KR20050068607A - Method for driving lcd - Google Patents

Abstract

The present invention relates to a method of driving a liquid crystal display device having an excellent display quality by improving color reproducibility of R, G, and B data without any circuitry. The present invention relates to a liquid crystal display device having an ODC (Over Driving Circuit) function. In the driving method of the, characterized in that to perform the ODC by applying the respective look-up table value to each of the input data of R, G, B. Therefore, the present invention can realize higher color reproducibility than the color reproducibility of the original color filter by applying each look-up table value for each data of R, G, and B, thereby improving the display quality of the liquid crystal display device. Not only that, but also to improve the competitiveness of the product.

Description

Driving method of liquid crystal display device {METHOD FOR DRIVING LCD}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a method of driving a liquid crystal display device suitable for improving color reproducibility without adding or changing circuits in a liquid crystal display device employing an over driving circuit (ODC).

In general, in a timing controller (T / CON) to which an ODC (Over Driving Circuit, ODC) function is added, data of each of R, G, and B uses the same look-up table value. In this case, the same color reproducibility as that of the liquid crystal display without using ODC is realized.

In general, color reproducibility is an important factor that determines the competitiveness of all display devices, and as the color reproducibility is higher, more colors can be expressed, thus acting as a factor for enhancing the competitiveness of a product in a multimedia such as a TV.

In this context, a technique for improving color reproducibility has been proposed. The simplest method is a method for improving color reproducibility of color filters. The gamma voltage is different for each of R, G, and B data. How to give.

Hereinafter, a method of driving a liquid crystal display device to improve color reproducibility by applying different gamma voltages to data of each of R, G, and B, according to the related art.

1 is a block diagram of a liquid crystal display device according to the prior art, FIG. 2 is a view showing a storage state of gradation data according to the prior art, and FIG. 3 is a reference gradation voltage of R, G and B according to the prior art. It is a schematic block diagram which shows the specific example of a generation circuit and a signal line drive circuit.

As shown in FIG. 1, the liquid crystal display according to the related art includes a liquid crystal panel 2, a display control circuit 3, a red (R), a green (G), and a blue (B) switching reference gradation voltage generation circuit ( 4), a scanning line driver circuit 5 and a signal line driver circuit 6 are provided.

The liquid crystal panel 2 is a plurality of scanning lines 21, in which wirings used are mounted in a horizontal direction with respect to the display surface, and wirings used as a plurality of signal lines 22 are mounted in a vertical direction with respect to the display surface. The pixel electrode 23 is formed at the intersection between each scan line 21 and each signal line 22, and the TFT 24 is each signal line 22 corresponding to each pixel electrode 23 and each pixel electrode 23. Connected to each other and each gate of the TFTs 24 is connected to each of the scanning lines 21.

In addition, the red pixel electrode 23, the green pixel electrode 23, and the blue pixel electrode 23 are sequentially arranged in the vertical direction, and each of them is connected to the same signal line 22 to form one pixel. A specific number of pixel electrodes 23 for R, G, and B colors are arranged in the vertical direction, and pixel electrodes 23 for the same color are arranged in the horizontal direction, and each of them is connected to the same scan line. The pixel electrodes arranged in the vertical direction and the horizontal direction form one screen.

Therefore, if the pixel configuration in one screen is the same, the number of signal lines 22 in the liquid crystal panel 2 is 1/3 compared with the number of signal lines in the normal liquid crystal panel, and the number of scanning lines is three times more.

On the other hand, the display control circuit 3 receives gradation data in which gradation data for R, G, and B colors are repeatedly arranged from the image recording apparatus 100, and the gradation data is arranged on the liquid crystal panel 2 The input gradation data is sorted according to the synchronization data for each of the scanning lines 21 so as to correspond to them, and at the same time, the scanning line control signal is output to the scanning line driver circuit 5 and the signal line control circuit to the signal line driver circuit 6. .

The RGB switching reference gradation voltage generation circuit 4 is each of R, G, and B colors in the liquid crystal panel 2 required when a signal having a voltage corresponding to the gradation data is output by the signal line driver circuit 6. Three reference gradation voltages are generated, including a reference gradation voltage for red, a reference gradation voltage for green, and a reference gradation voltage for blue.

The scan line driver circuit 5 outputs a scan line signal to each of the scan lines 21 every field period in accordance with the scan line control signal.

The signal line driver circuit 6 controls the signal lines for each syringe based on the aligned grayscale data supplied from the display control circuit 3 and three kinds of reference grayscale voltages supplied from the RGB switching reference grayscale voltage generation circuit 4. According to the signal, a signal subjected to gamma correction according to the VT characteristic of each color of the liquid crystal panel 2 is generated, and the signal is output to each of the signal lines 22.

