KR20060014551A - Display device and driving device thereof - Google Patents

Abstract

The present invention relates to a gray reference voltage generator, wherein the gray reference voltage generator includes one resistor string and a plurality of differential amplifiers. The gray reference voltage generator is divided into a plurality of voltages by the resistor string connected between the power supply voltage and the ground to generate a plurality of negative gray reference voltages, and each negative gray level connected to the power supply voltage input to the non-inverting terminal and the inverting terminal. The difference between the reference voltages is calculated to generate a plurality of positive gradation reference voltages.

Display, liquid crystal display, gradation voltage, differential amplifier, operational amplifier, reference voltage

Description

Display device and its driving device {DISPLAY DEVICE AND DRIVING DEVICE THEREOF}

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 detailed circuit diagram of a gray reference voltage generator according to an exemplary embodiment of the present invention.

The present invention relates to a display device and a driving device thereof.

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 data driver for applying a data voltage corresponding to a pixel through a switching element and a gray reference voltage generator for providing a gray reference voltage to the data driver.

The gradation reference voltage generator typically generates a positive value (hereinafter referred to as a positive polarity) of the data voltage polarity (hereinafter, referred to as the polarity of the data voltage by reducing the polarity of the data voltage with respect to the common voltage) for the inversion driving. A plurality of gray level reference voltages having a negative polarity (hereinafter referred to as negative polarity) of the plurality of gray level reference voltages and the data voltages are generated. The data driver generates a plurality of gray voltages based on the gray reference voltages from the gray reference voltage generator, selects gray voltages corresponding to image data among the plurality of gray voltages, and selects a pixel as a data voltage. To apply.

Instead of generating a plurality of gray voltages using the gray reference voltage generator and the data driver, there is a method of generating all necessary gray voltages in advance and supplying them to the data driver. While the number of gray voltages to be expressed also increases, a gray scale reference voltage generator is used.

However, these positive and negative gradation reference voltages are only opposite polarities, and the difference from the common voltage is substantially the same. Therefore, in order to generate such a gray scale reference voltage, the gray scale reference voltage generator is divided into a portion generating a positive gray scale reference voltage having a similar structure and a portion generating a negative gray reference voltage, and both of them need to be designed. There is a limit in reducing the volume and simplifying the structure of the reference voltage generator.

Therefore, the technical problem to be achieved by the present invention is to simplify the structure of the gradation reference voltage generator.

Another object of the present invention is to simplify the structure of a display device and to generate a stable gray scale reference voltage.

According to an aspect of the present invention, a liquid crystal panel assembly including a plurality of pixels, a gray reference voltage generator for generating a plurality of gray reference voltages, and a plurality of grays based on the plurality of gray reference voltages are provided. A data driver configured to generate a voltage and select and apply a gray voltage corresponding to an image signal to the pixel, wherein the plurality of gray reference voltages include a plurality of first gray reference voltages and a plurality of second gray reference voltages; The gray reference voltage generator divides a first voltage to generate the plurality of first gray reference voltages, and calculates a difference between a second voltage and each of the first gray reference voltages so as to calculate the plurality of second gray references. Generate a voltage.

The gray reference voltage generator may divide the second voltage to generate a first voltage, a first voltage reference voltage generator to divide the first voltage to generate the plurality of first gray reference voltages; And a second gray reference voltage coupled to the second voltage and the first gray reference voltage generator to generate a plurality of second gray reference voltages by calculating a difference between the second voltage and the first gray reference voltages. It is preferable to include a generation unit.

The reference voltage unit may include at least two resistors connected between the second voltage and the third voltage.

The first gray scale reference voltage generator may include a plurality of resistor strings connected between the reference voltage portion and the third voltage, and the first gray scale reference voltage generator is a voltage divider.

The second gray scale reference voltage generator may include a plurality of operational amplifiers having a non-inverting terminal connected to the second voltage and an inverting terminal connected to each of the first gray reference voltages. Is preferably a differential amplifier.

The plurality of first gray reference voltages may have different polarities from the plurality of second gray reference voltages with respect to the first voltage.

