RESONANCE TYPE WIRELESS CHARGER

PROBLEM TO BE SOLVED: To enable power transmission to stop when charging has been completed, by appropriately detecting a charging state of a secondary battery on the transmission side without providing communication means on the transmission and reception sides.SOLUTION: A power transmission device 1 comprises: a high frequency power supply part 7; a power transmission primary coil 3 for transmitting AC power; a reflection power detection part 9 for detecting reflection power reflected from the power transmission primary coil; and a power supply controller 10 for controlling generation of the AC power. A power reception device 2 comprises: a power reception secondary coil 5 for receiving the AC power transmitted from the power transmission device; a rectifier 12 for rectifying the received AC power; and a charger 14 for charging a secondary battery by constant voltage after charging it by constant current by using DC power output by the rectifier. The power supply controller detects a time change rate of the reflection power and performs control so as to stop the transmission of the AC power, when the time change rate of the reflection power detected in the process of the constant voltage charging has become equal to or lower than a lower threshold RCL set correspondingly to a predetermined charge rate.