POWER SUPPLY DEVICE, POWER RECEIVING DEVICE, AND CHARGING SYSTEM

Power supply device is provided with the following: a power supply unit (121) that includes a spiral coil or a solenoid coil; a frequency characteristic acquisition unit (211) that acquires the frequency characteristics of the efficiency of the supply of power from the power supply unit to the power receiving device; a peak determing unit (212) that determines peaks in the frequency characteristics of the efficiency of power supply; and a drive frequency determination unit (213) that, if two peaks have been found, determines as the drive frequency used for supplying power a frequency near the frequency that is the lower of the frequencies of the two peaks, with the lower frequency being given priority over a frequency near the higher frequency.