Noise filter and power conversion device

Abstract

A noise filter (1) comprises: a first ground capacitor (210) that is between a positive electrode bus bar (6) and the ground side, passes through the positive electrode bus bar and positive electrode wiring (610), and is connected to the ground side via ground wiring (810); and a second ground capacitor (220) that is between a negative electrode bus bar (7) and the ground side, passes through the negative electrode bus bar and negative electrode wiring (710), and is connected to the ground side via the ground wiring. The positive electrode wiring and the negative electrode wiring are each stacked and arranged with respect to the ground wiring. The first ground capacitor and the second ground capacitor are arranged on one end side of each wiring of the positive electrode wiring, the negative electrode wiring, and the ground wiring which are stacked and arranged, and a first connection part between the positive electrode bus bar and the positive electrode wiring, a second connection part between the negative electrode bus bar and the negative electrode wiring, and a third connection part between the ground side and the ground wiring are arranged on the other end side of said each wiring.

Description

Noise filter and power conversion device

[0001] The present invention relates to a noise filter and a power conversion device.

[0002] Power conversion devices that convert DC power to AC power and vice versa through the switching operation of semiconductor elements are widely used in hybrid vehicles, electric vehicles, etc. To reduce the effects of noise generated by the switching operation of these semiconductor elements, a noise filter is provided on the power connector side of the power conversion device.

[0003] Patent Document 1 discloses a noise filter in which the first earth capacitor and the second earth capacitor are arranged so that at least one of the direction from the third connection part to the fourth connection part of the first earth capacitor and the direction from the fifth connection part to the sixth connection part of the second earth capacitor forms a first adjustment angle greater than 0 degrees and less than 360 degrees with respect to the direction from the first connection part to the second connection part of the first line-to-line capacitor when viewed from a direction perpendicular to the plane.

[0004] International Publication No. WO2019 / 017003

[0005] The technology of Patent Document 1 does not take into consideration the reduction of parasitic inductance caused by wiring in the noise filter, and therefore is unable to improve the noise suppression of the noise filter.

[0006] A noise filter according to the present invention comprises: a first ground capacitor between a positive bus bar and a ground side, connected via the positive bus bar and positive wiring and also via the ground side and ground wiring; and a second ground capacitor between a negative bus bar and the ground side, connected via the negative bus bar and negative wiring and also via the ground side and ground wiring, wherein the positive wiring and the negative wiring are each arranged in a stack with respect to the ground wiring, the first ground capacitor and the second ground capacitor are arranged on one end side of each of the stacked positive wiring, negative wiring, and ground wiring, and a first connection portion between the positive bus bar and the positive wiring, a second connection portion between the negative bus bar and the negative wiring, and a third connection portion between the ground side and the ground wiring are arranged on the other end side of each of the wiring.

[0007] According to the present invention, the parasitic inductance caused by the wiring of the noise filter can be reduced, and the noise suppression of the noise filter can be improved.

[0008] FIG. 1 is an overall configuration diagram of a power conversion device according to a first embodiment. FIG. 2 is a perspective view of a wiring board of a noise filter according to the first embodiment. (A) (B) Top views of the wiring board of the noise filter according to the first embodiment. FIG. 3 is an equivalent circuit of the noise filter according to the first embodiment. FIG. 4 is a perspective view of a wiring board of a noise filter according to a comparative example. FIG. 5 is a top view of a wiring board of a noise filter according to the comparative example. FIG. 6 is a graph showing a coupling coefficient of mutual inductance in a noise filter. FIG. 7 is a graph showing input / output characteristics of a noise filter. (A) (B) Perspective views of a positive bus bar and a negative bus bar according to the first embodiment. FIG. 8 is a side view of a noise filter according to the first embodiment. (A) (B) Views of a wiring board according to a first modification. (A) (B) (C) Views of a wiring board according to a second modification. (A) (B) (D) (E) Views of a wiring board according to a third modification. FIG. 9 is an overall configuration diagram of a power conversion device according to a second embodiment. (A) (B) Top views of a wiring board according to the second embodiment. (A) (B) Top views of a wiring board according to a fourth modification. FIG. 10 is an overall configuration diagram of a power conversion device according to a third embodiment. FIG. 11 is an equivalent circuit diagram including a noise filter according to a third embodiment.

[0009] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The following description and drawings are examples for explaining the present invention, and some omissions and simplifications have been made as appropriate for clarity of explanation. The present invention can be implemented in various other forms. Unless otherwise specified, each component may be singular or plural.

[0010] In order to facilitate understanding of the invention, the position, size, shape, range, etc. of each component shown in the drawings may not represent the actual position, size, shape, range, etc. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings.

[0011] [First Embodiment] A first embodiment of the present invention will be described with reference to FIGS. 1 to 10. FIG. 1 is an overall configuration diagram of a power conversion device 10 in this embodiment. The power conversion device 10 converts power between a battery 20 and a motor 30. For example, the power conversion device 10 converts DC power supplied from the battery 20 into AC power and supplies the AC power to the motor 30. The power conversion device 10 also converts AC power supplied from the motor 30, which functions as a generator during regeneration, into DC power to charge the battery 20. It is sufficient for the power conversion device 10 to be able to perform at least one of the conversion from DC power to AC power and the conversion from AC power to DC power.

