Overvoltage protection against 60-70V for 5V application

Discussion in 'Homework Help' started by circuitfreelancer, Jul 24, 2015.

  1. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    Hello All,

    What kind of overvoltage circuit should I go for to protect my current circuit that is working at 5Volt. Input voltage is around 6.5V and I have a voltage regulator in it.
    If the input voltage is bumped to 60-70V what kind of protection can i do such that the voltage drops down to appropriate level. Zener diode? TVS diode?
    Not a fuse or a voltage regulator solution.

    Thank you in advance
     
  2. dl324

    Distinguished Member

    Mar 30, 2015
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    A TVS would be the easiest solution.
     
  3. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    Is the 60V a transient, or a prolonged condition?
     
  4. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    a prolonged condition...need to test it for couiple of minutes at that voltage
     
  5. dl324

    Distinguished Member

    Mar 30, 2015
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    I misread your question. Post a schematic so we can see how the 5V is generated. Not many 5V regulators will tolerate a 60V differential.
     
  6. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    It all depends on how many current is needed for this 5 Volts.
    The LM317HV will allow 60 Volts as absolute maximum as input voltage.
    And the TL783 will even allow 125 Volts at its input.

    Bertus
     
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  7. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    there is a voltage regulator and supply current is upto 400mA of the voltage regulator. It can take upto 18V max. So definitely the voltage In needs to be dropped way low if a 60V is connected.

    Not supposed to use a another voltage regulator to regulate the 60V input... need to use a zener diode or TVS diode or some overvoltage protection circuit to drop the voltage down to less than 12V.
     
  8. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    Curiosity...What are you building that takes 5V but could "somehow" be connected to 60-70V for a prolonged time? Or better.. where is that high voltage coming from or how could that happen..
     
  9. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    Its not coming from anywhere.. I am just supposed to design a overvoltage protection that can withstand such high voltage and connect to that voltage and demonstrate it
     
  10. ScottWang

    Moderator

    Aug 23, 2012
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    What is the load and how many current you need?
     
  11. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
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    ohhh.. so homework and you're cheating by having someone give you the answer :p
     
  12. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    load is a voltage regulator then the voltage regulator supplied power to PIC chip. I wont be using more than 500mA at max.
    I have already finished the schematic and completed the software... and now final step is the overvoltage protection... i have bunch of options such as use zener diode TVS diode but not really much experience behind such huge voltage input and providing a huge voltage drop.
     
  13. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    More like guidance in the right direction is what I am looking for... and also what sort of calculations. An article of some sort on this etc... its all about learning doesnt matter where I can learn from
     
  14. bertus

    Administrator

    Apr 5, 2008
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  15. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    Thanks Bertus I can do that... but does this page explain about zener diode how cna it be used for overvoltage protection for high voltages?
     
  16. ScottWang

    Moderator

    Aug 23, 2012
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    As what you need, the zener diode may not give you enough current, or you have to choose a big current one, so you may use TVS, and which voltage regular are you using?
     
  17. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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  18. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    Can you explain me why will zener diode not give enough current?
    TVs diode (transient voltage supressor) as the name suggests is good for ESD issues that give high transient voltages for a brief moment of time isn't ti? My application I am going to give high voltage for couple of minutes.
     
  19. Brownout

    Well-Known Member

    Jan 10, 2012
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    As far as I know there is no law that requires that.
     
  20. circuitfreelancer

    Thread Starter New Member

    Jul 24, 2015
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    It's part of the task I am supposed to do... using another regulator wouldn't be a overprotection circuit design anymore. It will be just using another IC.
     
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