KR100516049B1 - Driving device of liquid crystal display panel - Google Patents

Abstract

The liquid crystal display panel driver of the present invention processes a source driver for supplying a data voltage to a source electrode of a thin film transistor, a gate driver for supplying a gate-on voltage to a gate electrode of a thin film transistor, and a data voltage applied to the source driver. And a data processing unit. In the data processing unit, a data voltage having a positive value and a data voltage having a negative value are processed differently with respect to a common voltage, and then the processed data voltage is supplied to the source driving unit to supply a positive value due to the kickback voltage. Compensates for the difference between the data voltage and the negative data voltage.

Description

Driving device of liquid crystal display panel

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a device and method for driving a liquid crystal display panel (LCD), and more particularly, to an apparatus for preventing flicker of an LCD panel through signal processing of a data voltage. It is about a method.

An LCD is a display device that obtains a desired image signal by applying an electric field to a liquid crystal material having an anisotropic dielectric constant injected between two substrates, and controlling the amount of light transmitted through the substrate by adjusting the intensity of the electric field.

A plurality of gate lines parallel to each other and a plurality of data lines insulated from and intersecting the gate lines are formed on the substrate of the LCD, and an area surrounded by the gate lines and the data lines forms one pixel. A thin film transistor (hereinafter referred to as TFT) is formed at a portion where the gate line and the data line cross each other, and a gate electrode, a source electrode, and a drain electrode are connected to the gate, source, and drain of the TFT, respectively. A pixel electrode is connected to the drain electrode, and a liquid crystal material is injected between the pixel electrode and the opposite substrate on which the pixel electrode is formed.

Referring to the operation of the LCD panel as follows.

First, the TFT is turned on by applying a gate-on voltage to a gate electrode connected to the gate line to be displayed, and then a data voltage representing an image signal is applied to the source electrode to apply the data voltage to the drain electrode. Then, the data voltage is transmitted to the pixel electrode, and an electric field is formed by the potential difference between the pixel electrode and the common electrode. The intensity of this electric field is controlled by the magnitude of the data voltage, and the amount of light transmitted to the substrate is controlled by the intensity of this electric field.

In this case, since the liquid crystal deteriorates when the electric field is continuously applied in the same direction to the liquid crystal material between the pixel electrode and the counter substrate, the direction of the electric field must be continuously changed. That is, the pixel electrode voltage (data voltage) values of the common electrode voltage of the liquid crystal display should be alternating between positive and negative (hereinafter, referred to as 'positive voltage' or 'negative voltage').

1 shows an equivalent circuit of one pixel of an LCD panel.

As shown in FIG. 1, the liquid crystal capacitor Ccl is formed between the pixel electrode and the common electrode, and the storage capacitor Cst is formed between the pixel electrode and the front gate line. In addition, parasitic capacitance Cgd due to misalignment of the gate electrode and the drain electrode is generated. The liquid crystal capacitor Ccl and the storage capacitor Cst act as loads that the TFT LCD should drive.

Therefore, when the TFT is turned on by the gate-on voltage, the data voltage applied to the source of the TFT is applied to the liquid crystal capacitor Ccl and the storage capacitor Cst through the drain. At this time, the applied voltage must be maintained even after the TFT is turned off, but the parasitic capacitance between the gate and the drain causes the data voltage to be distorted by Vk. This Vk is calculated | required by the following formula.

Vk = {Cgd · ΔVg} / {Cgd + Cst + Clc}

Here, ΔVg means the amount of change in the gate voltage.

This voltage distortion always acts in the direction of bringing down the voltage of the pixel electrode regardless of the polarity of the data voltage. Such a data voltage distortion Vk is called a kickback voltage, and this kickback voltage is a cause of flicker generation as described later.

As mentioned above, in order to prevent deterioration of the liquid crystal, the LCD panel needs to drive the image signal to repeat the positive and negative with respect to the common electrode. 2 illustrates a conventional inversion driving method.

As shown in Fig. 2, for black data which is the same image signal, a positive black data voltage 000 (assuming that the data signal is 3 bits) is applied to the liquid crystal when the gate of the TFT is turned on in the first frame. In the second frame, the negative black data voltage 000 is applied when the gate of the TFT is turned on. That is, in the first frame, a voltage as large as V3 is applied to the common electrode, and in the second frame, a voltage as small as V4 is applied to the common electrode. At this time, since V3 and V4 are related to the same image signal, V3 = V4.

