A detection circuit is configured to detect the presence of an operating dimmer arranged to dim a lamp. The detection circuit includes a first circuit for measuring at a first frequency an impedance at a coupling arranged to carry a possibly dimmed feeding signal for the lamp. The first frequency is higher than the mains frequency of the mains which supplies the possibly dimmed feeding signal for the lamp. The first circuit provides a first output signal indicating the measured impedance at the first frequency. The detection circuit also includes a second circuit for analyzing the first output signal and providing a second output signal indicating whether the operating dimmer is present. The second output signal indicates that the operating dimmer is present if the measured impedance changes by at least a defined minimum deviation within a defined time interval.