Generic Derivation of Dynamic Model for Half-Cycle DCM Series Resonant Converters

The series resonant converter (SRC) operated in the half-cycle discontinuous-conduction-mode (HC-DCM) provides galvanic separation and a tight coupling of its input and output voltages in an open-loop operation, i. e., with minimum control complexity, which renders it suitable for a wide range of applications that require galvanic isolation. This letter first explains the “DC transformer” behavior of the converter and then provides a generic derivation of a passive equivalent circuit that accurately models the converter's terminal behavior. The proposed generic derivation yields the known analytic results for idealized cases, but additionally allows for a parametrization of the equivalent circuit based on simulated or measured waveforms, thereby facilitating high accuracy also in nonideal cases. Furthermore, it is shown that a noninfinite magnetizing inductance results in an additional load-independent difference between the input and the output voltage, and a corresponding extension of the equivalent circuit model is proposed. The considerations are verified by simulations and measurements of a 10 kW/350 V/350 V HC-DCM SRC system.