[0012] The power conversion device 10 is covered with a metal housing, which serves as the reference potential of the power conversion device 10 and is connected to the ground side. A high-voltage DC cable is connected from a battery 20 to a connector 21 of the power conversion device 10. The power conversion device 10 is also connected to a connector 31 from a motor 30 via a high-voltage AC cable. The motor 30 is, although not particularly limited, configured as a three-phase electric motor.

[0013] The power conversion device 10 includes a noise filter 1, a smoothing capacitor 2, a power module 3 constituting an inverter circuit, a driver circuit board 4, and a control circuit board 5. DC power from a battery 20 is supplied to the power module 3 via a connector 21, a positive bus bar 6, and a negative bus bar 7.

[0014] The noise filter 1 is connected to a positive bus bar 6, a negative bus bar 7, and a ground bus bar 8. The ground bus bar 8 is connected to the housing of the power conversion device 10. Details of the noise filter 1 will be described later. The smoothing capacitor 2 suppresses pulsation in the DC voltage generated by the switching operation of the semiconductor elements in the power module 3.

[0015] The power module 3 incorporates semiconductor elements to form an inverter circuit. When the motor 30 is driven, the semiconductor elements are switched in response to gate signals from the driver circuit board 4, and DC power supplied from the battery 20 is converted into AC power to drive the motor 30.

[0016] The driver circuit board 4 includes a driver circuit, converts the gate signal generated by the control circuit into a potential required for switching on and off the semiconductor elements in the power module 3 , and outputs the converted signal to the power module 3 .

[0017] The control circuit board 5 is equipped with a control circuit, and generates a gate signal based on a torque command value or the like given from a host controller (not shown) of an electric vehicle or the like, to control the torque of the motor 30. At the connection portion between the positive bus bar 6 and the negative bus bar 7 and the noise filter 1, ferrite cores 91 and 92 are provided on both sides of the connection portion so as to surround the positive bus bar 6 and the negative bus bar 7.

[0018] When the power module 3 is functioning as an inverter, noise is generated by the switching operation of the semiconductor elements. This noise is caused by fluctuations in the voltage to ground and is generally called common mode noise. This common mode noise is transmitted via the positive bus bar 6 and the negative bus bar 7 due to the stray capacitance of each component of the power conversion device 10, etc., and flows into the high-voltage DC cable connected between the connector 21 and the battery 20. The noise filter 1 is provided to reduce this common mode noise.

[0019] The noise filter 1 includes a positive Y capacitor 210 and a negative Y capacitor 220. These Y capacitors 210 and 220 are also referred to as ground capacitors. The positive Y capacitor 210 is connected between the positive bus bar 6 and the ground via a positive wiring 610 and a ground wiring 810. The negative Y capacitor 220 is connected between the negative bus bar 7 and the ground via a negative wiring 710 and a ground wiring 810. The positive wiring 610, the negative wiring 710, and the ground wiring 810 are, for example, wiring patterns formed on a multi-layer wiring board. The wiring connections of the noise filter 1 will be described in detail later.

[0020] FIG. 2 is a perspective view of the wiring substrate 11 of the noise filter 1, FIG. 3A is a top view of the wiring substrate 110, and FIG. 3B is a top view of the wiring substrate 120.

[0021] The positive electrode wiring 610, negative electrode wiring 710, and ground wiring 810 of the noise filter 1 are formed in a wiring pattern on a wiring board 11 made up of multiple layers. In the example shown in FIGS. 2, 3A, and 3B, the positive electrode wiring 610 and negative electrode wiring 710 are formed on a first-layer wiring board 110, and the ground wiring 810 is formed on a second-layer wiring board 120. Note that the wiring board made up of multiple layers may be a multilayer wiring board or may be a board in which wiring boards are stacked. These wiring boards 110 and 120 are fixed to the housing of the power conversion device 10 at multiple fixing points 12. The fixing points 12 are not electrically connected to the ground wiring 810.

[0022] As shown in Fig. 2, the positive wiring 610 and the negative wiring 710 are each arranged in a stacked manner with respect to the ground wiring 810. As shown in Fig. 2, 3(A), and 3(B), the positive Y capacitor 210 and the negative Y capacitor 220 are arranged on one end side of the stacked positive wiring 610, negative wiring 710, and ground wiring 810. Specifically, at one end side of each wiring, one terminal of the positive Y capacitor 210 is connected to the positive wiring 610 at a connection portion 211, and the other terminal of the positive Y capacitor 210 is connected to the ground wiring 810 of the second-layer wiring board 120 at a connection portion 212 via a through-hole without coming into contact with the positive wiring 610 of the first layer.

[0023] Similarly, at one end of each wiring, one terminal of the negative Y capacitor 220 is connected to the negative wiring 710 at a connection 221, and the other terminal of the negative Y capacitor 220 is connected to the ground wiring 810 of the second-layer wiring board 120 at a connection 222 via a through-hole without contacting the negative wiring 710 of the first layer. The connection means at the connections 211, 212, 221, 222 is, for example, solder.

