KR100915239B1 - Apparatus of driving liquid crystal display - Google Patents

Abstract

The present invention relates to a driving device of a liquid crystal display device capable of improving horizontal crosstalk.

A driving device of a liquid crystal display according to an exemplary embodiment of the present invention includes a reference voltage generation unit including a plurality of pixels and generating a plurality of reference voltages, and generating a plurality of gray voltages based on the reference voltages. And a data driver for selecting a gray voltage corresponding to an image signal among the gray voltages and supplying the gray voltage to the pixel as a data voltage, and a reference voltage compensator for amplifying the common voltage from the pixel and supplying it to the reference voltage generator. The reference voltage generator includes a resistor string in which a plurality of resistors are connected in series between a first power supply and ground, and the reference voltage compensator is connected to a center of the resistor string. The reference voltage compensator includes a non-inverting amplifier, first and second resistors connected between a second power supply and ground, and a capacitor connected between the first and second resistors, and the ratio of the non-inverting amplifier An inverting terminal is connected to the common voltage through the capacitor, and an output terminal of the non-inverting amplifier is connected to the center of the resistor string. In this manner, horizontal crosstalk can be improved by keeping the pixel voltage the same by receiving the distorted common voltage, amplifying it through the non-inverting amplifier, and applying the same to the reference voltage generator.

Description

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

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive device for a liquid crystal display device, and more particularly to a drive device for a liquid crystal display device capable of removing horizontal crosstalk.

A general liquid crystal display device includes two display panels and a liquid crystal layer having dielectric anisotropy interposed therebetween. An electric field is applied to 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. Such liquid crystal displays are typical among portable flat panel displays (FPDs) that are easy to carry. Among them, TFT-LCDs using thin film transistors (TFTs) as switching elements are mainly used.

Meanwhile, the LCD includes a pixel including a switching element, a data line and a gate line connected thereto, and applies a gate-on voltage for turning on the switching element through the gate line, and then applies the data voltage to the pixel through the turned-on switching element. Is authorized.

At this time, a horizontal crosstalk is a problem. When a data voltage of only one polarity of positive or negative polarity is applied to a pixel charged at the same time, the common voltage is distorted to be higher than the original voltage or The low change causes a difference in the voltage charged in the pixel, which is why the band appears on the screen.

In order to eliminate such horizontal crosstalk, driving is performed to compensate for the distortion by feeding back the distortion of the common voltage. One is to invert the distorted common voltage and compensate it in addition to the common voltage, and the other is to add and compensate the data voltage as much as the distorted common voltage.

At this time, the first method is limited in the effect of the increase in the load of the common electrode as the size of the LCD increases. On the other hand, the second method uses a capacitor, which makes it difficult to adjust the amount of distortion and more than 1 times.

Accordingly, an object of the present invention is to provide a driving device of a liquid crystal display device which can easily compensate for the amount of distortion and thereby eliminate horizontal crosstalk.

According to an embodiment of the present invention, a driving apparatus of a liquid crystal display including a plurality of pixels includes a reference voltage generator, a data driver, and a reference voltage compensator. The reference voltage generator generates two sets of reference voltages, the data driver generates a plurality of gray voltages based on the reference voltage, and selects a gray voltage corresponding to an image signal among the gray voltages as a data voltage. The reference voltage compensator amplifies a predetermined voltage from the pixel and supplies the amplified voltage to the reference voltage generator. The reference voltage generator includes a resistor string in which a plurality of resistors are connected in series between a first power supply and ground, and the reference voltage compensator is connected to a center of the resistor string.

Here, the reference voltage compensator may include a non-inverting amplifier, first and second resistors connected between a second power supply and ground, and a capacitor connected between the first and second resistors. Preferably, the non-inverting terminal of the inverting amplifier is connected to the predetermined voltage through the capacitor, and the output terminal of the non-inverting amplifier is connected to the center of the resistor string. The non-inverting amplifier may further include third and fourth resistors connected between the output terminal and ground, and an inverting terminal connected between the third and fourth resistors, and the output of the non-inverting amplifier. The voltage is preferably determined by the ratio of the third and fourth resistors. On the other hand, the predetermined voltage is preferably a common voltage.

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.

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 And a reference voltage generator 800 connected to 500 and a signal controller 600 for controlling them.

