This paper presents some novel synchronized quasi-resonant circuits for achieving soft-switching DC/DC boost and flyback power converters. These topologies use coupled inductors with capacitor for resonating the circuit to achieve zero voltage switching of the power converters. The circuits have minimum voltage stress across the switches. Moreover, they have reduced commutation losses and increased switching frequency. The paper explains the principle of operation of the circuit and describes the analysis of each mode of operation for both boost as well as flyback power converters. It also gives design criteria, derived from the mathematical analysis carried out, for achieving zero voltage switching under all loading conditions from no load to full load. The feasibility of the proposed circuits has been verified by PSPICE simulation. © 1998 IEEE.