Frequency Controller Resonant Converter

• US 20080211478A1
• Filed: 05/21/2004
• Published: 09/04/2008
• Est. Priority Date: 05/23/2003
• Status: Active Grant

• Current Assignee: Auckland UniServices Limited (Auckland University)
• Original Assignee: Auckland UniServices Limited (Auckland University)
• Inventors: Hu, Aiguo, Hussman, Stephan H.
• Granted Patent: US 8,050,068 B2
• Time in Patent Office: Days
• US Class Current: 323/355
• CPC Class Codes: H02J 1/002 Intermediate AC, e.g. DC supply with intermediated AC distribution
• CPC Class Codes: H02J 1/08 Three-wire systems; Systems having more than three wires
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02M 1/008 Plural converter units for generating at two or more independent and non-parallel outputs, e.g. systems with plural point of load switching regulators
• CPC Class Codes: H02M 3/3374 with preregulator, e.g. current injected push-pull
• CPC Class Codes: H02M 7/4815 Resonant converters H02M7/4811 and H02M7/4826 take precedence
• CPC Class Codes: H02M 7/4818 with means for adaptation of resonance frequency, e.g. by modification of capacitance or inductance of resonance circuits
• CPC Class Codes: Y02B 70/10 Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

A resonant converter is provided which may be used for supplying power to the primary conductive path of an inductively coupled power transfer (ICPT) system. The converter includes a variable reactive element in the resonant circuit which may be controlled to vary the effective inductance or capacitance of the reactive element. The frequency of the converter is stabilised to a nominal value by sensing the frequency of the converter resonant circuit, comparing the sensed frequency with a nominal frequency and varying the effective inductance or capacitance of the variable reactive element to adjust the converter frequency toward the nominal frequency.

Claims

1. A resonant converter including an input for connection to a substantially direct current electrical supply, a resonant circuit, first switching means to selectively provide current from the input to the resonant circuit, second switching means associated with a reactive component of the resonant circuit, and switch control means operable to control the second switching means to vary the effective reactance of the reactive element.

2. A resonant converter as claimed in claim 1 including phase sensing means to sense the phase of a voltage or current in the resonant circuit whereby the control means may actuate the second switching means to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed phase.

3. A resonant converter as claimed in claim 2 wherein the reactance comprises an inductor, the phase sensing means senses a voltage in the resonant circuit and the switch control means is operable to switch the second switching means to electrically connect the inductor to or disconnect the induction from the resonant circuit a predetermined time period after a sensed voltage zero crossing.

4. A resonant converter as claimed in claim 3 including frequency sensing means to sense the frequency of the resonant circuit whereby the control means may actuate the second switching means to allow the reactive element inductor to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the frequency of the resonant circuit.

5. A resonant converter as claimed in claim 3 wherein the phase sensing means sense the frequency of the resonant circuit whereby the control means may actuate the second switch means to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the frequency of the resonant circuit.

6. A resonant converter as claimed in claim 4 or claim 5 wherein the control means is operable to compare the sensed frequency with a nominal frequency and vary the predetermined time period to alter the resonant circuit frequency toward the nominal frequency.

7. A resonant converter as claimed in claim 6 wherein the control means is adapted to activate the second switching means to connect the inductor to the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed, and allow the second switching means to be deactivated when the voltage again reaches substantially zero.

8. A resonant converter as claimed in claim 7 wherein the control means is capable of varying the predetermined time period between substantially 0 electrical degrees and substantially 180 electrical degrees.

9. A resonant converter as claimed in claim 7 wherein the control means is capable of varying the predetermined time period between substantially 90 electrical degrees and substantially 150 electrical degreesA resonant converter as claimed in any one of claims 3 to 9 wherein the inductor is connected in parallel with a tuning capacitor of the resonant circuit.

11. A resonant converter as claimed in any one of claims 3 to 9 wherein the inductor has two terminals and the second switching means comprise two controllable semiconductor switching elements, one switching element being connected between each terminal and the resonant circuit.

12. A resonant converter as claimed in claim 11 wherein each switching element has an anti-parallel diode connected thereacross.

13. A resonant converter as claimed in claim 11 or claim 12 wherein the semiconductor switch elements comprise IGBT'"'"'s, MOSFETS, BJT'"'"'s, or other semiconductor switches.

14. A resonant converter as claimed in claim 3 wherein the inductor comprises a primary conductive path of an ICPT system.

15. A resonant converter as claimed in claim 3 wherein the inductor comprises an induction heating coil of an induction heating system.

16. A resonant converter as claimed in claim 2 wherein the reactance comprises a capacitor, the phase sensing means senses a voltage in the resonant circuit, and the switch control means is operable to switch the second switching means to electrically connect the capacitor to or disconnect the capacitor from the resonant circuit a predetermined time period after a sensed voltage zero crossing.

17. A resonant converter as claimed in claim 16 including frequency sensing means to sense the frequency of the resonant circuit whereby the control means may actuate the second switching means to allow the capacitor to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the frequency of the resonant circuit.

18. A resonant converter as claimed in claim 16 wherein the phase sensing means sense the frequency of the resonant circuit whereby the control means may actuate the second switching means to allow the capacitor to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the frequency of the resonant circuit.

19. A resonant converter as claimed in claim 17 or claim 18 wherein the control means is operable to compare the sensed frequency with a nominal frequency and vary the predetermined time period to alter the resonant circuit frequency toward the nominal frequency.

20. A resonant converter as claimed in claim 19 wherein the control means is adapted to activate the second switching means to disconnect the capacitor from the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed.

