KR102253678B1 - Power supply unit and display device including the same - Google Patents

Abstract

A power supply unit capable of generating and outputting a gate high voltage of a constant level even when the ambient temperature changes, and a display device including the same are provided. The power supply divides a reference voltage whose level varies according to the ambient temperature into a plurality of regions to generate a plurality of driving voltages corresponding to each region, and selects one of the plurality of driving voltages according to the level of the reference voltage to generate a gate high Output voltage.

Description

Power supply unit and display device including the same

The present invention relates to a power supply unit, and more particularly, to a power supply unit capable of preventing a gate-high voltage from fluctuating depending on an ambient temperature, and a display device including the same.

With the recent development of the information society, the demand for the display field is increasing in various forms, and in response to this, various flat panel displays (FPDs) having features such as thinner, lighter, and low power consumption are being studied. Such flat display devices include a liquid crystal display (LCD), a plasma display panel (PDP), and an organic light emitting diode (OLED).

Among them, a liquid crystal display is one of the most widely used flat panel displays, and is composed of two substrates on which a pixel electrode and a common electrode are formed, and a liquid crystal layer between the two substrates. In such a liquid crystal display, the alignment of liquid crystal molecules of the liquid crystal layer is determined according to an electric field generated by a voltage applied to two electrodes, and the polarization of incident light is controlled to display an image.

A liquid crystal display device includes a gate driver for supplying a gate signal to a display panel. Recently, a GIP (gate-in-panel) method in which the gate driver is built into a display panel has been widely used.

In a GIP type liquid crystal display device, since the gate driver is composed of an amorphous silicon thin film transistor (TFT), a single crystal constituting the driving integrated circuit (D-IC) type gate driver. Compared to a single crystalline silicon thin film transistor, it is sensitive to temperature, and in particular, in the case of a pixel thin film transistor, the on-current decreases with the temperature, and as a result, the pixel thin film transistor is turned on. While the data signal is not sufficiently charged in each pixel, image quality deterioration occurs.

In order to prevent the image quality from deteriorating due to the temperature, a method of compensating and supplying a gate high voltage (VGH) according to an ambient temperature has been proposed in a conventional liquid crystal display device.

1 is a diagram illustrating a power supply unit of a conventional liquid crystal display device.

Referring to FIG. 1, a conventional power supply unit 10 includes a voltage generator 20 and a low temperature compensation unit 30.

The voltage generator 20 is a part that generates a plurality of voltages used in each part of a liquid crystal display device, and FIG. 1 illustrates a voltage generator 20 that generates a gate high voltage VGH.

The voltage generator 20 includes a booster 21, a charge pump 23, and a level shifter 25. The booster 21 generates a power supply voltage VDD from an externally provided voltage. The charge pump 23 boosts the power supply voltage VDD to generate a gate high voltage VGH. The level shifter 25 switches the gate high voltage VGH according to a control signal provided from the outside and outputs it to a gate driver (not shown).

The low temperature compensation unit 30 controls the gate high voltage VGH generation operation of the charge pump 23 of the voltage generation unit 20 according to the ambient temperature. The low temperature compensating unit 30 outputs a reference voltage VC whose level is varied according to temperature to the charge pump 23, and the charge pump 23 generates a gate high voltage VGH according to the reference voltage VC. However, by setting one level of the reference voltage VC as a reference point, the gate high voltage VGH is generated.

2 is a diagram illustrating a gate high voltage output from a conventional power supply according to temperature.

1 and 2, the charge pump 23 of the voltage generator 20 sets two reference points Ref1 and Ref2 according to temperature at the reference voltage VC provided from the low temperature compensation unit 30. .

For example, in order to prevent the gate high voltage VGH from becoming greater than the maximum allowable voltage of the voltage generator 20 at a first temperature T1, that is, at a low temperature, the charge pump 23 A first reference point Ref1 for fixing the level is set. The first reference point Ref1 is set as a default. Further, the charge pump 23 sets a second reference point Ref2 for fixing the level of the gate high voltage VGH at the second temperature T2, that is, at a high temperature. In addition, the operation of the charge pump 23 is controlled to generate the gate high voltage VGH according to the reference voltage VC at a temperature between the first temperature T1 and the second temperature T2, that is, at room temperature.

As described above, in the conventional power supply unit 10, since only one reference point, that is, the second reference point Ref2, is set in addition to the first reference point Ref1, the power supply unit 10 at the actual operating region temperature, that is, room temperature. The level of the output gate high voltage VGH continuously changes according to a change in ambient temperature.

