Inductively coupled ballast circuit

• US 20030015479A1
• Filed: 09/18/2002
• Published: 01/23/2003
• Est. Priority Date: 06/21/1999
• Status: Active Grant

• Current Assignee: Philips IP Ventures B.V. (Koninklijke Philips N.V.)
• Original Assignee: Access Business Group International LLC (Alticor Incorporated)
• Inventors: Baarman, David W., Denen, Dennis J., Mollema, Scott A., Kuennen, Roy W., Markham, Ronald C.
• Granted Patent: US 6,825,620 B2
• Time in Patent Office: Days
• US Class Current: 210/748
• CPC Class Codes: A61L 2/10 Ultraviolet radiation
• CPC Class Codes: C02F 1/001 Processes for the treatment of water whereby the filtration technique is of importance C02F1/44 takes precedence; construction of filters in general B01D24/00 - B01D41/00
• CPC Class Codes: C02F 1/008 Control or steering systems not provided for elsewhere in subclass C02F
• CPC Class Codes: C02F 1/325 Irradiation devices or lamp constructions
• CPC Class Codes: C02F 2201/3222 Units using UV-light emitting diodes [LED]
• CPC Class Codes: C02F 2201/3228 Units having reflectors, e.g. coatings, baffles, plates, mirrors
• CPC Class Codes: C02F 2201/326 Lamp control systems
• CPC Class Codes: C02F 2209/005 Processes using a programmable logic controller [PLC]
• CPC Class Codes: C02F 2209/008 comprising telecommunication features, e.g. modems or antennas
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: C02F 9/20 Portable or detachable small-scale multistage treatment devices, e.g. point of use or laboratory water purification systems
• CPC Class Codes: H05B 41/24 in which the lamp is fed by high frequency ac, or with separate oscillator frequencyH05B41/26 takes precedence
• CPC Class Codes: H05B 41/36 Controlling
• CPC Class Codes: H05B 47/25 Circuit arrangements for protecting against overcurrent
• CPC Class Codes: Y02B 20/00 Energy efficient lighting technologies, e.g. halogen lamps or gas discharge lamps

Abstract

A ballast circuit is disclosed for inductively providing power to a load. The ballast circuit includes an oscillator, a driver, a switching circuit, a resonant tank circuit and a current sensing circuit. The current sensing circuit provides a current feedback signal to the oscillator that is representative of the current in the resonant tank circuit. The current feedback signal drives the frequency of the ballast circuit causing the ballast circuit to seek resonance. The ballast circuit preferably includes a current limit circuit that is inductively coupled to the resonant tank circuit. The current limit circuit disables the ballast circuit when the current in the ballast circuit exceeds a predetermined threshold or falls outside a predetermined range.

Claims

1. A ballast circuit, comprising:

a control circuit;

an oscillator electrically connected with said control circuit, wherein said oscillator is activated in response to predetermined electric signals from said control circuit;

a driver electrically connected with said oscillator, wherein the output from said oscillator controls said driver;

a half-bridge switching circuit electrically connected with said driver, wherein the output of said driver controls said half-bridge switching circuit;

a series resonant tank circuit electrically connected with said half-bridge switching circuit, wherein said series resonant tank circuit includes an inductive coupler;

a secondary coil inductively coupled with said series resonant tank circuit, wherein said series resonant tank circuit inductively energizes said secondary coil; and

a load electrically connected to said secondary coil, whereby power is provided to said load by said secondary coil.

2. The ballast circuit of claim 1, wherein said load is further defined as a resonant lamp circuit.

3. The ballast circuit of claim 1, wherein said resonant lamp circuit and said series resonant tank circuit resonate at about the same frequency.

4. The ballast circuit of claim 1, wherein said resonant lamp circuit includes an electromagnetic radiation emitting device.

5. The ballast circuit of claim 1, wherein said electromagnetic radiation emitting device is one of an ultraviolet lamp, an incandescent lamp, a light emitting diode lamp, a pulsed white light lamp and a dielectric barrier discharge lamp.

6. The ballast circuit of claim 1, wherein said oscillator includes a buffer circuit that prevents load changes from pulling the frequency of oscillation of said oscillator.

7. The ballast circuit of claim 1, wherein said driver comprises a multi-winding transformer.

8. The ballast circuit of claim 1, wherein said half-bridge switching circuit comprises a MOSFET totem pole half-bridge switching circuit.

