Noise reduction device

Abstract

A noise reduction device comprises a bus bar, a circuit board including a capacitor, a first conductive member that connects a first connection portion of the bus bar and a first terminal of the circuit board, and a second conductive member that connects a second connection portion of the bus bar and a second terminal of the circuit board. The bus bar includes an input portion to which a current is inputted, an intermediate portion through which the current inputted from the input portion passes, and an output portion which outputs the current that has passed through the intermediate portion. The intermediate portion is formed so as to be separated from a straight line connecting the input portion and the output portion.

Description

Noise reduction device

[0001] The present disclosure relates to a noise reduction device. This application claims priority based on Japanese Application No. 2025-026132 filed on February 20, 2025, and incorporates all the contents described in the Japanese application.

[0002] In vehicles that generate driving force by electricity, such as electric vehicles, hybrid vehicles, and plug-in hybrid vehicles, a power conversion device that converts DC power supplied from a storage battery into AC power is installed. The storage battery, which is a DC power source, and the power conversion device are connected by a bus bar capable of transmitting large power.

[0003] Patent Document 1 discloses a noise filter module connected to the output side of an in-vehicle switching power supply. The noise filter module includes a flat conductive bar (bus bar) extending linearly, a magnetic core through which the conductive bar passes, and two capacitors for noise removal. The first end of the conductive bar is connected to the output terminal VX of the switching power supply, and the second end is connected to the output terminal VO connected to the subsequent electronic device. A first capacitor is connected between the output terminal VX of the switching power supply and the ground potential, and a second capacitor is connected between the output terminal VO and the ground potential.

[0004] In the noise filter module disclosed in Patent Document 1, a mounting substrate on which two capacitors are mounted is arranged above the conductive bar, and two lead members are arranged between the conductive bar and the mounting substrate. Each of the two capacitors is connected to the conductive bar by each of the two lead members.

[0005] Japanese Unexamined Patent Application Publication No. 2018-019512

[0006] A noise reduction device according to one aspect of the present disclosure comprises a busbar, a circuit board including a capacitor, a first conductive member connecting a first connection portion of the busbar to a first terminal of the circuit board, and a second conductive member connecting a second connection portion of the busbar to a second terminal of the circuit board, wherein the busbar includes an input portion into which current is input, an intermediate portion through which the current input from the input portion passes, and an output portion that outputs the current that has passed through the intermediate portion, and the intermediate portion is formed to be spaced away from a straight line connecting the input portion and the output portion.

[0007] Figure 1 is a block diagram showing an example of the configuration of an in-vehicle system according to the embodiment. Figure 2 is a perspective view showing an example of the configuration of a noise reduction device according to the embodiment. Figure 3 is a side cross-sectional view taken along line A-A in Figure 2. Figure 4 is a side cross-sectional view showing a comparative example of the noise reduction device. Figure 5 is a circuit diagram showing the equivalent circuit configuration of the noise reduction device according to the embodiment. Figure 6 is a circuit diagram showing the equivalent circuit of the noise reduction device according to the comparative example. Figure 7 is a plan view showing an example of a common mode loop path in the noise reduction device according to the embodiment. Figure 8 is a plan view showing an example of a common mode loop path in a modified noise reduction device.

[0008] To improve the noise reduction effect, it is desirable to increase the inductance of the busbar.

[0009] According to this disclosure, the inductance of the busbar can be increased.

[0010] The embodiments of this disclosure are outlined below.

[0011] (1) The noise reduction device according to this embodiment comprises a busbar, a circuit board including a capacitor, a first conductive member connecting a first connection portion of the busbar and a first terminal of the circuit board, and a second conductive member connecting a second connection portion of the busbar and a second terminal of the circuit board, wherein the busbar includes an input portion into which current is input, an intermediate portion through which the current input from the input portion passes, and an output portion that outputs the current that has passed through the intermediate portion, and the intermediate portion is formed to be spaced away from the straight line connecting the input portion and the output portion. As a result, the current path in the busbar is longer compared to a flat busbar, and the inductance of the busbar can be increased.

