Optimization of bi-directional flyback converter for a high voltage capacitor charging application

This paper presents an optimization technique for a flyback converter with a bidirectional energy transfer. The main goal is to optimize the converter for driving an incremental dielectric electro active polymer actuator, which must be charged and discharged from 0 V to 2500 V DC, supplied from a 24 V battery. The proposed optimization routine sweeps through a database of low voltage switching devices, and transformer core types and sizes. For each core, important winding parameters such as, the vertical winding space allocation for primary and secondary windings, and the spacing between the secondary windings layers are also swept. This enables the optimization routine to calculate and optimize the losses caused by transformer parasitics such as leakage inductance, self-capacitance and AC resistance which is crucial in achieving a high energy efficiency and high power density required for this application. The efficiency and loss distribution results provided by the optimization routine provide a deep insight into the transformer design and its impact on total converter efficiency. Finally, experimental work on a prototype of the bi-directional flyback converter is presented. The maximum charging and discharging energy efficiencies of the optimized design, are 96.1% and 85%, respectively.