Switching Power Supply Unit

Abstract

This switching power supply device is provided with a circuit substrate (1) on which a plurality of inductor windings are formed, and common magnetic bodies mounted to both sides of the circuit substrate (1). The circuit substrate (1) includes common wiring that commonly electrically connects respective one ends of the plurality of inductor windings. The common magnetic bodies each includes an inner leg (4i) that is inserted to the inside of the plurality of inductor windings and an outer leg (4o) that is inserted to the outside of the plurality of inductor windings. A smoothing capacitor (Co0) connected between a common wiring (3E) and a ground wiring (7) is mounted on the circuit substrate (1), whereby a smoothing filter is configured with an inductance of the common wiring and the smoothing capacitor (Co0). The plurality of inductor windings are magnetically coupled to one another, while the common wiring and the plurality of inductor windings are substantially not magnetically coupled.

Description

[Technical field]

[0001] The present invention relates to a switching power supply device including a plurality of inductors that are magnetically coupled to one another and a composite inductor that constitutes a smoothing inductor that smoothes an output current and an output voltage. [Background technology]

[0002] In a switching power supply module that operates in multiphase, it is desirable for the current ripple flowing through the inductor to be small, and for the load response to be good to achieve high-speed load response. In the steady state, increasing the LC value in the output smoothing circuit reduces the ripple, but in the transient state of load fluctuations, decreasing the LC value will speed up the response speed and improve the characteristics. For this reason, it is necessary to determine the LC value taking into account both the steady state and the transient state.

[0003] In recent years, there has been active development of technology that magnetically couples inductors to multiphase power supplies. By utilizing the effect of canceling out the magnetic flux generated by the current flowing through one inductor and the current flowing through the other inductor, it is possible to make the inductor smaller and reduce ripple current. In particular, the more phases a multiphase power supply has and the more inductors it uses, the greater the effect and impact.

[0004] As a composite inductor in which a plurality of inductors are coupled, Patent Document 1 discloses a coupled inductor having a structure in which a conductor is wound around each crosspiece of a ladder-shaped rail. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] U.S. Patent No. 8,294,544 Summary of the Invention [Problem to be solved by the invention]

[0006] When using the ladder core shown in Patent Document 1, when increasing the number of inductors to be coupled, the cores must be arranged horizontally or vertically, making the overall structure complex. Such coupled inductors are mounted as components on a circuit board and modularized, so the assembled module becomes expensive. In addition, when using a ladder core, as the number of inductors to be coupled increases, the winding structure becomes more complex, and the assembly cost of the coupled inductor becomes an issue.

[0007] Furthermore, by providing multiple inductors, the current ripple flowing through each inductor can be reduced, but there is a problem in that the current ripple contained in the output current obtained by combining the currents flowing through the inductors and the voltage ripple superimposed on the output voltage are not reduced or may actually increase due to the unevenness of the combined output current.

[0008] Therefore, an object of the present invention is to provide a high-performance switching power supply device with excellent power integrity (ensuring power supply quality), which is equipped with a composite inductor that has excellent smoothing inductor performance and reduces the current ripple contained in the output current obtained by combining the currents flowing through each inductor and the voltage ripple contained in the output voltage, by configuring a plurality of inductors that are magnetically coupled to each other on a single circuit board, thereby forming a smoothing inductor that is magnetically independent from the coupled inductors. [Means for solving the problem]

[0009] As an example of a switching power supply device according to the present disclosure, A switching power supply device including a plurality of power conversion circuits each having a composite inductor and a control circuit for each of the power conversion circuits, The composite inductor includes a circuit board on which a plurality of inductor windings are formed, and a common magnetic body incorporated in the circuit board; the circuit board has an electrical connection point that connects one end of each of the plurality of inductor windings to a common potential; a common wiring electrically connecting the electrical connection point and one of the output terminals; the common magnetic body has an inner leg that passes through an inner side of the plurality of inductor windings and an outer leg that passes through an outer side of the plurality of inductor windings, a smoothing capacitor electrically connected between the one output terminal and the other output terminal and mounted on the circuit board; a smoothing filter is formed by an inductance of the common wiring and the smoothing capacitor, the plurality of inductor windings have a first magnetic coupling coefficient due to the common magnetic body, and the common wiring and the plurality of inductor windings have a second magnetic coupling coefficient; The absolute value of the first magnetic coupling coefficient is 5 times or more larger than the absolute value of the second magnetic coupling coefficient. It is characterized by: Effect of the Invention

