NONCONTACT POWER SUPPLY APPARATUS

A power reception device of a noncontact power supply apparatus has a resonance circuit that resonates at a first frequency, a voltage detection circuit that measures an output voltage from the resonance circuit and calculates a measured value of the output voltage, and a transmitter that transmits a signal including information about the measured value of the output voltage to a power transmission device . The power transmission device of the noncontact power supply apparatus has a transmission coil for supplying power to the power reception device, a power supply circuit that supplies AC power having an adjustable switching frequency to the transmission coil a receiver that receives the signal including the information about the measured value of the output voltage, and a control circuit that controls, in accordance with the measured value of the output voltage, the switching frequency so that the transmission coil and the power supply circuit can continue a soft switching operation.