KR20070099800A - Driving circuit of liquid crystal display device and method of driving the same - Google Patents

Abstract

A driving circuit of an LCD(Liquid Crystal Display) device and a method of driving the same are provided to prevent flicker by compensating a gray level using different gamma voltages from one another according to displayed image types. An external system generates control and data signals. A control signal generating unit(140) receives the control signal and generates an output signal corresponding to the control signal. A memory unit(110) receives data signals of former and latter input frames from the external system. A comparator(120) compares the data signals of former and latter input frames, and generates corresponding gamma control signals. An image processing unit(130) receives the data signals of the former data frame and rearranges the received data signals. A controller includes a gamma selection circuit(150), which receives the gamma control signal and selects a gamma compensation group for compensating gray levels of the data signals. A gamma unit(160) includes at least two gamma generating units for generating the gamma compensation group.

Description

Driving circuit of liquid crystal display device and driving method thereof {Driving circuit of Liquid crystal display device and method of driving the same}

1A and 1B are graphs showing light density over time of a CRT display and a liquid crystal display.

2A and 2B are graphs showing the voltage level of the data signal and the size of the light of the backlight light source with time of the data blinking and backlight scanning liquid crystal displays.

3A is a block diagram schematically illustrating the structure of a conventional liquid crystal display.

3B is a block diagram schematically illustrating a structure of a controller of the LCD of FIG. 3A.

4A is a block diagram schematically illustrating a structure of a driving apparatus of a liquid crystal display according to a preferred embodiment of the present invention.

FIG. 4B is a graph showing waveforms of gamma part gamma voltages in the driving device of the liquid crystal display of FIG. 4A.

<Name of symbols for main parts of drawing>

100: control unit 110: memory unit

112 and 114: first and second memories 120: comparison unit

130: image processor 140: control signal generator

150: gamma selection circuit 160: gamma part

162, 164, 166, 168: first to fourth gamma generating means 200: gate driver

400: data driver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving circuit of 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 preventing a decrease in luminance of an image according to the type of the displayed image.

In general, a liquid crystal display device (LCD) is a display device that displays an image by forming an electric field in a liquid crystal, which is a dielectric anisotropic material, and changing the light transmittance of the liquid crystal. The liquid crystal display device has features of miniaturization, thin film thickness, and low power consumption, and thus, replaces the conventional CRT display device in many fields.

Since the liquid crystal display has a slow response speed, the liquid crystal display displays an image in a hold method unlike an impulse method, which is a driving method of a conventional CRT display.

1A and 1B are graphs showing light density over time of a conventional CRT display and a liquid crystal display. In the CRT display, as shown in FIG. 1A, the optical density varies with time in a discontinuous form. An image is implemented by an impulse method, and the liquid crystal display implements an image by a hold method in which the light density changes in a continuous form with time as shown in FIG. 1B.

In particular, the hold method generates a screen drag, i.e., a motion blur, when a video is changed in each frame. Accordingly, an impulse driving type liquid crystal display device has been proposed to eliminate a hold type motion blur phenomenon.

2A and 2B are graphs illustrating voltage levels of data signals and magnitudes of backlight light over time of an impulse driving method of a liquid crystal display, a data blinking method and a backlight scanning method. As shown in FIG. 2A, the liquid crystal display device of the data blinking method has the same light source as the conventional light source, but is divided into a display period and a non-display period of an actual image for one frame. Accordingly, the impulse method is implemented by inputting a normal data signal in the display period of the image and a black data signal in the non-display period.

In addition, as shown in FIG. 2B, in the backlight scanning type liquid crystal display device, the input form of the data signal is the same as in the related art, but the display period of the actual image and the non-display period of the image for one frame as described above. In this case, the impulse method is implemented by turning on the backlight when the image is displayed and turning off the backlight during the non-display period of the image.

