Analysis and Design Aspects of Min-Type Switching Control Strategies for Synchronous Buck–Boost Converter

This paper presents a comparative study among switching control strategies for Buck–Boost converters, taking into account essential aspects in practical implementations, as the switching frequency variation concerning different output voltages and the responses in the transient and steady-states. More specifically, we have considered three switching strategies of min-type, where two of them permit high switching frequencies, while the other considers a limited frequency control strategy. Moreover, we have generalized the control techniques available in the literature to make them able to operate under changes in the equilibrium points without the need for a redesign. A conventional PI controller based on pulse-width modulation (PWM) is adopted for comparison purposes. In contrast to PWM-based control, which operates in the maximum switching frequency, the min-type strategies present variation in the switching frequency that depends on the operation point and may lead to a power loss reduction when compared to conventional techniques. To assure zero-error operation in the steady-state, a correction method is proposed. Experimental tests were made to compare the transient and steady-state responses of these control methodologies, verify the variation of the switching frequency according to the output voltages and the robustness concerning load variations.