9. The ballast circuit of claim 1, wherein said series resonant tank circuit comprises an inductive coupler, a pair of tank capacitors, a pair of diodes and a capacitor.

10. The ballast circuit of claim 1, wherein said resonant lamp circuit comprises a capacitor and a starter circuit.

11. A ballast circuit comprising:

an electromagnetic radiation emitting assembly comprising a secondary coil; and

an electronic assembly comprising an inductive coupler, said inductive coupler separated from said electromagnetic radiation emitting assembly by an air gap, said inductive coupler operable to induce a voltage in said secondary coil when said electronic assembly is energized.

12. The ballast circuit of claim 11, wherein said inductive coupler comprises inductive impedance in a series resonance tank circuit.

13. The ballast circuit of claim 11, wherein said inductive coupler is operable to generate an alternating flux in said air gap, said alternating flux operable to induce voltage in said secondary coil.

14. The ballast circuit of claim 11, wherein said air gap is operable to provide a mutual flux path between said inductive coupler and said secondary coil.

15. The ballast circuit of claim 11, wherein the permeance of said air gap is adjustable as a function of the distance between said inductive coupler and said secondary coil, an operating point of said electromagnetic radiation emitting assembly adjustable as a function of said permeance.

16. The ballast circuit of claim 11, wherein said air gap is operable to perform a current limiting function.

17. The ballast circuit of claim 11, wherein said inductive coupler and said secondary coil operably cooperate to form an air core transformer.

19. The ballast circuit of claim 11, wherein said electronic assembly further comprises an oscillator, a driver, a half-bridge switching circuit and a series resonant tank circuit.

18. The ballast circuit of claim I 1, wherein said electromagnetic radiation emitting assembly further comprises a resonance lamp circuit and an electromagnetic radiation emitting device.

20. A ballast circuit comprising:

an electromagnetic radiation emitting assembly comprising a secondary coil electrically connected with an electromagnetic radiation emitting device;

a series resonant tank circuit comprising an inductive coupler, said inductive coupler and said secondary coil operable to form an air core transformer to inductively couple said electromagnetic radiation emitting assembly and said series resonant tank circuit;

a half bridge switching circuit electrically connected with said series resonant tank circuit;

a driver electrically connected with said half bridge switching circuit; and

an oscillator electrically connected with said driver and said series resonant tank circuit, said oscillator operable to direct said half bridge switching circuit with said driver to energize said series resonant tank circuit as a function of feedback from said series resonant tank circuit, said series resonant tank circuit operable to inductively energize said electromagnetic radiation emitting device.

21. The ballast circuit of claim 20, wherein said electromagnetic radiation emitting assembly further comprises a resonant lamp circuit electrically connected with said secondary coil and said electromagnetic radiation emitting device.

22. The ballast circuit of claim 20, wherein said secondary coil is positioned adjacent said inductive coupler to form a coupling coefficient, an operating point of said electromagnetic radiation emitting device adjustable as a function of said coupling coefficient.

23. The ballast circuit of claim 20, wherein a resonant frequency of said series resonant tank circuit and said electromagnetic radiation emitting assembly are similar to optimize power transfer with said air core transformer.

24. The ballast circuit of claim 20, wherein said series resonant tank circuit further comprises a tank capacitor, a resonant frequency for said ballast circuit determined as a function of said inductive coupler, said tank capacitor and said electromagnetic radiation emitting assembly.

25. The ballast circuit of claim 20, wherein said electromagnetic radiation emitting assembly further comprises a capacitor, said capacitor electrically connected in series with said electromagnetic radiation emitting device to impedance match said electromagnetic emitting assembly and said series resonant tank circuit.

26. The ballast circuit of claim 20, wherein said electromagnetic radiation emitting assembly further comprises a starter circuit electrically connected with said electromagnetic radiation emitting device, said starter circuit independently operable to function as a short for a predetermined time constant when said electromagnetic radiation emitting device is inductively energized.

27. The ballast circuit of claim 20, wherein said electromagnetic radiation emitting assembly further comprises a starter circuit electrically connected with said secondary coil and said electromagnetic radiation emitting device, said starter circuit directed by an external control mechanism absent conductors.

28. The ballast circuit of claim 27, wherein said external control mechanism is operable to direct said starter circuit with at least one of optical control signals, radio frequency control signals and electromagnetic control signals.

