REDUNDANT POWER SUPPLY SYSTEM

A redundant power supply system comprising: a first load requesting power less than a first voltage; a second load requesting power less than or equal to a second voltage than the first voltage; and a redundant power supply supplying backup power to the first load and the second load when the main power supply fails, wherein the redundant power supply notifies the first load of a failure of the main power supply when the main power supply fails, and supplies backup power at an output voltage satisfying the request of the second load, and wherein the first load does not output an erroneous diagnosis when an input voltage from the redundant power supply is less than the first voltage or when a failure of the main power supply is notified from the redundant power supply.