KR20080055415A - Backlight and display having the same - Google Patents

Abstract

A back light and a display device having the same are provided to minimize the flicker phenomenon and to extend the lifetime of a light source. A light source unit(300) has at least one light source group. A light source driving block(200) controls the current applied to the plural light source groups. A light source control block(100) controls the light source driving block according to the motion degree of an image by image areas. The light source control block controls the light source driving block so that the intensity of current and duty ratio are generated differently from the light source driving block. The light source control block includes the first dimming control member for controlling the intensity of current generated from the light source driving block. The second dimming control member controls the duty ratio generated from the light source driving block.

Description

BACKLIGHT AND DISPLAY HAVING THE SAME

1 is a block diagram illustrating a backlight according to an embodiment of the present invention.

2 is a block diagram showing a light source control block according to an embodiment of the present invention.

3 is a plan view illustrating a display panel to which a backlight is applied according to an exemplary embodiment.

4 is a graph showing the relationship between the degree of image movement and the intensity of current in the backlight according to an embodiment of the present invention.

5 is a graph showing the relationship between the degree of image movement and the duty ratio of the current in the backlight according to an embodiment of the present invention.

6 is a graph showing the current applied to the light source unit in the backlight according to the embodiment of the present invention.

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

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

100: light source control block 200, 610: light source drive block

300, 620: light source unit 400: liquid crystal display panel

510: gate driver 520: data driver

530: driving voltage generator 540: signal controller

The present invention relates to a backlight and a display device having the same. More particularly, the present invention relates to a backlight and a display device having the same.

In general, a liquid crystal display includes a liquid crystal display panel including an upper substrate on which a black matrix, a color filter, and a common electrode are formed, a lower substrate on which a thin film transistor and a pixel electrode are formed, and a liquid crystal layer filled between two substrates. And a polarizing plate attached to both sides of the liquid crystal display panel. In addition, since the liquid crystal display panel does not emit light by itself, a backlight for providing light is disposed on the rear surface of the liquid crystal display panel so as to visually recognize the display contents. In addition, a driving circuit for controlling the operation of the liquid crystal display panel and the backlight is required.

Such a liquid crystal display exhibits a motion blur phenomenon in which a screen is blurry when a moving image is generated due to a slow response characteristic of a liquid crystal and a holding characteristic of the liquid crystal. The problem is that the light sources of the backlight are sequentially turned on along the scanning direction (or scanning direction) of the image, and the light sources are turned on only for half of one frame, that is, the light source sequential blinking lighting method. I can solve it. At this time, since the lighting time of the light source is reduced and the average brightness is reduced, it is common to increase the intensity of the current applied to each light source by more than two times.

However, the light source sequential blinking lighting method according to the prior art has a problem that the lifespan of the light source is rapidly shortened because the intensity of the current applied to the light source should be increased by more than twice. In addition, since the light sources flicker one or more times during one frame period, there is a problem in that an image flickers, that is, flicker.

The present invention is derived to solve the above problems, and by selectively sequentially blink and drive only the light source of the area of concern for screen drag phenomenon according to the degree of image movement, the life of the light source is maximized while minimizing the flicker phenomenon. An object of the present invention is to provide a backlight that can be extended and a display device having the same.

The backlight according to the present invention for achieving the above object is a light source unit having at least one light source group, a light source drive block for adjusting the current applied to the plurality of light source groups and the degree of movement of the image for each image area. And a light source control block for controlling the light source driving block.

The light source control block preferably controls the intensity and duty ratio of the current generated by the light source driving block to be differential.

The light source control block includes a first dimming controller for controlling the intensity of the current generated by the light source driving block and a second dimming controller for controlling the duty ratio of the current generated by the light source driving block. Herein, the first dimming controller controls the current intensity to increase as the degree of movement of the image for each image region increases, and the current intensity is preferably controlled within a range of 100% to 200% compared to the continuous lighting method. The second dimming control unit controls the duty ratio of the current to decrease as the degree of movement of the image for each image region increases, and the duty ratio of the current is controlled within a range of 50% to 100% compared to the continuous lighting method. .

Preferably, the first dimming control unit includes a motion analysis unit for analyzing the degree of movement of the image for each image area and designating the current intensity based thereon, and a first register group in which data regarding the intensity of the current for each image area is stored. Do.

