HYBRID LIGHT SOURCE

• US 20100060187A1
• Filed: 09/05/2008
• Published: 03/11/2010
• Est. Priority Date: 09/05/2008
• Status: Active Grant

• Current Assignee: Lutron Technology Company LLC
• Original Assignee: Lutron Electronics Company Incorporated (Lutron Electronics)
• Inventors: Newman, Robert C. JR., Spira, Joel S., Taipale, Mark S., Ozbek, Mehmet, Corrigan, Keith Joseph, Dobbins, Aaron
• Granted Patent: US 8,008,866 B2
• Time in Patent Office: Days
• US Class Current: 315/291
• CPC Class Codes: H05B 35/00 Electric light sources using a combination of different types of light generation
• CPC Class Codes: H05B 39/08 by shifting phase of trigger voltage applied to gas-filled controlling tubes also in controlled semiconductor devices in converters H02M5/00; with regulation G05F1/44
• CPC Class Codes: H05B 41/2822 using specially adapted components in the load circuit, e.g. feed-back transformers, piezoelectric transformers; using specially adapted load circuit configurations
• CPC Class Codes: H05B 45/382 with galvanic isolation between input and output
• CPC Class Codes: H05B 45/39 Circuits containing inverter bridges
• CPC Class Codes: Y10S 315/04 Dimming circuit for fluorescent lamps

Abstract

A hybrid light source comprises a high-efficiency lamp, for example, a fluorescent lamp, and a low-efficiency lamp, for example, a halogen lamp. A control circuit individually controls the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that a total light output of the hybrid light source ranges throughout a dimming range from a minimum total intensity to a maximum total intensity. The high-efficiency lamp is turned off and the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below a transition intensity. The low-efficiency lamp is controlled such that the correlated color temperature of the hybrid light source decreases as the total light intensity is decreased below the transition intensity. The hybrid light source is characterized by a low impedance throughout the dimming range.

Claims

1. A hybrid light source adapted to receive power from an AC power source and to produce a total light intensity, the total light intensity controlled throughout a dimming range from a low-end intensity and high-end intensity, the hybrid light source comprising:

a high-efficiency light source circuit having a high-efficiency lamp for producing a percentage of the total light intensity;

a low-efficiency light source circuit having a low-efficiency lamp for producing a percentage of the total light intensity; and

a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit for individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that the total light intensity of the hybrid light source ranges throughout the dimming range, the percentage of the total light intensity produced by the high-efficiency lamp being greater than the percentage of the total light intensity produced by the low-efficiency lamp when the total light intensity is near the high-end intensity;

wherein the percentage of the total light intensity produced by the high-efficiency lamp decreases and the percentage of the total light intensity produced by the low-efficiency lamp increases as the total light intensity is decreased below the high-end intensity, the control circuit operable to turn off the high-efficiency lamp when the total light intensity is below a transition intensity, such that the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity.

2. The hybrid light source of claim 1, wherein the high-efficiency lamp comprises a gas discharge lamp.

3. The hybrid light source of claim 2, wherein the high-efficiency light source drive circuit comprises a ballast circuit for driving the gas discharge lamp.

4. The hybrid light source of claim 3, further comprising:

two input terminals adapted to be operatively coupled to the AC power source; and

a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at an output.

5. The hybrid light source of claim 4, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage.

6. The hybrid light source of claim 5, wherein the ballast circuit comprises an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the gas discharge lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the gas discharge lamp.

7. The hybrid light source of claim 4, wherein the low-efficiency light source circuit comprises a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit, the control circuit coupled to the semiconductor switch for controlling the amount of power delivered to the low-efficiency lamp.

8. The hybrid light source of claim 7, wherein the low-efficiency lamp comprises a halogen lamp.

9. The hybrid light source of claim 1, wherein the low-efficiency light source circuit is controlled such that a correlated color temperature of the hybrid light source decreases as the total light intensity is decreased.

10. The hybrid light source of claim 9, wherein the low-efficiency light source circuit is controlled such that the correlated color temperature of the hybrid light source decreases as the total light intensity is decreased below the transition intensity.

11. The hybrid light source of claim 1, further comprising:

a housing, the high-efficiency lamp and low-efficiency lamp located within the housing.

