Time division modulation with average current regulation for independent control of arrays of light emitting diodes

• US 20080116818A1
• Filed: 11/21/2006
• Published: 05/22/2008
• Est. Priority Date: 11/21/2006
• Status: Active Grant

• Current Assignee: Chemtron Research LLC (Intellectual Ventures LLC)
• Original Assignee: Exclara, Inc. (Million Star Technology Ltd.)
• Inventors: Rodriguez, Harry, Shteynberg, Anatoly
• Granted Patent: US 7,902,771 B2
• Time in Patent Office: Days
• US Class Current: 315/192
• CPC Class Codes: H05B 45/22 using optical feedback
• CPC Class Codes: H05B 45/24 using electrical feedback from LEDs or from LED modules
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/38 using boost topology
• CPC Class Codes: H05B 45/46 having LEDs disposed in parallel lines
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

Exemplary apparatus, method and system embodiments provide for separately and independently sourcing current to a series of light emitting diodes of a plurality of series of light-emitting diodes. An exemplary apparatus comprises a power converter which generates a current, a first multiplexer, and a controller. The controller provides for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes for a corresponding period of time. An average current provided by the power converter is determined as substantially equal to a sum of the corresponding currents through the plurality of series of light-emitting diodes. A total period for switching current to all of the series of light-emitting diodes is also determined. A corresponding time period for switching current to a selected corresponding series of light-emitting diodes is substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

Claims

1. An apparatus for providing current independently to a series of light emitting diodes of a plurality of series of light-emitting diodes, the apparatus comprising:

a power converter couplable to the plurality of series of light-emitting diodes, the power converter adapted to generate a current;

a first multiplexer couplable to the plurality of series of light-emitting diodes; and

a controller coupled to the power converter and to the first multiplexer, the controller adapted to provide for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes, of the plurality of series of light-emitting diodes, for a corresponding period of time.

2. The apparatus of claim 1, wherein the controller is further adapted to provide for no switching of current through the first multiplexer to all remaining series of light-emitting diodes while current is switched to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes.

3. The apparatus of claim 1, wherein the controller is further adapted to determine an average current provided by the power converter as about equal to a sum of a plurality of corresponding currents through the plurality of series of light-emitting diodes.

4. The apparatus of claim 3, wherein the controller is further adapted to determine a total period for switching current to all of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

5. The apparatus of claim 4, wherein the controller is further adapted to determine a corresponding time period for switching current to a selected corresponding series of light-emitting diodes as substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

6. The apparatus of claim 1, further comprising:

a memory coupled to the controller, the memory adapted to store, as a look up table, a plurality of-parameters corresponding to the plurality of series of light-emitting diodes.

7. The apparatus of claim 6, wherein the controller is further adapted to predict an output voltage across a selected series of light-emitting diodes based on the device parameters stored in memory and to revise the predicted output voltage based upon a measured output voltage across a selected series of light-emitting diodes.

8. The apparatus of claim 1, wherein the power converter further comprises a first voltage divider, and wherein the controller is further adapted to determine an input voltage across the first voltage divider.

9. The apparatus of claim 1, wherein the power converter further comprises a current sensor, and wherein the controller is further adapted to determine a peak input current through the current sensor.

10. The apparatus of claim 1, further comprising a plurality of second voltage dividers, each second voltage divider couplable in parallel to a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes, and wherein the controller is further adapted to determine a corresponding output voltage across the corresponding second voltage divider of the plurality of second voltage dividers.

11. The apparatus of claim 10, further comprising:

a second multiplexer coupled to the plurality of second voltage dividers and the controller, and wherein the controller is further adapted to control switching of the second multiplexer to a selected second voltage divider of the plurality of second voltage dividers.

12. The apparatus of claim 1, further comprising:

a third multiplexer couplable to the plurality of series of light-emitting diodes and coupled to the controller, and wherein the controller is further adapted to control switching of the third multiplexer to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes for measuring a corresponding current through the selected series of light-emitting diodes.

