divides the applied second group of image information into odd-numbered pixel line image information and even-numbered pixel line image information, where the image information of the pixel line is actually displayed on the screen. Corresponds to the image. In this manner, one of the divided odd-numbered pixel line image information and the even-numbered pixel line image information is output to the second memory 151, and the remaining image information is output as an image signal. That is, only one image information of the odd-numbered pixel line image information and the even-numbered pixel line image information is modulated through the data comparison table 170, and the remaining image information is displayed on the screen in its original state without applying modulation.

The second memory 151 stores odd-numbered pixel line image information or even-numbered pixel line image information of the second group of image information selectively applied from the data processor 155, and stores the data comparison table 170. To apply.

The data comparison table 170 includes odd-numbered pixel lines of a first group of image information stored in the first memory 150 and a second group of image information applied from the second memory 151. Image information or even-numbered pixel line image information is compared, and a predetermined level is increased or decreased from the odd-numbered pixel line image information or even-numbered pixel line image information according to the variation, and the modulated image information is converted into an image signal. Output The image signal thus output and the image signal output as it is from the data processing unit 155 are displayed as the frame image.

Next, when the first group of image information is applied, the first switching unit 160 is turned on, the second switching unit 161 is cut off, so that the first group of image information is the first switching unit ( The data is applied to and stored in the first memory 150 through the 160. The image information of the first group is stored in the first memory 150 and applied to the data comparison table 170.

The data comparison table 170 compares the image information of the first group with the image information of the second group of the previous frame stored in the second memory, and sets a predetermined value from the image information of the first group according to the variation. The level of minute is increased or decreased to output modulated image information as an image signal.

In the driving of the driving device of the liquid crystal display as described above, all the driving processes are repeatedly performed except for the driving of the first group of image information that is first applied. Since the image information of the first group to be applied for the first time is output as it is without undergoing a modulation process because there is no image information of a previous frame to be compared, it corresponds to one-time driving in the driving process of the driving apparatus.

Further, in driving of the driving apparatus, odd-numbered pixel line image information and even-numbered pixel line image information of the second group of image information are stored in the second memory for two frames, respectively. Accordingly, the odd-numbered pixel line image information and the even-numbered pixel line image information are alternately stored in the second memory in units of two frames. However, in the comparison between the odd-numbered pixel line image information and the even-numbered pixel line image information, there is no significant difference in content or result in the comparison of the image information. Only one image information of the information may be stored continuously.

On the other hand, the driving device of the liquid crystal display device selectively stores the odd-numbered pixel line image information or the even-numbered pixel line image information of the second group of image information in the second memory 151, and thus is half of the conventional driving apparatus. There is a memory saver. Generally, Synchronous Dynamic Random Access Memory (SDRAM) is mainly used as the first memory 150 and the second memory 151. In the case of the second memory 151, the SDRAM having a smaller capacity than that of the first memory is used. Can reduce the size of the memory and reduce the production cost. And it becomes possible to package together in a drive apparatus.

The data comparison table 170 generally uses erasable programmable read-only memory (EPROM), which is a ROM that can erase and reuse contents stored in the memory. Intense UV light through a glass window attached to the chip's surface erases the contents of the ROM. In this way, the image information of the first memory and the image information of the second memory are compared to the easy-to-correct and delete E-ROM, and the image signal information to be output is stored in advance according to the variation. Therefore, the data comparison table 170 is called a look-up table (LUT).

The driving process of the driving device of the LCD will be described in detail with reference to FIG. 6.

6 is an exemplary view showing the driving of the driving device of the liquid crystal display according to the first embodiment of the present invention as a block.

Referring to FIG. 6, first, when image information of a first group is applied through a first switching unit, the first group of image information is stored in a first memory and output as an image signal, and the image information of the second group is transferred through a second switching unit. When is applied to, it is divided into odd pixel line image information and even pixel line image information, and selectively applied to the second memory.

