KR101147119B1 - Apparatus and method for generating common voltage of liquid crystal display device - Google Patents

Abstract

The present invention relates to a common voltage generator and a method of generating a liquid crystal display device in which a common voltage can be easily adjusted using a memory.

A common voltage generator of a liquid crystal display according to the present invention includes an analog-digital converter for converting a set voltage into digital data, a memory for storing the digital data, and a common voltage for analog conversion of the digital data stored in the memory. Characterized in that it comprises a digital-to-analog converter for generating a.

According to this configuration, the present invention can easily adjust the common voltage by analog-to-digital conversion of the common voltage set externally and stored in the memory, and digital-analog conversion of the digital signal stored in the memory to generate the common voltage. Since the present invention generates a common voltage by storing a set voltage set externally, the common voltage can be easily adjusted even from a long distance.

Description

Common voltage generator and method for generating liquid crystal display {APPARATUS AND METHOD FOR GENERATING COMMON VOLTAGE OF LIQUID CRYSTAL DISPLAY DEVICE}

1 is an equivalent circuit diagram showing an equivalent unit pixel of a typical TFT-LCD.

2 is a circuit diagram schematically showing a common voltage generator of a typical TFT-LCD.

3 is a schematic view of a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a schematic view of a common voltage generator of a liquid crystal display according to an exemplary embodiment of the present invention.

FIG. 5 is a diagram illustrating an apparatus for setting a common voltage in the common voltage generator and the method of generating the liquid crystal display according to the exemplary embodiment of the present invention.

<Explanation of Signs of Major Parts of Drawings>

102: liquid crystal panel 104: data driver

106: gate driver 108: timing controller

110: voltage generator 120: common voltage generator

122: analog-to-digital converter 124: memory

126: digital-to-analog converter

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a common voltage generator and a method of generating a liquid crystal display device in which a common voltage can be easily adjusted using a memory.

Recently, various flat panel display devices that can reduce weight and volume, which are disadvantages of cathode ray tubes, have emerged. Such flat panel displays include liquid crystal displays (hereinafter referred to as "LCDs"), field emission displays, plasma display panels, light emitting displays, and the like. There is this.

The LCD displays an image by adjusting the light transmittance of the liquid crystal using an electric field. The LCD includes a transistor array substrate and a color filter array substrate bonded to each other, a spacer for maintaining a constant cell gap between the two array substrates, and a liquid crystal filled in a liquid crystal space provided by the spacer.

The color filter array substrate includes a color filter and a black matrix for preventing light leakage, a common electrode supplying a reference voltage to the liquid crystal cells in common, and an upper alignment layer coated thereon for liquid crystal alignment. Here, the common electrode may be formed on the transistor array substrate according to the liquid crystal mode.

The transistor array substrate includes gate lines and data lines, a thin film transistor (hereinafter referred to as TFT) formed at each intersection of the gate lines and the data lines, and is formed in a liquid crystal cell unit and connected to a TFT. And a lower alignment film coated thereon for liquid crystal alignment.

1 is an equivalent circuit diagram of an equivalent unit pixel of a general TFT-LCD.

Referring to FIG. 1, a unit pixel of a typical TFT-LCD includes a TFT in which a source electrode s is electrically connected to a data line DLm, and a gate electrode is electrically connected to a gate line GLn, and a drain electrode of a TFT. the pixel electrode P electrically connected to (d), the liquid crystal capacitor Clc formed between the pixel electrode P and the common electrode Vcom, the pixel electrode P and the front gate line GLn-1. ) And a parasitic capacitance Cgd due to misalignment between the gate electrode g and the drain electrode d of the TFT.

The driving of a general TFT-LCD will be described as follows.

