KR20070109296A - Driving liquid crystal display and apparatus for driving the same - Google Patents

Abstract

An LCD device and a driving method thereof are provided to prevent unbalance of charge amounts by removing brightness difference generated between odd-number and even-number horizontal lines. An LCD(Liquid Crystal Display) device includes a liquid crystal panel(64), a gate driver(63) and a data driver(62). The liquid crystal panel includes plural data and gate lines, which are formed to cross with each other, and plural liquid crystal cells. The gate driver supplies a first scan pulse to odd-number gate lines and a second scan pulse, which is partially overlapped with the first scan pulse, to even-number gate lines. The data driver supplies data, whose polarity is periodically converted according to a predetermined polarity conversion pattern, to the data lines. The predetermined polarity conversion pattern is shifted for every frame so as to equalize summation of charge times during successive two frame periods between adjacent liquid crystal cells.

Description

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

1 is a view schematically showing the data polarity of a liquid crystal panel driven in a one dot inversion scheme.

FIG. 2 is a diagram schematically illustrating data polarity of a liquid crystal panel driven in a two dot inversion scheme. FIG.

3 is a diagram illustrating data polarity of a liquid crystal panel shifted in units of frames in a 2-dot inversion scheme;

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

5 is a block diagram illustrating a gate driving circuit according to an exemplary embodiment of the present invention.

6 is a waveform diagram of a scan pulse generated from a gate driving circuit.

7 is a block diagram illustrating a data driving circuit according to an exemplary embodiment of the present invention.

8 is a waveform diagram of a polarity signal shifted in units of frames supplied to a data driving circuit according to an exemplary embodiment of the present invention.

FIG. 9 illustrates a data output waveform in which polarity is shifted by one horizontal period in frame units and a gate output waveform overlapping by one horizontal period according to an overlap driving scheme according to an exemplary embodiment of the present invention.

10 is a waveform diagram of a polarity signal shifted in units of frames supplied to a data driving circuit according to another exemplary embodiment of the present invention.

FIG. 11 illustrates a data output waveform whose polarity is shifted by one horizontal period in frame units and a gate output waveform which is overlapped by one horizontal period according to an overlap driving scheme according to another embodiment of the present invention.

<Description of Symbols for Main Parts of Drawings>

61: timing controller 62: data driving circuit

63 gate driving circuit 64 liquid crystal panel

81: first latch 82: shift register

83: second latch 84: digital-to-analog converter

85: precharge voltage supply unit 86: buffer

1011 to 101n: level shifter

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 for improving display quality of a liquid crystal display device driven in an overlapping manner.

The liquid crystal display device displays an image by adjusting light transmittance of liquid crystal cells according to a video signal. In an active matrix type liquid crystal display, switching elements are formed in each liquid crystal cell, which is advantageous for displaying a moving image. As the switching device, a thin film transistor (hereinafter referred to as "TFT") is mainly used.

The LCD is driven in an inversion manner to reduce flicker and afterimage by periodically inverting the polarity of data charged in the liquid crystal cell. The inversion method includes a line inversion method for inverting polarities of data between adjacent liquid crystal cells in a vertical line direction, a column inversion method for inverting polarities of data between adjacent liquid crystal cells in a horizontal line direction, a vertical line direction and a horizontal line direction. There is a dot inversion method of inverting the polarity of data between adjacent liquid crystal cells. Of these inversion methods, the dot inversion method is mainly selected because flicker hardly appears in the vertical and horizontal directions.

In the dot inversion scheme, as illustrated in FIG. 1, polarities of data supplied to adjacent liquid crystal cells in the vertical direction are opposite to each other, and polarities of data supplied to adjacent liquid crystal cells in the horizontal direction are opposite to each other. The polarity of the data is inverted every frame (Fn-1, Fn). The dot inversion method is most widely used in liquid crystal display devices because flicker is minimized in both the vertical and horizontal directions.

The dot inversion scheme of FIG. 2 inverts the polarity of data in units of 2 dots in the vertical direction and in units of 1 dot in the horizontal direction. The vertical two-dot inversion method as shown in FIG. 2 has the advantage of lower power consumption than the one-dot inversion method as shown in FIG. The conventional liquid crystal display device driven according to the vertical two dot inversion scheme inverts the polarity of the data voltages supplied to the data lines (not shown) in two horizontal periods (2H) periods, and converts the data voltages into the source output enable signal. According to (Source Output Enable: SOE), data lines are supplied to data lines of a liquid crystal panel (not shown).

