advice please on "eFuse" concept

Discussion in 'Analog & Mixed-Signal Design' started by daz E, Dec 5, 2017.

  1. daz E

    Thread Starter Member

    Nov 7, 2017
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    Could you please suggest / point out any "gotchas" with the concept I have for a 10amp eFuse / circuit breaker , for automotive application. Ideas on component models/parts also welcome.

    A very simple design to protect motorcycles (12Vdc) by tripping a load at 10amp.
    Solution does not require too much precision I would imagine? eFuse.png
     
  2. wayneh

    Expert

    Sep 9, 2010
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    I don’t see the need for the Schmitt driver, if you use a genuine comparator instead of an opamp, although that may be fine also. You’d definitely want some hysteresis to prevent chatter.

    I don’t understand what you’re trying to do, turn the load off if it takes more than 10A? I’m pretty sure you could accomplish the latch-off by just feeding back to the comparator inputs.
     
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  3. daz E

    Thread Starter Member

    Nov 7, 2017
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    Yes, quite right. My bad.
    I shall use a non inverting comparator and set LTP and UTP ... What ratio would you recommend as Beta??

    I want to shut the whole circuit down when Iload reaches ~10a. Feedback wouldn't accomplish this.i could drive a latched relay but Id prefer a solid state solution.
     
  4. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    With a 12V supply you won't get more than 12V out of the comparator!
    You will need to find a high-side comparator: most are low-side. Google for "high side current sense" to identify a suitable IC.
    This article may help.
     
  5. daz E

    Thread Starter Member

    Nov 7, 2017
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    As per OP, 12v is all i seek.

    I have looked at HS sense ICs, but they overcomplicate the application introducing unnecessary logic and diagnostics

    Im going for a simple quad HS comparator each output driving a MOSFET. Some ICs already have both, just a case of finding/searching 100,000s !!
     
  6. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Is there a reason not to use one of the off the shelf ones available? They will be smaller and better than almost any thing home made, DIY. And less expensive. Plus they have a proven track record for reliability. And available in many different amperage values.

    Just one of the many places that sell them. https://www.waytekwire.com/products/1366/Circuit-Breakers/
     
  7. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    And the ones you link to are designed to cope with the electrical and environmental conditions in a vehicle.
     
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  8. daz E

    Thread Starter Member

    Nov 7, 2017
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    eFuse.png


    Guys ,

    I intend to build a box similar in fit,form and function to the PDM60 or Denali Power Hub or ClearWater monitor. All variants on the idea of motorcycle accessory wiring through a solid state box which provides internal busbar to battery V+ , individual fused circuits for upto "n" accessories with CB function. I simply intend to replicate this but I feel 4 circuits in addition to factory fitted accessories is more than ample. A quad Comparator would suffice.

    These OEM boxes are £150+ and totally overpriced.

    Aside from all this, this is a project for me , I want to do it. Its a hobby. Why would I buy OEM therefore !

    So, what I really require is help with the concept, maybe a few IC suggestions, or circuit snippets. Meanwhile I continue to scour the massive databases of ICs !!

    EDIT: Revised block diagram attached.
     
    Last edited: Dec 6, 2017
  9. daz E

    Thread Starter Member

    Nov 7, 2017
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    ...
    In fact, Linear make an IC just for the job and with that magic 10A max. If I were to assemble a board with x4 of these circuits,...? Could it be that easy? I suppose a quad equiv would be even better all round - anyone know of such a device??



    282_circuit_1.jpg
     
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  10. shortbus

    AAC Fanatic!

    Sep 30, 2009
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    Before spending too much time on that chip, you may want to figure out if it will withstand the very noisy electrical system in a automotive/motorcycle environment. They are far different than a normal electronic environment. Many chips made for vehicles have internal ways to prevent problems you may not for see.
     
  11. daz E

    Thread Starter Member

    Nov 7, 2017
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    Yes, I am aware of ESD , load dumps, transients etc consideration.

    if you have any practical offerings, say for example a specific device model/reference, now that would be really really useful .

    I would really like to move this thread forward beyond the "beware of this" , "think about that", and very simply seek some practical advice and constructive ideas and suggestions as to the OP.

    Thank you all the same and I await the model / devices you have in mind !;)
     
  12. daz E

    Thread Starter Member

    Nov 7, 2017
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