Accurate and computationally efficient modeling of flyback transformer parasitics and their influence on converter losses

Emerging renewable energy applications, such as PV micro inverters, demand for high step-up isolated DC-DC converters with high reliability and low cost, at high efficiency. Thanks to its low part-count the flyback converter is an optimal candidate for such applications. To achieve high efficiency over a wide load range, a decent transformer design must be performed, considering also the effects of the transformer parasitics. Therefore this work analyzes the influence of the transformer parasitic capacitances and leakage inductance in such a way, that it presents a complete tool to consider the transformer parasitics in the flyback-converter design process. A loss-analysis is performed for all three operation modes of the flyback-converter and methods for modeling the parasitic elements are discussed. To model the frequency dependence of the leakage inductance a new method is proposed. The applied models are explained in-depth and verified with measurements on prototype transformers.