| 摘要 |
A thyristor (4) is connected between the connections for the fluorescent tube. When the thyristor is conducting, a heating current flows through the electrode of the fluorescent tube, and starting signals are produced when the thyristor is switched off. In order that the disadvantage of continuous displacement of the thyristor triggering time can be avoided, a control electrode of the thyristor is connected via a switching element (15) to the pick-off of a resistive voltage divider (7, 8), which is connected in parallel with the thyristor, in order to supply a voltage, which is proportional to and in phase with the voltage between the said connections, at the voltage divider pick-off when the thyristor is not conducting. Connected to the control path of the thyristor (4) is a second thyristor (10) which is connected to a first control signal source (11, 12, 13, 14), which results in a number of identical starting attempts being terminated after a fixedly defined number of such attempts. The control path of the second thyristor (10) is also connected to a second signal source (20, 21), as a result of which the starting attempts can finally be divided into individual series of attempts, which are terminated after a specific number of series. The starting network in each case reaches its optimum starting conditions again with respect to its thermal behaviour during the interruptions between the individual series of attempts. <IMAGE>
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