Author Topic: 5v Overvoltage protection  (Read 1670 times)

0 Members and 1 Guest are viewing this topic.

Offline TianfengTopic starter

  • Contributor
  • Posts: 10
  • Country: ca
5v Overvoltage protection
« on: June 21, 2019, 02:35:35 pm »
I need to design add some over voltage protection for a 5v circuit.  I was thinking of trying to use a crowbar circuit but I haven't built one before.  I need something that can handle higher currents up to possibly 8 or 9 amps on the 5v.  I have seen things online like https://circuitdigest.com/electronic-circuits/crowbar-circuit-diagram but . don't really get how the parts relate to each other.  I undertsand that the zener diode could be chose at 5.1v or 5.6v and if it goes over that the current will be pulled to ground but I don't get how the fuse is blown to protect the circuit.
 

Offline Zero999

  • Super Contributor
  • ***
  • Posts: 20360
  • Country: gb
  • 0999
Re: 5v Overvoltage protection
« Reply #1 on: June 21, 2019, 02:53:02 pm »
The fuse is blown, when the thyristor is triggered, because a large current flows through it, causing the fuse wire to melt and go open circuit.
 

Offline TianfengTopic starter

  • Contributor
  • Posts: 10
  • Country: ca
Re: 5v Overvoltage protection
« Reply #2 on: June 21, 2019, 03:51:06 pm »
Ok so let me see if I am tracking this right

When selecting a fuse and thyristor pair the fuse should be above the current draw level of the circuit and the thyristor should be able to output a current level high enough to blow the fuse. And the the schottky diode needs to be rated high enough for the circuit current as well.
« Last Edit: June 21, 2019, 03:56:20 pm by Tianfeng »
 

Offline cur8xgo

  • Regular Contributor
  • *
  • Posts: 148
  • Country: us
Re: 5v Overvoltage protection
« Reply #3 on: June 21, 2019, 04:18:03 pm »
Ok so let me see if I am tracking this right

When selecting a fuse and thyristor pair the fuse should be above the current draw level of the circuit and the thyristor should be able to output a current level high enough to blow the fuse. And the the schottky diode needs to be rated high enough for the circuit current as well.

Yes. This may be useful as well:

https://www.eevblog.com/forum/beginners/actual-fuse-current-rating/

Also..your power source should be able to drive enough current to blow the fuse. If it can drive enough current to hurt your (fuse protected thing) but not enough to blow a fuse, fusing may not be the solution here.




 

Offline TianfengTopic starter

  • Contributor
  • Posts: 10
  • Country: ca
Re: 5v Overvoltage protection
« Reply #4 on: June 21, 2019, 04:45:03 pm »
I was reading that earlier.  Interesting.  Current is being drawn from arcade boards.  They vary in current requirements and some are very high. My goal is really to make sure no one is able to put the wrong voltage in and damage their equipment.  I had my buck converter circuit fail and 12v got shot through the 5v line.  It fired my arcade board, cables (ther have a built in rgb to ypbpr converter) and the game pcb attached to it. 
 

Offline cur8xgo

  • Regular Contributor
  • *
  • Posts: 148
  • Country: us
Re: 5v Overvoltage protection
« Reply #5 on: June 21, 2019, 04:57:27 pm »
I was reading that earlier.  Interesting.  Current is being drawn from arcade boards.  They vary in current requirements and some are very high. My goal is really to make sure no one is able to put the wrong voltage in and damage their equipment.  I had my buck converter circuit fail and 12v got shot through the 5v line.  It fired my arcade board, cables (ther have a built in rgb to ypbpr converter) and the game pcb attached to it.

Maybe instead of a fuse a back-to-back N-ch mosfet switch would be better. Much faster and doesn't need to be replaced if it blows. Could also be cheaper then fuses and fuse holders. Can have custom voltage limits with comparators and nice terminal blocks for hookup.

But the fuse idea could work. Just make sure the fuse can be blown by the power supply short circuit current.
 

Offline TianfengTopic starter

  • Contributor
  • Posts: 10
  • Country: ca
Re: 5v Overvoltage protection
« Reply #6 on: June 21, 2019, 05:59:49 pm »
Thanks,  I will look at n-ch mosfet switches as well.
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf