A single switch buck-boost converter with a high conversion ratio

To supply a high voltage load from a low voltage source (e.g. battery pack) often a converter is required with a high conversion ratio. Boost converter topologies with coupled inductors have emerged displaying a high efficiency, a low overall component count, a simple topology, and the need for only a single low-voltage active switch. However, in some applications the output of the converter must be capable of reaching voltages below the input voltage. To solve this problem, a buck-boost-converter topology can be derived from the boost converter with coupled inductors. However, if the different positions for the capacitors in the buck-boost topology are considered, several variants can be distinguished. The properties of the different topological variations are studied. Eventually, a topological choice is made based on the proposed criteria for a 175-V supply, converting 175 W from a 24-V battery. The theoretical results are compared to the results retrieved from a prototype converter.