EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: cbc02009 on September 29, 2018, 02:23:57 pm
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Hello all,
I'm still working on mppt controller, and I have another question that I can't seem to find an answer for on google.
In my schematic, I have a p mosfet on the output of my buck converter to protect from reverse polarity (the gate is tied to ground), but I just realized that a p mosfet won't actually do anything to protect the circuit if the battery has a higher voltage potential than the charger, because Vgs will still be negative because of the voltage of the battery.
I figure I could use a schottkey diode, but that's several watts of power loss. Is there a better solution that I'm missing? I'm surprised I can't seem to find anything about this issue online.
I'm using a 12V 12ah SLA battery, if that matters.
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How much load is on the buck input side?
You can connect FETs in anti-series (i.e., gates together, sources together, wire drain-to-drain for load) for a bidirectional switch, of course it incurs twice the Rds(on), which makes P-ch MOS that much less desirable. There are protection controllers (reverse, UVLO, OVLO, surge) that handle this, if you want a one-chip solution (and don't mind paying for it).
Tim