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UC3854: uc3854 gate pin problem

VAIDEES WARAN
Prodigy 80 points
Part Number: UC3854

Hello

I am working on AC/DC converter using UC3854 IC. I have a problem in GATE DRIVER pin.It is connected to source of Power MOSFET with 5 ohm 10 W resistor.once the input supply is turned on the resistor was blown out. What might be the problem for this and how to rectify it?

My power rating is 500W.

Thank you

  • 0
    TI__Expert 6080 points

    Hello,

    Thank you for your interest in UC3854. I think the problem might be the power rating of the 5ohm resistor is not enough to withstand the high current drive output. Looking at the maximum ratings on the datasheet the power output of the GT DRV will be between 12.8W-18W worst-case, I suggest increasing the power rating of this resistor should solve your problem.

    Another thing to look here is what is the size of your resistor eg: a 0402 will have more stress on the package and replacing it with say 1206/0805 will lower down the thermal stress.

    I hope this answers your question.

    Sonal

  • 0
    TI__Mastermind 34465 points

    Hello Vaidees,

    Two things:

    1. The gate drive output of the UC3854 needs to be connected to the gate of the MOSFET and not the source.
    2. Blowing a 10W resistor by connecting up to a pfc controller is a very difficult thing to do.
      The UC3854 simply is incapable of providing 10W to the resistor.

    Please check your circuit and see exactly how you connected this part.

    Regards

    John

  • 0 in reply to John Griffin1
    Prodigy 80 points
    thank you

    I have another doubt. Whether the ground of the UC3854 and the power circuit will be the same?
  • 0 in reply to VAIDEES WARAN
    TI__Mastermind 34465 points
    Hi Vaidees,
    Yes that could be.
    Or you might even have the gate drive connected to the drain of the MOSFET
    Please check that your circuit is wired up correctly
    Regards
    John