KR20070075796A - Circuit for generating driving voltage and liquid crystal display device having the same - Google Patents

Abstract

A circuit for generating a driving voltage and an LCD(Liquid Crystal Display) device having the same are provided to prevent distortion of images by outputting a gate voltage which is inversely proportional to ambient temperature, and a source voltage irrespective of the ambient temperature. A circuit for generating a driving voltage includes a switch voltage generator(510), a temperature compensation feedback unit(520), and a regulator(540). The switch voltage generator boosts up an external voltage(VCC) in response to a feedback voltage(VFB) and outputs a switch driving voltage(VSW) corresponding to the variation of ambient temperature. The temperature compensation feedback unit receives the switch driving voltage, compensates for the temperature variation, and outputs the feedback voltage. The regulator receives the switch driving voltage, and outputs a source voltage(AVDD) for maintaining a constant level irrespective of the temperature variation.

Description

A driving voltage generation circuit and a liquid crystal display including the same {CIRCUIT FOR GENERATING DRIVING VOLTAGE AND LIQUID CRYSTAL DISPLAY DEVICE HAVING THE SAME}

1 is a block diagram of a driving voltage generator according to an exemplary embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating a specific embodiment of the driving voltage generator shown in FIG. 1.

3 is a block diagram illustrating a liquid crystal display including the driving voltage generator illustrated in FIG. 1.

Explanation of symbols on the main parts of the drawings

10: liquid crystal display device 100: liquid crystal panel

110: gate driver 200: timing controller

300: source driver 400: gate input signal generator

500: driving voltage generator 510: switching voltage generator

520: temperature compensation feedback unit 530: gate voltage generation unit

540: regulator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (LCD), and more particularly, to a driving voltage generation circuit of a liquid crystal display device.

The liquid crystal display device is a display device in which a liquid crystal is injected between two substrates (glass substrates) bonded to each other with a predetermined space. The liquid crystal display device can control the amount of light transmitted to the substrate by applying an electric field to the liquid crystal and adjusting the intensity of the electric field. In this control manner, a desired image signal is displayed.

The liquid crystal display has a problem that the original image is distorted due to a change in ambient temperature. For example, when the temperature is low compared to the room temperature, the screen of the liquid crystal display becomes relatively white, and when the temperature is high, the screen turns black. The change in image quality according to the temperature change of the liquid crystal display device is due to the difference in characteristics depending on the temperature of the thin film transistor. In the thin film transistors, the operating characteristics are deteriorated at low temperatures, and thus the filling rate of the liquid crystal is reduced, and the operating characteristics are excessively improved at high temperatures, and the filling rate of the liquid crystal is excessive. Therefore, in order to prevent a change in the image quality of the liquid crystal display due to temperature, a voltage having a property inversely proportional to temperature must be applied as the gate voltage of the thin film transistor.

The driving voltage generation circuit of the liquid crystal display generates voltages necessary for the liquid crystal display, such as a power supply voltage AVDD and a gate voltage VON, using the switching pulse voltage as a reference. The power supply voltage AVDD output from the driving voltage generation circuit is used as a reference voltage when generating a gamma level voltage corresponding to the image data. Therefore, in order for the liquid crystal display to have a constant image quality characteristic regardless of the change in the ambient temperature, the power supply voltage AVDD must be maintained at a constant level regardless of the temperature.

Therefore, the driving voltage generation circuit must output the gate voltage VON that changes in response to the change in the ambient temperature and the power supply voltage AVDD that maintains a constant level regardless of the temperature.

Accordingly, an object of the present invention is to provide a driving voltage generation circuit that generates a constant power supply voltage regardless of temperature change.

Further, another object of the present invention is to provide a liquid crystal display device having the above-described driving voltage generation circuit.

The driving voltage generation circuit according to the present invention includes a switching voltage generator, a temperature compensation feedback unit, and a regulator. The switching voltage generator boosts a voltage input from the outside in response to the feedback voltage and outputs a switching driving voltage corresponding to a change in the ambient temperature. The temperature compensation feedback unit receives the switching driving voltage to compensate for the temperature change and outputs the feedback voltage. The regulator receives the switching driving voltage and outputs a power supply voltage at which a constant level is maintained regardless of the temperature change.

