A SEPIC fed buck converter

A new patented topology - the SEPIC fed buck converter [1, 2] - addresses two critical issues confronting the power electronics field today: efficiency and transient response. A buck converter is integrated into a SEPIC to receive energy from the SEPIC inductors and the outputs of both deliver energy to the load in parallel. When the controlling switch - shared by both converters - is ON, the buck portion delivers energy to the load while the SEPIC portion stores energy in the magnetic element and feeds the buck portion. When the controlling switch is OFF, the stored energy is delivered to the load through both the buck and the SEPIC portions. The new converter has a voltage transfer ratio E_OUT/E_IN = D/(2 - D) of and complementarily combines the characteristics of both buck and SEPIC converters, resulting in reduced voltage and current levels in the magnetic and switching devices and leading to reduced conduction and switching losses. Additionally, an inherent gate-charge-extraction mechanism facilitates extremely fast turn-off of the control switch, essentially eliminating its turn-off loss. Furthermore, a new volt-second structure on the magnetic element significantly improves transient response of the power stage.