Reduction of reverse recovery losses in auxiliary switch topologies by saturable reactors

Saturable cores were shown to be useful in easing the residual reverse recovery problem in auxiliary-switch ZVS topologies. The objective of this study was to investigate the effect of the saturable reactor on the reverse recovery process. Namely, to gain a better understanding of the intricate interaction between the elements so that a systematic design procedure can be formulated. This was done by PSPICE (MicroSim Inc.) simulation of an equivalent circuit that represents the problem on hand including a qualitative account of all major losses. The simulation results that were verified by experimental results, point out to the merit of connecting a bypass resistor in parallel with the saturable reactor. This helps to reduce the core losses of the reactor easing thereby the problem of temperature rise at high switching frequencies. The simulation methodology developed in the paper could be helpful in studying other reverse recovery problems.