Fluorescent lamp end-of-life protection circuit

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. A fluorescent lamp end-of-life protection circuit in accordance with the invention includes a rectifying effect protection circuit for a lamp tube and an overvoltage protection circuit for the lamp tube, characterized in that 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 triac are connected to two ends of the lamp tube respectively. The invention is used to prevent the cathodes at both ends of the lamp tube from hazard due to overheating, avoid extra power consumption, and protect a ballast, when fluorescent lamp reaches its end of life.

Dependencies are inferred from the claim text.