[0010] According to the present invention, a high-performance switching power supply device with excellent power integrity (ensuring power supply quality) is obtained by integrating a composite inductor that is configured by magnetically coupling a plurality of inductors to each other, canceling out the magnetic fluxes generated by passing current through a plurality of windings formed on a single circuit board, reducing the magnetic flux density distributed in the magnetic material and suppressing magnetic saturation, and is small, low-profile, and equipped with a coupled inductor with excellent power conversion characteristics, and a smoothing inductor with excellent smoothing characteristics for reducing output current ripple and output voltage ripple. This allows for a small and thin device that can achieve a highly accurate output voltage and suppression of output voltage fluctuations. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view of a power module 201 including a composite inductor according to a first embodiment. [Diagram 2] FIG. 2 is a perspective view of the circuit board of the power supply module 201. [Diagram 3] FIG. 3 is an exploded perspective view of the power supply module 201. [Figure 4] FIG. 4 is a circuit diagram of a multiphase power supply device 301 according to the first embodiment. [Diagram 5] Fig. 5(A) is a waveform diagram of a current flowing through one inductor of multiphase power supply device 301. Fig. 5(B) is a waveform diagram of a current flowing through one inductor of a multiphase power supply device as a comparative example. [Figure 6] FIG. 6 shows the relationship between the current ripple and the ratio of the leakage inductance Lk to the mutual inductance Lm. [Figure 7] 7(A) and 7(B) are partial cross-sectional views of power supply module 201, and FIG. 7(C) is a partial plan view of power supply module 201. FIG. [Figure 8] 8(A), 8(B), and 8(C) are partial cross-sectional and partial plan views of a power supply module 201 that is different from the examples shown in FIGS. 7(A), 7(B), and 7(C). [Figure 9] FIG. 9 is a partial cross-sectional view of a power supply module 201 which is further different from the example shown in FIG. 8(B). [Figure 10] FIG. 10 is an exploded perspective view of a power supply module 202 according to the second embodiment. [Figure 11] FIG. 11 is an exploded perspective view of a power supply module 203 according to the third embodiment. [Figure 12] FIG. 12 is a perspective view of a power supply module 204 including a composite inductor according to the fourth embodiment. [Figure 13] FIG. 13 is a perspective view of the circuit board of the power supply module 204. [Figure 14] FIG. 14 is an exploded perspective view of the power supply module 204. [Figure 15] FIG. 15 is a circuit diagram of a multiphase power supply device 304 according to the fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, several specific examples will be given with reference to the drawings to show several embodiments for carrying out the present invention. In each drawing, the same reference numerals are given to the same parts. In consideration of the ease of explanation or understanding of the main points, the embodiments are shown divided into several embodiments for convenience of explanation, but partial replacement or combination of the configurations shown in different embodiments is possible. In the second and subsequent embodiments, the description of matters common to the first embodiment will be omitted, and only the differences will be described. In particular, similar actions and effects due to similar configurations will not be mentioned in each embodiment.

[0013] First Embodiment Fig. 1 is a perspective view of a power module 201 including a composite inductor according to a first embodiment. Fig. 2 is a perspective view of a circuit board of the power module 201. Fig. 3 is an exploded perspective view of the power module 201.

[0014] The power supply module 201 includes a circuit board 1, a plurality of components mounted on the circuit board 1, and a lower magnetic body 4B and an upper magnetic body 4U into which the circuit board 1 is assembled from both sides. The lower magnetic body 4B and the upper magnetic body 4U constitute a "common magnetic body" according to the present invention.

[0015] As shown in Fig. 2, four inductor windings 2A, 2B, 2C, and 2D are formed on the circuit board 1. In addition, common wiring 3A, 3B, 3C, 3D, and 3E are formed on the circuit board 1 to electrically connect one end of each of the inductor windings 2A, 2B, 2C, and 2D in common. Furthermore, an input power supply wiring 6 and a ground wiring 7 are formed on the circuit board 1. The ground wiring 7 corresponds to the "reference potential wiring" according to the present invention. The inductor windings 2A, 2B, 2C, and 2D and the common wiring 3A, 3B, 3C, and 3D are formed in a 90° rotationally symmetric relationship along the surface of the circuit board 1.

[0016] Circuit board 1 is a multi-layer circuit board, and inductor windings 2A, 2B, 2C, and 2D include multiple layers of conductor patterns formed on circuit board 1 and multiple via conductors that connect these multiple conductor patterns between layers. With this configuration, the parasitic resistance of inductor windings 2A, 2B, 2C, and 2D can be reduced, and power loss can be reduced.

