Patent ID: 6845222

Claim:
An image forming apparatus having an electrostatic latent image carrier, a charging device and a developing device for forming an image by charging a surface of said electrostatic latent image carrier by said charging device, to which a charging voltage is applied, effecting image exposure on a charged region of the surface of said electrostatic latent image carrier to form an electrostatic latent image, and developing the electrostatic latent image by said developing device, to which a developing bias voltage is applied, and comprising: an output variable power source common to said charging device and said developing device for applying the charging voltage to said charging device and applying the developing bias voltage to said developing device; a power source output control portion for controlling an output of said power source; and a voltage changing device interposed between said charging device and said power source and/or between said developing device and said power source, wherein when the voltages applied to said charging and developing devices are raised to voltages required for image formation, respectively, said power source output control portion controls the output of said power source to perform the raising of said applied voltages for a predetermined time while keeping a potential difference for suppressing movement of developer onto said electrostatic latent image carrier between said voltages applied to said charging and developing devices, and wherein said voltage changing device can perform voltage transformation in two or more steps, and said power source output control portion controls the output of said power source for raising said applied voltages, while controlling an output of said voltage changing device to suppress movement of the developer to said electrostatic latent image carrier.