KR20070014705A - Liquid crystal display - Google Patents

Abstract

An LCD is provided to reduce the number of circuit parts of a gamma voltage supplying unit positioned at the outside of a source driver, thereby simplifying circuit design and soldering work. An LCD comprises an LCD panel, a gate driver, a source driver, a timing controller, and a gamma voltage supplying unit. The gamma voltage supplying unit generates reference gamma voltages according to gray levels, and supplies the generated reference gamma voltages to the source driver. The gamma supplying unit generates middle level reference gamma voltages and supplies the generated middle level reference gamma voltages to the source driver. The source driver includes a black level gamma voltage generating part(111) for generating white level or black level reference gamma voltages.

Description

Liquid crystal display

1 is a configuration diagram showing a part of a liquid crystal display according to the prior art.

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

3 is a graph illustrating a gamma curve applied to the liquid crystal display of FIG. 2.

FIG. 4 is a graph illustrating voltage-transmittance characteristics of the liquid crystal display according to the gamma curve of FIG. 3.

FIG. 5 is a diagram illustrating the source driver of FIG. 2.

6 and 7 are diagrams illustrating the black level gamma voltage generator of FIG. 5.

(Explanation of symbols for the main parts of the drawing)

100: liquid crystal panel 110: gate driver

120: source driver 130: timing controller

140: gamma voltage supply

The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device capable of simplifying a soldering process and a circuit design and generating reference gamma voltages of an accurate level.

The liquid crystal display device injects a liquid crystal material having anisotropic dielectric constant between a color filter substrate, which is an upper transparent insulating substrate, and an array substrate, which is an upper transparent insulating substrate, and adjusts the strength of an electric field formed in the liquid crystal material to adjust molecules of the liquid crystal material. A display device expresses a desired image by changing an arrangement and adjusting an amount of light transmitted through a transparent insulating substrate through the arrangement. As the liquid crystal display, a thin film transistor liquid crystal display (TFT LCD) using a thin film transistor (TFT) as a switching element is mainly used.

In general, a liquid crystal display device includes a liquid crystal panel in which an image is largely displayed, and a driving unit positioned at an outer side of the liquid crystal panel to drive the liquid crystal panel. The driving unit includes a source driver and a gate driver for driving the liquid crystal panel, a timing controller for controlling driving timing of the source driver and the gate driver, and the like.

In order to maintain stable display quality, the liquid crystal display needs reference gamma voltages that are accurate and always have a constant value. Therefore, the driver generates gamma voltage supply units for generating gray level reference gamma voltages and supplying them to the source driver. 10) in the form as shown in FIG. 1, and converts a video signal input from the outside into an analog pixel signal within a gradation range that can be expressed and applied to the liquid crystal panel. Here, the reference gamma voltage is set to a plurality of gray levels in order to match the feeling of the real and the screen according to the color reproduction characteristics of the liquid crystal material filled in the liquid crystal panel and the visual perception characteristics of the human, and the white level and the black level, Classified as intermediate levels of the stage. The analog pixel signal refers to a reference gamma voltage selected corresponding to a video signal input from the outside among the reference gamma voltages supplied through the gamma voltage supply unit 10.

FIG. 1 is a diagram illustrating a part of a liquid crystal display according to the related art, and illustrates a gamma voltage supply unit 10.

The gamma voltage supply unit 10 is formed of a resistor string in which a plurality of resistors are arranged in series as shown in FIG. 1, and is generally disposed on a printed circuit board connected to a source driver and a gate driver.

However, because a large number of resistors must be configured on the printed circuit board to generate reference gamma voltages for each gray level, the soldering process for connecting each resistor to the source driver is complicated and the circuit design becomes difficult. There was a problem that the circuit characteristics worsened, and the manufacturing cost increased.

In addition, when a reference gamma voltage of a white level or a black level GMA1 or GMA10 having a large voltage difference from the power supply voltage Vcc or the ground voltage GND is not generated by the external gamma voltage supply unit 10 and supplied to the source driver. Due to the complexity of the soldering process and the difficulty of circuit design, the voltage level may be implemented in an indefinite manner, and thus, the quality of the white level and the black level may be deteriorated.

