Smoothing circuit

Abstract

A smoothing circuit (10) is provided with a positive electrode wire (11), a negative electrode wire (12), and a first capacitor part (C1) and a second capacitor part (C2) connected in parallel between the positive electrode wire and the negative electrode wire. The positive electrode wire has a first positive electrode connection portion (P1) connected to the first capacitor part, and a second positive electrode connection portion (P2) connected to the second capacitor part. The negative electrode wire has a first negative electrode connection portion (N1) connected to the second capacitor part, and a second negative electrode connection portion (N2) connected to the first capacitor part. The positive electrode wire and the negative electrode wire cross each other three-dimensionally. The inductance of the positive electrode wire is substantially equal to the equivalent series inductance of the first capacitor part, and the inductance of the negative electrode wire is substantially equal to the equivalent series inductance of the second capacitor part. The smoothing circuit comprises a snubber circuit (Cs) connected between the positive electrode wire and the negative electrode wire.

Description

smoothing circuit CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on Japanese Application No. 2024-029107, filed on February 28, 2024, the contents of which are incorporated herein by reference.

[0002] The present disclosure relates to a smoothing circuit including a plurality of capacitors.

[0003] For example, there is a noise filter device that includes a positive wiring, a negative wiring, and a first capacitor and a second capacitor connected in parallel between the positive wiring and the negative wiring, where the positive wiring connects a first positive electrode connection part that connects to the first capacitor and a second positive electrode connection part that connects to the second capacitor, and the negative wiring connects a first negative electrode connection part that connects to the second capacitor and a second negative electrode connection part that connects to the first capacitor, and where the positive wiring and the negative wiring cross each other at an intersection (see Patent Document 1). In the noise filter device described in Patent Document 1, the inductance of the positive wiring and the negative wiring is made equal to the equivalent series inductance (ESL) of the first capacitor and the second capacitor, thereby canceling out the ESL of the first capacitor and the second capacitor and improving noise reduction performance.

[0004] Japanese Patent Application Laid-Open No. 2022-162441

[0005] When the noise filter device described in Patent Document 1 is connected between a DC power supply and a power conversion circuit, it can reduce noise transmitted from the power conversion circuit, which is a noise source, to the DC power supply. However, increasing the inductance of the positive and negative wiring to offset the ESL of the first and second capacitors increases the surge voltage applied to the power conversion circuit. In particular, the configuration described in Patent Document 1, in which the first and second capacitors are cross-connected to form an overpass between the positive and negative wiring, doubles the inductance compared to simply connecting the first and second capacitors in parallel. For this reason, the noise filter device described in Patent Document 1 significantly increases the surge voltage applied to the power conversion circuit, making it difficult to directly use it in a smoothing circuit connected between a DC power supply and a power conversion circuit, for example.

[0006] The present disclosure has been made to solve the above-mentioned problems, and its main objective is to provide a smoothing circuit that can suppress an increase in surge voltage while improving noise reduction performance.

[0007] A first means for solving the above problem is a smoothing circuit comprising a positive wiring, a negative wiring, and a first capacitor unit and a second capacitor unit connected in parallel between the positive wiring and the negative wiring, wherein the positive wiring has a first positive connection unit connected to the first capacitor unit and a second positive connection unit connected to the second capacitor unit, the negative wiring has a first negative connection unit connected to the second capacitor unit and a second negative connection unit connected to the first capacitor unit, the positive wiring and the negative wiring cross each other at an intersection, the inductance of the positive wiring is substantially equal to the equivalent series inductance of the first capacitor unit, and the inductance of the negative wiring is substantially equal to the equivalent series inductance of the second capacitor unit, and a snubber circuit is connected between the positive wiring and the negative wiring.

