Patent ID: 7680427

Claim:
An image forming apparatus comprising: a high voltage power supply apparatus that applies a bias voltage at least to a developing roller of a developing unit, the high voltage power supply apparatus comprising: a transformer that increases an AC voltage and includes a main winding and a sub winding on the secondary side thereof; a first capacitor whose first end is connected to a common connection point between the main and sub windings; a second capacitor whose first end is connected to one end of the sub winding which is not the common connection point side; a zener diode having a first end connected to the second end of the first capacitor and a second end connected to the second end of the second capacitor; and a DC voltage application section that applies a DC voltage to the zener diode, wherein a voltage generated in the second end of the first capacitor is used as a voltage to be applied to the developing roller, and the developing roller is made of metal.