KR20060079720A - Driving apparatus for liquid crystal display - Google Patents

Abstract

The present invention relates to a drive device for a liquid crystal display device.

According to an exemplary embodiment of the present invention, a driving apparatus of a liquid crystal display including a plurality of pixels may include a gray voltage generator which generates two sets of gray voltages, and a voltage corresponding to image data among the gray voltages. A plurality of data driving integrated circuits applied to the pixel as a data voltage, wherein the gray voltage generator includes a plurality of resistors arranged in a line and is connected between a power supply voltage and a ground, and the resistors The first and second operational amplifiers are respectively connected to the upper and lower sides with respect to the center of the column.

In this manner, an operational amplifier embedded in the data driving integrated circuit is used to generate the gray voltage generator, thereby reducing the cost and eliminating the need to change the overshoot voltage, thereby saving time for the gray voltage correction.

LCD, op amp, overshoot, DCC, gradation voltage, integrated circuit, resistance string

Description

Driving device of liquid crystal display {DRIVING APPARATUS FOR LIQUID CRYSTAL DISPLAY}

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

2 is an equivalent circuit diagram of one pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a circuit diagram of a gray voltage generator of FIG. 1.

4 is a diagram illustrating an operational amplifier included in a data driving integrated circuit.

The present invention relates to a drive device for a liquid crystal display device.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix and connected to switching elements such as thin film transistors (TFTs) to receive data voltages one by one in sequence. The common electrode is formed over the entire surface of the display panel and receives a common voltage. The pixel electrode, the common electrode, and the liquid crystal layer therebetween form a liquid crystal capacitor, and the liquid crystal capacitor becomes a basic unit forming a pixel together with a switching element connected thereto.

In such a liquid crystal display, a voltage is applied to two electrodes to generate an electric field in the liquid crystal layer, and the intensity of the electric field is adjusted to adjust the transmittance of light passing through the liquid crystal layer to obtain a desired image. In this case, in order to prevent degradation caused by an electric field applied to the liquid crystal layer for a long time, the polarity of the data voltage with respect to the common voltage is inverted frame by frame, row by pixel, or pixel by pixel.

The liquid crystal display includes a gray voltage generator that generates one or two gray voltages and a data driver which selects a voltage corresponding to the image data among the generated gray voltages and applies it as a data voltage.

On the other hand, the liquid crystal display device has an advantage that can be reduced in size and thinner than the cathode ray tube (CRT), but has a weak side in view angle and response speed.

In this case, the viewing angle has been greatly improved due to the vertical alignment (VA) mode or the in plane switching (IPS) mode having a plurality of domains.

However, the response speed is still slow to express moving images.

In order to improve the response speed, DCC (dynamic capacitance copmensation) method was introduced. The DCC method takes advantage of the fact that the larger the voltage across the liquid crystal capacitor is, the faster the response speed is. . A voltage higher than the target voltage is called an overshoot voltage, and the overshoot voltage is generated by the gray voltage generator.

The gray voltage generator includes a resistor string, and a portion for connecting a reference voltage to one end of the resistor string, outputting the divided voltage of the reference voltage as a gray voltage, and generating an overshoot voltage is determined.

However, when it is necessary to correct the gray voltage output from the gray voltage generator due to a change in driving conditions, the value of the resistor constituting the resistor string is adjusted. As a result, the overshoot voltage is changed to correct the voltage again. . Because of this, it takes a long time to find the overshoot voltage.

SUMMARY OF THE INVENTION The present invention has been made in an effort to provide a driving device for a liquid crystal display device capable of solving such a problem in the prior art.

According to an exemplary embodiment of the present invention, a driving apparatus of a liquid crystal display including a plurality of pixels includes a gray voltage generator configured to generate a plurality of gray voltages, and an image data of the gray voltages. A plurality of data driving integrated circuits selecting a corresponding voltage and applying the same to the pixel as a data voltage;

The gray voltage generator includes a plurality of resistors arranged in a line, and includes a resistor string connected between a power supply voltage and a ground and connected to an upper side and a lower side based on a center of the resistance string, respectively. It includes an operational amplifier.                     

In this case, the first and second operational amplifiers are preferably embedded in the data driving integrated circuit. Here, the first and second operational amplifiers preferably include input terminals to which voltage values obtained by dividing the power supply voltage are input.

Preferably, the first and second operational amplifiers are connected to first and second nodes between the resistors, respectively, and the voltages of the first and second nodes are greater than a data voltage to be applied to the pixel. .

