KR100900540B1 - Gamma viltage generating circuit and apparatus for driving liquid crystal device using the same - Google Patents

Abstract

The present invention relates to a gray voltage generator and a driving device of a liquid crystal display using the same.

In the driving apparatus according to the present invention, a plurality of gate lines and data lines are formed in row and column directions, respectively, and the switching is connected to the gate line and the data line, respectively, in an area defined by the intersection of the gate line and the data line. A driving device of a liquid crystal display including a liquid crystal panel having a device and a plurality of pixels having a liquid crystal capacitor positioned between the switching element and the common electrode, specifically, a gate driver for supplying a gate voltage to the gate line; A data driver supplying a corresponding gray voltage to the data line according to an applied data signal; And a gray voltage generator generating the gray voltage. The gray voltage generator may include a plurality of gamma resistors formed in series between the first reference voltage and the second reference voltage and output a gray voltage at a contact point between the gamma resistors; And a voltage corrector including a plurality of correction resistors for correcting a gray voltage generated by being connected between the contacts of the gamma resistors, wherein the first reference voltage and the second reference voltage are DC voltages.

According to the present invention, gamma correction can be easily performed without using a separate circuit to change the first and second reference voltages, which are gamma reference voltages.

LCD, gradation voltage correction, gamma correction, luminance measurement

Description

GAMMA viltage generating circuit and apparatus for driving liquid crystal device using the same

1 is a structural 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 illustrating a structure of a gray voltage generator according to an exemplary embodiment of the present invention.

4 is a waveform diagram illustrating gamma reference voltage characteristics according to an exemplary embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display (hereinafter, referred to as an LCD), and more particularly, a gray voltage generation circuit for generating a gray voltage supplied to a liquid crystal display, and a driving device of the liquid crystal display using the same. It is about.

A typical liquid crystal display (LCD) includes a liquid crystal layer having dielectric anisotropy interposed between two display panels. The desired image is obtained by applying an electric field to the liquid crystal layer and adjusting the intensity of the electric field to adjust the transmittance of light passing through the liquid crystal layer. 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.

Such a TFT-LCD includes a plurality of gate lines that transmit scan signals and data lines that are formed to intersect the gate lines, and which transfer image data, and are formed in areas surrounded by these gate lines and data lines, respectively, and are respectively gate lines and data. It includes a plurality of pixels in the form of a matrix connected through lines and switching elements.

As a method of applying image data to each pixel in such an LCD, first, a gate-on signal, which is a scanning signal, is sequentially applied to gate lines to sequentially turn on a switching element connected to the gate line, and simultaneously to the gate line. An image signal (more specifically, a gradation voltage) to be applied to the corresponding pixel row is supplied to each data line. Then, the image signal supplied to the data line is applied to each pixel through the turned-on switching element. At this time, by sequentially applying the gate-on signal to all the gate lines for one frame period and applying the image signal to all the pixel rows, an image of one frame is eventually displayed.

As such, the gray scale voltage applied to the data line of the LCD refers to the voltage applied to the source electrode of the switching element to generate gray scale (typically, bright and dark in color), and in the color TFT LCD, gray scale is a graphic controller. It is determined by the number of bits of red (R), green (G), and blue (G) data coming from the data. That is, for example, if the R data comes in 6 bits, gray scales of 2 ⁶ = 64 are generated, so that 64 gray scales can be represented.

 In order to express 64 gray levels, 64 gray voltages are required, and in order to generate these gray voltages, 64 voltages must be supplied to the data driver by dividing the voltage between 0V-10V (for high voltage driving) into 64 equal parts. . However, since there is a part that generates 8 equal voltages in the data driver, eight gray voltages may be supplied from the outside. Therefore, the nine gray scale voltages may be inserted into the data driver so that they can be divided into eight equal parts between 0V and 10V. There are two methods of generating such a gray scale voltage using a resistance string method and a voltage amplification method.

