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  • TI Thinks Resolved

LM5034: Flyback topology no-load issue (PMOS temp icrease)

Expert 5815 points

Replies: 3

Views: 79

Part Number: LM5034

Hi all,

My customer use LM5034 for flyback application. And there has a issue in it.(Schematic is showing below.)

PMOS1(Q11) & PMOS2(Q12) (temperature increase when no load)

yellow:Q11 red:Q12 blue:load current

yellow:Q11 red:Q1/Q2 blue:load current

schematic:

  • Hello Roy,

    The LM5034 is not a flyback controller. It is an interleaved active clamp forward type of controller.
    We have no reference material available for this part in a flyback application.

    Regards

    John

  • In reply to John Griffin1:

    Hi John,

    I'm not familiar with flyback and interleaved active clamp forward topology.

    As attached schematic, I think customer using  interleaved active clamp forward topology and it occurred the issue that I described.

    PMOS1(Q11) & PMOS2(Q12) (temperature increase when no load)

    Do you have any idea why the condition occurred? or we could test the which node waveform could verify the issue? Thank you.

    Roy

  • In reply to Roy Chou1:

    Hello Roy,

    Sorry about the delay in responding
    The schematic shows a flyback design
    Ican tell this because there is no output inductor and because of the out of phase relationship between the primary and secondary.

    The LM5034 is a forward controller and so the relationship between the main FET timing and the auxiliary FET timing will be only valid for a forward design..
    It is not designed for use in a flyback circuit.

    Regards

    John

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