In this way, since the level of the gate high voltage VGH changes according to the ambient temperature change at room temperature, the operation of the gate driver generating the gate signal by receiving the gate high voltage VGH becomes unstable. Such an unstable operation of the gate driver causes deterioration in image quality of the display device.

An object of the present invention is to provide a power supply unit capable of generating and outputting a gate high voltage of a constant level even when the ambient temperature changes, and a display device including the same.

A power supply unit according to an embodiment of the present invention for achieving the above object includes a low temperature compensation unit and a voltage generation unit.

The low temperature compensation unit outputs a reference voltage whose level is varied according to the ambient temperature.

The voltage generator divides a plurality of regions from a reference voltage, generates a plurality of driving voltages corresponding to each region, and outputs a gate high voltage by selecting one of a plurality of driving voltages according to the level of the reference voltage.

A display device according to an embodiment of the present invention for achieving the above object includes a timing control unit, a gate driving unit, and a power supply unit.

The timing control unit generates and outputs a gate control signal and a power control signal.

The gate driver is formed in the display panel and outputs a gate signal to the display panel according to the gate control signal.

The power supply unit outputs a gate high voltage to the gate driver according to the power control signal.

The power supply unit according to the present invention can generate and output a gate high voltage of a constant level even when the ambient temperature changes, thereby improving the operation stability of the gate driver.

Accordingly, in the display device of the present invention, it is possible to prevent image quality from deteriorating due to insufficient charging and overcharging of the thin film transistor of the pixel.

1 is a diagram illustrating a power supply unit of a conventional liquid crystal display device.
2 is a diagram illustrating a gate high voltage output from a conventional power supply according to temperature.
3 is a diagram illustrating a liquid crystal display device according to an exemplary embodiment of the present invention.
FIG. 4 is a diagram illustrating a configuration of a power supply unit shown in FIG. 3.
5 is a diagram showing a specific configuration of the selection circuit shown in FIG. 4.
6 is a diagram illustrating a gate high voltage output by a power supply according to the present invention according to temperature.

Hereinafter, a power supply unit and a display device including the same according to the present invention will be described in detail with reference to the accompanying drawings.

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

Referring to FIG. 3, the liquid crystal display 100 according to the present embodiment may include a display panel 110, a data driver 130, a timing control unit 140, and a power supply unit 150. The display panel 110 may include a display unit 115 and a gate driver 120.

The display unit 115 of the display panel 110 may display an image according to signals provided from the gate driving unit 120 and the data driving unit 130, for example, a gate signal and a data signal.

To this end, the display unit 115 may include a plurality of gate lines GL and a plurality of data lines DL crossing each other to define a plurality of pixel regions. In each of the plurality of pixel regions, a pixel P including a thin film transistor T connected to the gate line GL and the data line DL, a liquid crystal capacitor Clc, and a storage capacitor Cst may be formed.

The gate driver 120 of the display panel 110 may be composed of a circuit including a plurality of switching elements, for example, a plurality of thin film transistors (not shown), and according to the gate control signal provided through the data driver 130 A gate signal can be generated. The gate signals may be sequentially output to a plurality of gate lines GL of the display unit 115.

The display panel 110 may include an array substrate (not shown) and a color filter substrate (not shown) bonded to each other with a liquid crystal layer (not shown) therebetween. In addition, a plurality of gate lines GL, a plurality of data lines DL, and a pixel P of the display unit 115 described above, and a plurality of switching devices of the gate driver 120 may be formed on the array substrate.

In this way, the liquid crystal display 100 in which the gate driver 120 is built into the display panel 110 is referred to as a gate in panel (GIP) type liquid crystal display.

The data driver 130 may generate a data signal from image data and data control signals provided from the timing control unit 140. The data signal may be output to a plurality of data lines DL of the display panel 110. The data driver 130 may be composed of a plurality of driving integrated circuits (DICs), and the plurality of driving integrated circuits may be mounted on an array substrate in a Chip On Glass (COG) method.

The timing control unit 140 includes image data, gate control signals, and control signals, such as a data enable signal, a vertical synchronization signal, a horizontal synchronization signal, and a clock signal, input from an external system (not shown). Data control signals can be generated. The gate control signal may be output to the gate driver 120 of the display panel 110 through the data driver 130. Image data and data control signals may be output to the data driver 130. In addition, the timing control unit 140 may generate and output a power control signal capable of controlling the operation of the power supply unit 150.

The power supply unit 150 may generate and output a plurality of voltages for driving the display panel 110, such as a gate high voltage, a gate low voltage, a gamma voltage, a driving voltage, and the like according to the power control signal. have. A plurality of voltages may be supplied to the data driver 130, the display panel 110 and the gate driver 120.

