Foreign object detection in wireless energy transfer systems

• US 10,018,744 B2
• Filed: 05/07/2015
• Issued: 07/10/2018
• Est. Priority Date: 05/07/2014
• Status: Active Grant

Abstract

Systems and methods for detecting foreign object debris around a wireless power transfer system include a plurality of detectors, each detector featuring one or more loops of conducting material, and a controller configured to measure at least one of a voltage and a current in each detector and to determine, based on the measurements, whether foreign object debris is present around the wireless power transfer system, where at least some of the plurality of detectors include a first number of loops of the conducting material, and at least some of the plurality of detectors include a second number of loops of the conducting material larger than the first number.

Claims

1. A wireless power transfer system comprising:

a wireless power transfer source configured to generate a source magnetic field at a first frequency to transfer power to a wireless power receiver;

an auxiliary magnetic field source configured to generate an auxiliary magnetic field at a second frequency;

at least one detector configured to generate an electrical signal in response to perturbations in the auxiliary magnetic field generated by the auxiliary magnetic field source; and

a controller configured to determine whether foreign object debris is present around the wireless power transfer system based on the electrical signal.

2. The wireless power transfer system of claim 1, wherein the auxiliary magnetic field source comprises at least one auxiliary coil and at least one amplifier.

3. The wireless power transfer system of claim 1, wherein the first frequency is equal to the second frequency.

4. The wireless power transfer system of claim 1, wherein the first frequency is different from the second frequency.

5. The wireless power transfer system of claim 1, further comprising a power supply coupled to the wireless power transfer source and configured to provide power to drive the wireless power source, and wherein the power supply is turned off when the auxiliary magnetic field source is generating an auxiliary magnetic field.

6. The wireless power transfer system of claim 1, wherein the auxiliary magnetic field source comprises up to four auxiliary coils and up to four amplifiers.

7. The wireless power transfer system of claim 2, wherein the wireless power source comprises a source resonator coil wound over a first area, and wherein the at least one auxiliary coil is configured to be wound over the first area.

8. The wireless power transfer system of claim 7, wherein the at least one auxiliary coil comprises two sets of conductor windings connected in series, each of the two sets of conductor windings being wound over one of a second and a third area, respectively.

9. The wireless power transfer system of claim 8, wherein a sum of the second and third areas is substantially equal to the first area.

10. The wireless power transfer system of claim 7, wherein the at least one auxiliary coil comprises four sets of conductor windings connected in series, each of the four sets of conductor windings being wound over one of a second, third, fourth, and fifth area, respectively.

11. The wireless power transfer system of claim 10 wherein a sum of the second, third, fourth, and fifth areas is substantially equal to the first area.

12. The wireless power transfer system of claim 7, wherein the auxiliary magnetic field induces a current in the source resonator coil, and wherein the current in the source resonator coil generates a magnetic field having a strength greater than the auxiliary magnetic field.

13. The wireless power transfer system of claim 7, wherein the at least one auxiliary coil comprises a first portion of a conductor winding on a first circuit board and a second portion of a conductor winding on a second circuit board, and wherein a connector between the first and second circuit boards provides an electrical connection between the first and second portions of the conductor winding.

14. The wireless power transfer system of claim 1, wherein a phase of the source magnetic field at the first frequency differs by 30% or more from a phase of the auxiliary magnetic field at the second frequency.

15. The wireless power transfer system of claim 7, wherein the source resonator coil comprises a first set of one or more electrically conductive traces, and wherein the auxiliary coil comprises a second set of one or more electrically conductive traces.

16. The wireless power transfer system of claim 15, wherein the second set of traces is evenly distributed over the first set of traces such that the auxiliary magnetic field is of a similar shape to the source magnetic field.

17. The wireless power transfer system of claim 7, wherein at least a portion of windings of the at least one auxiliary coil is evenly distributed over at least a portion of windings of the source resonator coil such that the auxiliary magnetic field is of a similar shape to the source magnetic field.

18. The wireless power transfer system of claim 2, further comprising a switch electrically connected between the at least one amplifier and the at least one auxiliary coil.

19. The wireless power transfer system of claim 1, wherein the at least one detector comprises one or more loops of conducting material.