 FIG. 3A is a block diagram schematically illustrating a configuration of a conventional liquid crystal display device. The liquid crystal panel 1 includes a plurality of pixels and displays an image therethrough, and a gate output signal through the gate line GL. A data driver 4 for supplying an image signal to the pixel through a gate driver 2 for supplying the pixel and a data line DL, and a gamma voltage group for gray level compensation of the image signal. And a control unit 10 for determining the operation of each drive driver in response to a signal supplied from an external system.

3B is a block diagram schematically illustrating the controller 10 of the liquid crystal display of FIG. 3A. The image processor 30 that processes data signals and the control signal generator 40 that processes control signals are illustrated in FIG. Equipped.

Hereinafter, the configuration and operation of a conventional liquid crystal display device will be described with reference to FIGS. 3A and 3B.

In the liquid crystal panel 1, a plurality of gate lines GL and data lines DL are arranged to intersect in a matrix form, and a thin film transistor is provided as a switching element at the crossing point and defined as one pixel. Accordingly, the light transmittance of the liquid crystal material is changed by switching operation of the thin film transistor to display an image.

The controller 10 receives a control signal and a data signal from the outside, and generates a control signal and a data signal for driving the gate driver 2 and the data driver 4 in response to the control signal and the data signal. ) And the data driver 4.

In this case, the image processor 30 of the controller 10 rearranges the data signals R, G, and B input from an external system into a form that can be input to the data driver 4 and outputs the data signals to the data driver 4. .

In addition, the control signal generator 40 of the control unit 10 receives the horizontal synchronization signal (Hsync), the vertical synchronization signal (Vsync) and the data enable signal (DE) to the gate driver 2 and the data driver (4) Outputs a control signal.

The horizontal sync signal Hsync represents a time taken to display one line of one screen, and the vertical sync signal Vsync represents a time taken to display a screen of one frame. In addition, the data enable signal DE indicates a period in which data is supplied to an actual pixel.

The gate driver 2 generates a gate output signal in response to the control signal supplied from the controller 10, and sequentially supplies the gate output signal to the liquid crystal panel 1 through the gate line GL.

The data driver 4 generates an image signal by converting a data signal in a digital form into an analog form in response to a control signal and a data signal from the controller 10, and generates the image signal through the data line DL. Supply to 1).

At this time, the gamma part 6 supplies the DC voltages preset as the gamma voltage to the data driver 4 to have different levels for each luminance. Accordingly, the data driver 4 compensates the gradation voltage of the input digital video signal corresponding to the gamma voltage.

Accordingly, the liquid crystal panel 1 displays an image by changing the light transmittance of the pixels provided through the gate driving signal and the image signal supplied from the gate driver 2 and the data driver 4.

Such an impulse liquid crystal display device may improve a motion blur phenomenon when a video is implemented. However, when the still image is implemented, the period in which the image is displayed per frame is reduced, resulting in a decrease in luminance and flicker.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a method of driving the same, which compensate for an image signal according to the shape of an image, thereby preventing a decrease in luminance and flicker.

In order to achieve the above object, the driving apparatus of the liquid crystal display device according to the present invention includes an external system for generating a control signal and a data signal; A control signal generator which receives the control signal from the external system and generates an output signal corresponding to the control signal; A memory unit including a memory for receiving a pre-input frame of the data signal and a data signal of a subsequent input frame from the external system; A comparison unit which receives and compares data signals of the pre-input frame and the post-input frame stored in the memory unit, and generates a gamma control signal correspondingly; An image processor which receives and rearranges data signals of frames pre-input from the comparator; A control unit including a gamma selection circuit which receives the gamma control signal from the comparison unit and selects a gamma voltage group to compensate the gray level of the data signal; And a gamma part having two or more gamma generating means for generating the gamma voltage group.

The memory unit may include a first memory and a second memory in which data signals of the pre-input frame and data signals of the subsequent input frame are alternately input.

The gamma selection circuit is a 4x1 multiplexer which receives the gamma control signal to a selection terminal and receives the gamma voltage to a reference terminal and outputs one of the gamma voltage groups of the reference terminal in response to the gamma control signal. It is characterized by.

