Vehicular power supply system having a plurality of power supply voltages

A vehicular power supply system comprising:

• a generator including a first set of armature windings and a second set of armature windings electrically isolated from each other and a field winding supplying magnetic flux to said first and a second sets of armature windings;
• first rectifier means connected to the first set of armature windings of said generator to convert a first a.c. output of said first set of armature windings into a first d.c. voltage;
• second rectifier means connected to the second set of armature windings of said generator to convert a second a.c. output of said second set of armature windings into a second d.c. voltage;
• a first battery connected to an output terminal of said first rectifier means to supply power to an electrical load connected thereto and to be charged by the output of said first rectifier means;
• a second battery connected in series with said first battery and connected also to an output terminal of said second rectifier means to supply power to an electrical load connected thereto and to be charged by the output of said second rectifier means;
• a first voltage regulator detecting the terminal voltage of said first battery thereby controlling current supplied to the field winding of said generator so as to maintain constant the terminal voltage of said first battery;
• and
• a second voltage regulator connected between said second battery and said second rectifier means to regulate the charged voltage of said second battery, said second voltage regulator including switching means connected between said second battery and said second rectifier means, means for comparing the voltage of said second battery with a predetermined reference value, and conduction rate control means for controlling on-off of said switching means according to the result of comparison by said comparing means, said second voltage regulator further including means for transferring the result of comparison from said comparing means to said conduction ratio control means in synchronism with generating timing of a clock signal provided by the a.c. output of one of the phases of the second set of armature windings of said generator.