Patent ID: 8310160
Filing Date: 2012-11-13
Classification: H05B

Abstract:
1. A protection circuit for an electronic ballast, the circuit comprising: a lamp signal sensing circuit coupled across one or more lamps and designed to detect a signal through the lamps; a shutdown circuit coupled to the sensing circuit and operable to disable the ballast in response to a disturbance in the detected signal, at least a portion of the shutdown circuit defining a first time delay from detection of the disturbance in the signal during which the ballast operates normally, and after which the ballast may be disabled in response to the disturbance; an automatic restart circuit coupled to the shutdown circuit and operable to enable restarting of the ballast, at least a portion of the restart circuit defining a second time delay during which the ballast remains disabled, after which the ballast may be restarted; the shutdown circuit further comprising the shutdown circuit further comprising a first capacitor, the charging time of the first capacitor selectable to define the first time delay; and the automatic restart circuit further comprising a third switching element coupled to the DC voltage source and arranged to be turned on in association with the second switching element, a second capacitor coupled to the third switching element, the charging time of the second capacitor effective to prevent startup while the third switching element is on, and a third capacitor and a resistor coupled in parallel and selectable to define the second time delay.