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I´m reading for the past week about P-Channel mosfet reverse polarity protection circuits.

Then I´ve found this post

http://kaktuscircuits.blogspot.com/2014/07/reverse-polarity-and-overvoltage.html

So I grab the main concept and first I´m trying to build it with the less amount of components needed.

Then I wanted to add the overcurrent protection circuit (like a E-Fuse)

So if you have this on your input side of your DUT it will be protected against reverse polarity, overcurrent and overvoltage protection.

My main goal in doing this is to use it in combination with a Boost converter to charge a laptop on the go.

I´ll appreciate the input and hope that this idea is good for more people.

Last but not least I´m just a electronic amateur, I only have tangible knowledge of what I alredy done, burned or fixed, but no high degree education in the matter.

Thanksenter image description here

Fabio Cesperes
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  • Sorry, I don't see a question. – JRE Apr 26 '19 at 21:41
  • Sorry... i forgot to add "any ideas?" or "how about this schematic?" – Fabio Cesperes Apr 26 '19 at 21:46
  • We discourage broad, open-ended design review questions here on EE.SE, because the answer(s) tend to become long strings of unrelated edits and/or comments. While this might help you with your immediate problems, it is of no value to the site overall. We DO allow design review questions in which you explain your choices and then focus on a few points about which you still have doubts. To get a better feel of what is or is not acceptable, search for "design review" on the meta site. – Dave Tweed Apr 26 '19 at 23:39
  • $2 BMS cards have this feature included similar to this https://electronics.stackexchange.com/questions/298453/understanding-lipo-charging-protection-circuit – Tony Stewart EE75 Apr 27 '19 at 01:11

2 Answers2

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As you can see in al three of your circuits, the FETs may be off but the body diodes will conduct around them. At a minimum, reverse the source and drain connections for the FETs in series with the power flow. Note that this might cause an issue getting the correct Vgs for operation.

Seriously consider a power management chip from Linear Technology (now a part of analog Devices) They have parts tailor made for this application - reverse polarity, overvoltage, and overcurrent protection all in one, with an on-board charge pump to drive n-channel FETs. I used an LT4256-2 (auto-restart) back in the day with excellent results. That part required external reverse-polarity protection, but newer ones can tolerate something like -40 v.

AnalogKid
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  • I was just going to suggest the LT4256 as well. I've used it too and it gets the job done with little design complexity. – MapleTronix Apr 26 '19 at 22:19
  • Thanks for the input. But I´m seing in the datasheet that LT4256-2 is rated up to 48V and 2A. I intend to use these protections for 20V 3.5A up to 5A peak. Is there other way? – Fabio Cesperes Apr 26 '19 at 22:20
  • Those are just the numbers for the example circuit. The MOSFET is external (you can pick it), and you get to pick the shunt resistor value so you can use the IC for higher current. I've actually used the LT4356 which is nice too, there are examples for 4A in there: https://www.analog.com/media/en/technical-documentation/data-sheets/4356fb.pdf – MapleTronix Apr 26 '19 at 22:53
  • My project was MIL, 16-36 Vin, 11 A. Almost 500 in the field. – AnalogKid Apr 26 '19 at 23:56
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Check LTC4364 from Linear (now Analog). You will be amazed.

user159315
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