Active snubber network design and implementation on the primary side of an isolated Ćuk converter realizing soft-switching for efficiency improvement

This paper describes the process of improving the efficiency of an existing isolated DC/DC converter based on CUK topology with secondary side synchronous rectification, by means of the introduction of an active snubber network on the primary side. The snubber circuit reduces to zero the switching losses during the off-time interval of secondary SR. In particular, the efficiency improvement is due to the elimination of the primary MOSFET Coss output capacitance losses, and mainly of the reverse recovery losses on the secondary SR MOSFET. However, the insertion of the active snubber creates itself additional losses in the circuit, and therefore to measure the really introduced benefit it is necessary to carefully evaluate the overall efficiency of the modified converter. Complete analysis and design methodology of the introduced network are developed, with evaluation of the effects over the selected circuit and application. Experimental results are finally compared with theoretical analysis and design.