Switching power supply device

Abstract

A switching power supply device (10) comprises: an input capacitor (31); a first switching element (Q1) and a second switching element (Q2) electrically connected to the input capacitor (31); an inductor (20) having a first terminal and a second terminal; and an output capacitor (32). The switching power supply device (10) further comprises a circuit board (60) on which the input capacitor (31), the first switching element (Q1), the second switching element (Q2), the inductor (20), and the output capacitor (32) are mounted. The circuit board (60) is constituted by a laminated circuit board formed by laminating a plurality of insulator layers (601-603) each having a conductor pattern formed thereon, and is provided with a first main surface (61) and a second main surface (62). The inductor (20) is mounted on the first main surface (61). The conductor pattern has a first wiring pattern electrically connecting a connection node of each of the first switching element (Q1) and the second switching element (Q2) to the first terminal, a second wiring pattern electrically connecting the second terminal and the output capacitor, and a ground conductor pattern (50) formed on an inner layer of the laminated circuit board. The inductor (20) is disposed so that the magnetic flux can be perpendicular to the circuit board (60). A portion of the ground conductor pattern (50) that overlaps the inductor (20) when viewed in a direction orthogonal to the first main surface (61) is formed by a conductor part and a slit (SLIT). The area of the first wiring pattern is smaller than an projection area of the inductor (20) projected on the first main surface (61), and the area of the second wiring pattern is the same as or larger than the projection area of the inductor (20), and constitutes a noise balancing circuit, which is an electric closed circuit formed by the input capacitor (31), the first wiring pattern, the second wiring pattern, the output capacitor (32), and the ground conductor pattern (50).

Description

Switching Power Supply

[0001] The present invention relates to a structure of a switching power supply device.

[0002] Patent Document 1 describes a power supply system including a power inductor. In the power supply system of Patent Document 1, the power inductor is mounted on a first main surface of a printed circuit board.

[0003] Ground conductors are formed on the inner layers of the printed circuit board, including directly below the power inductor.

[0004] Patent No. 648553 specification

[0005] However, in the configuration of Patent Document 1, magnetic flux generated by the power inductor passes through the ground conductor, generating eddy currents in the ground conductor. While this can suppress noise radiation from the power inductor, it increases power loss in the power supply system and reduces power conversion efficiency.

[0006] Therefore, an object of the present invention is to suppress noise radiation from a power inductor while suppressing power loss and a decrease in power conversion efficiency.

[0007] A switching power supply according to one embodiment of the present invention comprises an input capacitor, a first switching element and a second switching element electrically connected to the input capacitor, an inductor having a first terminal and a second terminal, and an output capacitor.

[0008] The switching power supply device includes a circuit board on which an input capacitor, a first switching element, a second switching element, an inductor, and an output capacitor are mounted. The circuit board is a laminated circuit board formed by laminating multiple insulator layers, each having a conductor pattern formed thereon, and has a first main surface and a second main surface. The inductor is mounted on the first main surface.

[0009] The conductor pattern includes a first wiring pattern that electrically connects a connection node between the first switching element and the second switching element and the first terminal, a second wiring pattern that electrically connects the second terminal and the output capacitor, and a ground conductor pattern formed on an inner layer of the laminated circuit board. The inductor is arranged so that magnetic flux can be perpendicular to the circuit board. A portion of the ground conductor pattern that overlaps with the inductor when viewed in a direction orthogonal to the first main surface is formed by a conductor portion and a slit.

[0010] The area of ​​the first wiring pattern is smaller than the projected area of ​​the inductor projected onto the first principal surface, and the area of ​​the second wiring pattern is the same as or larger than the projected area of ​​the inductor, and a noise balancing circuit is formed, which is an electrically closed circuit, by the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the ground conductor pattern.

[0011] In this configuration, the generation of eddy currents due to the magnetic field generated by the inductor is suppressed by the presence of non-conductor areas formed by the slits in the ground conductor pattern. Furthermore, noise generated by the inductor is propagated to the ground conductor pattern by the conductor remaining after the slits are formed, and is then trapped by the noise balancing circuit. This suppresses noise radiation (leakage) to the outside.

[0012] A switching power supply device according to one embodiment of the present invention comprises an input capacitor, a first switching element and a second switching element electrically connected to the input capacitor, an inductor having a first terminal and a second terminal, and an output capacitor.

[0013] The switching power supply device includes a circuit board on which an input capacitor, a first switching element, a second switching element, an inductor, and an output capacitor are mounted. The circuit board is a laminated circuit board formed by laminating multiple insulator layers, each having a conductor pattern formed thereon, and has a first main surface and a second main surface. The inductor is mounted on the first main surface.

[0014] The conductor pattern includes an input power wiring pattern that electrically connects the input capacitor and the first switching element formed on the laminated circuit board, a first wiring pattern that electrically connects a connection node of the first switching element and the second switching element to the first terminal, and a second wiring pattern that electrically connects the second terminal to the output capacitor. The inductor is arranged so that magnetic flux is perpendicular to the circuit board. The input power wiring pattern has a slit where no conductor is formed in a portion that overlaps with the inductor when viewed in a direction perpendicular to the first main surface.

[0015] The area of ​​the first wiring pattern is smaller than the projected area of ​​the inductor when projected onto the first main surface, and the area of ​​the second wiring pattern is approximately the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrical closed circuit consisting of the input capacitor, the input power supply wiring pattern, the first wiring pattern, the second wiring pattern, and the output capacitor.

[0016] In this configuration, the generation of eddy currents due to the magnetic field generated by the inductor is suppressed by the presence of non-conductor areas formed by the slits in the input power wiring pattern. Furthermore, noise generated by the inductor is propagated to the input power wiring pattern by the conductor remaining after the slits are formed, and is then trapped by the noise balancing circuit. This suppresses noise radiation (leakage) to the outside.

[0017] A switching power supply device according to one embodiment of the present invention comprises an input capacitor, a first switching element and a second switching element electrically connected to the input capacitor, an inductor having a first terminal and a second terminal, and an output capacitor.

[0018] The switching power supply device includes a circuit board on which an input capacitor, a first switching element, a second switching element, an inductor, and an output capacitor are mounted. The circuit board is a laminated circuit board formed by laminating multiple insulator layers, each having a conductor pattern formed thereon, and has a first main surface and a second main surface. The inductor is mounted on the first main surface.

[0019] The conductor pattern includes a first wiring pattern that electrically connects a connection node between the first switching element and the second switching element to the first terminal, a second wiring pattern that electrically connects the second terminal to an output capacitor, and an output power wiring pattern that electrically connects the output capacitor formed on the laminated circuit board to the output terminal. The inductor is arranged so that magnetic flux is perpendicular to the circuit board. The output power wiring pattern has a slit where no conductor is formed in a portion that overlaps with the inductor when viewed in a direction orthogonal to the first main surface.

[0020] The area of ​​the first wiring pattern is smaller than the projected area of ​​the inductor projected onto the first main surface, and the area of ​​the second wiring pattern is approximately the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrical closed circuit consisting of the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the output power supply wiring pattern.

[0021] In this configuration, the generation of eddy currents due to the magnetic field generated by the inductor is suppressed by the presence of non-conductor areas formed by the slits in the output power wiring pattern. Furthermore, noise generated by the inductor is propagated to the output power wiring pattern by the conductor remaining after the slits are formed in the output power wiring pattern, and is then trapped by the noise balancing circuit. This suppresses noise radiation (leakage) to the outside.

