Input parasitic metal detection

• US 8,620,484 B2
• Filed: 02/08/2011
• Issued: 12/31/2013
• Est. Priority Date: 02/08/2010
• 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., Schwannecke, Joshua K., Liff, Dale R., Zeik, Andrew C., Blaha, Mark A., Amistadi, Jason L., Gruich, Robert D., Kuyvenhoven, Neil W., Umenei, A. Esai
• Primary Examiner(s): Bahta, Kidest
• Application Number:
  US13/022,944
• Publication Number:
  US 20110196544A1
• Time in Patent Office: 1,057 Days
• Field of Search: 700/291, 363/16, 363/40, 363/97, 336/83, 320/106
• US Class Current: 700/291
• CPC Class Codes: G01R 21/00 Arrangements for measuring electric power or power factor G01R7/12 takes precedence
• CPC Class Codes: G01V 3/02 operating with propagation of electric current
• 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 50/12 of the resonant type
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 50/70 involving the reduction of electric, magnetic or electromagnetic leakage fields
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/0047 with monitoring or indicating devices or circuits

Abstract

A system and method of controlling inductive power transfer in an inductive power transfer system and a method for designing an inductive power transfer system with power accounting. The method of controlling inductive power transfer including measuring a characteristic of input power, a characteristic of power in the tank circuit, and receiving information from a secondary device. Estimating power consumption based on the measured characteristic of tank circuit power and received information and comparing the measured characteristic of input power, the information from the secondary device, and the estimated power consumption to determine there is an unacceptable power loss. The method for designing an inductive power transfer system with power accounting including changing the distance between a primary side and a secondary side and changing a load of the secondary side. For each distance between the primary side and the secondary side and for each load, measuring a circuit parameter on the primary side in the tank circuit and a circuit parameter on the secondary side during the transfer of contactless energy. The method further including selecting a formula to describe power consumption in the system during the transfer of contactless energy based on coefficients and the circuit parameters, and determining the coefficients using the measured circuit parameters.

Claims

1. A method of controlling inductive power transfer in an inductive power transfer system, the system including a primary unit, having a tank circuit and switching circuit, 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 a characteristic of input power in the primary unit;

measuring a characteristic of power in the tank circuit of the primary unit;

receiving, in the primary unit, information from the at least one secondary device;

estimating power consumption in the inductive power transfer system as a function of at least the measured characteristic of power in the tank circuit of the primary unit;

comparing the measured characteristic of input power in the primary unit, the information from the at least one secondary device, and the estimated power consumption to determine there is an unacceptable amount of parasitic metal present in proximity to the primary unit; and

restricting or stopping the inductive power transfer from the primary unit in response to a determination that the unacceptable amount of parasitic metal is present in proximity to the primary unit.

2. The method as claimed in claim 1 wherein the estimating power consumption includes at least one of estimating power loss in the inductive power transfer system, estimating power used by a load of the secondary device, or a combination thereof.

3. The method as claimed in claim 1 wherein the estimating power consumption includes estimating power loss in the inductive power transfer system as a function of the measured characteristic of power in the tank circuit of the primary unit and the information from the secondary device.

4. The method as claimed in claim 1 wherein the switching circuit operates at an operating frequency that varies between a range of different operating frequencies during operation and estimating power consumption includes estimating power loss in the inductive power transfer system as a function of the measured characteristic of power in the tank circuit of the primary unit, the information from the secondary device, and the operating frequency of the switching circuit.

5. The method as claimed in claim 1 wherein estimating power consumption includes

estimating primary unit hysteresis power loss;

estimating primary unit eddy current power loss;

estimating primary unit voltage power loss;

estimating primary unit resistive power loss; and

estimating secondary device power consumption.

6. The method as claimed in claim 5 wherein estimating secondary device power consumption includes:

estimating secondary device eddy current power loss;

estimating secondary device voltage power loss; and

estimating secondary device resistive power loss.

7. The method as claimed in claim 5 wherein estimating secondary device power loss includes estimating secondary device eddy current power loss and estimating secondary device hysteresis as a function of the measured characteristic of power in the tank circuit of the primary unit.

8. The method as claimed in claim 1 wherein the information from the at least one secondary device includes a secondary device ID, a measurement of a characteristic of power in the secondary device, an estimation of power loss in the secondary device, one or more power loss coefficients, or a combination thereof.

9. The method as claimed in claim 1 wherein the information from the at least one secondary device includes synchronization information for synchronizing the measured characteristic of input power in the primary unit, the information from the at least one secondary device, and the estimated power consumption.

10. The method as claimed in claim 1 wherein the characteristic of input power includes a current or voltage in the primary unit before the switching circuit and the tank circuit.

