Switch mode power transformers are used extensively in electronic applications, usually within a switch mode power supply:

Switching Mode Power Transformers, Basic Application Circuits

The design of a switch mode power transformer will differ depending upon the type of circuit used. There are many variations of switching mode power supplies, but they can be narrowed down to three basic circuit configurations (each also has a mirrored configuration); Buck, Boost, and flyback. Be aware that the name for the Buck circuit varies from industry to industry and from person to person. It may also be referred to as an inverter, D.C. converter, forward converter, feed forward, and others. There are also unipolar and bipolar (push-pull) versions.