Switching power supply apparatus

A switching power supply apparatus comprising:

• a pair of input terminals configured to receive an input voltage, and including a first input terminal and a second input terminal;
• a pair of output terminals configured to output an output voltage;
• a transformer including a primary winding and a secondary winding;
• a switching circuit disposed between the pair of input terminals and the primary winding, and including a first coupling line, a second coupling line, first to fourth switching devices, a first input capacitor, a second input capacitor, a first diode, a second diode, a first clamp diode, a second clamp diode, and a resonant coil, the first coupling line and the second coupling line being disposed in parallel to each other between the first input terminal and the second input terminal,
• a rectifying circuit disposed between the pair of output terminals and the secondary winding, and including a plurality of rectifiers;
• a smoothing circuit disposed between the pair of output terminals and the rectifying circuit;
• and
• a control circuit configured to perform switching driving to control respective operations of the first to fourth switching devices, wherein
• in the switching circuit,
• the first input capacitor and the second input capacitor are disposed on the first coupling line in series to each other and in this order in a direction from the first input terminal toward the second input terminal;
• the first to fourth switching devices are disposed on the second coupling line in series to each other and in this order in the direction from the first input terminal toward the second input terminal;
• the first diode is disposed between a first node and a second node, and the second diode is disposed between a third node and the first node, the first node being a node between the first input capacitor and the second input capacitor, the second node being a node between the first switching device and the second switching device, the third node being a node between the third switching device and the fourth switching device;
• the resonant coil and the primary winding are disposed in series to each other between a fourth node and the first node, the fourth node being a node between the second switching device and the third switching device;
• and
• the first clamp diode is disposed between a fifth node and the first input terminal, and the second clamp diode is disposed between the second input terminal and the fifth node, the fifth node being a node between the resonant coil and the primary winding.