Power feeding system, power feeding device, and power feeding method

A power feeding device for a power feeding system, for supplying electric power to a power receiving device via electromagnetic induction,

• the power receiving device comprising a resonant circuit, the resonant circuit comprising:
• a receiving coil to be supplied with electric power from a feeding coil comprised in the power feeding device;
• a resonant capacitor configured to resonate with the receiving coil;
• and a first switching element configured to change a connection state of the resonant capacitor to control a resonant state of the resonant circuit,
• the power feeding device comprising:
• a second switching element connected in series to the feeding coil;
• a drive signal generation section configured to generate a drive signal for driving the feeding coil by changing a state of the second switching element between a conductive state and a non-conductive state;
• a variation detection section configured to detect a change in the resonant state of the resonant circuit, which occurs in accordance with the connection state of the resonant capacitor, as a periodic waveform variation in a voltage excited in the feeding coil;
• and
• a drive control section configured to determine whether or not electric power is suppliable to the power receiving device based on the periodic waveform variation detected by the variation detection section, and control whether or not to continuously supply the drive signal to the second switching element based on a result of the determination.

A power feeding method for a power feeding system configured to supply electric power from a power feeding device to a power receiving device via electromagnetic induction,

• the power feeding device comprising:
• a feeding coil;
• and a drive signal generation section configured to generate a drive signal for driving the feeding coil by changing a state of a second switching element connected in series to the feeding coil between a conductive state and a non-conductive state,
• the power receiving device comprising a receiving coil, the power feeding method comprising:
• varying, by the power receiving device, a resonant state of a resonant circuit,
• the resonant circuit comprising the receiving coil to be supplied with electric power from the feeding coil, a resonant capacitor configured to resonate with the receiving coil, and a first switching element configured to change a connection state of the resonant capacitor to control the resonant state of the resonant circuit;
• detecting, by the power feeding device, a change in the resonant state of the resonant circuit, which occurs in accordance with the connection state of the resonant capacitor, as a periodic waveform variation in a voltage excited in the feeding coil;
• and
• determining, by the power feeding device, whether or not electric power is suppliable to the power receiving device based on the periodic waveform variation detected in the detecting, and controlling, by the power feeding device, whether or not to continuously supply the drive signal to the second switching element based on a result of the determination.