KR101351380B1 - Driving apparatus of liquid crystal display device and driving method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a liquid crystal display device and a driving method thereof, and more particularly, to a driving apparatus for a liquid crystal display device and a driving method thereof capable of improving display quality by reducing a color shift phenomenon in the liquid crystal display device. will be.

According to an exemplary embodiment of the present invention, a driving apparatus of a liquid crystal display device includes a frame memory configured to sequentially store image data input continuously in units of frames, a frequency converter configured to double and output a frame frequency of the image data from the frame memory; An image data discriminating unit for discriminating and outputting image data input from the frequency converting unit, an image data converting unit for converting and outputting image data input from the image data discriminating unit, and converting the image data discriminating unit and image data And a multiplexer for aligning and outputting image data input from the unit.

In the image data, image data having a gray value corresponding to a section having a large color shift is converted symmetrically into image data having a gray value corresponding to a section having a small color shift. The display quality of the liquid crystal display may be improved by sorting the data into image data in units of frames to prevent color shift from a specific angle on the liquid crystal panel.

Description

Driving apparatus for liquid crystal display device and driving method thereof

1 is a graph showing light transmittance vs. gray scale characteristics of a liquid crystal display;

2 is a schematic view showing a liquid crystal display device including a driving device according to the present invention;

3 is a view showing a driving device of a liquid crystal display according to the present invention.

4 is a flowchart illustrating a driving method of a driving apparatus according to the present invention.

5A and 5B are diagrams for explaining a method of determining image data of a driving apparatus according to the present invention.

6A and 6B are views for explaining a method of converting image data of a driving apparatus according to the present invention.

Description of the Related Art

1 liquid crystal display 10 liquid crystal panel

12: pixel region 14: TFT

20: gate driver 30: data driver

40: gamma reference voltage generator 50 timing controller

100: drive device 110: frame memory

120: frequency converter 130: image data determination unit

140: image data converter 150: multiplexer

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for a liquid crystal display and a driving method thereof, and more particularly, to a liquid crystal display driving apparatus and a driving method thereof capable of improving display quality by reducing color shift in the liquid crystal display. .

As the information society develops, the demand for display devices is gradually increasing in various forms. Recently, liquid crystal display (LCD), plasma display panel (PDP), electro luminescent display (ELD), Various flat panel display devices such as VFD (Vacuum Fluorescent Display) have been studied, and some of them are already used as display devices.

Among them, LCD is the most widely used as a substitute for CRT (Cathode Ray Tube) for the use of mobile image display device because of the excellent image quality, light weight, thinness, and low power consumption, and mobile type such as monitor of notebook computer. In addition, it has been developed in various ways such as a television and a computer monitor for receiving and displaying broadcast signals.

In general, a liquid crystal display (LCD) displays an image by adjusting light transmittance of liquid crystal cells according to a video signal. Such a liquid crystal display may be classified into a liquid crystal panel displaying a video signal and a driving circuit applying a driving signal to the liquid crystal panel from the outside. Although not shown in the drawings, the liquid crystal panel is composed of two transparent substrates (glass substrates) bonded to each other with a predetermined space and a liquid crystal layer formed between the two substrates.

The liquid crystal display device configured as described above can be largely divided into TN (Twist Nematic) mode, IPS (In-Plane Switching) mode, VA (Vertical Alignment) mode, and the like according to the driving mode of the liquid crystal.

The TN mode liquid crystal display device has an advantage of excellent light efficiency, but has a disadvantage of poor display quality when driving a video due to poor viewing angle and response speed. Accordingly, in order to improve the viewing angle narrowness and the slow response speed of the TN mode liquid crystal display device, a VA mode liquid crystal display device has been developed and is currently being used.

In the VA mode liquid crystal display, when voltage is applied to the common electrode positioned on the color filter substrate and the pixel electrode positioned on the array substrate, the direction of the liquid crystal molecules in which vertical vertical electric fields formed by the difference between the applied voltages are located therebetween. Use a way to control it. In the VA mode liquid crystal display, since the common electrode and the pixel electrode are horizontally formed, and the liquid crystal is driven by vertical electric fields generated above and below, the VA mode liquid crystal display device has advantages such as light transmittance and aperture ratio. As shown, the larger the viewing angle is, the brighter the screen is due to the high light transmittance, so that the viewing angle characteristic is lowered. In particular, when the color displayed on the screen should display a white color, the color is distorted at a specific angle. Color shift phenomenon occurs. Such a color shift has a problem of degrading the display quality of the liquid crystal display.