[0024] As shown in Figures 3(A) and 3(B), the positive bus bar 6 and the positive wiring 610 are connected at a first connection portion 601. The negative bus bar 7 and the negative wiring 710 are connected at a second connection portion 701. The ground bus bar 8 to the ground side and the ground wiring 810 are connected at a third connection portion 801. Here, the first connection portion 601, the second connection portion 701, and the third connection portion 801 are arranged on the other end side of each of the wirings arranged in a stack. Note that the connection means at the first connection portion 601, the second connection portion 701, and the third connection portion 801 is, for example, fastening by a bolt, but other connection means may also be used.

[0025] That is, the positive wiring 610, the negative wiring 710, and the ground wiring 810 are arranged in a stacked manner, with the positive Y capacitor 210 and the negative Y capacitor 220 arranged on one end of each wiring, and the first connection part 601, the second connection part 701, and the third connection part 801 arranged on the other end of each wiring. The reason for this arrangement will be explained below with reference to FIG. 4.

[0026] 4 shows an equivalent circuit of the noise filter 1. A parasitic inductance L10 of the positive wiring 610 exists between the positive Y capacitor 210 and the first connection part 601, and a parasitic inductance L11 of the ground wiring 810 exists between the positive Y capacitor 210 and the third connection part 801. In addition, a parasitic inductance L12 of the negative wiring 710 exists between the negative Y capacitor 220 and the second connection part 701, and a parasitic inductance L13 of the ground wiring 810 exists between the negative Y capacitor 220 and the third connection part 801.

[0027] Furthermore, a positive mutual inductance M1 exists with a high electromagnetic coupling coefficient between the parasitic inductances L10 and L11 due to the stacked arrangement of the positive wiring 610 and the ground wiring 810. A negative mutual inductance M2 exists with a high electromagnetic coupling coefficient between the parasitic inductances L12 and L13 due to the stacked arrangement of the negative wiring 710 and the ground wiring 810.

[0028] Noise NS flowing from the power module 3 to the positive bus bar 6 and the negative bus bar 7 is bypassed from the first connection part 601 through the positive Y capacitor 210 to the third connection part 801, and from the second connection part 701 through the negative Y capacitor 220 to the third connection part 801. This suppresses noise flowing from the power module 3 to the battery 20 side through the positive bus bar 6 and the negative bus bar 7. However, if each of the parasitic inductances L10, L11, L12, and L13 is large, impedance increases depending on the frequency, and the bypass effect of the noise filter 1 on noise NS is suppressed.

[0029] 2, 3A, and 3B, the positive Y capacitor 210 and the negative Y capacitor 220 are disposed on one end of each wiring, and the first connection portion 601, the second connection portion 701, and the third connection portion 801 are disposed on the other end of each wiring. Furthermore, the positive wiring 610 and the negative wiring 710 are disposed in a stacked manner with respect to the ground wiring 810.

[0030] As a result, the current flowing through the positive wiring 610 and the current flowing through the ground wiring 810 are opposite in direction. Therefore, the parasitic inductances L10 and L11 are offset by the mutual inductance M1 and reduced. That is, the parasitic inductance of the path from the positive bus bar 6 to the ground side is reduced. Similarly, the current flowing through the negative wiring 710 and the current flowing through the ground wiring 810 are opposite in direction. Therefore, the parasitic inductances L12 and L13 are offset by the mutual inductance M2 and reduced. That is, the parasitic inductance of the path from the negative bus bar 7 to the ground side is reduced.

[0031] Therefore, even if the parasitic inductances L10, L11, L12, and L13 are individually large, they can be canceled out and the bypass effect of the noise NS by the noise filter 1 is not suppressed. In other words, the parasitic inductance caused by the wiring of the noise filter 1 can be reduced, and the noise suppression by the noise filter 1 can be improved.

[0032] Fig. 5 is a perspective view of the wiring substrate 110 of the noise filter 1 in the comparative example, and Fig. 6 is a top view of the wiring substrate 110 of the noise filter 1 in the comparative example. The comparative example shown in Figs. 5 and 6 shows an example to which the present invention is not applied, in order to deepen understanding of the present invention. The difference from this embodiment shown in Figs. 2, 3(A), and 3(B) is that the comparative example has wiring 610, 710, and wiring 810 arranged on a single wiring substrate 110. The same reference numerals are used to designate the same parts as in Figs. 2, 3(A), and 3(B).

[0033] 5 and 6 , in the comparative example, a positive electrode wiring 610 and a negative electrode wiring 710 are arranged on a wiring board 110, and further, a ground wiring 810 is arranged in the direction in which these wirings 610 and 710 extend. A first connection portion 601 and a second connection portion 701 with the bus bars 6 and 7 are arranged at one end of the positive electrode wiring 610 and the negative electrode wiring 710, and connection portions 211 and 221 with the Y capacitors 210 and 220 are arranged at the other end.

[0034] Furthermore, a ground wiring 810 is arranged from the connection parts 212, 222 of these Y capacitors 210, 220 in the direction in which the wiring 610, 710 extends, and a third connection part 801 is arranged at the end of the ground wiring 810. The positive wiring 610 and the ground wiring 810, and the negative wiring 710 and the ground wiring 810 are not arranged in a stacked manner. Therefore, the currents flowing in the positive wiring 610 and the ground wiring 810, and the negative wiring 710 and the ground wiring 810 flow in the same direction, so that the parasitic inductance is not canceled out by the mutual inductance, and the filter effect is reduced.