Alignment of the gradation data in the display control circuit 3 is performed in the manner shown in FIG. 2 shows an example of a video graphics array (VGA). As shown in FIG. 2, the grayscale data input from the image recording apparatus 100 is a signal in which a set of grayscale data arranged in the order of R, G, and B colors is repeatedly arranged from pixels 1 to 640 at every scan line position. And input in a manner corresponding to each of the scan line positions 1 to 480. The display control circuit 3 aligns the input gradation data in the manner as shown in FIG. 2, signals in which red signals are arranged from pixels 1 to 640, signals in which green signals are arranged from pixels 1 to 640, And the scanning line positions 1 to 1440 are outputted to the scanning line positions 1 to 1440 sequentially for each of the scanning line positions. At this time, the red reference gradation voltage, the green reference gradation voltage, and the blue reference gradation voltage are repeatedly applied to the red scanning line position, the green scanning line position, and the blue scanning line position by the RGB switching reference gradation voltage generation circuit 4. Supplied.

In addition, each of the RGB switching reference gradation voltage generation circuit 4 and the signal line driver circuit 6 has a configuration as shown in FIG.

In the RGB switching reference gradation voltage generation circuit 4, the voltages VOR obtained by dividing the reference voltage Vref by the red voltage divider circuit DR, the green voltage divider circuit DG, and the blue voltage divider circuit DB, respectively, are obtained. R, G, B colors using multiplexers (MPXs, M1, M2, ..., M9 and M10) according to the selection control signal SL from VOG, VOB, ... V9R, V9G, V9B The voltages obtained by selecting for each color of these are output as the reference gradation voltages V0, V1, ..., V9 through the voltage followers B1, B21, ..., B9, B10.

Each of the multiplexers selects a corresponding voltage in response to the selection control signal SL output in synchronization with the selection of the scan line 21 for each of the R, G, and B colors, and sets the reference voltage as the reference gradation voltage. Output to

On the other hand, in the signal line driver circuit 6, the MPX 61 divides the reference gray voltages V0 to V9 into sets of V0 to V4 and sets of V5 to V9, and divides them into digital-to-analog converters (DACs) 62. Output to In addition, the gray scale data supplied from the display control circuit 3, for example, 6-bit gray scale data D1, D2, and D3, are shift register sections controlled by the horizontal start pulse HSP and the clock signal HCK. It is held in parallel by the data register unit 64 controlled by the output at each stage of (63). The signals made up of the gradation data held in parallel in the data register unit 64 are all burned to the latch unit 65 by the latch signal STB and latched in the latch unit.

The gray level data latched in the latch unit is transmitted to the DAC 62 through the level shift unit 66. The gradation data transmitted to the DAC 62 is subjected to gamma correction based on the set of reference gradation voltages V0 to V4 and the set of reference gradation voltages V5 to V9 supplied from the MPX 61 and at the same time a voltage follower. Digital-analog converted signal voltages outputted to the corresponding signal lines 22 through the fields F1, F2, ... F640 are generated. As shown in FIG. 2, the switching is sequentially performed in a repeating manner for each dice. Furthermore, in this example, the gradation data D1, D2, D3 are transmitted to the data register portion 64 of the signal line driver circuit 6 through three ports as shown in Fig. 3, but the number of ports is not limited. Any port can be used.

However, in the conventional liquid crystal display device as described above, various circuits have to be added in order to increase color reproducibility, resulting in increased cost and complicated circuit configuration.

Of course, the color reproducibility of the color filter may be increased in addition to the method of providing the respective gamma voltages for each of the R, G, and B data as described above. However, this causes a problem of deterioration in luminance, and also a method of using the LED backlight. However, this is not effective in increasing color reproducibility because the algorithm is complicated and the backlight is changed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide a method of driving a liquid crystal display device suitable for achieving excellent display quality by improving color reproducibility of R, G, and B data without any additional configuration. have.

The driving method of the liquid crystal display device of the present invention for achieving the above object is a driving method of a liquid crystal display device having an ODC (Over Driving Circuit) function, each look for each input data R, G, B It is characterized by performing ODC by applying the up-up table value.

In this case, it is preferable to perform tuning using EEPROM to determine the respective look-up table values.

(Example)

Hereinafter, a driving circuit of the liquid crystal display according to the present invention will be described with reference to the accompanying drawings.

4 is a graph illustrating a general ODC method, and compares current data with previous data, performs an ODC operation with an appropriate value, and outputs data. If the previous data is "0011" and the current data is "1001", the current data is manipulated with an appropriate value. That is, when a value such as "1100" larger than the current data is output, the liquid crystal rises or falls at a faster speed than when the output is "1001".

