A Novel Optimized Snubber with Time-Varying Capacitor for Synchronous Rectification, Analysis and Implementation

This paper begins by illustrating the issue of switch stresses on synchronous rectifiers (SRs) which happens during the hot plug-in and plug-out operation turn on and off moment of the synchronous rectification in isolated non-regulated Dc-Dc converters, such as the single stage unregulated bus converter. Next, full analysis of the working principle of this unfavorable phenomenon is presented theoretically and experimentally. For conquering this difficulty, a novel snubber with time varying capacitor is proposed and experimentally demonstrated with detailed designing considerations and experimental results. Besides, to dig deeply into the idea exhibited from this novel method, this paper also extends the application of the novel snubber and propose many other time-varying snubber cells based on the idea with even more flexible applications. Finally, experiment results are presented to verify this idea by the improvements shown on the prototype of a 1/4 brick bus converter, which generates 12V-300W output from 48V bus input voltage.