KR20080073909A - Liquid crystal display device and driving method thereof - Google Patents

Abstract

An LCD(Liquid Crystal Display) device and a driving method thereof are provided to enhance display quality by supplying compensated signals to pixels based on effective image signals. An LCD(Liquid Crystal Display) device includes plural pixels, an image signal compensator, and a data driver(500). The image signal compensator receives consecutive first, second, and third frame image signals, outputs a compensation signal higher than the third frame image signal as much as a first compensation value when the second frame image signal is not higher than the first frame image signal as much as a reference value and the third frame image signal is higher than the second frame image signal as much as the reference value, and outputs a compensation signal higher or lower than the second frame image signal as much as a second compensation value when the second frame image signal is higher than the first frame image signal as much as the reference value. The data driver supplies data voltages corresponding to the compensation signal to the pixels.

Description

Liquid crystal display device and driving method thereof

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

FIG. 2 is an equivalent circuit diagram of one pixel of FIG. 1.

3 is a block diagram of an image signal corrector installed in the signal controller of FIG. 1.

4 is a flowchart illustrating an operation of an image signal corrector of FIG. 3.

5 and 6 are waveform diagrams for describing an operation of the image signal correcting unit of FIG. 3.

(Explanation of symbols for the main parts of the drawing)

100: first display panel 150: liquid crystal layer

200: second display panel 300: liquid crystal panel assembly

400: gate driver 500: data driver

600: signal controller 610: correction unit

700: frame memory 710, 720: first and second frame memory

800: lookup table 850: image signal correction unit

900: gray voltage generator

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 capable of improving display quality.

The liquid crystal display includes first and second display panels on which a pixel electrode and a common electrode are formed, and a liquid crystal layer injected therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the second display panel and receives a common voltage. An electric field is formed by the voltage difference applied to the pixel electrode and the common electrode, and the image is displayed by controlling the transmittance of light passing through the liquid crystal layer by adjusting the intensity of the electric field.

In such a liquid crystal display, since the response speed of the liquid crystal is slow, it takes some time for the voltage charged in the liquid crystal capacitor to reach a target voltage, that is, a voltage for a signal at which a desired luminance can be obtained. Depends on the difference from the voltage previously charged. Thus, for example, when the difference between the target voltage and the previous voltage is large, if only the voltage for the target voltage is applied from the beginning, the target voltage may not be reached during the time when the switching element is turned on. Therefore, in order to improve the response speed of the liquid crystal, a voltage higher than the target voltage is applied. Even in this case, the target voltage may not be accurately reached.

An object of the present invention is to provide a liquid crystal display device capable of improving display quality.

Another object of the present invention is to provide a method of driving such a liquid crystal display.

The technical problems of the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an exemplary embodiment of the present invention, a liquid crystal display device receives a plurality of pixels and continuous first, second, and third frame image signals, and the second frame image signal is the first frame. When the third frame image signal is greater than the reference value than the second frame image signal, when the third frame image signal is greater than the reference value than the frame image signal, a correction signal that is higher than the third frame image signal by a first correction value is output. An image signal correction unit including a correction unit configured to output a correction signal that is higher or lower than the second frame image signal by a second correction value when the two frame image signal is larger than the reference value than the first frame image signal; And a data driver for supplying a data voltage corresponding to the correction signal from the signal correction unit to the pixel.

According to another aspect of the present invention, there is provided a method of driving a liquid crystal display device, the method comprising: receiving continuous first, second, and third frame image signals; When the third frame image signal is greater than the reference value than the second frame image signal, when the third frame image signal is larger than the reference value than the first frame image signal, a correction signal higher by the first correction value than the third frame image signal is output. Outputting a correction signal higher or lower by a second correction value than the second frame image signal when the second frame image signal is larger than the reference value than the first frame image signal, and data corresponding to the correction signal; Supplying a voltage to the pixel.

Other specific details of the invention are included in the detailed description and drawings.

Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

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

A liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to FIGS. 1 and 2. 1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of FIG. 1.

Referring to FIG. 1, a liquid crystal display according to exemplary embodiments of the present invention may include a liquid crystal panel assembly 300, a gate driver 400 and a data driver 500 connected thereto, and a signal controller for controlling the liquid crystal panel assembly 300. 600, a frame memory 700, a lookup table 800, and a gray voltage generator 900.

The liquid crystal panel assembly 300 includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels PX connected to the display signal lines G ₁ -G _n and D ₁ -D _m , which are arranged in a matrix form. 2, the liquid crystal panel assembly 300 includes a first display panel 100, a second display panel 200, and a liquid crystal layer 150 interposed therebetween.

