Current-Mode Control of a Coupled-Inductor Buck-Boost DC-DC Switching Converter

This paper deepens in the study of the recently described coupled-inductor buck-boost converter. The output voltage of this dc-dc converter can be regulated above and/or below its input voltage with high efficiency and wide bandwidth. The control of the input and/or output nonpulsating converter currents is addressed in this paper. The small-signal control-to-input/output-current transfer functions in open-loop permits the design of the respective average current-mode controllers. The combination of the input-and output-current controllers with an additional output voltage limiter loop is proposed as a method to regulate one of the currents while limiting the maximum values of the other two variables. The theoretical analyses have been validated by means of simulations and also experimentally on a 48-V 800-W purpose built-prototype. In particular, the frequency response measurements that have been carried out for a representative set of the converter operating points are in good agreement with the simulations.