Phase shift full bridge converter with synchronous rectification

Discussion in 'The Projects Forum' started by shashi0007, Oct 4, 2013.

  1. shashi0007

    Thread Starter New Member

    Oct 3, 2013
    Hello all

    I am working on 3K phase shift Fullbridge converter here Iam getting softswitching in the primary and in the secondary I am using Diode rectification and Iam getting around 85% efficiency at 1Mhz But I would like to replace these Diodes with MOSFETS to improve the efficiency. How can i give the timing for Synchronous MOSFETS when it is operating in Phase shift mode?
    Here I am attaching the timing diagram which i followed

    Thank you
  2. crutschow


    Mar 14, 2008
    Why is there overlap of the signals during the "zero state" time. I would think you would want both control signals to be off during that time to prevent cross conduction.

    The polarity of Q5 and Q6 indicate you want a negative DC output. Is that correct?
  3. mik3

    Senior Member

    Feb 4, 2008
    There are ICs that generate all the signals for you.
  4. shashi0007

    Thread Starter New Member

    Oct 3, 2013
    Thank you all for reply,

    I guess there is something wrong with Q5 and Q6 timing in the above figure but I am using the same concept of diode rectification for the mosfets with some dead time between them and its working good. I need 28v Dc output with 95% efficiency what parameters i can change to increase the efficiency?