Current regulator for modulating brightness levels of solid state lighting

• US 20070182338A1
• Filed: 01/19/2007
• Published: 08/09/2007
• Est. Priority Date: 01/20/2006
• 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 7,902,769 B2
• Time in Patent Office: Days
• US Class Current: 315/200.R
• CPC Class Codes: H05B 45/10 Controlling the intensity of the light
• CPC Class Codes: H05B 45/345 Current stabilisation; Maintaining constant current
• CPC Class Codes: H05B 45/3575 by means of dummy loads or bleeder circuits, e.g. for dimmers
• CPC Class Codes: H05B 45/3577 Emulating the dimming characteristics, brightness or colour temperature of incandescent lamps
• CPC Class Codes: H05B 45/3725 Switched mode power supply [SMPS]
• CPC Class Codes: H05B 45/375 using buck topology
• CPC Class Codes: Y02B 20/30 Semiconductor lamps, e.g. solid state lamps [SSL] light emitting diodes [LED] or organic LED [OLED]

Abstract

An exemplary embodiment provides a current regulator for controlling variable brightness levels for solid state lighting. The current regulator is couplable to a phase-modulating switch, such as a dimmer switch, which is coupled to an AC line voltage. An exemplary current regulator includes a rectifier; a switching power supply providing a first current; an impedance matching circuit; and a controller. The impedance matching circuit is adapted to provide a second current through the phase-modulating switch when a magnitude of the first current is below a first predetermined threshold, such as a holding current of a triac of the phase-modulating switch. The controller is adapted to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage and to determine a duty cycle for pulse-width current modulation by the switching power supply in response to the comparison of the RMS voltage level to a nominal voltage level.

Claims

1. A current regulator for providing variable power to solid state lighting, the current regulator couplable through a phase-modulating switch to an AC line voltage, the current regulator comprising:

a rectifier;

a switching power supply providing a first current; and

an impedance matching circuit coupled to the switching power supply and couplable to the phase-modulating switch or to the AC line voltage, the impedance matching circuit adapted to provide a second current through the phase-modulating switch when a magnitude of the first current is below a first predetermined threshold.

2. The current regulator of claim 1, wherein the impedance matching circuit comprises:

a first resistor coupled to receive the first current from the switching power supply and provide a first voltage level;

a second resistor; and

a current switch coupled in series to the second resistor, the switch responsive to a control voltage to modulate the second current through the second resistor in response to the first voltage level.

3. The current regulator of claim 2, wherein the current switch is a depletion mode field effect transistor which is conductive when the magnitude of the control voltage is below a second predetermined threshold.

4. The current regulator of claim 2, wherein the first resistor is a current sense resistor coupled in series with the switching power supply.

5. The current regulator of claim 2, further comprising:

a controller coupled to the current switch, the controller adapted to provide the control voltage.

6. The current regulator of claim 2, further comprising:

a voltage limiter coupled in parallel to the first resistor.

7. The current regulator of claim 1, wherein phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.

8. The current regulator of claim 1, further comprising:

a controller couplable to the phase-modulating switch, the controller adapted to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage.

9. The current regulator of claim 8, wherein the controller is further adapted to compare the RMS voltage level to a nominal voltage level.

10. The current regulator of claim 9, wherein the controller is further adapted to determine a duty cycle for pulse-width current modulation by the switching power supply in response to the comparison of the RMS voltage level to the nominal voltage level.

11. The current regulator of claim 10, wherein the controller is further adapted to determine the duty cycle based on a ratio of about a power of 3.4 of the provided RMS voltage level (V_RMS) to about a power of 3.4 of the nominal voltage level (V_N) (V_RMS^3.4/V_N^3.4).

12. The current regulator of claim 10, wherein the controller is further adapted to determine the duty cycle “

D”

based on

13. The current regulator of claim 9, wherein the controller is further adapted to determine the nominal voltage level provided by the phase-modulating switch from the AC line voltage when a phase angle of a phase-modulated voltage level is about zero.

14. The current regulator of claim 9, wherein the controller is further adapted to determine the nominal voltage level provided by the AC line voltage.

15. The current regulator of claim 9, wherein the controller is further adapted to determine the nominal voltage level as a predetermined parameter stored in a memory.

16. The current regulator of claim 9, wherein the controller is further adapted to determine the RMS voltage level by determining an amplitude and a phase angle of a phase-modulated voltage level provided by the phase-modulating switch from the AC line voltage.

17. The current regulator of claim 1, wherein a capacitor of the switching power supply has a capacitance sufficient to provide energy to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

18. The current regulator of claim 1, wherein the switching power supply further comprises a first stage and a second stage, wherein the first stage is in an off-state when the phase-modulating switch is not providing power from the AC line voltage.

