KR20060116587A - Liquid crystal display - Google Patents

Abstract

An LCD is provided to prevent the crosstalk defect, thereby improving the reproducing characteristic of image, by reflecting the ripple component, which is inputted to common voltage, in gamma voltage and gray voltage. An LCD comprises a gamma voltage generating circuit(400) and a data driving IC(500). The gamma voltage generating circuit supplies a plurality of gamma voltages. The data driving IC includes a plurality of gamma voltage terminals, resistor lines, and capacitors. The resistor lines connect the plurality of gamma voltage terminals to one another to generate a plurality of gray voltages. The capacitors selectively transmit the feedback common voltage from an LCD panel to at least one gamma voltage terminal.

Description

Liquid crystal display

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

2 is an equivalent circuit diagram of a unit pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

3 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to another exemplary embodiment of the present invention.

5 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to another exemplary embodiment of the present invention.

6 is a diagram illustrating waveforms of a common voltage and a data signal of a liquid crystal display according to an exemplary embodiment of the present invention.

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

10 TFT substrate 12 pixel electrode

20: color filter substrate 22: color filter

24: common electrode 100: liquid crystal panel

150, 152, 154: switch 200: drive voltage generation circuit

300: gate drive IC 400: gamma voltage generator circuit

500: data drive IC 600: timing controller

The present invention relates to a liquid crystal display device, and more particularly, to provide a liquid crystal display device having improved crosstalk.

A liquid crystal display (LCD) includes a liquid crystal layer having dielectric anisotropy in which the arrangement direction is changed by a voltage applied from the outside. The liquid crystal display device displays an image such as letters, numbers, arbitrary icons, etc. by applying a voltage to the liquid crystal layer, and adjusting the intensity of the voltage to adjust the transmittance of light passing through the liquid crystal layer.

The liquid crystal display adjusts a voltage applied to a source electrode of a thin film transistor (hereinafter, referred to as TFT) to display light and dark colors, that is, gray levels. For example, in a color TFT liquid crystal display device, the gradation is determined by the number of bits of red, green, and blue data provided to the graphic controller. For example, if red data is provided in 6 bits, red of 64 (= 2 ⁶ ) gradation can be represented. In order to express 64 gray levels, 64 gray voltages are required.

In order to make these 64 gray voltages, 8 gamma voltages are generated in the gamma voltage generator circuit, and the data driver IC uses 64 gamma voltages generated by the gamma voltage generator circuit. Generate a voltage. In addition, a method of generating a gray scale voltage includes a resistive string method and a voltage amplification method. In particular, the resistor string method is a method of connecting a plurality of resistors in series between the power supply voltage (AVDD) and the ground voltage (VSS), and using the node voltage between the resistors as a gray scale voltage.

However, since a single power supply is applied to the driving circuit at the same time using a resistor divider, for example, when the display pattern is changed from a white display pattern to a black display pattern, the load for each case ( Because of the large difference in load, the instantaneous load change is large. In this case, a ripple component flows into the common voltage Vcom. As a result, a crosstalk phenomenon in which display quality is degraded due to signal interference between pixels on a gate line with a large load change occurs.

It is an object of the present invention to provide a liquid crystal display device having improved crosstalk.

The technical problem of the present invention is not limited to the technical problem mentioned above, and other technical problems not mentioned will be clearly understood by those skilled in the art from the following description.

According to an embodiment of the present invention, a liquid crystal display device includes a gamma voltage generation circuit providing a plurality of gamma voltages, a plurality of gamma voltage terminals connected to a plurality of gamma voltages, and a plurality of gamma voltage terminals. And a data driving IC including a resistor string for connecting the plurality of transistors to generate a plurality of gray voltages, and a capacitor for selectively transferring the common voltage fed back from the liquid crystal panel to at least one gamma voltage terminal.

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. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

1 is a block diagram of a liquid crystal display according to an exemplary embodiment of the present invention. 2 is an equivalent circuit diagram of a unit pixel of a liquid crystal display according to an exemplary embodiment of the present invention.