[0012] (2) In (1) above, the intermediate portion may include a straight portion along a second straight line parallel to a first straight line connecting the input portion and the output portion, a first connecting portion connecting the input portion and the first end of the straight portion, and a second connecting portion connecting the output portion and the second end of the straight portion. As a result, the current path of the busbar is longer than that of a flat busbar due to the first and second connecting portions.

[0013] (3) In the above (2), a magnetic core surrounding the linear portion may be further provided. This allows noise to be reduced by the magnetic core.

[0014] (4) In any one of (1) to (3) above, the circuit board, the first conductive member, and the second conductive member may be arranged along the straight line between the input section and the output section. This makes it possible to reduce the length of the first conductive member and the second conductive member. As a result, the inductive inductance in the first conductive member and the second conductive member is reduced, and the noise reduction effect can be improved.

[0015] (5) In any one of (1) to (4) above, the noise reduction device further comprises a ground member connected to ground potential, the capacitor includes a first capacitor and a second capacitor, the first terminal of the first capacitor is connected to the first terminal of the circuit board, the first terminal of the second capacitor is connected to the second terminal of the circuit board, and the ground member is connected to the second terminal of the first capacitor and the second terminal of the second capacitor. As a result, the noise currents of both the first capacitor and the second capacitor pass through the ground member, so that the lengths of the noise current paths of both the first capacitor and the second capacitor are equal. Therefore, the occurrence of unwanted resonance is suppressed, and the noise reduction effect can be improved.

[0016] (6) In any one of (1) to (5) above, the circuit board may be placed between the input section and the output section, and the capacitor may be placed in the space formed by the circuit board and the intermediate section. This makes it possible to miniaturize the noise reduction device.

[0017] (7) In the above (6), the noise reduction device may further include a metal housing that includes a recess for housing the intermediate portion. This allows the circuit board and capacitor to be electromagnetically shielded by the metal housing, thereby improving the noise reduction effect.

[0018] (8) In (7) above, at least a portion of the intermediate section may be connected to the metal housing via a heat conductive member. This allows the heat generated in the intermediate section to be dissipated to the metal housing.

[0019] This disclosure can be implemented not only as a noise reduction device having the characteristic configuration described above, but also as a power conversion device including the noise reduction device, or as a noise reduction method including characteristic steps.

[0020] The embodiments of the present invention will be described in detail below with reference to the drawings. At least some of the embodiments described below may be combined in any way.

[0021] [1. In-vehicle system] Figure 1 is a block diagram showing an example of the configuration of an in-vehicle system according to the embodiment. The in-vehicle system 10 is mounted on a vehicle.

[0022] The in-vehicle system 10 in this implementation includes a battery 40, a power converter 20, and an ECU (Electronic Control Unit) 50.

[0023] The battery 40 is an auxiliary battery that supplies power to multiple ECUs 50, which are on-board devices. Power lines extend from the battery 40 and are connected to the power converter 20.

[0024] The power conversion device 20 includes a DC / DC converter 30 and a noise reduction device 100. The DC / DC converter 30 converts the DC voltage output from the battery 40 into a DC voltage for output to the ECU 50. For example, the DC / DC converter 30 is a bidirectional voltage converter. That is, the DC / DC converter 30 is connected to a generator (not shown), and can also convert the DC voltage output from the generator into a DC voltage for output to the battery 40. As a result, the battery 40 is charged by the generator.

[0025] A noise reduction device 100 is connected to the output side of the DC / DC converter 30. The noise reduction device 100 reduces the noise contained in the output current from the DC / DC converter 30. The noise reduction device 100 includes a busbar 200, which is a power transmission line. The input terminal of the busbar 200 is connected to the DC / DC converter 30, and the output terminal of the busbar 200 is connected to power lines connected to multiple ECUs.

