APPARATUS, SYSTEM, AND METHOD FOR DETECTING A FOREIGN OBJECT IN AN INDUCTIVE WIRELESS POWER TRANSFER SYSTEM VIA COUPLING COEFFICIENT MEASUREMENT

• US 20130257165A1
• Filed: 03/30/2012
• Published: 10/03/2013
• Est. Priority Date: 10/13/2011
• Status: Active Grant

• Current Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Original Assignee: Integrated Device Technology Incorporated (Renesas Electronics Corporation)
• Inventors: Singh, Manjit
• Granted Patent: US 9,551,805 B2
• Time in Patent Office: Days
• US Class Current: 307/98
• CPC Class Codes: G01V 3/12 operating with electromagnetic waves operating with millimetre waves G01V8/005
• 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 50/80 involving the exchange of data, concerning supply or distribution of electric power, between transmitting devices and receiving devices
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment

Abstract

An inductive wireless power device comprises a transmitter configured to generate an electromagnetic field to a coupling region for wireless power transfer to a receiver, and control logic configured to determine a coupling coefficient of the wireless power transfer when the receiver is within the coupling region. The control logic also determines a presence of a foreign object within the coupling region responsive to a comparison of the determined coupling coefficient and an expected coupling coefficient for the wireless power transfer. An inductive wireless power device comprises a receiver configured to couple with an electromagnetic field in a coupling region for inductive wireless power transfer from a transmitter. The receiver is configured to alter a wireless power transfer characteristic of the transmitter for a determination of a presence of a foreign object within the coupling region responsive to a determination of a coupling coefficient of the wireless power transfer.

Claims

1. An inductive wireless power device, comprising:

a transmitter configured to generate an electromagnetic field to a coupling region for wireless power transfer to a receiver; and

control logic configured to determine a coupling coefficient of the wireless power transfer when the receiver is within the coupling region, and to determine a presence of a foreign object within the coupling region responsive to a comparison of the determined coupling coefficient and an expected coupling coefficient for the wireless power transfer.

2. The inductive wireless power device of claim 1, wherein the control logic is configured to determine that the foreign object is present within the coupling region when the determined coupling coefficient is below a predetermined threshold below the expected coupling coefficient.

3. The inductive wireless power device of claim 2, wherein the predetermined threshold is a determined as a percentage of the expected coupling coefficient.

4. The inductive wireless power device of claim 2, wherein the predetermined threshold is determined as a difference of the expected coupling coefficient and the determined coupling coefficient.

5. The inductive wireless power device of claim 1, further comprising a power sense element coupled to a transmit coil of the transmitter and to the control logic, the power sense element for measuring power components of the transmit coil of the transmitter and sending the measured power components to the control logic.

6. The inductive wireless power device of claim 5, wherein the measured power components includes a voltage across the transmit coil and a current flowing through the transmit coil.

7. The inductive wireless power device of claim 5, wherein the coupling coefficient is based, at least in part, on the power components.

8. The inductive wireless power device of claim 5, wherein the control logic is configured to compare the power components of the transmit coil at a first time when a receiver coil of the receiver is in a shorted state and at a second time when the receiver coil of the receiver is not in the shorted state.

9. An inductive wireless power device, comprising a receiver configured to couple with an electromagnetic field in a coupling region for inductive wireless power transfer from a transmitter, wherein the receiver is configured to alter a wireless power transfer characteristic of the transmitter for a determination of a presence of a foreign object within the coupling region responsive to a determination of a coupling coefficient of the wireless power transfer.

10. The inductive wireless power device of claim 9, wherein the receiver comprises a receive coil configured to generate an AC signal responsive to coupling with the electromagnetic field, wherein the receiver is configured to short the receive coil at a first time and not short the receive coil at a second time for altering the wireless power transfer characteristic of the transmitter.

11. The inductive wireless power device of claim 10, wherein the receiver further comprises a switch coupled parallel with the receive coil, wherein the switch is configured to close at the first time and open at the second time.

12. The inductive wireless power device of claim 11, wherein the receiver further comprises a rectifier configured to convert the AC signal from the receive coil to a DC signal to be output to a load.

13. The inductive wireless power device of claim 12, wherein the rectifier is a synchronous rectifier including a plurality of switches for converting the AC signal to the DC signal to be output to the load.

14. The inductive wireless power device of claim 13, wherein the switch coupled parallel with the receive coil for altering the wireless power transfer characteristic of the transmitter is one plurality of switches of the rectifier used for converting the AC signal to the DC signal to be output to the load.

15. The inductive wireless power device of claim 12, wherein the switch coupled parallel with the receive coil for altering the wireless power transfer characteristic of the transmitter is separate from the rectifier used for converting the AC signal to the DC signal to be output to the load.

16. An inductive wireless power transfer system, comprising:

a wireless power transmitting apparatus configured to generate an electromagnetic field in a coupling region for wireless power transfer; and

a wireless power receiving apparatus configured to couple with the electromagnetic field and generate an output signal in response thereto, wherein at least one of the wireless power transmitting apparatus and the wireless power receiving apparatus is configured to determine a presence of a foreign object within the coupling region based, at least in part, on determining a coupling coefficient for the wireless power transfer between the wireless power transmitting apparatus and the wireless power receiving apparatus.

17. The inductive wireless power transfer system of claim 16, wherein the wireless power receiving apparatus includes a mobile electronic device.

18. The inductive wireless power transfer system of claim 16, wherein the wireless power receiving apparatus includes a receiver configured to operate a receive coil in a short state and a non-short state, and wherein the wireless power transmitting apparatus is configured to determine a resistance for a transmitter during each of the short state and the non-short state to determine the coupling coefficient.

19. The inductive wireless power transfer system of claim 18, wherein the wireless power transmitting apparatus includes control logic configured to compare the determined coupling coefficient to a predetermined threshold to determine the presence of the foreign object.

20. The inductive wireless power transfer system of claim 19, wherein the predetermined threshold is relative to an expected coupling coefficient for a fixed distance between the transmitter and the receiver.

21. A method for detecting a foreign object in a coupling region of an inductive wireless power transfer system, the method comprising:

determining a coupling coefficient for wireless power transfer between a transmitter and receiver; and

determining a presence of a foreign object based, at least in part, on a comparison of the determined coupling coefficient and an expected coupling coefficient.

22. The method of claim 21, further comprising taking an action on the inductive wireless power transfer system in response determining the presence of the foreign object.

23. The method of claim 22, wherein the action is at least one of reducing the wireless power transfer, disabling wireless power transfer, and notifying a user that the foreign object is present within the coupling region.

24. A method for altering a wireless power transfer characteristic of a wireless power transmitter for a determination of a presence of a foreign object within a coupling region of a wireless power transfer system, the method comprising:

shorting a receive coil of a receiver at a first time for a wireless power transmitter to determine a wireless power transfer characteristic in a first state; and

operating the receive coil of the receiver in a non-shorted state for the wireless power transmitter to determine the wireless power transfer characteristic in a second state.

25. The method of claim 24, wherein shorting the receive coil includes closing a switch coupled parallel with the receive coil, and wherein operating the receive coil in the non-shorted state includes opening the switch.