Multiple-Input Power Supply and Control Method

A method includes providing a power conversion system having a first input coupled to a first ac power source and a second input coupled to a second ac power source, wherein the power conversion system comprises a first primary side power network comprising a first power converter, a first hold-up capacitor and a first primary switch coupled between the first ac power source and a first primary winding of a transformer, and a second primary side power network comprising a second power converter, a second hold-up capacitor and a second primary switch coupled in cascade the second ac power source and a second primary winding of the transformer, disabling the second power converter, and configuring the first primary switch and the second primary switch to operate in a sync manner so that a voltage across the second hold-up capacitor is maintained by a reflected voltage.