PURPOSE: To improve various properties such as the energy saving, the instant lighting, the flickerlessness, and the illumination deterioration in a low temperature, by utilizing a high-frequency inverter power supply whose voltage is lower than the rating tube voltage, connecting fluorescent discharge lamps in series in a series resonance circuit of LC, setting the Q value of coil in the scope 3 to 9, and carrying out a boosting start lighting.

CONSTITUTION: A high-frequency AC inverter 6 of the rectangular wave output operates in the scope of 100kHz±50kHz. A high-frequency choke coil L7 has 610μH, Q=4.8, and the DC resistance is 0.73Ω, when a fluorescent discharge lamp 3 is of 40W. A capacitor C4 is used by removing only a glow tube, and the capacity is 0.006μF. The average value of the result of operating the load in such a composition by connecting four lamps in parallel are compared with the conventional unit using the same level of commercial power supply in respect to the input power to present the same illumination, and the result at the constant illumination, 1200Lux, was the input power 36.4 W, the current 0.55A, and the power factor 0.98. Compared to the conventional power consumption 49W for 40W, about 26% of energy saving was accomplished.