Abstract: A switching power supply unit includes: a transformer; an inverter circuit including first to fourth switching devices, first to third capacitors, first and second rectifying devices, a resonant inductor, and a resonant capacitor; and a driver. The first to fourth switching devices are coupled in series. The first and second capacitors are coupled in series. The first rectifying device is disposed between a first connection point between the first and second capacitors and a second connection point between the first and second switching devices. The second rectifying device is disposed between the first connection point and a third connection point between the third and fourth switching devices. The third capacitor is disposed between the second and third connection points. The resonant capacitor, the resonant inductor, and a primary winding are coupled in series between a fourth connection point between the second and third switching devices and the first connection point.

Abstract: A switching power supply unit includes a pair of input terminals, a pair of output terminals, a transformer, an inverter circuit, a rectifying and smoothing circuit, and a driver. The inverter circuit includes first to fourth switching devices, a first capacitor, a resonant inductor, and a resonant capacitor. The rectifying and smoothing circuit includes a rectifying circuit including rectifying devices, and a smoothing circuit. The first to fourth switching devices are coupled in series in this order between two input terminals constituting the pair of input terminals. The first capacitor is disposed between a connection point between the first and second switching devices and a connection point between the third and fourth switching devices. The resonant inductor, the resonant capacitor, and a primary winding are coupled in series in no particular order between a connection point between the second and third switching devices and one of the two input terminals.

Abstract: A switching power supply unit includes: a transformer; an inverter circuit including first to fourth switching devices, first to third capacitors, first and second rectifying devices, a resonant inductor, and a resonant capacitor; and a driver. The first to fourth switching devices are coupled in series. The first and second capacitors are coupled in series. The first rectifying device is disposed between a first connection point between the first and second capacitors and a second connection point between the first and second switching devices. The second rectifying device is disposed between the first connection point and a third connection point between the third and fourth switching devices. The third capacitor is disposed between the second and third connection points. The resonant capacitor, the resonant inductor, and a primary winding are coupled in series between a fourth connection point between the second and third switching devices and the first connection point.

Abstract: A switching power supply unit includes a pair of input terminals, a pair of output terminals, a transformer, an inverter circuit, a rectifying and smoothing circuit, and a driver. The inverter circuit includes first to fourth switching devices, a first capacitor, a resonant inductor, and a resonant capacitor. The rectifying and smoothing circuit includes a rectifying circuit including rectifying devices, and a smoothing circuit. The first to fourth switching devices are coupled in series in this order between two input terminals constituting the pair of input terminals. The first capacitor is disposed between a connection point between the first and second switching devices and a connection point between the third and fourth switching devices. The resonant inductor, the resonant capacitor, and a primary winding are coupled in series in no particular order between a connection point between the second and third switching devices and one of the two input terminals.