KR20080000143A - Gamma generating circuit, lcd device using the same and driving method of gamma generating circuit - Google Patents

Abstract

A gamma generating circuit, an LCD(Liquid Crystal Display) device using the same, and a driving method of the gamma generating circuit are provided to compensate for data signals by implementing first and second gamma generating units for generating gamma signals. A gamma generating circuit includes a gamma unit(17) and a gamma selection unit(16). The gamma unit includes plural gamma generating parts for generating gamma voltages, which are different from one another, in response to gamma selection signal. The gamma selection unit includes a timer, a controller, and a selector. The timer supplies result values on elapsed time. The controller compares the result values with a threshold time as an operation interval of the gamma generating part and generates control signals corresponding to the comparison. The selector generates the gamma selection signals corresponding to the control signals.

Description

Gamma generating circuit, liquid crystal display and driving method using same {Gamma generating circuit, LCD device using the same and driving method of Gamma generating circuit}

1A is a block diagram schematically illustrating a basic configuration of a general liquid crystal display.

FIG. 1B is a resistance voltage dividing gamma part of FIG. 1A.

2 is a graph for explaining a gamma signal compensation principle.

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

FIG. 4 is a block diagram schematically illustrating a structure of a gamma selector and a gamma unit in the liquid crystal display of FIG. 3.

FIG. 5 is a flowchart for describing a method of driving a gamma selector of FIG. 4.

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

TFT: Thin Film Transistor GL: Gate Line

DL: Data line 10: Liquid crystal panel

12: Timing Controller 13: Gate Driver IC

14: source driver IC 15: power supply voltage generator

17: gamma part 17a, 17b: first and second gamma generator

19: interface

The present invention relates to a gamma generation circuit, a liquid crystal display device and a method of driving the gamma generation circuit using the same, and more particularly to at least two or more single chips for generating a gamma signal by replacing a gamma part of a general resistance distribution method. And a gamma generation circuit for generating a gamma signal by selectively enabling the single chip for a predetermined time, and a method of driving a liquid crystal display and a gamma generation circuit using the same.

Liquid crystal displays have low power consumption and are capable of thinning and realizing large screens. Therefore, LCDs are in the spotlight as next-generation advanced display devices with high added value as display devices such as notebook computers and large screen TVs.

The image realization principle of the liquid crystal display device uses the optical anisotropy and polarization of the liquid crystal. The liquid crystal has a thin and long molecular structure and has an optical anisotropy having an orientation in orientation and a molecule according to its size when placed in an electric field. It has a polarization property in which the direction of arrangement changes. Therefore, the liquid crystal display device is an essential component of a liquid crystal panel composed of a pair of transparent substrates each having a liquid crystal layer interposed therebetween by a predetermined distance from each other to form an electric field generating electrode. Through this, the alignment direction of the liquid crystal molecules is artificially adjusted and the light transmittance is changed accordingly to display various images.

Also, in order to supply a signal and a voltage capable of electrically driving the liquid crystal panel, a driving circuit and a power supply unit including a plurality of driver ICs are included.

FIG. 1A is a block diagram schematically illustrating a basic configuration of a general liquid crystal display device, and includes a liquid crystal panel 1 for displaying an image and a plurality of driving circuits 2, 3, 4, for driving the liquid crystal panel 1. 5, 7) are shown.

In each configuration, the interface 9 includes data signals (RGB Data), clock signals (CLK), horizontal and vertical synchronization signals (Hsync, Vsync), gate and data enable (GOE,) input to the drive circuit from an external system. The SOE signal is input to the timing controller 2. Low voltage differential signal (LVDS) interface and TTL interface are used to transmit data and control signals from external systems. In addition, the interface function may be collected and configured together with the timing controller 5 to form a single chip.

In the liquid crystal panel 1, as illustrated in FIG. 1A, a plurality of gate lines GL and a plurality of data lines DL are disposed on a substrate using glass, and the crossing points are defined as pixel regions. Each pixel area includes a thin film transistor TFT and a liquid crystal LC to display a screen.

The timing controller 2 uses a control signal input through the interface 9 to provide a gate driver IC 3 composed of a plurality of drive integrated circuits and a source driver IC 4 composed of a plurality of drive integrated circuits. Generates a control signal for driving. In addition, the signals input through the interface 9 are supplied to the source driver IC 4.

