Coupling coefficient improvement and electromagnetic induced noise reduction using short-circuited winding for loosely coupled inductor

A loosely coupled inductor for interleaved power converters has attracted interest for downsizing magnetic components. Although the loosely coupled inductor is usually designed by adjusting the coupling coefficient in order to meet the design specifications, the coupling coefficient is saturated by the fringing fluxes in the central leg and the external leakage fluxes in the case of the EE or EI magnetic core structures. It is a matter of concern that these fluxes are causes of electromagnetic induced noise and reduction in the downsizing performance. To solve this problem, this paper proposes a short-circuited winding for the coupled inductor in order to reduce the external leakage flux in the windings. The effectiveness of the coupled inductor with a short-circuit ring is evaluated with experimental tests.