[0008] According to the above configuration, a positive wiring having a first positive electrode connection portion connected to the first capacitor unit and a second positive electrode connection portion connected to the second capacitor unit intersects with a negative wiring having a first negative electrode connection portion connected to the second capacitor unit and a second negative electrode connection portion connected to the first capacitor unit. That is, the positive wiring and the negative wiring intersect on a plane projected in a predetermined first direction. The inductance of the positive wiring is substantially equal to the equivalent series inductance of the first capacitor unit, and the inductance of the negative wiring is substantially equal to the equivalent series inductance of the second capacitor unit. As a result, the equivalent series inductances (hereinafter referred to as "ESL") of the first capacitor unit and the second capacitor unit can be offset by the inductances of the positive wiring and the negative wiring, respectively, thereby improving the noise reduction performance of the smoothing circuit.

[0009] Furthermore, since the smoothing circuit includes a snubber circuit connected between the positive wiring and the negative wiring, an increase in surge voltage applied between the positive wiring and the negative wiring can be suppressed. Therefore, the smoothing circuit in which the first capacitor unit and the second capacitor unit are cross-connected to form a three-dimensional crossover between the positive wiring and the negative wiring can be used, for example, as a smoothing circuit connected between a DC power source and a power conversion circuit.

[0010] The above and other objects, features, and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which Fig. 1 is a circuit diagram of a smoothing circuit of a first embodiment, Fig. 2 is a front view showing the structure of the smoothing circuit of the first embodiment, Fig. 3 is a plan view of the smoothing circuit of Fig. 2, Fig. 4 is a plan view showing a case of the smoothing circuit of the first embodiment, Fig. 5 is a plan view showing a modified example of the structure of the smoothing circuit, Fig. 6 is a circuit diagram of a smoothing circuit of a second embodiment, Fig. 7 is a front view showing the structure of the smoothing circuit of the second embodiment, Fig. 8 is a plan view of the smoothing circuit of Fig. 7, Fig. 9 is a graph showing simulation results of surge peak voltages for a comparative example and the second embodiment, and Fig. 10 is a circuit diagram of a smoothing circuit of a third embodiment.

[0011] First Embodiment Hereinafter, a first embodiment embodied in a smoothing circuit connected between a DC power supply and a power conversion circuit (inverter) will be described with reference to the drawings.

[0012] As shown in FIG. 1, the smoothing circuit 10 includes a positive electrode wiring 11, a negative electrode wiring 12, a first capacitor section C1, a second capacitor section C2, and a capacitor Cs.

[0013] A first capacitor section C1 and a second capacitor section C2 are connected in parallel between the positive electrode wiring 11 and the negative electrode wiring 12. The first capacitor section C1 is composed of, for example, two capacitors C11 connected in parallel (see FIGS. 2 and 3). The second capacitor section C2 is composed of, for example, two capacitors C21 connected in parallel (see FIGS. 2 and 3).

[0014] The positive electrode wiring 11 has a first positive electrode connection portion P1 connected to the first capacitor portion C1 and a second positive electrode connection portion P2 connected to the second capacitor portion C2. The negative electrode wiring 12 has a first negative electrode connection portion N1 connected to the second capacitor portion C2 and a second negative electrode connection portion N2 connected to the first capacitor portion C1. The positive electrode wiring 11 and the negative electrode wiring 12 cross each other at an intersection. The structure for achieving this intersection will be described later.

[0015] The parasitic inductances of the first capacitor section C1 and the second capacitor section C2 are represented by equivalent series inductances Lc1 and Lc2, respectively. Furthermore, the inductance component of the positive wiring 11 between the first positive electrode connection section P1 and the second positive electrode connection section P2 (the inductance component of the positive electrode wiring 11) is represented by equivalent series inductance Lp. The inductance component of the negative wiring 12 between the first negative electrode connection section N1 and the second negative electrode connection section N2 (the inductance component of the negative electrode wiring 12) is represented by equivalent series inductance Ln. The inductance Lp is set equal (substantially equal) to the inductance Lc1. The inductance Ln is set equal (substantially equal) to the inductance Lc2. Note that the inductance Lp only needs to be substantially equal to the inductance Lc1, and may include a slight error. The inductance Ln only needs to be substantially equal to the inductance Lc2, and may include a slight error.

