KR20050005259A - Apparatus and method of driving liquid crystal display - Google Patents

Abstract

PURPOSE: A driver apparatus of a liquid crystal display device and its method are provided to correct a gamma constant in a screen by driving data driving IC into a plurality groups and supplying reference voltage to them. CONSTITUTION: According to the driver apparatus of a liquid crystal display device including a plurality of pixels, a reference voltage generation unit(800) generates a plurality of first reference voltages. A reference voltage dividing unit(850) divides the first reference voltage from the reference voltage generation unit into a plurality of second reference voltages having different amplitude. And a plurality of data driving integrated circuits(500) generate a plurality of gray voltages based on the second reference voltage, and applies a gray voltage corresponding to an image signal to the pixel.

Description

A driving device and method of a liquid crystal display device {APPARATUS AND METHOD OF DRIVING LIQUID CRYSTAL DISPLAY}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device and a method of a liquid crystal display device, and more particularly to a driving device and a method of a liquid crystal display device capable of correcting an intra gamma deviation.

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 level, and the LCD is adjusted to have a gamma curve having a gamma constant of 2.2.

At this time, the gamma constant value is slightly different for each screen position on the LCD screen. This is because the brightness of the left and right screens are different due to the kick-back voltage. The gamma constant in the center of the screen is 2.2 as set, but on the left side, 2.0 is measured by 0.2 away from the left side, and the left side is brighter than the center and the right side is darker. This causes the screen to be uneven in overall brightness, resulting in deterioration of display quality.

Accordingly, an object of the present invention is to provide a driving device of a liquid crystal display device capable of compensating for variations in gamma constants on a screen.

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 driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is an example of a reference voltage application method according to an embodiment of the present invention.

5 shows a conventional gamma curve and a gamma curve according to an embodiment of the present invention.

According to an embodiment of the present disclosure, a driving device of a liquid crystal display including a plurality of pixels includes a reference voltage generator, a reference voltage divider, and a plurality of data driver integrated circuits. The reference voltage generator generates two sets of first reference voltages, and the reference voltage divider divides and outputs the first reference voltage from the reference voltage generator into a plurality of second reference voltages having different magnitudes. The data driver integrated circuit generates a plurality of gray voltages based on the second reference voltage from the reference voltage divider, and selects and applies a gray voltage corresponding to an image signal to the pixel. Here, the data driving integrated circuits are grouped into a plurality of groups so that the same second reference voltage is supplied to the integrated circuits belonging to the same group.

The reference voltage divider may include a plurality of resistor strings connected in parallel, and the value of the second reference voltage is a gamma value of a gamma curve representing a transmittance of a liquid crystal corresponding to the gray voltage. It is preferable to determine according to. In this case, it is preferable that the value of the second reference voltage is lower as the gamma constant is smaller.

According to another exemplary embodiment of the present invention, a driving method of a liquid crystal display device including a plurality of pixels and a data driver which selects and applies a gray voltage corresponding to an image signal to the pixels as a data voltage may include a plurality of first reference voltages. Generating a second reference voltage; dividing the first reference voltage into a plurality of second reference voltages; applying the second reference voltage to the data driver; and generating a plurality of gray voltages based on the second reference voltage. Generating. The dividing of the second reference voltage may include determining the second reference voltage according to a gamma constant of a gamma curve representing a transmittance of a liquid crystal corresponding to the gray voltage. The applying of the voltage preferably includes applying a lower value as the gamma constant is smaller.

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 apparatus and method 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, a reference voltage divider 850, and a signal controller 600 controlling the reference voltage generator 800.

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 reference voltage divider 850 divides and outputs the reference voltages from the reference voltage generator 800 into a plurality of reference voltages.

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 generate a plurality of gray line voltages based on the reference voltages from the reference voltage divider 850. It is selected and applied to a pixel as a data signal, and usually consists of a plurality of integrated circuits (IC).

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 the 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 receives the reference voltage divider ( The reference voltage from 850 is divided into a plurality of gray voltages using a resistor string, and the gray voltages corresponding to each of the image data R ', G', and B 'are selected from the divided gray voltages, thereby obtaining image data ( R ', G', 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”) in 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, the reference voltage divider 850 divides and outputs the reference voltage from the generator of the reference voltage generator 800 into a plurality of voltages having different magnitudes, which will be described in detail with reference to FIGS. 3 and 4. .

