Method of driving a light source, light source apparatus for performing the method and display apparatus having the light source apparatus

• US 8,766,903 B2
• Filed: 07/15/2009
• Issued: 07/01/2014
• Est. Priority Date: 10/29/2008
• Status: Active Grant

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Inventors: Seo, Young-Jun, Yeo, Dong-Min, Kim, Gi-Cherl
• Primary Examiner(s): DINH, DUC Q
• Application Number:
  US12/503,332
• Publication Number:
  US 20100103202A1
• Time in Patent Office: 1,812 Days
• Field of Search: 345/690, 345/204, 345 76-103, 345/211, 345/212
• US Class Current: 345/102
• CPC Class Codes: G09G 2320/02 Improving the quality of display appearance
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• CPC Class Codes: G09G 2340/16 Determination of a pixel data signal depending on the signal applied in the previous frame
• CPC Class Codes: G09G 3/3426 the different display panel areas being distributed in two dimensions, e.g. matrix

Abstract

A light source apparatus includes a light source, a duty determining part, a luminance shifting determining part and a duty compensation part. The light source includes a plurality of light-emitting blocks. The duty determining part determines a duty of light-emitting blocks by using a block representative value obtained from a plurality of image blocks that are divided in accordance with a plurality of light-emitting blocks. The luminance shifting determining part compares block representative values of a previous frame with block representative values of a current frame to determine whether a luminance shifting is generated at an adjacent light-emitting block. The duty compensation part compensates a duty of the adjacent light-emitting blocks when the luminance shifting is generated at the adjacent light-emitting blocks. Thus, the duty of the adjacent light-emitting blocks determined as a block representative value is compensated so that an occurrence of flicker may be decreased.

Claims

1. A method of driving a light source, the method comprising:

determining the duty of each light-emitting block among m×

n light-emitting blocks by using a block representative value obtained from each of a plurality of m×

n image blocks that are divided from a frame to correspond with the plurality of light-emitting blocks, wherein m is an integer, and n is an integer;

comparing block representative values obtained from the image blocks of a previous frame with block representative values obtained from the image blocks of a current frame to determine whether a luminance shifting is occurring at first and second adjacent light-emitting blocks;

compensating at least one of the duty of the first adjacent light-emitting block and the duty of the second adjacent light-emitting block if the luminance shifting is occurring at the first and second adjacent light-emitting blocks; and

driving the first and second adjacent light-emitting blocks based on a compensated duties.

2. The method of claim 1, further comprising:

determining whether an input image includes the predetermined image at a background image of a low gradation by using a gradation data of a current frame,

wherein determining whether the luminance shifting is occurring in the first and second adjacent light-emitting blocks is performed only if it is determined that the input image includes the predetermined image at the background image of the low gradation.

3. The method of claim 2, wherein determining whether the luminance shifting is occurring in the adjacent light-emitting blocks includes determining that the luminance shifting is occurring at the first and second adjacent light-emitting blocks due to a shifting of the predetermined image, when a variation of a block representative value in a predetermined image block where the predetermined image is positioned is substantially equal to a variation of a block representative value at a plurality of peripheral image blocks positioned at a peripheral of a center of the predetermined image block.

4. The method of claim 1, further comprising:

determining an image of the following frame as a still image of the current frame if the total of the block representative values is substantially equal to the total of the block representative values of a following frame,

wherein compensating a duty of the adjacent to the light-emitting blocks maintains a duty of the following frame to a compensated duty of the current frame if it is determined that the following frame is the still image of the current frame.

5. The method of claim 4, wherein the block representative value is a gradation average value of each of the image blocks.

6. The method of claim 5, wherein compensating the duties of the first and second adjacent light-emitting blocks compensates the duties of the first and second light-emitting blocks by using the maximum gradation data of an image block corresponding to the predetermined image.

7. The method of claim 5, wherein compensating the duties of the first and second adjacent light-emitting blocks compensates the duties of the first and second light-emitting blocks by employing a weighted value to the duties of the first and second light-emitting blocks.

8. The method of claim 7, wherein the compensated duty of the first adjacent light-emitting block is calculated according to:

D_Bk(c)=(1+a)D_Bk,0≦

a≦

1

wherein D_Bk(c) is the compensated duty of the k^th light-emitting block of which a duty is varied, ‘

a’

is a weighted value and D_Bk (‘

k’

is a natural number) is a duty of the k^th light-emitting block of which a duty is varied.

9. The method of claim 5, wherein compensating the duties of the first and second adjacent light-emitting blocks calculates a duty decreasing by comparing the duty of the previous frame with the duty of the current frame, and distributes the duty decreasing to the light-emitting blocks of which the duty is varied to compensate the duty.