Accordingly, the technical problem of the present invention is to simplify the circuit by reducing the number of circuit components of the gamma voltage supply part located outside the source driver, simplifying the soldering process and circuit design, and accurately generating reference gamma voltages for each gray level. An object of the present invention is to provide a liquid crystal display device.

Technical problems to be achieved by the present invention are not limited to the above-mentioned technical problems, and other technical problems not mentioned above may be clearly understood by those skilled in the art from the following description. There will be.

According to an embodiment of the present invention, a liquid crystal display (LCD) includes a plurality of pixels divided into a gate line and a data line crossing each other, and a gate electrode at an intersection of the gate line and the data line. A thin film transistor comprising a source electrode and a drain electrode, the liquid crystal panel displaying an image on each pixel according to a scan signal supplied through the gate line and an analog pixel signal supplied through the data line; A gate driver for sequentially supplying the scan signal to the gate line, a source driver for converting an input video signal into the analog pixel signal using the reference gamma voltages, and supplying the analog signal to the data line, the gate driver and the source driver The timing control signal And a gamma voltage supply unit configured to generate the reference gamma voltages for each level within the gray scale range and to supply the source signal to the source driver, wherein the gamma voltage supply unit has a medium level. A reference gamma voltage is generated and supplied to the source driver, and the source driver includes a black level gamma voltage generator configured to generate a reference gamma voltage having a white level or a black level except for the intermediate level.

The black level gamma voltage generator includes a diode or a resistor string in which one resistor or a plurality of resistors are connected in series.

The reference gamma voltage of the white level or the black level has a value that is larger or smaller than the power supply voltage of the source driver, or has a value that is greater or smaller than the common voltage of the source driver.

The said offset voltage is 0.1V or more and 0.2V or less.

Specific details of other embodiments are included in the detailed description and the drawings. Advantages and features of the present invention and methods for achieving them will be apparent with reference to the embodiments described below in detail with the accompanying drawings. Like reference numerals refer to like elements throughout.

Hereinafter, a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to the accompanying drawings.

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

Referring to FIG. 2, the liquid crystal display according to the exemplary embodiment may include the liquid crystal panel 100, the gate driver 110, the source driver 120, the timing controller 130, and the gamma voltage supply unit 140. Include.

The liquid crystal panel 100 includes a plurality of pixels P divided into gate lines GL1, GL2,... GLn and data lines DL1, DL2..., DLm that cross each other. At the intersection of the gate lines GL1, GL2, ..., GLn and the data lines DL1, DL2, ..., DLm, a thin film transistor TFT composed of a gate electrode, a source electrode, and a drain electrode is disposed. Each pixel P is filled with a liquid crystal material that is equivalent to the liquid crystal capacitance Clc. The liquid crystal panel 100 according to the scan signal supplied through the gate lines GL1, GL2, ..., GLn and the analog pixel signal supplied through the data lines DL1, DL2, ..., DLm. An image is displayed on each pixel P. Here, the analog pixel signal is a reference gamma voltage selected in response to a video signal input from the outside of the reference gamma voltages supplied from the gamma voltage supply unit 140 and the reference gamma voltages generated by the source driver 120. Means.

The gate driver 110 sequentially supplies scan signals to the gate lines GL1, GL2,..., GLn in response to the timing control signal.

The source driver 120 converts the video signal input from the timing controller 130 into an analog pixel signal using reference gamma voltages for each gray level in response to the timing control signal, thereby converting the video signal into data lines DL1, DL2, ..., DLm. To feed.

The timing controller 130 controls the driving timing by supplying timing control signals to the gate driver 110 and the source driver 120, and supplies a video signal to the source driver 120.

The gamma voltage supply unit 140 generates reference gamma voltages for each gray level within the gray scale range and supplies the same to the source driver 120.

Here, the gamma voltage supply unit 140 generates the intermediate level reference gamma voltages and supplies them to the source driver 120, and the reference gamma voltages of the white level or the black level except for the intermediate level are themselves in the source driver 120. Is generated.

