Practical design considerations for coupled inductor based bi-directional converters of high voltage ratio

This work presents a study on the theoretical and practical design of Coupled Inductor based Non-Isolated bi-directional converters of high voltage ratio. Coupled Inductor can be regarded as a tapped Inductor having windings with different individual characteristics and it can be modeled in terms of an ideal transformer. Usually transformer based DC-DC topologies are utilized in conventional bi-directional DC-DC converters because of the natural property of a transformer to provide the benefit of isolation. Moreover soft switching techniques such as Zero-voltage switching (ZVS) and Zero-current switching (ZCS) are achieved to increase efficiency by decreasing the switching losses. Unfortunately the use of more than 4 switches along with several passive components in transformer based topologies increases the costs and makes the topology more complex in terms of working and control. In this work a coupled inductor based bi-directional DC-DC target converter is studied emphasizing the basics of Coupled Inductor including its physics, it modeling in terms of an ideal transformer and its operation in the transformer mode to get a high Voltage ratio. Simulation results of a Coupled Inductor based boost converter are also given for basic understanding of the characteristic waveforms of a Coupled Inductor. Experiment results of an 80 Watt prototype of the target converter are given to verify the successful Coupled Inductor operation in the transformer mode to achieve the required high voltage ratio.