Regulation of wavelength shift and perceived color of solid state lighting with temperature variation

• US 8,264,448 B2
• Filed: 10/29/2007
• Issued: 09/11/2012
• Est. Priority Date: 09/21/2007
• Status: Active Grant

• Current Assignee: Chemtron Research LLC (Intellectual Ventures LLC)
• Original Assignee: Point Somee LLC (Intellectual Ventures LLC)
• Inventors: Shteynberg, Anatoly, Rodriguez, Harry, Lehman, Bradley M., Zhou, Dongsheng
• Primary Examiner(s): Vo, Tuyet Thi
• Application Number:
  US11/927,173
• Publication Number:
  US 20090079358A1
• Time in Patent Office: 1,779 Days
• Field of Search: 315/102, 315/212, 315/211, 315/213, 315/214, 315 77- 82
• US Class Current: 345/102
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/28 using temperature feedback
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]

Abstract

Representative embodiments of the disclosure provide a system, apparatus, and method of controlling an intensity and spectrum of light emitted from a solid state lighting system. The solid state lighting system has a first emitted spectrum at full intensity and at a selected temperature, with a first electrical biasing for the solid state lighting system producing a first wavelength shift, and a second electrical biasing for the solid state lighting system producing a second, opposing wavelength shift. Representative embodiments provide for receiving information designating a selected intensity level or a selected temperature and providing a combined first electrical biasing and second electrical biasing to the solid state lighting system to generate emitted light having the selected intensity level and having a second emitted spectrum within a predetermined variance of the first emitted spectrum over a predetermined range of temperatures.

Claims

1. An illumination control apparatus for a solid state lighting system with compensation for spectral changes due to temperature variation, the apparatus comprising:

a memory configured to store a plurality of parameters corresponding to a predetermined range of temperatures, wherein the solid state lighting system is configured to have a first emitted spectrum at a selected intensity level and at a selected temperature, wherein a first electrical biasing for the solid state lighting system produces a first wavelength shift, and wherein a second electrical biasing for the solid state lighting system produces a second, opposing wavelength shift; and

a controller coupled to the memory, wherein the controller is configured to;

determine a temperature associated with the solid state lighting system;

retrieve from the memory a parameter from the plurality of parameters, wherein the parameter corresponds to the determined temperature; and

convert the parameter into a first control signal to provide a combined first electrical biasing and second electrical biasing to the solid state lighting system to thereby generate emitted light having a second emitted spectrum over the predetermined range of temperatures and within a predetermined variance of the first emitted spectrum.

2. The apparatus of claim 1, wherein the predetermined variance is substantially zero.

3. The apparatus of claim 1, wherein the predetermined variance is a selected tolerance level.

4. The apparatus of claim 1, wherein the first control signal is configured to provide the combined first electrical biasing and second electrical biasing as a superposition of the first electrical biasing and the second electrical biasing.

5. The apparatus of claim 1, wherein the first control signal is configured to provide the combined first electrical biasing and second electrical biasing as superposition of a symmetric or asymmetric AC signal on a DC signal having an average component.

6. The apparatus of claim 1, wherein the plurality of parameters comprises a duty cycle parameter and an average current level parameter for the combined first electrical biasing and second electrical biasing.

7. The apparatus of claim 1, wherein the combined first electrical biasing and second electrical biasing is a superposition of or an alternation between at least two of the following types of electrical biasing:

pulse width modulation, constant current regulation, pulse frequency modulation, and pulse amplitude modulation.

8. The apparatus of claim 1, wherein the controller is further configured to generate a second control signal for a cooling element coupled to the solid state lighting system, and wherein the cooling element is configured to cool the solid state lighting system to maintain the second emitted spectrum within the predetermined variance.

9. The apparatus of claim 1, wherein the controller is further configured to generate a second control signal to reduce the intensity of the light emitted from the solid state lighting system to maintain the second emitted spectrum within the predetermined variance.

10. The apparatus of claim 1, wherein the controller is further configured to determine the temperature associated with the solid state lighting system in response to a temperature signal received from a junction temperature sensor associated with the solid state lighting system.

11. The apparatus of claim 1, wherein the controller is further configured to determine the temperature associated with the solid state lighting system in response to a temperature signal received from a device having a temperature sensor associated with the solid state lighting system.

12. The apparatus of claim 11, wherein the device is a heat sink or an enclosure for the solid state lighting system.

13. The apparatus of claim 1, wherein the first control signal is configured to provide the combined first electrical biasing and second electrical biasing as an alternation of the first electrical biasing and the second electrical biasing.

