Time division light output sensing and brightness adjustment for different spectra of light emitting diodes

• US 8,299,722 B2
• Filed: 06/30/2009
• Issued: 10/30/2012
• Est. Priority Date: 12/12/2008
• Status: Expired due to Fees

• Current Assignee: Philips Lighting BV (Koninklijke Philips N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Melanson, John L.
• Primary Examiner(s): Cho, James H
• Application Number:
  US12/495,185
• Publication Number:
  US 20100148677A1
• Time in Patent Office: 1,218 Days
• Field of Search: 315149-159, 315/291, 315307-326
• US Class Current: 315/291
• CPC Class Codes: H05B 45/22 using optical feedback

Abstract

In at least one embodiment, brightness multiple LEDs is adjusted by modifying power to subgroups of the multiple LEDs during different times and detecting the brightness of the LEDs during the reductions of power. In at least one embodiment, once the brightness of the LEDs are determined, a controller determines if the brightness meet target brightness values, and, if not, the controller adjusts each LED with the goal meet the target brightness values. In at least one embodiment, a process of modifying power to the subgroups of multiple LEDs over time and adjusting the brightness of the LEDs is referred as “time division and light output sensing and adjusting. Thus, in at least one embodiment, a lighting system includes time division light output sensing and adjustment for different spectrum light emitting diodes (LEDs).

Claims

1. An apparatus comprising:

a controller configured to at least adjust brightness of light emitted from a first light emitting diode (LED) and adjust brightness of light emitted from a second LED, wherein, during operation of the controller, the light emitted from the first LED has a different spectrum than the light emitted from the second LED and the controller is further configured to at least;

i. receive a first signal indicating a brightness of received light at a first time from both the first and second LEDs;

ii. receive a second signal indicating a brightness of the received light at a second time from both the first and second LEDs, wherein a relative contribution to the brightness from the first and second LEDs is different for the first and second times;

iii. determine the brightness of light emitted from the first LED and the brightness of light emitted from the second LED using information from the first and second signals; and

iv. adjust the brightness of the light emitted from the first LED and the brightness of the light emitted from the second LED in accordance with one or more brightness related target values.

2. The apparatus of claim 1 wherein:

to receive the first signal indicating the brightness of received light at the first time comprises to receive the first signal from at least a first sensor indicating the brightness of received light at the first time; and

receive the second signal indicating the brightness of the received light at the second time comprises to receive the second signal from the at least first-sensor indicating a brightness of the received light at a second time.

3. The apparatus of claim 1 wherein:

to receive a first signal indicating a brightness of received light at a first time comprises to receive the first signal from at least a first sensor indicating a brightness of received light at a first time; and

to receive a second signal indicating a brightness of the received light at a second time comprises to receive the second signal from at least a second sensor indicating a brightness of the received light at a second time.

4. The apparatus of claim 1 wherein the first and second LEDs are members of groups consisting of:

red and green, red and yellow, amber and blue, green and blue, and red and blue.

5. The apparatus of claim 1 wherein the first LED is a member of a first set of multiple LEDs having approximately identical spectra and the second LED is a member of a second set of multiple LEDs having approximately identical spectra.

6. The apparatus of claim 1 wherein the controller is further configured to:

adjust the brightness of the light emitted from the first and second LEDs to compensate for at least one of (a) LED temperature changes and (b) light output changes over time.

7. The apparatus of claim 2 wherein at least one of the sensors is a broad spectrum light sensor.

8. The apparatus of claim 7 wherein a single, broad spectrum sensor provides the signals indicating brightness at the first and second times.

9. The apparatus of claim 1 wherein the controller is further configured to:

modulate current to the first and second LEDs so that the relative contribution to the brightness of the light received by one or more sensors is different for the first and second times.

10. The apparatus of claim 9 wherein to modulate current to the first and second LEDs comprises:

reducing current to the first LED to zero while providing current to the second LED during the first time; and

reducing current to the second LED to zero while providing current to the first LED during the second time.

