Switching power supply

Abstract

According to the present invention, a circuit board (60) comprises: a wiring pattern (41) that electrically connects nodes (ND0) of a switching element (Q1) and a switching element (Q2) to a first terminal (201); a wiring pattern (42) that electrically connects a second terminal (202) to an output capacitor (32); and a reference potential-side wiring pattern (50). When the circuit board is viewed from the front, the area of the wiring pattern (41) is smaller than the area of the wiring pattern (42). An inductor (20) has a parasitic capacitor (29) between the first terminal (201) and the second terminal (202) due to the structure of a winding conductor and a magnetic core (200). The circuit board (60) is arranged on a chassis (CHS) so that the parasitic capacitor (29) of the inductor (20) is larger than the parasitic capacitor (Cpm) between the magnetic core (200) and the chassis (CHS) at the switching frequencies of the switching element (Q1) and the switching element (Q2), thus forming a noise balancing circuit composed of an electric closed circuit formed by the parasitic capacitor (29) of the inductor (20), the wiring pattern (42), the output capacitor (32), the reference potential-side wiring pattern (50) of the circuit board (60), an input capacitor (31), and the wiring pattern (41).

Description

Technical Field

[0001] The present invention relates to a switching power supply device including a switching element for power conversion.

Background Art

[0002] Patent Document 1 describes a DC-DC converter. The DC-DC converter of Patent Document 1 includes a switching element and an inductor connected to the output side of the switching element. Further, the DC-DC converter of Patent Document 1 includes a shielding member.

[0003] The switching element, the inductor, and the shielding member are mounted on a substrate. The shielding member is disposed on the substrate so as to cover the inductor.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, by including a shielding member that is not related to power conversion, the DC-DC converter (switching power supply device) undesirably becomes large. Further, in the configuration of Patent Document 1, if the shielding member is not provided, switching noise is radiated to the outside from the inductor.

[0006] Therefore, an object of the present invention is to provide a highly efficient and small-sized switching power supply device that suppresses radiation of switching noise.

Means for Solving the Problems

[0007] The switching power supply device of this invention comprises an input capacitor, a first switching element and a second switching element electrically connected to the input capacitor, an inductor having a winding conductor and a magnetic core, with a first terminal electrically connected to one end of the winding and a second terminal electrically connected to the other end of the winding conductor, an output capacitor, and a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted.

[0008] The circuit board has a first wiring pattern that electrically connects the connection nodes of the first and second switching elements to the first terminal, a second wiring pattern that electrically connects the second terminal to the output capacitor, and a reference potential pattern. When the circuit board is viewed from the front, the area of ​​the first wiring pattern is smaller than the area of ​​the second wiring pattern. The inductor has an internal parasitic capacitance between the first and second terminals due to the structure of the wound conductor and magnetic core. When the circuit board is placed on the chassis, the internal parasitic capacitance of the inductor is larger than the external parasitic capacitance between the magnetic core and the chassis at the switching frequency that operates the first and second switching elements, and a noise balancing circuit is formed by the internal parasitic capacitance of the inductor, the second wiring pattern, the output capacitor, the reference potential pattern of the circuit board, the input capacitor, and the first wiring pattern, which are electrically closed circuits.

[0009] The noise balancing circuit cancels out electromagnetic noise generated by the switching operation of the first and second switching elements, and suppresses the generation of common-mode noise caused by switching noise radiated or conducted from the inductor. [Effects of the Invention]

[0010] According to this invention, a noise balancing circuit can be configured without using noise reduction components, and a switching power supply can be formed in a highly efficient and compact manner that cancels out the generation of electromagnetic noise caused by switching operation and suppresses the radiation or conduction of switching noise and the common-mode noise caused by this conduction. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a circuit diagram showing a schematic configuration of a switching power supply device according to the first embodiment of the present invention. [Figure 2] Figure 2 is an equivalent circuit diagram of an inductor according to the first embodiment of the present invention. [Figure 3] Figure 3(A) is a plan view of an inductor according to the first embodiment of the present invention, and Figure 3(B) is a side view of the inductor. [Figure 4] Figure 4(A) is a plan view showing the configuration of the winding conductors of an inductor according to the first embodiment of the present invention, Figure 4(B) is a side view showing the configuration of the winding conductors of this inductor, and Figures 4(C) and 4(D) are plan views of each winding conductor. [Figure 5] Figure 5(A) is a side cross-sectional view showing the configuration including the inductor mounting portion in a switching power supply device according to the first embodiment of the present invention, and Figure 5(B) is a plan view of the mounting portion. [Figure 6] Figure 6 is a schematic diagram showing the flow of EMI noise in a switching power supply device according to the first embodiment of the present invention. [Figure 7] Figure 7 is a schematic diagram showing the flow of EMI noise in a switching power supply with a comparative configuration. [Figure 8] Figure 8(A) is a graph showing the levels of conducted noise for the present configuration and the comparative configuration, and Figure 8(B) is a graph showing the levels of radiated noise for the present configuration and the comparative configuration. [Figure 9] Figure 9 is a side cross-sectional view of a configuration including the inductor mounting portion in a switching power supply device according to a second embodiment of the present invention. [Figure 10] Figure 10 is a side cross-sectional view of a configuration including the inductor mounting portion in a switching power supply device according to a third embodiment of the present invention. [Figure 11] Figure 11 is a side cross-sectional view of a configuration including the inductor mounting portion in a switching power supply device according to a fourth embodiment of the present invention. [Figure 12] FIG. 12 is a side perspective view showing the configuration of the winding conductor of the inductor according to the fifth embodiment of the present invention. [Figure 13] FIG. 13 is a side perspective view showing the configuration of the winding conductor of the inductor according to the sixth embodiment of the present invention. [Figure 14] FIGS. 14(A) and 14(B) are plan perspective views of the respective winding conductors of the inductor according to the seventh embodiment of the present invention. [Figure 15] FIG. 15 is a side perspective view showing the configuration of the winding conductor of the inductor according to the eighth embodiment of the present invention. [Figure 16] FIG. 16(A) is a side view showing the configuration of the inductor according to the ninth embodiment of the present invention, and FIG. 16(B) is a diagram conceptually showing the winding state of the conductor pattern around the magnetic core in this inductor. [Figure 17] FIG. 17 is a circuit diagram showing the schematic configuration of the switching power supply device according to the tenth embodiment of the present invention.

Embodiments for Carrying Out the Invention

[0012] [First Embodiment] The switching power supply device according to the first embodiment of the present invention will be described with reference to the drawings.

[0013] (Configuration of Switching Power Supply Device 10) FIG. 1 is a circuit diagram showing the schematic configuration of the switching power supply device according to the first embodiment of the present invention.

[0014] As shown in Figure 1, the switching power supply unit 10 includes a switching IC 11, an inductor 20, an input capacitor 31, and an output capacitor 32. The switching IC 11 includes a switching control circuit 111, a switching element Q1, and a switching element Q2. Switching element Q1 corresponds to the "first switching element," and switching element Q2 corresponds to the "second switching element." Switching elements Q1 and Q2 are power semiconductor elements, and are composed of, for example, N-type MOS-FETs.

