KR100994229B1 - Liquid crystal display apparatus and method for driving the same - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display and a driving method thereof capable of preventing deterioration of image quality due to interlace driving.

The driving method of the present invention includes the steps of adding dummy pixel data between pixel data input in an interlaced manner; Supplying the pixel data and the dummy pixel data to the liquid crystal panel such that the pixel data and the dummy pixel data are inverted by 2 dots vertically and in at least two frame units; Turning on the liquid crystal cells in a period during which the pixel data is supplied to the liquid crystal panel, and turning off the liquid crystal cells in a period during which the dummy pixel data is supplied to the liquid crystal panel.

Description

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

1 is a view showing a conventional liquid crystal panel display screen driven in an interlaced manner.

FIG. 2 is a diagram illustrating a dot inversion form of a conventional liquid crystal panel driven in an interlaced manner over time; FIG.

3A and 3B are diagrams illustrating charging characteristics of the first and second liquid crystal cells illustrated in FIG. 1 over time.

4A through 4D are views sequentially showing a display screen of a liquid crystal panel driven in an interlaced manner according to an exemplary embodiment of the present invention.

5A and 5D are diagrams illustrating charging characteristics of the first to fourth liquid crystal cells illustrated in FIGS. 4A to 4D over time.

6 is a block diagram illustrating a liquid crystal display for driving interlaces according to an exemplary embodiment of the present invention.

FIG. 7 is a driving waveform diagram of the liquid crystal display shown in FIG. 6.

FIG. 8 illustrates a vertical two-dot & two-frame inversion form of the liquid crystal panel illustrated in FIG. 6 over time.

<Short description of the symbols in the drawings>

2: liquid crystal panel 4: gate driver

6: data driver 8: timing controller

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device and a driving method thereof capable of preventing deterioration in image quality due to interlace driving.

A typical liquid crystal display device displays an image by adjusting the light transmittance of a liquid crystal having dielectric anisotropy using an electric field. To this end, the liquid crystal display includes a liquid crystal panel having a liquid crystal cell matrix for displaying an image, and a driving circuit for driving the liquid crystal panel. BACKGROUND ART An active matrix type liquid crystal display device that independently drives liquid crystal cells using thin film transistors is widely used not only for display devices of personal computers (PCs) but also for televisions (hereinafter, referred to as TVs).

The method of displaying an image signal on a display device is generally classified into a progressive driving method and an interlace driving method.

The progressive driving method displays image signals of one screen frame by frame as if the film is projected on the screen. Representative display devices using such a progressive driving method include digital display devices such as computer monitors, plasma display panels (PDPs), and liquid crystal displays.

On the other hand, the interlace driving method divides one screen, that is, one frame into an odd frame displaying odd horizontal lines and an even frame displaying even horizontal lines, and the odd frame and the even frame are sequentially displayed. Mark on. A representative display device using such an interlace driving method is a TV. In other words, the TV video signal is supplied in an interlaced manner.

In the case where a TV video signal supplied in an interlaced manner is to be displayed on a liquid crystal display device, a computer system driving the liquid crystal display device converts the interlaced TV video signal into a progressive method and supplies it to the liquid crystal display device. In this case, a computer system has a disadvantage in that a data conversion unit having a complicated circuit configuration for converting the interlaced video signals into a progressive method is added.

In order to solve this drawback, a method of supplying a liquid crystal display without converting an interlaced video signal to a progressive method has recently been proposed. For example, a method of displaying an image signal input by an interlace method on a liquid crystal display is as shown in FIGS. 1A and 1B.

FIG. 1A illustrates an odd frame (OF) in which pixel data supplied by an interlace method is displayed on a liquid crystal panel, and FIG. 1B illustrates an even frame (EF).

In the odd frame OF, as shown in FIG. 1A, the odd horizontal lines of the liquid crystal panel are filled with actual pixel data, and the even horizontal lines are filled with dummy pixel data (for example, white or black pixel data). . In other words, the pixel data of the odd frame OF is composed of actual pixel data to be supplied to the odd horizontal line and dummy pixel data to be supplied to the even horizontal line.

In the even frame EF, as shown in FIG. 1B, the odd horizontal lines of the liquid crystal panel are filled with dummy pixel data (eg, white pixel data), and the even horizontal lines are filled with actual pixel data. In other words, the pixel data of the even frame EF is composed of dummy pixel data to be supplied to the odd horizontal line and actual pixel data to be supplied to the even horizontal line.