1 and 2, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel 100, a switch 150, a driving voltage generation circuit 200, a gate driving IC 300, and a gamma voltage generation. A circuit 400, a data driver IC 500, and a timing controller 600.

The liquid crystal panel 100 is connected to a plurality of display signal lines G1-Gn and D1 -Dm as viewed in an equivalent circuit and includes a plurality of unit pixels arranged in a matrix form.

Here, the display signal lines G1-Gn and D1-Dm include a plurality of gate lines G1-Gn transferring gate signals and data lines D1-Dm transferring data signals. The gate lines G1-Gn extend in the row direction and are substantially parallel to each other, and the data lines D1-Dm extend in the column direction and are substantially parallel to each other.

Each unit pixel includes a switching element Q connected to the display signal lines G1-Gn and D1-Dm, a liquid crystal capacitor C _LC , and a storage capacitor C _ST connected thereto. . The holding capacitor C _ST may be omitted as necessary.

The switching element Q is provided in the TFT substrate 10, and a three-terminal element whose control terminal and input terminal are connected to the gate lines G1-Gn and the data lines D1-Dm, respectively, and the output terminal Is connected to the liquid crystal capacitor C _LC and the sustain capacitor C _ST .

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 12 of the TFT substrate 10 and the common electrode 24 of the color filter substrate 20, and the liquid crystal layer 30 between the two electrodes 12 and 24. Functions as a dielectric. The pixel electrode 12 is connected to the switching element Q, and the common electrode 24 is formed on the entire surface of the color filter substrate 20 and receives a common voltage Vcom. Unlike in FIG. 2, the common electrode 24 may be provided in the TFT substrate 10. In this case, both electrodes 12 and 24 may be linear or rod-shaped.

The sustain capacitor C _ST is formed by overlapping a separate signal line (not shown) and the pixel electrode 12 provided on the TFT substrate 10, and a predetermined voltage such as a common voltage Vcom is applied to the separate signal line. (Independent wiring system). However, the sustain capacitor C _ST may be formed such that the pixel electrode 12 overlaps the front end gate line directly above the insulator (shear gate method).

Meanwhile, in order to implement color display, each unit pixel should display color, which is possible by providing a red, green, or blue color filter 22 in a region corresponding to the pixel electrode 12. In FIG. 2, the color filter 22 is formed in a corresponding region of the color filter substrate 20, but may be formed above or below the pixel electrode 12 of the TFT substrate 10.

A polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the TFT substrate and the color filter substrates 10 and 20 of the liquid crystal panel 100.

The switch 150 is formed between the liquid crystal panel 100 and the data driving IC 500 to selectively transfer the common voltage Vcom 'applied to the liquid crystal panel 100 to the data driving IC 500.

The driving voltage generation circuit 200 generates a plurality of driving voltages. For example, the driving voltage generation circuit 200 generates a gate on voltage Von, a gate off voltage Voff, and a common voltage Vcom.

The gate driving IC 300 is connected to the gate lines G1-Gn of the liquid crystal panel 100 to receive a gate signal formed of a combination of a gate on voltage Von and a gate off voltage Voff from the outside. G1-Gn).

The gamma voltage generation circuit 400 may generate two sets of plural gamma voltages related to transmittance of a unit pixel. That is, one of the two sets is the positive voltage, and the other is the negative voltage. The positive voltage and the negative voltage mean voltages whose polarities of the data voltages are opposite to the common voltage Vcom, and are alternately provided to the liquid crystal panel during inversion driving.

The data driver IC 500 is connected to the data lines D1-Dm of the liquid crystal panel 100, and generates and generates a plurality of gray voltages based on the plurality of gamma voltages provided from the gamma voltage generation circuit 400. The selected gray voltage is selected and applied to the unit pixel as a data signal, and is usually composed of a plurality of integrated circuits.

