Analysis and Optimization of Sneak Circuit in QR Flyback Converter Considering Parasitic Parameters

Despite their structural simplicity, quasi‐resonant (QR) flyback converters suffer from performance degradation due to intricate parasitic elements. Conventional ideal‐mode analysis fails to capture these underlying mechanisms. To address this, this paper employs a mesh combination method to systematically identify sneak circuit modes excited by critical parasitic parameters (, , , and ). State equations and analytical voltage expressions are established for key MOSFET switching transitions (Mode2 and Mode5). Rather than merely extracting or eliminating parasitic values, the core objective of this work is to elucidate their dynamic impacts and leverage them for converter optimization. MATLAB‐based parameter scanning and experimental validations reveal that an increased secondary diode capacitance effectively suppresses turn‐off voltage spikes but simultaneously prolongs the turn‐on resonant valley time alongside the MOSFET capacitance , whereas the equivalent resistance shows negligible impact. Based on these dynamic characteristics, explicit parameter trade‐off guidelines for are proposed to optimally balance converter efficiency and device reliability.