JP2006323138A - Liquid crystal display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display apparatus which has a simple circuit and in which a source driver or a gate driver will not perform misoperations. <P>SOLUTION: The liquid crystal display apparatus is provided with a liquid crystal panel 11, having a plurality of column electrodes 18 and a plurality of row electrodes 17, a gate driver 16 for driving each column electrode 18, a source driver 15 for driving each row electrode 17, an integrated circuit 12 for control which outputs various kinds of signals to the source driver 15 and the gate driver 16, a gamma correction circuit 14 for supplying gamma correction voltage to the source driver 15 and a circuit 13 for power source supply. The circuit 13 for power source supply has a 1st power source section 20 for outputting a drive voltage to the integrated circuit 12 for control, the gate driver 16 and the source driver 15, a 1st switch 25 receiving a control signal from the integrated circuit 12 for control and a 2nd power source section 24 for outputting 2nd reference voltage to the gamma correction circuit 14 via the 1st switch 25. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device.

  Conventionally, this kind of apparatus is shown by patent document 1, for example. A block diagram of the liquid crystal display device disclosed in Patent Document 1 is shown in FIG. In FIG. 8, the liquid crystal display device 50 includes a liquid crystal panel 51 and a drive circuit unit 52.

The drive circuit unit 52 includes a gate driver 60, a source driver 65, a gamma correction voltage generation circuit 61, a gradation voltage generation circuit 62, a common voltage generation circuit 64, and a control IC 66. Although not shown, power supply circuits for supplying appropriate voltages to the components 51, 60, 65, 61, 62, 64, 66 and the like are provided.
JP 2003-295842 A

  In the above apparatus, since the gamma correction voltage generation circuit 61 and the common voltage generation circuit 64 are provided separately, there is a first drawback that the circuit becomes complicated, increases in size, and increases in cost. Moreover, in the said apparatus, the supply order of the voltage supplied to each components 51, 60, 65, 61, 62, 64, 66 is not defined. Therefore, for example, a gamma correction voltage may be supplied to the source driver 65 first and then a drive voltage may be supplied. As a result, the source driver 65 has a second drawback that malfunctions or breaks down.

  Accordingly, the present invention provides a liquid crystal display device in which a circuit is simple and a source driver and a gate driver do not malfunction in consideration of such conventional drawbacks.

  In order to solve the above problems, in the present invention of claim 1, a liquid crystal panel having a plurality of row electrodes and a plurality of column electrodes, a gate driver for driving each row electrode, a source driver for driving each column electrode, A control integrated circuit that outputs various signals to the gate driver and the source driver; a gamma correction circuit that supplies a gamma correction voltage to the source driver; and a power supply circuit. A first power supply unit that outputs a driving voltage to the control integrated circuit, the gate driver, and the source driver, a first switch that receives a control signal from the control integrated circuit, and the first switch A second power supply unit configured to output a second reference voltage to the gamma correction circuit;

  In the present invention of claim 2, first, the first switch is opened by the control signal, the first power supply unit outputs the driving voltage, and then the first switch is changed by the change of the control signal. Is closed, and the second power supply unit outputs the second reference voltage.

  According to a third aspect of the present invention, a first conversion unit for converting the output of the first power supply unit is provided, and the first conversion unit outputs a first reference voltage to the gamma correction circuit.

  According to a fourth aspect of the present invention, there is provided a second conversion unit for converting the output of the first power supply unit, and the second conversion unit includes a first charge pump and a first stabilization circuit, and is low with respect to the gate driver. Output voltage.

  According to a fifth aspect of the present invention, there is provided a third conversion unit for converting an output through the first switch, and the third conversion unit outputs a column voltage to the source driver.

  In a sixth aspect of the present invention, a fourth conversion unit for converting the output of the second power supply unit is provided, and the fourth conversion unit includes a second charge pump and a second stabilization circuit. A second switch connected to the output side and receiving a control signal from the control integrated circuit is provided.

  In the present invention of claim 7, first, the second switch is opened by the control signal, the first power supply unit outputs the driving voltage and the low voltage, and thereafter, by the change of the control signal. The second switch is closed, the second power supply unit outputs a high voltage to the gate driver, and both the low voltage and the high voltage are output.

  According to the present invention of claim 8, the gamma correction circuit is configured to supply a gamma correction voltage to the source driver and a common voltage to the liquid crystal panel.

