POWER SUPPLY APPARATUS

A power supply device supplies power to a load by combining a secondary battery and a capacitor connected in parallel to the secondary battery. The power supply device includes an insulation type DC-DC converter with a primary coil connected in parallel to the secondary battery and configured to accumulate energy by a current supplied from the secondary battery and a secondary coil configured such that an induction current flows thereinto from the primary coil by the accumulated energy, and a switching circuit configured to selectively connect the secondary coil in series to the capacitor in forward and opposite directions.