extra components and inevitably cause additional power loss.
In this paper, a design methodology is given for highefficiency
wireless power transfer without using impedance
matching networks. By analyzing the circuit model of the
coupling system, the optimum impedance attached to the
receiving coil is derived in order to achieve maximum transfer
efficiency. This impedance represents the equivalent input
impedance after the coupling system, which is the combination
of rectifier, DC/DC converter and load. By designing the
rectifier and DC/DC converter accordingly, the impedance
requirement of the coupling system is fulfilled. A 13.56 MHz
wireless power transfer system is demonstrated in this paper.
When transmitting 50 watts power, it can achieve an efficiency
of 73% for a resistive load and an efficiency of 66% for
charging batteries or supercapacitors.