A universal protection circuit for electronic ballasts

Electronic ballasts need a protection circuit to prevent high voltage and/or current stresses on circuit components in the case that the fluorescent lamp fails to be started or comes to the end of its life-time. In this paper, a reliable and cost-effective protection circuit is proposed for all types of electronic ballasts loaded with rapid-start fluorescent lamps. In addition, an electronic ballast circuit is developed for driving multi-lamps. In cooperating with the protection circuit, the load circuits with abnormal lamps can be isolated from the other lamps which are under normal operation. The protection circuit is implemented on various types of electronic ballasts, and experiments are carried out to test the protection functions under abnormal conditions.