CN1632647A - Liquid crystal display and display method thereof - Google Patents

Abstract

A liquid crystal display and a display method thereof. The liquid crystal display comprises a display panel, an adjusting circuit and a driving circuit. The display panel is provided with a common electrode. The adjusting circuit is electrically connected with the common electrode and outputs a distribution parameter according to the voltage distribution of the common electrode voltage on the common electrode. The driving circuit receives the distribution parameters and drives the display panel accordingly. The adjusting circuit further comprises a voltage comparator and a compensating circuit. The voltage comparator is used for measuring the voltage difference between two ends of the common electrode. The compensation circuit obtains a distribution parameter according to the voltage difference.

Description

Liquid crystal display and display method thereof

technical field

The invention relates to a liquid crystal display and a display method thereof, in particular to a liquid crystal display and a display method thereof for compensating the voltage offset of a common electrode.

Background technique

A general liquid crystal panel has a common electrode (Common electrode), a pixel electrode (Pixel electrode) and a liquid crystal layer located between the common electrode and the pixel electrode. By applying the common electrode voltage to the common electrode and the pixel voltage to the pixel electrode, the light transmittance of the liquid crystal layer can be changed by using the voltage difference between the common electrode and the pixel electrode.

The light transmittance of the liquid crystal layer is related to the magnitude of the voltage difference between the common electrode and the pixel electrode, but has nothing to do with the polarity of the voltage difference. If the voltage of the same polarity is continuously applied to the liquid crystal layer, the problem of image stiffness is likely to occur, so the polarity reversal is generally used to avoid this problem. As shown in FIG. 1 , it shows a graph showing the relationship between the pixel voltage V and the light transmittance I of liquid crystal molecules. Both the positive polarity pixel voltage Vp and the negative polarity pixel voltage Vn symmetrical to the common electrode voltage level Vcom can achieve the same light transmittance Ix. Therefore, the problem of image stiffness can be avoided by alternately driving the liquid crystal layer with voltages of different polarities by inverting the polarity.

However, the common electrode still has impedance, so that the common electrode voltage at each point on the common electrode will not maintain the same common electrode voltage level Vcom. Therefore, the positive and negative pixel voltages on the pixel electrodes, such as the aforementioned Vp and Vn, do not cause the same voltage difference on the liquid crystal layer. This will cause the actual voltage difference between the common electrode and the pixel electrode to be different from the predetermined target voltage difference, which will cause problems of image stiffness and flickering, and lower display quality.

Contents of the invention

In view of this, the object of the present invention is to provide a liquid crystal display and a display method thereof, so as to solve the problem caused by the attenuation of the common electrode voltage.

According to an object of the present invention, a display method of a liquid crystal display is provided. A liquid crystal display includes a display panel and a driving circuit. The display panel has common electrodes. The display method is described below. The distribution parameter is output according to the voltage distribution of the common electrode voltage on the common electrode. The driving circuit drives the display panel according to the distribution parameters. In the step of outputting the distribution parameters, the distribution parameters are obtained by measuring a voltage difference between the two ends of the common electrode.

According to another object of the present invention, a liquid crystal display is provided, which includes a display panel, an adjustment circuit and a driving circuit. The display panel has common electrodes. The adjustment circuit is electrically connected with the common electrode, and outputs a distribution parameter according to a voltage distribution of a common electrode voltage on the common electrode. The driving circuit receives the distributed parameters and drives the display panel accordingly. The adjustment circuit further includes a voltage comparator and a compensation circuit. The voltage comparator is used to measure the voltage difference between the two ends of the common electrode. The compensation circuit obtains distribution parameters according to the voltage difference.

In order to make the above-mentioned purpose, features, and advantages of the present invention more comprehensible, a preferred embodiment will be described in detail below together with the accompanying drawings.

Description of drawings

FIG. 1 is a graph showing the relationship between pixel voltage V and light transmittance I of liquid crystal molecules.

