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Our wide range of coupled inductors has a choice of inductance values from 50nH to 2mH – and RMS current ratings from 100mA to 38A.

Current flowing through a conductor generates a magnetic flux field. If the current varies over time, then so will the flux - and a current will flow in a second conductor if it is permeated by such a time varying magnetic field. This effect is known as inductance.

Coupled inductors comprise two coils of wire wrapped around a magnetic core. A varying magnetic field generated by current in the first coil will induce a current in the opposite direction in the second coil. The voltage across the second coil depends on the rate of change of current in the first, and the mutual inductance of the system.

Applications for coupled inductors

Purpose-designed coupled inductors are used in a variety of power conversion circuits such as flyback, SEPIC, Fly-Buck™, Cuk, ZETA and multi-phase topologies. These voltage regulation circuits use coupled inductors to efficiently provide the required output voltages, which may be stepped up or down from the input. To do this, SEPIC and Zeta circuits use 1:1 coupled inductors, whereas flyback and other circuits use 1:N inductors. In multi-phase power converters, coupled inductors provide inherent ripple current cancelling that is not provided by single inductors.

You can connect coupled inductor windings in different configurations to serve different purposes. The windings may be connected to circuits separately for use as isolation transformers or as common mode chokes. You may also connect them in series to achieve a higher inductance or for use as a tapped inductor.

How do I choose a coupled inductor?

Selection of a coupled inductor is application dependent. Coilcraft, for example, publishes datasheets that characterize coupled inductors for multiple circuit uses, and the company has developed online tools for selecting coupled inductors. Their MAGPro™ Coupled Inductor Finder is a powerful search and analysis tool that finds off-the-shelf coupled inductors for SEPIC and Zeta converters and many other applications.