Switching power supply device

A switching power supply device that converts a voltage input from a DC power supply into power and supplies the power to a load, the switching power supply device comprising:

• a power conversion circuit including an input capacitor, an output capacitor, a switching element, and an inductor;
• a common-mode choke coil between the DC power supply and the power conversion circuit;
• and
• a multilayer circuit board on which the power conversion circuit and the common-mode choke coil are mounted, wherein
• the multilayer circuit board includes an insulating base material, a first reference potential wiring pattern, a second reference potential wiring pattern, a DC positive potential wiring pattern, and an input positive potential wiring pattern,
• each of the first reference potential wiring pattern, the second reference potential wiring pattern, the DC positive potential wiring pattern, and the input positive potential wiring pattern is on the insulating base material,
• the common-mode choke coil includes
• a first winding of which one end is connected to a low-potential side of the DC power supply via the first reference potential wiring pattern and another end is connected to a low-potential side of the load via the second reference potential wiring pattern, and
• a second winding of which one end is connected to a high-potential side of the DC power supply via the DC positive potential wiring pattern and another end is connected to an input side of the power conversion circuit via the input positive potential wiring pattern,
• the power conversion circuit has a portion that overlaps the second reference potential wiring pattern in plan view in a direction orthogonal to a plane of the insulating base material,
• the second reference potential wiring pattern is not in a region that overlaps the first reference potential wiring pattern in plan view in the direction orthogonal to the plane of the insulating base material,
• the input positive potential wiring pattern is not in a region that overlaps the DC positive potential wiring pattern in plan view in the direction orthogonal to the plane of the insulating base material,
• the first reference potential wiring pattern, the second reference potential wiring pattern, the DC positive potential wiring pattern, the input positive potential wiring pattern, the power conversion circuit, and the common-mode choke coil configure a noise equalization circuit that is an electric closed circuit, and
• the noise equalization circuit is configured to cancel out noise caused by a switching operation of the switching element.