In addition, the voltage of the first node preferably has a positive polarity and the voltage of the second node has a negative polarity.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

Now, a driving device of a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of one pixel of the liquid crystal display according to an exemplary embodiment of the present invention. 3 is a circuit diagram of a gray voltage generator of FIG. 1, and FIG. 4 is a block diagram illustrating an operational amplifier included in a data driving integrated circuit.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver 500 connected thereto. The gray voltage generator 800 connected to the signal generator 500 and a signal controller 600 for controlling the gray voltage generator 800 are included.

The liquid crystal panel assembly 300 includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected to the plurality of display signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. .

The display signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a data line D for transmitting a data signal. ₁ -D _m ). The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Each pixel includes a switching element Q connected to a display signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q, such as a thin film transistor, is provided in the lower panel 100, and the control terminal and the input terminal are three-terminal elements, respectively, with gate lines G ₁ -G _n and data lines D ₁ -D _m . The output terminal is connected to a liquid crystal capacitor (C _LC ) and a holding capacitor (C _ST ).

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 190 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270. It functions as a dielectric. The pixel electrode 190 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives a common voltage V _com . Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, at least one of the two electrodes 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST , which serves as an auxiliary part of the liquid crystal capacitor C _LC , is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage V _com is applied to this separate signal line. However, the storage capacitor C _ST may be formed such that the pixel electrode 190 overlaps the front end gate line directly above the insulator.

On the other hand, to implement color display, each pixel uniquely displays one of the three primary colors (spatial division) or each pixel alternately displays the three primary colors over time (time division) so that the desired color can be selected by the spatial and temporal sum of these three primary colors. To be recognized. 2 shows that each pixel includes a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190 as an example of spatial division. Unlike FIG. 2, the color filter 230 may be formed above or below the pixel electrode 190 of the lower panel 100.

A polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the two display panels 100 and 200 of the liquid crystal panel assembly 300.

The gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage V _com and the other set has a negative value, which will be described in more detail.

Referring to FIG. 3, the gray voltage generator 800 according to an exemplary embodiment of the present invention includes a resistor string in which a plurality of resistors R1-R20 are arranged in a line, and operational amplifiers OP1 and OP2.

Once the resistance of the column is connected to a power supply voltage (AVDD), and the other end is connected to ground, the output voltage (VREF1-VREF18) is a a partial pressure of the supply voltage (AVDD) value, on the basis of the center voltage (V _CNT) a positive or It has negative polarity, which may be the same value as the common voltage V _com .

The operational amplifiers OP1 and OP2 are buffer to voltage followers, the input of which is connected between two resistors Ra and Rb and the two resistors Rc and Rd, respectively. It is connected between R3) and between two resistors R18 and R19, respectively.

At this time, the output voltages VREF2 and VREF17 connected to the output terminals of the operational amplifiers OP1 and OP2 have fixed values as the overshoot voltages of the positive and negative polarities, respectively. That is, the two reference voltages VREF2 and VREF17 only change based on the values of the resistors Ra, Rb, Rc, and Rd, but do not change by changing the values of the resistors R1-R20 forming the resistor string.

In this case, even when the values of the resistors R1-R20 are adjusted due to a change in driving conditions or the like, the values of the two voltages VREF2 and VREF17 do not change. Therefore, it is possible to save time for finding the overshoot voltages VREF2 and VREF17 again.

In this case, the overshoot voltage may be a voltage other than the above-described voltages VREF2 and VREF17.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to receive a gate signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off from the outside. It is applied to the gate lines G ₁ -G _n and usually consists of a plurality of integrated circuits.

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300 to select the gray voltage from the gray voltage generator 800 and apply the gray voltage to the pixel as a data signal. As illustrated, a plurality of integrated circuits 510 are usually provided.

Referring to FIG. 4, the data driver integrated circuit 510 includes two operational amplifiers OP1 and OP2 and is connected to the data line Dj.

Terminal lines 720a and 720b extending in the vertical direction are connected to the input and output terminals of each of the operational amplifiers OP1 and OP2, and a repair line 710 extending in the horizontal direction is connected to the terminal lines 720a and 720b. Crossing.                     

The repair line 710 may be formed of the same layer as the gate line 121, and the terminal lines 720a and 720b may be formed of the same layer as the data line 171.

In addition, the repair line 710 and the terminal lines 720a and 720b are formed outside the peripheral area of the lower display panel 100, that is, the display area D in which the pixels are formed.

In this case, since the operational amplifiers OP1 and OP2 included in the data driving integrated circuit 510 are not used for repairing the data line, the operational amplifiers OP1 and OP2 that are not used for repairing are used as shown in FIG. 3. It is used for the voltage generator 800. That is, the operational amplifiers OP1 and OP2 shown in FIG. 3 are the operational amplifiers OP1 and OP2 included in the data driving integrated circuit 510. Therefore, since the operational amplifiers OP1 and OP2 built in the data driving integrated circuit 510 are used instead of the separate operational amplifiers OP1 and OP2, cost can be reduced.