12. The hybrid light source of claim 11, wherein the housing is at least partially translucent.

13. The hybrid light source of claim 1, wherein the low-efficiency lamp comprises a low-voltage lamp and the low-efficiency light source drive circuit comprises a low-voltage drive circuit and a low-voltage transformer.

14. The hybrid light source of claim 13, wherein the low-efficiency lamp comprises a low-voltage halogen lamp and the low-efficiency light source drive circuit comprises a low-voltage halogen drive circuit and a low-voltage transformer.

15. The hybrid light source of claim 1, wherein the high-efficiency lamp comprises an LED light source and the high-efficiency light source drive circuit comprises an LED drive circuit.

16. The hybrid light source of claim 1, wherein the control circuit turns the high-efficiency lamp on and off around the transition intensity with some hysteresis.

17. A method of illuminating a light source to produce a total light intensity throughout a dimming range from a low-end intensity to a high-end intensity, the method comprising the steps of:

illuminating a high-efficiency lamp to produce a percentage of the total light intensity;

illuminating a low-efficiency lamp to produce a percentage of the total light intensity;

mounting the high-efficiency lamp and the low-efficiency lamp to a common support;

individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that the total light intensity of the hybrid light source ranges throughout the dimming range;

controlling the high-efficiency lamp and the low-efficiency lamp near the high-end intensity, such that first percentage of the total light intensity produced by the high-efficiency lamp is greater than the second percentage of the total light intensity produced by the low-efficiency lamp when the total light intensity is near the high-end intensity;

decreasing the first percentage of the total light intensity produced by the high-efficiency lamp as the total light intensity decreases;

increasing the second percentage of the total light intensity produced by the low-efficiency lamp as the total light intensity decreases;

turning off the high-efficiency lamp when the total light intensity is below a transition intensity; and

controlling the low-efficiency lamp such that the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity.

18. The method of claim 17, wherein the color temperature of the hybrid light source decreases as the total light intensity is decreased below the transition intensity.

94. The method of claim 17, further comprising the step of:

enclosing the high-efficiency lamp and the low-efficiency lamp together in a housing.

19. A hybrid light source adapted to receive power from an AC power source, the hybrid light source comprising:

two input terminals adapted to be operatively coupled to the AC power source;

a high-efficiency light source circuit having a high-efficiency lamp, the high-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the high-efficiency lamp;

a low-efficiency light source circuit having a low-efficiency lamp, the low-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the low-efficiency lamp; and

a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit to individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity;

wherein the hybrid light source is characterized by a low impedance between the first and second terminals throughout the length of each half-cycle of the AC power source.

20. The hybrid light source of claim 19, wherein the low-efficiency light source circuit contributes to the low impedance characteristic of the hybrid light source.

21. The hybrid light source of claim 20, further comprising:

a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at output terminals.

22. The hybrid light source of claim 21, wherein the low-efficiency light source circuit comprises a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit, the control circuit coupled to the semiconductor switch for controlling the amount of power delivered to the low-efficiency lamp.

23. The hybrid light source of claim 22, further comprising:

a zero-crossing detect circuit operatively coupled across the output terminals of the rectifier circuit for detecting when a phase-controlled voltage across the hybrid light source is approximately zero volts;

wherein the control circuit is operable to control the high-efficiency lamp and the low-efficiency lamp in response to the zero-crossing detect circuit.

24. The hybrid light source of claim 23, wherein the control circuit is operable to control the semiconductor switch of the low-efficiency light source circuit to pulse-width modulate the voltage provided across the low-efficiency lamp to control the amount of power delivered to the low-efficiency lamp when the phase-controlled voltage across the hybrid light source is above a predetermined zero-crossing threshold voltage.

25. The hybrid light source of claim 24, wherein the control circuit determines the total light intensity of the hybrid light source in response to the zero-crossing detect circuit.

26. The hybrid light source of claim 25, wherein the control circuit controls the amount of power delivered to the low-efficiency lamp to be greater than a minimum power level after the magnitude of the phase-controlled voltage becomes greater than the predetermined zero-crossing threshold each half-cycle

27. The hybrid light source of claim 26, wherein the control circuit controls the amount of power delivered to the low-efficiency lamp to the minimum power level when the total light intensity of the hybrid light source is at the maximum intensity and the magnitude of the phase-controlled voltage is above the predetermined zero-crossing threshold voltage.