  According to the configuration of the first aspect, the power supply system that outputs the driving voltage and the power supply system that outputs the second reference voltage can be made independent. As a result, the supply order of the driving voltage and the second reference voltage can be set.

  According to the configuration of the second aspect, the driving voltage is first supplied to the source driver, and then the first reference voltage is supplied, and the gamma correction voltage can be supplied to the source driver via the gamma correction circuit. As a result, malfunction and damage of the source driver can be prevented.

  According to the configuration of the third aspect, first, the first reference voltage can be supplied to the gamma correction circuit, and the gamma correction circuit is ready to output the gamma correction voltage.

  According to the configuration of the fourth aspect, the second conversion unit that supplies a low voltage to the gate driver includes the first charge pump and the first stabilization circuit. As a result, the second conversion unit itself can efficiently output a desired voltage with low power consumption.

  According to the fifth aspect of the present invention, the driving voltage is first supplied to the source driver, and then the first switch is closed to supply the column voltage to the source driver. As a result, malfunction and damage of the source driver can be prevented.

  According to the configuration of the sixth aspect, the fourth conversion unit that supplies the voltage to the second switch includes the second charge pump and the second stabilization circuit. As a result, the fourth conversion unit itself can efficiently output a desired voltage with low power consumption.

  According to the configuration of the seventh aspect, the driving voltage and the low voltage can be supplied to the gate driver first, and then the high voltage and the low voltage can be supplied to the gate driver. As a result, malfunction and damage of the gate driver can be prevented.

  According to the configuration of the eighth aspect, the gamma correction circuit can supply a gamma correction voltage and a common voltage to the liquid crystal panel. As a result, the conventional two circuits need only be one circuit, the circuit is simplified, the size can be reduced, and the cost is reduced.

  Hereinafter, the best mode for carrying out the present invention will be described in detail with reference to examples and drawings. The following embodiments exemplify an example of a liquid crystal display device for embodying the technical idea of the present invention. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims.

  Hereinafter, the liquid crystal display device 10 according to the present embodiment will be described with reference to FIGS. 1 to 3. FIG. 1 is a block diagram of the liquid crystal display device 10. FIG. 2 is a block diagram of the power supply circuit 13 used in the liquid crystal display device 10. FIG. 3 is a block diagram of the gamma correction circuit 14 used in the liquid crystal display device 10.

  In FIG. 1, a liquid crystal display device 10 includes a liquid crystal panel 11, a control integrated circuit 12, a power supply circuit 13, a gamma correction circuit 14, a plurality of source drivers 15, a plurality of gate drivers 16, and the like. It is composed of

  The liquid crystal panel 11 has, for example, a plurality of row electrodes 18 provided on the lower glass substrate, a plurality of column electrodes 17, TFTs provided in the vicinity of intersections thereof, pixel electrodes connected to the TFTs, and the like. . The liquid crystal panel 11 includes a common electrode provided on the upper glass substrate, a lower glass substrate, a liquid crystal (both not shown) provided between the upper glass substrate and the like.

  The control integrated circuit 12 receives a data enable signal DE sent from a computer, a television device, a video playback device, a DVD playback device (both not shown), etc. via an input interface (not shown). The

  The control integrated circuit 12 receives, for example, RGB 8-bit digital image data IRD, IGD, and IBD sent from the above device or the like. The control integrated circuit 12 receives the clock signal DOTCL, the vertical synchronization signal VSYN, and the horizontal synchronization signal HSYN.

  The control integrated circuit 12 processes the input signal and outputs image data ORD, OGD, OBD, polarity inversion signal POL, strobe signal STRB, start pulse signal SP, and the like to the source driver 15.

  Further, the control integrated circuit 12 supplies the clock pulse signal CPV to the power supply circuit 13 and the gate driver 16. The control integrated circuit 12 supplies the frame signal FLM to the gate driver 16.

  Further, the control integrated circuit 12 outputs a control signal CTRL indicating the power supply sequence to each component to the power supply circuit 13. In this way, the control integrated circuit 12 outputs various signals to the power supply circuit 13, the gate driver 16, and the source driver 15.

  The power supply circuit 13 outputs an appropriate DC voltage to each component based on the input DC voltage VIN (for example, 12 volts). Specifically, the power supply circuit 13 outputs a first reference voltage VCOM1 (for example, -1.0 volts) and a second reference voltage VCOM2 (for example, 5.5 volts) to the gamma correction circuit 14. To do.

