Solid State Circuit Breaker design with discrete SiC MOSFET' s for Aircraft Electrification Application

Paralleling discrete FETs and achieving acceptable current sharing is a challenge since it is difficult to achieve perfect symmetry related to circuit layout and due to the component variations caused by manufacturing limitations. Hence, high-voltage, high-current switching power converter/motor drives utilize power semiconductor modules more often than paralleling multiple discrete components to achieve different design requirements. However, for certain applications, such as solid-state circuit breakers, discrete paralleling option may be feasible as there is no continuous ON/OFF switching operation of the power switches. The study in this paper proposes a symmetrical design for paralleling six discreate FET's for a solid-state circuit breaker application. Initially, a symmetrical layout is proposed to achieve near identical impedances between all of the FETs and a simulation study is performed in LTspice to verify the current sharing performance. Secondly, a simulation model is developed to highlight the importance of DC resistance of the bus bar for current sharing between FETs. Thirdly, an experimental prototype is developed using SiC FETs, and the transient current sharing performance is analyzed for different DC resistance conditions. Finally, conclusion remarks are made to highlight major design constrains in paralleling of discreate FETs and ways to overcome such challenges.