Abstract: The disclosure relates to the protection circuits interposed between a DC supply and a load circuit to protect the load circuit against short-circuits or reversals in polarity of the supply. The protection is obtained by means of a MOS power transistor connected between the supply and the load circuit. This transistor is turned on if it receives a voltage Vg from a bias circuit through a control circuit. The bias circuit delivers the voltage Vg only if the voltage given to it by the supply is sufficient while the control circuit turns the power transistor off if the output of the supply gets short-circuited or gives a voltage with reversed polarity.