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Proction circuit for the output of a protection recharger

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Hi all,


The title is wrong ! I am sorry!

That should be "Protection circuit for the output of a battery recharger".

Any way, I am implementing a way to protect my recharger output against reverse battery polarity connection.

I am using a P-MOSFET (low Rds during ON state) and a TIP31C (or any other NPN) as its driver, the way that is shown above.

8795-negr3b.png



What do you think about it ?

Is there any common way to do the protection I am looking for?

During simulations (using Multisim) it seems to work fine.

Is there any other suggestion?

Thank you
 
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MikeMl

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What turns on the TIP31C? It seems that it is off if the battery polarity is correct, meaning that the P-Fet is off too. Something is wrong. Maybe if you reverse the emitter and collector of the TIP31?
 
What turns on the TIP31C? It seems that it is off if the battery polarity is correct, meaning that the P-Fet is off too. Something is wrong. Maybe if you reverse the emitter and collector of the TIP31?


The TIP31 is turned on by a correct connection of the battery (+Vbat at the R4 and -Vbat at the TIP emitter).
 
A common way would be just a single rectifier diode.


That could be the simplest way for me, but the battery recharger uses the voltage level from the battery to control the current to supply. (It's a tree state recharger for 12V baterries), so the drop at the diode is not wellcome.
 

MikeMl

Well-Known Member
Most Helpful Member
The TIP31 is turned on by a correct connection of the battery (+Vbat at the R4 and -Vbat at the TIP emitter).

I dont see it. For that to happen, as I said above, the emitter and collector would have to be reversed... You are saying the right words, but your diagram has the transistor backwards...
 
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MikeMl

Well-Known Member
Most Helpful Member
... so the drop at the diode is not wellcome.

So just set the trip points for the controller higher by Vf of the diode. Use a Schottky.
 
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