In addition, in order to improve display quality, the liquid crystal panel has polarities opposite to those of the other liquid crystal cells adjacent to the liquid crystal cells based on the common voltage Vcom, and the polarities of the liquid crystal cells are shown in FIG. 2. In the same manner, it is driven by a dot inversion method that is inverted in units of frames.

For example, as illustrated in FIG. 3A, the first liquid crystal cell P1 of the odd horizontal line receives actual pixel data having positive polarity (+) based on the common voltage Vcom in the odd frame OF, and even-frame EF. Charges negative pixel white pixel data which is dummy pixel data. As shown in FIG. 3B, the second liquid crystal cell P2 of the even horizontal line has black pixel data of negative polarity, which is dummy pixel data, in the odd frame OF, and positive polarity (+) in the even frame EF. Charge the pixel data. The first and second liquid crystal cells P1 and P2 repeat the polar inversion as the odd and even frames OF and EF are repeated. In this case, the actual pixel data supplied to the first and second liquid crystal cells P1 and P2 may have the same polarity, that is, the positive polarity (+), and the dummy pixel data may have the negative polarity (−). Further, the positive pixel positive pixel data is supplied to charge the first and second liquid crystal cells P1 and P2, and the negative pixel data of negative polarity is supplied to the first and second liquid crystals. It can be seen that the difference between the voltages charged in the cells P1 and P2 is large. For this reason, as time passes, voltages applied to the first and second second liquid crystal cells P1 and P2 are biased toward the positive polarity (+). In other words, as time passes, the first and second second liquid crystal cells P1 and P2 are induced to have a positive voltage (DC) biased with positive polarity, as shown by the dotted lines shown in FIGS. 3A and 3B. do. Accordingly, a problem of deterioration of image quality such as an afterimage occurs in the liquid crystal panel. In addition, since the dummy pixel data applied as the black (white) data is displayed on the liquid crystal panel, a problem of deterioration of image quality such as screen blur occurs.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a driving method thereof capable of preventing the deterioration of image quality due to interlace driving.

In order to achieve the above object, a liquid crystal display according to an aspect of the present invention comprises a liquid crystal panel having a liquid crystal cell matrix; A timing controller for adding dummy pixel data between pixel data supplied in an interlaced manner and for generating a plurality of control signals; The polarity of the pixel data and the dummy pixel data from the timing controller is inverted by 2 dots vertically according to the first control signal from the timing controller and inverted by at least two frames. A data driver for supplying; According to the second control signal from the timing controller, the scan signal is supplied to the gate lines of the liquid crystal cell matrix to turn on the liquid crystal cells to which the pixel data is to be supplied, and the liquid crystal cells to which the dummy pixel data are to be supplied are And a gate driver to turn off.

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The data driver supplies the pixel data to an odd horizontal line of the liquid crystal panel and the dummy pixel data to an even horizontal line in an odd frame, the dummy pixel data to the odd horizontal line in an even frame, and the even horizontal line. The pixel data is supplied.

A driving method of a liquid crystal display according to the present invention includes the steps of adding dummy pixel data between pixel data input in an interlaced manner; Supplying the pixel data and the dummy pixel data to the liquid crystal panel such that the pixel data and the dummy pixel data are inverted by 2 dots vertically and in at least two frame units; Turning on the liquid crystal cells in a period during which the pixel data is supplied to the liquid crystal panel, and turning off the liquid crystal cells in a period during which the dummy pixel data is supplied to the liquid crystal panel.

In the odd frame, the pixel data is supplied to an odd horizontal line of the liquid crystal panel, and the dummy pixel data is supplied to an even horizontal line, and the dummy pixel data is supplied to the odd horizontal line in an even frame, and the pixel data is provided in the even horizontal line. To supply.

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

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to FIGS. 4A to 8.

4A through 4D sequentially illustrate display screens of a liquid crystal panel driven by an interlace method according to an exemplary embodiment of the present invention, and FIGS. 5A through 5D are charging characteristic diagrams of specific liquid crystal cells P1 through P4. .

In the first odd frame OF, actual pixel data is charged in the odd horizontal lines of the liquid crystal panel, and dummy pixel data is charged in the even horizontal lines as shown in FIG. 4A. To this end, the pixel data of the odd frame OF is composed of actual pixel data to be supplied to the odd horizontal line and dummy pixel data to be supplied to the even horizontal line. In addition, the liquid crystal cells of the liquid crystal panel are driven by a vertical 2-dot inversion method in which the polarity is inverted in a unit of 1 dot in the horizontal direction and in units of 2 dots in the vertical direction. Here, the dummy pixel data is black (white) data or a half-tone data that is close to the common voltage Vcom.

