Point-of-load inductor with high swinging and low loss at light load

Point-of-load converter at light load has low efficiency owing to the “fixed losses” such as core loss and ac winding loss. This paper focuses on two-dimensional (2D) gapping of a ferrite core to shape inductance versus load current to reduce inductor loss at light load. Since the maximum inductance of conventional stepped gap is limited by the cross-sectional area of the thin gap, a 2D gap is formed by joining two orthogonal gaps to gain flexibility. Higher inductance is achieved at light load compared with uniform-gap and stepped-gap geometries having the same volume and dc resistance. Ac resistance is reduced at light load thanks to a magnetic path that steers ac flux away from the winding. Two C-cores with 2D gap were fabricated and tested on a buck converter with 50% reduced total inductor loss at 10% load current.