28. The hybrid light source of claim 23, wherein the semiconductor switch is rendered conductive when the phase-controlled voltage across the hybrid light source is below a predetermined zero-crossing threshold voltage.

29. The hybrid light source of claim 21, wherein the high-efficiency lamp comprises a fluorescent lamp, and the high-efficiency light source drive circuit comprises a ballast circuit for driving the fluorescent lamp.

30. The hybrid light source of claim 29, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage, an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp.

31. The hybrid light source of claim 19, wherein the low impedance between the first and second terminals has an average magnitude of approximately 1.44 kΩ

or less throughout the length of each half-cycle.

32. The hybrid light source of claim 31, wherein the low impedance between the first and second terminals has an average magnitude of approximately 360 Ω

or less throughout the length of each half-cycle.

33. A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:

two input terminals adapted to receive the phase-controlled voltage;

a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at output terminals;

a high-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a high-efficiency lamp;

a low-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a low-efficiency lamp, the low-efficiency light source circuit comprising a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit;

a zero-crossing detect circuit operatively coupled between the input terminals for detecting when the magnitude of the phase-controlled voltage becomes greater than a predetermined zero-crossing threshold voltage each half-cycle of the phase-controlled voltage; and

a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit for individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the zero-crossing detect circuit, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity, the control circuit operable to turn off the high-efficiency lamp when the total light intensity is below a transition intensity, such that the low-efficiency lamp produces all of the total light intensity of the hybrid light source when the total light intensity is below the transition intensity, the control circuit operable to control the amount of power delivered to the low-efficiency lamp to be greater than a minimum power level when the total light intensity is above the transition intensity;

wherein the control circuit controls the amount of power delivered to the low-efficiency lamp to the minimum power level when the total light intensity of the hybrid light source is at the maximum intensity.

34. The hybrid light source of claim 33, wherein the high-efficiency lamp comprises a fluorescent lamp, and the high-efficiency light source drive circuit comprises a ballast circuit for driving the fluorescent lamp.

35. The hybrid light source of claim 34, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage.

36. The hybrid light source of claim 35, wherein the ballast circuit comprises an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp.

37. The hybrid light source of claim 33, wherein the control circuit is operable to control the semiconductor switch of the low-efficiency light source circuit to pulse-width modulate the voltage provided across the low-efficiency lamp to control the amount of power delivered to the low-efficiency lamp when the magnitude of the phase-controlled voltage is above the predetermined zero-crossing threshold voltage.

38. The hybrid light source of claim 33, wherein the low-efficiency lamp comprises a halogen lamp and the low-efficiency light source drive circuit comprises a halogen drive circuit.

39. The hybrid light source of claim 33, wherein the low-efficiency lamp comprises a low-voltage halogen lamp and the low-efficiency light source drive circuit comprises a low-voltage halogen drive circuit and a low-voltage transformer.

40. A dimmable hybrid light source adapted to receive a phase-controlled voltage, the hybrid light source comprising:

two input terminals adapted to receive the phase-controlled voltage;

a full-wave rectifier circuit coupled between the input terminals and generating a rectified voltage at output terminals;

a high-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a high-efficiency lamp;

a low-efficiency light source circuit coupled to the output terminals of the rectifier circuit and having a low-efficiency lamp, the low-efficiency light source circuit comprising a semiconductor switch coupled in series electrical connection with the low-efficiency lamp, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit;

a zero-crossing detect circuit operatively coupled between the input terminals for detecting when the magnitude of the phase-controlled voltage is approximately zero volts; and

a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit for individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the zero-crossing detect circuit;

wherein the semiconductor switch is rendered conductive when the phase-controlled voltage across the hybrid light source is approximately zero volts.

41. The hybrid light source of claim 40, wherein the high-efficiency lamp comprises a fluorescent lamp, and the high-efficiency light source drive circuit comprises a ballast circuit for driving the fluorescent lamp.

42. The hybrid light source of claim 41, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage.

43. The hybrid light source of claim 42, wherein the ballast circuit comprises an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp.

