EMI Mitigation of GaN Power Inverter Leg by Local Shielding Techniques

Abstract

This paper presents local shielding techniques applied to a half-bridge inverter leg with the aim to reduce the common mode (CM) current noise at converter's DC input. The research study is conducted for 650V Enhancement mode Gallium Nitride (GaN) power transistor switches. Main contributors of parasitic capacitances referred to the inverter-leg middle point node are identified. Then, shielding solutions are proposed to reduce CM current emission by these capacitances. Respecting the precautions concerning the isolation of CM currents of the half-bridge inverter leg, the electromagnetic compatibility measurement setup is developed. Experimental step-by-step addition of local shielding copper layers to different contributors of middle point capacitance shows progressive attenuation of CM noise spectra.