KR101144009B1 - Driving unit of liquid crystal display device for setting detailed voltage - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving unit of a liquid crystal display device capable of precisely setting a common voltage, wherein a plurality of pixels are arranged in a matrix form on a substrate, and a pixel electrode and a common electrode for driving a liquid crystal corresponding to the pixels are provided. An apparatus comprising: a reference resistor for dropping a power supply voltage applied from an external source to generate a reference voltage, a first voltage setting unit for calculating the reference voltage to output a first voltage, and calculating the reference voltage for a second voltage; And a second voltage setting unit for outputting a voltage, and a voltage selecting unit for selecting a third voltage between the first voltage and the second voltage and applying the voltage to the common electrode according to externally input setting data.

Description

DRIVING UNIT OF LIQUID CRYSTAL DISPLAY DEVICE FOR SETTING DETAILED VOLTAGE}

1 is an equivalent circuit diagram of a unit pixel of a liquid crystal display panel.

2 is an exemplary view showing a circuit configuration of a common common voltage generator.

3 is a view showing a conventional programmable common voltage generator.

4 is a view showing a driving unit of the liquid crystal display according to the present invention;

5 is a diagram illustrating a circuit configuration of the common voltage generator of FIG. 4.

*** Description of the symbols for the main parts of the drawings **

210: first voltage setting unit 220: second voltage setting unit

230: voltage selector Vref: reference voltage

Rref: reference resistance S_DATA10: setting data

Rs1: first source resistor Rs2: second source resistor

Rf1: first feedback resistor Rf2: second feedback resistor

Vcom10: common voltage

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving unit of a liquid crystal display device, and more particularly, to a driving unit of a liquid crystal display device, which can be used for various purposes and can precisely set a common voltage range.

Recently, flat panel displays such as liquid crystal display devices (LCDs), which are easy to manufacture by making them lighter and thinner than CRTs, have been developed in various fields. It is put to practical use.

Among them, low power consumption, thin and light manufacturing, and high-definition liquid crystal display devices are increasingly being used not only for notebook computers and desktop computers but also various measuring devices.

BACKGROUND ART In general, a liquid crystal display device is a display device that displays a desired image by individually supplying data voltages corresponding to image information to a plurality of pixels arranged in a matrix, and adjusting light transmittance of the pixels. .

The liquid crystal display includes a liquid crystal display panel for implementing an image through a plurality of pixels, a gate driver and a data driver for driving the pixels.

The liquid crystal display panel includes a color filter substrate and a thin film transistor array substrate bonded together to have a constant cell-gap, and the color filter substrate and the thin film transistor array substrate. It consists of a liquid crystal layer formed in a cell gap.

In the liquid crystal display panel, a plurality of data lines for transmitting the data signal supplied from the data driver to the pixels and a plurality of gate lines for transmitting the scan signal supplied from the gate driver to the pixels cross each other. A pixel is defined at each intersection of the data line and the gate line.

The pixel may include a thin film transistor that switches a data voltage transmitted from the data driver through a data line, and a pixel electrode to which the data voltage is applied through the thin film transistor.

The gate driver sequentially supplies scan signals to the gate lines so that pixels arranged in a matrix form are sequentially selected one by one, and a data voltage is supplied from the data driver to the pixels of the selected one line.

A common electrode is formed on the color filter substrate, and a pixel electrode is formed on the thin film transistor array substrate to apply an electric field to the liquid crystal layer. Therefore, when the data voltage applied to the pixel electrode is controlled while the common voltage is applied to the common electrode, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to an electric field between the common electrode and the pixel electrode. Transmittance of light is changed for each pixel to display a character or an image.

1 is an equivalent circuit diagram of a unit pixel of a liquid crystal display panel.

Referring to FIG. 1, a unit pixel has a thin film transistor 100 having a gate electrode connected to a gate line 101, a source electrode connected to a data line 103, and a drain electrode of the thin film transistor 100. It consists of a liquid crystal capacitor 102 and a storage capacitor 104 connected in parallel between the voltages Vcom.

When the thin film transistor 100 is turned on by the scan signal applied from the gate driver, a data voltage is applied to the pixel electrode through the gate electrode of the thin film transistor.

The data voltage applied to the pixel electrode changes the light transmittance of the liquid crystal by applying an electric field to the liquid crystal together with the common voltage Vcom applied to the common electrode. The data voltage is charged in the storage capacitor 104 and the liquid crystal capacitor 102 to drive the pixel to the same voltage for one frame.