[0035] 7 is a graph showing the coupling coefficients of the mutual inductances M1 and M2 in the noise filter 1. The left side shows the coupling coefficients in the present embodiment described with reference to FIGS. 1 to 4, and the right side shows the coupling coefficients in the comparative example described with reference to FIGS. 5 and 6.

[0036] The larger the absolute value of the electromagnetic coupling coefficient, the larger the mutual inductances M1 and M2 become. When the coupling coefficient is positive, the parasitic inductances L10, L11, L12, and L13 decrease due to the mutual inductances M1 and M2, and when the coupling coefficient is negative, they increase. In this embodiment, the coupling coefficients of the mutual inductances M1 and M2 are positive. The positive wiring 610 and the ground wiring 810, and the negative wiring 710 and the ground wiring 810 are arranged in layers, so the coupling coefficients are also large. According to this embodiment, since the coupling coefficients are also large, it can be seen that the reduction in the parasitic inductances L10, L11, L12, and L13 is large.

[0037] On the other hand, in the comparative example, because the current directions are the same, the coupling coefficient between the mutual inductance M1 and the mutual inductance M2 is a negative value, as shown in Figure 7. Therefore, the effect of reducing parasitic inductance is not obtained. Furthermore, in the comparative example, the positive electrode wiring 610 and the ground wiring 810, and the negative electrode wiring 710 and the ground wiring 810 are not arranged in a stacked manner, so the absolute value of the coupling coefficient is small. Even if it were possible to arrange them so that the current directions are opposite on a single wiring board 110, the reduction effect would not be as great as in this embodiment, where the wiring is arranged in a stacked manner.

[0038] Furthermore, there is a demand for higher voltage and smaller size for the power conversion device 10, and accordingly, there is a demand for a lower profile and smaller size for the noise filter. To achieve this, it is advantageous to arrange the wiring, capacitors, etc. on the wiring board 11. However, as in the example shown in the comparative example, depending on the layout of the wiring, capacitors, etc., parasitic inductance increases, and the noise reduction effect of the noise filter cannot be fully obtained.

[0039] Fig. 8 is a graph showing the input / output characteristics of the noise filter 1. The vertical axis represents the input / output characteristics (dB), and the horizontal axis represents frequency (MHz). The input / output characteristics of the present embodiment described with reference to Figs. 1 to 4 are shown by solid lines, while the input / output characteristics of the comparative example described with reference to Figs. 5 and 6 are shown by dashed lines. At each frequency shown in Fig. 8, the lower the level of the input / output characteristics, the greater the noise reduction effect of the noise filter. It can be seen that the noise filter 1 of this embodiment has a greater parasitic inductance reduction effect, as indicated by arrow R, in a frequency band higher than the resonance point RP, compared to the comparative example, resulting in a greater overall noise reduction effect.

[0040] 2, 3(A), and 3(B), the positive Y capacitor 210 and the negative Y capacitor 220 are arranged side by side in a direction perpendicular to the direction connecting one end of each wiring 610, 710 to the other end of each wiring 610, 710. Specifically, the orientation of the positive Y capacitor 210 (the direction connecting the connection portion 211 and the connection portion 212) and the orientation of the negative Y capacitor 220 (the direction connecting the connection portion 221 and the connection portion 222) are arranged side by side in a direction perpendicular to the direction connecting the first connection portion 601 and the second connection portion 701 of each wiring 610, 710 to each Y capacitor 210, 220.

[0041] By arranging each Y capacitor 210, 220 in this manner, the area in which the current flowing through the positive wiring 610 and the negative wiring 710 and the current flowing through the ground wiring 810 are in opposite directions is maximized, and the mutual inductances M1 and M2 are increased, making it possible to further improve the effect of reducing parasitic inductance.

[0042] 9(A) and 9(B) are perspective views of the positive bus bar 6 and the negative bus bar 7 in this embodiment. Fig. 9(A) is a view from above, and Fig. 9(B) is a view from below, which is the substrate side. Both are near the first connection portion 601 and the second connection portion 701, and show a state in which ferrite cores 91 and 92 are installed on the positive bus bar 6 and the negative bus bar 7.

[0043] 9(A) and 9(B), the first connection portion 601 of the positive bus bar 6 and the second connection portion 701 of the negative bus bar 7 are convex. Although not shown, the third connection portion 801 of the ground bus bar 8 is also convex. Note that at least one of the first connection portion 601, the second connection portion 701, and the third connection portion 801 may be convex, as appropriate, depending on the installation form, etc. This convex portion of the convex shape is connected to the wiring pattern of each wire on the wiring board 11.

[0044] By forming each connection portion 601, 701, 801 of each bus bar 6, 7, 8 in such a convex shape, it becomes possible to contact each wiring 610, 710, 810 only around each connection portion 601, 701, 801. Furthermore, each of the convex-shaped bus bars 6, 7, 8 can be formed as a single component, which eliminates the need for welding compared to when the bus bars are formed as separate components, and is also effective in terms of cost reduction. Ferrite cores 91, 92 are installed on both sides of the first connection portion 601 and the second connection portion 701 so as to surround the positive bus bar 6 and the negative bus bar 7.

