KR20070100040A - Lcd backlight unit using leds - Google Patents

Abstract

A back light unit for a liquid crystal display apparatus using LED(Light Emitting Diode) is provided to implement local dimming by adjusting only luminance of white color LED, thereby implementing a simple driving circuit for driving red, green, and blue LED and reducing manufacturing cost of the back light unit. A back light unit for a liquid crystal display apparatus using LED(Light Emitting Diode) comprises the following parts: a plurality of LED sets(23) for projecting light to each division area; a plurality of white color LED driving units(27) for driving a white color LED to each division area; a red, green, and blue LED driving unit(24,25,26) for maintaining regular luminance of the red, green, and blue LED and driving the red, green, and blue LED; and a control unit(28) for controlling an operation of the white color LED driving unit, red, green, and blue LED driving unit.

Description

LCD backlight unit using LCD {LCD BACKLIGHT UNIT USING LEDs}

1 is a block diagram of a liquid crystal display for implementing local dimming according to the prior art.

2 is a block diagram of a liquid crystal display for implementing local dimming according to the present invention.

3 to 6 are layout views showing the arrangement of LEDs according to various embodiments of the present invention.

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

21 liquid crystal panel 22 backlight substrate

24: red LED driver 25: green LED driver

26: blue LED driver 27: white LED driver

28: signal processor 29: control unit

23, 31, 32, 41, 51, 52, 61: LED set

The present invention relates to a backlight unit for a liquid crystal display device using LED, and more particularly, further comprising a white LED in a backlight unit of a liquid crystal display device consisting of red, green, and blue LEDs. The present invention relates to a backlight unit for a liquid crystal display device using an LED that can implement local dimming of the liquid crystal display device by adjusting the divided regions.

Cold Cathode Fluorescent Lamps (CCFLs), which are used as backlight sources for conventional LCDs, use mercury gas, which can cause environmental pollution, slow response, and low color reproducibility. In addition, it has disadvantages that are not suitable for light and thin reduction of the liquid crystal panel. In contrast, light emitting diodes (LEDs) are environmentally friendly and have fast response times of several nanoseconds, which are effective for video signal streams and enable impulsive driving. In addition, the color reproducibility is 100% or more, and the brightness, color temperature, and the like can be arbitrarily changed by adjusting the light amounts of the red, green, and blue LEDs. In addition, the LED light source is suitable for light and short reduction of the liquid crystal panel. Due to these advantages, the LED has been actively adopted as a light source for a backlight such as a liquid crystal display device.

In general, a backlight unit employing an LED may be classified into an edge type backlight unit and a direct type backlight unit according to a position of a light source. The edge type backlight unit adopts a method in which a long bar-shaped light source is positioned at the side of the light guide plate to irradiate light to the front of the liquid crystal panel through the light guide plate. The direct type backlight unit adopts a method of irradiating light directly to the front surface of the liquid crystal panel from a surface light source that is located under the liquid crystal panel and has an area substantially the same as that of the LCD panel.

On the other hand, in order to more vividly display the image displayed on the liquid crystal display device, the liquid crystal panel of the liquid crystal display device is divided into a plurality of areas, and the luminance of the backlight in each divided area unit according to the gray level value of each divided area. The values can be adjusted individually. In this way, dividing the liquid crystal panel of the liquid crystal display into divided regions and adjusting the backlight luminance value of each divided region is referred to as local dimming. For example, a more vibrant and distinct explosion scene can be realized through local dimming to increase the luminance of the backlight of an area corresponding to the explosion image in an image such as an explosion scene.

1 is a block diagram of a liquid crystal display for implementing local dimming according to the prior art.

As shown in FIG. 1, the liquid crystal display according to the related art includes a liquid crystal panel 11 having a plurality of divided regions, a plurality of red LED drivers 14, a plurality of green LED drivers 15, and a plurality of blue LEDs. The driver 14 includes a local dimming controller 17 and a signal processor 18.

The plurality of red, green, and blue LEDs 13 are disposed on the backlight substrate 12 and irradiate light to the liquid crystal panel for each divided region.