13. The apparatus of claim 12, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on a comparison of the measured corresponding current to a predetermined current level for the selected series of light-emitting diodes.

14. The apparatus of claim 1, wherein the first multiplexer further comprises:

a plurality of switches, each switch of the plurality of switches correspondingly couplable to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

15. The apparatus of claim 1, wherein the first multiplexer further comprises:

a plurality of switches, each switch of the plurality of switches correspondingly couplable to a second, low side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

16. The apparatus of claim 1, wherein the first multiplexer further comprises:

a plurality of first switches, each switch of the plurality of first switches correspondingly couplable to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes; and

a plurality of second switches, each switch of the plurality of second switches correspondingly couplable to a second, low side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

17. The apparatus of claim 1, further comprising:

a plurality of capacitors, each capacitor of the plurality of capacitors couplable to a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

18. The apparatus of claim 17, wherein the first multiplexer further comprises:

a plurality of first switches, each switch of the plurality of first switches correspondingly couplable to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes; and

a second switch couplable to the plurality of capacitors.

19. The apparatus of claim 1, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on an integer multiple of a period of switching of the power converter.

20. The apparatus of claim 1, wherein the controller is further adapted to control switching of the first multiplexer to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes when current through the power converter is substantially zero.

21. The apparatus of claim 1, wherein the controller is further adapted, in response to a first input, to adjust an output brightness of the plurality of series of light-emitting diodes by modifying each corresponding period of time of current switching to each of the series of light-emitting diodes.

22. The apparatus of claim 1, wherein the controller is further adapted, in response to a second input, to adjust an output color of the plurality of series of light-emitting diodes by modifying at least one corresponding period of time of current switching to at least one of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

23. A lighting system, comprising:

a plurality of series of light-emitting diodes;

a power converter coupled to the plurality of series of light-emitting diodes, the power converter adapted to generate a current;

a first multiplexer coupled to the plurality of series of light-emitting diodes; and

a controller coupled to the power converter and to the first multiplexer, the controller adapted to provide for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes, of the plurality of series of light-emitting diodes, for a corresponding period of time.

24. The system of claim 23, wherein the controller is further adapted to provide for no switching of current through the first multiplexer to all remaining series of light-emitting diodes while current is switched to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes.

25. The system of claim 23, wherein the controller is further adapted to determine an average current provided by the power converter as substantially equal to a sum of a plurality of corresponding currents through the plurality of series of light-emitting diodes.

26. The system of claim 25, wherein the controller is further adapted to determine a total period for switching current to all of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

27. The system of claim 26, wherein the controller is further adapted to determine a corresponding time period for switching current to a selected corresponding series of light-emitting diodes as substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

28. The system of claim 23, further comprising:

a memory coupled to the controller, the memory adapted to store, as a look up table, a plurality of parameters corresponding to the plurality of series of light-emitting diodes.

29. The system of claim 28, wherein the controller is further adapted to predict an output voltage across a selected series of light-emitting diodes based on the device parameters stored in memory and to revise the predicted output voltage based upon a measured output voltage across a selected series of light-emitting diodes.

30. The system of claim 23, wherein the power converter further comprises a first voltage divider, and wherein the controller is further adapted to determine an input voltage across the first voltage divider.

31. The system of claim 23, wherein the power converter further comprises a current sensor, and wherein the controller is further adapted to determine a peak input current through the current sensor.

32. The system of claim 23, further comprising a plurality of second voltage dividers, each second voltage divider coupled in parallel to a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes, and wherein the controller is further adapted to determine a corresponding output voltage across the corresponding second voltage divider of the plurality of second voltage dividers.

33. The system of claim 32, further comprising:

a second multiplexer coupled to the plurality of second voltage dividers and the controller, and wherein the controller is further adapted to control switching of the second multiplexer to a selected second voltage divider of the plurality of second voltage dividers.

