what is function of diode over power transistor?

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  • harp
    Badcaps Veteran
    • Jun 2022
    • 605
    • Planet Earth

    #1

    what is function of diode over power transistor?

    I see on some schematic a diode over power transistor, and dont know is in it some trick to carry current, or what is the point?
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  • stj
    Great Sage 齊天大聖
    • Dec 2009
    • 31084
    • Albion

    #2
    it protects the transistor from reverse polarity spikes when driving a coil.

    Comment

    • CapLeaker
      Leaking Member
      • Dec 2014
      • 8210
      • Canada

      #3
      EMF blocking diode.

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      • harp
        Badcaps Veteran
        • Jun 2022
        • 605
        • Planet Earth

        #4
        Aha, like on mosfets... but on first pictures of psu, how current can pass R15 and R16 its 510 ohm in parallel... 5A!? Thank you

        Comment

        • truclacicr
          Badcaps Veteran
          • Apr 2019
          • 321
          • australia

          #5
          I think the R15 and R16 current sharing resistors should be R510, 5W.

          P = I^2 x R = 2.5^2 x 0.510 = 3.2W

          Comment

          • harp
            Badcaps Veteran
            • Jun 2022
            • 605
            • Planet Earth

            #6
            Yes, it make sense... I was confusing with too many repeated errors and think there is some catch with diode to help pass current... lame...

            Comment

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