Charging System Operation

Charging System:

Rotation of the excited field coil generates AC voltage in the stator.
This alternating current is rectified through diodes to DC voltage having a waveform shown in the illustration at left. The average output voltage fluctuates slightly with the generator load condition.

When the MFI relay (ASD relay) is on and the control circuit is grounded by the power train control module (PCM), current flows to the field coil and initial energization of the field coil occurs. The stator coil starts to generate power after the engine is started.

The generator output voltage rises as the field current increases and it falls as the field current decreases.

Accordingly, when the battery positive voltage reaches the target voltage value, the PCM turns the field current off. When the battery positive voltage is below the target value*, it turns the field current on to maintenance generator voltage at a constant level. If the field current is constant, the generator output voltage will increase in line with increases in the engine speed.

*: The target voltage is programmed in the PCM according to the battery temperature.