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 signal line or data for transmitting a data signal. Line D 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 is provided on the lower panel 100, and the control terminal and the input terminal are connected to the gate line G ₁ -G _n and the data line D ₁ -D _m, respectively. The output terminal is connected to the liquid crystal capacitor C _LC and the storage 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, both electrodes 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100, and a predetermined voltage such as a common voltage V _com is applied to the separate signal line. Is approved. 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.

Meanwhile, in order to implement color display, each pixel must display color, which is possible by providing a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190. In FIG. 2, the color filter 230 is formed in a corresponding region of the upper panel 200. Alternatively, 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 reference voltage generator 800 generates two sets of reference 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.

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 .

The data driver 500 is connected to the data lines D ₁ -D _m of the liquid crystal panel assembly 300, and generates and generates a plurality of gray voltages based on the reference voltages from the reference voltage generator 800. The selected gradation voltage is selected and applied to the pixel as a data signal, and is usually composed of a plurality of integrated circuits.

The signal controller 600 generates control signals for controlling operations of the gate driver 400 and the data driver 500, and provides the corresponding control signals to the gate driver 400 and the data driver 500.

Next, the display operation of the liquid crystal display will be described in more detail.

The signal controller 600 inputs an input control signal for controlling the RGB 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 generates a gate control signal CONT1 and a data control signal CONT2 based on the input control signal, and adjusts the image signals R, G, and B to match the operating conditions of the liquid crystal panel assembly 300. After appropriately processing, the gate control signal CONT1 is sent to the gate driver 400, and the data control signal CONT2 and the processed image signals R ', G', and B 'are sent to the data driver 500.

The gate control signal CONT1 includes a vertical synchronization start signal STV indicating the start of output of the gate on pulse (gate on voltage section), a gate clock signal CPV for controlling the output timing of the gate on pulse, and a gate on pulse. An output enable signal OE or the like that defines a width.

The data control signal CONT2 is a load for applying a corresponding data voltage to the horizontal synchronization start signal STH indicating the start of input of the image data R ', G', and B 'and the data lines D ₁ -D _m . Signal LOAD, inverted signal RVS and data that inverts the polarity of the data voltage with respect to common voltage V _com (hereinafter referred to as " polarity of data voltage " by reducing " polarity of data voltage with respect to common voltage "). Clock signal HCLK and the like.

The data driver 500 sequentially receives image data R ′, G ′, and B ′ corresponding to one row of pixels according to the data control signal CONT2 from the signal controller 600, and displays each image among the gray voltages. By selecting the gray scale voltages corresponding to the data R ', G', and B ', the image data R', G ', and B' are converted into the corresponding data voltages.

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. Turn on the switching element (Q) connected to.

The gate-on voltage V _on is applied to one gate line G ₁ -G _n so that a row of switching elements Q connected thereto is turned on (this period is "1H" or "1 horizontal period). (horizontal period) "and equal to one period of the horizontal sync signal Hsync, the data enable signal DE, and the gate clock CPV], and the data driver 500 converts each data voltage to a corresponding data line D. ₁ -D _m ). The data voltage supplied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

The liquid crystal molecules change their arrangement according to the electric field generated by the pixel electrode 190 and the common electrode 270, and thus the polarization of light passing through the liquid crystal layer 3 changes. 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.

In this manner, the gate-on voltages V _{on are} sequentially applied to all the gate lines G ₁ -G _n during one frame to apply data voltages 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). "). In this case, the polarity of the data voltage flowing through one data line may be changed (“line inversion”) within one frame or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS ( "Dot reversal").

Meanwhile, as shown in FIG. 1, the reference voltage generator 800 receives and compensates a common voltage V _com applied to the liquid crystal panel assembly 300, and outputs the same in detail with reference to FIGS. 3 and 4. Explain.

3 is an example of a reference voltage generator 800 according to an embodiment of the present invention, and FIG. 4 is a waveform diagram of a signal according to an embodiment of the present invention.

As shown in FIG. 3, the reference voltage generator 800 includes a non-inverting amplifier OP, a resistor R1 and R2 connected between a power supply AVDD and ground, and a capacitor.

