Filter unit

Abstract

The filter unit comprises a substrate; a capacitor mounted on the substrate; and two inductors. The inductor comprises wiring and a core. The core comprises two core bodies. The core body is annular and has wiring holes. The capacitor is positioned between the two core bodies. An opposing portion extends from each of the two core bodies to a position opposing the capacitor C. The opposing portion opposes all of the capacitors.

Description

Technical Field

[0001] The present invention relates to a filter unit. Background Art

[0002] An electronic device includes a filter for attenuating noise. The filter described in Patent Document 1 includes an inductor and a capacitor. The inductor includes wiring and a core surrounding the wiring.

[0003] Patent Document 1: Japanese Patent Application Laid-Open No. 2015-167154

[0004] When miniaturizing filters, capacitors are placed near the core. When current flows through the wiring, a magnetic field caused by noise is generated in the core. If the capacitors are affected by this magnetic field, the filter's attenuation characteristics may be degraded. Summary of the Invention

[0005] An object of the present invention is to provide a filter unit capable of suppressing a decrease in attenuation characteristics against noise.

[0006] In order to solve the above-mentioned problems, according to a first embodiment of the present invention, there is provided a filter unit comprising: a capacitor; and an inductor having wiring and a core, wherein the core comprises: an annular core body for the wiring to pass through; and an opposing portion extending from the core body to a position opposite to the capacitor. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Figure 1 This is a schematic diagram of the structure of a power conversion device mounted on a vehicle.

[0008] Figure 2 It is a three-dimensional diagram of the filter unit.

[0009] Figure 3 yes Figure 2 3-3 line cross-sectional view.

[0010] Figure 4 This is a cross-sectional view showing a partial cutaway portion of the filter unit.

[0011] Figure 5 It is an exploded perspective view of the core.

[0012] Figure 6 yes Figure 2 6-6 line cross-sectional view.

[0013] Figure 7 It is a perspective view of a filter unit of a comparative example.

[0014] Figure 8 Schematic diagram showing simulation results of magnetic field distribution of a filter unit according to a comparative example.

[0015] Figure 9 It is a schematic diagram showing the simulation results of the magnetic field distribution of the filter unit according to the embodiment.

[0016] Figure 10 It is a graph showing the attenuation characteristics of the filter unit according to the embodiment and the attenuation characteristics of the filter unit according to the comparative example. DETAILED DESCRIPTION

[0017] Hereinafter, one embodiment of the filter unit will be described.

[0018] like Figure 1 As shown, vehicle 10 includes a battery 11 and a power conversion device 12. Power conversion device 12 includes a DC / DC converter 13, a filter 20, and a filter unit 30. Vehicle 10 is an electric vehicle or a hybrid vehicle driven by an electric motor. Battery 11 serves as a power source for the electric motor mounted on vehicle 10. Battery 11 can be, for example, a rechargeable power storage device such as a lithium-ion secondary battery or a nickel-metal hydride battery. Power conversion device 12 is electrically connected to a household load 19. Power conversion device 12 supplies power to household load 19.

[0019] The DC / DC converter 13 includes a bridge circuit 14, a transformer 15, and a rectifier circuit 16. The bridge circuit 14 is provided on the primary side of the transformer 15 and includes four switching elements Q1 to Q4. Switching elements Q1 and Q2 are connected in series with each other. Switching elements Q3 and Q4 are connected in series with each other.

[0020] The rectifier circuit 16 is provided on the secondary side of the transformer 15 and includes four diodes D1 to D4. Diodes D1 and D2 are connected in series with each other. Diodes D3 and D4 are connected in series with each other.

[0021] Transformer 15 includes a primary winding 17 and a secondary winding 18. Primary winding 17 is connected to the connection point between switching elements Q1 and Q2 and the connection point between switching elements Q3 and Q4. Secondary winding 18 is connected to the connection point between diodes D1 and D2 and the connection point between diodes D3 and D4.

