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Systems, methods, and apparatus for foreign object detection loop based on inductive thermal sensing

  • US 10,564,307 B2
  • Filed: 05/16/2019
  • Issued: 02/18/2020
  • Est. Priority Date: 05/15/2014
  • Status: Active Grant
First Claim
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1. An apparatus for detecting a presence of an object located in a power transfer area of a wireless power transmitter, the apparatus including:

  • a first inductive sense circuit and a second inductive sense circuit, each including a sense coil configured to inductively sense the presence of the object based on an electrical characteristic of the sense coil that varies as a function of a temperature of the object when the object is exposed to an alternating magnetic field generated by the wireless power transmitter in the power transfer area at an operating frequency of the wireless power transmitter,each of the first and second inductive sense circuits comprising a location for measuring the electrical characteristic and configured to reduce a disturbance voltage measured at the location; and

    a controller configured to;

    schedule an exposure cycle for the alternating magnetic field generated by the wireless power transmitter,transmit a signal to the wireless power transmitter to control the exposure cycle for the alternating magnetic field,measure the electrical characteristic of each sense coil over time based on measuring at least one of a voltage and a current signal at the location of each of the first and second inductive sense circuits,suppress effects of the disturbance voltage at fundamental and harmonic frequencies of the wireless power transmitter by filtering to achieve a target detection sensitivity of the apparatus,determine a first correlation result between the measured electrical characteristic and the exposure cycle for the first sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle and determine a second correlation result between the measured electrical characteristic and the exposure cycle for the second sense circuit based on comparing the measured electrical characteristic with the exposure cycle over at least a portion of a duration of the exposure cycle, anddetermine the presence of the object based on a comparison of the first correlation result with the second correlation result.

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