KR20030054880A - Liquid crystal display device and method of driving the same - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a method for driving the same are provided to remove an afterimage by detecting still pictures of video data and periodically inverting the detected still pictures before supplying the still pictures to a liquid crystal panel. CONSTITUTION: A plurality of liquid crystal cells are arranged on a liquid crystal panel(32) in a matrix form. A data driver(34) drives data lines on the liquid crystal panel. A gate driver(36) drives gate lines on the liquid crystal panel. A still picture detector(40) detects still pictures of the video data. A timing controller(38) supplies control signals necessary for the data driver and the gate driver, and inverts the detected still pictures before supplying the still pictures to the data driver.

Description

Liquid crystal display and its driving method {LIQUID CRYSTAL DISPLAY DEVICE AND METHOD OF DRIVING THE SAME}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a driving method thereof, and more particularly to a liquid crystal display device and a driving method thereof for removing an afterimage generated in a liquid crystal panel.

lately. A flat panel display of an active matrix driving type displays an image by adjusting a light transmittance of a liquid crystal using a thin film transistor (hereinafter, referred to as TFT) as a switching element. Such a liquid crystal display device can be miniaturized compared to the CRT and commercialized as a display such as a portable television or a laptop-type personal computer.

Referring to FIG. 1, a conventional liquid crystal display device drives a data driver 4 for driving data lines DL on a liquid crystal panel 2, and gate lines GL on a liquid crystal panel 2. The gate driver 6 is provided with a timing controller 8 for supplying control signals necessary for the data driver 4 and the gate driver 6, and the data driver 4.

The liquid crystal panel 2 displays an image corresponding to a video signal such as a television signal through the pixels 11 arranged at the intersections of the data lines DL and the gate lines GL. Each of the pixels 11 includes a liquid crystal cell that adjusts the amount of transmitted light according to the voltage level of the data signal from the data line DL. The TFT is installed at the intersection of the gate line GL and the data line DL to switch the data signal to be transmitted to the liquid crystal cell in response to the scan signal (gate pulse) from the gate line GL.

The data driver 4 selects reference voltages according to the input data, converts them into analog image signals, and supplies them to the liquid crystal panel 2 in response to the control signals input from the timing controller 8.

The gate driver 6 controls the gate terminals of the TFTs arranged on the liquid crystal panel 2 on / off line by line in response to control signals input from the timing controller 8. The analog image signals supplied from the driver 4 are applied to the respective pixels 11 connected to the respective TFTs.

The timing controller 8 controls the driving timing of the gate driver 6 and the data driver 4 in response to a clock signal, horizontal and vertical synchronization signals, etc. input from the outside. In other words, the timing controller 8 generates and supplies the gate shift clock GSC, the gate start pulse GSP, and the like to the gate driver 6 in response to the clock signal and the horizontal and vertical synchronization signals. In addition, the timing controller 8 generates a data clock signal, a data control signal, a polarity control signal, and the like in response to the input clock signal and the horizontal and vertical synchronization signals, and supplies the data clock signal to the data driver 4 and synchronizes with the data clock signal. Red (R), green (G), and blue (B) video data input from the outside are supplied to the data driver 4.

In such a liquid crystal display, a line inversion system, a column inversion system, a dot inversion system, and the like are used to drive liquid crystal cells on a liquid crystal panel.

In such a conventional liquid crystal display device, an afterimage occurs when a still image is displayed for at least several frames. For example, as shown in FIG. 2, when a still image is displayed for several frames or more in a liquid crystal display using a mosaic pattern, the same data information is applied to the liquid crystal panel to generate an afterimage. That is, the afterimage is generated when a direct current (DC) voltage of the same data information is continuously applied to an unillustrated liquid crystal layer of the liquid crystal panel so that residual charges are concentrated on one electrode and do not disappear for a long time.

Accordingly, an object of the present invention is to provide a liquid crystal display and a driving method thereof for removing an afterimage generated in a liquid crystal panel.

1 is a block diagram showing a conventional liquid crystal display device.

FIG. 2 is a diagram illustrating a mosaic pattern supplied to the liquid crystal panel shown in FIG. 1.

3 is a block diagram illustrating a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a circuit diagram illustrating a data inverting unit of the timing controller shown in FIG. 3.

FIG. 5 is a diagram illustrating a mosaic pattern supplied to the liquid crystal panel illustrated in FIG. 3.

FIG. 6 is a waveform diagram illustrating data applied to a liquid crystal cell shown in FIG. 5.

