A Dynamic Current Sharing Model of Multichip Parallel SiC MOSFETs Considering Layout-Dominated Mutual Inductance Coupling
Zexiang Zheng, Cai Chen, Jianwei Lv, Yiyang Yan, Jiaxin Liu, Yong Kang
Abstract
Dynamic current imbalance of parallel SiC MOSFETs can lead to uneven losses and even thermal runaway. Unbalanced parasitic parameters dominated by layout are one of the main causes of unbalanced dynamic currents. However, a current sharing model that comprehensively considers all inductances and mutual inductances is still lacking. Aiming at the problem, a quantitative model is proposed to analyze the dynamic current sharing mechanism and performance considering all inductances and mutual inductances. The phenomenon that the high-side dynamic currents are more balanced than the low-side currents is explained from a new perspective in a baseline module. Further, more accurate judgment coefficients (JCs) than existing models are obtained to evaluate the dynamic current sharing performance. When JCs = 0, balanced currents are achieved. The connection points of bonding wires are adjusted to validate the model through simulation and experiments, and this method yields better results due to the consideration of mutual inductance coupling. Finally, to further describe the contribution of the model, a model-based layout optimization by adjusting mutual inductances is discussed and presented.