MHz WPT with Load-Insensitive Power and Efficiency Through Improved Impedance Compression Matching Network

Class E inverter as a most critical module for MHz wireless power transfer (WPT) suffers from load-sensitive power and efficiency fluctuation. To solve above mentioned problem, an improved impedance compression matching network (I²CMN) is proposed, whose impedance region to facilitate simultaneous high efficiency and constant power is first defined in the Smith Chart. For validation, a 6.78 MHz Class E² WPT system is designed and fabricated with voltage feedback and control, which maintains P_dc=40 W, η_total=85% when relative positions for TX/RX coils undergoes changes in the distance (2.5 cm), angle (15°), and lateral (5.3 cm) misalignments.