Design of the zero-voltage-switching quasi-square-wave resonant switch

Zero-voltage-switching, quasi-square-wave (ZVS-QSW) power converters with controllable rectifiers feature constant-frequency, PWM-like operation with low voltage and relatively low current stresses on active devices. New closed-form analytic results are derived and applied to construct a detailed design procedure for the ZVS-QSW switch. Starting with usual design constraints, resonant elements are selected so that zero-voltage switching is achieved under all operating conditions, with favorable tradeoff between switching and conduction losses. Results are derived in a form applicable to a wide variety of ZVS-QSW power converter topologies. The design procedure is illustrated on a flyback power converter example and is supported by simulation results.