| 摘要 |
The novelty is an electronic ballast for low-pressure discharge lamps = fluorescent lamps having an operating frequency of 20 kHz to 40 kHz, the current path from the positively switching transistor to the negatively switching transistor being passed via inductances. Furthermore, a series circuit = tandem circuit of fluorescent lamps of any desired power level is provided, the preheating current being passed via an inductance to the starting capacitors, which inductance triggers a current-limiting pre-heating effect. For the tandem circuit having fluorescent lamps of relatively high performance, the pre-heating current is split via a diode and capacitor circuit in order that the heating filament is not overloaded. Furthermore, the operating frequency is maintained by means of an LC element, even if the smoothing level on the supply voltage and on the operating voltage of the lamps falls. Furthermore, elements which limit switching are used, which prevents the transistors being overdriven from the base. A separate contact holder of the supply voltage of the lamp and of the starting capacitor is provided for adaptation of two-pin lamps having built-in starters. Furthermore, power conversions are possible, with the same circuit arrangement for tandem operation and the operation of an individual lamp.
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