Cuk-Based Converter Concepts: Part 1
Basic Converter Configurations with Ripple-Current Steering
by Dennis L Feucht
The essence of the converter idea introduced in the 1970s by Slobodan Ćuk (rhymes with book) of Cal Tech is that of ripple-current steering. The idea is to operate a transductor (see inset box for terminology) at the boundary between transformer and coupled-inductor operation.
This is done by applying the same (or nearly the same) voltages to both windings simultaneously. What is the point to this? It effects a magnetic bootstrapping, whereby the externally voltage-driven winding, which would undergo an increase in current, is opposed by the magnetic flux of the other winding. If done right, the two effects cancel, leaving the current in the externally driven winding constant. Elimination of current ripple in a transductor winding is ideal in converter design, and current-ripple “steering” using a second winding essentially accomplishes it.
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