Non-contact power feeding device

A non-contact power feeding device, comprising a power transmission device and a power receiving device to which power is transmitted from the power transmission device in a non-contact manner, wherein

• the power transmission device comprises:
• a transmission coil, supplying power to the power receiving device;
• a power supply circuit, comprising an inverter that comprises a plurality of switching elements connected in a bridge or half-bridge shape, the power supply circuit supplying AC power to the transmission coil;
• a current detection circuit, detecting current flowing through a first switching element among the plurality of switching elements;
• and
• a control circuit, controlling a voltage of AC power supplied from the power supply circuit to the transmission coil;
• the power receiving device comprises:
• a resonant circuit, comprising a receiving coil and a resonant capacitor connected to the receiving coil, the resonant circuit receiving power from the transmission coil by resonating with current flowing through the transmission coil of the power transmission device;
• a rectifier circuit, rectifying power received via the resonant circuit;
• a voltage detection circuit, measuring an output voltage of power output from the rectifier circuit;
• a resonance suppression coil, arranged to be able to be electromagnetically coupled with the receiving coil;
• a switch circuit, connected to the resonance suppression coil and capable of switching between short-circuiting and opening of the resonance suppression coil;
• and
• a switch control circuit, controlling the switch circuit to short-circuit the resonance suppression coil in response to a measured value of the output voltage becoming equal to or greater than a predetermined upper limit threshold, and controlling the switch circuit to open the resonance suppression coil in response to the measured value of the output voltage becoming equal to or less than a predetermined lower limit threshold that is lower than the predetermined upper limit threshold;
• the control circuit of the power transmission device estimates a duty ratio related to a period during which the resonance suppression coil is short-circuited based on current detected by the current detection circuit, and controls a voltage of AC power supplied from the power supply circuit to the transmission coil so that the estimated duty ratio falls within a predetermined allowable range.