44. The hybrid light source of claim 40, wherein the low-efficiency lamp comprises a halogen lamp and the low-efficiency light source drive circuit comprises a halogen drive circuit.

45. The hybrid light source of claim 40, wherein the low-efficiency lamp comprises a low-voltage halogen lamp and the low-efficiency light source drive circuit comprises a low-voltage halogen drive circuit and a low-voltage transformer.

46. A lighting control system receiving power from an AC power source, the lighting control system comprising:

a hybrid light source comprising a high-efficiency light source circuit having a high-efficiency lamp and a low-efficiency light source circuit having a low-efficiency lamp, the hybrid light source adapted to be coupled to the AC power source and to individually control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp;

a dimmer switch comprising a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the hybrid light source, the bidirectional semiconductor switch operable to be rendered conductive for a conduction period each half-cycle of the AC power source, such that the hybrid light source is operable to control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the conduction period of the bidirectional semiconductor switch, the dimmer switch further comprising a power supply coupled in parallel electrical connection with the bidirectional semiconductor switch and operable to conduct a charging current through the hybrid light source when the bidirectional semiconductor switch is non-conductive;

wherein the low-efficiency light source circuit of the hybrid light source is operable to conduct the charging current when the bidirectional semiconductor switch is non-conductive.

47. The lighting control system of claim 46, wherein the hybrid light source further comprises a control circuit coupled to the high-efficiency light source circuit and the low-efficiency light source circuit for individually control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp.

48. The lighting control system of claim 47, wherein the low-efficiency light source circuit comprises a low-efficiency drive semiconductor switch coupled in series electrical connection with the low-efficiency lamp for controlling the amount of power delivered to the low-efficiency lamp.

49. The lighting control system of claim 48, wherein the hybrid light source comprises a full-wave rectifier circuit adapted to be coupled in series between the dimmer switch and the AC power source and to generate a rectified voltage at output terminals, the series combination of the low-efficiency drive semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit.

50. The lighting control system of claim 49, wherein the high-efficiency lamp comprises a gas discharge lamp, and the high-efficiency light source drive circuit comprises a ballast circuit for driving the gas discharge lamp, the ballast circuit coupled to the output terminals of the rectifier circuit for receipt of the rectified voltage.

51. The lighting control system of claim 50, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage, an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp.

52. The lighting control system of claim 48, wherein the low-efficiency drive semiconductor switch is rendered conductive when the bidirectional semiconductor switch of the dimmer switch is non-conductive, such that the low-efficiency lamp is operable to conduct the charging current of the power supply.

53. The lighting control system of claim 48, wherein the low-efficiency light source circuit is operable to pulse-width modulate the voltage provided across the low-efficiency lamp to control the amount of power delivered to the low-efficiency lamp.

54. A lighting control system receiving power from an AC power source, the lighting control system comprising:

a hybrid light source comprising a high-efficiency light source circuit having a high-efficiency lamp and a low-efficiency light source circuit having a low-efficiency lamp, the hybrid light source adapted to be coupled to the AC power source and to individually control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp;

a dimmer switch comprising a thyristor adapted to be coupled in series electrical connection between the AC power source and the hybrid light source, the thyristor operable to be rendered conductive for a conduction period each half-cycle of the AC power source, such that the hybrid light source is operable to control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the conduction period of the thyristor;

wherein the low-efficiency light source circuit of the hybrid light source provides a path for enough current to flow from the AC power source through the hybrid light source, such that the magnitude of the current exceeds a rated holding current of the thyristor of the dimmer switch after the thyristor is rendered conductive.

55. The lighting control system of claim 54, wherein the hybrid light source further comprises a control circuit coupled to the high-efficiency light source circuit and the low-efficiency light source circuit for individually control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp.

56. The lighting control system of claim 55, wherein the low-efficiency light source circuit comprises a semiconductor switch coupled in series electrical connection with the low-efficiency lamp for controlling the amount of power delivered to the low-efficiency lamp.

57. The lighting control system of claim 56, wherein the hybrid light source comprises a full-wave rectifier circuit adapted to be coupled in series between the dimmer switch and the AC power source and to generate a rectified voltage at output terminals, the series combination of the semiconductor switch and the rectifier circuit coupled between the output terminals of the rectifier circuit.

