METHODS AND SYSTEMS FOR DETECTING FOREIGN OBJECTS IN A WIRELESS CHARGING SYSTEM
First Claim
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1. A wireless power charging system for charging a separate device having a power receiver coil, the wireless power charging system comprising:
- a power transmitter coil; and
a foreign object sensor that includes a resonant tank circuit formed by a foreign object detection (FOD) coil coupled to a capacitor, wherein the FOD coil has a smaller lateral area than the power transmitter coil;
wherein;
the power transmitter coil pre-charges the power receiver coil in the separate device;
the foreign object sensor determines a quality factor Q2 of the resonant tank circuit while the power receiver coil is pre-charged;
the foreign object sensor determines whether a foreign object is present, based on a comparison of the quality factor Q2 with a quality factor Q1 of the resonant tank circuit when no foreign object is present; and
the power transmitter coil transmits power by inductive coupling to the power receiver coil in the separate device, if the foreign object sensor determines that no foreign object is present.
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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.
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Citations
20 Claims
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1. A wireless power charging system for charging a separate device having a power receiver coil, the wireless power charging system comprising:
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a power transmitter coil; and a foreign object sensor that includes a resonant tank circuit formed by a foreign object detection (FOD) coil coupled to a capacitor, wherein the FOD coil has a smaller lateral area than the power transmitter coil; wherein; the power transmitter coil pre-charges the power receiver coil in the separate device; the foreign object sensor determines a quality factor Q2 of the resonant tank circuit while the power receiver coil is pre-charged; the foreign object sensor determines whether a foreign object is present, based on a comparison of the quality factor Q2 with a quality factor Q1 of the resonant tank circuit when no foreign object is present; and the power transmitter coil transmits power by inductive coupling to the power receiver coil in the separate device, if the foreign object sensor determines that no foreign object is present. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15)
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16. A wireless power charging system for charging a separate device having a power receiver coil, the wireless power charging system comprising:
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a plurality of power transmitter coils; and a foreign object sensor that includes a plurality of resonant tank circuits each formed by a foreign object detection (FOD) coil coupled to a capacitor, wherein each FOD coil has a lateral area that is smaller than a lateral area of any of the power transmitter coils; wherein; one or more of the power transmitter coils pre-charge the power receiver coil in the separate device; the foreign object sensor determines quality factors Q2 of some of the resonant tank circuits while the power receiver coil is pre-charged; for each of said resonant tank circuits, the foreign object sensor determines whether a foreign object is present, based on a comparison of the quality factor Q2 for that resonant tank circuit with a quality factor Q1 of that resonant tank circuit when no foreign object is present; and at least one power transmitter coil transmits power by inductive coupling to the power receiver coil in the separate device, if the foreign object sensor determines that no foreign object is disposed between that power transmitter coil and the power receiver coil. - View Dependent Claims (17, 18, 19, 20)
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Specification