[0026] Multiple ECUs 50 are positioned in various parts of the vehicle. Each ECU 50 individually controls the hardware of each part of the vehicle and monitors the status of the hardware of each part of the vehicle. For example, the ECUs 50 are control system, body system, and information system ECUs. Each of the ECUs 50 is connected to each other via an in-vehicle network so that they can communicate with one another.

[0027] [2. Noise Reduction Device] Figure 2 is a perspective view showing an example of the configuration of a noise reduction device according to an embodiment, and Figure 3 is a side cross-sectional view taken along line A-A in Figure 2.

[0028] The noise reduction device 100 includes a busbar 200, a circuit board 300, and a magnetic core 600.

[0029] The busbar 200 is made of a plate-shaped conductor such as copper, aluminum, or brass, and can carry a large current. The busbar 200 includes an input section 210, an intermediate section 220, and an output section 230.

[0030] The input unit 210 is connected to the output side of the DC / DC converter 30, and receives the DC current output from the DC / DC converter 30. Specifically, the input unit 210 is provided with a hole (bolt hole) through which a bolt shaft passes, and the input unit 210 is fixed by a bolt 240 to, for example, the output terminal of the DC / DC converter 30 or a power line connected to the output terminal.

[0031] The intermediate section 220 is the part between the input section 210 and the output section 230, and the current input from the input section 210 passes through it. The current that has passed through the intermediate section 220 is output from the output section 230.

[0032] The output unit 230 is connected to the power line connected to the ECU 50 and outputs a noise-reduced DC current to the power line. Specifically, the output unit 230 is provided with bolt holes, and the output unit 230 is fixed to the power line connected to the ECU 50 by bolts 250.

[0033] Each of the input section 210 and the output section 230 is a rectangular, flat plate-shaped portion in a plan view. The input section 210 and the output section 230 are aligned along a straight axis SL1 and extend along axis SL1. Hereinafter, the direction of axis SL1 will be referred to as the "front-back direction," the left side when facing backward will be referred to as the "left direction," and the right side when facing backward will be referred to as the "right direction." The vertical direction will be referred to as the "up-down direction." The input section 210 is located in front of the output section 230, and the output section 230 is located behind the input section 210. Axis SL1 is the central axis of the input section 210 and the output section 230. Axis SL1 is a straight line connecting the input section 210 and the output section 230, and is an example of a "first straight line." Here, the input section 210 and the output section 230 are described as rectangular, flat plate-shaped conductors in a plan view, but they are not limited to this. That is, the input section 210 and the output section 230 may be bent or curved. In that case, axis SL1 may be a straight line connecting at least a portion of the input section 210 and the output section 230, for example, a straight line connecting the connection portions of the input section 210 and the output section 230 with the branch busbars 510 and 520, which will be described later.

[0034] The intermediate portion 220 is formed to be separated from the axis SL1. That is, the intermediate portion 220 is bent or curved and has a shape that does not follow the axis SL1.

[0035] Specifically, the intermediate section 220 includes a first connecting section 221, a second connecting section 222, and a straight section 223. The straight section 223 is a rectangular, flat plate-like portion in plan view, extending along an axis SL2 parallel to axis SL1. Axis SL2 is located below axis SL1. Axis SL2 is the central axis of the straight section 223 and is an example of a "second straight line".

[0036] The first connecting portion 221 and the second connecting portion 222 are each rectangular, flat portions that extend vertically when viewed from the front. The first connecting portion 221 connects the rear end of the input portion 210 to the front end of the straight portion 223. That is, the upper end of the first connecting portion 221 is connected to the rear end of the input portion 210, and the lower end of the first connecting portion 221 is connected to the front end of the straight portion 223. The second connecting portion 222 connects the rear end of the straight portion 223 to the front end of the output portion 230. That is, the upper end of the second connecting portion 222 is connected to the front end of the output portion 230, and the lower end of the second connecting portion 222 is connected to the rear end of the straight portion 223. In other words, the intermediate portion 220 is formed in a rectangular shape with one side (the top side) open when viewed from the side.

