Methods and Systems for Detecting Foreign Objects in a Wireless Charging System

• US 20180331584A1
• Filed: 07/02/2018
• Published: 11/15/2018
• 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 10,305,332 B2
• Time in Patent Office: Days
• 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 method for wireless power charging by inductive coupling between a power transmitter coil in a transmitter device and a power receiver coil in a separate receiver device, the method comprising:

pre-charging a receiver circuit that includes the power receiver coil;

executing a foreign object detection (FOD) process that detects foreign object presence based on a behavior of a detection circuit containing a FOD coil, wherein foreign object presence affects the behavior of the detection circuit via interaction of the foreign object with the FOD coil; and

wherein the behavior of the detection circuit is also affected by the receiver circuit via interaction of the power receiver coil with the FOD coil and pre-charging the receiver circuit reduces the effect of the receiver circuit on said behavior; and

upon a lack of detection of foreign object presence, wirelessly power charging the receiver device by inductive coupling between the power transmitter coil and the power receiver coil.

2. The method of claim 1 wherein the detection circuit is a resonant circuit containing the FOD coil, and foreign object presence is detected based on a behavior of the resonant circuit.

3. The method of claim 2 wherein executing the FOD process comprises:

charging the resonant circuit; and

detecting foreign object presence based on a behavior of the resonant circuit after the resonant circuit has been charged.

4. The method of claim 2 wherein the FOD process is based on a decay in a response of the resonant circuit.

5. The method of claim 4 wherein the decay in the response of the resonant circuit is affected by the receiver circuit, and pre-charging the receiver circuit reduces the effect of the receiver circuit on said behavior.

6. The method of claim 1 wherein pre-charging the receiver circuit reduces energy absorbed by the power receiver coil during execution of the FOD process.

7. The method of claim 1 wherein pre-charging the receiver circuit reduces a rate at which the FOD process detects foreign object presence when no foreign object is present.

8. The method of claim 1 further comprising:

upon detection of foreign object presence, not wirelessly power charging the receiver device by inductive coupling between the power transmitter coil and the power receiver coil.

9. The method of claim 1 further comprising:

upon detection of foreign object presence, producing a warning.

10. The method of claim 1 wherein wirelessly power charging the receiver device by inductive coupling between the power transmitter coil and the power receiver coil does not occur simultaneously with the behavior of the detection circuit used to detect foreign object presence.

11. The method of claim 10 wherein pre-charging the receiver circuit is suspended during the behavior of the detection circuit used to detect foreign object presence.

12. The method of claim 1 further comprising:

executing the foreign object detection (FOD) process more than once during wireless power charging of the receiver device.

13. The method of claim 1 wherein wirelessly power charging the receiver device is suspended during the behavior of the detection circuit used to detect foreign object presence.

14. The method of claim 1 wherein pre-charging the receiver circuit comprises:

energizing the power transmitter coil to wirelessly transfer power to the power receiver coil by inductive coupling, the receiver circuit pre-charged by the wirelessly transferred power.

15. The method of claim 1 wherein the power transmitter coil is also the FOD coil.

16. The method of claim 1 wherein the power transmitter coil and the FOD coil are two different coils.

17. The method of claim 16 wherein the power transmitter coil and the FOD coil are both in the transmitter device.

18. The method of claim 16 wherein the FOD coil has a smaller lateral area than the power transmitter coil.

19. The method of claim 1 wherein the receiver circuit includes a capacitor and pre-charging the receiver circuit comprises pre-charging the capacitor.

20. A method for wireless power charging by inductive coupling between a power transmitter coil in a transmitter device and a power receiver coil in a separate receiver device, the method comprising:

pre-charging a receiver circuit that includes the power receiver coil;

executing a foreign object detection (FOD) process that detects foreign object presence based on a behavior of a resonant circuit containing a FOD coil, the FOD process comprising;

charging the resonant circuit; and

detecting foreign object presence based on a decay in a response of the resonant circuit after the resonant circuit has been charged, wherein foreign object presence affects said decay via interaction of the foreign object with the FOD coil; and

wherein said decay is also affected by the receiver circuit via interaction of the power receiver coil with the FOD coil and pre-charging the receiver circuit reduces reduces the effect of the receiver circuit on said decay; and

upon a lack of detection of foreign object presence, wirelessly power charging the receiver device by inductive coupling between the power transmitter coil and the power receiver coil.