Power supply device and image forming apparatus

An image forming apparatus comprising:

• an image forming unit configured to form an image onto a recording material;
• a power supply device configured to supply electric power to said image forming unit, said power supply device including,
• a transformer including a primary winding, a secondary winding and an auxiliary winding;
• a first circuit in which a first capacitor and a first rectifying element are connected in series, said first circuit being connected to said primary winding in parallel;
• a switching element of which one end is connected to one end of said primary winding and configured to be switched between an ON state and an OFF state;
• a second circuit in which said auxiliary winding and a second rectifying element are connected in series, said second circuit being connected between a connecting point, to which said first capacitor and said first rectifying element are connected, and the other end of said switching element;
• a control portion including a control terminal and configured to control the ON state and the OFF state of said switching element, and
• a third circuit including at least one resistor and a third rectifying element, and connected to a gate terminal of said switching element,
• wherein in a case in which said control portion turns on said switching element, a current flows from said control portion via said third circuit to said gate terminal of said switching element and a current flows from said first capacitor to said switching element,
• wherein in a case in which said control portion turns off said switching element, a current flows from said gate terminal of said switching element to said control portion via said third circuit, and
• wherein, in said third circuit, a resistance value in the case in which the current flows from said control portion via said third circuit to said gate terminal of said switching element is smaller than a resistance value in the case in which the current flows to said control portion via said third circuit out of said gate terminal of said switching element.