The plurality of red LED drivers 14 drives the red LEDs for each divided area. The plurality of green LED drivers 15 and the plurality of blue LED drivers 14 drive the green and blue LEDs for each divided area. The local dimming controller 17 controls local dimming of the red, green, and blue LED drivers 14-16, and the signal processor 18 processes the input video signal to supply an image signal to the liquid crystal panel 11. The gray level signal is supplied to the local dimming control unit 17.

When the video signal is input to the signal processor 18, the signal processor 18 supplies an image signal for driving each pixel constituting the liquid crystal panel. In addition, the signal processor 18 analyzes the video signal, calculates the gray level for each divided region of the liquid crystal panel 11, generates a gray level signal, and supplies the gray level signal to the local dimming controller 17. The local dimming control unit 17 controls each of the red, green, and blue LED drivers 14-16 to operate according to the gray level signal.

The plurality of red LED drivers 14 drives red LEDs that emit red light for each divided area of the liquid crystal panel 11, and the plurality of green LED drivers 15 emits green light for each divided area of the liquid crystal panel 11. The green LED is driven, and the plurality of blue LED drivers 15 drive the blue LEDs for irradiating blue light for each divided area of the liquid crystal panel 11. The red, green, and blue LED drivers 14-16 are provided as many as the divided regions of the liquid crystal panel 11, respectively.

In order to implement local dimming, the LCD according to the related art has to separately control the red LED driver 14, the green LED driver 15, and the blue LED driver 16 for each divided region. However, in the conventional red, green, blue, when adjusting the driving current color of the LED, there is a problem that each color is not uniformly adjusted to reduce color uniformity and color reproducibility.

In addition, when the driving current is increased to increase the brightness of each LED, the current duty ratio is increased to be driven. In this case, there is a problem of further shortening the life of the LED.

In addition, since the driving circuit for driving the LED must be provided for each color and each divided region, when the size of the liquid crystal panel is increased and the divided region is increased, the driving circuit becomes complicated and the circuit implementation cost increases accordingly.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the prior art, and an object thereof is to provide a backlight unit that simplifies the design of a driving circuit, reduces manufacturing costs, and realizes effective local dimming.

In order to achieve the above technical problem, the present invention, in a backlight unit for a liquid crystal display device using an LED having a liquid crystal panel having a plurality of divided regions, each of the red, green, blue and white LEDs A plurality of LED sets for irradiating light to each rear region of the liquid crystal panel; A plurality of white LED drivers for driving the white LEDs for each of the partitions so that the white LEDs in the at least some LED sets have different luminance than the white LEDs in the other LED sets; A red, green, and blue LED driver for driving the red, green, and blue LEDs so that the red, green, and blue LEDs of the LED set have a constant brightness; And a control unit for controlling the operation of the white LED driver and the red, green, and blue LED drivers to individually adjust the luminance of each of the divided regions of the liquid crystal panel. to provide.

According to one embodiment of the invention, the control unit, the white LED of the LED set is a control signal for controlling the operation of the white LED according to the gray level value of the divided region of the liquid crystal panel to which the LED set is irradiated light The plurality of white LED drivers may be configured to drive the white LEDs in at least some of the LED sets to have different luminance from the white LEDs in the other LED sets according to the control signal.

According to one embodiment of the present invention, the white LED may be formed including any one of an ultraviolet LED, a near ultraviolet LED, or a blue LED and a phosphor.

According to an embodiment of the present invention, the LED set may include a red LED, a green LED, and a blue LED forming a triangular structure and a white LED disposed inside the triangular structure.

According to an embodiment of the present invention, the LED set may include one red LED, two green LEDs, one blue LED, and a white LED disposed inside the rectangular structure.

According to an embodiment of the present invention, the LED set may include a red LED, a green LED, a blue LED, and a white LED forming a rectangular structure.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below. Embodiments of the present invention are provided to more completely explain the present invention to those skilled in the art. Therefore, the shape and size of the components shown in the drawings may be exaggerated for more clear description, components having substantially the same configuration and function in the drawings will use the same reference numerals.

2 is a block diagram of a liquid crystal display for implementing local dimming according to the present invention.

Referring to FIG. 2, the backlight unit according to the present invention includes a plurality of LED sets 23, a plurality of white LED drivers 27, red, green, and blue LED drivers 24-26, and a controller 28. It is configured by.

