KR20080057931A - Apparatus of generating gamma voltage - Google Patents

Abstract

A gamma voltage generating device is provided to improve display characteristics by supplying uniform gamma reference voltages to a data driver even when an analog driving voltage varies according to the variation of ambient temperature. A gamma voltage generating device includes a DC/DC converter(510), a common voltage generator(530), and a gamma voltage generator(540). The DC/DC(Direct Current) converter generates an analog driving voltage based on a source voltage from outside. The common voltage generator including plural diodes and resistors in series generates a common voltage varied according to ambient temperature based on the analog driving voltage. The gamma voltage generator including plural diodes and resistors in series, generates plural gamma reference voltages varied according to the ambient temperature based on the analog driving voltage and the common voltage.

Description

Gamma Voltage Generator {APPARATUS OF GENERATING GAMMA VOLTAGE}

1 is a block diagram illustrating a display device according to an exemplary embodiment of the present invention.

FIG. 2 is a circuit diagram illustrating the temperature compensator shown in FIG. 1.

3 is a diagram for describing an operating characteristic of the diode illustrated in FIG. 2.

4 is a circuit diagram of the common voltage generator illustrated in FIG. 1.

FIG. 5 is a circuit diagram of the gamma generator illustrated in FIG. 1.

<Description of the symbols for the main parts of the drawings>

100: display panel 200: gate driver

300: data driver 400: timing controller

510: DC-DC converter 520: temperature compensation unit

530: common voltage generator 540: gamma generator

AVDD: analog drive voltage Vcom: common voltage

VREF: Gamma Reference VFB: Feedback Voltage

GL1 to GLn: gate wires DL1 to DLm: data wires

CONT: Sync signals DATA: Raw data signals

CLC: liquid crystal capacitor TFT: thin film transistor

The present invention relates to a gamma voltage generating device, and more particularly, to a gamma voltage generating device for improving a display characteristic degradation due to changes in ambient temperature.

In general, a liquid crystal display includes a display panel in which a liquid crystal layer having an anisotropic dielectric constant is interposed between two substrates, and a driving circuit unit for driving the display panel, wherein the display panel includes a plurality of gate lines and data lines. Is formed, and an image is displayed by applying an electric field to the pixel to adjust the light transmittance.

The driving circuit unit includes a gate driver that sequentially supplies gate signals to the gate lines, a data driver that supplies image data signals to the data lines, and a DC-DC converter that generates an analog driving voltage.

Recently, a method of integrating the gate driver in the form of an integrated circuit in the display panel has been attracting attention. However, in the case of forming the gate driver in the form of an integrated circuit, there is a disadvantage in that low temperature characteristics are deteriorated. To improve this problem, a method of changing the analog driving voltage according to the ambient temperature by adding a temperature compensation circuit to the DC-DC converter has been proposed.

However, there is a problem in that display characteristics are deteriorated by changing the gamma curve of the gamma reference voltage provided to the data driver by changing the analog driving voltage according to the ambient temperature.

Accordingly, the technical problem of the present invention is to solve such a conventional problem, and an object of the present invention is to generate a uniform gamma reference voltage even when the ambient temperature changes, thereby ensuring the reliability of the gray voltage, thereby improving the display characteristics. It is to provide a voltage generator.

The gamma voltage generator according to the embodiment for realizing the object of the present invention includes a DC-DC converter, a common voltage generator, and a gamma generator. The DC-DC converter generates an analog driving voltage based on a power supply voltage from the outside. The common voltage generator includes a plurality of diodes and resistors connected in series, and generates a common voltage that varies according to the ambient temperature based on the analog driving voltage. The gamma generator includes a plurality of diodes and resistors connected in series, and generates a plurality of gamma reference voltages that vary according to the ambient temperature based on the analog driving voltage and the common voltage.

According to the gamma voltage generator, even if the potential of the analog driving voltage generated by the DC-DC converter by the temperature compensator varies according to the ambient temperature, the gamma voltage generator generates and provides a uniform gamma reference voltage, thereby improving display characteristics. have.

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

1 is a block diagram illustrating a display device according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a display device according to an exemplary embodiment of the present invention includes a display panel 100 and a driving circuit unit for driving the display panel 100.

The display panel 100 includes an array substrate, a counter substrate (also referred to as a color filter substrate) coupled to the array substrate, and a liquid crystal layer having anisotropic dielectric constant interposed between the array substrate and the counter substrate, the array substrate and the opposing substrate An electric field is artificially formed therebetween, and an image is displayed by adjusting the light transmittance of the liquid crystal layer according to the intensity of the electric field.

