KR20040110266A - Liquid crystal display and method for controlling light device of liquid crystal display - Google Patents

Abstract

PURPOSE: An LCD(Liquid Crystal Display) and a method for controlling a light source for the LCD are provided to display full black screen by putting out a backlight when all image data of one frame are for displaying a black screen. CONSTITUTION: An LCD comprises a lighting part(900), a frame memory part, and a controller(600). The lighting part includes a light source and controls brightness of a screen. The frame memory part memorizes image data at a frame unit. The controller generates a control signal according the image data in the frame memory and transmits the control signal to the lighting part. When all of image data of a frame are within the range of the predetermined data, the controller generates a control signal to put out the lamp.

Description

Liquid crystal display device and light source control method for liquid crystal display device {LIQUID CRYSTAL DISPLAY AND METHOD FOR CONTROLLING LIGHT DEVICE OF LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device and a light source control method for a liquid crystal display device, and more particularly, to a light source control method for a liquid crystal display device when the entire display device screen is completely black.

A display device used for a monitor or a TV of a computer includes a cathode ray tube (CRT) and a field emission device (FED) that emit light by themselves, and do not emit light by themselves and require a light source. Liquid crystal displays (LCDs).

A general liquid crystal display device includes two display panels provided with a field generating electrode and a liquid crystal layer having dielectric anisotropy interposed therebetween. A voltage is applied to the field generating electrode to generate an electric field in the liquid crystal layer, and the voltage is changed to adjust the intensity of the electric field, thereby adjusting the transmittance of light passing through the liquid crystal layer to obtain a desired image. In this case, the light may be a separate artificial light source or natural light.

A light source for a liquid crystal display, that is, a backlight device, typically uses several fluorescent lamps as a light source and includes an inverter for driving the lamp. The inverter converts an input DC voltage into an AC voltage and then applies it to a lamp to light the lamp, and adjusts the brightness of the LCD screen by controlling the light source according to the brightness control voltage input from the system.

As described above, adjusting the brightness of the screen of the liquid crystal display is referred to as dimming control. A smart inverter control (SIC) has been developed as a method of dimming the backlight according to the data of the frame memory. In this SIC system, for example, when one frame image data has a large amount of black gradation, dimming control is performed in a direction of lowering the luminance of the screen of the liquid crystal display.

On the other hand, the entire LCD screen is often displayed in black. For example, the entire screen is gradually lightened in black at the beginning of a movie such as a TV program or a movie, or an actor's name or movie title is displayed. It is true.

However, even in this situation, the entire screen of the liquid crystal display should be completely black, but since the backlight is always turned on so that the light from the backlight penetrates the liquid crystal display to some extent, the entire screen of the liquid crystal display may not be completely black, but may be stained. Looks blurred.

Even if the brightness of the liquid crystal display is adjusted using the above-mentioned SIC method, the luminance variation of the liquid crystal display corresponding to 100% dimming control is about ± 10% at medium brightness, so it is still a problem to express the whole screen in black. Becomes

Accordingly, an aspect of the present invention is to provide a liquid crystal display and a method of expressing the entire screen of a liquid crystal display in full black by controlling the backlight for the 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 exploded perspective view of a liquid crystal display according to an exemplary embodiment of the present invention.

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

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

According to an exemplary embodiment of the present invention, a liquid crystal display includes a light source for irradiating light and adjusts a brightness of a screen, a frame memory for storing image data in units of frames, and the frame memory. A control unit for generating a control signal according to the image data stored in the controller and transmitting the control signal to the lighting unit

The control signal is generated to turn off the light source if the image data of one frame is within a predetermined data range.

Preferably, the predetermined data range is a data range that displays black.

The frame memory may be provided in the controller.

The apparatus may further include a signal controller configured to process the image data to be displayed on the screen, and the controller may receive information about the image data from the outside and transmit the received information to the signal controller.

A method of controlling a light source for a liquid crystal display according to another exemplary embodiment of the present invention may include storing image data in a frame memory, comparing image data of one frame stored in the frame memory with a predetermined data range, and Turning off the light source if the entire frame image data is within the predetermined data range, and turning on the light source if at least one of the frame image data is outside the predetermined data range.

