APPARATUS AND METHOD FOR DISPLAY CONTROL USING AMBIENT LIGHT MEASUREMENT SIGNAL FROM AN INFRARED RECEIVER

• US 20090127461A1
• Filed: 11/13/2008
• Published: 05/21/2009
• Est. Priority Date: 11/15/2007
• Status: Active Grant

• Current Assignee: Silicon Laboratories Incorporated
• Original Assignee: Silicon Laboratories Incorporated
• Inventors: Holcombe, Wayne T., Svajda, Miroslav
• Granted Patent: US 7,868,294 B2
• Time in Patent Office: Days
• US Class Current: 250/338.100
• CPC Class Codes: H04B 10/1141 One-way transmission
• CPC Class Codes: H04B 10/116 Visible light communication

Abstract

A system having an infrared receiver is shown, where the system includes an infrared receiver circuit configured to receive an infrared data signal using a receive photodiode and compensate for an ambient light level incident on the receive photodiode by generating a DC ambient current signal, where the DC ambient current signal is accessible external to the infrared receiver circuit. The system also includes a control circuit configured to receive the DC ambient current signal and, responsive thereto, determine the ambient light level and generate a display illumination control signal accordingly.

Claims

1. An infrared receiver circuit configured to generate an ambient light output signal at an output pin, the receiver circuit including:

an ambient correction current transistor having a first current terminal coupled to a first power supply rail, a second current terminal for coupling to a receive photodiode, and a control terminal;

an ambient correction amplifier having an output coupled to the control terminal of the ambient correction current transistor, a first input, and a second input coupled to a reference voltage source;

a capacitor coupled between the output of the ambient correction amplifier and the first power supply rail;

a transimpedance amplifier having an output coupled to the first input of the ambient correction amplifier through a first resistor, a first input coupled to the second current terminal of the ambient correction current transistor and coupled to the output of the transimpedance amplifier through a second resistor, and a second input coupled to the reference voltage source; and

an output transistor having a first current terminal coupled to the first power supply rail, a second current terminal coupled to the output pin, and a control terminal coupled to the control terminal of the ambient correction current transistor.

2. The infrared receiver circuit of claim 1, the circuit further comprising a logic buffer having an input coupled to the output pin and an output at which an illumination control signal is generated.

3. The infrared receiver circuit of claim 1, the circuit further comprising an analog to digital converter having an input coupled to the output pin and an output at which a digital ambient light level signal is generated.

4. The infrared receiver circuit of claim 3, wherein the analog to digital converter is further configured to logarithmically compress the digital ambient light level signal.

5. The infrared receiver circuit of claim 1, the circuit further comprising pulse width modulation encoder having an input coupled to the output pin and an output at which a pulse width encoded ambient light level signal is generated.

6. The infrared receiver circuit of claim 5, wherein the pulse width modulation encoder is configured to logarithmically compress the pulse width encoded ambient light level signal.

7. The infrared receiver circuit of claim 1, the circuit further comprising a current amplifier configured to control a backlight for illuminating a display.

8. A system having an infrared receiver, the system comprising:

an infrared receiver circuit configured to receive an infrared data signal using a receive photodiode and compensate for an ambient light level incident on the receive photodiode by generating a DC ambient current signal, where the DC ambient current signal is accessible external to the infrared receiver circuit; and

a control circuit configured to receive the DC ambient current signal and, responsive thereto, determine the ambient light level and generate a display illumination control signal accordingly.

9. The system of claim 8, where the control circuit further comprises a processor.

10. The system of claim 9, where the processor is configured to monitor the DC ambient current signal to detect outdoor light conditions and adjust the display illumination control signal for outdoor light conditions.

11. The system of claim 9, where the processor is further configured to monitor the DC ambient current signal for amplitude modulation to detect amplitude modulation corresponding to indoor light conditions and adjust the display illumination control signal for indoor light conditions.

12. The system of claim 11, where the processor is further configured to distinguish a type of source for the indoor light conditions and adjust the display illumination control signal for the type of source for the indoor light conditions.

13. The system of claim 8, where the control circuit further comprises control means for converting the DC ambient current signal to the display illumination control signal.

14. A method for display illumination control in a system having an infrared receiver, the method comprising the steps of:

providing an infrared receiver circuit for receiving an infrared data signal;

compensating for an ambient light level by generating a DC ambient current signal in the infrared receiver circuit;

determining the ambient light level from the DC ambient current signal; and

generating a display illumination control signal based on the ambient light level determined from the DC ambient current signal.

15. The method of claim 14, wherein:

the step of determining the ambient light level from the DC ambient current signal includes monitoring the DC ambient current signal to detect outdoor light conditions; and

the step of generating a display illumination control signal based on the ambient light level determined from the DC ambient current signal further comprises adjusting the display illumination control signal for outdoor light conditions.

16. The method of claim 14, wherein:

the step of determining the ambient light level from the DC ambient current signal includes monitoring the DC ambient current signal for amplitude modulation to detect amplitude modulation corresponding to indoor light conditions; and

the step of generating a display illumination control signal based on the ambient light level determined from the DC ambient current signal further comprises adjusting the display illumination control signal for indoor light conditions.

17. The method of claim 16, wherein:

the step of monitoring the DC ambient current signal for amplitude modulation to detect amplitude modulation corresponding to indoor light conditions further comprises detecting indoor light conditions corresponding to an incandescent light source; and

the step of generating a display illumination control signal based on the ambient light level determined from the DC ambient current signal further comprises adjusting the display illumination control signal for indoor light conditions corresponding to the incandescent light source.

18. The method of claim 16, wherein:

the step of monitoring the DC ambient current signal for amplitude modulation to detect amplitude modulation corresponding to indoor light conditions further comprises detecting indoor light conditions corresponding to a fluorescent light source; and

the step of generating a display illumination control signal based on the ambient light level determined from the DC ambient current signal further comprises adjusting the display illumination control signal for indoor light conditions corresponding to the fluorescent light source.

19. The method of claim 14, the method further comprising the steps of:

accessing the DC ambient current signal externally to the infrared receiver circuit; and

providing a control circuit external to the infrared receiver circuit for converting the DC ambient current signal to the display illumination control signal.

20. The method of claim 19, where the step of providing a control circuit external to the infrared receiver circuit further comprises at least one of providing a processor and providing a control means.