Modeling and control of a step-down composite DC-DC converter

A step-down composite DC-DC architecture is introduced, which can lead to reduced semiconductor voltage and current stresses and improved efficiency in applications that require operation over a wide range of conversion ratios. The step-down composite architecture, which consists of a series-input, parallel-output connection of a regulating buck stage and a number of unregulated fixed conversion ratio (DCX) stages, enables the use of lower-voltage semiconductors. The paper is focused on modeling and control of the composite converter. Modes of operation and closed loop voltage regulation are verified on a 1 kW, 48 V prototype with an input voltage range of 48-to-192 V.