[0015] The switching power supply unit 10 is electrically connected to the DC power supply 81. More specifically, the input capacitor 31 is electrically connected in parallel to the DC power supply 81. The connection point between the positive terminal of the DC power supply 81 and the input capacitor 31 is node ND1H, and the connection point between the negative terminal of the DC power supply 81 and the input capacitor 31 is node ND1L.

[0016] Switching elements Q1 and Q2 are electrically connected in series. More specifically, the source of switching element Q1 and the drain of switching element Q2 are electrically connected. The connection point between switching elements Q1 and Q2 is node ND0.

[0017] Switching elements Q1 and Q2 are electrically connected to the input capacitor 31. More specifically, the drain of switching element Q1 is connected to the Hi-side node ND1H of the input capacitor 31. The source of switching element Q2 is connected to the Low-side node ND1L of the input capacitor 31.

[0018] A switching control circuit 111 is electrically connected to the gates of switching element Q1 and switching element Q2. Switching elements Q1 and Q2 conduct or open the drain-source electrical connection according to the switching control signal from the switching control circuit 111.

[0019] The inductor 20 has a first terminal 201 and a second terminal 202. The specific electrical and physical configuration of the inductor 20 and the specific wiring pattern connected to the inductor 20 will be described later and are omitted here.

[0020] The first terminal 201 of the inductor 20 is connected to node ND0 of the switching IC 11 via wiring pattern 41. The second terminal 202 of the inductor 20 is connected to one terminal (Hi-side terminal) of the output capacitor 32 via wiring pattern 42. The connection point between the second terminal 202 of the inductor 20 and one terminal of the output capacitor 32 is node ND2H.

[0021] The other terminal (low-side terminal) of the output capacitor 32 is connected to the reference potential-side wiring pattern 50. The connection point between the other terminal of the output capacitor 32 and the reference potential-side wiring pattern 50 is node ND2L.

[0022] The reference potential side wiring pattern 50 is connected to node ND1L (the connection point between the negative terminal of the DC power supply 81 and the input capacitor 31). The reference potential side wiring pattern 50 corresponds to the "reference potential pattern".

[0023] With this configuration, the switching power supply unit 10 realizes a non-isolated, step-down DC-DC converter (power conversion circuit).

[0024] Load 82 is electrically connected in parallel to output capacitor 32. More specifically, one terminal of load 82 is connected to node ND2H, and the other terminal of load 82 is connected to node ND2L.

[0025] Furthermore, node ND1L of the switching power supply unit 10 (the connection point between the negative terminal of the DC power supply 81 and the input capacitor 31) is electrically connected to the chassis CHS of the vehicle on which the switching power supply unit 10, the DC power supply 81, and the load 82 are mounted. The chassis CHS is connected to ground potential as appropriate.

[0026] Specifically, the switching IC 11, inductor 20, input capacitor 31, and output capacitor 32 are implemented using mounted electronic components. Furthermore, the wiring pattern for realizing the above-described circuit configuration of the switching power supply unit 10 is formed on the circuit board 60 (see Figure 5(B), etc., described later). The switching power supply unit 10 is realized by mounting the switching IC 11, inductor 20, input capacitor 31, and output capacitor 32 on the circuit board 60. This circuit board 60 is then physically and electrically connected to the chassis CHS.

[0027] (Specific configuration of inductor 20 and specific configuration of the wiring pattern connected to inductor 20) (Equivalent circuit of inductor 20) Figure 2 is an equivalent circuit diagram of an inductor according to the first embodiment of the present invention. The inductor 20 comprises a first winding 21, a second winding 22, a magnetic core 200, a first terminal 201, and a second terminal 202. The first winding 21 and the second winding 22 are connected in series between the first terminal 201 and the second terminal 202.

[0028] Furthermore, the inductor 20 has a parasitic capacitor 29 connected between the first terminal 201 and the second terminal 202. In other words, the inductor 20 has a parasitic capacitor 29 connected in parallel to the series circuit of the first winding 21 and the second winding 22. The capacitance of the parasitic capacitor 29 is determined by the structure of the first winding 21, the second winding 22, and the magnetic core 200. The parasitic capacitor 29 corresponds to the "internal parasitic capacitance of the inductor."

[0029] Furthermore, the inductor 20 has a resistive component due to the magnetic core 200 between the first terminal 201 and the second terminal 202.

[0030] (Specific structure of inductor 20) Figure 3(A) is a plan view of an inductor according to the first embodiment of the present invention, and Figure 3(B) is a side view of the inductor. Figure 4(A) is a plan perspective view showing the configuration of the winding conductors of the inductor according to the first embodiment of the present invention, Figure 4(B) is a side perspective view showing the configuration of the winding conductors of the inductor, and Figures 4(C) and 4(D) are plan perspective views of each winding conductor.

[0031] Structurally, the inductor 20 comprises a first winding 21, a second winding 22, a magnetic core 200, a first terminal 201, and a second terminal 202.

[0032] The magnetic core 200 has a roughly rectangular parallelepiped shape and comprises a top surface FU200, a bottom surface FB200, a side surface FS201, a side surface FS202, and two other sides. Side surfaces FS201 and FS202 are opposite each other. The other two sides are opposite each other, perpendicular to and connected to sides FS201 and FS202. Side surface FS201 corresponds to the "first side surface," and side surface FS202 corresponds to the "second side surface."

[0033] The first winding 21 and the second winding 22 are wound conductors formed by winding a flat plate conductor.

[0034] The first winding 21 is wound in a plan view and has a predetermined height. The height of the first winding 21 is greater than the thickness of the first winding 21 and the flat conductor when viewed in a plan view. The first winding 21 has a wound inner end Ei21 and an outer end Eo21.

[0035] The second winding 22 has the same configuration as the first winding 21. The second winding 22 includes a wound inner end Ei 22 and an outer end Eo 22.

[0036] The first winding 21 and the second winding 22 are embedded in the magnetic core 200 in such a wound shape when viewed from above. That is, the magnetic core 200 surrounds the first winding 21 and the second winding 22, and also fills the inside of the central opening of the wound shape of the first winding 21 and the second winding 22.

[0037] The first winding 21 and the second winding 22 are stacked in the height direction of the magnetic core 200. In this case, the first winding 21 is positioned closer to the bottom surface FB200 than the second winding 22. In other words, the first winding 21 and the second winding 22 are arranged in that order from the bottom surface FB200 toward the top surface FU200 of the magnetic core 200.

[0038] In this configuration, the first winding 21 and the second winding 22 are capacitively coupled, forming a parasitic capacitor 29 (internal parasitic capacitance of the inductor 20). In addition, this configuration creates a resistive component due to the magnetic core 200.

[0039] The inner end Ei21 of the first winding 21 and the inner end Ei22 of the second winding 22 are connected by a connecting conductor 28. The outer end Eo21 of the first winding 21 is exposed on the side surface FS201 of the magnetic core 200. The outer end Eo22 of the second winding 22 is exposed on the side surface FS202 of the magnetic core 200.