In addition, the power supply unit 150 compensates for a change in the gate high voltage according to the ambient temperature and outputs it to the gate driver 120 so that the gate driver 120 can operate stably.

FIG. 4 is a diagram illustrating a configuration of a power supply unit shown in FIG. 3.

3 and 4, the power supply unit 150 may include a voltage generator 151 and a low temperature compensation unit 155. In FIG. 4, only a part of the power supply unit 150, that is, a part that generates the gate high voltage VGH, is illustrated.

The voltage generator 151 may include a booster 161, a charge pump 163, a selection circuit 165, and a level shifter 167.

The booster 161 may generate and output the power voltage VDD from an external voltage.

The charge pump 163 may boost the power voltage VDD to generate and output a plurality of driving voltages VH. Here, the charge pump 163 may output a plurality of driving voltages VH according to the reference voltage VC output from the low temperature compensation unit 155.

The selection circuit 165 may select one of a plurality of driving voltages VH output from the charge pump 163 and output it as a gate high voltage VGH. The selection circuit 165 defines a plurality of regions for the reference voltage VC, and selects one of the plurality of driving voltages VH when the level of the reference voltage VC corresponds to one of the plurality of regions. Thus, it can be output as a gate high voltage (VGH).

Meanwhile, each of the plurality of driving voltages VH generated by the charge pump 163 may be generated and output as a representative voltage corresponding to each of the plurality of regions from the reference voltage VC.

The level shifter 167 may switch the gate high voltage VGH output from the selection circuit 165 according to the power control signal provided from the timing control unit 140 and output it to the gate driver 120.

The low temperature compensating unit 155 generates a reference voltage VC that varies according to the ambient temperature of the liquid crystal display 100, and uses the generated reference voltage VC to the charge pump 163 of the voltage generation unit 151 and It can be output to the selection circuit 165. The reference voltage VC output from the low temperature compensation unit 155 may be a voltage whose level increases as the ambient temperature decreases. The low temperature compensation unit 155 may be configured as an element such as a thermistor, or the like, in which a resistance value is changed according to a temperature and a level of an output voltage is changed.

5 is a diagram showing a specific configuration of the selection circuit shown in FIG. 4.

4 and 5, the selection circuit 165 may include a region division module 171, a switching signal generation module 173, and a switch module 175.

The region dividing module 171 may divide the reference voltage VC into a plurality of regions. For example, the region dividing module 171 may divide the reference voltage VC into a plurality of regions R1 to R4 according to the voltage range or temperature range of the reference voltage VC.

For example, the region dividing module 171 may define a voltage range of the reference voltage VC, that is, three different levels between the lowest voltage level and the highest voltage level as reference points, respectively. In addition, the reference voltage VC may be divided into four regions R1 to R4 between the lowest voltage level and the highest voltage level according to the voltage level of each reference point.

In addition, the region division module 171 may define a temperature range of the reference voltage VC, that is, three different temperatures between the lowest temperature and the highest temperature as reference points, respectively. In addition, the reference voltage VC may be divided into four regions R1 to R4 between the lowest temperature and the highest temperature according to the voltage level corresponding to each reference point.

Here, the region dividing module 171 divides a plurality of regions R1 to R4 at equal intervals, or divides a plurality of regions R1 to R4 at different intervals in consideration of the operating environment of the liquid crystal display 100. Can be divided.

In the present embodiment, it has been described as an example that the region dividing module 171 divides the reference voltage VC into four regions R1 to R4, but the present invention is not limited thereto. For example, the region dividing module 171 may divide the reference voltage VC into one or more regions according to the operating environment of the liquid crystal display 100.

The switching signal generation module 173 may generate a plurality of switching signals Φ1 to Φ4 respectively corresponding to the plurality of regions R1 to R4 generated by the region dividing module 171. And, it is possible to output the corresponding switching signals (Φ1 ~ Φ4) according to the level of the input reference voltage (VC).

For example, the switching signal generation module 173 includes a first switching signal Φ1 corresponding to the first region R1 of the region dividing module 171 and a second switching signal Φ2 corresponding to the second region R2. , A third switching signal Φ3 corresponding to the third region R3 and a fourth switching signal Φ4 corresponding to the fourth region R4 may be generated.

