Method for regulating the excitation current in a motor vehicle alternator by digital processing, and a regulating device for carrying out the method

Claim 1

In a vehicle having an alternator and a battery connected to the alternator, a method of regulating the excitation current in a rotor winding of the alternator, the alternator comprising: a stator; a rotor including said rotor winding, the stator comprising stator windings; and a rectifier bridge connected to the said stator windings for delivering a rectified voltage to be regulated by the said method, the said rectified voltage having a waveform comprising a low frequency, variable amplitude, component produced by the said excitation current, whereby the said rectified voltage is a periodic voltage of period T, with each said period T consisting of a first phase and a second phase, the said first phase being a phase in which the voltage of the battery is applied to the stator winding, and the second phase being a phase in which application of the battery voltage to the stator winding is absent, wherein the said method includes the steps of: starting a measurement of the rectified voltage during each said period T, carrying out the said measurement by sampling over a predetermined sampling period, that is to say by carrying out successive measurements close together, calculating a reference value of the rectified voltage, making a comparison between the measured value of the rectified voltage and the said calculated reference value, and deducing from the said comparison the duration of the said first phase of the next following period T, and wherein the said sampling ends, in each period T, at an instant T-ε, where ε is a time period which is very short by comparison with the length of the period T.