The second memory stores odd-numbered pixel line image information or even-numbered pixel line image information, which is selectively applied to a data comparison table and compared with the image information stored in the first memory, thereby modulating according to the variation. Image information is output as an image signal. When the first group of image information is applied to the first memory through the first switching unit, the first frame is stored in the first memory and the first group of image information is applied to the data comparison table to store the previous frame. Is compared with the odd-numbered pixel line image information or the even-numbered pixel line image information, and the image information modulated according to the variation is output as an image signal.

The driving step in the image information of the first group and the image information of the second group is repeatedly performed. As described above, in the over-driving driving process, over-driving is performed in every frame except for the first first group of image information. The second group of image information includes odd-numbered pixel line image information or even-numbered pixel line. Since only image information performs over-driving, the processing speed is improved as compared with the conventional over-driving drive.

As described above, the driving apparatus and the driving method thereof according to the present invention reduce the image information to be processed compared to the driving apparatus in the related art, thereby reducing the memory capacity required for driving, thereby reducing the production cost of the liquid crystal display apparatus. It is possible to reduce the size and weight of the liquid crystal display device.

Also, by over-driving the reduced image information, the speed of the liquid crystal display device can be improved.

1A and 1B are exemplary views schematically showing image quality deterioration in a moving image implementation through a liquid crystal display.

2 is an exemplary view showing a luminance change according to image display of a general liquid crystal display device.

3 is a diagram illustrating a modulated image signal and a luminance waveform when a moving image is changed every frame according to an over-driving method of a liquid crystal display;

4 is an exemplary view showing a conventional over-driving apparatus for implementing the over-driving method of a liquid crystal display as described above.

5 is an exemplary view showing a block configuration of a driving device of the liquid crystal display device according to the first embodiment of the present invention.

6 is an exemplary view showing the driving of the driving device of the liquid crystal display device according to the first embodiment of the present invention as a block;

*** Explanation of symbols for main parts of drawing ***

150: first memory 151: second memory

155: data processor 160: first switching unit

161: second switching unit 170: data comparison table

Claims (9)

The first group of image information applied through the first switching unit is divided into odd-numbered pixel line image information and even-numbered pixel line image information, and odd-numbered pixel line image information and even-numbered pixel line of the first group of image information A data processor for selectively outputting any one of image information; A first memory for storing odd-numbered pixel line image information or even-numbered pixel line image information selectively output from the data processor; A second memory configured to receive image information of a second group through a second switching unit and store the image information in a frame unit; The odd-numbered pixel line image information or the even-numbered pixel line image information of the first group of image information stored in the first memory is compared with the image information of the frame unit stored in the second memory, and image information modulated according to the variation is obtained. And a data comparison table for outputting an image signal. 2. The driving apparatus of claim 1, wherein the first group is an even-numbered frame and the second group is an odd-numbered frame. 2. The driving apparatus of claim 1, wherein the first memory is a synchronous dynamic random access memory (SDRAM). The apparatus of claim 1, wherein the data comparison table is an erasable programmable read-only memory (EPROM). A first step of storing the first group of image information in a first memory and outputting the image information as an image signal; One of the odd-numbered pixel line image information and the even-numbered pixel line image information of the second group of image information is selectively stored in the second memory, and compared with the previous frame image information stored in the first memory, A second step of outputting, as an image signal, modulated image information of which the predetermined level is increased or decreased from odd-numbered pixel line image information or even-numbered pixel line image information among the second group of image information; The image information of the first group is stored in the first memory and compared with the previous frame image information stored in the second memory, and a predetermined level is increased or decreased from the first group of image information according to the variation. And a third step of outputting image information as an image signal, wherein the second step and the third step are repeatedly performed. 6. The driving method of claim 5, wherein the first group is an odd frame and the second group is an even frame. 6. The driving method of claim 5, wherein the first memory stores the first group of image information in frame units. 6. The driving apparatus of claim 5, wherein the second memory alternately stores odd pixel line image information and even pixel line image information of the second group of image information every two frames. Driving method. 6. The driving apparatus of claim 5, wherein the second memory stores the same image information every two frames among odd-numbered pixel line image information and even-numbered pixel line image information of the second group of image information. Method of driving the device.