A power supply system comprising: a switching power supply that includes a transformer configured to have a voltage induced on a secondary side by oscillation of a primary side and a rectifying/smoothing circuit which is configured to rectify and smooth the induced voltage, the switching power supply being configured to output a first output voltage in a normal output mode; a step-down circuit that is provided on an output side of the switching power supply and is configured to reduce the first output voltage to a second output voltage; wherein the switching power supply is configured to output a third output voltage, less than the first output voltage, in a low output mode; wherein the power supply system further comprises: a control device that is configured to control the switching of the switching power supply between the normal output mode, the low output mode, and an off mode that stops the oscillation of the primary side of the transformer; and an electric storage unit configured to be charged by the output of the second output voltage by the step-down circuit in the normal output mode, to be charged by the output of the third output voltage by the switching power supply in the low output mode, and to supply power to the control device in the off mode, wherein the control device is configured to, when charging is needed in the off mode, control the switching power supply to output the third output voltage, thereby charging the electric storage unit. a switching power supply that includes a transformer configured to have a voltage induced on a secondary side by oscillation of a primary side and a rectifying/smoothing circuit which is configured to rectify and smooth the induced voltage, the switching power supply being configured to output a first output voltage in a normal output mode; a step-down circuit that is provided on an output side of the switching power supply and is configured to reduce the first output voltage to a second output voltage; wherein the switching power supply is configured to output a third output voltage, less than the first output voltage, in a low output mode; wherein the power supply system further comprises: a control device that is configured to control the switching of the switching power supply between the normal output mode, the low output mode, and an off mode that stops the oscillation of the primary side of the transformer; and an electric storage unit configured to be charged by the output of the second output voltage by the step-down circuit in the normal output mode, to be charged by the output of the third output voltage by the switching power supply in the low output mode, and to supply power to the control device in the off mode, a control device that is configured to control the switching of the switching power supply between the normal output mode, the low output mode, and an off mode that stops the oscillation of the primary side of the transformer; and an electric storage unit configured to be charged by the output of the second output voltage by the step-down circuit in the normal output mode, to be charged by the output of the third output voltage by the switching power supply in the low output mode, and to supply power to the control device in the off mode, wherein the control device is configured to, when charging is needed in the off mode, control the switching power supply to output the third output voltage, thereby charging the electric storage unit.