DC–DC converter with a high step-down ratio for water desalination applications

A single-stage 600 : 1 ratio voltage step-down dc–dc converter designed to produce a voltage of between 1 and 1.5 V from a rectified single/three-phase AC supply, for application in a desalination process, is presented. A coupled-inductor design is used, and a novel snubber circuit with energy recovery manages the effects of imperfect coupling (leakage) between the coupled windings. The circuit, which is bidirectional, allows for the power devices to be rated for either high current or high voltage. This presents significant cost and performance advantages compared to a conventional single-stage buck converter where such a large step-down ratio would require a small duty ratio and components with high ratings for both voltage and current: in this case, ratings of 1200 V to withstand input dc voltage switching, and 1000 A to deliver the output current, would be required.