Vrrm on a secondary rectifying diode for a full bridge forward converter

Discussion in 'General Electronics Chat' started by reggiereggie, Jun 1, 2008.

  1. reggiereggie

    Thread Starter New Member

    Jun 1, 2008
    Hi all,

    I have found a formula that I would like to understand the derivation of.

    I am trying to work out the peak reverse voltage on a secondary side full bridge forward converter rectifier diode. The secondary is centre tapped with two diodes, top diode D1 and bottom diode D2, an output choke and capacitor.

    I understand the operation of the circuit and would assume the reverse voltage is the primary voltage referred to the secondary during the time that say D1 turns off. But I have found this formula that states

    Vrrm >= [((Vout +Vf).Vinmax)/(duty max . Vinmax)] + leakage inductance spike

    Vrrm = diode repeat reverse voltage
    Vout= dc output voltage of converter
    Vf = it doesn’t state which diode voltage drop this is, maybe it’s the other secondary diode (when d1=off d2=on)
    Vinmax = max dc bus voltage = input voltage to converter

    I have found a link that has the waveforms which I understand but not how to work out the magnitude of the Vd1s reverse voltage. it’s the waveform titled: These are typical waveforms in a full-bridge PWM topology


    Please can someone explain this formula or explain how they would work out the Vrrm on a secondary rectifying diode for a full bridge forward converter.