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Wireless charging system with object detection

  • US 10,511,197 B2
  • Filed: 01/31/2018
  • Issued: 12/17/2019
  • Est. Priority Date: 02/02/2017
  • Status: Active Grant
First Claim
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1. A wireless power transmitting device, comprising:

  • a coil;

    wireless power transmitting circuitry coupled to the coil and configured to transmit wireless power signals to a wireless power receiving device with a receiving coil in a wireless power receiving circuit that is configured to resonate at a wireless power receiving circuit resonant frequency;

    control circuitry configured to control transmission of the wireless power signals;

    an oscillator coupled to the coil that is configured to apply a probe signal to the coil at a probe frequency; and

    an analog-to-digital converter configured to measure signals at the probe frequency, wherein the control circuitry is configured to;

    in a standby mode, determine whether an external object is present by directing the oscillator to supply the probe signal to the coil in bursts separated by respective periods of time in which no probe signals are supplied to the coil by the oscillator, wherein the probe frequency of the probe signal is the same during each of the bursts, wherein the probe frequency is equal to 101% to 150% of the wireless power receiving circuit resonant frequency, wherein each burst has a first duration greater than 0.5 milliseconds, and wherein each period of time in which no probe signals are supplied to the coil by the oscillator has a second duration greater than 100 milliseconds.

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