DISPLAY APPARATUS AND CONTROL METHOD THEREOF FOR SAVING POWER

• US 20090109246A1
• Filed: 09/17/2008
• Published: 04/30/2009
• Est. Priority Date: 10/26/2007
• Status: Active Grant

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: OH, Jang-Geun
• Granted Patent: US 8,368,724 B2
• Time in Patent Office: Days
• US Class Current: 345/690
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

A display apparatus and a control method thereof, wherein output of a backlight is reduced depending on the remaining amount of a battery or a pixel of an input image, and a brightness value of an output image is increased to compensate for the reduced output of the backlight. A display apparatus according to the present invention includes a display controller for controlling brightness of an image displayed on a display panel and output of a backlight of the display panel; and a control unit for detecting the remaining amount of a battery and controlling the display controller in accordance with the remaining amount of the battery. The control unit includes an operation unit for calculating an output value of the backlight and a pixel brightness correction value of the output image.

Claims

1. A display apparatus, comprising:

a display panel;

a display controller configured to control a brightness of an image displayed on the display panel and to control an output of a backlight of the display panel; and

a control unit configured to detect the remaining amount of a battery and to control the display controller in accordance with the remaining amount of the battery,

wherein the control unit includes an operation unit configured to calculate an output value of the backlight and a pixel brightness correction value of the output image.

2. The display apparatus as claimed in claim 1, wherein the operation unit is configured to calculate a brightness limit value (BR_lim) and the output value of the backlight (OP_out) in accordance with the remaining amount of the battery, and to calculate the pixel brightness correction value (BR_out) in accordance with the brightness limit value.

3. The display apparatus as claimed in claim 2, wherein the control unit is configured to set the brightness limit value to a value with which a decrease in the brightness of the image is compensated in accordance with a decrease ill the output value of the backlight.

4. The display apparatus as claimed in claim 3, wherein the control unit is configured to determine the output value of the backlight in proportion to the remaining amount of the battery, to determine the brightness limit value in inverse proportion to the output value of the backlight, and to determine the pixel brightness correction value in proportion to the brightness limit value.

5. The display apparatus as claimed in claim 1, further comprising:

a storage unit storing a brightness upper limit value and the output value of the backlight in accordance with the remaining amount of the battery,

wherein the operation unit is configured to calculate the brightness upper limit value and the output value of the backlight by reading a lookup table stored in the storage unit.

7. The display apparatus as claimed in claim 2, wherein the operation unit is configured to calculate the output value of the backlight and the pixel brightness correction value using a pixel brightness maximum value (BR_hig) detected by the detector.

8. The display apparatus as claimed in claim 7, wherein the output value of the backlight is in proportion to the pixel brightness maximum value, and the pixel brightness correction value is in inverse proportion to the pixel brightness maximum value.

9. The display apparatus as claimed in claim 8, wherein the control unit is configured to set the output value of the backlight to offset an increase in brightness of the image, the control unit configured to increase the brightness of the image when the pixel brightness maximum value is changed to a maximum brightness value.

10. The display apparatus as claimed in claim 9, wherein the operation unit is configured to calculate the pixel brightness maximum value from an average brightness of images outputted for a specified period of time.

6. A display apparatus, comprising:

a display panel;

a display controller configured to control a brightness of an image displayed on the display panel and output of a backlight of the display panel; and

a control unit configured to control the display controller,

wherein the controller comprises;

a detector configured to detect pixel brightness of an input image; and

an operation unit configured to calculate an output value of the backlight and a pixel brightness correction value using the pixel brightness detected by the detector.

11. A display control method for saving power, comprising the steps of:

(A) measuring a remaining amount of a battery;

(B) calculating an output value of a backlight and a pixel brightness correction value of an output image using the remaining amount of the battery; and

(C) changing a display setting using the calculated output value of the backlight and pixel brightness correction value, thereby displaying an image.