The second dimming control unit receives information on the degree of motion of the image for each image area from the first dimming control unit and specifies a duty ratio adjusting unit for designating a duty ratio of the current based on the information, and data about the duty ratio of the current for each image area. Preferably includes a second register group in which is stored.

A display device according to the present invention for achieving the above object includes a display panel for displaying an image and a backlight for providing light to the display panel, the backlight unit comprises a light source unit having at least one light source group; And a light source control block for controlling the current applied to the plurality of light source groups, and a light source control block for controlling the light source driving block according to the degree of movement of the image for each image region.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to 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 embodiments are intended to complete the disclosure of the present invention, and to those skilled in the art the scope of the invention. It is provided for complete information. Like reference numerals in the drawings refer to like elements.

1 is a block diagram showing a backlight according to an embodiment of the present invention, Figure 2 is a block diagram showing a light source control block according to an embodiment of the present invention.

1 and 2, the backlight includes a light source unit 300 including at least one light source group 310, and a light source driving block 200 for adjusting current applied to the plurality of light source groups 310. And a light source control block 100 for controlling the intensity and duty ratio of the current generated by the light source driving block 200 to be differentiated according to the degree of movement of the image for each image region.

The light source unit 300 provides light for image display on the rear surface of the non-light emitting display device so that the user can visually recognize the display contents of the non-light emitting display device. The light source unit 300 includes at least one light source, and a plurality of light sources electrically connected to each other form a group of light source 310. For example, if eight light sources arranged in a line are used and two adjacent light sources are electrically connected, a total of four light source groups are formed as a whole. On the other hand, the light source is a cold cathode fluorescent lamp comprising a glass tube filled with a discharge gas in the interior space, a fluorescent material is applied to the inner surface, and a pair of electrodes formed on both sides of the glass tube; ) Is effective. Here, the discharge gas for generating primary light may include a rare gas such as argon, neon, xenon, or a mixed gas containing argon, neon, xenon, and the like and a predetermined amount of mercury, and the fluorescent material for generating secondary light may include white light. The light emitting device may include phosphors having three wavelength bands of red, green, and blue to emit light. In the present embodiment, a line light source such as a cold cathode fluorescent lamp is used as the light source. However, the present invention is not limited thereto, and a point light source such as a light emitting diode may be used.

The light source driving block 200 includes a plurality of light source driving units 210 for applying a current to the plurality of light source groups 310. The light source driving unit 210 may be changed in accordance with the type of the light source. In the case of using a cold cathode fluorescent lamp as a light source as in the present embodiment, an inverter circuit (not shown) for converting DC into AC and A transformer (not shown) for boosting alternating current suitably for driving a cold cathode fluorescent lamp and a pulse width modulation circuit (not shown) for pulse width modulating the boosted alternating current according to a predetermined duty ratio may be included. The light source driving unit 210 may be provided in the same number as the total number of the light source group 310 to drive each light source group 310 individually.

The light source control block 100 may include the first dimming controller 110 for controlling the intensity of the current generated by the light source driving block 200 according to the degree of movement of the image for each image area and the degree of movement of the image for each image area. The second dimming control unit 120 controls the duty ratio of the current generated by the light source driving block 200. Here, the first dimming controller 110 analyzes the degree of movement of the image for each image region and stores the data about the intensity of the current and the image region for each of the image analysis regions. The first dimming control unit 120 includes a first register group 112, and the second dimming control unit 120 receives information on the degree of motion of the image for each image area from the motion analysis unit 111 to determine the duty ratio of the current based on the information. A duty ratio adjusting unit 121 and a second register group 122 in which data relating to a duty ratio of current for each image region is stored.

Referring to the operation of the backlight according to the present embodiment having such a configuration in more detail as follows.

In general, the display panel may be divided into a plurality of image areas. For example, as shown in FIG. 3, the display panel may be divided into four image regions (first to fourth image regions) having the same area divided in the horizontal direction. 3 is a plan view illustrating the display panel to which the backlight is applied according to the present exemplary embodiment, in which the first image region and the fourth image region are regions of no movement, such as a still image, and the second image region and the third image region are It is an area where there is motion like a moving picture.