The gate driver IC 3 performs on / off control of thin film transistors TFTs arranged on the liquid crystal panel 1 in response to control signals input from the timing controller 12. By sequentially enabling the gate line GL by one horizontal synchronizing time, the thin film transistors TFT on the liquid crystal panel 1 are sequentially driven by one line, so that analog image signals supplied from the source driver IC 4 may be supplied. It is applied to the pixels connected to the thin film transistors (TFTs).

The source driver IC 4 selects a reference voltage of the input data in response to control signals input from the timing controller 2, and supplies the selected reference voltage to the liquid crystal panel 1 to control the rotation angle of the liquid crystal molecules. do.

The power supply voltage generator 5 supplies operating power of each component and generates and supplies a common electrode voltage of the liquid crystal panel 2.

The gamma unit 8 generates a gamma signal that becomes a reference for the digital to analog converter (DAC) used in the source driver IC 4. The gamma signal is set by the producer based on the transmittance-voltage characteristics of the panel.

As shown in FIG. 1B, the gamma part 8 includes a plurality of resistors and capacitors between the power supply voltage terminal VDD and the ground voltage terminal GND, and generates a plurality of gamma voltages. GMA1,3,5,6,7,10 are output to the gamma signal stage.

In more detail, a plurality of resistors and capacitors are designed in a fixed value, and the gamma part 8 for the conventional gamma correction determines the value of the resistor at the time of design so that the power supply voltage terminal Vcc and ground Comprising a plurality of resistors between the voltage terminals (Vss), a voltage obtained by using the voltage drop by each resistor is finally amplified by an amplifying means (not shown) to generate a gamma signal (GMAS).

Compensating the data signal by using the gamma signal, when the display device is implemented for the input image data signal, as shown in the graph shown in Fig. 2 (a) of the human visual characteristics, the luminance for the gray level This is because the nonlinearity deteriorates and the image feels dark. Accordingly, in a display device such as a liquid crystal display device, gamma compensation as shown in the graph shown in Fig. 2B is performed to compensate for the decrease in luminance of the image.

Accordingly, the liquid crystal panel 2 turns on / off the thin film transistor T through the gate driver IC 3, compensates the data signal with a gamma signal, and supplies the data through the source driver IC 4. The data signal is supplied to the thin film transistor T, and the light transmittance of the liquid crystal cell is changed to display an image.

In the liquid crystal display having the above characteristics, the liquid crystal molecules of the liquid crystal cell do not respond quickly to the change of the electric field as the polymer material, and the liquid crystal molecules are arranged in the same direction as the electric field for a predetermined time, thereby becoming a stable state. The delay of the response time of the liquid crystal molecules is a major cause of deterioration of the image quality when implementing the image by leaving an afterimage on the screen.

Accordingly, various methods have been proposed to remove the afterimage phenomenon. In the present invention, a gamma generation circuit and a liquid crystal display device for realizing clear image quality by removing the afterimage phenomenon through the driving method thereof are proposed.

To this end, a gamma generation circuit according to an embodiment of the present invention, a gamma unit including a plurality of gamma generators for generating different gamma voltages in response to a gamma selection signal; A timer for supplying a result value over time, a control means for comparing the result value with a threshold time which is an operation period of the gamma generator, and generating a control signal corresponding thereto; And a gamma selection unit having selection means for generating a gamma selection signal.

The plurality of gamma parts may include first and second gamma generators.

The first and second gamma generators may be configured of an ASIC.

The first and second gamma generators may generate gamma signals having different gamma voltages corresponding to black gray levels.

The threshold time is characterized in that 2 hours.

The means for selecting is characterized in that a 1x2 multiplexer.

To this end, a liquid crystal display device using a gamma generation circuit according to an embodiment of the present invention includes a liquid crystal panel having a gate line and a data line intersecting and having a thin film transistor at the intersection thereof. An interface for transmitting control signals and data signals from an external system; A timing controller connected to the interface; A gate driver IC and a source driver IC connected to the timing controller; A gamma part including first and second gamma generators generating first and second gamma signals for compensating the data signal in the source driver IC; A power supply voltage generator for supplying a power voltage to the timing controller, the gate driver IC, the source driver IC, and the gamma part; And a gamma selector included in the timing controller to enable the first and second gamma generators.

The gamma selector may be provided separately from the timing controller.