In detail, the plurality of gate lines GL1 to GLn extend in parallel in one direction, and the data lines DL1 to DLm extend in parallel in the direction crossing the gate lines GL1 to GLn in the array substrate. A plurality of pixel portions defined by the gate lines GL1 to GLn and the data lines DL1 to DLm are formed. Each pixel portion includes a thin film transistor TFT as a switching element, a pixel electrode as a first electrode of a liquid crystal capacitor CLC, and a storage capacitor CST. The gate electrode and the source electrode of the thin film transistor TFT are connected to the gate line GL and the data line DL, respectively, and the pixel electrode and the storage capacitor CST are formed on the drain electrode. A color filter is formed at a position corresponding to each pixel portion on the opposing substrate, and a common electrode which is a second electrode of the liquid crystal capacitor CLC is formed.

The driving circuit for driving the display panel 100 includes a gate driver 200, a data driver 300, a timing controller 400, a DC-DC converter 510, a temperature compensator 520, and a common voltage. The generator 530 and the gamma generator 540 are included. Here, a gamma voltage generator that generates a gamma reference voltage VREF is defined by the DC-DC converter 510, the temperature compensator 520, the common voltage generator 530, and the gamma generator 540. .

The timing controller 400 receives the raw data signal DATA and the synchronization signals CONT for controlling the display thereof from an image source such as an external graphic device, and the synchronization signals CONT receive the main clock signal ( MCLK), horizontal sync signal (HSYNC), vertical sync signal (VSYNC) and data enable signal (DE). The timing controller 400 generates a gate control signal CONT1 for driving the gate driver 200 and a data control signal CONT2 for driving the data driver 300 based on the synchronization signals CONT. To provide each. In addition, the raw data signal DATA is processed as a data signal DATA ′ corresponding to an operating condition of the display panel 100 and provided to the data driver 300 together with the data control signal CONT2.

The gate driver 200 outputs a gate signal formed of a combination of the gate on voltage Von and the gate off voltage Voff to the gate lines GL1 to GLn based on the gate control signal CONT1. Here, the gate control signal CONT1 includes a vertical start signal STV for indicating the start of output of the gate on signal and a gate clock signal GCLK for controlling the output timing of the gate on signal. The gate driver 200 may be formed of a plurality of gate driving chips, and may be integrated on the display panel 100 in an integrated circuit form.

The data driver 300 generates a data signal corresponding to the data signal DATA ′ based on the plurality of gamma reference voltages VREF provided from the gamma generator 540 according to the control of the provided data control signal CONT2. Is converted to the data lines DL1 to DLm. Here, the data control signal CONT2 is a horizontal start signal STH that indicates the start of input of the data signal DATA ′, a load signal TP that indicates the application of the data voltage, and an inverted signal that inverts the polarity of the data voltage. (RVS) and data clock signal DCLK. The data driver 300 usually consists of a plurality of data driver chips.

The DC-DC converter 510 generates an analog driving voltage AVDD according to the feedback voltage VFB fed back from the temperature compensator 520 based on a power supply voltage supplied from the outside, and DC-DC The analog driving voltage AVDD generated by the converter 510 is inversely proportional to the feedback voltage VFB. That is, when the potential of the feedback voltage VFB is high, the potential of the analog driving voltage AVDD is relatively low. When the potential of the feedback voltage VFB is low, the potential of the analog driving voltage AVDD is relatively low. Rises to.

The temperature compensator 520 generates a feedback voltage VFB based on the analog driving voltage AVDD generated and output from the DC-DC converter 510 and converts the generated feedback voltage VFB into DC-DC conversion. The feedback to the unit 510 is performed. Here, the feedback voltage VFB generated by the temperature compensator 520 is varied according to the ambient temperature.

The common voltage generator 530 generates a common voltage Vcom based on the analog driving voltage AVDD provided by the DC-DC converter 510, and the common voltage Vcom is variable according to the ambient temperature. The generated common voltage Vcom is provided to the common electrode of the display panel 100 (the second electrode of the liquid crystal capacitor) and is also provided to the gamma generator 540.

The gamma generator 540 receives an analog driving voltage AVDD from the DC-DC converter 510, receives a common voltage Vcom from the common voltage generator 530, and based on this, the plurality of gamma references The voltage VREF is generated and provided to the data driver 300. In this case, the potentials of the plurality of gamma reference voltages VREF generated by the gamma generator 540 may vary according to the ambient temperature.

The temperature compensator 520, the common voltage generator 530, and the gamma generator 540 will be described in more detail with reference to the accompanying drawings.

