KR20070072675A - Driving apparatus of display device - Google Patents

Abstract

A driving apparatus of a display device is provided to reduce manufacturing cost by varying gamma value of a gamma curve using a gamma selection signal without changing resistance. A driving apparatus of a display device includes a memory(700), a reference grayscale voltage generator(800), and a data driver(500). The memory receives a gamma selection signal whose value is varied according to a user operation selects a reference grayscale data group corresponding to the value of the gamma selection signal from plural reference grayscale data groups, and outputs the selected reference grayscale data group. The reference grayscale voltage generator generates plural reference grayscale voltages, selects a reference grayscale voltage corresponding to respective reference grayscale data of the selected reference grayscale data group, and outputs the selected reference grayscale voltage as a final reference grayscale voltage. The data driver generates plural grayscale voltages based on the final reference grayscale voltage, selects a grayscale voltage corresponding to an image signal, and supplies the selected grayscale voltage to a pixel(PX).

Description

Drive device for display device {DRIVING APPARATUS OF DISPLAY DEVICE}

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

The present invention relates to a driving device of a display device.

A typical liquid crystal display (LCD) includes two display panels provided with pixel electrodes and a common electrode, and a liquid crystal layer having dielectric anisotropy interposed therebetween. The pixel electrodes are arranged in a matrix form and connected to a switching element such as a thin film transistor (TFT) through a gate line and a data line to sequentially receive data voltages one by one. 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 that forms 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.

The liquid crystal display includes a reference gray voltage generator that generates a plurality of reference gray voltages corresponding to the transmittance based on a change in transmittance with respect to a gray scale (hereinafter referred to as a gamma curve), and a plurality of reference gray voltages based on the plurality of reference gray voltages. And a data driver for generating a gray scale voltage, selecting a gray voltage corresponding to the gray level of the input image signal from among the plurality of gray voltages, and applying the gray voltage to the pixel electrode through the switching element as a data voltage.

As such, the gamma curve that affects the data signal depends on many factors that affect the transmittance, for example, the gap between two display panels or the thickness of a color filter formed to implement color display of a liquid crystal display, or a reference gray voltage. The driving voltage applied to the reference gray scale voltage generating unit or the characteristics of the plurality of resistor lines provided to generate the? For this reason, even a plurality of liquid crystal display devices manufactured under the same conditions may be different from each other in the gamma value of each gamma curve.

In addition, although the luminance state varies depending on the user, since the liquid crystal display is manufactured based on a gamma curve having one gamma value, the gamma value may not be changed according to a user's taste.

Accordingly, an object of the present invention is to improve the user's satisfaction by allowing the user to adjust the transmittance of the display device.

According to an aspect of the present invention, a driving device for a display device having a plurality of pixels is a driving device of a display device having a plurality of pixels, and a gamma selection in which a value changes according to a user's operation is provided. A signal is input, a memory in which one reference gradation data group corresponding to the value of the gamma selection signal is selected from among the plurality of reference gradation data groups, and a plurality of reference gradation voltages are generated, and among the plurality of reference gradation voltages A reference gray voltage generator that selects one reference gray voltage corresponding to each reference gray data of the selected reference gray data group and outputs the plurality of final reference gray voltages, and a final reference gray voltage from the reference gray voltage generator Generate a plurality of gray voltages based on the Select a gray voltage corresponding to the video signal to be applied after a data driver for applying to the pixel.

The reference gray voltage generator includes a plurality of resistors connected in series between a driving voltage and a reference voltage and outputs a first reference gray voltage group, and a plurality of resistors connected in series between the reference voltage and ground. And a second resistance string configured to output a second reference gray voltage group and the first reference gray voltage group, respectively, and are respectively based on the reference gray data of the selected reference gray data group. A plurality of first D / A converters for selecting one reference gray voltage and outputting the same to the first final reference gray voltage group, and the second reference gray voltage group, respectively, and applying reference gray levels of the selected reference gray data group Select one reference gray voltage among the second reference gray voltage groups based on the data, and output the second reference gray voltage group as a second final reference gray voltage group. It may include a plurality of second D / A converter.

The gamma selection signal is preferably changed in value depending on the gamma value selected by the user.

The first reference gray voltage group has the opposite polarity with respect to the second reference gray voltage group and the reference voltage and has the same magnitude.

