Power Converter

Abstract

To provide a power converter which effectively depresses an increase in a wiring inductance on a bus bar connected with a capacitor.SOLUTION: A power converter comprises a capacitor having a first electrode and a second electrode, and a specific bus bar connected with a specific electrode as each of one or both of the first electrode and the second electrode. The specific bus bar is folded on the specific electrode and has a folding-back wiring part having parts confronted with each other. An end portion of the folding-back wiring part is connected with the specific electrode.SELECTED DRAWING: Figure 6

Description

[Technical Field]

[0001] The present application relates to power converters. [Background technology]

[0002] A power converter is a device that converts an input current from DC to AC, AC to DC, or an input voltage to a different voltage. In recent years, there has been a demand for power converters with high power density and low power loss. To meet this demand, switching elements, such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal Oxide Semiconductor Field Effect Transistors), that supply power, are becoming larger in current, voltage, and switching speed. These higher current, voltage, and switching speed of switching elements increase surge voltages generated during switching. The increased surge voltages increase switching loss and heat generation in the switching elements. To suppress this heat generation, it is conceivable to provide a high-heat-dissipating component in the power converter. However, providing a high-heat-dissipating component in the power converter inevitably increases the cost and size of the power converter.

[0003] The magnitude of surge voltages caused by switching of switching elements depends on the magnitude of wiring inductance, such as the bus bars of capacitors electrically connected to the switching elements. High wiring inductance leads to high surge voltages. Effective methods for reducing wiring inductance include shortening the bus bars or making currents flow in opposite directions through a pair of bus bars so that the magnetic flux generated in the bus bars cancels out.

[0004] A configuration has been disclosed in which current flows in opposite directions through a pair of bus bars (see, for example, Patent Document 1). In Patent Document 1, a pair of opposing bus bars are overlapped, and each opposing bus bar is electrically connected to both poles of each capacitor. With this configuration, current flows in opposite directions through each of the opposing bus bars, canceling out magnetic flux generated around the bus bars and thereby suppressing an increase in wiring inductance in the bus bars. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 3583034 Summary of the Invention [Problem to be solved by the invention]

[0006] In the above-mentioned Patent Document 1, current flows in opposite directions through the opposing positive and negative bus bars, thereby suppressing an increase in the wiring inductance of the bus bars. However, when the capacitor electrodes are provided separately from the main body of the capacitor as in Patent Document 1 (on both sides of the main body of the capacitor in Patent Document 1), the positive and negative connection wirings are positioned far apart in the connection between the capacitor electrodes and the bus bars, and therefore the arrangement does not cancel out the magnetic flux generated around each connection wiring. As a result, the wiring inductance of the connection wiring connecting the capacitor electrodes and the bus bars is not reduced, posing a problem in that it is not possible to sufficiently suppress an increase in the wiring inductance of the bus bars connected to the capacitor.

[0007] Therefore, an object of the present application is to provide a power converter that effectively suppresses an increase in wiring inductance in a bus bar connected to a capacitor. [Means for solving the problem]

[0008] The power converter disclosed in the present application includes a capacitor having a first electrode and a second electrode, and a specific bus bar connected to the specific electrode, which is one or both of the first electrode and the second electrode, and the specific bus bar is a main body portion; and a A folded wiring portion having portions folded back and facing each other on a specific electrode and, The end of the folded wiring portion is connected to a specific electrode. [Effects of the Invention]

