Switching power supply device

A switching power supply device comprising:

• a power conversion circuit that is provided at a multilayer printed board and includes a plurality of switching circuits and a controller configured to control the plurality of switching circuits;
• a plurality of windings that are at the multilayer printed board, each of the plurality of windings configuring an inductor having a first end and a second end;
• and
• a magnetic sheet that is provided on one or both of an upper face of the multilayer printed board and a lower face of the multilayer printed board, the magnetic sheet being made of a soft magnetic body configuring a magnetic layer,
• wherein
• the plurality of windings have conductor patterns at the multilayer printed board,
• the plurality of windings are arranged along a plane of the multilayer printed board,
• the first ends of the plurality of windings are connected to the plurality of switching circuits, and the second ends of the plurality of windings are connected to a common output,
• the controller is configured to control the plurality of switching circuits to periodically vary a position and a time at which magnetic flux generated by current flowing to the plurality of windings reaches maximum magnetic flux density, and
• the magnetic sheet is made of soft ferrite and an Ni—Zn—Cu sintered ferrite material with a maximum relative permeability at a frequency of 10 MHz or more.

A switching power supply device comprising:

• a power conversion circuit that is provided at a multilayer printed board and includes a plurality of switching circuits and a controller configured to control the plurality of switching circuits;
• a plurality of windings that are at the multilayer printed board, each of the plurality of windings configuring an inductor having a first end and a second end;
• and
• a magnetic sheet that is provided on one or both of an upper face of the multilayer printed board and a lower face of the multilayer printed board, the magnetic sheet being made of a soft magnetic body configuring a magnetic layer,
• wherein
• the plurality of windings have conductor patterns at the multilayer printed board,
• the plurality of windings are arranged along a plane of the multilayer printed board,
• the first ends of the plurality of windings are connected to the plurality of switching circuits, and the second ends of the plurality of windings are connected to a common output,
• the controller is configured to control the plurality of switching circuits to periodically vary a position and a time at which magnetic flux generated by current flowing to the plurality of windings reaches maximum magnetic flux density,
• using a build-up method for forming a plurality of base material layers, the plurality of windings are formed at the multilayer printed board by electrically connecting the conductor patterns formed at the plurality of base material layers, and
• of the plurality of base material layers configuring the multilayer printed board, the conductor patterns configuring the plurality of windings at an intermediate layer sandwiched between a bottom layer and a front layer include conductor patterns of two types, and the conductor patterns of two types are arranged alternately in a lamination direction.