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Wireless power transmission system and power transmission device

  • US 9,595,834 B2
  • Filed: 05/14/2015
  • Issued: 03/14/2017
  • Est. Priority Date: 05/27/2014
  • Status: Active Grant
First Claim
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1. A power transmission device that transmits first AC power in a noncontact manner to a first resonator of a power receiving device including a power receiving circuit, the first resonator receiving the first AC power, the power receiving circuit converting the first AC power received by the first resonator to first DC power and supplying the first DC power to a load, the power transmission device comprising:

  • a memory that stores a requested voltage value of the first DC power supplied to the load;

    a receiving circuit that receives, from the power receiving device, an actual voltage value of the first DC power supplied to the load;

    an inverter that generates and transmits the first AC power to the first resonator via a second resonator;

    an oscillator that generates second AC power smaller than the first AC power and transmits the second AC power to the first resonator via a third resonator;

    a foreign substance detector that determines whether or not a foreign substance is present between the first resonator and the third resonator based on a physical quantity in the third resonator that changes according to the second AC power; and

    power transmission control circuitry operative to;

    set a foreign substance detection period in which foreign substance is detected by the foreign substance detector, between i) a first power transmission period in which the first AC power is transmitted from the second resonator to the first resonator and ii) a second power transmission period subsequent to the first power transmission period;

    set sequentially to the inverter, in the first power transmission period, frequencies i) from a frequency f1 of a power transmission voltage in an initial state ii) to a frequency f2 of the requested voltage value;

    cause the inverter to transmit the first AC power at each of the set frequencies;

    compare the requested voltage value with the actual voltage value of each of the frequencies, received by the receiving circuit;

    store a value indicating a frequency f0 of the actual voltage value in the memory if the actual voltage value equals to the requested voltage value;

    cause the inverter to transmit the first AC power at the frequency f0 if the actual voltage value equals to the requested voltage value;

    cause the inverter to stop the first AC power temporarily after the elapse of a predetermined period of time;

    cause the foreign substance detector to determine whether or not the foreign substance is present in the foreign substance detection period; and

    cause the inverter to resume a transmission of the first AC power in the second power transmission period by the value indicating the frequency f0 in the memory if it is determined that the foreign substance is not present within a predetermined period that starts from the stopping of the first AC power and that is regulated to cause the inverter to resume a transmission of the first AC power from the frequency f1.

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