Passive regenerative snubber cell applied to isolated DCM SEPIC converter

Isolated converter such as SEPIC has a high voltage stress in the main switch due to transformer leakage inductance. To solve this issue an active or passive clamp action is necessary. The common passive solution based on a RCD snubber is simple but impractical when the value of the leakage inductance is significant. In other hands, passive regenerative solutions generally compromise the isolation, making the search for a suitable snubber a challenge. In this paper, an effective passive regenerative snubber cell for isolated DCM SEPIC converters is presented. It is intended to improve the converter efficiency by transferring the energy stored in the transformer leakage inductance to the output. Analysis is presented in detail together with a practical design procedure. To validate the proposal, simulated and experimental results are performed for a 100 W, 100 V input and 50 V output voltage converter.