Multi-Domain Modeling and Design Optimization of Synchronous Rectifiers for SiC-Based High- Load-Current LLC Converter

摘要

The synchronous rectifier (SR) related electromagnetic and thermal models of a high-load- current LLC resonant converter are deduced, which is used for reliability analysis and optimization of print circuit board (PCB) layout. The impact of the parasitic inductance in the SR FETs' package and the strong secondary-side electromagnetic field on the SR controller is considered. Then the LLC time-domain model is adopted to calculate the losses. Finally, the SR FETs' junction temperature is acquired through the thermal model to evaluate the design reliability. Compared with traditional design methods based on numerical simulation models, this analytical model-based design method is cost-effective and efficient while high accuracy preserved. This scheme is used to optimize the SiC-based on-board DC-DC converter in an integrated electric vehicle (EV) power supply to make it stably output 180A while occupying less PCB area. After the optimization, the occupied PCB width of the output structure is reduced to 62mm, which is nearly half of conventional designs.