The gamma part generates a first gamma generating means for generating a first gamma voltage group having the same gray level compensation degree as the prior art, and a gamma voltage group having a larger gray level compensation degree than the first gamma generating means and having a different gray level compensation degree. It characterized in that it further comprises a second to fourth gamma generating means.

The driving method of a liquid crystal display driving apparatus according to the present invention includes an external system for generating a control signal and a data signal, and a control signal generator for receiving the control signal from the external system and generating an output signal corresponding to the control signal. And a memory unit configured to receive and store a data signal of a pre-input frame and a post-input frame of the data signal from the external system, and a data signal of the pre-input frame and the post-input frame stored in the memory unit. A comparator for receiving input and comparing and generating a gamma control signal corresponding thereto, an image processor for receiving and rearranging a data signal of the pre-input frame from the comparator, and receiving the gamma control signal from the comparator Gamma selection for selecting a gamma voltage group for compensating the gray level of the data signal A control method comprising a circuit and a gamma part having at least two gamma generating means for generating the gamma voltage group, the driving method of a liquid crystal display device driving apparatus, comprising: a data signal of a line input frame; Storing data signals of the frames to be input later in different memories of the memory unit; Generating the gamma control signal in response to a data signal of the pre-input frame and a data signal of a later input frame; And selecting one of the gamma voltage groups in response to the gamma control signal.

The step of selecting the gamma voltage group in response to the gamma control signal may include selecting a first gamma voltage group having the same gray level compensation as in the prior art when the value of the gamma control signal has no change degree of an image; If the value of the gamma control signal has a degree of change in the image, selecting one of the second to fourth gamma voltage groups having a gray level compensation degree larger than the first gamma voltage group according to the change. do.

Hereinafter, a configuration of a liquid crystal display driving apparatus according to a preferred embodiment of the present invention will be described with reference to FIG. 4A.

The driving apparatus of the liquid crystal display according to an exemplary embodiment of the present invention receives a control signal and a data signal from an external system and generates a signal for driving the gate driver 200 and the data driver 400. ) And a gamma unit 160 in which a plurality of gamma values are stored.

The controller 100 may store at least one data signal of a frame pre-input from an external system and at least one data signal Rn, Gn, Bn and Rn + 1, Gn + 1, Bn + 1 of the next frame. The memory unit 110 including the memory 112 and 114 and the values stored in the memory unit 110 are inputted and compared with the data signals Rn, Gn, Bn and Rn + 1, Gn + 1, Bn + 1) and a comparator 120 for outputting a gamma control signal (hereinafter referred to as a GCS) and data signals R, G, and B output from the comparator 120, and receive the data. The image processing unit 130 rearranges and outputs the signals R, G, and B in a form that can be input to the data driver, and the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the data enable signal DE from an external system. ) And a control signal generator 140 for outputting control signals of the gate driver 200 and the data driver 400, and the gamma. A gamma selection circuit 150 is provided which receives the control signal GCS at the selection terminal and receives a plurality of gamma voltage groups at the reference terminal and outputs one gamma voltage group.

The gamma unit 160 includes gamma voltage generation means 162, 164, 166, and 168 for generating DC voltages which are preset to have different levels for at least one luminance, and the gamma voltage group generated from the gamma voltage generation means 162, 164, 166, and 168. GAMMA1 to GAMMA4) are output to the gamma selection circuit 150.

Hereinafter, an operation of a liquid crystal display driving apparatus according to a preferred embodiment of the present invention will be described with reference to FIG. 4A.

When data signals Rn, Gn, Bn and Rn + 1, Gn + 1, Bn + 1 are input to the controller 100 from an external system, the data signals Rn, Gn, Bn and Rn + 1, Gn + 1 , Bn + 1 is stored in the memory unit 110 in units of frames. In this case, the data signals Rn, Gn, and Bn of the pre-input frame are stored in the first memory 112, and the data signals Rn + 1, Gn + 1 and Bn + 1 of the next input frame are second. Stored in memory 114. In addition, the data signals Rn + 2, Gn + 2, and Bn + 2, which are input later, are stored in the first memory 112 in which the data signals Rn, Gn, and Bn of the pre-input frame are stored. Stored. Further, the data signal Rn + 1, Gn + 1, Bn + 1 of the next input frame is stored with respect to the data signal Rn + 3, Gn + 3, Bn + 3 that is input thereafter. 2 is stored in the memory unit 114.

