Inductor design for low loss with dual foil windings and quasi-distributed gap

In order to maximize efficiency for waveforms that contain low frequency and high frequency components, an inductor design using quasi-distributed gaps with thin and thick foil windings connected in parallel is presented. Compared to a single foil winding, this allows having more flexibility in design, improving packing factor, and pushing the upper frequency limit higher for a wide range of power electronics applications. For this configuration and for high-frequency foil inductors in general, a difficulty is developing low-resistance winding terminations and avoiding eddy-current losses in those terminations. A dual-winding structure which allows both terminations to be located in a low-field region to avoid eddy-current losses is introduced. An inductor prototype has been built and tested, and measurement results confirm the benefits. Simulation results show that improved detailed positioning of individual air-gaps in the centerpost could further reduce high-frequency resistance.