KR100631018B1 - Method for driving of liquid crystal display device - Google Patents

Abstract

The driving method of the liquid crystal display device of the present invention blurs by applying a data addressing technique for controlling data by analyzing the degree of blur according to the brightness of an image and an adaptive dynamic image control (ADIC) technique for controlling the backlight. 1. A method for simultaneously solving resolution and peak luminance, the method comprising: receiving an image signal; Analyzing the image signal to fix the duty ratio of the data signal; Dividing each frame into two sub-frames, inputting image data in a first sub-frame and black data in a second sub-frame; And adjusting the duty ratio of the backlight according to the image brightness of the analyzed image signal while maintaining the duty ratio of the data signal within each frame.

Video, blur, peak luminance, ADIC, duty ratio

Description

Driving method of liquid crystal display {METHOD FOR DRIVING OF LIQUID CRYSTAL DISPLAY DEVICE}

1A to 1C are exemplary views schematically illustrating deterioration of image quality in implementing a video through a liquid crystal display.

2A and 2B are exemplary views for explaining a method of driving a liquid crystal display device according to an exemplary embodiment of the present invention.

3A and 3B are schematic diagrams illustrating a black data insertion technique applied to driving a liquid crystal display according to an exemplary embodiment of the present invention.

4 is an exemplary view schematically showing an ADIC technology applied to driving a liquid crystal display according to an embodiment of the present invention.

5 is a block diagram of an entire system for driving a liquid crystal display according to an embodiment of the present invention.

** Explanation of symbols for main parts of drawings **

A, A1 ~ A3: Backlight On Time B, B1 ~ B3: Backlight Off Time

D1: first sub-frame D2: second sub-frame

The present invention relates to a method of driving a liquid crystal display device, and more particularly, to a method of driving a liquid crystal display device, which is suitable to improve image quality by simultaneously implementing blur reduction and peak luminance when a video is implemented in a liquid crystal display device. .

Liquid Crystal Display (LCD) is a device that displays an image by using optical anisotropy of liquid crystal and is a flat panel that can replace a cathode ray tube (CRT) with the advantages of thin, small size, low power consumption and high quality. It has become the main product of flat panel display (FPD).

However, the liquid crystal display device has a disadvantage in that the video implementation characteristics are lower than those of the CRT, and research on this is being conducted. In particular, the liquid crystal display device applied to the television display device should be able to display a moving picture in high quality.

Hereinafter, the liquid crystal display device will be described in detail with reference to FIG. 1.

1A to 1C are exemplary views schematically illustrating deterioration of image quality in implementing a video through a liquid crystal display.

First, as shown in FIG. 1A, when the image of the white object 50 moving in the direction of the arrow is displayed on the black background displayed on the liquid crystal display panel 10, the liquid crystal display panel 10 is illustrated in FIG. 1B. As described above, a blur phenomenon occurs in which the outline of the object 50 is blurred.

In addition, as shown in FIG. 1C, a ghost phenomenon in which the afterimage of the object 50 ′ is perceived before moving is also generated.

The problem of the moving picture realization characteristic as described above is firstly due to the long 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 a desired light transmittance is changed. The electro-optical response time required to reach is several times longer than 16.7 msec, which is a display period of a general screen (or frame). Therefore, even if a voltage for white display is applied to the liquid crystal that is performing black display as shown in FIG. 1, the electro-optical response time of the liquid crystal is required until the liquid crystal completely reaches the state of the white display, and one frame The optical response of the liquid crystal is not completed within the period. The blur phenomenon or ghost is observed due to the delay of the optical response of the liquid crystal.

 In particular, the cause of the ghost is different from the response time of the liquid crystal between the region 52 overwritten from the black image to the white image and the region 53 overwritten from the white image to the white image. There is even a system based on. In addition, since the response time of the general twisted nematic liquid crystal is several times longer than one frame period, the liquid crystal optical response corresponding to the area 52 overwritten from the black image to the white image and the area overwritten from the back image to the white image ( The luminance difference also exists between the liquid crystal optical response corresponding to 53) even in the period in which the backlight is turned on. Since the difference in luminance is completely eliminated several frames after overwriting, no matter how short the lighting period of the backlight is limited, ghost remains.