FIG. 2 is a flowchart of a display method of a liquid crystal display according to a preferred embodiment of the present invention.

FIG. 3 is a block diagram of a liquid crystal display according to a preferred embodiment of the present invention.

FIG. 4 is a graph showing the relationship between positive and negative polarity pixel voltages and common electrode voltage levels.

FIG. 5 is a schematic diagram showing the voltage distribution of the common electrode on the common electrode.

FIG. 6 is a block diagram of a liquid crystal display according to another preferred embodiment of the present invention.

FIG. 7 is a graph showing the relationship between pixel voltage and gray scale value.

Description of reference symbols

200, 400: LCD display

202: display panel

204, 404: Adjustment circuit

206, 406: timing control circuit

208(1)-208(N): driver chip

210: common electrode

212, 412: voltage comparator

214, 414: compensation circuit

216, 416: drive circuit

218: Voltage regulator

Detailed ways

Please refer to FIG. 2 , which shows a flow chart of a display method of a liquid crystal display according to a preferred embodiment of the present invention. First, enter step 602, measure the voltage difference between the two ends of the common electrode. Next, enter step 604, and obtain distribution parameters according to the voltage difference. Finally, enter step 606 to drive the display panel according to the distribution parameters. Furthermore, the driving circuit of the liquid crystal display adjusts the gray scale value according to the distribution parameters and drives the liquid crystal display panel of the liquid crystal display accordingly. Alternatively, when the driving circuit has multiple driving chips, each driving chip can adjust the grayscale value according to the distribution parameters to compensate for the attenuation of the common electrode voltage, because each driving chip corresponds to a group of gamma voltages. Therefore, without changing the gray scale value, the driving circuit can adjust these groups of gamma voltages according to the distribution parameters, so that each driving chip can drive the display panel according to the adjusted gamma voltage to compensate for the attenuation of the common electrode voltage . Therefore, the problem caused by the attenuation of the common electrode voltage in the traditional display process can be solved no matter by adjusting the gray scale value or the gamma voltage.

Further, please refer to FIG. 3 , which shows a block diagram of a liquid crystal display according to a preferred embodiment of the present invention. The liquid crystal display 200 includes a liquid crystal display panel 202 , an adjustment circuit 204 and a driving circuit 216 . The liquid crystal display panel 202 has a common electrode 210 . The adjustment circuit 204 includes a voltage comparator 212 and a compensation circuit 214 . The voltage comparator 212 is electrically connected to the common electrode 210 and used for measuring the voltage difference ΔV between the two ends of the common electrode 210 , such as point A and point B. The compensation circuit 214 outputs the distribution parameter ADJ according to the voltage difference ΔV. The driving circuit 216 further includes a timing control circuit 206 and a plurality of driving chips 208(1)-208(N). The timing control circuit 206 receives the pixel data data and generates a plurality of grayscale values G(1)-G(N) according to the distribution parameter ADJ. Each driver chip 208(1)-208(N) corresponds to a set of gamma voltages. Each group of gamma voltages represents a gamma curve. For example, the driver chip 208(1) refers to the corresponding gamma curve (not shown in FIG. 3 ) according to the received gray scale value G(1), for example, 1 to generate corresponding pixel voltages to drive the liquid crystal display panel 202.

Assume that the pixel corresponding to point A of the common electrode 210 is P(A) (not marked in FIG. 3 ), and the pixel corresponding to point B is P(B) (not marked in FIG. 3 ). Traditionally, to make the pixels P(A) and P(B) display the same brightness, for example, the brightness corresponds to a certain grayscale value GX, the corresponding driver chips, such as 208(1) and 208(N ), to drive the pixels P(A) and P(B) to produce the same brightness according to the gray scale value GX. That is, both pixels P(A) and P(B) are driven by the same pixel voltage (positive polarity pixel voltage Vp(GX) and negative polarity pixel voltage Vn(GX)), ideally, pixels P(A), P(B) shows the same brightness.

