Methods And Systems For Detecting Foreign Objects In A Wireless Charging System

• US 20140084857A1
• Filed: 09/27/2012
• Published: 03/27/2014
• Est. Priority Date: 09/27/2012
• Status: Active Grant

• Current Assignee: ConvenientPower HK Limited
• Original Assignee: ConvenientPower HK Limited
• Inventors: Liu, Xun, Swaans, Laurens Henricus, Chan, Ka Wai Paul, Low, Ho Kan, Chan, Wing Kwong
• Granted Patent: US 9,178,361 B2
• Time in Patent Office: Days
• US Class Current: 320/108
• 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

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; and

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 the lateral dimension of the FOD coil and that is smaller than the transmitter coil dimension.

2. The system of claim 1, wherein the at least one FOD coil comprises two or more FOD coils.

3. The system of claim 2, 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.

4. The system of claim 2, wherein the two or more FOD coils comprise an array of FOD coils.

5. The system of claim 2, wherein the two or more FOD coils comprise two layers of FOD coils.

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

7. The system of claim 2, wherein the FOD coils are disposed within a perimeter of the power transmitter coil.

8. The system of claim 2, wherein the at least one power transmitter coil comprises two or more power transmitter coils.

9. The system of claim 2, 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.

10. The system of claim 1, wherein the lateral dimension of the FOD coil is not more than 25 mm.

11. The system of claim 1, wherein the lateral dimension of the FOD coil is approximately 20 mm.

12. The system of claim 1, wherein the power transmitter coil and the FOD coil are rectangular and the lateral dimension of the coil is a length of a side of the coil.

13. The system of claim 1, wherein the power transmitter coil and the FOD coil are circular and the lateral dimension of the coil is a diameter of the coil.

14. The system of claim 1, wherein the lateral dimension of a coil is a maximum width of the coil.

15. The system of claim 1, wherein the lateral dimension of a coil is an area of the coil.

16. The system of claim 1, wherein the transmitter coil dimension is at least two times the FOD coil dimension.

17. The system of claim 1, further comprising:

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

18. The system of claim 17 wherein the detection circuitry detects a foreign object based on a decay of the response of the resonant circuit.

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

20. The system of claim 17 wherein the resonant circuit is one of an L-C resonant circuit and an L-R-C resonant circuit.

21. The system of claim 17 wherein the detection circuitry detects a foreign object only when the power transmitter coil is not transmitting power.

22. The system of claim 1, 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, the system further comprising:

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

23. The system of claim 22, 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.

24. The system of claim 1, 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, the system further comprising:

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

25. A method for wireless power charging of a separate device having a power receiver coil, the method comprising:

energizing a transmitter coil for transmitting power by inductive coupling to the receiver coil of the separate device;

transmitting power from the transmitter coil to the receiver coil, the transmitted power pre-charging the receiver coil prior to using a foreign object detection (FOD) coil to detect a foreign object;

suspending the transmission of power from the transmitter coil to the receiver coil; and

energizing the FOD coil to identify foreign objects using power dissipation, the power dissipation in the receiver coil reduced by the pre-charging.

26. The method of claim 25, wherein transmitting power comprises pre-charging at least one capacitor of the receiver coil, the receiver coil including a resonant circuit.

27. The method of claim 25, wherein the FOD coil is characterized by an FOD coil dimension that is the lateral dimension of the FOD coil, the lateral dimension of the FOD coil is smaller than a transmitter coil dimension.

28. The method of claim 26, further comprising de-energizing the FOD coil and resuming the transmission of power from the transmitter coil.