Winding concepts for high frequency inductors with reduced DC resistance

DC-DC converters with wide-bandgap semiconductors facilitate the operation at higher switching frequencies. Thus, inductors can be reduced in size which is beneficial in regard to power density and weight of the converter. As a drawback, high frequency inductors suffer from considerably large winding losses caused by skin and proximity effects. Litz wire is a possible solution but it results in a poor copper fill factor. Therefore, this paper discusses a mixed winding consisting of litz and solid wires in parallel. By means of calorimetric measurement it was shown that the winding losses can be reduced up to 9.8% with this solution.