DISCHARGE LAMP LIGHTUP DEVICE

PURPOSE:To improve drop of the input power factor when the power consumption of the same phase load has sunk, by varying the constants of circuit components of a noise preventive filter circuit, and furnishing a power factor control means to match the phase of input current with the phase of input voltage. CONSTITUTION:Through a noise preventive filter circuit 2, AC power is supplied to a power-variable power supply device A consisting of a smoother capacitor, inverter, etc., and a lamp l is lighted up with the high frequency output of this power supply device A, which thus makes dim control of the brightness of the lamp l is in response to the dim signal. The constants of components of the noise preventive filter circuit 2 is varied by a power factor control means, and the phase of the input current is matched with the input voltage. This allows the load side for the AC power supply to be the same phase load at all times even when the power consumption of the power supply device A has sunk, and thereby drop of the input power factor is improved.