Backlight unit of liquid crystal display device and method for driving the same

• US 8,721,096 B2
• Filed: 06/28/2005
• Issued: 05/13/2014
• Est. Priority Date: 06/29/2004
• Status: Expired due to Fees

• Current Assignee: LG Philips LCD Company Limited (LG Display Co., Ltd.)
• Original Assignee: LG Display Co., Ltd.
• Inventors: Park, Hee Jeong
• Primary Examiner(s): Lee, Jong-Suk (James)
• Assistant Examiner(s): Tsidulko, Mark
• Application Number:
  US11/168,959
• Publication Number:
  US 20060007112A1
• Time in Patent Office: 3,241 Days
• Field of Search: 362/26, 362/27, 362/600, 362/611, 362/612, 362/613, 362/231, 362/23.09, 362/23.1, 349 61- 63, 349 69- 71, 345/88, 345/89, 345/102, 345/690, 315/169.3, 315/169.4, 315/185.S, 315/200.A
• US Class Current: 362/23.09
• CPC Class Codes: G09G 2310/0235 Field-sequential colour display
• CPC Class Codes: G09G 2360/16 Calculation or use of calculated indices related to luminance levels in display data
• CPC Class Codes: G09G 3/3413 Details of control of colour illumination sources
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix
• CPC Class Codes: G09G 3/3611 Control of matrices with row and column drivers

Abstract

A backlight unit of an LCD device includes a first light source unit including a plurality of red, green and blue LEDs and a second light source unit including a plurality of white LEDs, the white LED provided between each of the first light source unit. A control unit divides the plurality of first and second light source units into a plurality of blocks and outputs control signals to the first and second light source units by detecting the luminance of inputted video signals. The backlight unit includes a first light source driving unit for driving the first light source and a second light source driving unit for driving the second light source by corresponding block to the first light source unit.

Claims

1. A backlight unit of an LCD device that receives video data, comprising:

a printed circuit board (PCB) substrate facing a rear surface of an LCD panel and extending along the rear surface of the LCD panel;

a plurality of first light source units including a plurality of red, green and blue LEDs;

a plurality of second light source units corresponding to the plurality of first light source units and including a plurality of white LEDs, wherein the plurality of the first light source units and the plurality of the second light source units are positioned alternately on the PCB substrate, wherein the plurality of red, green, blue and white LEDs being divided into a plurality of blocks, wherein each block includes red, green, blue and white LEDs, wherein the red, green and blue LEDs evenly spread across the PCB substrate to form an array of LEDs including a plurality of rows and columns;

a control unit that outputs a first control signal to the first light source units and a second control signal to the second light source units based upon a luminance signal, wherein the control unit detects the luminance signal by analyzing inputted video data from a video system by each block, and the control unit includes a histogram analyzing unit that analyzes the luminance of white light emitted from the first light source units in accordance with a histogram containing luminance values for each gray scale of a video frame to obtain an analyzed luminance;

a first light source driving unit that drives the first light source units according to the first control signal; and

a second light source driving unit that drives the second light source units by each block according to the second control signal;

wherein the second light source driving unit selectively drives the white LEDs of a corresponding block so that the white LEDs of the corresponding blocks are turned on in case where the detected luminance signal of the corresponding block is below a predetermined reference value, thereby a white light emitted from the white LEDs in the corresponding block is mixed with a white light emitted from the first light source units in the corresponding block to improve entire luminance of the white light and to achieve a uniform white light in the entire backlight unit;

wherein the white LEDs emit the white light after a white light is emitted from the first light source units and after luminance of the white light emitted from the first light source units is analyzed;

wherein the video frame is divided into three sub-frames of red, green and blue;

wherein the first light source driving unit turns on the first light source units during a liquid crystal response block when the video data is provided to and maintained in a liquid crystal cell in each sub-frame by the control signal of the first light source unit;

wherein the control unit detects the luminance signals by analyzing the video data;

wherein the control unit comprises a luminance and color division unit and a histogram analyzing unit, the luminance and color division unit divides the video data into luminance element and chromatic elements.

2. A method for driving a backlight unit of an LCD device that receives video data from a video system, comprising:

preparing the backlight unit which includes a plurality of first light source units including a plurality of red, green and blue LEDs, a plurality of second light source units including a plurality of white LEDs, wherein the plurality of the first light source units and the plurality of the second light source units being positioned alternately, wherein the plurality of red, green, blue and white LEDs being divided into a plurality of blocks, wherein each block includes red, green, blue and white LEDs, wherein the red, green and blue LEDs evenly spread across a PCB substrate;

providing the PCB substrate along a rear surface of the LCD panel;

providing the plurality of first and second light source units on the PCB facing the rear surface of an LCD panel to form an array of LEDs including a plurality of rows and columns;

detecting a luminance signal by analyzing the video data for each block using a controller;

driving the first light source units to emit white light according to the detected luminance signal;

analyzing luminance of the white light emitted from the first light source units according to a histogram containing luminance values for each gray scale of a video frame to obtain an analyzed luminance; and

selectively turning on the white LEDs of a corresponding block after the white light is emitted from the first light source units and after luminance of the white light emitted from the first light source units is analyzed when the analyzed luminance of the corresponding block is below a predetermined reference value;

mixing white light emitted from the white LEDs with the white light emitted from the first light source units in the corresponding block to improve entire luminance of the white light and to achieve a uniform white light in the entire backlight unit.