[0022] According to the present invention, it is possible to suppress noise radiation from a power inductor, and at the same time, it is possible to suppress power loss and a decrease in power conversion efficiency.

[0023] FIG. 1 is a circuit diagram showing an example of the configuration of a switching power supply device according to a first embodiment of the present invention. FIG. 2A is a plan view showing a portion of the physical and electrical structure of the switching power supply device according to the first embodiment of the present invention, and FIG. 2B is a cross-sectional view of the portion shown in FIG. 2A. FIG. 3A is a plan view of slits formed in a ground conductor pattern, FIG. 3B is a cross-sectional view of the slit formation portion, and FIG. 3C is a plan view comparing the positional relationship and size of the slit with an inductor. FIG. 4 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to a first embodiment of the present invention. FIG. 5A is a graph showing the change in power conversion efficiency versus output current value when eddy currents are generated and when eddy currents are not generated, and FIG. 5B is a diagram showing the frequency characteristics of noise levels for the configuration of the present invention and a comparative configuration. FIG. 6A is a plan view of an example inductor according to the first embodiment of the present invention, and FIG. 6B is a side view thereof. FIG. 7 is a cross-sectional view showing a portion of the physical and electrical structure of a switching power supply device according to a second embodiment of the present invention. FIG. 8 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to a second embodiment of the present invention. FIG. 9 is a cross-sectional view showing a portion of the physical and electrical structure of a switching power supply device according to a third embodiment of the present invention. FIG. 10 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the third embodiment of the present invention. FIG. 11 is a cross-sectional view showing a portion of the physical and electrical structure of a switching power supply device according to a fourth embodiment of the present invention. FIG. 12 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the fourth embodiment of the present invention. FIG. 13 is a cross-sectional view showing a portion of the physical and electrical structure of a switching power supply device according to a fifth embodiment of the present invention. FIG. 14 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the fifth embodiment of the present invention.

[0024] First Embodiment A switching power supply device according to a first embodiment of the present invention will be described with reference to the drawings.

[0025] (Configuration of Switching Power Supply Device 10) FIG. 1 is a circuit diagram showing an example of the configuration of a switching power supply device according to a first embodiment of the present invention.

[0026] As shown in FIG. 1, the switching power supply device 10 includes a switching IC 11 , an inductor 20 , an input capacitor 31 , and an output capacitor 32 .

[0027] The switching power supply device 10 is electrically connected to a DC power supply 81 and a load 82 .

[0028] The input capacitor 31 is electrically connected in parallel to the DC power supply 81. The input capacitor 31 includes a structure that forms a capacitor, a capacitor external terminal 3101, and a capacitor external terminal 3102.

[0029] The positive electrode of the DC power supply 81 and the capacitor external terminal 3101 are connected to the input-side high potential wiring pattern 43. The input-side high potential wiring pattern 43 corresponds to the "input power supply wiring pattern." The connection point between the positive electrode of the DC power supply 81 and the input capacitor 31 (capacitor external terminal 3101) is node ND1H.

[0030] The negative electrode of the DC power supply 81 and the capacitor external terminal 3102 are connected to the ground conductor pattern 50. The ground conductor pattern 50 is a conductor pattern that serves as the ground (reference potential) for the switching power supply device 10. The connection point between the negative electrode of the DC power supply 81 and the input capacitor 31 (capacitor external terminal 3102) is node ND1L.

[0031] The switching IC 11 includes a switching control circuit 111, a switching element Q1, and a switching element Q2. The switching element Q1 corresponds to the "first switching element," and the switching element Q2 corresponds to the "second switching element." The switching elements Q1 and Q2 are power semiconductor elements and are configured, for example, by N-type MOS-FETs.

[0032] The switching IC 11 includes a high-side input terminal P01, a reference potential connection terminal P02, a switching element external terminal P11, and a switching element external terminal P12. The switching IC 11 also includes other terminals, but these are not shown in FIG. 1 and are not described here.

[0033] The high-side input terminal P01 is connected to the input-side high-potential wiring pattern 43. The reference potential connection terminal P02 is connected to the ground conductor pattern 50.

[0034] The switching element Q1 and the switching element Q2 are electrically connected in series via the switching element external terminals P11 and P12. More specifically, the source of the switching element Q1 is connected to the switching element external terminal P11, and the drain of the switching element Q2 is connected to the switching element external terminal P12. The switching element external terminal P11 and the switching element external terminal P12 are connected via a wiring pattern 41. This connects the source of the switching element Q1 and the drain of the switching element Q2. The connection point between the switching element Q1 and the switching element Q2 is node ND0.

[0035] The switching elements Q1 and Q2 are electrically connected to the input capacitor 31. More specifically, the drain of the switching element Q1 is connected to a node ND1H on the high side of the input capacitor 31 via the high-side input terminal P01 and the input-side high-potential wiring pattern 43. The source of the switching element Q2 is connected to a node ND1L on the low side of the input capacitor 31 via the reference potential connection terminal P02 and the ground conductor pattern 50.

[0036] The gate of the switching element Q1 and the gate of the switching element Q2 are electrically connected to a switching control circuit 111. The switching elements Q1 and Q2 are on / off controlled by a switching control signal from the switching control circuit 111, and electrically connect or disconnect the drain-source of the switching element Q1 and the switching element Q2.

[0037] The inductor 20 includes a linear conductor (winding) 23, a magnetic core 200, a first inductor terminal 201, and a second inductor terminal 202 (see FIG. 6 ). The first inductor terminal 201 is electrically connected to one end E231 of the linear conductor 23. The second inductor terminal 202 is electrically connected to the other end E232 of the linear conductor 23 (see FIG. 6 ). The inductor 20 is a so-called inductor (power inductor) for a power conversion circuit. The specific configuration of the inductor 20 will be described later with reference to FIG. 6 .

[0038] The output capacitor 32 includes a structure that constitutes a capacitor, a capacitor external terminal 321 , and a capacitor external terminal 322 .

[0039] The node ND0 is connected to the first inductor terminal 201 of the inductor 20 through a wiring pattern 41. The wiring pattern 41 corresponds to the "first wiring pattern."

[0040] The second inductor terminal 202 of the inductor 20 is connected to the capacitor external terminal 321 of the output capacitor 32 through the wiring pattern 42. The wiring pattern 42 corresponds to the "second wiring pattern." The connection point between the second inductor terminal 202 of the inductor 20 and the capacitor external terminal 321 of the output capacitor 32 is a node ND2H.

[0041] The second inductor terminal 202 and the capacitor external terminal 321 are disposed adjacent to each other. In this case, it is preferable that the physical distance and the electrical distance between the second inductor terminal 202 and the capacitor external terminal 321 are as short as possible.

[0042] The capacitor external terminal 322 of the output capacitor 32 is connected to the ground conductor pattern 50. The connection point between the capacitor external terminal 322 of the output capacitor 32 and the ground conductor pattern 50 is a node ND2L.

[0043] With this configuration, the switching power supply device 10 functions as a step-down DC-DC converter. At this time, the switching elements Q1 and Q2 are controlled to be turned on and off at a predetermined switching frequency.

[0044] The load 82 is electrically connected in parallel to the output capacitor 32. More specifically, one terminal of the load 82 is connected to a node ND2H of the output capacitor 32. The other terminal of the load 82 is connected to a node ND2L of the output capacitor 32.

