High-Frequency Split-Bobbin Transformer Design with Adjustable Leakage Inductance

Abstract

While designing a high-frequency transformer, its parasitic components should be modeled with caution as it influences the performance of the transformer. In many converter topologies, a transformer with specific parasitic components could be needed. For example, in the phase-shifted full-bridge converter, bidirectional dual active bridge converter dc-dc converters, or LLC resonant converters, the leakage inductance of the transformer needs to be precise as it influences the overall performance of the converter. In this paper, a simple yet effective technique has been investigated to design high-frequency transformers with adjustable leakage inductance. The transformer is designed to be used in a 100 kHz series resonant dc-dc converter, where the leakage inductance of the transformer is used as the resonant inductor. The proposed design technique utilizes the variation of the winding structures where a split bobbin separates primary and secondary windings. At first, the finite element analysis (FEA) based simulation is performed to estimate and analyze the leakage inductance with different winding structures, and then the experimental investigations are performed. Both the simulation and experimental results demonstrate that by simply varying the winding arrangements in the hybrid split-bobbin transformer, the leakage inductance can be changed while keeping the magnetizing inductance of the transformer constant.