KR101055196B1 - Driving circuit of liquid crystal display device - Google Patents

Abstract

The present invention relates to a driving circuit of a liquid crystal display device and a method of driving the same, comprising a plurality of gray voltage generators to easily correct gamma values according to characteristics of an image, and a reference voltage generator for outputting a plurality of reference voltages. ; A plurality of gray voltage generators outputting gray voltages representing gamma curves having different gamma values with respect to the reference voltages input; The reference voltage switching unit may be configured to switch the plurality of reference voltages output from the reference voltage generator according to the input external control signal, and input the at least one of the plurality of gray voltage generators.

LCD, gradation voltage, luminance, gamma curve, gamma value, reference voltage

Description

The driving circuit of liquid crystal display device and the method for driving the same}

1 is a circuit diagram of a liquid crystal display device including a gray scale voltage generation unit of a conventional resistance column method.

2 is a graph showing a gamma curve

3 is a circuit diagram of a driving circuit of a liquid crystal display according to a first embodiment of the present invention.

4 is a circuit diagram of a driving circuit of a liquid crystal display according to a second embodiment of the present invention.

* Explanation of symbols on the main parts of the drawings

130: reference voltage generator 100: reference voltage switching unit

125: data driver Vref0 to Vref13: reference voltage

SW: switch GMA0 to GMA127: gradation voltage

GMA0` to GMA127`: gradation voltage 180a: first terminal

180b: second terminal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a driving circuit of a liquid crystal display device having a plurality of gradation voltage generators having gamma curves having different gamma values to correct a gamma value according to an image.

A typical liquid crystal display (LCD) includes two opposing substrates and a liquid crystal layer having dielectric anisotropy therebetween.

Such a liquid crystal display device applies a electric field to the liquid crystal layer, and adjusts the intensity of the electric field 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 TFT-LCD includes a plurality of gate lines for transmitting a scan signal and data lines perpendicular to the gate lines, and includes data lines for transmitting image data. The TFT-LCDs are formed in a pixel area surrounded by the gate lines and the data lines. Each pixel includes a plurality of pixels in the form of a matrix connected through the gate line, the data line, and the thin film transistor.

In the LCD, image data is applied to each pixel. First, a thin film transistor connected to the gate line is sequentially turned on by sequentially applying a gate-on signal, which is a scan signal, to the gate lines. An image signal (more specifically, a gradation voltage) to be applied to the pixel row corresponding to the line is supplied to each of the data lines. Then, the image signal supplied to the data line is applied to each pixel through the turned-on thin film transistor. 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 a voltage applied to the source electrode of the thin film transistor to generate a gray scale (typically, the color is bright and dark). It is determined by the number of bits of red (R), green (G) and blue (G) data coming from the controller. 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.

 64 gray scale voltages are required to express 64 gray scales. To make these gray scale voltages, 64 voltages must be supplied to the data driver by dividing the voltage between 0V-10V (for high voltage driving) in 64 equal parts. do. However, in practice, since there are parts that generate 8 equal voltages in the data driver, 8 gray voltages need to be supplied from the outside. Therefore, nine gray voltages may be inputted to the data driver so as to be divided into eight equal portions between 0V and 10V. There are two methods of generating the gray scale voltages, a resistance heat method and a voltage amplification method.

Hereinafter, a driving circuit of a liquid crystal display device provided with a gray scale voltage generator of a conventional resistance column method will be described in detail with reference to the accompanying drawings.

1 is a circuit diagram of a liquid crystal display device including a gray scale voltage generation unit of a conventional resistance heat method.

As shown in FIG. 1, a driving circuit of a conventional liquid crystal display device having a gray scale voltage generator of a resistance column type is provided outside the data driver 25 and includes a plurality of reference voltages Vref0, Vref1,. A reference voltage generator 30 providing Vref13 and the data driver 25 are provided in the data driver 25 and reference voltages Vref0, Vref1, ... of the reference voltage generator 30 are provided. , A gray voltage generator for outputting a plurality of gray voltages GMA0, GMA1, ..., GMA127 by voltage-dividing each of the reference voltages Vref0, Vref1, ...., Vref13 by receiving Vref13. 40 is comprised. Although not shown in the drawing, the reference voltage generator 30 may include the positive reference voltages Vref0, Vref1, ..., Vref7 among the reference voltages Vref0, Vref1, ..., Vref13. A negative reference voltage unit for outputting a negative reference voltage unit for outputting negative reference voltages Vref8, Vfef9, ... Vref13 among the reference voltages Vref0, Vref1, ..., Vref13. It is composed.