[0040] A first conductive terminal 201 is formed on the magnetic core 200, extending from the side surface FS201 to the bottom surface FB200. As a result, the outer end Eo21 of the first winding 21 is electrically connected to the first terminal 201.

[0041] A second conductive terminal 202 is formed on the magnetic core 200, extending from the side surface FS202 to the bottom surface FB200. As a result, the outer end Eo22 of the second winding 22 is electrically connected to the second terminal 202.

[0042] With this configuration, the inductor 20 realizes the equivalent circuit configuration shown in Figure 2.

[0043] (Configuration of the mounting location for inductor 20) Figure 5(A) is a side cross-sectional view showing the configuration including the inductor mounting portion in a switching power supply device according to the first embodiment of the present invention, and Figure 5(B) is a plan view of the mounting portion. In Figures 5(A) and 5(B), the first winding 21 and the second winding 22 inside the inductor 20 are illustrated so that the internal wiring of the inductor 20 can be seen. In addition, in Figure 5(A), a circuit symbol for a parasitic capacitor is also included for the sake of clarity in the explanation.

[0044] The circuit board 60 comprises an insulating substrate and various conductor patterns formed on the insulating substrate. The circuit board 60 has a surface 61. Schematically, the switching IC 11, inductor 20, input capacitor 31, and output capacitor 32 are mounted on the surface 61 of the circuit board 60. The various conductor patterns include wiring patterns 41, 42, and a reference potential side wiring pattern 50, and together with the switching IC 11, inductor 20, input capacitor 31, and output capacitor 32, are formed on the circuit board 60 to realize the circuit configuration of the switching power supply 10 shown in Figure 1.

[0045] The circuit board 60 is physically fixed to the chassis CHS by a fixing structure (not shown in the diagram). Furthermore, the ground potential of the circuit board 60 is electrically connected (grounded) to the chassis CHS by an electrical connection structure (not shown in the diagram).

[0046] The specific structure of the mounting portion of the inductor 20 is as follows:

[0047] As shown in Figure 5, wiring patterns 41 and 42, each consisting of a conductive pattern, are formed on the surface 61 of the circuit board 60.

[0048] One end of the wiring pattern 41 has a land formed thereon on which the source terminal of switching element Q1 of the switching IC 11 is mounted, and a land formed thereon on which the drain terminal of switching element Q2 of the switching IC 11 is mounted. The source terminal of switching element Q1 and the drain terminal of switching element Q2 are mounted on the land by bumps BP111 and BP112, respectively. Therefore, one end of the wiring pattern 41 corresponds to node ND0.

[0049] A first land for the inductor is formed at the other end of the wiring pattern 41. The first terminal 201 of the inductor 20 is mounted on the first land for the inductor by solder or the like. As a result, the first terminal 201 of the inductor 20 is electrically and physically connected to the wiring pattern 41.

[0050] One end of the wiring pattern 42 is positioned at a distance corresponding to the planar shape of the inductor 20 from the other end of the wiring pattern 41. A second land for the inductor is formed at one end of the wiring pattern 42. The second terminal 202 of the inductor 20 is mounted on the second land for the inductor by solder or the like. As a result, the second terminal 202 of the inductor 20 is electrically and physically connected to the wiring pattern 42.

[0051] Although not shown in the diagram, one terminal (Hi-side terminal) of the output capacitor 32 and one terminal of the load 82 are electrically and physically connected to a predetermined position on the wiring pattern 42.

[0052] Here, the inductor 20 is mounted on the circuit board 60 such that the space distance between the magnetic core 200 and the chassis CHS becomes longer. More specifically, when the magnetic core 200 and the chassis CHS are arranged with a space therebetween, a parasitic capacitor Cpm occurs between the magnetic core 200 and the chassis CHS. The parasitic capacitor Cpm corresponds to the "external parasitic capacitance of the inductor". The inductor 20 is mounted on the circuit board 60 at a position where, at the switching frequencies of the switching element Q1 and the switching element Q2, the impedance Z29 due to the parasitic capacitor 29 (the internal parasitic capacitance of the inductor 20) is smaller than the impedance Zcpm due to the parasitic capacitor Cpm (the external parasitic capacitance of the inductor 20). That is, the inductor 20 is mounted on the circuit board 60 at a position where the relationship Z29 < Zcpm holds. At this time, it is preferable that the relationship Z << Zcpm holds, and further, at the frequencies of various harmonics of the switching frequency, it is preferable that the relationships Z29 < Zcpm and Z << Zcpm hold.

[0053] The impedance Z29 due to such a parasitic capacitor 29 and the impedance Zcpm due to the parasitic capacitor Cpm can be measured by a device or system capable of measuring the impedance of an electric circuit such as an impedance analyzer or a network analyzer.

[0054] With such a configuration, the switching power supply device 10 constitutes an electrical closed circuit for the following switching noise (electromagnetic noise) and realizes a noise balancing circuit.

[0055] FIG. 6 is a diagram schematically showing the flow of EMI noise in the switching power supply device according to the first embodiment of the present invention.

[0056] As described above, the inductor 20 is equipped with a parasitic capacitor 29, which is connected between the first terminal 201 and the second terminal 202. At the switching frequencies of the switching elements Q1 and Q2, the impedance Z29 due to the parasitic capacitor 29 (internal parasitic capacitance of the inductor 20) is smaller than the impedance Zcpm ​​due to the parasitic capacitor Cpm (external parasitic capacitance of the inductor 20).

[0057] Therefore, as shown by the thick arrow in Figure 6, the switching noise from node ND0 of the switching IC 11 returns to the switching IC 11 through the wiring pattern 41, the parasitic capacitor 29 of the inductor 20, the wiring pattern 42, the output capacitor 32, the reference potential side wiring pattern 50, the input capacitor 31, and the input side Hi potential pattern. The input side Hi potential pattern is the wiring pattern that connects the Hi side terminal of the input capacitor 31 to the Hi side input terminal of the switching IC 11 (the terminal connected to the drain terminal of the switching element Q1).

[0058] Furthermore, because the impedance due to the external parasitic capacitance of the inductor 20 is large relative to the switching noise, the propagation (leakage) of switching noise from the magnetic core 200 of the inductor 20 to the chassis CHS is suppressed.

[0059] With this configuration, the switching power supply 10 is equipped with an electrically closed circuit that protects against switching noise, consisting of the switching IC 11, wiring pattern 41, parasitic capacitor 29 of the inductor 20, wiring pattern 42, output capacitor 32, reference potential side wiring pattern 50, input capacitor 31, and input side high potential pattern.

[0060] Switching noise generated from the switching IC 11 is confined by this electrically closed circuit. Switching noise radiated from the first winding 21 is also guided to this electrically closed circuit by the second winding 22. Since the phase of the continuously generated switching noise is not constant, it cancels each other out by being confined within the electrically closed circuit. In other words, this electrically closed circuit functions as a noise balancing circuit that balances the switching noise and suppresses the generation of common-mode noise. To put it another way, the switching power supply 10 is equipped with a noise balancing circuit.