[0045] Furthermore, the ground conductor pattern 50 of the switching power supply device 10 is electrically connected to a chassis CHS of a vehicle or the like on which the switching power supply device 10, the DC power supply 81, and the load 82 are mounted. The chassis CHS is connected to an external ground potential as appropriate.

[0046] (Physical Configuration of Switching Power Supply Device 10) Fig. 2(A) is a plan view showing part of the physical and electrical structure of the switching power supply device according to the first embodiment of the present invention, and Fig. 2(B) is a cross-sectional view of the portion shown in Fig. 2(A). Note that the cross-sectional views of each embodiment of the present invention, including the cross-sectional view shown in Fig. 2(B), do not show cross-sections cut along a plane, but rather cross-sections cut so that the configuration of the switching power supply device 10 can be easily understood.

[0047] The switching IC 11, the inductor 20, the input capacitor 31, and the output capacitor 32 are configured as so-called mounted electronic components. More specifically, the switching IC 11 is configured as an IC with bumps, and the inductor 20, the input capacitor 31, and the output capacitor 32 are configured as chip-type electronic components having a pair of external terminals.

[0048] The switching power supply device 10 includes a circuit board 60. The circuit board 60 includes a first main surface 61 and a second main surface 62. The circuit board 60 is configured as a laminated circuit board formed by laminating a plurality of insulator layers 601, 602, and 603. The plurality of insulator layers 601, 602, and 603 are laminated in the order of insulator layer 603, insulator layer 602, and insulator layer 601 from the second main surface 62 side to the first main surface 61 side.

[0049] Conductor patterns for realizing the circuit pattern of the switching power supply device 10 are formed on the first main surface 61, the second main surface 62, the interface between the insulator layer 601 and the insulator layer 602 (first interface), and the interface between the insulator layer 602 and the insulator layer 603 (second interface) of the circuit board 60.

[0050] The first main surface 61 is formed with land conductors on which the switching IC 11, inductor 20, input capacitor 31, and output capacitor 32 are respectively mounted, wiring patterns 41, wiring patterns 42, and other wiring patterns for realizing the circuit pattern of the switching power supply device 10.

[0051] On the second main surface 62, an external terminal conductor pattern is formed for mounting the switching power supply device 10 on an external circuit board.

[0052] A flat-film-shaped ground conductor pattern 50 is formed at the first interface. The flat-film shape refers to a shape that extends in a direction perpendicular to the stacking direction (the surface direction of the inner layer) and whose length (thickness) in the stacking direction is smaller than the dimension in the extending direction. The ground conductor pattern 50 is formed over substantially the entire first interface. In other words, the ground conductor pattern 50 is formed on an inner layer of the circuit board 60.

[0053] A conductor pattern for wiring is formed on the second interface to realize the circuit pattern of the switching power supply device 10. In addition, via conductors that penetrate the multiple insulator layers 601-603 are appropriately formed on the circuit board 60.

[0054] With this configuration, the switching power supply device 10 is configured as a circuit module that realizes the circuit shown in FIG.

[0055] (Specific Mounting Configuration of First Main Surface 61) More specifically, the portion of the first main surface 61 where the switching IC 11 and the inductor 20 are mounted has the following configuration.

[0056] The switching IC 11 includes bump-shaped external terminals P11 and P12 for the switching element, which are arranged side by side along one side of the body of the switching IC 11.

[0057] The switching IC 11 and the inductor 20 are arranged side by side along the DIR1 direction (see FIGS. 2A and 2B). No other mount-type electronic components are mounted between the switching IC 11 and the inductor 20 in the DIR1 direction. In other words, the switching IC 11 and the inductor 20 are adjacent to each other in the DIR1 direction.

[0058] In this case, the switching IC 11 is mounted so that the side on which the switching element external terminals P11 and P12 are arranged faces the inductor 20 side.

[0059] The inductor 20 is mounted so that the first inductor terminal 201 faces the switching IC 11. In this case, the inductor 20 is mounted so that a main magnetic flux is generated in a direction perpendicular to the first main surface 61. In other words, the inductor 20 is disposed on the first main surface 61 so that the magnetic flux generated by the inductor 20 can be perpendicular to the first main surface 61 of the circuit board 60.

[0060] The wiring pattern 41 is a conductor pattern having a predetermined width, and is disposed between the switching IC 11 and the inductor 20 in a plan view (when viewed in a direction parallel to the DIRH in FIG. 2B (when viewed in a direction perpendicular to the first main surface 61)).

[0061] The wiring pattern 41 is connected to the land conductors on which the switching element external terminals P11, P12 are mounted and the land conductor on which the first inductor terminal 201 is mounted. The wiring pattern 41 connects the land conductors on which the switching element external terminals P11, P12 are mounted and the land conductor on which the first inductor terminal 201 is mounted over the shortest distance.

[0062] The width of the wiring pattern 41 is appropriately set so as not to be too wide, taking into consideration transmission loss and noise radiation.

[0063] The area of ​​the wiring pattern 41 is, for example, specifically smaller than the projected area of ​​the inductor 20 projected onto the first main surface 61 .

[0064] The wiring pattern 42 is a conductor pattern having a predetermined width and is disposed on the opposite side of the wiring pattern 41 with respect to the inductor 20 in the DIR1 direction.

[0065] The wiring pattern 42 is connected to a land conductor on which the second inductor terminal 202 is mounted.

[0066] The width of the wiring pattern 42 is wider than the width of the wiring pattern 41 .

[0067] The area of ​​the wiring pattern 42 is, for example, specifically, approximately the same as or larger than the area of ​​the inductor 20 projected onto the first main surface 61 .

[0068] (Specific configuration of the ground conductor pattern 50 at the first interface) Fig. 3(A) is a plan view of a slit formed in the ground conductor pattern. Fig. 3(B) is a cross-sectional view of the slit formation portion. Fig. 3(C) is a plan view comparing the positional relationship and size of the slit with the inductor.

[0069] As shown in FIGS. 3A, 3B, 3C, and 2B, the ground conductor pattern 50 has a slit SLIT formed therein.

[0070] The slit SLIT is composed of a plurality of linear conductors 71, a plurality of linear conductors 72, and a conductor-free portion 73. The slit SLIT has a comb-tooth shaped conductor pattern.

[0071] The plurality of linear conductors 71 and the plurality of linear conductors 72 extend in the DIR1 direction.

[0072] The conductor-free portion 73 has a shape that penetrates the ground conductor pattern 50 in the thickness direction.

[0073] The plurality of linear conductors 71 and the plurality of linear conductors 72 are arranged alternately in a DIR2 direction perpendicular to the DIR1 direction, with a non-conductor portion 73 sandwiched between each of them.

[0074] One end of each of the linear conductors 71 is connected to the ground conductor pattern 50. The other end of each of the linear conductors 71 is physically separated from the ground conductor pattern 50 by a non-conductor portion 73.

[0075] One end of each of the linear conductors 72 is physically separated from the ground conductor pattern 50 by a conductor-free portion 73. The other end of each of the linear conductors 72 is connected to the ground conductor pattern 50.

[0076] The slit SLIT overlaps with the inductor 20 when the circuit board 60 is viewed from above. In other words, in the region overlapping with the inductor 20 when the circuit board 60 is viewed from above, at least a portion of the plurality of linear conductors 71 and the plurality of linear conductors 72 constituting the slit SLIT and a portion of the conductor-free portion 73 constituting the slit SLIT overlap.