[0037] The magnetic core 600 is a ferrite core made of soft magnetic material. The magnetic core 600 is ring-shaped and surrounds the linear portion 223. The linear portion 223 and the magnetic core 600 constitute an inductor. The hysteresis loss of the magnetic core 600 attenuates the high-frequency noise current flowing through the linear portion 223.

[0038] The circuit board 300 is positioned between the input section 210 and the output section 230. More specifically, the circuit board 300 is positioned along the axis SL1 together with the input section 210 and the output section 230.

[0039] The circuit board 300 has a rectangular, flat shape when viewed from above, and capacitors 400A and 400B are mounted on its lower surface. A first terminal 310 is provided at the front end of the circuit board 300, and a second terminal 320 is provided at the rear end of the circuit board 300.

[0040] A branch busbar 510 is positioned between the input unit 210 and the circuit board 300. The branch busbar 510 is made of a conductive material such as copper, aluminum, or brass. The front end of the branch busbar 510 is connected to the rear end of the input unit 210, and the rear end of the branch busbar 510 is connected to the first terminal 310 at the front end of the circuit board 300. The branch busbar 510 is an example of a "first conductive member".

[0041] A branch busbar 520 is positioned between the output unit 230 and the circuit board 300. The branch busbar 520 is made of a conductive material such as copper, aluminum, or brass. The front end of the branch busbar 520 is connected to the second terminal 320 at the rear end of the circuit board 300, and the rear end of the branch busbar 520 is connected to the front end of the output unit 230. The branch busbar 520 is an example of a "second conductive member".

[0042] The busbar 200 is constructed by bending a single metal plate. Specifically, it is bent 90° between the input section 210 and the first connection section 221, bent 90° between the first connection section 221 and the straight section 223, bent 90° between the straight section 223 and the second connection section 222, and bent 90° between the second connection section 222 and the output section 230. In this way, the busbar 200 is bent in a rectangular shape between the input section 210 and the output section 230, and a space exists between the input section 210 and the output section 230. The circuit board 300 and the branch busbars 510 and 520 are arranged in the front-to-back direction in the space between the input section 210 and the output section 230. That is, the input section 210, branch busbar 510, circuit board 300, branch busbar 520, and output section 230 are arranged along axis SL1 in this order.

[0043] The busbar 200 has a shape that is recessed downward between the input section 210 and the output section 230, and the circuit board 300 and the branch busbars 510 and 520 are housed in this recess. Furthermore, the capacitors 400A and 400B mounted on the circuit board 300 are also housed in the above recess. That is, the capacitors 400A and 400B are arranged in the space formed by the circuit board 300 and the intermediate section 220. In this way, each element of the noise reduction device 100 is efficiently arranged, and the noise reduction device 100 is configured compactly.

[0044] Capacitors 400A and 400B are arranged side by side in the front-rear direction on the lower surface of the circuit board 300. More specifically, capacitor 400A is arranged in front of capacitor 400B, and capacitor 400B is arranged behind capacitor 400A. A first terminal (not shown) is provided at the front end of capacitor 400A, and a second terminal (not shown) is provided at the rear end of capacitor 400A. The first terminal of capacitor 400A is connected to the first terminal 310 of the circuit board 300 by a printed wiring provided on the circuit board 300. A first terminal (not shown) is provided at the rear end of capacitor 400B, and a second terminal (not shown) is provided at the front end of capacitor 400B. The first terminal of capacitor 400B is connected to the second terminal 320 of the circuit board 300 by a printed wiring provided on the circuit board 300.

[0045] Capacitors 400A and 400B are connected to the branch bus bar 530. Specifically, the branch bus bar 530 is arranged between capacitors 400A and 400B. More specifically, the front end of the branch bus bar 530 is connected to the second terminal at the rear end of capacitor 400A, and the rear end of the branch bus bar 530 is connected to the second terminal at the front end of capacitor 400B.

