KR20080034573A - Driving circuit of lcd and driving method of the same - Google Patents

Abstract

A method and a circuit for driving an LCD(Liquid Crystal Display) device are provided to minimize a flicker due to different common voltages for different grayscales by compensating for a gamma voltage using a reference common voltage. An LCD device includes an LCD panel and a data driver. A driving circuit for the LCD device includes a gamma unit(170), a common voltage unit(190), a memory(210), a compensator(220), and a calculator(230). The gamma unit generates plural positive and negative gamma voltages. The common voltage unit generates a common voltage. The memory temporarily stores the positive and negative gamma voltages and the reference common voltage. The comparator compares an optimal common voltage, which corresponds to the positive and negative gamma voltages, with the reference common voltage, and obtains the voltage difference between them. The calculator adds or subtracts the voltage difference to or from the positive and negative gamma voltages according to the result from the comparator.

Description

Driving circuit of liquid crystal display device and driving method thereof {Driving circuit of LCD and driving method of the same}

1 is a block diagram schematically illustrating a configuration of a general liquid crystal display device.

2 is a graph illustrating a conventional gamma voltage and a common voltage.

3A is a diagram illustrating one embodiment of a gamma circuit of a conventional liquid crystal display.

3B is a diagram showing one embodiment of a conventional common voltage circuit.

4 is a block diagram schematically illustrating a data driver of a liquid crystal display according to an exemplary embodiment of the present invention.

5 is a block diagram schematically illustrating a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention.

6 is a flowchart illustrating a driving method of a liquid crystal display driving circuit according to an embodiment of the present invention.

<Description of the symbols for the main parts of the drawings>

1: liquid crystal panel 150: data driver

170: gamma part 190: common voltage part

200: gamma and common voltage unit 210: memory unit

220: comparison unit 230: calculation unit

300: Programmable IC

The present invention relates to a driving circuit of a liquid crystal display and a driving method thereof, and more particularly, to integrate and mount a gamma circuit and a common voltage circuit in one integrated circuit, thereby compensating for the initially set gamma voltage and the common voltage. And a driving method thereof.

Liquid crystal displays have low power consumption and are capable of thinning and realizing large screens. Therefore, LCDs are in the spotlight as next-generation advanced display devices with high added value as display devices such as notebook computers and large screen TVs.

In the field of liquid crystal display devices, active matrix liquid crystal displays (AMLCDs) are mainstream. In this AMLCD, one thin film transistor (TFT) defines one pixel, and one TFT controls the voltage level of the pixel as a switching element to change the light transmittance of the pixel to display an image.

FIG. 1 is a block diagram schematically illustrating a configuration of a general liquid crystal display, and a thin film transistor T is provided in a matrix form at a point where a plurality of gate lines GL and data lines DL intersect to display an image. A liquid crystal panel (1), a timing controller (2) for receiving a control signal and a data signal from the outside and controlling the driving circuit of the liquid crystal panel (1) in response to the signals; A gate driver 3 for supplying a gate signal to the panel 1 and a data driver 5 for supplying a data signal to the liquid crystal panel 1, and also having a gamma voltage (GMA) for the data driver 5. And a common voltage circuit 9 for supplying a common voltage Vcom to the liquid crystal panel 1.

In particular, the liquid crystal panel 1 is formed by bonding the first and second substrates with the liquid crystal layer interposed therebetween, and controls the light transmittance of the liquid crystal according to the magnitude of the electric field formed by the voltage difference between the two substrates. In detail, a gray scale voltage corresponding to an image signal is applied to one of the two substrates, and a common voltage Vcom is applied to the other substrate to form an electric field by the voltage difference between the two signals. The light transmittance is controlled.

Hereinafter, the operation of a general liquid crystal display device will be described.

The liquid crystal panel 1 displays an image by controlling the light transmittance of the liquid crystal capacitor Clc through the on / off operation of the plurality of thin film transistors T arranged in a matrix form.

The timing controller 2 receives a control signal from the outside, generates a gate control signal for driving the gate driver and a data control signal for driving the data driver, and supplies the control signal to each driving circuit.

In addition, the timing controller 2 receives a data signal from the outside, rearranges the data signal into a form that the data driver 5 can process, and supplies the data signal to the data driver 5 as an image signal.