In the second even frame EF, dummy pixel data is charged in the odd horizontal lines of the liquid crystal panel, and actual pixel data is charged in the even horizontal lines as shown in FIG. 4B. To this end, the pixel data of the even frame EF includes dummy pixel data to be supplied to the odd horizontal line and actual pixel data to be supplied to the even horizontal line. Each of the liquid crystal cells driven in the vertical 2-dot inversion scheme charges pixel data having the same polarity as the odd frame period.

In the third odd frame OF, actual pixel data is charged in the odd horizontal lines of the liquid crystal panel, and dummy pixel data is charged in the even horizontal lines as shown in FIG. 4C. In this case, each of the liquid crystal cells driven in a vertical 2-dot inversion scheme charges pixel data having polarities opposite to those of the first odd frame and the second even frame.

In the fourth even frame EF, dummy pixel data is charged in the odd horizontal lines of the liquid crystal panel, and actual pixel data is filled in the even horizontal lines as shown in FIG. 4D. In this case, each of the liquid crystal cells driven in the vertical 2-dot inversion scheme charges pixel data having the same polarity as the third odd frame.

Here, when the liquid crystal cells to which dummy pixel data is to be supplied turn off their thin film transistors so that the dummy pixel data is not charged in the liquid crystal cell, screen blur due to the dummy pixel data can be prevented. For example, in the odd frame OF, the thin film transistors of the even horizontal lines to which dummy pixel data are to be supplied are turned off, and in the even frame EF, the thin film transistors of the odd horizontal lines to which the dummy pixel data are to be supplied are turned off. Let's go.

5A to 5D, in the first odd frame OF, the first liquid crystal cell P1 of the first horizontal line stores the actual pixel data of positive polarity (+) and the second liquid crystal cell of the second horizontal line ( P2) represents positive dummy pixel data, and the third liquid crystal cell P3 of the third horizontal line represents actual pixel data of negative polarity, and the fourth liquid crystal cell P4 of the fourth horizontal line. Is charged with negative pixel data of negative polarity (-). Subsequently, in the second even frame OF, each of the first to fourth liquid crystal cells P1 to P4 respectively includes dummy, real, dummy, and actual pixel data in which only pixel data is changed while maintaining polarity with the first odd frame OF. To charge.

In the third odd frame OF, the first to fourth liquid crystal cells P1 to P4 have polarities opposite to those of the first odd frame OF and the second even frame EF, and the actual, dummy, In fact, dummy pixel data is charged respectively. In the fourth even frame OF, each of the first to fourth liquid crystal cells P1 to P4 charges dummy, actual, dummy, and actual pixel data in which only pixel data is changed while maintaining polarity with the third odd frame OF. do.

Accordingly, the pixel data values charged with the same polarity in the first odd frame OF and the second even frame EF in each of the first to fourth liquid crystal cells P1 to P4 are the third odd frame OF and the fourth even. By canceling the pixel data value charged with the opposite polarity in the frame EF, it is possible to prevent the DC voltage DC from being induced as in the related art. In addition, the first to fourth liquid crystal cells P1 to P4 have the polarization inverted in the vertical two-dot unit to minimize flicker due to the difference in the charge amount between the actual pixel data and the dummy pixel data, compared to the case where the first to fourth liquid crystal cells P1 to P4 are inverted in the one-dot unit. You can do it. Furthermore, when the thin film transistors of the liquid crystal cells to which dummy pixel data is to be applied are turned off, the dummy pixel data is not displayed on the liquid crystal panel, thereby preventing screen blur due to the dummy pixel data.

FIG. 6 illustrates a liquid crystal display device driven in an interlaced manner according to an exemplary embodiment of the present invention, and FIG. 7 is a driving waveform diagram of the liquid crystal display device illustrated in FIG. 6.

The liquid crystal display shown in FIG. 6 includes a liquid crystal panel 2 having a liquid crystal cell matrix, a gate driver 4 for driving gate lines GL1 to GLn of the liquid crystal panel 2, and a liquid crystal panel 2. A data driver 6 for driving the data lines DL1 to DLm, and a timing controller 8 for controlling the gate driver 4 and the data driver 6.