The non-inverting terminal of the non-inverting amplifier OP is connected to the common voltage V _com 'through the capacitor C, and the output terminal is connected to the center of the resistor string generating a plurality of reference voltages. In addition, the non-inverting amplifier OP includes resistors R3 and R4 connected between the output terminal and ground and an inverting terminal connected therebetween.

Here, for the convenience of description, only a part of the resistor string is shown in the drawings, and only a part of the reference voltage is shown.

The common voltage V _com ′ input to the reference voltage generator 800 has a waveform shown in FIG. 4. That is, the common voltage V _com ′ is a waveform in which distortion is made up or down according to the data voltage compared to the normal common voltage V _com shown by a dotted line.

The values of the resistors R1 and R2 dividing the power source AVDD have the same value to derive the intermediate value of the power source AVDD. At this time, when the common voltage V _com 'is applied, the node N1 is connected in parallel, so the voltage V _N1 of the node N1 changes to the value of the common voltage V _com '. Here, the actual change amount of the node voltage V _N1 changes by the amount of distortion of the common voltage V _com ′. That is, the intermediate value of the power source AVDD is equal to the original common voltage V _com and the amount of distortion is added thereto.

On the other hand, the voltage of the node N2 becomes the reference voltage V _ref4 as an output voltage of the non-inverting amplifier OP. As is known, the relationship between the input voltage V _N1 and the output voltage V _{N2 of the} non-inverting amplifier OP is expressed by Equation 1 below.

V _N2 = (1 + R4 / R3) * V _N1

Here, V _N2 is a voltage of the node N2.

Then, when the distorted common voltage V _com ′ is input, the reference voltage V _ref4 is increased or decreased by the amplification operation of the non-inverting amplifier OP, and the remaining reference voltages V _ref1 , V _ref2 , and V _{ref3 are increased.} , V _ref5 , V _ref6 , V _ref7 ) also rise or fall.

As described above, the data driver 500 generates a plurality of gray voltages based on the compensated reference voltages V _ref1 to V _ref7 , and selects a gray voltage corresponding to the image data among the gray voltages, thereby selecting the data voltage. Is applied to the pixel.

On the other hand, it will be appreciated that the amount of distortion of the common voltage V _com 'can be compensated by appropriately adjusting the values of the resistors R3 and R4. In addition, it was difficult to compensate more than one time in the past, but it can be compensated more than one time by using a non-inverting amplifier (OP), and it can be applied to large LCDs, which are difficult to improve horizontal crosstalk due to the large load of the common electrode. will be.

In this way, by connecting the non-inverting amplifier (OP) to the center of the resistor string that generates the reference voltage and input the distorted common voltage (V _com ') at its input terminal, the data voltage as much as the distortion of the common voltage (V _com ') The same pixel voltage can be maintained by rising or falling. Therefore, the horizontal crosstalk caused by the difference in pixel voltage can be improved.

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.

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 reference voltage generator according to an exemplary embodiment of the present invention.

4 is a waveform diagram of a signal according to an embodiment of the present invention.

Claims (4)

A driving device of a liquid crystal display device including a plurality of pixels, A reference voltage generator for generating two sets of reference voltages; A data driver which generates a plurality of gray voltages based on the reference voltage, selects a gray voltage corresponding to an image signal among the gray voltages, and supplies the gray voltage to the pixel as a data voltage; A reference voltage compensator amplifies a predetermined voltage from the pixel and supplies the amplified voltage to the reference voltage generator Including, The reference voltage generator includes a resistor string in which a plurality of resistors are connected in series between a first power supply and a ground. The reference voltage compensator is connected to the center of the resistor string Driving device for liquid crystal display device. In claim 1, The reference voltage compensator Non-inverting amplifier, First and second resistors connected between the second power source and ground; and A capacitor connected between the first and second resistors Including, A non-inverting terminal of the non-inverting amplifier is connected to the predetermined voltage through the capacitor, and an output terminal of the non-inverting amplifier is connected to the center of the resistor string. Driving device for liquid crystal display device. In claim 2, The non-inverting amplifier further includes third and fourth resistors connected between the output terminal and ground, and an inverting terminal connected between the third and fourth resistors, The output voltage of the non-inverting amplifier is determined by the ratio of the third and fourth resistors. Driving device for liquid crystal display device. In claim 1, And the predetermined voltage is a common voltage.