Abstract: An ideal filament preheat technique in flourescence lamp is supplied by an adjusting circuit, an output circuit and a control circuit. At the filament preheating stage, an adequate preheating voltage is provided for the filament of the lamp tube, and the voltage cross over both ends of the lamp tube is reduced, thereby preventing glow current in preheating. When the preheating stage is finished and starting stage begins, the voltage between both ends of the lamp tube increases simultaneously, and then reaches a break-down voltage of the lamp tube, then the lamp tube is lit to enter a normal operation stage, the preheating voltage of the filament is cutoff under the control circuit, so as to save the filament power consumption. Therefore, the efficiency of the electronic ballast is improved, and the operation life of the flourescent lamp tube is extended.

Abstract: An electronic ballast includes a power supply circuit comprising an electromagnetic compatible filter circuit, a rectifier circuit, a power factor correcting circuit, a DC filter circuit, and a DC/AC converter circuit connected successively, wherein: the electronic ballast further includes an adjusting circuit, an output circuit, and a control circuit. At a preheating stage, a preheating voltage is provided to the filament of the lamp tube, and the voltage applied between both ends of the lamp tube is reduced at the preheating stage, thereby preventing glow discharge in preheating from occurring. At a starting stage, the voltage between both ends of the lamp tube increases instantly, and reaches a break-down voltage of the lamp tube, at this time the lamp tube is lit, entering a normal operation stage and the preheating voltage of the filament is removed via the control circuit, so as to make the filament power consumption in conventional electronic ballast non-existent when the lamp tube operates normally.