Secondly, the display type of a moving image is also a cause of a hold type in which the liquid crystal display maintains light emission until image information of the next frame is applied.

In general, a liquid crystal display device is driven in a hold type in which charge accumulated in liquid crystal molecules by an applied electric field is maintained at a relatively high ratio until the next electric field is applied. For this reason, each pixel of the liquid crystal display maintains light emission until image information of the next frame is applied.

One frame of the liquid crystal display is generally driven at a cycle of 1/60 sec.

On the other hand, in a CRT display device that displays an image by scanning an electron beam to emit phosphors on the CRT surface, luminance waveforms of each pixel appear in an impulse form.

Therefore, the liquid crystal display device has a lower temporal frequency characteristic of light for displaying a moving image and a lower spatial frequency characteristic than the CRT, causing blur of the moving image. Particularly, even if the response time of the liquid crystal is several msec or less, the characteristics of the moving picture are lower than those of the CRT, which is an impulse type, due to the characteristics of the LCD.

As described above, a general liquid crystal display device displays an image by selectively transmitting or blocking light of a backlight, so that the brightness of the image is determined by the brightness of light generated in the backlight.

Therefore, as in the above-described CRT display device, it is impossible to selectively adjust the brightness and contrast of the image, which makes it difficult to realize a realistic image.

In order to solve this problem, studies are being actively conducted to drive the liquid crystal display as an impulse type.

An object of the present invention is to provide a method of driving a liquid crystal display device, which is suitable for improving image quality by simultaneously implementing blur reduction and peak brightness when moving images are implemented in a liquid crystal display device.

Other objects and features of the present invention will be described in the configuration and claims of the invention described below.

In order to achieve the above object, the driving method of the liquid crystal display device of the present invention comprises the steps of receiving an image signal; Analyzing the image signal to fix the duty ratio of the data signal; Dividing each frame into two sub-frames, inputting image data in a first sub-frame and black data in a second sub-frame; And adjusting the duty ratio of the backlight according to the image brightness of the analyzed image signal while maintaining the duty ratio of the data signal within each frame.

Hereinafter, a preferred embodiment of a method of driving a liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

2A and 2B are exemplary views illustrating a method of driving a liquid crystal display according to an exemplary embodiment of the present invention. The liquid crystal display is a combination of a data addressing method and a backlight control method to simultaneously reduce blur and implement peak luminance. The driving method of is shown.

As shown in the figure, in the present embodiment, a black data insertion technique and an adaptive dynamic image control (ADIC) technique for controlling a data signal are simultaneously implemented to maintain peak resolution while maintaining blur. It will be implemented at the same time. That is, the black data insertion technology controls only the data signal and the ADIC technology controls only the backlight, thereby having independent characteristics from each other. Therefore, it is not dependent on the implementation of the technology as compared with the scanning backlight technology and the ADIC technology simultaneously, so that individual control is possible.

As described above, the scanning backlight technology and the ADIC technology may be combined to eliminate blur and to realize peak luminance for the purpose of improving the image quality of the liquid crystal display.

The scanning backlight technology implements impulse driving by dividing a backlight installed on a rear surface of a liquid crystal display panel into a plurality of light emitting regions and sequentially turning on and off lamps in each light emitting region by a control circuit.

However, when implementing the scanning backlight technology alone for the purpose of eliminating blur, the duty ratio is fixed while when implemented with ADIC, the dimming duty ratio of the backlight inverter is used to change the luminance according to the image. duty ratio), and thus, the duty ratio of the scanning backlight is varied. Therefore, when the dark image input, the duty ratio is reduced to reduce the blur, while in the bright image input, the duty ratio is increased to reduce the blur.

Accordingly, in the present invention, the black data insertion technique and the ADIC technique, which are independently controlled as described above, are simultaneously implemented to simultaneously implement peak luminance while maintaining blur resolution. Hereinafter, the black data insertion technique and the ADIC technique are attached. It will be described in detail with reference to.