In this case, when the gate of the TFT is turned off, kickback voltages Vk1 and Vk2 are generated by the parasitic capacitance Cgd between the drain and gate of the TFT, and the voltage drops by the kickback voltages Vk1 and Vk2. Will be generated. As a result, a positive V1 voltage is applied to the pixel electrode in the first frame, and a negative V2 voltage is applied to the pixel electrode in the second frame. In this case, since the value of V2 is larger than V1, the voltage difference applied to the pixel is different, and thus the electric field applied to the liquid crystal when driving the image signal with a positive voltage and when driving with a negative voltage is different. There is a problem that flicker occurs.

The present invention solves the problems of the conventional inversion driving method as described above, and compensates for the difference between the positive data voltage and the negative data voltage caused by the kickback voltage when driving each image signal in the inversion method. This is to prevent the flicker by adding the kickback compensation voltage to the data voltage and correcting the voltage difference according to the kickback voltage.

According to the liquid crystal display panel driving apparatus of the present invention for achieving the above object, the positive and negative voltages are alternately driven to the liquid crystal for the same image signal, and the data voltage is supplied to the source electrode of the thin film transistor. A source driver, a gate driver for supplying a gate-on voltage to the gate electrode of the thin film transistor, and a positive data voltage and a negative data voltage for the same image signal differently, and then processing the processed data voltage into the source driver. And a data processor for supplying a signal to compensate for a difference between a positive data voltage and a negative data voltage due to a kickback voltage, thereby equalizing the positive voltage and the negative voltage with respect to the same image signal. A buffer unit to which the image signal is input, a switching connected to the buffer unit And a test table selectively connected to the buffer unit through the switching unit and storing a kickback compensation value for each image signal.

In this case, the test table may store a kickback voltage compensation value for one polarity or a kickback voltage compensation value for each polarity.

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

3 is a view showing a driving method of the LCD panel according to an embodiment of the present invention. As shown in Fig. 3, the positive black data voltage 000 is applied to the same black image signal when the gate of the TFT is turned on in the first frame. In this case, when the gate is turned off, the voltage drop by the kickback voltage Vk5 due to the parasitic capacitance between the gate and the drain is generated so that the voltage finally applied to the pixel becomes V5.

In the second frame, when the same image data applied to the first frame is applied at a negative voltage when the gate of the TFT is turned on, for example, 001 that is not the same data as the black data voltage 000 of the first frame. Apply a data signal of. In other words, a voltage V8 different from the voltage V5 applied in the first frame is applied. Then, when the gate of the TFT is turned off, such a voltage drop is caused by the kickback voltage Vk6 so that the voltage finally applied to the pixel becomes a negative voltage V6 compared to the common electrode. Therefore, the data signal of 001, that is, V8 can be adjusted appropriately so that V5 = V6.

That is, in the present invention, the positive data voltage and the negative data voltage are differently processed with respect to the same image signal, and then the processed data voltage is supplied to the source driving unit so that the positive data voltage and the negative data voltage of the kickback voltage The difference is compensated so that the voltage finally applied to the pixel is the same. At this time, the positive data value and the negative data value processed differ from the black image signal to the white image signal for each image signal, which can be accurately calculated by measuring the kickback voltage Vk for each image signal of the TFT panel. Can be.

4 is a diagram illustrating an example of a circuit block diagram for implementing the signal driving method of FIG. 3. As shown in FIG. 4, the gate driver 30 for supplying a gate on-off voltage to the gate electrode of the LCD panel 10 and the source driver 20 for applying a data voltage to the source electrode of the LCD panel 10. ) Is provided. The gate driver 30 receives a Von voltage for driving the gate on, a Voff voltage for turning off the gate, and a common voltage Vcom serving as a reference voltage from the Von Voff Vcom generator 50.

The image signal applied from the graphic controller (not shown) is transmitted to the source driver 20 through the data processor 40. The image signal is subjected to data processing by the data processing unit 40, so that a case where a positive voltage is applied to the liquid crystal and a case where a negative voltage is applied to the same image signal is the same. Such a data processing unit is shown in Fig. 5A.

As shown in FIG. 5A, the data processing unit 40 includes a buffer unit 42, a switching unit 44, an adder 46, and a look-up table 48. The image signal from the graphic controller is first received by the buffer unit 42. Thereafter, the image signal passing through the buffer unit 42 is directly transmitted to the source driver 20 by the switching operation of the switching unit 44 or supplied to the source driver 20 through the adder 46. The switching operation is determined according to whether the voltage applied to the liquid crystal is a positive value or a negative value. For example, when the voltage applied to the liquid crystal is positive, the switching operation is directly supplied to the source driver 20 without passing through the adder 46. When the voltage applied to the liquid crystal is negative, it is supplied to the source driver 20 via the adder 46.

