FAULT PROTECTION SYSTEM AND METHOD FOR FLUORESCENT LAMP BALLASTS

摘要

Provided is a lighting ballast system and method for fluorescent lamps. The system and method utilize a lamp current control loop to control the light level of a fluorescent lamp. The ballast includes an open loop detector that recognizes an open current control loop as an indication of a fault or hazard condition, and causes the ballast to output a safe lamp voltage or no voltage. The fault or hazard condition may be, for example, a very high voltage at the lamp or very low current across the lamp. The ballast also includes a disable circuit that prevents the open loop detector from triggering at times when the loop is expected to be open such as during ignition and maintenance restarting of the lamp.

主权项

1. A lighting system, comprising:
a ballast inverter having a frequency controller, the ballast inverter providing a voltage to a lamp; a summing junction in communication with a current detector and a current command interface, the summing junction determining an error between a first output and a second output and providing a third output to the frequency controller; a current detector in communication with the lamp and the summing junction, the current detector determining a current across the lamp and providing a first output to the summing junction; a current command interface in communication with the summing junction, the current command interface providing a second output to the summing junction; and an open loop detector in communication with the summing junction and the frequency controller, the open loop detector receiving the third output from the summing junction and determining whether a fault condition exists.