Preferably, the predetermined data range is a data range that displays black.

DETAILED DESCRIPTION Embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention.

In the drawings, the thickness of layers, films, panels, regions, etc., are exaggerated for clarity. Like parts are designated by like reference numerals throughout the specification. When a portion of a layer, film, region, plate, etc. is said to be "on top" of another part, this includes not only when the other part is "right on" but also another part in the middle. On the contrary, when a part is "just above" another part, there is no other part in the middle.

A liquid crystal display and a light source control method for a liquid crystal display according to an exemplary embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of a liquid crystal display according to an embodiment of the present invention, FIG. 2 is an exploded perspective view of a liquid crystal display according to an embodiment of the present invention, and FIG. 3 is a liquid crystal according to an embodiment of the present invention. It is an equivalent circuit diagram of one pixel of a display device.

As shown in FIG. 1, a liquid crystal display according to an exemplary embodiment of the present invention includes a liquid crystal panel assembly 300, a gate driver 400, a data driver 500, and a data driver 500 connected thereto. The gray voltage generator 800 connected to the 500, the lighting unit 900 for irradiating light to the liquid crystal panel assembly 300, a signal controller 600 for controlling them, and various signals to the signal controller 600. It includes a system control unit 40 for transmitting.

Meanwhile, as shown in FIG. 2, when the LCD according to the exemplary embodiment of the present invention is structurally shown, the liquid crystal module 350 and the liquid crystal module 350 including the display unit 330 and the backlight unit 340 are shown. It includes a front and rear case (361, 362) for receiving.

The display unit 330 includes a liquid crystal panel assembly 300, a gate flexible printed circuit (FPC) substrate 410 and a data FPC substrate 510 attached thereto, and a gate PCB attached to the corresponding FPC substrates 410 and 510. printed circuit board 450 and data PCB 550.

The liquid crystal panel assembly 300 includes a lower panel 100 and an upper panel 200 and a liquid crystal layer 3 interposed therebetween, as shown in FIGS. 2 and 3. As shown in FIG. _1, the display circuit includes a plurality of display signal lines G ₁ -G _n , D ₁ -D _m , and a plurality of pixels connected thereto and arranged in a substantially matrix form.

The display signal lines G ₁ -G _n and D ₁ -D _m are a plurality of gate lines G ₁ -G _n for transmitting a gate signal (also called a “scan signal”) and a data signal line or data for transmitting a data signal. Line D ₁ -D _m . The gate lines G ₁ -G _n extend substantially in the row direction and are substantially parallel to each other, and the data lines D ₁ -D _m extend substantially in the column direction and are substantially parallel to each other.

Each pixel includes a switching element Q connected to a display signal line G ₁ -G _n , D ₁ -D _m , and a liquid crystal capacitor C _LC and a storage capacitor C _ST connected thereto. It includes. The holding capacitor C _ST can be omitted as necessary.

The switching element Q is provided on the lower panel 100, and the control terminal and the input terminal are connected to the gate line G ₁ -G _n and the data line D ₁ -D _m, respectively. The output terminal is connected to the liquid crystal capacitor C _LC and the storage capacitor C _ST .

The liquid crystal capacitor C _LC has two terminals, the pixel electrode 190 of the lower panel 100 and the common electrode 270 of the upper panel 200, and the liquid crystal layer 3 between the two electrodes 190 and 270. It functions as a dielectric. The pixel electrode 190 is connected to the switching element Q, and the common electrode 270 is formed on the front surface of the upper panel 200 and receives a common voltage V _com . Unlike in FIG. 2, the common electrode 270 may be provided in the lower panel 100. In this case, both electrodes 190 and 270 may be linear or rod-shaped.

The storage capacitor C _ST is formed by overlapping a separate signal line (not shown) and the pixel electrode 190 provided on the lower panel 100, and a predetermined voltage such as a common voltage V _com is applied to the separate signal line. Is approved. However, the storage capacitor C _ST may be formed such that the pixel electrode 190 overlaps the front end gate line directly above the insulator.

Meanwhile, in order to implement color display, each pixel must display color, which is possible by providing a red, green, or blue color filter 230 in a region corresponding to the pixel electrode 190. In FIG. 2, the color filter 230 is formed in a corresponding region of the upper panel 200. Alternatively, the color filter 230 may be formed above or below the pixel electrode 190 of the lower panel 100.

