NON-CONTACT POWER SUPPLY SYSTEM AND POWER TRANSMISSION DEVICE

A wireless power supply system includes a power transmission device (10) having a power transmission coil (14) and a power receiving device (40) having a power receiving coil (41). The power transmission coil (14) transmits electric power to the power receiving coil (41) via a wireless connection, so as to supply the electric power to a battery (44) installed in the power receiving device (40). The power transmission device (10) includes a power factor calculator (31) configured to calculate a power factor (cosθ) based on a phase difference between a voltage and a current supplied to the power transmission coil (14), and a control amount calculator (29) configured to control electric power supplied to the power transmission coil (14) according to a power command value (Pbat*), and regulate the electric power supplied to the power transmission coil (14) when the power factor falls to a predetermined threshold power factor or less. The power transmission can therefore be regulated immediately when the power receiving coil (41) is shifted from the power transmission coil (14).