In response to the gate control signal supplied from the timing controller 2, the gate driver 3 sequentially applies the gate driving signal Vg by 1H for one frame through each gate line GL. To feed.

The data driver 5 receives a digital data signal from the timing controller 2 and converts it into an analog video signal corresponding to a reference voltage, and converts the video signal of one horizontal line through all the data lines DL. At the same time, it is supplied to the liquid crystal panel.

In more detail the digital-analog conversion process of the data signal described above, the data driver 5 includes a digital-to-analog converter (DAC), which is a gamma circuit 7. Is supplied with a plurality of gamma voltages (GMA). The DAC divides the gamma voltage GMA in response to the digital data signal, converts the gamma voltage GMA as a reference signal into an image signal, and supplies the same to the liquid crystal panel 1 through the data line DL.

This process is called gamma tuning, and in gamma tuning, it is necessary to consider algebraically the stimulus value according to the visual perception characteristic when a person sees an image. Thus, as shown in FIG. Similarly, gamma voltages corresponding to the respective gray levels of the data signal are generated.

FIG. 3A illustrates a form of a gamma circuit of a conventional liquid crystal display device. The conventional gamma circuit includes a plurality of resistors R1 to R10 connected in series with a power supply unit, and a voltage strengthened from the resistors. A voltage follower is provided to stabilize the output.

3B is a conventional common voltage circuit, and includes resistors R1 to R3, a variable resistor VR, and a voltage follower. As described above, the image displayed on the liquid crystal panel 1 is displayed by the voltage difference between the video signal and the common voltage Vcom. Accordingly, the quality of the image is affected by the common voltage Vcom value.

More specifically, the setter supplies a predetermined test video signal to the liquid crystal panel to display a predetermined image, and then adjusts the resistance value of the variable resistor VR included in the common voltage unit, thereby flickering. Find the optimal common voltage (Vcom) value that is the minimum.

However, this work process takes a lot of time because the setter manually sets the resistance value of the variable resistor, and in general, its reliability is inferior because the adjustment of the resistance value is manual.

In addition, the optimum value of the common voltage Vcom is slightly different for each gray. For example, a liquid crystal panel displaying a total of 256 gray levels with 8 bits, the positive-gamma voltage {P-GMA (255G)} and the negative-gamma voltage {N-GMA (255G)} corresponding to the 255th gray level are respectively. The positive-gamma voltage {P-GMA (127G)} and the negative-gamma voltage {N-GMA (127G)} corresponding to the 127th gradation are 8.2V and 2.2, respectively. If the voltage value is V, the optimum common voltage {Vcom.i (255G)} corresponding to the 255th gray scale is 5V, whereas the optimum common voltage corresponding to the 127th gray scale {Vcom.i (127G) } The value is 5.1V. Since the common voltage Vcom is a signal supplied over the entire surface of the second substrate of the liquid crystal panel, there is a problem in that it is impossible to supply different optimum common voltages Vcom.i to respective pixels displaying different gray levels.

The present invention has been made to solve the above problems, the present invention is to compensate for the gamma voltage to minimize the flicker generated by the common voltage having a different voltage value between each gray level driving circuit and its driving The purpose is to provide a method.

In order to achieve the above object, a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel including a switching element connected to a pixel electrode, a gate driver to turn on / off the switching element, and the A driving circuit for a liquid crystal display device having a data driver for supplying an image signal to a pixel electrode, comprising: a gamma unit for generating a plurality of positive and negative gamma voltages; A common voltage unit generating a common voltage; A memory unit for temporarily storing a positive gamma voltage and a negative gamma voltage specified by a setter among the gamma voltages, a reference common voltage corresponding thereto, and the reference common voltage; A comparison unit comparing the optimum common voltage corresponding to the positive gamma voltage and the negative gamma voltage to be compensated with the reference common voltage to obtain a voltage difference; According to a result of the comparison unit, it characterized in that it comprises a calculation unit for adding or subtracting the voltage difference to the positive gamma voltage and negative gamma voltage to be compensated.

The positive gamma voltage and the negative gamma voltage specified by the setter among the gamma voltages are gamma voltages corresponding to the 255th grayscale 255G.

