Patent ID: 8520349

Claim:
A supply voltage monitoring device for monitoring over voltage conditions of an AC power supply, comprising: a switch circuit configured to couple an input conductor connectable to the AC power supply to an output conductor connectable to a load, the switch circuit being controllable into a conductive state, where the input conductor is electrically connected to the output conductor through the switch circuit, and controllable into a non-conductive state, where the input conductor is electrically disconnected from the output conductor by the switch circuit; a supply signal conditioning circuit configured to generate a supply voltage signal representative of a voltage of the AC power supply; and a control circuit configured to monitor the supply voltage signal and to: control the switch circuit into the conductive state in response to the supply voltage signal being below a first over voltage threshold while the switch circuit is in the non-conductive state; record an indication of an occurrence of an over voltage event and control the switch circuit to remain in the conductive state in response to the supply voltage signal exceeding a second over voltage threshold that is higher than the first over voltage threshold while the switch circuit is in the conductive state; and control the switch circuit into the non-conductive state in response to the supply voltage signal exceeding a third over voltage threshold that is higher than the second over voltage threshold while the switch circuit is in the conductive state.