[0009] The power converter disclosed in the present application includes a capacitor having a first electrode and a second electrode, and a specific busbar connected to a specific electrode, which is one or both of the first electrode and the second electrode. The specific busbar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other. Since the ends of the folded wiring portion are connected to the specific electrode, the portion of the wiring in the folded wiring portion before being folded back and the portion of the wiring after being folded back are arranged opposite each other, and currents flow in opposite directions in each of the facing wiring portions. This cancels out magnetic flux generated by the current flowing in the folded wiring portion, thereby effectively suppressing an increase in wiring inductance in the specific busbar connected to the capacitor. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a diagram showing a circuit configuration of a power converter according to a first embodiment. [Figure 2] 3 is a circuit diagram illustrating a switching operation in a U-phase arm of the power converter according to the first embodiment. FIG. [Figure 3] 1 is a plan view of a capacitor module of a power converter according to a first embodiment. [Figure 4] 1 is a plan view of a capacitor module of a power converter according to a first embodiment. [Figure 5] 4 is a cross-sectional view of a capacitor module of a power conversion device taken along the line AA in FIG. 3. [Figure 6]1 is a plan view of a main part of a capacitor module of a power converter according to a first embodiment. [Figure 7] 5 is a plan view of a main part of another capacitor module of the power converter according to the first embodiment. FIG. [Figure 8] FIG. 4 is a diagram showing a reduction rate of wiring inductance in the power converter according to the first embodiment. [Figure 9] FIG. 10 is a plan view of a main part of a capacitor module of a power converter according to a second embodiment. [Figure 10] 10 is a plan view of a main part of another capacitor module of the power converter according to the second embodiment. FIG. [Figure 11] 10 is a plan view of a main part of another capacitor module of the power converter according to the second embodiment. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a power converter according to an embodiment of the present invention will be described with reference to the drawings. Note that the same or equivalent members and parts in each drawing will be denoted by the same reference numerals.

[0012] Embodiment 1 Fig. 1 is a diagram showing a circuit configuration of a power converter 1 according to a first embodiment, Fig. 2 is a circuit diagram illustrating the switching operation of a U-phase arm of the power converter 1, Fig. 3 is a plan view of a capacitor module 100 of the power converter 1, with a portion of the molded resin 205 removed to show one side in the Z direction, Fig. 4 is a plan view of the capacitor module 100 of the power converter 1, with a portion of the molded resin 205 removed to show the other side in the Z direction, Fig. 5 is a cross-sectional view of the capacitor module 100 of the power converter 1 taken at the AA cross section position in Fig. 3, Fig. 6 is a plan view of a main part of the capacitor module 100 of the power converter 1, Fig. 7 is a plan view of a main part of another capacitor module 100 of the power converter 1, and Fig. 8 is a diagram showing the reduction rate of wiring inductance in the power converter 1. The power converter 1 is a device that converts an input current from DC to AC, AC to DC, or an input voltage to a different voltage. In this application, the power converter 1 is described as a three-phase inverter that converts DC power into AC power to drive a three-phase AC motor, but the power converter disclosed in this application is not limited to a three-phase inverter.

[0013] <Power converter 1> The circuit configuration of the power converter 1 will be explained with reference to Fig. 1. Fig. 1 shows a three-phase inverter circuit that drives a three-phase AC motor 3. The power converter 1 includes a capacitor module 100 and a switching circuit 101. The capacitor module 100 is connected to a DC power supply 2 that is external to the power converter 1. The switching circuit 101, connected to a smoothing capacitor 102 included in the capacitor module 100, includes a semiconductor element that converts the DC voltage applied to the smoothing capacitor 102 into power by switching. The switching circuit 101 converts the DC power into AC power. The AC power is output to the external three-phase AC motor 3, driving it.

[0014] The capacitor module 100 includes a smoothing capacitor 102 that smooths a DC voltage, and a specific bus bar 106 that connects the smoothing capacitor 102 and the switching circuit 101. In this embodiment, the capacitor included in the capacitor module 100 is described as the smoothing capacitor 102, but the capacitor is not limited to the smoothing capacitor 102. The capacitor may be a decoupling capacitor provided on a power supply line or a filter capacitor for noise removal. The smoothing capacitor 102 has a first electrode and a second electrode. One of the first electrode and the second electrode is a positive electrode, and the other is a negative electrode.

[0015] The switching circuit 101 is a three-phase inverter circuit having a U-phase arm in which U-phase switching elements 103a and 103b, which are semiconductor elements, are connected in series, a V-phase arm in which V-phase switching elements 104a and 104b, which are semiconductor elements, are connected in series, and a W-phase arm in which W-phase switching elements 105a and 105b, which are semiconductor elements, are connected in series. The switching elements of each phase arm are controlled to be turned on and off in a predetermined order, thereby generating a three-phase AC current. The generated three-phase AC current drives a three-phase AC motor 3.

[0016] The switching elements of each phase arm may be self-extinguishing semiconductor switching elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors) with diodes connected in anti-parallel. In this embodiment, a MOSFET is used with its parasitic diode as a freewheeling diode, but a freewheeling diode may be provided in parallel when using a switching element without a parasitic diode, such as an IGBT. Alternatively, an RC-IGBT (Reverse Conducting IGBT) in which the switching element and freewheeling diode are integrated may be used.

