Power supply system, image forming apparatus having the power supply system, and control method of the power supply system

A power supply system comprising:

• a switching power supply configured to convert an AC voltage from an AC power supply into a predetermined DC voltage and to output the DC voltage;
• a latching relay, which is provided on an AC input line, and which is configured to switch a connection state of the switching power supply with respect to the AC power supply in response to an input of a relay drive signal;
• a storage circuit configured to store electricity by supply of electric power from the switching power supply;
• a control device configured to receive supply of electric power from the storage circuit in a disconnection state of the switching power supply and the AC power supply;
• and
• a relay drive circuit configured to generate the relay drive signal in response to an input of a relay control signal for controlling the latching relay, and to output the relay drive signal to the latching relay,
• wherein the control device is configured to perform:
• a determining process of determining whether an amount of charge of the storage circuit has decreased to a predetermined amount of charge, which is equal to or larger than an amount of charge necessary to drive the latching relay, in the disconnection state;
• and
• a connecting process of, in a case where it is determined in the determining process that the amount of charge of the storage circuit has decreased to the predetermined amount of charge, generating the relay control signal for connecting the switching power supply and the AC power supply and outputting the relay control signal to the relay drive circuit.