Power supply device

A power supply device adapted to be used for an apparatus which includes a parallel assembly and a power generator, the parallel assembly including a main power supply and a load connected to the main power supply in parallel, the power generator having a first output terminal, said power supply device comprising:

• a first input port connected to the first output terminal of the power generator;
• an output port connected to the parallel assembly;
• an electric storage element charged with electric power generated by the power generator;
• a switching unit connected to the first input port, the output port, and the electric storage element;
• a current switcher for restricting a current flowing from the main power supply to the electric storage element;
• and
• a controller for controlling the power generator such that a voltage of the output port becomes a predetermined voltage, wherein
• the switching unit is operable to
• connect the electric storage element, the power generator, and the parallel assembly in parallel to each other when the electric storage element is charged with the electric power generated by the power generator, and
• connect the electric storage element, the power generator, and the parallel assembly in series to each other when the electric storage element is discharged to supply electric power stored in the electric storage element to the parallel assembly, and
• the controller is operable to control an output voltage of the power generator according to the voltage of the electric storage element so as to cause the voltage of the output port to become the predetermined voltage when the electric storage element is discharged.