In order to achieve the above object, a driving method of a liquid crystal display driving circuit according to an embodiment of the present invention includes: a liquid crystal panel to which first and second substrates are bonded; a gate driver and a data driver for driving the liquid crystal panel; A driving method of a liquid crystal display driving circuit comprising a driving circuit for supplying a common voltage to the second substrate and a gamma voltage serving as a reference for converting a digital data signal into an analog video signal. Setting maximum positive and negative voltages in consideration of response speed and maximum brightness; Setting a plurality of positive gamma voltages and negative gamma voltages having different voltage values in consideration of the maximum positive and negative voltages; Setting a gamma voltage corresponding to one gray level specified among the plurality of positive gamma voltages and negative gamma voltages, and a reference common voltage corresponding to the gamma voltages; Generating an optimum gamma voltage by comparing and calculating an optimum common voltage corresponding to the gamma voltage corresponding to the grayscale to be compensated with the reference common voltage; And outputting the reference common voltage and the optimum gamma voltage.

The setting of the plurality of gamma voltages may include setting several reference gamma voltages with reference to a T-V curve according to the maximum positive and negative voltages; And setting the positive gamma voltage and the negative gamma voltage corresponding to each gray level in consideration of the reference gamma voltage.

The step of setting a gamma voltage corresponding to one gray level specified among the plurality of positive gamma voltages and negative gamma voltages and a reference common voltage corresponding to the gamma voltage may include a positive-gamma corresponding to a 255th grayscale 255G. And setting an optimum common voltage corresponding to the voltage and the negative-gamma voltage.

Comparing and calculating the optimum common voltage corresponding to the gamma voltage corresponding to the grayscale to be compensated with the reference common voltage to generate the optimum gamma voltage, the gamma voltage corresponding to the remaining gray scales other than the specified one gray scale is generated. Setting an optimum common voltage corresponding to the second common voltage; Comparing the optimum common voltage with the reference common voltage; And subtracting a voltage difference between the optimal common voltage and the reference common voltage to a gamma voltage.

The step of setting the optimum common voltage with the minimum flicker corresponding to the remaining gamma voltage except for the specified one gray level may include the positive corresponding to the 0th to 254th grayscales (0 to 254G) except the 255th grayscale (255G). And setting an optimum common voltage with a minimum flicker for the gamma voltage and the negative gamma voltage, respectively.

The step of adding or subtracting a voltage difference between the reference common voltage and the optimum common voltage to a gamma voltage may include: when the voltage value of the reference common voltage is greater than the voltage value of the optimum common voltage, the positive gamma voltage of the gray level corresponding to the optimal common voltage. And adding a difference of the voltage values to a negative gamma voltage; If the voltage value of the reference common voltage is smaller than the voltage value of the optimum common voltage, subtracting the difference between the positive and negative gamma voltages of the gray level corresponding to the optimum common voltage. do.

Among the gamma voltages other than the specified one gray level, the step of comparing and calculating the optimum common voltage corresponding to the gamma voltage to be compensated with the reference common voltage to generate the optimum gamma voltage may include an optimum gamma voltage corresponding to all gray levels. It characterized in that it further comprises the step of setting.

According to an exemplary embodiment of the present invention, a liquid crystal display device includes: a liquid crystal panel in which a first substrate including a pixel electrode and a second substrate including a common electrode are bonded; A gate driver for turning on / off the switching element in response to a control signal and a data signal input from an external system, and receiving the data signal and converting the data signal into an analog image signal and supplying it to the pixel electrode A gamma part for generating a gamma voltage as a reference for converting the driver and the data driver into the analog image signal; A common voltage unit generating a common voltage corresponding to the image signal and supplying the common voltage to the common electrode; A memory unit for storing a reference common voltage corresponding to one gamma voltage specified among the gamma voltages; A comparison unit for comparing a voltage difference between an optimum common voltage corresponding to the gamma voltage and the reference common voltage for each gray level; And an operation unit which adds or subtracts the voltage difference to a gamma voltage of a corresponding gray level.

Hereinafter, a driving circuit and a driving method thereof of a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

In the following description, only a programmable IC for generating and compensating the gamma voltage and the common voltage, which are important features of the present invention, and a data driver for receiving and driving the gamma voltage are described. The other driving circuits have the same configuration as the driving circuits of the general liquid crystal display device and perform the same operation.

