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Wireless power transmission system and power transmission device

  • US 9,991,748 B2
  • Filed: 11/09/2015
  • Issued: 06/05/2018
  • Est. Priority Date: 07/31/2013
  • Status: Active Grant
First Claim
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1. A power transmission device comprising:

  • an oscillator including four switching devices, which are a first switching device and a third switching device connected to a high-potential side of DC power supplied from a DC source and a second switching device and a fourth switching device connected to a low-potential side of the DC power, a first output end of the oscillator connected to a side of the first switching device opposite to the high-potential side being connected to a side of the second switching device opposite to the low-potential side, a second output end of the oscillator connected to a side of the third switching device opposite to the high-potential side being connected to a side of the fourth switching device opposite to the low-potential side, the oscillator converting the DC power into AC power by pulses supplied to each of the first through fourth switching devices via the first and second output terminals, and outputting the AC power;

    a power transmission antenna that transmits the AC power output from the oscillator to output to a load of a power receiving device;

    a memory that holds a predetermined required voltage of the power receiving device;

    a receiving circuit that receives a voltage supplied to the load of the power receiving device; and

    control circuitry that causes the oscillator to change a voltage of the AC power by changing a phase shift value between a pulse supplied to the first switching device and a pulse supplied to the second switching device,wherein the control circuitry performs operations comprising;

    causing the power transmission antenna to transmit the AC power of the oscillator set to an initial transmission frequency and an initial phase shift value;

    causing the receiving circuit to receive a first voltage of the AC power received by the power receiving device;

    changing the initial phase shift value to a first phase shift value such that a difference between the predetermined required voltage and the first voltage converges within a predetermined range;

    determining a first transmission efficiency of the AC power at the initial transmission frequency and the first phase shift value;

    causing the power transmission antenna to transmit the AC power of the oscillator set to the initial transmission frequency and the first phase shift value;

    causing the receiving circuit to receive a second voltage of the AC power received by the power receiving device;

    changing the first phase shift value to a second phase shift value such that a difference between the predetermined required voltage and the second voltage converges within the predetermined range;

    determining a second transmission efficiency of the AC power at a first transmission frequency and at the second phase shift value;

    changing the first transmission frequency and the second phase shift value until the second transmission efficiency becomes lower than the first transmission efficiency;

    determining that the second transmission efficiency is the maximum when the second transmission efficiency becomes lower than the first transmission efficiency; and

    causing the power transmission antenna to transmit the AC power of the oscillator set to the first transmission frequency and the second phase shift value.

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