The positive reference voltage unit includes a positive voltage power source, a common voltage terminal, and a plurality of resistors connected in series between the positive voltage source and the common voltage terminal. The negative reference voltage unit includes a negative voltage power source, the common voltage terminal, and a plurality of resistors connected in series between the negative voltage power source and the common voltage terminal.

The positive reference voltage unit configured as described above outputs a plurality of positive reference voltages Vref0, Vref1, ..., Vref7 in which the positive voltage of the positive voltage power supply is divided from the node of each resistor. The polar reference voltage unit outputs a plurality of negative reference voltages Vref8, Vfef9, ... Vref13 obtained by dividing the negative voltage of the negative voltage power supply from the node of each resistor.

Meanwhile, the gray voltage generator 40 receives the positive reference voltages Vref0, Vref1, ..., Vref7 and receives the positive gray level among the gray voltages GMA0, GMA1, ..., GMA127. The gray scale voltages GMA0 and GMA1 are input by receiving the positive gray voltage unit that outputs the voltages GMA0, GMA1, ..., GMA63 and the negative reference voltages Vref8, Vfef9, ... Vref13. And a negative gray voltage unit 40b which outputs negative gray voltages GMA64, GMA65, ..., GMA127 among the GMA127. Here, the positive gray voltage unit 40a includes a plurality of resistors connected in series, and each of the positive reference voltages Vref0, Vref1,..., And Vref7 is voltage-distributed from a node of each resistor. A plurality of positive gray voltages GMA0, GMA1, ..., GMA127 are output. The negative gray voltage unit 40b includes a plurality of resistors connected in series, and each of the negative reference voltages Vref8, Vfef9, ... Vref13 is voltage-divided from a node of each resistor. Negative gray voltages GMA64, GMA65, ..., GMA127 are output.

Here, the relationship between the gray scale voltages GMA0, GMA1, ..., GMA127 outputted from the gray voltage generator 40 and the transmittance according to the magnitude of the gray voltages GMA0, GMA1, ..., GMA127 Referring to the gamma curve shown in detail as follows.

2 is a graph showing a gamma curve.

The gamma curve of FIG. 2 is a graph showing the relationship between the positive grayscale voltages GMA0, GMA1,..., GMA63 and the transmittance, and the positive grayscale voltages GMA0, GMA1,. As this increases, it shows a normally black mode in which transmittance increases.

The gamma curve indicates luminance of an image displayed on the liquid crystal panel of the liquid crystal display. As the gamma value of the gamma curve increases, the transmittance according to the positive gray voltages GMA0, GMA1,..., GMA63 is increased. The image becomes dark as a whole, and as the gamma value of the gamma curve decreases, transmittance according to each of the positive gray voltages GMA0, GMA1,..., GMA63 increases to brighten the image as a whole. . Meanwhile, although not described separately, the gamma curve represented by the negative gray voltages GMA64, GMA65, ..., GMA67 is also determined by the positive gray voltages GMA0, GMA1, ..., GMA63. It has the same characteristics as the gamma curve represented.

In general, the gray scale voltage generator 40 provided in the same resolution and the same size liquid crystal display devices manufactured in the same process line shows a gamma curve having the same gamma value, and the liquid crystal to which the gamma curve having the same gamma value is applied. Even the display device may display different luminance according to the characteristics of each liquid crystal display device.