14. The apparatus of claim 13, wherein the first electrical biasing is configured to use pulse width modulation having a first duty cycle lower than a duty cycle at a full intensity level, and wherein the second electrical biasing is configured to use constant current regulation having an average current level lower than a current level at the full intensity level.

15. The apparatus of claim 14, wherein the first electrical biasing is configured to be provided for a first modulation period, wherein the second electrical biasing is configured to be provided for a second modulation period, and wherein the first duty cycle, the average current level, the first modulation period, and the second modulation period are configured to be predetermined and stored in the memory as the plurality of parameters to produce the second emitted spectrum within the predetermined variance for the determined temperature.

16. The apparatus of claim 13, wherein the solid state lighting system comprises a light emitting diode (“

LED”

), wherein the apparatus is couplable to a switch mode LED driver, and wherein the alternation of the first electrical biasing and second electrical biasing is configured to be provided during one of the following;

within a single dimming cycle of the switch mode LED driver, alternately every dimming cycle of the switch mode LED driver, alternately every second dimming cycle of the switch mode LED driver, alternately every third dimming cycle of the switch mode LED driver, alternately an equal number of consecutive dimming cycles of the switch mode LED driver, or alternately an unequal number of consecutive dimming cycles of the switch mode LED driver.

17. The apparatus of claim 1, wherein the plurality of parameters is configured to be predetermined from a statistical characterization of the solid state lighting system in response to a plurality of temperature levels.

18. The apparatus of claim 17, wherein the plurality of parameters is configured to be predetermined from a statistical characterization of the solid state lighting system in response to the first electrical biasing and the second electrical biasing at a plurality of intensity levels.

19. The apparatus of claim 1, wherein the plurality of parameters comprises a linear equation, and wherein the controller is further configured to generate the first control signal in real time from the linear equation to provide the combined first electrical biasing and second electrical biasing to produce the second emitted spectrum within the predetermined variance for the predetermined range of temperatures.

20. The apparatus of claim 1, wherein the solid state lighting system comprises a light emitting diode (“

LED”

).

21. The apparatus of claim 20, wherein the first electrical biasing and the second electrical biasing are configured to be a forward current or an LED bias voltage.

22. The apparatus of claim 20, wherein the controller is further configured to synchronize the first control signal with a switching cycle of a switch mode LED driver.

23. The apparatus of claim 1, wherein the solid state lighting system comprises a plurality of arrays of light emitting diodes, and wherein the controller is further configured to generate separate, corresponding control signals to provide a corresponding combined first electrical biasing and second electrical biasing to each array from the plurality of arrays of light emitting diodes to generate an overall second emitted spectrum within the predetermined variance of the first emitted spectrum and over the predetermined range of temperatures.

24. The apparatus of claim 23, wherein each combined first electrical biasing and second electrical biasing corresponds to a type of light emitting diode comprising the corresponding array from the plurality of arrays of light emitting diodes.

25. The apparatus of claim 24, wherein at least three arrays of the plurality of arrays of light emitting diodes have corresponding emission spectra of different colors.

26. The apparatus of claim 24, wherein the controller is further configured to generate a second control signal to modify a temperature of a selected array from the plurality of arrays of light emitting diodes to maintain the overall second emitted spectrum within the predetermined variance of the first emitted spectrum and over the predetermined range of temperatures.

27. The apparatus of claim 1, wherein the solid state lighting system comprises a plurality of arrays of light emitting diodes coupled to a corresponding plurality of driver circuits, and wherein the apparatus further comprises:

a plurality of controllers, wherein each controller from the plurality of controllers is couplable to a corresponding driver circuit, and wherein each controller is further configured to generate a separate, corresponding control signal to the corresponding driver circuit to provide a corresponding combined first electrical biasing and second electrical biasing to the corresponding array from the plurality of arrays of light emitting diodes to generate an overall second emitted spectrum within the predetermined variance of the first emitted spectrum over the predetermined range of temperatures.

28. The apparatus of claim 27, wherein each combined first electrical biasing and second electrical biasing corresponds to a type of light emitting diode comprising the corresponding array from the plurality of arrays of light emitting diodes.

29. The apparatus of claim 27, wherein at least three arrays from the plurality of arrays of light emitting diodes have corresponding emission spectra of different colors.

