Power generated by an alternator 2 and power generated by an electric
motor 12 are controlled such that a power generation amount of either the
alternator 2 or the electric motor 12, whichever has a higher power
generation efficiency, becomes larger than a power generation amount of either
the alternator 2 or the electric motor 12, whichever has a lower
power generation efficiency. Consequently, power needed for power generation, that
is, power consumed by an engine 1 can be decreased, thereby making it possible
to improve the fuel economy of a vehicle.
