Apparatus, Method and System for Providing AC Line Power to Lighting Devices

• US 20100308739A1
• Filed: 06/04/2009
• Published: 12/09/2010
• Est. Priority Date: 06/04/2009
• Status: Active Grant

• Current Assignee: Chemtron Research LLC (Intellectual Ventures LLC)
• Original Assignee: Exclara, Inc. (Million Star Technology Ltd.)
• Inventors: Riordan, Thomas J., Dreyer, Stephen F., Rodriguez, Harry, Shteynberg, Anatoly, Eason, Mark, Zhou, Dongsheng, Lehman, Bradley M.
• Granted Patent: US 8,324,840 B2
• Time in Patent Office: Days
• US Class Current: 315/193
• CPC Class Codes: H05B 45/12 using optical feedback
• CPC Class Codes: H05B 45/48 having LEDs organised in strings and incorporating parallel shunting devices
• CPC Class Codes: H05B 45/50 responsive to malfunctions or undesirable behaviour of LEDs; responsive to LED life; Protective circuits
• CPC Class Codes: H05B 45/56 involving measures to prevent abnormal temperature of the LEDs

Abstract

An apparatus, method and system are disclosed for providing AC line power to lighting devices such as light emitting diodes (“LEDs”). An exemplary apparatus comprises: a plurality of LEDs coupled in series to form a first plurality of segments of LEDs; a plurality of switches coupled to the plurality of segments of LEDs to switch a selected segment into or out of a series LED current path in response to a control signal; a memory; and a controller which, in response to a first parameter and during a first part of an AC voltage interval, determines and stores in the memory a value of a second parameter and generates a first control signal to switch a corresponding segment of LEDs into the series LED current path; and during a second part of the AC voltage interval, when a current value of the second parameter is substantially equal to the stored value, generates a second control signal to switch a corresponding segment of LEDs out of the first series LED current path.

Claims

1. A method of providing power to a plurality of light emitting diodes couplable to receive an AC voltage, the plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes each comprising at least one light emitting diode, the plurality of segments of light emitting diodes coupled to a corresponding plurality of switches to switch a selected segment of light emitting diodes into or out of a series light emitting diode current path, the method comprising:

in response to a first parameter during a first part of an AC voltage interval, determining and storing a value of a second parameter and switching a corresponding segment of light emitting diodes into the series light emitting diode current path; and

during a second part of the AC voltage interval, monitoring the second parameter and when the current value of the second parameter is substantially equal to the stored value, switching a corresponding segment of light emitting diodes out of the series light emitting diode current path.

2. The method of claim 1, wherein the AC voltage comprises a rectified AC voltage, and the method further comprising:

determining when the rectified AC voltage is substantially close to zero; and

generating a synchronization signal.

3. The method of claim 2, further comprising:

determining the AC voltage interval from at least one determination of when the rectified AC voltage is substantially close to zero.

4. The method of claim 3, further comprising:

determining a first plurality of time intervals corresponding to a number of segments of light emitting diodes for the first part of the AC voltage interval; and

determining a second plurality of time intervals corresponding to the number of segments of light emitting diodes for the second part of the AC voltage interval.

5. The method of claim 4, further comprising:

during the first part of the AC voltage interval, at the expiration of each time interval of the first plurality of time intervals, switching a next segment of light emitting diodes into the series light emitting diode current path; and

during the second part of the AC voltage interval, at the expiration of each time interval of the second plurality of time intervals, in a reverse order, switching the next segment of light emitting diodes out of the series light emitting diode current path.

6. The method of claim 1, wherein the first parameter and the second parameter are time, or one or more time intervals, or time-based, or one or more clock cycle counts.

7. The method of claim 1, further comprising:

rectifying the AC voltage to provide a rectified AC voltage.

8. The method of claim 7, wherein the first parameter is a light emitting diode current level and the second parameter is a rectified AC input voltage level.

9. The method of claim 8, further comprising:

when a light emitting diode current level has reached a predetermined peak value during the first part of the AC voltage interval, determining and storing a first value of the rectified AC input voltage level and switching a first segment of light emitting diodes into the series light emitting diode current path;

monitoring the light emitting diode current level; and

when the light emitting diode current subsequently has reached the predetermined peak value during the first part of the AC voltage interval, determining and storing a second value of the rectified AC input voltage level and switching a second segment of light emitting diodes into the series light emitting diode current path.

