| 摘要 |
PROBLEM TO BE SOLVED: To provide a discharge lamp lighting unit in which harmonics of input current are reduced through simple circuitry. SOLUTION: A transistor Q1 is turned on/off to apply an AC high frequency voltage to a fluorescent lamp FL thus lighting the lamp. A third capacitor C4 is charged when the transistor Q1 is turned on. The third capacitor C and an inductor L2 are oscillated by turning the transistor Q1 on/off and harmonics are suppressed by overlapping the high frequency at a lower part of the envelope of a rectified pulsating voltage from a full-wave rectifier 12. At a part of AC commercial power supply e where the instantaneous voltage is low, a current flows through the third capacitor C4, a parallel resonance circuit 17, a choke coil L4, the fluorescent lamp FL, a second capacitor C3, the full- wave rectifier 12, a first diode D1, the inductor L2 and the third capacitor C4 when the second and third capacitors C3, C4 are discharged and the transistor Q1 is turned off. Consequently, the input voltage is made continuous and harmonics are suppressed. |
