Investigation of Mutual Inductance on GaN-HEMT Switching in a Half-Bridge Circuit

In this paper, the influence of parasitic inductance including self inductance and mutual inductance on GaN-HEMT switching waveforms are thoroughly analysed in a half-bridge layout. The parasitic inductance of the power and gate driver loops are first extracted using Ansys Q3D, and are further simplified into a lumped inductance. The approach using lumped inductance produces the same switching waveforms as an equivalent circuit exported via Q3D, but makes the simulation 3 times faster. Afterwards, the influence of common source inductance, which is primarily due to mutual inductance between power loop and gate driver loops, on switching waveforms are illustrated and validated by experimental measurement. It is shown that GaN-HEMT turn-ON switching is very sensitive to common source inductance, and the variation of each 100 pH brings a change of 2 A in turn-ON peak current, so it is challenging to achieve good accuracy by simply using Q3D results. Instead, the proposed lumped inductance approach helps people to understand the influence of parasitic inductance on switching waveforms in an easy way.