The liquid crystal display according to the present invention includes a liquid crystal panel, a driving voltage generator, a gate input signal generator, and a source driver. The liquid crystal panel includes a plurality of gate lines, a plurality of data lines intersecting the gate lines, and a gate driver configured to generate a driving signal for driving the gate lines in response to a gate control signal. The driving voltage generation circuit outputs a gate voltage corresponding to the temperature change and a power supply voltage at which a constant level is maintained regardless of the temperature by using a switching driving voltage that changes according to an ambient temperature. A gate input signal generator outputs the gate control signal in response to the gate voltage, and a source driver drives the data lines in response to the power supply voltage.

(Example)

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

1 is a block diagram of a driving voltage generator according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the driving voltage generator 500 includes a switching voltage generator 510, a temperature compensation feedback unit 520, a gate voltage generator 530, and a regulator 540. The driving voltage generation unit 500 generates voltages necessary for the liquid crystal display, for example, a power supply voltage AVDD or a gate voltage VON, using the input voltage VCC from the outside.

The switching voltage generator 510 boosts the input voltage VCC by a predetermined multiple to generate a switching pulse voltage VSW swinging between voltage levels boosted at 0V. For example, when the input voltage VCC of 3.3V passes through the switching voltage generator 510 having the capability of triple boost, a switching pulse voltage VSW swinging between 0V and about 10V is generated. The switching voltage generator 510 receives the feedback voltage VFB from the temperature compensation feedback unit 520 and generates a switching pulse voltage VSW maintaining a constant level.

The temperature compensation feedback unit 520 receives the switching pulse voltage VSW from the switching voltage generator 510 and generates a feedback voltage VFB which has undergone a voltage compensation process according to a temperature change. For example, when the level of the switching pulse voltage VSW input to the temperature compensation feedback unit 520 is lowered, the level of the feedback voltage VFB output from the temperature compensation feedback unit 520 is also lowered. On the other hand, when the level of the switching pulse voltage VSW input to the temperature compensation feedback unit 520 increases, the level of the feedback voltage VFB output from the temperature compensation feedback unit 520 also increases. Accordingly, when the level of the feedback voltage VFB input to the switching voltage generator 510 is increased, the level of the output switching pulse voltage VSW is lowered, and the feedback voltage input to the switching voltage generator 510 is reduced. When the level of the VFB is lowered, the level of the output switching pulse voltage VSW is increased.

In order for the liquid crystal display to have a constant image quality characteristic regardless of the change in the ambient temperature, the temperature compensation feedback unit 520 compensates for the feedback voltage VFB to have a characteristic proportional to the temperature. For example, at high temperatures the feedback voltage is compensated to be large and at low temperatures the feedback voltage is compensated to be small. Accordingly, the feedback voltage VFB applied to the switching voltage generator 510 generates a switching pulse voltage VSW having a small amplitude at high temperature, and generates a switching pulse voltage VSW having a large amplitude at low temperature.

The gate voltage generator 530 receives the switching pulse voltage VSW lowered as the temperature increases from the switching voltage generator 510 to generate the gate voltage VON. The gate voltage generator 530 is configured of a charge pump circuit to generate the gate voltage VON by a multiple (two or three times) of the switching pulse voltage VSW. Therefore, the gate voltage VON output from the gate voltage generator 530 has a property inversely proportional to temperature.

The regulator 540 receives the switching pulse voltage VSW lowered as the temperature increases from the switching voltage generator 510, and generates a power supply voltage AVDD that maintains a constant level regardless of the change in temperature.

FIG. 2 is a circuit diagram illustrating a specific embodiment of the driving voltage generator shown in FIG. 1.

Referring to FIG. 2, the switching voltage generator 510 is configured of a DC-DC converter (not shown) or the like to boost the input voltage VCC by a predetermined multiple to generate a switching pulse voltage VSW. The switching voltage generator 510 includes an input terminal to which the input voltage VCC is applied, an output terminal to which the switching pulse voltage VSW is output, and a feedback terminal to receive the feedback voltage VFB from the temperature compensation feedback unit 520. It consists of. The level of the switching pulse voltage VSW output from the switching voltage generator 510 corresponding to the input voltage VCC is determined according to the boosting capability of the switching voltage generator 510. The switching pulse voltage VSW output from the switching voltage generator 510 may be lowered as the ambient temperature increases.

