Power supply apparatus with overload protection comprising a switch responsive to an input signal for switching between an ON-state for supplying current from a source of power to a load and an OFF-state for interrupting the supply of current to the load, and protection means responsive to an overload condition to switch the switch to the OFF-state. The protection means is responsive to a first overload condition during an initial phase after the switch switches to the ON-state so as to switch the switch back to the OFF-state and maintain the switch in the OFF-state. The protection means is subsequently responsive to a second overload condition if the first overload condition is not detected during the initial phase so as to switch the switch to the OFF-state and subsequently switch the switch back to the ON-state after an interval of time.The protection means is responsive to the current exceeding a first threshold value in detecting the first overload condition, and is responsive to the current exceeding a second threshold value in detecting the second overload condition, the second threshold value being lower than the first threshold value. The protection means is responsive to a temperature of the switch means exceeding a temperature threshold value in detecting at least the first overload condition.