More general definition of energy factor and its application in isolated converters

Energy factor proposed as a goodness factor for dc system is reviewed in this paper. More general definitions of energy storage and energy factor are presented based on the analysis of energy process. By these new definitions, energy factor and energy storage can be extended into ac system. They can be used to compare the performance of different topologies of dc converters. The investigation of transformer's energy storage indicates that transformer has important influence to the characteristics of whole circuit. It depends on the way that transformer operates. If the transformer run as inductor (like Flyback converter), then it will improve the energy factor of the whole converter. But if the transformer run as a real transformer, then it will increase the non-active power consumption and make the energy factor worse. Simulation results explain BuckBoost and Flyback converter absorb the same amount of non-active power from front-end power supply. But the latter has better inner characteristics. Both input and inner characteristics of Buck converter are better than those of its isolated version which is Forward converter.