According to another aspect of the present invention, a driving device is a device for driving a display device including a plurality of pixels, and divides a first voltage to generate the plurality of first gray reference voltages, and a second voltage and each of A gray reference voltage generator configured to calculate a difference between one gray reference voltage and generate the plurality of second gray reference voltages, and a plurality of gray voltages based on the first gray reference voltage and the second gray reference voltage, respectively; And a data driver which selects and applies a gray voltage corresponding to an image signal to the pixel.

The driving device of the display device may further include a reference voltage unit configured to generate the first voltage by dividing the second voltage.

The gray reference voltage generator according to the feature may include a resistor string connected in series between the first voltage and the third voltage to generate the plurality of first gray reference voltages, and from the second voltage and the resistor string. The first and second input terminals may be respectively connected to the first gray level reference voltage, and may include a plurality of differential amplifiers, and the resistor string may be a voltage divider.

According to another aspect of the present invention, a reference voltage unit connected between a first voltage and a second voltage and generating a third voltage, and a plurality of first gray level reference voltages connected between the third voltage and the second voltage A first gray scale reference voltage generator configured to generate a first gray scale reference voltage; and a first gray scale reference voltage input to the first gray scale reference voltage and a plurality of second gray scale references based on a difference between the first voltage and the first gray scale reference voltage; And a second gray scale reference voltage generator configured to generate a voltage.

Preferably, the reference voltage unit is a voltage divider having at least two resistors, and the first gradation reference voltage generator is also a voltage divider having a plurality of resistors.                     

The second gray scale reference voltage generator includes a plurality of calculations for inputting the first voltage to a non-inverting terminal, inputting the first gray reference voltage to an inverting terminal, and outputting the second gray reference voltages through an output terminal. It may include an amplifier. In this case, each of the operational amplifier is preferably a differential amplifier.

Preferably, the plurality of first gray reference voltages have different polarities from the plurality of second gray reference voltages with respect to the third 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 part of a layer, film, region, plate, etc. is said to be "on" another part, this includes not only the other part being "right over" 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.

A display device according to an exemplary embodiment of the present invention and a driving device thereof will now 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 connected thereto. And a gray reference voltage generator 800 connected to 500 and a signal controller 600 for controlling the gray level 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 line D ₁ -for transmitting a data signal. 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.

Polarizers (not shown) for polarizing light are 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 reference voltage generator 800 generates two sets of gray reference voltages related to the transmittance of a pixel, that is, a positive gray reference voltage and a negative gray reference voltage. The gray scale reference voltage generator 800 according to an embodiment of the present invention will be described in detail below.

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 use the plurality of divided resistors (not shown) to convert the gray reference voltage from the gray reference voltage generator 800. After dividing the voltage into a plurality of gray voltages, a corresponding gray voltage is selected from the plurality of gray voltages and applied to the pixel as a data signal, which is usually composed of a plurality of integrated circuits.

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 a circuit performing the same functions as those integrated circuit chips may be directly formed on the liquid crystal panel assembly 300 together with the thin film transistors of the pixel. You may.

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 is configured to control the input image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical synchronization signal Vsync and a horizontal synchronization signal ( Hsync, main clock MCLK, and data enable signal DE are 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 transmission 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 ( An inversion signal RVS and a data clock signal HCLK for inverting the polarity of the data voltage with respect to V _com (hereinafter, referred to as the polarity of the data voltage by reducing the polarity of the data voltage with respect to the common voltage).

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 outputs a plurality of data from the gray reference voltage generator 800. After generating a plurality of gray voltages based on the gray reference voltage of, converting the image data DAT to the corresponding data voltage by selecting a gray voltage corresponding to each of the image data DAT from among the gray voltages. It is applied to the 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. ) 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 synchronization signal Hsync, the data enable signal DE, and the gate clock CPV), the data driver 500 and the gate driver 400 are arranged in the next row of pixels. Repeat the same operation for. 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. When one frame ends, 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 (row inversion or dot 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. (Heat inversion, dot inversion).

The gray scale reference voltage generator 800 generates two gray scale reference voltages using only one resistor string. Next, the gray reference voltage generator 800 according to the exemplary embodiment of the present invention will be described in detail with reference to FIG. 3.

3 is a detailed circuit diagram of a gray reference voltage generator according to an exemplary embodiment of the present invention.