The first final reference gray voltage group may have the same polarity as that of the second final reference gray voltage group and the polarity of the reference voltage.

The reference voltage may be the same as the common voltage.

The memory may be an electrically erasable programmable read-only memory (EEPROM).

The number of bits of the gamma selection signal may vary according to the number of selectable gamma values, and the number of bits of the reference grayscale data may vary depending on the number of reference gray voltages.

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.

A driving device of the liquid crystal display device, which is an embodiment of the driving device of the display device according to the present invention, 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 500 connected thereto. A reference gray voltage generator 800 connected to 500, a signal controller 600 controlling them, and a memory 700 to which a gamma selection signal Sin is applied from the outside and connected to the reference gray voltage generator 800. .

The liquid crystal panel assembly 300 may include a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels PX connected to the plurality of signal lines G ₁ -G _n , D ₁ -D _m , and arranged in a substantially matrix form. Include. On the other hand, in the structure shown in FIG. 2, the liquid crystal panel assembly 300 includes lower and upper panels 100 and 200 facing each other and a liquid crystal layer 3 interposed therebetween.

The 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 plurality of data lines for transmitting a data signal ( 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 PX, for example, the i-th (i = 1, 2, ..., n) gate line G _i and the j-th (j = 1, 2, ..., m) data line D _The pixel PX connected to _j ) includes a switching element Q connected to the signal line G _i D _j , a liquid crystal capacitor Clc, and a storage capacitor Cst connected thereto. Holding capacitor Cst can be omitted as needed.

The switching element Q is a three-terminal element of a thin film transistor or the like provided in the lower panel 100, the control terminal of which is connected to the gate line G _i , and the input terminal of which is connected to the data line D _j . The output terminal is connected to the liquid crystal capacitor Clc and the storage capacitor Cst.

The liquid crystal capacitor Clc has two terminals, the pixel electrode 191 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 191 and 270 is a dielectric material. Function as. The pixel electrode 191 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 the common voltage Vcom. 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 191 and 270 may be formed in a linear or bar shape.

The storage capacitor Cst, which serves as an auxiliary part of the liquid crystal capacitor Clc, is formed by overlapping a separate signal line (not shown) and the pixel electrode 191 provided on the lower panel 100 with an insulator interposed therebetween. A predetermined voltage such as the common voltage Vcom is applied to the separate signal line. However, the storage capacitor Cst may be formed such that the pixel electrode 191 overlaps the front gate line directly above the insulator.

On the other hand, in order to implement color display, each pixel PX uniquely displays one of the primary colors (spatial division) or each pixel PX alternately displays the primary colors over time (time division). The desired color is recognized by the spatial and temporal sum of these primary colors. Examples of the primary colors include three primary colors such as red, green, and blue. FIG. 2 illustrates that each pixel PX includes a color filter 230 representing one of the primary colors in an area of the upper panel 200 corresponding to the pixel electrode 191 as an example of spatial division. Unlike FIG. 2, the color filter 230 may be formed above or below the pixel electrode 191 of the lower panel 100.

At least one polarizer (not shown) for polarizing light is attached to an outer surface of the liquid crystal panel assembly 300.

1 and 3, the reference gray voltage generator 800 receives a reference gray selection signal SEL from the reference gray voltage generator 810 and the memory 700 and is connected to the reference gray voltage generator 810. The reference gray voltage selection unit 820 is included.

The reference gray voltage generator 810 includes a plurality of resistors connected in series between the driving voltage AVDD and the ground, and the plurality of resistors convert the voltage values between the driving voltage AVDD and the ground into a plurality of voltages. The voltage is divided into (V1 + to V8 +, V1- to V8-) and output. At this time, the divided voltage higher than the common voltage Vcom is output as the positive reference gray voltage groups V1 + to V8 +, and the divided voltage lower than the common voltage Vcom is the negative reference gray voltage groups V1- to V8-. Is output as.

The reference gray voltage selection unit 820 selects a predetermined number of reference gray voltages from the reference gray voltage groups V1 + to V8 + of the positive polarity and outputs the first gray level voltages to the final reference gray voltages VG1 +, VG2 +, and VG3 +. A predetermined number of reference gray voltages are selected from the digital-analog conversion unit 821 and the negative reference gray voltage groups V1-V8- and output as the final reference gray voltages VG1-, VG2-, and VG3-. A second D / A converter 822 is included. Each of the D / A converters 821 and 822 may include first to third D / A converters 831 for selecting corresponding final reference gray voltages VG1 +, VG2 +, VG3 +, VG1-, VG2-, and VG3-, respectively. -833, 841-843).