[0017] The switching elements of each phase arm are formed on a semiconductor substrate made of a material such as silicon, SiC (Silicon Carbide), or GaN (Gallium Nitride). Wide bandgap semiconductor elements, which have a wider bandgap than silicon, can be used for the switching elements. When using a MOSFET made of silicon carbide, which is a wide bandgap semiconductor element, the time change di / dt of current generated during switching can be made larger than that of a MOSFET made of silicon. Furthermore, wide bandgap semiconductor elements have low on-resistance, little loss, and little heat generation, allowing for a reduction in chip area. Because the chip area is reduced, the switching circuit 101 can be made smaller.

[0018] <Wiring inductance and surge voltage> The relationship between wiring inductance and surge voltage will be explained using Fig. 2. For simplification, Fig. 2 is a circuit diagram showing only U-phase switching elements 103a and 103b of switching circuit 101, and replacing three-phase AC motor 3 with inductance load 109. In Fig. 2, the wiring inductance on the positive electrode side of smoothing capacitor 102 is designated as wiring inductance 107, and the wiring inductance on the negative electrode side is designated as wiring inductance 108. Specifically, wiring inductances 107 and 108 are wiring inductances resulting from specific bus bar 106 in capacitor module 100.

[0019] The off-surge voltage ΔVs when the U-phase switching element 103a changes from an ON state to an OFF state will be described. In FIG. 2, when the U-phase switching element 103a is ON, a current path indicated by a solid arrow is formed. When the U-phase switching element 103a is OFF, a current path indicated by a dashed arrow is formed. When the U-phase switching element 103a changes from ON to OFF, the current path is switched, so the current flowing through the wiring changes with a slope of di / dt. Let the magnitude of the wiring inductance 107 be L. 107, the magnitude of the wiring inductance 108 is L 108 Then, the off-surge voltage ΔVs can be expressed by the formula (1).

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[0020] As shown in equation (1), the off-surge voltage ΔVs is proportional to the wiring inductance L 107 , L 108 Therefore, if these wiring inductance components can be reduced, the surge voltage can be reduced.

[0021] <Capacitor module 100> The capacitor module 100 will be described with reference to Figs. 3 to 5. In the figures, the height direction of the capacitor module 100 is the Z direction, and the directions perpendicular to the Z direction are the X and Y directions. That is, the X and Y directions are planar directions in the capacitor module 100. In this embodiment, the X direction is the first direction, and the Y direction is the second direction. Fig. 3 is a plan view of the capacitor module 100 in the XY directions, Fig. 4 is a bottom view of the capacitor module 100 in the XY directions, and Fig. 5 is a cross-sectional view of the capacitor module 100 in the XZ directions. Note that Figs. 3 and 4 only show the outline of the molded resin 205.

[0022] The capacitor module 100 includes a plurality of smoothing capacitors 102, each having an electrode at each end. In this embodiment, as shown in FIG. 3, the capacitor module 100 includes four smoothing capacitors 102a, 102b, 102c, and 102d. The number of smoothing capacitors 102 is not limited to four and may be one. In this embodiment, as shown in FIG. 5, a positive electrode 207d, which is a first electrode, and a negative electrode 208d, which is a second electrode, are provided on both sides of the smoothing capacitor 102d. However, the arrangement of the positive electrode 207d and the negative electrode 208d is not limited to this. If a specific bus bar, which will be described later, has a folded wiring portion, the arrangement of the positive electrode 207d and the negative electrode 208d can effectively suppress an increase in wiring inductance in the specific bus bar regardless of where the positive electrode 207d and the negative electrode 208d are located. Therefore, the arrangement of the positive electrode 207d and the negative electrode 208d is not limited to both sides of the smoothing capacitor 102d.

[0023] The capacitor module 100 includes specific bus bars 106 connected to specific electrodes, which are either or both of the first and second electrodes. In the present embodiment, both the positive electrodes 207a, 207b, 207c, and 207d, which are first electrodes, and the negative electrodes 208a, 208b, 208c, and 208d, which are second electrodes, are specific electrodes. Therefore, both the positive bus bar 201 connected to the positive electrodes 207a, 207b, 207c, and 207d and the negative bus bar 202 connected to the negative electrodes 208a, 208b, 208c, and 208d are specific bus bars 106. In the present embodiment, both the positive bus bar 201 and the negative bus bar 202 are specific bus bars 106, but this is not a limitation, and either the positive bus bar 201 or the negative bus bar 202 may be the specific bus bar 106.

