Coil Optimization for Common-Mode Choke in Over-Molded GaN Power Modules

Due to the sensitivity of wide-bandgap (WBG) power electronic devices to parasitics, research to optimize WBG power module package design for realizing better electrical performance and reliability has become a priority. Also, the highly integrated package is one of the design targets for achieving modules with high power density and multi-functions. Over-molding a common-mode filter (CMF) onto a GaN power module can effectively accomplish these design targets. To maximize the filter performance and fully utilize the limited space and volume of the GaN power module, the common-mode choke (CMC) coil design should be optimized. In this paper, by taking an over-molded CMC coil design in GaN power modules as an example, an optimization methodology is developed for over-molding designs based on design-of-experiments (DoEs) method. Over-molded CMF with the optimized coils is manufactured and measured. The measurement results align with the optimization results thus verifying the developed optimization methodology. A simplified equivalent model of the over-molded CMC with optimized coils is built for further understanding the custom over-molding design. Design suggestions are concluded for over-molding applications.