A cost effective magnetic design for a 900 kHz high frequency voltage regulator module: analysis and experimentation

In this paper, a novel structured micro power transformer is developed for high frequency DC-DC converters. In order to avoid the flux fringing problem, based on the industrial data sheets, a multi-material core is introduced with a "Kool Mu" material on a part of the outer legs and "3F35" material on the center leg. Thin air gaps filled with ferrite powder are introduced to get rid of the discrete air gap and avoid the fringing effect. An optimization algorithm is solved to get the most suitable dimensions of the core. The suggested structure offers low leakage inductance, low DC and AC winding resistances, higher magnetizing inductance and a low design cost compared to that of the planar magnetic. Design guidelines and experimental measurements are presented to provide the proof of concept