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I would hope to replace my Schottky diode that is acting as a as or diode. I do not like how high voltage drop the Schottky diode is making thus I would like to switch to a MOSFET. And the simplest circuit I could with a MOSFET kind of like this. I do not know if this MOSFET will work

enter image description here

Correct me if I’m wrong on these points which I think is correct.

The MOSFET I have chosen will have a voltage drop of 0.01 V assuming I have a current of 250 mA (the expected current of the load).

With the circuit I have protected both my inputs from reverse voltage inputs. When both inputs are present the higher voltage input cannot go back through the other input.

Is my circuit sufficient? Would there be complimentary components needed?

winny
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DrakeJest
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2 Answers2

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With the circuit i have protected both my inputs from reverse voltage inputs.

Yes, reverse protection is functional.

When both inputs are present the higher voltage input cannot go back through the other input.

When both inputs are present, they will be shorted to each other because both MOSFETs are on and they will conduct current in either direction.

If you want one MOSFET to turn-off when both power inputs are present you need to have extra circuits that monitor supply A and turn off MOSFET B when supply A is present. But, there's an added complication if supply A is valid when below the value of supply B because, switching MOSFET B off will not prevent supply B passing current through MOSFET B's diode to supply A.

Andy aka
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  • I just realized what you ment, seems like there is no simple way for oring supplies without a dedicated IC. Thank you for you answer. – DrakeJest Dec 26 '20 at 18:21
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your circuit turns on both MOSFETs when Vin is powered,

Something like this could give protection when both sources are present

schematic

but it only works when the voltage of the sources are significantly different to each other, if both are near equal the both MOSFETS will be off and there will be the diode drop associated with the MOSFET body diode.

Jasen Слава Україні
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