Link efficiency-led design of mid-range inductive power transfer systems

For mid-range inductive power transfer (IPT) systems, improving link efficiency entails operating in the multi-MHz region in order to increase coil Q factors. However, designing end-to-end systems at such frequencies poses challenges associated with the efficiency of the power electronics. This paper presents a set of design principles with the aim of achieving maximal DC-to-load efficiency of such systems. These include the selection of semiconductor devices and power converter topologies that are suitable for high frequencies. Through these design methods, a 6.78 MHz ISM-band IPT system has been implemented, transferring 120 W of power across 30 cm with a DC-to-load efficiency of ~70 %.