First, the TFT is turned on by applying a gate-on voltage to the gate electrode g connected to the gate line GLn of each pixel to be displayed, and then applying a data voltage indicating an image signal to the data line DLm. To the pixel electrode P through the TFT. Accordingly, the data voltage is applied to the liquid crystal capacitor Clc and the storage capacitor Cst through the pixel electrode P, respectively, and the data voltage applied to the pixel electrode P and the common voltage Vcom applied to the common electrode. An electric field is formed by the potential difference of. Accordingly, each pixel displays a desired image by adjusting the transmittance of the incident light according to the electric field generated by the pixel electrode P and the common electrode.

On the other hand, if the electric field in the same direction is continuously applied to the liquid crystal cell, the liquid crystal deteriorates, so that the data voltage is repeated with a positive polarity and a negative polarity around the common voltage Vcom applied to the common electrode to prevent deterioration of the liquid crystal. Reverse driving. This is because when the voltage of the pixel electrode P is asymmetric about the common voltage Vcom, a flicker phenomenon occurs whenever the data voltage is inverted due to a change in the magnitude of the data voltage charged in each pixel. .

2 is a circuit diagram schematically showing a common voltage generator of a general TFT-LCD.

Referring to FIG. 2, a general common voltage generator includes a first resistor R1, a variable resistor VR, and a second resistor R2 connected in series between a first voltage VDD and a second voltage VSS. Equipped.

The first and second resistors R1 and R2 have a fixed resistance value.

In the variable resistor VR, a resistance value is changed by an operator when the voltage value of the common voltage Vcom is adjusted.

The common voltage generator of a general LCD generates a common voltage Vcom by voltage-dividing the first driving voltage VDD using the first resistor R1, the variable resistor VR, and the second resistor R2. The generated common voltage Vcom is supplied to the common electrode.

The common voltage generator of such a general LCD manually adjusts the variable resistor VR to adjust the common voltage Vcom applied to the common electrode. That is, the resistance value of the variable resistor VR is manually adjusted to remove the flicker phenomenon generated when the common voltage Vcom is not constant.

Therefore, the common voltage generator of general LCD sets the resistance value of the variable resistor VR because the operator manually adjusts the resistance value of the variable resistor VR using a driver or the like to adjust the common voltage Vcom. There is a problem that takes a lot of time. In addition, since the operator manually adjusts the resistance value of the variable resistor VR, it is difficult to set an optimum common voltage Vcom for minimizing flicker.

Accordingly, in order to solve the above problems, the present invention is to provide a common voltage generator and a method of generating a liquid crystal display device that can easily adjust the common voltage using a memory.

The common voltage generator of the liquid crystal display according to the embodiment of the present invention for achieving the above object is an analog-to-digital converter for converting a set voltage into digital data, a memory for storing the digital data, and the memory And a digital-to-analog converter configured to analog convert the digital data stored in the digital data to generate a common voltage.

The common voltage generator of the liquid crystal display may further include a voltage supply unit for adjusting the set voltage externally, and a switch for generating a control signal for controlling the driving of the memory.

A common voltage generating method of a liquid crystal display according to an exemplary embodiment of the present invention includes converting a set voltage into digital data using an analog-digital converter, storing the digital data in a memory, and a digital-analog converter. And analog converting the digital data stored in the memory to generate a common voltage.

The common voltage generating method of the liquid crystal display may further include adjusting the set voltage externally and generating a control signal for controlling the driving of the memory.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings and embodiments.

3 is a view schematically illustrating a driving device of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, a driving device of a liquid crystal display according to an exemplary embodiment of the present invention may include a plurality of data lines DL1 through DLm and a plurality of gate lines GL1 through GLm that vertically intersect to form a liquid crystal cell. A liquid crystal panel 102 which displays an image by driving a liquid crystal by a voltage between the pixel electrode and the common electrode; To the data driver 104 and the gate lines GL1 to GLn, which generate an analog image signal corresponding to the gray level of the input digital data Data and supply the analog image signal to the pixel electrode through the data lines DL1 to DLm. A gate driver 106 for supplying a scan pulse; A timing controller 108 for aligning and supplying digital data to the data driver 104 and controlling driving timing of the data driver 104 and the gate driver 106; Supply from the voltage generator 110 and the voltage generator 110 for generating various voltages (VDD, VCC, VGH, VGL, etc.) required for driving the timing controller 108 and the data and gate drivers 104 and 106. The common voltage generator 120 converts and stores the set voltage by the operator into digital data using the driving voltage VDD, and generates and supplies the common voltage Vcom corresponding to the stored digital data to the liquid crystal panel 102. ).

