Ballast circuit for fluorescent lamp

摘要

An electronic starter for fluorescent lamps equipped with heatable electrodes (HW). It includes a switch (SW), designed as a bipolar transistor (VI) in the form of an IGBT, having a high ohmic gate connection. To this is supplied a voltage led off from the intermediate circuit voltage of an inverter (WR, fig. 1). The emitter-collector circuit of the transistor (V1) lies between bridge connections representing a positive or a negative pole at A DC rectifier bridge BGL1, BGL2). Whilst their other bridge connection forms the switch connections for the capacitor system. The timer circuit (tau) has a trip stage (V2, V3) supplied with the intermediate circuit voltage and a timing element (R31, R36, R37, C33) in series with the input of the trip stage. A specified delay time limits the preheating time. The transistor (V1) assumes a blocking condition after the trip stage is reached. A limit circuit is allocated to the transistor (V1), which limits the intermediate circuit voltage effective between the gate and emitter connections of the IGBT (V1) to a specified permitted value.