Image forming apparatus and bias power supply apparatus and method

A bias power supply apparatus comprising:

• an output transformer that includes a primary winding and a secondary winding and outputs an alternating current voltage to a load connected to the secondary winding;
• a switching unit that supplies a current to the primary winding of the output transformer by performing switching on the basis of an alternating current setting signal for setting a frequency of the alternating current voltage;
• and
• a current controller that is disposed between the primary winding of the output transformer and the switching unit and has first impedance and second impedance, the second impedance being greater than the first impedance, wherein the first impedance is set when the frequency of the alternating current voltage is a first frequency and the second impedance is set when the frequency of the alternating current voltage is a second frequency, the second frequency being lower than the first frequency, thereby controlling a current flowing between the primary winding of the output transformer and the switching unit,
• wherein the current controller includes a current control transformer haying a primary winding and a secondary winding, and connects the primary winding of the output transformer and the switching unit via the primary winding of the current control transformer, and controls inductance of the primary winding of the current control transformer by using a current flowing through the secondary winding of the current control transformer, thereby setting the first impedance and the second impedance.

A bias power supply method comprising:

• outputting an alternating current voltage to a load connected to a secondary winding of an output transformer;
• supplying a current to a primary winding of the output transformer by performing switching on the basis of an alternating current setting signal for setting a frequency of the alternating current voltage;
• setting a first impedance when the frequency of the alternating current voltage is a first frequency and setting a second impedance when the frequency of the alternating current voltage is a second frequency, the second frequency being lower than the first frequency, the second impedance being greater than the first impedance, thereby controlling a current flowing between the primary winding of the output transformer and a switching unit;
• and
• controlling an inductance of a primary winding of a current control transformer by using a current flowing through a secondary winding of the current control transformer, thereby setting the first impedance and the second impedance, the primary winding of the current control transformer connecting the primary winding of the output transformer and the switching unit.