3 is a graph illustrating an example of a gamma curve applied to the liquid crystal display of FIG. 2, and FIG. 4 is a graph illustrating voltage-transmittance characteristics of the liquid crystal display according to the gamma curve of FIG. 3. FIG. 3 illustrates a liquid crystal display filled with a twisted nematic liquid crystal material (TN) operating in a normally white (TN) mode.

3 and 4, the voltage levels for setting the reference gamma voltage are black levels GMA1 and GMA10, white levels GMA5 and GMA6, and gray levels GMA2, GMA3, GMA4, GMA7, and GMA8 in the entire gray scale range. , GMA9).

The video signal (digital value) input to the liquid crystal display is transmitted to the source driver 120 through the timing controller 130, and the source driver 120 generates reference gamma voltages that are set according to the gamma curve shown in FIG. 3. The video signal is converted into an analog pixel signal, and the converted analog pixel signal is applied to the liquid crystal panel 100.

For convenience of explanation, hereinafter, assuming a liquid crystal display having such a gamma curve, reference gamma voltages of the black levels GMA1 and GMA10 are generated in the source driver 120 by itself, and other reference gamma voltages. The present invention will be described on the assumption that GMA2 to GMA9 are generated by the gamma voltage supply unit 140 and supplied to the source driver 120.

FIG. 5 is a diagram illustrating the source driver of FIG. 2.

Referring to FIG. 5, the source driver 120 may include a black level gamma voltage generator 111, a middle level gamma voltage generator 112, a signal controller 113, a shift register unit 114, and a latch unit 115. , A digital-to-analog converter 116, an output buffer unit 117, and the like.

The black level gamma voltage generator 111 generates the reference gamma voltages of the black levels GMA1 and GMA10 and supplies them to the middle level gamma voltage generator 112.

Here, the reference gamma voltages of the black levels GMA1 and GMA10 have a value larger or smaller than the power supply voltage Vdd or the ground voltage Vss of the source driver 120 by an offset voltage. It is preferable that the offset voltage is set to a value of 0.1V to 0.2V, and the range may be varied according to the setting reference of the reference gamma voltage.

Although not shown, the black level gamma voltage generator 111 may generate the reference gamma voltages of the white levels GMA5 and GMA6 by itself, and in this case, the reference gamma voltages of the white levels GMA5 and GMA6 may be the source. The driver 120 has a value larger or smaller than the common voltage Vcom by the offset voltage.

The middle level gamma voltage generator 112 supplies the positive and negative gamma voltages required by the digital-to-analog converter 116. The middle level gamma voltage generator 112 uses the internal resistance string to reference the gamma voltages GMA2 to GMA9 input from the gamma voltage supply unit 140 and the reference input from the black level gamma voltage generator 111. Gamma voltages GMA1 and GMA10 are divided into gray levels and output. In this case, the intermediate level gamma voltage generator 112 includes an internal resistance string, that is, a plurality of resistors, connected in series between the power supply voltage Vdd, the ground voltage Vss, and the common voltage Vcom of the source driver 120. 256 positive and negative gamma voltages having different voltage levels are output from the node between them to the digital-to-analog converter 116.

The signal controller 113 relays the timing control signal received from the timing controller 130 and the video signal, which is a digital value, to be output to appropriate components.

The shift register 114 supplies a sequential sampling signal to the latch unit 115, and the latch unit 115 sequentially latches the video signal by a predetermined unit in response to the sampling signal and simultaneously outputs the sampling signal.

The digital analog converter 116 converts a video signal received from the latch unit 115 into an analog pixel signal by using the positive and negative gamma voltages supplied from the middle level gamma voltage generator 112 and outputs an output buffer unit ( 117, and the output buffer unit 117 outputs the analog pixel signal received from the digital analog converter 116 to the data lines DL1, DL2, ..., DLm.

As such, when the video signal output from the timing controller 130 is converted into an analog pixel signal using the positive and negative gamma voltages supplied from the intermediate level gamma voltage generator 112 and supplied to the liquid crystal panel 100, The liquid crystal panel 100 applies an analog pixel signal between black and white during one horizontal period (about 16.7 ms) of each pixel P to which a scan signal is supplied through the gate lines GL1, GL2, ..., GLn. The desired image is displayed.