[0022] In DC / DC converter 13, the DC power input from battery 11 is stepped down through the switching operation of switching elements Q1 to Q4. In this embodiment, the switching frequency of switching elements Q1 to Q4 is 150 kHz to 200 kHz. DC / DC converter 13 outputs the stepped-down DC power to filter 20. In this embodiment, a full-bridge DC / DC converter 13 is used, but any other type of DC / DC converter, such as a half-bridge type, may also be used.

[0023] Filter 20 includes a smoothing coil 21 and a smoothing capacitor 22. Filter 20 is an LC filter composed of smoothing coil 21 and smoothing capacitor 22. Filter 20 attenuates noise in a desired frequency band. Smoothing coil 21 smoothes the output power including ripple rectified by rectifier circuit 16.

[0024] like Figure 1 and Figure 2 As shown, the filter unit 30 includes a substrate 31 , a capacitor C mounted on the substrate 31 , and two inductors L1 and L2 . Although not shown, the DC / DC converter 13 and the filter 20 are also mounted on the substrate 31 .

[0025] like Figure 2 and Figure 3 As shown, inductors L1 and L2 include wiring 36 serving as power lines and a core 50. Substrate 31 includes an insulating layer 32, a pattern 35 for connecting capacitor C, and vias 37 connecting pattern 35 and wiring 36. One of the two surfaces in the thickness direction of insulating layer 32 is designated as first surface 33, and the other surface is designated as second surface 34. Pattern 35 is provided on first surface 33. Wiring 36 is provided on second surface 34. When viewed in the thickness direction of substrate 31, pattern 35 and wiring 36 intersect. For example, copper foil can be used as pattern 35. Busbars are used as wiring 36. Capacitor C is connected to pattern 35 using a bonding material such as solder.

[0026] like Figure 4 As shown, the insulating layer 32 has four holes 41 to 44 extending through the thickness of the substrate 31. When viewed from the thickness of the substrate 31, the intersection X is defined as the location where the pattern 35 and the wiring 36 intersect. When viewing the insulating layer 32 from the thickness of the substrate 31, the area surrounding the intersection X is divided into four regions A1, A2, A3, and A4 by the pattern 35 and the wiring 36. One hole 41 to 44 is provided in each of the four regions A1 to A4. The four holes 41 to 44 are located on either side of the pattern 35 and on either side of the wiring 36. In the following description, the first hole 41 is one of the four holes 41 to 44. The second hole 42 is provided so that the wiring 36 is located between the second hole 42 and the first hole 41. The third hole 43 is provided so that the pattern 35 is located between the third hole 43 and the first hole 41. The fourth hole 44 is provided so that the wiring 36 is located between the fourth hole 44 and the third hole 43. The spacing distance between the center axis of the first hole 41 and the center axis of the second hole 42 is the same as the spacing distance between the center axis of the third hole 43 and the center axis of the fourth hole 44. The spacing distance between the center axis of the first hole 41 and the center axis of the third hole 43 is the same as the spacing distance between the center axis of the second hole 42 and the center axis of the fourth hole 44.

[0027] The capacitor C is disposed at two locations. The capacitor C is disposed between the first hole 41 and the third hole 43 and between the second hole 42 and the fourth hole 44. Figure 4 As shown, a plurality of capacitors C are provided on the pattern 35 . Figure 1 The combined capacity of multiple capacitors C is expressed as one capacitor C.

[0028] like Figure 5 As shown, the core 50 is divided into two. As the core 50, a powder core made by high-pressure pressing of metal magnetic powder and a binder can be used. As the core 50, any core such as a ferrite core can also be used. The core 50 includes a first core 51 and a second core 71. The first core 51 includes a rectangular plate-shaped base 52 and legs 53 to 56 respectively provided at the four corners of the base 52. The legs 53 to 56 are columnar. The legs 53 to 56 protrude in the thickness direction of the base 52. The legs 53 to 56 protrude in the same direction from the base 52. In the following description, the first leg 53 is one of the four legs 53 to 56. In the short side direction of the base 52, the second leg 54 is arranged adjacent to the first leg 53. In the long side direction of the base 52, the third leg 55 is arranged adjacent to the first leg 53. The fourth leg 56 is arranged adjacent to the third leg 55 in the short-side direction of the base 52. The distance between the center axis of the first leg 53 and the center axis of the second leg 54 is the same as the distance between the center axis of the first hole 41 and the center axis of the second hole 42. The distance between the center axis of the first leg 53 and the center axis of the third leg 55 is the same as the distance between the center axis of the first hole 41 and the center axis of the third hole 43.