11. The apparatus of claim 9 wherein to modulate current to the first and second LEDs comprises:

providing less average current to the first LED than the second LED during the first time and providing less average current to the second LED than the first LED during the second time.

12. The apparatus of claim 9 wherein to modulate current to the first and second LEDs comprises:

modulating current to the first and second LEDs during sequential times.

13. The apparatus of claim 9 wherein to modulate current to the first and second LEDs comprises:

interspersing reductions in current to the first and second LEDs over time.

14. The apparatus of claim 1 wherein the controller is further configured to adjust brightness of light emitted from at least a third LED, wherein during operation of the controller, the light emitted from the third LED has a different spectrum than light emitted from the first and second LEDs, wherein the controller is further configured to at least:

i. receive a third signal indicating a brightness of the received light at a third time, wherein a relative contribution to the brightness from the first, second, and third LEDs is different for the first, second, and third times;

ii. determine the brightness of light emitted from the first LED, the brightness of light emitted from the second LED, and the brightness of light emitted from the third LED using information from the signals; and

iii. adjust the brightness of the light emitted from the first LED, the brightness of the light emitted from the second LED, and the brightness of light emitted from the third LED in accordance with one or more brightness related target values.

15. The apparatus of claim 14 wherein the first LED is a red LED, the second LED is a green LED, and the third LED is a blue LED.

16. An apparatus comprising:

a lamp having at least a first light emitting diode (LED) and a second LED, wherein, during operation, light output of the first LED has a different spectrum than light output from the second LED;

one or more sensors to sense brightness of received light; and

a controller coupled to the lamp and the sensor, wherein the controller is configured to at least;

i. receive a first signal from at least one of the sensors indicating a brightness of the received light at a first time from both the first and second LEDs;

ii. receive a second signal from at least one of the sensors indicating a brightness of the received light at a second time from both the first and second LEDs, wherein a relative contribution to the brightness from the first and second LEDs is different for the first and second times;

iii. determine the brightness of light emitted from the first LED and the brightness of light emitted from the second LED using information from the first and second signals; and

iv. adjust the brightness of the light emitted from the first LED and the brightness of the light emitted from the second LED in accordance with one or more brightness related target values.

17. The apparatus of claim 16 wherein the first and second LEDs are members of groups consisting of:

red and green, red and yellow, amber and blue, green and blue, and red and blue.

18. The apparatus of claim 16 wherein the first LED is a member of a first set of multiple LEDs having approximately identical spectra and the second LED is a member of a second set of multiple LEDs having approximately identical spectra.

19. The apparatus of claim 16 wherein the controller is further configured to:

adjust the brightness of the first and second LEDs to compensate for at one of (a) LED temperature changes and (b) light output changes over time.

20. The apparatus of claim 16 wherein at least one of the sensors is a broad spectrum sensor.

21. The apparatus of claim 20 wherein a single, broad spectrum sensor provides the signals indicating brightness at the first and second times.

22. The apparatus of claim 16 wherein the controller is further configured to:

modulate current to the first and second LEDs so that the relative contribution to the brightness of the light received by the one or more sensors is different for the first and second times.

23. The apparatus of claim 22 wherein to modulate current to the first and second LEDs comprises:

reducing current to the first LED to zero while providing current to the second LED during the first time; and

reducing current to the second LED to zero while providing current to the first LED during the second time.

24. The apparatus of claim 22 wherein to modulate current to the first and second LEDs comprises:

providing less average current to the first LED than the second LED during the first time and providing less average current to the second LED than the first LED during the second time.

25. The apparatus of claim 22 wherein to modulate current to the first and second LEDs comprises:

modulating current to the first and second LEDs during sequential times.

26. The apparatus of claim 22 wherein to modulate current to the first and second LEDs comprises:

interspersing reductions in current to the first and second LEDs over time.

