A Virtually Isolated Transformerless Off Line Power Supply

摘要

This paper describes a new method of isolation between a.c. mains and d.c. voltage output without the use of a transformer. It consists of two buck converters, connected in series, each one using a pair of two MOSFET transistors. Each pair of transistors is conducting at different time intervals, thus under the assumption that the impedance of an OFF state MOSFET is practically infinite, there is transfer of energy from the a.c side to the d.c. side without actual ohmic continuation in the circuit. If the maximum limit of the drain to source voltage is not exceeded, the power supply becomes virtually isolated, making redundant the transformer used in classic power supplies. This configuration is suitable for output powers above 50watts. The proposed circuit is analysed and simulated results are derived.