[0029] On the base 52, the portion connecting the first leg 53 and the second leg 54 is designated as a first connecting portion 61, and the portion connecting the third leg 55 and the fourth leg 56 is designated as a second connecting portion 62. In the base 52, the first connecting portion 61 includes a portion facing the first leg 53, a portion facing the second leg 54, and a portion between the first and second legs 53, 54. In the base 52, the second connecting portion 62 includes a portion facing the third leg 55, a portion facing the fourth leg 56, and a portion between the third and fourth legs 55, 56.

[0030] In the base 52, the portion connecting the first leg 53 and the third leg 55 is referred to as the third connection portion 63, and the portion connecting the second leg 54 and the fourth leg 56 is referred to as the fourth connection portion 64. In the base 52, the third connection portion 63 includes a portion facing the first leg 53, a portion facing the third leg 55, and a portion between the first and third legs 53 and 55. In the base 52, the fourth connection portion 64 includes a portion facing the second leg 54 and a portion facing the fourth leg 56, and a portion between the second and fourth legs 54 and 56. In the base 52, the third connection portion 63 and the first connection portion 61 share the portion facing the first leg 53. In the base 52, the third connection portion 63 and the second connection portion 62 share the portion facing the third leg 55. In the base 52, the fourth connection portion 64 and the first connection portion 61 share the portion facing the second leg 54. In the base 52 , the fourth link portion 64 and the second link portion 62 share a portion opposite to the fourth leg portion 56 .

[0031] In the base 52, the portion between the first connection portion 61 and the second connection portion 62 is defined as the facing portion 65, and the facing portion 65 connects the first connection portion 61 and the second connection portion 62. Part of the facing portion 65 constitutes part of the third connection portion 63 and the fourth connection portion 64.

[0032] The second core 71 is in the shape of a quadrilateral plate. The second core 71 only needs to be large enough to allow all four legs 53 to 56 to contact each other when it overlaps the first core 51. In this embodiment, the thickness-direction surface of the second core 71 and the thickness-direction surface of the base 52 have the same shape.

[0033] like Figure 2 、 Figure 4 as well as Figure 6 As shown, the first core 51 and the second core 71 are arranged so that the substrate 31 is located between the base 52 and the second core 71. The first core 51 is arranged so that the base 52 faces the first surface 33 of the substrate 31. The second core 71 is arranged so that it faces the second surface 34 of the substrate 31. The legs 53 to 56 of the first core 51 are inserted into the holes 41 to 44. The first leg 53 is inserted into the first hole 41, the second leg 54 is inserted into the second hole 42, the third leg 55 is inserted into the third hole 43, and the fourth leg 56 is inserted into the fourth hole 44. Each leg 53 to 56 passes through the insulating layer 32. Each leg 53 to 56 contacts the second core 71. Specifically, each leg 53 to 56 of the first core 51 contacts the four corners of the second core 71. With respect to the second core 71, the substrate 31 is arranged between the second core 71 and the first core 51, and faces the entire first core 51.

[0034] like Figure 2 and Figure 6As shown, the core 50 includes two core bodies 81 and 82 formed by the base 52, the legs 53 to 56, and the second core 71, with the legs 53 to 56 in contact with the second core 71. The first leg 53, the second leg 54, the first connecting portion 61, and the first portion 72 of the second core 71 form a single core body 81. The first portion 72 is the portion of the second core 71 that faces the first connecting portion 61 across the substrate 31, the first leg 53, and the second leg 54. The third leg 55, the fourth leg 56, the second connecting portion 62, and the second portion 73 of the second core 71 form a single core body 82. The second portion 73 is the portion of the second core 71 that faces the second connecting portion 62 across the substrate 31, the third leg 55, and the fourth leg 56. The opposing portion 65 connects the core bodies 81 and 82. The second core 71 has a third portion 74 between the first portion 72 and the second portion 73. The third portion 74 also connects the core bodies 81 and 82.

