Display apparatus and control method thereof for saving power

• US 8,368,724 B2
• Filed: 09/17/2008
• Issued: 02/05/2013
• Est. Priority Date: 10/26/2007
• Status: Expired due to Fees

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Oh, Jang-Geun
• Primary Examiner(s): Lefkowitz, Sumati
• Assistant Examiner(s): HERNANDEZ, JESUS J
• Application Number:
  US12/212,347
• Publication Number:
  US 20090109246A1
• Time in Patent Office: 1,602 Days
• Field of Search: 345/102, 345/211
• 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 detect a 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 image displayed on the display panel,

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, and

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 non-zero correction coefficients.

2. The display apparatus as claimed in claim 1, 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.

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

a storage unit configured to store 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.

4. A display control method for saving power by a display apparatus, comprising the steps of:

(A) measuring a remaining amount of a battery;

(B) calculating an output value of a backlight using the remaining amount of the battery;

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

(D) calculating a pixel brightness correction value using the pixel brightness limit value

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

wherein the pixel 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 non-zero correction coefficients.

5. The method as claimed in claim 4, wherein steps (A) to (E) are performed only when the remaining amount of the battery is below a predetermined value.

6. The method as claimed in claim 4, wherein in steps (B) and (C), the output value of the backlight and the pixel brightness limit value are read and calculated from a lookup table.

7. The method as claimed in claim 4, wherein in step (D), the pixel brightness correction value is read and calculated from a lookup table.

8. The method as claimed in claim 4, 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.

9. The method as claimed in claim 4, 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.