Extended Bucking Range Fifth-Order Buck-Boost Converter

An extended bucking range buck-boost converter of order five, suitable for standalone applications is presented in this paper. It has the attribute of providing finely tuned bucking range with more degree of freedom on duty ratio. The converter provides successful buck-boost conversion with low source current ripple which results in reduced source side filtering requirements. The key feature of this converter is the extended bucking duty-ratio range. State-space and steady-state analysis is presented to identify the performance features of the proposed converter. For arriving at the voltage gain transformation ratio, continuous inductor current mode of operation is considered. L, C component equations are derived thereafter. Small-signal transfer function derived after state-space analysis is then obtained and controller designing is performed. A 24 to 42 Watt, 50 kHz prototype of the proposed converter is also built for experimentation. Load voltage adopted is either 15 or 42 V. For powering the converter prototype, a dc source supplying 24 V is used for both simulation and experimentation. Proposed converter's effectiveness is also verified experimentally.