Control of Fifth-order Buck-Boost Converter

A fifth-order buck-boost converter suitable for feeding point of load applications is presented in this paper. It offers finely tuned buck-boost conversion together with less ripple content in the source current thereby reducing the filtering requirements at the source side. The salient feature of this proposed converter is that it offers more duty ratio range for bucking operation. Mathematical analysis is presented to predetermine the salient features of the proposed converter. Voltage transformation ratio is formulated for CCM operation and the relevant equations defining the L and C components are evolved. A set of small-signal transfer functions are obtained and used in the controller design. A 50Watt, 100 kHz prototype of fifth-order buck-boost converter is built for experiment. The adopted load voltage is either 48 or 15 V. A 36V dc-source is used for powering the prototype converter operation both in simulation and experimentation. The effectiveness of the proposed converter is verified.