[0016] The positive input terminal Pin and the negative input terminal Nin are connected to a switching element (not shown) of a power conversion circuit, which is a noise source. The positive output terminal Pout and the negative output terminal Nout are connected to a DC power supply (not shown). A capacitor Cs (C snubber circuit) is connected between the portion of the positive wiring 11 between the second positive connection part P2 and the positive input terminal Pin, and the portion of the negative wiring 12 between the second negative connection part N2 and the negative input terminal Nin.

[0017] Here, let Cs be the capacitance of capacitor Cs, Lp be the inductance of the positive wiring 11, I be the current flowing through the positive wiring 11 when the switching element is turned off, and Vb be the allowable value of the surge voltage. The allowable value Vb is set, for example, to be lower than the withstand voltage of the switching element of the power conversion circuit by a predetermined voltage. In this case, if the electrostatic energy (½·Cs·Vb^2) that can be stored in capacitor Cs is made greater than the electromagnetic energy (½·Lp·I^2) stored in the inductance Lp of the positive wiring 11, the surge voltage can be made lower than the allowable value Vb. "b^2" represents the square of b. To achieve this, the following inequality (1) must be satisfied: (½·Cs·Vb^2) > (½·Lp·I^2) (1) Inequality (1) can be transformed to the following inequality (2). Cs>Lp(I / Vb)^2 (2) In this embodiment, the capacitance of the capacitor Cs is set so that the inequality (2) holds.

[0018] 2 and 3, the capacitors C11 and C12 are formed in an elongated cylindrical shape. The axial direction of the capacitors C11 and C12 (the vertical direction in FIG. 2) corresponds to the longitudinal direction of the capacitors C11 and C12. The arrangement direction of the capacitor sections C1 and C2 (the horizontal direction in FIGS. 2 and 3) corresponds to the longitudinal direction of the smoothing circuit 10.

[0019] The positive electrode wiring 11 and the negative electrode wiring 12 cross each other at an intersection with the first capacitor portion C1 and the second capacitor portion C2 therebetween. That is, the positive electrode wiring 11 and the negative electrode wiring 12 cross each other on a projection plane in a direction (a predetermined first direction) perpendicular to the arrangement direction of the capacitor portions C1 and C2 (the longitudinal direction of the smoothing circuit 10, the left-right direction in FIGS. 2 and 3) and the axial direction of the capacitors C11 and C12 (the longitudinal direction of the capacitors C11 and C12, the up-down direction in FIG. 2). The outer peripheral surfaces of the capacitors C11 and C12 are insulated from the positive electrode wiring 11 and the negative electrode wiring 12.

[0020] The first capacitor unit C1 has a positive electrode C13 (first electrode) and a negative electrode C14 (second electrode). The second capacitor unit C2 has a positive electrode C23 (first electrode) and a negative electrode C24 (second electrode). The first capacitor unit C1 and the second capacitor unit C2 are arranged so that the orientations of their positive and negative electrodes are opposite in the vertical direction (predetermined direction) of FIG. 2 . For example, in the first capacitor unit C1, the positive electrode C13 is arranged on the upper side and the negative electrode C14 is arranged on the lower side, while in the second capacitor unit C2, the positive electrode C23 is arranged on the lower side and the negative electrode C24 is arranged on the upper side. The positive electrodes C13 and C23 of the capacitor units C1 and C2 (respective capacitors C11 and C21) are connected to the positive wiring 11 by solder S. The negative electrodes C14 and C24 of the capacitor units C1 and C2 (respective capacitors C11 and C12) are connected to the negative wiring 12 by solder S.

[0021] The positive electrode wiring 11 connects the positive electrode C13 of the first capacitor unit C1 and the positive electrode C23 of the second capacitor unit C2 obliquely with respect to the vertical direction in Figure 2 (the axial direction of the capacitors C11 and C12, the predetermined direction). The negative electrode wiring 12 connects the negative electrode C14 of the first capacitor unit C1 and the negative electrode C24 of the second capacitor unit C2 obliquely with respect to the vertical direction in Figure 2 (the axial direction of the capacitors C11 and C12, the predetermined direction).