In addition, the switching signal generation module 173 outputs the first switching signal Φ1 when the reference voltage VC is input at a level corresponding to the first region R1, and corresponds to the second region R2. When the input level is inputted, the second switching signal Φ2 may be output. In addition, when the reference voltage VC is input at a level corresponding to the third region R3, the third switching signal Φ3 is output, and when the reference voltage VC is input at a level corresponding to the fourth region R4, the 4 A switching signal (Φ4) can be output. Here, the first switching signal Φ1 to the fourth switching signal Φ4 may be output at different times and may not overlap.

The switch module 175 may include a plurality of switches SW1 to SW4 connected to correspond to each of the plurality of driving voltages VH output from the charge pump 163. The switch module 175 is connected to the first switch SW1 connected to the first driving voltage VH1, the second switch SW2 connected to the second driving voltage VH2, and the third driving voltage VH3. A third switch SW3 and a fourth switch SW4 connected to the fourth driving voltage VH4 may be included.

The first switch (SW1) to the fourth switch (SW4) of the switch module 175 corresponds to the corresponding switching signal (Φ1 to Φ4) among the plurality of switching signals (Φ1 to Φ4) output from the switching signal generation module 173. It can be turned on accordingly.

For example, the first switch SW1 is turned on according to the first switching signal Φ1, the second switch SW2 is turned on according to the second switching signal Φ2, and the third switch SW3 Is turned on according to the third switching signal Φ3, and the fourth switch SW4 may be turned on according to the fourth switching signal Φ4.

Here, since the first switching signal Φ1 to the fourth switching signal Φ4 output from the switching signal generation module 173 do not overlap, the first switch SW1 to the fourth switch SW4 of the switch module 175 ) May also be redundant and may not be turned on.

When the first switch SW1 of the switch module 175 is turned on by the first switching signal Φ1 output from the switching signal generation module 173, the first driving voltage VH1 becomes the gate high voltage VGH. ) Can be output.

Here, the first driving voltage VH1 may be a voltage generated to correspond to the first region R1 among the four regions R1 to R4 divided from the reference voltage VC. The charge pump 163 may generate the first driving voltage VH1 by selecting one representative level, for example, the maximum level among the plurality of reference voltage VC levels in the first region R1. In addition, the charge pump 163 may generate the first driving voltage VH1 according to the average value of the levels of the plurality of reference voltages VC in the first region R1.

When the second switch SW2 of the switch module 175 is turned on by the second switching signal Φ2 output from the switching signal generation module 173, the second driving voltage VH2 becomes the gate high voltage VGH. ) Can be output. Likewise, the second driving voltage VH2 may be a voltage generated by the charge pump 163 to correspond to the second region R2 of the reference voltage VC.

In addition, the third switch SW3 of the switch module 175 is turned on by the third switching signal Φ3 output from the switching signal generation module 173, so that the third driving voltage VH3 becomes the gate high voltage ( VGH), the fourth switch SW4 is turned on by the fourth switching signal Φ4, and the fourth driving voltage VH4 may be output as the gate high voltage VGH. Similarly, the third driving voltage VH3 is a voltage generated to correspond to the third region R3 of the reference voltage VC, and the fourth driving voltage VH4 is the fourth region R4 of the reference voltage VC. It may be a voltage generated to correspond to.

As described above, in the voltage generator 151 of this embodiment, the reference voltage VC is divided into a plurality of regions R1 to R4, and a driving voltage corresponding to each region is selected to be output as the gate high voltage VGH. I can.

Accordingly, even if the ambient temperature of the liquid crystal display device 100 changes, a gate high voltage VGH having a predetermined size may be output from the voltage generator 151, thereby improving the operation stability of the gate driver 120. Accordingly, it is possible to prevent the occurrence of deterioration in image quality due to insufficient charging of pixels due to an unstable operation of the gate driver 120 in the liquid crystal display device 100.

6 is a diagram illustrating a gate high voltage output by a power supply according to the present invention according to temperature.

As shown in FIG. 6, the selection circuit 165 of the voltage generator 151 may divide the reference voltage VC into four regions R1 to R4 according to the voltage range.

Here, the first region R1 is a region between the highest level of the reference voltage VC and the first level VC1, and the second region R2 is a region between the first level VC1 and the first level of the reference voltage VC. It may be an area between two levels VC2. Further, the third region R3 is a region between the second level VC2 and the third level VC3 of the reference voltage VC, and the fourth region R4 is the third level ( It may be a region between VC3) and the lowest level.

In addition, the selection circuit 165 selects one of the plurality of driving voltages VH generated by the charge pump 163 corresponding to each of the regions R1 to R4 and outputs the gate high voltage VGH to each region. The gate high voltage VGH of a certain level can be output from (R1 to R4).

