Excitation circuit of a motor vehicle alternator, voltage regulator, and alternator which incorporates it

Excitation circuit (1, 14) of a motor vehicle alternator, of the type which can control an excitation current (lexc) in an excitation winding (2) of said alternator, according to a command (EXC_ON) of a voltage control loop (Vbat+) of an on-board network (3) of said vehicle which is supplied by a battery (4) to which said alternator is connected, comprising at least:

• a first ground (5) terminal, which is designed to be connected to a ground of said on-board network (3);
• a first supply terminal (6), which is designed to be connected to a positive line (Vbat+) of said on-board network (3);
• first and second excitation terminals (7, 8) which are designed to be connected to said excitation winding (2);
• and comprising:
• a first power transistor (9) of the MOS type, which is connected between said first supply terminal (6) and said first excitation terminal (7), and can be controlled by said control loop by means of a first control circuit (10) of a first gate voltage (GHS);
• a second power transistor (11) of the MOS type, which is connected between said first and second excitation terminals (7, 8), and to said first ground terminal (5) which acts as a free wheel diode, whilst being controlled by means of a second control circuit (12) of a second gate voltage (GLS);
• wherein it additionally comprises a control loop (15) of a drain-source voltage (Vds) of said second power transistor (11).