[0022] The positive electrode wiring 11 and the negative electrode wiring 12 are formed by bus bars, which are, for example, copper (metal) plates. The inductance components of the positive electrode wiring 11 and the negative electrode wiring 12 can be controlled by adjusting the length, width, and thickness of the bus bars. As a result, the inductance Lp of the positive electrode wiring 11 is made equal (substantially equal) to the equivalent series inductance Lc1 of the first capacitor section C1. The inductance Ln of the negative electrode wiring 12 is made equal (substantially equal) to the equivalent series inductance Lc2 of the second capacitor section C2.

[0023] 3, a gap G is formed between the first capacitor portion C1 and the second capacitor portion C2. The gap G is formed between the outer peripheral surface of the oval cylindrical capacitor C11 and the outer peripheral surface of the oval cylindrical capacitor C12, and extends in the axial direction (longitudinal direction) of the capacitors C11 and C12. The capacitor Cs (snubber circuit) is disposed in the gap G.

[0024] The smoothing circuit 10 includes a positive terminal 16 connected to the positive wiring 11 and a negative terminal 26 connected to the negative wiring 12. The positive terminal 16 and the negative terminal 26 are arranged side by side and extend in a direction (a predetermined first direction) perpendicular to the axial direction (longitudinal direction) of the capacitors C11 and C12 and the longitudinal direction of the smoothing circuit 10 (the direction in which the capacitors C11 and C12 are arranged).

[0025] The smoothing circuit 10 includes a positive terminal 18 including a connection 17 with a positive terminal 16 of the positive wiring 11 and the positive terminal 16, and a negative terminal 28 including a connection 27 with a negative terminal 26 of the negative wiring 12 and the negative terminal 26. The capacitor Cs is connected between the positive terminal 18 and the negative terminal 28. More specifically, the capacitor Cs is connected between the connection 17 and the connection 27.

[0026] As shown in Fig. 4, the positive electrode wiring 11, the negative electrode wiring 12, the first capacitor unit C1, the second capacitor unit C2, and the capacitor Cs are housed in a case 30. The case 30 is formed, for example, from an insulating material in the shape of a rectangular cylinder with a bottom (hollow box) and has a lid (not shown). After the positive electrode wiring 11, the negative electrode wiring 12, the first capacitor unit C1, the second capacitor unit C2, and the capacitor Cs are housed inside the case 30, the case 30 is filled with, for example, epoxy resin (insulating resin), and the lid of the case 30 is closed. In this way, the smoothing circuit 10 is configured as a smoothing circuit module (capacitor module).

[0027] The present embodiment described above in detail has the following advantages.

[0028] The positive wiring 11, which has a first positive connection P1 connected to the first capacitor section C1 and a second positive connection P2 connected to the second capacitor section C2, and the negative wiring 12, which has a first negative connection N1 connected to the second capacitor section C2 and a second negative connection N2 connected to the first capacitor section C1, intersect at an intersection. The inductance Lp of the positive wiring 11 is substantially equal to the equivalent series inductance Lc1 of the first capacitor section C1, and the inductance Ln of the negative wiring 12 is substantially equal to the equivalent series inductance Lc2 of the second capacitor section C2. Therefore, the equivalent series inductances Lc1 and Lc2 (hereinafter referred to as "ESL") of the first capacitor section C1 and the second capacitor section C2 can be canceled out by the inductances Lp and Ln of the positive wiring 11 and the negative wiring 12, respectively, thereby improving the noise reduction performance of the smoothing circuit 10.

[0029] The smoothing circuit 10 includes the capacitor Cs of the C snubber circuit connected between the positive electrode wiring 11 and the negative electrode wiring 12, and is therefore capable of suppressing an increase in surge voltage applied between the positive electrode wiring 11 and the negative electrode wiring 12. Therefore, a smoothing circuit 10 in which the first capacitor unit C1 and the second capacitor unit C2 are cross-connected to form a multilevel intersection between the positive electrode wiring 11 and the negative electrode wiring 12 can be used as a smoothing circuit 10 connected between a DC power supply and a power conversion circuit.

