Input Protection Circuit

[ghasant]

Hello Everyone,
I have a spec given as, there is a output voltage of 12V from an external connector. This 12V should be used to power our circuit board (Our Circuit needs 12V). But before connecting we should have input protection circuit in our circuit board because from the external connector there could be transients, ESD pulse and also the 12V raise or fall down.

The question is

1. What protection circuit should we have in our circuit board? I can use a TVS and a Schottky and also fuse in by board. But Is there any other circuit.
2. How would i prevent the other side (Means External Connector Side in case of any Short from by Board).


Please advise
Ghasant

 

[ArticCynda]

A fuse in series with a schottky diode (to prevent accidental reverse polarization of the input) followed by a TVS diode should be sufficient for this application. A filter capacitor is recommended to eliminate any noise.

- transients on the 12V line will be caught by the TVS diode, and dissipated into heat in the TVS diode.
- voltage surges that last longer than a few µs will forwad bias the TVS diode, thus tripping the fuse and disconnecting your board.
- reverse polarization (switching 12V and ground) will reverse bias the schottky diode, so no current will flow to destroy your board.
- a fault in your circuit will also trigger the fuse, disconnecting your board from the external supply to protect it.