6 and 7 are diagrams illustrating the black level gamma voltage generator of FIG. 5 and illustrate two embodiments of the black level gamma voltage generator 111 included in the source driver 120.

The black level gamma voltage generator 111 includes a diode as shown in FIG. 6 to implement an offset voltage of 0.1V to 0.2V level with a voltage drop, or as shown in FIG. 7, one resistor or a plurality of resistors. The series of resistor strings connected in series creates an offset voltage between 0.1V and 0.2V.

In the case of the conventional source driver, since the middle level gamma voltage generator made of a resistor string is generally included, the black level gamma voltage generator 111 may be easily implemented using a diode or a resistor.

In addition, when the black level gamma voltage generator 111 is added in this manner, the reference gamma voltage of the white level (not shown) or the black levels GMA1 and GMA10 is the power supply voltage Vdd of the source driver 120. Since it is set to 0.1V ~ 0.2V difference from the ground voltage (Vss) and the common voltage (Vcom), the reference gamma voltage of the white level (not shown) or the black level (GMA1, GMA10) is the gamma voltage on the printed circuit board. Although not separately generated outside the source driver 120 through the supply unit 140, the source 140 may be stably generated by the power supply voltage Vdd, the ground voltage Vss, and the common voltage Vcom. have.

In this way, the black level gamma voltage generator 111 is formed of a diode or a resistor inside the source driver 120, so that the power source voltages Vdd and Vss and the common voltage Vcom of the source driver 120 are relatively small. Of the gamma voltage supply unit 140 that supplies the reference gamma voltage of the white level (not shown) or the black levels GMA1 and GMA10 set to a range by itself and is disposed on a printed circuit board outside the source driver 120. By making the resistance string simpler, the number of parts of the printed circuit board can be reduced, and the cost reduction effect can be achieved.

Although embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that.

Therefore, since the embodiments described above are provided to completely inform the scope of the invention to those skilled in the art, it should be understood that they are exemplary in all respects and not limited. The invention is only defined by the scope of the claims.

The liquid crystal display according to the exemplary embodiment of the present invention as described above simplifies the circuit by reducing the number of circuit components of the gamma voltage supply unit located outside the source driver, thereby simplifying the soldering process and the circuit design, and Reference gamma voltages may be generated.

Claims (6)

A thin film transistor including a plurality of pixels divided into a gate line and a data line crossing each other, and a thin film transistor including a gate electrode, a source electrode, and a drain electrode is disposed at an intersection of the gate line and the data line. A liquid crystal panel configured to display an image on each pixel according to a scan signal supplied through the analog signal and an analog pixel signal supplied through the data line; A gate driver which sequentially supplies the scan signal to the gate line; A source driver for converting a video signal input using reference gamma voltages into the analog pixel signal and supplying the analog video signal to the data line; A timing controller supplying a timing control signal to the gate driver and the source driver and supplying the video signal to the source driver; And A gamma voltage supply unit generating the reference gamma voltages for each level within a gray scale range and supplying the reference gamma voltages to the source driver, The gamma voltage supply unit generates a middle level reference gamma voltages and supplies them to the source driver, and the source driver includes a black level gamma voltage generator that generates a reference gamma voltage of a white level or a black level except the middle level. A liquid crystal display device, characterized in that. The method of claim 1, The black level gamma voltage generator, Liquid crystal display comprising a diode. The method of claim 1, The black level gamma voltage generator, A liquid crystal display device comprising a resistor string in which one resistor or a plurality of resistors are connected in series. The method of claim 1, The reference gamma voltage of the white level and the black level is And a value larger or smaller than the power supply voltage of the source driver by an offset voltage. The method of claim 1, The reference gamma voltage of the white level and the black level is And a value greater or smaller than the common voltage of the source driver by an offset voltage. The method according to claim 4 or 5, The offset voltage is 0.1V or more and 0.2V or less.

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