[0030] The first capacitor portion C1 and the second capacitor portion C2 are arranged side by side in a direction perpendicular to the predetermined direction, which makes it easy to arrange the first capacitor portion C1 and the second capacitor portion C2 together in one location. Furthermore, the capacitor Cs is arranged in the gap G between the first capacitor portion C1 and the second capacitor portion C2, which makes it easy to miniaturize the smoothing circuit 10, including the capacitor Cs.

[0031] Since the positive electrode terminal 16 and the negative electrode terminal 26 are arranged side by side, the distance between the positive electrode terminal 16 and the negative electrode terminal 26 can be shortened. Furthermore, the capacitor Cs is connected between the positive electrode terminal 18 and the negative electrode terminal 28. This allows the length of the wiring from the connection portion 17 of the positive electrode wiring 11 with the positive electrode terminal 18 to the positive electrode terminal 16, and the length of the wiring from the connection portion 27 of the negative electrode wiring 12 with the negative electrode terminal 28 to the negative electrode terminal 26 to be shortened. This reduces the inductance of the wiring from the positive electrode terminal 16 to the capacitor Cs and the inductance of the wiring from the negative electrode terminal 26 to the capacitor Cs. As a result, the surge voltage applied between the positive electrode terminal 16 and the negative electrode terminal 26 can be reduced.

[0032] The capacitance Cs of the capacitor Cs of the C snubber circuit, the inductance Lp of the positive wiring 11, the current I flowing through the positive wiring 11, and the allowable value Vb of the surge voltage satisfy the relationship Cs > Lp(I / Vb)^2. With this configuration, the electrostatic energy (½ Cs Vb^2) that can be stored in the capacitor Cs can be made greater than the electromagnetic energy (½ Lp I^2) stored in the inductance Lp of the positive wiring 11. Therefore, the surge voltage applied between the positive wiring 11 and the negative wiring 12 can be made lower than the allowable value Vb.

[0033] The smoothing circuit 10 includes a case 30 that houses the positive electrode wiring 11, the negative electrode wiring 12, the first capacitor unit C1, the second capacitor unit C2, and the capacitor Cs. With this configuration, the positive electrode wiring 11, the negative electrode wiring 12, the first capacitor unit C1, the second capacitor unit C2, and the capacitor Cs are housed inside the case 30, and the smoothing circuit 10 can be modularized. This makes the smoothing circuit 10 easier to handle.

[0034] The first capacitor unit C1 and the second capacitor unit C2 are arranged so that the orientations of their positive and negative electrodes are opposite to each other in a predetermined direction. The positive electrode wiring 11 connects the positive electrode C13 of the first capacitor unit C1 to the positive electrode C23 of the second capacitor unit C2 at an angle with respect to the predetermined direction. The negative electrode wiring 12 connects the negative electrode C14 of the first capacitor unit C1 to the negative electrode C24 of the second capacitor unit C2 at an angle with respect to the predetermined direction. With this arrangement, the configuration in which the positive electrode wiring 11 and the negative electrode wiring 12 cross over each other can be achieved with shorter positive electrode wiring 11 and negative electrode wiring 12.

[0035] The positive electrode wiring 11 and the negative electrode wiring 12 cross each other at an intersection with the first capacitor portion C1 and the second capacitor portion C2 in between. This configuration makes it easier to arrange the positive electrode wiring 11 and the negative electrode wiring 12 when the positive electrode wiring 11 and the negative electrode wiring 12 cross each other at an intersection with the second capacitor portion C2.

[0036] The above embodiment can be modified as follows: The same parts as those in the above embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0037] A capacitor Cs that does not satisfy Cs>Lp(I / Vb)^2 may be employed. Even in this case, the increase in surge voltage applied between the positive wiring 11 and the negative wiring 12 can be suppressed compared to a configuration that does not include a capacitor Cs (C snubber circuit).

[0038] 5, the negative electrode wiring 12 may be extended in the opposite direction to the negative electrode terminal 26 (upward in FIG. 5), and a capacitor Cs may be connected between the end of the positive electrode wiring 11 opposite the positive electrode terminal 16 and the end of the negative electrode wiring 12 opposite the negative electrode terminal 26. Then, the capacitor Cs (snubber circuit) may be disposed in the gap G2 between the first capacitor portion C1 and the second capacitor portion C2 on the side opposite to the positive electrode terminal 16 and the negative electrode terminal 26.