This is the ODC (Over Driving Circuit) that uses the principle that the response speed of the module is faster. Therefore, the ODC compares the previous data with the current data according to the value of the look-up table to determine the R, G, and B data to be output.

However, according to the conventional LCD, the look-up table is equally applied to the R, G, and B data. Therefore, when a color filter having 60% color reproducibility is used, only 60% color reproducibility is expressed.

Accordingly, the present invention has technical features in that it expresses color reproducibility more than the color reproducibility of the original color filter, but does not constitute an additional circuit.

That is, Figure 5 is a block diagram of an ODC block according to the present invention, Figure 6 is a block diagram of a conventional ODC block. For reference, the configuration of the ODC block according to the present invention is the same as the existing ODC block shown in FIG. This means that the present invention is free of additional configuration of the circuit.

As shown in Fig. 5, the ODC execution unit 51, the memory controller 53 for controlling the frame memory 52 for storing the data of the previous frame, the look-up table 54 and the logic unit ( 55).

However, in comparison with FIG. 6, in the present invention, one look-up table 64 simultaneously uses R, G, and B data, whereas in the present invention, as shown in FIG. 5, the look-up table (54) exists for each of R, G, and B data.

Therefore, while the expressive power of color reproducibility can express only the color reproducibility of the original color filter, according to the present invention, it is possible to express higher color reproducibility than the color reproducibility of the original color filter.

This will be described in more detail as follows.

First, when the look-up table is equally applied to the R, G, and B data, data input from a timing controller (not shown) is stored in the frame memory 62. At this time, SDRAM is used as the frame memory 62.

The reason for storing the data of the previous frame in the frame memory 62 is to compare with the current data, compare the previous frame data with the current frame data and manipulate the current data with an ODC value suitable for the difference of the data. To print.

Thus, as shown in FIG. 5, the present invention can increase color reproducibility without additional circuitry as compared with the conventional (FIG. 6). According to the present invention, first, in order to determine the value of the look-up table, tuning is required. To this end, an EEPROM not included in the ODC timing controller is installed externally for tuning, and when the tuning is completed, the ODC timing controller is internally tuned. Mask is in ROM.

First, if the previous data value of the input data is assumed to be L15 (00001111b) and the current data value is assumed to be L180 (10110100b), the output data is determined by the values of the R, G, and B look-up tables. For example, the value of the look-up table of R data of Rising from L15 to L180 is 70, the value of the look-up table of G data is 67, and the value of the look-up table of B data is 73, the output data values of R, G, and B are output to L197 (11000101b), L188 (10111100b), and L205 (11001101b).

That is, although the original value was L180, the output value is output with a different value from the data input such as R data L197, G data L188, and B data L205. Therefore, the data value to be output is changed so that no circuit addition is necessary.

FIG. 7 is a graph showing an output waveform of data according to a conventional method of driving a liquid crystal display, and FIG. 8 is a graph showing an output waveform of data according to the present invention. In the case of FIG. You can see that the B data has the same output.

However, according to the present invention, as shown in FIG. 8, when ODC is generated, it can be seen that the R, G, and B data have different data outputs, which are different from those of the module of FIG. 6. This means that higher color reproducibility can be expressed in modules like.

Although the preferred embodiments of the present invention have been described above, it is clear that the present invention can use various changes, modifications, and equivalents, and that the above embodiments can be appropriately modified and applied in the same manner. Accordingly, the above description does not limit the scope of the invention as defined by the limitations of the following claims.

As described above, the driving method of the liquid crystal display device of the present invention has the following effects.

By applying separate look-up table values for each data of R, G, and B without adding a separate circuit to the existing ODC block or changing circuits, it is possible to realize higher color reproducibility than that of the original color filter. As a result, the display quality of the liquid crystal display device can be improved, and the competitiveness of the product can be improved.

1 is a block diagram of a liquid crystal display according to the related art

2 is a diagram illustrating a storage state of grayscale data according to the related art.

3 is a schematic block diagram showing a concrete example of the R, G, B switching reference gradation voltage generation circuit and the signal line driving circuit according to the prior art;

4 is a graph for explaining a general ODC method

5 is a block diagram of an ODC block according to the present invention

6 is a block diagram of a conventional ODC block

7 is a graph illustrating a data output waveform when the ODC block of FIG. 6 is applied.

8 is a graph illustrating a data output waveform when the ODC block of FIG. 5 is applied.

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

51: ODC execution unit 52: frame memory

53: memory controller 54: R, G, B look-up table

55 logic section

Claims (2)

In the driving method of a liquid crystal display device having an ODC (Over Driving Circuit) function, A method of driving a liquid crystal display device, characterized in that ODC is performed by applying respective look-up table values to input data of R, G, and B. 2. The method of claim 1, wherein tuning is performed using an EEPROM to determine the respective look-up table values.