[0061] As described above, by having the above configuration, the switching power supply unit 10 can suppress the generation and conduction of common-mode noise by suppressing the radiation or conduction of switching noise to the chassis CHS and the outside, and can also suppress the level of switching noise by the noise balancing circuit. In other words, the switching power supply unit 10 can more effectively suppress the radiation and conduction of switching noise and the generation and conduction of common-mode noise. Furthermore, by suppressing the superposition of switching noise to the chassis CHS, and suppressing the generation of common-mode noise caused by switching noise and its conduction in the chassis CHS, the switching power supply unit 10 can suppress the adverse effects of switching noise on various electronic devices of a vehicle equipped with a chassis CHS.

[0062] In this case, the switching power supply unit 10 does not require separate components (shielding members) for suppressing the radiation and conduction of switching noise and the generation and conduction of common-mode noise, thus enabling a simple configuration and miniaturization.

[0063] In contrast, in the switching power supply unit 10P of the comparative configuration, which does not have the configuration of the switching power supply unit 10 according to this embodiment, common-mode noise flows into the chassis CHS.

[0064] Figure 7 is a schematic diagram showing the flow of EMI noise in a comparative switching power supply. If the configuration and mounting manner of the inductor 20 are not adopted as in the switching power supply 10 of the present invention, the capacitance of the parasitic capacitor Cpm formed by the magnetic core 200 of the inductor 20 and the chassis CHS will be greater than the capacitance of the parasitic capacitor 29 of the inductor 20, as shown in Figure 7.

[0065] As a result, the parasitic capacitor Cpm (external parasitic capacitance of inductor 20) becomes dominant over the parasitic capacitor 29 (internal parasitic capacitance of inductor 20) in the transmission of switching noise. Consequently, common-mode noise flows to the chassis CHS through the parasitic capacitor Cpm.

[0066] Thus, in the comparative configuration of the switching power supply unit 10P, common-mode noise leaks into the chassis CHS. However, by having the above configuration, the switching power supply unit 10 of this embodiment can suppress the generation and conduction of common-mode noise caused by the coupling of switching noise to the chassis CHS.

[0067] Figure 8(A) is a graph showing the conducted noise levels of the present invention configuration and the comparative configuration, and Figure 8(B) is a graph showing the radiated noise levels of the present invention configuration and the comparative configuration. Note that Figure 8(A) shows only a portion of the frequency band, but similar noise is distributed over a wider frequency band. In Figures 8(A) and 8(B), the solid line shows the noise level of the present invention, and the dashed line shows the noise level of the comparative configuration. Furthermore, where the noise level of the present invention and the noise level of the comparative configuration overlap, the illustration shows the noise level of the present invention overwriting the noise level of the comparative configuration.

[0068] As shown in Figure 8(A), the configuration of the switching power supply 10 allows for the suppression of conducted noise levels in each frequency band. As shown in Figure 8(C), the configuration of the switching power supply 10 allows for the suppression of radiated noise levels in each frequency band. For example, the radiated noise level in the 10MHz band, which is greater than 10[dBuV / m] in the comparative configuration, can be suppressed to less than 10[dBuV / m].

[0069] In particular, the inductor 20 has a laminated structure of a first winding 21 and a second winding 22. The first winding 21 and the second winding 22 are in close proximity in the thickness direction of the magnetic core 200. As a result, the inductor 20 can easily increase the capacitance of the parasitic capacitor 29. Therefore, by having the configuration of the inductor 20, the switching power supply 10 can more reliably realize a noise balancing circuit consisting of the electrically closed circuit described above against switching noise.

[0070] Furthermore, the inductor 20 is mounted on the surface 61 of the circuit board 60 such that its bottom surface FB200 is on the surface 61 of the circuit board 60 rather than its top surface FU200, and the bottom surface FB200 faces the surface 61.

[0071] In this configuration, the first winding 21 is positioned closer to the circuit board 60 than the second winding 22. In other words, the second winding 22 is positioned further outward than the first winding 21 in a direction perpendicular to the surface 61 of the circuit board 60. To put it another way, the first winding 21 is positioned between the second winding 22 and the surface 61 of the circuit board 60.

[0072] One end of the wiring pattern 41 corresponds to node ND0 of switching elements Q1 and Q2. Therefore, noise from the switching operation of switching elements Q1 and Q2 flows through the wiring pattern 41. In other words, the wiring pattern 41 can be called a switching node pattern.

[0073] The other end of the wiring pattern 41 is connected to the first winding 21. Therefore, switching noise flows into the first winding 21.

[0074] On the other hand, one end of the second winding 22 is not directly connected to node ND0 of switching elements Q1 and Q2, but is connected to node ND0 through the first winding 21. Furthermore, the other end of the second winding 22 is connected to wiring pattern 42. Wiring pattern 42 is connected to output capacitor 32, and its potential is stable. In other words, wiring pattern 42 can be described as a stable potential pattern.

[0075] As described above, with reference to the surface 61 of the circuit board 60, the second winding 22, which is connected to the stable potential pattern, is positioned outside the first winding 21, which is connected to the switching node pattern. Therefore, even if switching noise is radiated from the first winding 21, this switching noise is suppressed from being radiated to the outside of the switching power supply 10 by the second winding 22.

[0076] Furthermore, it is preferable that the switching power supply 10 has the following configuration.

[0077] Although not shown in the diagram, in the switching power supply unit 10, the area of ​​wiring pattern 41 is smaller than the area of ​​wiring pattern 42. That is, the area of ​​the switching node pattern is smaller than the area of ​​the stable potential pattern. Therefore, the radiation of switching noise from wiring pattern 41, which is the source of switching noise, to the outside of the switching power supply unit 10 and the chassis CHS is suppressed.

[0078] Furthermore, in order to reduce the area, the wiring pattern 41 is designed to shorten its length without significantly reducing its width. This reduces the resistance component of the wiring pattern 41. As a result, the switching power supply 10 can suppress current-induced losses and achieve highly efficient power conversion. In particular, the switching power supply 10 can achieve even more efficient power conversion when high currents are required.

[0079] Furthermore, the area of ​​the wiring pattern 41 is smaller than the area of ​​the inductor 20 projected onto the surface 61 of the circuit board 60 (the projected area of ​​the inductor 20). As a result, the switching power supply 10 can suppress the radiation and conduction of switching noise to the outside and the chassis CHS, and the generation and conduction of common-mode noise as a result.

[0080] Furthermore, in this case, the area of ​​the wiring pattern 42 is approximately the same as, or larger than, the projected area of ​​the inductor 20. As a result, the area with a relatively stable potential becomes larger with respect to the total area of ​​the switching power supply 10 when viewed from above. Therefore, the influence of switching noise on the outside of the switching power supply 10 and the chassis CHS can be suppressed.

[0081] Furthermore, the switching power supply unit 10 constitutes a step-down DC-DC converter, and the voltage across the inductor 20 (rectified and smoothed voltage) is lower than the voltage of the DC power supply 81. In such cases, the above configuration is more effective. Also, if the input is obtained by converting a commercial AC power supply to DC, for example, through an inverter circuit, instead of using a DC power supply 81, the voltage across the inductor 20 (rectified and smoothed voltage) is lower than the commercial AC voltage. In this case as well, the above configuration is more effective.

