Any diode-based circuit that protects against reversal of the supply polarity introduces a certain voltage drop.Also, when relatively high currents are involved, the choice of a suitable diode,and its dissipation, may become problematic.
This circuit utilized a relay contact to break the positive supply line when the input voltage has the wrong polarity. the coil voltage of the relay may be lower than the input voltage, because Re is activated within a fiw milliseconds, and then receives the correct coil voltage via T1-D1. Since
the hold voltage of a relay is generally lower than the actuation voltage, D2 can be dimensioned such that the relay operates reliably with a minimum of zener current taken from the supply.
0 comments:
Post a Comment