In the above, an example of the memory unit 110 having two memories has been described as a preferred embodiment, but the number of memories included in the memory unit may be more than this, if necessary. That is, the data signals sequentially input are alternately stored as many as the number of memories provided in the memory unit 110, and the data signals input in the following order are stored by being replaced with the data signals stored at the highest priority. .

The comparison unit 120 simultaneously receives data signals Rn, Gn, Bn and Rn + 1, Gn + 1, Bn + 1 stored in the first and second memories 112 and 114 of the memory unit 110. The data signals Rn, Gn, and Bn of the pre-input frame are output to the image processor 130 and are stored in the first memory 112 and the second memory 114 of the memory unit 110. By comparing the data signals Rn, Gn, Bn and Rn + 1, Gn + 1, Bn + 1, a gamma control signal GCS is generated in response to the degree of difference of the values, and output to the gamma selection circuit 150. do. The gamma control signal GCS is a signal for selecting a gamma voltage group. Preferably, four values of [0,0], [0,1], [1,0], and [1,1] are selected. It is a signal.

The image processor 130 receives the data signals R, G, and B from the comparator 120, rearranges them in a form that the data driver 400 can process, and outputs the data signals to the data driver 400.

The gamma selection circuit 150 receives a gamma control signal GCS at a selection terminal and receives a plurality of gamma voltage groups GAMMA1 to GAMMA4 from the gamma unit 160 at a reference terminal. Preferably, the gamma selection circuit 150 outputs one gamma voltage group GAMMA with reference to the four gamma voltage groups GAMMA1 to GAMMA4 using the gamma control signal GCS as the selection signal. It consists of a multiplexer (4 x 1 Multiplexer).

The gamma part 160 includes a plurality of gamma generating means 162, 164, 166, and 168. The first gamma generator 162 generates the first gamma voltage group GAMMA1 having the same gray level compensation as that of the conventional gamma generator, and selects when the signal value of the gamma control signal GCS is [0,0]. It is done.

The second gamma generating means 164 generates a second gamma voltage group GAMMA2 having a voltage level at least greater than the first gamma voltage group GAMMA1, and the signal value of the gamma control signal GCS is [ 0,1] is selected.

The third gamma generator 166 generates a third gamma voltage group GAMMA3 having a voltage level at least greater than that of the second gamma voltage group GAMMA2, and the signal value of the gamma control signal GCS is increased. [1,0] is selected.

The fourth gamma generating means 168 generates a fourth gamma voltage group GAMMA4 having a voltage level at least greater than that of the third gamma voltage group GAMMA3, and the signal value of the gamma control signal GCS is increased. [1,1] is selected.

FIG. 4B is a graph illustrating waveforms of the gamma part gamma voltage group in the driving device of the liquid crystal display of FIG. 4A. As shown in FIG. 4B, the first to fourth gamma voltage groups GAMMA1 to GAMMA4 are each grayscale. The degree of compensation for Here, the first gamma voltage group GAMMA1 is a waveform that is the same as or similar to the conventional gamma voltage, and the second to fourth gamma voltage groups GAMMA2 to GAMMA4 are waveforms having a large degree of compensation for gray levels, respectively.

In the above, an embodiment in which the gamma part 160 includes four gamma generating means 162, 164, 166, and 168, and thus generates four gamma voltage groups GAMMA1 to GAMMA4 has been described. The number of gamma generating means (162, 164, 166, 168) provided in the) may be more than this if necessary. That is, the gray level may be compensated by referring to more gamma voltage groups according to the degree of change of the image for each frame, thereby preventing the luminance decrease according to various image types.