The plurality of LED sets 23 include red, green, blue, and white LEDs that radiate light to the rear surface of the liquid crystal panel 21 having a plurality of divided regions. Each divided area of the liquid crystal panel 21 is supplied with a light source by one LED set 23.

The white LED driver 27 is configured such that the white LEDs in the at least some LED sets 23 have different luminance from the white LEDs in the other LED sets in order to individually adjust the luminance of each of the divided regions of the liquid crystal panel 21. The white LED is driven for each partition. The red, green, and blue LED drivers 24-26 drive the red, green, and blue LEDs so that the red, green, and blue LEDs of the LED set 23 have a constant brightness.

In addition, the controller 28 controls the operations of the white LED driver 26 and the red, green, and blue LED drivers 24, 25, and 26.

The liquid crystal panel 21 is divided into a plurality of regions, and luminance is adjusted for each region. In FIG. 2, regions divided by a dotted line on the liquid crystal panel 21 correspond to divided regions of each liquid crystal panel.

Light is irradiated to each divided area of the liquid crystal panel 21 by one LED set 23. Typically, when the backlight unit is configured using red, green, and blue LEDs, adjacent red LEDs, green LEDs, and blue LEDs emit red light, green light, and blue light, respectively, and the emitted red light, green light, and blue light are mixed to form a liquid crystal. The panel is examined. In general, it is known that implementing white light with a red LED, a green LED, and a blue LED can obtain better color reproducibility than when implementing a white light using a single white LED.

According to the present invention, by adding a white dimming white LED to a backlight unit in which red, green, and blue LEDs are disposed, the same color uniformity and color reproducibility as a backlight having a red, green, and blue LED as a light source are provided. You can still implement local dimming.

The LED set 23 includes red, green, blue and white LEDs arranged in a uniform arrangement on the backlight substrate 22. The backlight substrate 22 has a size substantially similar to that of the liquid crystal panel 21. The LED set 23 is disposed corresponding to the divided area of the liquid crystal panel, and the red, green, blue, and white LEDs of the LED set 23 emit light, and thus, the rear of the divided area of the liquid crystal panel corresponding to the LED set 23. Irradiate light on.

As the backlight substrate 22, a metal core PCB (MCPCB) which is typically used for an LED backlight may be used. The metal core PCB is a PCB having an insulator plate formed on upper and lower surfaces of a core of a metal material (for example, Al), and has a characteristic of easily dissipating heat when a large number of LEDs having high heat generation are mounted.

Between the backlight substrate 22 and the liquid crystal panel 21, a diffusion sheet for uniformly diffusing the light incident from the LED light source, a light collecting sheet for condensing the light diffused from the diffusion sheet in a direction perpendicular to the liquid crystal panel 22, and the like. It may be provided.

The white LED may be manufactured by forming a phosphor on an LED such as an ultraviolet LED, a near ultraviolet LED, or a blue LED, but the present invention is not limited thereto.

The arrangement of the red, green, blue, and white LEDs in the LED set 23 will be described later.

Referring back to FIG. 2, when the signal processor 29 receives a video signal, the signal processor 29 processes the video signal to generate a gray level signal for each partition, and generates the gray level signal. It supplies to the control part 28. For example, the gray level signal may be a peak value of the gray level for each divided region. The controller 28 controls the operation of the white LED driver 27 according to the gray level signal, and also allows the red, green, and white LEDs to emit light of uniform luminance. 24, 25, 26).

In the exemplary embodiment of the present invention, the red, green, and blue LED drivers 24-27 may emit red, green, and blue light so that the red, green, and blue LEDs belonging to the backlight unit irradiate the liquid crystal panel with light having the same luminance for each color. Drive the blue LEDs. That is, the red, green, and blue LEDs irradiate the entire liquid crystal screen with uniform light regardless of the division region of the corresponding liquid crystal panel. Therefore, all of the red LEDs of the backlight unit can be driven by one red LED driver 24, and all of the green LEDs of the backlight unit can be driven by one green LED driver 25, and the blue of the backlight unit can be driven. The LEDs may all be driven by one blue LED driver 26.

