KR20100017041A - Liquid crystal display device and driving voltage generation unit the same - Google Patents

Abstract

PURPOSE: A liquid crystal display device and a driving voltage generation unit with the same are provided to possessively deal with the change of characteristic of a thin film transistor by establishing the output level of the driving voltage in various level. CONSTITUTION: A driving voltage generation unit comprises a plurality of resistances, and an operational amplifier(142) and a thermistor(144). A first resistance(R1) among the plurality of resistances is connected to the negative voltage input terminal of the operational amplifier. A second resistance(R2) is connected between the negative voltage input terminal and the output terminal of the operational amplifier. The reference voltage is applied to the positive voltage input terminal of the operational amplifier. The thermistor is connected in parallel with the second resistance. A NTC(Negative Temperature Coefficient) type of the thermistor is employed for the thermistor because a resistance value of the NTC drops as the temperature rises. The driving voltage generation unit outputs different voltages in various temperature environments using the thermistor showing the resistance value that is inverse proportional to the temperature change.

Description

Driving voltage generation circuit for temperature characteristic compensation and liquid crystal display device having the same {Liquid crystal display device and driving voltage generation unit the same}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving voltage generating circuit and a liquid crystal display device having the same, and more particularly to a driving voltage generating circuit for providing stable display quality in response to changes in characteristics of liquid crystals according to temperature and a liquid crystal display device having the same. .

Currently widely used liquid crystal display (LCD) is a plurality of liquid crystal pixels arranged in a matrix form on the substrate and to control the amount of light transmission by controlling the rotation angle of the liquid crystal in each of these liquid crystal pixels Through the light supplied from the backlight unit to the liquid crystal panel provided with a thin film transistor (TFT) for controlling the supply of the image data for displaying the desired gray scale on the screen.

In such a liquid crystal display, a phenomenon in which the display image is different depending on the temperature of the use environment may occur. For example, the display image appears black at a high temperature compared to a normal temperature, and a display image appears white at a low temperature compared to the normal temperature.

This image distortion phenomenon is caused by the change in the filling rate of the liquid crystal due to the change in the operating characteristics of the thin film transistor, and at the low temperature, the operating characteristic of the thin film transistor is decreased, thereby reducing the filling rate of the liquid crystal. This is because the excess improvement and the filling rate of the liquid crystal is also exceeded.

1 is a circuit for compensating a driving voltage temperature compensation circuit of a liquid crystal display according to the related art, and generating a gate-on voltage Von for controlling switching of a thin film transistor.

Looking briefly at the configuration, the switching voltage generation unit 10 is composed of a DC-DC converter or the like to output the switching pulse voltage (VSW) by boosting the input voltage (Vin) by a predetermined multiple. At this time, the switching pulse voltage VSW has a voltage level characteristic inversely proportional to temperature under the influence of the feedback voltage VFB to be described below.

The temperature compensation feedback unit 20 receives a feedback voltage VFB that varies according to a temperature environment by a forward voltage (VF) characteristic inversely proportional to the temperatures of the first diodes to the third diodes D1, D2, and D3. Create Therefore, the feedback voltage VFB becomes large in a high temperature environment, and the feedback voltage VFB becomes small in a low temperature environment.

The power supply voltage generator 30 configures a plurality of capacitors C1 to C5 to provide the power supply voltage AVDD which rectifies the input switching pulse voltage VSW. Therefore, the power supply voltage AVDD also has a property inversely proportional to temperature.

The gate-on voltage generator 40 generates a gate-on voltage Von that pumps the switching pulse voltage VSW in multiples of the number based on the power source voltage AVDD, wherein the power-on voltage AVDD and the switching are performed. Since the pulse voltage VSW is input in inverse proportion to temperature, the gate-on voltage Von is also output in inverse proportion to temperature.

However, in the related art, the design is complicated because the number of circuit elements constituting the compensation for the gate-on voltage Von according to the temperature is complicated, and thus the area occupied by the driving circuit board for the liquid crystal display device is large. In addition, the increase in manufacturing cost and the manufacturing process is complicated.

Accordingly, the present invention has been made to solve the above problems, to provide a drive voltage generation circuit for providing a stable display quality in response to changes in the characteristics of the liquid crystal with temperature, in particular to simplify the circuit configuration of the manufacturing cost It aims at realizing the reduction and the simplification of the manufacturing process.

In order to achieve the above object, the present invention provides a drive voltage generation circuit for generating a drive voltage by including an operational amplifier to which a reference voltage is input and a first resistor, a second resistor, and a thermistor are connected to drive the liquid crystal display. to provide.