The liquid crystal panel 102 includes a thin film transistor TFT formed in a region defined by n gate lines GL1 through GLn and m data lines DL1 through DLm, and a liquid crystal connected to the thin film transistor TFT. With cells. The thin film transistor TFT supplies an analog image signal from the data lines DL1 to DLm to the liquid crystal cell in response to the scan pulses from the gate lines GL1 to GLn. The liquid crystal cell is composed of a common electrode facing each other with a liquid crystal interposed therebetween and a pixel electrode connected to the thin film transistor TFT, so that the liquid crystal cell may be equivalently represented as a liquid crystal capacitor Clc. The liquid crystal cell includes a storage capacitor Cst connected to the previous gate line to maintain the analog image signal charged in the liquid crystal capacitor Clc until the next analog image signal is charged.

As described above, the liquid crystal panel 102 changes the liquid crystal arrangement state between the pixel electrode and the common electrode according to digital data for each liquid crystal cell, thereby displaying a desired image by adjusting the light transmittance. In this case, if an electric field in the same direction is continuously applied to the liquid crystal cell, the liquid crystal deteriorates, so that the data voltage is repeated with a positive polarity and a negative polarity around the common voltage Vcom applied to the common electrode. Reverse driving.

The timing controller 108 aligns the source data RGB supplied from the outside so as to suit the liquid crystal panel 102 and supplies the aligned digital data Data to the data driver 104. In addition, the timing controller 108 generates a data control signal DCS and a gate control signal GCS by using the main clock MCLK inputted from the outside and the horizontal and vertical synchronization signals Hsync and Vsync. The driving timing of each of the 104 and the gate driver 106 is controlled.

The gate driver 106 sequentially shifts the scan pulse, that is, the gate high pulse, in response to the gate start pulse GSP and the gate shift clock GSC of the gate control signal GCS from the timing controller 108. It includes. In response to this scan pulse, the thin film transistor TFT is turned on. When the thin film transistor TFT is turned on, the analog image signal on the data lines DL1 to DLm is supplied to the pixel electrode of the liquid crystal cell Clc.

The data driver 104 converts the digital data Data from the timing controller 108 into an analog image signal according to the data control signal DCS supplied from the timing controller 108 to the gate lines GL1 to GLn. The analog image signal is supplied to the data lines DL1 to DLm every horizontal period in which the scan pulse is supplied. That is, the data driver 104 selects a gamma voltage having a predetermined level as an analog image signal according to the gray value of the digital data and supplies the same to the data lines DL1 to DLm.

The voltage generator 110 generates various voltages VGH, VGL, VDD, and VCC required to drive the timing controller 108 and the data and gate drivers 104 and 106 by using an input power source Vin from the outside. do.

As shown in FIG. 4, the common voltage generator 110 may convert the set voltage Vset of the operator into digital data DS and an analog signal according to the control signal WS. A memory 124 storing the digital data DS from the digital converter 122 and a common voltage Vcom corresponding to the stored digital data MS supplied from the memory 124 according to the control signal WS. And a digital-analog converter 126 for supplying the generated liquid crystal panel 102 to the liquid crystal panel 102.

The set voltage Vset of the operator is set to a voltage for flicker removal in the inspection process of the liquid crystal display, that is, the flicker inspection process.

To this end, in the flicker inspection process, an operator connects a separate jig to a connector provided in the liquid crystal display as shown in FIG. 5 to set the set voltage Vset. A switch mode power supply (SMPS) is electrically connected to the jig, and a switch SW for generating a control signal WS is provided. Accordingly, the operator finely adjusts the voltage of the common voltage Vcom supplied to the common voltage generator 110 using the switch mode power to set the common voltage Vcom for removing the flicker. In order to set the voltage when the flicker is removed to the set voltage Vset, the switch SW is turned on to generate the control signal WS and supply it to the common voltage generator 110.

