Abstract: Provided is a power supply system in which two or more power supply units are optionally connected and used in any operation mode.

Abstract: An object of the present invention is to enable two or more power supply units constituting a power supply system to be synchronized to stably operate the power supply system.

Abstract: 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 100 includes two or more power supply units 10 to 13, the power supply units 10 to 13 cooperating to supply DC power to a shared load 22, the power supply units 10 to 13 including a power supply main circuit 30 that converts AC power inputted from the outside into DC power; a control unit 36 that controls the power supply main circuit 30; a pair of synchronous terminals Z1, Z2 respectively connected to a pair of synchronous signal lines ZCL; a transmission unit 35 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 35 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 30 stops outputting based on timing of receiving the error signal ER.