3 illustrates an example of a reference voltage divider 850 according to an embodiment of the present invention, and FIG. 4 illustrates an example of a reference voltage applied to a data driver according to an embodiment of the present invention.

As shown, the reference voltage divider 850 includes a reference voltage divider circuit including two resistor strings connected in parallel. In the drawings, only one of the plurality of reference voltage dividing circuits is shown for convenience of description, and it is actually required by the number of reference voltages. For example, in the case of 128 grayscales including positive polarity and negative polarity, 16 pieces of 8 pieces are required.

The reference voltage divider 850 divides the reference voltage V _ref from the reference voltage generator 800 into three reference voltages V _ref1 , V _ref2 , and V _ref3 using a resistor string. At this time, the value of each reference voltage is determined according to the state of the screen. That is, it is determined according to the gamma constant of the gamma curve indicating the transmittance of the liquid crystal corresponding to the gray scale voltage. If the gamma constant is small, the reference voltage is determined to have a small value and applied to the corresponding part of the screen.

For example, as shown in Fig. 4, the reference voltage is applied to the data driving ICs # 6, # 7, and # 8 in the right screen portion as it is, and the data driving ICs # 4 and # in the center screen portion are applied. The lower voltage is applied to 5) and the lower voltage is applied to the data driving ICs # 1, # 2, and # 3 on the left screen part. That is, the relationship between V _ref1 > V _ref2 > V _ref3 , and each resistance value is a value for outputting a corresponding voltage, and can be adjusted as much as possible.

As described above, because the kickback voltage, etc., it becomes brighter toward the left side of the screen, that is, since the gamma constant becomes smaller, the lower voltage is applied while going to the left side to display the same brightness as the right side.

Meanwhile, in one embodiment of the present invention, the voltage is divided into three, but may be divided into more or less depending on the state of the screen, and the method of applying to the data driving ICs # 1 to # 8 is also appropriately selected. It is possible. For example, the gray voltages may be divided into two, and the driving ICs # 1 to # 8 may be grouped and applied in the same manner as five, three, four, or four.

5 shows a conventional gamma curve and a gamma curve according to an embodiment of the present invention.

This is a gamma curve in which the gamma constant is measured on the left side of the screen. In the conventional gamma curve, the gamma constant is measured as 2.0. However, in the exemplary embodiment of the present invention, the gamma constant is 2.18, which is almost the target value of 2.2. have.

Therefore, the screen is almost the same brightness.

As described above, by dividing the data driver IC into several groups and applying a reference voltage, the portion where the brightness differs can be corrected.

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 (7)

A driving device of a liquid crystal display device including a plurality of pixels, A reference voltage generator configured to generate a plurality of first reference voltages; A reference voltage divider for dividing the first reference voltage from the reference voltage generator into a plurality of second reference voltages having different magnitudes, and outputting the divided reference voltages; A plurality of data driving integrated circuits generating a plurality of gray voltages based on the second reference voltages from the reference voltage divider, and selecting and applying a gray voltage corresponding to an image signal to the pixel; Including, The data driving integrated circuits are grouped into a plurality of groups, The same second reference voltage is supplied to the integrated circuits belonging to the same group. Driving device for liquid crystal display device. In claim 1, And the reference voltage divider includes a plurality of resistor strings connected in parallel. In claim 1, And a value of the second reference voltage is determined according to a gamma value of a gamma curve representing a transmittance of a liquid crystal corresponding to the gray voltage. In claim 3, The value of the second reference voltage has a lower value as the gamma constant is smaller. A driving method of a liquid crystal display device comprising a plurality of pixels and a data driver to select and apply a gray voltage corresponding to an image signal to the pixels as a data voltage. Generating two plurality of first reference voltages, Dividing the first reference voltage into a plurality of second reference voltages; Applying the second reference voltage to the data driver, and Generating a plurality of gray voltages based on the second reference voltage Method of driving a liquid crystal display comprising a. In claim 5, The dividing of the second reference voltage may include determining the second reference voltage according to a gamma constant of a gamma curve representing a transmittance of a liquid crystal corresponding to the gray voltage. In claim 5, The applying of the second reference voltage may include applying a lower value as the gamma constant is smaller.