| 摘要 |
PROBLEM TO BE SOLVED: To provide the long life of a lamp even if a fluorescent lamp is normally preheated and lighted by DC current. SOLUTION: DC power is supplied from a DC source 3 to an inverter 2, transistors Q1, Q2 are switched on, AC voltage is generated on the secondary side 213 of a transformer 21, this AC voltage is applied to a filament 121 of the fluorescent lamp (a lamp) 1 to light the fluorescent lamp 1. Electric power to be supplied from the secondary side 213 to the lamp 1 is adjusted by PWM- controlling the switching, and the lamp 1 is dimmed and lighted on. In this case, DC is supplied from a DC source 61 to the filament 121 side of the lamp 1 through a diode D, and the lamp 1 is normally preheated and lighted by dc current. When electrons are allowed to the high-voltage side filament 121 side in a positive electrode cycle, scattering of the electrons of an electron emitting material of the filament 121 is not generated since the electrons are allowed to flow to an anode 123 and hardly allowed to flow to the filament 121, and the life is prevented from being shortened. |