In addition, the conventional liquid crystal display device is driven according to the polarity signal POL shown in FIG. 3 to invert the polarity of data every frame Fn-1, Fn. As shown, when the vertical two-dot inversion method is used, the current frame (Nth Frame) has a polarity signal up or down by one horizontal period (2H) compared to the previous frame (N-1th Frame). On the vertical line).

However, in order to operate according to the inversion method, the conventional liquid crystal display device shifts the polarity signal up or down by 2 horizontal periods (2H) every frame, thereby causing an unbalance of charge between the odd and even horizontal lines. do. In particular, in the case of GIP (Gate-Drive-Ic In Panel) method in which the gate driving circuit is mounted on the glass substrate of the liquid crystal panel to reduce the circuit cost and the number of processes, the charging time should be increased to improve the charging characteristics. In this case, there is a problem that the charge amount imbalance is further deepened, leading to an increase in luminance difference between lines.

Accordingly, it is an object of the present invention to provide a liquid crystal display device and a driving method thereof to improve the display quality of the liquid crystal display device.

In addition, another object of the present invention is to provide a liquid crystal display device and a driving method thereof to improve the display quality of the liquid crystal display device driven according to the overlap method.

In order to achieve the above object, a liquid crystal display according to an embodiment of the present invention includes a liquid crystal panel in which a plurality of data lines and a plurality of gate lines intersect and a plurality of liquid crystal cells are disposed; A gate driving circuit configured to supply a first scan pulse to an odd gate line and a second scan pulse partially overlapping the first scan pulse to an even gate line; A data driving circuit for supplying data to the data lines whose polarities are periodically inverted along a predetermined polarity inversion pattern; The polarity inversion pattern is shifted in units of frame periods such that the sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells is the same.

The polarity inversion pattern is characterized in that the polarity is inverted every two horizontal periods.

The polarity inversion pattern is shifted by one horizontal period in one frame period.

Each of the first and second scan pulses is generated to maintain a high logic level for two horizontal periods, and the second scan pulses are generated to overlap the first scan pulse by one horizontal period.

The data driving circuit allows data to be filled in the odd-numbered liquid crystal cell of the n-th frame in response to the first scan pulse for one horizontal period, and in the even-numbered liquid crystal cell of the n-th frame in response to the second scan pulse. Allow data to be charged for two horizontal periods; Data is filled in the odd-numbered liquid crystal cell of the n + 1 th frame in response to the first scan pulse for two horizontal periods, and one horizontal in the even-numbered liquid crystal cell of the n + 1 th frame in response to the second scan pulse. Characterized in that data is charged for a period of time.

In addition, the driving method of the liquid crystal display according to the embodiment of the present invention is the step of supplying the first scan pulse to the odd gate line and the second scan pulse partially overlapping the first scan pulse to the even gate line Wow; Supplying data lines with data whose polarity is periodically inverted along a predetermined polarity inversion pattern;

The polarity inversion pattern may be shifted in units of frame periods such that the sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells is equal in the supplying of data.

In the supplying of the data, the polarity of the data may be inverted every two horizontal periods.

In the supplying of the data, the polarity inversion pattern is shifted by one horizontal period by one frame period.

In the supplying of the scan pulses, the first and second scan pulses are maintained at a high logic level for two horizontal periods, respectively, and the second scan pulses are supplied by overlapping the first scan pulses by one horizontal period. It is characterized by.

The supplying of data may include supplying data to an odd-numbered liquid crystal cell of an n-th frame for one horizontal period in response to the first scan pulse, and n-th frame for two horizontal periods in response to the second scan pulse. Supplying data to the even-numbered liquid crystal cell of the first step; Data is supplied to the odd-numbered liquid crystal cell of the n + 1 th frame in two horizontal periods in response to the first scan pulse, and the even-numbered liquid crystal cell of the n + 1 th frame in one horizontal period in response to the second scan pulse. And supplying data to the second step.

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

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 4 to 11.

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

Referring to FIG. 4, the liquid crystal display according to the exemplary embodiment of the present invention uses a data voltage whose polarity is reversed in a 2-dot inversion scheme in response to the control signal DDC from the timing controller 61. The scan pulse is supplied to the data driving circuit 62 for supplying the data lines D1 to Dm and the gate lines G1 to Gn of the liquid crystal panel 64 in response to the control signal GDC from the timing controller 61. ), And a timing controller 61 for controlling the data driving circuit 62 and the gate driving circuit 63.

