Disclosed herein is a power supply apparatus, including: a first switch configured to change over electric connection to an electric power generation section; a voltage sensor configured to acquire a magnitude of an input voltage; a control section configured to control the first switch in response to an input from the voltage sensor; and a voltage conversion circuit configured to convert an input voltage into a desired voltage and output the converted voltage, wherein, when the input voltage is lower than a voltage necessary for starting up of the voltage conversion circuit, switching on and off of the first switch are repeated until the input voltage reaches the voltage necessary for starting up of the voltage conversion circuit.