Greetings smdFan,
smdFan:
Suppose a user by mistake put a battery in reverse in the battery holder of your circuit. Can your circuit be damaged? If yes, how to protect your circuit against such mishaps.
A power diode is series with the positive lead will block
accidental reverse connections. However, a silicon diode
drops a half volt or so, and wastes power.
A power diode in parallel with the supply (cathode of
diode to positive supply) will “short out” the supply
and protect the circuit from reverse polarity. No power
is wasted or voltage dropped for correct connections.
A zener diode in parallel with the supply will protect
the circuit from both reverse polarity connection and
over-voltage. The zener voltage should be slightly higher
than the worst case normal supply voltage.
If the circuit draws a high current, or the suppply is
capable of high currents, a fuse should be included
before the diode.
If the circuit is isolated from the ground of the supply
a common bridge rectifier in series with the supply will
work correctly for either polarity connection, but there
will be two diode voltage drops (allow 1.5V).
Comments Welcome!