[0024] Positive bus bar 201 and negative bus bar 202 are molded with mold resin 205, with the ends of the terminals that are connected to the outside exposed. Molding resin 205 is an insulating resin material such as epoxy resin. After each component to be molded is placed in a molding die, molding resin 205 is injected into the molding die and sealed, thereby forming capacitor module 100.

[0025] Positive bus bar 201 has main body portion 201a, multiple folded wiring portions 301, 302, 303, and 304, power supply connection terminal 203a, and multiple switching circuit connection terminals 203b, 203c, and 203d. In the present embodiment, as shown in FIG. 3 , main body portion 201a extends in a second direction perpendicular to the first direction, folded wiring portions 301, 302, 303, and 304 are provided on one side of main body portion 201a in the first direction, power supply connection terminal 203a is provided on the other side of main body portion 201a in the second direction, and switching circuit connection terminals 203b, 203c, and 203d are provided on the other side of main body portion 201a in the first direction. An end of power supply connection terminal 203a and ends of switching circuit connection terminals 203b, 203c, and 203d are exposed from molded resin 205.

[0026] The ends of the folded wiring portions 301-304 are connected to the positive electrodes 207a-207d of the plurality of smoothing capacitors 102a-102d, respectively, via connecting members 206 such as solder. The power supply connection terminal 203a is a terminal connected to the positive electrode side of the DC power supply 2. The switching circuit connection terminals 203b-203d are connected to the switching elements constituting the respective phase arms. For example, the switching circuit connection terminal 203b is connected to the U-phase switching element 103a, the switching circuit connection terminal 203c is connected to the V-phase switching element 104a, and the switching circuit connection terminal 203d is connected to the W-phase switching element 105a. The ends of the switching circuit connection terminals 203b-203d and the positive electrode side of a power terminal (not shown) of the switching circuit 101 are joined by arc welding such as TIG welding.

[0027] Negative bus bar 202 has main body portion 202a, multiple folded wiring portions 305, 306, 307, and 308, power supply connection terminal 204a, and multiple switching circuit connection terminals 204b, 204c, and 204d. In the present embodiment, as shown in FIG. 4 , main body portion 202a extends in a second direction perpendicular to the first direction, folded wiring portions 305, 306, 307, and 308 are provided on one side of main body portion 202a in the first direction, power supply connection terminal 204a is provided on the other side of main body portion 202a in the second direction, and switching circuit connection terminals 204b, 204c, and 204d are provided on the other side of main body portion 202a in the first direction. An end of power supply connection terminal 204a and ends of switching circuit connection terminals 204b, 204c, and 204d are exposed from molded resin 205.

[0028] The ends of the folded wiring portions 305-308 are connected to the negative electrodes 208a-208d of the plurality of smoothing capacitors 102a-102d, respectively, via connecting members 206 such as solder. The power supply connection terminal 204a is a terminal connected to the negative electrode of the DC power supply 2. The switching circuit connection terminals 204b-204d are connected to the switching elements constituting the respective phase arms. For example, the switching circuit connection terminal 204b is connected to the U-phase switching element 103b, the switching circuit connection terminal 204c is connected to the V-phase switching element 104b, and the switching circuit connection terminal 204d is connected to the W-phase switching element 105b. The ends of the switching circuit connection terminals 204b-204d and the negative electrode of a power terminal (not shown) of the switching circuit 101 are joined by arc welding such as TIG welding.

[0029] In this embodiment, each of folded wiring portions 301-308 is connected to a specific electrode, that is, positive electrodes 207a-207d or negative electrodes 208a-208d, only at the end of folded wiring portion 301-308. A large current flows through positive bus bar 201 and negative bus bar 202, causing positive bus bar 201 and negative bus bar 202 to generate heat. This configuration minimizes the number of contact points between the positive bus bar 201 and negative bus bar 202, which have folded wiring portions, and prevents thermal interference between smoothing capacitors 102a-102d, which have specific electrodes.