As described above, the common voltage Vcom performs an important function of controlling the light transmittance of the liquid crystal along with the data voltage. Accurately adjusting the light transmittance of the liquid crystal is directly related to the image quality, so it is important to set the common voltage Vcom at an accurate level and keep it constant. A device for generating the common voltage Vcom and outputting it to the common electrode is a common voltage generator.

2 is an exemplary view showing a circuit configuration of a common common voltage generator.

Referring to FIG. 2, the common voltage generating unit includes first and second resistors R1 and R2 connected in series between a power supply voltage Vdd and a base voltage Vss, and between the first and second resistors R1 and R2. It is composed of a variable resistor (VR1) is connected in series to the power supply voltage (Vdd) to distribute the desired level to the common voltage (Vcom1).

The common voltage Vcom1 generated from the common voltage generator is applied to the common electrode formed on the color filter substrate, which is the upper substrate of the liquid crystal display panel, and applied to the pixel electrode of the thin film transistor array substrate, which is the lower substrate of the liquid crystal display panel. By applying an electric field to the liquid crystal layer formed in the cell gap between the color filter substrate and the thin film transistor array substrate together with the data voltage, the liquid crystal molecules of the liquid crystal layer are rotated by dielectric anisotropy to control the light transmittance for each pixel.

On the other hand, a phenomenon such as flicker among the poor image quality generated in the liquid crystal display device is caused when the voltage difference between the data voltage and the common voltage Vcom1 is different from the desired voltage difference. The common voltage Vcom1 may be adjusted by changing the resistance value of the variable resistor VR1 in order to improve the poor image quality.

Initially, in order to adjust the common voltage Vcom1, the resistance value of the variable resistor VR1 is manually adjusted by a screw driver or the like to adjust the level of the common voltage. A programmable common voltage generator for receiving the voltage regulation data and setting the resistance value of the variable resistor in accordance with the voltage regulation data is widely used.

3 is a diagram illustrating a conventional programmable common voltage generator.

Referring to FIG. 3, the common voltage generator includes a first and second resistors R11 and R12 connected in series between a power supply voltage Vdd and a base voltage Vss and between the first and second resistors R11 and R12. The resistance variable unit 100 is connected to the power supply voltage Vdd at a desired level according to the external setting data S_DATA1 and outputs the common voltage Vcom2.

The resistance variable part 100 is a circuit that performs the function of the variable resistor VR1 shown in FIG. 2, and may be integrated and manufactured as an integrated circuit (IC).

However, while the variable resistor VR1 of FIG. 2 is manually adjusted, the voltage setting unit 100 of FIG. 3 automatically sets the common voltage Vcom2 by the setting data S_DATA1 input from the outside. That is, the voltage range between the power supply voltage Vdd and the base voltage Vss is divided with the first and second resistors R11 and R12 and output as the common voltage Vcom2.

On the other hand, the common voltage generating unit shown in Figures 2 and 3 are both connected to the maximum voltage and the lowest voltage to set a constant voltage range. That is, two voltage sources are required, a power supply voltage Vdd and a base voltage Vss. Therefore, in order to set the voltage range of the common voltage generator, both the maximum voltage and the minimum voltage must be set, and since different voltage sources are used, it is difficult to narrow the voltage range. Accordingly, when the level of the common voltage is adjusted to improve the image quality defect in the LCD, it is difficult to precisely adjust the level.

The present invention has been devised to solve the above-described problems, and an object of the present invention is to set a narrower voltage range than the conventional one by applying one voltage to more accurately set a common voltage. To provide a drive of the.

The driving unit of the liquid crystal display according to the present invention is a liquid crystal display device having a plurality of pixels arranged in a matrix form on a substrate, and having a pixel electrode and a common electrode for driving a liquid crystal corresponding to the pixels, which are applied from the outside. A reference resistor for generating a reference voltage from a power supply voltage, a first voltage setting unit for calculating the reference voltage and outputting a first voltage, a second voltage setting unit for calculating the reference voltage and outputting a second voltage; And a voltage selector which selects a third voltage between the first voltage and the second voltage and applies the selected voltage to the common electrode according to externally input setting data.

A feature of the present invention is that the conventional voltage range can be set by two voltage sources, and only one voltage source can set a narrower voltage range than the conventional one. It can be set precisely.

The driving unit of the liquid crystal display of the present invention is a common voltage generating unit for generating and outputting a common voltage in detail.

4 is a view showing a driving unit of the liquid crystal display according to the present invention.

Although not shown in the drawings, a liquid crystal display device includes a liquid crystal panel in which two substrates are bonded to a predetermined cell gap, and a liquid crystal layer is formed in the cell gap, a plurality of gate lines and data lines arranged vertically and horizontally on the liquid crystal panel; And a plurality of pixels defined at each intersection of the gate line and the data line, a pixel electrode individually provided in the pixel to receive a data voltage, and a common electric field applied to the liquid crystal together with the pixel electrode to control light transmittance. It is configured to include an electrode.