29. The ballast circuit of claim 20, wherein said ballast circuit is operable to self oscillate to maintain resonate frequency as a function of reflected impedance of said electromagnetic radiation emitting assembly.

30. The ballast circuit of claim 20, wherein said ballast circuit is operable in a water treatment system.

31. A method of energizing an electromagnetic radiation emitting device, the method comprising:

a) energizing a half-bridge switching circuit;

b) energizing a series resonant tank circuit with an output of the half-bridge switching circuit to generate voltage across an inductive coupler;

c) inducing voltage in a secondary winding with said inductive coupler, said secondary winding separated by an air gap from said inductive coupler; and

d) energizing an electromagnetic radiation emitting device with voltage induced in said secondary winding.

32. The method of claim 31, wherein a) comprises controlling energization of said half-bridge switching circuit with a feedback signal from said series resonant tank circuit to maximize power transfer.

33. The method of claim 31, comprising the initial step of impedance matching said series resonant tank circuit and said secondary coil with a capacitor connected in series with said electromagnetic radiation emitting device.

34. The method of claim 33, wherein b) comprises energizing said series resonant tank circuit at a resonant frequency of said secondary coil, said capacitor and said electromagnetic radiation emitting device.

35. The method of claim 31, wherein c) comprises changing the distance between said inductive coupler and said secondary coil to adjust a coupling coefficient, wherein an operating point of said electromagnetic radiation emitting device is adjustable as a function of said coupling coefficient.

36. The method of claim 31, wherein d) comprises shorting a starter circuit electrically connected in series with said electromagnetic radiation emitting device for a predetermined time to maximize current in said secondary coil during startup absent control external to said starter circuit.

37. The method of claim 31, wherein c) comprises performing current limiting as a function of said air gap.

38. The method of claim 31, wherein c) comprises forming an air core transformer with said inductive coupler and said secondary winding.

39. The method of claim 31, wherein c) comprises generating an alternating flux in said air gap.

40. The method of claim 31, wherein b) comprises oscillating the frequency of said voltage applied across said inductive coupler as a function of impedance reflected by said electromagnetic radiation emitting device to said series resonant tank circuit.

41. A ballast circuit comprising:

an oscillator;

a driver electrically connected with said oscillator, wherein the output from said oscillator controls said driver;

a switching circuit electrically connected with said driver, wherein the output of said driver controls said switching circuit;

a resonant tank circuit electrically connected with said switching circuit, wherein said resonant tank circuit includes a primary coil; and

a current sensing circuit electrically connected with said oscillator and said resonant tank circuit, said current sensing circuit sensing current in said resonant tank circuit and providing an input to said oscillator as a function of said sensed current.

42. The ballast circuit of claim 41 wherein said switching circuit is a half-bridge switching circuit.

43. The ballast circuit of claim 41 wherein said resonant tank circuit is a series resonant tank circuit.

44. The ballast circuit of claim 41 wherein said resonant tank circuit is a parallel resonant tank circuit.

45. The ballast circuit of claim 41 wherein said current sensing circuit includes a current sensing transformer coupled to said resonant tank circuit.

46. The ballast circuit of claim 41 wherein said current sensing circuit includes a current sensing transformer coupled to a pair of primary coils in said resonant tank circuit.

47. The ballast circuit of claim 46 wherein said resonant tank circuit is a series resonant tank circuit including an inductive coupler and a pair of tank capacitors.

48. The ballast circuit of claim 47 wherein said switching circuit is a half-bridge switching circuit including a pair of secondary coils and a pair of transistors, said secondary coils being opposite in polarity to provide alternating operation of said transistors.

49. The ballast circuit of claim 48 wherein said half-bridge switching circuit is electrically connected to said series resonant circuit wherein alternating operation of said transistors alternately charges and discharges said tank capacitors.

50. The ballast circuit of claim 49 wherein said current sensing transformer is coupled to said ballast circuit between said switching circuit and said primary coil.

51. The ballast circuit of claim 41 further comprising a current limit circuit.

52. The ballast circuit of claim 51 wherein said current limit circuit includes a current sensing transformer coupled to said tank circuit.

53. The ballast circuit of claim 52 wherein said current limit circuit includes an operational amplifier, said current sensing transformer being electrically connected to a first input of said operational amplifier of said current limit circuit.