30. A solid state lighting system, comprising:

a plurality of arrays of light emitting diodes, wherein the plurality of arrays of light emitting diodes has a first emitted spectrum at a selected intensity level, a first electrical biasing for an array from the plurality of arrays producing a first wavelength shift, and a second electrical biasing for the array from the plurality of arrays producing a second, opposing wavelength shift;

a temperature sensor coupled to the array from the plurality of arrays of light emitting diodes;

a plurality of driver circuits, wherein each driver circuit is coupled to a corresponding array from the plurality of arrays of light emitting diodes;

an interface configured to receive information designating the selected intensity level;

a memory configured to store a plurality of parameters corresponding to a predetermined range of temperatures; and

a controller coupled to the memory and to a first driver circuit from the plurality of driver circuits, wherein the controller is configured to;

receive a temperature signal associated with the solid state lighting system;

retrieve a parameter from the plurality of parameters, wherein the parameter corresponds to the temperature signal from the memory; and

convert the parameter into a first control signal for the first driver circuit to provide a combined first electrical biasing and second electrical biasing to the solid state lighting system to thereby generate emitted light having a second emitted spectrum over the predetermined range of temperatures and within a predetermined variance of the first emitted spectrum.

31. The system of claim 30, wherein the predetermined variance is substantially zero or is a selected tolerance level.

32. The system of claim 30, wherein the first control signal is configured to provide the combined first electrical biasing and second electrical biasing as a superposition of or an alternation between at least two of the following types of electrical biasing:

pulse width modulation, constant current regulation, pulse frequency modulation, and pulse amplitude modulation.

33. The system of claim 30, wherein the plurality of parameters comprises a duty cycle parameter and an average current level parameter for the combined first electrical biasing and second electrical biasing.

34. The system of claim 30, wherein the controller is further configured to synchronize the first control signal with a switching cycle of the first driver circuit.

35. The system of claim 30, wherein the controller is further configured to modify the first control signal in response to the selected intensity level.

36. The system of claim 30, further comprising:

a cooling element coupled to a selected array from the plurality of arrays of light emitting diodes;

wherein the controller is further configured to generate a second control signal for the cooling element to lower a temperature of the array to maintain the overall second emitted spectrum within the predetermined variance of the first emitted spectrum.

37. The system of claim 30, wherein the controller is further configured to generate a second control signal to reduce the intensity of the light emitted from the array from the plurality of arrays of light emitting diodes to maintain the second emitted spectrum within the predetermined variance.

38. The system of claim 30, wherein the temperature sensor is configured to determine a junction temperature of the array from the plurality of arrays of light emitting diodes.

39. The system of claim 30, wherein the temperature sensor is configured to determine a temperature of a device of the array from the plurality of arrays of light emitting diodes.

40. The system of claim 39, wherein the device is a heat sink or an enclosure for the solid state lighting system.

41. The system of claim 30, wherein the system further comprises:

a plurality of controllers, wherein each controller from the plurality of controllers is coupled to a corresponding driver circuit, and wherein each controller is further configured to generate a separate, corresponding control signal to the corresponding driver circuit to provide a corresponding combined first electrical biasing and second electrical biasing to the corresponding array from the plurality of arrays of light emitting diodes to generate an overall second emitted spectrum within the predetermined variance of the first emitted spectrum.

42. The system of claim 30, wherein each combined first electrical biasing and second electrical biasing corresponds to a type of light emitting diode comprising the corresponding array from the plurality of arrays of light emitting diodes.

43. The system of claim 30, wherein the plurality of arrays of light emitting diodes comprises an array of red light emitting diodes, an array of green light emitting diodes, and an array of blue light emitting diodes.

44. A solid state lighting system, comprising:

a plurality of arrays of light emitting diodes, wherein a first array from the plurality of arrays has a first emitted spectrum at a full intensity level, wherein a first electrical biasing for the first array from the plurality of arrays produces a first wavelength shift, and wherein a second electrical biasing for the first array from the plurality of arrays produces a second, opposing wavelength shift;

a temperature sensor coupled to the first array from the plurality of arrays of light emitting diodes;

a driver circuit coupled to the first array from the plurality of arrays of light emitting diodes;

an interface configured to receive information designating a selected intensity level lower than the full intensity level;

a memory configured to store a plurality of parameters corresponding to a predetermined range of temperatures; and

a controller coupled to the memory and to the driver circuit, wherein the controller is configured to;

receive a temperature signal associated with the solid state lighting system;

retrieve a parameter from the plurality of parameters, wherein the parameter corresponds to the temperature signal from the memory; and

convert the parameter into a first control signal for the driver circuit to provide a combined first electrical biasing and second electrical biasing to the solid state lighting system to thereby generate emitted light having a second emitted spectrum over the predetermined range of temperatures and within a predetermined variance of the first emitted spectrum.

45. The system of claim 44, wherein the predetermined variance is substantially zero or is a selected tolerance level.

46. The system of claim 44, wherein the second emitted spectrum is an overall color generated within the predetermined variance, a sequence of a single color emitted at a given time, or a dynamic lighting effect as requested by a second signal received by the interface.

