Single Transistor Forward in Power Supply

Discussion in 'General Electronics Chat' started by wael.sadek, May 23, 2016.

  1. wael.sadek

    Thread Starter New Member

    Dec 12, 2015

    The below is for a switching transistors in an SMPS power supply
    Could anyone explain how it works, i understand that when the MOSFET is on the current flows through the primary coil of the transformer (upper one)
    While it's off the capacitor charges and then discharges when the MOSFET is on ?
    Also the lower coil is meant to oscillate ?
    Why the diode is needed ?

  2. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
    The diode is to remove the back emf ftom the bottom coil when the capacitor has been discharged.