To this end, the driving method of the gamma generation circuit according to the embodiment of the present invention, in the driving method of the gamma generation circuit including a first and second gamma generator for selecting a predetermined period for generating a different gamma signal, the control Setting a signal value and a threshold time which is the predetermined period; Selecting the first and second gamma portions; Receiving a result value for a time elapsed from a time point at which one of the first and second gamma generators is selected; And comparing the resultant value with the threshold time.

The selecting of the first and second gamma parts may include: enabling the first gamma part when the control signal value is 0; And when the control signal value is 1, enabling the second gamma part.

The comparing of the result value and the threshold time may include: inverting the control signal value if the result value is equal to the threshold time; And if the result value is different from the threshold time, receiving the result value again.

Hereinafter, a gamma generation circuit according to a preferred embodiment of the present invention, a liquid crystal display device and a method of driving the gamma generation circuit using the same will be described.

3 is a block diagram schematically illustrating a liquid crystal display according to a preferred embodiment of the present invention. Referring to FIG. 3, a liquid crystal panel 10 displaying an image and a plurality of driving circuits for driving the liquid crystal panel ( 12, 13, 14, 15, 16, 17, 19).

Hereinafter, the configuration and functions of the liquid crystal panel 10 and the driving circuits 12, 13, 14, 15, 16, 17, and 19 will be described. The interface 19 may include a data signal (RGB Data) input from an external system to the driving circuit. ), A clock signal CLK, horizontal and vertical synchronization signals Hsync and Vsync, gate and data enable signals GOE and SOE, and the like are supplied to the timing controller 12. LVDS interface and TTL interface are used for data and control signal transmission from external system. In addition, the interface function may be collected and configured together with the timing controller 12 to form a single chip.

In the liquid crystal panel 10, as illustrated in FIG. 3, a plurality of gate lines GL and a plurality of data lines DL are disposed on a substrate using glass, and the intersection points are defined as pixel regions. Each pixel area includes a thin film transistor (TFT) and a liquid crystal (LC) to display a screen.

The timing controller 12 includes a gate driver IC 13 composed of a plurality of gate drive integrated circuits and a source driver IC 14 composed of a plurality of source drive integrated circuits using a control signal input through the interface 19. To generate a control signal for driving. In addition, the data signals input through the interface 19 are supplied to the source driver IC 14. In addition, the gamma selection unit 16 is provided to supply the gamma selection signal GSS to the gamma unit 17.

The gate driver IC 13 performs on / off control of thin film transistors TFTs arranged on the liquid crystal panel 10 in response to control signals input from the timing controller 12. By sequentially enabling the gate line GL on the LCD panel by one horizontal synchronizing time, the analog image signals supplied from the source driver IC 14 are sequentially driven by driving the thin film transistors TFT on the liquid crystal panel 10 by one line. Each pixel is applied to the pixels connected to the TFTs.

The source driver IC 14 converts the digital data signal input in response to the control signals input from the timing controller 12 into an analog data signal, and gamma-compensates the analog data signal to form a liquid crystal panel. Supply to (10) to control the rotation angle of the liquid crystal molecules.

The power supply voltage generator 15 supplies the operating power of each component and generates and supplies a common electrode voltage of the liquid crystal panel 12.

As shown, the gamma selection unit 16 may be mounted in the timing controller 12 or provided as a separate circuit, and a gamma selection signal for selecting the first and second gamma generators 17a and 17b. (GSS) is generated and supplied to the gamma unit 17.

The gamma unit 17 generates a gamma signal GMAS of a digital to analog converter (DAC) used in the source driver IC 14. The gamma part 17 includes at least one gamma generator, and is preferably composed of first and second gamma generators 17a and 17b.

The first gamma generator 17a and the second gamma generator 17b are customized semiconductors that generate a plurality of gamma voltages GMA1 to GMA8 by programming a gamma signal set by a producer based on the transmittance-voltage characteristics of the panel. It consists of. Here, the application specific semiconductor is referred to as an application specific integrated circuit (ASIC), and an EEPROM (not shown) is embedded therein.

The use of the ASIC method is because a plurality of gamma generators in a single chip form in a limited space and it is easy to control them.

The first and second gamma generators 17a and 17b generate gamma signals GMAS having different gamma voltages GMA1 to GMA8, respectively. Preferably, the first gamma generator 17a and the second gamma generator 17b have the same gamma voltages GMA1 to GMA4 corresponding to white and intermediate gray levels, and are equal to the black gray levels. The voltage at the corresponding level produces gamma voltages GMA5 to GMA8 with a difference in levels.