In Fig. 3, the number of voltages of each of the reference gray voltage groups V1 + to V8 + and V1- to V8- is made up of eight, respectively, but the number of these voltages is not limited to this as an example only, and is changed according to the number of grayscales and the like. The number of final reference gray voltages may also be changed.

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 the gate on voltage Von and the gate off voltage Voff. 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 the final reference gray voltages VG1 + to VG3 + and VG1 to VG3- from the gray voltage generator 800. ) To generate a gray voltage for the entire gray level, and to select a data signal among them.

The memory 700 stores a plurality of reference gradation data groups corresponding to the values of the gamma selection signal Sin at respective addresses, and stores one of the plurality of reference gradation data groups according to the value of the gamma selection signal Sin. The reference grayscale data group is selected and applied to the reference grayscale voltage selector 820 of the reference grayscale voltage generator 800 as the reference tone select signal SEL. The memory 610 may be an electrically erasable programmable read-only memory (EEPROM). In FIG. 1, the memory 610 is mounted separately from the signal controller 600 and the like, but may be embedded in the signal controller 600 or the like.

The signal controller 600 controls the gate driver 400, the data driver 500, and the like.

Each of the driving devices 400, 500, 600, and 800 may be mounted directly on the liquid crystal panel assembly 300 in the form of at least one integrated circuit chip, or may be a flexible printed circuit film (not shown). It may be mounted on the liquid crystal panel assembly 300 in the form of a tape carrier package (TCP) or mounted on a separate printed circuit board (not shown). Alternatively, these driving devices 400, 500, 600, and 800 may be integrated in the liquid crystal panel assembly 300 together with the signal lines G ₁ -G _n , D ₁ -D _m and the thin film transistor switching element Q. It may be. In addition, the driving devices 400, 500, 600, and 800 may be integrated into a single chip, in which case at least one of them or at least one circuit element constituting them may be outside the single chip.

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

The signal controller 600 receives input image signals R, G, and B and an input control signal for controlling the display thereof from an external device (not shown). The input video signals R, G, and B contain luminance information of each pixel PX, and the luminance is a predetermined number, for example, 1024 (= 2 ¹⁰ ), 256 (= 2 ⁸ ), or 64 (= 2 ⁶ ) It has gray. Examples of the input control signal include a vertical sync signal Vsync, a horizontal sync signal Hsync, a main clock MCLK, and a data enable signal DE.

The signal controller 600 properly processes the input image signals R, G, and B according to 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. After generating the signal 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 scan start signal STV indicating a scan start and at least one clock signal controlling the output of the gate-on voltage Von. The gate control signal CONT1 may also further include an output enable signal OE that defines the duration of the gate-on voltage Von.

The data control signal CONT2 is a load signal LOAD for applying a data signal to the horizontal synchronization start signal STH indicating the start of the transmission of the image signal for one row of pixels PX and the data lines D ₁ -D _m . ) And a data clock signal HCLK. The data control signal CONT2 is also an inverted signal that inverts the voltage polarity of the data signal relative to the common voltage Vcom (hereinafter referred to as " polarity of the data signal " by reducing the " voltage polarity of the data signal for the common voltage ") RVS) may be further included.

According to the data control signal CONT2 from the signal controller 600, the data driver 500 receives the digital image signal DAT for the pixel PX in one row and corresponds to each digital image signal DAT. The gradation voltage is selected to convert the digital image signal DAT into an analog data signal and then apply it to the data lines D ₁ -D _m .

The gate driver 400 applies the gate-on voltage Von 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. Then, the data signal applied to the data lines D ₁ -D _m is applied to the pixel PX through the switching element Q turned on.

The difference between the voltage of the data signal applied to the pixel PX and the common voltage Vcom is shown as the charging voltage of the liquid crystal capacitor Clc, that is, the pixel voltage. The arrangement of the liquid crystal molecules varies depending on the size of the pixel voltage, and thus the polarization of light passing through the liquid crystal layer 3 changes. The change in polarization is represented as a change in transmittance of light by a polarizer attached to the display panel assembly 300, and thus a desired image may be displayed.