[0045] 10 is a side view of the noise filter 1 according to this embodiment. This side view is a view of the noise filter 1 as seen from the side surface SV shown in FIG. 2, and shows a state in which the positive bus bar 6, the negative bus bar 7, and the ground bus bar 8 are connected to the wiring board 11, and the ferrite cores 91 and 92 are installed.

[0046] 10 , tall Y capacitors 210, 220 and bus bars 6, 7 and their connection portions 601, 701 are installed on the upper surface of wiring boards 110, 120, and ferrite cores 91, 92 are also installed to surround positive bus bar 6 and negative bus bar 7. By making connection portions 601, 701 of bus bars 6, 7 convex, space for mounting ferrite cores 91, 92 is secured on the upper surface of wiring boards 110, 120. In other words, ferrite cores 91, 92 are arranged close to the same surface of wiring boards 110, 120 on which Y capacitors 210, 220 are arranged.

[0047] In this way, the wiring 610, 710, 810 and the capacitors are arranged on the wiring board 11, thereby enabling miniaturization and reducing the parasitic inductance caused by the wiring of the noise filter, thereby improving the noise suppression of the noise filter. Note that the noise filter 1 may be equipped with either one of the ferrite cores 91, 92, or may not be equipped with any of them in some cases.

[0048] 11A and 11B are diagrams showing the wiring substrate 11 of the noise filter 1 in Modification 1 of the present embodiment. Fig. 11A is a top view of the first-layer wiring substrate 110, and Fig. 11B is a top view of the second-layer wiring substrate 120.

[0049] 11(A) and 11(B), the difference is that the width of each wiring 610, 710, 810 is narrowed, and the Y capacitors 210, 220 are arranged side by side along each wiring 610, 710. The same parts as those in FIGS. 3(A) and 3(B) are denoted by the same reference numerals, and their description will be simplified. As shown in FIGS. 11(A) and 11(B), the positive bus bar 6 and the positive wiring 610 are connected at a first connection portion 601. The negative bus bar 7 and the negative wiring 710 are connected at a second connection portion 701.

[0050] The Y capacitors 210 and 220 are arranged with their polarities facing opposite directions. A connection portion 211 of the Y capacitor 210 is connected to the positive wiring 610. A connection portion 212 of the Y capacitor 210 is connected to the ground wiring 810 of the second-layer wiring board 120 via a through-hole without contacting the positive wiring 610 of the first layer. A connection portion 221 of the Y capacitor 220 is connected to the negative wiring 710. A connection portion 222 of the Y capacitor 220 is connected to the ground wiring 810 of the second-layer wiring board 120 via a through-hole without contacting the negative wiring 710 of the first layer.

[0051] In other words, the Y capacitors 210 and 220 are arranged side by side in the same direction as the direction connecting one end of each of the wirings 610 and 710 to the other end of each of the wirings 610 and 710. Furthermore, the Y capacitors 210 and 220 are arranged with their polarities facing opposite directions.

[0052] In the first modification, the width of each of the wirings 610, 710, and 810 can be narrowed, thereby enabling the miniaturization of the wiring board 11 and the noise filter 1. Also in the first modification, the currents flowing in the positive wiring 610 and the ground wiring 810, and the negative wiring 710 and the ground wiring 810, are opposite in direction, so that the parasitic inductance caused by the wiring is cancelled out by the mutual inductance, thereby enabling the noise suppression of the noise filter to be improved.

[0053] 12(A), 12(B), and 12(C) are diagrams showing the wiring substrate 11 of the noise filter 1 in Modification 2 of the present embodiment. Fig. 12(A) is a top view of the first-layer wiring substrate 110, Fig. 12(B) is a top view of the second-layer wiring substrate 120, and Fig. 12(C) is a top view of the third-layer wiring substrate 130.

[0054] 3(A) and 3(B) in that a ground wiring 810 is arranged on the first-layer wiring board 110, a positive wiring 610 and a negative wiring 710 are arranged on the second-layer wiring board 120, and a ground wiring 810 is arranged on the third-layer wiring board 130. The same parts as those in FIGS. 3(A) and 3(B) are denoted by the same reference numerals and will be described briefly.

[0055] 12(A) and 12(B), the positive wiring 610 and the negative wiring 710 arranged on the second-layer wiring board 120 are connected to the positive bus bar 6 and the negative bus bar 7 at a first connection portion 601 and a second connection portion 701, respectively, via through holes in the first-layer wiring board 110. As shown in FIGS. 12(A), 12(B), and 12(C), the ground wiring 810 arranged on the first-layer wiring board 110 and the third-layer wiring board 130 is connected to the ground bus bar 8 at a third connection portion 801 via through holes in the second-layer wiring board 110. The connection portion 211 of the Y capacitor 210 is connected to the positive bus bar 6, and the connection portion 212 is connected to the ground wiring 810. The connection portion 221 of the Y capacitor 220 is connected to the positive bus bar 6, and the connection portion 222 is connected to the ground wiring 810.

