Patent ID: 8295724

Claim:
An image forming apparatus comprising: an image carrier configured to carry a developer image developed by a developer; a transfer device configured to transfer the developer image to a recording medium; an applying circuit configured to apply a transfer bias voltage to the transfer device, the applying circuit including an active device; and a controller configured to control the applying circuit with a predetermined control signal during a start-up mode of the applying circuit and during a normal mode of the applying circuit, the normal mode being subsequent to the start-up mode; wherein the control signal is a PWM signal, wherein during the start-up mode of the applying circuit, the controller sets a first duty ratio of the PWM signal for a first term and a second duty ratio of the PWM signal for a second term, the second duty ratio being larger than the first duty ratio, wherein an interval period is interposed subsequent to the first term, the second term being subsequent to the interval period, the controller setting a third duty ratio of the PWM signal for the interval period, the third duty ratio being larger than zero and smaller than both the first duty ratio and the second duty ratio, and wherein the PWM signal with the third duty ratio does not activate the active device in the interval period.