10. The method of claim 9, further comprising:

monitoring the rectified AC voltage level;

when the rectified AC voltage level has reached the second value during the second part of the AC voltage interval, switching the second segment of light emitting diodes out of the series light emitting diode current path; and

when the rectified AC voltage level has reached the first value during the second part of the AC voltage interval, switching the first segment of light emitting diodes out of the series light emitting diode current path.

11. The method of claim 8, further comprising:

during the first part of the AC voltage interval, as a light emitting diode current successively reaches a predetermined peak level, determining and storing a corresponding value of the rectified AC voltage level and successively switching a corresponding segment of light emitting diodes into the series light emitting diode current path; and

during the second part of the AC voltage interval, as the rectified AC voltage level decreases to a corresponding voltage level, switching the corresponding segment of light emitting diodes out of the series light emitting diode current path.

12. The method of claim 11, wherein the switching of the corresponding segment of light emitting diodes out of the series light emitting diode current path is in a reverse order to the switching of the corresponding segment of light emitting diodes into the series light emitting diode current path.

13. The method of claim 8, further comprising:

when a light emitting diode current has reached a predetermined peak level during the first part of the AC voltage interval, determining and storing a first value of the rectified AC input voltage level; and

when the first value of the rectified AC input voltage is substantially equal to or greater than a predetermined voltage threshold, switching the corresponding segment of light emitting diodes into the series light emitting diode current path.

14. The method of claim 1, further comprising:

determining whether the AC voltage is phase modulated.

15. The method of claim 14, further comprising:

when the AC voltage is phase modulated, switching a segment of light emitting diodes into the series light emitting diode current path which corresponds to a phase modulated AC voltage level.

16. The method of claim 14, further comprising:

when the AC voltage is phase modulated, switching a segment of light emitting diodes into the series light emitting diode current path which corresponds to a time interval of the phase modulated AC voltage.

17. The method of claim 14, further comprising:

when the AC voltage is phase modulated, maintaining a parallel light emitting diode current path through a first switch concurrently with switching a next segment of light emitting diodes into the series light emitting diode current path through a second switch.

18. The method of claim 1, further comprising:

determining whether sufficient time remains in the first part of the AC voltage interval for a light emitting diode current to reach a predetermined peak level if a next segment of light emitting diodes is switched into the series light emitting diode current path.

19. The method of claim 18, further comprising:

when sufficient time remains in the first part of the AC voltage interval for the light emitting diode current to reach the predetermined peak level, switching the next segment of light emitting diodes into the series light emitting diode current path.

20. The method of claim 18, further comprising:

when sufficient time does not remain in the first part of the AC voltage interval for the light emitting diode current to reach the predetermined peak level, not switching the next segment of light emitting diodes into the series light emitting diode current path.

21. The method of claim 1, further comprising:

monitoring a light emitting diode current level; and

during the second part of the AC voltage interval, when the light emitting diode current level is greater than a predetermined peak level by a predetermined margin, determining and storing a new value of the second parameter and switching the corresponding segment of light emitting diodes into the series light emitting diode current path.

22. The method of claim 1, further comprising:

switching a plurality of segments of light emitting diodes to form a first series light emitting diode current path; and

switching a plurality of segments of light emitting diodes to form a second series light emitting diode current path in parallel with the first series light emitting diode current path.

23. The method of claim 1, further comprising:

during a third part of the AC voltage interval, switching a second plurality of segments of light emitting diodes to form a second series light emitting diode current path having a polarity opposite the series light emitting diode current path formed in the first part of the AC voltage interval; and

during a fourth part of the AC voltage interval switching the second plurality of segments of light emitting diodes out of the second series light emitting diode current path.

24. The method of claim 1, wherein selected segments of light emitting diodes of the plurality of segments of light emitting diodes each comprise light emitting diodes having light emission spectra of different colors or wavelengths.

25. The method of claim 24, further comprising:

selectively switching the selected segments of light emitting diodes into the series light emitting diode current path to provide a corresponding lighting effect.