As illustrated in FIG. 3, the gray reference voltage generator 800 includes a reference voltage unit 810 connected to a power supply voltage Vdd, a negative gray reference voltage generator 820 connected to a reference voltage unit 810, and a power supply. And a positive gray reference voltage generator 830 connected to the voltage Vdd and the negative gray reference voltage generator 820.                     

The reference voltage unit 810 is a first voltage divider including two voltage divider resistors R11 and R12 connected in series between the power supply voltage Vdd and ground.

The negative gray scale reference voltage generator 820 is a second voltage divider including a plurality of, for example, eight voltage divider resistors R21 to R28 connected in series between the output of the first voltage divider and ground. At this time, the voltage divided by each of the resistors R21-R28 generates the negative gradation reference voltages 7G-, ..., 1G-.

The resistance number of the first and second voltage dividers may vary as needed, and in particular, the resistance number of the second voltage divider may vary based on the number of gray reference voltages to be generated. In addition, the number of gray reference voltages output from the negative gray reference voltage generator 820 and the positive gray reference voltage generator 830 is seven, but the present invention is not limited thereto.

The positive gray scale reference voltage generator 830 has a non-inverting terminal connected to the power supply voltage Vdd, and an inverting terminal connected to each of the gray reference voltages 7G-,..., 1G- from the second voltage divider. A plurality of operational amplifiers OP1-OP7, for example. These operational amplifiers OP1-OP7 act as differential amplifiers and generate positive gradation reference voltages 1G, ..., 7G.

The operation of the gray scale reference voltage generator 800 having such a structure is as follows.

The reference voltage unit 810 divides the power supply voltage Vdd using the resistors R11 and R12, and supplies the divided voltage to the second voltage divider. In this case, the voltage supplied to the second voltage divider is substantially the same as the common voltage V _com .

The negative gray reference voltage generator 820 sequentially divides the voltage from the reference voltage unit 810 and outputs the negative gray reference voltages 7G-,..., 1G-. As described above, since the polarity of the gray reference voltage is determined based on the common voltage V _com , the gray reference voltages 7G-,..., 1G- become negative polarity reference voltages. Among these gray reference voltages 7G-, ..., 1G-, the value of the gray reference voltage 7G- is the largest, and the value of the gray reference voltage 1G- is the smallest.

Each of the gray reference voltages 7G-, ..., 1G- from the negative gray reference voltage generator 820 is connected to an inverting terminal of the operational amplifiers OP1-OP7 of the positive gray reference voltage generator 830. Since the input voltage, the output voltages of the operational amplifiers OP1-OP7 operating as differential amplifiers are the voltages input to the non-inverting terminals, that is, the power supply voltage Vdd and the respective gray level reference voltages 7G-, ... , 1G-). At this time, since these gray reference voltages 1G, ..., 7G are determined based on the common voltage V _com , the gray reference voltages 1G, ..., 7G become positive gray reference voltages.

For this reason, the value of the gradation reference voltage 1G output from the operational amplifier OP1 is the smallest, and the gradation reference voltage 7G output from the operational amplifier OP7 is largest.

In this case, each of the pair of negative gray reference voltages 1G-, ..., 7G- and the positive gray reference voltages 1G, ..., 7G should display the same luminance, and thus the common voltage (V). _com ) is preferably the same size.

When the liquid crystal display is normally white, since the voltage value corresponding to the white gray is the smallest and the voltage value corresponding to the black gray is the largest, the white gray voltage is generated based on the gray reference voltages 1G and 1G-. The black gradation voltage is generated based on the gradation reference voltages 7G and 7G-. However, when the liquid crystal display device is normally black, the voltage value corresponding to the black gray value is the smallest and the voltage value corresponding to the white gray value is the largest, so that the black gray voltage corresponds to the gray reference voltages 1G and 1G-. The white gray voltage is generated based on the gray reference voltages 7G and 7G-.

The gray scale reference voltage generator according to the present invention generates a pair of gray scale reference voltages using one resistor string, so that the number of resistors is reduced by almost half. As a result, the error of the gray scale reference voltage due to the tolerance of the resistance is reduced to generate a more accurate gray scale voltage, thereby improving the image quality of the display device. In addition, power consumption is reduced by the reduced number of resistors, and malfunctions due to heat generation are also reduced.

