Dynamic backlight control system

• US 7,825,891 B2
• Filed: 06/02/2006
• Issued: 11/02/2010
• Est. Priority Date: 06/02/2006
• Status: Expired due to Fees

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yao, Wei, Chen, Wei
• Primary Examiner(s): TRAN, MY CHAU T
• Application Number:
  US11/446,469
• Publication Number:
  US 20070279369A1
• Time in Patent Office: 1,614 Days
• Field of Search: 345/55, 345/84, 345/87, 345/102, 345/104, 345/204, 345/211, 345/212
• US Class Current: 345/102
• CPC Class Codes: G09G 2310/08 Details of timing specific for flat panels, other than clock recovery
• CPC Class Codes: G09G 2320/0247 Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes
• 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 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336

Abstract

Embodiments are provided herein which may be utilized to eliminate stray light emissions from an LED while ambient light is being sensed. As such, dynamic backlight control systems for use with an electronic display are presented including: an ambient light sensor for sensing ambient light intensity; a backlight for illuminating the electronic display; a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF in response to a backlight-off frequency such that the ambient light sensor senses the ambient light intensity in the absence of the backlight; a logic module for determining a backlight level in response to the ambient light intensity; and a backlight control circuit for adjusting the backlight to the backlight level in response to the ambient light intensity.

Claims

1. A backlight control system for use with an electronic display comprising:

an ambient light sensor for sensing an ambient light intensity;

a backlight for illuminating the electronic display;

a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF according to a backlight-off frequency, the ambient light sensor sensing the ambient light intensity only when the backlight condition is set to the OFF and when in absence of light provided by the backlight, wherein said backlight-off frequency results in a recurring backlight-off interval, and wherein said backlight-off interval corresponds to a fraction of the time for a frame refresh of said electronic display;

at least one of a set of circuitry and a software module for determining a backlight level in response to the ambient light intensity; and

a backlight control circuit for adjusting the backlight to the backlight level in response to the ambient light intensity.

2. The system of claim 1 further comprising:

an analog-to-digital circuit for converting the ambient light intensity into ambient light intensity data; and

a data bus configured to send the backlight level to a processor.

3. The system of claim 1 further comprising a processor for determining a power consumption level based on at least the backlight level.

4. The system of claim 3 further comprising a graphical representation displaying the power consumption level and displayed on the electronic display.

5. The system of claim 1 wherein the at least one of the set of circuitry and the software module includes:

at least one of a set of circuitry and a software module for determining a periodicity of the electronic display;

at least one of a set of circuitry and a software module for determining the backlight-off frequency based on the periodicity of the electronic display such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the electronic display; and

at least one of a set of circuitry and a software module for controlling the switch in accordance with the backlight-off frequency.

6. The system of claim 1 further comprising:

at least one of a set of circuitry and a software module for determining whether the ambient light intensity exceeds a maximum threshold for a threshold time interval; and

at least one of a set of circuitry and a software module for turning off the backlight when the ambient light intensity exceeds the maximum threshold over the threshold time interval.

7. The system of claim 1 further comprising a timer for providing a timing element to the at least one of the set of circuitry and the software module.

8. The system of claim 1 further comprising at least one of a set of circuitry and a software module for determining whether the ambient light intensity exceeds a maximum threshold for a threshold time interval.

9. A backlight control system for use with an electronic display comprising:

an ambient light sensor for sensing an ambient light intensity;

a backlight for illuminating the electronic display;

a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF according to a backlight-off frequency, the ambient light sensor sensing the ambient light intensity only when the backlight condition is set to the OFF and when in absence of light provided by the backlight;

at least one of a set of circuitry and a software module for determining a backlight level in response to the ambient light intensity, wherein said at least one of a set of circuitry and software module includes

at least one of a set of circuitry and a software module for determining a periodicity of the electronic display,

at least one of a set of circuitry and a software module for determining the backlight-off frequency based on the periodicity of the electronic display such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the electronic display, and

at least one of a set of circuitry and a software module for controlling the switch in accordance with the backlight-off frequency; and

a backlight control circuit for adjusting the backlight to the backlight level in response to the ambient light intensity.

10. A computing device, comprising:

an outer housing;

a processor disposed within said outer housing;

an electronic display coupled to said processor and adapted to provide a display output from the processor to a user of the computing device; and

a backlight control system including

an ambient light sensor for sensing an ambient light intensity;

a backlight for illuminating the electronic display;

a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF according to a backlight-off frequency, the ambient light sensor sensing the ambient light intensity only when the backlight condition is set to the OFF and when in absence of light provided by the backlight, wherein said backlight-off frequency results in a recurring backlight-off interval, and wherein said backlight-off interval corresponds to a fraction of the time for a frame refresh of said electronic display;

at least one of a set of circuitry and a software module for determining a backlight level in response to the ambient light intensity; and

a backlight control circuit for adjusting the backlight to the backlight level in response to the ambient light intensity.

11. The computing device of claim 10, wherein said backlight control system further includes:

an analog-to-digital circuit for converting the ambient light intensity into ambient light intensity data; and

a data bus configured to send the backlight level to a processor.

12. The computing device of claim 10, wherein the at least one of the set of circuitry and the software module includes:

at least one of a set of circuitry and a software module for determining a periodicity of the electronic display;

at least one of a set of circuitry and a software module for determining the backlight-off frequency based on the periodicity of the electronic display such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the electronic display; and

at least one of a set of circuitry and a software module for controlling the switch in accordance with the backlight-off frequency.

13. The computing device of claim 10, wherein said backlight control system further includes:

at least one of a set of circuitry and a software module for determining whether the ambient light intensity exceeds a maximum threshold for a threshold time interval; and

at least one of a set of circuitry and a software module for turning off the backlight when the ambient light intensity exceeds the maximum threshold over the threshold time interval.

14. The computing device of claim 10, wherein said computing device is a portable electronic device.