The timing controller 8 uses gate control signals for controlling the gate driver 4 by using a vertical synchronization signal, a horizontal synchronization signal, a data enable signal, etc. input from the outside, and source control for controlling the data driver 6. Generate signals. The gate control signals include a gate start pulse GSP and a gate shift clock GSC used for the shift operation of the gate driver 4, and a gate output enable (hereinafter referred to as GOE) that controls the output of the gate driver 4. Traffic lights are included. The source control signals include a source start pulse SSP and a source shift clock SSC used for the shift operation of the data driver 6, a polarity control (hereinafter referred to as POL) signal for determining the polarity of the pixel data, and a data driver ( And a source output enable signal SOE for controlling the output of 6).

In particular, the timing controller 8 supplies a modulated GOE signal (hereinafter referred to as IGOE) to prevent the dummy pixel data from being displayed on the liquid crystal panel 2 when the pixel data input from the outside is supplied in an interlaced manner. The IGOE signal is composed of an IGOE_O signal supplied to an odd frame and an IGOE_E supplied to an even frame.

Specifically, the GOE signal includes an enable period on for turning on the thin film transistor TFT of the liquid crystal panel 2 and a disable period for turning off every one horizontal period 1H as shown in FIG. 7. (off) is included. In the odd horizontal periods 1H, 3H, ..., where the actual pixel data is supplied to the liquid crystal panel 2, the IGOE_O supplied to the odd frame has the same enable period on and disable period as the GOE. And even horizontal periods 2H, 4H, ..., in which the dummy pixel data is supplied to the liquid crystal panel 2, include only the disable period off. On the other hand, IGOE_E supplied to the even frame includes only the disable period (off) in the odd horizontal periods (1H, 3H, ...) in which the dummy pixel data is supplied to the liquid crystal panel 2, and the actual pixel data is the liquid crystal. The even horizontal periods 2H, 4H, ... supplied to the panel 2 include only the enable period on and the disable period off like the GOE.

In addition, the timing controller 8 generates a POL signal whose polarity is inverted in units of two horizontal periods (2H) as shown in FIG. 8 so that the liquid crystal cell 12 of the liquid crystal panel 2 is driven in a vertical two-dot inversion manner. Supply. Also, the POL signal is inverted again in units of two frames.

The timing controller 8 adds dummy pixel data to the pixel data input from the outside in an interlaced manner, and supplies the dummy pixel data to the data driver 6. For example, the timing controller 8 adds the dummy pixel data of the even horizontal line to the actual pixel data of the odd frame composed of the pixel data to be supplied to the odd horizontal line, and supplies it to the data driver 6. The timing controller 8 adds dummy pixel data of an odd horizontal line to the data driver 6 to actual pixel data of an even frame composed of pixel data to be supplied to an even horizontal line.

The gate driver 4 shifts the gate start pulse GSP from the timing controller 8 according to the gate shift clock GSC to sequentially scan the gate high voltage VGH to the gate lines GL1 to GLm. To supply. The gate driver 4 supplies the gate low voltage VGL to the gate lines GL1 through GLm in the remaining period in which the scan pulse of the gate high voltage VGH is not supplied. At this time, the gate driver 4 controls the pulse width of the scan pulse in accordance with the gate output enable signal GOE from the timing controller 8.

Specifically, when the GOE signal is supplied from the timing controller 8 as shown in FIG. 8, the gate driver 4 applies the gate high voltage VGH in the enable period on every horizontal period 1H, and the disable period ( off), the gate low voltage VGL is alternately supplied.

In contrast, when IGOE_O is supplied as shown in FIG. 7 in the odd frame OF, the gate high voltage VGH and the gate low voltage VGL are supplied in the odd horizontal periods 1H, 3H, ..., and even horizontal. In the periods 2H, 4H, ... only the gate low voltage VGL is supplied. In addition, when IGOE_E is supplied in the even frame EF, only the gate low voltage VGL is supplied in the odd horizontal periods 1H, 3H, ..., and in the even horizontal periods 2H, 4H, ... The high voltage VGH and the gate low voltage VGL are sequentially supplied.

The data driver 6 shifts the source start pulse SSP from the timing controller 8 in accordance with the source shift clock SSC to generate a sampling signal. In addition, the data driver 6 latches pixel data input from the timing controller 8 according to the sampling signal according to the source shift clock SSC, and then relies on a line unit in response to a source output enable signal SOE. To supply. The data driver 6 digital-analog converts the pixel data supplied in line units using different gamma voltages and supplies them to the data lines DL1 to DLm. In this case, the data driver 6 determines the polarity of the pixel data in accordance with the POL signal from the timing controller 8 during the digital-analog conversion of the pixel data.

