In a power supply apparatus for a vehicle, an inverter circuit inputs a voltage
from a first battery unit through switches. A smoothing condenser is provided between
the first battery unit and the inverter circuit in parallel. A DC-DC converter
is provided between the smoothing condenser and a second battery unit to voltage-convert
electric energy stored in the first battery unit or the smoothing condenser to
supply to the second battery unit, and to voltage-convert electric energy stored
in the second battery unit to supply to the smoothing condenser. An electronic
control unit controls the DC-DC converter before starting power supply to the inverter
circuit, such that the switches are closed after the smoothing condenser is charged
to a voltage within a predetermined permission voltage range from the voltage of
the first battery unit.
