KR20050045169A - Driving apparatus of liquid crystal display and driving method thereof - Google Patents

Abstract

The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof. The driving apparatus for a liquid crystal display device according to the present invention includes a first frame memory for receiving and storing image information of a first group frame through a first switching unit; ; In the first group frame, the image information of the first group frame is applied through the first switching unit and output as an image signal. In the second group frame, the image information of the second group frame and the first group frame are applied through the second switching unit. Compares the image information of the previous first group frame stored in the frame memory, and compares the data outputting the modulated image information as an image signal by increasing or decreasing a certain level from the image information of the second group frame according to the variation. And a driving device of the liquid crystal display device, the method comprising: storing image information of a first group frame in a first group frame and outputting an image signal; In the second group frame, the image information of the second group frame is compared with the image information of the stored first group frame, and a predetermined level is increased or decreased from the image information of the second group frame according to the variation. The step of outputting image information as an image signal is repeated.

Description

     DRIVING APPARATUS OF LIQUID CRYSTAL DISPLAY AND DRIVING METHOD THEREOF

The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof, and more particularly, by over-driving a liquid crystal, the production cost is reduced when the moving image realization characteristic of the liquid crystal display panel is improved, The present invention relates to a driving device of a liquid crystal display device and a method of driving the same, which can reduce the size and weight of a 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 the liquid crystal display.

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 problem of the moving picture realization characteristics as described above is firstly due to the response time (RT) of the liquid crystal to the image signal.

In general, 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 is generated. 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 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 display panel is moved in an arrow direction. Even if a signal 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 such a delay in the electro-optic response time of the liquid crystal, motion blurring is observed.

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-optical 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 in every frame unit. However, as shown in FIG. In this case, since the actual luminance of the pixel does not reach the level of the image signal sufficiently, it changes in response to the image signal of the next frame, so that the image displayed on the liquid crystal display device does not have the desired luminance in every frame. For example, contrast decreases.

In consideration of the above problem, an over-driving method of a liquid crystal display device for compensating an electro-optical 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 the liquid crystal display, when the level of the next frame image signal is increased by comparing the current frame image signal with the next frame image signal, a predetermined level is added to the image signal of the next frame. The increased modulated image signal MVD is supplied to the liquid crystal.

On the contrary, when the level of the next frame image signal is lowered by comparing the current frame image signal with the next frame image signal, 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 is shown in Fig. 3, when a moving picture in which the brightness of an image changes in units of frames as shown in Fig. 3 is realized, the luminance of the pixel changes in response to the image signal of the next frame in a state where the level of the image signal is reached. The image displayed on the liquid crystal display device has a desired luminance in every frame, thereby preventing deterioration of image quality (for example, a 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, and the modulated image signal MVD is increased or decreased by a predetermined level as indicated by an arrow in the waveform of the image signal. Is 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.

Referring to FIG. 4, a conventional over-driving apparatus of a liquid crystal display includes: a first frame memory 50 configured to receive and store image information DATA_ODD of an odd-numbered frame through a 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 and the image information DATA_ODD of the odd-numbered frame stored in the first frame memory 51 are compared and odd-numbered 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 blocked, so the image information DATA_ODD of the first frame is switched to the first switching. It is applied through the unit to be stored in the first frame memory 50 and to the data comparison table 70.

Since 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 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 cut off and the second switching unit 61 is turned on so that the image information DATA_EVEN of the second frame is switched to the second switching unit. It is applied through the unit 61 and stored in the second frame memory 51 and is applied to the data comparison table 70 through.

The data comparison table 70 receives the image information DATA_ODD of the first frame stored in the first frame memory 50, and the image information DATA_EVEN of the second frame applied through the second switching unit 61. In comparison, a certain level is increased or decreased from the image information DATA_EVEN of the second frame according to the variation and output as the image signal MVD of the second frame.

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, a certain level is increased or decreased from the image information DATA_ODD of the third frame in accordance with the variation and output as the image signal MVD of the third frame.

As described above, in the over-driving apparatus of the conventional LCD, the first frame memory 50 and the second frame memory 51 are odd-numbered frames by the first switching unit 60 and the second switching unit 61. The image information DATA_ODD and the image information DATA_EVEN of the even-numbered frame are alternately stored, and the data comparison table 70 stores the image information DATA_ODD of the odd-numbered frame applied through the first switching unit 60. 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.

On the other hand, liquid crystal display devices have recently become large, thin, and lightweight, and are being mass-produced due to many demands.

In mass-produced liquid crystal displays, the reduction of one component or device causes a large difference in production cost. Price competitiveness is an important issue in production and a great consideration for consumers.

However, in the over-driving apparatus of the conventional LCD, the production cost increases as two frame memories are used to store the image information of the odd frame and the image information of the even frame. There was a problem that weight reduction is disadvantageous.

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

 SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems as described above, and an object of the present invention is to over-drive the liquid crystal, thereby improving the moving image realization characteristic of the liquid crystal display panel, and the number of frame memories used in the prior art. The present invention provides a driving device for a liquid crystal display device and a method of driving the same, which reduce production costs and reduce the size and weight of the liquid crystal display device.

The driving apparatus of the liquid crystal display device for achieving the object of the present invention includes a first frame memory for receiving and storing the image information of the first group frame through the first switching unit; In the first group frame, the image information of the first group frame is applied through the first switching unit and output as an image signal. In the second group frame, the image information of the second group frame and the first group frame are applied through the second switching unit. Compares the image information of the previous first group frame stored in the frame memory, and compares the data outputting the modulated image information as an image signal by increasing or decreasing a certain level from the image information of the second group frame according to the variation. It is characterized by comprising a table.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method including: storing image information of a first group frame in a first group frame and outputting an image signal; In the second group frame, the image information of the second group frame is compared with the image information of the stored first group frame, and a predetermined level is increased or decreased from the image information of the second group frame according to the variation. And repeatedly outputting image information as an image signal.

