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    Quality and System Reliability Including EMI/EMC

    T29.3 - Comparative Study of Nanocrystalline and Ferrite Chokes in Hybrid EMI Filters for High Power-Density Flyback SMPS

    Thursday, March 26, 2026
    9:00 AM - 9:20 AM CT
    Location: 217A
    Modern switching-mode power supplies (SMPS) using GaN power switches operate at extremely high frequencies, resulting in increased high-frequency electromagnetic interference (EMI) emissions. A compact hybrid EMI filter (HEFs) can be effectively applied by combining Active EMI filters (AEFs) and passive filters, offering a promising solution to minimize the size of common-mode (CM) chokes and mitigate high-frequency noise. However, the low self-resonant frequencies (SRF) of commonly adopted ferrite chokes can limit the advantages of HEFs at higher frequency noise mitigation. To understand the SRF effects, this digest compares the HEFs with a custom-designed nanocrystalline choke and commercial ferrite choke in application to a GaN-based active clamp flyback (ACF) converter. Theoretical and experimental results demonstrate that, due to significantly lower parasitic capacitances, the nanocrystalline choke offers substantial advantages in high-frequency EMI reduction compared to the commercial ferrite choke.