CONTACTLESS POWER SUPPLY SYSTEM, POWER SUPPLY DEVICE, AND METHOD FOR CONTROLLING CONTACTLESS POWER SUPPLY SYSTEM

The transmission device 10 acquires from the positioning device 14 a direction α in which the power receiving device 20 exists, makes an oriented direction of the transmission element 12 face the direction of the power receiving device 20 and starts transmission, acquires a distance between the transmission device itself and the power receiving device 20 based on the position of the power receiving device 20 acquired from the positioning device 14, obtains a permissible range of transmission efficiency, which corresponds to the acquired distance, receives a power value that is currently being supplied from the transmission device 10, which is sent from the power receiving device 20, obtains a current transmission efficiency based on the received power value and a power value of the current transmission power, and in the case that the current transmission efficiency deviates from the permissible range, acquires again from the positioning device 14 a direction α in which the power receiving device 20 exists, and based on the acquired direction α, controls the oriented direction of the transmission element 12 so that the oriented direction of the transmission element 12 faces the direction of the power receiving device 20.