Here, the data driver IC 500 receives the common voltage Vcom 'from the liquid crystal panel 100 and provides a ripple introduced to the common voltage Vcom' to the gamma voltage terminal, thereby providing a ripple component to a plurality of gray voltages. Will reflect. For example, when the display pattern is changed from a white display pattern to a black display pattern, the ripple component may be introduced into the common voltage Vcom since the load difference in each case is large. Therefore, the crosstalk phenomenon can be prevented by compensating for the gray voltage by receiving the feedback of the common voltage Vcom 'to which the ripple component is introduced. This will be described later in detail with reference to FIG. 3.

The timing controller 600 generates control signals for controlling operations of the gate driver IC 300 and the data driver IC 500, and transmits the corresponding control signals to the gate driver IC 300 and the data driver IC 500. To provide.

Hereinafter, the display operation of the liquid crystal display will be described in more detail.

The timing controller 600 is an input control signal for controlling the RGB image signals R, G, and B and their display from an external graphic controller (not shown), for example, a vertical synchronization signal Vsync and a horizontal synchronization signal ( Hsync, main clock MCLK, and data enable signal DE are provided. The timing controller 600 generates a gate control signal CONT1, a data control signal CONT2, and the like based on the input control signal, and appropriately matches the image signals R, G, and B with the operating conditions of the liquid crystal panel 100. After processing, the gate control signal CONT1 is provided to the gate driving IC 300, and the data control signal CONT2 and the processed image signals R ', G', and B 'are provided to the data driving IC 500. do.

Here, the gate control signal CONT1 includes a vertical synchronization start signal STV indicating the start of output of the gate on pulse (gate on voltage section), a gate clock signal CPV controlling the output timing of the gate on pulse, and a gate on. An output enable signal OE or the like that defines the width of the pulse. Among these, the output enable signal OE and the gate clock signal CPV are provided to the driving voltage generation circuit 200.

The data control signal CONT2 is a horizontal synchronization start signal STH indicating the start of input of the image data R ', G', and B 'and a load signal for applying a corresponding data voltage to the data lines D1-Dm. LOAD), an inversion signal (RVS) and a data clock signal (inverting the polarity of the data voltage relative to the common voltage Vcom (hereinafter referred to as 'polarity of the data voltage by reducing the polarity of the data voltage for the common voltage') HCLK) and the like.

The data driver IC 500 sequentially receives image data R ', G', and B 'corresponding to one row of unit pixels according to the data control signal CONT2 from the timing controller 600, and among the gray voltages. The image data R ', G', B 'is converted into the corresponding data voltage by selecting the gray voltage corresponding to each of the image data R', G ', and B'.

As illustrated in FIG. 1, the data driver IC 500 compensates the gray voltage by receiving feedback from the common voltage Vcom ′ applied to the liquid crystal panel 100. It explains in detail.

The gate driving IC 300 applies a gate-on voltage Von to the gate lines G1-Gn according to the gate control signal CONT1 from the timing controller 600, and is connected to the gate lines G1-Gn. The device Q is turned on.

While a gate-on voltage Von is applied to one gate line G1-Gn, and a row of switching elements Q connected thereto is turned on (this period is '1H' or '1 horizontal period'). Is equal to one period of the horizontal sync signal Hsync, the data enable signal DE, and the gate clock CPV.], And the data driver IC 500 converts each data voltage to a corresponding data line D1-Dm. To feed. The data voltage supplied to the data lines D1-Dm is applied to the corresponding unit pixel through the turned-on switching element Q.

The liquid crystal molecules change their arrangement according to the change of the electric field generated by the pixel electrode 12 and the common electrode 24, and thus the polarization of light passing through the liquid crystal layer 30 changes. This change in polarization is represented by a change in transmittance of light by polarizers (not shown) attached to the TFT substrate and the color filter substrates 10 and 20.

