Here are 4 simple 12V power supply circuits with output voltages around 12V. First power supply circuit is built with BD139, one zener diode and a few. ... This power supply circuit has a over-current ...

The diode conducts only when the power supply protection is correct. But the incovenient is that at higher current levels, the voltage drops and power loss of the diode affects the power level ...

For power-supply controllers with an external soft-start pin, however, a simple circuit can be added to convert its non-latching fault protection into one with latched protection.