Charging Systems: Operation

The voltage regulator controls the field using a Pulse Width Modulated (PWM) signal, measured in duty cycles. A PWM signal continuously cycles on and off. On-time can vary within each cycle.

When the ignition switch is turned to the RUN position, the PCM applies a low voltage to the regulator before engine is started. The regulator, now in field strobe function, applies a small percentage of the duty cycle to the field windings, which produce a magnetic field. As generator RPM increases, the field strobe function is disabled and normal regulation occurs. The PCM monitors the regulator from the "F" terminal of the generator.

When field current is on, the regulator switches the field current on and off at a fixed frequency of about 400 cycles per second. By varying the overall time on and off, correct average field current for proper system voltage control is achieved. At high speeds, the on-time may be 10 percent. At low speeds with a heavy electrical load, the on-time may be as much as 90 percent.

A battery thermistor is mounted on battery. Thermistor is connected between battery and generator terminal "S". This circuit supplies a temperature compensated voltage to generator. Generator varies output depending on temperature.