[0077] In this configuration, the magnetic flux generated by the inductor 20 mainly passes through the portion of the first interface where the slit SLIT is formed. The slit SLIT includes a non-conductor portion 73. The non-conductor portion 73 does not include a conductor (electrode) for generating eddy currents. Therefore, by providing such a slit SLIT in the ground conductor pattern 50, the switching power supply 10 can suppress eddy currents that are generated in the ground conductor pattern 50 due to the magnetic flux generated by the inductor 20.

[0078] Furthermore, in this configuration, by providing the slits SLIT in the ground conductor pattern 50, EMI noise is suppressed as follows.

[0079] 4 is a diagram schematically illustrating the flow of EMI noise in the switching power supply device according to the first embodiment of the present invention. Although the structural illustration is omitted, as shown in FIGS. 4 and 1, the ground conductor pattern 50 is connected to the reference potential connection terminal P02 of the switching IC 11 by a conductor pattern (referred to as a reference potential connection via conductor) (not shown).

[0080] Switching noise is generated by the switching operation of the switching elements Q1 and Q2 of the switching IC 11. This switching noise is input to the inductor 20 through the wiring pattern 41. The inductor 20 generates EMI noise due to this switching noise.

[0081] Noise (EMI noise) generated by the inductor 20 flows through the plurality of linear conductors 71 and 72 of the slits SLIT to the ground conductor pattern 50. This is equivalent in terms of noise to a circuit in which a parasitic capacitor Cps is connected between the inductor 20 and the plurality of linear conductors 71 and 72 of the slits SLIT.

[0082] Therefore, as shown by the thick arrow in FIG. 4 , noise generated in the inductor 20 returns to the switching IC 11 through the parasitic capacitor Cps, the plurality of linear conductors 71 and 72, the ground conductor pattern 50, the reference potential connection via conductor, and the reference potential connection terminal P02 of the switching IC 11.

[0083] That is, the switching power supply device 10 includes an electric closed circuit for noise protection, which is made up of the switching IC 11, the wiring pattern 41, the inductor 20, the parasitic capacitor Cps, the plurality of linear conductors 71 and 72, and the ground conductor pattern 50.

[0084] The switching noise generated by the switching IC 11 is confined by this closed electrical circuit. As a result, common mode noise generated in the chassis CHS due to this switching noise is suppressed. Furthermore, the switching noise radiated from the inductor 20 is guided to this closed electrical circuit by the parasitic capacitor Cps. Since the phase of continuously generated switching noise is not constant, the noise is confined in the closed electrical circuit and cancels out each other. In other words, this closed electrical circuit functions as a noise balancing circuit that balances the switching noise and suppresses the generation of common mode noise. In other words, the switching power supply 10 is equipped with a noise balancing circuit.

[0085] Thus, with the above-described configuration, the switching power supply 10 suppresses the generation of common-mode noise by suppressing the radiation of switching noise to the outside and the conduction of switching noise to the chassis CHS, and the noise balancing circuit can suppress the levels of switching noise and EMI noise. In other words, the switching power supply 10 can more effectively suppress the radiation of switching noise and the generation of common-mode noise. In this case, the switching power supply 10 does not require a separate component (shield member) for suppressing the generation of common-mode noise, thereby achieving a simple configuration and compact size.

[0086] The switching power supply device 10 suppresses switching noise and EMI noise caused by the switching noise, thereby suppressing superposition of the switching noise and EMI noise on the chassis CHS. This suppresses the generation of common mode noise on the chassis CHS caused by the switching noise and EMI noise. As a result, the switching power supply device 10 can suppress the adverse effects of switching noise and common mode noise on various electronic devices in a vehicle equipped with the chassis CHS.

[0087] Fig. 5A is a graph showing the change in power conversion efficiency with respect to the output current value when an eddy current is generated and when an eddy current is not generated, and Fig. 5B is a graph showing the frequency characteristics of noise levels for the configuration of the present invention and a comparative configuration.

[0088] In Fig. 5(A), the case where no eddy current occurs corresponds to the configuration of the present invention, and the case where eddy current occurs corresponds to the comparative configuration (a configuration without the slit SLIT of the present invention). In the comparative configuration of Fig. 5(B), the entire area of ​​the ground conductor pattern that overlaps with the inductor is an opening (a non-conductor portion). In Fig. 5(B), the solid line shows the characteristics of the present invention, and the dashed line shows the characteristics of the comparative configuration.

[0089] As shown in FIG. 5A, by using a configuration in which no eddy current is generated, that is, the configuration of the present invention, it is possible to achieve a higher power conversion efficiency than a configuration in which eddy current is generated.

[0090] 5B, by using the configuration of the present invention, the noise level can be suppressed over a wide frequency band, particularly in a frequency band exceeding 20 kHz, that is, in the case of the switching power supply device 10 of the present invention, in the band of harmonic frequencies of the switching frequency.

[0091] As described above, the switching power supply 10 suppresses the electromagnetic noise generated by the power inductor (inductor 20) from the source by forming a noise balancing circuit using the conductor portion of the ground conductor pattern 50 formed on the circuit board 60. Furthermore, the switching power supply 10 equalizes the potential of the generated electromagnetic noise and suppresses noise radiation from the power inductor. At the same time, the switching power supply 10 suppresses the generation of eddy currents by using the slits (portions where no conductor is formed) in the ground conductor pattern 50 formed on the circuit board 60, thereby suppressing power loss and a decrease in power conversion efficiency.

[0092] As a result, the switching power supply device 10 can suppress power loss and a decrease in power conversion efficiency while suppressing noise radiation from the power inductor (inductor 20). The switching power supply device 10 can simultaneously achieve low EMI noise, small size and light weight, high power conversion efficiency, and low cost, and can configure a power supply system that is excellent in noise, small size and light weight, power conversion efficiency, and cost.

[0093] It is more preferable that the slit SLIT has the following shape.

[0094] The size of the outer shape of the slit SLIT is preferably equal to or larger than the size of the central opening of the linear conductor 23 of the inductor 20 when viewed in a direction perpendicular to the first main surface 61. The outer shape of the slit SLIT is a shape obtained by connecting the outermost edges of the conductor-free portions 73 formed in the ground conductor pattern 50 with imaginary lines.

[0095] As a result, the slit SLIT is formed in a region where the magnetic field generated by the inductor 20 mainly passes, and therefore the switching power supply device 10 can more reliably suppress the generation of eddy currents.

[0096] Furthermore, the size of the outer shape of the slit SLIT is preferably equal to or smaller than twice the size of the inductor 20 when viewed in a direction perpendicular to the first main surface 61. This prevents the conductor-free portion 73 of the slit SLIT from becoming large. Therefore, the switching power supply 10 can prevent deterioration of the electrical characteristics of the ground conductor pattern 50, which may be caused by providing the slit SLIT.

[0097] The thickness D71 of the plurality of linear conductors 71 in the slit SLIT (and the same applies to the thickness of the linear conductors 72) is preferably less than the skin depth of EMI noise, which is determined by the physical properties of the material forming the ground conductor pattern and the switching frequency.

[0098] Specifically, the skin depth D is expressed by the following equation, where f is the switching frequency, μ is the dielectric constant of the insulating layers 601-603, and σ is the conductivity of the linear conductors 71 and 72.

[0099] d=√(1 / πfμσ) By making the thickness D71 of the linear conductor 71 less than the skin depth D expressed by this formula, the generation of eddy currents can be more effectively suppressed.