The temperature compensation feedback unit 520 includes resistors R1, R2, R3, R4, and R5 and diodes D1, D2, D3, D4, D5, and D6. The first resistor R1 and the second resistor R2 are connected in series between the output terminal of the switching voltage generator 510 and the ground voltage. The third resistor R3 and the fourth resistor R4 are connected in series between a feedback terminal of the switching voltage generator 510 and a contact between the first resistor R1 and the second resistor R2. The fifth resistor R5 is connected between the feedback terminal of the switching voltage generator 510 and the ground voltage.

The diodes D1, D2, D3, D4, D5, and D6 are divided into the first diode units D1, D2, and D3 and the second diode units D4, D5, and D6. The first diode units D1, D2, and D3 and the second diode units D4, D5, and D6 are disposed between the feedback terminal of the switching voltage generator 510 and the contacts of the first resistor R1 and the second resistor R2. Is connected to. Each diode of the first diode units D1, D2, and D3 and the second diode units D4, D5, and D6 includes a feedback terminal of the switching voltage generator 510, the first resistor R1, and the second resistor R2. It is connected in reverse between the contacts of. The third resistor R3 is connected between the feedback terminal of the switching voltage generator 510 and the contacts of the first diode units D1, D2, and D3 and the second diode units D4, D5, and D6, and the fourth resistor R4 is connected between the contacts of the first diode unit D1, D2, D3 and the second diode unit D4, D5, D6 and the contact of the first resistor R1 and the second resistor R2.

The value of the feedback voltage VFB output from the temperature compensation feedback unit 520 may be equal to the diodes D1, D2, D3, D4, and D5 at voltage values between the contacts of the first resistor R1 and the second resistor R2. , Subtracting the forward voltage (VF) by the number of D6). The forward voltage VF of the diodes D1, D2, D3, D4, D5, and D6 decreases as the temperature increases. For example, at a high temperature, the forward voltage VF of the diode is small, so that the value of the feedback voltage VFB is large, and at low temperatures, the value of the feedback voltage VFB is small because the diode's forward voltage VF is large. do.

Although the temperature compensation feedback unit 520 of FIG. 2 is composed of six diodes D1, D2, D3, D4, D5, and D6 in one embodiment, the number of diodes may be reduced. As the number of diodes constituting the temperature compensation feedback unit 520 increases, the temperature compensation feedback unit 520 generates a feedback voltage VFB sensitive to temperature change. This increases the sensitivity to the change in temperature of the switching pulse voltage (VSW).

The gate voltage generator 530 is a charge pump circuit composed of diodes D7, D8, D9, and D10 and capacitors. The diodes D7, D8, D9, and D10 are connected in a forward direction between the reference voltage VREF and the gate voltage VON. The first capacitor C1 is connected between the output terminal of the switching voltage generator 510 and the contact point of the seventh diode D7 and the eighth diode D8. The second capacitor C2 is connected between the input of the reference voltage VREF and the contact of the seventh diode D7 and the contacts of the eighth diode D8 and the ninth diode D9. The third capacitor C3 is connected between the output terminal of the switching voltage generator 510 and the contact point of the ninth diode D9 and the tenth diode D10. The fourth capacitor C4 is connected between the second capacitor C2, the tenth diode D10, and the contact point of the gate voltage VON output unit.

The gate voltage generator 530 generates the gate voltage VON pumped by a predetermined multiple of the switching pulse voltage VSW input from the switching voltage generator 510 using the reference voltage VREF as a starting voltage. In this case, since the switching pulse voltage VSW input to the gate voltage generator 530 decreases as the temperature increases, the output gate voltage VON also decreases as the temperature increases.

The regulator 540 receives the switching pulse voltage VSW from the switching voltage generator 510 and outputs a power supply voltage AVDD that maintains a constant level regardless of temperature change.

3 is a block diagram illustrating a liquid crystal display including the driving voltage generator illustrated in FIG. 1.

Referring to FIG. 3, the liquid crystal display 10 includes a liquid crystal panel 100, a timing controller 200, a source driver 300, a gate input signal generator 400, and a driving voltage generator 500. do.

The liquid crystal display device 10 of FIG. 3 has a structure (Gate IC-Less structure) excluding the use of a gate driver IC in order to reduce manufacturing costs and facilitate design. The excluded function of the gate driver IC is replaced by the gate driver 110 and the gate input signal generator 400 using an amorphous-silicon thin film transistor (a-Si thin film transistor) in the liquid crystal panel 100.

