KR100495792B1 - A liquid crystal display having the capability of compensating for flikers by dajusting gamma reference voltages - Google Patents

Abstract

The present invention relates to a liquid crystal display device having a flicker compensation function.

A liquid crystal panel 1 having a plurality of pixels arranged in a matrix form; A gate driving circuit 2 sequentially scanning pixels of the liquid crystal panel one by one; A source driving circuit 3 generating a plurality of gray voltages based on a reference voltage, selecting the gray voltages according to input color signals, and applying the selected gray voltages to pixels on the scanned liquid crystal panel every scanning; and First and second gamma reference voltage generators 41 and 42 which generate two types of gamma reference voltages having different voltage levels and provide them as reference voltages to the source driving circuit.

By setting the gamma reference voltage so that the liquid crystal driving voltage to be applied to one pixel of the liquid crystal panel is smaller than the other, the level of the kickback voltage is made to be substantially equal to the level of the liquid crystal driving voltage applied to the left and right pixels of the liquid crystal panel. The effects of deviations can be reduced.

Description

A LIQUID CRYSTAL DISPLAY HAVING THE CAPABILITY OF COMPENSATING FOR FLIKERS BY DAJUSTING GAMMA REFERENCE VOLTAGES}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having flicker compensation, and more particularly, to a liquid crystal display using two gamma reference voltage generators to apply different gray voltages to the left and right sides of the liquid crystal panel. will be.

1 illustrates a configuration of a general liquid crystal display.

Referring to FIG. 1, the liquid crystal display includes a liquid crystal panel 1, a gate driving circuit 2, a source driving circuit 3, and a gamma reference voltage generator 4. The liquid crystal panel 1 has a plurality of pixels arranged in a matrix form. The gate driving circuit 2 sequentially scans the pixels of the liquid crystal panel 1 by one column. The source driving circuit 3 generates a liquid crystal driving voltage by performing digital / analog conversion on the reference voltage output from the gamma reference voltage generator 4 based on the color signal RGB, and generates the generated liquid crystal driving voltage. It is applied to the liquid crystal panel 1 every scanning. The gamma reference voltage generator 4 generates a voltage which is a reference for generating the liquid crystal driving voltage.

However, in the above-described general liquid crystal display device, as the liquid crystal panel becomes high resolution and large in size, a deviation in kickback voltage occurs on the left and right sides of the liquid crystal panel due to the resistance-capacitor delay (RC delay) of the gate signal. It is difficult to obtain a uniform degree of flicker over the left and right. Referring to FIG. 1, it can be seen that when the gate signal proceeds from left to right, the kickback voltage is greater than the pixels on the right side of the pixels on the left side of the liquid crystal panel. This is because the kickback voltage has a smaller signal delay and is larger as the gate voltage changes.

At present, since the flicker is usually set based on the center part of the panel in products developed and shipped, it is fundamentally impossible to obtain a liquid crystal display device of excellent quality.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned technical problems, and by setting different gamma reference voltages that are the basis for generating liquid crystal drive voltages to be applied to the left and right sides of the liquid crystal panel, a good uniform flicker can be obtained at the left and right sides of the panel. The object is to provide a liquid crystal display device that can be obtained.

The liquid crystal display device according to the present invention for achieving the above object,

A liquid crystal panel having a plurality of pixels arranged in a matrix form, a gate driving circuit sequentially scanning pixels of the liquid crystal panel one by one, and generating a plurality of gray scale voltages based on a reference voltage, A source driving circuit which selects a gray scale voltage and applies the selected gray scale voltage to the pixels on the scanned liquid crystal panel every scan, and generates two kinds of gamma reference voltages having different voltage levels, thereby generating a reference voltage to the source driving circuit. And first and second gamma reference voltage generators provided as reference, wherein the levels of the two types of gamma reference voltages are set to cancel the deviation of the left and right kickback voltages on the liquid crystal panel.

The objects, features and advantages of this invention described above will become more apparent from the following detailed description of the embodiments with reference to the drawings.

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

2A and 2B are configuration diagrams and graphs illustrating deviations in kickback voltage due to gate signal delay;

3 is a configuration diagram of a liquid crystal display device according to a first embodiment of the present invention;

4 is a configuration diagram of a gamma reference voltage generation circuit applied to the liquid crystal display according to the second embodiment of the present invention.