58. The lighting control system of claim 57, wherein the high-efficiency lamp comprises a gas discharge lamp, and the high-efficiency light source drive circuit comprises a ballast circuit for driving the gas discharge lamp, the ballast circuit coupled to the output terminals of the rectifier circuit for receipt of the rectified voltage.

59. The lighting control system of claim 58, wherein the ballast circuit comprises a bus capacitor coupled between the output terminals of the rectifier circuit for producing a bus voltage, an inverter circuit for converting the bus voltage to a high-frequency AC voltage, and a resonant tank circuit for coupling the high-frequency AC voltage to the fluorescent lamp, the control circuit coupled to the inverter circuit for controlling the magnitude of a lamp current conducted through the fluorescent lamp.

60. The lighting control system of claim 56, wherein the low-efficiency light source circuit is operable to pulse-width modulate the voltage provided across the low-efficiency lamp to control the amount of power delivered to the low-efficiency lamp.

61. The lighting control system of claim 60, wherein the low-efficiency light source circuit is operable to pulse-width modulate the voltage provided across the low-efficiency lamp after the thyristor of the dimmer switch is rendered conductive to provide the path for enough current to flow from the AC power source through the hybrid light source, such that the magnitude of the current exceeds the rated holding current of the thyristor of the dimmer switch after the thyristor is rendered conductive.

62. The lighting control system of claim 61, wherein the dimmer switch is operable to control the total light intensity of the hybrid light source between a minimum intensity and a maximum intensity;

and

wherein the low-efficiency light source circuit is operable to control a duty cycle of the voltage provided across the low-efficiency lamp to a minimum duty cycle when the dimmer switch is controlling the total light intensity of the hybrid light source to the maximum intensity and the thyristor of the dimmer switch is conductive to provide the path for enough current to flow from the AC power source through the hybrid light source, such that the magnitude of the current exceeds the rated holding current of the thyristor after the thyristor is rendered conductive.

63. The lighting control system of claim 54, wherein the low-efficiency lamp provides the path for enough current to flow from the AC power source through the hybrid light source when the thyristor of the dimmer switch is conductive, such that the magnitude of the current exceeds the rated holding current of the thyristor after the thyristor is rendered conductive.

64. The lighting control system of claim 54, wherein the low-efficiency light source circuit of the hybrid light source provides a path for enough current to flow from the AC power source through the hybrid light source, such that the magnitude of the current exceeds a rated latching current of the thyristor of the dimmer switch after the thyristor is rendered conductive.

65. A lighting control system receiving power from an AC power source, the lighting control system comprising:

a hybrid light source comprising a high-efficiency light source circuit having a high-efficiency lamp and a low-efficiency light source circuit having a low-efficiency lamp, the hybrid light source adapted to be coupled to the AC power source and to individually control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp;

a dimmer switch comprising a bidirectional semiconductor switch adapted to be coupled in series electrical connection between the AC power source and the hybrid light source and a timing circuit coupled in parallel electrical connection with the bidirectional semiconductor switch, the timing circuit operable to conduct a timing current through the hybrid light source when the bidirectional semiconductor switch is non-conductive, the bidirectional semiconductor switch operable to be rendered conductive for a conduction period each half-cycle of the AC power source in response to the timing circuit, such that the hybrid light source is operable to control the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the conduction period of the bidirectional semiconductor switch;

wherein the low-efficiency light source circuit of the hybrid light source conducts the timing current when the bidirectional semiconductor switch is non-conductive.

66. A method of illuminating a light source in response to a phase-controlled voltage from a dimmer switch, the dimmer switch coupled in series electrical connection with an AC power source and the light source, the dimmer switch comprising a bidirectional semiconductor switch for generating the phase-controlled voltage and a power supply operable to conduct a charging current through from the AC power source through the light source when the bidirectional semiconductor switch is non-conductive, the method comprising the steps of:

mounting the high-efficiency lamp and the low-efficiency lamp to a common support;

individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the phase-controlled voltage; and

conducting the charging current through the low-efficiency lamp when the bidirectional semiconductor switch is non-conductive.

95. The method of claim 66, further comprising the step of:

enclosing the high-efficiency lamp and the low-efficiency lamp together in a housing.

