| 摘要 |
PURPOSE:To reduce harmonic distortion by supplying an input current to a total continuity angle as a preheating mode in which a lamp current is not supplied in a period in which a non-smooth DC voltage is a specified voltage or less. CONSTITUTION:A voltage from a commercial power supply 1 is converted by a full wave rectifier 3 into a non-smooth DC voltage. When a device is started, a filament preheating current is supplied from a switching element 4 through a choke coil, a fluorescent lamp 9, a resonance capacitor 10, and a lamp 9 filament. Next, the element 4 is put off, while an element 5 is put on, and the filament preheating current is supplied from the element 5 through the lamp 9, the capacitor 10, and a coil 8. When an input DC voltage becomes a specified value or less, an inverter frequency is decreased gradually, both end voltages of the capacitor 10 are increased, and the lamp 9 is started. By change of an action frequency, both end voltages of the lamp 9 are quickly decreased, filament consumption of the lamp 9 is reduced, and a lamp life is increased. By supplying the preheating current continuously to supply an input current continuously without becoming zero, a continuity angle is enlarged, thereby harmonic distortion can be reduced. |
