Inductor optimization for multiphase interleaved synchronous bidirectional Boost converter working in discontinuous conduction mode with zero voltage switching

Multiphase interleaved synchronous boost converter is one of the most interesting topologies for non-isolated bidirectional applications regarding its high efficiency, reliability and few components. Focusing on the increase of efficiency, this converter can work in Discontinuous Conduction Mode (DCM) but close to Boundary Conduction Mode (BCM) to achieve soft switching condition. Nevertheless the main disadvantage of this particular control mode is the complexity of the inductor design. First, the inductors have to conduct a high current ripple due to get a negative current value that warranties soft switching condition. Second, the inductor value is low and a large air gap is needed, so parasitic effects like fringing have to be considered in loss calculation. Taking into account these two conditions, three different inductor winding designs are presented in this paper in order to optimize the overall efficiency in a multiphase interleaved bidirectional boost converter. A theoretical comparison for each inductor design is presented. Moreover, simulation results for equivalent flux and magnetic field using 3D FEM software tool (PExprt) are also done. The theoretical and simulated results for the three proposed winding designs are verified with a two phase bidirectional synchronous boost converter prototype of 1 kW.