Patent ID: 8729817

Claim:
A ballast comprising: a rectifier configured to receive an alternating current (AC) voltage signal from a power source and to produce a rectified voltage signal therefrom; an inverter circuit configured to receive the rectified voltage signal and to provide an oscillating voltage signal to energize one or more lamps; a control circuit connected to the inverter circuit and configured to control operation of the inverter circuit; a voltage supply circuit connected to the control circuit and configured to provide a supply voltage to the control circuit so as to power the control circuit; a fault detection circuit connected to the one or more lamps and configured to detect a fault condition and, in response, to generate a voltage pulse; and a latching circuit connected to the fault detection circuit and configured to disable the control circuit so that operation of the inverter circuit is discontinued during a fault condition, the latching circuit comprising: a first switching circuit comprising a first switch, wherein the first switching circuit is connected to the rectifier and is configured to receive the rectified voltage signal from the rectifier, wherein the first switch includes a conductive state and a non-conductive state, and wherein the first switch is connected to the fault detection circuit and configured to switch states in response to receiving the voltage pulse from the fault detection circuit; a second switching circuit comprising a second switch, wherein the second switching circuit is connected to the first switching circuit and to the rectifier and is configured to receive the rectified voltage signal, wherein the second switch includes a conductive state and a non-conductive state, and wherein the second switch and the first switch are configured to operate complementary relative to each other between the conductive state and the non-conductive state; and a third switch having a conductive state and a non-conductive state, wherein the third switch is connected to the second switch so that the state of the third switch is a function of the state of the second switch, and wherein the third switch is connected to the voltage supply circuit so that the supply voltage to the control circuit is drained when the third switch operates in the conductive state and the control circuit is thereby disabled.