[0035] In this embodiment, the core bodies 81 and 82 have the same shape. They are annular and have wiring holes 83. Wiring 36 is passed through wiring holes 83. The core bodies 81 and 82 are arranged so that their central axes face the same direction. The term "same direction" here allows for some deviation within a tolerance range.

[0036] Wiring 36 is linearly passed through wiring holes 83 of core bodies 81 and 82. The magnetic field generated by the current flowing through wiring 36 acts on core 50, forming inductors L1 and L2. In this embodiment, wiring 36 and core bodies 81 and 82 respectively form inductors L1 and L2, but it can also be understood that wiring 36 and core 50 form a single inductor.

[0037] Each capacitor C is disposed between the core bodies 81 and 82. The capacitor C is located between the first leg 53 and the third leg 55, and between the second leg 54 and the fourth leg 56. The opposing portion 65 opposes the capacitor C in the thickness direction of the substrate 31. The thickness direction of the substrate 31 can also be referred to as the direction in which the insulating layer 32 and the pattern 35 overlap. The opposing portion 65 extends from the core bodies 81 and 82 to a position opposing the capacitor C. The opposing portion 65 opposes all of the multiple capacitors C. The capacitor C is sandwiched between the opposing portion 65 and the substrate 31 in the thickness direction of the substrate 31.

[0038] The third portion 74 of the second core 71 extends from the core bodies 81 and 82 to a position facing the capacitors C across the substrate 31. The third portion 74 of the second core 71 faces all of the plurality of capacitors C across the substrate 31. In other words, the capacitors C are sandwiched between the opposing portion 65 and the third portion 74 in the thickness direction of the substrate 31.

[0039] like Figure 2 and Figure 4 As shown, the core 50 includes two annular portions 91 and 92 formed by the base 52, the legs 53 to 56, and the second core 71. The first leg 53, the third leg 55, the third connecting portion 63, and the second core 71 form the annular portion 91. The second leg 54, the fourth leg 56, the fourth connecting portion 64, and the second core 71 form the annular portion 92.

[0040] The annular portions 91 and 92 include a connection hole 93. The connection hole 93 is a hole through which the pattern 35 passes. The annular portions 91 and 92 are arranged so that their central axes face the same direction. The so-called same direction here allows for a certain error within the tolerance range. The direction along the central axis of the annular portions 91 and 92 and the direction along the central axis of the core body 81 and 82 are orthogonal to each other. The core 50 includes: a wiring hole 83 through which the wiring 36 for constituting the inductors L1 and L2 passes; and a connection hole 93 through which the pattern 35 for connecting the capacitor C passes. The wiring hole 83 has a dimension in a length direction that is orthogonal to the central axis of the wiring hole 83 and the thickness direction of the substrate 31. The connection hole 93 has a dimension in a length direction that is orthogonal to the central axis of the connection hole 93 and the thickness direction of the substrate 31. The length of the wiring hole 83 is smaller than the length of the connection hole 93.

[0041] Filter unit 30 attenuates noise contained in the DC power output from filter 20 before outputting it. Filter unit 30 in this embodiment attenuates noise in the frequency band below 150 kHz to 200 kHz, which is the switching frequency of switching elements Q1 to Q4, and in the frequency band above 500 kHz, which is the frequency used for AM broadcasting. The power output from filter unit 30 is supplied to load 19 within the home.

[0042] The operation of this embodiment will be described.

[0043] The inductors L1 and L2 are formed by the wiring 36 and the annular core bodies 81 and 82 surrounding the wiring 36. The impedance of the inductors L1 and L2 increases as the frequency increases, thereby blocking high-frequency noise.

