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

A power receiving device configured to receive electric power from a power feeding device having a feeding coil through electromagnetic induction,

• the power receiving device comprising:
• a resonant circuit including:
• a receiving coil configured to receive the electric power from the feeding coil;
• a resonant capacitor configured to resonate with the receiving coil;
• and
• a first switching element configured to control a resonant state by changing an electrical connection state of the resonant capacitor;
• a rectifying diode configured to rectify received power received by the receiving coil from the feeding coil into DC power to supply the DC power to a load;
• and
• a resonance control unit configured to control the first switching element to a non-conductive state, based on the received power and power consumption of the load to which the received power is supplied, to set the resonant circuit is to a non-resonant state, during a period including a subsequent conducting period from a beginning during which a current flows to the rectifying diode, and which is estimated in a resonant state of the resonant circuit.

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

• the power receiving device comprising:
• a resonant circuit including:
• a receiving coil configured to receive the electric power from a feeding coil;
• a resonant capacitor configured to resonate with the receiving coil;
• and
• a first switching element configured to perform switching between a resonant state and a non-resonant state by changing an electrical connection state of the resonant capacitor;
• and
• a rectifying diode configured to rectify received power by the receiving coil from the feeding coil, into DC power to supply the DC power to a load,
• the power feeding device comprising the feeding coil, and a second switching element connected in series to the feeding coil,
• the power feeding method comprising:
• generating a drive signal by the power feeding device to supply the second switching element with the drive signal for driving the feeding coil by periodically switching the second switching element between a conductive state and a non-conductive state;
• setting the first switching element to the non-conductive state by the power receiving device to set the resonant circuit to the non-resonant state by controlling the first switching element, based on the received power and power consumption of the load to which the received power is supplied, during a period including a subsequent conducting period from a beginning during which a current flows to the rectifying diode, and which is estimated in the resonant state of the resonant circuit;
• and
• determining, by the power feeding device, whether or not a supply of the electric power is allowed to the power receiving device based on a periodic waveform variation in an excited voltage excited in the feeding coil, the periodic waveform variation being detected based on a change in electrical connection state of the resonant capacitor, and controlling the second switching element through continual supply or no supply of the drive signal based on a result of the determination.