Sheet post-processing apparatus, image forming system and power saving control method

A power saving method in a sheet post-processing apparatus connected to an image forming apparatus,

• said sheet post-processing apparatus having:
• a conveying portion which receives and conveys a sheet discharged from an apparatus on an upstream side, and discharges the sheet to an apparatus on a downstream side or a discharge tray;
• and
• a sheet post-processing portion which carries out post-processing on the sheet, and
• said power saving method comprising:
• a power saving control step of rendering said sheet post-processing apparatus into a power saving state in which electric power supply to said sheet post-processing portion is interrupted and electric power supply to said conveying portion is maintained;
• a judging step of judging whether there is instructions for a post-processing operation or not;
• and
• a sheet conveying step of conveying the sheet to the apparatus on the downstream side or the discharge tray with use of said conveying portion to which the electric power is maintained, when it is judged that there is no instructions for the post-processing operation in said judging step, and even if said sheet post-processing apparatus is in said power saving state.