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. The lighting method, comprising:
providing a voltage to a lamp, the lamp comprising fluorescent lamps; determining a current across the lamp; providing an output based on the current across the lamp; providing an output based on a light setting, wherein the light setting may indicate a desired light level of the lamp; determining a difference between the current across the lamp and the desired light level of the lamp; determining whether a fault or hazard condition exists based on the difference between the current across the lamp and the desired light level; controlling, when a fault or hazard condition is determined, the current across the lamp to go to a safe level or to be cut off; and controlling, when no fault or hazard condition is determined, a voltage frequency applied to the lamp based on the determined difference between the current across the lamp and the desired current level.