POWER SUPPLY SYSTEM AND POWER SUPPLY UNIT

Provided is a power supply system in which two or more power supply units are optionally connected and used in any operation mode. A power supply system includes two or more power supply units to , the power supply units to cooperating to supply DC power to a shared load , the power supply units to including a power supply main circuit that converts AC power inputted from the outside into DC power; a control unit that controls the power supply main circuit ; a pair of synchronous terminals Z, Z respectively connected to a pair of synchronous signal lines ZCL; a transmission unit that outputs an error signal ER by establishing conduction between the pair of synchronous signal lines ZCL upon detection of an abnormality; and a reception unit that detects a conductive state between the pair of synchronous signal lines ZCL and that receives the error signal ER, wherein the power supply main circuit stops outputting based on timing of receiving the error signal ER.