KR20110096424A - Temperature compensation circuit and liquid crystal display device having thereof - Google Patents

Abstract

The temperature compensation circuit of the present invention is to prevent a defect due to the temperature drop by correcting the output voltage according to the temperature change, the thermistor variable resistance according to the temperature; A resistor connected in parallel with the thermistor Rntc to divide the voltage; The feedback voltage is input to one terminal and the variable voltage is applied by the thermistor to the other terminal, so that the temperature decreases, and thus the comparator increases the output voltage input to the gate driver of the liquid crystal panel.

Description

TEMPERATURE COMPENSATION CIRCUIT AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THEREOF

The present invention relates to a temperature compensating circuit and a liquid crystal display device having the same, and a temperature compensating circuit and a liquid crystal display device having the same, which can prevent a defect due to a temperature drop by changing the level of a gate voltage according to a change in temperature. will be.

Liquid crystal display devices are transmissive flat panel displays, and are widely applied to various electronic devices such as mobile phones, PDAs, and notebook computers. Such LCDs are currently being practically used in comparison with other flat panel displays in that they can be made light and small and have high image quality. Moreover, as the demand for digital TVs, high-definition TVs, and wall-mounted TVs increases, studies on large-area LCDs applicable to TVs are being actively conducted.

In general, LCDs can be divided into several methods depending on how the liquid crystal molecules are operated. However, LCDs are mainly active matrix thin film transistors because of their fast response speed and low afterimage. Is mainly used.

The liquid crystal display device is a flat panel display device in which data signals corresponding to image information are individually supplied to a plurality of pixels arranged in a matrix form, and a desired image can be displayed by adjusting light transmittance of the pixels. .

Accordingly, the liquid crystal display device includes a liquid crystal panel in which pixels are arranged in a matrix and a driver for driving the pixels.

The liquid crystal panel includes a thin film transistor array substrate and a color filter substrate bonded together to maintain a uniform cell-gap opposite to each other, and a liquid crystal formed between the thin film transistor array substrate and the color filter substrate. It is composed of layers. In addition, a common electrode and a pixel electrode are formed in the liquid crystal panel in which the thin film transistor array substrate and the color filter substrate are bonded to each other to apply an electric field to the liquid crystal layer.

Therefore, when the voltage of the data signal applied to the pixel electrode is controlled while the voltage is applied to the common electrode, the liquid crystal of the liquid crystal layer rotates by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode. For example, characters or images are displayed by transmitting or blocking light for each pixel.

The driver includes a gate driver for applying a scan signal to the gate line and a data driver for applying a data signal to the data line. A control signal is input to the gate driver and the data driver, and a thin film transistor formed in each pixel is turned on by a scan signal output from the gate driver, and a data signal input from the data driver is applied to the pixel electrode through the thin film transistor. The image is implemented by being applied.

The gate driver supplies a gate signal consisting of gate on and off sections to a corresponding gate line on the liquid crystal panel. That is, the gate driver outputs the gate signal in a manner of supplying the gate high signal VGH only in the enable period in response to the gay out enable signal and supplying the gate low signal VGL in other periods.

However, the gate driver of the conventional liquid crystal display cannot adaptively adjust the level of the gate signal according to the temperature change around the liquid crystal panel. As a result, when the temperature around the liquid crystal panel is low, the level of the gate signal supplied to the gate line of the liquid crystal panel is lower than the reference value. As a result, the thin film transistor, which is a switching element of the data signal, does not switch normally, resulting in poor driving of the liquid crystal panel. There was a problem appearing.

An object of the present invention is to provide a temperature compensation circuit and a liquid crystal display device having the same, which can prevent a defect due to a temperature drop by changing a level of a gate voltage according to a temperature change. .

In order to achieve the above object, the temperature compensation circuit according to the present invention includes a thermistor having a resistance variable according to temperature; A resistor connected in parallel with the thermistor Rntc to divide the voltage; The feedback voltage is input to one terminal and the variable voltage is applied by the thermistor to the other terminal, so that the temperature is lowered.

The thermistor is a static characteristic thermistor whose reference temperature is -30 to 20 ° C or -20 to 20 ° C.

