Converter Topologies

Abstract

This chapter gives an overview on some interesting DC–DC (direct current) power converter topologies that are seldom discussed in the literature. It also provides, from a circuit-theory viewpoint, a discussion on the derivation of such converters and their relationships with fundamental converters. A family of current converters and their modified versions, which are derivable from fundamental voltage converters using the principle of circuit duality, are discussed. These current converters, which could also be formulated using the framework of a switching-capacitor cell, may be useful for applications where the energy source and load behave like current sources and sinks. A discussion on how fourth-order Ćuk, SEPIC (single ended primary inductor converter), and zeta converters can be derived using a two-inductor–two-switch circuit cutset approach is provided. It is shown that there is a missing circuit from this family of fourth-order converters under this cutset. The details of this circuit will be provided. An alternative, but more systematic approach of cascading two fundamental converters to result in a fourth-order converter is discussed. With this approach, nine possible types of cascaded fourth-order converters can be obtained. Out of these nine types of cascaded converters, there are seven types which are possibly quadratic converters, if properly configured. Single-switched quadratic converters are useful for applications that require a wide conversion range, e.g. in ultra-low-voltage devices. Finally, fourth-order converters which can be obtained from fundamental converters through the addition of second-order inductive-capacitive filters are described.