For example, when there are first and second liquid crystal display devices having the same resolution and size as each other, the gamma value of the first gamma curve applied to the first and second liquid crystal display devices is equal to the first liquid crystal display. Even if the luminance of the image displayed on the device is properly expressed, a problem may occur in that the luminance of the image displayed on the second liquid crystal display device cannot be properly expressed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and includes a plurality of gray voltage generators having different gamma curve characteristics and a reference voltage switching unit for selecting one of the plurality of gray voltage generators. It is an object of the present invention to provide a driving circuit of a liquid crystal display device capable of improving the quality of the device.

The driving circuit of the liquid crystal display according to the embodiment of the present invention for achieving the above object includes a reference voltage generator for outputting a plurality of reference voltages; A plurality of gray voltage generators outputting gray voltages representing gamma curves having different gamma values with respect to the reference voltages input; The reference voltage switching unit may be configured to switch the plurality of reference voltages output from the reference voltage generator according to the input external control signal, and input the at least one of the plurality of gray voltage generators.

Hereinafter, a driving circuit 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.

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3 is a circuit diagram of a driving circuit of the liquid crystal display according to the first embodiment of the present invention.

As shown in FIG. 3, the driving circuit of the liquid crystal display according to the first exemplary embodiment of the present invention may include a reference voltage generator for providing a plurality of reference voltages Vref0, Vref1,. 130 and a plurality of gray voltages GMA0 and GMA1 representing the characteristics of the first gamma curve by voltage-dividing each of the reference voltages Vref0, Vref1, ..., Vref13 of the reference voltage generator 130. Voltage distribution of the first gray voltage generator 140 outputting the GMA127 and the reference voltages Vref0, Vref1, ..., Vref13 of the reference voltage generator 130, respectively. The second gray voltage generator 150 outputs a plurality of gray voltages GMA0`, GMA1`, ..., GMA127` representing the characteristics of the second gamma curve, and according to the input external control signal. Select one of the first and second gray voltage generators 140 and 150, and switch the reference voltages Vref0, Vref1,..., And Vref13 of the reference voltage generator 130. A reference voltage switching unit 100 selectively applied only to the selected gradation voltage generator, and the first and second gradation voltage generators 140 and 150, and the first and second gradation voltage generators 140, A gray level voltage corresponding to an input data signal among the gray level voltages GMA0, GMA1, ..., GMA127 and GMA0`, GMA1`, ..., GMA127` outputted from 150 is selected to be displayed on the display unit of the LCD panel. And a digital-to-analog converter (not shown) of the data driver 125 to apply.

Although not shown in the drawing, the reference voltage generator 130 may include the positive reference voltages Vref0, Vref1, ..., Vref7 among the reference voltages Vref0, Vref1, ..., Vref13. A negative reference voltage unit for outputting a negative reference voltage unit for outputting negative reference voltages Vref8, Vref9, ... Vref13 among the reference voltages Vref0, Vref1, ..., Vref13. It is composed. The positive reference voltage unit includes a positive voltage power supply for outputting a positive voltage, a common voltage terminal to which a common voltage is applied, and a plurality of resistors connected in series between the positive voltage power source and the common voltage terminal. . The negative reference voltage unit includes a negative voltage power supply for outputting a negative voltage, a plurality of resistors connected in series between the common voltage terminal and the negative voltage power supply and the common voltage terminal.

The positive reference voltage unit configured as described above outputs a plurality of positive reference voltages Vref0, Vref1, ..., Vref7 in which the positive voltage of the positive voltage power supply is divided from the node of each resistor. The polar reference voltage unit outputs a plurality of negative reference voltages Vref8, Vref9, ... Vref13 in which the negative voltage of the negative voltage power supply is divided from the node of each resistor.

Meanwhile, the first gray voltage generator 140 receives the positive reference voltages Vref0, Vref1,..., And Vref7, and determines among the gray voltages GMA0, GMA1,..., GMA127. The gray level voltage is input by receiving the positive gray level voltage unit 140a that outputs the polar gray level voltages GMA0, GMA1, ..., GMA63 and the negative reference voltages Vref8, Vfef9, ... Vref13. And a negative gray voltage unit 140b for outputting negative gray voltages GMA64, GMA65, ..., GMA127 among the fields GMA0, GMA1, ..., GMA127. Here, the positive gray voltage unit 140a includes a plurality of resistors R connected in series, and the positive reference voltages Vref0, Vref1, ..., from the node of each resistor R. The positive gray level voltages GMA0, GMA1, ..., GMA63, each of which is divided by voltage, are output. In addition, the negative gray voltage unit 140b includes a plurality of resistors R connected in series, and the negative reference voltages Vref8, Vfef9, ... Vref13 from a node of each resistor R. The negative gray voltages GMA64, GMA65, ..., GMA127, each of which is divided by voltage, are output.

