Power supply system having auxiliary winding and blocking module

Abstract

A power supply system includes a primary side circuit, a secondary side circuit, an auxiliary winding, a blocking module, a control module, and a controller. The auxiliary winding is magnetically coupled to the secondary side winding and includes a first sub winding and a second sub winding in series. The auxiliary winding has a first tap at the dotted end of the first sub winding, a second tap at the dotted end of the second sub winding, and a ground tap coupling the second sub winding to the ground. The blocking module receives a first auxiliary voltage and a second auxiliary voltage and outputs a selected voltage. The control module controls the blocking module according to the second auxiliary voltage to output the first auxiliary voltage or the second auxiliary voltage as the selected voltage. The controller is electrically coupled to the blocking module and the control module.