12. The method as claimed in claim 11, wherein steps (A) to (C) are performed only when the remaining amount of the battery is below a predetermined value.

13. The method as claimed in claim 12, wherein step (B) comprises the steps of:

(B1) calculating the output value of the backlight using the remaining amount of the battery;

(B2) calculating a pixel brightness limit value using the remaining amount of the battery; and

(B3) calculating the pixel brightness correction value using the pixel brightness limit value.

14. The method as claimed in claim 13, wherein in steps (B1) and (B2), the output value of the backlight and the pixel brightness limit value are read and calculated from a lookup table.

15. The method as claimed in claim 13, wherein in step (B3), the pixel brightness correction value is read and calculated from a lookup table.

16. The method as claimed in claim 13, further comprising:

setting the brightness limit value to a value; and

compensating a decrease in brightness of the image in accordance with a decrease in the output value of the backlight.

17. The method as claimed in claim 13, wherein the output value of the backlight is expressed by:

OP_out=I₂*[(BA_rem−

BA_min)/(BA_max−

BA_min)]*(OP_max−

OP_min)+J₂*OP_min+K₂,

where OP_out is the output value of the backlight, BA_rem is the remaining amount of the battery, BA_min is a minimum capacity of the battery, BA_max is a maximum capacity of the battery, OP_max is a maximum output value, OP_min is a minimum output value, and I₂, J₂ and K₂ are correction coefficients.

18. The method as claimed in claim 17, wherein the brightness limit value is expressed by:

BR_lim=I₁*[(BA_max−

BA_min)/(BA_rem−

BA_min)]*(BR_max−

BR_limmax)+J₁*BR_min+K₁,

where BR_lim is the brightness limit value, BA_rem is the remaining amount of the battery, BA_min is the minimum capacity of the battery, BA_max is the maximum capacity of the battery, BR_max is a maximum brightness value, BR_limmax is a maximum brightness limit value, BR_min is a minimum brightness value, and I₁, J₁ and K₁ are correction coefficients.

19. The method as claimed in claim 18, wherein the pixel brightness correction value is expressed by:

BR_out=I₃*[(BR_max−

BR_lim)/BR_max]*BR_in+BR_lim+K₃,

where BR_out is the pixel brightness correction value, BR_lim is the brightness limit value, BR_max is the maximum brightness value, BR_in is an input brightness value, and I₃ and K₃ are correction coefficients.

20. A display control method for saving power, comprising the steps of:

(A) detecting a maximum brightness value of an input image;

(B) calculating an output value of a backlight using the maximum brightness value;

(C) calculating a pixel brightness correction value using the maximum brightness value; and

(D) changing display setting using the calculated output value of the backlight and pixel brightness correction value.

21. The method as claimed in claim 20, wherein steps (A) to (D) are performed only when the remaining amount of the battery is below a predetermined value.

22. The method as claimed in claim 20, further comprising:

setting the output value of the backlight to offset an increase in brightness of the image, and increasing the brightness of the image when a pixel brightness maximum value is changed to the maximum brightness value.

23. The method as claimed in claim 22, further comprising:

calculating the pixel brightness maximum value from an average brightness of images outputted for a specified period of time.

24. The method as claimed in claim 23, wherein the output value of the backlight is expressed by:

OP_out=OP_max−

I₄*[(BR_max−

BR_hig)/BR_max]*OP_max+K₄,

where OP_out is the output value of the backlight, OP_max is a maximum output value, BR_max is the maximum brightness value, BR_hig is the pixel brightness maximum value, and I₄ and K₄ are correction coefficients.

25. The method as claimed in claim 23, wherein the pixel brightness correction value is expressed by:

BR_out=BR_in+(BR_max−

BR_hig)+K₅,

where BR_out is the pixel brightness correction value, BR_in is an input brightness value, BR_max is the maximum brightness value, BR_hig is the pixel brightness maximum value, and K₅ is a correction coefficient.