WIRELESS POWER TRANSMITTING DEVICE AND WIRELESS POWER TRANSMISSION SYSTEM

A wireless power transmitting device transmits power by wireless to a wireless power receiving device through magnetic coupling between a feeding coil and a receiving coil and includes: a feeding circuit including a power conversion circuit that converts DC power into AC power of a drive frequency and a feeding coil unit including the feeding coil that receives the AC power supplied from the power conversion circuit to generate an AC magnetic field; and a control circuit Stu that controls the amount of magnetic flux generated from the feeding coil. The control circuit Stu calculates a separation distance between the feeding and receiving coils in their opposing direction from the circuit characteristic value of the wireless power transmitting device in a state where the amount of magnetic flux generated from the feeding coil is controlled so as to be constant.