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    Reverse polarity protection using N-channel MOSFET

    Hi Guys,

    I need to protect my circuit from reverse polarity.
    The relevant part of the circuit if an MPPT charger for a battery.
    The input is a solar panel.

    The voltage of the panel is to high for the MOSFET so I need a Zener diode to reduce the voltage.
    My question is how to connect the Zener in this case?

    I attached two circuits, does it matter if I use the left one or the right one?
    Other ideas or comments are appreciated.

    V+ and V- are the solar panel connections. GND is the circuit GND

    Thanks,
    Tomer

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    Re: Reverse polarity protection using N-channel MOSFET

    How is the battery connected?



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  3. #3
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    Re: Reverse polarity protection using N-channel MOSFET

    The battery is connected to the MPPT output.
    What you see is the MPPT input.

    See attachment below for the complete circuit (not fully designed yet).

    The question is what is better (if there is any difference) for the Zener.

    Click image for larger version. 

Name:	Reverse Polarity Protection3.JPG 
Views:	11 
Size:	42.7 KB 
ID:	151000



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    Re: Reverse polarity protection using N-channel MOSFET

    Zener diode needs to be connected between gate and source to protect the transistor. The other circuit doesn't disconnect a reversed power source at all.

    It's not quite plausible to have an efficient MOSFET protection in the V- line and another series diode in the V+ line.


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  5. #5
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    Re: Reverse polarity protection using N-channel MOSFET

    Thanks.
    That was helpful.
    As for the diode, you are right - it is a remanent of an old design, it will be removed.



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