Patent ID: 8538282

Claim:
An image forming apparatus comprising: one or a plurality of photosensitive drums; a plurality of chargers each having a grid, which are provided for the one photosensitive drum or are respectively provided for the plurality of photosensitive drums and charge the one or plurality of photosensitive drums; a voltage applying unit that generates a charging voltage and applies the generated charging voltage to the plurality of chargers in common; a plurality of grid constant voltage circuits which are respectively provided for the plurality of chargers, each of the plurality of grid constant voltage circuits including: a voltage detecting unit that detects a voltage based on a grid voltage which is generated in the grid in accordance with the applied charging voltage; a first current detecting unit that detects a first current flowing into the voltage detecting unit; a voltage control line that makes the grid voltage constant; and an operation control device that performs a feedback control through the voltage control line such that the detected voltage detected by the voltage detecting unit has a predetermined voltage value; at least one of second current detecting units which are respectively provided for at least one of the grid constant voltage circuits, and detect a second current flowing into the voltage control line; and a controller that controls the voltage applying unit such that a sum of the first current and the second current corresponding to one of the plurality of chargers becomes a predetermined current value.