Need advice with ZVS full bridge design!

Discussion in 'General Electronics Chat' started by Liam Bowman, May 20, 2014.

  1. Liam Bowman

    Thread Starter New Member

    May 20, 2014
    3
    0
    Hi,

    Currently i am using a full bridge phase shifted converter with ZVS topology, i was given a design which had several faults within and have been working through them. Initially there as jittering on the high side MOSFET switching and noise from the magnetics which has been resolved. The design specification is a 24V DC to 350V DC, with a input range of 18V to 30V. Unfortunately when the input voltage drops below 24V the output also decreases. has anyone had similar issues in the past or have any idea what could be the issue, any help is much appreciated.

    The controller is a LTC3722-1 and the MOSFET drivers are LM5101ASD. The board is stable from 24.5V to 30V. When it reaches below 24.5V-23.8V noise is produced from the magnetics and the high side MOSFET switching becomes unstable. From 23.8V and below the output voltage seems to drop. I have changed the ZVS delay mode from adaptive to fixed. Also i have tweaked the feedback compensation loop with no effect on the issue. The board is designed with 120W power output at 350V. The oscillations frequency of the controller is 750kHz.It may be hard to upload the schematic due to my company policy on data security. However the design setup is similar to that of the controller development board, apart from the secondary side driver and the LM5101ASD drivers are used for both HI and LO MOSFET stages. Which can be seen attached. Is this a deep routed problem with a combination of component section, or a certain aspect of the design that has been done incorrectly?
     
  2. Liam Bowman

    Thread Starter New Member

    May 20, 2014
    3
    0
    The design will regulate the output under lower loads but under full load the output voltage drops.
     
  3. Liam Bowman

    Thread Starter New Member

    May 20, 2014
    3
    0
    Problem solved the transformer winding ratio was incorrect.
     
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