27. The apparatus of claim 16 wherein the lamp includes at least a third LED, wherein during operation of the controller, the light emitted from the third LED has a different spectrum than light emitted from the first and second LEDs, wherein the controller is further configured to at least:

i. receive a third signal indicating a brightness of the received light at a third time, wherein a relative contribution to the brightness from the first, second, and third LEDs is different for the first, second, and third times;

ii. determine the brightness of light emitted from the first LED, the brightness of light emitted from the second LED, and the brightness of light emitted from the third LED using information from the signals; and

iii. adjust the brightness of the light emitted from the first LED, the brightness of the light emitted from the second LED, and the brightness of light emitted from the third LED in accordance with one or more brightness related target values.

28. The apparatus of claim 27 wherein the first LED is a red LED, the second LED is a green LED, and the third LED is a blue LED.

29. A method to at least adjust brightness of light emitted from a first light emitting diode (LED) and adjust brightness of light emitted from a second LED, wherein the light emitted from the first LED has a different spectrum than the light emitted from the second LED, the method comprising:

receiving a first signal indicating a brightness of received light at a first time;

from both the first and second LEDs

receiving a second signal indicating a brightness of the received light at a second time from both the first and second LEDs, wherein a relative contribution to the brightness from the first and second LEDs is different for the first and second times;

determining the brightness of light emitted from the first LED and the brightness of light emitted from the second LED using information from the first and second signals; and

adjusting the brightness of the light emitted from the first LED and the brightness of the light emitted from the second LED in accordance with one or more brightness related target values.

30. The method of claim 29 wherein the first and second LEDs are members of groups consisting of:

red and green, red and yellow, amber and blue, green and blue, and red and blue.

31. The method of claim 29 wherein the first LED is a member of a first set of multiple LEDs having approximately identical spectra and the second LED is a member of a second set of multiple LEDs having approximately identical spectra.

32. The method of claim 29 further comprising:

adjusting the brightness of the light emitted from the first and second LEDs to compensate for at one of (a) LED temperature changes and (b) light output changes over time.

33. The method of claim 29 further comprising:

receiving the signal indicating the brightness of received light at the first and second times from a single broad spectrum sensor.

34. The method of claim 29 further comprising:

receiving the signal indicating the brightness of received light at the first and second times from one or more sensors; and

modulating current to the first and second LEDs so that the relative contribution to the brightness of the light received by the one or more sensors is different for the first and second times.

35. The method of claim 34 wherein modulating current to the first and second LEDs comprises:

reducing current to the first LED to zero while providing current to the second LED during the first time; and

reducing current to the second LED to zero while providing current to the first LED during the second time.

36. The method of claim 34 wherein modulating current to the first and second LEDs comprises:

providing less power to the first LED than the second LED during the first time and providing less power to the second LED than the first LED during the second time.

37. The method of claim 34 wherein modulating current to the first and second LEDs comprises:

modulating power to the first and second LEDs during sequential times.

38. The method of claim 34 wherein modulating current to the first and second LEDs comprises:

interspersing reductions in power to the first and second LEDs over time.

39. The method of claim 29 wherein the lamp includes at least a third LED, wherein during operation of the controller, light output of the third LED has a different spectrum than light output from the first and second LEDs, the method further comprising:

receiving a third signal indicating a brightness of the received light at a third time, wherein a relative contribution to the brightness from the first, second, and third LEDs is different for the first, second, and third times;

determining the brightness of light emitted from the first LED, the brightness of light emitted from the second LED, and the brightness of light emitted from the third LED using information from the signals; and

adjusting the brightness of the light emitted from the first LED, the brightness of the light emitted from the second LED, and the brightness of light emitted from the third LED in accordance with one or more brightness related target values.

40. The method of claim 39 wherein the first LED is a red LED, the second LED is a green LED, and the third LED is a blue LED.