Current regulator for modulating brightness levels of solid state lighting
View Patent ↗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.
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 to provide a second current through the phase-modulating switch when a magnitude of the first current is below a first predetermined threshold; 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.
2. The current regulator of claim 1 , 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.
3. The current regulator of claim 1 , wherein the first resistor is a current sense resistor coupled in series with the switching power supply.
4. The current regulator of claim 1 , further comprising:
a controller coupled to the current switch, the controller to provide the control voltage.
5. The current regulator of claim 1 , further comprising:
a voltage limiter coupled in parallel to the first resistor.
6. The current regulator of claim 1 , wherein the phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.
7. The current regulator of claim 1 , further comprising:
a controller couplable to the phase-modulating switch, the controller to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage.
8. The current regulator of claim 7 , wherein the controller further is to compare the RMS voltage level to a nominal voltage level.
9. The current regulator of claim 8 , wherein the controller further is 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.
10. The current regulator of claim 8 , wherein the controller further is to determine the nominal voltage level provided by the AC line voltage.
11. The current regulator of claim 8 , wherein the controller further is to determine the nominal voltage level as a predetermined parameter stored in a memory.
12. The current regulator of claim 8 , wherein the controller further is 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.
13. The current regulator of claim 8 , wherein the controller further is 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.
14. The current regulator of claim 13 , wherein the controller further is 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 ).
15. The current regulator of claim 13 , wherein the controller further is to determine the duty cycle “D” based on
D
≈
V
RMS
3.4
V
NOMINAL
3.4
,
in which V RMS is the provided RMS voltage level and V N is the nominal voltage level.
16. 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.
17. 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.
18. 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.
19. The current regulator of claim 18 , wherein the second stage is to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.
20. The current regulator of claim 1 , further comprising:
a controller couplable to the phase-modulating switch and to the switching power supply, the controller to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.
21. The current regulator of claim 20 , wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.
22. The current regulator of claim 20 , wherein the controller further is 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.
23. The current regulator of claim 22 , wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.
24. The current regulator of claim 20 , wherein the controller further is to determine the first predetermined level as voltage level “V C ” with
V
C
≈
V
LED
+
I
m
l
·
T
·
V
RMS
3.4
C
·
V
NOMINAL
3.4
,
where I ml is an amplitude of current through the solid state lighting, T is a half-cycle time of the AC line voltage, and C is the capacitance of the capacitor, V RMS is an RMS voltage level provided by the phase-modulating switch, and V N is a nominal voltage level of the AC line voltage.
25. The current regulator of claim 20 , wherein the controller is further is to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.
26. The current regulator of claim 1 , wherein the switching power supply further comprises:
an AC to DC converter; and
a buck converter.
27. The current regulator of claim 1 , wherein the current regulator is coupled in parallel with an incandescent lamp.
28. 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 to provide a variable, second current in response to a magnitude of the first current; wherein the active 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 transistor coupled in series to the second resistor, the transistor responsive to a control voltage to modulate the second, variable current through the second resistor in response to the first voltage level.
29. The power converter of claim 28 , wherein the active impedance matching circuit is to provide the variable, second current when the magnitude of the first current is below a first predetermined threshold.
30. The power converter of claim 29 , wherein phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.
31. The power converter of claim 28 , wherein the transistor is a depletion mode field effect transistor which is conductive when the control voltage is above a second predetermined threshold.
32. The power converter of claim 28 , further comprising:
a controller coupled to the transistor, the controller to provide the control voltage.
33. The power converter of claim 28 , further comprising:
a controller couplable to the phase-modulating switch, the controller to determine a root-mean-square (RMS) voltage level provided by the phase-modulating switch from the AC line voltage.
34. The power converter of claim 33 , wherein the controller further is to compare the RMS voltage level to a nominal voltage level.
35. The power converter of claim 34 , wherein the controller further is 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.
36. The power converter of claim 35 , wherein the controller further is 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 ).
37. The power converter of claim 35 , wherein the controller further is to determine the duty cycle “D” based on
D
≈
V
RMS
3.4
V
NOMINAL
3.4
,
in which V RMS is the RMS voltage level and V N is the nominal voltage level.
38. The power converter of claim 33 , wherein the controller further is 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.
39. The power converter of claim 33 , wherein the controller further is to determine the nominal voltage level as a predetermined parameter stored in a memory.
40. The power converter of claim 33 , wherein the controller further is to determine the nominal voltage level provided by the AC line voltage.
41. The power converter of claim 33 , wherein the controller further is 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.