[0056] Although the positive wiring 610 and the negative wiring 710 are arranged on the second-layer wiring board 120, the wiring board 11 may be made four-layered, with the ground wiring 810 arranged on the first-layer wiring board 110, the positive wiring 610 on the second-layer wiring board 120, the negative wiring 710 on the third-layer wiring board 120, and the ground wiring 810 on the fourth-layer wiring board 130. Alternatively, the negative wiring 710 may be arranged on the second-layer wiring board 120, and the positive wiring 610 on the third-layer wiring board 120.

[0057] In Modification 2, wiring boards 110 and 130, on which ground wiring 810 is arranged, are arranged so as to sandwich wiring board 120, on which positive wiring 610 and negative wiring 710 are arranged. Even in this Modification 2, the currents flowing through positive wiring 610 and ground wiring 810, and negative wiring 710 and ground wiring 810, are in opposite directions, so that the parasitic inductance caused by the wiring is canceled out by mutual inductance, thereby improving noise suppression by the noise filter. Furthermore, by making wiring board 11 three or more layers and appropriately arranging each of the wirings 610, 710, and 810 on each layer, it is possible to further improve the parasitic inductance reduction effect compared to a two-layer structure.

[0058] 13(A), 13(B), 13(C), 13(D), and 13(E) are diagrams showing the wiring substrate 11 of the noise filter 1 in Modification 3 of this embodiment. Fig. 13(A) is a top view of the first-layer wiring substrate 110, Fig. 13(B) is a top view of the second-layer wiring substrate 120, Fig. 13(C) is a top view of the third-layer wiring substrate 130, Fig. 13(D) is a top view of the fourth-layer wiring substrate 140, and Fig. 13(E) is a top view of the fifth-layer wiring substrate 150.

[0059] 3(A) and 3(B) is that a ground wiring 810 is arranged on the first-layer wiring board 110, a positive wiring 610 on the second-layer wiring board 120, a ground wiring 810 on the third-layer wiring board 120, a negative wiring 710 on the fourth-layer wiring board 130, and a ground wiring 810 on the fifth-layer wiring board 110. The same reference numerals are used to designate the same parts as those in FIGS. 3(A) and 3(B), and their description will be simplified.

[0060] As shown in Figures 13(A) and 13(B), positive wiring 610 arranged on second-layer wiring board 120 is connected to positive bus bar 6 at first connection portion 601 via a through-hole in first-layer wiring board 110. As shown in Figures 13(A), 13(B), 13(C), and 13(D), negative wiring 710 arranged on fourth-layer wiring board 120 is connected to negative bus bar 7 at second connection portion 701 via a through-hole in first-layer to third-layer wiring boards 110, 120, and 130. As shown in Figures 13(A), 13(B), and 13(C), ground wiring 810 arranged on first-layer wiring board 110, third-layer wiring board 130, and fifth-layer wiring boards 110, 130, and 150 is connected to ground bus bar 8 at third connection portion 801 via a through-hole in second-layer and fourth-layer wiring boards 120 and 140. A connection portion 211 of the Y capacitor 210 is connected to the positive bus bar 6, and a connection portion 212 is connected to the ground wiring 810. A connection portion 221 of the Y capacitor 220 is connected to the positive bus bar 6, and a connection portion 222 is connected to the ground wiring 810.

[0061] In Modification 3, wiring board 120 with positive wiring 610 and wiring board 140 with negative wiring 710 are sandwiched between wiring boards 110, 130, and 150 with ground wiring 810, respectively. Even in Modification 3, the currents flowing through positive wiring 610 and ground wiring 810, and negative wiring 710 and ground wiring 810, are opposite in direction. Therefore, the parasitic inductance caused by the wiring is canceled out by mutual inductance, thereby improving noise suppression by the noise filter. Furthermore, by forming wiring board 11 into three or more layers and appropriately arranging each of wiring 610, 710, and 810 on each layer, the parasitic inductance reduction effect can be further improved compared to a two-layer structure. Note that negative wiring 710 may be arranged on wiring board 120 in the second layer, and positive wiring 610 on wiring board 130 in the fourth layer.

[0062] [Second Embodiment] A second embodiment of the present invention will be described with reference to Figures 14 to 16. Figure 14 is a diagram showing the overall configuration of a power conversion device 10 in this embodiment. The difference from the first embodiment shown in Figure 1 is that a pair of Y capacitors 230, 240 is added, and an X capacitor 300 is also added. The other configurations are the same as in Figure 1, and the same parts are designated by the same reference numerals and will be described briefly.

[0063] The noise filter 1 includes two pairs of Y capacitors, specifically Y capacitors 210 and 220 and Y capacitors 230 and 240. It also includes one X capacitor 300. The X capacitor 300 is connected between the positive bus bar 6 and the negative bus bar 7 and is used to suppress normal mode noise. The X capacitor 300 is also called a line capacitor. Details of the wiring connections of the noise filter 1 will be described later.