11. The method as claimed in claim 1 wherein the characteristic of power in the tank circuit includes a current or voltage in the tank circuit.

12. The method as claimed in claim 1 wherein comparing the measured characteristic of input power in the primary unit, information from the at least one secondary device, and the estimated power consumption to determine there is an unacceptable amount of parasitic metal present in proximity to the primary unit includes:

calculating the total power consumption based on the characteristic of input power in the primary unit and the information from the at least one secondary device; and

determining that there is a foreign object present in proximity to the primary unit by detecting a difference between the calculated total power consumption and the estimated power consumption.

13. The method as claimed in claim 1 including determining that the unacceptable amount of parasitic metal is present in proximity to the primary unit when the difference between the calculated total power consumption and the estimated power consumption exceeds a threshold value.

14. The method as claimed in claim 1 including:

placing the secondary device in a plurality of different positions with respect to the primary unit;

for each position, determining an equivalent series resistance value of the secondary device;

determining an eddy current power loss coefficient for estimating secondary device eddy current power loss based on the equivalent series resistance values of the secondary device.

15. The method as claimed in claim 1 including:

placing the secondary device in a plurality of different positions with respect to the primary unit and operating the primary unit at a plurality of different operating frequencies;

for each position and operating frequency combination, determining an equivalent series resistance value of the secondary device;

determining an eddy current power loss coefficient for estimating secondary device eddy current power loss based on the equivalent series resistance values of the secondary device.

16. The method as claimed in claim 15 wherein determining an equivalent series resistance value of the secondary device includes measuring an equivalent series resistance of the primary unit alone, measuring an equivalent series resistance of the inductive power transfer system, and subtracting the equivalent series resistance of the primary unit alone from the equivalent series resistance of the inductive power transfer system to determine the equivalent series resistance value of the secondary device.

17. The method as claimed in claim 15 wherein the primary unit includes a primary unit shield, a primary unit magnet, and the primary unit tank circuit includes a primary unit coil, the secondary device includes a secondary coil, a secondary shield, and secondary friendly parasitic metal.

18. The method as claimed in claim 1 including:

placing the secondary device in a plurality of different positions with respect to the primary unit;

operating the primary unit at a plurality of different operating frequencies;

connecting a plurality of different loads to the secondary device;

for each position, operating frequency, and load combination, determining an equivalent series resistance value of the secondary device;

determining an eddy current power loss coefficient for estimating secondary device eddy current power loss based on the equivalent series resistance values of the secondary device.

19. A method for designing an inductive power transfer system with power accounting comprising:

providing a primary side with a tank circuit for transferring contactless energy;

providing a secondary side including a secondary coil for receiving the contactless energy and a load in electrical communication with a load;

changing the distance between the primary side and the secondary side;

changing the load of the secondary side;

for a plurality of distances between the primary side and the secondary side and for a plurality of loads, measuring at least one circuit parameter on the primary side in the tank circuit during the transfer of contactless energy;

for a plurality of distances between the primary side and the secondary device and for a plurality of loads of the secondary side, measuring at least one circuit parameter on the secondary side during the transfer of contactless energy;

selecting a formula to describe power consumption in the system during the transfer of contactless energy based on a plurality of coefficients, the at least one circuit parameter on the primary side in the tank circuit, and the at least one circuit parameter on the secondary side;

determining the coefficients using the measured circuit parameters on the secondary side and the measured circuit parameters on the primary side; and

storing the coefficient in the indicative power transfer system for use in predicting whether unaccounted for losses during operation are present.

20. The method of claim 19 wherein determining the coefficients of the formula includes determining the coefficients based on the type of power loss through physical observation of components in the system.

21. The method of claim 19 wherein determining the coefficients of the formula includes determining the coefficients by curve fitting.

22. The method of claim 21 wherein the curve fitting is performed using multivariate polynomial regression.

23. The method of claim 19 including storing one or more coefficients in a primary unit and storing one or more coefficients on a secondary device.

24. The method as claimed in claim 19 wherein the formula includes an estimation of power loss in the primary side, an estimation of power loss in the secondary side, and an estimation of power used by the load.

25. The method as claimed in claim 19 wherein the formula includes an estimation of power loss in the inductive power transfer system as a function of the circuit parameter of the primary side and the circuit parameter of the secondary side.

26. The method as claimed in claim 19 wherein:

for a plurality of operating frequencies in the primary unit, measuring at least one circuit parameter on the secondary side during the transfer of contactless energy and measuring at least one circuit parameter on the primary side in the tank circuit during the transfer of contactless energy.