In addition, the second gray voltage generator 150 receives the positive reference voltages Vref0, Vref1, ..., Vref7 and receives the gray voltages GMA0`, GMA1`, ..., GMA127`. ) And the positive gray voltage unit 150a for outputting the positive gray voltages GMA0`, GMA1`, ..., GMA63`, and the negative reference voltages Vref8`, Vfef9`, ... Negative gradation to receive the negative gradation voltages GMA64`, GMA65`, ..., GMA127` among the gradation voltages GMA0`, GMA1`, ..., GMA127`. The voltage unit 150b is included. Here, the positive gray voltage unit 150a includes a plurality of resistors R ′ connected in series, and the positive reference voltages Vref0, Vref1,... From the node of each resistor R ′. , Vref7) is outputted by the positive gradation voltages GMA0`, GMA1`, ..., GMA63` each of which voltage is divided. The negative gray voltage unit 150b includes a plurality of resistors R ′ connected in series, and the negative reference voltages Vref8, Vfef9,... From the node of each resistor R ′. The negative gray level voltages GMA64 ', GMA65', ..., GMA127 ', each of which is voltage-divided, are output.

Here, although the first gray voltage generator 140 and the second gray voltage generator 150 are applied with the same reference voltages Vref0, Vref1, ..., Vref13, respectively, the first gray voltage Since the resistance values of the resistors R configured in the generator 140 and the resistance values of the resistors R ′ configured in the second gray voltage generator 150 have different values, the first gray levels may be different. The gamma value of the first gamma curve according to the gray voltages GMA0, GMA1,..., GMA127 output from the voltage generator 140 and the gray voltages output from the second gray voltage generator 150 ( Gamma values of the second gamma curve according to GMA0`, GMA1`, ..., GMA127`) are different from each other.

The reference voltage switching unit 100 switches the reference voltages Vref0, Vref1,..., And Vref13 output from the reference voltage generator 130 to generate the first and second gray voltage generators. A plurality of switches (SW) for applying to any one of (140, 150). Here, the switches SW are switched so that the reference voltages Vref0, Vref1, ..., Vref13 are all applied to the same gray voltage generator. That is, if the reference voltage switching unit 100 selects the first gray voltage generator 140 by the external control signal, the switches SW may be configured as the reference voltages Vref0, Vref1,... And Vref13 are all switched to the first terminal 180a to be applied to the first gray voltage generator 140, and the reference voltage switch 100 generates the second gray voltage by the external control signal. If the unit 150 is selected, the switches SW may include the second terminal such that all of the reference voltages Vref0, Vref1,..., Vref13 are applied to the second gray voltage generator 150. 180b).

Although not shown in the drawings, the external control signal is output and applied to the reference voltage switching unit 100 to change the switching states of the switches SW configured in the reference voltage switching unit 100. It further includes a timing controller. That is, the timing controller may include a first external control signal for switching all of the switches SW to the first terminal 180a and a second external control signal for switching the switches SW to the second terminal 180b. Can be output selectively.

Hereinafter, the operation of the driving circuit of the liquid crystal display according to the first embodiment of the present invention configured as described above will be described in detail.

First, assume that all of the switches SW of the reference voltage switching unit 100 are switched to the first terminal 180a by the first external control signal output from the timing controller. Then, the reference voltages Vref0, Vref1,..., And Vref13 output from the reference voltage generator 130 are switched to the first gray level voltage through the switches SW that are switched to the first terminal 180a. It is input to the generation unit 140.

