Experiences with Coupling Inductances between Commutation Loop and Gate Circuit in Power Modules

The fast commutation of the load current in power modules during switching events causes distortions of the gate voltages due to inductive coupling. In this paper, the relevant coupling inductances are extracted from 3D field simulations taking into account magnetic coupling between all sections of the involved current loops inside the module. For different module layouts, the impact of the coupling inductances on measured and simulated dynamic module behavior is examined, including switching speed, dynamic current sharing and short circuit. Several approaches to improve dynamic current sharing between parallel transistors inside a module are presented and evaluated.