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 at a preceding stage of the switching power supply on an AC input line, and which is configured to switch a connection state of the switching power supply with the AC power supply in response to an input of a relay drive signal;
• a control device configured to generate a relay control signal for controlling the latching relay;
• a relay drive circuit configured to generate the relay drive signal in response to an input of the relay control signal, and to drive the latching relay by the relay drive signal;
• a battery configured to supply electric power to the control device and the relay drive circuit in a case where the control device and the relay drive circuit are connected;
• and
• a switch configured to switch the connection state of the battery with respect to the control device and the relay drive circuit.