10. The method of claim 9, wherein the compensated duties of the first and second light-emitting blocks is calculated according to:

11. A light source apparatus comprising:

a light source comprising a plurality of m×

n light-emitting blocks, wherein m is an integer, and n is an integer;

a duty determining part determining the duty of each light-emitting block among them □

n light-emitting blocks by using a block representative value obtained from a plurality of m×

n image blocks that are divided from a frame to correspond with the plurality of m×

n light-emitting blocks;

a luminance shifting determining part comparing block representative values obtained from the image blocks of a previous frame with block representative values obtained from the image blocks of a current frame to determine whether a luminance shifting is occurring at first and second adjacent light-emitting blocks; and

a duty compensation part compensating at least one of the duty of first adjacent light-emitting block and the duty of second adjacent light-emitting block if the luminance shifting is occurring at the first and second adjacent light-emitting blocks.

12. The light source apparatus of claim 11, wherein the luminance shifting determining part comprises:

a first determining part determining whether an input image includes a predetermined image of a high gradation in a background image of a low gradation by using gradation data of the current frame;

a register storing the block representative values for the previous frame; and

a second determining part comparing the block representative values of the previous frame with the block representative values of the current frame to determine whether the luminance shifting is occurring in the adjacent light-emitting blocks, only if the input image includes the predetermined image of the high gradation in a background image of the low gradation.

13. The light source apparatus of claim 12, whether the luminance shifting determining part further comprises a third determining part determining an image of the following frame as a still image of the current frame if the sum of the block representative values of the current frame is equal to that of the block representative value of the following frame, and

the duty compensation part maintains the duty of the following frame to the duty of the current frame if it is determined that the following frame is a still image of the current frame.

14. The light source apparatus of claim 13, wherein the duty compensation part compensates the duty of the first and second adjacent light-emitting blocks by using the maximum gradation data of an image block corresponding to the predetermined image.

15. The light source apparatus of claim 13, wherein the duty compensation part compensates the duties of the first and second adjacent light-emitting blocks by employing a weighted value into the duties of the first and second light-emitting blocks.

16. The light source apparatus of claim 13, wherein the duty compensation part comprises a register storing a duty for the previous frame, and

the duty compensation part calculates a duty decreasing amount of the first and second adjacent light-emitting blocks by comparing a duty for the previous frame with a duty for the current frame, and distributes the duty decreasing amount into the duties of first and second adjacent light-emitting blocks.

17. A display apparatus comprising:

a display panel;

a light source comprising a plurality of light-emitting blocks to provide the display panel with light; and

a local dimming driving part for determining a duty of the light-emitting blocks by using a block representative value obtained from image blocks corresponding to the light-emitting blocks, and driving the light source by compensating the duties of first and second adjacent light-emitting blocks if a luminance shifting is occurring in the first and second adjacent light-emitting blocks,

wherein the local dimming driving part comprises a luminance shifting determining part for comparing block representative values obtained from the image blocks of a previous frame with block representative values obtained from the image blocks of a current frame to determine whether a luminance shifting is occurring at the first and second adjacent light-emitting blocks.

18. The display apparatus of claim 17, wherein the local dimming driving part further comprises:

a duty determining part for determining a duty of light-emitting blocks by using a block representative value obtained from a plurality of image blocks that are divided to correspond with a plurality of light-emitting blocks;

a duty compensation part for compensating the duty of the first and second adjacent light-emitting blocks if the luminance shifting is occurring at the first and second adjacent light-emitting blocks; and

a light source driving part driving the first and second adjacent light-emitting blocks based on the compensated duties of the first and second adjacent light-emitting blocks.

19. The display apparatus of claim 17, wherein the luminance shifting determining part comprises:

a first determining part determining whether an input image includes a predetermined image of a high gradation in a background image of a low gradation by using gradation data of the current frame;

a register storing the block representative values for the previous frame; and

a second determining part comparing the block representative values of the previous frame with the block representative values of the current frame to determine whether the luminance shifting is occurring in the first and second adjacent light-emitting blocks, if the input image includes the predetermined image of the high gradation in a background image of the low gradation.

20. The display apparatus of claim 17, whether the luminance shifting determining part further comprises a third determining part determining an image of the following frame as a still image of the current frame if the sum of the block representative values of the current frame is equal to that of the block representative value of the following frame, and

the duty compensation part maintains the duties of light-emitting blocks during the following frame the same as the duties of the light-emitting blocks during the current frame if it is determined that the following frame is a still image of the current frame.