26. The method of claim 24, further comprising:

selectively switching the selected segments of light emitting diodes into the series light emitting diode current path to provide a corresponding color temperature.

27. An apparatus couplable to receive an AC voltage, the apparatus comprising:

a rectifier to provide a rectified AC voltage;

a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes;

a plurality of switches correspondingly coupled to the plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a series light emitting diode current path;

a current sensor to sense a light emitting diode current level;

a voltage sensor to sense a rectified AC voltage level;

a memory to store a plurality of parameters; and

a controller coupled to the plurality of switches, to the memory, to the current sensor and to the voltage sensor, during a first part of a rectified AC voltage interval and when the light emitting diode current level has reached a predetermined peak light emitting diode current level, the controller to determine and store in the memory a corresponding value of the rectified AC voltage level and to switch a corresponding segment of light emitting diodes into the series light emitting diode current path; and

during a second part of a rectified AC voltage interval, the controller to monitor the rectified AC voltage level and when the current value of the rectified AC voltage level is substantially equal to the stored corresponding value of the rectified AC voltage level, to switch the corresponding segment of light emitting diodes out of the series light emitting diode current path.

28. The apparatus of claim 27, wherein when the rectified AC voltage level is substantially close to zero, the controller further is to generate a corresponding synchronization signal.

29. The apparatus of claim 27, wherein the controller further is to determine the rectified AC voltage interval from at least one determination of the rectified AC voltage level being substantially close to zero.

30. The apparatus of claim 27, wherein the controller, when the light emitting diode current level has reached the predetermined peak light emitting diode current level during the first part of a rectified AC voltage interval, further is to determine and store in the memory a first value of the rectified AC voltage level, switch a first segment of light emitting diodes into the series light emitting diode current path, monitor the light emitting diode current level, and when the light emitting diode current level subsequently has reached the predetermined peak light emitting diode current level during the first part of the rectified AC voltage interval, the controller further is to determine and store in the memory a second value of the rectified AC voltage level and switch a second segment of light emitting diodes into the series light emitting diode current path.

31. The apparatus of claim 30, wherein the controller further is to monitor the rectified AC voltage level and when the rectified AC voltage level has reached the stored second value during the second part of a rectified AC voltage interval, to switch the second segment of light emitting diodes out of the series light emitting diode current path, and when the rectified AC voltage level has reached the stored first value during the second part of a rectified AC voltage interval, to switch the first segment of light emitting diodes out of the series light emitting diode current path.

32. The apparatus of claim 27, wherein the controller further is to monitor the light emitting diode current level and when the light emitting diode current level has again reached the predetermined peak level during the first part of a rectified AC voltage interval, the controller further is to determine and store in the memory a corresponding next value of the rectified AC voltage level and switch a next segment of light emitting diodes into the series light emitting diode current path.

33. The apparatus of claim 32, wherein the controller further is to monitor the rectified AC voltage level and when the rectified AC voltage level has reached the next rectified AC voltage level during the second part of a rectified AC voltage interval, to switch the corresponding next segment of light emitting diodes out of the series light emitting diode current path.

34. The apparatus of claim 27, wherein during the first part of the rectified AC voltage interval, as the light emitting diode current level reaches the predetermined peak level, the controller further is to determine and store a corresponding value of the rectified AC voltage level and successively switch a corresponding segment of light emitting diodes into the series light emitting diode current path;

and during the second part of a rectified AC voltage interval, as the rectified AC voltage level decreases to a corresponding value, the controller further is to switch the corresponding segment of light emitting diodes out of the series light emitting diode current path.

35. The apparatus of claim 34, wherein the controller further is to switch the corresponding segments of light emitting diodes out of the series light emitting diode current path is in a reverse order to the switching of the corresponding segments of light emitting diodes into the series light emitting diode current path.

36. The apparatus of claim 27, wherein the controller further is to determine whether the rectified AC voltage is phase modulated.

37. The apparatus of claim 36, wherein the controller, when the rectified AC voltage is phase modulated, further is to switch a segment of light emitting diodes into the series light emitting diode current path which corresponds to the rectified AC voltage level.

38. The apparatus of claim 36, wherein the controller, when the rectified AC voltage is phase modulated, further is to switch a segment of light emitting diodes into the series light emitting diode current path which corresponds to a time interval of the rectified AC voltage level.