Also, in general, each light source group of the backlight may be controlled by a continuous lighting method or a blinking lighting method. In the continuous lighting method, the extinction time of the light source is maintained at approximately 100% in one frame. On the other hand, in the blinking lighting method, instead of reducing the lighting time of the light source to about 50% in one frame, the intensity of the light source is increased to about 200% to compensate for the luminance. Hereinafter, the intensity of the current, the duty ratio of the current, the lighting time of the light source, and the intensity of the light source are expressed in the blinking lighting method as compared to the continuous lighting method.

First, the motion analysis unit 111 receives image signals R, G, and B of one frame (one screen) from the outside and analyzes and quantifies the motion of the image for each image area. For example, when the degree of motion of the image is divided into six stages, the portion of the image which does not move as in the first image area is '0', and the portion of the image which moves much in the area like the area 3 is '5'. . In addition, the motion analysis unit 111 generates data regarding the intensity of the current to be applied to each light source group 310 in consideration of the degree of motion of the image for each image region. In this case, the generated intensity data is data to adjust the intensity of the current as the degree of movement of the image increases as shown in Figure 4, the intensity of the current is adjusted within the range of 100% to 200% compared to the general desirable. The intensity data of the current is stored in the first register group 112 and then output to the light source driving block 200 as first dimming signals Dim11 to Dim1n. 4 is a graph showing the relationship between the degree of image movement and the intensity of current in the backlight according to the embodiment of the present invention.

The duty ratio controller 121 receives the luminance selection signal from an external user or system. The luminance selection signal is a signal that designates a basic duty ratio of a current to be applied to the entire light source group to achieve a target luminance. Accordingly, the pulse width of the current generated by the light source driving block 200 is changed to thereby change the light source unit 300. The overall brightness of is adjusted to the desired goal. The basic duty ratio of the current can be changed from time to time, and the changed value is stored in the memory of the system and becomes the default value for subsequent driving. In addition, the duty ratio adjusting unit 121 considers the basic duty ratio of the current specified by the luminance selection signal in consideration of the degree of motion of the image for each image area provided by the motion analysis unit 111, and the duty ratio of the current to be applied to the individual light source groups. Create new data for. At this time, the duty ratio data of the generated current is data to adjust the duty ratio of the current as the degree of motion of the image increases as shown in Figure 5, the duty ratio of the current is within the range of 50% to 100% compared to the general It is preferred to be adjusted. The duty ratio data of the current is stored in the second register group 122 and then output to the light source driving block 200 as the second dimming signals Dim21 to Dim2n. 5 is a graph showing the relationship between the degree of image movement and the duty ratio of current in the backlight according to the embodiment of the present invention.

The light source driving block 200 receives a predetermined power from the outside to generate a current suitable for driving the light source unit 200. That is, the predetermined input power is converted into alternating current through the inverter, boosted through the transformer, and pulse width modulated through the pulse width modulator to generate a current suitable for driving the light source unit 200. In this case, since the current is controlled according to the first and second dimming signals Dim11 to Dim1n and Dim21 to Dim2n, respectively, the intensity and the duty ratio vary according to the degree of image movement for each image area.

The current output from the light source driving block 200 is sequentially applied to each light source group 310 of the light source unit 300. In this case, since the intensity and duty ratio of the current applied to each light source group 310 varies depending on the degree of image movement for each image region, the output luminance and the lighting time vary according to each light source group 310. The following description is made with reference to 6. 6 is a graph showing the current applied to the light source unit in the backlight according to the embodiment of the present invention, and the dotted line shows the current applied to the light source unit in the general sequential blinking lighting method, and the solid line is shown in the present embodiment. The current applied to the light source unit in the sequential blinking lighting method is shown.

Referring to FIG. 6, a current having a intensity of 100% and a duty ratio of 100% is applied to the first light source group dimming the first image area having the degree of motion of image '0', and the degree of motion of the image. A current having a intensity of 200% and a duty ratio of 50% is applied to the third light source group dimming the third image area having a value of '5'. Here, the intensity of the current is 200% compared to the general means that the intensity of twice the current applied in the general continuous lighting method. In addition, the duty ratio of the current is 100% means that the current is applied to the entire section of one frame, and the duty ratio of the current is 50% means that the current is applied only to the half section of one frame. As a result, the light source group for illuminating an area with little motion of the image like the first image area is driven in a continuous lighting method, and the light source group for illuminating an area with high motion of the image like the third image area is a blinking lighting method. Driven by.

