A study of losses in planar transformers with different layer structure

Planar transformers in DC-to-DC converters are attractive due to compactness at high power applications. Usually, converters work in the sub-MHz range and naturally the questions of losses both in-core and in-winding appears. The present work provides a comparative analysis of winding losses in two types of planar transformer PCB stack structure. The study aims to analyze the influence of winding arrangement on a step-up planar transformer over the leakage inductance based on the magneto motive force. The results show the impact of losses on the full converter in two FR4 structure embodiments: one with the secondary on a single inner layer and the second with the winding in multiple layers. For this approach a planar core transformer was modeled for sub-MHz range (0.4-1.0 MHz) analysis.