| 摘要 |
A power supply apparatus for a vehicle includes an alternator for generating an output voltage for charging a first battery and a second battery having a higher voltage than the first battery. The output voltage of the alternator is controlled by a voltage regulator in accordance with the rotational speed of the alternator. When the rotational speed is in a low speed range, the voltage regulator controls the output voltage of the alternator to a first value suitable for charging the first battery. When the rotational speed is in a high speed range, the voltage regulator controls the output voltage of the alternator to a second value higher than the first value and suitable for charging the second battery. The output voltage of the alternator is switched between the first value and the second value at a rotational speed at which the output power of the alternator at the first output voltage equals the output power at the second output voltage. The apparatus may include a voltage converter which reduces the output voltage of the alternator to a voltage suitable for charging the first battery when the alternator is generating power at the second voltage. Alternatively, when the alternator is generating power at the second voltage, a point of the armature winding of the alternator having a voltage less than the output voltage of the alternator may be connected to the first battery to charge the first battery.
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