[0100] Furthermore, the width W71 of the plurality of linear conductors 71 and the width W72 of the plurality of linear conductors 72 in the slit SLIT are set based on the switching frequency. More specifically, the width W71 and the width W72 are preferably less than one wavelength corresponding to the switching frequency, and more preferably less than one-half wavelength. This more effectively suppresses the generation of eddy currents.

[0101] Furthermore, as described above, in the switching power supply 10, the connection distance between the switching IC 11 and the inductor 20 in the wiring pattern 41 is short and the area thereof is small. This allows the switching power supply 10 to suppress switching noise emitted from the wiring pattern 41. Furthermore, this configuration also reduces the opposing area between the wiring pattern 41 and the ground conductor pattern 50. This allows the switching power supply 10 to suppress undesired capacitive coupling between the wiring pattern 41 and the ground conductor pattern 50.

[0102] Furthermore, in the switching power supply device 10, as described above, the area of ​​the wiring pattern 42 is larger than the area of ​​the wiring pattern 41 and the projected area (area in plan view) of the inductor 20. This allows the switching power supply device 10 to reduce conductor loss relative to the output current.

[0103] Furthermore, the inductor 20 preferably has the following configuration: Fig. 6A is a plan view showing an example of the inductor according to the first embodiment of the present invention, and Fig. 6B is a side view thereof.

[0104] As shown in FIGS. 6A and 6B, the inductor 20 includes a magnetic core 200, a linear conductor 23, a first inductor terminal 201, and a second inductor terminal 202.

[0105] The magnetic core 200 is columnar and has a top surface FU200 and a bottom surface FB200.

[0106] The linear conductor 23 has a spiral (wound) shape and has one end E231 and the other end E232.

[0107] The first inductor terminal 201 is arranged on a first side surface and a bottom surface FB200 of the magnetic core 200. The second inductor terminal 202 is arranged on a second side surface (a side surface opposite to the first side surface) of the magnetic core 200 and on the bottom surface FB200.

[0108] The linear conductor 23 is wound around the magnetic core 200 from the bottom surface FB200 to the top surface FU200. One end E231 of the linear conductor 23 on the bottom surface FB200 side is electrically connected to the first inductor terminal 201. The winding end of the linear conductor 23 on the top surface FU200 side is electrically connected to the second inductor terminal 202.

[0109] The inductor 20 configured as described above is mounted on the first main surface 61 of the circuit board 60 so that the bottom surface FB200 is adjacent to and faces the first main surface 61 of the circuit board 60. This makes the axial direction of the magnetic core 200 and the axial direction of the spiral linear conductor 23 perpendicular to the first main surface 61. This allows the magnetic flux generated by the inductor 20 to be perpendicular to the first main surface 61 of the circuit board 60.

[0110] With this configuration, in the inductor 20, one end E231 of the linear conductor 23 connected to the wiring pattern 41 is located closer to the circuit board 60 than the other end E232 of the linear conductor 23 connected to the wiring pattern 42.

[0111] Here, with the above-described circuit configuration, the wiring pattern 41 is a pattern (switching node pattern) on which switching noise is superimposed, and the wiring pattern 42 is a pattern (stable potential pattern) on which almost no switching noise is superimposed. Therefore, with this configuration, the side of the inductor 20 that connects to the switching node pattern of the linear conductor 23 faces the circuit board 60, and the side of the inductor 23 that connects to the stable potential pattern faces outward. This allows the switching power supply 10 to suppress EMI noise radiated to the outside from the inductor 20.

[0112] In this embodiment, the inductor 20 has a configuration including the linear conductor 23 whose winding starts on the bottom surface FB200 side and ends on the top surface FU200 side of the magnetic core 200. However, the linear conductor 23 may have a configuration in which it is wound multiple times in order from the circumferential surface (inside) of the magnetic core 200 to the outside (outside) when viewed in a direction perpendicular to the top surface FU200.

[0113] In this case, the inductor 20 connects the inner winding start of the linear conductor 23 to the first inductor terminal 201. The inductor 20 connects the outer winding end of the linear conductor 23 to the second inductor terminal 202.

[0114] With this configuration, the side of the inductor 20 that is connected to the switching node pattern of the linear conductor 23 is on the inside of the winding, and the side of the inductor 20 that is connected to the stable potential pattern is on the outside of the winding. This allows the switching power supply 10 to suppress EMI noise radiated to the outside from the inductor 20.

[0115] Furthermore, the inductor 20 preferably includes a shield electrode that covers the linear conductor 23. In this case, the shield electrode is electrically connected to at least one of the wiring pattern 42 and the ground conductor pattern 50. This further suppresses EMI noise emitted from the inductor 20 to the outside.

[0116] In the above description, the slit SLIT has a comb-tooth shape. However, the linear conductor constituting the slit SLIT may have other shapes, such as a meandering shape. The minimum configuration required for the slit SLIT is to have at least one conductor portion and one non-conductor portion in the region overlapping with the inductor 20.

[0117] [Second Embodiment] A switching power supply device according to a second embodiment of the present invention will be described with reference to the drawings. Fig. 7 is a cross-sectional view showing part of the physical and electrical structure of the switching power supply device according to the second embodiment of the present invention.

[0118] The switching power supply device 10A according to the second embodiment has the same circuit configuration as the switching power supply device 10 according to the first embodiment, but differs in some physical and electrical structures. Therefore, only the differences between the switching power supply device 10A and the switching power supply device 10 will be specifically described below.

[0119] 7, the switching power supply device 10A includes a circuit board 60A. The circuit board 60A differs from the circuit board 60 according to the first embodiment in that it includes via conductors VIAGi.

[0120] The circuit board 60A includes, on the first main surface 61, a land conductor 40G on which the reference potential connection terminal P02 of the switching IC 11 is mounted.

[0121] The via conductors VIAGi have a shape that penetrates the insulator layer 601, and in plan view overlap the land conductors 40G and the ground conductor patterns 50. The land conductors 40G and the ground conductor patterns 50 are electrically and physically connected by the via conductors VIAGi.

[0122] With this configuration, the switching power supply device 10A forms a noise balancing circuit as follows.

[0123] FIG. 8 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the second embodiment of the present invention.

[0124] The switching power supply device 10A includes a closed electrical circuit for noise protection, which is made up of a switching IC 11, a wiring pattern 41, an inductor 20, a parasitic capacitor Cps, a plurality of linear conductors 71 and 72, a ground conductor pattern 50, via conductors VIAGi, and a land conductor 40G.

[0125] The switching noise generated by the switching IC 11 is trapped by this closed electrical circuit. Since the phase of continuously generated switching noise is not constant, the noise is trapped in the closed electrical circuit and cancels out each other. In other words, this closed electrical circuit functions as a noise balancing circuit that balances the switching noise and suppresses the generation of common mode noise.

[0126] In this way, the switching power supply device 10A can achieve the same effects as the switching power supply device 10. Furthermore, in the switching power supply device 10A, the via conductor VIAGi is connected to the land conductor 40G on which the reference potential connection terminal P02 of the switching IC 11 is mounted. This allows the switching power supply device 10A to further shorten the loop length of the noise balancing circuit.

[0127] [Third Embodiment] A switching power supply device according to a third embodiment of the present invention will be described with reference to the drawings. Fig. 9 is a cross-sectional view showing part of the physical and electrical structure of the switching power supply device according to the third embodiment of the present invention.

