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I am using LM2596 Step Down module to regulate 12VDC to 5VDC on a pcb board.

enter image description here

The board specs are: Voltage = 5 VDC Current = 3 Amps

Normally the setting on the module will be correct and the output correctly tuned to 5V. BUT, for some reason if it isn't, it will fry the electronics on the board.

How would you suggest overvoltage-overcurrent protection be put in place in this scenario?

I can't seem to find such high ampere rated OV/OC protection IC available on the marker. If you know one, kindly name it in the answer.

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  • \$\begingroup\$ This is an XY problem. What you really need to do is monitor the output and kill the regulators input if and when the voltage goes over 5.3V or whatever. \$\endgroup\$ – Trevor_G Nov 2 '17 at 14:36
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    \$\begingroup\$ Why do you need to? First test and adjust/fix/reject any modules that don't meet the need. Second, if you have need for redundancy, add something to measure the voltage and current, and use the LM2596's shutdown input to shut it off if they are exceeeded. \$\endgroup\$ – Brian Drummond Nov 2 '17 at 14:37
  • \$\begingroup\$ @Trevor what will be that something which monitors and kills the input :P \$\endgroup\$ – Mohsin Nov 2 '17 at 14:41
  • \$\begingroup\$ As far as I can see there are only 7 or 8 parts on that thing... why the heck would you not just copy the design in your system and get rid of that POT. \$\endgroup\$ – Trevor_G Nov 2 '17 at 14:49
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    \$\begingroup\$ Why not use the fixed 5 V version of the LM2596? \$\endgroup\$ – Andrew Morton Nov 2 '17 at 14:58
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You could use something more complex like LTC4366HDDB-2#PBF to Limit the voltage. But based on my experience overvoltage protection is rather unusual at the output of a DCDC converter.

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  • \$\begingroup\$ The IC you mentioned is quite complex and I am not worried about surges. I am worried that due to human error, if someone forgot to tune the varistor on the board to set the output voltage to 5V, the board will receive more than 5V thus damaging electronics. \$\endgroup\$ – Mohsin Nov 2 '17 at 14:37
  • \$\begingroup\$ That's not a varistor it's a potentiometer. And if you're worried about somebody fiddling with it, replace it with fixed resistors. \$\endgroup\$ – Brian Drummond Nov 2 '17 at 14:46
  • \$\begingroup\$ I am worried that due to human error Then why not deal with that then? Make sure all boards are set to output 5 V before they are used. When set to 5 V fix the screw in position with some glue, lacquer, nail polish even. Then instruct whoever connects the modules to the rest of the electronics not to use modules without a fixed screw. \$\endgroup\$ – Bimpelrekkie Nov 2 '17 at 14:55
  • \$\begingroup\$ @Mohsin seriously, if this is for production, DO NOT tie your livelihood to someone else's gizmo. If they go belly up, or can't meet your supply demands, you are screwed. It's OK to use these patch board for prototyping, but never use them in a product. Not unless you can source, and afford to buy enough of them NOW to last the lifetime of YOUR product. \$\endgroup\$ – Trevor_G Nov 2 '17 at 15:30
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Just monitor the output and shut the regulator off if it goes over a zener voltage.

schematic

simulate this circuit – Schematic created using CircuitLab

But really, the power supply board is pretty trivial. You would be much better to recreate it in your design with a fixed voltage output.

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