I'm trying to design a circuit with reverse polarity protection. I have found numerous of examples but I can't get it to work for me with a non-isolated power supply. I'm open for suggestions.

I changed the circuit to this Reverse polarity V2

I'm working on a school project and i thought it was smart to include a reverse polarity protection. I need +20 and -20 Volt and these are not isolated. Here is what i come up with.

I use the following MOSFETS: SI4825DY-T1-E3 IRFI4410ZPBF

Can anyone confirm if i choose the right MOSFETS?

  • \$\begingroup\$ Pay attention to the diodes between drain and source of the MOSFETs, at this moment they're forward biased to they will conduct all the current instead of the MOSFETs. Reversing the Source/drain of the MOSFETs will not help either as then these diodes would become in forward mode under reverse polarity condition ! Solution: you need to connect two FETS in (anti) series on both power rails. \$\endgroup\$ – Bimpelrekkie Apr 11 '17 at 10:25
  • \$\begingroup\$ You mean like this? In this case your ground is not really 0 Volt. Reverse Polarity V2 \$\endgroup\$ – Dylan Apr 11 '17 at 11:10
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    \$\begingroup\$ @FakeMoustache - The body diodes being forward biased in the normal polarity battery is just fine in this type of circuit. As the input voltage comes up the FET comes on and effectively shorts out the diode due to the low ON resistance of the (hopefully carefully chosen) FET. \$\endgroup\$ – Michael Karas Apr 11 '17 at 11:19
  • \$\begingroup\$ @Dylan - Did you actually try to build this circuit or just attempting to model it? \$\endgroup\$ – Michael Karas Apr 11 '17 at 11:20
  • \$\begingroup\$ @MichaelKaras Indeed you're right, I was thinking battery protection circuits. \$\endgroup\$ – Bimpelrekkie Apr 11 '17 at 11:35

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