Patent ID: 7496312

Claim:
An auxiliary power supply unit, which is attachable to and detachable from an image forming apparatus that receives electric power from a commercial power supply and the auxiliary power supply unit, comprising: a charge unit including one or more capacitors configured to store electric charge; a terminal configured to establish electrical connection for discharge with the apparatus; and a discharge unit situated on a discharge path that is provided inside the auxiliary power supply unit to electrically connect between said charge unit and said terminal, said discharge path having an open/closed state thereof controlled to be open at one time and closed at another time during a period when the auxiliary power supply unit is attached to and receives an electric power based on the commercial power supply from a power supply unit of the image forming apparatus, said discharge path in the closed state thereof supplying an electric power from the charge unit to the image forming apparatus, said discharge path being opened in response to a stoppage of supply of the electric power that is based on the commercial power supply from the image forming apparatus when the auxiliary power supply unit is detached from the image forming apparatus.