In addition, the programmable IC is mounted on the PCB in place of the conventional voltage divider gamma circuit and the common voltage circuit.

FIG. 4 is a block diagram schematically illustrating a structure of a data driver among driving circuits of a liquid crystal display according to an exemplary embodiment of the present invention. Referring to the drawings, the data driver 150 receives data input from a timing controller (not shown). A control unit 151 which receives a control signal and a data signal to control each circuit, a shift register unit 152 which sequentially stores the data signal in the latch unit 153, and a data signal corresponding to one horizontal line. A latch unit 153 for storing and outputting to the DAC unit 155, a gamma reference unit 154 for receiving and dividing a gamma voltage, and converting the analog data signal into a digital form and outputting the digital buffer. And a output buffer unit 159 for outputting the digital data signal as a video signal to the data line DL.

In addition, the DAC unit 155 divides the data signal stored in the latch unit 153 into a positive and negative signal, and receives a gamma-tuned reference signal supplied from a programmable IC (300 of FIG. 5) corresponding to the data signal. A mux for selectively outputting reference signals of the P-decoder unit and the N-decoder units 156 and 157 to the output buffer unit under the control of the selected P-decoder and N-decoder units 156 and 157 and the control unit 151. Section 158.

Hereinafter, an operation of a data driver among driving circuits of a liquid crystal display according to an exemplary embodiment of the present invention will be described with reference to the accompanying drawings.

First, when the source start pulse SSP is applied from the timing controller (not shown) to the controller 151, the controller 151 latches the data signal data having R, G, and B information supplied thereto. Store in At this time, the shift register unit 152 sequentially activates the latch unit 153 in synchronization with the source sampling clock SSC applied to the control unit 151, and sequentially transmits the data signal data to the latch unit 153. Save it.

When the data signal data corresponding to one horizontal line is stored, the latch unit 153 supplies the same to the DAC 155.

The DAC unit 155 receives the data signal data supplied from the latch unit 153 to the P-decoder unit 156 and the N-decoder unit 157, and compensates from the programmable IC (300 in FIG. 5). The positive gamma voltage P-GMA 'and the negative gamma voltage N-GMA' are supplied.

The P-decoder 156 and the N-decoder 157 select a positive gamma voltage P-GMA 'and a negative gamma voltage N-GMA' corresponding to the data signal data, respectively. Output as a video signal.

Thereafter, the mux unit 158 selects the P-decoder unit 156 and the N-decoder unit 157 in synchronization with the polarity inversion signal POL applied to the controller 151, and selects one of these. The video signal is supplied to the output buffer unit 159.

The output buffer unit 159 supplies the supplied image signal to the liquid crystal panel (not shown) through the data line DL.

Through this operation, the data driver 150 of the driving circuit of the liquid crystal display according to the exemplary embodiment of the present invention supplies an analog image signal to the first substrate.

FIG. 5 is a block diagram schematically illustrating a configuration of a gamma circuit and a common voltage circuit implemented as a programmable IC among driving circuits of a liquid crystal display according to an exemplary embodiment of the present invention. Referring to the drawings, FIG. The programmable IC 300 includes a gamma unit 170 generating a plurality of gamma voltages GMA, a common voltage unit 190 generating a common voltage Vcom, and a reference common voltage Vcom.ref. ), A memory unit 210 for storing the reference unit, a comparison unit 220 for comparing the reference common voltage Vcom.ref and the optimum common voltage Vcom.i corresponding to each nth gray level, and the comparison unit ( According to the result of the operation 220, the operation unit 230 for correcting the tuned positive-gamma voltage (P-GMA) and negative-gamma voltage (N-GMA) of each nth gray scale and supplying the same to the data driver 150 is performed. It consists of.

Here, the functions of the gamma unit 170 and the common voltage unit 190 are the same as those of the conventional gamma circuit (7 of FIG. 1) and the common voltage circuit (9 of FIG. 1). The difference is the use of programmable ICs, not partial voltages.

In addition, the gamma unit 170 and the common voltage unit 190 may be implemented as one block unit circuit 200 by the intention of the setter, which is expected to be advantageous in terms of cost.