[0082] [Second Embodiment] A switching power supply device according to a second embodiment of the present invention will be described with reference to the figures. Figure 9 is a side cross-sectional view of the configuration including the inductor mounting portion in the switching power supply device according to the second embodiment of the present invention.

[0083] The switching power supply 10A according to the second embodiment differs from the switching power supply 10 according to the first embodiment in the wiring pattern of the reference potential side wiring pattern 50. The other components of the switching power supply 10A are the same as those of the switching power supply 10, and a description of the similar parts will be omitted.

[0084] The switching power supply 10A is formed by a circuit board 60A. The circuit board 60A includes a reference potential side wiring pattern 50 consisting of a conductor pattern.

[0085] The reference potential side wiring pattern 50 is formed inside the circuit board 60A. When viewed from above (viewed in a direction perpendicular to the surface 61), the reference potential side wiring pattern 50 overlaps the inductor 20 (the mounting area of ​​the inductor 20) and the wiring pattern 41.

[0086] With this configuration, a parasitic capacitor is formed between the inductor 20 and the wiring pattern 41 and the reference potential side wiring pattern 50. This parasitic capacitor is not through which the main current for power conversion flows, but rather through which switching noise with a higher frequency flows.

[0087] This configuration allows the internal parasitic capacitance forming the electrically closed circuit in the switching power supply unit 10A to be larger than the external parasitic capacitance to the chassis CHS. As a result, switching noise is more effectively confined within the noise balancing circuit, and the generation of common-mode noise is more effectively suppressed.

[0088] Therefore, the switching power supply 10A can more effectively suppress the radiation and conduction of switching noise to the outside, as well as the generation and conduction of common-mode noise.

[0089] The reference potential side wiring pattern 50 only needs to overlap with a portion of at least one of the inductor 20 and the wiring pattern 41, but it is preferable that it overlaps with both the inductor 20 and the wiring pattern 41.

[0090] [Third Embodiment] A switching power supply device according to a third embodiment of the present invention will be described with reference to the figures. Figure 10 is a side cross-sectional view of the configuration including the inductor mounting portion in the switching power supply device according to the third embodiment of the present invention.

[0091] The switching power supply 10B according to the third embodiment differs from the switching power supply 10 according to the first embodiment in the wiring pattern of the input side Hi potential pattern 43. The input side Hi potential pattern 43 corresponds to the "input wiring pattern". The other configurations of the switching power supply 10B are the same as those of the switching power supply 10, and the description of the similar parts will be omitted.

[0092] The input-side high-potential pattern 43 is a wiring pattern that connects node ND1H on the high-potential side of the input capacitor 31 to the switching IC 11.

[0093] The switching power supply unit 10B is formed by a circuit board 60B. The circuit board 60B includes an input-side Hi potential pattern 43 consisting of a conductive pattern.

[0094] The input-side Hi potential pattern 43 is formed inside the circuit board 60B. When viewed from above, the input-side Hi potential pattern 43 overlaps the inductor 20 and the wiring pattern 41.

[0095] In this configuration, a parasitic capacitor is formed between the inductor 20 and wiring pattern 41 and the input-side Hi-potential pattern 43. This parasitic capacitor is not through which the main power conversion current flows, but rather through which switching noise with a higher frequency flows.

[0096] This configuration allows the internal parasitic capacitance forming the electrically closed circuit in the switching power supply unit 10B to be larger than the external parasitic capacitance to the chassis CHS. As a result, switching noise is more effectively confined within the noise balancing circuit, and the generation of common-mode noise is more effectively suppressed.

[0097] Therefore, the switching power supply unit 10B can more effectively suppress the radiation and conduction of switching noise to the outside, as well as the generation and conduction of common-mode noise.

[0098] The input-side Hi potential pattern 43 only needs to overlap with a portion of at least one of the inductor 20 and the wiring pattern 41, but it is preferable that it overlaps with both the inductor 20 and the wiring pattern 41.

[0099] [Fourth Embodiment] A switching power supply device according to a fourth embodiment of the present invention will be described with reference to the figures. Figure 11 is a side cross-sectional view of the configuration including the inductor mounting portion in the switching power supply device according to the fourth embodiment of the present invention.

[0100] The switching power supply unit 10C according to the fourth embodiment differs from the switching power supply unit 10 according to the first embodiment in its wiring pattern 42C. The other components of the switching power supply unit 10C are the same as those of the switching power supply unit 10, and a description of the similar parts will be omitted.

[0101] The switching power supply unit 10C is formed by a circuit board 60C. The circuit board 60C includes a wiring pattern 42C consisting of a conductor pattern.

[0102] The wiring pattern 42C comprises a wiring pattern 420, a wiring pattern 421, and a connecting conductor via 42. The wiring pattern 420 is formed on the surface 61 of the circuit board 60C. The wiring pattern 420 includes lands for the inductor 20. The wiring pattern 421 is formed inside the circuit board 60C. The wiring pattern 421 is connected to the wiring pattern 420 through the connecting conductor via 42. In plan view, the wiring pattern 421 overlaps the inductor 20 and the wiring pattern 41.

[0103] In this configuration, a parasitic capacitor is formed between the inductor 20 and wiring pattern 41 and wiring pattern 421. This parasitic capacitor is not through which the main current for power conversion flows, but rather through which switching noise with a higher frequency flows.

[0104] This configuration allows the internal parasitic capacitance forming the electrically closed circuit in the switching power supply unit 10C to be larger than the external parasitic capacitance to the chassis CHS. As a result, switching noise is more effectively confined within the noise balancing circuit, and the generation of common-mode noise is more effectively suppressed.

[0105] Therefore, the switching power supply unit 10C can more effectively suppress the radiation and conduction of switching noise, including common-mode noise, to the outside, as well as the generation and conduction of common-mode noise.

[0106] Note that the wiring pattern 421 only needs to overlap with a portion of at least one of the inductor 20 and the wiring pattern 41, but it is preferable that it overlaps with both the inductor 20 and the wiring pattern 41.

[0107] [Fifth Embodiment] A switching power supply device according to a fifth embodiment of the present invention will be described with reference to the figures. Figure 12 is a side perspective view showing the configuration of the winding conductor of an inductor according to the fifth embodiment of the present invention.

[0108] The switching power supply according to the fifth embodiment differs from the switching power supply 10 according to the first embodiment in the inductor 20D. The other configurations of the switching power supply according to the fifth embodiment are the same as those of the switching power supply 10, and the description of the similar parts will be omitted.

[0109] As shown in Figure 11, the inductor 20D has a first terminal 201D and a second terminal 202D. The first terminal 201D is formed across the side surface FS201 and the bottom surface FB200 of the magnetic core 200. The second terminal 202D is formed across the side surface FS202 and the bottom surface FB200 of the magnetic core 200.

[0110] The height H201D of the first terminal 201D is lower than the height H202D of the second terminal 202D. The first terminal 201D is formed across the entire width of the side surface FS201. The second terminal 202D is formed across the entire width of the side surface FS202. As a result, the area of ​​the first terminal 201D formed on the side surface FS201 is smaller than the area of ​​the second terminal 202D formed on the side surface FS202.

