POWER TRANSMISSION DEVICE AND WIRELESS POWER TRANSMISSION SYSTEM

A power transmission device which can increase a frequency change width (frequency dispersion region) while curbing output fluctuations. The power transmission device that wirelessly transmits power to a power receiving device includes an inverter configured to convert a voltage into an alternating current voltage with a drive frequency, a power supply configured to generate the voltage to be supplied to the inverter, a power transmission coil configured to be supplied with the alternating current voltage and generate an alternating current magnetic field, and a voltage changing unit configured to spontaneously change an output voltage of the power supply, wherein the inverter is configured to control the drive frequency in response to a change in the output voltage.