A very robust method uses a passive, resistive and
diode network, that is shown in Figure 4. When the
capacitor reverses, the diode and resistor R2 start to
conduct. The resistor R2 limits the peak current in the
protection diode. A small amount of current also flows in
the resistor RI and the power supply output diodes. This
current is driven by the voltage drop across the protection
diode and should be very small. It is very important to
use care in routing wiring using this technique. Inductive
voltage drop in the R2 protection diode loop can be
significant. If RI and its return are not connected very
close to the diode significant current can he developed in
R1 which may lead to failures in the power supply.