[0030] <Wiring inductance> The wiring inductance in capacitor module 100 shown in this embodiment will be described. The wiring inductance caused by positive bus bar 201 corresponds to wiring inductance 107 shown in Fig. 2, and the wiring inductance caused by negative bus bar 202 corresponds to wiring inductance 108 shown in Fig. 2. The dashed arrow in Fig. 5 indicates the direction of current when a surge voltage occurs.

[0031] 5, main body portion 201a of positive bus bar 201 and main body portion 202a of negative bus bar 202 are arranged side by side in the Z direction and facing each other, and currents flow in opposite directions through main body portion 201a and main body portion 202a. Therefore, magnetic fluxes generated by currents flowing through main body portion 201a and main body portion 202a are canceled out, making it possible to reduce the wiring inductance of main body portion 201a and main body portion 202a.

[0032] 3, the power supply connection terminals 203a and 204a are arranged side by side in the X direction, and currents flow in opposite directions through the power supply connection terminals 203a and 204a, respectively. As a result, magnetic fluxes generated by the currents flowing through the power supply connection terminals 203a and 204a are canceled out, and the wiring inductance of the power supply connection terminals 203a and 204a can be reduced.

[0033] Switching circuit connection terminals 203b and 204b, switching circuit connection terminals 203c and 204c, and switching circuit connection terminals 203d and 204d are arranged side by side in the Y direction, and currents flow in opposite directions through switching circuit connection terminals 203b and 204b, switching circuit connection terminals 203c and 204c, and switching circuit connection terminals 203d and 204d. As a result, magnetic fluxes generated by currents flowing through switching circuit connection terminals 203b and 204b, switching circuit connection terminals 203c and 204c, and switching circuit connection terminals 203d and 204d are canceled out, making it possible to reduce the wiring inductance of switching circuit connection terminals 203b and 204b, switching circuit connection terminals 203c and 204c, and switching circuit connection terminals 203d and 204d.

[0034] 5, the portion of negative bus bar 202 extending from main body portion 202a in the direction of negative electrode 208d is arranged along the other side of smoothing capacitor 102d in the first direction, and currents flow in opposite directions through this portion of negative bus bar 202 and smoothing capacitor 102d. Therefore, magnetic fluxes generated by currents flowing through this portion of negative bus bar 202 and smoothing capacitor 102d are canceled out, and the wiring inductance of this portion of negative bus bar 202 can be reduced.

[0035] On the other hand, if the positive electrode 207d and the negative electrode 208d are spaced apart, such as by providing the positive electrode 207d and the negative electrode 208d on both sides of the smoothing capacitor 102d, the positions of the positive-side folded wiring portion 304 and the negative-side folded wiring portion 308, through which currents flow in opposite directions, are far apart, and therefore the magnetic fluxes generated in the folded wiring portion 304 and the folded wiring portion 308 cannot cancel each other out. Therefore, the wiring inductance cannot be reduced between the folded wiring portions 304 and 308, the folded wiring portions 303 and 307, the folded wiring portions 302 and 306, and the folded wiring portions 301 and 305.

[0036] <Folded wiring section> The folded wiring portions, which are a key feature of the present application, will now be described. Each folded wiring portion is not disposed adjacent to other wiring, and each effectively suppresses an increase in wiring inductance. A specific bus bar has a folded wiring portion that is folded back on a specific electrode and has portions facing each other, and ends of the folded wiring portion are connected to the specific electrode. In this embodiment, positive bus bar 201 has folded wiring portions 301-304 that are folded back on each of positive electrodes 207a-207d and have portions facing each other. Negative bus bar 202 has folded wiring portions 305-308 that are folded back on each of negative electrodes 208a-208d and have portions facing each other.

[0037] Suppression of an increase in wiring inductance by the folded wiring portion will be described using FIG. 6. FIG. 6 is a diagram showing the folded wiring portion 301 and its surrounding area in FIG. 3. The dashed arrow in FIG. 6 indicates the direction of current in the folded wiring portion 301 when a surge voltage occurs. The folded wiring portion 301 is provided, for example, in a U-shape with the bottom of the U located on one side in the first direction. A portion of the wiring before being folded in the folded wiring portion 301 and a portion of the wiring after being folded are arranged opposite each other, and currents flow in opposite directions in each of the opposing wiring portions. Therefore, magnetic fluxes generated due to the current flowing in the folded wiring portion 301 are canceled, thereby effectively suppressing an increase in wiring inductance of the folded wiring portion 301.

