Methods and apparatus for control of inductively coupled power transfer systems

• US 20070109708A1
• Filed: 05/21/2004
• Published: 05/17/2007
• 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
• Granted Patent: US 8,093,758 B2
• Time in Patent Office: Days
• US Class Current: 361/113
• CPC Class Codes: H02J 1/002 Intermediate AC, e.g. DC supply with intermediated AC distribution
• 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 3/33523 with galvanic isolation between input and output of both the power stage and the feedback loop
• CPC Class Codes: H02M 7/217 using semiconductor devices only
• 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
• CPC Class Codes: Y02P 80/10 Efficient use of energy, e.g. using compressed air or pressurized fluid as energy carrier

Abstract

A power pick-up for an Inductively Coupled Power Transfer (ICPT) system is provided having a resonant pick up circuit. The natural frequency of the pick-up circuit may be varied by controlling the conductance or capacitance of a variable reactive in the resonant circuit. The load being supplied by the pick-up circuit is sensed, and the effective capacitance or inductance of the variable reactive component is controlled to vary the natural resonant frequency of the pick-up circuit to thereby control the power flow into the pick-up to satisfy the power required by the load.

Claims

1. An ICPT pick-up comprising:

a pick-up resonant circuit, the circuit comprising a capacitive element and an inductive element adapted to receive power from a magnetic field associated with a primary conductive path to supply a load;

a sensor configured to sense a condition of the load; and

a controller configured to selectively tune or de-tune the pick-up in response to the load sensed by the sensor by varying the effective capacitance or inductance of the capacitive or the inductive element of the pick-up circuit to control the transfer of power to the pick-up dependant on the sensed load condition.

2. A pick-up as claimed in claim 1 wherein the controller comprises:

a reactive element; and

a switching device configured to allow the reactive element to be selectively electrically connected to the pick-up circuit.

3. A pick-up as claimed in claim 2 wherein the controller is operable to control the switching device so that the apparent capacitance or inductance of the reactive element is varied to thereby tune or detune the pick-up circuit.

4. A pick-up as claimed in claim 1 wherein the sensor senses the power required by the load.

5. A pick-up as claimed in claim 2, comprising:

a phase device configured to sense the phase of a voltage or current in the resonant circuit; and

whereby the controller may actuate the switching device to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed phase.

6. A pick-up as claimed in claim 5 wherein:

the reactive element comprises an inductor,

the phase device senses a voltage in the resonant circuit, and

the controller is operable to switch the switching device to electrically connect or disconnect the inductor to or from the resonant circuit a predetermined time period after a sensed voltage zero crossing.

7. A pick-up as claimed in claim 4 further comprising:

a frequency sensing device configured to sense the frequency of the resonant circuit whereby the controller may actuate the switching device to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the natural resonant frequency of the resonant circuit.

8. A pick-up as claimed in claim 4 wherein:

the phase sensing device senses the frequency of the resonant circuit, and

whereby the controller may actuate the switching device to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the natural resonant frequency of the resonant circuit.

9. A pick-up as claimed in claim 6, wherein the controller is adapted to activate the switching device to connect the inductor to the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed, and further adapted to allow the switching device to be deactivated when the voltage again reaches substantially zero.

10. A pick-up as claimed in claim 6, wherein the controller is capable of varying the predetermined time period between substantially 0 electrical degrees and substantially 180 electrical degrees.

11. A pick-up as claimed in claim 6 wherein the controller is capable of varying the predetermined time period between substantially 90 electrical degrees and substantially 150 electrical degrees.

12. A pick-up as claimed in claim 6 wherein the inductor is connected in parallel with a tuning capacitor of the resonant circuit.

13. A pick-up as claimed in claim 6 further comprising:

an inductor comprising two terminals; and

the switching device comprising at least two controllable semiconductor switching elements, a respective semiconductor switching element being connected between each terminal and the resonant circuit.

14. A pick-up as claimed in claim 13 wherein each switching element comprises an anti-parallel diode connected thereacross.

15. A pick-up as claimed in claim 13 wherein the semiconductor switch elements comprises at least one of IGBT'"'"'s, MOSFETS, MCT'"'"'s, and BJT'"'"'s.

16. A pick-up as claimed in claim 3 wherein an inductor comprises the pick-up coil.

17. A pick-up as claimed in claim 5 wherein:

the reactive element comprises a capacitor,

the phase sensing device senses a voltage in the resonant circuit, and

the controller is operable to switch the switching device to electrically connect or disconnect the capacitor to or from the resonant circuit in a predetermined time period after a sensed voltage zero crossing.

18. A pick-up as claimed in claim 17 further comprising:

a frequency sensing device configured to sense the frequency of the resonant circuit, and

whereby the controller may actuate the switching device to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the natural resonant frequency of the resonant circuit.

19. A pick-up as claimed in claim 17 wherein:

the phase sensing device senses the frequency of the resonant circuit; and

whereby the controller may actuate the switching device to allow the reactive element to be electrically connected to or disconnected from the resonant circuit dependant on the sensed frequency to alter the natural resonant frequency of the resonant circuit.