In the driving voltage generation circuit, the reference voltage is input to the positive input terminal of the operational amplifier.

In the driving voltage generation circuit, the first resistor is configured between the negative input terminal and the ground potential of the operational amplifier, and the second resistor is configured between the negative input terminal and the output terminal of the operational amplifier.

In the driving voltage generation circuit, the thermistor may be connected in parallel with the second resistor.

In the driving voltage generation circuit, the thermistor is characterized in that the NTC type.

In addition, the present invention, the liquid crystal panel; A driving voltage generation circuit having a reference voltage input thereto and having an operational amplifier connected to the first resistor, the second resistor, and the thermistor to output a driving voltage; A gate-on voltage generator configured to generate a gate-on voltage by pumping the driving voltage; A gate driver which receives the gate-on voltage and applies the gate-on voltage to the liquid crystal panel; A liquid crystal display device including a source driver for outputting an image data voltage to the liquid crystal panel is proposed.

In the liquid crystal display device, the liquid crystal panel comprises: a liquid crystal pixel comprising a thin film transistor switched by the gate-on voltage and a liquid crystal connected to the thin film transistor; A gate line applied with the gate-on voltage and connected to the thin film transistor; And a data line connected to the thin film transistor to which the image data voltage is applied.

In the liquid crystal display, the thermistor is characterized in that the NTC type.

In addition, the present invention provides an operational amplifier, comprising: an operational amplifier connected to a first resistor, a second resistor, and a thermistor to receive a reference voltage, a first operating voltage, and a second operating voltage to output a driving voltage; A driving voltage generation circuit comprising an operation voltage pumping circuit receiving a switching control signal and a power supply voltage and charge pumping the switching control signal using the power supply voltage to provide the first control voltage or the second operation voltage; Suggest.

In the driving voltage generation circuit, the reference voltage is input to the positive input terminal of the operational amplifier.

In the driving voltage generation circuit, the first resistor is configured between the negative input terminal and the ground potential of the operational amplifier, and the second resistor is configured between the negative input terminal and the output terminal of the operational amplifier.

In the driving voltage generation circuit, the thermistor may be connected in parallel with the second resistor.

In the driving voltage generation circuit, the thermistor is characterized in that the NTC type.

In the driving voltage generating circuit, the first operating voltage and the second operating voltage may be a positive operating voltage and a negative operating voltage, respectively.

In the driving voltage generating circuit, the operating voltage pumping circuit includes a first pumping circuit capacitor to which the switching control signal is applied, an anode connected to the first pumping circuit capacitor, and outputting the first operating voltage. A second pumping circuit capacitor to a fifth configured between a circuit diode, a second pumping circuit diode having a cathode connected to the first pumping circuit capacitor, and a cathode of the first pumping circuit diode and an anode of the second pumping circuit diode. And a first pumping circuit resistor and a second pumping circuit resistor connected to a pumping circuit capacitor and an anode of the second pumping circuit diode in parallel to each other to which different power voltages are applied.

In the driving voltage generation circuit, the switching control signal is a PWM signal.

In the driving voltage generation circuit, the power supply voltage is characterized by consisting of two voltages having different voltage levels.

In addition, the present invention, the liquid crystal panel; An operational amplifier connected with a first resistor, a second resistor, and a thermistor and receiving a reference voltage, a first operating voltage, and a second operating voltage, and outputting a driving voltage; and a switching control signal and a power supply voltage. A driving voltage generation circuit having an operation voltage pumping circuit configured to charge pump the switching control signal to provide the first operating voltage or the second operating voltage; A gate-on voltage generator configured to generate a gate-on voltage by pumping the driving voltage; A gate driver which receives the gate-on voltage and applies the gate-on voltage to the liquid crystal panel; A source driver for outputting an image data voltage to the liquid crystal panel; A liquid crystal display device includes a power supply voltage supply unit configured to provide the switching control signal and the power supply voltage.

In the liquid crystal display device, the liquid crystal panel comprises: a liquid crystal pixel comprising a thin film transistor switched by the gate-on voltage and a liquid crystal connected to the thin film transistor; A gate line applied with the gate-on voltage and connected to the thin film transistor; And a data line connected to the thin film transistor to which the image data voltage is applied.

In the liquid crystal display, the thermistor is characterized in that the NTC type.

According to the present invention having the above characteristics, it is possible to actively cope with the change of the characteristics of the thin film transistor (TFT) configured for each liquid crystal pixel according to the change of temperature, and to simplify the design with a simplified circuit configuration and to reduce the manufacturing cost and There is an advantage that the manufacturing process is simplified.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 2 is a schematic diagram illustrating a configuration of a liquid crystal display according to a first embodiment of the present invention. The liquid crystal panel 110, the source driver 120, the gate driver 130, the driving voltage generation circuit 140, And a gate-on voltage generator 150.

