A circuit arrangement may include an input for coupling to a supply voltage; n semiconductor light source units comprising a driver device; wherein the units are coupled in parallel, wherein each driver device comprises a PWM controller. A respective controller is designed to provide a PWM signal at a respectively predefinable frequency to a control electrode of a respective converter switch. The arrangement includes current measuring devices which are designed for measuring the current through a respective string having at least one semiconductor light source; and a control device having control outputs, wherein each controller has a clock input, wherein a respective control output is coupled to a respective clock input of the controllers, wherein the control device is designed to provide clock signals at its control outputs, said clock signals being phase-shifted by 360°/n with respect to one another.