Patent ID: 7365999

Claim:
A circuit arrangement comprising circuit input terminals for connection to a low frequency supply voltage source that provides a low frequency supply voltage, circuit output terminals, a rectifier coupled to the circuit input terminals and equipped with rectifier output terminals for outputting a rectified low frequency supply voltage, a DC-DC-converter coupled between the rectifier output terminals and the circuit output terminals and comprising: an inductive element, a unidirectional element coupled to the inductive element, a switching element coupled to the inductive element and the unidirectional element, a control circuit coupled to a control electrode of the switching element for rendering the switching element alternately conductive and non-conductive at a high frequency and for generating a control signal for controlling the conduction time of the switching element in each high frequency period, said control circuit comprising a first circuit part for generating a first signal S 1 that is either a constant or exclusively depends on the actual voltage between the output terminals and a desired value of the voltage between the output terminals, wherein the control circuit is further equipped with a second circuit part for generating a second signal S 2 that is periodical and has a same phase and frequency as the rectified low frequency supply voltage and for generating the control signal by superimposing the second signal S 2 on the first signal S 1 so that the control signal includes a periodic signal having a DC bias.