Abstract: A circuit arrangement for the compensation of voltage variations of the electrical AC polyphase power line for an AC-DC converter (3).The invention comprises a first circuit (5) for determining the voltage variations at the input of each trigger rectifier (Th.sub.1, Th.sub.2, Th.sub.3) of a converter (3) and a compensating circuit (6) for compensating the firing angle of each trigger rectifier. The compensating circuit (6) is connected to an output (7) of the first circuit (5) for determining the variations in the input voltage of each rectifier. Outputs of the compensating circuit (6) are connected to control inputs of the pulse generator (4) for controlling the firing angle of each rectifier so as to adjust the period of the firing pulses of each trigger rectifier (Th.sub.1, Th.sub.2, Th.sub.3). The invention is particularly applicable to electrical DC power supplys for data processing systems.