KR20080020319A - Liquid crystal display and control method thereof - Google Patents

Abstract

A liquid crystal display device and a control method thereof are provided to improve brightness of the display device by regulating a black section according to the brightness of an image signal. A liquid crystal display device includes an LCD panel(100), a gate driver(110), a data driver(120), and a controller(160). The LCD panel includes gate lines, data lines, and pixels. The gate driver applies first and second gate signals to the gate lines during one frame period. The data driver applies a black signal to the pixels corresponding to the first gate signal and applies the data signal to the pixels corresponding to the second gate signal. The controller controls the gate and data drivers, so that a black period is regulated according to a brightness of a current frame. During the black period, a black signal is applied during one frame. During a data period, the data signal is applied to the LCD(Liquid Crystal Display) panel.

Description

Liquid crystal display and its control method {LIQUID CRYSTAL DISPLAY AND CONTROL METHOD THEREOF}

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

2 is a liquid crystal panel including a black section according to an embodiment of the present invention,

3 is a liquid crystal panel for explaining the adjustment of the black section according to an embodiment of the present invention,

4 is a control flowchart illustrating a control method of a liquid crystal display according to an exemplary embodiment of the present invention.

Explanation of symbols on the main parts of the drawings

10: gate line 20: data line

30: pixel 100: liquid crystal panel

110: gate driver 120: data driver

130: gray voltage generator 140: gate voltage generator

150: storage unit 160: control unit

The present invention relates to a liquid crystal display device and a control method thereof, and more particularly, to a liquid crystal display device including a liquid crystal layer having a fast response speed and a control method thereof.

The liquid crystal display device includes a liquid crystal panel including a thin film transistor substrate on which a thin film transistor is formed, a color filter substrate on which a color filter is formed, and a liquid crystal layer injected between both substrates. Since the liquid crystal panel is a non-light emitting device, a backlight unit for supplying light is disposed on the rear surface of the thin film transistor substrate, and the light emitted from the backlight unit is adjusted according to the arrangement of liquid crystals. The liquid crystal panel and the backlight unit are housed in the chassis.

Since the liquid crystal display is a hold type display device that maintains a voltage applied to a pixel for one frame, an image blur phenomenon does not occur in an impulsive type display device such as a CRT. Image blurring occurs more frequently as a video is a moving image, and as the size of the display device increases, image blurring increases.

In order to prevent an image blur phenomenon of a liquid crystal display, a driving method of inserting a black screen into a screen on which an image is displayed is used. Although the above-described method has an effect of reducing an image blur occurring in the display device, the black screen causes a problem of lowering the brightness of the display device.

Accordingly, an object of the present invention is to provide a liquid crystal display device and a control method for improving the brightness by adjusting the black period according to the brightness of the video signal.

According to an aspect of the present invention, there is provided a liquid crystal panel including a pixel defined by an insulating crossing gate line and a data line and an intersection area of the gate line and the data line; A gate driver configured to apply a first gate signal and a second gate signal to the gate line during one frame forming time; A data driver configured to apply a black signal to the pixel in response to the first gate signal and to apply a data signal to the pixel in response to the second gate signal; The black section to which the black signal is applied and the data section to which the data signal is applied are formed in the liquid crystal panel during one frame formation time, and the gate driver and the data driver are adjusted so that the black section is adjusted according to the luminance of the frame to be currently formed. It is achieved by a liquid crystal display including a control unit for controlling the.

The storage unit may further include a storage unit configured to store a data signal corresponding to one frame, wherein the controller counts the data value of the data signal stored in the storage unit and calculates the black period for the data section based on the counted data value. I can regulate it.

In order to improve the brightness of the image signal displayed on the liquid crystal panel, the controller preferably decreases the black period as the data value is larger.

The controller may adjust the ratio of the data section to the black section to 1-5.

During one frame, the black section scans the liquid crystal panel along an extension direction of the data line.

The liquid crystal panel further includes a first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate, wherein the liquid crystal layer is aligned with an OCB (Optically Compensated Birefringency) mode. It may include.

