KR101006448B1 - Driving apparatus of liquid crystal display - Google Patents

Abstract

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 that can reduce manufacturing costs.

A reference voltage generator configured to generate a plurality of reference voltages including a plurality of pixels and a resistor string formed of a plurality of resistors, and generate a plurality of gray voltages based on the reference voltages, and a gray level corresponding to an image signal among the gray voltages; A plurality of data driving integrated circuits for selecting a voltage to generate the data voltage, and a data line connected to the pixel to transfer the data voltage, each of the plurality of data driving integrated circuits including a plurality of operational amplifiers; Some of the reference voltages are output through the operational amplifier.

In this way, manufacturing cost can be lowered by using an operational amplifier included in the data driver IC.

Reference voltage, gradation voltage, operational amplifier, data line, repair, gamma curve

Description

Driving device of liquid crystal display {DRIVING APPARATUS OF 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 diagram schematically illustrating a data driving IC according to an exemplary embodiment of the present invention.

4 is a diagram illustrating a reference voltage generator and the data driver IC shown in FIG. 3.

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

A general liquid crystal display (LCD) 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.

The LCD includes a pixel including a switching element, a data driver for applying a corresponding data voltage to the pixel, and a reference voltage generator for generating a reference voltage and supplying the reference voltage to the pixel.

The reference voltage generator generates a gray voltage of positive and negative polarity for inversion driving, and the data driver selects a gray voltage corresponding to an image signal among a plurality of gray voltages and applies it to the pixel as a data voltage.

At this time, a method of supplying a gray voltage includes a method of generating all necessary gray voltages in advance and supplying them to the data driver, and supplying some gray voltages as a reference, and dividing the rest within the data driver IC. Recently, as the number of bits of data increases, the number of gradation voltages to be expressed also increases, and usually the latter method is employed.

For example, in the latter method, in case of 6-bit data, all of the gray scale voltages required are 64 gray scale voltages, of which eight are referred to as reference voltages (hereinafter referred to as "reference voltages"). The values in between are generated by a certain rule in the IC of the data driver.

What is needed to obtain such a constant rule is gamma correction, which is to correct the light transmittance of the liquid crystal so that it is intended to obtain uniform light transmission characteristics. In addition, a kind of curve used for gamma correction is called a gamma curve.

On the other hand, the brightness is measured and corrected for each position of the screen by using a gamma curve indicating the relation between the transmittance or luminance of the liquid crystal and the gray scale, and the LCD is adjusted to have a gamma curve having a gamma constant of 2.2.

At this time, the reference voltage generator keeps the gamma curve constant and prevents the reference voltage from being shaken due to external conditions or variations in the resistance string that constitutes the reference voltage generator and the voltage follower or buffer. Use the same op amp.

These op amps use as many as 10 depending on their characteristics, which is a burden on the LCD module cost.

Accordingly, an object of the present invention is to provide a driving device of a liquid crystal display device which can reduce manufacturing costs.

The driving apparatus of the liquid crystal display according to the exemplary embodiment of the present invention includes a plurality of pixels, a reference voltage generator, a plurality of data driving ICs, and a data line. The reference voltage generator generates a plurality of reference voltages including a resistor string formed of a plurality of resistors, and the data driving integrated circuit generates a plurality of gray voltages based on the reference voltages, and generates a plurality of gray voltages based on the reference voltage. A corresponding gray voltage is selected and generated as a data voltage, and the data line is connected to the pixel to transfer the data voltage. Each of the plurality of data driving integrated circuits includes a plurality of operational amplifiers, some of the reference voltages being output through the operational amplifiers.

Meanwhile, the operational amplifier includes an input terminal and an output terminal, some of the operational amplifiers are connected to the output terminal at the center of the resistor string, and the other operational amplifier is symmetrically with respect to the center of the resistor string. May be connected.

In addition, the operational amplifier may be a voltage follower, and the operational amplifier is preferably the operational amplifier for the data line repair.

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.

FIG. 1 is a block diagram of a liquid crystal display device according to an embodiment of the present invention, and FIG. 2 is an equivalent circuit diagram of a pixel of a liquid crystal display device according to an 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. It includes the 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 to select the gray voltage from the reference voltage generator 800 and apply the gray voltage to the pixel as a data signal. It consists of a circuit.

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 and shifts 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 generates a reference voltage. By dividing the reference voltage from the unit 800 into a plurality of gradation voltages using a resistance string, and selecting gradation voltages corresponding to the respective image data R ', G', and B 'among the divided gradation voltages, The image data R ', G', and B 'are converted into corresponding data voltages and applied to the corresponding data lines D ₁ -D _m .