[0128] The switching power supply device 10B according to the third embodiment has the same basic circuit configuration as the switching power supply device 10 according to the first embodiment, but differs in some physical and electrical structures. Therefore, only the differences between the switching power supply device 10B and the switching power supply device 10 will be specifically described below.

[0129] 9, the switching power supply device 10B includes a circuit board 60B. The circuit board 60B differs from the circuit board 60 according to the first embodiment in that it includes an input-side High potential wiring pattern 432 and via conductors VIAi.

[0130] The input-side high potential wiring pattern 432 is formed on the first interface (the contact surface between the insulator layer 601 and the insulator layer 602) of the circuit board 60B. The input-side high potential wiring pattern 432 has a portion that overlaps with the inductor 20 in a plan view of the circuit board 60B.

[0131] A slit SLIT is formed in the input side high potential wiring pattern 432 at a portion overlapping the inductor 20 .

[0132] The circuit board 60B includes, on the first main surface 61, a land conductor 431 on which the high-side input terminal P01 of the switching IC 11 is mounted.

[0133] The via conductor VIAi has a shape that penetrates the insulator layer 601, and in plan view overlaps with the land conductor 431 and the input side High potential wiring pattern 432. The land conductor 431 and the input side High potential wiring pattern 432 are electrically and physically connected by the via conductor VIAi.

[0134] With this configuration, the switching power supply device 10B forms a noise balancing circuit as follows.

[0135] FIG. 10 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the third embodiment of the present invention.

[0136] The switching power supply device 10B includes an electrical closed circuit for noise protection, which is made up of a switching IC 11, a wiring pattern 41, an inductor 20, a parasitic capacitor Cps, a plurality of linear conductors 71, 72, an input side high potential wiring pattern 432, a via conductor VIAi, and a land conductor 431.

[0137] The switching noise generated by the switching IC 11 is trapped by this closed electrical circuit. Since the phase of continuously generated switching noise is not constant, the noise is trapped in the closed electrical circuit and cancels out each other. In other words, this closed electrical circuit functions as a noise balancing circuit that balances the switching noise and suppresses the generation of common mode noise.

[0138] In this way, the switching power supply device 10B can achieve the same effects as the switching power supply device 10.

[0139] The circuit board 60B includes a ground conductor pattern 50 (not shown), similar to the circuit board 60 according to the first embodiment, and the ground conductor pattern 50 is formed on an inner layer of the circuit board 60B. In this case, if the ground conductor pattern 50 overlaps the inductor 20, a slit (SLIT) is provided at the overlapping position. This allows the switching power supply device 10B to achieve the same effects as the switching power supply device 10.

[0140] [Fourth Embodiment] A switching power supply device according to a fourth embodiment of the present invention will be described with reference to the drawings. Fig. 11 is a cross-sectional view showing part of the physical and electrical structure of the switching power supply device according to the fourth embodiment of the present invention.

[0141] The switching power supply device 10C according to the fourth embodiment has the same basic circuit configuration as the switching power supply device 10 according to the first embodiment, but differs in some physical and electrical structures. Therefore, only the differences between the switching power supply device 10C and the switching power supply device 10 will be specifically described below.

[0142] 11, the switching power supply device 10C includes a circuit board 60C. The circuit board 60C differs from the circuit board 60 according to the first embodiment in that it includes an inner layer wiring pattern 429 and a via conductor VIAo.

[0143] The inner layer wiring pattern 429 is formed on the first interface (the contact surface between the insulator layer 601 and the insulator layer 602) of the circuit board 60C. The inner layer wiring pattern 429 has a portion that overlaps with the inductor 20 in a plan view of the circuit board 60C.

[0144] A slit SLIT is formed in the portion of the inner layer wiring pattern 429 that overlaps with the inductor 20 .

[0145] The via conductor VIAo has a shape that penetrates the insulator layer 601, and in plan view overlaps the wiring pattern 42 and the inner layer wiring pattern 429. The wiring pattern 42 and the inner layer wiring pattern 429 are electrically and physically connected by the via conductor VIAo.

[0146] Although not shown, the circuit board 60B also includes a ground conductor pattern 50 on an inner layer.

[0147] With this configuration, the switching power supply device 10C forms a noise balancing circuit as follows.

[0148] FIG. 12 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to a fourth embodiment of the present invention.

[0149] The switching power supply device 10C includes an electrical closed circuit for noise protection, which is made up of a switching IC 11, a wiring pattern 41, an inductor 20, a parasitic capacitor Cps, multiple linear conductors 71 and 72, an inner layer wiring pattern 429, a via conductor VIAo, a wiring pattern 42, an output capacitor 32, and a ground conductor pattern 50.

[0150] The switching noise generated by the switching IC 11 is trapped by this closed electrical circuit. Since the phase of continuously generated switching noise is not constant, the noise is trapped in the closed electrical circuit and cancels out each other. In other words, this closed electrical circuit functions as a noise balancing circuit that balances the switching noise and suppresses the generation of common mode noise.

[0151] In this way, the switching power supply device 10C can achieve the same effects as the switching power supply device 10.

[0152] In the circuit board 60C, if the ground conductor pattern 50 overlaps the inductor 20, a slit SLIT is provided at the overlapping position. This allows the switching power supply device 10C to achieve the same effects as the switching power supply device 10.

[0153] Fifth Embodiment A switching power supply device according to a fifth embodiment of the present invention will be described with reference to the drawings. Fig. 13 is a cross-sectional view showing part of the physical and electrical structure of the switching power supply device according to the fifth embodiment of the present invention.

[0154] The switching power supply device 10D according to the fifth embodiment has the same basic circuit configuration as the switching power supply device 10 according to the first embodiment, but differs in some physical and electrical structures. Therefore, only the differences between the switching power supply device 10D and the switching power supply device 10 will be specifically described below.

[0155] 13, the switching power supply device 10D includes a circuit board 60D. The circuit board 60D differs from the circuit board 60 according to the first embodiment in that the output capacitor 32 is mounted at a different position and that the circuit board 60D includes via conductors VIAGo.

[0156] When the first main surface 61 is viewed from above, the output capacitor 32 is mounted immediately adjacent to the second inductor terminal 202 of the inductor 20. Here, "immediately adjacent" means, for example, that the length of one side of the inductor 20 is approximately the same as or shorter than the length of one side when viewed from above.

[0157] The capacitor external terminal 321 of the output capacitor 32 is mounted on the wiring pattern 42 on which the second inductor terminal 202 is mounted. The capacitor external terminal 322 of the output capacitor 32 is mounted on the ground wiring pattern 42G formed on the first main surface 61.

[0158] The via conductor VIAGo has a shape that penetrates the insulator layer 601, and in plan view overlaps the ground wiring pattern 42G and the ground conductor pattern 50. The ground wiring pattern 42G and the ground conductor pattern 50 are electrically and physically connected by the via conductor VIAGo.

[0159] With this configuration, the switching power supply device 10D forms a noise balancing circuit as follows.

[0160] FIG. 14 is a diagram schematically showing the flow of EMI noise in a switching power supply device according to the fifth embodiment of the present invention.