The liquid crystal panel 110 includes a plurality of data lines DL1 to DLm and a plurality of gate lines GL1 to GLn connected to the source driver 120 and the gate driver 130, respectively. A thin film transistor TFT and a liquid crystal pixel having a liquid crystal are respectively formed in an intersection area between the data lines DL1 to DLm and the gate lines GL1 to GLn.

Image data voltages output from the source driver 120 are applied to the plurality of data lines DL1 to DLm, and the gate driver GL1 to GLn are provided to the plurality of gate lines GL1 to GLn. The output gate-on voltages Von are respectively applied.

The source driver 120 converts image data of a digital format input from an external circuit unit into an analog voltage corresponding to a corresponding gray level and outputs the converted analog data to the plurality of data lines DL1 to DLm.

The gate driver 130 controls the switching of the thin film transistor TFT by sequentially outputting the gate-on voltage Von input from the gate-on voltage generator 150 to the plurality of gate lines GL1 to GLn. do.

The driving voltage generation circuit 140 generates a driving voltage Vdrv that is adapted to the characteristics of the thin film transistor TFT that varies with temperature using a reference voltage Vref, and the driving voltage Vdrv is The gate-on voltage generator 150 is provided to the gate driver 130 at a gate-on voltage Von by boosting the charge-pump in the gate-on voltage generator 150.

The present invention is characterized in that the driving voltage Vdrv capable of generating the gate-on voltage Von in accordance with the temperature environment in which the liquid crystal display device is driven is provided in accordance with the temperature environment. It demonstrates in detail with reference to FIG.

3 is a detailed implementation circuit diagram of the driving voltage generation circuit 140 of FIG. 2 according to the first embodiment of the present invention, and includes a plurality of resistors R1 and R2, an operational amplifier 142, and a thermistor 144. It is composed.

A first resistor R1 of the plurality of resistors is connected to a negative input terminal (−) of the operational amplifier 142, and the second resistor R2 is a negative input terminal (−) of the operational amplifier 142. And a reference voltage Vref is applied to the positive input terminal (+) of the operational amplifier 142.

In addition, the thermistor 144 is connected in parallel with the second resistor (R2), wherein the thermistor 144 employs a negative temperature coefficient (NTC) type of the resistance value is lowered as the temperature rises.

At this time, the resistance value of the first resistor (R1) and the second resistor (R2) can be variously adopted according to the needs of the designer, the reference voltage (Vref) can be applied in various ways, but mainly used in the liquid crystal display device Becoming 3.0V is suitable.

Accordingly, the driving voltage generation circuit 140 outputs different driving voltages Vdrv in various temperature environments by the thermistor 144 representing a resistance value inversely proportional to temperature change.

Equation 1 Vdrv = {1+ (Z2 / R1)} * Vref

In this case, Z2 is a combined resistance value according to the parallel connection of the second resistor R2 and the thermistor 144.

Accordingly, when the temperature of the driving voltage generation circuit 140 decreases with respect to room temperature, the resistance value of the thermistor 144 increases. Accordingly, the driving voltage Vdrv increases due to the increase of Z2, and the temperature of the driving voltage generating circuit 140 increases. When the resistance of the thermistor 144 is lowered, the driving voltage Vdrv is also lowered.

As such, the driving voltage Vdrv output at different voltage levels according to the temperature is then pumped by a predetermined multiple by the gate-on voltage generation unit 150 of FIG. 2 to be used as the gate-on voltage Von, and eventually the gate-on voltage. (Von) gives results that vary with temperature. That is, when the temperature is lower than room temperature, the gate-on voltage Von is increased. When the temperature is higher than room temperature, the gate-on voltage Von is lowered.

Therefore, the driving voltage generation circuit 140 according to the present invention can actively cope with the change in the characteristics of the thin film transistor (TFT) configured for each liquid crystal pixel according to the change of temperature, and the design of the simplified circuit configuration facilitates the design cost. There is an advantage that the savings and manufacturing process is simplified.

In addition, when the resistance values of the first resistor R1 and the second resistor R2 and the thermistor 144 are adjusted as necessary, for example, among the first resistor R1 and the second resistor R2. In the case of configuring one resistor as a variable resistor, the output level of the driving voltage Vdrv may be set in various ways, thereby more precisely coping with a characteristic change of the thin film transistor TFT.