The conventional gray voltage generation circuit which generates the gray scale voltage by using the resistive string method modulates and supplies a gamma reference voltage for generating the gray scale voltage by one line during line inversion driving. The transmittance curve of most liquid crystals is not symmetrical between the white side when the first voltage is applied based on the intermediate luminance and the black side when a very large voltage is applied, and the visual perception ability of the human being also makes a difference between white and black. Therefore, a gamma correction that changes the gamma reference voltage according to the change of the common voltage should be performed.

In order to change the gamma reference voltage, a separate circuit is used, and when such a circuit is used, the charge / discharge is performed by a load of an input unit for inputting a gray voltage input to a digital / analog (D / A) converter in the data driver. Current consumption occurs in the. In addition, the power consumption increases according to the power consumption of the circuit itself.

Therefore, the technical problem to be achieved by the present invention is to solve the conventional problems as described above, to provide a gray scale voltage generation circuit that can facilitate gamma correction without using a separate circuit for changing the gamma reference voltage It is.

Another object of the present invention is to provide a liquid crystal display device having excellent gamma characteristics and low power consumption by using the gray voltage generator.

According to an aspect of the present invention, a gray voltage generation circuit includes a plurality of gamma resistors formed in series between a first reference voltage and a second reference voltage, and a gray level at a contact point between the respective gamma resistors. A voltage generator for outputting a voltage; And a voltage corrector including a plurality of correction resistors configured to correct the gray voltages generated by being connected between the contacts of the gamma resistors, respectively.

In addition, in the driving apparatus of the liquid crystal display according to another aspect of the present invention, a plurality of gate lines and data lines are formed in row and column directions, respectively, and the gates are respectively defined in regions defined by intersections of the gate lines and data lines. And a liquid crystal panel including a switching element connected to a line and a data line, and a liquid crystal panel having a plurality of pixels having a liquid crystal capacitor positioned between the switching element and the common electrode. A gate driver supplying a gate voltage; A data driver supplying a corresponding gray voltage to the data line according to an applied data signal; And a gray voltage generator generating the gray voltage, wherein the gray voltage generator includes a plurality of gamma resistors formed in series between a first reference voltage and a second reference voltage, and a gray level at a contact point between the gamma resistors. A voltage generator for outputting a voltage; And a voltage corrector including a plurality of correction resistors connected to the contacts of the gamma resistors, respectively, to correct the gray voltages. The first reference voltage and the second reference voltage are DC voltages.

In the present invention having such a feature, wherein the gamma resistors R1, R2, .. Rn and the correction resistors r1, r2, ... r _n when,

(R1 ∥ r1) = (R _n ∥ r _n ) ≠ (R2 ∥r2) = (R _n-1 ∥r _n-1 ) ≠. ≠ (R _{n / 2} ∥r _{n / 2} ) = (R _{(n / 2) +1} ∥r _{(n / 2) +1} )

Satisfies.

At this time, the common voltage applied to the common electrode is variable.

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. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention.                     

1 illustrates a structure of a liquid crystal display device showing an embodiment of the present invention.

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 according to an exemplary embodiment of the present invention.

As shown in FIG. 1, the liquid crystal display according to the present invention includes a liquid crystal panel assembly 300 or a gate driver 400 and a data driver connected thereto. data driver 500, a driving voltage generator 700 connected to the gate driver 400, a gray voltage generator 800 connected to the data driver 500, first and The second data line shared switching unit 910 and 920 and the shared signal generator 600 are included.

The liquid crystal panel assembly 300 includes a plurality of signal lines G ₁ -G _n , D ₁ -D _m and a plurality of pixels connected thereto in an equivalent circuit, and each pixel includes the signal lines G ₁ -G. _n , D ₁ -D _m ), a switching element Q connected to the liquid crystal capacitor C _lc and a storage capacitor C _st connected thereto. The signal lines G ₁ -G _n , D ₁ -D _m transmit a scanning signal or a gate signal, and the plurality of scanning signal lines or gate lines G ₁ -G _n extending in the row direction. And a data signal line or data line D ₁ -D _m which transmits an image signal or a data signal and extends in the column direction. The switching element Q is a three-terminal element, the control terminal of which is connected to the gate line G ₁ -G _n , the input terminal of which is connected to the data line D ₁ -D _m , and the output terminal of the liquid crystal capacitor ( C _lc ) and one terminal of the holding capacitor C _st .

