Evaluation and Suppression of High-Frequency Radiated EMI in Inductive Power Transfer System

Inductive power transfer (IPT) employs an antenna-like inductive coupler for wireless charging, which inevitably leads to electromagnetic interference (EMI) affecting nearby objects. This article is dedicated to examining the radiated EMI, exploring its mechanisms, and proposing approaches for suppression. The frequency-dependent behaviors of capacitors and inductors are thoroughly examined to guide the comprehensive study of the coupler's characteristics. Several factors that impact EMI would couple with each other. To address this challenge, various scenarios are defined to isolate and investigate these potential factors independently, ultimately identifying the most influential ones. Subsequently, the Class DE inverter is optimized to achieve the EMI suppression in a wide frequency range. The experimental setup utilizes a 1-MHz IPT system to replicate the simulation analysis, incorporating a measurement platform for assessing high-frequency voltage, current, and magnetic field. The optimized Class DE inverter exhibits a maximum attenuation of approximately 20 dB for both coil current and field strength in the frequency band exceeding 30 MHz.