Please also refer to FIG. 4 , which shows the relationship between positive and negative polarity pixel voltages and common electrode voltage levels. However, since the two ends of the common electrode 210 have a voltage difference ΔV, the common electrode voltage corresponding to the pixel P(A) is the common electrode voltage level Vcom, and the common electrode voltage corresponding to the pixel P(B) is the common electrode voltage level Vcom. The voltage difference ΔV is subtracted from the flat Vcom, that is, Vcom-ΔV. Therefore, the positive polarity voltage difference (Vp(GX)-Vcom) and the negative polarity voltage difference (Vcom-Vn(GX)) of the pixel P(A) have the same absolute value, so the positive polarity voltage Vp(GX) and the negative polarity voltage Vn(GX) will produce the same light transmittance at pixel P(A).

However, if the same positive polarity pixel voltage Vp(GX) is applied to the pixel P(B), the positive polarity voltage difference of the pixel P(B) is (Vp(GX)-Vcom+ΔV), compared to the pixel P(A) The positive polarity voltage difference is also higher by ΔV, so the pixel P(B) will be brighter than the pixel P(A); if the negative polarity pixel voltage Vn(GX) is applied to the pixel P(B), the negative polarity voltage difference is (Vcom -ΔV-Vn(GX)), which is ΔV less than the negative polarity voltage difference of the pixel P(A), so the pixel P(B) will be darker than the pixel P(A). In this way, when the polarity is reversed, problems of flickering and image stiffness will occur.

Therefore, the spirit of the embodiments of the present invention is to adjust the pixel voltage corresponding to each pixel on the display panel according to the voltage distribution of the common electrode voltage on the common electrode 210 . That is, the positive polarity voltage difference and the negative polarity voltage difference of the pixel P(B) are adjusted to be the same. As shown in Figure 4, adjust the positive polarity pixel voltage of pixel P(B) to Vp'(GX)=(Vp(GX)-ΔV); adjust the negative polarity pixel voltage to Vn'(GX)=(Vn( GX)-ΔV), that is, the positive polarity voltage difference and the negative polarity voltage difference of the pixel P(B) are the same, so as to solve the problem caused by the common electrode voltage attenuation in the traditional display process.

Further, please refer to FIG. 5 , which is a schematic diagram showing the distribution of the common electrode voltage on the common electrode. The vertical axis is the common electrode voltage in volt V, and the horizontal axis is the position of each point on the common electrode 210 . At point A of the common electrode 210 , the measured common electrode voltage is the common electrode voltage level Vcom, and the measured common electrode voltage at the other end of the point B is (Vcom-ΔV). Therefore, the common electrode voltage (X) corresponding to any point X between point A and point B can be estimated by the slope L, that is:

Common electrode voltage (X)＝Vcom-ΔV*D(X, A)/D(B, A) (1)

Among them, D is a distance function, D(X, A) represents the distance from X to A, and D(B, A) represents the distance from B to A. For example, point C is located in the middle of point A and point B, therefore, its common electrode voltage is (Vcom-ΔV/2). Therefore, the voltage difference ΔV between the two ends of the common electrode 210, point A and point B, is measured by the voltage comparator 212, and then the common electrode voltage change in the horizontal direction of the common electrode 210 can be obtained by the compensation circuit 214 according to the voltage difference ΔV. The slope, and based on this, the offset of the common electrode voltage at each point is obtained, that is, the distribution parameter ADJ. In this embodiment, only the voltage change in the horizontal direction of the common electrode 210 is measured, and the voltage change in the vertical direction is very small, which is assumed to be zero and not considered. However, the spirit of the present invention can still easily take the voltage variation in the horizontal direction and the vertical direction into consideration, which will not be repeated here.

Therefore, after obtaining the offset of the common electrode voltage at each point, compensation can be performed accordingly, so that when the common electrode voltage of the pixel P(B) is offset, the positive polarity voltage difference of the pixel voltage is equal to The negative polarity voltage difference still maintains the same magnitude. Therefore, the shift of the common electrode voltage of the common electrode 210 is compensated by adjusting the output gray scale value G by the timing control circuit 206 .