The plurality of gate driving integrated circuits or data driving integrated circuits may be mounted in a tape carrier package (TCP) (not shown) in the form of a chip to attach the TCP to the liquid crystal panel assembly 300, and may be advantageous without using TCP. These integrated circuit chips may be directly attached onto a substrate (chip on glass, COG mounting method), and circuits performing the same functions as those integrated circuit chips may be directly formed on the liquid crystal panel assembly 300.

The signal controller 600 controls operations of the gate driver 400 and the data driver 500.

The display operation of such a liquid crystal display device will now be described in detail.                     

The signal controller 600 may control the input image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical sync signal V _sync and a horizontal sync signal. (H _sync ), a main clock (MCLK), a data enable signal (DE) is provided. The signal controller 600 properly processes the image signals R, G, and B according to the operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate control signal. After generating the CONT1 and the data control signal CONT2, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signal DAT are transmitted to the data driver 500. Export to

The gate control signal (CONT1) includes a gate-on voltage vertical synchronization start signal (STV) for instructing the start of output of the (V _on), the gate-on voltage gated clock signal that controls the output timing of the (V _on) (CPV) and the gate-on An output enable signal OE or the like that defines the duration of the voltage V _on .

The data control signal CONT2 includes a horizontal synchronization start signal STH indicating the start of input of the image data DAT, a load signal LOAD for applying a corresponding data voltage to the data lines D ₁ -D _m , and a common voltage ( V inverted signal (RVS), data clock signal (HCLK), etc. to invert the polarity of the data voltage for the _com (hereinafter referred to as "polarity of the data voltage by reducing the polarity of the data voltage for the common voltage"), etc. do.

The data driver 500 sequentially receives and shifts the image data DAT for one row of pixels according to the data control signal CONT2 from the signal controller 600, and the gray voltage from the gray voltage generator 800. The grayscale voltage corresponding to each image data DAT is selected to convert the image data DAT into a corresponding data voltage, and then apply the grayscale voltage to the corresponding data lines D ₁ -D _m . At this time, the above-mentioned overshoot voltage is first applied to the start point of one frame, and then a target data voltage is applied (DCC method).

The gate driver 400 applies the gate-on voltage V _on to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n. ) Turns on the switching element Q connected thereto, so that the data voltage applied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

The difference between the data voltage applied to the pixel and the common voltage V _com is shown as the charging voltage of the liquid crystal capacitor C _LC , that is, the pixel voltage. The arrangement of the liquid crystal molecules varies according to the magnitude of the pixel voltage, thereby changing the polarization of light passing through the liquid crystal layer 3. The change in polarization is represented by a change in transmittance of light by a polarizer (not shown) attached to the display panels 100 and 200.

After one horizontal period (or “1H”) (one period of the horizontal sync signal H _sync , the data enable signal DE, and the gate clock CPV), the data driver 500 and the gate driver 400 are next. The same operation is repeated for the pixels in the row. In this manner, the gate-on voltage V _on is sequentially applied to all the gate lines G ₁ -G _n during one frame to apply the data voltage to all the pixels. At the end of one frame, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each pixel is opposite to that of the previous frame ("frame inversion). "). At this time, the polarity of the data voltage flowing through one data line is changed according to the characteristics of the inversion signal RVS even in one frame (eg, "row inversion", "point inversion"), or the voltage of the data voltage applied to one pixel row. The polarities can also be different (eg "heat inversion", "point inversion").

As described above, the operation amplifiers OP1 and OP2 included in the data driving integrated circuit 510 are used in the gray voltage generator 800 to reduce the cost, and do not need to change the overshoot voltage. You can save lifting time.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

Claims (5)

A driving device of a liquid crystal display device including a plurality of pixels, A gradation voltage generator for generating two plural gradation voltages, and A plurality of data driving integrated circuits selecting a voltage corresponding to the image data among the gray scale voltages and applying the voltage to the pixel as a data voltage; Including, The gray voltage generator A resistor string comprising a plurality of resistors arranged in a line and connected between the supply voltage and ground; and First and second operational amplifiers connected to an upper side and a lower side with respect to the center of the resistor string; Containing Driving device for liquid crystal display device. In claim 1, And the first and second operational amplifiers are embedded in the data driving integrated circuit. In claim 2, The first and second operational amplifiers include an input terminal to which a voltage value obtained by dividing the power supply voltage is input. In claim 3, The first and second operational amplifiers are respectively connected to first and second nodes between the resistors, The voltages of the first and second nodes are greater than the data voltage to be applied to the pixel. Driving device for liquid crystal display device. In claim 4, And a voltage of the first node is positive and a voltage of the second node is negative.

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