CONTACTLESS POWER FEED APPARATUS AND POWER TRANSMISSION METHOD

A power reception device includes: an estimation circuit estimating a load resistance of an entire contactless power feed apparatus and a reception-side communicator transmitting an estimated value of the load resistance of the entire contactless power feed apparatus to a power transmission device The power transmission device has a power supply circuit supplying AC power to a transmission coil supplying power to the power reception device The power transmission device further includes a control circuit decreasing an input/output gain of a transmission-side DC-DC converter included in the power supply circuit by a predetermined amount when the estimated value of the load resistance is less than a predetermined allowed lower limit, and maintaining or increasing the input/output gain when the estimated value of the load resistance is equal to or greater than the predetermined allowed lower limit.