[0064] Fig. 15(A) is a top view of the wiring board 110 of the noise filter 1 of this embodiment, and Fig. 15(B) is a top view of the wiring board 120 of the noise filter 1. The positive wiring 610, negative wiring 710, and ground wiring 810 of the noise filter 1 are formed in a wiring pattern of the wiring board 11 consisting of multiple layers. In the example shown in Figs. 15(A) and 15(B), the positive wiring 610 and negative wiring 710 are formed on the first-layer wiring board 110, and the ground wiring 810 is formed on the second-layer wiring board 120. The positive bus bar 6 and the positive wiring 610 are connected at a first connection portion 601. The negative bus bar 7 and the negative wiring 710 are connected at a second connection portion 701. The ground bus bar 8 to the ground side and the ground wiring 810 are connected at a third connection portion 801.

[0065] The positive wiring 610, negative wiring 710, and ground wiring 810, that is, each wiring 610, 710, 810, are arranged in parallel in the same direction between the connection parts 211, 212, 221, 222, 231, 232, 241, 242 with the two pairs of Y capacitors 210, 220, 230, 243 and the connection parts 601, 701, 801 with each bus bar 6, 7, 8.

[0066] The Y capacitors 210, 220 and the Y capacitors 230, 240 are arranged side by side in the same direction as the direction connecting one end of each wiring 610, 710 to the other end of each wiring 610, 710. Furthermore, the Y capacitors 210, 220 and the Y capacitors 230, 240 are arranged with their polarities facing the same direction. In the examples shown in Figures 15(A) and 15(B), two pairs of Y capacitors are shown, but three or more pairs may be provided.

[0067] The X capacitor 300 is disposed between one end of each of the wirings 610, 710 and the other end of each of the wirings 610, 710, and is connected to the positive wiring 610 at a connection portion 301 and to the negative wiring 710 at a connection portion 302. In the examples of Figures 15(A) and 15(B), the X capacitor 300 is disposed approximately midway between one end of each of the wirings 610, 710 and the other end of each of the wirings 610, 710. Furthermore, a plurality of X capacitors 300 may be provided between one end of each of the wirings 610, 710 and the other end of each of the wirings 610, 710.

[0068] (Modification 4) Fig. 16(A) is a top view of the wiring substrate 110 of the noise filter 1 in Modification 4 of the present embodiment, and Fig. 16(B) is a top view of the wiring substrate 120 of the noise filter 1. The difference from the examples shown in Figs. 15(A) and 15(B) is that the polarities of the Y capacitors 230 and 240 are arranged in a direction different from the polarities of the Y capacitors 210 and 220. The other configurations are the same as Figs. 15(A) and 15(B), and the same parts are assigned the same reference numerals and will be described briefly.

[0069] As shown in Figures 16(A) and 16(B), the Y capacitors 210, 220 and the Y capacitors 230, 240 are arranged with their polarities facing in opposite directions. In this example, two pairs of Y capacitors are shown, but three or more pairs may be provided. In this case, too, the polarities of the Y capacitors are arranged so that they face alternate directions. By arranging them in this manner, the direction of current from the positive wiring 610 and the negative wiring 710 to the ground wiring 810 alternates, further improving the effect of reducing parasitic inductance.

[0070] [Third Embodiment] A third embodiment of the present invention will be described with reference to Fig. 17 and Fig. 18. Fig. 17 is an overall configuration diagram of a power conversion device 10 according to this embodiment. Fig. 18 is an equivalent circuit diagram including a noise filter 1 according to this embodiment.

[0071] 17, in this embodiment, the ground side of the ground wiring of the noise filter 1 is connected to the ground wiring of the power module 3. The other configuration is the same as in Fig. 1, and the same parts are assigned the same reference numerals and will be described briefly.

[0072] 18 is an equivalent circuit diagram that includes some parasitic elements such as the housing of the power conversion device 10 and the power module 3 in addition to the noise filter 1. Reducing the parasitic inductances L10, L11, L12, and L13 of the noise filter 1 is effective for reducing noise, but in addition to the noise filter 1, there are also parasitic inductances such as L33 due to the grounding structure of the housing, positive parasitic inductance L33 of the power module 3, and negative parasitic inductance L34 of the power module 3. Reducing these parasitic inductances L33, L34, and L35 is effective in reducing common-mode noise.

[0073] In the first embodiment, the parasitic inductance 33 is caused by the housing and the ground strap 820 to which the ground bus bar 8 is connected. On the other hand, in the present embodiment, the ground bus bar 8 is connected to the ground wiring of the power module 3, and therefore the ground wiring of the power module 3 is also included in the configuration of the parasitic inductance. In this case, by appropriately arranging the wiring structure on the power module 3 side, it is possible to reduce the parasitic inductances L33, L34, and L35 using the mutual inductances M31 and M32 between the positive electrode parasitic inductance L33 and the negative electrode parasitic inductance L34 of the power module 3, which is effective in reducing common-mode noise.

[0074] Furthermore, since common-mode noise flowing through each wiring generates radiated noise as an antenna, reducing the radiation efficiency of each wiring as an antenna is effective in reducing the radiated noise in addition to reducing the common-mode noise. The larger the area of ​​the loop path of each wiring through which common-mode noise flows, the higher the radiation efficiency, so wiring that minimizes the loop area is desirable. From this perspective, compared to the first embodiment, this embodiment can reduce the common-mode loop area because the noise current passes through the ground wiring within the power module 3, which is effective in reducing radiated noise.

