The invention relates to an operating circuit for an LED series, having: a converter, particularly a DC-DC converter, having a controllable switch (S1) and an inductor (LBUCK) for converting an input voltage (Vin) fed to the operating circuit into a supply voltage for the LED series; —a control unit (SR) for driving the switch (S1); —a secondary-side inductor (L2) coupled to the inductor (LBUCK); —an envelope curve demodulator (30) for detecting the envelope curve of the voltage (V′LED) present at the secondary-side inductor (L2); and—a compensating circuit (31) for compensating an error caused by the envelope curve demodulator (30) relating to the detection of the envelope curve.