39. The apparatus of claim 36, wherein the controller, when the rectified AC voltage is phase modulated, further is to maintain a parallel light emitting diode current path through a first switch concurrently with switching a next segment of light emitting diodes into the series light emitting diode current path through a second switch.

40. The apparatus of claim 27, wherein the controller further is to determine whether sufficient time remains in the first part of the rectified AC voltage interval for the light emitting diode current level to reach the predetermined peak level if a next segment of light emitting diodes is switched into the series light emitting diode current path.

41. The apparatus of claim 40, wherein the controller, when sufficient time remains in the first part of the rectified AC voltage interval for the light emitting diode current level to reach the predetermined peak level, further is to switch the next segment of light emitting diodes into the series light emitting diode current path;

and when sufficient time does not remain in the first part of the rectified AC voltage interval for the light emitting diode current level to reach the predetermined peak level, the controller further is not to switch the next segment of light emitting diodes into the series light emitting diode current path.

42. The apparatus of claim 27, wherein the controller further is to monitor a light emitting diode current level;

and during the second part of the rectified AC voltage interval, when the light emitting diode current level is greater than a predetermined peak level by a predetermined margin, the controller further is to determine and store another corresponding value of the rectified AC voltage level and switch the corresponding segment of light emitting diodes into the series light emitting diode current path.

43. The apparatus of claim 27, wherein the controller further is to switch a plurality of segments of light emitting diodes to form a first series light emitting diode current path, and to switch a plurality of segments of light emitting diodes to form a second series light emitting diode current path in a parallel with the first series light emitting diode current path.

44. The apparatus of claim 27, wherein selected segments of light emitting diodes of the plurality of segments of light emitting diodes each comprise light emitting diodes having light emission spectra of different colors or wavelengths.

45. The apparatus of claim 44, wherein the controller further is to selectively switch the selected segments of light emitting diodes into the series light emitting diode current path to provide a corresponding lighting effect.

46. The apparatus of claim 44, wherein the controller further is to selectively switch the selected segments of light emitting diodes into the series light emitting diode current path to provide a corresponding color temperature.

47. An apparatus couplable to receive an AC voltage, the apparatus comprising:

a first plurality of light emitting diodes coupled in series to form a first plurality of segments of light emitting diodes;

a first plurality of switches coupled to the first plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a first series light emitting diode current path in response to a control signal;

a memory; and

a controller coupled to the plurality of switches and to the memory, the controller, in response to a first parameter and during a first part of an AC voltage interval, to determine and store in the memory a value of a second parameter and to generate a first control signal to switch a corresponding segment of light emitting diodes of the first plurality of segments of light emitting diodes into the first series light emitting diode current path; and

during a second part of the AC voltage interval, when a current value of the second parameter is substantially equal to the stored value, to generate a second control signal to switch a corresponding segment of light emitting diodes of the first plurality of segments of light emitting diodes out of the first series light emitting diode current path.

48. The apparatus of claim 47, wherein the first parameter and the second parameter comprise at least one of the following:

a time parameter, or one or more time intervals, or a time-based parameter, or one or more clock cycle counts.

49. The apparatus of claim 48, wherein the controller further is to determine a first plurality of time intervals corresponding to a number of segments of light emitting diodes of the first plurality of segments of light emitting diodes for the first part of the AC voltage interval, and to determine a second plurality of time intervals corresponding to the number of segments of light emitting diodes for the second part of the AC voltage interval.

50. The apparatus of claim 48, wherein the controller further is to retrieve from the memory a first plurality of time intervals corresponding to a number of segments of light emitting diodes of the first plurality of segments of light emitting diodes for the first part of the AC voltage interval, and a second plurality of time intervals corresponding to the number of segments of light emitting diodes for the second part of the AC voltage interval.

51. The apparatus of claim 50, wherein during the first part of the AC voltage interval, at the expiration of each time interval of the first plurality of time intervals, the controller further is to generate a corresponding control signal to switch a next segment of light emitting diodes into the series light emitting diode current path, and during the second part of the AC voltage interval, at the expiration of each time interval of the second plurality of time intervals, in a reverse order, to generate a corresponding control signal to switch the next segment of light emitting diodes out of the series light emitting diode current path.