In addition, the liquid crystal display device according to the present invention is a liquid crystal panel for implementing an image as a gate line and a data line is disposed and a signal is input; A gate driver and a data driver for applying a gate signal and a data signal to gate lines and data lines of the liquid crystal panel, respectively; An interface unit to which a data signal, a power supply voltage, a vertical synchronization signal, and a data enable signal are input from the outside; A controller which processes a data signal input through the interface unit and outputs the data signal to the gate driver and the data driver; A DC / DC converter converting a level of a power supply voltage input through the interface unit and supplying the level to the gate driver and the data driver; A gate signal generator connected to the controller and the DC / DC converter to generate a gate signal according to a control signal of the controller and output the gate signal to the gate driver; And a thermistor disposed in the gate signal generator and having a variable resistance according to a temperature, a resistor connected in parallel with the thermistor Rntc to divide a voltage, a feedback voltage is input at one terminal, and a thermistor at the other terminal. It is composed of a temperature compensation circuit including a comparator for increasing the output voltage input to the gate driver of the liquid crystal panel as a variable voltage is applied to decrease the temperature.

In the present invention, by changing the level of the gate voltage in accordance with the temperature change it is possible to prevent the failure due to the temperature decrease.

1 is a block diagram showing the structure of a liquid crystal display device according to the present invention;
2 is a block diagram showing the structure of a gate voltage generating circuit according to the present invention;
3 is a diagram briefly showing a structure of a temperature compensation unit of a gate voltage generation circuit.
4 is a view showing a switch of a temperature compensation unit.

Hereinafter, a temperature compensation circuit and a liquid crystal display device having the same according to the present invention will be described with reference to the accompanying drawings.

1 is a view showing the structure of a liquid crystal display device according to the present invention. As shown in FIG. 1, in a liquid crystal display device, data, a clock signal, a horizontal sync signal (H _sync ), a vertical sync signal (V _sync ) and an enable from an external host such as a CPU of a computer. An interface unit 20 into which various signals such as signals are input, a controller 22 connected to the interface unit 20 to process data input through the interface unit 20, and generate and output a control signal; A DC / DC converter 24 connected to the interface unit 20 to convert a level of a power supply voltage supplied through the interface unit 20 to a voltage required for the liquid crystal display device, and the control unit; A gate signal generator 30 connected to the 22 and the DC / DC converter 24 to generate a gate signal, and converting the generated gate signal to a level compensated according to a temperature change and outputting the gate signal; ) And gate signal A gate driver integrated circuit (10) connected to the unit (30) and configured to sift and output a gate signal input from the gate signal generator (26), the controller (20) and the DC / DC converter (24). ) Is connected to the data driver IC 12 and outputs a data signal by driving according to a signal input from the controller 20, and a signal is applied from the gate driver 10 and the data driver 12 to actually output the data signal. It consists of the liquid crystal panel 1 which implements an image.

Although not shown, the liquid crystal panel 1 includes a thin film transistor array substrate on which a thin film transistor array is formed and a color filter substrate on which a color filter is formed, and a liquid crystal layer is formed between the thin film transistor array substrate and the color filter substrate. It is. As shown in the figure, the thin film transistor array substrate of the liquid crystal panel 1 has a plurality of pixels defined by the gate lines 3 and the data lines 5 arranged vertically and horizontally. 7) is formed. The gate electrode of the thin film transistor 7 is connected to the gate line 3 and the drain electrode is connected to the data line 5 so that a scan signal is applied to the gate electrode from the gate driver 10 through the gate line 3. When the semiconductor layer (not shown) of the thin film transistor is activated, a data signal supplied from the data driver 12 to the data line 5 is applied to the pixel electrode formed in the pixel through the source / drain electrodes, thereby liquid crystal molecules. Will be activated.

The control unit 22 and the DC / DC converter 24 are supplied with a DC voltage, for example, a DC voltage Vcc of about 3.3 V through the interface unit 20, and the DC / DC converter 24. In the step of converting the level of the input DC voltage, and outputs a DC voltage (Vdd) of about -5V, 8.7V, 16V, for example. At this time, the DC voltage level converted by the DC / DC converter 24 is to operate the gate driver 10 and the data driver 12. The DC / DC converter 24 is provided with a boost to adjust the strength of the input DC voltage Vcc.