[0017] As shown in Fig. 3, the circuit board 1 has an opening 5i formed inside the inductor windings 2A, 2B, 2C, and 2D. Also, an opening 5o is formed outside the inductor windings 2A, 2B, 2C, and 2D. The upper surface of the lower magnetic body 4B has an inner leg 4i that passes through the opening 5i, and an outer leg 4o that passes through the opening 5o. The lower surface of the upper magnetic body 4U has an outer leg 4o that passes through the opening 5o. The height of the outer leg 4o of the lower magnetic body 4B plus the height of the outer leg 4o of the upper magnetic body 4U is equal to the height of the inner leg 4i.

[0018] The lower magnetic body 4B and the upper magnetic body 4U are assembled so as to sandwich the circuit board 1 from both sides. An adhesive layer having a relative permeability of 1 or more is provided on the opposing surfaces of the lower magnetic body 4B and the upper magnetic body 4U to bond the lower magnetic body 4B and the upper magnetic body 4U. This adhesive layer having a relative permeability of 1 or more is a solidified layer of an adhesive in which magnetic powder such as ferrite powder or metal powder is kneaded into an adhesive.

[0019] Four inductors are formed by the lower magnetic body 4B, the upper magnetic body 4U and the inductor windings 2A, 2B, 2C, and 2D. The inductors are also formed by a common wiring 3E. The inductor windings 2A, 2B, 2C, and 2D are magnetically coupled to each other by the lower magnetic body 4B and the upper magnetic body 4U, and the inductors formed by the common wiring are not substantially magnetically coupled to the inductor windings 2A, 2B, 2C, and 2D.

[0020] Inductor windings 2A, 2B, 2C, and 2D are in a 90° rotationally symmetric relationship along the surface of circuit board 1, so that each inductor has an equal magnetic coupling relationship with the other inductors, thereby reducing the variation in inductance of each inductor.

[0021] 4 is a circuit diagram of a multiphase power supply device 301 according to this embodiment. This multiphase power supply device 301 is composed of a power supply module 201 and a control circuit for the power supply module 201. The power supply module 201 is mounted on a circuit board of an electronic device. The control circuit for the power supply module 201 is provided on this circuit board.

[0022] The multi-phase power supply device 301 has an input power source E of a voltage Vi connected to an input section, and outputs an output voltage Vo from an output section.

[0023] The power supply module 201 includes switching ICs IC1, IC2, IC3, and IC4, inductors L0, L1, L2, L3, and L4, and smoothing capacitors Co0, Co1, Co2, Co3, and Co4. The inductors L1, L2, L3, and L4 are configured as a composite inductor 101. These inductors L1, L2, L3, and L4 are configured with inductor windings 2A, 2B, 2C, and 2D, a lower magnetic body 4B, and an upper magnetic body 4U. Each of IC1, IC2, IC3, and IC4 includes a high-side switching element and a low-side switching element.

[0024] The inductor L0 is configured from the common wiring 3E. The inductance of this common wiring 3E and the smoothing capacitors Co1, Co2, Co3, Co4, and Co0 configure a π-type smoothing filter. The cutoff frequency of this smoothing filter is set to the switching frequency or higher, thereby effectively reducing ripple voltage and switching noise.

[0025] As shown in FIG. 1 and FIG. 2, the circuit board 1 is equipped with switching ICs IC1, IC2, IC3, and IC4, and smoothing capacitors Co0, Co1, Co2, Co3, and Co4. The smoothing capacitors Co1, Co2, Co3, and Co4 are connected between the common wirings 3A, 3B, 3C, and 3D and the ground wiring 7. The smoothing capacitors Co1, Co2, Co3, and Co4 are connected between the vicinity of the connection between the inductor windings 2A, 2B, 2C, and 2D and the common wirings 3A, 3B, 3C, and 3D and the ground wiring 7. The smoothing capacitor Co0 is connected between the common wiring 3E and the ground wiring 7. This configuration can reduce the parasitic inductance generated in series with each of the smoothing capacitors Co1, Co2, Co3, Co4, and Co0, and can increase the attenuation in the attenuation range of the frequency characteristics of the smoothing filter.

