Abstract: A motor vehicle power supply system for supplying current to the direct voltage loads on a motor vehicle. The system has two alternating generators which are driven by the engine of the motor vehicle. The output windings of the respective generators are connected to bridge rectifiers that supply current to a common motor vehicle direct current load. Each generator has a field winding and the current supplied to a respective field winding is controlled by a respective voltage regulator. The voltage regulators cause pulses of current to be supplied to the field windings. The system has a control circuit for controlling the pulse width of the current pulses supplied to the respective field windings such that the pulse width of the current pulses supplied to one field winding are substantially equal to the pulse width of the current pulses supplied to the other field winding.

Abstract: A dual voltage motor vehicle electrical system wherein batteries are series connected across the direct voltage output terminals of a generator. The system has a DC to DC converter that operates in a first mode as an equalizer to maintain the batteries in a substantially equal state of charge. When an electric starting motor is energized to crank the engine of the vehicle the converter is switched to a second mode of operation wherein it provides a substantially constant output voltage that is applied to certain electrical loads on the vehicle that require a stable voltage. The converter responds to a first reference voltage that is provided by a voltage divider connected across the batteries when operating in the first mode and responds to a second reference voltage provided by a constant voltage device when operating in the second mode. The system switches between the reference voltages, depending upon the mode of operation that is being used.