Experimental Characterization of High-frequency Transformers for Isolated DC-DC Converters

Parameterization & characterization of highfrequency (HF) transformer is a critically important facet in advanced DC-DC converter applications. In the traditional (lowfrequency) power transformer, this is carried out by leveraging open- and short-circuit tests and parameterizing the T equivalent-circuit model. In the case of HF transformers in power-converter applications, as their thermal performance assumes central importance, the focus is often placed on resistance characterization, high-frequency loss evaluation & efficiency, with remaining (typical) parameters receiving peripheral attention. Frequency response analysis (FRA) is a known parameterization tool, but primarily used in transformers for signature analysis, fault detection, and insulation diagnostics. FRA-based equivalent circuit models often yield higher-order systems with multiple passive elements, making analysis complex and intractable. We examine both methods on a common canvas by analyzing a well-designed HF transformer for a phaseshifted full-bridge converter and parameterizing it. We conduct experimental characterization via (a) open- and short-circuit tests and (b) frequency response characterization, deriving a fully parameterized T equivalent-circuit model. Dowell’s equation is used to derive HF losses for verification. We briefly provide a comparative analysis & results with commentary on various parameters obtained via different techniques for a T model, which have not been delineated clearly in pertinent HF-transformer literature so far.