Fig. 2A shows each point of the lower left point ①, the upper left point ② and the upper right point ③ of the liquid crystal panel 1, and the gradation level measured at each point ①, ②, ③. The kickback voltage for is shown in Figure 2b. In Fig. 2A, reference numeral 2 is a gate driving circuit, and 3 is a source driving circuit.

The gate signal propagates from left to right in the liquid crystal panel of FIG. 2A, and the delay of the gate signal also acts in the same direction. That is, the delay of the gate signal is more severe in the pixel at the right point of the liquid crystal panel.

In general, the kickback voltage is larger as the degree of delay of the signal is smaller and the amount of change in the gate voltage is larger. Therefore, the kickback voltage at each pixel becomes smaller toward the right side of the panel in FIG. 2A. The graph of FIG. 2B illustrates this fact. It can be seen that the kickback voltage variation reaches 0.12V in the pixels on the left and right edges of the liquid crystal panel, and the kickback voltage variation hardly occurs in the pixels on the upper and lower edges. have.

Therefore, since it is necessary to adjust the gamma reference voltage so that the deviation of the kickback voltage is corrected, in the present invention, two liquid crystal driving voltages of the left and right sides of the liquid crystal panel are independently generated using two gamma reference voltage generators.

For example, if the kickback voltage is greater than the left side of the pixel on the right side of the liquid crystal panel, the liquid crystal applied to the left and right pixels of the liquid crystal panel by setting the gamma reference voltage so that the liquid crystal driving voltage to be applied to the left side pixel is smaller than the right side. Since the level of the driving voltage becomes substantially the same, it is possible to reduce the effect due to the deviation of the kickback voltage.

3 shows a liquid crystal display according to a first embodiment of the present invention.

The liquid crystal display according to the first embodiment includes a liquid crystal panel 1, a gate driving circuit 2, a source driving circuit 3, and first and second gamma reference voltage generators 41 and 42.

The liquid crystal panel 1 has a plurality of pixels arranged in a matrix form, and the gate driving circuit 2 sequentially scans the pixels of the liquid crystal panel 1 by one column.

The source driving circuit 3 generates a plurality of gray voltages based on the reference voltages provided from the gamma reference voltage generators 41 and 42, and selects the gray voltages according to the input color signal RGB. Each scanning is applied to the scanned pixels on the liquid crystal panel 1.

The first and second gamma reference voltage generators 41 and 42 generate a plurality of gamma reference voltages having different levels and provide them to the source driving circuit 3. The source driving circuit 3 generates two kinds of gradation voltages according to the two kinds of gamma reference voltages, and one kind of gradation voltages is used to drive pixels located in the left half of the liquid crystal panel 1. Another kind of gradation voltage is used to drive the pixel located in the right half portion on the liquid crystal panel 1.

In particular, as shown in Fig. 3, since the kickback voltage at the pixel located on the left side of the liquid crystal panel 1 is larger than the pixel located on the right side, the liquid crystal driving voltage applied to the left side needs to be smaller.

Accordingly, in generating the gamma reference voltage as a reference for generating the gray scale voltage, the level of the reference voltage output from the second gamma reference voltage generator 42 corresponds to the deviation of the kickback voltage on the left and right sides of the liquid crystal panel 1. One gamma reference voltage generator 41 is set to be lower than the level of the reference voltage output.

Here, the reference voltage output from the second gamma reference voltage generator 42 serves as a basis for generating a gray scale voltage for driving the left pixel of the liquid crystal panel 1. Since the first and second gamma reference voltage generators 41 and 42 are implemented by a resistor string, the level setting of the reference voltage can be achieved simply by adjusting the ratio of the resistance values.

When the method according to the first embodiment is applied, there is a fear that a stitch defect occurs at the central portion of the liquid crystal panel 1. This is because the levels of the gradation voltages applied to the left and right pixels of the panel 1 are different.

In order to reduce such defects, the conditions of the manufacturing process on the left and right sides of the panel 1 should be made different. More specifically, when performing the photoresist process for forming the pattern, the luminance properties on the left and right sides of the panel 1 should be adjusted to offset the brightness difference caused by the difference in the level of the gray voltage due to the difference in kickback voltage. This adjustment can be accomplished by fine tuning.