Here, the gamma unit 170 generates a predetermined gamma voltage GMA according to the maximum positive and negative voltages set in consideration of the response speed and the maximum luminance of the liquid crystal by the setter.

The common voltage unit 190 generates an optimum common voltage Vcom.i having a minimum flicker for the gamma voltage corresponding to the nth gray level specified by the setter among the gamma voltages GMA.

At this time, the setter must specify the common voltage (Vcom.ref) that is the reference for all the gray scales, and the nth gray scale specified for setting the reference common voltage (Vcom.ref) is 255 in the 8-bit driving LCD. It is preferable that it is the 1st grayscale (255G) (n = 255). In other words, the setter sets the optimum common voltage {Vcom with the minimum flicker for the positive-gamma voltage {P-GMA (255G)} and the negative-gamma voltage {N-GMA (255G)} corresponding to the 255th grayscale (255G). .i (255G)}.

The memory unit 210 stores the optimum common voltage Vcom.i (255G) corresponding to the 255th grayscale 255G, and supplies it to the comparator 220.

That is, the optimum common voltage Vcom.i (255G) corresponding to the 255th grayscale 255G is defined as the reference common voltage Vcom.ref.

The comparator 220 is an optimum common voltage {Vcom.i (0 ~ 254G)} and the reference common voltage corresponding to the gamma voltage to be compensated among the gamma voltages corresponding to the 0th to 254th gradations except the 255th gradation. Take (Vcom.ref) and compare it.

When the calculation unit 230 receives the result of the comparison unit 220 and the optimum common voltage {Vcom.i (0 to 254G)} and the reference common voltage (Vcom.ref) for each of the 0th to 254th gradations are different, the voltage The difference is the positive-gamma voltage {P-GMA (0-254G)} and the negative-gamma voltage {corresponding to the 0th to 254th gradation (0 to 254G) of the optimum common voltage {Vcom.i (0 to 254G)}. N-GMA (0 to 254G)} is added to or subtracted from the voltage value.

For example, the positive-gamma voltage {P-GMA (127G)} and the negative-gamma voltage {N-GMA (127G)} corresponding to the 127th grayscale 127G are 8.2V and 2.2V, respectively, and their optimum common. When the voltage {Vcom.i (127G)} is 5.1V and the voltage value of the reference common voltage Vcom.ref is 5V, the optimum common voltage {Vcom.i (127G)} of the 127th grayscale is the common reference. The voltage value is 0.1V greater than the voltage Vcom.ref.

Therefore, the positive-gamma voltage {P-GMA (127G)} and the negative-gamma voltage {N-GMA (127G)} corresponding to the 127th grayscale are set to 8.1V and 2.1V which are 0.1V subtracted from the voltage value before compensation. do.

Thereafter, the set reference common voltage Vcom.ref is supplied to the second substrate of the liquid crystal panel 1, and the positive-gamma voltage {P-GMA (0 to 255G)} and the negative-gamma voltage {N-GMA (0 to 255G)} is supplied to the data driver 150 to convert the light transmittance of the liquid crystal layer into a voltage difference between the corresponding image signal and the reference common voltage Vcom.ref to display an image.

The gamma voltage compensation process described above may be set for every gray level as necessary, and thus, the gamma voltage optimal for flicker may be set for each nth gray level.

FIG. 6 is a sequential diagram illustrating a method of setting a gamma voltage and a common voltage in a driving circuit of a liquid crystal display according to an exemplary embodiment of the present invention. Referring to FIG. In this case, the setter sets the maximum positive and negative voltages in consideration of the response speed and the maximum luminance of the liquid crystal.

In setting the gamma corresponding voltage (ST2), several reference gamma voltages (GMAs) are set with reference to the TV curve according to the maximum positive and negative voltages, and the corresponding positive gamma voltages are corresponding to each gray level through the reference gamma voltages. In this step, the gamma voltage P-GMA and the negative gamma voltage N-GMA are set.

In the setting of the reference common voltage Vcom.ref (ST3), the positive gamma voltage (P-GMA) and the negative gamma voltage (N-GMA) of the gamma voltage, preferably the positive corresponding to the 255th gray scale, are included. In this step, the optimum common voltage {Vcom.i (255G)} of the gamma voltage {P-GMA (255G)} and the negative-gamma voltage {N-GMA (255G)} is defined as the reference common voltage (Vcom.ref). .