On the other hand, the object is, according to the present invention, storing a data value corresponding to one frame, and counting the data value; Determining a ratio of a black section to which a black signal is applied and a data section to which a data signal is applied according to the counted data values; It is also achieved by a method of controlling a liquid crystal display including forming a frame according to a ratio of the black section and the data section.

In order to improve the luminance of the image signal displayed on the liquid crystal panel, it is preferable that the black period is reduced as the data value is larger.

The ratio of the data section to the black section may be adjusted to 1 to 5.

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

In various embodiments, like reference numerals refer to like elements, and like reference numerals refer to like elements in the first embodiment and may be omitted in other embodiments.

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

In the present embodiment, a liquid crystal display device is described as an example, and a display device driven by a thin film transistor and driven by inserting a black screen is not limited to the liquid crystal display device.

As shown in the drawing, the liquid crystal display includes a gray voltage generator 130 and a gate driver 110 connected to the liquid crystal panel 100, the gate driver 110, the data driver 120, and the data driver 120. The gate voltage generator 140, the storage 150, and a controller 150 for controlling the gate voltage generator 140 are connected.

The liquid crystal panel 100 includes a thin film transistor substrate on which a thin film transistor is formed, a color filter substrate facing a thin film transistor substrate and having a color filler formed therein, and a liquid crystal layer injected between both substrates. .

The liquid crystal layer according to the present exemplary embodiment includes a plurality of liquid crystal molecules (not shown) whose orientation varies according to the applied voltage, and the liquid crystal molecules are aligned in an OCB (Optically Compensated Birefringency) mode. That is, the nematic liquid crystal is splay oriented, and a predetermined voltage is applied to switch to the bend orientation, and then the light transmittance is controlled by adjusting the applied voltage. Liquid crystal molecules oriented in the OCB mode has excellent response speed and easy implementation of a wide viewing angle, and thus, research for the application thereof has been actively conducted in recent years. According to the present exemplary embodiment, since the gate voltage is applied to each pixel 30 during the time when one conventional frame is formed, the response speed of the liquid crystal molecules should be very fast. Liquid crystal molecules oriented in the OCB mode can be said to be a preferred liquid crystal mode in order to implement the present invention because the response speed is possible up to 3 ~ 4 ms. If the response speed is excellent, it may include liquid crystal molecules of modes other than OCB mode.

The liquid crystal panel 100 includes a gate line G ₁ to G _n ; 10 extending in a predetermined direction on the thin film transistor substrate, and a data line D ₁ to D _n 20 intersecting and insulated from the gate line 10. A plurality of pixels 30 defined by the gate line 10 and the data line 20 and arranged in a matrix form are formed. A thin film transistor (not shown) is formed at the intersection of the gate line 10 and the data line 20, and the thin film transistor applies various voltages to the pixel 30. In the present exemplary embodiment, the portion defined as the pixel 30 includes a pixel electrode made of indium tin oxide (ITO) or indium zinc oxide (IZO), and the pixel electrode may be a physical transparent electrode forming the pixel 30. it means.

The gate voltage generator 140 generates a gate on voltage Von for turning on the thin film transistor T and a gate off voltage Voff for turning off the thin film transistor T. The gate on voltage and the gate off voltage are sequentially applied to the gate line 10, and the gate voltage is applied to the gate electrode of the thin film transistor T connected to one gate line 10 by one gate on voltage. do.

The gate driver 110 may also be referred to as a scan driver. The gate driver 110 may be connected to the gate line 10 and may include a gate signal formed by a combination of a gate on voltage Von and a gate off voltage Voff from the gate voltage generator 140. Is applied to the gate line 10. The gate driver 110 according to the present exemplary embodiment applies the first gate signal and the second gate signal to each gate line 10 during one frame formation time. Typically, one gate signal is applied to one gate line 10 while one frame is formed, but in the liquid crystal display according to the present embodiment, a first gate signal for a black signal and a data signal corresponding to an image signal Output a second gate signal for. When the pixel 30 connected to the gate line 10 is activated by the first gate signal, the second gate signal is applied to the first gate line 10 again after a predetermined time elapses. The interval at which the second gate signal is applied after the first gate signal is applied may increase or decrease according to the black period where the black voltage formed in the frame is applied. As the black section increases, the interval at which the second gate signal is applied after applying the first gate signal increases, and as the black section decreases, the interval at which the second gate signal is applied after applying the first gate signal decreases.

