Lighting circuit for discharge lamp

摘要

A lighting circuit for a discharge lamp comprises detection means for detecting a voltage and/or a current to be applied to a discharge lamp or a voltage and/or a current equivalent thereto, input voltage/current detection means for detecting an input voltage and/or an input current to the lighting circuit, and abnormality detection means for stopping power supply to the discharge lamp when detecting an abnormality in the discharge lamp or a circuit abnormality based on those detection signals. In the abnormality detection means, a plurality of reference values for comparison or a plurality of reference ranges are set for the detection signals, and determination times are set in association with the reference values or reference ranges. The abnormality detection means compares the levels of the detection signals with each of the reference values or the reference ranges and determines that an abnormality in the discharge lamp or a circuit abnormality has occurred when a certain comparison result continues for an associated determination time or longer.