Power source device, image forming apparatus and device

A power source device of a full bridge system comprising:

• a rectifying circuit configured to rectify an AC voltage of an AC power source;
• a smoothing capacitor connected to the rectifying circuit in parallel and configured to smooth the voltage rectified by the rectifying circuit;
• a first switching element;
• a second switching element connected to the first switching element in series;
• a third switching element;
• a fourth switching element connected to the third switching element in series;
• an inductor element of which one end is connected to a connecting point of the first switching element and the second switching element and of which the other end is connected to a connecting point of the third switching element and the fourth switching element;
• and
• a control portion configured to control a switching operation of the first switching element, the second switching element, the third switching element and the fourth switching element,
• wherein the first switching element and the second switching element which are connected in series are connected to the smoothing capacitor in parallel, and the third switching element and the fourth switching element which are connected in series are connected to the smoothing capacitor in parallel, and
• the power source device further comprising:
• a first capacitor connected to the first switching element in parallel;
• a second capacitor connected to the second switching element in parallel;
• a third capacitor connected to the third switching element in parallel;
• and
• a fourth capacitor connected to the fourth switching element in parallel,
• wherein when
• a combined capacitance of an electrostatic capacitance between a drain terminal and a source terminal of the first switching element and an electrostatic capacitance of the first capacitor is defined as a first electrostatic capacitance,
• a combined capacitance of an electrostatic capacitance between a drain terminal and a source terminal of the second switching element and an electrostatic capacitance of the second capacitor is defined as a second electrostatic capacitance,
• a combined capacitance of an electrostatic capacitance between a drain terminal and a source terminal of the third switching element and an electrostatic capacitance of the third capacitor is defined as a third electrostatic capacitance, and
• a combined capacitance of an electrostatic capacitance between a drain terminal and a source terminal of the fourth switching element and an electrostatic capacitance of the fourth capacitor is defined as a fourth electrostatic capacitance,
• at least one value of electrostatic capacitance of the first electrostatic capacitance, the second electrostatic capacitance, the third electrostatic capacitance and the fourth electrostatic capacitance is a value different from the other electrostatic capacitances.