52. The apparatus of claim 47, further comprising:

a rectifier to provide a rectified AC voltage;

wherein when the rectified AC voltage is substantially close to zero, the controller further is to generate a corresponding synchronization signal.

53. The apparatus of claim 52, wherein the controller further is to determine the AC voltage interval from at least one determination of the rectified AC voltage being substantially close to zero.

54. The apparatus of claim 47, further comprising:

a current sensor coupled to the controller; and

a voltage sensor coupled to the controller.

55. The apparatus of claim 54, wherein the first parameter is a light emitting diode current level and the second parameter is a voltage level.

56. The apparatus of claim 55, wherein the controller, when a light emitting diode current has reached a predetermined peak level during the first part of the AC voltage interval, further is to determine and store in the memory a first value of the AC voltage level and to generate the first control signal to switch a first segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path;

and when the light emitting diode current subsequently has reached the predetermined peak level during the first part of the AC voltage interval, the controller further is to determine and store in the memory a next value of the AC voltage level and to generate a next control signal switch a next segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path.

57. The apparatus of claim 56, wherein when the AC voltage level has reached the next value during the second part of a rectified AC voltage interval, the controller further is to generate another control signal to switch the next segment out of the first series light emitting diode current path;

and when the AC voltage level has reached the first value during the second part of a rectified AC voltage interval, to generate the second control signal to switch the first segment out of the first series light emitting diode current path.

58. The apparatus of claim 55, wherein during the first part of the AC voltage interval, as a light emitting diode current successively reaches a predetermined peak level, the controller further is to determine and store a corresponding value of the AC voltage level and successively generate a corresponding control signal to switch a corresponding segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path;

and during the second part of the AC voltage interval, as the AC voltage level decreases to a corresponding voltage level, the controller further is to successively generate a corresponding control signal to switch the corresponding segment of the first plurality of segments of light emitting diodes out of the first series light emitting diode current path.

59. The apparatus of claim 58, wherein the controller further is to successively generate a corresponding control signal to switch the corresponding segment out of the first series light emitting diode current path in a reverse order to the switching of the corresponding segment into the first series light emitting diode current path.

60. The apparatus of claim 47, wherein the controller further is to determine whether the AC voltage is phase modulated.

61. The apparatus of claim 60, wherein the controller, when the AC voltage is phase modulated, further is to generate a corresponding control signal to switch a segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path which corresponds to a phase modulated AC voltage level.

62. The apparatus of claim 60, wherein the controller, when the AC voltage is phase modulated, further is to generate a corresponding control signal to switch a segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path which corresponds to a time interval of the phase modulated AC voltage level.

63. The apparatus of claim 60, wherein the controller, when the AC voltage is phase modulated, further is to generate corresponding control signals to maintain a parallel second light emitting diode current path through a first switch concurrently with switching a next segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path through a second switch.

64. The apparatus of claim 47, wherein the controller further is to determine whether sufficient time remains in the first part of the AC voltage interval for a light emitting diode current to reach a predetermined peak level if a next segment of the first plurality of segments of light emitting diodes is switched into the first series light emitting diode current path.

65. The apparatus of claim 64, wherein the controller, when sufficient time remains in the first part of the AC voltage interval for the light emitting diode current to reach the predetermined peak level, further is to generate a corresponding control signal to switch the next segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path.

66. The apparatus of claim 47, wherein during the second part of the AC voltage interval and when the light emitting diode current level is greater than a predetermined peak level by a predetermined margin, the controller further is to determine and store a new value of the second parameter and generate a corresponding control signal to switch the corresponding segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path.

67. The apparatus of claim 47, wherein the controller further is to generate corresponding control signals to switch a plurality of segments of the first plurality of segments of light emitting diodes to form a second series light emitting diode current path in parallel with the first series light emitting diode current path.

68. The apparatus of claim 47, further comprising:

a second plurality of light emitting diodes coupled in series to form a second plurality of segments of light emitting diodes; and

a second plurality of switches coupled to the second plurality of segments of light emitting diodes to switch a selected segment of the second plurality of segments of light emitting diodes into or out of a second series light emitting diode current path;

wherein the controller is further coupled to the second plurality of switches, and further is to generate corresponding control signals to switch a plurality of segments of the second plurality of segments of light emitting diodes to form the second series light emitting diode current path in parallel with the first series light emitting diode current path.