FIG. 4 is a detailed implementation circuit diagram of the driving voltage generation circuit 140 of FIG. 2 according to the second embodiment of the present invention, in which an operating voltage pumping circuit 146 is further added to the above-described implementation circuit of FIG. 3.

That is, in the driving voltage generation circuit 140 according to the embodiment of the present invention described with reference to FIG. 3, a change in the resistance value of the thermistor 144 occurs as the temperature is changed, and thus through the operational amplifier 142. The amplification ratio Av, where Av = Vdrv / Vin = (R1 + Z2) / R1, is also changed to fail to generate a desired driving voltage Vdrv, and also to drive the operational amplifier 142. The driving is performed by a first operating voltage VDD (hereinafter referred to as positive operating voltage) and a second operating voltage (VCC referred to as negative operating voltage) provided to the (V +) terminal and the (V-) terminal of the operational amplifier 142, respectively. The maximum output value of the voltage Vdrv cannot output a voltage higher than the positive operating voltage VDD.

Accordingly, the operating voltage pumping circuit 146 provides the operational amplifier 142 with the positive operating voltage VDD higher to provide the operational amplifier 142 with a higher voltage level as necessary. In order to be able to output or to raise the output more, it is preferably a charge pumping circuit (Charge pumping circuit).

5, the operation voltage pumping circuit 146 receives power supply voltages V1 and V2 and switching control signals LX having different voltage levels, and receives the power supply voltages V1 and. The switching control signal LX is pumped and output using V2).

When the configuration of the operating voltage pumping circuit 146 is described in more detail, an anode is connected to the first pumping circuit capacitor Cp1 to which the switching control signal LX is applied, and the first pumping circuit capacitor Cp1. A first pumping circuit diode Dp1 for outputting the positive operating voltage VDD, a second pumping circuit diode Dp2 having a cathode connected to the first pumping circuit capacitor Cp1, and the first pumping circuit diode Between the second pumping circuit capacitor Cp2 and the fifth pumping circuit capacitor Cp5 configured between the cathode of Dp1 and the anode of the second pumping circuit diode Dp2, and the second pumping circuit diode Dp2. The first pumping circuit resistor Rp1 and the second pumping circuit resistor Rp2 are connected in parallel to the anode and to which power voltages V1 and V2 of different voltage levels are respectively applied.

In this case, the switching control signal LX is preferably a pulse width modulation (PWM) signal, and the voltage level is amplified by the power supply voltages V1 and V2 to the high and low level voltages of the switching control signal LX. In addition to the circuit shown in FIG. 5, the charge pumping circuit may be applied to various circuits.

6 is an output signal diagram for explaining the effect of the operating voltage pumping circuit 146 according to the second embodiment of the present invention as described above, the absence of the operating voltage pumping circuit 146 in the first embodiment of FIG. According to the second embodiment, the driving voltage generation circuit 140 outputs a driving voltage Vdrv of about 28.5V, but according to the second embodiment, the operating voltage pumping circuit 146 is further configured to show a voltage increase of about 34V. .

In this case, in order to drive the operating voltage pumping circuit 146, referring to FIG. 7, the power voltage supply unit 160 is additionally configured to the liquid crystal display of FIG. 2 according to the first embodiment of the present invention. It is preferable to provide a switching control signal LX and the power supply voltages V1 and V2 to the operating voltage pumping circuit 146.

According to the driving voltage generation circuit 140 according to each embodiment of the present invention described above, it is possible to actively cope with the characteristic change of the thin film transistor (TFT) configured for each liquid crystal pixel according to the change of temperature, as well as the driving voltage. The output level of the (Vdrv) can be set more variously to actively cope with the characteristic change of the thin film transistor (TFT).

1 is a driving voltage temperature compensation circuit of a liquid crystal display according to the related art.

2 is a schematic view showing the configuration of a liquid crystal display according to a first embodiment of the present invention.

3 is a circuit diagram illustrating a driving voltage generation circuit 140 of FIG. 2 according to a first embodiment of the present invention.

4 is a circuit diagram illustrating a driving voltage generation circuit 140 of FIG. 2 according to a second embodiment of the present invention.

5 is a circuit diagram of an operating voltage pumping circuit 146 according to a second embodiment of the present invention.

6 is an output signal diagram for explaining the effect of the configuration of the operating voltage pumping circuit 146 according to a second embodiment of the present invention

7 is a schematic view showing the configuration of a liquid crystal display according to a second embodiment of the present invention.