  The power supply circuit 13 outputs a drive voltage VDD1 (for example, 3.3 volts) to the control integrated circuit 12, the source driver 15, and the gate driver 16, respectively.

  The power supply circuit 13 outputs a column voltage VGEN (for example, 5 volts) to be applied to the column electrode 17 of the liquid crystal panel 11 via the source driver 15.

  The power supply circuit 13 outputs a high voltage VGH (for example, 12 volts) and a low voltage VGL (for example, −15 volts) to be applied to the row electrodes 18 of the liquid crystal panel 11 via the gate driver 16.

  The power supply circuit 13 outputs another drive voltage VDD2 (for example, −11.7 volts) to the gate driver 16.

  The gamma correction circuit 14 outputs gamma correction voltages VGM <b> 1 to VGM <b> 10 to each source driver 15 by resistance-dividing the first reference voltage VCOM <b> 1 and the second reference voltage VCOM <b> 2 supplied from the power supply circuit 13.

  The source driver 15 uses the gamma correction voltages VGM1 to VGM10 as reference voltages for the built-in D / A converter. As a result, the source driver 15 analog-converts the input image data ORD, OGD, OBD, and outputs the analog-converted voltage to each column electrode 17.

  A specific example of the power supply circuit 13 will be described with reference to FIG. In FIG. 2, the power supply circuit 13 includes a power supply voltage detection circuit 19, a first power supply unit 20, a first conversion unit 21, a second conversion unit 22, a Zener diode 23, and a second power supply unit 24. The first switch 25, the third conversion unit 26, the fourth conversion unit 27, the second switch 28, and the like.

  The power supply voltage detection circuit 19 includes, for example, a reset IC and two transistors. When the input voltage VIN exceeds a predetermined value (for example, DC 12 volts), the internal circuit is made conductive and a voltage is output. When the input voltage VIN becomes less than a predetermined value, the voltage output is stopped.

  The first power supply unit 20 is composed of, for example, a voltage step-down switching regulator. The first power supply unit 20 outputs a drive voltage VDD1 obtained by dropping the voltage VIN input via the power supply voltage detection circuit 19 to 3.3 volts.

  As described above, the power supply circuit 13 includes the first power supply unit 20 that outputs the drive voltage VDD1 to the control integrated circuit 12, the gate driver 16, and the source driver 15.

  The first conversion unit 21 includes, for example, a polarity inversion unit 29 and a series regulator 30. The polarity inversion unit 29 inverts the output (for example, 3.3 volts) of the first power supply unit 20 to −3.3 volts. The series regulator 30 boosts this inverted voltage and outputs the first reference voltage VCOM1 (−1.0 volts).

  That is, a first conversion unit 21 that converts the output of the first power supply unit 20 is provided. The first converter 21 outputs the first reference voltage VCOM1 to the gamma correction circuit 14.

  The second conversion unit 22 includes a first charge pump and a first stabilization circuit. The second conversion unit 22 receives a switching pulse from the first power supply unit 20 and outputs a low voltage VGL (−15 volts).

  That is, the second conversion unit 22 that converts the output of the first power supply unit 20 outputs the low voltage VGL to the gate driver 16.

  The Zener diode 23 receives the low voltage VGL of the second conversion unit 22 and outputs another drive voltage VDD2 (−11.7 volts) to the gate driver 16.

  The second power supply unit 24 is composed of, for example, a voltage step-down switching regulator. The second power supply unit 24 drops the voltage VIN input through the power supply voltage detection circuit 19 to 5.5 volts and outputs it.

  The first switch 25 is made of, for example, a transistor, and its control terminal receives a control signal CTRL from the control integrated circuit 12.

  When the control signal CTRL is a Hi signal, the first switch 25 is closed and the second power supply unit 24 outputs a second reference voltage VCOM2 (for example, 5.5 volts).

  When the control signal CTRL is a Lo signal, the first switch 25 is opened and the first switch 25 is turned off.

  That is, a first switch 25 that receives the control signal CTRL from the control integrated circuit 12 is provided. A second power supply unit 24 that outputs a second reference voltage VCOM2 to the gamma correction circuit 14 via the first switch 25 is provided.

  First, since the control signal CTRL from the control integrated circuit 12 is a Lo signal, the first switch 25 is opened, and the first power supply unit 20 outputs the drive voltage VDD1 to the components 12, 15, and 16. To do.