The check table 48 has a kickback voltage compensation for overcoming a mismatch between a positive voltage value and a negative voltage value due to the kickback voltage when a positive data voltage and a negative data voltage are applied to the liquid crystal for the same image signal. The value is stored. This kickback voltage compensation value is stored corresponding to each image signal.

The adder 46 adds an image signal transmitted from the buffer unit 42 and a kickback voltage compensation value corresponding to the image signal stored in the examination table 48 to apply to the source driver.

The operation of the data processing unit will be described below.

Assume that the black data voltage, which is the same image signal, is applied from the graphak controller over the first frame to which the positive voltage is applied to the liquid crystal and the second frame to which the negative voltage is applied. The black data applied in the first frame is transmitted directly to the source driver 20 without passing through the adder 46 and applied to the liquid crystal in the LCD panel. The black data applied in the second frame is not directly transmitted to the source driver 20, but the adder 46 adds the kickback voltage compensation value corresponding to the black data and the black data value to add the black driver. 20) to be applied to the liquid crystal. At this time, the value for the kickback voltage is to compensate for a mismatch between the positive voltage value and the negative value due to the kickback voltage when the same image signal is directly applied to the liquid crystal, and thus the polarity of the voltage supplied to the liquid crystal through the data processor. Matches regardless.

5B illustrates another embodiment of the data processing unit. Unlike in FIG. 5A, the data processor shown in FIG. 5B does not include an adder. Therefore, the image signal is supplied directly to the source driver via the buffer 42 or to the source driver via the inspection table. The kickback voltage compensation value for each image signal is stored in the inspection table as shown in FIG. 5A, but the kickback voltage compensation value is different from the value stored in FIG. The value stored in (a) is added to the value of the image signal.

The operation of the data processing unit shown in Fig. 5B is as follows.

For example, suppose that a positive voltage value of black data is applied in the first frame and a negative voltage that is the same black data in the second frame. At this time, the positive black data is transmitted directly to the source driver without passing through the adder 46, and the negative black data is a kickback voltage compensation value corresponding to the black data stored in the test table. ) As it is. Also in this case, the positive and negative voltages applied to the liquid crystal for the same image signal are equal by the kickback voltage compensation value supplied to the source driver.

According to the data processor of the present embodiment, the positive voltage value applied to the liquid crystal is output to the source driver as it is, and the negative voltage value is processed and supplied to the source driver. However, the negative voltage value is supplied to the source driver as it is. It is also possible to output data with only positive voltage values. It is also possible to perform data processing on both positive and negative voltages simultaneously.

As described above, according to the present invention, the kickback compensation voltage for compensating the difference between the positive data voltage value and the negative data voltage value generated by the kickback voltage when each image signal is driven in an inverted manner is a data voltage. In addition to this, it is possible to prevent the flicker of the LCD panel by correcting the voltage difference according to the kickback voltage.

1 is a diagram illustrating an equivalent circuit of one pixel of a liquid crystal display panel.

2 is a diagram illustrating an inversion driving method of a conventional liquid crystal display panel.

3 is a diagram illustrating an inversion driving method of a liquid crystal display panel according to an exemplary embodiment of the present invention.

FIG. 4 is a block diagram for implementing the inversion driving method shown in FIG. 3.

5A and 5B are diagrams showing examples of the data processing unit shown in FIG.

Claims (3)

In a liquid crystal display panel drive device which alternately drives positive voltage and negative voltage to liquid crystal for the same image signal, A source driver supplying a data voltage to a source electrode of the thin film transistor, A gate driver supplying a gate-on voltage to the gate electrode of the thin film transistor, and After the positive data voltage and the negative data voltage are differently processed with respect to the same image signal, the processed data voltage is supplied to the source driver to compensate the difference between the positive data voltage and the negative data voltage due to a kickback voltage. Thereby including a data processor for equalizing the positive voltage and the negative voltage with respect to the same image signal, The data processing unit A buffer unit to which the image signal is input, A switching unit connected to the buffer unit, and An inspection table selectively connected to the buffer unit through the switching unit and storing a kickback compensation value for each image signal Containing Liquid crystal display panel drive device. In claim 1, And the test table stores a kickback voltage compensation value for one polarity. In claim 1, The test table stores a kickback voltage compensation value for each polarity.

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