Magnetics are essential components in power topologies but they are perhaps the least understood and often deferred until the very end of the design. With basic knowledge about the functions magnetics perform, engineers can better understand how to select the appropriate components to optimise for power performance. This understanding is critical regardless of the application.

Magnetics are passive components which use an internal magnetic field to change the phase of electrical current. They are commonly divided into two camps–transformers and inductors.

An inductor consists of a wire loop or coil which is used to store energy in a magnetic field. The inductance of any particular component is directly proportional to the number of turns in the coil. This value also depends on the radius of the coil and the type of material used.

Transformers are used to change, filter and stabilise voltage levels. The main purpose of magnetic transformers is to transfer power between two different levels. Conversely, an inductor resists changes in electric current passing through it. Energy is stored in a magnetic field in the coil as long as current flows. When the current flowing through an inductor changes, the magnetic field induces a voltage in the conductor.

Having a basic understanding of how transformers work, what they are used for and where they are used provide designers with a starting point for the decision-making process and the topic of this article.

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