As described above, the analog-digital converter 122 converts the set voltage Vset input through the set voltage input terminal 121 into digital data DS and supplies it to the memory 124. At this time, when the set voltage Vset input to the set voltage input terminal 121 is 0.7 V or more, the set voltage Vset switches the memory 124 to the read mode through the bypass voltage line 123. Here, the analog-to-digital converter 122 converts the set voltage Vset set by the operator into at least 4 bits of digital data DS to supply the memory 124 to make a fine setting of the common voltage Vcom. .

The memory 124 is converted into a read mode by a control signal WS by a set voltage Vset of 0.7 V or more supplied through the bypass voltage line 123 and an off state of the switch SW, thereby converting the analog-digital conversion. At least four bits of digital data DS supplied from the unit 122 are bypassed to the digital-to-analog converter 126 without storing them.

In addition, the memory 124 is switched to the write mode by the control signal WS caused by the set voltage Vset of 0.7 V or more supplied through the bypass voltage line 123 and the on state of the switch SW. At least 4 bits of digital data DS supplied from the digital converter 122 are stored.

In addition, the memory 124 has at least four bits of digital data DS stored in the bypass voltage line 123 in an open state and converted into a read mode by a control signal WS by an off state of the switch SW. Is supplied to the digital-to-analog converter 126.

The digital-analog converter 126 receives a plurality of bits of digital data MS stored in the memory 124 and converts the plurality of bits of digital data DS into an analog voltage and outputs the analog voltage. That is, the digital-analog converter 126 divides the driving voltage VDD according to the plurality of bits of digital data MS supplied from the memory 124 to generate and output the common voltage Vcom.

As described above, the common voltage generator and the generation method of the liquid crystal display according to the exemplary embodiment of the present invention will be described.

First, an inspection jig is electrically connected to a liquid crystal display including a switch mode power supply and a switch SW.

Then, the operator adjusts the set voltage Vset by using the switch mode power supply. The set voltage Vset adjusted by the operator is converted into a plurality of bits of digital data DS by the analog-digital converter 122 through the set voltage input line 121. At this time, the memory 124 is converted to a read mode when the control voltage WS is set to a voltage Vset of 0.7 V or more supplied through the bypass voltage line 123 and the switch SW is turned off. Bypass the digital-to-analog converter 126 without storing at least 4 bits of digital data (DS) supplied from the digital converter 122.

Accordingly, the digital-analog converter 126 analog-converts at least 4 bits of digital data DS bypassed from the memory 124 to generate a common voltage Vcom, and generates the generated common voltage Vcom. Supply to the common electrode.

Therefore, the operator inspects the flicker by displaying an image on the liquid crystal panel 102 using the common voltage Vcom supplied to the common electrode, the gate pulse, and the analog image signal.

When the common voltage Vcom is set to repeat the above process to remove the flicker, the operator turns on the switch SW. Accordingly, the memory 124 is switched to the write mode by the control signal WS by the set voltage Vset or more than 0.7V supplied through the bypass voltage line 123 and the on state of the switch SW. At least 4 bits of digital data DS supplied from the digital converter 122 are stored.

Then, the operator stores the final set voltage Vset in the memory 124, and then separates the set voltage input line 121 and the test jig connected to the memory 124 to set the set voltage input line 121. Open Accordingly, the memory 124 has at least four bits of digital data DS stored in the bypass voltage line 123 in an open state and converted into a read mode by a control signal WS by an off state of the switch SW. ) Is supplied to the digital-to-analog converter 126.

Accordingly, the digital-to-analog converter 126 receives a plurality of bits of digital data MS stored in the memory 124 switched to the read mode and has a common voltage corresponding to the value of at least 4 bits of digital data MS. Vcom) is generated and supplied to the common electrode of the liquid crystal display.

