Controlling inductive power transfer systems

• US 8,508,077 B2
• Filed: 09/19/2011
• Issued: 08/13/2013
• Est. Priority Date: 05/11/2004
• Status: Active Grant

• Current Assignee: Philips IP Ventures B.V. (Koninklijke Philips N.V.)
• Original Assignee: Access Business Group International LLC (Alticor Incorporated)
• Inventors: Stevens, Michael Craig, Knill, Alexander Charles, Dunton, John Robert, Fells, Julian Andrew John
• Primary Examiner(s): AMAYA, CARLOS DAVID
• Application Number:
  US13/236,066
• Publication Number:
  US 20120068536A1
• Time in Patent Office: 694 Days
• Field of Search: 307/11, 307/17, 307/39, 307/104, 320/106, 320/108
• US Class Current: 307/104
• CPC Class Codes: G05F 1/66 Regulating electric power
• CPC Class Codes: H01F 38/14 Inductive couplings for wireless supply or distribution of electric power using inductive coupling H02J50/10
• CPC Class Codes: H02J 50/10 using inductive coupling
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/40 using two or more transmitting or receiving devices H02J50/50 takes precedence
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices

Abstract

An inductive power transfer system comprises a primary unit operable to generate an electromagnetic field and at least one secondary device, separable from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power can be received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween. The system detects if there is a substantial difference between, on the one hand, a power drawn from the primary unit, and on the other hand, a power required by the secondary device or, if there is more than one secondary device, a combined power required by the secondary devices. Following such detection, the system restricts or stops the inductive power supply from the primary unit. Such a system can detect the presence of unwanted parasitic loads in the vicinity of the primary unit reliably.

Claims

1. A method of controlling inductive power transfer in an inductive power transfer system, the system comprising a primary unit operable to generate an electromagnetic field and at least one secondary device, separate from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween, the method comprising:

measuring, in the secondary device or devices therefrom, a characteristic of a secondary power being supplied to a load of the secondary device;

receiving, in the primary unit, power requirement information of the secondary device or devices therefrom, the power requirement information includes information relating to the measured characteristic of the secondary power;

determining, in the primary unit, in dependence upon the power requirement information of the secondary device a power supplied to the secondary device or, if there is more than one secondary device, a combined power supplied to the secondary devices;

measuring a primary power drawn from the primary unit, and determining if there is a substantial difference between the measured primary power and the power supplied; and

following such determination of a substantial difference, restricting or stopping the inductive power supply from the primary unit.

2. A method as claimed in claim 1, wherein the characteristic of the secondary power is at least one of a current and a voltage supplied to the load.

3. A method as claimed in claim 1, wherein the power requirement information represents the amount of power used by the secondary device or devices therefrom.

4. A method as claimed in claim 1, wherein the inductive power supply is restricted or stopped in the event that the measured primary power is greater than a threshold value.

5. A method as claimed in claim 1, further comprising restricting or stopping the inductive power supply in the event that the measured primary power is less than a standby threshold value.

6. A method as claimed in claim 1, wherein the inductive power supply from the primary unit is restricted or stopped in dependence upon a difference between the measured primary power and the power supplied to the secondary device or devices therefrom.

7. A method as claimed in claim 6, wherein the inductive power supply is restricted or stopped in the event that the measured primary power exceeds the power supplied by more than a threshold value.

8. A method as claimed in claim 1, wherein the at least one secondary device transmits the power requirement information to the primary unit using a communication link that is separate from an inductive power transfer link between the primary unit and the secondary device concerned.

9. A method as claimed in claim 1, wherein the or each secondary device transmits the power requirement information to the primary unit by varying a load imposed by the secondary device on the primary unit.

10. A method as claimed in claim 9, wherein the load is varied to amplitude modulate or to pulse width modulate transmission of the power requirement information to the primary unit.

11. A method as claimed in claim 10, wherein the power requirement information is transmitted as a series of bits or symbols.

12. A method as claimed in claim 9, wherein the load is a dummy load.

13. A method as claimed in claim 1, wherein the power requirement information transmitted includes information relating to a parasitic load imposed on the primary unit by the secondary device.

14. A method as claimed in claim 1, wherein the power requirement information generated from at least one secondary device is representative of a sum of an amount of power supplied to the secondary device concerned and a parasitic load imposed on the primary unit by the secondary device concerned.

