Failing lamp monitoring and deactivating circuit

摘要

A discharge lamp monitoring and deactivating circuit includes a normally closed switch in series with the discharge lamp and its ballast and a detector circuit connected across the lamp to monitor lamp operating voltage. The detector circuit includes a capacitor which is charged and discharged through separate paths so that a lamp electrical waveform change waveform can be detected, resulting in a net charge. The charge is used to open the switch after a time delay which is only manually resetable.