This process is repeated in units of one horizontal period (also referred to as "1H" and equal to one period of the horizontal sync signal Hsync and the data enable signal DE), thereby all the gate lines G ₁ -G _n. ), The gate-on voltage Von is sequentially applied to the data signal to all the pixels PX, thereby displaying an image of one frame.

When one frame ends, the state of the inversion signal RVS applied to the data driver 500 is controlled so that the next frame starts and the polarity of the data signal applied to each pixel PX is opposite to the polarity of the previous frame. "Invert frame"). In this case, the polarity of the data signal flowing through one data line is changed (eg, row inversion and point inversion) or the polarity of the data signal applied to one pixel row is different depending on the characteristics of the inversion signal RVS within one frame. (E.g. column inversion, point inversion).

Next, the reference gray voltage generator 800 which changes the gamma value of the gamma curve by adjusting the value of the final reference gray voltage applied to the data driver 500 according to an exemplary embodiment of the present invention with reference to FIG. 3 described above. Will be described in detail.

As described above with reference to FIG. 3, a reference gray voltage generator including a plurality of resistors and outputting a reference gray voltage group (V1 + to V8 +) and a reference gray voltage group (V1-V8-) of negative polarity is provided. 810 and a reference gray voltage selection unit 820 including D / A converters 821 and 822 to which reference gray selection signals SEL are applied, respectively.

Each of the D / A converters 821 and 822 outputs first and third D / A converters 831 to 833 and 841 to 843 respectively outputting corresponding final reference gray voltages VG1 + to VG3 + and VG1 to VG3-. ).

The operation of the reference gray voltage generator 800 is as follows.

First, when a gamma selection signal Sin whose value changes according to a gamma value selected by a user is applied to the memory 700, the memory 700 stores a reference grayscale data group stored at a corresponding address according to the value of the gamma selection signal Sin. Is transmitted to the reference gray voltage selection unit 820 of the reference gray voltage generator 800.

For example, when the gamma values of the gamma curve selectable by the user are 2.2, 2.3, 2.4, and 2.5, the gamma selection signal Sin is two bits of data. If the gamma value selected by the user is 2.2, the gamma selection signal Sin is 00. If the gamma value is 2.3, the gamma selection signal Sin is 01. If the gamma value is 2.4, the gamma selection signal Sin is 10 and the gamma value is In this case, the gamma selection signal Sin may be 11. As the number of selectable gamma values increases, the number of bits of the gamma selection signal Sin increases.

In the memory 700, reference gray level data groups corresponding to the plurality of reference grayscales G1-G3 are stored at corresponding addresses in accordance with the values of these gamma selection signals Sin.

As an example, as shown in [Table 1], the memory 700 includes the first to third reference gradations G1, G2, and G3 at respective corresponding addresses according to the values of these gamma selection signals Sin. Reference grayscale data groups respectively corresponding to the plurality of reference grayscales are stored. The number of reference gradations is arbitrarily determined. In Table 1, the number of reference gradations is three, and the number of bits of reference gradation data corresponding to each reference gradation is the number of reference gradation voltages (V1 + to V8 + or V1- to V8-). And the number of reference gray scales. That is, each of the D / A converters 831-833 and 841-843 needs to select one reference gray voltage from eight reference gray voltages V1 + to V8 + or V1- to V8-, as the reference gray level selection signal SEL. The acting reference gradation data is 3 bits.

G1 G2 G3 00 000 011 110 01 001 010 101 10 000 100 110 11 010 101 111

Therefore, in [Table 1], when the gamma selection signal Sin is 00, the reference grayscale data for the reference grayscale G1-G3 are selected as 000, 011, and 110, respectively, and 000 is the first final reference grayscale voltage. It serves as the reference gray level selection signal SEL of the first D / A converters 831 and 841 to select (VG1 + and VG1−), respectively, and 011 denotes the second final reference gray level voltages VG2 + and VG2-, respectively. Acts as a reference gradation selection signal SEL of the second D / A converters 832 and 842 to select, 110 denotes a third D / A to select the third final reference gradation voltages VG3 + and VG3- respectively. It serves as a reference gradation selection signal SEL of the converters 833 and 843.

The number of normal gray levels, the gamma selection signal, and the reference gray level data shown in [Table 1] are just one example and can be changed as necessary.

