Patent ID: 7667940

Claim:
Power switching apparatus comprising: a switch having a control terminal and output terminals for connection in series between a power supply and a load, said switch being responsive to a control signal applied to said control terminal to switch between an ON-state in which it supplies power supply current from said power supply through said output terminals to said load and an OFF-state in which it interrupts the supply of power through said output terminals to said load; and a detection circuit for detecting an open-load condition of said load at least during the ON-state of said switch; wherein said detection circuit comprises a circuit operable in the ON-state of said switch for modifying said control signal so as to start switching said switch to said OFF-state during a lapse of time substantially less than the time required for said switch to reach said OFF-state and for restoring said control signal to a value corresponding to said ON-state at or before the end of said lapse of time; and a comparator circuit responsive to variation of voltage at said output terminals during said lapse of time.