[0046] The branch bus bar 530 extends rightward along the lower surface of the circuit board 300 from the connection portion with capacitors 400A and 400B, and bends downward at 90° near the right end of the circuit board 300. The branch bus bar 530 extends downward from the lower surface of the circuit board 300, and a connection portion 531 that bends at 90° is provided at the lower end. The connection portion 531 is connected to the bottom surface of the housing 700 of the noise reduction device 100. The housing 700 is made of a conductive metal, and the potential of the housing 700 is set to the ground potential. That is, each of capacitors 400A and 400B is connected to the ground potential via the branch bus bar 530. The branch bus bar 530 is an example of a "ground member".

[0047] With the above connection relationship, an LC circuit, which is a noise filter, is constituted by the magnetic core 600 and capacitors 400A and 400B.

[0048] The housing 700 houses the bus bar 200, the circuit board 300, and the magnetic core 600. A recess is provided on the bottom surface of the housing 700, and the magnetic core 600 and the intermediate portion 220 of the bus bar 200 are arranged in this recess.

[0049] The bus bar 200 and the magnetic core 600 are fixed to the inner surface of the housing 700 via the heat conduction sheet 800. More specifically, the input portion 210, the first connection portion 221, the front end portion and the rear end portion of the straight portion 223, the second connection portion 222, and the output portion 230 of the bus bar 200 are connected to the housing 700 via the heat conduction sheet 800. That is, a part of the intermediate portion 220 (the portion excluding the portion surrounded by the magnetic core 600) is connected to the housing 700 via the heat conduction sheet 800. As a result, many parts of the bus bar 200 are in contact with the heat conduction sheet 800, and the heat generated in the bus bar 200 is radiated to the housing 700 via the heat conduction sheet 800.

[0050] [3. Comparative Example]Fig. 4 is a side cross-sectional view showing a comparative example of the noise reduction device.

[0051] The noise reduction device 100A according to the comparative example includes a single flat bus bar 200A. The bus bar 200A is not bent and is configured to extend linearly in the front-rear direction. In other words, the input portion 210A, the intermediate portion 220A, and the output portion 230A of the bus bar 200A are arranged along a straight line.

[0052] The magnetic core 600 surrounds the intermediate portion 220A. Above the intermediate portion 220A, the circuit board 300 is arranged.

[0053] A branch bus bar 510A is arranged on the upper surface of the input portion 210A. The branch bus bar 510A extends upward and is connected to a first terminal provided at the front end of the circuit board 300 at the upper end.

[0054] A branch bus bar 520A is arranged on the upper surface of the output portion 230A. The branch bus bar 520A extends upward and is connected to a second terminal provided at the rear end of the circuit board 300 at the upper end.

[0055] Capacitors 400A and 400B are located on the underside of the circuit board 300. The first terminal at the front of capacitor 400A is connected to the first terminal of the circuit board 300 by printed wiring, and the first terminal at the rear of capacitor 400B is connected to the second terminal of the circuit board 300 by printed wiring. A branch busbar 530A is connected to the second terminal at the rear of capacitor 400A. A branch busbar 530B is connected to the second terminal at the front of capacitor 400B. Branch busbar 530A is located in front of branch busbar 530B. Both branch busbars 530A and 530B extend downward from the underside of the circuit board 300, and the lower ends of branch busbars 530A and 530B are connected to the housing 700A.

[0056] The bottom surface of the housing 700A has a recess formed therein that corresponds to the shape of the magnetic core 600. The lower portion of the magnetic core 600 is housed in this recess.

[0057] The busbar 200A and the magnetic core 600 are fixed to the inner surface of the housing 700A via a thermal conductive sheet 800A. More specifically, the input section 210A and output section 230A of the busbar 200A are connected to the housing 700 via the thermal conductive sheet 800A. That is, the intermediate section 220A is not connected to the housing 700 via the thermal conductive sheet 800.