In FIG. 2, the backlight unit 340 is positioned between the plurality of lamps 341 and the assembly 300 and the lamp 341, which are mounted under the liquid crystal panel assembly 300, and collects light from the lamps 341. A light guide plate 342 and a plurality of optical sheets 343, which guide and diffuse to 300, and a reflector plate 344 positioned below the lamp 341 and reflecting light from the lamp 341 toward the assembly 300. It includes.

Referring to FIG. 1, the lighting unit 900 blinks the lamp unit 910 and the lamp unit 910 corresponding to the lamp 341 in FIG. 2, and controls the blinking time to control the brightness of the screen (inverter) 920. ). The inverter 920 may be provided in an inverter PCB (not shown) mounted separately or may be provided in the gate PCB 450 or the data PCB 550.

The gray voltage generator 800 generates two sets of gray voltages related to the transmittance of the pixel. One of the two sets has a positive value for the common voltage (V _com ) and the other set has a negative value.

The gate driver 400 is connected to the gate lines G ₁ -G _n of the liquid crystal panel assembly 300 to receive a gate signal formed by a combination of a gate on voltage V _on and a gate off voltage V _off from the outside. It is applied to the gate lines G ₁ -G _n and usually consists of a plurality of integrated circuits.

The data driver 500 is connected to the data lines D ₁ -Dm of the liquid crystal panel assembly 300 to select the gray voltage from the gray voltage generator 800 and apply the gray voltage to the pixel as a data signal. Is made of.

The signal controller 600 generates control signals for controlling operations of the gate driver 400 and the data driver 500, and provides the corresponding control signals to the gate driver 400 and the data driver 500.

The system controller 40 receives information about image data from an external device (not shown), generates RGB image signals R, G, and B, and transmits a plurality of control signals to the signal controller 600. Among the plurality of control signals, a control signal related to lighting, that is, a brightness control signal V _dim , a horizontal sync signal H _sync , and a lamp lighting command signal EN may be directly transmitted to the lighting unit 900, or may be transmitted to a signal controller 600 may be transmitted. The system control unit 40 may be a graphic controller of a computer or may be a system controller of a TV board.

The signal controller 600 or the system controller 40 includes a frame memory 50 (not shown). The frame memory 50 is a memory that stores image data R, G, and B in units of frames.

Meanwhile, a polarizer (not shown) for polarizing light is attached to an outer surface of at least one of the two display panels 100 and 200 of the liquid crystal panel assembly 300.

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

The signal controller 600 inputs an input control signal for controlling the RGB image signals R, G, and B and a display thereof from the system controller 40, for example, a vertical sync signal V _sync and a horizontal sync signal H _sync . , A main clock MCLK, a data enable signal DE, and the like are provided. The signal controller 600 properly processes the image signals R, G, and B according to the operating conditions of the liquid crystal panel assembly 300 based on the input image signals R, G, and B and the input control signal, and controls the gate control signal. After generating the CONT1 and the data control signal CONT2 and the like, the gate control signal CONT1 is sent to the gate driver 400 and the data control signal CONT2 and the processed image signals R ', G', and B 'are processed. ) Is sent to the data driver 500.

The gate control signal CONT1 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 CPV for controlling the output timing of the gate-on pulse, and a gate-on pulse. And an output enable signal OE that defines the width of the signal.

The data control signal CONT2 is a load for applying a corresponding data voltage to the horizontal synchronization start signal STH indicating the start of input of the image data R ', G', and B 'and the data lines D ₁ -D _m . Signal LOAD, inverted signal RVS and data that inverts the polarity of the data voltage with respect to common voltage V _com (hereinafter referred to as " polarity of data voltage " by reducing " polarity of data voltage with respect to common voltage "). Clock signal HCLK and the like.

The data driver 500 sequentially receives image data R ′, G ′, and B ′ corresponding to one row of pixels according to the data control signal CONT2 from the signal controller 600, and generates a gray voltage generator ( 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' among the gray voltages from the 800.

