LAMP PROTECTIVE, ELECTRONIC BALLAST

摘要

A lamp protective, electronic ballast includes a lamp voltage detector having a capacitor (112, 145, 165) and resistor (110, 142, 163) series connected across a discharge lamp (73). The junction of the resistor and capacitor is coupled to a voltage sensitive switch (114, 147, Q8/Q12) for detecting DC offset on the lamp and excessive AC voltage on the lamp. The switch is more sensitive to DC offset than to excessive AC voltage and is disabled while the lamp is started.