First, FIGS. 3A and 3B are exemplary views schematically illustrating a black data insertion technique applied to driving a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIGS. 2A and 3, the black data insertion technique, which is one of data addressing methods, constitutes one frame of the liquid crystal display with two sub-frames D1 and D2, and includes a first sub-frame D1. Image data, which is an image signal, is applied, and black data is input (120 Hz driving or 180 Hz driving) to the second sub-frame D2 to drive the liquid crystal.

That is, black data is input to the second sub-frame D2 while fixing the data at the optimum duty ratio for the purpose of blur.

4 is an exemplary view schematically illustrating an ADIC technology applied to driving a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIGS. 2B and 4, the ADIC technique is a technique of correcting the gray scale of the current frame according to the pixel-specific luminance (Y signal) distribution of the previous frame and adjusting the luminance of the backlight to the image brightness.

That is, as a result of analyzing the luminance signal, in order to compensate for the reduction of image recognition in a dark screen, the backlight off time (B1 to B3) is long and even in a bright screen, the backlight off time (B1 to B3) is short (i.e. By increasing the on time (A1 to A3) of the backlight, the dark screen darkens the backlight and the bright screen brightens the backlight to increase the image contrast.

As shown in the figure, the backlight on time (A1 to A3) of the backlight becomes longer in the dark image to the bright image, while the backlight off time (B1 to B3) of the backlight decreases, thereby actively turning on the brightness of the backlight according to the brightness of the image. The peak luminance of the CRT can be realized by selectively adjusting the image.

As described above, the backlight may be changed for each input image to achieve peak luminance while fixing the data signal at the optimum duty ratio to eliminate blur. In some cases, the duty ratio of the data signal may be varied for each input image. In other words, by analyzing the degree of blur according to the brightness of the image by applying a specific data duty ratio corresponding to the specific brightness, it is possible to implement the ADIC for each image. If the blur is weak on brighter screens, the brightness is increased by increasing the data duty ratio on bright screens. On the contrary, if the blur is severe, the blur is reduced by reducing the duty ratio to compensate for the brightness by increasing the backlight brightness. Phosphorus application is possible.

On the other hand, the present embodiment is a display type (for example, a liquid crystal display device, an organic light emitting diode (EL), etc.) and a type of light source (for example, a cold cathode fluorescent lamp (Cold Cathode Fluorescent) CCFL, External Electrode Fluorescent Lamp (EEFL), Light Emitting Diode (LED, etc.) can be applied.

The overall driving method will be described with reference to the liquid crystal display as an example.

5 is an exemplary view for explaining a method of driving a liquid crystal display according to an exemplary embodiment of the present invention.

First, referring to the configuration of the liquid crystal display device, as shown in the drawing, the liquid crystal display device is provided on the rear of the liquid crystal display panel 300 and the liquid crystal display panel 300 for outputting an image, the liquid crystal display panel 300 It comprises a backlight unit (400) for emitting light over the front of the. In particular, since the liquid crystal display is not a self-light emitting device, the backlight unit 400 is used as the light source as described above.

In this case, although not shown in the figure, the liquid crystal display panel 300 is largely composed of a color filter substrate and an array substrate and a liquid crystal layer formed between the color filter substrate and the array substrate. do.

The color filter substrate may include a black matrix that distinguishes between a color filter including sub-color filters R, G, and B that implements color, and the sub-color filter, and blocks light transmitted through the liquid crystal layer; And a transparent common electrode applying a voltage to the liquid crystal layer.

The array substrate may include a thin film transistor that is a pixel electrode formed on a pixel region, a gate line (or scan line) and a data line (or signal line) arranged vertically and horizontally on the substrate, and a switching element formed in an intersection region of the gate line and the data line. Thin Film Transistor (TFT). Each of the scan lines and the signal lines extends to an outer region of the array substrate and is connected to the scan line driver and the signal line driver.