  Then, the control integrated circuit 12 outputs a Hi signal as the control signal CTRL when a predetermined time has elapsed from the above operation. Thus, the first switch 25 is closed by the change of the control signal CTRL (changed to the Hi signal). As a result, the second power supply unit 24 outputs the second reference voltage VCOM2 to the gamma correction circuit 14.

  The third conversion unit 26 includes, for example, a series regulator or the like, and receives the second reference voltage VCOM2 via the first switch 25.

  That is, a third conversion unit 26 is provided for converting the output VCOM2 (5.5 volts) via the first switch 25 into the column voltage VGEN (5 volts). The third converter 26 outputs the column voltage VGEN to the source driver 15.

  A fourth conversion unit 27 that converts the output of the second power supply unit 24 is provided. The fourth conversion unit 27 includes a second charge pump and a second stabilization circuit.

  A second switch 28 that is connected to the output side of the fourth conversion unit 27 and receives the control signal CTRL from the control integrated circuit 12 is provided.

  First, the second switch 28 is opened by the control signal CTRL (Lo signal) from the control integrated circuit 12. At this time, the first power supply unit 20 outputs the drive voltage VDD1 to each of the components 12, 15, and 16. In addition, the first power supply unit 20 outputs a low voltage VGL to the gate driver 16.

  Then, the control integrated circuit 12 outputs a Hi signal as the control signal CTRL when a predetermined time has elapsed from the above operation. Thus, the second switch 28 is closed by the change of the control signal CTRL. As a result, the second power supply unit 24 outputs a high voltage VGH (for example, 12 volts) to the gate driver 16.

  In this way, both the low voltage VGL and the high voltage VGH are output to the gate driver 16. The power supply circuit 13 is configured by the above components.

  Next, the gamma correction circuit 14 will be described with reference to FIG. In FIG. 3, the gamma correction circuit 14 includes voltage dividing circuits 31 to 41, operational amplifiers 42 to 53, RC circuits 54 to 66, and the like.

  The voltage dividing circuits 31 to 41 are provided between the second reference voltage VCOM2 and the ground voltage. The + terminals of the operational amplifiers 43 to 52 are connected to the voltage dividing points of the voltage dividing circuits 31 to 41.

  The output sides of the operational amplifiers 43 to 52 output gamma correction voltages VGM1 to VGM10. In this manner, the gamma correction circuit 14 supplies the source driver 15 with the gamma correction voltages VGM1 to VGM10.

  The + terminal of the operational amplifier 53 is connected to the first reference voltage VCOM1 via a lead wire. The negative terminal of the operational amplifier 53 is connected to the output side via the RC circuit 66. The output side is connected to the RC circuit 65.

  The operational voltage 53, the lead wires, the RC circuits 66 and 65, and the like constitute a common voltage generation circuit 67. The operational amplifiers 42 to 53 are built in one IC 68. The common voltage generation circuit 67 outputs a common voltage VCOM.

  That is, the gamma correction circuit 14 is configured to supply the gamma correction voltages VGM1 to VGM10 to the source driver 15 and to supply the common voltage VCOM to the liquid crystal panel 11. The liquid crystal display device 10 is constituted by the above components.

Next, gamma correction will be described. In a cathode ray tube (CRT, etc.), the relationship between the drive voltage V and the light emitting luminance Y is not a proportional relationship is expressed by the relational expression Y = KV ^gamma. This constant γ is called gamma, and in the Japanese television system, this characteristic is considered in advance and γ = 2.2 is corrected on the transmission side in advance.

  The gamma correction added to the original signal on the transmission side changes not only the brightness of the image but also the ratio of red, green and blue. However, when the receiving side displays the γ-corrected signal on a CRT, the relationship between the drive voltage V and the light emission luminance Y becomes a proportional relationship, and the original color can be reproduced.

  However, in the liquid crystal display device, the relationship between the driving voltage and the luminance or transmitted light amount is different from that in the case of the CRT. Therefore, in the liquid crystal display device for TV receiver, γ correction is performed on the receiving side, and the CRT It is necessary to be able to reproduce the same color as when displayed with.

  For example, FIG. 4 shows the relationship between the voltage V applied to each pixel electrode of a liquid crystal panel in a general liquid crystal display device and the light transmittance T, that is, the VT characteristic. In this case, in order to obtain a liquid crystal display device capable of displaying gradation of 8 bits = 256, the applied voltage is divided equally to obtain a signal level of 256 gradations. If normalization is performed with the black level transmittance set to 0 and the white level transmittance set to 100%, the relationship between the signal level and the transmittance shown in FIG. 5 is obtained.