In this manner, the gate-on voltages Von are sequentially applied to all the gate lines G1 -Gn during one frame to apply data voltages to all the unit pixels. When one frame ends, the state of the inversion signal RVS applied to the data driver IC 500 is controlled so that the next frame starts and the polarity of the data voltage applied to each unit pixel is opposite to that of the previous frame (' Invert frame '). In this case, the polarity of the data voltage flowing through one data line may be changed ('line inversion') or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS within one frame ( 'Dot reversal').

3 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 3, the data driver IC 500 receives a plurality of gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ from the gamma voltage generation circuit 400. For example, in the gamma voltage generator circuit 400, resistance strings R ₀ , R ₁ ,... R ₁₂ having resistances formed in series between the power supply voltage AVDD and the ground voltage VSS are formed, and each resistance string is formed. Each node voltage between (R ₀ , R ₁ ,... R ₁₂ ) may be provided to the data driver IC 500 as a gamma voltage V ₁₀ , V ₂₀ ,..., V ₁₀₀ .

The data driver IC 500 generates a plurality of gray voltages using the provided gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ , and selects the generated gray voltages and applies them to the unit pixel as data signals. Here, the data driving IC (500) is a gray-scale voltage terminal _{(VGMA 10, VGMA 11, VGMA} 12, VGMA 13 ... VGMA 100), resistance heating _{(R 21, R 22, ...} R 26), capacitors (C _10, C ₂₀ ,… C ₁₀₀ ).

Here, the gray voltage terminals VGMA ₁₀ , VGMA ₂₀ ,... VGMA ₁₀₀ are connected to a plurality of gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ generated by the gamma voltage generation circuit 400. In detail, the gamma voltage terminal connected to the plurality of gamma voltages V ₁₀ , V ₂₀ ,..., And V _{100 in the} gamma voltage generation circuit 400 and the gray voltage terminals VGMA ₁₀ and VGMA _{20 of the} data driver IC 500. ,… VGMA ₁₀₀ ) are connected. In one embodiment of the present invention, since the power supply voltage AVDD and the ground voltage VSS are divided into ten gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ , the gray voltage terminals VGMA ₁₀ , VGMA ₂₀ ,. VGMA ₁₀₀ ) is connected to ten gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ , respectively.

The resistor rows R ₂₁ , R ₂₂ , ... R _{26 are} formed between the plurality of gray voltage terminals VGMA ₁₀ , VGMA ₂₀ , ... VGMA ₁₀₀ , respectively, and the resistor rows R ₂₁ , R ₂₂ , ... R ₂₆ are respectively formed. The voltage at each node in between is connected to the gray voltage terminals VGMA ₁₁ , VGMA ₁₂ ,... VGMA ₁₅ .

Therefore, as a result, the voltage section between the power supply voltage AVDD and the ground voltage VSS is the resistance strings R ₀ , R ₁ ,... R ₁₂ of the gamma voltage generation circuit 400 and the data driving IC 500. It is divided twice by the resistor strings R ₂₁ , R ₂₂ ,... R ₂₆ to generate a plurality of gray voltages.

In an embodiment of the present invention, the capacitors C ₁₀ , C ₂₀ ,... C ₁₀₀ selectively select the common voltage Vcom 'fed back from the liquid crystal panel to all the gray voltage terminals VGMA ₁₀ , VGMA ₂₀ ,... VGMA ₁₀₀ . To pass. For example, when the black display pattern is changed from the white display pattern, the change in the instantaneous load is large because the difference in the load for each case is large. In particular, in this case, ripple is likely to flow into the common voltage Vcom connected to the color filter substrate 20. Therefore, signal interference, that is, crosstalk, may occur between pixels on the gate line with a large load change. In the embodiment of the invention a capacitor _{(C 10, C 20, ...} C 100) each of the gradation voltage terminal _{(VGMA 10, VGMA 20, ...} VGMA 100) the common voltage (Vcom ') the ripple is introduced using a to provide. Since the capacitors C ₁₀ , C ₂₀ , ... C ₁₀₀ have a characteristic of passing an alternating current component, the ripple component also has the same gamma voltages V ₁₀ , V ₂₀ , ..., V ₁₀₀ in the same manner as the common voltage Vcom '. It will flow in. In addition, all of the ripple components also flow into the gray scale voltage formed by separating the gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ . Therefore, since the voltage difference between the gamma voltages V ₁₀ , V ₂₀ ,..., V ₁₀₀ , the gray voltage and the common voltage Vcom 'is constant, the crosstalk phenomenon can be improved.