19. The current regulator of claim 1, wherein the switching power supply further comprises a first stage and a second stage, wherein the second stage is in an on-state when the phase-modulating switch is not providing power from the AC line voltage.

20. The current regulator of claim 19, wherein the second stage is adapted to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

21. The current regulator of claim 1, further comprising:

a controller couplable to the phase-modulating switch and to the switching power supply, the controller adapted to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.

22. The current regulator of claim 21, wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.

23. The current regulator of claim 21, wherein the controller is further adapted to determine the first predetermined level based upon a minimum voltage level of the solid state lighting and a voltage drop of the capacitor during a second time interval.

24. The current regulator of claim 23, wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.

25. The current regulator of claim 21, wherein the controller is further adapted to determine the first predetermined level voltage level “

V_C”

as

26. The current regulator of claim 21, wherein the controller is further adapted to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.

27. The current regulator of claim 1, wherein the switching power supply further comprises:

an AC to DC converter; and

a buck converter.

28. The current regulator of claim 1, wherein the current regulator is coupled in parallel with an incandescent lamp.

29. A power converter for providing variable brightness levels for solid state lighting, the power converter couplable to a phase-modulating switch which is couplable to an AC line voltage, the power converter comprising:

a switching power supply providing a first current; and

an active impedance matching circuit coupled to the switching power supply, the active impedance matching circuit adapted to provide a variable, second current in response to a magnitude of the first current.

30. The power converter of claim 29, wherein the active impedance matching circuit is adapted to provide the variable, second current when the magnitude of the first current is below a first predetermined threshold.

31. The power converter of claim 30, wherein phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.

32. The power converter of claim 29, wherein the impedance matching circuit comprises:

a first resistor coupled to receive the first current from the switching power supply and provide a first voltage level;

a second resistor;

a transistor coupled in series to the second resistor, the transistor responsive to a control voltage to modulate the second current through the second resistor in response to the first voltage level.

33. The power converter of claim 32, wherein the transistor is a depletion mode field effect transistor which is conductive when the control voltage is above a second predetermined threshold.

34. The power converter of claim 32, further comprising:

a controller coupled to the transistor, the controller adapted to provide the control voltage.

35. The power converter of claim 29, further comprising:

a controller couplable to the phase-modulating switch, the controller adapted to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage.

36. The power converter of claim 35, wherein the controller is further adapted to compare the RMS voltage level to a nominal voltage level.

37. The power converter of claim 36, wherein the controller is further adapted to determine a duty cycle for pulse-width current modulation by the switching power supply in response to the comparison of the RMS voltage level to the nominal voltage level.

38. The power converter of claim 37, wherein the controller is further adapted to determine the duty cycle based on a ratio of about a power of 3.4 of the RMS voltage level (V_RMS) to about a power of 3.4 of the nominal voltage level (V_N) (V_RMS^3.4/V_N^3.4).

39. The power converter of claim 37, wherein the controller is further adapted to determine the duty cycle “

D”

based on

40. The power converter of claim 35, wherein the controller is further adapted to determine the nominal voltage level provided by the phase-modulating switch from the AC line voltage when a phase angle of a phase-modulated voltage level is about zero.

41. The power converter of claim 35, wherein the controller is further adapted to determine the nominal voltage level as a predetermined parameter stored in a memory.

42. The power converter of claim 35, wherein the controller is further adapted to determine the nominal voltage level provided by the AC line voltage.

43. The power converter of claim 35, wherein the controller is further adapted to determine the RMS voltage level by determining an amplitude and a phase angle of a phase-modulated voltage level provided by the phase-modulating switch from the AC line voltage.

44. The power converter of claim 29, wherein the switching power supply has at least two stages.

45. The power converter of claim 29, wherein a capacitor of the switching power supply has a capacitance sufficient to provide energy to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

46. The power converter of claim 29, wherein the switching power supply further comprises a first stage and a second stage, wherein the first stage is in an off-state when the phase-modulating switch is not providing power from the AC line voltage.

47. The power converter of claim 29, wherein the switching power supply further comprises a first stage and a second stage, wherein the second stage is in an on-state when the phase-modulating switch is not providing power from the AC line voltage.

48. The power converter of claim 47, wherein the second stage is adapted to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

49. The power converter of claim 29, further comprising:

a controller couplable to the phase-modulating switch and to the switching power supply, the controller adapted to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.