54. The ballast circuit of claim 53 wherein said current limit circuit includes a reference signal electrically connected to a second input of said operational amplifier of said current limit circuit, said reference signal corresponding to a desired threshold value.

55. The ballast circuit of claim 54 further including a control circuit for enabling and disabling said ballast circuit;

and

wherein said current limit circuit includes a latch having an output electrically connected to said control circuit, said control circuit enabling and disabling said ballast circuit in response to said output received from said latch, an output of said operational amplifier of said current limit circuit being electrically connected to an input of said latch.

56. The ballast circuit of claim 55 wherein said current limit circuit includes a reset for resetting said latch.

57. The ballast circuit of claim 56 wherein said latch is a flip-flop.

58. The ballast circuit of claim 57 wherein said current sensing transformer of said current sensing circuit includes a secondary coil wrapped around a core, said current sensing transformer of said current limit circuit including a secondary coil wrapped around said core.

60. The ballast circuit of claim 59 wherein said current limit circuit includes a current sensing transformer coupled to said tank circuit.

61. The ballast circuit of claim 60 wherein said current limit circuit includes an operational amplifier, said current sensing transformer being electrically connected to a first input of said operational amplifier of said current limit circuit.

62. The ballast circuit of claim 61 wherein said current limit circuit includes a reference signal electrically connected to a second input of said operational amplifier of said current limit circuit, said reference signal corresponding to a desired threshold value.

63. The ballast circuit of claim 62 wherein said current limit circuit includes a latch having an output electrically connected to said control circuit, said control circuit enabling and disabling said ballast circuit in response to the output received from said latch.

64. The ballast of claim 63 wherein an output of said operational amplifier of said current limit circuit is electrically connected to an input of said latch.

65. The ballast of claim 64 wherein said operational amplifier provides a signal output when said first input exceeds said second input.

66. The ballast circuit of claim 65 wherein said current limit circuit includes a reset for resetting said latch.

67. The ballast circuit of claim 66 wherein said latch is a flip-flop.

68. The ballast circuit of claim 67 wherein said current sensing transformer of said current sensing circuit includes a secondary coil wrapped around a core, said current sensing transformer of said current limit circuit including a secondary coil wrapped around said core.

69. The ballast circuit of claim 59 wherein said resonant tank circuit is a series resonant tank circuit.

70. The ballast circuit of claim 59 wherein said resonant tank circuit is a parallel resonant tank circuit.

71. The ballast circuit of claim 59 wherein said resonant tank circuit is a series resonant tank circuit including an inductive coupler and a pair of tank capacitors.

72. The ballast circuit of claim 71 wherein said switching circuit is a half-bridge switching circuit.

73. The ballast circuit of claim 71 wherein said switching circuit is a half-bridge switching circuit including a pair of secondary coils and a pair of transistors, each of said secondary coils being uniquely electrically connected with one of said pair of transistors, said secondary coils being opposite in polarity to provide alternating operation of said transistors.

74. The ballast circuit of claim 59 wherein said current sensing circuit includes a current sensing transformer coupled to said resonant tank circuit.

75. The ballast circuit of claim 74 wherein said half-bridge switching circuit is electrically connected to said series resonant circuit wherein alternating operation of said transistors alternately charges and discharges said tank capacitors.

59. A ballast circuit comprising:

a control circuit;

an oscillator electrically connected with said control circuit;

a driver electrically connected with said oscillator, wherein the output from said oscillator controls said driver;

a switching circuit electrically connected with said driver, wherein the output of said driver controls said switching circuit;

a resonant tank circuit electrically connected with said switching circuit, wherein said resonant tank circuit includes a primary coil;

a current sensing circuit electrically connected with said oscillator and said resonant tank circuit, said current sensing circuit sensing current in said resonant tank circuit and providing an input to said oscillator as a function of said sensed current; and

a current limit circuit inductively coupled to said resonant tank circuit and electrically connected to said control circuit, wherein said control circuit disables the ballast circuit in response to a predetermined signal from said current limit circuit.

76. A method for supplying power to a load through an inductive coupling, comprising the steps of:

applying a signal at a frequency to a primary coil of an inductive coupling;

monitoring at least one characteristic of the signal applied to the primary; and

adjusting the frequency of the signal applied to the primary as a function of the monitored characteristic of the signal applied to the primary.

77. The method of claim 76 wherein the characteristic is further defined as at least one of the phase and the amplitude of the signal.