Technique for reducing power consumed by electric equipment

An image forming apparatus having a normal power supply mode and a power saving mode that consumes less power than the normal power supply mode, the apparatus comprising:

• an AC cutting circuit, connected serially to a power supply line through which AC current is input, configured to turn the supply of the AC current on and off;
• a rectifying and smoothing circuit configured to rectify the AC current and smoothes the AC current using a capacitor;
• a DC voltage generating circuit, connected to the rectifying and smoothing circuit, configured to generate a DC voltage;
• and
• a controller, operating under the DC voltage generated by the DC voltage generating circuit, configured to cause the AC cutting circuit to turn the supply of the AC current off when the electric equipment shifts to the power saving mode, and then cause the AC cutting circuit to turn the supply of the AC current on every predetermined amount of time in order to charge the capacitor.

An image forming apparatus comprising:

• a switch serially connected to one of two power supply lines through which AC current is input;
• a rectifying circuit configured to rectify the AC current and smoothes the AC current using a capacitor;
• a DC voltage generating circuit configured to generate a DC voltage based on an output of the rectifying circuit;
• and
• a controller, operating under the DC voltage generated by the DC voltage generating circuit, configured to repeatedly turn the switch on and off when the image forming apparatus shifts from an image forming mode in which the image forming apparatus can form images to a power saving mode that consumes less power than the image forming mode,
• wherein the DC voltage generating circuit is further configure to generate the DC voltage using a voltage supplied by the capacitor when the controller sets the switch to off, and the controller is configured to set the switch on before a both-end voltage at the capacitor drops below a lower limit of operation voltage of the DC voltage generating circuit.