BACKUP POWER SUPPLY SYSTEM AND CONTROL METHOD THEREOF

A backup power supply system and a control method thereof are provided. The backup power supply system includes a power supply circuit and an uninterruptible power supply. The power supply circuit is configured to receive utility power, and the uninterruptible power supply is connected to the power supply circuit and stores backup power. When the utility power is normal, the power supply circuit supplies power to the uninterruptible power supply, and the uninterruptible power supply outputs a first alternating current voltage that meets a utility power specification to the alternating current load. When the utility power is abnormal, the uninterruptible power supply outputs a second alternating current voltage that meets the utility power specification to the alternating current load.