Abstract: The present invention is directed to accurately sensing and regulating lamp current, and thus lamp output, over a range of lamp outputs, down to and below 10% of total lamp output. Exemplary embodiments can be used with a single set of power elements to drive multiple lamps in either an isolated or a non-isolated condition.

Abstract: Method for detecting the rectification effect in at least one gas discharge lamp (10) and electronic ballast for operating at least one gas discharge lamp, which recognises the appearance of the rectification effect in the gas discharge lamp (10). In order to be able to detect the appearance of the rectification effect in the gas discharge lamp (10) simply and with high sensitivity there is monitored the current (i.sub.1) flowing via a primary winding (7A), connected parallel to the gas discharge lamp (10), of a heating transformer (7A-C) or a parameter (i.sub.2, u.sub.3) dependent upon this current (i.sub.1) , and in the event that a predetermined limit value is overshot the presence of the rectification effect in the gas discharge lamp (10) is determined.

Abstract: There is provided a ballast for at least one gas discharge lamp havingan inverter which has two switches (S1, S2) in series, connected to a d.c. voltage source and switched with complementary timings, and a load circuit connected in parallel with one of the two switches (S1, S2) which load circuit includes a series resonant circuit (L1, C1) and the lamp (LA). Additionally there is provided a heating circuit (T, S3,R1) for current supply of the lamp coils, likewise connected to the inverter, which heating circuit includes a further periodically switchable switch (S3) for control of the heating current, whereby the heating circuit is likewise connected in parallel to one of the two switches of the inverter.