The controller 22 generates and outputs a signal for driving the liquid crystal display device. The output signal is a sync signal (H _sync , V _sync ) and a data enable signal input through the interface unit 20. Is generated by the clock signal. In general, a case in which an output signal is generated by the synchronization signals H _sync and V _sync is called a synchronization mode, and a case in which an output signal is generated by the data enable signal DE is called a data enable mode. ) Selects and executes the two modes according to the input synchronization signals H _sync and V _sync .

The signal generated by the controller 22 is input to the gate signal generator 30, and the gate signal 30 generated by the gate signal generator 30 is shifted by the gate driver 10 and then the liquid crystal panel ( 1), the signal generated by the controller 22 is also input to the data driver 12 to drive the liquid crystal panel 1.

The gate signal generator 30 generates a gate signal according to a signal input from the controller 22. A detailed structure of the gate signal generator 30 is shown in FIG.

As shown in FIG. 2, the gate signal generator 30 again boosts the DC voltage Vdd whose size is adjusted from the first boost 24a of the DC / DC converter 24. ) And a voltage boosted by the second boost 33 is connected to the second boost 33, and the voltage is fed back to the second boost 33 according to an external temperature to control the voltage. The temperature compensation unit 35 outputs the driving unit 10.

The second boost 33 boosts the voltage boosted by the first boost 24a again to generate a gate signal. The temperature compensator 35 adjusts the temperature by the second boost 33 by feeding back a voltage that varies according to ambient temperature to the second boost 33.

3 is a diagram schematically showing the temperature compensation unit 35.

As shown in FIG. 3, the temperature compensator 35 is switched according to the ambient temperature and outputs a gate voltage VGH to the gate driver 1 when the ambient temperature is higher than the reference temperature, and the ambient temperature is higher than the reference temperature. In the low case, the switch 64 is configured to feed a voltage higher than the reference voltage Vref to the second boost 33 as the feedback voltage VFB. In this case, the reference temperature may be set differently as needed, but it may be preferable to set the temperature to -30 to 20 ° C or -20 to 20 ° C. Of course, this reference temperature may be set differently.

A second boost 33 made of a transformer 61 is disposed at the front end of the switch 64 so that the voltage Vdd input by being boosted by the first boost 24a is boosted by the transformer 61. At this time, a diode 63 is provided at the rear end of the transformer 61.

4 is a circuit diagram illustrating in detail the switch 64 of the temperature compensator 35 shown in FIG. 3.

As shown in FIG. 4, the switch 64 includes a thermistor Rntc whose resistance varies according to temperature, a resistor R3 connected in parallel with the thermistor Rntc to distribute voltage, and the thermistor Rntc. The selector 72 selects and outputs a high voltage among the output voltages according to the variable resistance of the variable, and the variable reference voltage Vref output from the selector 72 to the other terminal and the feedback voltage Vfb is input to the other terminal. The input comparator 74 is configured.

The thermistor Rntc may use a static thermistor whose resistance value is increased in inverse proportion to a temperature rise, and may use a negative characteristic thermistor whose resistance value is in inverse proportion to a temperature rise. Mainly use static thermistor with low cost. However, it is of course possible to use a negative thermistor.

In the case of using a static thermistor, when the temperature around the liquid crystal panel 1 falls, the resistance value of the dummy resistor Rntc is increased in inverse proportion thereto, and the proportion of the comparator 74 is increased in proportion to the increased value. The input voltage rises.

The operation of temperature compensation in the gate signal generator of the liquid crystal display according to the present invention configured as described above is as follows.

When the temperature around the liquid crystal panel 1 is a set reference temperature, for example, about -30 to 20 ° C or -20 to 20 ° C, the thermistor Rntc does not vary in resistance, so the thermistor Rntc and the resistor R3 are The reference voltage of 1.2 to 1.5V divided by is outputted. In this case, the reference voltage is not fixed but may be changed as necessary.

When the temperature around the liquid crystal panel 1 is set to a reference temperature, for example, about −30 to 20 ° C. or below −20 to 20 ° C. or less, the thermistor Rntc rises in resistance, so that the thermistor Rntc and the resistor R3 The reference voltage divided by this becomes 1.2 to 1.5 V or more. These reference voltages increase in inverse proportion as the temperature decreases.

