Patent ID: 8946997
Filing Date: 2015-02-03
Classification: G01R,H05B

Abstract:
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.