Patent ID: 11996730

Abstract:
A backup power supply device having a short charging time is provided. The backup power supply device for supplying power when a main power supply is under a power failure includes first and second battery packs connected in parallel, a charging circuit for charging the first and second battery packs, first and second discharging switches for causing the first and second battery packs to discharge to the load device respectively, and a control unit. The control unit compares the battery voltages of the first and second battery packs with an output voltage from the main power supply. The control unit sets the first and second discharging switches to ON when the battery voltages are lower than the output voltage. When the battery voltage of the battery pack exceeds the output voltage of the main power supply due to charging, the control unit sets the first discharging switch and the second discharging switch to OFF. Thereafter, after the first and second battery packs are fully charged, the control unit switches the first and second discharging switches to ON when the battery voltage has dropped to a dischargeable upper limit voltage.