A description of inductive spiking, why it happens, and how a diode can save your circuits. Make sure you enable annotations as there is an error in one of the diagrams.
Example diodes on Amazon: http://www.amazon.com/exec/obidos/ASIN/B00W17LOBO/afromods-20
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26 Comments

  1. Hi.
    So the current will circulate in the closed loop and slowly dissipates as heat, and some also flows back to the source?

  2. But what about the MOSFET body diode? How does that play into this?

  3. The voltage at the drain builds up because of the rate of change of current with respect to time, or V = L (dI/dt). The shorter the transient time (and larger the inductor), the higher the drain voltage becomes.

  4. The energy/current in the inductor can not return to the voltage source in this single switch freewheeling configuration. You need an H-Bridge (four switches) for that.

  5. Oh hey, guess what I forgot to put in my motor driver circuit yesterday?
    I'm almost disapointed the mosfet didn't die now.

  6. IRFZ44… rated 55V, not 60V!
    By the way, better to use IRF3205, also rated 55V but has almost three times lower on state resistance than IRFZ44 and can handle more than double the maximum current of the IRFZ44!

  7. Would the addition of a small valued ceramic capacitor offer any benefit (in terms of cleaning up harmonic distortion on the waveform) to this diode + inductive load circuit? And if so, how would you connect it in this circuit?

  8. Is there any alternative way to remove the inductive spiking? Any advance way or efficient way?

  9. I noticed even with the diode you didn’t have a square wave it was more of a chair shape. I just wondered how you explain that. I have just built a similar mosfet driver for a spindle motor upgrade on my mini CNC on my channel so your video came around just in time. Thanks

  10. In the video it mentioned that putting the diode in the opposite direction will burn the diode. In this case, if the load is a bipolar motor, is it better to use a zener diode?

  11. Thanks for all the information. Suppose the engine will change direction from time to time. Like CW CCW. Do I need to connect the two opposite diodes in parallel with the motor? What kind of diode should I choose for a 24V 15A (nominal) 895 model number 12000 rpm high torque Dc motor. Please help, I'm trying to build an electric skateboard thanks.

  12. I have a question my friend so the snubber capacitor like you said in the comments that removes the current spikes and that's right I think so my question is what do you think will happen if you don't use one ????

    for the record I have been making alot of Igbts like six one of them to drive a motor but failed I think because I didnt use snubber

    do you think that this is my problem

    please want to hear from you……

  13. Very interesting. About 8 years ago I had some projects with the ignition coils on my car and I observed the Voltage on the primary side of them with an O-scope and it had the same pattern.

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