The display signal lines G ₁ -G _n and D ₁ -D _{m each} include a plurality of gate lines G ₁ -G _n transmitting gate signals and a plurality of data lines D ₁ -D _m transmitting data signals. Include. The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend in the column direction so as to cross each other and are substantially parallel to each other. One gate line and one data line are formed thereon.

Referring to FIG. 2, the color filter CF may be formed in a portion of the common electrode CE of the second display panel 200 to face the pixel electrode PE of the first display panel 100. Each pixel, for example, a pixel connected to the i-th (i = 1, 2, ..., n) gate line Gi and the j-th (j = 1, 2, ..., m) data line Dj, is connected to the signal line Gi. And a first switching element Q connected to Dj, a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. The holding capacitor Cst can be omitted as necessary.

Meanwhile, the gate driver 400 of FIG. 1 is connected to the gate lines G ₁ -G _n so that the gate-on voltage Von and gate-off from the gate on / off voltages Von and Voff generators (not shown) are shown. A gate signal composed of a combination of the voltages Voff is applied to the gate lines G ₁ -G _n .

The gate driver 400 transfers the gate-on voltage Von from the gate on / off voltage generator (not shown) to the gate lines G ₁ -G _n according to the gate control signal CONT1 from the signal controller 600. And turns on the first switching element Q of FIG. 2 connected to the gate lines G ₁ -G _n . Then, the data signal applied to the data lines D ₁ -D _m is applied to the pixel PX through the turned-on first switching element Q.

The difference between the voltage of the data signal applied to the pixel PX and the common voltage Vcom is charged in the liquid crystal capacitor Clc to serve as the pixel voltage. The arrangement of the liquid crystal molecules varies according to the magnitude of the pixel voltage. Accordingly, the polarization of the light passing through the liquid crystal layer 150 changes, thereby displaying an image.

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 to select a gray voltage corresponding to data from the gray voltage generator 900, and selects the selected gray voltage as the data voltage. Is applied to the pixel. Here, when the gray voltage generator 900 does not provide all the voltages for all grays but only the basic gray voltages, the data driver 500 divides the basic gray voltages to generate gray voltages for all grays. The data voltage can be selected from these.

The gate driver 400 or the data driver 500 may be mounted directly on the liquid crystal panel assembly 300 in the form of a plurality of driving integrated circuit chips, or may be mounted on a flexible printed circuit film (not shown). The liquid crystal panel assembly 300 may be attached to the liquid crystal panel assembly 300 in the form of a tape carrier package. Alternatively, the gate driver 400 or the data driver 500 may be integrated in the liquid crystal panel assembly 300 together with the display signal lines G ₁ -G _n , D ₁ -D _m and the first switching element Q. It may be.

The signal controller 600 receives an input image signal DATn and an input control signal for controlling the display thereof from an external graphic controller (not shown). Examples of the input control signal include a vertical sync signal Vsync, a vertical sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 600 controls the gate control signal CONT1 and data based on the first, second and third frame image signals DATn-2, DATn-1, and DATn, the effective image signal DATeft, and an input control signal. The control signal CONT2 and the correction signal DATn 'are generated, the gate control signal CONT1 is transmitted to the gate driver 400, and the data control signal CONT2 and the correction signal DATn' are transmitted to the data driver 500. to provide. In this case, the first and second frame image signals DATn-1 and DATn-2 are provided from the frame memory 700, and the effective image signal DATeft is provided from the lookup table 800. In addition, the image data ID provided in the lookup table 800 may be used. For example, the correction signal DATn 'may be the image data ID.

The gray voltage generator 900 generates a gray voltage of positive or negative polarity based on the common voltage. The gray voltage generator 900 includes a plurality of resistors connected in series between the node to which the driving voltage AVDD is applied and the ground, and distributes the voltage level of the driving voltage to generate the gray voltage, but not illustrated. . The internal circuit of the gray voltage generator 900 is not limited thereto and may be variously implemented.

Hereinafter, the image signal correcting unit and its correction method will be described in detail with reference to FIGS. 3 to 6. 3 is a block diagram of an image signal corrector for explaining the signal controller of FIG. 1, FIG. 4 is a flowchart illustrating an operation of the image signal corrector of FIG. 3, and FIGS. 5 and 6 are image signal beams of FIG. 3. This is a waveform diagram for explaining the operation of the government.