Liquid crystal is injected between the two glass substrates, and the liquid crystal panel 64 is formed such that the data lines D1 to Dm and the gate lines G1 to Gn cross each other on the lower glass substrate. TFTs formed at the intersections of the data lines D1 to Dm and the gate lines G1 to Gn have data on the data lines D1 to Dm in response to scan pulses from the gate lines G1 to Gn. Is supplied to the liquid crystal cell Clc. For this purpose, the gate electrodes of the TFTs are connected to the gate lines G1 to Gn, and the source electrodes are connected to the data lines D1 to Dm. The drain electrode of the TFT is connected to the pixel electrode of the liquid crystal cell Clc. The common voltage Vcom is supplied to the common electrode facing the pixel electrode.

The data driving circuit 62 responds to the digital data RGB input from the timing controller 61 and the data lines D1 to Dm of the liquid crystal panel 64 in response to the control signal DDC input from the timing controller 61. ) Will be supplied. That is, the data driving circuit 62 generates data having the same polarity for two horizontal periods according to the polarity control signal POL included in the control signal DDC from the timing controller 61, and then reverses the polarity of the data. Inverts the polarities of horizontally neighboring data to each other. In addition, the data driving circuit 62 has a charging time for two consecutive frame periods between adjacent liquid crystal cells in accordance with the polarity control signal POL included in the control signal DDC from the timing controller 61. The polarity inversion pattern is shifted in units of frame periods so that the sum is equal. The data driving circuit 62 will be described in detail with reference to FIGS. 7 and 8.

The gate driving circuit 63 sequentially supplies scan pulses to the gate lines G1 to Gn in response to the control signal GDC from the timing controller 61. In particular, the gate driving circuit 63 takes an overlap driving method of supplying the first scan pulse to the odd-numbered gate line and supplying the second scan pulse partially overlapping the first scan pulse to the even-numbered gate line. do. The gate driving circuit 63 will be described in detail with reference to FIGS. 5 and 6.

The timing controller 61 controls the gate control signal GDC for controlling the gate driving circuit 63 and the data driving circuit 622 by using the vertical / horizontal synchronization signals V and H and the clock CLK. A data control signal DDC is generated. The data control signal DDC includes a source start pulse SSP, a source shift clock SSC, a source output signal SOE, a polarity signal POL, and the like. The gate control signal GDC includes a gate shift clock GSC, a gate output signal GOE, a gate start pulse GSP, and the like.

5 is a block diagram illustrating a gate driving circuit according to an exemplary embodiment of the present invention, and FIG. 6 is a waveform diagram of a scan pulse generated from the gate driving circuit.

Referring to FIG. 5, the gate driving circuit 63 includes a shift register 102 having a plurality of stages 1001 to 100n, and level shifters 1011 to 101n input to the shift register 102.

The first stage 1001 of the shift register 102 generates a scan pulse in response to the gate start pulse GSP and the gate shift clock GSC from the timing controller 61. The second to nth stages 1002 to 100n receive a voltage on the front gate lines G1 to Gn-1 as gate start pulses and sequentially generate scan pulses in response to the signal and the gate shift clock GSC. do. At this time, each scan pulse is generated to maintain a high logic level for two horizontal periods, and the first scan pulse supplied to the odd-numbered gate line and the second scan pulse supplied to the even-numbered gate line are overlapped for one horizontal period. Overlap). This overlap driving method is widely used as a method of increasing the charging time in order to improve the charging characteristics in the gate-drive-in panel (GIP) method in which the gate driving circuit is mounted on the glass substrate of the liquid crystal panel.

The level shifters 1011 to 101n are respectively connected to the output terminals of the shift register 102 to convert the swing width of each output signal of the shift register 102 into a swing width for driving the liquid crystal cell Clc. The scan pulses output from the level shifters 1011 to 101n have two voltage levels, Vgh and Vgl. A buffer may be provided between the level shifters 1011 to 101n and the gate lines G1 to Gn.

7 is a block diagram illustrating a data driving circuit according to an exemplary embodiment of the present invention, and FIG. 8 is a waveform diagram of a polarity signal shifted in units of frames supplied to the data driving circuit.