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.

Referring to FIG. 5, the driving apparatus of the liquid crystal display device includes a first frame memory 150 that receives and stores image information of the first group frame through the first switching unit 160, and the first group frame includes the first frame memory 150. The image information of the first group frame is received through the first switching unit and output as an image signal, and in the second group frame, the image information of the second group frame and the first frame memory applied through the second switching unit 161. Data for comparing the image information of the previous first group frame stored in 150, and outputting the modulated image information as an image signal by increasing or decreasing a certain level from the image information of the second group frame according to the variation. The comparison table 170 is provided.

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

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 image information of the first group frame is applied, the first switching unit 160 is turned on, and the second switching unit 161 is blocked, so that the image information of the first group frame is the first switching unit 160. It is applied through the first frame memory 150 and is applied to the data comparison table 170. Since there is no image information of the previous frame to be compared with the image information of the first group frame, it is output as an image signal.

When the image information of the second group frame is supplied, the first switching unit 160 is blocked and the second switching unit 161 is turned on so that the image information of the second group frame is changed to the second switching unit ( 161 is applied to the data comparison table 170.

In this case, the data comparison table 170 compares the image information of the second group frame with the image information of the first group frame previously applied and stored in the first frame memory 150, and compares the image information of the first group frame with the variation. Accordingly, a predetermined level is increased or decreased from the image information of the second group frame to output modulated image information as an image signal.

Next, when the image information of the first group frame is applied in the first group frame, the first switching unit 160 is turned on, and the second switching unit 161 is blocked so that the image information of the first group frame is It is applied through the first switching unit 160 and is stored in the first frame memory 150 and is applied to the data comparison table 170. Since the image information of the previous second group frame which is the data to be compared is not stored, The image information of the first group frame is output as an image signal as it is.

Meanwhile, the first frame memory 150 generally uses synchronous dynamic random access memory (SDRAM) in consideration of the size of a storage space which is relatively inexpensive and stores all the image information of a frame. Therefore, it is difficult to configure the driving device of the liquid crystal display as a single chip.

As described above, the driving device of the liquid crystal display device stores the image information of the first group frame in the first frame memory through the first switching unit 160 and outputs the image signal as an image signal, and the image information of the frame of the second group. Is directly applied to the data comparison table 170 through the second switching unit 161, and the data comparison table 170 is connected to the image information of the first group frame stored in the first frame memory 150. The image information of the second group frame is compared, and a predetermined level is increased or decreased from the image information of the second group frame and the modulated image information is outputted as an image signal according to the variation. The image information of the first group frame and the image information of the second group frame are alternately applied and repeated.

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, the image information of the first group frame and the image information of the second group frame which are alternately applied are driven differently. When the image information of the first group frame is applied through the first switching unit, the first frame When the image information of the second group frame is applied to the data comparison table through the second switching unit, the first group frame is stored in the first frame memory. Image information of the second group frame is compared with the image information of the second group frame, and a predetermined level is increased or decreased from the image information of the second group frame and modulated image information is output as an image signal. That is, the over-driving is performed only when the image information of the second group frame is applied.

As described above, the driving step in the image information of the first group frame and the image information of the second group frame is repeatedly performed.

The conventional driving apparatus of the liquid crystal display device uses two frame memories to store image information of all frames in the first frame memory or the second frame memory, and the previous frame in the data comparison table whenever image information of each frame is applied. Although over-driving was performed by comparing the image information of the image information of the current frame with the image information of the current frame, the driving apparatus of the liquid crystal display according to the present invention performs only the image information of the first group frame in the first frame memory. The image information of the second group frame is compared with the first group image information stored in the first frame memory of the previous frame, and outputs a modulated image signal. That is, by over-driving only when the image information of the second group frame is applied, the overall driving step is simplified to increase the speed of the liquid crystal display.

The over-driving as described above may be performed at the time of applying the image information of the first group frame in the reverse order to the over-driving sequence described above.

As described above, the driving apparatus and driving method thereof according to the present invention can reduce the production cost by reducing the number of frame memories as compared to the driving apparatus to which two frame memories are conventionally applied, and reduce the size of the liquid crystal display apparatus. And weight can be reduced.

In addition, by performing over-driving using one frame memory, it is possible to improve the speed of the liquid crystal display by simplifying the driving step rather than the over-driving using conventional two frame memories.

1A and 1B are exemplary views schematically illustrating image quality deterioration in a moving image implementation using the 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 frame memory 160: first switching unit

161: second switching unit 170: data comparison table

Claims (5)

A first frame memory configured to receive and store image information of the first group frame through the first switching unit; In the first group frame, the image information of the first group frame is received through the first switching unit and output as an image signal. In the second group frame, the image information of the second group frame and the first group frame are applied through the second switching unit. Compare the image information of the previous first group frame stored in the frame memory, and compare the data outputting the modulated image information as an image signal by increasing or decreasing a certain level from the image information of the second group frame according to the variation. A drive device for a liquid crystal display device comprising a table. The apparatus of claim 1, wherein the first frame memory is a synchronous dynamic random access memory (SDRAM). Storing image information of the first group frame in the first group frame and outputting the image information as an image signal; In the second group frame, the image information of the second group frame is compared with the image information of the stored first group frame, and a predetermined level is increased or decreased from the image information of the second group frame according to the variation. And repeating the step of outputting the image information as an image signal. 4. The driving method of claim 3, wherein the first group frame is an odd frame and the second group frame is an even frame. 4. The driving method of claim 3, wherein the second group frame is an even-numbered frame, and the first group frame is an odd-numbered frame.