3 to 5, the image signal corrector 850 receives first, second and third frame image signals DATn-2, DATn-1, and DATn and an effective image signal DATeft. A compensator 850 for comparing the one-frame video signal DATn-2 and the second frame video signal DATn-1, and outputting a correction signal DATn 'according to a comparison result, and a third frame video signal ( A first frame memory 710 that receives and stores the DATn and provides a second frame image signal DATn-1, and receives and stores a second frame image signal DATn-1 and stores the first frame image signal (DATn-1). And a second frame memory 720 providing DATn-3). In this case, the first and second frame memories 710 and 720 may be included in one frame memory, and the correction unit 610 may be included in the signal controller. However, it is not limited to this. Also, the image signal corrector 850 includes a lookup table 800 that provides image data ID and an effective image signal DATeft for the frame image signal.

Hereinafter, the correction operation of the correction unit will be described in detail.

Here, for convenience of description, the case of n = 3 (third frame) will be described.

Referring to FIG. 4, the corrector 610 receives continuous first, second, and third frame image signals DATn-2, DATn-1, and DATn (S10).

Here, the first and second frame image signals DAT1 and DAT2 are both the lowest gray level, and the voltage level corresponding to the lowest gray level may be the common voltage Vcom.

Next, the first frame image signal DAT1 and the second frame image signal DAT2 are compared (S20). As a result of the comparison, when the second frame image signal DAT2 is not greater than the reference value Vref greater than the first frame image signal DAT1, the second frame image signal DAT2 and the third frame image signal DAT3 are compared. (S30). As a result of the comparison, when the third frame image signal DAT3 is not larger than the second frame image signal DAT2 by more than the reference value Vref, the third frame image signal DAT3 is output as a corrected signal DAT3 'as it is ( S40, S50). Here, the reference value Vref is not limited to the specified value but may be variously set.

Therefore, the second frame video signal DAT2 of (G1) gray is not larger than the reference value G1 by more than the first frame video signal of (G1) gray, and the third frame video signal DAT3 of (G1) gray is ( G1) Since the reference value G1 is not larger than the second frame video signal DAT2 of gray, the third frame video signal DAT3 of (G1) gray is output as the corrected signal DAT3 'of (G1) gray as it is. do.

Next, the case of n = 4 (fourth frame) will be described.

The second frame image signal DAT2 and the third frame image signal DAT3 are compared (S20). As a result of the comparison, when the third frame image signal DAT3 is not greater than the reference value Vref greater than the second frame image signal DAT2, the third frame image signal DAT3 and the fourth frame image signal DAT4 are compared. (S30). As a result of comparison, when the fourth frame image signal DAT4 is greater than or equal to the reference value Vref than the third frame image signal DAT3, the corrected signal higher than the fourth frame image signal DAT4 by the first correction value CV1 ( DAT4 ') are output (S41, S50).

Therefore, the third frame video signal DAT3 of (G1) gray is not larger than the reference value G1 by more than the second frame video signal DAT2 of (G1) gray, and the fourth frame video signal DAT4 of (G4) gray ) Is greater than or equal to the reference value G1 than the third frame video signal DAT3 of (G1) gray, and (G6) higher than the first correction value G2 than the fourth frame video signal DAT4 of the (G4) gray. A gray corrected signal DAT4 'is output.

Next, a case where n = 5 (fifth frame) will be described.

The third frame image signal DAT3 and the fourth frame image signal DAT4 are compared (S20). As a result of the comparison, when the fourth frame image signal DAT4 is larger than the third frame image signal DAT3 by more than the reference value Vref, the effective image signal DATeft is compared with the fourth frame image signal DAT4 (S31). . As a result of the comparison, when the effective video signal DATeft is smaller than the fourth frame video signal DAT4, the correction signal DAT5 ′ that is higher than the fourth frame video signal DAT4 by the second correction value CV2 is output. (S42, S50). In this case, the effective image signal DATeft may be a liquid crystal test test value for the correction signal DAT4 ′ in the fourth frame. In addition, the second correction value CV2 may be a value obtained by dividing the first correction value CV1 by n (where n is a natural number), where n = 2. Here, the correction unit 610 receives the effective image signal DATeft from the lookup table 800, compares it with the fourth frame image signal DAT4, and outputs a correction signal DAT5 ′ according to the comparison result. The result of the comparison between the effective image signal DATeft and the fourth frame image signal DAT4 may be provided from the lookup table 800.