[0161] The switching power supply device 10D includes a first closed electrical circuit for noise, which is made up of the switching IC 11, the wiring pattern 41, the inductor 20, the parasitic capacitor Cps, the plurality of linear conductors 71 and 72, and the ground conductor pattern 50. The switching power supply device 10D further includes a second closed electrical circuit for noise, which is made up of the switching IC 11, the wiring pattern 41, the inductor 20, the wiring pattern 42, the ground wiring pattern 42G, the via conductor VIAGo, and the ground conductor pattern 50.

[0162] The switching noise generated from the switching IC 11 is trapped by these first and second electric closed circuits. Since the phase of continuously generated switching noise is not constant, the noise is trapped in the first and second electric closed circuits and cancels out each other. In other words, these first and second electric closed circuits function as noise balancing circuits that balance the switching noise and suppress the generation of common-mode noise.

[0163] In this way, the switching power supply 10D can achieve the same effects as the switching power supply 10. Furthermore, even if noise leaks to the wiring pattern 42 side, the switching power supply 10D confines it by the second closed electric circuit. Therefore, the switching power supply 10D can more reliably suppress the generation of common mode noise by suppressing the radiation of switching noise to the outside and the conduction of switching noise to the chassis CHS, and can more reliably suppress the levels of switching noise and EMI noise by the noise balancing circuit.

[0164] The configurations of the above-described embodiments can be combined as appropriate, and effects can be achieved according to the combination.

[0165] <1> A switching power supply device comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, the switching power supply device comprising: a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted; the circuit board being configured as a laminated circuit board formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, the circuit board having a first main surface and a second main surface; the inductor being mounted on the first main surface; the conductor patterns including: a first wiring pattern electrically connecting a connection node of the first switching element and the second switching element to the first terminal; and a second wiring pattern electrically connecting the second terminal to the output capacitor; and a ground conductor pattern formed in an inner layer of the laminated circuit board, the inductor being arranged so that a magnetic flux can be perpendicular to the circuit board; and a portion of the ground conductor pattern that overlaps with the inductor when viewed in a direction orthogonal to the first main surface being formed by a conductor portion and a slit, an area of ​​the first wiring pattern is smaller than a projected area of ​​the inductor projected onto the first principal surface, and an area of ​​the second wiring pattern is equal to or larger than the projected area of ​​the inductor, and a noise balancing circuit is formed as an electrically closed circuit by the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the ground conductor pattern.

[0166] <2> The switching power supply device according to <1>, wherein the first switching element and the second switching element form a power conversion circuit, the power conversion circuit includes a ground connection terminal, and the circuit board includes a first ground via conductor immediately adjacent to or immediately below the ground connection terminal when viewed in a direction perpendicular to the first main surface, the first ground via conductor connecting the ground connection terminal and the ground conductor pattern.

[0167] <3> The switching power supply device according to <2>, wherein the output capacitor comprises an output capacitor power supply terminal directly and electrically connected to the second wiring pattern, and an output capacitor ground terminal indirectly electrically connected to the ground conductor pattern, the output capacitor power supply terminal being disposed adjacent to the second terminal of the inductor, the second wiring pattern connecting the output capacitor power supply terminal and the second terminal over the shortest distance, and the circuit board comprises a second ground via conductor immediately adjacent to or immediately below the output capacitor ground terminal when viewed in a direction orthogonal to the first main surface, connecting the output capacitor ground terminal and the ground conductor pattern.

[0168] <4> A switching power supply device comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, the switching power supply device comprising: a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted; the circuit board being formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, and having a first main surface and a second main surface; the inductor being mounted on the first main surface; and the conductor pattern having: an input power supply wiring pattern formed on the laminated circuit board, which electrically connects the input capacitor and the first switching element; a first wiring pattern electrically connecting a connection node of the first switching element and the second switching element to the first terminal; and a second wiring pattern electrically connecting the second terminal to the output capacitor; the inductor being arranged so that a magnetic flux is perpendicular to the circuit board, the input power supply wiring pattern has a slit where no conductor is formed in a portion that overlaps with the inductor when viewed in a direction orthogonal to the first main surface, the area of ​​the first wiring pattern is smaller than a projected area of ​​the inductor when projected onto the first main surface, and the area of ​​the second wiring pattern is approximately the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrically closed circuit consisting of the input capacitor, the input power supply wiring pattern, the first wiring pattern, the second wiring pattern, and the output capacitor.

[0169] <5> A switching power supply device comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, the switching power supply device comprising: a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted; the circuit board being formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, the circuit board having a first main surface and a second main surface; the inductor being mounted on the first main surface; the conductor patterns comprising: a first wiring pattern electrically connecting a connection node of the first switching element and the second switching element to the first terminal; a second wiring pattern electrically connecting the second terminal and the output capacitor; and an output power supply wiring pattern formed on the laminated circuit board and electrically connecting the output capacitor to the output terminal; the inductor being arranged so that magnetic flux is perpendicular to the circuit board; and the output power supply wiring pattern having a slit where no conductor is formed in a portion overlapping with the inductor when viewed in a direction orthogonal to the first main surface, an area of ​​the first wiring pattern that is smaller than a projected area of ​​the inductor projected onto the first principal surface, and an area of ​​the second wiring pattern that is substantially the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrically closed circuit consisting of the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the output power supply wiring pattern.

[0170] <6> The switching power supply device according to any one of <1> to <5>, wherein the slits have a comb-tooth shape.

[0171] <7> The switching power supply device according to any one of <1> to <5>, wherein the slit has a meandering shape.

[0172] <8> The switching power supply device according to any one of <1> to <7>, wherein the inductor includes a magnetic core and a wound linear conductor wound around the magnetic core, and has a bottom surface on which the first terminal and the second terminal are formed, and a top surface opposite the bottom surface, and when viewed in a direction perpendicular to the first main surface, the size of the outer shape of the slit is equal to or larger than the size of a central opening of the wound linear conductor of the inductor and is equal to or smaller than twice the size of the bottom surface of the inductor.

[0173] <9> The switching power supply device according to any one of <1> to <8>, wherein the inductor includes a magnetic core and a wound linear conductor wound around the magnetic core, and has a bottom surface on which the first terminal and the second terminal are formed, and a top surface opposite the bottom surface, and the linear conductor is wound from the bottom surface toward the top surface, with a start of the winding on the bottom surface side electrically connected to the first terminal and an end of the winding on the top surface side connected to the second terminal.

[0174] <10> The switching power supply device according to any one of <1> to <8>, wherein the inductor includes a magnetic core and a wound linear conductor wound around the magnetic core, the inductor having a bottom surface on which the first terminal and the second terminal are formed and a top surface opposite the bottom surface, the linear conductor having a shape wound sequentially from the inside to the outside, the inside winding start being electrically connected to the first terminal and the outside winding end being connected to the second terminal.

[0175] <11> The switching power supply device according to any one of <1> to <10>, wherein the inductor includes a magnetic core, a wound linear conductor wound around the magnetic core, and a shield electrode covering the linear conductor, and the shield electrode is electrically connected to at least one of the second wiring pattern and the ground conductor pattern.

[0176] <12> The switching power supply device according to any one of <1> to <11>, wherein a thickness of a portion of the ground conductor pattern that overlaps with the inductor when viewed in a direction orthogonal to the first main surface is less than a skin depth, and the skin depth is determined by physical properties of a material forming the ground conductor pattern and a switching frequency.