The driving device of the liquid crystal display device according to the embodiment of the present invention has been devised to solve the above problems, and the driving device of the liquid crystal display device and its driving which can improve display quality by reducing color shift The purpose is to provide a method.

A driving device of a liquid crystal display device according to an embodiment of the present invention for achieving the above object is a driving device of a liquid crystal display device for displaying an image by driving the liquid crystal panel, the image data input continuously in units of frames A frame memory to be stored in a memory, a frequency converter which doubles and outputs a frame frequency of the image data from the frame memory, an image data discriminator that discriminates and outputs image data input from the frequency converter, and discriminates the image data. And an image data converting unit for converting and outputting image data input from the unit, and a multiplexer for sorting and outputting image data input from the image data discriminating unit and the image data converting unit.

A driving method of a driving apparatus according to an embodiment of the present invention includes a first step of storing input first image data; Converting a frequency of the stored image data; A third step of comparing the second image data having the changed frequency with each of the first and second gray level regions different from each other; A fourth step of modulating data of any one of the first and second gray areas according to the comparison result; And a fifth step of generating data signals in units of frames by aligning data of the modulated region with data of the remaining region.

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

Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.

2 is a schematic view showing a liquid crystal display including a driving device according to the present invention.

Referring to FIG. 2, a liquid crystal display including a driving device according to the present invention includes a pixel region formed for each region defined by a plurality of gate lines GL1 to GLn and a plurality of data lines DL1 to DLm. The liquid crystal panel 10, the gate driver 20 sequentially supplying the gate driving signals to the plurality of gate lines GL1 to GLn, and the image data R, G, and B, and the gate driving signal GCS. A data driver 30 for supplying the plurality of data lines DL1 to DLm so as to be synchronized with the data source, a gamma reference voltage generator 40 for generating a gamma reference voltage and supplying the data driver 30 to the data driver 30, and from the outside. And a timing controller 50 for converting and arranging the image data R, G, and B to be supplied to the data driver 30 and controlling the driving of the gate driver 20 and the data driver 30. do.

Although not shown, the liquid crystal display including the driving device according to the present invention includes a backlight assembly for irradiating light to the liquid crystal panel 10, an inverter for applying an alternating voltage and a current to the backlight assembly, and a common voltage. It further comprises a common voltage generator for generating and supplying to the common electrode of the liquid crystal cell of the liquid crystal panel 10.

The liquid crystal panel 10 includes a transistor array substrate and a color filter array substrate bonded to each other, a spacer for maintaining a constant cell gap between the two array substrates, and a liquid crystal filled in a space provided by the spacer.

The liquid crystal panel 10 is connected to a thin film transistor (TFT) 14 formed in a pixel region defined by n gate lines and m data lines, and a TFT 14. The liquid crystal cell 12 is included.

The TFT 14 supplies the analog video signal from the data lines DL1 to DLm to the liquid crystal cell 12 in response to the gate driving signal from the gate lines GL1 to GLm.

Since the liquid crystal cell 12 includes a common electrode facing each other with a liquid crystal interposed therebetween and a pixel electrode connected to the TFT 14, the liquid crystal cell 12 may be equivalently represented as a liquid crystal capacitor Clc. The liquid crystal cell 12 includes a storage capacity Cst for maintaining the analog video signal charged in the liquid crystal capacitor Clc until the next analog video signal is charged. The common voltage Vcom is supplied to the common electrode of the liquid crystal cell 12.

The TFT 14 includes a gate electrode connected to the gate lines GL1 to GLn, a source electrode connected to the data lines DL1 to DLm, and a drain electrode connected to the pixel electrode.

The timing controller 50 includes a driving device that aligns the image data R, G, and B input from the digital video card in units of frames, and determines and processes the image data in units of aligned frames. Such a driving apparatus doubles the image data R, G, and B having a frequency of 60 Hz input from the outside into the image data R, G, and B having a frequency of 120 Hz, and the assigned image data R, Among the G and B), a color shift converts large data at a specific viewing angle. Thereafter, the converted image data is aligned to be suitable for driving the liquid crystal panel 10 and supplied to the data driver 30.

In addition, the timing controller 50 uses the dot clock DLCK, the data enable signal DE, and the horizontal and vertical synchronization signals Hsync and Vsync that are input from the outside, and the data control signal DCS and the gate control signal ( GCS) is generated to control driving timing of each of the data driver 30 and the gate driver 20.