In addition, the array substrate includes a storage capacitance C _st for maintaining a constant voltage applied to the liquid crystal layer. The storage capacitor is installed in parallel to the liquid crystal capacitor C _lc of the liquid crystal itself to assist in maintaining a voltage applied to the liquid crystal layer for one frame period.

In this case, a luminance signal is input to a signal line driver that controls the luminance of the pixel, and the luminance signal generally has luminance information in the form of a digital signal. Thereafter, the signal line driver generates a potential difference corresponding to the luminance signal and transmits it to the corresponding pixel to drive the liquid crystal layer in the pixel.

The driving of the liquid crystal display device configured as described above is performed by the timing controller of the liquid crystal display device in which image data of R, G, and B output from a graphic controller (not shown) of the system 100 such as a computer is used. controller 200). Since the LCD operates in a digital manner, when the input image data is analog, an analog / digital conversion circuit for converting an analog signal into a digital signal should be used together with the timing controller 200.

The timing controller 200 converts the input image data into a digital signal that can be processed by a data driver IC (not shown), and converts the input image data into a data driver IC and a gate driver IC. Control signals such as various timing control signals required for driving are generated.

In addition, the backlight unit 400 receives power from a DC power source to adjust screen brightness of the liquid crystal display.

The timing controller 200 receives a clock signal and horizontal / vertical synchronization signals Hsync and Vsync as well as image data from the graphic controller. Thereafter, the timing controller processes the signal and image data in accordance with the liquid crystal display panel 300, transmits a control signal according to a horizontal synchronization signal to a gate driver integrated circuit, and applies a vertical synchronization signal and image data to a data driver integrated circuit. Transfer control signal accordingly.

The vertical synchronization signal is a signal indicating the end of each frame. In the case of a low logic section, it indicates the end of each frame, and during the high logic section, image data is applied to each pixel through the data line.

In this embodiment, in order to eliminate blur, each frame is divided into two sub-frames to have an optimum duty ratio, so that image data is arranged in the first sub-frame and black data is formed in the second sub-frame. It is applied to each pixel through the frame so that a black image exists between each frame. Inserting a black image every frame has the effect of visually not distinguishing an interference phenomenon between the nth frame and the n + 1th frame. Therefore, blur effect can be prevented by inserting a black image every frame in a high speed moving image.

In addition, the ADIC technique, which is controlled independently of the black data insertion technique, is applied together to realize peak luminance. That is, by controlling the backlight to have a variable duty ratio for each input image in the timing controller 200, it is possible to implement a peak luminance like a CRT without reducing the blur effect.

Many details are set forth in the foregoing description but should be construed as illustrative of preferred embodiments rather than to limit the scope of the invention. Therefore, the invention should not be defined by the described embodiments, but should be defined by the claims and their equivalents.

As described above, the driving method of the liquid crystal display according to the present invention provides the effect of simultaneously eliminating blur and peak luminance by independently controlling the data signal and the backlight by using the black data insertion technique and the ADIC technique.

Claims (9)

Receiving an image signal; Analyzing the image signal to fix the duty ratio of the data signal; Dividing each frame into two sub-frames, inputting image data in a first sub-frame and black data in a second sub-frame; And And adjusting the duty ratio of the backlight according to the image brightness of the analyzed image signal while maintaining the duty ratio of the data signal within each frame. The method of claim 1, wherein the image signal comprises R, G, and B image data and is input from a system to a timing controller. The method of claim 1, wherein the data driving duty ratio is fixed to a predetermined value and input to the liquid crystal display panel in order to remove a blur phenomenon. The method of claim 1, wherein the backlight duty ratio has a variable value to implement peak luminance and is input to a backlight unit. The method of claim 1, wherein the backlight on / off time is controlled in one frame according to the image brightness of the analyzed image signal. The driving method of claim 5, wherein when the analyzed image signal is a dark image, the off time of the backlight is increased in one frame. 6. The method of claim 5, wherein when the analyzed image signal is a bright image, the off time of the backlight is shortened within one frame. delete The driving method of claim 1, wherein the image signal is analyzed to compensate for luminance by reducing the data driving duty ratio to reduce blur and increasing luminance of a backlight in a bright screen.

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