Therefore, the fourth frame video signal DAT4 of (G4) gray is larger than the reference frame G1 of the third frame video signal DAT3 of (G1) gray, and the effective video signal DATeft of (G3) gray is ( G4) Since it is smaller than the gray fourth frame video signal DAT4, the (G4) gray correction signal DAT5 'which is higher than the fourth frame video signal DAT4 of gray by a second correction value G1. Outputs

Similarly, when n = 6 and 7 (sixth and seventh frames), the correction unit 610 outputs second correction signals DAT6 'and DAT7', respectively.

4 and 6, a case in which the correction unit outputs a correction signal lower by a second correction value than the second frame image signal will be described.

Here, a case in which n = 5 (fifth frame) will be described.

First, the correction unit 610 receives the continuous first, second, and third frame image signals DAT3, DAT4, and DAT5 (S10).

The third frame image signal DAT3 and the fourth frame image signal DAT4 are compared (S20). As a result of the comparison, when the fourth frame image signal DAT4 is larger than the third frame image signal DAT3 by more than the reference value Vref, the effective image signal DATeft is compared with the fourth frame image signal DAT4 (S31). . As a result of the comparison, if the effective video signal DATeft is greater than the fourth frame video signal DAT4, the correction signal DAT5 ′ lower than the fourth frame video signal DAT4 by the second correction value CV2 is output (S43). , S50).

Therefore, the fourth frame image signal DAT4 of (G4) gray is larger than the reference value G1 of the third frame image signal DAT3 of (G1) gray, and the effective image signal DATeft of (G5) gray is ( G4) Since it is larger than the fourth frame image signal DAT4 of gray, the correction signal DAT5 'of (G3) gray lower than the fourth frame image signal DAT4 of gray (G3) by the second correction value G1. Outputs

The structure of the image signal corrector is not limited thereto, and may further include a corrector configured to pretilt to improve the liquid crystal response speed.

Conventional liquid crystal display devices may appear higher or lower than the target signal on the liquid crystal panel even when the liquid crystal panel is charged higher than the target signal in order to improve the response speed of the liquid crystal. However, the liquid crystal display according to the present invention supplies the corrected signal higher than the target signal to the pixel, and supplies the corrected signal to the pixel by referring to the effective image signal with respect to the corrected signal and the target signal to the pixel. Can be reached quickly and accurately to represent an image of desired luminance. Thus, better display quality can be obtained.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the liquid crystal display and the driving method of the liquid crystal display as described above, the response speed of the liquid crystal is improved, and the desired image can be accurately displayed, thereby improving the quality of the liquid crystal display.

Claims (8)

A plurality of pixels; When the first, second, and third frame video signals are consecutive and the second frame video signal is not greater than the reference value than the first frame video signal, the third frame video signal is greater than the second frame video signal. When the reference value is larger than the reference value, a correction signal higher than the third frame image signal by a first correction value is output, and when the second frame image signal is larger than the reference value than the first frame image signal, the second frame image signal An image signal correction unit including a correction unit outputting a correction signal higher or lower by a second correction value; And And a data driver for supplying a data voltage corresponding to the correction signal from the image signal corrector to the pixel. The method of claim 1, The correction unit is higher than the second frame video signal by the second correction value when the effective video signal is smaller than the second frame video signal when the second frame video signal is larger than the reference value by the first frame video signal. And outputting a correction signal and outputting a correction signal lower than the second frame image signal by the second correction value if an effective image signal is larger than the second frame image signal. The method of claim 1, And wherein the second correction value has a value obtained by dividing the first correction value by n (where n is a natural number). The method of claim 1, A first frame memory receiving and storing the third frame image signal and providing the second frame image signal; A second frame memory which receives and stores the second frame video signal and provides the first frame video signal; And a lookup table referenced by the correction unit. The method of claim 4, wherein And the lookup table includes the effective image signal. Receiving a continuous first, second, and third frame video signal; When the second frame image signal is not greater than the reference value than the first frame image signal, when the third frame image signal is greater than the reference value than the second frame image signal, by the first correction value than the third frame image signal. Outputting a high correction signal and outputting a correction signal that is higher or lower by a second correction value than the second frame image signal when the second frame image signal is larger than the reference value than the first frame image signal; And And supplying a data voltage corresponding to the correction signal to the pixel. The method of claim 7, wherein The correction signal is equal to or greater than the second frame image signal when the second frame image signal is larger than the first frame image signal when the effective image signal is smaller than the second frame image signal. And outputting a higher output value and an effective image signal greater than the second frame image signal, and outputting a value lower than the second frame image signal by the second correction value. The method of claim 6, And wherein the second correction value has a value obtained by dividing the first correction value by n (where n is a natural number).

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