A coupled inductor has two or more windings on a common core. Coupled inductors function in dc-dc converters by transferring energy from one winding to the other through the common core. They are available in many sizes, inductance values, and current ratings and most are magnetically shielded for low electromagnetic interference (EMI). The windings may have equal (1:1) or unequal turns ratios (1:N). Due to widespread demand in a variety of circuits, many 1:1 and 1:N standard coupled inductors are readily available off-the-shelf.