34. The system of claim 23, further comprising:

a third multiplexer coupled to the plurality of series of light-emitting diodes and to the controller, and wherein the controller is further adapted to control switching of the third multiplexer to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes for measuring a corresponding current through the selected series of light-emitting diodes.

35. The system of claim 34, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on a comparison of the measured corresponding current to a predetermined current level for the selected series of light-emitting diodes.

36. The system of claim 23, wherein the first multiplexer further comprises:

a plurality of switches, each switch of the plurality of switches correspondingly coupled to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

37. The system of claim 23, wherein the first multiplexer further comprises:

a plurality of switches, each switch of the plurality of switches correspondingly coupled to a second, low side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

38. The system of claim 23, wherein the first multiplexer further comprises:

a plurality of first switches, each switch of the plurality of first switches correspondingly coupled to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes; and

a plurality of second switches, each switch of the plurality of second switches correspondingly coupled to a second, low side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

39. The system of claim 23, further comprising:

a plurality of capacitors, each capacitor of the plurality of capacitors coupled to a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes.

40. The apparatus of claim 39, wherein the first multiplexer further comprises:

a plurality of first switches, each switch of the plurality of first switches correspondingly coupled to a first, high side of a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes; and

a second switch coupled to the plurality of capacitors.

41. The system of claim 23, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on an integer multiple of a period of switching of the power converter.

42. The system of claim 23, wherein the controller is further adapted to control switching of the first multiplexer to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes when current through the power converter is substantially zero.

43. The system of claim 23, wherein the controller is further adapted, in response to a first input, to adjust an output brightness of the plurality of series of light-emitting diodes by modifying each corresponding period of time of current switching to each of the series of light-emitting diodes.

44. The system of claim 23, wherein the controller is further adapted, in response to a second input, to adjust an output color of the plurality of series of light-emitting diodes by modifying at least one corresponding period of time of current switching to at least one of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

45. A method of selectively and independently providing power to a series of light emitting diodes of a plurality of series of light-emitting diodes, the method comprising:

generating an input DC current having a first average level; and

sequentially and separately switching the DC current to each of the series of light-emitting diodes, of the plurality of series of light-emitting diodes, for a corresponding period of time.

46. The method of claim 45, further comprising:

switching no current to all remaining series of light-emitting diodes while switching the DC current to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes.

47. The method of claim 45, further comprising:

determining the first average level of DC current as substantially equal to a sum of a plurality of corresponding currents through the plurality of series of light-emitting diodes.

48. The method of claim 47, further comprising:

determining a total period for switching current to all of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

49. The method of claim 48, further comprising:

determining a corresponding time period for switching current to a selected corresponding series of light-emitting diodes as substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

50. The method of claim 45, further comprising:

storing, as a look up table, a plurality of parameters corresponding to the plurality of series of light-emitting diodes.

51. The method of claim 50, further comprising:

predicting an output voltage across a selected series of light-emitting diodes, of the plurality of series of light-emitting diodes, based on the stored device parameters.

52. The method of claim 51, further comprising:

measuring a corresponding output voltage for each series of light emitting diodes of the plurality of series of light-emitting diodes.

53. The method of claim 52, further comprising:

updating the predicted output voltage across a selected series of light-emitting diodes, of the plurality of series of light-emitting diodes, based on a corresponding measured output voltage.

54. The method of claim 45, further comprising:

determining an input voltage.

55. The method of claim 45, further comprising:

determining a peak input DC current.

56. The method of claim 45, further comprising:

determining a corresponding output voltage for each series of light emitting diodes of the plurality of series of light-emitting diodes.

57. The method of claim 45, further comprising:

measuring a corresponding current through each series of light-emitting diodes of the plurality of series of light-emitting diodes.