20. A pick-up as claimed in claim 17 wherein the controller is adapted to activate the switching device to disconnect the capacitor from the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed.

21. A pick-up as claimed in claim 17 wherein the controller is capable of varying the predetermined time period between substantially 0 electrical degrees and substantially 90 electrical degrees.

22. A pick-up as claimed in claim 17 wherein the capacitor is connected in parallel with a tuning capacitor of the resonant circuit.

23. A pick-up as claimed in claim 22 wherein a capacitance of the capacitor is substantially equal to a capacitance of the tuning capacitor.

24. A pick-up as claimed in claim 17 wherein:

the capacitor comprises two terminals, and

the switching device comprises two controllable semiconductor switching elements, a respective semiconductor switching element being connected between each terminal and the resonant circuit.

25. A pick-up as claimed in claim 24 wherein each switching element comprises an anti-parallel diode connected thereacross.

26. A pick-up as claimed in claim 24 wherein the semiconductor switch elements comprise at least one of IGBT'"'"'s, MOSFETS, of and BJT'"'"'s.

27. A pick-up as claimed in claim 17 wherein the variable reactance comprises the tuning capacitor of the resonant circuit.

28. An ICPT system comprising:

a power supply comprising a resonant converter to provide alternating current to a primary conductive path of the ICPT system;

one or more secondary pick-ups, each pick-up comprising;

a pick-up resonant circuit including comprising;

a capacitive element; and

an inductive element adapted to receive power from a magnetic field associated with a primary conductive path to supply a load;

a sensor configured to sense a condition of the load; and

a controller configured to selectively tune or de-tune the pick-up in response to the load sensed by the sensor by varying the effective capacitance or inductance of the capacitive element or the inductive element of the pick-up circuit to control the transfer of power to the pick-up dependant on the sensed load condition.

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 comprises 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 comprises one or more lumped inductances or one or more distributed inductances.

33. An ICPT system as claimed in claim 28 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 claim 28 wherein the pick-up comprises an amorphous magnetic material adjacent to the pick-up coil to provide a desired magnetic flux path.

35. An ICPT system as claimed in claim 28 wherein the pick-up is battery-free.

36. An ICPT system as claimed in claim 28 wherein the pick-up comprises a super-capacitor.

37. A method for controlling power drawn by an ICPT pick-up, the method comprising the steps of:

sensing a load condition of the pick-up; and

selectively tuning or detuning the pick-up circuit depending upon the sensed load condition.

38. A method as claimed in claim 37 wherein the step of tuning or detuning the pickup circuit comprises the step of moving a resonant frequency of the pick-up circuit toward or away from a tuned condition.

39. A method as claimed in claim 37 wherein the step of tuning or detuning the pick-up circuit comprises the step of controlling a variable capacitor or inductor.

40. A method as claimed in claim 37 further comprising the step of sensing a frequency of a current or voltage in the resonant circuit.

41. A method as claimed in claim 40 further comprising the steps of:

comparing the sensed frequency with a nominal frequency for the resonant circuit; and

tuning or de-tuning toward or away from a nominal frequency dependant on the sensed load.

42. A method as claimed in claim 37 further comprising the step of:

selectively switching a reactive element into or out of the resonant circuit to alter an apparent inductance or capacitance of the reactive element to thereby tune or de-tune the resonant circuit.

43. A method as claimed in claim 42 further comprising the steps of:

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.

44. A method as claimed in claim 43 further comprising the steps of:

sensing a phase of a voltage; and

electrically connecting the reactive element to the resonant circuit in a predetermined time period after a sensed voltage zero crossing.

45. A method as claimed in claim 42 further comprising the steps of:

sensing the frequency of the resonant circuit; and

activating a switching device to electrically connect or disconnect the reactive element to or from the resonant circuit dependant on the sensed frequency to alter the natural resonant frequency of the resonant circuit.

46. A method as claimed in claim 42 further comprising the steps of:

comparing the sensed frequency with a nominal frequency; and

varying the predetermined time period to tune the resonant circuit toward or away from the nominal frequency.

47. A method as claimed in claim 42 further comprising the steps of:

activating a switching device to connect the reactive element to the resonant circuit after the predetermined time period following a voltage zero crossing has elapsed; and

allowing the switching device to be deactivated when the voltage again reaches substantially zero.

48. A method as claimed in claim 42 further comprising the step of selecting the predetermined time period from a range between substantially 0 electrical degrees and substantially 180 electrical degrees.

49. A method as claimed in claim 42 further comprising the step of selecting the predetermined time period from a range between substantially 90 electrical degrees and substantially 150 electrical degrees.

50. A method as claimed in claim 43, further comprising the steps of:

including sensing the phase of a voltage; and

electrically disconnecting the reactive element from the resonant circuit in a predetermined time period after a sensed voltage zero crossing.

51. A method as claimed in claim 50 wherein:

the reactive element comprises a capacitor; and

the predetermined time period is selected from a range between substantially 0 electrical degrees and substantially 90 electrical degrees.

52-54. -54. (canceled)