As described above, the backlight according to the embodiment of the present invention does not always drive all light sources by blinking light, but selectively drives the blinking light selectively only for the light sources in areas where screen drag is a concern depending on the degree of image movement. . Therefore, the intensity of the average current applied to the light source can be reduced, thereby extending the life of the light source as much as possible, and minimizing the flicker phenomenon generated during the blinking lighting operation. That is, it is possible to extend the life of the light source while minimizing the flicker phenomenon, and at the same time, it is possible to reduce power consumption and eliminate screen drag.

Meanwhile, the backlight according to the exemplary embodiment of the present invention may be used in various display devices. As an example of such a possibility, a liquid crystal display device having the backlight will be described. In this case, a description overlapping with the above-described embodiment will be omitted or briefly described.

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

Referring to FIG. 7, the liquid crystal display includes a liquid crystal display panel 400, a gate driver 510, a data driver 520, a driving voltage generator 530, a backlight 610, 620, 600, and a signal controller for controlling them. 540.

The liquid crystal display panel 400 includes a plurality of gate lines G1 to Gm extending in one direction and a plurality of data lines D1 to Dn extending in the other direction crossing the gate lines G1 to Gm and a plurality of gate lines G1 to Dn provided in the intersection regions thereof. It includes the unit pixel of. A thin film transistor Q, a liquid crystal capacitor Clc, a liquid crystal capacitor Clc, and the like are formed in the unit pixel.

Here, the gate terminal of the thin film transistor Q is connected to the gate lines G1 to Gm, the source terminal is connected to the data lines D1 to Dn, and the drain terminal is a pixel electrode (not shown) of the liquid crystal capacitor Clc. Is connected). The thin film transistor Q operates according to the gate turn-on voltage Von applied to the gate lines G1 to Gm to supply the data signals of the data lines D1 to Dn to the pixel electrodes of the liquid crystal capacitor Clc. In addition, the liquid crystal capacitor Clc includes a liquid crystal layer (not shown) positioned as a dielectric between an opposing pixel electrode and a common electrode (not shown). The liquid crystal capacitor Clc is charged with a data signal when the thin film transistor Q is turned on. It serves to control the molecular arrangement of the layers. In addition, the storage capacitor Cst is formed by forming an insulating layer (not shown) with a dielectric between the opposite pixel electrode and the storage electrode, and when the next data signal is charged with the data signal charged in the liquid crystal capacitor Clc. It plays a role of maintaining stable until. Of course, the sustain capacitor Cst, which plays an auxiliary role of the liquid crystal capacitor Clc, may be omitted. On the other hand, it is preferable that each unit pixel of the present embodiment uniquely displays one of three primary colors (red, green, blue). To this end, a color filter is provided in each unit pixel, and a black matrix is provided between each unit pixel region to prevent light leakage.

The signal controller 540 receives an input image signal and an input control signal from an external graphic controller (not shown). For example, an input image signal including the input image data R, G, and B, and a vertical synchronization signal Vsync, a horizontal synchronization signal Hsync, a main clock MCLK, and a data enable signal DE are included. Is provided with an input control signal. In addition, the signal controller 540 generates an internal image signal, that is, internal image data R ', G', and B 'based on the input image signal, and based on the input control signal, A gate control signal including a vertical synchronization start signal STV and a gate clock signal CPV for controlling the operation of the gate driver 510 is generated, and a horizontal synchronization start signal STH for controlling the operation of the data driver 520. And a data latch signal including the data latch signal DL.

The driving voltage generator 530 generates and outputs various driving voltages for driving the liquid crystal display panel 400 using an external power source input from an external power supply device (not shown). For example, a gate turn-on voltage Von for turning on the switching element Q, a gate-off voltage Voff for turning off the switching element Q, and the like are generated and output to the gate driver 510, and the reference voltage is generated. (AVDD) is generated and output to the data driver 520, and a common voltage Vcom is generated and applied to the liquid crystal capacitor Clc and the sustain capacitor Cst.

The gate driver 510 starts operation according to the vertical synchronization start signal STV, and the gate turn-on voltage Von and the gate-off voltage Voff input from the driving voltage generator 530 according to the gate clock signal CPV. ) And a gate signal of an analog type is sequentially output to the plurality of gate lines G1 to Gm formed in the liquid crystal display panel 400.