Referring to FIG. 4, the driving unit of the liquid crystal display device generates a reference voltage by dropping the power supply voltage Vdd applied from the outside, and calculates the reference voltage by receiving the reference voltage. And a common voltage generator 200 for generating a plurality of voltages and selecting a specific voltage in the voltage range between the two voltages according to the setting data S_DATA10 provided from the outside and outputting the specific voltage as the common voltage Vcom10. .

Since the driving unit of the liquid crystal display sets the voltage based on a reference voltage obtained by dropping the power supply voltage Vdd applied from the outside, an additional voltage source other than the power supply voltage Vdd is not required.

The detailed configuration and operation of the common voltage generator 200 are as shown in FIG.

5 is a diagram illustrating a circuit configuration of the common voltage generator of FIG. 4.

Referring to FIG. 5, the common voltage generator receives a reference voltage Vref and outputs the first voltage VH to the first voltage setting unit 210, and receives the reference voltage Vref to receive the second voltage (Vref). VL) to the external setting data within the voltage range between the second voltage setting unit 220 and the first and second voltages VH and VL output from the first and second voltage setting units 210 and 220. Accordingly, the voltage selector 230 selects and outputs one voltage.

The first voltage setting unit 210 and the second voltage setting unit 220 are operational amplifiers (OP-AMPs). In particular, a non-inverting op amp is used to obtain a positive output.

The first voltage setting unit 210 receives a reference voltage Vref through a non-inverting input terminal, and a first source resistor Rs1 and a first feedback resistor Rf1 are connected in parallel to the inverting input terminal. Here, the first feedback resistor Rf1 is also connected to the output terminal of the first voltage setting unit 210. That is, the first feedback resistor Rf1 feeds back the output voltage of the first voltage setting unit 210 to the inverting input terminal.

Similarly, the second voltage setting unit 220 receives the reference voltage Vref through the non-inverting input terminal, and the second source resistor Rs2 and the second feedback resistor Rf2 are connected in parallel to the inverting input terminal. do. The second feedback resistor Rf2 is simultaneously connected to the inverting input terminal and the output terminal of the second voltage setting unit 220 to feed back the output voltage toward the inverting input terminal.

The reference voltage Vref of the same voltage level is applied to the non-inverting input terminals of the first and second voltage setting units 210 and 220. The reference voltage Vref is a voltage obtained by dropping a power supply voltage applied from the outside, and is commonly applied to the first and second voltage setting units 210 and 220.

The first voltage VH output from the first voltage setting unit 210 may be obtained through Equation 1 indicating a relationship between a voltage gain and an input voltage of a general non-inverting operational amplifier.

As shown in Equation 1, the first voltage VH output from the first voltage setting unit 210 is equal to the value of the first feedback resistor Rf1 / the first source resistor Rs1 to the reference voltage Vref. Is determined by the addition.

Similarly, the second voltage VL of the second voltage setting unit 220 may be obtained by Equation 2.

Referring to Equation 2, the second voltage VL output from the second voltage setting unit 220 is the value of the second feedback resistor Rf2 / the second source resistor Rs2 to the reference voltage Vref. Is the sum of

As described above, the reference voltage Vref of the same level is applied to each of the non-inverting input terminals of the first voltage setting unit 210 and the second voltage setting unit 220. However, the first voltage setting unit 210 outputs the first voltage VH by calculating the value of the first feedback resistor Rf1 / first source resistor Rs1 to the reference voltage Vref, and the second voltage. The voltage setting unit 220 outputs the second voltage VL by calculating the value of the second feedback resistor Rf2 / the second source resistor Rs2 to the reference voltage Vref, thereby varying the resistance value. The first voltage VH and the second voltage VL may be output to have different values.

In addition, since both the first voltage setting unit 210 and the second voltage setting unit 220 determine an output voltage with a constant voltage level added to the reference voltage Vref based on the reference voltage Vref, each source The voltage difference between the first voltage VH and the second voltage VL may be narrowed by adjusting the values of the resistors Rs1 and Rs2 and the feedback resistors Rf1 and Rf2.

As such, when the voltage levels of the first voltage VH and the second voltage VL become narrow enough to be almost indistinguishable, the common voltage Vcom10 can be selected precisely in smaller voltage units within the voltage range. Will be.