The data control signal DCS includes a source shift clock SSC, a source start pulse SSP, a polarity control signal POL, a source output enable signal SOE, and the gate control signal GCS. Gate start pulse (GSP) and gate output enable (GOE);

The gate driver 20 includes a shift register that sequentially generates the gate driving signal in response to the gate control signal GCS from the timing controller 50. The gate driver 20 sequentially applies the gate driving signals to the gate lines GL1 to GLn in response to the gate control signal GCS input from the timing controller 50, thereby providing the respective gate lines GL1 to GLn. The TFT 14 connected to GLn is turned on. At this time, the gate driver 20 determines the high level voltage and the low level voltage of the gate driving signal according to the gate high voltage VGH and the gate low voltage VGL.

The data driver 30 converts the image data supplied from the driving device of the timing controller 50 into an analog video signal in response to the data control signal DCS supplied from the timing controller 50 to the gate lines GL1 to GLn. The analog video signal corresponding to the line is supplied to the data lines DL1 to DLm for each period in which the gate driving signal is supplied. In this case, the data driver 30 may invert the polarity of the analog video signal supplied to the data lines DL1 to DLm in response to the polarity control signal POL.

The gamma reference voltage generator 40 receives a high potential power supply voltage VDD to generate a positive gamma reference voltage and a negative gamma reference voltage to output the data to the data driver 30.

The backlight assembly, not shown, is disposed on the rear side of the liquid crystal panel 10 and emits light by an AC voltage and a current supplied from an inverter (not shown) to irradiate light to each pixel of the liquid crystal panel 10. The inverter converts the square wave signal generated therein into a triangular wave signal and compares the triangular wave signal with a DC power supply voltage (VCC) to generate a burst dimming signal proportional to the comparison result. When a burst dimming signal determined according to an internal square wave signal is generated, a driving IC controlling generation of an AC voltage and a current in the inverter controls generation of an AC voltage and a current supplied to the backlight assembly according to the burst dimming signal. . The common voltage generator receives the high potential power supply voltage VDD to generate the common voltage Vcom and supplies the common voltage Vcom to the common electrodes of the liquid crystal cells Clc included in each pixel of the liquid crystal panel 10.

3 is a view showing a driving device of the liquid crystal display according to the present invention.

Referring to FIG. 3, the driving apparatus 100 of the liquid crystal display according to the present invention continuously outputs a frame memory 110 for storing image data input from an input terminal in units of frames and converts a frequency of the input image. A frequency converter 120 to determine the image data in units of frames input from the frequency converter 120, and output the image data to the image data converter 140 or the multiplexer 150. And the image data converter 140, the image data converter 140, and the frequency converter 120 for converting the gradation value for each pixel of the image data input from the image data discriminator 130. And a multiplexer 150 for merging and outputting video frames input in response to the frame frequency.

As described above, a driving process of the driving apparatus according to the embodiment of the present invention having the configuration will be described with reference to FIG. 4.

The frame memory 110 aligns and stores the image data continuously inputted from the input unit in units of frames, and outputs the aligned image data in units of frames to the frequency converter 120 (S210). The frame memory 110 The image data is stored in frame units and may be implemented as a memory device or a virtual memory.

The frequency converter 120 converts the frame image data having the first frequency input from the frame memory 110 into frame image data having the second frequency and determines the frame image data having the converted second frequency. The frequency converter 120 outputs the frame image data having the first frequency input from the frame memory 110 to the output unit 130 or the multiplexer 150. The image data of the frame having the frequency is output to the image data discriminator 130 or the multiplexer 150.

For example, the frequency converter 120 may double the frame frequency by using a dynamic data insertion (DDI) method. The Dynamic Data Insertion (DDI) method reads frame image data having a frequency of 60 Hz stored in the frame memory 110 in units of frames twice in a predetermined period of time, thereby obtaining frame image data having a frequency of 120 Hz. To.

In addition, the frame memory 110 receives frame image data having a frequency of 60 Hz stored in a frame unit, and then converts the received frame image data into frame image data having a frequency of 120 Hz.

The frequency converter 120 of the driving device 100 according to the present invention is implemented to convert a frame having a first frequency to a double speed by converting the frame having a first frequency into a frame having a second frequency, but is not limited thereto. It may be implemented by arbitrarily setting the ratio of frequency double speeds so that a frame having a frequency has a higher frequency than a frame having a first frequency.

The image data determination unit 130 determines the image data in the frame unit inputted from the frequency converter 120, and outputs the determined image data to the image data converter 140 or the multiplexer 150. (S230)

The image data determination unit 130 calculates a gray level value for each pixel displayed on the liquid crystal panel from the frame image data having a frequency of 120 kHz input from the frequency converter 120. When the calculated gray level for each pixel is a gray level (“B” illustrated in FIGS. 5A and 5B) corresponding to a small color shift, the frame image data input from the frequency converter 120 may be multiplied without conversion. Output to flexure 150.