Referring to FIG. 7, the data driving circuit 62 includes a plurality of integrated circuits (ICs), each integrated circuit including a shift register 82 and a first latch (13) connected in a dependent manner between an input line and a data line. 81, a second latch 83, a digital-to-analog converter (hereinafter referred to as "DAC") 84, a precharge voltage supply 85 and a buffer 86.

The shift register 82 shifts the source start pulse SSP from the timing controller 61 in accordance with the source shift clock signal SSC to generate a sampling signal. In addition, the shift register 82 shifts the source start pulse SSP to transfer a carry signal CAR to the next stage shift register 82.

The first latch 81 samples and stores the digital data RGB according to the sampling signal input from the shift register 82, and supplies the stored digital data to the second latch 83.

The second latch 83 latches the data EFD and RGB input from the first latch 81 and then a second latch in another integrated circuit in response to the source output signal SOE from the timing controller 61. The digital data for one horizontal line latched together with 83 is simultaneously output.

The DAC 84 converts the digital data RGB from the second latch 83 to the positive analog data voltage VPG or the negative analog data voltage VNG according to the polarity signal POL from the timing controller 61. Convert to In response to the polarity signal POL from the timing controller 61, the DAC 84 generates data having the same polarity for two horizontal periods according to the vertical two-dot inversion scheme, and then reverses the polarity of the data and horizontally neighbors the data. Invert the polarities of the data. In addition, as shown in FIG. 8, the DAC 84 shifts the polarity signal POL from the timing controller 61, that is, the polarity inversion pattern (vertical two-dot inversion method) by one horizontal period every frame. The sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells is made equal.

The precharge voltage supply unit 85 supplies two horizontal periods to the second liquid crystal cell (eg, even-numbered liquid crystal cell in the N-1th frame and the odd-numbered liquid crystal cell in the Nth frame) having the same polarity. During the scan pulse supply period, the data supplied to the front end liquid crystal cell is precharged during the preceding one horizontal period. Accordingly, in the N-1th frame, the charging time of the even-numbered liquid crystal cells is increased to two horizontal periods, and in the N-th frame, the charging time of the odd-numbered liquid crystal cells is increased to two horizontal periods. As a result, the sum of the charging times during two consecutive frame periods between vertically neighboring liquid crystal cells becomes the same, and the charging characteristic in the GIP method is good.

The buffer 186 outputs the analog data voltages VPG and VNG input from the DAC 184 and the modulated data voltages input from the modulation voltage supply unit 85 to the data lines D1 to Dm without signal attenuation. .

In Fig. 7, reference numeral 'R' denotes a line resistance between the output terminal of the data driving circuit 62 and the data lines D1 to Dm.

9 is a diagram illustrating a data output waveform whose polarity is shifted by one horizontal period in frame units and a gate output waveform which is overlapped by one horizontal period according to an overlap driving scheme according to an exemplary embodiment of the present invention.

As shown in FIG. 9, the driving method of the liquid crystal display according to the exemplary embodiment of the present invention is one horizontal line of the polarity of the output waveform of the data whose polarity is inverted according to the vertical two-dot inversion method. Shift by period. Accordingly, the liquid crystal cells connected to the odd horizontal lines Hn and Hn + 2 have a charging time of one horizontal period in the N−1th frame but a charging time of two horizontal periods in the Nth frame. In addition, the liquid crystal cells connected to even-numbered horizontal lines Hn + 1 and Hn + 3 have a charging time of two horizontal periods in the N-1th frame but a charging time of one horizontal period in the Nth frame. As a result, the sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells becomes equal, and the even-numbered horizontal line (Hn, Hn + 2) and the even-numbered horizontal line (Hn + 1, Hn + 3) The problem of imbalance in the amount of charge generated in the liver is solved.

10 is a waveform diagram of a polarity signal shifted in units of frames supplied to a data driving circuit according to another exemplary embodiment of the present invention, and FIG. 11 is a polarity shifted by one horizontal period in units of frames according to another exemplary embodiment of the present invention. FIG. 1 is a diagram illustrating gate output waveforms overlapping by one horizontal period according to a data output waveform and an overlap driving scheme.

Referring to FIGS. 10 and 11, the driving method of the liquid crystal display according to another exemplary embodiment of the present invention shifts the polarity of the output waveform of the data whose polarity is inverted according to the vertical two-dot inversion method to the right whenever the frame is changed. 1 Shift by horizontal period.