Specifically, the positive reference voltages Vref0, Vref1, ..., Vref7 among the reference voltages Vref0, Vref1, ..., Vref13 generate a first gray voltage through the switches SW. The negative reference voltages Vref8, Vfef9, ... Vref13 are applied to the positive gray scale voltage unit 140a of the unit 140, and among the reference voltages Vref0, Vref1, ..., Vref13, The voltage is applied to the negative gray voltage unit 140b of the first gray voltage generator 140 through the switches SW. Then, gray voltages GMA0, GMA1,..., GMA127 representing the characteristics of the first gamma curve are output from each node of the resistors provided in the first gray voltage generator 140.

Thereafter, the digital-to-analog converter (not shown) of the data driver 125 applies gradation voltages GMA0, GMA1,..., GMA127 representing the characteristics of the first gamma curve to the liquid crystal panel, thereby providing An image corresponding to the characteristics of the first gamma curve is displayed on the display unit of the panel.

In this case, if the image expressed according to the characteristics of the first gamma curve is darker or brighter than normal, the gamma curve may be changed to optimize the brightness of the image. For example, assume that the image expressed according to the characteristics of the first gamma curve is darker than normal, and assume that the gamma value of the second gamma curve is smaller than the gamma value of the first gamma curve (the gamma value is The higher the brightness is lower)

First, the second external control signal of the timing controller is applied to the reference voltage switching unit 100 to switch the switches SW of the reference voltage switching unit 100 from the first terminal 180a to the second terminal 180b. Switch to). Then, the reference voltages Vref0, Vref1,..., And Vref13 output from the reference voltage generator 130 generate the second gray voltage through the switches SW that are switched to the second terminal 180b. It is input to the unit 150.

Specifically, the positive reference voltages Vref0, Vref1, ..., Vref7 among the reference voltages Vref0, Vref1, ..., Vref13 generate a second gray voltage through the switches SW. The negative gradation voltage unit 150a of the unit 150 is applied, and the negative reference voltages Vref8, Vfef9, ... Vref13 of the reference voltages Vref0, Vref1, ..., Vref13 are The second gray voltage generator 150 is applied to the negative gray voltage unit 150b of the second gray voltage generator 150 through the switch SW. Then, gray voltages GMA0`, GMA1`, ..., GMA127` representing the gamma curve of the second gamma value are output from each node of the resistors provided in the second gray voltage generator 150.                     

Thereafter, the digital-to-analog converter of the data driver 125 applies the gray scale voltages GMA0`, GMA1`, ..., GMA127` representing the characteristics of the second gamma curve to the liquid crystal panel. An image corresponding to the characteristics of the second gamma curve is displayed on the display unit. Here, as described above, since the gamma value of the second gamma curve is lower than the gamma value of the first gamma curve, the image expressed according to the characteristics of the second gamma curve is displayed more brightly. That is, the image is represented with the optimized luminance.

In the first embodiment of the present invention, two gray voltage generators are used, but in order to obtain a more accurate and optimized image, it is preferable to use three or more gray voltage generators.

Meanwhile, only the first reference voltage corresponding to the white level and the second reference voltage corresponding to the black level may be applied to the first and second gray voltage generators.

Hereinafter, the driving circuit of the liquid crystal display according to the second embodiment of the present invention will be described in detail.

4 is a circuit diagram of a driving circuit of a liquid crystal display according to a second embodiment of the present invention.

In the driving circuit of the liquid crystal display according to the second exemplary embodiment of the present invention, as shown in FIG. 4, a reference voltage generator for providing a plurality of reference voltages Vref0, Vref1,. 230 and the first reference voltages Vref0 and Vref13 corresponding to the white level and the black level among the reference voltages Vref0, Vref1,..., And Vref13 of the reference voltage generator 230. The first gray voltage generator 240 outputs a plurality of gray voltages GMA0, GMA1,..., GMA127 representing the characteristics of the first gamma curve by voltage-dividing each of the second reference voltages Vref7 and Vref8. ) And a plurality of gray voltages GMA0 representing characteristics of a second gamma curve by voltage-dividing each of the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 of the reference voltage generator 230. ', GMA1`, ..., GMA127`) and the first and second gray voltages according to the external control signal inputted therein. Select one of the generation units 240 and 250, and switch the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 of the reference voltage generator 230 to selectively select only the selected gray voltage generator. Built-in reference voltage switching unit 200 and the first and second gray voltage generators 240 and 250 and the gray voltages of the first gray voltage generator GMA0, GMA1, ..., GMA127 ) And data applied to the display unit of the liquid crystal panel by selecting a gray voltage corresponding to the data signal input from the gray voltages GMA0`, GMA1`, ..., GMA127` of the second gray voltage generator 250. And a digital-to-analog converter (not shown) of the driver 225.

