Backlight control of electronic device

• US 8,194,031 B2
• Filed: 10/21/2010
• Issued: 06/05/2012
• 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:
  US12/909,536
• Publication Number:
  US 20110032285A1
• Time in Patent Office: 593 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. An electronic device, comprising:

an outer housing;

a display processor disposed within said outer housing;

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

a backlight control system including

a backlight adapted to illuminate the visual display,

a switch configured to set the backlight to an ON or OFF state according to a backlight-off frequency, wherein the backlight-off frequency is determined such that flicker in the visual display is avoided, and

an ambient light sensor adapted to sense an ambient light intensity when the backlight is temporarily off during the backlight-ON state, and to provide an indication thereof to a backlight control processor when the ambient light intensity is greater than a threshold value.

2. The electronic device of claim 1, wherein the backlight-off frequency results in a recurring backlight-off interval, and wherein the backlight-off interval corresponds to a fraction of the time for a frame refresh of the visual display.

3. The electronic device of claim 1, further comprising:

an analog-to-digital circuit adapted to convert the ambient light intensity into ambient light intensity data; and

a data bus configured to send the ambient light intensity data to a backlight control processor.

4. The electronic device of claim 1, wherein the display processor is also the backlight control processor.

5. The electronic device of claim 1, wherein said electronic device is a portable electronic device.

6. The electronic device of claim 1, wherein the backlight control system further includes:

at least one of a set of circuitry and a software module adapted to determine a periodicity of the visual 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 visual display such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the visual 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.

7. The electronic device of claim 1, wherein the backlight control processor is adapted to respond to the indication by reducing power consumption of the portable device by adjusting the level of the backlight.

8. The electronic device of claim 7, wherein the backlight control processor causes the backlight to turn to a backlight-OFF state when the threshold value is sufficiently high.

9. A power control system in a battery powered portable device having an electronic display, comprising:

a processor associated with an electronic display;

a backlight that illuminates the electronic display coupled to the processor, wherein the backlight is adapted to switch on and off automatically according to a backlight-off frequency while the backlight is in a backlight-ON state; and

an ambient light sensor adapted to detect an ambient light intensity while the backlight is temporarily off during the backlight-ON state and provide an indication thereof to the processor when the ambient light intensity is greater than a first threshold value, wherein the processor is adapted to respond to the indication by reducing power consumption of the portable device by adjusting the level of the backlight.

10. The power control system of claim 9, wherein the processor causes the backlight to turn to a backlight-OFF state when the first threshold value is sufficiently high.

11. The power control system of claim 9, further comprising:

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

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

12. The power control system of claim 9, wherein the backlight-off frequency results in a recurring backlight-off interval, and wherein the backlight-off interval corresponds to a fraction of the time for a frame refresh of the electronic display.

13. The power control system of claim 9, further including:

at least one of a set of circuitry and a software module adapted to determine a periodicity of the electronic display; and

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.

14. A method of conserving power in an electronic device, comprising:

determining the periodicity of an electronic display on an electronic device;

setting a backlight-off frequency of a backlight adapted to illuminate the electronic display, wherein the backlight-off frequency is set according to the periodicity such that flicker in the electronic display is avoided;

sensing an ambient light intensity associated with the electronic display when the backlight is off;

providing an indication to a backlight control processor when the ambient light intensity is greater than a first threshold value; and

reducing power consumption of the electronic device by lowering the level of the backlight when the backlight control processor receives said indication.

15. The method of claim 14, wherein the backlight-off frequency results in a recurring backlight-off interval, and wherein the backlight-off interval corresponds to a fraction of the time for a frame refresh of the electronic display.

16. The method of claim 14, wherein said reducing step includes setting the backlight to an OFF state when the first threshold value is sufficiently high.

17. The method of claim 14, wherein the backlight-off frequency is set such that the backlight-off frequency is at a non-integer ratio with respect to the periodicity of the visual display.

18. The method of claim 14, furthering including the steps of:

determining whether the ambient light intensity exceeds a maximum threshold value for a threshold time interval; and

turning off the backlight when the ambient light intensity exceeds the maximum threshold value over the threshold time interval.

19. The method of claim 14, wherein said electronic device is a portable electronic device.