The gray voltage generator 130 generates a plurality of gray scale voltages related to the luminance of the liquid crystal display.

The data driver 120 may also be referred to as a source driver. The data driver 120 receives a gray voltage from the gray voltage generator 130 and selects a gray voltage under the control of the controller 160 to select the data voltage in the data line 20. Vd) is applied. In addition, the data driver 120 applies a black voltage to the pixel 30 to form a black section at a predetermined portion during one frame. One frame is divided into a black section to which a black voltage is applied and a data section to which a data voltage is applied, and the width of the black section is changed according to the luminance of the frame.

The storage unit 150 stores a data signal corresponding to one frame. When a data signal corresponding to an image signal is externally applied to the controller 160, the controller 160 temporarily stores the data signal in the storage 150 and adjusts the black section and outputs the black signal to the data driver 120.

The controller 160 generates control signals for controlling operations of the gate driver 110, the data driver 120, the gate voltage generator 140, the gray voltage generator 130, and the storage 150. , To each component.

Hereinafter, the operation of the liquid crystal display device 1 will be described in detail.

The controller 160 controls the RGB gray level signals R, G, and B from an external graphic controller, an input control signal for controlling the display thereof, for example, a vertical synchronizing signal, Vsync), a horizontal synchronizing signal (Hsync), a main clock (CLK), and a data enable signal (DE). The controller 160 generates a gate control signal, a data control signal and a voltage selection control signal (VSC) based on the control input signal, and outputs the gate control signal to the gate driver 110 and the gate voltage generator. The data control signal and the data signals R, G, and B are sent to the storage unit 150, and the voltage selection control signal VSC is sent to the gray voltage generator 130.

The gate control signal includes a vertical synchronization start signal (STV) for indicating the start of output of the gate-on pulse (high period of the gate signal), a gate clock signal for controlling the output timing of the gate-on pulse, and And a gate on enable signal (OE) that limits the width of the gate on pulse.

The data control signal includes a horizontal synchronization start signal (STH) indicating the start of input of the gray scale signal and a load signal (load signal, LOAD or TP) for applying a corresponding data voltage Vd to the data line 20. And an inversion control signal RVS and a data clock signal HCLK for inverting the polarity of the data voltage.

First, the gray voltage generator 130 supplies a gray voltage having a voltage value determined according to the voltage selection control signal VSC to the data driver 120.

The controller 160 stores the data signal corresponding to the frame in the storage unit 150 before forming one frame in the liquid crystal panel 100 and counts the data value of the stored data signal. The data value according to the present embodiment is a gradation voltage representing a gradation of an image. Based on the counted data value, the controller 160 adjusts the ratio of the black section for one frame and outputs information on the black section to the data driver 120.

2 illustrates a liquid crystal panel including a black section according to an embodiment. As shown, the gate driver 110 first applies the first gate signal to the gate line 10 according to the gate control signal from the controller 160 to turn on the thin film transistor T connected to the gate line 10. . When the first gate signal is applied, the data driver 120 applies a black voltage to the pixel 30 connected to the turned on thin film transistor.

Then, the controller 160 controls the gate driver 110 to apply the second gate signal to the gate line 10 to form a data section in which the data signal is applied instead of the black section. The data signal is applied to the pixel 30 by the second gate signal. The first gate signal and the second gate signal are applied to the gate line 10 spaced apart in time. That is, when one line of black voltage is applied by the first gate signal, one line of data voltage is applied by the second gate signal to the gate line 10 where the black section ends. For example, assume that the total gate lines 10 are 100. If the black section has a ratio of 30% of one frame, the black voltage is applied from the first gate line to the thirtieth gate line by the first gate signal. After the black voltage is applied to the thirty-first gate line and the second gate signal is applied to the first gate line, the data voltage is applied to the first gate line. Then, a black voltage is applied to the 32nd gate line, a data voltage is applied to the second gate line, and one frame is formed in this way. That is, the black section scans the liquid crystal panel 100 while moving from the upper portion of the liquid crystal panel 100 to the lower portion, that is, the extension direction of the data line 20, during the formation of one frame.