[0058] [4. Circuit Configuration of Noise Reduction Device] Figure 5 is a circuit diagram showing the equivalent circuit configuration of the noise reduction device according to the embodiment, and Figure 6 is a circuit diagram showing the equivalent circuit of the noise reduction device according to the comparative example.

[0059] In the noise reduction device 100 according to this embodiment, a first connection part 221, an inductor composed of a magnetic core 600, and a second connection part 222 are connected in series between the input part 210 and the output part 230. Furthermore, a branch bus bar 510 is connected to the connection point between the input part 210 and the first connection part 221, and the branch bus bar 510, capacitor 400A, and branch bus bar 530 are connected in series. A branch bus bar 520 is connected to the connection point between the output part 230 and the second connection part 222, and the branch bus bar 520, capacitor 400B, and branch bus bar 530 are connected in series. The branch bus bar 530 is connected to ground potential.

[0060] The first connection section 221 has an inductance L1. The second connection section 222 has an inductance L2. Therefore, if we consider the first connection section 221 and the second connection section 222 as inductors, in the equivalent circuit shown in Figure 5, an inductor having an inductance L1, an inductor made of a magnetic core 600 (inductance L_C), and an inductor having an inductance L2 are connected in series between the input section 210 and the output section 230.

[0061] Similarly, the branch busbar 510 can be viewed as an inductor having inductance L_B1, and the branch busbar 520 can be viewed as an inductor having inductance L_B2. The connection portion of the branch busbar 530 with capacitor 400A can be viewed as an inductor having inductance L_G1, and the connection portion of the branch busbar 530 with capacitor 400B can be viewed as an inductor having inductance L_G2. Therefore, in the equivalent circuit shown in Figure 5, the circuit branches from MP1, which is the midpoint between the input section 210 and the inductor having inductance L1, and the inductor having inductance L_B1, capacitor 400A, and the inductor having inductance L_G1 are connected in series. The circuit branches from MP2, which is the midpoint between the output section 230 and the inductor having inductance L2, and the inductor having inductance L_B2, capacitor 400B, and the inductor having inductance L_G2 are connected in series. The inductor having inductance L_G1 and the inductor having inductance L_G2 are connected to each other, and this connection point is connected to ground potential.

[0062] In the comparative example noise reduction device 100A, an inductor made of a magnetic core 600 is present between the input section 210A and the output section 230A. A branch busbar 510A is connected to the connection point between the input section 210A and the intermediate section 220A, and branch busbars 510A, capacitor 400A, and 530A are connected in series. A branch busbar 520A is connected to the connection point between the output section 230 and the intermediate section 220A, and branch busbars 520A, capacitor 400B, and 530B are connected in series. Each of the branch busbars 530A and 530B is individually connected to ground potential.

[0063] The noise reduction device 100A does not have a first connection part 221 and a second connection part 222. Therefore, inductances L1 and L2 caused by the first connection part 221 and the second connection part 222 are not generated. Consequently, as shown in Figure 6, the only inductance (inductance L_C) between the input part 210A and the output part 230A is the inductor (inductance L_C) formed by the magnetic core 600.

[0064] The branch busbar 510A can be viewed as an inductor having inductance L_B1A, and the branch busbar 520A can be viewed as an inductor having inductance L_B2A. The branch busbar 530A can be viewed as an inductor having inductance L_G1A, and the branch busbar 530B can be viewed as an inductor having inductance L_G2A. Therefore, in the equivalent circuit shown in Figure 6, a branch is made from MP1, the midpoint between the input section 210 and the inductor made of the magnetic core 600, and an inductor having inductance L_B1A, a capacitor 400A, and an inductor having inductance L_G1A are connected in series. A branch is made from MP2, the midpoint between the output section 230 and the inductor made of the magnetic core 600, and an inductor having inductance L_B2A, a capacitor 400B, and an inductor having inductance L_G2A are connected in series. The inductor having inductance L_G1A and the inductor having inductance L_G2A are connected to ground potential independently of each other.

