Lamps such as discharge lamps, in particular compact fluorescent lamps (CFL), are usually operated on the power supply system by means of a rectifier circuit for rectifying an AC voltage supply and charging a capacitor, which is often referred to as a smoothing capacitor. The term lamp used here relates in particular to the compact fluorescent lamps mentioned, but may also be understood to mean other lamps such as halogen lamps. The DC voltage present across the capacitor serves the purpose of supplying power to an inverter, which operates the compact fluorescent lamp. The invention generally relates to varying the power consumption of capacitive loads, the term “capacitive” in the case of lamp circuits meaning the so-called smoothing capacitor at the input of the inverter.