The controller 160 increases the black period when the data value of the data signal forming the frame is small and shows low luminance as a whole, and decreases the black period when the data value is large. FIG. 3 illustrates a liquid crystal panel for explaining the adjustment of the black section. If the frame exhibits a dark gradation as a whole, the ratio of the black section to the data section is formed in a ratio of 1: 1 as shown in (a). As shown in b), the ratio between the data section and the black section is 3: 1, and if the frame is a bright gray, the ratio between the data section and the black section is 5: 1 as shown in (c). As such, the brightness and contrast ratio of the liquid crystal panel 100 are improved by adjusting the ratio of the black section according to the gray level of the frame, that is, the data value. The ratio of the black section is not limited to the above-described one, and the controller 160 may adjust the ratio of the data section with respect to the black section to 1 to 5 and may adjust the ratio to various ratios as necessary. In addition, since the black voltage is applied to each pixel 30 once during one frame formation, the image blur phenomenon may be improved. The controller 160 stores a table in which a ratio of the black section is set to the calculated data value, and the user may be designed to change the black section of the table.

4 is a control flowchart illustrating a control method of a liquid crystal display according to an exemplary embodiment of the present invention. Referring to FIG. 4, the control method of the liquid crystal display is summarized as follows.

First, the controller 160 stores a data signal corresponding to one frame in the storage 150 and counts the data value of the data signal (S10).

Then, the data section and the black section are calculated in one frame according to the counted data value to determine the ratio of the black section to the data section (S20).

Thereafter, the gate driver 110 and the data driver 120 are controlled to apply the first gate signal and the black voltage, and the second gate signal and the data voltage are applied to form one frame (S30).

Although some embodiments of the invention have been shown and described, it will be apparent to those skilled in the art that modifications may be made to the embodiment without departing from the spirit or spirit of the invention. . It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.

As described above, according to the present invention, there is provided a liquid crystal display device and a control method for improving the luminance by adjusting the black period according to the luminance of the image signal.

Claims (9)

A liquid crystal panel comprising a pixel defined by an insulating crossing gate line and a data line and an intersection region of the gate line and the data line; A gate driver configured to apply a first gate signal and a second gate signal to the gate line during one frame forming time; A data driver configured to apply a black signal to the pixel in response to the first gate signal and to apply a data signal to the pixel in response to the second gate signal; The black section to which the black signal is applied and the data section to which the data signal is applied are formed in the liquid crystal panel during one frame formation time, and the gate driver and the data driver are adjusted so that the black section is adjusted according to the luminance of the frame to be currently formed. Liquid crystal display device comprising a control unit for controlling. The method of claim 1, Further comprising a storage unit for storing a data signal corresponding to one frame, And the control unit adjusts the black section for the data section based on the counted data value by counting data values of the data signal stored in the storage unit. The method of claim 2, And the controller decreases the black section as the data value increases. The method of claim 3, And the controller controls the ratio of the data section to the black section to 1-5. The method of claim 1, And the black section scans the liquid crystal panel along an extension direction of the data line for one frame. The method of claim 1, The liquid crystal panel further includes a first substrate, a second substrate, and a liquid crystal layer provided between the first substrate and the second substrate, Wherein the liquid crystal layer comprises liquid crystal molecules oriented in OCB (Optically Compensated Birefringency) mode. Storing a data value corresponding to one frame and counting the data value; Determining a ratio of a black section to which a black signal is applied and a data section to which a data signal is applied according to the counted data values; And forming a frame according to a ratio of the black section and the data section. The method of claim 7, wherein And the black period is reduced as the data value is larger. The method of claim 8, The control method of the liquid crystal display device, characterized in that the ratio of the data section to the black section is adjusted to 1 to 5.

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