The liquid crystal capacitor C _lc is connected to the output terminal of the switching element Q and a common voltage V _com or a reference voltage. The other terminal of the holding capacitor C _st is connected to another voltage, for example a reference voltage V _com . However, the other terminal of the holding capacitor C _st may be connected to the gate line directly above (hereinafter referred to as "previous gate line"). The former connection method is called an independent wiring method, and the latter connection method is called a prior gate type.

Meanwhile, the liquid crystal panel, that is, the liquid crystal panel assembly 300 may be schematically illustrated as shown in FIG. 2. For convenience, only one pixel is shown in FIG. 2.

As shown in FIG. 2, the liquid crystal panel assembly 300 includes a lower panel 100 and an upper panel 200 facing each other and a liquid crystal layer 3 therebetween. The lower panel 100 includes gate lines G _i-1 , G _i , a data line D _j , a switching element Q, and a storage capacitor C _st . The liquid crystal capacitor C _lc has two terminals as the pixel electrode 190 of the lower panel 100 and the reference electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270 is It functions as a dielectric.

The pixel electrode 190 is connected to the switching element Q, and the reference electrode 270 is formed on the entire surface of the upper panel 200 and is connected to the common voltage V _com .

Herein, the liquid crystal molecules change their arrangement according to the change of the electric field generated by the pixel electrode 190 and the reference 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 the pixel electrode 190, a separate wiring to which a reference voltage is applied is provided on the lower panel 100 to overlap the pixel electrode 190 to form the storage capacitor C _st . For the previous gate way form the two terminals of the pixel electrode 190 is maintained with a previous gate line (G _i-1) by being overlapped with the previous gate line (G _i-1), an insulator as a medium capacitor (C _st).

FIG. 2 shows a MOS transistor as an example of the switching element Q, which is implemented as a thin film transistor having amorphous silicon or polysilicon as a channel layer in an actual process.

Unlike in FIG. 2, the reference electrode 270 may be provided in the lower panel 100. In this case, both electrodes 190 and 270 are linearly formed.

On the other hand, in order to implement color display, each pixel should be able to display color, which is provided by a color filter 230 of red, green, or blue in a region corresponding to the pixel electrode 190. It is possible. The color filter 230 is mainly formed in the corresponding region of the upper panel 200 as shown in FIG. 2, but may be formed above or below the pixel electrode 190 of the lower panel 100.

Referring back to FIG. 1, the driving voltage generator 700 may turn on the gate-on voltage V _on for turning _on the switching element Q of each pixel, and the gate-off voltage V _off for turning off the switching element Q. FIG. ), And so on.

The gate driver 400, also referred to as a scan driver, is connected to the gate line Gi of the liquid crystal panel assembly 300, and includes a gate on voltage V _on provided from the driving voltage generator 700. A gate signal composed of a combination of the gate off voltage V _off is applied to the gate line Gi. The gate driver 400 includes at least one gate driver IC.

The data driver 500 may also be referred to as a source driver. The data driver 500 may be connected to the data line Di of the liquid crystal panel assembly 300 to select a gray voltage from the gray voltage generator 800 to select a gray voltage as a data signal. Di). The data driver 500 includes at least one data driver IC.

The timing controller 600 generates a control signal for controlling operations of the gate driver 400, the data driver 500, and the driving voltage generator 700, and outputs a corresponding control signal to the gate driver 400, The data driver 500 and the driving voltage generator 700 are supplied to the data driver 500 and the driving voltage generator 700.