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. When the switching element Q connected to the () is turned on, 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 liquid crystal molecules vary in arrangement depending on the magnitude of the pixel voltage. As a result, 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.

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 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 is started 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 the polarity of the previous frame. "). In this case, the polarity of the data voltage flowing through one data line may be changed (“column inversion”) or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS within one frame ( "Dot reversal")

Next, the driving device of the liquid crystal display according to the exemplary embodiment of the present invention will be described in more detail with reference to FIGS. 3 and 4.

3 is a diagram schematically illustrating a data driver IC according to an exemplary embodiment of the present invention, and FIG. 4 is a diagram illustrating the data driver IC and the reference voltage generator shown in FIG. 3.

First, as shown in FIG. 3, the data driver IC 501 has one to about 80 pins, which communicate with the outside. The figures only show pins 13 and 14 and 16-33 and pins 73 and 74.

Pins 13 and 14, and pins 73 and 74 are input / output pins of the operational amplifier for data repair lines, and op amps OP31 and OP32 embedded in the data driving IC 501 are shown on the right side of the drawing.

The data repair line operational amplifiers OP31 and OP32 are usually provided with two to four data driver ICs 501, and two are shown in the figure.

16 to 33 pins are pins for receiving a reference voltage (V _REF1 -V _REF18) from the reference voltage generator 800, the fins of the reference voltage (V _REF1 -V _REF18) is again input through the data The resistor IC is divided into a gray voltage required through a resistor string provided in the driver IC 501.

4 shows the reference voltage generator 800 and the data driver 500.

As shown, the reference voltage generator 800 includes a resistor string formed of a plurality of resistors R1-R20.

A constant driving voltage AVDD is connected to one end of the resistor string, a ground voltage is connected to the other end, and the driving voltage AVDD is divided by the resistor strings R1-R20. The divided voltages are supplied to the data driver ICs 501 constituting the data driver 500 as _reference voltages V _{REF1 to} V _REF18 .

In the middle of the resistor string, a plurality of operational amplifiers OP41-OP43 are connected to hold a constant reference voltage.

Here, the operational amplifiers OP41-OP43 transfer the voltage values divided as voltage followers or buffers without loss, while each of the positive and negative reference voltages V _REF1 -V _REF18 . The reference voltages V _{REF1 to} V _REF18 are uniformly supplied to the data driver 500 by supplying these voltages one by one and constantly connected to the center voltage V _CNT .

The operational amplifiers OP41-OP43 are included in the data driver 500 as shown in FIG. 4, and are the same as the operational amplifiers OP31 and OP32 shown in FIG. 3.

In this case, since there are two operational amplifiers in FIG. 3 and three operational amplifiers in FIG. 4, one more operational amplifier is needed. This can be achieved by using an operational amplifier provided in the other data driving IC 501.

For example, if the number of the data driver ICs 510 is 10, there are 20 data line repair operational amplifiers, and only 2 to 4 of them are used for data line repair and the remaining 16 to 18 are not used. The wiring can be connected to one of these.

In addition, although three operational amplifiers OP41-OP43 are illustrated in the figure, more operational amplifiers may be used as necessary. That is, the position and number of operational amplifiers can be appropriately adjusted based on the output characteristics of the liquid crystal display.

As described above, manufacturing cost can be reduced by using the data line repair operational amplifier provided in the data driving IC 501.

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 (4)

A driving device of a liquid crystal display device including a plurality of pixels, A reference voltage generator configured to generate a plurality of reference voltages, including a resistor string comprising a plurality of resistors; A plurality of data driving integrated circuits generating a plurality of gray voltages based on the plurality of reference voltages, selecting a gray voltage corresponding to an image signal among the gray voltages, and generating the plurality of gray voltages as data voltages; A data line connected to the pixel to transfer the data voltage Including, Each of the plurality of data driving integrated circuits includes a plurality of operational amplifiers, At least one reference voltage among the plurality of reference voltages is output through the operational amplifier. Driving device for liquid crystal display device. In claim 1, The operational amplifier includes an input terminal and an output terminal, Some of the operational amplifiers have the output terminal connected to the center of the resistor string, and the remaining operational amplifiers have the input terminals symmetrically connected to the center of the resistor string. Driving device for liquid crystal display device. In claim 2, And the operational amplifier is a voltage follower or a buffer. 4. The method of claim 3, And the operational amplifier is the operational amplifier for repairing the data line.

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