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LM5157EVM-FLY: how to modify to coupler feedback

Guru 11170 points
Part Number: LM5157EVM-FLY
Other Parts Discussed in Thread: LM5155

Hello E2E,

I'd like to modify the LM5157EV-FLY from string voltage FB to coupler FB.
I checked the User's guide, that the FB circuit with coupler has not connect to Vout.
To change to coupler feedback, do I need to modify it as shown below?

BR,
ACGUY

  • Hi ACGUY,

    Thank you for using E2E forums, Yes you are correct, as you can also see here for LM5155 EVM fly-back circuit, the Vout has to be connected to the FB circuit with coupler as you mentioned.

      

    BR,

    Haroon

  • Hi Haroon,

    Thank you for your reply.
    "The schematic on User's Guide has not mistake, the FB circuit is not connected to VOUT on realy EVM board."
    Is it correct?

    Regards,
    ACGUY

  • Hi ACGUY,

    I am not sure I follow with your question, is the question whether or not there is no mistake in the user's guide regarding the Vout and FB circuit not being connected? the answer to which is yes in the schematic as you see in the LM5157EVM FLY is the way you have described it, and there is possibility to connected the Vout to FB as I previously suggested with LM5155EVM flyback's schematic.

    BR,

    Haroon