Patent ID: 9728982
Date: 2017-08-08
CPC Classifications: G01V,H02J

Claim:
1. A power transmission device that transmits first AC power in a noncontact manner to a power receiving device having a first resonator, the first resonator receiving the first AC power, the power transmission device comprising: a second resonator that electromagnetically couples with the first resonator to transmit the first AC power to the first resonator; a third resonator that electromagnetically couples with the first resonator to transmit second AC power to the first resonator; an inverter that generates the first AC power by using either a frequency f an oscillator that generates the second AC power by using either a frequency f a foreign object detector that determines whether or not a foreign object 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 of either the frequency f power transmission control circuitry operative to: set a foreign object detection period in which foreign object is detected by the foreign object 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 to the inverter, one of the frequency f set to the inverter, the other of the frequency f