Then, the compensation method of the gray scale value will be described in detail. In the display panel 202 of this embodiment, the pixel voltage of the driving pixel and the voltage difference of the common electrode are 0, and the brightness of the pixel is the largest as an example for illustration. Since the positive polarity pixel voltage of pixel P(B) needs to be Vp'(GX)=(Vp(GX)-ΔV), this value is smaller than Vp(GX), so the grayscale value GX corresponding to pixel P(B) should be The increase is (GX+Δg), where Δg is determined corresponding to the voltage difference ΔV. In addition, the negative polarity pixel voltage of pixel P(B) needs to be Vn'(GX)=(Vn(GX)-ΔV), the absolute value of this value is larger than Vn(GX), so the corresponding grayscale value GX should be reduced is (GX-Δg). Therefore, corresponding to the pixel P(B), the timing control circuit 206 outputs different gray scale values (GX+Δg) and (GX-Δg) according to the voltage difference ΔV of points A and B in positive and negative polarities, so as to adjust The positive and negative pixel voltages Vp'(GX) and Vn'(GX) of the pixel P(B) after the offset are symmetrical to the common electrode voltage after the offset is Vcom-ΔV, and then the pixel P(B) and the pixel P( A) shows the same brightness.

Let's take the compensation method of the gamma curve as an example to illustrate. Please refer to FIG. 6 , which shows a block diagram of a liquid crystal display according to another preferred embodiment of the present invention. The liquid crystal display 400 includes a display panel 202 , an adjustment circuit 404 and a driving circuit 416 . The display panel 202 has a common electrode 210 . The adjustment circuit 204 includes a voltage comparator 412 and a compensation circuit 414 . The voltage comparator 412 is electrically connected to the common electrode 210 and used for measuring the voltage difference ΔV between the two ends of the common electrode 210 , such as point A and point B. The compensation circuit 414 outputs the distribution parameter ADJ' according to the voltage difference ΔV. The driving circuit 416 further includes a timing control circuit 406, a plurality of driving chips 208(1)-208(N) and voltage regulators 218(1)-218(N). Since each driver chip 208(1)-218(N) receives a set of gamma voltages, and the driver chips 208(1)-218(N) are based on the corresponding gamma curve g(1)-g(N) and Grayscale values G(1)-G(N) to output pixel voltage. Therefore, by changing the gamma voltage received by each driver chip 208(1)-208(N), the pixel voltage can be changed without adjusting the gray scale value G(1)-G(N), so as to control the common The electrode voltage offset is compensated. Therefore, an approach utilizing gamma voltage compensation is applicable to the LCD 400 with multiple driver chips 208(1)-208(N). Each driver chip 208(1)-208(N) is used to drive multiple rows of data lines, for example, the driver chip 208(1) is used to drive the first area of the display panel 202, which includes data lines 1- 384 (not shown in FIG. 6 ), the driver chip 208 (2) is used to drive the second area of the display panel 202, which includes, for example, data lines 385-769 (not shown in FIG. 6 ), and so on, Each driver chip 208 drives a different area. The offset of the common electrode voltage in each area can be obtained from the average value of the offset of the common electrode voltage in the area.