The first D / A converters 831 and 841 correspond to one reference corresponding to the reference gray level selection signal SEL of "000" among the eight input gray level voltage groups V1 + to V8 and V1- to V8- respectively input. The gray voltages are respectively selected and transferred to the data driver 500 as the first final reference gray voltages VG1 + and VG1-, and the second D / A converters 832 and 842 each input eight reference gray voltage groups ( One reference gray voltage corresponding to the reference gray scale selection signal SEL of "011" is selected from among V1 + to V8 and V1- to V8-, respectively, and the data driver (VG2 +, VG2-) is used as the second final reference gray voltage (VG2 +, VG2-). 500, and the third D / A converters 833 and 843 provide a reference gray level selection signal SEL of " 110 " among the eight input gray level voltage groups V1 + to V8 and V1- to V8-. Each of the one reference gray voltages corresponding to the second reference gray voltages VG3 + and VG3- is transmitted to the data driver 500.

As described above, the value of the gamma selection signal Sin varies according to the user's gamma value selection, and the reference gray level data group selected in the memory 700 varies according to the value of the gamma selection signal Sin. As a result, the values of the final reference gradation voltages VG1 +, VG1-, VG2 +, VG2-, VG3 +, and VG3- selected according to the values of the respective reference gradation data of the reference gradation data group change, and these final reference gradation voltages ( According to the values of VG1 +, VG1-, VG2 +, VG2-, VG3 +, and VG3-), the gamma value of the gamma curve has a gamma value selected by the user.

In this case, communication between the gray voltage generator 800 and the memory 700 may be performed through an I ² C communication protocol.

By the change of the gamma selection signal, a plurality of reference gray voltages having a gamma curve having a desired gamma value are generated.

According to the present invention, the gamma value of the gamma curve can be arbitrarily changed by the user by using the gamma selection signal without replacing the resistance value of the resistance string composed of the plurality of divided resistors. As a result, manufacturing cost is reduced, and a simple operation makes it easy to change the gamma value suitable for the characteristics of the display device, thereby increasing user satisfaction and improving image quality.

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 (9)

A driving device of a display device having a plurality of pixels, A memory in which a gamma selection signal whose value changes according to a user's operation is input, and one reference gray level data group corresponding to the value of the gamma selection signal is selected and output from among a plurality of reference gray level data groups; A reference gradation voltage generated by generating a plurality of reference gradation voltages, selecting one reference gradation voltage corresponding to each reference gradation data of the selected reference gradation data group among the plurality of reference gradation voltages, and outputting the reference gradation voltage as a plurality of final reference gradation voltages Generating unit, and A data driver which generates a plurality of gray voltages based on a final reference gray voltage from the reference gray voltage generator, selects a gray voltage corresponding to an image signal applied from the outside, and applies the gray voltage to the pixel. Driving device for a display device comprising a. In claim 1, The reference gray voltage generator, A first resistor string comprising a plurality of resistors connected in series between the driving voltage and the reference voltage and outputting a first reference gray voltage group; A second resistor string comprising a plurality of resistors connected in series between the reference voltage and ground and outputting a second reference gray voltage group; Each of the first reference gray voltage groups is applied, selects one reference gray voltage among the first reference gray voltage groups based on the reference gray data of the selected reference gray data group, and then selects a reference gray voltage as the first final reference gray voltage group. A plurality of first D / A converters to output, and Each of the second reference gray voltage groups is applied, selects one reference gray voltage among the second reference gray voltage groups based on the reference gray data of the selected reference gray data group, and then selects the second reference gray voltage group as the second final reference gray voltage group. A plurality of second D / A converters to output Driving device for a display device comprising a. In claim 1, And a gamma selection signal whose value varies according to a gamma value selected by a user. In claim 2, The first reference gray voltage group has a polarity opposite to the second reference gray voltage group and the reference voltage and has the same magnitude. In claim 2, The first final reference gray level voltage group has a polarity opposite to the second final reference gray level voltage group and the reference voltage, and has the same size as each other. In claim 2, And the reference voltage is the same as the common voltage. In claim 1, And the memory is an electrically erasable programmable read-only memory (EEPROM). In claim 1, And the number of bits of the gamma selection signal varies depending on the number of selectable gamma values. In claim 1, And a number of bits of the reference gray scale data varies depending on the number of the reference gray voltages.

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