Specifically, the data driver 6 has a polarity in which the pixel data of each channel is opposite to the pixel data of the adjacent channel according to the POL signal for vertical two-dot and two-frame inversion driving, and every two horizontal periods 2H. Causes the polarity to be reversed. The data driver 6 causes the pixel data of each channel in two frame units to be inverted.

The data driver 6 determines a period in which the pixel data is supplied to the data lines DL1 to DLm in response to the source output enable signal SOE.

The liquid crystal panel 2 includes a liquid crystal cell matrix composed of liquid crystal cells 12 formed at regions defined by intersections of the gate lines GL and the data lines DL. Each of the liquid crystal cells includes a liquid crystal capacitor Clc for adjusting the light transmittance according to a pixel signal, and thin film transistors TFT for driving the liquid crystal capacitor Clc.

The thin film transistor TFT is turned on when the scan signal from the gate line GL, that is, the gate high voltage VGH is supplied, and supplies the modulated pixel signal from the data line DL to the liquid crystal capacitor Clc. . The thin film transistor TFT is turned off when the gate low voltage VGL is supplied from the gate line GL to maintain the modulated pixel signal charged in the liquid crystal capacitor Clc. The liquid crystal capacitor Clc is composed of a common electrode facing each other with a liquid crystal interposed therebetween and a pixel electrode connected to the thin film transistor TFT. The liquid crystal capacitor Clc realizes gradation by adjusting the light transmittance by changing the arrangement state of the liquid crystal having dielectric anisotropy according to the modulated pixel signal charged through the thin film transistor TFT.

The liquid crystal cells 12 of the liquid crystal panel 2 are driven in a vertical 2-dot inversion manner as shown in FIG. 8. Each of the liquid crystal cells 12 charges pixel data having the same polarity in the odd frame and the even frame. Subsequently, each of the liquid crystal cells 12 charges pixel data having polarities opposite to each other in two frame units, that is, a frame unit including an odd frame and an even frame. Accordingly, the DC voltage DC can be prevented from being induced in the liquid crystal cell. In addition, when the IGOE_O and IGOE_E signals are supplied from the timing controller 8 to the gate driver 4, the dummy pixel data is not charged in the liquid crystal cells 12, thereby preventing screen blur due to the dummy pixel data. .

As described above, the liquid crystal display and the driving method thereof according to the present invention can prevent the afterimage caused by the DC voltage by inverting the polarity of the pixel data in the unit of 2 dots and 2 frames while performing the interlace driving. Rather, flicker can be minimized rather than dot inversion.

In addition, the liquid crystal display and the driving method thereof according to the present invention can prevent the screen blur due to the dummy pixel data by preventing the interlace driving dummy pixel data from being charged in the liquid crystal cell.

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. 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 (8)

A liquid crystal panel having a liquid crystal cell matrix; A timing controller for adding dummy pixel data between pixel data supplied in an interlaced manner and for generating a plurality of control signals; The polarity of the pixel data and the dummy pixel data from the timing controller is inverted by 2 dots vertically according to the first control signal from the timing controller and inverted by at least two frames. A data driver for supplying; The scan signal is supplied to the gate lines of the liquid crystal cell matrix according to the second control signal from the timing controller to turn on the liquid crystal cells to which the pixel data is to be supplied, and the liquid crystal cells to which the dummy pixel data are to be supplied. A liquid crystal display device comprising: supplying a gate driver to turn off. delete delete The method of claim 1, The data driver In the odd frame, the pixel data is supplied to an odd horizontal line of the liquid crystal panel, and the dummy pixel data is supplied to an even horizontal line. And the dummy pixel data is supplied to the odd horizontal line and the pixel data is supplied to the even horizontal line in an even frame. Adding dummy pixel data between pixel data input in an interlaced manner; Supplying the pixel data and the dummy pixel data to the liquid crystal panel such that the pixel data and the dummy pixel data are inverted by 2 dots vertically and in at least two frame units; And turning on corresponding liquid crystal cells in a period during which the pixel data is supplied to the liquid crystal panel, and turning off the liquid crystal cells in a period during which the dummy pixel data is supplied to the liquid crystal panel. Method of driving the device. delete delete The method of claim 5, In the odd frame, the pixel data is supplied to an odd horizontal line of the liquid crystal panel, and the dummy pixel data is supplied to an even horizontal line. The dummy pixel data is supplied to the odd horizontal line and the pixel data is supplied to the even horizontal line in an even frame.

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