More specifically, in a liquid crystal display device operating in a normally white mode, the white gray level or the middle gray level corresponds to a low level of gamma voltages (GMA1 to GMA4), and the black gray level corresponds to a high level of gamma voltages (GMA5 to GMA8). Therefore, the first and second gamma generators 17a and 17b which generate gamma signals GMAS having different levels of gamma voltages GMA5 to GMA8 corresponding to the black gray levels are provided.

This is because the afterimage resulting from the delay of the response time of the liquid crystal molecules is greatly highlighted with respect to the black gradation having a large inclination angle of the liquid crystal molecules.

Further, in the liquid crystal display device operating in the normally black mode, the first and second gamma generators 17a and 17b each have a level of gamma voltages GMA1 to GMA4 corresponding to white gray levels with a large inclination angle of the liquid crystal molecules. It will generate another gamma signal (GMAS).

The gamma unit 17 receives the gamma selection signal GSS of the gamma selection unit 16 included in the timing controller 12, and selects the first and second gamma generators 17a and 17b accordingly. To generate a gamma signal GMAS and supply it to the source driver IC 14.

Here, the gamma selection signal (GSS) is inverted the signal value according to the threshold time (T), the threshold time is determined by the setter, but the preferred threshold time (T) determined in consideration of the visual characteristics of the person is 2 It's time. That is, the gamma selector 16 alternately enables the first and second gamma generators 17a and 17b every two hours.

Therefore, the liquid crystal display according to the preferred embodiment of the present invention gamma-compensates the data signal through another gamma signal GMAS at a period of time T.

FIG. 4 is a block diagram schematically illustrating the structure of the gamma selection unit 16 and the gamma unit 17 in the liquid crystal display shown in FIG. 3, and with reference to FIG. 4, gamma generation according to a preferred embodiment of the present invention. The circuit is described as follows.

A gamma selection unit 16 for generating a gamma selection signal GSS and a gamma unit 17 for generating a gamma signal GMAS in response to the gamma selection signal GSS.

In addition, the gamma selector 16 receives a timer 16a, a control means 16b for receiving a result value for the threshold time T from the timer 16a, and generating a control signal corresponding thereto; And a selection means 16c for receiving a control signal from the control means 16b and generating a corresponding gamma selection signal GSS, wherein the gamma part 17 has eight gamma voltages GMA1 to GMA8, respectively. ) And first and second gamma generators 17a and 17b for generating N).

Hereinafter, referring to FIG. 4, a configuration and a function of the gamma generation circuit will be described. The timer 16a of the gamma selection unit 16 serves to provide the control means 16b with a result value over time.

The control means 16b is a result value for a time elapsed from the time at which one of the first or second gamma generators 17a and 17b of the gamma unit 17 supplied from the timer 16a is enabled, The set threshold time T is compared and the control signal corresponding thereto is supplied to the selection means 16c. In other words, the control signal is a signal having a value of 0 or 1, and each time the threshold time T elapses, the control signal alternately has a value of 0 or 1, and is supplied to the selection means 16c.

The selecting means 16c receives the control signal and supplies a gamma selection signal GSS corresponding to the control signal. Preferably, the selecting means 16c may be implemented as a 1 × 2 multiplexer. Accordingly, when the control signal is 0, the selecting means 16c outputs a first gamma selection signal GSS [0]. Enable the first gamma generator 17a of the gamma unit 17, and output the second gamma selection signal GSS [1] when the control signal is 1 to output the second gamma generator 17a. The gamma generator 17b is enabled.

The gamma portion 17 includes at least one gamma generator 17a, 17b, and preferably, as described above, is composed of two first and second gamma generators 17a, 17b. If the gamma part is configured in a form including three or more gamma generators, the structure of the gamma selection part 16 may be configured differently accordingly, and thus, the control means presented as a preferred embodiment. The value of the control signal of 16b is different from the number of input / output terminals of the selecting means 16c.

The gamma signal GMAS generated by the first gamma generator 17a is at the same level as a general gamma signal, and the gamma signal GMAS generated by the second gamma generator 17b is a gamma voltage corresponding to white and gray scale. GMA1 to GMA4 are at the same level as the gamma voltages GMA1 to GMA4 of the first gamma generator 17a, and the gamma voltages GMA5 to GMA8 corresponding to the black gray level are at least the first gamma generator 17a. ) Has a level lower than the gamma voltage (GMA5 to GMA8) corresponding to the black gradation generated.

