ZMI usb-c power adapter - wrong mosfet?

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  • W1ngl3t
    Member
    • Feb 2022
    • 11
    • Hungary
    #1

    ZMI usb-c power adapter - wrong mosfet?

    Hi all,

    The pictured ZMI ac-dc power adapter stopped working a little while ago. Using my multimeter I could see that there was DC voltage being produced, but it cycling between 0v and 1v.
    I suspected it was the TK11A65D (datasheet) mosfet acting up and ordered a similar TK15A50D (datasheet)

    I've now installed the TK15A50D and the cycling has stopped, but it's only outputting 3.9v rather than 5v.
    I'm guessing the problem is that the TK15A50D is not a suitable replacement, but what parameter/characteristic did I miss that could be causing lower output voltage?
    Shouldn't the driver (FAN602) know that the voltage is low and adjust the pwm accordingly?

    I'm a noob so apologies for the noob question.


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    • R_J
      Badcaps Legend
      • Jun 2012
      • 9534
      • Canada
      #2
      Re: ZMI usb-c power adapter - wrong mosfet?

      The mosfet was likely ok, but I do suspect the fan602, vcc to be low, likely due to a bad Cvdd Capacitor (see datasheet)

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