50. The power converter of claim 49, wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.

51. The power converter of claim 49, wherein the controller is further adapted to determine the first predetermined level based upon a minimum voltage level of the solid state lighting and a voltage drop of the capacitor during a second time interval.

52. The power converter of claim 51, wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.

53. The power converter of claim 49, wherein the controller is further adapted to determine the first predetermined level voltage level “

V_C”

as

54. The power converter of claim 49, wherein the controller is further adapted to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.

55. The power converter of claim 29, wherein the switching power supply further comprises:

an AC to DC converter; and

a buck converter.

56. A current regulator for providing variable brightness levels for solid state lighting, the current regulator couplable to a phase-modulating switch coupled to an AC line voltage, the current regulator comprising:

a rectifier;

a switching power supply providing a first current;

an impedance matching circuit coupled to the switching power supply and couplable to the phase-modulating switch or to the AC line voltage, the impedance matching circuit adapted to provide a second current through the phase-modulating switch when a magnitude of the first current is below a first predetermined threshold; and

a controller coupled to the switching power supply and couplable to the phase-modulating switch, the controller adapted to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage and to determine a duty cycle for pulse-width current modulation by the switching power supply in response to the comparison of the RMS voltage level to a nominal voltage level.

57. The current regulator of claim 56, wherein the impedance matching circuit comprises:

a first resistor coupled to receive the first current from the switching power supply and provide a first voltage level;

a second resistor;

a current switch coupled in series to the second resistor, the switch responsive to a control voltage to modulate the second current through the second resistor in response to the first voltage level.

58. The current regulator of claim 56, wherein phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.

59. The current regulator of claim 56, wherein the controller is further adapted to determine the duty cycle based on a ratio of about a power of 3.4 of the RMS voltage level (V_RMS) to about a power of 3.4 of the nominal voltage level (V_N) (V_RMS^3.4/V_N^3.4).

60. The current regulator of claim 56, wherein the controller is further adapted to determine the duty cycle “

D”

based on

61. The current regulator of claim 56, wherein the controller is further adapted to determine the nominal voltage level provided by the phase-modulating switch from the AC line voltage when a phase angle of a phase-modulated voltage level is about zero.

62. The current regulator of claim 56, wherein the controller is further adapted to determine the nominal voltage level as a predetermined parameter stored in a memory.

63. The power converter of claim 56, wherein the controller is further adapted to determine the nominal voltage level provided by the AC line voltage.

64. The current regulator of claim 56, wherein the controller is further adapted to determine the RMS voltage level by determining an amplitude and a phase angle of a phase-modulated voltage level provided by the phase-modulating switch from the AC line voltage.

65. The current regulator of claim 56, wherein a capacitor of the switching power supply has a capacitance sufficient to provide energy to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

66. The current regulator of claim 56, wherein the switching power supply further comprises a first stage and a second stage, wherein the first stage is in an off-state when the phase-modulating switch is not providing power from the AC line voltage.

67. The current regulator of claim 56, wherein the switching power supply further comprises a first stage and a second stage, wherein the second stage is in an on-state when the phase-modulating switch is not providing power from the AC line voltage.

68. The current regulator of claim 67, wherein the second stage is adapted to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.

69. The current regulator of claim 56, wherein the controller is further adapted to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.

70. The current regulator of claim 69, wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.

71. The current regulator of claim 69, wherein the controller is further adapted to determine the first predetermined level based upon a minimum voltage level of the solid state lighting and a voltage drop of the capacitor during a second time interval.

72. The current regulator of claim 71, wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.

73. The current regulator of claim 69, wherein the controller is further adapted to determine the first predetermined level voltage level “

V_C”

as

74. The current regulator of claim 69, wherein the controller is further adapted to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.

75. A current regulator for providing variable brightness levels for a plurality of light emitting diodes, the current regulator couplable to a phase-modulating switch coupled to an AC line voltage, the current regulator comprising:

a switching power supply providing a first current; and

a controller coupled to the switching power supply and couplable to the phase-modulating switch, the controller adapted to provide power to the plurality of light emitting diodes when the phase-modulating switch is not providing power from the AC line voltage.

76. The current regulator of claim 75, wherein the controller is further adapted to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.

77. The current regulator of claim 76, wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.

78. The current regulator of claim 76, wherein the controller is further adapted to determine the first predetermined level based upon a minimum voltage level of the plurality of light emitting diodes and a voltage drop of the capacitor during a second time interval.

79. The current regulator of claim 78, wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.

80. The current regulator of claim 76, wherein the controller is further adapted to determine the first predetermined level voltage level “

V_C”

as

81. The current regulator of claim 76, wherein the controller is further adapted to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.