Input Supply Voltage Protection

Discussion in 'General Electronics Chat' started by Dritech, Mar 7, 2017.

  1. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
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    Hi all,

    I have a small module which I need to protect from over-voltage. The input can be anywhere from 2.5V up to 5V.
    What techniques can I use to achieve this with minimal components?
    I was looking at clamping diode circuits, but to use such method one needs to connect Vmax to the maximum supply allowed. Since I will be using this for the main supply input, this method cannot be used.
    Any type of suggestion would be highly appreciated.
     
  2. ian field

    AAC Fanatic!

    Oct 27, 2012
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    The simplest is probably the age old and time tested crowbar SCR and fuse.

    There were 1N5401 size Zeners that often turned up on the old 5 1/4" FH HDDs and various high value logic boards - those were probably also designed to "hard fail" to protect the equipment.

    Manufacturers like GI and Littlefuse offer extensive ranges of voltage clamp protection devices..

    You could also go the non crowbar route with a comparator controlled power management pass transistor - but its certainly not minimalist.
     
  3. dl324

    AAC Fanatic!

    Mar 30, 2015
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    Assuming you want to protect the load, the easiest method is to use a TVS diode which is just a high power zener diode. If a standard value won't cover your situation, we'll need more information. What current, what voltage range, etc.
     
  4. Dritech

    Thread Starter Well-Known Member

    Sep 21, 2011
    812
    6
    Thanks for the replies. This is a low power module with a voltage range of 2.5V up to 5V and consumes around 10mA.
     
  5. ian field

    AAC Fanatic!

    Oct 27, 2012
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    The TL431 "programmable Zener" can handle 100mA provided you don't exceed the TO92 (or SMD) dissipation capability.

    You just need a preset pot to set the clamp voltage between the 5V upper limit and whatever the absolute maximum rating is.
     
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  6. #12

    Expert

    Nov 30, 2010
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    Yebbut...what are you protecting it from?
    There is no overvoltage danger from a stack of (4) 1.2V batteries.
    And the circuit needs what voltage?

    For instance, if you applied 5V and the circuit can function on 2.5V, you could put a 250 ohm resistor in series with the power supply and a 3 volt zener to ground. If you use the 100 ma TL431 adjusted to 3V, you can reduce the resistance to 20 ohms.

    You still haven't given us all the clues.
     
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  7. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Details... pfft... who needs them when you have so many mind readers around here..
     
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