69. The apparatus of claim 68, wherein the second series light emitting diode current path has a polarity opposite the first series light emitting diode current path.

70. The apparatus of claim 68, wherein a first current flow through the first series light emitting diode current path has an opposite direction to second current flow through the second series light emitting diode current path.

71. The apparatus of claim 68, wherein the controller further is to generate corresponding control signals to switch a plurality of segments of the first plurality of segments of light emitting diodes to form the first series light emitting diode current path during a positive polarity of the AC voltage and further is to generate corresponding control signals to switch a plurality of segments of the second plurality of segments of light emitting diodes to form the second series light emitting diode current path during a negative polarity of the AC voltage.

72. The apparatus of claim 47, wherein the first plurality of switches comprise a plurality of bipolar junction transistors or a plurality of field effect transistors.

73. The apparatus of claim 47, wherein each switch of the first plurality of switches is coupled to a first terminal of a corresponding segment of the first plurality of segments of light emitting diodes and coupled to a second terminal of the last segment of the first plurality of segments of light emitting diodes.

74. The apparatus of claim 47, further comprising:

a plurality of tri-state switches, comprising;

a plurality of operational amplifiers correspondingly coupled to the first plurality of switches;

a second plurality of switches correspondingly coupled to the first plurality of switches; and

a third plurality of switches correspondingly coupled to the first plurality of switches.

75. The apparatus of claim 47, wherein each switch of the first plurality of switches is coupled to a first terminal of a corresponding segment of the first plurality of segments of light emitting diodes and coupled to a second terminal of the corresponding segment of the first plurality of segments of light emitting diodes.

76. The apparatus of claim 47, further comprising:

a second plurality of switches.

77. The apparatus of claim 76, wherein each switch of the first plurality of switches is coupled to a first terminal of the first segment of the first plurality of segments of light emitting diodes and coupled to a second terminal of a corresponding segment of the first plurality of segments of light emitting diodes;

and wherein each switch of the second plurality of switches is coupled to a second terminal of a corresponding segment of the first plurality of segments of light emitting diodes and coupled to a second terminal of the last segment of the first plurality of segments of light emitting diodes.

78. The apparatus of claim 47, further comprising:

a current limiting circuit.

79. The apparatus of claim 47, further comprising:

a dimming interface circuit.

80. The apparatus of claim 47, further comprising:

a DC power source circuit coupled to the controller.

81. The apparatus of claim 47, further comprising:

a temperature protection circuit.

82. The apparatus of claim 47, wherein selected segments of light emitting diodes of the plurality of segments of light emitting diodes each comprise light emitting diodes having light emission spectra of different colors.

83. The apparatus of claim 82, wherein the controller further is to generate corresponding control signals to selectively switch the selected segments of light emitting diodes into the first series light emitting diode current path to provide a corresponding lighting effect.

84. The apparatus of claim 82, wherein the controller further is to generate corresponding control signals to selectively switch the selected segments of light emitting diodes into the first series light emitting diode current path to provide a corresponding color temperature.

85. The apparatus of claim 47, wherein the controller further comprises:

a first analog-to-digital converter couplable to a first sensor;

a second analog-to-digital converter couplable to a second sensor;

a digital logic circuit; and

a plurality of switch drivers correspondingly coupled to the first plurality of switches.

86. The apparatus of claim 47, wherein the controller comprises a plurality of analog comparators.

87. The apparatus of claim 47, wherein the first parameter and the second parameter comprise at least one of the following parameters:

a time period, a peak current level, an average current level, a moving average current level, an instantaneous current level, a peak voltage level, an average voltage level, a moving average voltage level, an instantaneous voltage level, an average output optical brightness level, a moving average output optical brightness level,a peak output optical brightness level, or an instantaneous output optical brightness level.

