A dual mode forward/flyback converter

This paper presents a single transistor dc-dc converter that combines both forward and flyback action. The resulting circuit is ohmically isolated and can operate over a wide range of input-to-output voltage ratios. An analysis of the circuit indicates that the forward and flyback portions of the circuit interact to produce three distinct regions of operation. With the design information presented, the circuit can be tailored to utilize the desirable characteristics of either converter action for a specific application. The dynamics of the dual mode circuit are modeled by means of the state-space averaging technique. An ac-dc regulator that takes advantage of the wide operating range of the dual mode circuit operating off the ac line, with only a small input filter, is described.