The gate driver 400 applies the gate-on voltage V _on to the gate lines G ₁ -G _n in response to the gate control signal CONT1 from the signal controller 600, thereby applying the gate lines G ₁ -G _n. Turn on the switching element (Q) connected to.

The gate-on voltage V _on is applied to one gate line G ₁ -G _n so that a row of switching elements Q connected thereto is turned on (this period is "1H" or "1 horizontal period). (horizontal period) "and the same as one period of the horizontal sync signal (H _sync ), the data enable signal (DE), and the gate clock (CPV)], and the data driver 500 stores each data voltage as a corresponding data line ( D ₁ -D _m ). The data voltage supplied to the data lines D ₁ -D _m is applied to the corresponding pixel through the turned-on switching element Q.

In this manner, the gate-on voltages V _{on are} sequentially applied to all the gate lines G ₁ -G _n during one frame to apply data voltages to all the pixels. At the end of one frame, the next frame starts and the state of the inversion signal RVS applied to the data driver 500 is controlled so that the polarity of the data voltage applied to each pixel is opposite to that of the previous frame ("frame inversion). "). In this case, the polarity of the data voltage flowing through one data line may be changed (“line inversion”) within one frame or the polarity of the data voltage applied to one pixel row may be different according to the characteristics of the inversion signal RVS ( "Dot reversal").

On the other hand, the inverter 920 uses the brightness control signal V _dim from the system control unit 40 or the signal control unit 600, the horizontal synchronizing signal H _sync , and the lamp lighting command signal EN. ).

The inverter 920 turns on or off the backlight according to the lamp lighting command signal EN transmitted from the system controller 40 or the signal controller 600.

Next, a light source control method for a liquid crystal display according to an exemplary embodiment of the present invention will be described in detail with reference to FIG. 4.

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

First, video data is stored in the frame memory 50 (S10). That is, the system control unit 40 stores the information regarding the image data input from the external device in the frame memory 50. In the present embodiment, the control operation is described in that the frame memory 50 is provided in the system controller 40. However, as described above, the signal controller 600 includes the frame memory 50 to perform the control operation of the present embodiment. It can also be done.

The system controller 40 compares the entirety of one frame of image data (hereinafter referred to as "frame image data") stored in the frame memory 50 with data values in a predetermined range (S20). The predetermined range is a data range displayed in black on the screen of the liquid crystal display.

If the entire frame image data is within a predetermined data range, the system controller 40 transmits a control signal, that is, a lamp lighting command signal EN, to the lighting unit 900 so that the backlight is turned off. The inverter 920 of the lighting unit 900 turns off the backlight according to the lamp lighting command signal EN transmitted from the system control unit 40 (S30).

Similarly, if at least one of the frame image data is outside the predetermined data range, the system controller 40 transmits a lamp lighting command signal EN to the lighting unit so that the backlight is turned on. The inverter 920 of the lighting unit turns on the backlight according to the lamp lighting command signal EN transmitted from the system controller (S40). If at least one of the frame image data is out of the predetermined data range, the screen is no longer black and the backlight is turned on.

Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the present invention, when the entire frame image data is black data, the entire screen of the liquid crystal display device can be represented by completely black by turning off the backlight for the liquid crystal display device.

Claims (6)

It includes a light source for irradiating light, the lighting unit for adjusting the brightness of the screen, A frame memory for storing image data in frame units, and A control unit for generating a control signal according to the image data stored in the frame memory and transmitting the control signal to the lighting unit Including; The control signal is generated to turn off the light source when the entire image data of one frame is within a predetermined data range. Liquid crystal display. In claim 1, And the predetermined data range is a data range displaying black. The method of claim 1 or 2, The frame memory is provided in the control unit. The method of claim 1 or 2, And a signal controller configured to process the image data to be displayed on the screen. The controller receives information about the image data from the outside and transmits it to the signal controller. Liquid crystal display. As a method of controlling the light source for liquid crystal display devices, Storing the image data in the frame memory, Comparing image data of one frame stored in the frame memory with a predetermined data range, Turning off the light source if the entire frame image data is within the predetermined data range, and Lighting the light source if at least one of the frame image data is outside the predetermined data range Light source control method for a liquid crystal display comprising a. In claim 5, And said predetermined data range is a data range for displaying black.