When the power of the wireless power transmitter 100 is transferred in an inductive coupling method, if the strength of a current flowing through a primary coil within the power transmission unit 110 is changed, then a magnetic field passing through the primary coil will be changed by the current. The changed magnetic field generates an induced electromotive force at a secondary coil in the wireless power receiver 200.
According to the foregoing method, the power conversion unit 111 of the wireless power transmitter 100 may include a transmitting (Tx) coil 1111a being operated as a primary coil in magnetic induction. Furthermore, the power receiving unit 291 of the wireless power receiver 200 may include a receiving (Rx) coil 2911a being operated as a secondary coil in magnetic induction.
First, the wireless power transmitter 100 and wireless power receiver 200 are disposed in such a manner that the transmitting coil 1111a at the side of the wireless power transmitter 100 and the receiving coil at the side of the wireless power receiver 200 are located adjacent to each other. Then, if the power transmission control unit 112 controls a current of the transmitting coil (Tx coil) 1111a to be changed, then the power receiving unit 291 controls power to be supplied to the wireless power receiver 200 using an electromotive force induced to the receiving coil (Rx coil) 2911a.
The efficiency of wireless power transfer by the inductive coupling method may be little affected by a frequency characteristic, but affected by an alignment and distance between the wireless power transmitter 100 and the wireless power receiver 200 including each coil.