Although not shown in the drawing, the reference voltage generator 230 may select the first and second positive reference voltages Vref0 and Vref7 among the reference voltages Vref0, Vref1,..., And Vref13. The first and second portions of the positive reference voltage unit for outputting the positive reference voltages Vref0, Vref1, ..., Vref7, and the reference voltages Vref0, Vref1, ..., Vref13, respectively. And a negative reference voltage section for outputting negative reference voltages Vref8, Vfef9, ... Vref13 including the polar reference voltages Vref13 and Vref8. The positive reference voltage unit includes a positive voltage power supply for outputting a positive voltage, a common voltage terminal to which a common voltage is applied, and a plurality of resistors connected in series between the positive voltage power source and the common voltage terminal. . The negative reference voltage unit includes a negative voltage power supply for outputting a negative voltage, a plurality of resistors connected in series between the common voltage terminal and the negative voltage power supply and the common voltage terminal.

The positive reference voltage unit configured as described above outputs a plurality of positive reference voltages Vref0, Vref1, ..., Vref7 in which the positive voltage of the positive voltage power supply is divided from the node of each resistor. The polarity reference voltage unit outputs a plurality of negative reference voltages Vref8, Vfef9, ... Vref13 in which the negative voltage of the negative voltage power supply is divided from the node of each resistor.

Meanwhile, the first gray voltage generator 240 receives the first and second reference voltages Vref0 and Vref7 among the positive reference voltages Vref0, Vref1,..., And Vref7. The positive gray voltage unit 240a which outputs the positive gray voltages GMA0, GMA1, ..., GMA63 among the gray voltages GMA0, GMA1, ..., GMA127, and the negative reference voltages. Negative gradation voltages of the gradation voltages GMA0, GMA1, ..., GMA127 by receiving the negative first and second reference voltages Vref13 and Vref8 among Vref8, Vfef9, ... Vref13. And a negative gray voltage unit 240b for outputting (GMA64, GMA65, ..., GMA127). Here, the positive gray voltage unit 240a includes a plurality of resistors R connected in series, and the first and second reference voltages Vref0 and Vref7 are positive from the node of each resistor R. FIG. The positive gray voltages GMA0, GMA1, ..., GMA63, each of which is divided by voltage, are output. In addition, the negative gray voltage unit 240b includes a plurality of resistors R connected in series, and the first and second reference voltages Vref13 and Vref8 are negative from the node of each resistor R. FIG. The negative gray voltages GMA64, GMA65, ..., GMA127, each of which is divided by voltage, are output.

The second gray voltage generator 250 receives the first and second positive reference voltages Vref0 and Vref7 among the positive reference voltages Vref0, Vref1,..., And Vref7. A positive gradation voltage unit 250a for outputting the positive gradation voltages GMA0`, GMA1`, ..., GMA63` among the gradation voltages GMA0`, GMA1`, ..., GMA127`, The first and second negative reference voltages Vref13 and Vref8 of the negative reference voltages Vref8, Vfef9, and Vref13 are input to the grayscale voltages GMA0 ′, GMA1 ′, ..., And a negative gray voltage unit 250b for outputting negative gray voltages GMA64 ', GMA65', ..., GMA127 '. Here, the positive gray voltage unit 250a includes a plurality of resistors R ′ connected in series, and the positive first and second reference voltages Vref0 from a node of each resistor R ′. , Vref7) and the positive gray level voltages GMA0`, GMA1`, ..., GMA63` each of which voltage is divided are output. In addition, the negative gray voltage unit 250b includes a plurality of resistors R ′ connected in series, and the first and second reference voltages Vref13 are negative from the node of each resistor R ′. The negative gradation voltages GMA64 ', GMA65', ..., GMA127 'are respectively output.

