Dynamic Wireless Charging: Reflexive Field Containment Using Saturable Inductors

Abstract

In dynamic wireless charging applications, segmented transmitter coils transfer power to a moving receiver coil. This article proposes a method in which the field strength in coupled transmitter coils automatically adjusts based on the position of the receiver. Specifically, a saturable inductor is applied to provide a high uncompensated inductive reactance in the uncoupled condition. By exploiting the reflected reactance as the system approaches the maximum coupled condition, the inductor saturates and the field strength in the coupled transmitter coils automatically increases. The field strength is at its peak when the transmitting and receiving coils reach their maximum coupling and sharply decreases when the receiver is decoupled from the transmitter. Consequently, the difference between the coupled and uncoupled currents in the transmitter coil is maximized, resulting in a near six-fold improvement in field containment performance compared to previously reported findings. This allows for system-level efficient power transfer and compliance with electromagnetic emission standards without complex shielding circuits and auxiliary active position detection approaches. We present the analysis, design criteria of the compensation network, and experimental validation for the proposed method.