67. A method of illuminating a light source in response to a phase-controlled voltage from a dimmer switch, the dimmer switch coupled in series electrical connection with between an AC power source and the light source, the dimmer switch comprising a thyristor for generating the phase-controlled voltage, the thyristor characterized by a rated holding current, the method comprising the steps of:

mounting the high-efficiency lamp and the low-efficiency lamp to a common support;

individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp in response to the phase-controlled voltage; and

conducting enough current from the AC power source and through the thyristor of the dimmer switch and the low-efficiency lamp to exceed the rated holding current of the thyristor of the dimmer switch.

96. The method of claim 67, further comprising the step of:

enclosing the high-efficiency lamp and the low-efficiency lamp together in a housing.

97. The method of claim 67, wherein the thyristor is characterized by a rated latching current, and the step of conducting further comprises conducting enough current from the AC power source and through the thyristor and the low-efficiency lamp to exceed the rated latching current of the thyristor of the dimmer switch.

68. A dimmable hybrid lamp comprising:

a high-efficiency lamp including at least first and second U-shaped gas filled tubes;

a low-efficiency lamp;

a common support for said high-efficiency lamp and said low-efficiency lamp, said first and second U-shaped gas-filled tubes of said high-efficiency lamp extending from said common support and spaced around a central axis extending from said common support;

a post having one end fixed to said common support and extending co-axially with said common axis to said low-efficiency lamp;

a dimmable ballast circuit for said high-efficiency lamp, said ballast circuit housed within said common support;

a dimmable drive circuit for said low-efficiency lamp, said drive circuit housed within said common support; and

a control circuit coupled to said ballast circuit and said drive circuit for simultaneously adjusting the intensities of said high-efficiency and low-efficiency lamps between a low-end intensity and a high-end intensity across a dimming range of said hybrid lamp.

69. The hybrid lamp of claim 68, wherein only said low-efficiency lamp is turned on below a transition intensity, and said high-efficiency lamp is only turned on above said transition intensity, whereby said low-efficiency lamp is turned on before said high-efficiency lamp is turned on as said hybrid lamp is dimmed from said low-end intensity to said high-end intensity.

70. The hybrid lamp of claim 69, wherein all of a total intensity of said hybrid lamp is obtained from said low-efficiency lamp below said transition intensity, and a greater percentage of said total intensity of said hybrid lamp is obtained from said high-efficiency above said transition intensity.

71. The hybrid lamp of claim 70, wherein a controlled maximum intensity of said low-efficiency lamp near said transition intensity is less than approximately 80% of a rated maximum intensity of said low-efficiency lamp.

72. The hybrid lamp of claim 68, wherein said high-efficiency lamp comprises three U-shaped tubes which encircle said post of said low-efficiency lamp.

73. The hybrid lamp of claim 72, wherein the outermost free ends of said tubes are approximately co-planar.

74. The hybrid lamp of claim 68, wherein said high-efficiency lamp is a compact fluorescent lamp.

75. The hybrid lamp of claim 74, wherein said low-efficiency lamp is a halogen lamp.

76. The hybrid lamp of claim 68, further comprising:

a screw-in Edison base extending from said common support and concentric with said central axis.

77. The hybrid lamp of claim 68, wherein said low-efficiency lamp produces output light with a red color shift as said total light intensity is dimmed toward said low-end intensity of said hybrid lamp.

78. A dimmable hybrid lamp comprising:

a high-efficiency dimmable lamp;

a low-efficiency dimmable lamp; and

a common control means coupled to each of said dimmable lamps and operable to simultaneously dim said dimmable lamps from their respective minimum intensities to maximum intensities to control a total light intensity of said hybrid lamp from a low-end intensity to a high-end intensity across a dimming range;

wherein only said low-efficiency lamp is turned on when said total light intensity is less than a transition intensity, and said high-efficiency lamp is only turned on when said total light intensity is above said transition intensity, whereby said low-efficiency lamp turns on before said high-efficiency lamp turns on as said hybrid lamp is dimmed from said low-end intensity to said high-end intensity.

79. The hybrid lamp of claim 78, wherein all of said total intensity of said hybrid lamp is obtained from said low-efficiency lamp below said transition intensity, and a greater percentage of said total intensity of said hybrid lamp is obtained from said high-efficiency above said transition intensity.

