Lighting circuit for discharge lamp

摘要

A lighting circuit for a discharge lamp incorporates a DC-DC converter for converting DC voltage and a control circuit for controlling the output voltage from the converter by controlling the ON/OFF operation of an FET which is configured as the converter. The electric current which flows in the FET is monitored by detecting the voltage between the drain and the source to turn the field effect transistor off when the voltage level is at the reference value or higher. Thus, a pulse-by-pulse current limitation is performed. Limitation of an electric current in a switching device in a DC-DC converter of a lighting circuit for a discharge lamp is achieved while reducing the size and cost of the circuit apparatus.