Here, the first gray voltage generator 240 and the second gray voltage generator 250 receive the same first and second reference voltages Vref0, Vref13, Vref7, and Vref8, respectively, Since resistance values of the resistors R configured in the first gray voltage generator 240 and resistances of the resistors R ′ configured in the second gray voltage generator 250 have different values, The gamma value of the first gamma curve according to the gray voltages GMA0, GMA1,..., GMA127 output from the first gray voltage generator 240 and the second gray voltage generator 250 are output. Gamma values of the second gamma curve according to the gray voltages GMA0`, GMA1`, ..., GMA127` are different from each other.

In addition, the reference voltage switching unit 200 switches the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 output from the reference voltage generation unit 230, so that the first and second grayscales. It includes a plurality of switches (SW) applied to any one of the voltage generator (240, 250). Here, the switches SW are switched so that the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 are all applied to the same gray voltage generator. That is, when the reference voltage switching unit 200 selects the first gray voltage generator 240 according to the external control signal, the switches SW are configured to include the first and second reference voltages Vref0,. Vref13, Vref7, and Vref8 are all switched to the first terminal 280a to be applied to the first gray voltage generator 240, and the reference voltage switch 200 is controlled by the external control signal. When the voltage generator 250 is selected, the switches SW are configured such that all of the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 are applied to the second gray voltage generator 250. It is switched to the second terminal 280b.

Although not shown in the drawings, the external control signal is output and applied to the reference voltage switching unit 200 to change the switching states of the switches SW configured in the reference voltage switching unit 200. It further includes a timing controller. That is, the timing controller may include a first external control signal for switching all of the switches SW to the first terminal 280a and a second external control signal for switching the switches SW to the second terminal 280b. Can be output selectively.

Hereinafter, the operation of the driving circuit of the liquid crystal display according to the second embodiment of the present invention configured as described above will be described in detail.

First, assume that all of the switches SW of the reference voltage switching unit 200 are switched to the first terminal 280a by the first external control signal output from the timing controller. Then, the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 output from the reference voltage generator 230 are first switched through the switches SW that are switched to the first terminal 280a. The gray voltage generator 240 is input to the gray voltage generator 240.

Specifically, the positive first and second reference voltages Vref0 and Vref7 among the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 are connected to the first grayscale voltage through the switches SW. The negative gradation voltage unit 240a of the generator 240 is applied to the negative first and second reference voltages Vref13, Vref0, Vref13, Vref7, and Vref8. Vref8 is applied to the negative gray voltage unit 240b of the first gray voltage generator 240 through the switches SW. Then, gray voltages GMA0, GMA1,..., GMA127 representing the characteristics of the first gamma curve are output from each node of the resistors R provided in the first gray voltage generator 240.

Thereafter, the digital-to-analog converter of the data driver 225 applies the grayscale voltages GMA0, GMA1,..., GMA127 representing the characteristics of the first gamma curve to the liquid crystal panel so that the display unit of the liquid crystal panel is applied. An image according to the characteristics of the first gamma curve is displayed.

In this case, if the image expressed according to the characteristics of the first gamma curve is darker or brighter than normal, the gamma curve may be changed to optimize the brightness of the image. For example, assume that the image expressed according to the characteristics of the first gamma curve is darker than normal, and assume that the gamma value of the second gamma curve is smaller than the gamma value of the first gamma curve (the gamma value is The higher the brightness is lower)

First, the second external control signal of the timing controller is applied to the reference voltage switching unit 200 to switch the switches SW of the reference voltage switching unit 200 from the first terminal 280a to the second terminal 280b. Switch to). Then, the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 output from the reference voltage generator 230 are second grayscale through the switches SW that are switched to the second terminal 280b. It is input to the voltage generator 250.