Meanwhile, the gray voltage generator 800 according to the embodiment of the present invention generating and supplying a gray voltage to the data driver 500 has a structure as shown in FIG. 3.

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

Referring to FIG. 3, the gray voltage generator 800 includes a voltage generator 810 and a voltage corrector 820 that generate gray voltages.

The voltage generator 810 includes a plurality of gamma resistors RA, R1, R2, ..., R9, R10, which are formed in series between the first reference voltage VA: AVDD and the second reference voltage VB: GND. RB). The voltages V0, V1, V2, ..., V9, V10 of the contacts between the gamma resistors are the resistors RA, R1, R2, ..., R9, R10, RB and a first reference voltage. Obtained by (AVDD).

The voltage corrector 820 includes a plurality of correction resistors r1, r2, r3, ..., r9, respectively connected between the contacts of the gamma resistors RA, R1, R2, ..., R9, R10, and RB. r10).

In an embodiment of the present invention, the first and second reference voltages, which are gamma reference voltages, are fixed direct current (DC), and the common voltage Vcom is variable. 4, a characteristic waveform diagram of each voltage according to this embodiment of the present invention is shown.

Although the gamma correction is performed to change the gamma reference voltage according to the change of the common voltage according to the asymmetry in the curve representing the transmittance characteristic of the liquid crystal display and the human visual perception characteristic, in the exemplary embodiment of the present invention, the gamma reference voltage is fixed. Since the voltage correction unit 820 applies the appropriate gray level voltage according to the change of the common voltage, the gray level voltages V0, V1, V2, ..., of the contacts between the gamma resistors of the voltage generator 810 are applied. Correct the V9, V10).

To this end, each of the correction resistors r1, r2, r3,..., R9, r10 of the voltage corrector 820 is connected between each contact point at which the gray scale voltage is output, and gamma connected in parallel to each other. The relationship between the resistance and the compensation resistor satisfies

(R1∥r1) = (R10∥r10) ≠ (R2∥r2) = (R9∥r9) ≠ (R3∥r3) = (R8∥r8) ≠ (R4∥r4) = (R7∥r7) ≠ (R5 ∥r5) = (R6 ∥r6)

Here, the total resistance (RT) of the gray voltage generator 800 is RA + (R 1 ∥ r 1) + (R 2 ∥ r 2) +. + (R10∥r10) + RB.

In the exemplary embodiment of the present invention, a plurality of gray voltages are generated using a single resistor string instead of generating a negative gray voltage and a positive gray voltage using a separate resistor string. The gray scale voltage is generated in consideration of asymmetry and human visual perception.

 To this end, as described in Equation 1 above, the values of the gamma resistors and the correction resistors at the corresponding positions are the same as those of the gamma resistors and the correction resistors located opposite to the reference point. Set the resistance value of each resistor to have.

For example, the voltages in the order of 0, V1, V2, and V3 .. are taken as positive gray voltages, and the voltages in the order of V10, V9, V8, V7 ... are taken as negative gray voltages.

Accordingly, when the gray scale voltage of the positive polarity is to be output, for example, in response to the change of the common voltage, the data driver 600 may output the data driver 600 from the timing controller 600 among the gray voltages formed in the order of V0, V1, ..V9, V10. The gradation voltage corresponding to the applied image data is selected and output.

On the other hand, when the gray scale voltage of negative polarity is to be outputted, the gray scale voltage corresponding to the image data applied from the timing controller 600 is selected from among the gray voltages formed in the order of V10, V9, 8, ..., V1, V0. Select and print.

Therefore, an appropriate gray scale voltage may be selected and provided to each pixel according to the change of the common voltage without changing the gamma reference voltage using one resistor string.