The step of setting the optimum gamma voltage and the common voltage (ST4-1 to ST4-3) includes the step of setting the optimum common voltage Vcom.i for each gray level (ST4-1) and the optimum common voltage Vcom. i) comparing the reference common voltage Vcom.ref with (ST4-2) and subtracting the voltage difference between the optimum common voltage Vcom.i and the reference common voltage Vcom.ref to a gamma voltage It is divided into steps.

First, the step (ST4-1) of setting the optimum common voltage Vcom.i for each gray level may include the remaining 0s ˜ except for the gamma voltage of the 255th gray level 255G corresponding to the reference common voltage Vcom.ref. Optimal common voltage {Vcom.i for positive-gamma voltage {P-GMA (0-254G)} and negative-gamma voltage {N-GMA (0-254G)} selected among 254th grayscales (0-254G) (0 ~ 254G)}.

Comparing the optimum common voltage {Vcom.i (0 to 254G)} with the reference common voltage (Vcom.ref) (ST4-2), the optimum common voltage corresponding to the 0th to 254th grayscale (0 to 254G) { This step compares the voltage difference between Vcom.i (0 ~ 254G)} and the reference common voltage (Vcom.ref).

Step of adding or subtracting the voltage difference between the reference common voltage (Vcom.ref) and the optimum common voltage {Vcom.i (0 to 254G)} corresponding to the 0th to 254th gradations (0 to 254G) to the gamma voltage (ST4-3) Corresponds to the case where there is a voltage difference in step ST4-2, and when the reference common voltage Vcom.ref is greater than the optimum common voltage Vcom.i (0 to 254G), the optimum common voltage {Vcom.i ( 0 to 254G)}, and the voltage difference is added to the positive-gamma voltage {P-GMA (0 to 254G)} and the negative-gamma voltage {N-GMA (0 to 254G)} of gray scales, In the opposite case, the step of subtracting.

The steps ST4-1 to ST4-3 may repeat the above process for gamma voltages corresponding to all gray levels (0 to 255G) for more accurate gamma voltage compensation.

The step ST5 of outputting the reference common voltage and the gamma voltage is set through the above process, supplies the reference common voltage Vcom.ref to the liquid crystal panel, and compensates the positive-gamma voltage {P-GMA ′ ( 0-255G)} and negative-gamma voltage {N-GMA '(0-255G)}.

In the above-described steps, steps ST1 to ST3 and step ST4-1 are performed by the setter, and steps ST4-2 to ST6 are performed by the programmable IC of the present invention.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art will be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below I can understand that you can.

Therefore, the driving circuit and driving method thereof of the liquid crystal display according to the exemplary embodiment of the present invention generate a gamma voltage and a common voltage for each gray level using a programmable IC, define the same reference common voltage for all gray levels, and define the reference common voltage. By compensating the gamma voltage to correspond to, there is an effect of minimizing flicker caused by a common voltage having a different value for each gray level.

Claims (10)