[0039] Second Embodiment The second embodiment will be described below, focusing on the differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be incorporated herein.

[0040] 6, in this embodiment, the smoothing circuit 10 includes an RC snubber circuit (snubber circuit) configured with a resistor Rs and a capacitor Cs. The resistor Rs and the capacitor Cs are connected in series between a portion of the positive wiring 11 between the second positive electrode connection point P2 and the positive electrode input terminal Pin, and a portion of the negative wiring 12 between the second negative electrode connection point N2 and the negative electrode input terminal Nin.

[0041] 7 and 8 , the capacitor Cs is disposed in the gap G. The resistor Rs and the capacitor Cs are connected between the positive electrode terminal 18 and the negative electrode terminal 28. The resistor Rs is formed in a plate shape. The largest surface Rsa of the resistor Rs is in close contact with the positive electrode wiring 11 (bus bar).

[0042] According to the above configuration, the largest surface Rsa of the resistor Rs is in close contact with the positive electrode wiring 11 formed by the bus bar. This allows the bus bar to function as a heat sink that dissipates heat from the resistor Rs, thereby preventing the resistor Rs from overheating. This embodiment also provides the same effects as the first embodiment.

[0043] FIG. 9 is a graph showing the simulation results of surge peak voltages in the comparative example and this embodiment.

[0044] In Comparative Example 1, the first capacitor section C1 (two capacitors C11) and the second capacitor section C2 (two capacitors C12) are simply connected in parallel between the positive electrode wiring 11 and the negative electrode wiring 12, and no snubber circuit is provided. In this case, the peak of the surge voltage is 615 V.

[0045] In Comparative Example 2, the first capacitor section C1 and the second capacitor section C2 are connected in a cross-connected manner and no snubber circuit is provided. In this case, the surge voltage peaks at 734 V. The surge voltage increases because the inductance of the positive electrode wiring 11 and the negative electrode wiring 12 is increased to offset the ESL of the first capacitor section C1 and the second capacitor section C2. In particular, because the first capacitor section C1 and the second capacitor section C2 are connected in a cross-connected manner to form an overpass between the positive electrode wiring 11 and the negative electrode wiring 12, the inductance is doubled, resulting in a higher surge voltage than in Comparative Example 1.

[0046] In this embodiment, the first capacitor C1 and the second capacitor C2 are connected in a cross-connected manner, and an RC snubber circuit is provided, which is composed of a resistor Rs and a capacitor Cs. In this case, the peak surge voltage is 608 V. In other words, the RC snubber circuit can suppress the rise in surge voltage applied between the positive wiring 11 and the negative wiring 12.

[0047] It is also possible to employ a configuration in which the surface Rsa of the resistance Rs with the largest resistance is not in close contact with the positive electrode wiring 11 formed by the bus bar.It is also possible to employ a configuration in which the resistance Rs is not in close contact with the positive electrode wiring 11 formed by the bus bar.

[0048] Third Embodiment Hereinafter, a third embodiment will be described, focusing on differences from the first embodiment. Note that the same parts as those in the first embodiment are denoted by the same reference numerals and the description thereof will be incorporated.

[0049] As shown in FIG. 10 , in this embodiment, the smoothing circuit 10 includes an RCD snubber circuit (snubber circuit) composed of a resistor Rs, a capacitor Cs, and a diode Ds. The resistor Rs and the diode Ds are connected in parallel to the capacitor Cs. The RCD snubber circuit is connected between a portion of the positive wiring 11 between the second positive electrode connection point P2 and the positive input terminal Pin, and a portion of the negative wiring 12 between the second negative electrode connection point N2 and the negative input terminal Nin. This configuration allows the RCD snubber circuit to suppress an increase in surge voltage applied between the positive wiring 11 and the negative wiring 12. This embodiment also provides the same advantages as the first and second embodiments.