80. The hybrid lamp of claim 79, wherein a controlled maximum intensity of said low-efficiency lamp near said transition intensity is less than approximately 80% of a rated maximum intensity of said low-efficiency lamp.

81. The hybrid lamp of claim 78, wherein said high-efficiency lamp is a compact fluorescent lamp.

82. The hybrid lamp of claim 81, wherein said low-efficiency lamp is a halogen lamp.

83. The hybrid lamp of claim 78, wherein high-efficiency and low-efficiency lamps are supported from a common support.

84. The hybrid lamp of claim 83, wherein said high-efficiency lamp comprises three U-shaped tubes which encircle said tube of said low-efficiency lamp.

85. The hybrid lamp of claim 83, further comprising:

a screw-in Edison base extending from said common support.

86. The hybrid lamp of claim 78, wherein said low-efficiency lamp produces output light with a red color shift as said total light intensity is dimmed toward said low-end intensity of said hybrid lamp.

87. A lighting control system comprising:

a dimmable hybrid lamp including a high-efficiency lamp and a dimmable ballast therefor, a low-efficiency lamp and a dimmable drive circuit therefor, a common support for said high-efficiency lamp and said low-efficiency lamp, said high-efficiency lamp extending from said common support and spaced around a common central axis expending from said common support, said hybrid lamp comprising a tube having one end fixed to said common support and extending co-axially with said common axis to said low-efficiency lamp, said ballast and said drive circuit supported within said common support, said hybrid lamp further including a control circuit coupled to said dimmable ballast and said drive circuit for simultaneously adjusting the intensities of said high-efficiency and low-efficiency lamps between a low-end intensity and a high-end intensity across a dimming range of said hybrid lamp; and

a dimmer switch coupled to said dimmable hybrid lamp, said control circuit responsive to said dimmer switch control to control said dimmable ballast for said high-efficiency lamp and said dimmable drive circuit for said low-efficiency lamp for simultaneously adjusting the intensities of said high-efficiency and low-efficiency lamps, respectively.

88. The lighting control system of claim 87, wherein only said low-efficiency lamp is turned on below a transition intensity, and said high-efficiency lamp is only turned on above said transition intensity, whereby said low-efficiency lamp is turned on before said high-efficiency lamp is turned on as said hybrid lamp is dimmed from said low-end intensity to said high-end intensity.

89. The lighting control system of claim 88, wherein all of a total intensity of said hybrid lamp is obtained from said low-efficiency lamp below said transition intensity, and a majority of said total intensity of said hybrid lamp is obtained from said high-efficiency above said transition intensity.

90. The lighting control system of claim 87, wherein said high-efficiency lamp is a compact fluorescent lamp.

91. The lighting control system of claim 90, wherein said high-efficiency lamp is a halogen lamp.

92. A process of dimming a hybrid lamp comprising the steps of:

positioning a low-efficiency lamp in close proximity to a high-efficiency lamp;

continuously dimming a high-efficiency gas discharge lamp from a first minimum intensity to a first maximum intensity;

dimming said low-efficiency lamp from a second minimum intensity to a second maximum intensity which is lower said first minimum intensity of said high-efficiency lamp; and

simultaneous controlling both of said lamps to control a light output of said hybrid lamp from a low-end intensity to a high-end intensity, such that said light output of said hybrid lamp has a red color shift as said hybrid lamp is dimmed toward said low-end intensity.

93. A hybrid light source adapted to receive power from an AC power source, the hybrid light source comprising:

two input terminals adapted to be operatively coupled to the AC power source;

a high-efficiency light source circuit having a high-efficiency lamp, the high-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the high-efficiency lamp;

a low-efficiency light source circuit having a low-efficiency lamp, the low-efficiency light source circuit drawing current from the AC power source through the input terminals for powering the low-efficiency lamp; and

a control circuit coupled to both the high-efficiency light source circuit and the low-efficiency light source circuit to individually controlling the amount of power delivered to each of the high-efficiency lamp and the low-efficiency lamp, such that a total light output of the hybrid light source ranges from a minimum total intensity to a maximum total intensity;

wherein the hybrid light source has a monotonically decreasing power consumption as the total light intensity decreases from the maximum total intensity to the minimum total intensity.