[0026] The MPU shown in FIG. 4 is a control circuit for the power supply module 201. This MPU receives a power supply voltage from an input power supply E through a resistor Reg. An input capacitor Ci smoothes the input power supply voltage of the power supply module 201. The MPU provides multiphase switching control signals to IC1, IC2, IC3, and IC4. IC1, IC2, IC3, and IC4 pass multiphase (four-phase) currents through inductors L1, L2, L3, and L4. Smoothing capacitors Co0, Co1, Co2, Co3, and Co4 smooth the output voltage Vo.

[0027] Fig. 5(A) is a waveform diagram of a current flowing through one inductor of multiphase power supply device 301. Fig. 5(B) is a waveform diagram of a current flowing through one inductor of a multiphase power supply device as a comparative example. The conditions are as follows.

[0028] Via: 12V Vo: 1.8V Switching frequency: 500kHz Total capacitance of smoothing capacitor: 400μF Output current: 8A Here, when the mutual inductance of inductors L1, L2, L3, and L4 is represented by Lm and the leakage inductance is represented by Lk, in multiphase power supply device 301, Lm / Lk=1 and Lm+Lk=0.1 μF, and in the comparative multiphase power supply device, Lm=0 μF.

[0029] As is clear from comparing Figure 5(A) and Figure 5(B), by configuring the inductors L1, L2, L3, and L4 as a composite inductor, the ripple of the current flowing through each inductor L1, L2, L3, and L4 is suppressed. In this example, the current ripple is suppressed from 31A to 18A.

[0030] Figure 6 shows the relationship between the current ripple and the ratio of the leakage inductance Lk to the mutual inductance Lm. When Lm / Lk=1, the current ripple is at its minimum.

[0031] Next, some detailed structures of the inductor windings described above will be illustrated. Figures 7(A) and 7(B) are partial cross-sectional views of power supply module 201, and Figure 7(C) is a partial plan view of power supply module 201. Figure 7(C) shows only inductor winding 2A shown in Figures 2, 3, etc. Figure 7(A) is a cross-sectional view of part AA in Figure 7(C), and Figure 7(B) is a cross-sectional view of part BB in Figure 7(C).

[0032] The inductor winding 2A includes a plurality of layers of conductor patterns P formed on the circuit board 1, and via conductors V that connect the conductor patterns P of the plurality of layers between layers.

[0033] Figures 8(A), 8(B), and 8(C) are partial cross-sectional views and partial plan views of a power supply module 201 different from the examples shown in Figures 7(A), 7(B), and 7(C). Figures 8(A) and 8(B) are partial cross-sectional views of the power supply module 201, and Figure 8(C) is a partial plan view of the power supply module 201. Figure 8(C) shows only the inductor winding 2A shown in Figures 2, 3, etc. Figure 8(A) is a cross-sectional view of the AA portion in Figure 8(C), and Figure 8(B) is a cross-sectional view of the BB portion in Figure 8(C).

[0034] The inductor winding 2A includes multiple layers of conductor patterns P formed on the circuit board 1, and via conductors V that connect the multiple layers of conductor patterns P between layers. In this example, multiple via conductors are distributed in the planar direction. In this manner, the conductor patterns P may be connected between layers at multiple locations.

[0035] Fig. 9 is a partial cross-sectional view of a power supply module 201 which is further different from the example shown in Fig. 8(B). Fig. 7(B), Fig. 8(B) and the like show examples in which four layers of conductor patterns P are interlayer-connected by three layers of via conductors V, but in the example of Fig. 9, nine layers of conductor patterns P are interlayer-connected by eight layers of via conductors V. In this way, the conductor patterns may be further multi-layered.

[0036] Although inductor winding 2A is illustrated in Figures 7(A), 7(B), 7(C), 8(A), 8(B), 8(C), and 9, the same applies to other inductor windings.

[0037] Second Embodiment In the second embodiment, a power module having a different configuration of a common magnetic body and an opening portion from the power module shown in the first embodiment will be illustrated.

[0038] Fig. 10 is an exploded perspective view of a power module 202 according to the second embodiment. The power module 202 differs from the power module 201 of the first embodiment shown in Fig. 3 in the structure of the outer leg 4o and the opening 5o of the common magnetic body.

[0039] 3, the lower magnetic body 4B and the upper magnetic body 4U are provided with outer legs 4o that surround the entire circumference of the inner legs 4i, but in the second embodiment, the lower magnetic body 4B and the upper magnetic body 4U are provided with outer legs 4o that shield the spaces between the adjacent inner legs 4i. The other configurations are the same as those shown in the first embodiment.

