SWITCHING POWER SUPPLY FOR THE OPERATION OF ELECTRIC LAMPS

摘要

PCT No. PCT/DE95/00653 Sec. 371 Date Nov. 11, 1996 Sec. 102(e) Date Nov. 11, 1996 PCT Filed May 17, 1995 PCT Pub. No. WO95/33299 PCT Pub. Date Dec. 7, 1995The invention relates to a radio interference suppression circuit for switching power supplies which are suitable for operating both discharge lamps and incandescent lamps. The radio interference suppression circuit has at least one controlled additional source (ZW, F) and one open-loop control circuit (TR1). The additional source or additional sources (ZW, F) generate targeted compensation signals, which are inverted with respect to the interference signals caused by the fast switching transistors (T1, T2). The additional source is either coupled parallel to the interference source and capacitively to the environment (ZW, F) or electrically connected into the supply leads in series with the interference source. In the first case, the additional source preferably includes a metal face (F), mounted in the vicinity of the switches (T1, T2), the potential changes of which face are inverted relative to those of the interference source-which is essentially the region around the junction point (M) of the switching transistors (T1, T2)-for instance by means of a transformer (TR1). In the second case, the additional sources are preferably formed by two secondary windings of the transformer. The primary winding is triggered by the potential changes of the interference source and in the secondary-side supply leads induces a phase-opposition common mode compensation signal. Optionally, the interference suppression can also be in the form of a closed-loop control circuit, in which the common-mode noise of the supply leads acts as the controlled variable.