[0065] The greater the inductance between the intermediate point MP1, which is the branching point from the input section 210 to the capacitor 400A, and the intermediate point MP2, which is the branching point from the output section 230 to the capacitor 400B, the greater the noise reduction effect. In the noise reduction device 100 according to the embodiment, the inductance between the intermediate points MP1 and MP2 includes the inductance L_C due to the magnetic core 600, as well as the inductance L1 due to the first connection section 221 and the inductance L2 due to the second connection section 222 (see Figure 5). On the other hand, in the noise reduction device 100A according to the comparative example, the inductance between the intermediate points MP1 and MP2 is only the inductance L_C due to the magnetic core 600 (see Figure 6). Therefore, it can be seen that the noise reduction device 100 according to the embodiment has a higher noise reduction effect than the comparative example.

[0066] On the other hand, the inductance at the branch points from the intermediate points MP1 and MP2 hinders the noise reduction effect. In the comparative example, the noise reduction device 100A has long branch busbars 510A and 520B, and the inductances L_B1A and L_B2A are large. Therefore, the inductances L_B1A and L_B2A greatly hinder the noise reduction effect. In the embodiment, the length of branch busbars 510 and 520 is small. Therefore, the inductances L_B1 and L_B2 are small, and the noise reduction effect is not greatly hindered.

[0067] [5. Common Mode Loop] Figure 7 is a plan view showing an example of a common mode loop path in a noise reduction device according to an embodiment, and Figure 8 is a plan view showing an example of a common mode loop path in a modified noise reduction device.

[0068] In the examples shown in Figures 7 and 8, a noise source 900 is located on the input side of the noise reduction device. In the noise reduction device 100 according to this embodiment, the common-mode noise current from the noise source 900 flows through path R11A from the input section 210, through the branch busbar 510, and through capacitor 400A, and is output from capacitor 400A and flows through path R12A. Furthermore, the noise current flows through path R3A, which goes through the branch busbar 530, through ground (enclosure 700), and returns to the noise source 900. On the other hand, a portion of the noise current flows through path R21A from the noise source 900, through the input section 210, intermediate section 220, and branch busbar 520, and through capacitor 400B, and is output from capacitor 400B and flows through path R22A. Furthermore, the noise current merges with the noise current flowing through path R12A at branch busbar 530 and returns to the noise source 900 through path R3A.

[0069] On the other hand, in the modified noise reduction device 100A, as shown in Figure 8, the common-mode noise current from the noise source 900 flows through path R11B from the input section 210A through the branch busbar 510A and through the capacitor 400A, and then flows through path R12B from the output of the capacitor 400A through the branch busbar 530A to the ground (enclosure 700A). Furthermore, the noise current flows through path R3B, returning to the noise source 900 via the ground. A portion of the noise current flows through path R21B from the noise source 900 through the input section 210, the intermediate section 220, and the branch busbar 520A and through the capacitor 400B, and then flows through path R22B from the output of the capacitor 400B through the branch busbar 530B to the ground (enclosure 700A). Furthermore, the noise current merges with the noise current flowing through path R12B at ground and returns to the noise source 900 through path R3B.

[0070] In the modified noise reduction device 100A, the lengths of the path R12B after capacitor 400A and the path R22B after capacitor 400B are different. The difference in path lengths causes resonance, and this resonance hinders the noise reduction effect. On the other hand, in the noise reduction device 100A according to the embodiment, the lengths of the path R12A after capacitor 400A and the path R22A after capacitor 400B are equal. Furthermore, the noise currents that merge from paths R12A and R22A respectively pass through a single branch busbar 530 to ground. In this way, by sharing the branch busbar 530 connected to ground potential with capacitors 400A and 400B, the paths of the noise currents output from capacitors 400A and 400B become equal in length, preventing the occurrence of unwanted resonance. Reducing resonance suppresses the inhibition of the noise reduction effect.