Please refer to FIG. 7 , which shows the relationship between the pixel voltage and the gray scale value, the vertical axis represents the gray scale value G, and the horizontal axis represents the pixel voltage in volt V. Taking the gamma curve g(1) as an example, it is the curve before adjustment, and it is symmetrical to the common electrode voltage level Vcom. In this example, it is applicable to the first area, that is, the area where point A is located, and its area The average value of the offset of the inner common electrode voltage is assumed to be 0. When the grayscale value G is assumed to be GX, the positive polarity pixel voltage of the pixel P(A) is Vp(GX), and the negative polarity pixel voltage is Vn(GX). The gamma curve g(N) is used for the Nth area, such as the area of the pixel P(B), and the average value of the offset of the common electrode voltage in the area is assumed to be ΔV'. When the gray scale value G is GX, the voltage comparator 212 is based on the voltage difference ΔV between the two terminals (A, B). ΔV' is calculated via the compensation circuit 214 to obtain the adjustment parameter ADJ'. The voltage regulator 218(N) outputs the compensated one-resistance gamma voltage according to the adjustment parameter ADJ' as the gamma curve g(N), so as to compensate the positive polarity pixel voltage of the pixel P(B) as Vp'=Vp-ΔV ', the negative polarity pixel voltage is Vn'=Vn-ΔV'. Therefore, the positive and negative polarity voltages Vp', Vn' of the pixel P(B) can still be symmetrical to the shifted common electrode voltage.

In the liquid crystal display and its display method disclosed in the above-mentioned embodiments of the present invention, a distribution parameter can be obtained from the voltage difference of the common electrode voltage on the common electrode, and gray scale value compensation or gamma curve compensation can be performed accordingly. In this way, pixel voltages with different adjustment ranges are obtained for different offsets of the common voltage at each position of the display panel to compensate for the offset of the common electrode voltage. Therefore, the present invention can effectively improve the problem of flickering or image rigidity of the liquid crystal screen.

In summary, although the present invention has been disclosed as above with a preferred embodiment, it is not intended to limit the present invention. Anyone skilled in this art can make various modifications without departing from the spirit and scope of the present invention. Changes and modifications, so the scope of protection of the present invention should be defined by the scope of the appended patent application.

Claims (10)

1. A liquid crystal display, comprising: A display panel has a common electrode; an adjustment circuit, electrically connected to the common electrode, and outputs a distribution parameter according to a voltage distribution of a common electrode voltage on the common electrode; and A drive circuit receives the distribution parameters and drives the display panel accordingly. 2. The liquid crystal display as claimed in claim 1, wherein the adjustment circuit comprises: a voltage comparator for measuring a voltage difference across the common electrode; and A compensation circuit obtains the distribution parameter according to the voltage difference. 3. The liquid crystal display as claimed in claim 1, wherein the driving circuit adjusts a plurality of grayscale values according to the distribution parameters, and the driving circuit drives the liquid crystal display panel according to the grayscale values. 4. The liquid crystal display as claimed in claim 1, wherein, the driving circuit further comprises a plurality of driving chips, each of the driving chips corresponds to a group of gamma voltages, and each of the driving chips is based on the corresponding group of gamma voltages and The corresponding multiple grayscale values are used to drive the liquid crystal display panel. 5. The liquid crystal display as claimed in claim 4, wherein the driving circuit further comprises a plurality of voltage regulators, the voltage regulators are electrically connected to the corresponding driving chips, and the voltage regulators are based on the distribution parameters to adjust the set of gamma voltages corresponding to the driver chips. 6. A display method of a liquid crystal display, the liquid crystal display comprising a display panel and a drive circuit, the display panel having a common electrode, the method comprising: outputting a distribution parameter according to a voltage distribution of a common electrode voltage on the common electrode; and The driving circuit drives the display panel according to the distribution parameters. 7. The method as claimed in claim 6, wherein, in the step of outputting the distribution parameter, the distribution parameter is obtained by measuring a voltage difference between two ends of the common electrode. 8. The method according to claim 6, wherein, in the step of driving the display panel, the driving circuit adjusts a plurality of grayscale values according to the distribution parameters, and the driving circuit drives the display panel according to the grayscale values display panel. 9. The method of claim 6, wherein the driving circuit further comprises a plurality of driving chips, and each of the driving chips corresponds to a set of gamma voltages. 10. The method according to claim 9, wherein the driving circuit further comprises a plurality of voltage regulators, and in the step of driving the display panel, the voltage regulators adjust the voltage of the driving chip according to the distribution parameters. Each corresponding to the set of gamma voltages.

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