Method and apparatus for power conversion with wide input voltage range

A power conversion system includes an input terminal that is arranged to be connected to a voltage source; a transformer having a first winding connected to the input terminal and a second winding connected to an output terminal of the power conversion system, either the first winding or the second winding is provided with at least three taps that are arranged to divide the first winding or the second winding into at least two sub-windings; at least one tap switch connected to the at least two sub-windings; a control circuit connected to the at least one tap switch; and at least one switch connected to the at least one tap switch. The control circuit is arranged to control the at least one tap switch to control the turn ratio of the transformer.