Electrical – Why is there a gate-source short on the n-channel mosfet? (circuit attached)

mosfetpowermosfetshort-circuitswitch-mode-power-supplyswitching

I am having a problem with the circuit below.

I am trying to use the IRLR8726TRPBF to switch a 24V pump by turning the Gate HIGH and LOW using the Arduino. However, there when I connect power to the board, there is a short between the Gate and the Source of the MOSFET.

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Here is my power supply circuit. The GND common everywhere.
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Before I noticed the short, I would turn the Gate HIGH and the MOSFET would get really hot quite fast. And it would switch an LED but for long, then it would go off.

What am I doing wrong? Any suggestions on how to solve the problem? Thank you.

Best Answer

Check that the flyback diode is installed with the correct polarity.

That is the only thing I see that would explain all three of your observations.

The MOSFET getting hot would be due to excessive current. You have enough gate drive voltage.

Gate-source short could be due to overheating of the die.

The LED going out could be due to the diode melting inside into a short or due to MOSFET damage. It's only a 1A diode and that MOSFET is quite capable of driving enough current to get sufficient forward voltage to light a red LED (some tens of A or more).

Incidentally, it's important to check the actual PCB and part and not just the silk screen vs. component, because it's possible to get the mapping from schematic symbol to footprint wrong, especially the first time you've used a newly minted symbol-footprint combo.

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