In particular, in one embodiment of the present invention, since a plurality of capacitors C ₁₀ , C ₂₀ , ... C ₁₀₀ are commonly connected to the fed back common voltage Vcom ', one switch 150 is turned on / off. Whether to transfer the common voltage Vcom 'fed back by the data driver IC 500 may be determined.

4 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to another exemplary embodiment of the present invention.

Referring to FIG. 4, the data driving IC 510 of the liquid crystal display according to another exemplary embodiment may be disposed between the fed back common voltage Vcom ′ and the gray voltage terminals VGMA ₁₀ , VGMA ₂₀ ,..., VGMA ₁₀₀ . Each switch 152 is formed. Accordingly, the turn-on / turn-off of the switch 152 may be adjusted to reflect the ripple component of the fed back common voltage Vcom 'only to the specific gray voltage terminals VGMA ₁₀ , VGMA ₂₀ ,..., VGMA ₁₀₀ . By providing the switches 152 in this way, it is possible to provide the common voltage Vcom 'fed back only to the gradation voltage among which the crosstalk among the plurality of gradation voltages is visually recognized.

5 is a circuit diagram illustrating a data driving IC of a liquid crystal display according to another exemplary embodiment of the present invention.

Referring to FIG. 5, the data driving IC 520 of the liquid crystal display according to the exemplary embodiment of the present invention may include a gray voltage terminal in which crosstalk among the fed back common voltage Vcom ′ and a plurality of gray voltages are particularly viewed. Only install capacitors (C ₃₀ , C ₈₀ ) on (VGMA ₃₀ , VGMA ₈₀ ). In addition, the turn-on / turn-off of the switch 154 may be adjusted to control whether the fed back common voltage Vcom 'is transmitted.

6 is a diagram illustrating waveforms of a common voltage and a data signal of a liquid crystal display according to an exemplary embodiment of the present invention.

Referring to FIG. 6, it can be seen that the fed back common voltage Vcom ′, that is, the common voltage into which the ripple is introduced, has a constant distortion in the up and down directions compared to the common voltage Vcom before the ripple is introduced. However, since the ripple is introduced in the data voltage Data as in the common voltage Vcom ', the voltage difference between the common voltage Vcom' and the data voltage Data is kept constant. Accordingly, it can be seen that the liquid crystal display according to the exemplary embodiments of the present invention can prevent the crosstalk phenomenon.

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, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the liquid crystal display according to the present invention as described above has one or more of the following effects. That is, the crosstalk phenomenon can be prevented by reflecting the ripple component introduced into the common voltage to the gamma voltage and the gray voltage. Therefore, the image reproduction characteristic can be improved.

Claims (4)

A gamma voltage generator circuit for providing a plurality of gamma voltages; The at least one gamma voltage terminal includes a plurality of gamma voltage terminals respectively connected to the plurality of gamma voltages, a resistor string connecting the plurality of gamma voltage terminals to generate a plurality of gray voltages, and a common voltage fed back from the liquid crystal panel. A liquid crystal display comprising a data driver IC comprising a capacitor for selectively transferring to. The method of claim 1, And at least one switch for determining whether to transmit the fed back common voltage to the at least one gamma voltage terminal. The method of claim 1, The data driving IC includes a plurality of capacitors respectively connecting the fed back common voltage and a plurality of gray voltage terminals. The method of claim 3, wherein And a plurality of switches that respectively determine whether to transfer the feedback common voltage to the plurality of gamma voltage terminals.

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