In addition, since the space occupied by the gray scale reference voltage generator is reduced, the design margin increases.

While only a few gradation reference voltages are generated through an operational amplifier acting as a voltage follower, in the present invention, all positive gradation reference voltages are generated through an operational amplifier, thereby providing a more stable gradation reference voltage to the data driver. to provide.

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 (18)

A liquid crystal panel assembly comprising a plurality of pixels, A gray reference voltage generator which generates a plurality of gray reference voltages, and A data driver generates a plurality of gray voltages based on the plurality of gray reference voltages, and selects and applies a gray voltage corresponding to an image signal to the pixel. Including, The plurality of gray reference voltages include a plurality of first gray reference voltages and a plurality of second gray reference voltages. The gray reference voltage generator divides a first voltage to generate the plurality of first gray reference voltages, and calculates a difference between a second voltage and each of the first gray reference voltages to generate the plurality of second gray reference voltages. doing Display device. In claim 1, The gray reference voltage generator, A reference voltage unit which divides the second voltage to generate the first voltage; A first gray scale reference voltage generator which divides the first voltage to generate the plurality of first gray scale reference voltages, and A second gray scale reference that is applied with the second voltage and is connected to the first gray scale reference voltage generator to calculate a difference between the second voltage and the first gray scale reference voltage to generate the plurality of second gray scale reference voltages Including a voltage generator Display device. In claim 2, The reference voltage unit includes at least two resistors connected between the second voltage and the third voltage. In claim 3, The first gray scale reference voltage generator includes a plurality of resistor lines coupled between the reference voltage unit and the third voltage. In claim 4, And the first gray reference voltage generator is a voltage divider. In claim 5, The second gray scale reference voltage generator includes a plurality of operational amplifiers having a non-inverting terminal connected to the second voltage and an inverting terminal connected to each of the first gray reference voltages. In claim 6, Wherein each operational amplifier is a differential amplifier. In claim 1, The display device of claim 1, wherein the plurality of first gray reference voltages have different polarities from the plurality of second gray reference voltages. An apparatus for driving a display device including a plurality of pixels, A gray reference voltage generator configured to generate a plurality of first gray reference voltages by dividing a first voltage, and to calculate a difference between a second voltage and each of the first gray reference voltages to generate the plurality of second gray reference voltages. , And A data driver which generates a plurality of grayscale voltages based on the first grayscale reference voltage and the second grayscale reference voltage, respectively, and selects and applies a grayscale voltage corresponding to an image signal to the pixel. Driving device for a display device comprising a. In claim 9, And a reference voltage unit which divides the second voltage to generate the first voltage. The method of claim 9 or 10, The gray reference voltage generator, A resistance string connected in series between the first voltage and a third voltage to generate the plurality of first gray reference voltages; and A plurality of differential amplifiers each having first and second input terminals coupled to the second voltage and the respective first gray reference voltages from the resistor string; Containing Drive device for display device. In claim 11, And the resistance heat is a voltage divider. A reference voltage portion connected between the first voltage and the second voltage and generating a third voltage, A first gray reference voltage generator connected between the third voltage and the second voltage to generate a plurality of first gray reference voltages, and A second gray reference voltage generator configured to input the first voltage and the respective first gray reference voltages and to generate a difference between the first voltage and each of the first gray reference voltages as a plurality of second gray reference voltages; Gray reference voltage generating device comprising a. In claim 13, And the reference voltage unit is a voltage divider having at least two resistors. In claim 13, And the first gray scale reference voltage generator is a voltage divider having a plurality of resistors. The method according to any one of claims 13 to 15, The second gray scale reference voltage generator Generating a gradation reference voltage including a plurality of operational amplifiers for inputting the first voltage to a non-inverting terminal, inputting the first gradation reference voltage to an inverting terminal, and outputting each of the second gradation reference voltages through an output terminal Device. The method of claim 16, Each of the operational amplifiers is a differential amplifier. The method of claim 16, And a plurality of first gray reference voltages having different polarities from the plurality of second gray reference voltages.

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