 Accordingly, the liquid crystal cells connected to the odd horizontal lines Hn and Hn + 2 have a charging time of one horizontal period in the N−1th frame but a charging time of two horizontal periods in the Nth frame. In addition, the liquid crystal cells connected to even-numbered horizontal lines Hn + 1 and Hn + 3 have a charging time of two horizontal periods in the N-1th frame but a charging time of one horizontal period in the Nth frame. As a result, the sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells becomes equal, and the even-numbered horizontal line (Hn, Hn + 2) and the even-numbered horizontal line (Hn + 1, Hn + 3) The problem of imbalance in the amount of charge generated in the liver is solved.

As described above, the liquid crystal display device and the driving method thereof according to the embodiment of the present invention shift the polarity of the output waveform of the data whose polarity is inverted according to a predetermined polarity inversion pattern to the left or the right every time the frame is changed to be vertical. As a result, the sum of charging times during two consecutive frame periods between neighboring liquid crystal cells may be equal to solve the unbalance problem of charge amount generated between the odd-numbered horizontal line and the even-numbered horizontal line.

In addition, the liquid crystal display device and the driving method thereof according to the embodiment of the present invention can improve the display quality of the display device of the liquid crystal display device by eliminating the luminance difference between the lines generated between the odd-numbered horizontal line and the even-numbered horizontal line.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. For example, although the embodiment of the present invention has been described based on the two dot inversion method, N (where N is a positive integer of 2 or more) may also be applied to the dot inversion method. In addition, it may be applied to the non-GIP method as well as the GIP method. 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 (10)

A liquid crystal panel in which a plurality of data lines and a plurality of gate lines intersect and a plurality of liquid crystal cells are disposed; A gate driving circuit configured to supply a first scan pulse to an odd gate line and a second scan pulse partially overlapping the first scan pulse to an even gate line; A data driving circuit for supplying data to the data lines whose polarities are periodically inverted along a predetermined polarity inversion pattern; And the polarity inversion pattern is shifted in units of frame periods so that the sum of charge times during two consecutive frame periods between vertically neighboring liquid crystal cells is the same. The method of claim 1, And wherein the polarity inversion pattern is inverted in polarity every two horizontal periods. The method of claim 2, And the polarity inversion pattern is shifted by one horizontal period in one frame period. The method of claim 3, wherein Wherein the first and second scan pulses are generated to maintain a high logic level for two horizontal periods, respectively, and the second scan pulses are generated to overlap the first scan pulses by one horizontal period. . The method of claim 4, wherein The data driving circuit, The odd-numbered liquid crystal cell of the n-th frame is filled with data for one horizontal period in response to the first scan pulse, and the even-numbered liquid crystal cell of the n-th frame is filled with data for two horizontal periods in response to the second scan pulse. To be charged; Data is filled in the odd-numbered liquid crystal cell of the n + 1 th frame in response to the first scan pulse for two horizontal periods, and one horizontal in the even-numbered liquid crystal cell of the n + 1 th frame in response to the second scan pulse. Liquid crystal display characterized in that the data is to be charged during the period. Supplying a first scan pulse to an odd-numbered gate line and supplying a second scan pulse partially overlapping the first scan pulse to an even-numbered gate line; Supplying data lines with data whose polarity is periodically inverted along a predetermined polarity inversion pattern; The polarity inversion pattern is shifted in units of frame periods so that the sum of charging times for two consecutive frame periods between vertically neighboring liquid crystal cells is the same in the step of supplying the data. Driving method. The method of claim 6, In the step of supplying the data, And inverting the polarity of the data every two horizontal periods. The method of claim 7, wherein In the step of supplying the data, And the polarity inversion pattern is shifted by one horizontal period in one frame period. The method of claim 8, In the step of supplying the scan pulse, Driving the first and second scan pulses at a high logic level for two horizontal periods, and supplying the second scan pulses overlapping the first scan pulses for one horizontal period. Way. The method of claim 9, Supplying the data, Supply data to the even-numbered liquid crystal cell of the n-th frame in one horizontal period in response to the first scan pulse, and supply data to the even-numbered liquid crystal cell of the n-th frame in two horizontal periods in response to the second scan pulse. A first step of doing; Data is supplied to the odd-numbered liquid crystal cell of the n + 1 th frame in two horizontal periods in response to the first scan pulse, and the even-numbered liquid crystal cell of the n + 1 th frame in one horizontal period in response to the second scan pulse. And a second step of supplying data to the liquid crystal display device.

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