Another way of reducing the difference in brightness at the central interface of the liquid crystal panel 1 is disclosed in the second embodiment of the present invention.

According to the second embodiment of the present invention, a separate gamma reference voltage is generated for driving the pixel of the central portion of the liquid crystal panel 1, and the reference voltage is generated by the first and second gamma reference voltage generators 41,. The outputs of 42 are alternately produced one after the other.

4 shows a gamma reference voltage generator circuit according to a second embodiment of the present invention.

The gamma reference voltage generator circuit according to the second embodiment includes a first gamma reference voltage generator 41, a second gamma reference voltage generator 42, and a buffer 43.

The first gamma reference voltage generator 41 generates a plurality of gamma reference voltages GA1 to GAn for the left line of the liquid crystal panel 1, and the second gamma reference voltage generator 42 generates the gamma reference voltage for the right line. Generate a large number of (GB1-GBn).

The buffer 43 inputs odd-numbered voltages GA2n-1 among the outputs of the first gamma reference voltage generator 41 and even-numbered voltages GB2n among the outputs of the second gamma reference voltage generator 42. They are then alternately arranged one by one and output as a gamma reference voltage for the intermediate line.

Therefore, the output of the buffer 43 is provided to the source driving circuit and used to drive the pixel of the center portion of the liquid crystal panel 1, and the brightness of the left and right grayscales becomes intermediate, so that a sudden difference in brightness may be canceled out. .

In the gamma reference voltage generation circuit according to the second embodiment of the present invention, when a technology of embedding a resistor string in an integrated circuit chip is easy to manufacture by embedding a buffer, a space and a manufacturing cost of a liquid crystal display module can be obtained. It is very advantageous in saving.

As described above, the liquid crystal display according to the present invention sets the gamma reference voltage so that the liquid crystal driving voltage to be applied to one pixel of the liquid crystal panel is smaller than the other liquid crystal applied to the left and right pixels of the liquid crystal panel. By making the level of the driving voltage substantially the same, it is possible to reduce the influence due to the deviation of the kickback voltage.

Although this invention has been described with reference to the most practical and preferred embodiments, the invention is not limited to the embodiments disclosed above, but also includes various modifications and equivalents which fall within the scope of the following claims.

1 is a configuration diagram of a general liquid crystal display device.

2A and 2B are configuration diagrams and graphs illustrating variation in kickback voltage due to gate signal delay.

3 is a configuration diagram of a liquid crystal display device according to a first embodiment of the present invention.

4 is a configuration diagram of a gamma reference voltage generation circuit applied to the liquid crystal display according to the second embodiment of the present invention.

Claims (3)

A liquid crystal panel having a plurality of pixels arranged in a matrix form; A gate driving circuit sequentially scanning pixels of the liquid crystal panel one by one; A source driving circuit which generates a plurality of gray voltages based on a reference voltage, selects the gray voltages according to the input color signal, and applies the selected gray voltages to the pixels on the scanned liquid crystal panel every scanning; First and second gamma reference voltage generators comprising a resistor string and generating two types of gamma reference voltages having different voltage levels by adjusting a ratio of resistance values of the resistor strings, and providing the source voltage to the source driving circuit as a reference voltage. Include, The liquid crystal panel is divided into a left half and a right half, and a half formed at a position far from the gate driving circuit in the liquid crystal panel is called a first half, and a second half formed at a position close to the gate driving circuit. time, The first gamma reference voltage generator generates a reference voltage for driving the pixels of the first half portion, the second gamma reference voltage generator generates a reference voltage for driving the pixels of the second half portion, The level of the two types of gamma reference voltage is set to cancel the deviation of the left and right kickback voltage on the liquid crystal panel, Liquid crystal display. The method of claim 1, The first half and the second half of the liquid crystal panel are manufactured under different process conditions, and the left and right brightness attributes are adjusted to cancel the brightness difference due to the deviation of the kickback voltage. Liquid crystal display. The method according to claim 1 or 2, The odd-numbered voltage among the outputs of the first gamma reference voltage generator and the even-numbered voltage among the outputs of the second gamma reference voltage generator are input, and both are alternately arranged one by one so that the first half and the second of the liquid crystal panel are alternately arranged. And further including a buffer which serves as a gamma reference voltage for driving the pixels of the portions in contact with the halves. Liquid crystal display.

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