Analysis of Influencing Factors of Parallel Current Sharing of High Power Module

The multi-chip power module serves as the core component of high-power Solid State Power Controller (SSPC). However, discrepancies in the intrinsic parameters of parallel-connected chips and the layout structure of the module result in uneven current distribution among parallel chips, significantly compromising the reliability of SSPC. This paper focuses on a developed 270V/200A power module and establishes an equivalent circuit model considering the parasitic parameters of the module's actual structure. Firstly, simulations were conducted to observe the current sharing among parallel power Metal Oxide Semiconductor Field Effect Transistors (MOSFETs) under various operating modes. Secondly, a typical equivalent circuit model of a power module with three parallel branches was established. By altering the parasitic parameters of the MOSFET itself and the module's layout structure, an analysis was carried out to investigate the impact of the imbalance in internal parasitic parameters on the module's parallel current-sharing capability. Simulation results indicate that the steady-state current sharing capability of the power module is significantly influenced by stray resistances and MOSFET's on-state resistances. Transient current sharing capability, on the other hand, is greatly affected by MOSFET's threshold voltage, transconductance, gate drive resistance, and the parasitic inductance of the power circuit's source busbar. Parasitic inductances of the gate drive circuit and drain copper busbar have minimal impact on transient current balance.