Influence of Shielding on Conducted EMI in High-Power Wireless Power Transfer Systems

Wireless power transfer (WPT) systems are widely used in automotive and consumer electronics due to the many benefits they can offer. However, according to the inherent presence of power electronics and extended electromagnetic parts, they can be the source of significant electromagnetic interference (EMI). This paper investigates the conducted emissions (CEs) of a 1 kW WPT system, assessing the effect of the conductive shields of the coil assemblies on the CEs through a purely experimental approach. The study also considers the effect of power modulation implemented by a phase-shift control and highlights its impact on the overall CE behavior. The objective is to provide a quantitative insight into the role of the shielding in WPT conducted emissions, considering both the conditions of grounded and ungrounded shields. The measurements are conducted over the DC bus of a GaN-based commercially available evaluation board in order to guarantee the highest level of reproducibility of the results. The CEs are measured with an EMI receiver and the impedance seen from the system under test to the power supply is stabilized with a line impedance stabilization network (LISN).