In addition, in some cases, the gamma signal GMAS corresponding to the black gradation presented in the preferred embodiment is not limited to a specific number, as described above, and may be designed more or less.

The gamma signal GMAS generated by the selected first or second gamma generators 17a and 17b is input to the source driver IC.

FIG. 5 is a flowchart illustrating a method of driving the gamma selection unit of FIG. 4. In the driving method of a liquid crystal display driving apparatus according to an exemplary embodiment of the present invention, setting an initial control signal value and a threshold time T may be performed. (S1); Selecting one of the first and second gamma generators (S2-1, S2-2, and S2-3) in response to the control signal value; Receiving a time-lapse result value from a timer (S3); And comparing the resultant value with the threshold time T to determine a control signal value (S4-1, S4-2).

In the step S1 of setting the initial control signal value and the threshold time T, the initial control signal value is set to 0, and the threshold time T is set to 2 hours by the setter.

Selecting the first and second gamma parts in response to the control signal value (S2-1, S2-2, S2-3),

When the initial control value is 0, the first gamma part is enabled. When the initial control value is 1, the second gamma part is enabled.

 In step S3 of receiving a time elapsed result value from the timer, the first and second gamma generators of one of the gamma parts are supplied with a result value for a time elapsed from an enable time through a timer provided in the gamma selector. The receiving step is made.

Determining a control signal value by comparing the result value with the threshold time T (S4-1, S4-2), one of the first or second gamma generator of the gamma part has elapsed since the enable time When the result value for time is 2 hours, the control signal value is inverted.

Therefore, the first gamma generator and the second gamma generator alternately generate a gamma signal every two hours that is the threshold time T.

Although described above with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and variations of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

According to a gamma generation circuit according to a preferred embodiment of the present invention, and a method of driving a liquid crystal display device and a gamma generation circuit using the same, the first and second gamma generators generating gamma signals having different gamma voltages corresponding to black gray levels are provided. In addition, by alternately selecting this for 2 hours to generate a gamma signal and gamma compensation of the data signal through this, there is an effect of improving the afterimage phenomenon.

Claims (11)

A gamma part including a plurality of gamma generators generating different gamma voltages in response to a gamma selection signal; A timer for supplying a result value over time, a control means for comparing the result value with a threshold time which is an operation period of the gamma generator, and generating a control signal corresponding thereto; A gamma selection unit having selection means for generating a gamma selection signal; Gamma generation circuit comprising a. According to claim 1, The plurality of gamma parts, the gamma generator circuit characterized in that it comprises a first and second gamma generator. The method of claim 2, The gamma generator is characterized in that the first and second gamma generator is composed of an ASIC. The method of claim 2, And the first and second gamma generators generate gamma signals having different gamma voltages corresponding to black gray levels. According to claim 1, The threshold time is a gamma generation circuit, characterized in that 2 hours. According to claim 1, And said selecting means is a 1x2 multiplexer. A liquid crystal display device comprising a liquid crystal panel having a gate line and a data line intersecting and having a thin film transistor at an intersection thereof. An interface for transferring control signals and data signals from an external system; A timing controller connected to the interface; A gate driver IC and a source driver IC connected to the timing controller; A gamma part including first and second gamma generators generating first and second gamma signals for compensating the data signal in the source driver IC; A power supply voltage generator for supplying a power voltage to the timing controller, the gate driver IC, the source driver IC, and the gamma part;  A gamma selector included in the timing controller to enable the first and second gamma generators; Liquid crystal display comprising a. The method of claim 7, wherein And the gamma selector is separately provided outside the timing controller. A driving method of a gamma generation circuit including first and second gamma generators selected for a predetermined period and generating different gamma signals, Setting a control signal value and a threshold time which is the predetermined period; Selecting the first and second gamma portions; Receiving a result value for a time elapsed from a time point at which one of the first and second gamma generators is selected; Comparing the resultant value with the threshold time; Method of driving a gamma generation circuit comprising a. The method of claim 9, Selecting the first and second gamma parts, Enabling the first gamma part when the control signal value is 0; Enabling the second gamma part when the control signal value is 1; Method of driving a gamma generation circuit comprising a. The method of claim 10, Comparing the result value and the threshold time, Inverting the control signal value if the result value is equal to the threshold time; If the result value is different from the threshold time, receiving the result value again; Method of driving a gamma generation circuit comprising a.

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