[0075] According to the embodiment described above, the following effects can be obtained: (1) The noise filter 1 includes a first ground capacitor (Y capacitor 210) between the positive bus bar 6 and the ground side, connected via the positive bus bar 6 and the positive wiring 610 and also via the ground side and the ground wiring 810, and a second ground capacitor (Y capacitor 220) between the negative bus bar 7 and the ground side, connected via the negative bus bar 7 and the negative wiring 710 and also via the ground side and the ground wiring 810. Each of the positive wiring 610 and the negative wiring 710 is connected to the ground wiring. The first ground capacitor (Y capacitor 210) and the second ground capacitor (Y capacitor 220) are arranged in layers on the wire 810, and are arranged on one end side of each of the stacked positive wiring 610, negative wiring 710, and ground wiring 810, and the first connection portion 601 between the positive bus bar 6 and the positive wiring 610, the second connection portion 701 between the negative bus bar 7 and the negative wiring 710, and the third connection portion 801 between the ground side and the ground wiring 810 are arranged on the other end side of each of the wirings 610, 710, 810. This reduces parasitic inductance caused by the wiring of the noise filter, and improves noise suppression by the noise filter.

[0076] The present invention is not limited to the above-described embodiments, and other forms that can be conceived within the scope of the technical concept of the present invention are also included within the scope of the present invention as long as they do not impair the characteristics of the present invention. Furthermore, configurations that combine each of the above-described embodiments with multiple of the above-described modifications may also be used.

[0077] 1... noise filter, 2... smoothing capacitor, 3... power module, 4... driver circuit board, 5... control circuit board, 6... positive bus bar, 7... negative bus bar, 8... ground bus bar, 10... power conversion device, 11, 110, 120, 130, 140, 150... wiring board, 12... fixed point, 20... battery, 21, 31... connector, 30... motor, 91, 92... ferrite core, 210, 220... Y capacitor, 211, 212, 221, 222... connection portion, 300... X capacitor, 601... first connection portion, 610... positive wiring, 701... second connection portion, 710... negative wiring, 801... third connection portion, 810... ground wiring, L10, L11, L12, L13... parasitic inductance, M1, M2... mutual inductance.

Claims

1. A noise filter comprising: a first earth capacitor between a positive bus bar and a ground side, and connected via the positive bus bar and a positive wiring and also via the ground side and a ground wiring; and a second earth capacitor between a negative bus bar and the ground side, and connected via the negative bus bar and a negative wiring and also via the ground side and the ground wiring, wherein each of the positive wiring and the negative wiring are arranged in a stack with respect to the ground wiring, the first earth capacitor and the second earth capacitor are arranged on one end side of each of the stacked positive wiring, negative wiring and ground wiring, and a first connection portion between the positive bus bar and the positive wiring, a second connection portion between the negative bus bar and the negative wiring, and a third connection portion between the ground side and the ground wiring are arranged on the other end side of each of the wiring.

2. A noise filter as claimed in claim 1, wherein the first earth capacitor and the second earth capacitor are arranged side by side in a direction perpendicular to a direction connecting the one end of each of the wirings to the other end of each of the wirings.

3. A noise filter as claimed in claim 1, wherein the first earth capacitor and the second earth capacitor are arranged side by side in a direction connecting the one end side of each of the wirings to the other end side of each of the wirings.

4. A noise filter according to claim 1, wherein the positive wiring, the negative wiring and the ground wiring are formed as wiring patterns on a wiring board made up of multiple layers.

5. A noise filter according to claim 4, wherein the first earth capacitor and the second earth capacitor are disposed on the wiring board.

6. A noise filter according to claim 5, wherein at least one of the connection parts with the positive bus bar, the negative bus bar and the ground side is convex, and the convex part of the convex shape is connected to the wiring pattern on the wiring board.

7. A noise filter as described in claim 6, further comprising a ferrite core surrounding each of the positive bus bar connected to the first connection portion and the negative bus bar connected to the second connection portion, the ferrite cores being positioned close to the same side of the wiring board on which the first earth capacitor and the second earth capacitor are positioned.

8. A noise filter as claimed in claim 4, wherein the first earth capacitor and the second earth capacitor are provided in multiple numbers and are arranged side by side in the same direction as the direction connecting the one end side of each of the wirings to the other end side of each of the wirings.

9. A noise filter according to claim 8, wherein the plurality of first earth capacitors and the plurality of second earth capacitors are arranged with the polarities of the capacitors alternating.

10. A noise filter as claimed in claim 4, further comprising a line capacitor between the positive wiring and the negative wiring, the line capacitor being disposed between the one end side of each of the wiring and the other end side of each of the wiring.

11. A noise filter as claimed in claim 4, wherein the layer in which the positive wiring is arranged and the layer in which the negative wiring is arranged are sandwiched between the layer in which the ground wiring is arranged, and the noise filter is a wiring board made up of multiple layers.

12. A power conversion device comprising: a noise filter according to any one of claims 1 to 11; and a power module that constitutes an inverter circuit and converts DC power supplied from the positive bus bar and the negative bus bar via the noise filter into AC power.

13. A power conversion device according to claim 12, wherein the ground side of the ground wiring is connected to the ground wiring of the power module.

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