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: A fluorescent lamp end-of-life protection circuit in an illuminating electric appliance, includes a rectifying effect protection circuit for a lamp tube and an overvoltage protection circuit for the lamp tube, in which a circuitry of two series resistors and a capacitor in series is connected in parallel with the lamp tube. A cathode of a transient voltage suppresser is connected to one end of the lamp tube, its anode is connected to an anode of a diode, and a cathode of the diode is connected to a common node of two series resistors. One end of a trigger diode is connected to a common node of the capacitor and the resistor, and the other end thereof is connected to a gate terminal G of a triac, a first electrode and a second electrode of of which are connected to two ends of the lamp tube respectively.

Abstract: The present invention relates to a fluorescent lamp end-of-life protection circuit in an illuminating electric appliance. A need exists for a simple and all-sided protection circuit in view of hazard occurring at end of life of a lamp tube.

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.