Lagrange-Multiplier-Based Control Method to Optimize Efficiency for Four-Switch Buck–Boost Converter Over Whole Operating Range

Four-mode modulation (FMM) method is the most advanced for four-switch buck–boost converter among existing control strategies. But its efficiency is still not optimal. In this article, all FMM methods are analyzed, and the minimum inductor current root mean square value of each FMM method is obtained via the generalized Lagrange multiplier method. Under this circumstance, the optimal FMM methods are selected to form a control method that improves operating efficiency over the whole operating range. Experimental results and comparison with state-of-the-art methods demonstrate the effectiveness and superiority of proposed method.