Discharge lamp lighting circuit

Abstract

A discharge lamp lighting circuit 1 has a DC power supply circuit 3 for outputting a DC voltage, a DC-AC conversion circuit 4 for converting the output voltage of the DC power supply circuit into an AC voltage and then supplying the AC voltage to a discharge lamp 6, and a current detection circuit 8 for detecting an electric current flowing into the discharge lamp. Just after the discharge lamp 6 is lighted, the output frequency of the DC-AC conversion circuit 4 is temporarily changed for defining the lighting frequency of the discharge lamp as a low frequency, to perform DC lighting over a predetermined time. A control circuit 7 determines the duration of the DC lighting by the time it takes for the product of the time and the value of current flowing into the discharge lamp 6 to equal a predetermined value.

Dependencies are inferred from the claim text.