US Patent 7831158 Image forming apparatus capable of controlling toner supply

An image forming apparatus, including a toner supplying unit to supply toner, a toner transporting unit to transport the toner supplied from the toner supplying unit, a sensor to sense a density of the toner transported by the toner transporting unit, a compensating signal generating unit to compensate for amounts of the toner pre-supplied by the toner supplying unit, and a control unit to generate a control signal to control the toner supplying unit by receiving a sensing signal of the sensor as an input signal and a compensating signal of the compensating signal generating unit as a feedback signal.