The data driver 520 converts the input digital pixel data R ', G', B 'into analog data signals DS1 to DSn based on the reference voltage AVDD and latches the data. The data is output to the plurality of data lines D1 to Dn formed in the liquid crystal display panel 400 according to the signal DL.

The backlight 600 includes a light source unit 620 including at least one light source group, a light source driving block 610 for adjusting a current applied to the plurality of light source groups, and a degree of movement of an image for each image region. And a light source control block (not shown) for controlling the intensity and duty ratio of the current generated by the driving block 610 to be differential. That is, it is preferable to use the backlight according to the above-described embodiment. In this embodiment, the light source control block is manufactured integrally with the signal controller 540. However, the present invention is not limited thereto, and the light source control block may be manufactured separately. The backlight 600 provides an incident light source for displaying an image on the liquid crystal display panel 400. That is, the light generated by the light source unit 620 and incident on the rear surface of the light is transmitted through the liquid crystal display panel 400, and the transmittance is changed, and color is emitted to the front to implement a color image.

As mentioned above, although this invention was demonstrated with reference to the above-mentioned Example and an accompanying drawing, this invention is not limited to this, It is limited by the following claims. Therefore, it will be apparent to those skilled in the art that the present invention may be variously modified and modified without departing from the technical spirit of the following claims.

As described above, the present invention selectively drives sequential blinking lighting only for the light source in the region where the screen drag phenomenon is concerned depending on the degree of movement of the image. Therefore, the intensity of the average current applied to the light source can be reduced, thereby extending the life of the light source as much as possible, and minimizing the flicker phenomenon generated during the blinking lighting operation. That is, it is possible to extend the life of the light source while minimizing the flicker phenomenon, and at the same time can reduce the power consumption and drag phenomenon.

Claims (16)

A light source unit having at least one light source group, A light source driving block controlling a current applied to the plurality of light source groups; And a light source control block for controlling the light source driving block according to the degree of movement of the image for each image region. The method according to claim 1, The light source control block, And a backlight for controlling the intensity and duty ratio of the current generated by the light source driving block to be differential. The method according to claim 2, The light source control block, A first dimming controller which controls the intensity of the current generated by the light source driving block; And a second dimming controller configured to control a duty ratio of the current generated by the light source driving block. The method according to claim 3, The first dimming control unit controls the current intensity to increase as the degree of movement of the image for each image region increases. The method according to claim 4, The intensity of the current is controlled in the range of 100% to 200% compared to the continuous lighting method. The method according to claim 3, And the second dimming controller controls the duty ratio of the current to decrease as the degree of movement of the image for each image region increases. The method according to claim 6, The duty ratio of the current is the backlight is controlled within the range of 50% to 100% compared to the continuous lighting method. The method according to claim 3, The first dimming control unit, A motion analysis unit for analyzing the degree of movement of the image for each image area and designating a current intensity based on the image; And a first register group in which data relating to the intensity of current for each image area is stored. The method according to claim 3, The second dimming control unit, A duty ratio adjuster configured to receive information on the degree of motion of each image region from the first dimming controller and designate a duty ratio of a current based on the information; And a second register group in which data relating to a duty ratio of the current for each image area is stored. Display panel for displaying images and A backlight for providing light to the display panel; The backlight is, A light source unit having at least one light source group, A light source driving block controlling a current applied to the plurality of light source groups; And a light source control block for controlling the light source driving block according to the degree of movement of the image for each image region. The method according to claim 10, The light source control block, And a display panel for controlling the intensity and duty ratio of the current generated by the light source driving block to be differential. The method according to claim 11, The light source control block, A first dimming controller which controls the intensity of the current generated by the light source driving block; And a second dimming controller configured to control a duty ratio of a current generated by the light source driving block. The method according to claim 12, And the first dimming controller controls the current intensity to increase as the degree of movement of the image for each image region increases. The method according to claim 13, The intensity of the current is controlled within the range of 100% to 200% compared to the continuous lighting method. The method according to claim 12, And the second dimming controller controls the duty ratio of the current to decrease as the degree of movement of the image for each image region increases. The method according to claim 15, The duty ratio of the current is adjusted within the range of 50% to 100% compared to the continuous lighting method.

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