27. The method as claimed in claim 19 wherein the formula includes an estimation of primary side hysteresis power loss;

primary side eddy current power loss;

primary side voltage power loss;

primary side resistive power loss; and

secondary side power consumption.

28. The method as claimed in claim 27 wherein the secondary side power consumption includes:

secondary side eddy current power loss;

secondary side voltage power loss; and

secondary side resistive power loss.

29. The method as claimed in claim 27 wherein the formula includes an estimation of secondary side eddy current power loss and secondary side hysteresis power loss as a function of the circuit parameter in the tank circuit.

30. The method as claimed in claim 19 wherein the circuit parameter in the tank circuit includes at least one of a current and a voltage in the tank circuit.

31. The method as claimed in claim 19 including:

for each distance between the primary side and the secondary side, determining an equivalent series resistance value of the secondary side; and

determining an eddy current power loss coefficient based on the equivalent series resistance values.

32. The method as claimed in claim 26 including:

for each combination of distance between the primary side and the secondary side and operating frequency, determining an equivalent series resistance value of the secondary device;

determining an eddy current power loss coefficient based on the equivalent series resistance values.

33. A primary unit, having a tank circuit and switching circuit, operable to generate an electromagnetic field for transferring power to 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 primary unit comprising:

a sensor for measuring a characteristic of input power in the primary unit;

a sensor for measuring a characteristic of power in the tank circuit of the primary unit;

a receiver for receiving information from the at least one secondary device;

a controller programmed for;

estimating power consumption in the inductive power transfer system as a function of at least the measured characteristic of power in the tank circuit of the primary unit;

comparing the measured characteristic of input power in the primary unit, the information from the at least one secondary device, and the estimated power consumption to determine there is an unacceptable amount of parasitic metal present in proximity to the primary unit; and

restricting or stopping the inductive power transfer from the primary unit in response to a determination that the unacceptable amount of parasitic metal is present in proximity to the primary unit.

34. The primary unit as claimed in claim 33 wherein the estimating power consumption includes at least one of estimating power loss in the inductive power transfer system, estimating power used by a load of the secondary device, or a combination thereof.

35. The primary unit as claimed in claim 33 wherein the estimating power consumption includes estimating power loss in the inductive power transfer system as a function of the measured characteristic of power in the tank circuit of the primary unit and the information from the secondary device.

36. The primary unit as claimed in claim 33 wherein the switching circuit operates at an operating frequency that varies between a range of different operating frequencies during operation and estimating power consumption includes estimating power loss in the inductive power transfer system as a function of the measured characteristic of power in the tank circuit of the primary unit, the information from the secondary device, and the operating frequency of the switching circuit.

37. The primary unit as claimed in claim 33 wherein estimating power consumption includes

estimating primary unit hysteresis power loss;

estimating primary unit eddy current power loss;

estimating primary unit voltage power loss;

estimating primary unit resistive power loss; and

estimating secondary device power consumption.

38. The primary unit as claimed in claim 37 wherein estimating secondary device power consumption includes:

estimating secondary device eddy current power loss;

estimating secondary device voltage power loss; and

estimating secondary device resistive power loss.

39. The primary unit as claimed in claim 37 wherein estimating secondary device power loss includes estimating secondary device eddy current power loss and estimating secondary device hysteresis as a function of the measured characteristic of power in the tank circuit of the primary unit.

40. The primary unit as claimed in claim 33 wherein the information from the at least one secondary device includes a secondary device ID, a measurement of a characteristic of power in the secondary device, an estimation of power loss in the secondary device, one or more power loss coefficients, or a combination thereof.

41. The primary unit as claimed in claim 33 wherein the information from the at least one secondary device includes synchronization information for synchronizing the comparing the measured characteristic of input power in the primary unit, the information from the at least one secondary device, and the estimated power consumption.

42. The primary unit as claimed in claim 33 wherein the characteristic of input power includes a current or voltage in the primary unit before the switching circuit and the tank circuit.

43. The primary unit as claimed in claim 33 wherein the characteristic of power in the tank circuit includes a current or voltage in the tank circuit.

44. The primary unit as claimed in claim 33 wherein comparing the measured characteristic of input power in the primary unit, information from the at least one secondary device, and the estimated power consumption to determine there is an unacceptable amount of parasitic metal present in proximity to the primary unit includes:

calculating the total power consumption based on the characteristic of input power in the primary unit and the information from the at least one secondary device; and

determining that there is a foreign object present in proximity to the primary unit by detecting a difference between the calculated total power consumption and the estimated power consumption.

45. The primary unit as claimed in claim 33 including determining that the unacceptable amount of parasitic metal is present in proximity to the primary unit when the difference between the calculated total power consumption and the estimated power consumption exceeds a threshold value.