As mentioned above, although embodiment of this invention was described, this invention is not limited only to the above-mentioned embodiment, A various other deformation | transformation and a change are possible. For example, the gamma resistance and the correction resistor of the gray voltage generator described above may include R1 to R10, r1 to r10, and the like. However, the gamma resistance and the correction resistor may be used. Even in this case, according to the above equation (R1 ∥ r1) = (R _n ∥ r _n ) ≠ (R2 ∥r2) = (R _n-1 ∥r _n-1 ) ≠…. The condition of (R _{n / 2} ∥r _{n / 2} ) = (R _{(n / 2) +1} ∥r _{(n / 2) +1} ) is established.

According to the present invention described above, gamma correction can be facilitated without using separate circuits to change the first and second reference voltages which are gamma reference voltages. Accordingly, a liquid crystal display device having excellent gamma characteristics and low power consumption can be provided.

Claims (5)

A plurality of gate lines and data lines are formed in row and column directions, respectively, and a switching element connected to the gate line and the data line in a region defined by the intersection of the gate line and the data line, respectively, and the switching element and the common electrode. A drive device for a liquid crystal display device comprising a liquid crystal panel in which a plurality of pixels having liquid crystal capacitors positioned therebetween are formed. A gate driver supplying a gate voltage to the gate line; A data driver supplying a corresponding gray voltage to the data line according to an applied data signal; And A gray voltage generator to generate the gray voltage Including, The gray voltage generator A voltage generator including a plurality of gamma resistors formed in series between the first reference voltage and the second reference voltage, and outputting a gray voltage at a contact point between the gamma resistors; And A voltage correction unit including a plurality of correction resistors for correcting a gray voltage generated by being connected between the contacts of the gamma resistors, respectively Wherein the first reference voltage and the second reference voltage are DC voltages, A first correction resistor of the plurality of correction resistors is connected in parallel to a first gamma resistor of the plurality of gamma resistors, A second gamma resistor of the plurality of gamma resistors is symmetrical with a first gamma resistor based on a reference point, and a second correction resistor of the plurality of correction resistors is connected in parallel to the second gamma resistor, And a resistance value of the first gamma resistor and the first correction resistor has a same value as that of the second gamma resistor and the second correction resistor. The method of claim 1, Drive device for a liquid crystal display device according to the gamma resistance from the gray voltage generator satisfy R1, R2, .. Rn, in which the said compensation resistors r1, r2, ... r _n one time, the following relationship. (R1 ∥ r1) = (R _n ∥ r _n ) ≠ (R2 ∥r2) = (R _n-1 ∥r _n-1 ) ≠. ≠ (R _{n / 2} ∥r _{n / 2} ) = (R _{(n / 2) +1} ∥r _{(n / 2) +1} ) The method of claim 1, A driving device of the liquid crystal display device, wherein the common voltage applied to the common electrode is variable. A voltage generator including a plurality of gamma resistors formed in series between the first reference voltage and the second reference voltage, and outputting a gray voltage at a contact point between the gamma resistors; And A voltage correction unit including a plurality of correction resistors for correcting a gray voltage generated by being connected between the contacts of the gamma resistors, respectively Wherein the first reference voltage and the second reference voltage are DC voltages, A first correction resistor of the plurality of correction resistors is connected in parallel to a first gamma resistor of the plurality of gamma resistors, A second gamma resistor of the plurality of gamma resistors is symmetrical with a first gamma resistor based on a reference point, and a second correction resistor of the plurality of correction resistors is connected in parallel to the second gamma resistor, And a gray value voltage generating circuit having a resistance value of the first gamma resistor and the first correction resistor having the same value as that of the second gamma resistor and the second correction resistor. The method of claim 4, wherein The gamma resistors R1, R2, .. Rn, and the gray level voltage generation circuit in which the correction resistors satisfy the following relationship when the r1, r2, ... r _n. (R1 ∥ r1) = (R _n ∥ r _n ) ≠ (R2 ∥r2) = (R _n-1 ∥r _n-1 ) ≠. ≠ (R _{n / 2} ∥r _{n / 2} ) = (R _{(n / 2) +1} ∥r _{(n / 2) +1} )

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