End-of-life detector for gas discharge lamp and the ballast incorporating the same

摘要

Disclosed is an end-of-life detector for gas discharge lamp and the ballast incorporating the same. The end-of-life detector includes a lamp state signal detecting circuit for detecting the lamp state signal of at least one first gas discharge lamp and generating a positive voltage signal and a negative voltage signal accordingly; a comparing circuit for comparing the positive voltage signal with a positive selecting voltage and comparing the negative voltage signal with a negative selecting voltage, and in response thereto generating a positive control signal and a negative control signal; and a positive/negative duty time interval detecting circuit for generating a lamp life state signal which is generated by a difference between a positive duty time interval and a negative duty time interval. The lamp life state signal is varied along with the difference between the positive duty time interval and the negative duty time interval.

主权项

1. An end-of-life detector for gas discharge lamp for detecting a lamp state of at least one first gas discharge lamp, comprising:
a lamp state signal detecting circuit connected to the at least one first gas discharge lamp for detecting a lamp state signal of the at least one first gas discharge lamp and in response thereto generating a positive voltage signal during a positive half-cycle of the lamp state signal and a negative voltage signal during a negative half-cycle of the lamp state signal; a comparing circuit connected to the lamp state signal detecting circuit for comparing the positive voltage signal with a positive selecting voltage and comparing the negative voltage signal with a negative selecting voltage, and in response thereto generating a positive control signal and a negative control signal; and a positive/negative duty time interval detecting circuit connected to the comparing circuit for generating a lamp life state signal which is generated by a difference between a positive duty time interval defined by the positive control signal and a negative duty time interval defined by the negative control signal; wherein the lamp life state signal is varied along with the difference between the positive duty time interval and the negative duty time interval.