<Brief description of the main parts of the drawing>

110: liquid crystal panel 120: source driver

130: gate driver 140: drive voltage generation circuit

150: gate on voltage generation unit 160: power voltage supply unit

Claims (20)

To drive the liquid crystal display, A driving voltage generation circuit configured to generate a driving voltage by inputting a reference voltage and having an operational amplifier connected to a first resistor, a second resistor, and a thermistor; The method according to claim 1, The reference voltage is input to the driving voltage generation circuit, characterized in that the input to the positive input terminal of the operational amplifier The method according to claim 2, The first resistor is configured between the negative input terminal and the ground potential of the operational amplifier, and the second resistor is configured between the negative input terminal and the output terminal of the operational amplifier. The method according to claim 3, The thermistor is a drive voltage generation circuit, characterized in that connected in parallel with the second resistor The method according to claim 4, The thermistor is a drive voltage generation circuit, characterized in that the NTC type A liquid crystal panel; A driving voltage generation circuit having a reference voltage input thereto and having an operational amplifier connected to the first resistor, the second resistor, and the thermistor to output a driving voltage; A gate-on voltage generator configured to generate a gate-on voltage by pumping the driving voltage; A gate driver which receives the gate-on voltage and applies the gate-on voltage to the liquid crystal panel; A source driver for outputting an image data voltage to the liquid crystal panel Liquid crystal display comprising a The method of claim 6, The liquid crystal panel, A liquid crystal pixel comprising a thin film transistor switched by the gate-on voltage and a liquid crystal connected to the thin film transistor; A gate line applied with the gate-on voltage and connected to the thin film transistor; A data line connected to the thin film transistor to which the image data voltage is applied Liquid crystal display comprising a The method of claim 7, wherein The thermistor is a liquid crystal display, characterized in that the NTC type To drive the liquid crystal display, An operational amplifier connected to the first resistor, the second resistor, and the thermistor, and receiving a reference voltage, a first operating voltage, and a second operating voltage to output a driving voltage; An operating voltage pumping circuit which receives a switching control signal and a power supply voltage, charge charges the switching control signal using the power supply voltage, and provides the switching control signal as the first operating voltage or the second operating voltage. Drive voltage generation circuit comprising a The method of claim 9, The reference voltage is input to the driving voltage generation circuit, characterized in that the input to the positive input terminal of the operational amplifier The method of claim 10, The first resistor is configured between the negative input terminal and the ground potential of the operational amplifier, and the second resistor is configured between the negative input terminal and the output terminal of the operational amplifier. The method of claim 11, The thermistor is a drive voltage generation circuit, characterized in that connected in parallel with the second resistor The method according to claim 12, The thermistor is a drive voltage generation circuit, characterized in that the NTC type The method of claim 13, The first and second operating voltages are driving voltage generation circuits, characterized in that the positive operating voltage and the negative operating voltage, respectively. The method of claim 14, The operating voltage pumping circuit, A first pumping circuit capacitor to which the switching control signal is applied, an anode connected to the first pumping circuit capacitor, and a first pumping circuit diode to output the first operating voltage, and a cathode connected to the first pumping circuit capacitor A second pumping circuit capacitor, a fifth pumping circuit capacitor, and a second pumping circuit diode configured between a second pumping circuit diode, a cathode of the first pumping circuit diode, and an anode of the second pumping circuit diode, and an anode of the second pumping circuit diode. The first pumping circuit resistor and the second pumping circuit resistor are connected in parallel and applied with different power supply voltages, respectively. Drive voltage generation circuit comprising a The method of claim 15, The switching control signal is a drive voltage generation circuit, characterized in that the PWM signal The method according to claim 16, The power supply voltage is a drive voltage generation circuit, characterized in that consisting of two voltages having different voltage levels A liquid crystal panel; An operational amplifier connected with a first resistor, a second resistor, and a thermistor and receiving a reference voltage, a first operating voltage, and a second operating voltage, and outputting a driving voltage; and a switching control signal and a power supply voltage. A driving voltage generation circuit having an operation voltage pumping circuit configured to charge pump the switching control signal to provide the first operating voltage or the second operating voltage; A gate-on voltage generator configured to generate a gate-on voltage by pumping the driving voltage; A gate driver which receives the gate-on voltage and applies the gate-on voltage to the liquid crystal panel; A source driver for outputting an image data voltage to the liquid crystal panel; A power supply voltage supply unit providing the switching control signal and the power supply voltage Liquid crystal display comprising a The method of claim 18, The liquid crystal panel, A liquid crystal pixel comprising a thin film transistor switched by the gate-on voltage and a liquid crystal connected to the thin film transistor; A gate line applied with the gate-on voltage and connected to the thin film transistor; A data line connected to the thin film transistor to which the image data voltage is applied Liquid crystal display comprising a The method of claim 19, The thermistor is a liquid crystal display, characterized in that the NTC type

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