Switching power supply device

A switching power supply device, comprising:

• a passive electromagnetic interference (EMI) filter to receive an alternating current (AC) input or a direct current (DC) input through an input terminal of the switching power supply device, the passive EMI filter including capacitors respectively coupled to an output terminal of the passive EMI filter and a ground GND;
• a first soft switching converter coupled to the output terminal of the passive EMI filter and the ground GND, the first soft switching converter including:
• a primary side switching circuit coupled to the output terminal of the passive EMI filter;
• an isolation transformer including a primary winding coupled to the primary side switching circuit and a secondary winding, a homonymous end of the primary winding being coupled to a node coupling windings in the primary side switching circuit;
• and
• a rectification circuit coupled to the secondary winding and an output terminal of the switching power supply device, and including a rectifier;
• and
• a first common-mode noise reduction path coupled between a node that couples one of the capacitors of the passive EMI filter and the output terminal of the passive EMI filter and a node that couples a homonymous end of the secondary winding and the rectifier in the rectification circuit;
• wherein
• the first common-mode noise reduction path includes an impedance.