Common-Mode EMI Filter Integration for WBG Power Module Package

Wide-bandgap (WBG) devices are widely adopted in power electronics systems for their superior characteristics, reducing system size while improving efficiency. However, their implementation introduces electrical, thermal, and mechanical concerns, necessitating advanced WBG power module packaging techniques.

Despite progress, two critical challenges remain in WBG power module packages: (1) lack of integration, and (2) severe electromagnetic interference (EMI) issues. Rapid voltage and current transients from WBG device switching worsen EMI, however, existing power module packaging struggles to deliver highly integrated solutions with effective EMI mitigation. Conventional EMI mitigation methods, such as bulky EMI filters, increase system size and reduce power density. Therefore, innovative packaging solutions that address EMI while maintaining compactness are essential.

Hence, this dissertation addresses these challenges by integrating a π-type common-mode filter (CMF) into a GaN-based half-bridge power module, combining the traditional EMI mitigation method with advanced WBG power module packaging. Common-mode equivalent circuit analysis and parasitics management validate improved EMI noise attenuation achieved by CMF integration, verified by simulations and EMI measurements for both hard-switching operations and converter applications of the power module.

One major drawback of CMF integration is the reduced package power density due to integrating magnetic core. To overcome this, a novel, air-cured, flexible magnetic composite, and corresponding package-compatible manufacturing methodology are developed for over-molding the common-mode choke (CMC) within the module, enabling a low-profile CMF, and improving space utilization and power density. Issues such as low inductance of the over-molded CMC, caused by complicated CMC coil structure and air voids in the over-molded magnetic composite, are addressed through a coil optimization method based on design-of-experiments (DoE) and an improved manufacturing process incorporating coating and degassing. Effectiveness of the over-molded CMF in EMI noise reduction and power density improvement is confirmed through impedance and EMI measurements.

Furthermore, the influence of over-molded CMF on parasitics and thermal performance of the package is analyzed, with design recommendations provided.

Finally, this dissertation concludes its main contributions and proposes future work, including reliability evaluation and system-level application of the CMF-integrated GaN power module, and broader uses of the developed flexible magnetic composite, manufacturing and coil optimization methodologies.