Patent ID: 8294544

Claim:
An M-phase coupled inductor, M being an integer greater than one, the coupled inductor comprising: a magnetic core formed of core material, the magnetic core including: first and second opposing end magnetic elements, M adjacent inner legs, each of the M adjacent inner legs disposed between and connecting the first and second opposing end magnetic elements, and a first outer leg: connected to the first opposing end magnetic element at a first end thereof outside of the M adjacent inner legs, connected to an innermost edge of the first opposing end magnetic element nearest an innermost edge of the second opposing end magnetic element, and extending along a first lengthwise direction toward a first end of the second opposing end magnetic element outside of the M adjacent inner legs, and including a first gap along the first lengthwise direction, the first gap having a thickness less than a distance between the respective innermost edges of the first and second opposing end magnetic elements at their respective first ends, the first gap including first gap material having lower magnetic permeability than the core material; and M windings, each winding wound at least partially around at least a portion of a respective one of the inner legs, each winding having a respective leakage inductance, wherein the first gap provides a path for leakage flux, the leakage flux contributing to the respective leakage inductances of the M windings, and wherein each inner leg has a respective width, and adjacent inner legs are separated by a separation distance that is less than 25% of the respective width of either adjacent inner leg.