A software-based method for energy losses decreasing in cascaded buck + boost DC-DC converter

A MOSFETs switching times calculation method for the known modulation strategy for bidirectional buck + boost DC-DC converter is presented. A former low-loss, constant-frequency modulation strategy based on a negative inductor offset current takes place at the beginning of each conversion period which provides the ability to turn on converter’s MOSFET switches under zero-voltage and zero current switching (ZVS/ZCS) condition. Time interval between switching times of half-bridge MOSFETs is needed to provide the ability to turn on the MOSFET under ZVS/ZCS due to its antiparallel diode takes over an inductor current. Described method based on a switching delay time estimation for the worst case of converter’s circuit components spread which allows to calculate proper MOSFETs switching times by Digital Control Unit (DCU). The article describes in detail the switching of the input half-bridge MOSFETs at first switching time. The clarified offset current calculation method, based on an estimated switching delay and converter’s input voltage is presented.