Therefore, the gamma selection circuit 150 reduces luminance when the data signals Rn, Gn, Bn of the line frame and the data signals Rn + 1, Gn + 1, Bn + 1 of the subsequent frame have a large degree of change. Is relatively increased, thereby compensating the data signal with a gamma voltage group (GAMMA3 or GAMMA4) having a high gradation compensation degree, and the data signals Rn, Gn, Bn of the line frame and the data signals Rn + 1 of the subsequent frame. When the degree of change is small in Gn + 1 and Bn + 1), the data is reduced to the gamma voltage group GAMMA2 having a small gray level compensation level or the gamma voltage group GAMMA1 having the same gray level compensation level as the conventional method. Compensate for the signal.

The operation of the control signal generator 140 is the same as in the prior art. That is, the horizontal synchronization signal Hsync, the vertical synchronization signal Vsync, and the data enable signal DE are input from an external system to generate and output control signals of the gate driver 200 and the data driver 400.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

Therefore, the driving device of the liquid crystal display according to the preferred embodiment of the present invention has an effect of preventing flicker and reducing luminance by performing appropriate gray level compensation according to the displayed image.

Claims (6)

An external system for generating a control signal and a data signal; A control signal generator which receives the control signal from the external system and generates an output signal corresponding to the control signal; A memory unit including a memory for receiving a pre-input frame of the data signal and a data signal of a subsequent input frame from the external system; A comparison unit which receives and compares data signals of the pre-input frame and the post-input frame stored in the memory unit, and generates a gamma control signal correspondingly; An image processor which receives and rearranges data signals of frames pre-input from the comparator; A control unit including a gamma selection circuit which receives the gamma control signal from the comparison unit and selects a gamma voltage group to compensate the gray level of the data signal; A gamma part including two or more gamma generating means for generating the gamma voltage group; Driving device of the liquid crystal display device comprising a. According to claim 1, And the memory unit includes a first memory and a second memory in which data signals of the line input frame and data signals of the subsequent input frame are alternately input. According to claim 1, The gamma selection circuit is a 4x1 multiplexer which receives the gamma control signal to a selection terminal and receives the gamma voltage to a reference terminal and outputs one of the gamma voltage groups of the reference terminal in response to the gamma control signal. A drive device for a liquid crystal display device, characterized in that. According to claim 1, The gamma part includes first gamma generating means for generating a first gamma voltage group having the same gray level compensation as in the prior art; And second to fourth gamma generating means for generating a gamma voltage group having a greater degree of gradation compensation than the first gamma generating means and having a different gradation compensation degree from each other. An external system for generating a control signal and a data signal, a control signal generator for receiving the control signal from the external system and generating an output signal corresponding to the control signal, and a pre-input frame of the data signal from the external system And a memory unit having a memory for receiving and storing data signals of a later input frame, and receiving and comparing data signals of the line input frame and the subsequent input frame stored in the memory unit, and generating a gamma control signal correspondingly. Selects a comparison unit, an image processing unit for receiving data signals of the pre-input frame from the comparing unit, and a gamma voltage group for receiving the gamma control signal from the comparing unit to compensate the gray level of the data signal A control unit having a gamma selection circuit to generate the gamma voltage group Is a method for driving a liquid crystal display device drive device, characterized in that including a gamma having at least two gamma-generating means, Storing data signals of the pre-input frame and data signals of the next-input frame in different memories of the memory unit; Generating the gamma control signal in response to a data signal of the pre-input frame and a data signal of a later input frame; Selecting one of the gamma voltage groups in response to the gamma control signal; Method of driving a liquid crystal display device driving apparatus comprising a. The method of claim 5, Selecting the gamma voltage group in response to the gamma control signal, When the value of the gamma control signal has no change degree of an image, selecting a first gamma voltage group having the same level of gradation compensation as in the prior art; If the value of the gamma control signal has a degree of change in the image, selecting one of the second to fourth gamma voltage groups having a gray level compensation degree greater than the first gamma voltage group; Method of driving a liquid crystal display device driving apparatus comprising a.

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