15. An inductive power transfer system comprising:

a primary unit operable to generate an electromagnetic field;

at least one secondary device, separate from the primary unit, and adapted to couple with the field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween;

a load-measuring unit for determining information relating to a power requirement of the secondary device or devices therefrom;

communication circuitry for receiving, in the primary unit, the power requirement of the secondary device or devices therefrom;

power measuring circuitry; and

a control unit for determining if there is a substantial difference between the measured power and the power requirement, and

the control unit operable, following such determination of a substantial difference, to restrict or stop the inductive power supply from the primary unit.

16. A system as claimed in claim 15, wherein the information relating to the power requirement is the voltage or current supplied to a load of the secondary device or devices therefrom.

17. A system as claimed in claim 15, wherein the power requirement is an amount of power supplied to the secondary device or devices therefrom.

18. A system as claimed in claim 15, wherein the power measuring circuitry is operable to measure a power drawn from the primary unit.

19. A system as claimed in claim 15, wherein the at least one secondary device is adapted to transmit the power requirement information by modulating a load imposed on the primary unit.

20. A system as claimed in claim 19, wherein amplitude modulation or pulse width modulation are used to transmit the power requirement information to the primary unit.

21. A system as claimed in claim 20, wherein the power requirement information is transmitted as a series of bits or symbols.

22. A primary unit, for use in an inductive power transfer system that also has at least one secondary device separate from the primary unit, the primary unit comprising:

a primary coil for generating an electromagnetic field which couples with the at least one secondary device when it is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween;

communication circuitry for receiving information relating to a power requirement of the secondary device or devices therefrom;

power obtaining circuitry for obtaining a power drawn from the primary unit; and

a control unit for determining in dependence upon the received information a power supplied to the secondary device or, if there is more than one secondary device, a combined power supplied to the secondary devices, the control unit for determining if there is a substantial difference between the obtained power and the supplied power, and the control unit operable, following such determination of a substantial difference, to restrict or stop the inductive power supply from the primary unit.

23. A primary unit as claimed in claim 22, further comprising restricting or stopping circuitry operable to restrict or stop the inductive power supply in the event that the obtained power is less than a standby threshold value.

24. A primary unit as claimed in claim 22, wherein the communication circuitry is adapted to receive the power requirement from the or each secondary device using a communication link that is separate from an inductive power transfer link between the primary unit and the secondary device concerned.

25. A primary unit as claimed in claim 22, wherein the communication circuitry is adapted to receive the power requirement from the or each secondary device based on a varying load in the secondary device concerned.

26. A primary unit as claimed in claim 25, wherein the communication circuitry is adapted to receive amplitude modulated communication or pulse width modulated communication from the secondary device concerned.

27. A primary unit as claimed in claim 26, wherein the amplitude modulated communication or pulse width modulated communication is transmitted as a series of bits or symbols.

28. A primary unit as claimed in claim 22, wherein the power requirement information received by the communication circuitry from at least one secondary device is representative of a sum of a power supplied to an actual load of the secondary device concerned and a parasitic load imposed on the primary unit by the secondary device concerned.

29. A secondary unit, for use in an inductive power transfer system that also has a primary unit, said secondary unit comprising:

a secondary coil adapted to couple with a field generated from said primary unit when in proximity to said primary unit so that power is received inductively by said secondary unit without direct electrical conductive contacts therebetween;

a load-measuring unit for determining information relating to a power requirement of said secondary unit; and

communication circuitry for sending said power requirement to said primary unit, wherein the primary unit includes a controller configured to determine a power supplied to said secondary unit based on said power requirement, wherein the controller is configured to determine if there is a substantial difference between a power measured in the primary unit and the power supplied, and following such determination of a substantial difference, to restrict or stop supply of inductive power from the primary unit; and

said communication circuitry varying a load to communicate said power requirement to said primary unit.

30. A secondary unit as claimed in claim 29, wherein said information relating to said power requirement of said secondary unit includes at least one of current and voltage supplied to said secondary unit from said primary unit.

31. A secondary unit as claimed in claim 29, wherein said communication circuitry employs a dummy load to communicate said power requirement to said primary unit.

32. A secondary unit as claimed in claim 29, wherein said power requirement includes a parasitic load of said secondary unit imposed on said primary unit.

33. A secondary unit as claimed in claim 32, wherein said communication circuitry employs amplitude modulation or pulse width modulation to communicate said power requirement to said primary unit.

34. A secondary unit as claimed in claim 33, wherein said power requirement is communicated as a series of bits or symbols.