Loss minimization for coupled inductors with significant AC flux

Core loss is often ignored in the popular methods to design inductors. Thus, a design methodology (Kgac) for coupled inductors (and one-winding inductor) with dominant core loss is described to identify the core volume that yields the lowest total loss. The excitation frequency is assumed sufficiently low so that eddy-current effects in the winding can be neglected. The methodology is demonstrated for the coupled inductors in the flyback topology with large ac flux. It is verified experimentally for the inductors of a 30-W converter switched at 200 kHz. The Kgac method could lead to significant volume or loss reduction compared to the conventional design methods.