The voltage selection unit 230 is connected between the first voltage setting unit 210 and the second voltage setting unit 220. Therefore, the first voltage VH and the second voltage VL are applied to both ends of the voltage selector 230. The voltage selector 230 includes a variable resistor that divides a voltage between the first voltage VH and the second voltage VL to obtain a desired level of voltage. The level of the common voltage Vcom10 to be output from the voltage selector 230 is determined according to the external setting data S_DATA10.

The common voltage Vcom10 output from the voltage selector 230 is applied to the common electrode to form an electric field together with the pixel electrode provided in the pixel to change the arrangement of liquid crystals.

As described above, since the first voltage VH and the second voltage VL are both voltage values calculated from the reference voltage Vref, only the source resistors Rs1 and Rs2 and the feedback resistors Rf1 and Rf2 are adjusted. It can be set to a very narrow voltage range. As such, when the voltage range between the first voltage VH and the second voltage VL is narrowed, the voltage selector 230 selects the common voltage Vcom10 by varying the resistance within the narrow voltage range. , It can select precisely by adjusting common voltage (Vcom10) in small scale unit.

When the common voltage Vcom10 can be precisely set as described above, when the common voltage Vcom10 is adjusted to improve the quality defect of the liquid crystal display, the quality defect may be more accurately corrected than in the related art.

Meanwhile, since the common voltage generator including the first and second voltage setters 210 and 220 and the voltage selector 230 may be integrated in a single chip, voltages may be applied in addition to the common voltage generator of the liquid crystal display. It can be used selectively for many devices that need to be precisely set.

As described above, the driving unit of the liquid crystal display according to the present invention calculates a single voltage to set a narrow voltage range and selects a common voltage within the narrow voltage range, so that a precise common voltage can be set so that the liquid crystal display When the device's image quality is improved, more precise common voltage control is possible to maximize the quality improvement effect.

In addition to the liquid crystal display device, it can be applied to various devices requiring precise voltage setting.

Claims (13)

In the liquid crystal display device having a plurality of pixels arranged in a matrix form on a substrate, and provided with a pixel electrode and a common electrode for driving the liquid crystal corresponding to the pixels, A reference resistor for generating a reference voltage from a power supply voltage applied from the outside; A first resistor and a second resistor are connected in parallel to the first input terminal, and the second resistor is also connected to the output terminal, and calculates the reference voltage applied through the second input terminal to output the first voltage. A first voltage setting unit; A third resistor and a fourth resistor are connected in parallel to the first input terminal, and the fourth resistor is also connected to the output terminal, and outputs the second voltage by calculating the reference voltage applied through the second input terminal. A second voltage setting unit; And a voltage selector which selects a third voltage between the first voltage and the second voltage and applies the applied voltage to the common electrode according to externally input setting data. 2. The driving unit of claim 1, wherein the first voltage setting unit and the second voltage setting unit are operational amplifiers (OP-AMPs). The driving unit of claim 2, wherein the first voltage setting unit and the second voltage setting unit are non-inverting operational amplifiers. The liquid crystal display driver of claim 1, wherein the third voltage is a common voltage. The liquid crystal display of claim 1, wherein the voltage selector comprises a variable resistor for distributing a voltage between the first voltage and the second voltage to obtain a third voltage having a desired level according to the setting data. Drive part. A first resistor and a second resistor are connected in parallel to the first input terminal, and the second resistor is also connected to the output terminal, and outputs the first voltage by calculating a reference voltage applied through the second input terminal. Single operational amplifier; A third resistor and a fourth resistor are connected in parallel to the first input terminal, and the fourth resistor is also connected to the output terminal, and outputs a second voltage by calculating a reference voltage applied through the second input terminal. Dual operational amplifiers; And a voltage selector configured to select and output a specific voltage within a voltage range between the first and second voltages output from the first and second operational amplifiers according to setting data input from the outside. Driver of liquid crystal display device. 7. The driving unit of claim 6, wherein the value of the second resistor / first resistor and the value of the fourth resistor / third resistor are set different from each other. 7. The liquid crystal of claim 6, wherein the voltage range between the first operational amplifier and the second operational amplifier is determined by the value of the second resistor / first resistor and the value of the fourth resistor / third resistor. Drive part of display device. 7. The driving unit of claim 6, wherein the first input terminal is an inverting input terminal, and the second input terminal is a noninverting input terminal. 7. The driving unit of claim 6, wherein both the first and second operational amplifiers are non-inverting operational amplifiers. 7. The liquid crystal display driver of claim 6, wherein the reference voltage applied to the first and second operational amplifiers is a voltage obtained by dropping a power supply voltage applied from the outside. The liquid crystal display of claim 6, wherein the voltage selector divides the resistance according to the setting data to divide the voltage between the first voltage and the second voltage to output a voltage of a desired level. Drive part. delete

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