Thermal loss measurements of high frequency planar transformers

This article presents the capability of using a tailor made thermal loss measurement tool to evaluate different winding designs for resonant switch mode transformers in power supplies with frequencies above 500 kHz. The measurement tool can meter losses, directly displaying them in only a few minutes (depending on the heat capacity of the material under test). Different winding designs for a planar transformer have been tested. A revolved parallel winding lay-out has performed best in a short-circuit loss test.