[0071] [6. Modifications] In the above embodiment, the intermediate portion 220 between the input portion 210 and the output portion 230 of the busbar 200 has a shape that is bent downward in a rectangular shape, but is not limited thereto. Any shape can be selected for the intermediate portion 220 as long as it is spaced away from the axis SL1, which is the straight line connecting the input portion 210 and the output portion 230. For example, the intermediate portion 220 between the input portion 210 and the output portion 230 of the busbar 200 may have a shape that is bent upward in a rectangular shape, or the intermediate portion 220 may have a shape that is bent to the left or to the right in a rectangular shape. In another example, at least a part of the 90° bent corner of the busbar 200 may be replaced with an R shape that curves with a constant curvature.

[0072] [7. Supplementary Notes] The embodiments disclosed herein are illustrative in all respects and are not restrictive. The scope of the present invention is indicated by the claims rather than by the embodiments described above, and includes the meaning of equivalents of the claims and all modifications within that scope.

[0073] 10 In-vehicle system 20 Power converter 30 DC / DC converter 40 Battery 50 ECU 100, 100A Noise reduction device 200, 200A Busbar 210, 210A Input section 220, 220A Intermediate section 221 First connection section 222 Second connection section 223 Linear section 230, 230A Output section 240, 250 Volts 300 Circuit board 310 First terminal 320 Second terminal 400A, 400B Capacitor 510, 510A, 520, 520A, 530, 530A, 530B Branch busbar 531 Connection section 600 Magnetic core 700, 700A Housing 800, 800A Thermal conductive sheet 900 Noise source SL1 Axis (first straight line) SL2 Axis (second straight line) L1, L2, L_B1, L_B2, L_G1, L_G2, L_B1A, L_B2A, L_G1A, L_G2A Inductance MP1, MP2 Midpoint R11A, R12A, R3A, R21A, R22A, R11B, R12B, R3B, R21B, R22B Route

Claims

1. A noise reduction device comprising: a busbar; a circuit board including a capacitor; a first conductive member connecting a first connection portion of the busbar to a first terminal of the circuit board; and a second conductive member connecting a second connection portion of the busbar to a second terminal of the circuit board, wherein the busbar includes: an input portion into which current is input; an intermediate portion through which the current input from the input portion passes; and an output portion that outputs the current that has passed through the intermediate portion, wherein the intermediate portion is formed to be spaced away from a straight line connecting the input portion and the output portion.

2. The noise reduction device according to claim 1, wherein the intermediate section includes: a straight section along a second straight line parallel to a first straight line connecting the input section and the output section; a first connecting section connecting the input section and the first end of the straight section; and a second connecting section connecting the output section and the second end of the straight section.

3. The noise reduction device according to claim 2, further comprising a magnetic core surrounding the linear portion.

4. The noise reduction device according to any one of claims 1 to 3, wherein the circuit board, the first conductive member, and the second conductive member are arranged along the straight line between the input section and the output section.

5. A noise reduction device according to any one of claims 1 to 4, further comprising a ground member connected to ground potential, wherein the capacitor includes a first capacitor and a second capacitor, the first terminal of the first capacitor is connected to the first terminal of the circuit board, the first terminal of the second capacitor is connected to the second terminal of the circuit board, and the ground member is connected to the second terminal of the first capacitor and the second terminal of the second capacitor.

6. The noise reduction device according to any one of claims 1 to 5, wherein the circuit board is disposed between the input section and the output section, and the capacitor is disposed in the space formed by the circuit board and the intermediate section.

7. The noise reduction device according to claim 6, further comprising a metal housing including a recess for accommodating the intermediate portion.

8. The noise reduction device according to claim 7, wherein at least a portion of the intermediate portion is connected to the metal housing via a heat conductive member.

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