Switching power supply apparatus and electric power supply system

A switching power supply apparatus comprising:

• a pair of input terminals configured to receive an input voltage;
• a pair of output terminals configured to output an output voltage;
• a transformer including a primary winding and a secondary winding;
• an inverter circuit disposed between the pair of input terminals and the primary winding, and including:
• a first switching device and a second switching device;
• a first rectifying device and a second rectifying device;
• a resonant inductor;
• and a resonant capacitor;
• a rectifying and smoothing circuit disposed between the pair of output terminals and the secondary winding, and including a rectifying circuit and a smoothing circuit, the rectifying circuit including two or more rectifying devices, the smoothing circuit including a smoothing capacitor;
• a current detector configured to detect whether a current is flowing through at least one of the first rectifying device or the second rectifying device, the current detector being configured to only detect the current while a predetermined overcurrent condition occurs;
• and
• a driver configured to perform switching driving to control respective operations of the first switching device and the second switching device in the inverter circuit, wherein
• the first switching device and the second switching device are coupled in series to each other between a pair of coupling lines, each of the coupling lines being coupled to corresponding one of the pair of input terminals,
• the first rectifying device and the second rectifying device are coupled in series to each other between the pair of coupling lines,
• the resonant inductor and the primary winding are coupled in series to each other in no particular order between a first node and a second node, the first node being a node between the first switching device and the second switching device, the second node being a node between the first rectifying device and the second rectifying device,
• the resonant capacitor is disposed between the second node and one of the pair of coupling lines, and
• the driver is configured to perform the switching driving to cause both the first switching device and the second switching device to be set to an OFF state in a case where the current detector detects that the current is flowing through the at least one of the first rectifying device or the second rectifying device.