[0040] As shown in this embodiment, the outer leg 4o provided on the common magnetic body does not have to be shaped to completely surround each of the inner legs 4i.

[0041] Third embodiment In the third embodiment, a power supply module having a different configuration of a common magnetic body and an opening portion from the power supply modules shown in the first and second embodiments will be illustrated.

[0042] Fig. 11 is an exploded perspective view of a power module 203 according to the third embodiment. The power module 203 differs from the power module 202 of the first embodiment shown in Fig. 10 in the structure of the outer legs 4o of the common magnetic body.

[0043] 10, the outer legs 4o that shield the adjacent inner legs 4i are provided on the lower magnetic body 4B and the upper magnetic body 4U, but in the third embodiment, the outer legs 4o are provided on the lower magnetic body 4B and the upper magnetic body 4U at positions surrounded by four inner legs 4i. The other configurations are the same as those shown in the first embodiment.

[0044] As shown in this embodiment, the outer leg 4o provided on the common magnetic body may be a single common outer leg formed at a position surrounded by each of the inner legs 4i.

[0045] Fourth embodiment In the fourth embodiment, a power supply module in which the inductor of the smoothing filter is configured by a common wiring and a common magnetic body will be illustrated.

[0046] Fig. 12 is a perspective view of a power module 204 including a composite inductor according to a fourth embodiment. Fig. 13 is a perspective view of a circuit board of the power module 204. Fig. 14 is an exploded perspective view of the power module 204.

[0047] The power supply module 204 includes a circuit board 1, a plurality of components mounted on the circuit board 1, and a lower magnetic body 4B and an upper magnetic body 4U into which the circuit board 1 is assembled from both sides. The lower magnetic body 4B and the upper magnetic body 4U constitute a "common magnetic body" according to the present invention.

[0048] 13, four inductor windings 2A, 2B, 2C, and 2D are formed on the circuit board 1. In addition, common wirings 3A, 3B, 3C, 3D, and 3E are formed on the circuit board 1 to electrically connect one end of each of the multiple inductor windings 2A, 2B, 2C, and 2D in common.

[0049] 14, an opening 5i is formed on the circuit board 1 inside the inductor windings 2A, 2B, 2C, and 2D. Also, an opening 5o is formed outside the inductor windings 2A, 2B, 2C, and 2D. Furthermore, openings 5o1 and 5o2 are formed on both sides of the common wiring 3E. On the upper surface of the lower magnetic body 4B, an inner leg 4i that passes through the opening 5i, an outer leg 4o that passes through the opening 5o, and outer legs 4o1 and 4o2 that pass through the openings 5o1 and 5o2 are formed.

[0050] Four inductors are formed by the lower magnetic body 4B, the upper magnetic body 4U and the inductor windings 2A, 2B, 2C, and 2D. Also, an inductor is formed by the lower magnetic body 4B, the upper magnetic body 4U and the common wiring 3E. The inductor windings 2A, 2B, 2C, and 2D are magnetically coupled to each other by the lower magnetic body 4B and the upper magnetic body 4U, and there is substantially no magnetic coupling between the inductor formed by the common wiring 3E and the inductor windings 2A, 2B, 2C, and 2D.

[0051] Inductor windings 2A, 2B, 2C, and 2D are in a 180° rotationally symmetric relationship along the surface of circuit board 1, so that each inductor has an equal magnetic coupling relationship with the other inductors, thereby reducing the variation in inductance of each inductor.

[0052] 15 is a circuit diagram of a multiphase power supply device 304 according to this embodiment. This multiphase power supply device 304 is composed of a power supply module 204 and a control circuit for the power supply module 204. The power supply module 204 is mounted on a circuit board of an electronic device. The control circuit for the power supply module 204 is provided on this circuit board.

[0053] The multi-phase power supply device 304 has an input power source E with a voltage Vi connected to an input section, and outputs an output voltage Vo from an output section.

[0054] The power supply module 204 includes switching ICs IC1, IC2, IC3, and IC4, inductors L0, L1, L2, L3, and L4, and smoothing capacitors Co0, Co1, Co2, Co3, and Co4. The inductors L0, L1, L2, L3, and L4 are configured as a composite inductor 104. The inductors L1, L2, L3, and L4 are configured as inductor windings 2A, 2B, 2C, and 2D, a lower magnetic body 4B, and an upper magnetic body 4U. Each of IC1, IC2, IC3, and IC4 includes a high-side switching element and a low-side switching element.