<Description of Symbols for Main Parts of Drawings>

2, 32: liquid crystal panel 4, 34: data driver

6, 36: gate driver 8, 38: timing controller

40: still picture detection unit 42: control signal generation unit

44: data inversion unit 46: data alignment unit

48: multiplexer 50: counter

In order to achieve the above object, a liquid crystal display device according to the present invention comprises a liquid crystal panel in which liquid crystal cells are arranged in a matrix form, a data driver for supplying video data to the liquid crystal panel, and detecting a still image of the video data. And a control unit for inverting the still image detected by the detection unit and supplying the inverted image to the data driver.

The controller further includes a data inversion unit for periodically inverting the still image.

The data inversion unit further includes an inverter for inverting the still image, and a multiplexer for selecting any one of the still image and the inverted still image.

The data inverting unit further includes a counter for supplying a selection control signal to the multiplexer so as to output the inverted still image from the multiplexer.

The counter may be configured to supply the selection signal to a control terminal of the multiplexer according to an input vertical synchronization signal.

A driving method of a liquid crystal display according to the present invention includes supplying input video data to a liquid crystal panel, detecting a still image of the video data, and inverting the detected still image to supply the liquid crystal panel. Steps.

The still picture is characterized in that it is periodically inverted.

Other objects and features of the present invention in addition to the above objects will be apparent from the description of the embodiments with reference to the accompanying drawings.

A preferred embodiment of the present invention will be described with reference to FIGS. 3 to 6.

Referring to FIG. 3, a liquid crystal display according to an exemplary embodiment of the present invention may include a data driver 34 for driving data lines DL on a liquid crystal panel 32, and gate lines on the liquid crystal panel 32. Timing for supplying the video driver and the inverted video data to the data driver 34 as well as supplying the gate driver 36 for driving the GL) and the control signals necessary for the data driver 34 and the gate driver 36. The controller 38 and a still picture detection unit 40 for detecting whether or not the same data Data is supplied to the data Data supplied from the interface.

The liquid crystal panel 32 displays an image corresponding to a video signal such as a television signal through the pixels 31 arranged at the intersections of the data lines DL and the gate lines GL. Each of the pixels 31 includes a liquid crystal cell that adjusts the amount of transmitted light according to the voltage level of the video data from the data line DL. The TFT is installed at the intersection of the gate line GL and the data line DL to switch the data signal to be transmitted toward the liquid crystal cell in response to the scan signal (gate pulse) from the gate line GL.

The data driver 34 selects reference voltages according to the input video data in response to the control signals input from the timing controller 38, converts the reference voltages into analog image signals, and supplies them to the liquid crystal panel 32.

The gate driver 36 controls the gate terminals of the TFTs arranged on the liquid crystal panel 32 on / off line by line in response to control signals input from the timing controller 38. The analog image signals supplied from the driver 34 are applied to the respective pixels 31 connected to the respective TFTs.

The still picture detection unit 40 receives data from the interface and compares the data with the previous video data to determine whether they have the same data value. On the other hand, the still picture detection unit 40 may be installed inside the timing controller 38 to compare the video data output from the data driver 34 with the previous video data output to determine whether they have the same data value. In addition, the still picture detection unit 40 is installed between the data driver 34 and the timing controller 38 to determine whether the video data output from the data driver 34 and the output previous video data have the same data value. You may.

The timing controller 38 controls the driving timing of the gate driver 36 and the data driver 34 in response to a clock signal, horizontal and vertical synchronization signals, etc. input from the outside. In other words, the timing controller 38 generates and supplies a gate shift clock GSC, a gate start pulse GSP, and the like to the gate driver 36 in response to the clock signal and the horizontal and vertical synchronization signals. In addition, the timing controller 38 generates a data clock signal, a data control signal, a polarity control signal, and the like in response to the input clock signal and the horizontal and vertical synchronization signals, and supplies the same to the data clock signal 34. Red (R), green (G), and blue (B) video data input from the outside are supplied to the data driver 34.

To this end, the timing controller 38 receives the horizontal synchronizing signal, the vertical synchronizing signal, the data enable and the timing synchronization signals of the clock pulses from the interface (not shown) and supplies them to the data driver 34 and the gate driver 36. A control signal generator 42 for generating signals, a data aligner 46 for receiving and aligning data Data input from an interface (not shown), and video data supplied from the data aligner 46. A data inversion section 44 for supplying the data driver 34 to the data driver 34 or inverting the video data to the data driver 34.

