Light emitting diode based lighting system with time division ambient light feedback response

• US 8,362,707 B2
• Filed: 06/30/2009
• Issued: 01/29/2013
• Est. Priority Date: 12/12/2008
• Status: Active Grant

• Current Assignee: Signify Holding B.V. (Signify N.V.)
• Original Assignee: Cirrus Logic Incorporated
• Inventors: Draper, William A., Melanson, John L.
• Primary Examiner(s): Chang, Daniel D
• Application Number:
  US12/495,206
• Publication Number:
  US 20100171442A1
• Time in Patent Office: 1,309 Days
• Field of Search: 315/291, 315/294, 315/149, 315/300, 315/307, 315/308, 315/302, 315/312, 315/224
• US Class Current: 315/291
• CPC Class Codes: H05B 45/20 Controlling the colour of the light
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 47/11 by determining the brightness or colour temperature of ambient light
• CPC Class Codes: H05B 47/175 by remote control
• CPC Class Codes: Y02B 20/40 Control techniques providing energy savings, e.g. smart controller or presence detection

Abstract

A lighting system includes time division light output sensing and adjustment for ambient light. In at least one embodiment, time division light output sensing involves modulating power to a light emitting diode (LED) set, and the set of LEDs includes one or more LEDs. In at least one embodiment, each LED in the LED set is included in a single lamp, and, in at least one embodiment, the set of LEDs is contained in multiple lamps. In at least one embodiment, for each lamp, a controller modulates power to the LED set by selectively reducing power to the LED set using time division algorithm to allow a light sensor to sense the brightness of ambient light with a reduced contribution from the LED set. In at least one embodiment, a lighting system also includes time division light output sensing and adjustment for different spectra LEDs.

Claims

1. An apparatus comprising:

a controller configured to couple to a sensor and a first light emitting diode (LED) of a lamp, wherein the controller is further configured to;

i. reduce power to a first light emitting diode (LED) coupled to the controller to a value greater than zero;

ii. receive a signal from the sensor indicating a brightness of light received by the sensor while the power to the first LED is reduced; and

iii. adjust the brightness of the first LED in accordance with a brightness related target value and the brightness indicated by the signal from the sensor.

2. The apparatus of claim 1 wherein the controller is configured to receive a sense signal from a light sensor indicating a brightness of ambient light and adjust the brightness of the LED to complement the ambient light.

3. The apparatus of claim 1 wherein reducing power to the first LED comprises reducing current to the first LED.

4. The apparatus of claim 1 wherein the controller is further configured to synchronize multiple controllers, wherein each of the multiple controllers is configured to:

i. reduce power to an LED coupled to the controller during a same period of time as a reduction in power to LEDs coupled to each of the other controllers;

ii. receive a signal from a sensor indicating a brightness of light received by the sensor while the power to the LED coupled to the controller is reduced; and

iii. adjust the brightness of the LED coupled to the controller in accordance with a brightness related target value.

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

i. receive a first signal indicating a brightness of received light at a first time;

ii. receive a second signal indicating a brightness of the received light at a second time, wherein a relative contribution to the brightness from the first LED and a second LED is different for the first and second times and wherein the light emitted from the first LED has a different spectrum than the light emitted from the second LED;

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 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.

6. The apparatus of claim 5 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.

7. The apparatus of claim 5 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.

8. The apparatus of claim 5 wherein the controller is further configured to:

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

9. The apparatus of claim 5 wherein at least one of the sensors is a broad spectrum sensor.

10. The apparatus of claim 9 wherein a single, broad spectrum sensor provides the signals indicating brightness at the first and second times.

11. The apparatus of claim 5 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.

12. The apparatus of claim 11 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.

13. The apparatus of claim 11 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.

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

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

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

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

16. The apparatus of claim 1 wherein to reduce the power to a first LED comprises to reduce the power to the first LED from a first brightness level and the controller is further configured to:

increase the power to the first brightness level with compensation for ambient light after receiving the signal from the sensor.

17. The apparatus of claim 1 wherein the controller comprises:

a time division module configured to facilitate time division power modulation to (i) reduce the power to the LED for no more than 0.02 seconds to sense the brightness of light from the LED and ambient light and then (ii) increase the power to the LED.

18. The apparatus of claim 17 wherein the time division module is further configured to repeat the time division power modulation at least every 1 second for multiple cycles of the time division power modulation.

