Quasi-ZVS active auxiliary commutation circuit for two switches forward converter

This paper presents a family of single-ended power converters that, adequately designed and commanded, can perform ZVS turn-off and turn-on with a value near to zero namely quasi-ZVS (QZVS) at main switches. The auxiliary circuit presents low reactive energy and is composed of one inductor, one diode and one switch, which operate with ZCS. To demonstrate the feasibility of the proposed technique, it is applied to a two switch forward converter. It is not necessary the use of a third winding in the transformer nor auxiliary voltage sources to achieve soft switching. The implementation is possible due to the use of an appropriate command, different than is used conventionally in two switch forward converters. Complete analysis of the operation stages, as well as the design procedures for the correct operation of the converter are presented. Experimental results obtained from a prototype of 250W/48V@100kHz demonstrate the feasibility of this active auxiliary commutation circuit (AACC) applied to two switch forward converters. Furthermore, a new concept of switching is introduced, where the main switches commutate with QZVS