Low profile coupled inductors and integrated magnetics

Abstract

In a dc-to-dc converter, input and output inductors loosely coupled and isolation transformer windings closely coupled are implemented on a UI magnetic core in such a manner as to satisfy a zero-ripple condition k.sub.1 =n of current in the output inductor, where n is a turns ratio of the loosely coupled input and output inductors, and both inductors are chosen to have the same number of turns, and that number is an integer such that the value of the coupling coefficient k.sub.1 required to satisfy the zero-ripple condition is one achieved by modeling of core leakages instead of by adjusting the turns ratio n, thus making it feasible to implement the coupled inductors, and the transformer windings as well, in a single UI core and modeling the core losses by configuring the core. It is then possible to implement the core legs that are long enough to just accommodate a printed circuit board on which all of the windings are manufactured for a low profile package with both inductor windings on the same leg opposite the transformer windings. If the input inductor is on the same leg of the core as the transformer windings, adding an external inductor in series with the input inductor will filter any ripple current coupled into it by the transformer flux.