Specifically, the positive first and second reference voltages Vref0 and Vref7 among the first and second reference voltages Vref0, Vref13, Vref7 and Vref8 are connected to the second grayscale voltage through the switches SW. The negative gradation voltage unit 250a of the generator 250 is applied to the first and second reference voltages Vref0, Vref13, Vref7, and Vref8 of the first and second reference voltages Vref13, Vref8 is applied to the negative gray voltage unit 250b of the second gray voltage generator 250 through the switches SW. Then, gray voltages GMA0`, GMA1`, ..., GMA127` representing the second gamma curve are output from each node of the resistors R provided in the second gray voltage generator 250. .

Thereafter, the digital-to-analog converter of the data driver 225 applies the gray scale voltages GMA0`, GMA1`, ..., GMA127` representing the characteristics of the second gamma curve to the liquid crystal panel. An image corresponding to the characteristics of the second gamma curve is displayed on the display unit. Here, as described above, since the gamma value of the second gamma curve is lower than the gamma value of the first gamma curve, the image expressed according to the characteristics of the second gamma curve is displayed more brightly. That is, the image is represented with the optimized luminance.

In the second embodiment of the present invention, two gray voltage generators are used, but it is preferable to use three or more gray voltage generators in order to obtain a more accurate and optimized image.

The present invention described above is not limited to the above-described embodiment and the accompanying drawings, and it is common in the art that various substitutions, modifications, and changes can be made without departing from the technical spirit of the present invention. It will be evident to those who have knowledge of.

As described above, the driving circuit of the liquid crystal display according to the present invention has the following effects.

The driving circuit of the liquid crystal display according to the present invention includes a plurality of gray voltage generators having characteristics of different gamma curves, and reference voltage switching for applying a reference voltage to one of the plurality of gray voltage generators according to an external control signal. It contains wealth.

Therefore, the quality of the image can be improved by applying a gamma curve having a gamma value that matches the characteristics of the image represented on the liquid crystal panel of the liquid crystal display.

Claims (7)

delete delete delete A reference voltage generator for outputting a plurality of reference voltages; Among the reference voltages, different gamma values are applied by receiving a first positive reference voltage and a first negative reference voltage corresponding to a white level, and a second positive reference voltage and a second negative reference voltage corresponding to a black level. A plurality of gray voltage generators outputting gray voltages representing gamma curves of the plurality of gray voltages; The plurality of first and second negative reference voltages, the first negative reference voltage, the second positive reference voltage and the second negative reference voltages outputted from the reference voltage generator are switched according to the input external control signal. A reference voltage switching unit for inputting at least one of the gray scale voltage generators; The plurality of reference voltages are divided into a plurality of positive reference voltages including the first and second positive reference voltages, and a plurality of negative reference voltages including the first and second negative reference voltages; The reference voltage generator includes a positive reference voltage unit for outputting the plurality of positive reference voltages and a negative reference voltage unit for outputting the plurality of negative reference voltages; The positive reference voltage unit includes a positive voltage power supply for outputting a positive voltage, a common voltage terminal to which a common voltage is applied, and a plurality of resistors connected in series between the positive voltage power source and the common voltage terminal; The negative reference voltage unit includes a negative voltage power supply for outputting a negative voltage, a plurality of resistors connected in series between the common voltage terminal and the negative voltage power supply and the common voltage terminal; The reference voltage switching unit includes a first switch for switching the first positive reference voltage, a second switch for switching a second positive reference voltage, a third switch for switching a first negative reference voltage, and a second negative reference A fourth switch for switching a voltage; Each of the reference voltage generators outputs the positive grayscale voltages corresponding to all the positive grayscales based on the first positive reference voltage and the second positive reference voltage, and outputs the first negative reference voltage and the second negative reference voltage. Outputting negative gray voltages corresponding to all negative gray levels based on the negative reference voltage; The first to fourth switches are switched such that the first positive reference voltage, the second positive reference voltage, the first negative reference voltage and the second negative reference voltage are all applied to the same gray voltage generator. A driving circuit for a liquid crystal display device, characterized in that. delete The method of claim 4, wherein And the external control signal is generated by a timing controller. delete

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