[0111] This configuration suppresses the radiation of switching noise from the first terminal 201D.

[0112] [Sixth Embodiment] A switching power supply device according to the sixth embodiment of the present invention will be described with reference to the figures. Figure 13 is a side perspective view showing the configuration of the winding conductor of an inductor according to the sixth embodiment of the present invention.

[0113] The switching power supply according to the sixth embodiment differs from the switching power supply 10 according to the first embodiment in the inductor 20E. The other components of the switching power supply according to the sixth embodiment are the same as those of the switching power supply 10, and a description of the similar parts will be omitted.

[0114] As shown in Figure 12, the inductor 20E has a first terminal 201E and a second terminal 202E. The first terminal 201E is formed on the bottom surface FB200 of the magnetic core 200 and is not formed on the side surface FS201. The second terminal 202E is formed across the side surface FS202 and the bottom surface FB200 of the magnetic core 200.

[0115] This configuration suppresses the radiation of switching noise from the first terminal 201E.

[0116] [Seventh Embodiment] A switching power supply device according to the seventh embodiment of the present invention will be described with reference to the figures. Figures 14(A) and 14(B) are plan perspective views of each winding conductor of the inductor according to the seventh embodiment of the present invention.

[0117] The switching power supply according to the seventh embodiment differs from the switching power supply 10 according to the first embodiment in the inductor 20F. The other components of the switching power supply according to the seventh embodiment are the same as those of the switching power supply 10, and a description of the similar parts will be omitted.

[0118] As shown in Figures 14(A) and 14(B), the inductor 20F comprises a first winding 21F and a second winding 22F. The number of turns of the second winding 22F is greater than that of the first winding 21F, and in a plan view, the area S22F of the external shape of the second winding 22F is larger than the area S21F of the external shape of the first winding 21F.

[0119] Furthermore, in a plan view, the wound portion of the second winding 22F overlaps with the wound portion of the first winding 21F.

[0120] With this configuration, the second winding 22F can more effectively suppress the radiation of switching noise from the first winding 21F to the chassis CHS and the outside.

[0121] [Eighth Embodiment] A switching power supply device according to the eighth embodiment of the present invention will be described with reference to the figures. Figure 15 is a side perspective view showing the configuration of the winding conductor of an inductor according to the eighth embodiment of the present invention.

[0122] The switching power supply according to the eighth embodiment differs from the switching power supply 10 according to the first embodiment in the inductor 20G. The other configurations of the switching power supply according to the eighth embodiment are the same as those of the switching power supply 10, and the description of the similar parts will be omitted.

[0123] As shown in Figure 14, the inductor 20G comprises a first winding 21G, a second winding 22G, and a third winding 23G. The first winding 21G, the second winding 22G, and the third winding 23G are wound conductors, similar to the first winding 21 and the second winding 22 described above.

[0124] The first winding 21G, the second winding 22G, and the third winding 23G are arranged in the order of first winding 21G, third winding 23G, and second winding 22G, from the bottom surface FB200 of the magnetic core 200 toward the top surface FU200.

[0125] The inner end Ei21 of the first winding 21G is connected via a connecting conductor 281 to the portion (bottom surface) formed on the bottom surface of the magnetic core 200 at the first terminal 201G. More specifically, the inner end of the first winding 21G is connected to a position near the center of the bottom surface of the first terminal 201G when viewed from above. Note that the first terminal 201G may be formed only on the bottom surface of the magnetic core 200. The outer end Eo21 of the first winding 21G is connected via a connecting conductor 282 to the outer end Eo23 of the third winding 23G. The inner end Ei23 of the third winding 23G is connected via a connecting conductor 283 to the inner end Ei22 of the second winding 22G. The outer end Eo22 of the second winding 22G is connected to the second terminal 202G.

[0126] Thus, the inductor used in the switching power supply may be composed of three or more layers of wound conductors.

[0127] In this configuration, the first winding 21G, which is electrically closest to the switching node pattern and the first terminal 201G, is connected to the first terminal 201G and the switching node pattern through its inner end Ei21, as is the case with inductor 20G. As a result, the area with the highest noise level is the central portion when viewing inductor 20G from above. Therefore, noise radiation from inductor 20G to the chassis CHS and the outside is suppressed more effectively.

[0128] [Ninth Embodiment] A switching power supply device according to the ninth embodiment of the present invention will be described with reference to the figures. Figure 16(A) is a side view showing the configuration of an inductor according to the ninth embodiment of the present invention, and Figure 16(B) is a conceptual diagram showing the winding state of the conductor pattern around the magnetic core in this inductor.

[0129] The switching power supply according to the ninth embodiment differs from the switching power supply 10 according to the first embodiment in the inductor 20H. The other configurations of the switching power supply according to the ninth embodiment are the same as those of the switching power supply 10, and descriptions of the similar parts are omitted.

[0130] The inductor 20H comprises a magnetic core 200H, a fourth winding 21H, a fifth winding 22H, a first terminal 201H, and a second terminal 202H.

[0131] The magnetic core 200H comprises a base plate 2001, a top plate 2002, and a support column 2003. The support column 2003 is positioned between the base plate 2001 and the top plate 2002 and is connected to both the base plate 2001 and the top plate 2002.

[0132] The fourth winding 21H is a wound conductor wrapped around the support column 2003. One end of the fourth winding 21H is connected to the first terminal 201H formed on the base plate 2001.

[0133] The fifth winding 22H is a winding conductor wound around the support column 2003 with the fourth winding 21H in between. That is, the fifth winding 22H is positioned outside the fourth winding 21H with respect to the support column 2003. One end of the fifth winding 22H is connected to the other end of the fourth winding 21H. The other end of the fifth winding 22H is connected to the second terminal 202H formed on the base plate 2001.

[0134] The first terminal 201H is connected to wiring pattern 41, which is a switching node pattern. The second terminal 202H is connected to wiring pattern 42, which is a stable potential pattern.

[0135] Even when using an inductor 20H with this configuration, the same effects and advantages as those of the switching power supply 10 using the inductor 20 described above can be achieved.

[0136] [Tenth Embodiment] A switching power supply device according to the tenth embodiment of the present invention will be described with reference to the figures. Figure 17 is a circuit diagram showing the schematic configuration of a switching power supply device according to the tenth embodiment of the present invention.

[0137] While the switching power supply 10 according to the first embodiment was a step-down DC-DC converter, the switching power supply 10I according to the tenth embodiment is a step-up DC-DC converter. The configuration of the inductor 20, the shape of the wiring pattern 41, and the shape of the wiring pattern 42 in the switching power supply 10I are the same as those of the switching power supply 10.

[0138] As shown in Figure 17, the switching power supply unit 10I includes a switching IC 11I, an inductor 20, an input capacitor 31, and an output capacitor 32. The switching IC 11I includes a switching control circuit (not shown), a switching element D1, and a switching element Q2. Switching element D1 corresponds to the "first switching element," and switching element Q2 corresponds to the "second switching element." Switching elements D1 and Q2 are power semiconductor elements.

