CONTACTLESS POWER TRANSMISSION APPARATUS

A contactless power transmission apparatus includes a receiver that includes a resonant circuit that receives electric power from a transmitter. The receiver causes, in response to a measurement value of an output voltage of electric power output from the resonant circuit being out of a predetermined allowable range of voltages, a short circuit to short-circuit the resonant circuit and transmits determination information indicating that the contactless power transmission apparatus is not outputting a constant voltage. In response to the determination information, the transmitter in the contactless power transmission apparatus detects a switching frequency of alternating current power to be supplied to a transmitter coil from a power supply circuit at which the contactless power transmission apparatus outputs a constant voltage in accordance with a measurement value of a current through the transmitter coil.