Symmetric Circuit Layout With Decoupled Modular Switching Cells for Multiparalleled SiC mosfets

Abstract

Parallel connection of silicon carbide (SiC) metal-oxide-semiconductor transistors (MOSFETs) are widely used in large-current-capacity applications or power modules. However, current imbalance caused by the tolerance of device parameters or asymmetric circuit layout is still a challenge for the reliability of the paralleled devices. The asymmetry of power circuit layout is inevitable when more than two devices are paralleled, which will lead to serious dynamic current imbalance. In this paper, an equivalently symmetric power circuit layout based on decoupled paralleled modular switching cells (MSCs) is presented. The current sharing mechanisms of typical asymmetric power circuit layouts are firstly illustrated. The layout with distributed DC decoupling capacitors turns out to have the potential to modify the current paths but requires further optimization. Based on the mechanisms, the construction of the symmetric layout with the concept of MSC is elaborated by mathematical analysis. DC decoupling capacitors are used to decouple the paralleled symmetric MSCs. Thereafter, the key considerations for the decoupling capacitors are discussed. Experiments are finally carried out to validate the analysis. The test results show that the peak current imbalance is reduced to only 4.1% by the equivalently symmetric power circuit layout, which confirms the effect of decoupled MSCs method.