Such a common voltage generator and method for generating a liquid crystal display according to an exemplary embodiment of the present invention set a common voltage Vcom by using an external switch mode power supply, and convert the set common voltage Vcom into analog-digital conversion. The digital data MS stored in the memory 124 is digital-analog-converted to generate a common voltage Vcom, and is supplied to the common electrode of the liquid crystal panel 102.

Accordingly, the common voltage generator and the method of the liquid crystal display according to the exemplary embodiment of the present invention can easily adjust the common voltage using a memory.

On the other hand, the present invention described above is not limited to the above-described embodiment and the accompanying drawings, it is possible that various substitutions, modifications and changes within the scope without departing from the technical spirit of the present invention It will be apparent to those skilled in the art.

The common voltage generator and the method of generating the liquid crystal display according to the embodiment of the present invention as described above are stored in a memory by analog-to-digital conversion of the common voltage set from the outside, and digital-to-analog conversion by the digital signal stored in the memory By generating a common voltage, the common voltage can be easily adjusted.

Since the present invention generates a common voltage by storing a set voltage set externally, the common voltage can be easily adjusted even from a long distance.

Claims (11)

delete An analog-digital converter for converting the set voltage into digital data; A memory for storing the digital data; A digital-analog converter configured to generate a common voltage by analog converting the digital data stored in the memory; A voltage supply unit configured to externally adjust the set voltage; And And a switch for generating a control signal for controlling the driving of the memory. The memory is switched to one of a bypass mode, a write mode, and a read mode according to the control of the control signal corresponding to the voltage level of the set voltage and the state of the switch, thereby bypassing the digital data. And storing the digital data or outputting the stored digital data. The method of claim 2, The voltage supply unit is a common voltage generator of the liquid crystal display, characterized in that the switch mode power (Switch Mode Power Supply). The method of claim 2, The memory, When the voltage level of the set voltage is input higher than the set level, and the control signal corresponding to the turn off state of the switch is input, the control mode is switched to the bypass mode, from the analog-to-digital converter. And bypassing the digital data to the digital-analog converter. The method of claim 4, wherein The memory, When the voltage level of the set voltage is higher than the set level and the control signal corresponding to the turn on state of the switch is input, the control mode is switched to the write mode, and the digital data from the analog-to-digital converter is input. The common voltage generator of the liquid crystal display, characterized in that for storing. 6. The method of claim 5, The memory, When the input line of the set voltage is electrically open and the control signal corresponding to the turn off state of the switch is input, the control mode is switched to the read mode, and the stored digital data is stored in the digital- A common voltage generator of a liquid crystal display device, characterized in that it is supplied to an analog converter. delete Converting the set voltage into digital data using an analog-digital converter; Storing the digital data in a memory; Generating a common voltage by analog converting the digital data stored in the memory using a digital-analog converter; Adjusting the set voltage externally; And Generating a control signal for controlling the driving of the memory; The memory is switched to any one of a bypass mode, a write mode, and a read mode according to the control of the control signal corresponding to the voltage level of the set voltage and the state of the switch to bypass the digital data. Or storing the digital data or outputting the stored digital data. The method of claim 8, The memory, When the voltage level of the set voltage is input higher than the set level, and the control signal corresponding to the turn off state of the switch is input, the control mode is switched to the bypass mode, from the analog-to-digital converter. And digital data is bypassed to the digital-analog converter. The method of claim 9, The memory, When the voltage level of the set voltage is higher than the set level and the control signal corresponding to the turn on state of the switch is input, the control mode is switched to the write mode, and the digital data from the analog-to-digital converter is input. Method of generating a common voltage of the liquid crystal display, characterized in that for storing. 11. The method of claim 10, The memory, When the input line of the set voltage is electrically open and the control signal corresponding to the turn off state of the switch is input, the control mode is switched to the read mode, and the stored digital data is stored in the digital- A common voltage generating method of a liquid crystal display device, characterized in that the supply to the analog converter.

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