Meanwhile, when the calculated gray level for each pixel is a gray level corresponding to a large gray scale interval, the frame image data input from the frequency converter 120 is output to the video data converter 140.

5A and 5B, when the image having a rectangular shape (A) is displayed on a white or black background (“B”) on the liquid crystal panel 10, the present invention is described. The image data determination unit 130 of the driving apparatus calculates a gray level value for each pixel on the liquid crystal panel 10 from the frame image data having a frequency of 120 kHz input from the frequency converter 120.

For example, when the image ("A") having a large grayscale value is displayed on the background ("B") having a small grayscale value, the frame image data If the gray level calculated by the pixel corresponds to a section having a small color shift, that is, a gray level range of the pixel from 0 gray to 255 gray, the frequency converter 120 corresponds to 0 gray to 49 gray and 181 gray to 255 gray. ) Outputs the frame image data input from the multiplexer 150 without conversion.

On the other hand, when the gray level of each pixel calculated from the frame image data corresponds to a gray level section in which a color shift is large, that is, a gray level range of the pixel from 0 gray level to 255 gray levels, the frame image data is displayed. Output to the image data converter 140.

The image data converter 140 may determine the gray level of each pixel from the image data determination unit 130 as a gray level having a large color shift, and perform color shift on the gray level value of each pixel on the liquid crystal panel of the input image data. A shift) is converted into a gray value corresponding to a small section, and the converted image data is output to the multiplexer 150.

Referring to FIG. 6B, the image data converting unit 140 determines the gray level of the color shift from the image data determining unit 130 with respect to each pixel on the liquid crystal panel. The gray value is converted into a gray value corresponding to a section having a small color shift. That is, when the gray scale range of the pixel is expressed as 0 gray to 255 gray, the gray scale value of the pixel having the gray scale value corresponding to the 50 gray scale to 180 gray scale ranges from 0 gray scale to 49 gray scale or 181 gray scale to small color shift. The image data is converted into grayscale values corresponding to 255 grayscales, and the converted image data is output to the multiplexer 150.

For example, if the gray level for each pixel of the input image data (“A” shown in FIGS. 5A and 5B) has a 100 gray level value, the gray level value for each pixel of the two frame image data having the 120 kHz frequency is symmetrical. (S240)

The driving method for symmetrically converting the grayscale value is a color shift such that when the grayscale value of the image data to be converted in the i-th frame having the 120 kHz frequency is 100 gray scales, the average value of the gray scale values is 100 gray scales. Extracts an arbitrary first gradation value from 0 to 49 gradations, converts the gradation value of each pixel of the image data into the extracted first gradation value, and outputs the converted image data to the multiplexer 150. .

Subsequently, in the i + 1th frame, the second grayscale value corresponding to the 181 to 255 grayscale regions symmetrical with the first grayscale value converted in the ith frame is extracted, and the grayscale value of each pixel of the image data is converted and converted. The output image data is output to the multiplexer 150 (S250).

The symmetrical conversion of the average grayscale values of the i < th > and i + 1 < th > frame image data can display a low gray scale of 0 gray to 49 gray in succession to a specific pixel, or 181 gray to 255 gray scale in succession to a specific pixel. If is displayed, the average gradation value of successive frames is expressed as the original gradation to be displayed, but this is to prevent such a flicker phenomenon because flicker may occur when the screen is flickered when the video is implemented.

Of course, this is one example. In the driving method of the driving apparatus according to the exemplary embodiment of the present invention, the image data converter 140 converts the gray level value of each pixel of the image data of two frames having a large gray scale value. Although the color shift has been described as being symmetrically converted to a grayscale value having a small grayscale value, the symmetric conversion method described above may not be applied to a grayscale value that cannot be symmetrically converted.

For example, when the gradation value to be converted is a gradation value close to the interval of the gradation value with small color shift, that is, when the gradation value is 51 to 60 gradations or 171 to 180 gradations, It is also possible to convert the color shift into the nearest gray level value among the gray level values of the small gray level range without converting them symmetrically.

The multiplexer 150 aligns and outputs image data input from the image data determination unit 130 and the image data conversion unit 140 in response to the frame frequency from the frequency converter 120.