In other words, when the level of the reference voltage VC corresponds to the first region R1, the selection circuit 165 turns on the first switch SW1 to apply the first driving voltage VH1 to the gate high voltage ( VGH) can be output.

In addition, when the level of the reference voltage VC corresponds to the second region R2, the selection circuit 165 turns on the second switch SW2 to reduce the second driving voltage VH2 to the gate high voltage VGH. ) Can be printed.

In addition, when the level of the reference voltage VC corresponds to the third region R3, the third switch SW3 is turned on to output the third driving voltage VH3 as the gate high voltage VGH, and When corresponding to the fourth region R4, the fourth switch SW4 is turned on to output the fourth driving voltage VH4 as the gate high voltage VGH.

As described above, the power supply unit 150 of the present invention can output a gate high voltage (VGH) of a certain level even when the ambient temperature of the liquid crystal display device 100 changes, so that the operation stability of the gate driver 120 can be improved. have. Accordingly, it is possible to prevent occurrence of defects such as deterioration in image quality in the liquid crystal display device 100.

Although many items are specifically described in the above description, this should be construed as an example of a preferred embodiment rather than limiting the scope of the invention. Therefore, the invention should not be determined by the described embodiments, but should be determined by the claims and equivalents to the claims.

100: liquid crystal display 110: display panel
120: gate driving unit 130: data driving unit
140: timing control unit 150: power supply unit
151: voltage generation unit 155: low temperature compensation unit
163: charge pump 165: selection circuit
171: area division module 173: switching signal generation module
175: switch module

Claims (11)

A low temperature compensation unit outputting a reference voltage whose level is varied according to the ambient temperature; And
A voltage generator configured to generate a plurality of driving voltages corresponding to each of the plurality of regions divided from the reference voltage, select one of the plurality of driving voltages according to the level of the reference voltage, and output a gate high voltage,
The voltage generator,
A charge pump generating the plurality of driving voltages corresponding to each of the plurality of regions; And
A selection circuit for dividing the reference voltage into the plurality of regions and selecting one of the plurality of driving voltages and outputting the gate high voltage when the level of the reference voltage corresponds to one of the plurality of regions,
The selection circuit,
A region dividing module for dividing the reference voltage into the plurality of regions;
A switching signal generation module outputting a plurality of switching signals corresponding to the plurality of regions; And
One side is connected to each of the plurality of driving voltages, including a switch module provided with a plurality of switches for selectively switching operation according to the plurality of switching signals to output one of the plurality of driving voltages as the gate high voltage Power supply.
delete delete The method of claim 1
Wherein the region dividing module divides the reference voltage into the plurality of regions according to a voltage range of the reference voltage. The method of claim 1
Wherein the region dividing module divides the reference voltage into the plurality of regions according to a temperature range of the reference voltage. The method of claim 1
Wherein the region dividing module divides the reference voltage into the plurality of regions having the same width. The method of claim 1
Wherein the region dividing module divides the reference voltage into the plurality of regions having different widths. The method of claim 1
Wherein the switching signal generation module outputs each of the plurality of switching signals at different times. The method of claim 1
Wherein the charge pump generates the plurality of driving voltages from a maximum level among the levels of the reference voltages corresponding to each of the plurality of regions. The method of claim 1
Wherein the charge pump generates the plurality of driving voltages according to an average level of the reference voltage corresponding to each of the plurality of regions. A timing control unit generating and outputting a gate control signal and a power control signal;
A gate driver formed in the display panel and outputting a gate signal to the display panel according to the gate control signal; And
And a power supply for outputting a gate high voltage to the gate driver according to the power control signal,
The power supply unit,
A low temperature compensation unit outputting a reference voltage whose level is varied according to the ambient temperature; And
A voltage generator configured to generate a plurality of driving voltages corresponding to each of the plurality of regions divided from the reference voltage, select one of the plurality of driving voltages according to the level of the reference voltage, and output a gate high voltage,
The voltage generator,
A charge pump generating the plurality of driving voltages corresponding to each of the plurality of regions; And
A selection circuit for dividing the reference voltage into the plurality of regions and selecting one of the plurality of driving voltages and outputting the gate high voltage when the level of the reference voltage corresponds to one of the plurality of regions,
The selection circuit,
A region dividing module for dividing the reference voltage into the plurality of regions;
A switching signal generation module outputting a plurality of switching signals corresponding to the plurality of regions; And
One side is connected to each of the plurality of driving voltages, including a switch module provided with a plurality of switches for selectively switching operation according to the plurality of switching signals to output one of the plurality of driving voltages as the gate high voltage Display device.

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