  On the other hand, it is known that the human eye naturally feels the displayed image without a sense of incongruity because the relationship between the signal level of the image and the luminance must be a characteristic as shown in the TV mode curve of FIG. ing.

In this case, the relationship between the signal level X and the relative luminance value Z is expressed by Z = X ^gamma. This constant γ is also called gamma, and it is said that γ = 2.0 to 2.6 is good for a liquid crystal panel. The TV mode curve in FIG. 6 shows a curve when γ = 2.2.

  Therefore, in order to obtain the liquid crystal display device 10 having the TV mode characteristics shown in FIG. 6 using the liquid crystal panel having the characteristics shown in FIGS. 4 and 5, the pixels of the liquid crystal panel 11 having the characteristics shown in FIG. As a voltage applied to the electrodes, an analog value corresponding to a signal level that can obtain the same luminance as the output of the TV mode shown in FIG. 6 may be applied to the pixel electrode. FIG. 7 shows the relationship between the signal gradation level and the applied voltage.

1 is a block diagram showing a liquid crystal display device 10 according to an embodiment of the present invention. 3 is a block diagram of a power supply circuit 13 used in the liquid crystal display device 10. FIG. 3 is a block diagram of a gamma correction circuit 14 used in the liquid crystal display device 10. FIG. It is a figure which shows the relationship between the voltage applied to each pixel electrode of a general liquid crystal panel, and the light transmittance. It is a figure which shows the relationship between the signal level applied to each pixel electrode of a general liquid crystal panel, and the light transmittance. FIG. 4 is a diagram illustrating a relationship between luminance and a signal level of an image that is naturally felt without an uncomfortable feeling with respect to an image on which human eyes are displayed in the liquid crystal display device 10. FIG. 7 is a diagram showing a relationship between a signal level (gradation signal voltage) and an applied voltage for obtaining the relationship shown in FIG. 6 in the liquid crystal display device 10. It is a block diagram which shows the conventional liquid crystal display device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal display device 11 Liquid crystal panel 12 Control integrated circuit 13 Power supply circuit 14 Gamma correction circuit 15 Source driver 16 Gate driver 17 Column electrode 18 Row electrode 20 1st power supply part 24 2nd power supply part 25 1st switch 28 2nd switch

Claims (8)

Liquid crystal panel having a plurality of row electrodes and a plurality of column electrodes, a gate driver for driving each row electrode, a source driver for driving each column electrode, and a control integrated circuit for outputting various signals to the gate driver and the source driver A circuit, a gamma correction circuit for supplying a gamma correction voltage to the source driver, and a power supply circuit, the power supply circuit for the control integrated circuit, the gate driver, and the source driver, A first power source that outputs a driving voltage; a first switch that receives a control signal from the control integrated circuit; and a second power source that outputs a second reference voltage to the gamma correction circuit via the first switch. A liquid crystal display device characterized by having a portion. First, the first switch is opened by the control signal, the first power supply unit outputs the driving voltage, and then the first switch is closed by the change of the control signal, and the second The liquid crystal display device according to claim 1, wherein the power supply unit outputs the second reference voltage. The liquid crystal display device according to claim 1, further comprising: a first conversion unit that converts an output of the first power supply unit, wherein the first conversion unit outputs a first reference voltage to the gamma correction circuit. A second conversion unit for converting the output of the first power supply unit is provided. The second conversion unit includes a first charge pump and a first stabilization circuit, and outputs a low voltage to the gate driver. The liquid crystal display device according to claim 1. The liquid crystal display device according to claim 1, further comprising: a third conversion unit that converts an output through the first switch, wherein the third conversion unit outputs a column voltage to the source driver. A fourth conversion unit for converting the output of the second power supply unit, the fourth conversion unit including a second charge pump and a second stabilization circuit, connected to an output side of the fourth conversion unit; and 5. The liquid crystal display device according to claim 4, further comprising a second switch for receiving a control signal from the control integrated circuit. First, the second switch is opened by the control signal, the first power supply unit outputs the driving voltage and the low voltage, and then the second switch is closed by a change in the control signal. The liquid crystal display device according to claim 6, wherein the second power supply unit outputs a high voltage to the gate driver, and both the low voltage and the high voltage are output. 2. The liquid crystal display device according to claim 1, wherein the gamma correction circuit is configured to supply a gamma correction voltage to the source driver and to supply a common voltage to the liquid crystal panel.

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