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LM25180-Q1: question about the ringing of waveform of the DS of the internal MOS

shaojun leng
Prodigy 10 points
Part Number: LM25180-Q1

Tool/software:

there is obvious ringings  when MOS is off,  as shown in below picture, the ringing almost touches 0V. As it's a primary-side regulated (PSR) flyback converter, will this almost reaching 0V ringing cause MOS be mis-turned on?

  • 0
    TI__Guru* 78240 points

    Hi Shaojun,

    Thank you for posting.  I don't think the MOSFET is falsely turned on:  it's channel is off and the waveform implies some issue in your primary snubber circuit. The overview of the waveform looks okay, though.  Could you share your schematic with component values or part  numbers accurately labeled for a review?  Also please tell the operating conditions:  Vin, Vo and Vo2 or Vo3...  if you have multiple output rails and their load condition. 

    Regard,

    Youhao

  • 0 in reply to Youhao Xi
    TI__Guru* 78240 points

    Hi Shaojun,

    May I close this thread for no activities in 2 weeks?  You are welcome to reopen it by adding a new post.

    Thanks,

    Youhao