Control device for controlling a motor vehicle alternator of the type which controls a DC voltage (B+A) generated by said alternator at a predefined voltage setpoint (Uo) by controlling the intensity of an excitation current (I EXC) flowing in an excitation circuit including an excitation winding of a rotor of said alternator and furthermore maintaining a current temperature of said alternator below a predefined maximum admissible temperature (T max), comprising a voltage control loop including: - acquisition means for acquiring said DC voltage (B+A) and which delivers a measured voltage (U b+); - a first comparator for comparing said measured voltage (U b+) of said voltage setpoint (Uo) and which generates a voltage error (ε V); and in that it furthermore comprises a temperature control loop (15, 16, 17) including: - a first temperature measurement/estimation means which delivers said current temperature; - a second comparator which generates a temperature error (ε T) between said maximum admissible temperature (T max) and said current temperature; - input means for inputting a current rotation speed of said alternator; characterized in that the voltage control loop includes: - first conditioning means for conditioning said voltage error (ε V) which deliver an input excitation percentage (r i); - a saturation module which delivers, in accordance with said input excitation percentage (r i), an output excitation percentage (r o) limited to a maximum admissible excitation percentage (rmax); - a generator for generating a pulse-width modulated signal having a duty cycle equal to said output excitation percentage (r o); - a semi-conductor switch controlled by said pulse-width modulated signal and which controls said intensity (I EXC); and in that the temperature control loop (15, 16, 17) includes a control module (19, 20, 21) delivering said maximum admissible excitation percentage (r max) in accordance with said temperature error (ε T) and with a speed correction (V cor) delivered by speed correction means according to a predefined correction law in accordance with said current rotation speed. - acquisition means for acquiring said DC voltage (B+A) and which delivers a measured voltage (U b+); - a first comparator for comparing said measured voltage (U b+) of said voltage setpoint (Uo) and which generates a voltage error (ε V); - a first temperature measurement/estimation means which delivers said current temperature; - a second comparator which generates a temperature error (ε T) between said maximum admissible temperature (T max) and said current temperature; - input means for inputting a current rotation speed of said alternator; - first conditioning means for conditioning said voltage error (ε V) which deliver an input excitation percentage (r i); - a saturation module which delivers, in accordance with said input excitation percentage (r i), an output excitation percentage (r o) limited to a maximum admissible excitation percentage (rmax); - a generator for generating a pulse-width modulated signal having a duty cycle equal to said output excitation percentage (r o); - a semi-conductor switch controlled by said pulse-width modulated signal and which controls said intensity (I EXC);