FIG. 2 is a circuit diagram illustrating the temperature compensator illustrated in FIG. 1, and FIG. 3 is a diagram for describing an operating characteristic of the diode illustrated in FIG. 2.

2 and 3, the temperature compensator 520 according to an exemplary embodiment of the present invention may include a first resistor R11 and a second resistor R12 connected in series, and first and second resistors R11, It is connected to the node between R12), and consists of a plurality of diodes (D) connected in series. An analog driving voltage AVDD output from the DC-DC converter 510 is applied to one end of the first resistor R11, and the other end of the second resistor R12 is grounded. The analog driving voltage AVDD applied to the first resistor R11 is distributed by the first and second resistors R11 and R12 and applied to one end of the diodes D connected in series, and fed back through the diodes D. It is fed back to the DC-DC converter 510 by the voltage VFB. Here, the feedback voltage VFB has a potential different from the potential divided by the first and second resistors R11 and R12 due to the predetermined forward voltage VF drop characteristic of each diode D. FIG.

The forward voltage VF drop of each diode D is inversely proportional to the ambient temperature as shown in FIG. 3. That is, as the ambient temperature increases, the forward voltage VF of the diode D decreases, and when the ambient temperature decreases, the forward voltage VF of the diode D increases. Along with forward voltage VF, forward current IF also varies with ambient temperature.

Therefore, when the ambient temperature increases, the voltage drop caused by the diodes D decreases, so that the temperature compensator 520 feeds back a relatively high potential feedback voltage VFB to the DC-DC converter 510, and When the temperature decreases, the voltage drop by the diodes D increases, so the temperature compensator 520 feeds back a feedback voltage VFB of a relatively low potential to the DC-DC converter 510.

As described above, since the DC-DC converter 510 generates the analog driving voltage AVDD in inverse proportion to the feedback voltage VFB, the analog driving voltage AVDD is inversely proportional to the ambient temperature. For example, when the ambient temperature is increased, the potential of the feedback voltage VFB is increased, so that the potential of the analog driving voltage AVDD is relatively low, and when the ambient temperature is lowered, the potential of the feedback voltage VFB is lowered, thereby reducing the analog. The potential of the driving voltage AVDD becomes relatively high.

4 is a circuit diagram of the common voltage generator illustrated in FIG. 1.

1 and 4, the common voltage generator 530 according to the embodiment of the present invention may be largely divided into a voltage divider and a compensator, and the voltage divider may include a plurality of diodes D connected in series. The first resistor R21 and the second resistor R22 are included.

One end of the diodes D connected in series is provided with an analog driving voltage AVDD from the DC-DC converter 510, and one end of the first and second resistors R21 and R22 connected in series is connected to the other end thereof. . An output terminal is provided at the node between the first and second resistors R21 and R22, and the other end of the second resistor R22 is grounded.

Accordingly, the analog driving voltage AVDD is applied to one end of the first resistor R21 via the diodes D and distributed by the resistance ratios of the first and second resistors R21 and R22. Here, as described above, since the diodes D have a forward voltage VF drop characteristic inversely proportional to the ambient temperature, the voltage applied to one end of the first resistor R21 varies according to the ambient temperature, thereby distributing the diode D. The potential of the voltage to be varied also. For example, as the ambient temperature increases, the voltage drop caused by the diodes D decreases, thereby increasing the potential of the voltage provided to one end of the first resistor R21, thereby increasing the potential of the divided voltage. On the contrary, when the ambient temperature decreases, the voltage drop caused by the diodes D increases, so that the potential of the voltage provided to one end of the first resistor R21 is lowered, thereby lowering the potential of the divided voltage.

The compensator includes an op amp AMP, and the op amp AMP buffers and compensates the voltage divided by the diodes D and the first and second resistors R21 and R22 to the common voltage Vcom. Output The op amp includes an inverting input terminal (-), a non-inverting input terminal (+), and an output terminal, and the non-inverting input terminal receives the voltage divided by the diodes D and the first and second resistors R21 and R22. The input and output signals are fed back to the inverting input terminal (-) to buffer and compensate the input voltage and output the same to the common voltage Vcom.

As described above, the common voltage generator 530 generates the common voltage Vcom that is changed in proportion to the ambient temperature based on the analog driving voltage AVDD.

FIG. 5 is a circuit diagram of the gamma generator illustrated in FIG. 1.

1 and 5, the gamma generator 540 according to an exemplary embodiment of the present invention includes a plurality of diodes D and a plurality of resistors RS1 to RS14 connected in series.

