PURPOSE: To perform smooth controlling of light by sufficiently preheating the preheating electrodes of an electric-discharge lamp by preheating the said electrodes during part of the time when a d.c. electric power is applied to an inverter from a dimmer and when the electric-discharge lamp is lit.
CONSTITUTION: When the output of a delay circuit 21 becomes "L" at the phase (θ4), a transistor 28 cuts off, and an oscillation circuit 27 stops oscillating. Thus, the discharge current of an electric-discharge lamp 7 flows during the time (T3) when a d.c. electric power is applied to an inverter 6. Here, preheating electrodes 7f1 and 7f2 are preheated during the period (T5) between the phase (θ3) and the phase (θ4), which is part of the time (T3) when a discharge current is flowing. Since the time during which the discharge current doesn't flow becomes short by performing a sufficient preheating during the period (T5), the reduction of the temperature of the electrodes 7f1 and 7f2 is not caused almost entirely. As a result, the temperature of the electrodes 7f1 and 7f2 at the re- initiation of discharge current feeding can be maintained sufficiently high. In addition, the electric discharge of the lamp 7 is made to discontinue during the time when a d.c. electric power is not supplied to the inverter 6 from a dimmer 2, thereby performing light controlling smoothly.
MORIMOTO SHIYUNICHI
YAMAZAKI HIROYOSHI
SHIMIZU KAZUTAKA
TSUGITA KAZUHIKO
