A power supply system includes: a switching power supply, which rectifies and smoothes an AC voltage of an AC power supply to generate a first DC voltage in a normal mode; a control unit, which controls the switching power supply to switch between the normal mode and a power saving mode; and a low-capacity power supply circuit, which supplies power to the control unit in the power saving mode, and which includes: a first capacitor, which includes a first electrode connected to one end of the AC power supply, and a second electrode; a second capacitor, which includes a first electrode connected to the other end of the AC power supply, and a second electrode; a rectifying circuit, which rectify an AC voltage applied to both capacitors; and a smoothing circuit, which smoothes the rectified AC voltage to generate a smooth voltage.