HIGH-EFFICIENCY DC BALLAST ARRANGEMENT WITH AUTOMATIC POLARITY PROTECTION AND EMERGENCY BACK-UP FOR LIGHTING FIXTURE IN A SUSPENDED DC-POWERED CEILING SYSTEM

摘要

A high-efficiency ballast arrangement for a lighting fixture has an automatic polarity protection circuit for supplying an output DC voltage of constant polarity no matter in which orientation the fixture is mounted in a DC-powered suspended ceiling system having a DC power supply. A main DC ballast circuit includes a main DC ballast powered by the output DC voltage from the protection circuit to enable a lamp in the fixture to be illuminated during normal operation. An emergency back-up DC ballast circuit includes a battery charged to a charged DC voltage by the output DC voltage during the normal operation, and an emergency DC ballast powered by the charged DC voltage from the battery to enable the lamp in the fixture to be illuminated during emergency operation upon failure of the DC power supply.