Magnetic Optimizations for High-Power Density Bidirectional Cascaded-Buck-Boost Converter

This paper presents various innovative techniques to achieve high efficiency for the cascaded-buck-boost converter. A rigorous loss model with component nonlinearities was developed to determine the power loss distribution and validated by simulations and experiments. A low profile planar-nanocrystalline inductor was designed based on the results of power loss distribution and various design aspects of core and winding were discussed. Two different types of windings: copper foil and litz wire, were compared. Finite-Element-Analysis (FEA) method was used to examine and visualize the inductor design. By implementing the planar-nanocrystalline inductor, a peak efficiency of 99.08 % and 98.88% was achieved for the buck mode and the boost mode, respectively. And a converter power density of 91.8 W/in
³
with an inductor profile height of 0.276 inches was reported.