[0055] The inductor L0 is composed of the common wiring 3E, the lower magnetic body 4B, and the upper magnetic body 4U. The inductor L0 and the smoothing capacitors Co1, Co2, Co3, Co4, and Co0 constitute a π-type smoothing filter.

[0056] According to this embodiment, since the inductor L0 having a predetermined inductance can be formed even with a short common wiring 3E, the area of ​​the smoothing filter forming portion can be reduced. Also, since the line length of the common wiring 3E can be shortened, the parasitic resistance can be reduced and the attenuation amount in the attenuation region of the frequency characteristic of the smoothing filter can be increased.

[0057] Finally, the present invention is not limited to the above-described embodiments. Appropriate modifications and changes are possible by those skilled in the art. The scope of the present invention is indicated by the claims, not the above-described embodiments. Furthermore, the scope of the present invention includes modifications and changes from the embodiments within the scope of the claims and the equivalent scope. [Explanation of symbols]

[0058] Ci: Input capacitor Co0, Co1, Co2, Co3, Co4...smoothing capacitors E…Input power supply L0, L1, L2, L3, L4...Inductors P…Conductor pattern V…Via conductor Reg…Register 1...Circuit board IC1, IC2, IC3, IC4...Switching ICs 2A, 2B, 2C, 2D...Inductor windings 3A,3B,3C,3D,3E…Common wiring 4B…Lower magnetic body 4i…inner leg 4o, 4o1, 4o2...outside leg 4U…Upper magnetic body 5i,5o,5o1,5o2…opening 6…Input power wiring 7…Ground wiring 101, 104...Composite inductor 201, 202, 203, 204…Power supply modules 301, 304...Multiphase power supply

Claims

1. A switching power supply device including a plurality of power conversion circuits each having a composite inductor and a control circuit for each of the power conversion circuits, The composite inductor includes a circuit board on which a plurality of inductor windings are formed, and a common magnetic body incorporated in the circuit board; the circuit board has an electrical connection point that connects one end of each of the plurality of inductor windings to a common potential; a common wiring electrically connecting the electrical connection point and one of the output terminals; the common magnetic body has an inner leg that passes through an inner side of the plurality of inductor windings and an outer leg that passes through an outer side of the plurality of inductor windings, a smoothing capacitor electrically connected between the one output terminal and the other output terminal and mounted on the circuit board; the plurality of inductor windings have a first magnetic coupling coefficient due to the common magnetic body, and the common wiring and the plurality of inductor windings have a second magnetic coupling coefficient; an absolute value of the second magnetic coupling coefficient is smaller than an absolute value of the first magnetic coupling coefficient; a smoothing filter is formed by an inductor using the common magnetic material and the smoothing capacitor. A switching power supply device characterized by:

2. The plurality of power conversion circuits each include a switching element, The control circuit switches the switching elements with a phase difference between the switching operations.

2. The switching power supply device according to claim 1.

3. the circuit board has an opening located outside the common wiring and through which the outer leg is inserted; 3. The switching power supply device according to claim 1 or 2.

4. the plurality of inductor windings are arranged in a rotationally symmetric relationship along the surface of the circuit board; 3. The switching power supply device according to claim 1 or 2.

5. The circuit board is a multi-layer board, The plurality of inductor windings include a plurality of layers of conductor patterns formed on the circuit board and via conductors that connect the plurality of layers of conductor patterns to each other.

3. The switching power supply device according to claim 1 or 2.

6. a plurality of smoothing capacitors connected between the common wiring and the common potential; the smoothing capacitors are each disposed near a connection between the inductor windings and the common wiring, 3. The switching power supply device according to claim 1 or 2.

7. the common magnetic body includes a lower magnetic body and an upper magnetic body that are mounted on both sides of the circuit board, The lower magnetic body and the upper magnetic body are adhered to each other with an adhesive layer having a relative magnetic permeability of 1 or more therebetween, or with an adhesive layer containing magnetic powder therebetween.

3. The switching power supply device according to claim 1 or 2.

8. The common wiring is composed of a first common wiring surrounding the plurality of inductor windings and a linear second common wiring connected to the first common wiring; an inductor constituting the smoothing filter uses both the first common wiring and the second common wiring; 2. The switching power supply device according to claim 1.

9. The second common wiring is shorter than the plurality of inductor windings.

9. The switching power supply device according to claim 8.

10. The second common wiring is wider than the plurality of inductor windings.

9. The switching power supply device according to claim 8.

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