A liquid crystal display device comprising: a liquid crystal panel including a switching element connected to a pixel electrode; a gate driver for turning on / off the switching element; and a data driver for supplying an image signal to the pixel electrode. A gamma unit for generating a plurality of positive and negative gamma voltages; A common voltage unit generating a common voltage; A positive gamma voltage and a negative gamma voltage specified by a setter among the gamma voltages, a memory unit for temporarily storing the reference common voltage and the reference common voltage; A comparison unit comparing the optimum common voltage corresponding to the positive gamma voltage and the negative gamma voltage to be compensated with the reference common voltage to obtain a voltage difference; A calculator which adds or subtracts the voltage difference to the positive gamma voltage and the negative gamma voltage to be compensated according to a result of the comparator; The driving circuit of the liquid crystal display device comprising a. The method of claim 1, The positive gamma voltage and the negative gamma voltage specified by the setter among the gamma voltages are gamma voltages corresponding to the 255th grayscale (255G). A liquid crystal panel to which the first and second substrates are bonded, a gate driver and a data driver to drive the liquid crystal panel, a common voltage to the second substrate, and converting a digital data signal into an analog image signal to the data driver. In a driving method of a liquid crystal display driving circuit comprising a driving circuit for supplying a gamma voltage as a reference, Setting maximum positive and negative voltages in consideration of response speed and maximum luminance of the liquid crystal; Setting a plurality of positive gamma voltages and negative gamma voltages having different voltage values in consideration of the maximum positive and negative voltages; Setting a gamma voltage corresponding to one gray level specified among the plurality of positive gamma voltages and negative gamma voltages, and a reference common voltage corresponding to the gamma voltages; Generating an optimum gamma voltage by comparing and calculating an optimum common voltage corresponding to the gamma voltage corresponding to the grayscale to be compensated with the reference common voltage; Outputting the reference common voltage and the optimum gamma voltage; Method of driving a liquid crystal display device driving circuit comprising a. The method of claim 3, wherein The setting of the plurality of gamma voltages may include setting several reference gamma voltages with reference to a T-V curve according to the maximum positive and negative voltages;  Setting the positive gamma voltage and the negative gamma voltage corresponding to each gray level in consideration of the reference gamma voltage; Method of driving a liquid crystal display device driving circuit comprising a. The method of claim 3, wherein The step of setting a gamma voltage corresponding to one gray level specified among the plurality of positive gamma voltages and negative gamma voltages and a reference common voltage corresponding to the gamma voltages include: a positive-gamma corresponding to a 255th gray level (255G) And setting an optimal common voltage corresponding to the voltage and the negative gamma voltage. The method of claim 3, wherein Comparing and calculating the optimum common voltage corresponding to the gamma voltage corresponding to the grayscale to be compensated with the reference common voltage to generate an optimum gamma voltage, Setting an optimum common voltage corresponding to a gamma voltage corresponding to the remaining gray levels except for the one gray level specified above; Comparing the optimum common voltage with the reference common voltage; Subtracting a voltage difference between the optimal common voltage and the reference common voltage to a gamma voltage; Method of driving a liquid crystal display device driving circuit comprising a. The method of claim 6, The step of setting the optimum common voltage with the minimum flicker corresponding to the remaining gamma voltage except for the specified one gray level may include the positive corresponding to the 0th to 254th grayscales (0 to 254G) except the 255th grayscale (255G). A method of driving a liquid crystal display device driving circuit comprising the step of setting an optimum common voltage with minimum flicker for the gamma voltage and the negative gamma voltage, respectively. The method of claim 6, In the step of adding or subtracting a voltage difference between the reference common voltage and the optimum common voltage to a gamma voltage, If the voltage value of the reference common voltage is greater than the voltage value of the optimum common voltage, adding a difference between the voltage value to the positive gamma voltage and the negative gamma voltage of the gray level corresponding to the optimum common voltage; Subtracting the difference between the positive gamma voltage and the negative gamma voltage of the gray level corresponding to the optimum common voltage when the voltage value of the reference common voltage is smaller than the voltage value of the optimum common voltage; Method of driving a liquid crystal display device driving circuit comprising a. The method of claim 3, wherein Among the gamma voltages other than the specified one gray level, the step of comparing and calculating the optimum common voltage corresponding to the gamma voltage to be compensated with the reference common voltage to generate the optimum gamma voltage may include an optimum gamma voltage corresponding to all gray levels. The method of driving a liquid crystal display device driving circuit further comprising the step of setting. A liquid crystal panel in which a first substrate including a pixel electrode and a second substrate including a common electrode are bonded; A gate driver for turning on / off the switching element in response to a control signal and a data signal input from an external system, and receiving the data signal and converting the data signal into an analog image signal and supplying it to the pixel electrode Driver, A gamma unit generating a gamma voltage as a reference for converting the data driver into an analog image signal; A common voltage unit generating a common voltage corresponding to the image signal and supplying the common voltage to the common electrode; A memory unit for storing a reference common voltage corresponding to one gamma voltage specified among the gamma voltages; A comparison unit for comparing a voltage difference between an optimum common voltage corresponding to the gamma voltage and the reference common voltage for each gray level; A calculator configured to add or subtract the voltage difference to a gamma voltage of a corresponding gray level; Liquid crystal display comprising a.

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