21. A resonant converter as claimed in claim 20 wherein the control means is capable of varying the predetermined time period between substantially 0 electrical degrees and substantially 90 electrical degrees.

22. A resonant converter as claimed in any one of claims 16 to 21 wherein the capacitor is connected in parallel with a tuning capacitor of the resonant circuit.

23. A resonant converter as claimed in claim 22 wherein the capacitance of the capacitor is substantially equal to the capacitance of the tuning capacitor.

24. A resonant converter as claimed in any one of claims 16 to 23 wherein the capacitor has two terminals and the second switching means comprise two controllable semiconductor switching elements, one switching element being connected between each terminal and the resonant circuit.

25. A resonant converter as claimed in claim 24 wherein each switching element has an anti-parallel diode connected thereacross.

26. A resonant converter as claimed in claim 24 or claim 25 wherein the semiconductor switch elements comprise IGBT'"'"'s, MOSFETS, BJT'"'"'s, or other semiconductor switches.

27. A current fed push-pull resonant converter including an input for connection to a substantially direct current electrical supply, a resonant circuit including a primary conductive path of an ICPT system, first switching means to selectively provide current from the input to the resonant circuit, second switching means associated with a reactive component of the resonant circuit, and switch control means operable to control the second switching means to vary the effective reactance of the reactive element.

28. An ICPT system including:

a. A power supply comprising a resonant converter having a resonant circuit including a primary conductive path of an ICPT system, first switching means to selectively provide current from the input to the resonant circuit, second switching means associated with a reactive component of the resonant circuit, and switch control means operable to control the second switching means to vary the effective reactance of the reactive element;

b. One or more secondary pick-ups, each pick-up having a pick resonant circuit comprising a pick-up coil and a tuning capacitor whereby power from the primary conductive path may be transferred to the pick-up by mutual induction between the primary conductive path and the coil.

29. An ICPT system as claimed in claim 28 wherein the primary conductive path comprises one or more turns of electrically conductive material.

30. An ICPT system as claimed in claim 29 wherein the primary conductive path is provided beneath a substantially planar surface.

31. An ICPT system as claimed in claim 28 wherein the primary conductive path includes at least one region about which there is a greater magnetic field strength than one or more other regions of the path.

32. An ICPT system as claimed in claim 28 wherein the primary conductive path includes one or more lumped inductances or one or more distributed inductances.

33. An ICPT system as claimed in any one of claims 28 to 32 wherein the primary conductive path is mounted adjacent to an amorphous magnetic material to provide a desired magnetic flux path.

34. An ICPT system as claimed in any one of claims 28 to 33 wherein the pick-up includes an amorphous magnetic material adjacent to the pick-up coil to provide a desired magnetic flux path.

35. An ICPT system as claimed in any one of claims 28 to 34 wherein the pick-up is battery-free.

36. An ICPT system as claimed in any one of claims 28 to 34 wherein the pick-up includes a super-capacitor.

37. A method of frequency stabilisation for a resonant converter having a resonant circuit comprising an inductive reactive element and a capacitive reactive element, the method including the steps of selectively switching one of the reactive elements into or out of the resonant circuit to alter the effective inductance or capacitance of the reactive element to thereby control the frequency of the resonant circuit.

38. A method as claimed in claim 37 including sensing the phase of a voltage or current in the resonant circuit and electrically connecting or disconnecting the reactive element to or from the resonant circuit dependant on the sensed phase.

39. A method as claimed in claim 38 wherein the phase of a voltage is sensed and the reactive element is electrically connected to the resonant circuit a predetermined time period after a sensed voltage zero crossing.

40. A method as claimed in any one of claims 37 to 39 including sensing the frequency of the resonant circuit activating a switching means to electrically connect or disconnect the reactive element to or from the resonant circuit dependant on the sensed frequency to alter the frequency of the resonant circuit.

41. A method as claimed in any one of claims 37 to 40 including comparing the sensed frequency with a nominal frequency and varying the predetermined time period to alter the resonant circuit frequency toward the nominal frequency.

42. A method as claimed in any one of claims 37 to 41 wherein the reactive element comprises an inductor and the method includes activating the switching means to connect the reactive element to the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed, and allowing the second switching means to be deactivated when the voltage again reaches substantially zero.

43. A method as claimed in claim 42 including selecting the predetermined time period from a range between substantially 0 electrical degrees and substantially 180 electrical degrees.

44. A method as claimed in claim 42 or claim 43 including selecting the predetermined time period from a range between substantially 90 electrical degrees and substantially 150 electrical degrees.

45. A method as claimed in any one of claims 39 to 41 wherein the reactive element comprises a capacitor and the method includes activating the switching means to disconnect the reactive element from the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed.

46. A method as claimed in claim 45 wherein the switching means connects the reactive element to the resonant circuit at a predetermined interval prior to a voltage zero crossing, the predetermined interval being of substantially the same duration as the predetermined time period.

47. A method as claimed in claim 45 or claim 46 including selecting the predetermined time period from a range between 0 electrical degrees and 90 electrical degrees.

48. A resonant converter substantially as herein described with reference to any one of the embodiments illustrated in the accompanying drawings.

49. A current fed push-pull resonant converter substantially as herein described with reference to any one of the embodiments illustrated in the accompanying drawings.

50. An ICPT system substantially as herein described with reference to any one of the embodiments illustrated in the accompanying drawings.

51. A method of frequency stabilisation for a resonant converter substantially as herein described with reference to any one of the embodiments illustrated in the accompanying drawings.