Power switching apparatus comprising switch means having a control terminal and output terminals for connection in series between a power supply and a load. The switch means is responsive to a control signal applied to the control terminal to switch between an ON-state in which it supplies power supply current from the power supply through the output terminals to the load and an OFF-state in which it interrupts the supply of power through the output terminals to the load. The apparatus includes detection means for detecting an open-load condition of the load at least during the ON-state of the switch means, comprising detection control means operable in the ON-state of the switch means for modifying the control signal so as to start switching the switch means to the OFF-state during a lapse of time substantially less than the time required for the switch means to reach the OFF-state and for restoring the control signal to a value corresponding to the ON-state at or before the end of the lapse of time, and comparator means responsive to variation of voltage at the output terminals during the lapse of time. The duration of the variation of voltage during the open-load detection is too short and its magnitude too small for the variation of load current to be perceptible, notably in the case where the load is a lamp.