An analog driving voltage AVDD provided from the DC-DC converter 510 is applied to one end of the diodes D connected in series, and one end of the plurality of resistors RS1 to RS14 connected in series is connected to the other end thereof. . The common voltage Vcom generated by the common voltage generator 530 is applied to the center node among the nodes between the resistors RS1 to RS14. That is, the common voltage Vcom is applied to the node between the seventh resistor RS7 and the eighth resistor RS8. An output terminal is provided for each node between the plurality of resistors RS1 to RS14 except for the center node, and the other end of the plurality of resistors RS1 to RS14 connected in series is grounded.

Accordingly, the common voltage Vcom applied to the center node between the analog driving voltage AVDD applied to the first resistor RS1 and the seventh and eighth resistors RS7 and RS8 via the diodes D is the resistance of the resistors. The voltage is divided into the gamma reference voltage VREF according to the resistance ratio, and the voltage of each node according to the resistance ratio may be defined as the gamma reference voltage VREF.

Here, as described in the temperature compensator 520 and the common voltage generator 530, since the diodes D have a forward voltage VF drop characteristic that is inversely proportional to the ambient temperature, the diode D is connected to one end of the first resistor RS1. The potential of the applied voltage varies according to the ambient temperature, and thus the potential of the distributed gamma reference voltage VREF also varies. For example, as the ambient temperature increases, the voltage drop by the diodes D decreases, so that the potential of the voltage applied to the first resistor RS1 increases, so that the potential of the distributed gamma reference voltage VREF also increases. When the voltage is lowered, the voltage drop caused by the diodes D increases, so that the potential of the voltage applied to the first resistor RS1 is lowered, thereby lowering the potential range of the distributed gamma reference voltage VREF.

Meanwhile, the gamma reference voltages VREFs distributed by the resistors RS1 to RS14 are defined as gamma reference voltages VREF of positive and negative polarities with respect to the common voltage Vcom. do. Since the common voltage Vcom is applied to the center node, the first through seventh resistors RS1 ˜ between the analog driving voltage AVDD and the common voltage Vcom applied to the first resistor RS1 through the diodes D are applied. RS7) is divided into six positive (+) gamma reference voltages (VREF). Similarly, the common voltage Vcom and the ground voltage are divided into six negative (−) gamma reference voltages VREF by the eighth through fourteenth resistors RS14.

As described above, the display device according to the exemplary embodiment of the present invention generates and outputs an analog driving voltage AVDD inversely proportional to the ambient temperature from the DC-DC converter 510. However, when the common voltage generator 530 and the gamma generator 540 correct the analog driving voltage AVDD in proportion to the ambient temperature and generate the gamma reference voltage VREF by using the same, the ambient temperature changes. Even a gamma reference voltage VREF can be generated.

As described above, according to the present invention, when the analog driving voltage is changed according to the change of the ambient temperature, a uniform gamma reference voltage is generated and provided to the data driver, thereby ensuring the reliability of the gray voltage and improving display characteristics. It can be improved.

Although described above with reference to the embodiments, those skilled in the art can be variously modified and changed within the scope of the invention without departing from the spirit and scope of the invention described in the claims below. I can understand.

Claims (8)

A DC-DC converter configured to generate an analog driving voltage based on a power supply voltage from the outside; A common voltage generator including a plurality of diodes and resistors connected in series and generating a common voltage that varies according to the ambient temperature based on the analog driving voltage; And And a gamma generator including a plurality of diodes and resistors connected in series and generating a plurality of gamma reference voltages that vary according to the ambient temperature based on the analog driving voltage and the common voltage. The gamma voltage generator of claim 1, wherein the common voltage generator generates the common voltage in proportion to the ambient temperature. The gamma voltage generator of claim 2, wherein the common voltage generator further comprises an OP-AMP buffering and compensating for the common voltage generated by the diodes and the resistors. The gamma voltage generator of claim 2, wherein the gamma generator generates the plurality of gamma reference voltages proportional to the ambient temperature. The gamma voltage generator of claim 4, wherein the diodes of the common voltage generator and the gamma generator have a forward voltage drop characteristic proportional to the ambient temperature. The gamma voltage generator of claim 4, further comprising a temperature compensator configured to generate a feedback voltage that varies according to an ambient temperature based on the analog driving voltage and feed it back to the DC-DC converter. The method of claim 6, wherein the temperature compensator includes two resistors and a plurality of diodes connected in series to a node between the two resistors to generate the feedback voltage in proportion to the ambient temperature. Gamma voltage generator. The gamma voltage generator of claim 7, wherein the DC-DC converter generates the analog driving voltage in inverse proportion to the feedback voltage fed back.

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