[0177] 10, 10A, 10B, 10C, 10D: Switching power supply device 11: Switching IC 20: Inductor 23: Linear conductor 31: Input capacitor 32: Output capacitor 40G: Land conductor 41, 42: Wiring pattern 42G: Ground wiring pattern 43: Input-side high-potential wiring pattern 50: Ground conductor pattern 60, 60A, 60B, 60C, 60D: Circuit board 61: First main surface 62: Second main surface 71, 72: Linear conductor 73: Conductor-free portion 81: DC power supply 82: Load 111: Switching control circuit 200: Magnetic core 201: First inductor terminal 202: Second inductor terminal 321, 322: Capacitor external terminal 429: Inner layer wiring pattern 431: Land conductor 432: Input-side high-potential wiring pattern 601-603: Insulator layers 3101, 3102: Capacitor external terminals CHS: Chassis Cps: Parasitic capacitor D: Skin depth D71: Thickness E231: One end E232: Other end FB200: Bottom surface FU200: Top surface ND0, ND1H, ND1L, ND2H, ND2L: Nodes P01: Hi-side input terminal P02: Reference potential connection terminal P11, P12: External terminals for switching elements Q1, Q2: Switching elements SLIT: Slit VIAGi, VIAGo, VIAi, VIAo: Via conductors

Claims

1. A switching power supply comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, the switching power supply comprising: a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted; the circuit board being a laminated circuit board formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, the circuit board having a first main surface and a second main surface; the inductor being mounted on the first main surface; the conductor patterns comprising: a first wiring pattern electrically connecting a connection node of the first switching element and the second switching element to the first terminal; a second wiring pattern electrically connecting the second terminal to the output capacitor; and a ground conductor pattern formed in an inner layer of the laminated circuit board; the inductor is arranged so that magnetic flux can be perpendicular to the circuit board; and a portion of the ground conductor pattern that overlaps with the inductor when viewed in a direction orthogonal to the first main surface is formed by a conductor portion and a slit, an area of ​​the first wiring pattern is smaller than a projected area of ​​the inductor projected onto the first principal surface, and an area of ​​the second wiring pattern is equal to or larger than the projected area of ​​the inductor, and a noise balancing circuit is formed as an electrically closed circuit by the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the ground conductor pattern.

2. The switching power supply device according to claim 1, wherein the first switching element and the second switching element form a power conversion circuit, the power conversion circuit includes a ground connection terminal, and the circuit board includes a first ground via conductor immediately adjacent to or immediately below the ground connection terminal when viewed in a direction perpendicular to the first main surface, connecting the ground connection terminal and the ground conductor pattern.

3. The switching power supply device according to claim 2, wherein the output capacitor comprises an output capacitor power supply terminal directly and electrically connected to the second wiring pattern, and an output capacitor ground terminal indirectly electrically connected to the ground conductor pattern, the output capacitor power supply terminal being disposed adjacent to the second terminal of the inductor, the second wiring pattern connecting the output capacitor power supply terminal and the second terminal over the shortest distance, and the circuit board comprises a second ground via conductor immediately adjacent to or immediately below the output capacitor ground terminal when viewed in a direction perpendicular to the first main surface, connecting the output capacitor ground terminal and the ground conductor pattern.

4. A switching power supply device comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, comprising a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted, the circuit board being formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, and having a first main surface and a second main surface, the inductor being mounted on the first main surface, the conductor pattern comprising: an input power supply wiring pattern formed on the laminated circuit board, which electrically connects the input capacitor and the first switching element; a first wiring pattern which electrically connects a connection node of the first switching element and the second switching element to the first terminal; and a second wiring pattern which electrically connects the second terminal to the output capacitor, the inductor being arranged so that magnetic flux is perpendicular to the circuit board, the input power supply wiring pattern has a slit where no conductor is formed in a portion that overlaps with the inductor when viewed in a direction orthogonal to the first main surface, the area of ​​the first wiring pattern is smaller than a projected area of ​​the inductor when projected onto the first main surface, and the area of ​​the second wiring pattern is approximately the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrically closed circuit consisting of the input capacitor, the input power supply wiring pattern, the first wiring pattern, the second wiring pattern, and the output capacitor.

5. A switching power supply device comprising: an input capacitor; a first switching element and a second switching element electrically connected to the input capacitor; an inductor having a first terminal and a second terminal; and an output capacitor, the switching power supply device comprising: a circuit board on which the input capacitor, the first switching element, the second switching element, the inductor, and the output capacitor are mounted; the circuit board being a laminated circuit board formed by laminating a plurality of insulator layers, each having a conductor pattern formed thereon, the circuit board having a first main surface and a second main surface; the inductor being mounted on the first main surface; the conductor patterns comprising: a first wiring pattern electrically connecting a connection node of the first switching element and the second switching element to the first terminal; a second wiring pattern electrically connecting the second terminal to the output capacitor; and an output power supply wiring pattern formed on the laminated circuit board and electrically connecting the output capacitor to the output terminal; the inductor being arranged so that magnetic flux is perpendicular to the circuit board; and the output power supply wiring pattern having a slit where no conductor is formed in a portion overlapping with the inductor when viewed in a direction orthogonal to the first main surface, an area of ​​the first wiring pattern is smaller than a projected area of ​​the inductor projected onto the first principal surface, and an area of ​​the second wiring pattern is approximately the same as or larger than the projected area of ​​the inductor, thereby forming a noise balancing circuit that is an electrically closed circuit made up of the input capacitor, the first wiring pattern, the second wiring pattern, the output capacitor, and the output power supply wiring pattern.

6. A switching power supply device according to any one of claims 1 to 5, wherein the slits are comb-teeth shaped.

7. A switching power supply device according to any one of claims 1 to 5, wherein the slits are meandering shaped.

8. A switching power supply device according to any one of claims 1 to 7, wherein the inductor comprises a magnetic core and a wound linear conductor wound around the magnetic core, has a bottom surface on which the first terminal and the second terminal are formed, and a top surface opposite the bottom surface, and when viewed in a direction perpendicular to the first main surface, the size of the outer shape of the slit is equal to or larger than the size of a central opening of the linear conductor of the inductor and is equal to or smaller than twice the size of the bottom surface of the inductor.

9. A switching power supply device as claimed in any one of claims 1 to 8, wherein the inductor comprises a magnetic core and a wound linear conductor wound around the magnetic core, has a bottom surface on which the first terminal and the second terminal are formed, and a top surface opposite the bottom surface, the linear conductor being wound from the bottom surface towards the top surface, with the start of the winding on the bottom surface side electrically connected to the first terminal and the end of the winding on the top surface side connected to the second terminal.

10. A switching power supply device as described in any one of claims 1 to 8, wherein the inductor comprises a magnetic core and a wound linear conductor wound around the magnetic core, has a bottom surface on which the first terminal and the second terminal are formed, and a top surface opposite the bottom surface, and the linear conductor is wound in order from the inside to the outside, with the start of the inner winding electrically connected to the first terminal and the end of the outer winding connected to the second terminal.

11. A switching power supply device according to any one of claims 1 to 10, wherein the inductor comprises a magnetic core, a wound linear conductor wound around the magnetic core, and a shield electrode covering the linear conductor, and the shield electrode is electrically connected to at least one of the second wiring pattern and the ground conductor pattern.

12. A switching power supply device according to any one of claims 1 to 11, wherein the thickness of a portion of the ground conductor pattern that overlaps with the inductor when viewed in a direction perpendicular to the first principal surface is less than a skin depth, and the skin depth is determined by the physical properties of a material forming the ground conductor pattern and a switching frequency.

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