EMI modeling and experiment of a GaN based LLC half-bridge converter

This paper focuses on the electromagnetic interference (EMI) research and analysis of the MHz switching frequency GaN MOSFET based on the LLC resonant DC-DC converter. In this paper, first, the CM coupling paths are studied to get simplified models. Then the impact of the parasitic capacitors (both the capacitors to the ground and the capacitors in the devices) on the CM current are analyzed. Finally the high frequency model is derived from the work above. Moreover this paper makes the comparison between normal Si MOSFET and GaN-based MOSFET behavior in EMI. The modeling result proves that GaN MOSFET has a worse behavior on EMI test. An experiment layout which is aimed at minimizing the irrelevant factors is designed and the experiment result proves the accuracy of the modeling.