The control signal generator 42 receives a horizontal synchronization signal, a vertical synchronization signal, a data enable signal, and a clock signal from an interface to generate various control signals for driving the liquid crystal panel 32, and generates the generated control signals as data drivers. 34 and the gate driver 36. Here, the vertical synchronization signal represents a time required to display a screen of one frame. The horizontal sync signal indicates the time required to display one line of the screen. Therefore, the horizontal synchronization signal includes as many pulses as the number of pixels included in one line. The data enable signal indicates a time point at which data is supplied to the pixel.

The data aligner 46 receives data from the interface and rearranges the data so that the supplied video data is supplied to the liquid crystal panel 32 and supplies the data to the data inverter 44.

As shown in FIG. 4, the data inversion unit 44 is provided with a video multiplexer MUX supplied with the data data supplied from the data aligning unit 46 and the video data Data is inverted, and a multiplexer. A counter 50 for supplying a control signal to the selection terminal of the MUX is provided.

The multiplexer (MUX) consists of two input terminals and one output terminal. That is, video data Data is supplied from the data alignment unit 46 to the first input terminal, and video data Data supplied from the data alignment unit 46 is inverted by the inverter IVT to the second input terminal. Video data BData is supplied. For example, the video data BData inverted by the inverter IVT when the video data Data supplied to the second input terminal of the multiplexer MUX is 3 bits is shown in Table 1 below.

Data BData 000 111 001 110 010 101 011 100 100 011 101 010 110 001 111 000

The counter 50 counts the input vertical synchronization signal Vsync to a set value, and generates a control signal and supplies the control signal to the selection terminal of the multiplexer MUX.

The multiplexer MUX selects one of the video data and the inverted video data BData by the control signal supplied from the counter 50 and supplies the selected data to the data driver 34.

In the liquid crystal display according to the exemplary embodiment of the present invention, when video data of a still image for a long time is supplied at least several frames from an interface, the video data is periodically inverted to be supplied to the liquid crystal panel to remove an afterimage. do.

For example, as shown in FIG. 5, when a mosaic pattern, which is a still picture, is supplied from an interface, a still picture is detected from the still picture detection unit 40. The detected still picture video data is supplied to the multiplexer MUX. At this time, the counter 50 counts according to the vertical synchronization signal Vsync. When the counted value is equal to the set value (assuming "9"), the counter 50 outputs a control signal such that the video data BData inverted by the inverter IVT is output from the multiplexer MUX. Supply to the multiplexer (MUX). Accordingly, in the ninth frame period, the video data BData inverted by the inverter IVT in the multiplexer MUX is output and supplied to the liquid crystal panel through the data driver. For this reason, in the liquid crystal panel, afterimage of inverted still image is supplied, afterimage of the DC voltage applied to the liquid crystal layer (not shown) is reversed, thereby preventing afterimages. Then, after the tenth frame, the inverted video data Data is again supplied to the liquid crystal panel.

FIG. 6 is applied to the liquid crystal layer of the upper left dot of the mosaic pattern, which is the still image, in the driving method of the frame inversion type liquid crystal display device shown in FIG. The magnitude of the electric field applied to is increased.

Therefore, when the still image is supplied for a long time, the driving method of the liquid crystal display device of the present invention can prevent the afterimage by inverting the still image at periodic frame intervals and supplying the still image to the liquid crystal panel.

Meanwhile, the present invention for periodically inverting and supplying the still image data is not limited to a liquid crystal display device but can be applied to other flat panel display devices such as a plasma display panel, a field emission display device, an electroluminescence display device, and the like.

As described above, the liquid crystal display and the driving method thereof according to the present invention can remove the afterimage by detecting the still image of the input video data and periodically inverting the detected still image and supplying it to the liquid crystal panel.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. For example, the data can be inverted non-periodically or randomly, without being limited to periodically inverting the data as in the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (7)

A liquid crystal panel in which liquid crystal cells are arranged in a matrix form; A data driver for supplying video data to the liquid crystal panel; A detector for detecting a still picture of the video data; And a control unit for inverting the still image detected by the detection unit and supplying the still image to the data driver. The method of claim 1, And the controller further comprises a data inversion unit for periodically inverting the still image. The method of claim 2, The data inversion unit, An inverter for inverting the still image; And a multiplexer for selecting any one of the still image and the reversed still image. The method of claim 3, wherein And the data inverting unit further comprises a counter for supplying a selection control signal to the multiplexer so as to output the inverted still image from the multiplexer. The method of claim 4, wherein And the counter supplies the selection signal to a control terminal of the multiplexer according to an input vertical synchronization signal. Supplying input video data to the liquid crystal panel; Detecting a still picture of the video data; And inverting the detected still image and supplying the detected still image to the liquid crystal panel. The method of claim 6, And the still picture is inverted periodically.