BACKUP POWER SUPPLY DEVICE

A backup power supply device includes: a storage battery charged with power from an external power supply; charge switches for charging the storage batter; discharge switches that are made from a field-effect transistor and that discharge the storage battery to a load device; a control unit for controlling the charge switches and the discharge switches; and a discharge suppression section connected in series to the discharge switches. The discharge suppression section suppresses leakage of current from the storage battery only when the control unit charges the storage battery, and the battery voltage exceeds an input voltage and the difference voltage between the battery voltage and the input voltage is less than a prescribed value.