DISCHARGE LAMP LIGHTING EQUIPMENT AND ILLUMINATING SYSTEM

摘要

DC current of a source of DC (E) is inverted to high-frequency waves by means of an inverter circuit (11) to preheat filaments (FL1a, FL1b). Under this condition, a discharge detecting circuit (12) does not form a closed circuit for DC, and therefore a DC component is not applied to a capacitor (C3) and the capacitor (C3) is not charged. When a fluorescent lamp (FL1) discharges and then lights up, a DC component is applied to the capacitor (C3). When the voltage of the capacitor C3 becomes higher than that of the reference power supply (E1), it is judged that the fluorescent lamp (FL1) has discharged and lighted up. When the discharging is detected under the condition that preheating is necessary, the output of the inverter circuit (11) is lowered by negative feedback and the filaments (FL1a, FL1b) are preheated again while they are kept in a glow discharging state. When the filaments are sufficiently preheated, the voltage of the reference power supply (E1) is increased by a timer or other method to increase the output of the inverter circuit (11) and then start up the fluorescent lamp (FL1) to be lighted up.