[SOLVED] Reverse Voltage Protection Circuit Question

[rhnrgn]

Hello Friends, :grin:

I designed a reverse polarity protection circuit at the enterence of my circuits power stage.

P channel mosfets ope circuit if reverse voltage applies, and tvs and varistor will remove high voltage case above 7V.

But i am not sure whether C21 can be damaged or not if reverse voltage applied to circuit?

P-Mos will be open circuit but can a capacitor get damage if Caps (+) pin open circuit and 5V applied on Caps (-) pin?

Circuit below.

Another question is can i use a Zener diode after C17 in order to remove voltage above 5.5V? Because voltage shoul be above 6 Volts.
if this suitible?
**broken link removed**

If you have any other suggestions pls tell me. Thank you :thumbsup:

This is the circuit without zener


This is the circuit with zener

 

[kam1787]

I did not look up the specs for D1 - the zener - but it will be carrying the 5V when Vin > Vz - it will burn out. If the voltage was reversed, it would also carry nearly the full load.

What is VR1 for?

 

[rhnrgn]

VR1 is for protecting circuit from ESD events and over voltage. TVS current capacity is not enough for wrong voltage applience.

Now what do you think about this edition.

 

[ravindragudi]

The reverse polarity protection diode D2 should be at the very beginning in the power circuit. The Varistor is of no use ... TVS is better. The way the parts selected the varistor will never get activated as TVS has got low Vbd and low Vcl. Also TVS acts faster than varistor so in any case, first TVS gets activated in fault conditions.
To limit current try using low value series resistance, if it is feasible in your application.

 

[andre_luis]

According to title of the thread the circuit above was intended to protect the target from reverse polarity, and for this purpose the circuit above should work. However, for protecting the load from ESD, the circuit also should have some kind of series protection, such as bead ferrite cores for inrush current suppression.