Dynamic backlight control system

• US 20070279369A1
• Filed: 06/02/2006
• Published: 12/06/2007
• Est. Priority Date: 06/02/2006
• Status: Active Grant

• Current Assignee: Apple Inc.
• Original Assignee: Apple Inc.
• Inventors: Yao, Wei, Chen, Wei
• Granted Patent: US 7,825,891 B2
• Time in Patent Office: Days
• 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 dynamic 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 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.

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 2 wherein the processor includes logic for determining a power consumption level based on at least the backlight level.

4. The system of claim 3 wherein a graphical representation corresponding to the power consumption level is displayed on the electronic display.

5. The system of claim 1 wherein the logic module includes:

logic for determining a periodicity of the electronic display;

logic for determining the backlight-off frequency at a non-integer ratio with respect to the periodicity of the electronic display; and

logic for controlling the switch in accordance with the backlight-off frequency wherein flicker is substantially avoided.

6. The system of claim 1 wherein the electronic display is selected from the group consisting of:

an LCD, an LED, and an OLED.

7. An integrated circuit for controlling a backlight, the backlight for use with an electronic display comprising:

a switch for controlling the backlight, the switch configured to set a backlight condition to ON or OFF such that an ambient light sensor senses an ambient light intensity in the absence of the backlight;

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

a logic module for determining a backlight level in response to the ambient light intensity;

a timer for providing a timing element for the logic module; and

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

8. The integrated circuit of claim 7 further comprising:

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

9. The integrated circuit of claim 7 wherein the logic module includes:

logic for determining a periodicity of the electronic display;

logic for determining a backlight-off frequency at a non-integer ratio with respect to the periodicity of the electronic display; and

logic for controlling the switch in accordance with the frequency wherein flicker is substantially avoided.

10. The integrated circuit of claim 7 wherein the electronic display is selected from the group consisting of:

an LCD, an LED, and an OLED.

11. A method of dynamically controlling a backlight for use with an electronic display comprising the steps of:

determining a periodicity of the electronic display;

determining a backlight-off frequency corresponding to the periodicity of the electronic display, the backlight-off frequency limited to a non-integer ratio of the periodicity of the electronic display;

for each backlight-off frequency,

turning off the backlight, and

sampling an ambient light intensity; and

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

12. The method of claim 11 further comprising:

converting the ambient light intensity to an ambient light intensity data, the ambient light intensity data configured as a digital signal.

13. The method of claim 12 further comprising:

sending the backlight level to a processor; and

updating a power consumption level based on at least the backlight level.

14. The method of claim 13 further comprising displaying a graphical representation corresponding to the power consumption level on the electronic display.

15. The method of claim 11 further comprising:

if the ambient light intensity exceeds a maximum threshold over a threshold time interval, turning off the backlight.

16. The method of claim 11 wherein the electronic display is selected from the group consisting of:

an LCD, an LED, and an OLED.