Bidirectional continuous-mode flyback invertor

This paper describes a high frequency single-stage inverter utilising a bidirectional continuous-mode flyback topology intended for use in an offline UPS. The inverter consists of an input switching-stage connected to the primary of a coupled inductor (flyback transformer) and uses a synchronous rectifier on the secondary to allow bidirectional power flow. The inverter requires one wound component and may be realised using only four power switches resulting in a low component count. Average current-mode control is employed using the weighted sum of inductor primary and secondary currents as a continuous control parameter representing the magnetising current of the inductor core. This allows the use of the continuous conduction mode without the risk of core saturation, so that the core may be fully utilised. Operation of the inverter has been examined and verified experimentally on a prototype inverter with a design rating of 400 VA