The liquid crystal panel 100 includes a substrate having a common electrode and a substrate having a pixel electrode, and a liquid crystal is injected between the substrates. In the substrate having the pixel electrode, a plurality of gate lines and a plurality of data lines intersecting the gate lines are arranged at regular intervals. The liquid crystal panel 100 includes a gate driver 110 that performs the same function as the gate driver IC.

The timing controller 200 adjusts and outputs image data signals Data to match the timings required by the source driver 300 and the gate input signal generator 400. In addition, the timing controller 200 outputs control signals for controlling the source driver 300 and the gate input signal generator 400.

The source driver 300 is composed of a plurality of source driver ICs. The source driver 300 drives the data lines of the liquid crystal panel 100 in response to the control signal input from the timing controller 200 and the power voltage AVDD output from the driving voltage generator 500.

The gate input signal generator 400 may respond to the control signal applied by the timing controller 200 and the gate voltage VON output from the driving voltage generator 500. To control the operation.

The driving voltage generator 500 uses the input voltage VCC input from the outside to decrease the gate voltage VON as the temperature increases, and the power voltage AVDD to maintain a constant level regardless of the temperature change. Outputs Since the structure and operation of the driving voltage generator 500 are the same as those of FIGS. 1 and 2, detailed descriptions thereof will be omitted.

As described above, the gate voltage VON output from the driving voltage generator 500 decreases as the temperature increases. The gate voltage VON is applied to the thin film transistor of the liquid crystal panel 100 to compensate for the difference in characteristics according to the temperature of the thin film transistor. Therefore, the change in image quality according to the temperature of the liquid crystal display 10 can be prevented.

In addition, the power voltage AVDD output from the driving voltage generator 500 maintains a constant level regardless of temperature. The constant power supply voltage AVDD is used as a reference voltage when generating the gray scale voltage, so that the liquid crystal display 10 may have a constant image quality characteristic regardless of the change in the ambient temperature.

As described above, the optimum embodiment has been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

According to the present invention as described above, the driving voltage generation unit outputs a power supply voltage that maintains a constant level regardless of the gate voltage and ambient temperature change decreases as the ambient temperature increases, so that the liquid crystal display device regardless of the temperature change The original image is not distorted and there is an effect of maintaining a constant image quality. In addition, since the power supply voltage maintains a constant level, it is possible to obtain an effect of reducing power consumption of the liquid crystal display.

Claims (9)

A switching voltage generator for boosting a voltage input from the outside in response to the feedback voltage to output a switching driving voltage corresponding to a change in the ambient temperature; A temperature compensation feedback unit configured to receive the switching driving voltage and compensate for the temperature change to output the feedback voltage; And And a regulator configured to receive the switching driving voltage and output a power supply voltage at which a predetermined level is maintained regardless of the temperature change. The method of claim 1, And the switching driving voltage decreases as the temperature increases. The method of claim 1, And a gate voltage generator configured to output the gate voltage which decreases as the temperature increases by pumping the switching driving voltage. The method of claim 1, And the temperature compensation feedback unit comprises one or more diodes connected in a reverse direction between a feedback terminal of the switching voltage generator and the regulator. A liquid crystal panel including a plurality of gate lines and a plurality of data lines intersecting the gate lines, the liquid crystal panel including a gate driver configured to generate a driving signal for driving the gate lines in response to a gate control signal; A driving voltage generation circuit for outputting a gate voltage corresponding to the temperature change and a power supply voltage at which a constant level is maintained regardless of the temperature, by using a switching driving voltage that changes according to an ambient temperature; A gate input signal generator configured to output the gate control signal in response to the gate voltage; And And a source driver configured to drive the data lines in response to the power supply voltage. The method of claim 5, The driving voltage generation circuit, A switching voltage generator for boosting a voltage input from an external device in response to a feedback voltage to output the switching driving voltage; A temperature compensation feedback unit configured to receive the switching driving voltage and compensate for the temperature change to output the feedback voltage; And And a regulator configured to receive the switching driving voltage and output the power supply voltage. The method of claim 6, And the switching driving voltage decreases as the temperature increases. The method of claim 6, The driving voltage generation circuit may further include a gate voltage generation unit configured to output the gate voltage that decreases as the temperature increases by pumping the switching driving voltage. The method of claim 6, And the temperature compensation feedback unit includes one or more diodes connected in a reverse direction between a feedback terminal of the switching voltage generator and the regulator.

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