47. The system of claim 44, wherein the first control signal is configured to provide the combined first electrical biasing and second electrical biasing as a superposition of or an alternation between at least two of the following types of electrical biasing:

pulse width modulation, constant current regulation, pulse frequency modulation, and pulse amplitude modulation.

48. The system of claim 44, wherein the plurality of parameters comprises a duty cycle parameter and an average current level parameter for the combined first electrical biasing and second electrical biasing.

49. The system of claim 44, wherein the controller is further configured to synchronize the first control signal with a switching cycle of the driver circuit.

50. The system of claim 44, wherein the plurality of parameters further corresponds to a plurality of intensity levels.

51. The system of claim 50, wherein the controller is further configured to select corresponding parameters and to provide the first control signal in response to a selected intensity level from the plurality of intensity levels.

52. The system of claim 44, wherein the system further comprises:

a plurality of driver circuits, wherein each driver circuit from the plurality of driver circuits is coupled to a corresponding array from the plurality of arrays of light emitting diodes;

wherein the controller is further coupled to each driver circuit, and wherein the controller is further configured to generate a separate, corresponding control signal for the corresponding driver circuit to provide a corresponding combined first electrical biasing and second electrical biasing to the corresponding array from the plurality of arrays of light emitting diodes to thereby generate a corresponding second emitted spectrum over the predetermined range of temperatures and within the predetermined variance of the corresponding first emitted spectrum.

53. The system of claim 44, wherein the system further comprises:

a plurality of driver circuits, wherein each driver circuit from the plurality of driver circuits is coupled to a corresponding array from the plurality of arrays of light emitting diodes; and

a plurality of controllers, wherein each controller from the plurality of controllers is coupled to a corresponding driver circuit, and wherein each controller is configured to generate a separate, corresponding control signal for the corresponding driver circuit to provide a corresponding combined first electrical biasing and second electrical biasing to the corresponding array from the plurality of arrays of light emitting diodes to thereby generate a corresponding second emitted spectrum over the predetermined range of temperatures and within the predetermined variance of the corresponding first emitted spectrum.

54. The system of claim 44, wherein each combined first electrical biasing and second electrical biasing corresponds to a type of light emitting diode comprising the corresponding array from the plurality of arrays of light emitting diodes.

55. The system of claim 44, wherein the plurality of arrays of light emitting diodes comprises an array of red light emitting diodes, an array of green light emitting diodes, and an array of blue light emitting diodes.

56. The system of claim 44, further comprising:

a cooling element coupled to an array from the plurality of arrays of light emitting diodes;

wherein the controller is further configured to generate a second control signal for the cooling element to lower a temperature of the array to maintain the overall second emitted spectrum within the predetermined variance of the first emitted spectrum.

57. The system of claim 44, wherein the controller further comprises:

a dimming frame register;

an intensity register;

a programmable look-up table memory;

a programmable frame counter and cycle counter;

a block of operational signal registers;

an analog multiplexer; and

a digital-to-analog converter.

58. The system of claim 57, wherein the controller is further configured to program the operational signal registers with at least two peak current amplitude values, at least two current amplitude modulation values, and two current duty cycle values to thereby provide the first control signal to the driver circuit to provide the combination of the first electrical biasing and the second electrical biasing for the selected intensity level and emission wavelength control specified by the user interface.

59. The system of claim 58, wherein the controller is further configured to vary the intensity of the light emitting diodes without substantial optical output flickering by alternatively multiplexing the first control signal for the driver circuit from a first set of operational signal registers synchronously to an end of a current dimming frame counter while programming asynchronously a second set of operational signal registers with a second control signal.

60. The system of claim 59, wherein the controller is further configured to queue the second control signal to a current status at the end of the current dimming frame counter.

61. An apparatus for controlling an emitted spectrum from an array of light emitting diodes, the apparatus comprising:

an interface configured to receive information designating a selected intensity level lower than a full intensity level, wherein the array of light emitting diodes is configured to have a first emitted spectrum at the selected intensity level and at a selected temperature, wherein a first electrical biasing for the array produces a first wavelength shift, and wherein a second electrical biasing for the array produces a second, opposing wavelength shift;

a memory configured to store a plurality of parameters corresponding to a plurality of intensity levels and a plurality of temperatures, wherein a parameter from the plurality of parameters corresponds to the selected intensity level and a sensed or determined temperature; and

a controller coupled to the memory, wherein the controller is configured to retrieve the parameter from the memory and to convert the parameter into a corresponding control signal to provide a combined first electrical biasing and second electrical biasing to the array to thereby generate emitted light having the selected intensity level and having a second emitted spectrum within a predetermined variance of the first emitted spectrum over a predetermined range of temperatures.