[0050] The first to third embodiments can be modified as follows: The same parts as those in the first to third embodiments are denoted by the same reference numerals and the same explanations will be used.

[0051] A configuration may be adopted in which the capacitor Cs is disposed in a location other than the gaps G, G2 between the first capacitor portion C1 and the second capacitor portion C2.

[0052] The bus bars forming the positive electrode wiring 11 and the negative electrode wiring 12 may be made of, for example, copper (metal) rods. Even in this case, the same effects as those of the first to third embodiments and their modifications can be achieved.

[0053] The smoothing circuit 10 may be configured without the case 30, that is, may not be modularized.

[0054] The positive electrode wiring 11 and the negative electrode wiring 12 may cross each other at different levels without sandwiching the first capacitor portion C1 and the second capacitor portion C2 therebetween.

[0055] The first capacitor section C1 may be composed of one capacitor C11 or three or more capacitors C11. The second capacitor section C2 may be composed of one capacitor C21 or three or more capacitors C21.

[0056] The smoothing circuit 10 according to the first to third embodiments and their modifications may be applied to a smoothing circuit connected between a DC charger and a battery.

[0057] The above-described embodiment and modifications may be combined within the scope of possible combinations.

[0058] Characteristic configurations extracted from the above-described embodiments and modifications will be described below. [Configuration 1] A smoothing circuit (10) comprising a positive wiring (11), a negative wiring (12), and a first capacitor unit (C1) and a second capacitor unit (C2) connected in parallel between the positive wiring and the negative wiring, wherein the positive wiring has a first positive connection unit (P1) connected to the first capacitor unit and a second positive connection unit (P2) connected to the second capacitor unit, the negative wiring has a first negative connection unit (N1) connected to the second capacitor unit and a second negative connection unit (N2) connected to the first capacitor unit, the positive wiring and the negative wiring cross each other at an intersection, the inductance of the positive wiring is substantially equal to the equivalent series inductance of the first capacitor unit, and the inductance of the negative wiring is substantially equal to the equivalent series inductance of the second capacitor unit, and the smoothing circuit comprises a snubber circuit (Cs, Rs, Rd) connected between the positive wiring and the negative wiring. [Configuration 2] The smoothing circuit of Configuration 1, wherein the first capacitor unit and the second capacitor unit are arranged side by side, and the snubber circuit is arranged in a gap (G, G2) between the first capacitor unit and the second capacitor unit. [Configuration 3] The smoothing circuit of Configuration 1 or 2, further comprising: a positive terminal (16) connected to the positive wiring; and a negative terminal (26) connected to the negative wiring and arranged side by side with the positive terminal, and the snubber circuit is connected between a connection portion (17) of the positive wiring with the positive terminal and a positive terminal portion (18) including the positive terminal, and a connection portion (27) of the negative wiring with the negative terminal and a negative terminal portion (28) including the negative terminal. [Configuration 4] The smoothing circuit according to any one of Configurations 1 to 3, wherein the snubber circuit includes a capacitor (Cs) and a plate-shaped resistor (Rs), the positive electrode wiring and the negative electrode wiring are formed by bus bars that are conductive plates or rods, and the surface with the largest resistance (Rsa) is in close contact with the positive electrode wiring or the negative electrode wiring.[Configuration 5] The smoothing circuit according to any one of configurations 1 to 4, wherein the snubber circuit includes a capacitor (Cs), and wherein a capacitance Cs of the capacitor, an inductance Lp of the positive electrode wiring, a current I flowing through the positive electrode wiring, and an allowable value Vb of a surge voltage satisfy Cs > Lp(I / Vb)^2. [Configuration 6] The smoothing circuit according to any one of configurations 1 to 5, comprising a case (30) that houses the positive electrode wiring, the negative electrode wiring, the first capacitor unit, the second capacitor unit, and the snubber circuit therein. [Configuration 7] The smoothing circuit according to any one of Configurations 1 to 6, wherein the first capacitor unit has a first electrode (C13) and a second electrode (C14), the second capacitor unit has a first electrode (C23) and a second electrode (C24), the first capacitor unit and the second capacitor unit are arranged such that the orientations of the first electrode and the second electrode are opposite to each other in a predetermined direction and are arranged side by side in a direction perpendicular to the predetermined direction, the positive electrode wiring connects the first electrode of the first capacitor unit and the first electrode of the second capacitor unit obliquely with respect to the predetermined direction, and the negative electrode wiring connects the second electrode of the first capacitor unit and the second electrode of the second capacitor unit obliquely with respect to the predetermined direction. [Configuration 8] The smoothing circuit according to Configuration 7, wherein the positive electrode wiring and the negative electrode wiring cross each other at an intersection with the first capacitor unit and the second capacitor unit therebetween.