[0044] Furthermore, when high-frequency noise current flows into wiring 36, a magnetic field corresponding to the noise current is generated within core 50. The noise current is converted into a magnetic field and consumed as magnetic loss, thereby reducing the noise current.

[0045] like Figure 1As shown, filter unit 30 has an inductance component L3 caused by capacitor C and pattern 35. If magnetic field coupling occurs between inductors L1 and L2 and inductance component L3 due to the influence of a magnetic field, a voltage is generated. This voltage may degrade the attenuation characteristics of filter unit 30. The filter unit 30 of this embodiment suppresses the magnetic field effect on capacitor C, thereby suppressing magnetic field coupling between inductors L1 and L2 and inductance component L3. This is described in detail below.

[0046] First, a filter unit according to a comparative example will be described. The filter unit according to the comparative example has the same structure as the filter unit according to the present embodiment, except for a difference in the shape of the core.

[0047] like Figure 7 As shown, the filter unit 100 of the comparative example includes a core 101. The core 101 includes annular core bodies 102 and 103. The core 101 is not provided at a position opposing the capacitor C in the thickness direction of the substrate 31. In other words, the core 101 used in the filter unit 100 of the comparative example omits the opposing portion 65 of the core 50 of the present embodiment.

[0048] Figure 8 36 shows the magnetic field distribution generated inside the core 101 of the filter unit 100 of the comparative example when current flows through the wiring 36. The magnetic field distribution shows the strength of the magnetic field, that is, the magnetic flux density. Figure 8 In the diagram, dots are used to represent the strength of the magnetic field. It can be said that the denser the dots are, the stronger the magnetic field is. Figure 8 As can be seen, in the filter unit 100 of the comparative example, the capacitor C is located in a portion where the magnetic field strength is relatively strong, and the inductors L1 and L2 and the inductance component L3 are easily magnetically coupled.

[0049] Figure 9 The magnetic field distribution generated inside the core 50 of the filter unit 30 of this embodiment when current flows through the wiring 36 is shown. Figure 9 As understood, by providing the facing portion 65 so as to face the capacitor C, the magnetic field can be guided so that the magnetic field intensity at the position where the capacitor C is provided is weakened compared to a case where the facing portion 65 is not provided.

[0050] Figure 10The vertical axis is set to gain = attenuation rate, and the horizontal axis is set to frequency, showing the attenuation characteristics of the filter units 30 and 100. The attenuation characteristics of the filter unit 100 of the comparative example are shown with a single-dot dashed line, and the attenuation characteristics of the filter unit 30 of the present embodiment are shown with a solid line. In the filter unit 100 of the comparative example, the attenuation characteristics decrease at a range of 150kHz to 200kHz. In contrast, in the filter unit 30 of the present embodiment, the decrease in attenuation characteristics is suppressed even in the band below 150kHz to 200kHz. In this way, by guiding the magnetic field through the opposing portion 65, the magnetic field strength at the location where the capacitor C is set is weakened, thereby suppressing the decrease in attenuation characteristics.

[0051] When the output power from the DC / DC converter 13 is supplied to a load 19 in a home, it is sometimes necessary to expand the frequency band in which noise is attenuated so that the noise contained in the output power from the DC / DC converter 13 does not flow into the home. In the filter unit 30 of this embodiment, it is required to attenuate noise in frequency bands below the switching frequency and above the frequency used in AM broadcasting. In order to attenuate noise in a larger frequency band, it is also possible to consider increasing the number of filters and the number of capacitors C. However, increasing the number of filters and capacitors C results in an increase in the size of the power conversion device 12. In contrast, in this embodiment, the noise attenuation characteristics are improved by changing the magnetic field distribution. Therefore, compared to the case of increasing the number of filters and capacitors C, the size of the power conversion device 12 is suppressed and the attenuation characteristics of the filter unit 30 are improved.

[0052] The effects of this embodiment will be described.

