Beyond the three basic, nonisolated switch-mode power-supply topologies discussed in Part 1, many more topologies are available. However, they all require additional power components, which typically makes them higher cost and lowers their power-conversion efficiency. With certain exceptions, adding additional components in the power path will generally add losses.
Some of the most popular topologies are SEPIC, Zeta, Ćuk, and the four-switch buck-boost. They each offer features not available with the three basic topologies.