Methods and systems for detecting foreign objects in a wireless charging system

• US 9,178,361 B2
• Filed: 09/27/2012
• Issued: 11/03/2015
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: ConvenientPower HK Limited
• Original Assignee: ConvenientPower Limited
• Inventors: Liu, Xun, Swaans, Laurens Henricus, Chan, Ka Wai Paul, Low, Ho Kan, Chan, Wing Kwong
• Primary Examiner(s): Levin, Naum B
• Application Number:
  US13/628,348
• Publication Number:
  US 20140084857A1
• Time in Patent Office: 1,132 Days
• US Class Current: 1/1
• CPC Class Codes: H02J 50/005 Mechanical details of housing or structure aiming to accommodate the power transfer means, e.g. mechanical integration of coils, antennas or transducers into emitting or receiving devices
• CPC Class Codes: H02J 50/12 of the resonant type
• CPC Class Codes: H02J 50/402 the two or more transmitting or the two or more receiving devices being integrated in the same unit, e.g. power mats with several coils or antennas with several sub-antennas
• CPC Class Codes: H02J 50/60 responsive to the presence of foreign objects, e.g. detection of living beings
• CPC Class Codes: H02J 7/00309 Overheat or overtemperature protection

Abstract

Methods and systems are described for using detection coils to detect metallic or conductive foreign objects that can interfere with the wireless transfer of power from a power transmitter to a power receiver. In particular, the detection coils are targeted to foreign objects that are smaller than a power transmitter coil in the power transmitter.

Claims

1. A wireless power charging system for charging a separate device having a power receiver coil, the wireless power charging system comprising:

at least one power transmitter coil configured for transmitting power by inductive coupling to the power receiver coil in the separate device, the power transmitter coil characterized by a transmitter coil dimension that is a lateral dimension of the power transmitter coil;

at least one foreign object detection (FOD) coil located proximate to the power transmitter coil and oriented to detect foreign objects that disturb the power transmission, the FOD coil characterized by a FOD coil dimension that is a lateral dimension of the FOD coil and that is smaller than the lateral dimension of the power transmitter coil, wherein the at least one FOD coil comprises two or more FOD coils, the at least one power transmitter coil comprises two or more power transmitter coils; and

a controller configured to select power transmitter coils for activation based on which FOD coils have detected foreign objects.

2. The system of claim 1, further comprising a location unit in communication with the FOD coils, the location unit using a set of detection responses from the FOD coils to identify a location of a foreign object with an accuracy that is better than the transmitter coil dimension.

3. The system of claim 1, wherein the two or more FOD coils comprise an array of FOD coils.

4. The system of claim 1, wherein the two or more FOD coils comprise two layers of FOD coils.

5. The system of claim 4, wherein the layers of FOD coils are laterally overlapping but offset from each other.

6. The system of claim 1, wherein the FOD coils are disposed within a perimeter of the power transmitter coil.

7. The system of claim 1, wherein the at least one power transmitter coil is configured for transmitting power through a lateral interface area and the FOD coils are configured for detecting foreign objects located anywhere in the lateral interface area.

8. The system of claim 1, wherein the lateral dimension of the at least one FOD coil is not more than 25 mm.

9. The system of claim 1, wherein the lateral dimension of the at least one FOD coil is approximately 20 mm.

10. The system of claim 1, wherein the at least one power transmitter coil and the at least one FOD coil are rectangular and the lateral dimension of the at least on power transmitter coil and the at least one FOD coil is a length of a side of the respective coil.

11. The system of claim 1, wherein the at least one power transmitter coil and the at least one FOD coil are circular and the lateral dimension of the at least one power transmitter coil and the at least one FOD coil is a diameter of the respective coil.

12. The system of claim 1, wherein the lateral dimension of the at least on power transmitter coil and the at least one FOD coil is a maximum width of the respective coil.

13. The system of claim 1, wherein the lateral dimension of the at least on power transmitter coil and the at least one FOD coil is an area of the respective coil.

14. The system of claim 1, wherein the lateral dimension of the at least one power transmitter coil is at least two times the lateral dimension of the at least one FOD coil dimension.

15. The system of claim 1, further comprising:

detection circuitry connected to the at least one FOD coil, the detection circuitry configured for detecting a foreign object based on a response of a resonant circuit that includes the at least one FOD coil.

16. The system of claim 15, wherein the detection circuitry detects a foreign object based on a decay of the response of the resonant circuit.

17. The system of claim 15, wherein the detection circuitry detects a foreign object based on a change in the Q-factor of the resonant circuit.

18. The system of claim 15, wherein the resonant circuit is one of an L-C resonant circuit and an L-R-C resonant circuit.

19. The system of claim 15, wherein the detection circuitry detects a foreign object only when the power transmitter coil is not transmitting power.

20. The system of claim 1, wherein the controller is configured to select power transmitter coils for activation based on avoiding wireless power transmission in areas where FOD coils have detected foreign objects.

21. The system of claim 1, wherein the

controller configured to select which FOD coils to activate based on which power transmitter coils are transmitting power.