[0139] The switching power supply unit 10I is electrically connected to the DC power supply 81. More specifically, the input capacitor 31 is electrically connected in parallel to the DC power supply 81. The connection point between the positive terminal of the DC power supply 81 and the input capacitor 31 is node ND1H, and the connection point between the negative terminal of the DC power supply 81 and the input capacitor 31 is node ND1L.

[0140] Switching element D1 and switching element Q2 are electrically connected in series. More specifically, the anode of switching element D1 and the drain of switching element Q2 are electrically connected. The connection point between switching element D1 and switching element Q2 is node ND0.

[0141] The wiring pattern 42 is connected to node ND1L. The second terminal 202 of inductor 20 is connected to wiring pattern 42. The first terminal 201 of inductor 20 is connected to wiring pattern 41, and wiring pattern 41 is connected to node ND0.

[0142] One terminal (the Hi-side terminal) of the output capacitor 32 is connected to the cathode of the switching element D1. The connection point between the cathode of the switching element D1 and one terminal of the output capacitor 32 is node ND2H.

[0143] The other terminal (low-side terminal) of the output capacitor 32 is connected to the reference potential-side wiring pattern 50. The connection point between the other terminal of the output capacitor 32 and the reference potential-side wiring pattern 50 is node ND2L.

[0144] The reference potential side wiring pattern 50 is connected to node ND1L (the connection point between the negative terminal of the DC power supply 81 and the input capacitor 31).

[0145] With this configuration, the switching power supply 10I can realize a noise balancing circuit comprising a wiring pattern 41, an inductor 20, a wiring pattern 42, an input capacitor 31, a reference potential side wiring pattern 50, and an output capacitor 32. As a result, the switching power supply 10I, like the switching power supply 10, can suppress the radiation of switching noise to the outside and the generation, conduction, and radiation of common mode noise to the outside, and the noise level can be suppressed by the noise balancing circuit. Therefore, the switching power supply 10I can more effectively suppress the radiation, conduction, and radiation of switching noise to the chassis CHS, as well as the generation and conduction of common mode noise.

[0146] Furthermore, in the switching power supply devices of each of the embodiments described above, the common-mode noise suppression effect can be confirmed, for example, as follows.

[0147] As a first example, a delta-type LISN is connected to the positive and negative wiring patterns of a DC power supply 81, and a spectrum analyzer is connected to the delta-type LISN. By measuring the output voltage of the delta-type LISN with the spectrum analyzer, the common-mode noise suppression effect can be confirmed.

[0148] As a second example, current sensors (current probes) are installed on the positive and negative wiring patterns of the DC power supply 81, and a spectrum analyzer is connected to the current sensors. By measuring the output current of the current sensors with the spectrum analyzer, the common-mode noise suppression effect can be confirmed.

[0149] As a third example, a LISN is connected to the negative terminal wiring pattern of the DC power supply 81, and this LISN is connected to the chassis CHS. A current sensor (current probe) is installed on the connection line between the LISN and the chassis CHS, and a spectrum analyzer is connected to the current sensor. By measuring the output current of the current sensor with the spectrum analyzer, the common-mode noise suppression effect can be confirmed.

[0150] Furthermore, the configurations of each of the above embodiments can be combined as appropriate, and the effects corresponding to each combination can be achieved.

[0151] <1> Input capacitor and, A first switching element and a second switching element are electrically connected to the input capacitor, An inductor comprising a wound conductor and a magnetic core, having a first terminal electrically connected to one end of the wound conductor and a second terminal electrically connected to the other end of the wound conductor, Output capacitor and, A circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted, Equipped with, The aforementioned circuit board is A first wiring pattern that electrically connects the connection nodes of the first switching element and the second switching element to the first terminal, A second wiring pattern that electrically connects the second terminal and the output capacitor, Reference potential pattern, It has, Viewing the circuit board from the front, The area of ​​the first wiring pattern is smaller than the area of ​​the second wiring pattern. The inductor has an internal parasitic capacitance between the first terminal and the second terminal due to the structure of the winding conductor and the magnetic core. By arranging the circuit board on the chassis, the internal parasitic capacitance of the inductor is greater than the external parasitic capacitance between the magnetic core and the chassis at the switching frequency that operates the first and second switching elements. A switching power supply device wherein the internal parasitic capacitance of the inductor, the second wiring pattern, the output capacitor, the reference potential pattern of the circuit board, the input capacitor, and the first wiring pattern constitute a noise balancing circuit consisting of an electrically closed circuit that cancels out the generation of electromagnetic noise caused by the switching operation of the first switching element and the second switching element and suppresses the generation of common-mode noise radiated or conducted from the inductor.

[0152] <2> The winding conductor comprises a first winding and a second winding arranged spaced apart in the thickness direction of the magnetic core. The internal parasitic capacitance is formed by the first winding and the second winding. <1> A switching power supply unit.

[0153] <3> The second winding is positioned further away from the circuit board than the first winding. When the inductor is viewed from above, the outer shape of the second winding is smaller than that of the first winding, and the second winding overlaps the first winding. <1> or <2> A switching power supply unit.

[0154] <4> The aforementioned inductor is The first winding has at least one third winding electrically connected between it and the first winding, The inner end of the first winding is electrically connected to the first terminal. The outer end of the second winding is electrically connected to the second terminal. <1> ~ <3> One of the following switching power supplies.

[0155] <5> The aforementioned reference potential pattern is formed in a region that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. <1> ~ <4> One of the following switching power supplies.

[0156] <6> The circuit board has an input wiring pattern that is electrically connected to the input capacitor. The input wiring pattern is formed in a region that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. <1> ~ <5> One of the following switching power supplies.

[0157] <7> A portion of the second wiring pattern is formed in an area that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. <1> ~ <6> One of the following switching power supplies.

[0158] <8> The magnetic core has a bottom surface, a first side surface, and a second side surface. The first terminal is formed across the bottom surface and the first side surface, The second terminal is formed across the bottom surface and the second side surface, The area formed on the first side surface of the first terminal is smaller than the area formed on the second side surface of the second terminal. <1> ~ <7> One of the following switching power supplies.

[0159] <9> The magnetic core has a bottom surface, a first side surface, and a second side surface. The first terminal is formed only on the bottom surface, The second terminal is formed across the bottom surface and the second side surface, <1> ~ <8> One of the following switching power supplies.

[0160] <10> The area of ​​the first wiring pattern is smaller than the area of ​​the inductor viewed from above. <1> ~ <9> One of the following switching power supplies.

[0161] <11> The first switching element, the second switching element, and the inductor constitute a non-isolated power conversion circuit. The rectified and smoothed voltage applied to the inductor is less than the rectified and smoothed voltage of the commercial AC voltage. <1> of <10> One of the following switching power supplies.