58. The method of claim 45, further comprising:

determining the corresponding period of time for switching of current to a selected series of light-emitting diodes based on a comparison of the measured corresponding current to a predetermined current level for the selected series of light-emitting diodes.

59. The method of claim 45, further comprising:

determining the corresponding period of time for switching of current to a selected series of light-emitting diodes based on an integer multiple of a period of switching of a power converter.

60. The method of claim 45, further comprising:

switching current to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes when the input DC current is substantially zero.

61. The method of claim 45, further comprising:

in response to a first input, adjusting an output brightness of the plurality of series of light-emitting diodes by modifying each corresponding period of time of current switching to each of the series of light-emitting diodes.

62. The method of claim 45, further comprising:

in response to a second input, adjusting an output color of the plurality of series of light-emitting diodes by modifying at least one corresponding period of time of current switching to at least one of the series of light-emitting diodes of the plurality of series of light-emitting diodes.

63. An apparatus for providing current independently to a series of light emitting diodes of a plurality of series of light-emitting diodes, the apparatus comprising:

a power converter couplable to the plurality of series of light-emitting diodes, the power converter adapted to generate a current;

a first multiplexer couplable to the plurality of series of light-emitting diodes;

a memory adapted to store, as a look up table, a plurality of parameters corresponding to the plurality of series of light-emitting diodes; and

a controller coupled to the power converter, to the first multiplexer and to the memory, the controller adapted to provide for sequential and separate switching of the current through the first multiplexer to each of the series of light-emitting diodes, of the plurality of series of light-emitting diodes, for a corresponding period of time;

the controller further adapted to determine an average current provided by the power converter as a substantially equal to sum of a plurality of corresponding currents through the plurality of series of light-emitting diodes, to determine a total period for switching current to all of the series of light-emitting diodes of the plurality of series of light-emitting diodes, and to determine a corresponding time period for switching current to a selected corresponding series of light-emitting diodes as substantially equal to a proportion of the total period determined as a ratio of the corresponding current for the selected corresponding series of light-emitting diodes to the average current provided by the power converter.

64. The apparatus of claim 63, wherein the controller is further adapted to predict an output voltage across a selected series of light-emitting diodes based on the device parameters stored in memory and to revise the predicted output voltage based upon a measured output voltage across a selected series of light-emitting diodes.

65. The apparatus of claim 63, further comprising:

a plurality of second voltage dividers, each second voltage divider couplable in parallel to a corresponding series of light-emitting diodes of the plurality of series of light-emitting diodes;

a second multiplexer coupled to the plurality of second voltage dividers and the controller; and

wherein the controller is further adapted to control switching of the second multiplexer to a selected second voltage divider of the plurality of second voltage dividers and to determine a corresponding output voltage across the corresponding second voltage divider of the plurality of second voltage dividers.

66. The apparatus of claim 63, further comprising:

a third multiplexer couplable to the plurality of series of light-emitting diodes and coupled to the controller; and

wherein the controller is further adapted to control switching of the third multiplexer to a selected series of light-emitting diodes of the plurality of series of light-emitting diodes for measuring a corresponding current through the selected series of light-emitting diodes.

67. The apparatus of claim 63, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on a comparison of the measured corresponding current to a predetermined current level for the selected series of light-emitting diodes.

68. The apparatus of claim 63, wherein the controller is further adapted to determine the corresponding period of time for switching of current to a selected series of light-emitting diodes based on an integer multiple of a period of switching of the power converter.

69. The apparatus of claim 63, wherein the controller is further adapted, in response to a first input, to adjust an output brightness of the plurality of series of light-emitting diodes by modifying each corresponding period of time of current switching to each of the series of light-emitting diodes.

70. The apparatus of claim 63, wherein the controller is further adapted, in response to a second input, to adjust an output color of the plurality of series of light-emitting diodes by modifying at least one corresponding period of time of current switching to at least one of the series of light-emitting diodes of the plurality of series of light-emitting diodes.