BACKUP POWER SUPPLY

A backup power supply includes a battery module including battery cells, a power conversion unit configured to adjust a voltage of an output of the battery module and output the adjusted output to a load, and a health diagnosis circuit for the power conversion unit, the health diagnosis circuit includes a determination circuit configure to diagnose health of the power conversion unit by detecting input power and output power of the power conversion unit and comparing a ratio of the input power and the output power with a threshold.