Accordingly, the number of driving units for driving the red, green, and blue LEDs can be reduced compared to the prior art, and the number of control signals for controlling the red LEDs is reduced, so that the configuration of the control unit is simpler.

In the exemplary embodiment of the present invention, one or more white LED drivers 27 are provided for each divided area of the liquid crystal panel 21, and the liquid crystal panel 21 is used to individually adjust the luminance of each divided area of the liquid crystal panel 21. The white LED of each LED set 23 which irradiates light on each divided region of the X) is driven to have different luminance. The controller 28 controls the white LED driver 27 for each divided region according to the gray level signal for each divided region of the liquid crystal panel 21, thereby driving the white LED of the LED set for each divided region. Local dimming will be implemented.

In this way, the red, green, and blue LEDs of the LED set 23 are irradiated with light of uniform brightness, and only the white LEDs have different luminance for each of the divided regions of the liquid crystal panel, thereby making it possible to obtain the red, green, and blue LEDs from High quality local dimming can be achieved while maintaining the color uniformity and color reproducibility obtained.

In order to irradiate the liquid crystal panel with uniform white light, the red, green, blue, and white LEDs in each LED set preferably have a disposition structure in which the light of each color can be uniformly mixed. In addition, it is preferable that each LED set also has a disposition structure in which light between adjacent LEDs can be uniformly mixed.

3 is a layout view showing an arrangement of LEDs according to an embodiment of the present invention.

Referring to FIG. 3A, the red, green, blue, and white LEDs 31a, 31b, 31c, and 31d included in each LED set 31 are arranged in the order of red-green-blue-white, and the arrangement is the same. To the backlight substrate 22 in a matrix form.

The region divided by the dotted line illustrated in the backlight substrate 22 represents a region in which light is radiated corresponding to each divided region of the liquid crystal panel, and the LED set 31 is disposed in a predetermined array structure in each region.

In another embodiment of the present invention, the plurality of red, green, blue, and white LEDs included in the plurality of LED sets may be disposed on the backlight substrate in a matrix form, and the LED arrays arranged in each column may be different from each other. .

Referring to FIG. 3B, the plurality of red, green, blue, and white LEDs 32a, 32b, 32c, and 32d disposed on the backlight substrate 22 have different arrangement structures for each column. The LEDs belonging to the first row are arranged in the order of red, green, blue, and white, and the LED arrays of the LED set 32 belonging to the second row are arranged in the order of green, blue, white, and red, and the third row. The LED arrays of the LED set 32 belonging to the are arranged in the order of blue, white, red, green, and the LED arrays of the LED set 32 belonging to the fourth row are arranged in the order of white, red, green, and blue. This array is repeated over and over again. Thus, each LED set 32 may have a different arrangement of LED arrangements.

The arrangement of LEDs in each of the LED sets is exemplary, and various types of arrangements are possible.

4 is a layout view showing an arrangement of LEDs according to another embodiment of the present invention.

Referring to FIG. 4, the LED set 41 includes red, green, blue, and white LEDs 41a, 41b, 41c, and 41d forming a rectangular structure. In the first row of the LED set 41, the red LED 41a and the green LED 41b are arranged in the order of red, green, and in the second row, the blue LED 41c and the white LED 41d are blue, then white. However, the LED placement of the LED set is merely exemplary. In addition, LEDs included in each LED set 41 of FIG. 4 all have the same arrangement, but are not limited thereto. Each LED set may have a different LED arrangement.

5 is a layout view showing an arrangement of LEDs according to another embodiment of the present invention.

As shown in FIG. 5A, the red LED 51a, the green LED 51b, the blue LED 51c forming a triangular structure in the LED set 51, and the white LED 51d disposed inside the triangular structure are shown. Include. Preferably, the red LED 51a, the green LED 51b, and the blue LED 51c may be disposed on the backlight substrate 51d so as to have an equilateral triangle structure, and the white LED 51d may be disposed at the center of the equilateral triangle. have.

In FIG. 5A, each LED set 51d, red LED 51a, green LED 51b, and blue LED 51c are disposed so as to have a triangular structure in the order of red, green, and blue in the counterclockwise direction, and the white LED 51d. ) Shows a structure disposed therein, and each LED set 51 has the same arrangement and is arranged in a matrix structure on the backlight substrate 22. However, the LEDs of the LED set 51 may have a different arrangement, and each LED set 51 may also have a different LED arrangement.