In the selector 72, a reference voltage generated by the thermistor Rntc is input, and the selector 72 selects a high voltage among the input voltages and outputs the high voltage to the comparator 74.

In the comparator 74, when the reference voltage of 1.2 to 1.5V, that is, the temperature around the liquid crystal panel 1 is not low temperature, the voltage output from the second booster 33 is used as the gate voltage VGH as the gate driver 10. Will output When the reference voltage is 1.2 to 1.5 V or more, that is, when the temperature around the liquid crystal panel 1 is lower than the set temperature, the associating amplifier 74 outputs the amplified voltage as the gate voltage VGH to the gate driver 10. do. As the temperature decreases, the reference voltage input to the comparator 74 increases, thereby increasing the gate voltage VGH, thereby compensating for the level drop of the gate voltage due to the temperature decrease.

As described above, in the present invention, the voltage boosted by the booster is varied according to the temperature by the thermistor and the comparator so as to increase the gate voltage input to the gate driver when the temperature decreases, thereby effectively preventing defects caused by the temperature drop. It becomes possible.

On the other hand, in the above detailed description, the liquid crystal display device of the present invention has a specific structure, but the present invention is not limited to this structure. Modifications to variations of the invention using the basic concepts of the invention shall fall within the scope of the invention.

In other words, other examples or modifications of the present invention can be easily created by anyone in the technical field to which the liquid crystal display device using the basic concept of the present invention belongs.

30: gate signal generator 35: temperature compensation unit
Rntc: Thermistor 74: Comparator

Claims (9)

A thermistor whose resistance varies with temperature;
A resistor connected in parallel with the thermistor Rntc to divide the voltage;
A temperature compensating circuit of a liquid crystal display device comprising a comparator configured to increase an output voltage input to a gate driver of a liquid crystal panel as a feedback voltage is input to one terminal and a variable voltage is applied to the other terminal by a thermistor. The temperature compensating circuit of a liquid crystal display device according to claim 1, wherein the reference temperature of the thermistor is set to -30 to 20 占 폚 or -20 to 20 占 폚. 3. The temperature compensating circuit of a liquid crystal display device according to claim 2, wherein the reference temperature is -30 to 20 DEG C or -20 to 20 DEG C, and the voltage value input to one terminal of the comparator is 1.2 to 1.5 V. The temperature compensation circuit of claim 2, wherein a voltage value input to one terminal of the comparator is varied with respect to the reference temperature of −30 to 20 ° C. or −20 to 20 ° C. 4. The temperature compensating circuit of a liquid crystal display device according to claim 1, wherein the thermistor is a positive characteristic thermistor. The temperature compensation circuit of claim 1, further comprising a selector configured to select and output a high voltage among the variable voltages arranged at one terminal of the comparator. A liquid crystal panel in which a gate line and a data line are disposed to implement an image as a signal is input;
A gate driver and a data driver for applying a gate signal and a data signal to gate lines and data lines of the liquid crystal panel, respectively;
An interface unit to which a data signal, a power supply voltage, a vertical synchronization signal, and a data enable signal are input from the outside;
A controller which processes a data signal input through the interface unit and outputs the data signal to the gate driver and the data driver;
A DC / DC converter converting a level of a power supply voltage input through the interface unit and supplying the level to the gate driver and the data driver;
A gate signal generator connected to the controller and the DC / DC converter to generate a gate signal according to a control signal of the controller and output the gate signal to the gate driver; And
A thermistor disposed in the gate signal generator and having a variable resistance according to a temperature, a resistor connected in parallel with the thermistor (Rntc) to divide a voltage, and a feedback voltage is input at one terminal and is changed by a thermistor at the other terminal. And a compensator for increasing the output voltage input to the gate driver of the liquid crystal panel as the applied voltage is lowered. The liquid crystal display device of claim 7, wherein the DC / DC converter boosts an input voltage including a first boost. The liquid crystal display of claim 7, wherein the gate signal generator comprises a second boost for boosting the voltage input from the DC / DC converter.

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