Optimisation of primary transistors in flyback converters with high input voltage

In spite of various efforts to replace high voltage MOSFETs by devices with lower conduction losses, the formers can still be found in many power supplies. In the following, an analysis of basic device properties with respect to use in flyback converters is given. The result is surprising with respect to the influence of different conduction characteristics and parasitics; it permits to focus on particularly relevant transistor parameters