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Forward Converter Issue with Conducted EMI - UC2825A

Cory Wasniewski
Prodigy 10 points

 

Hi All,

We are having some EMI issues with a forward converter design using a TI chipset.  There is weird spike mid wave with some ringing on the Drain of our FET during the pulse.  I have not seen this before and we believe it is causing some conducted EMI issues.  Do you  or do you know anyone that would be able to give a quick review and make some recommendations for us this morning?

 Attached is a screen shot of the Drain and Gate (labels in the graph are incorrect) and a page of the schematic showing the converter is also attached.

 

Any help you can provide would be appreciated, we are in a extreme time crunch and need this issue solved to pass conducted emissions.

  • 0
    Intellectual 410 points

    Hi Cory,

    For conducted interference failure you have to check you input filter (CMC and differential mode chokes, X and Y caps) and very important : PCB design. If is not possible to make  cancellation trace for current loop make it small as possible. Separate power and signal ground , enclosure ( metal) grounded in one point .Transformer shield should be connected on primary side ...This is not end of list.

    If you did not take this in to consideration I am afraid you have to update or redesign PCB.

     PDF of schematic included input filtration I will halp.

    Dragan