• US 20090322158A1
  • Filed: 09/09/2009
  • Published: 12/31/2009
  • Est. Priority Date: 05/11/2004
  • Status: Active Grant
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First Claim
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1. A method of controlling inductive power transfer in an inductive power transfer system, the system comprising a primary unit operable to generate an electromagnetic field and at least one secondary device, separate from the primary unit, and adapted to couple with said field when the secondary device is in proximity to the primary unit so that power is received inductively by the secondary device from the primary unit without direct electrical conductive contacts therebetween, the method comprising:

  • receiving, in the primary unit, information relating to a power required by the secondary device or devices therefrom;

    determining, in the primary unit, in dependence upon the received information the power required by the secondary device or, if there is more than one secondary device, a combined power required by the secondary devices;

    measuring a power, and determining that there is a foreign object present in said proximity to the primary unit by detecting a substantial difference between, on the one hand, the measured power and, on the other hand, the required power; and

    following such determination of the presence of the foreign object, restricting or stopping the inductive power supply from the primary unit.

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