Image forming apparatus

An image forming apparatus comprising:

• a main body housing;
• a plurality of cartridges, each of which includes a photoconductor and a charger configured to charge the photoconductor, the cartridges being detachably installable in the main body housing;
• a voltage application unit to which chargers are connected in parallel and which is configured to apply a voltage to the chargers;
• a cartridge installation determination unit configured to determine whether or not each of the cartridges is installed;
• and
• a controller configured to exercise control over the voltage application unit, which control includes a constant-voltage control in which the voltage applied by the voltage application unit to the chargers is maintained at a predetermined voltage value, and a constant-current control in which an amount of an electric current found to be smallest among those of electric currents flowing through the chargers is maintained at a predetermined current value,
• wherein the controller is further configured to execute the constant-voltage control upon startup of an initial operation for preparation of printing, and to switch from the constant-voltage control to the constant-current control if the cartridge installation determination unit determines that all the cartridges are installed.