[0162] <12> Input capacitor and, An inductor comprising a wound conductor and a magnetic core, having a first terminal electrically connected to one end of the wound conductor and a second terminal electrically connected to the other end of the wound conductor, A first switching element and a second switching element are electrically connected to the inductor, Output capacitor and, A circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted, Equipped with, The aforementioned circuit board is A first wiring pattern that electrically connects the connection nodes of the first switching element and the second switching element to the first terminal, A second wiring pattern that electrically connects the second terminal and the input capacitor, Reference potential pattern, It has, The area of ​​the first wiring pattern is smaller than the area of ​​the second wiring pattern. The inductor has an internal parasitic capacitance between the first terminal and the second terminal due to the structure of the winding conductor and the magnetic core. By arranging the circuit board on the chassis, the internal parasitic capacitance of the inductor is made greater than the external parasitic capacitance between the magnetic core and the chassis at the switching frequencies of the first and second switching elements. A switching power supply device wherein the internal parasitic capacitance of the inductor, the second wiring pattern, the output capacitor, the reference potential pattern of the circuit board, the input capacitor, and the first wiring pattern constitute a noise balancing circuit consisting of an electrically closed circuit that cancels out the generation of electromagnetic noise caused by the switching operation of the first switching element and the second switching element and suppresses the generation of common-mode noise radiated or conducted from the inductor. [Explanation of Symbols]

[0163] 10, 10A, 10B, 10C, 10I, 10P: Switching power supply 20, 20D, 20E, 20F, 20G, 20H: Inductors 21, 21F, 21G: First winding 22, 22F, 22G: Second winding 23G: Third winding 21H: Fourth winding 22H: Fifth winding 28: Connecting conductor 29: Parasitic Capacitor 31: Input Capacitor 32: Output Capacitor 41, 42, 42C, 420, 421: Wiring patterns 43: Input side high potential pattern 50: Reference potential side wiring pattern 60, 60A, 60B, 60C: Circuit board 61: Surface 81:DC power supply 82: Load 111: Switching control circuit 200, 200H: Magnetic core 201, 201D, 201E, 201G, 201H: Terminal 1 202, 202D, 202E, 202G, 202H: Second terminal 281, 282, 283: Connecting conductors 2001: Bottom plate 2002: Tabletop 2003: Prop BP111, BP112: Bump CHS: Chassis Cpm: Parasitic Capacitor D1, Q1, Q2: Switching elements Ei21, Ei22, Ei23: Inner end Eo21, Eo22, Eo23: Outer end FB200: Bottom FS201, FS202: Side view FU200: Top surface H201D, H202D: Height 11, 11I: Switching IC ND0, ND1H, ND1L, ND2H, ND2L, ND1L: Nodes VIA42: Connecting conductor Z29, Zcpm: Impedance

Claims

1. Input capacitor and, A first switching element and a second switching element are electrically connected to the input capacitor, An inductor comprising a wound conductor and a magnetic core, having a first terminal electrically connected to one end of the wound conductor and a second terminal electrically connected to the other end of the wound conductor, Output capacitor and, A circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted, Equipped with, The aforementioned circuit board is A first wiring pattern that electrically connects the connection nodes of the first switching element and the second switching element to the first terminal, A second wiring pattern that electrically connects the second terminal and the output capacitor, Reference potential pattern, It has, When the circuit board is viewed from the front, the area of ​​the first wiring pattern is smaller than the area of ​​the second wiring pattern. The inductor has an internal parasitic capacitance between the first terminal and the second terminal due to the structure of the winding conductor and the magnetic core. By arranging the circuit board on the chassis, the internal parasitic capacitance of the inductor is greater than the external parasitic capacitance between the magnetic core and the chassis at the switching frequency that operates the first and second switching elements. The internal parasitic capacitance of the inductor, the second wiring pattern, the output capacitor, the reference potential pattern of the circuit board, the input capacitor, and the first wiring pattern constitute a noise balancing circuit consisting of an electrically closed circuit that cancels out electromagnetic noise generated due to the switching operation of the first switching element and the second switching element, and suppresses the generation of common-mode noise radiated or conducted from the inductor. Switching power supply.

2. The winding conductor comprises a first winding and a second winding arranged spaced apart in the thickness direction of the magnetic core. The internal parasitic capacitance is formed by the first winding and the second winding. A switching power supply device according to claim 1.

3. The second winding is positioned further away from the circuit board than the first winding. When the inductor is viewed from above, the external shape of the second winding is smaller than that of the first winding, and the second winding overlaps the first winding. The switching power supply device according to claim 2.

4. The aforementioned inductor is The first winding has at least one third winding electrically connected between it and the first winding, The inner end of the first winding is electrically connected to the first terminal. The outer end of the second winding is electrically connected to the second terminal. The switching power supply device according to claim 2.

5. The aforementioned reference potential pattern is formed in a region that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. A switching power supply device according to claim 1.

6. The circuit board has an input wiring pattern that is electrically connected to the input capacitor. The input wiring pattern is formed in a region that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. A switching power supply device according to claim 1.

7. A portion of the second wiring pattern is formed in a region that overlaps with the mounting area of ​​the inductor when the circuit board is viewed in plan view. A switching power supply device according to claim 1.

8. The magnetic core has a bottom surface, a first side surface, and a second side surface. The first terminal is formed across the bottom surface and the first side surface, The second terminal is formed across the bottom surface and the second side surface, The area formed on the first side surface of the first terminal is smaller than the area formed on the second side surface of the second terminal. A switching power supply device according to claim 1.

9. The magnetic core has a bottom surface, a first side surface, and a second side surface. The first terminal is formed only on the bottom surface, The second terminal is formed across the bottom surface and the second side surface, A switching power supply device according to claim 1.

10. The area of ​​the first wiring pattern is smaller than the area of ​​the inductor viewed from above. A switching power supply device according to claim 1.

11. The first switching element, the second switching element, and the inductor constitute a non-isolated power conversion circuit. The voltage applied to the inductor is less than the rectified and smoothed voltage of the commercial AC voltage. A switching power supply device according to claim 1.

12. Input capacitor and, An inductor comprising a wound conductor and a magnetic core, having a first terminal electrically connected to one end of the wound conductor and a second terminal electrically connected to the other end of the wound conductor, A first switching element and a second switching element are electrically connected to the inductor, Output capacitor and, A circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted, Equipped with, The aforementioned circuit board is A first wiring pattern that electrically connects the connection nodes of the first switching element and the second switching element to the first terminal, A second wiring pattern that electrically connects the second terminal and the input capacitor, Reference potential pattern, It has, The area of ​​the first wiring pattern is smaller than the area of ​​the second wiring pattern. The inductor has an internal parasitic capacitance between the first terminal and the second terminal due to the structure of the winding conductor and the magnetic core. By arranging the circuit board on the chassis, the internal parasitic capacitance of the inductor is made greater than the external parasitic capacitance between the magnetic core and the chassis at the switching frequencies of the first and second switching elements. The internal parasitic capacitance of the inductor, the second wiring pattern, the output capacitor, the reference potential pattern of the circuit board, the input capacitor, and the first wiring pattern constitute a noise balancing circuit consisting of an electrically closed circuit that cancels out electromagnetic noise generated due to the switching operation of the first switching element and the second switching element, and suppresses the generation of common-mode noise radiated or conducted from the inductor. Switching power supply.

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