Diamond-Window Resonant Inductor with Significant AC Flux

Resonant inductor with significant ac flux at MHz switching frequency is challenging because of high core loss and winding loss due to skin and proximity effect. Air gap brings in fringing magnetic field resulting in uneven current distribution and therefore higher winding loss. The conventional rectangular-window core is replaced by the diamond-window core to reduce the fringing flux on the winding and therefore results in smaller inductor loss. An inductor prototype was built and was placed into a 200W Series-Resonator Buck (SRB) converter at 48V input voltage and 40A output. Experimental results are discussed to verify the theoretical analysis.