[0053] (1) The core 50 includes an opposing portion 65 that faces the capacitor C. By using the opposing portion 65 to guide the magnetic field, the magnetic field intensity at the location where the capacitor C is located can be weakened compared to a case where the opposing portion 65 is not provided. By suppressing the influence of the magnetic field on the capacitor C, it is possible to suppress a decrease in the attenuation characteristics of the filter unit 30.

[0054] (2) The pattern 35 intersects the wiring 36 when viewed in the thickness direction of the substrate 31. Since the wiring 36 and the pattern 35 can be arranged to overlap when viewed in the thickness direction of the substrate 31, the filter unit 30 can be miniaturized.

[0055] (3) Two core bodies 81 and 82 are provided, and the capacitor C is disposed between the core bodies 81 and 82. This arrangement allows the space between the two core bodies 81 and 82 to be used as an area for arranging the capacitor C. This allows the filter unit 30 to be miniaturized compared to a case where the capacitor C is disposed at a position different from the space between the two core bodies 81 and 82.

[0056] (4) The facing portion 65 connects the core bodies 81 and 82. By connecting the core bodies 81 and 82 with each other using the facing portion 65, it is easy to guide the magnetic field so as to weaken the magnetic field at the location where the capacitor C is provided.

[0057] (5) Filter unit 30 is an output filter provided on the secondary side of transformer 15. Since DC / DC converter 13 steps down the voltage, the current flowing through the secondary side of transformer 15 is larger than the current flowing through the primary side of transformer 15. High currents make it difficult to attenuate noise. As in the embodiment, by suppressing the degradation of the attenuation characteristics of filter unit 30, noise can be efficiently attenuated even with high currents.

[0058] The embodiment can be implemented by being modified as follows. The embodiment and the following modifications can be implemented in combination with each other within the scope of no technical contradiction.

[0059] The facing portion 65 may not connect the core bodies 81 and 82 . In this case, the facing portion 65 is provided on one of the core bodies 81 and 82 .

[0060] The core 50 may include either the core main bodies 81 or 82. In this case, the capacitor C may be disposed at any position as long as it is around the core main bodies 81 or 82.

[0061] The shape of the opposing portion 65 can also be modified. The opposing portion 65 only needs to face the capacitor C, and the portion not facing the capacitor C can be omitted. When the shape of the opposing portion 65 is modified, the shape of the second core 71 can also be modified to accommodate the shape of the opposing portion 65. The second core 71 is preferably positioned so that the substrate 31 is disposed between the first core 51 and the second core 71, facing the opposing portion 65.

[0062] The pattern 35 may not intersect the wiring 36 when viewed in the thickness direction of the substrate 31 .

[0063] Alternatively, the opposing portion 65 may face the capacitor C in a direction perpendicular to both the thickness direction of the substrate 31 and the central axis of the core bodies 81 and 82. That is, the opposing portion 65 only needs to extend from the core bodies 81 and 82 to a position facing the capacitor C and may face the capacitor C in any direction.

[0064] The facing portion 65 only needs to face at least part of the plurality of capacitors C.

[0065] The core 50 may not be divided into the first core 51 and the second core 71 .

[0066] The wiring 36 may be wound around the core bodies 81 and 82 .

[0067] The filter unit 30 may be used to attenuate noise included in the AC power.

[0068] The filter unit 30 can be provided in any device as long as it is a device that needs to attenuate noise.

Claims

1. A filter unit, characterized in that: have: capacitors; and an inductor having wiring and a core; and a substrate on which the capacitor is mounted, The core has: an annular core body for the wiring to pass through; and An opposing portion extends from the core body to a position opposite to the capacitor, In the thickness direction of the substrate, the opposing portion faces the capacitor. The substrate has a pattern for connecting the capacitor. When viewed from the thickness direction of the substrate, the pattern intersects the wiring. The core body is one of two annular core bodies. The capacitor is arranged between the two annular core bodies and outside each of the two annular core bodies.

2. The filter unit according to claim 1, characterized in that The facing portion connects the two core bodies.

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