Patent ID: 6619774
Filing Date: 2003-09-16
Classification: B41J

Abstract:
An image forming device for use in combination with an external device, the image forming device comprising:a printing unit that normally performs an image forming operation by a primary power source installed in the external device; an auxiliary power source unit connectable to the printing unit for supplying power to the printing unit instead of the primary power source; detecting means that detects a power supply condition of at least one of the primary power source and the auxiliary power source unit; means for stopping power supply from the primary power source to the printing unit in accordance with the power supply condition detected by the detecting means, wherein the power supply condition is a voltage level of the primary power source, the detecting means detecting the voltage level of the primary power source; and wherein the stopping means stops power supply from the primary power source to the printing unit if the voltage level detected by the detecting means is lower than a predetermined voltage level, the printing unit comprising: a print head that forms an image on a printing sheet; driving means for driving the print head; and control means for processing printing data and controlling the driving means; and wherein the stopping means further comprises a switching means that switches a power connection to the driving means from the primary power source to the auxiliary power source unit if the detection means detects the voltage level lower than the predetermined voltage level during a printing operation, wherein the switching means comprises means for maintaining the power connection between the primary power source and the control means during the printing operation even if the detection means detects the voltage level lower than the predetermined voltage level.