Method and device for regulation of a rotary electrical machine for a motor vehicle

A rotary electrical machine regulation device of the type which can control the electrical machine using a predetermined set value of a direct voltage (B+) of the on-board electrical network of the vehicle in which the machine is installed. An excitation current (EXC) is supplied to the alternator (machine), and has a duty cycle (RC) which is determined by a digital processing block (9), on the basis of an error voltage between the predetermined set value and the direct voltage of the electrical network. Accordingly, a system (11) is provided herein for making the digital block electrically self-sufficient. The system includes a voltage maintenance device with a self-sufficient capacitor (110), and a self-sufficient control element (111).