Elimination of Transient Current Mutation and Voltage Spike for Buck–Boost Current-Fed Isolated DC–DC Converter

Abstract

The bidirectional buck-boost current-fed isolated dc-dc converter is an emerging topology and has the advantages of low current stress, high efficiency, and wide power/voltage conversion range. However, it suffers from the inductor current mutation and transient voltage spike when the converter is directly switched between the buck and boost modes in the actual operation. By analyzing in detail the process of directly switching the two operation modes, it reals the reason of causing these transient problems is the duty ratio, and shoot-through duty ratio is not correctly set when the operation mode is switched. In order to solve this problem, a smooth switching scheme between the buck/boost operation modes is proposed by setting a special relationship between the closed-loop controller output of the inductor current and the two control variables based on the system model. The detailed simulation and experimental results verify the theoretical analysis and the proposed solutions.