[0059] Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments or structures. The present disclosure also encompasses various modifications and equivalent modifications. In addition, various combinations and forms, including only one element, more than one element, or less than one element, are also within the scope and spirit of the present disclosure.

Claims

1. A smoothing circuit (10) comprising a positive wiring (11), a negative wiring (12), and a first capacitor unit (C1) and a second capacitor unit (C2) connected in parallel between the positive wiring and the negative wiring, wherein the positive wiring has a first positive connection unit (P1) connected to the first capacitor unit and a second positive connection unit (P2) connected to the second capacitor unit, the negative wiring has a first negative connection unit (N1) connected to the second capacitor unit and a second negative connection unit (N2) connected to the first capacitor unit, the positive wiring and the negative wiring cross each other at an intersection, the inductance of the positive wiring is substantially equal to the equivalent series inductance of the first capacitor unit, and the inductance of the negative wiring is substantially equal to the equivalent series inductance of the second capacitor unit, and the smoothing circuit comprises a snubber circuit (Cs, Rs, Rd) connected between the positive wiring and the negative wiring.

2. A smoothing circuit as described in claim 1, wherein the first capacitor section and the second capacitor section are arranged side by side, and the snubber circuit is arranged in a gap (G, G2) between the first capacitor section and the second capacitor section.

3. A smoothing circuit according to claim 1 or 2, comprising: a positive terminal (16) connected to the positive wiring; and a negative terminal (26) connected to the negative wiring and arranged alongside the positive terminal, wherein the snubber circuit is connected between a connection portion (17) of the positive wiring with the positive terminal and a positive terminal portion (18) including the positive terminal, and a connection portion (27) of the negative wiring with the negative terminal and a negative terminal portion (28) including the negative terminal.

4. A smoothing circuit as described in claim 1 or 2, wherein the snubber circuit includes a capacitor (Cs) and a plate-shaped resistor (Rs), the positive wiring and the negative wiring are formed by bus bars that are conductive plates or rods, and the surface with the largest resistance (Rsa) is in close contact with the positive wiring or the negative wiring.

5. The smoothing circuit according to claim 1 or 2, wherein the snubber circuit includes a capacitor (Cs), and the capacitance Cs of the capacitor, the inductance Lp of the positive wiring, the current I flowing through the positive wiring, and the allowable value Vb of the surge voltage satisfy Cs > Lp (I / Vb)^2.

6. A smoothing circuit as described in claim 1 or 2, comprising a case (30) that houses the positive wiring, the negative wiring, the first capacitor section, the second capacitor section, and the snubber circuit.

7. A smoothing circuit as described in claim 1 or 2, wherein the first capacitor unit has a first electrode (C13) and a second electrode (C14), the second capacitor unit has a first electrode (C23) and a second electrode (C24), the first capacitor unit and the second capacitor unit are arranged so that the orientations of the first electrode and the second electrode are opposite to each other in a predetermined direction and are arranged side by side in a direction perpendicular to the predetermined direction, the positive wiring connects the first electrode of the first capacitor unit and the first electrode of the second capacitor unit obliquely with respect to the predetermined direction, and the negative wiring connects the second electrode of the first capacitor unit and the second electrode of the second capacitor unit obliquely with respect to the predetermined direction.

8. The smoothing circuit according to claim 7, wherein the positive wiring and the negative wiring cross each other at an intersection with the first capacitor unit and the second capacitor unit therebetween.

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