19. An apparatus comprising:

a lamp having at least a first light emitting diode (LED);

a sensor to sense brightness of received light; and

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

i. reduce power to the first LED to a value greater than zero;

ii. receive a signal from the sensor indicating the brightness of light received by the sensor while the power to the first LED is reduced; and

iii. adjust the brightness of the first LED in accordance with a brightness related target value and the brightness indicated by the signal from the sensor.

20. The apparatus of claim 19 wherein the controller is configured to receive a sense signal from a light sensor indicating a brightness of ambient light and adjust the brightness of the LED to complement the ambient light.

21. The apparatus of claim 19 wherein reducing power to the first LED comprises reducing current to the first LED.

22. The apparatus of claim 19 wherein the controller is further configured to synchronize multiple controllers, wherein each of the multiple controllers is configured to:

i. reduce power to an LED coupled to the controller during a same period of time as a reduction in power to LEDs coupled to each of the other controllers;

ii. receive a signal from a sensor indicating a brightness of light received by the sensor while the power to the LED coupled to the controller is reduced; and

iii. adjust the brightness of the LED coupled to the controller in accordance with a brightness related target value.

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

i. receive a first signal indicating a brightness of received light at a first time;

ii. receive a second signal indicating a brightness of the received light at a second time, wherein a relative contribution to the brightness from the first LED and a second LED is different for the first and second times and wherein the light emitted from the first LED has a different spectrum than the light emitted from the second LED;

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 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.

24. The apparatus of claim 19 wherein to reduce the power to a first LED comprises to reduce the power to the first LED from a first brightness level and the controller is further configured to:

increase the power to the first brightness level with compensation for ambient light after receiving the signal from the sensor.

25. The apparatus of claim 19 wherein the controller comprises:

a time division module configured to facilitate time division power modulation to (i) reduce the power to the LED for no more than 0.02 seconds to sense the brightness of light from the LED and ambient light and then (ii) increase the power to the LED.

26. The apparatus of claim 25 wherein the time division module is further configured to repeat the time division power modulation at least every 1 second for multiple cycles of the time division power modulation.

27. A method for light harvesting, the method comprising:

reducing power to a first light emitting diode (LED) to a value greater than zero;

receiving a signal indicating a brightness of light while the power to the first LED is reduced; and

adjusting the brightness of the first LED in accordance with a brightness related target value and the brightness indicated by the signal.

28. The method of claim 27 wherein the method further comprises:

receiving a sense signal from a light sensor indicating a brightness of ambient light; and

adjusting the brightness of the LED to complement the ambient light.

29. The method of claim 27 wherein reducing power to the first LED comprises reducing current to the first LED.

30. The method of claim 27 further comprising:

operating multiple controllers in synchronization, wherein operating multiple controllers in synchronization comprises;

reducing power to an LED coupled to the controller during a same period of time as a reduction in power to LEDs coupled to each of the other controllers;

receiving a signal from a sensor indicating a brightness of light received by the sensor while the power to the LED coupled to the controller is reduced; and

adjusting the brightness of the LED coupled to the controller in accordance with a brightness related target value.

31. The method of claim 27 further comprising:

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

receiving a second signal indicating a brightness of the received light at a second time, wherein a relative contribution to the brightness from the first LED and a second LED is different for the first and second times and wherein light emitted from the first LED has a different spectrum than the light emitted from the second LED;

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

32. The method of claim 31 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.

33. The method of claim 31 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.

34. The method of claim 31 further comprising:

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

35. The method of claim 31 wherein at least one of the sensors is a broad spectrum sensor.

36. The method of claim 35 wherein a single, broad spectrum sensor provides the signals indicating brightness at the first and second times.

37. The method of claim 31 further comprising:

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.

38. The method of claim 37 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.

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

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

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

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

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

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

42. The method of claim 27 wherein reducing power to a first LED comprises reducing the power to the first LED from a first brightness level, and the method further comprises:

increasing the power to the first brightness level with compensation for ambient light after receiving the signal indicating the brightness of light while the power to the first LED is reduced.

43. The method of claim 27 wherein the method further comprises:

reducing power for no more than 0.02 seconds and then increasing power to the first LED using time division power modulation to respectively (i) reduce the power to the LED to sense the brightness of light from the LED and ambient light and (ii) increase the power to the LED.

44. The method of claim 43 further comprising:

repeating the time division power modulation at least every 1 second for multiple cycles of the time division power modulation.

45. An apparatus for light harvesting comprising:

means for reduce power to a first light emitting diode (LED) to a value greater than zero;

means for receiving a signal indicating a brightness of light while the power to the first LED is reduced; and

means for adjusting the brightness of the first LED in accordance with a brightness related target value and the brightness indicated by the signal from the sensor.