In the multiplexer 150, the image data input from the image data determining unit 130, that is, the gray level of each pixel displayed on the liquid crystal panel 10 as shown in FIG. 6A, is small in color shift. The image data having a gray level corresponding to the image data and the image data input from the image data converter 140, that is, the gray level of each pixel displayed on the liquid crystal panel 10 as shown in FIG. 6B, are color shifted. Is determined as having a large gray level, and the image data converter 140 sorts and outputs the image data obtained by symmetrically converting the gray level value of each pixel of the two frames (i-th and i + 1-th frame) image data in units of frames. .

The driving method of the driving apparatus of the liquid crystal display according to the embodiment of the present invention is suitable for all frame inversion driving methods for changing the polarity of the image data in units of frames among the inversion methods for converting the polarity of the data applied to the liquid crystal cell. It is a driving method, and in particular, it can be optimized for a driving method for changing the polarity of image data in units of two frames.

The driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention doubles the image data of one frame to the image data having a double frame frequency through the above-described configuration and driving method. Subsequently, image data having a gray scale value corresponding to a large color shift section in the double-frame image data is symmetrically as image data having a gray scale value corresponding to a section having a small color shift. The display quality of the liquid crystal display may be improved by converting the transformed image data into the image data in units of frames to prevent color shift from a specific angle on the liquid crystal panel.

As described above, the driving apparatus and the driving method of the liquid crystal display according to the embodiment of the present invention double the image data of one frame to the image data having twice the frame frequency. Subsequently, image data having a gray scale value corresponding to a large color shift section in the double-frame image data is symmetrically as image data having a gray scale value corresponding to a section having a small color shift. Then, the converted image data and the unconverted image data are aligned and merged into image data in units of frames. Through such a driving method, a color shift phenomenon may be prevented at a specific angle on the liquid crystal panel, thereby improving display quality of the liquid crystal display.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the 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 (15)

In the driving device of the liquid crystal display device for driving the liquid crystal panel to display an image, A frame memory for memorizing continuously input image data in frame units; A frequency converter which doubles and outputs the frame frequency of the image data from the frame memory; An image data discriminating unit for discriminating and outputting image data input from the frequency converting unit; An image data converter for converting and outputting image data input from the image data discriminator; A multiplexer for sorting and outputting image data inputted from the image data determination unit and the image data conversion unit; The image data determination unit calculates a gray level value for each pixel displayed on the liquid crystal panel from the image data; The image data determination unit outputs image data having a gray scale value corresponding to a small color shift section among the calculated gray scale values for each pixel to the multiplexer, and a section having a large color shift among the calculated gray scale values for each pixel. The image data having a gray value corresponding to the driving device of the liquid crystal display device, characterized in that for outputting to the image data converter. The method of claim 1, And the frame memory comprises a memory element or a virtual memory. The method of claim 1, And the frequency converter doubles the frame frequency of the image data. delete delete The method of claim 1, And the image data converting unit symmetrically converts and outputs the gray level value of each pixel of the input two frame image data so as to have a gray level value of a section having a small color shift. 7. The method according to claim 1 or 6, The multiplexer driving apparatus of the liquid crystal display device, wherein the multiplexer merges and outputs the image data input from the image data discriminator and the image data converter in units of frames in response to the frame frequency from the frequency converter. . A first step of storing input first image data; A second step of converting a frequency of the stored image data; A third step of comparing the second image data having the changed frequency with each of the first and second gray level regions different from each other; A fourth step of modulating data of any one of the first and second gray areas according to the comparison result; And And a fifth step of generating data signals in units of frames by aligning data of the modulated area with data of the remaining area. 9. The method of claim 8, In the second step, the frequency of the video data is doubled. 9. The method of claim 8, And wherein the third step determines whether the gray level value of each pixel of the second image data corresponds to one of the first gray level region and the second gray level region. The method of claim 9, And wherein the fourth step modulates image data corresponding to a pixel having a gray scale value corresponding to the first gray scale region according to the determination. The method of claim 11, The driving method of claim 5, wherein the modulated image data and the image data corresponding to the second gray scale region are aligned to generate an image data signal in a frame unit. The method of claim 11, The modulating of the image data is driven in a two frame inversion method. 14. The method of claim 13, In the modulating the image data, And symmetrically modulating the gray level value of each pixel of the image data of two frames so as to have a gray level value corresponding to the second gray area. 14. The method of claim 13, In the modulating the image data, If the gray value of the image data corresponding to the second gray area is a gray value close to the first gray area, the driving method of the driving apparatus, characterized in that to modulate the closest gray value of the gray value of the first gray area. .

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