In addition, the arrangement of the backlight unit according to an embodiment of the present invention, as shown in Figure 5b, the red LED 52a, green LED 52b, blue LED 52c of each LED set 52 is a clock In the opposite direction, red, green, and blue may be arranged in a triangular structure, and the LED set 52 belonging to the same column may be arranged to have an inverted structure with an adjacent set.

6 is a layout view showing an arrangement of LEDs according to another embodiment of the present invention.

High quality white light requires more green light than red light and blue light. For this purpose, one LED set 61 includes one red LED 61a, two green LEDs 61b, one blue LED 61c, One white LED 61d may be included.

As shown in FIG. 6, the LED set 61 includes one red LED 61a, two green LEDs 61b, one blue LED 61c, and one white LED 61d having a rectangular structure. And a white LED 61d disposed inside the rectangular structure. Preferably, the red LED 61a, the green LED 61b, and the blue LED 61c form a square structure and are disposed on the backlight substrate 22, and the white LED 61d may be disposed at the center of the square. have.

6, the red LED 61a, the green LED 61b, the blue LED 61c, and the green LED 61b of each LED set 61 have a rectangular structure in the order of red, green, blue green in the counterclockwise direction. The white LED 61d is disposed therein. While each LED set 61 is shown to be disposed on the backlight substrate 22 with the same arrangement, each LED set 61 may have a different LED arrangement.

The present invention is not limited by the above-described embodiment and the accompanying drawings, but by the appended claims. Therefore, it will be apparent to those skilled in the art that various forms of substitution, modification, and alteration are possible without departing from the technical spirit of the present invention described in the claims, and the appended claims. Will belong to the technical spirit described in.

As described above, according to the present invention, by driving only to adjust the brightness of the white LED to implement local dimming, it is possible to reduce the manufacturing cost of the backlight unit simply by driving a drive circuit for driving the red, green, blue LED have.

In addition, by maintaining the luminance of the red, green, and blue LED uniformly, and by adjusting only the luminance of the white LED when local dimming, it is possible to implement the image quality having a good color uniformity and color reproducibility.

Claims (6)

In the backlight unit for a liquid crystal display device using an LED having a liquid crystal panel having a plurality of divided regions, A plurality of LED sets including at least one of red, green, blue, and white LEDs, the plurality of LEDs irradiating light to each rear region of the liquid crystal panel; A plurality of white LED drivers for driving the white LEDs for each of the partitions such that the white LEDs in the at least some LED sets have different luminance than the white LEDs in other LED sets; A red, green, and blue LED driver for driving the red, green, and blue LEDs so that the red, green, and blue LEDs of the LED set have a constant brightness; And Control unit for controlling the operation of the white LED driver and the red, green, blue LED driver The backlight unit for a liquid crystal display device using the LED, characterized in that for individually adjusting the brightness of each divided region of the liquid crystal panel. The method of claim 1, wherein the control unit, The white LED of the LED set generates a control signal for controlling the operation of the white LED according to the gray level value of the partition area of the liquid crystal panel to which the LED set is irradiated light, the plurality of white LED driver is the control signal The backlight unit for a liquid crystal display device using an LED according to claim 1, wherein the white LED in at least part of the LED set is driven to have a different brightness than the white LED in the other LED set. The method of claim 1, The white LED is a backlight unit for a liquid crystal display device using an LED, characterized in that formed of any one of ultraviolet LED, near-ultraviolet LED or blue LED and a phosphor. The method of claim 1, wherein the LED set, And a red LED, a green LED, and a blue LED having a triangular structure and a white LED disposed inside the triangular structure. The method of claim 1, wherein the LED set, 1. A backlight unit for a liquid crystal display device using an LED comprising: a red LED, two green LEDs, one blue LED, and a white LED disposed inside the rectangular structure. The method of claim 1, wherein the LED set, A backlight unit for a liquid crystal display device using an LED comprising a red LED, a green LED, a blue LED, and a white LED having a rectangular structure.

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