Fluorescent lamp electronic starting and protection circuit - has bistable, astable and monostable sawtooth waveform generators to operate thyristor firing transistor

摘要

The electronic starting and protection circuit is for fluorescent lamps having different loadings, e.g. between 20 and 65W and having preheated electrodes and includes a switching system incorporating three sawtooth waveform generator stages. These carry out three ignition testing operations in sequence to control a transistor so that a thyristor acting as the switch is fired, to ignite the lamp. The three generators are formed by a bistable stage (3), an astable stage (4) and a monostable stage (5). The bistable stage after operation by the astable stage through a transistor, releases an output signal to the transistor connected to the thyristor. After the monostable stage has been operated, it takes up a quasi-stable state and is returned to the stable by a back coupling through an output signal from two transistors, then one of these transistors passes an output signal to the thyristor control transistor.