88. The apparatus of claim 47, wherein the first parameter and the second parameter are the same parameter.

89. An apparatus couplable to receive an AC voltage, the apparatus comprising:

a first plurality of light emitting diodes coupled in series to form a first plurality of segments of light emitting diodes;

a first plurality of switches coupled to the first plurality of segments of light emitting diodes to switch a selected segment of light emitting diodes into or out of a first series light emitting diode current path in response to a control signal;

at least one sensor; and

a control circuit coupled to the plurality of switches and to the at least one sensor, the controller, in response to a first parameter and during a first part of an AC voltage interval, to determine a value of a second parameter and to generate a first control signal to switch a corresponding segment of light emitting diodes of the first plurality of segments of light emitting diodes into the first series light emitting diode current path; and

during a second part of the AC voltage interval, when a current value of the second parameter is substantially equal to a corresponding determined value, to generate a second control signal to switch a corresponding segment of light emitting diodes of the first plurality of segments of light emitting diodes out of the first series light emitting diode current path.

90. The apparatus of claim 89, wherein the first parameter and the second parameter comprise at least one of the following:

a time parameter, or one or more time intervals, or a time-based parameter, or one or more clock cycle counts.

91. The apparatus of claim 90, wherein the control circuit further is to calculate or obtain from a memory a first plurality of time intervals corresponding to a number of segments of light emitting diodes of the first plurality of segments of light emitting diodes for the first part of the AC voltage interval, and to calculate or obtain from a memory a second plurality of time intervals corresponding to the number of segments of light emitting diodes for the second part of the AC voltage interval.

92. The apparatus of claim 91, wherein during the first part of the AC voltage interval, at the expiration of each time interval of the first plurality of time intervals, the control circuit further is to generate a corresponding control signal to switch a next segment of light emitting diodes into the series light emitting diode current path, and during the second part of the AC voltage interval, at the expiration of each time interval of the second plurality of time intervals, in a reverse order, to generate a corresponding control signal to switch the next segment of light emitting diodes out of the series light emitting diode current path.

93. The apparatus of claim 89, further comprising:

a memory to store a plurality of determined values.

94. The apparatus of claim 93, wherein the first parameter is a light emitting diode current level and the second parameter is a voltage level, and wherein during the first part of the AC voltage interval, as a light emitting diode current successively reaches a predetermined level, the control circuit further is to determine and store in the memory a corresponding value of the AC voltage level and successively generate a corresponding control signal to switch a corresponding segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path;

and during the second part of the AC voltage interval, as the AC voltage level decreases to a corresponding voltage level, the controller further is to successively generate a corresponding control signal to switch the corresponding segment of the first plurality of segments of light emitting diodes out of the first series light emitting diode current path.

95. The apparatus of claim 89, wherein the first parameter and the second parameter are the same parameter comprising a voltage or a current level, and wherein during the first part of the AC voltage interval, as the voltage or current level successively reaches a predetermined level, the control circuit further is to successively generate a corresponding control signal to switch a corresponding segment of the first plurality of segments of light emitting diodes into the first series light emitting diode current path;

and during the second part of the AC voltage interval, as the voltage or current level decreases to a corresponding level, the controller further is to successively generate a corresponding control signal to switch the corresponding segment of the first plurality of segments of light emitting diodes out of the first series light emitting diode current path.

96. An apparatus couplable to receive an AC voltage, the apparatus comprising:

a rectifier to provide a rectified AC voltage;

a plurality of light emitting diodes coupled in series to form a plurality of segments of light emitting diodes;

a plurality of switches, each switch of the plurality of switches coupled to a first terminal of a corresponding segment of the first plurality of segments of light emitting diodes and coupled to a second terminal of the last segment of the first plurality of segments of light emitting diodes;

a current sensor to sense a light emitting diode current level;

a voltage sensor to sense a rectified AC voltage level;

a memory to store a plurality of parameters; and

a controller coupled to the plurality of switches, to the memory, to the current sensor and to the voltage sensor, during a first part of a rectified AC voltage interval and when the light emitting diode current level has reached a predetermined peak light emitting diode current level, the controller to determine and store in the memory a corresponding value of the rectified AC voltage level and to generate corresponding control signals to switch a corresponding segment of light emitting diodes into the series light emitting diode current path; and

during a second part of a rectified AC voltage interval and when the current value of the rectified AC voltage level is substantially equal to the stored corresponding value of the rectified AC voltage level, the controller to generate corresponding control signals to switch the corresponding segment of light emitting diodes out of the series light emitting diode current path.