42. The power converter of claim 28 , wherein the switching power supply has at least two stages.
43. The power converter of claim 28 , 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.
44. The power converter of claim 28 , 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.
45. The power converter of claim 28 , 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.
46. The power converter of claim 45 , wherein the second stage is to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.
47. The power converter of claim 28 , further comprising:
a controller couplable to the phase-modulating switch and to the switching power supply, the controller to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.
48. The power converter of claim 47 , wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.
49. The power converter of claim 47 , wherein the controller further is 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.
50. The power converter of claim 49 , wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.
51. The power converter of claim 47 , wherein the controller further is to determine the first predetermined level as voltage level “V C ” with
V
C
≈
V
LED
+
I
ml
·
T
·
V
RMS
3.4
C
·
V
NOMINAL
3.4
,
where I ml is an amplitude of current through the solid state lighting, T is a half-cycle time of the AC line voltage, and C is the capacitance of the capacitor, V RMS is an RMS voltage level provided by the phase-modulating switch, and V N is a nominal voltage level of the AC line voltage.
52. The power converter of claim 47 , wherein the controller further is to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.
53. The power converter of claim 28 , wherein the switching power supply further comprises:
an AC to DC converter; and
a buck converter.
54. 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 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 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.
55. The current regulator of claim 54 , 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.
56. The current regulator of claim 54 , wherein phase-modulating switch has a triac, and wherein the first predetermined threshold is at least a minimum holding current for the triac.
57. The current regulator of claim 54 , wherein the controller further is 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 ).
58. The current regulator of claim 54 , wherein the controller further is to determine the duty cycle “D” based on
D
≈
V
RMS
3.4
V
NOMINAL
3.4
,
in which V RMS is the RMS voltage level and V N is the nominal voltage level.
59. The current regulator of claim 54 , wherein the controller further is 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.
60. The current regulator of claim 54 , wherein the controller further is to determine the nominal voltage level as a predetermined parameter stored in a memory.
61. The power converter of claim 54 , wherein the controller further is to determine the nominal voltage level provided by the AC line voltage.
62. The current regulator of claim 54 , wherein the controller further is 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.
63. The current regulator of claim 54 , 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.
64. The current regulator of claim 54 , 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.
65. The current regulator of claim 54 , 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.
66. The current regulator of claim 65 , wherein the second stage is to provide power to the solid state lighting when the phase-modulating switch is not providing power from the AC line voltage.
67. The current regulator of claim 54 , wherein the controller further is to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.
68. The current regulator of claim 67 , wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.
69. The current regulator of claim 67 , wherein the controller further is 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.
70. The current regulator of claim 69 , wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.
71. The current regulator of claim 67 , wherein the controller further is to determine the first predetermined level as voltage level “V C ” with
V
C
≈
V
LED
+
I
ml
·
T
·
V
RMS
3.4
C
·
V
NOMINAL
3.4
,
where I ml is an amplitude of current through the solid state lighting, T is a half-cycle time of the AC line voltage, and C is the capacitance of the capacitor, V RMS is an RMS voltage level provided by the phase-modulating switch, and V N is a nominal voltage level of the AC line voltage.
72. The current regulator of claim 67 , wherein the controller further is to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.
73. 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 to provide power to the plurality of light emitting diodes when the phase-modulating switch is not providing power from the AC line voltage; and
an impedance matching circuit comprising:
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.
74. The current regulator of claim 73 , wherein the controller further is to control a charging of a capacitor in the switching power supply to a first predetermined level during a first time interval.
75. The current regulator of claim 74 , wherein the first time interval is when the phase-modulating switch is providing power from the AC line voltage.
76. The current regulator of claim 74 , wherein the controller further is 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.
77. The current regulator of claim 76 , wherein the second time interval is when the phase-modulating switch is not providing power from the AC line voltage.
78. The current regulator of claim 74 , wherein the controller further is to determine the first predetermined level as voltage level “V C ” with
V
C
≈
V
LED
+
I
ml
·
T
·
V
RMS
3.4
C
·
V
NOMINAL
3.4
,
where I ml is an amplitude of current through the solid state lighting, T is a half-cycle time of the AC line voltage, and C is the capacitance of the capacitor, V RMS is an RMS voltage level provided by the phase-modulating switch, and V N is a nominal voltage level of the AC line voltage.
79. The current regulator of claim 74 , wherein the controller further is to determine the first predetermined level voltage level as a function of the phase modulation performed by the phase-modulating switch.