[0038] In this embodiment, smoothing capacitors 102a-102d are provided on one side in the first direction of main body portion 201a of positive busbar 201, and folded wiring portions 301-304 are provided on one side in the first direction of main body portion 201a of positive busbar 201. Similarly, smoothing capacitors 102a-102d are provided on one side in the first direction of main body portion 202a of negative busbar 202, and folded wiring portions 305-308 are provided on one side in the first direction of main body portion 202a of negative busbar 202. Folded wiring portion 301 extends from main body portion 201a of positive busbar 201 to one side in the first direction, then folds back and extends to the other side in the first direction, and is connected to positive electrode 207a at the end of folded wiring portion 301 on the other side in the first direction after being folded back. The other folded wiring portions 302-308 have a similar configuration.

[0039] Although the configuration of the folded wiring portion 301 is not limited to this, by configuring it in this way, the length of the wiring in the folded wiring portion can be minimized and the opposing portion can be sufficiently secured, which makes it possible to more effectively suppress an increase in the wiring inductance of the folded wiring portion 301. Furthermore, since the length of the folded wiring portion is shortened, the specific bus bar can be made smaller.

[0040] In this embodiment, power converter 1 includes multiple smoothing capacitors 102a-102d, and main body portion 201a of positive bus bar 201 and main body portion 202a of negative bus bar 202 extend in a second direction perpendicular to the first direction. The multiple smoothing capacitors 102a-102d are arranged side by side in the second direction on one side of main body portion 201a of positive bus bar 201 and main body portion 202a of negative bus bar 202 in the first direction. Positive bus bar 201 includes multiple folded wiring portions 301-304, and negative bus bar 202 includes multiple folded wiring portions 305-308. Each of the multiple folded wiring portions 301-308 is connected to a specific electrode of each of the multiple smoothing capacitors 102a-102d, i.e., positive electrodes 207a-207d or negative electrodes 208a-208d.

[0041] With this configuration, multiple smoothing capacitors 102a-102d are provided side by side in the second direction on one side in the first direction of main body portion 201a of positive bus bar 201 and main body portion 202a of negative bus bar 202, thereby making it possible to reduce the size of power converter 1. Furthermore, all of smoothing capacitors 102a-102d are connected to positive bus bar 201 and negative bus bar 202 by folded wiring portions 301-308, making it possible to effectively suppress an increase in wiring inductance of positive bus bar 201 and negative bus bar 202.

[0042] <Modification> The configuration of the smoothing capacitor and the folded wiring section is not limited to the configuration shown in FIG. 6. FIG. 7 shows four modified configurations of the smoothing capacitor and the folded wiring section. First, modified configurations of the smoothing capacitor will be explained. In FIG. 6, the smoothing capacitor 102a is arranged so that its long side is along the X direction and its short side is along the Y direction. As shown in FIG. 7(a), the smoothing capacitor 102a may be arranged so that its short side is along the X direction and its long side is along the Y direction. Also, the smoothing capacitor 102a may be arranged so that its short side is along the X direction and its long side is along the Y direction. 7 As shown in (b), a round shape is also acceptable.

[0043] Next, modified examples of the folded wiring portion will be described. In FIG. 6, the folded wiring portion 301 is provided so as to extend from the main body portion 201a of the positive bus bar 201 to one side in the first direction, and then be folded back to extend to the other side in the first direction. As shown in FIG. 7(c), the folded wiring portion 301 may be provided so as to extend to the other side in the second direction, and then be folded back to extend to one side in the second direction. The configuration of the folded wiring portion 301 is not limited to these, and as long as the folded wiring portion 301 has portions that are folded back and facing each other, an increase in wiring inductance can be effectively suppressed.

[0044] In FIG. 6, almost all of the wiring portions in the folded wiring portion 301 are configured to face each other. The configuration of the facing portions is not limited to this, and it is also possible for only some of the wiring portions to face each other. As shown in FIG. 7(d), in cases where there are restrictions due to the placement of the connecting member 206, it is also possible for at least some of the wiring portions to face each other. If the folded wiring portion 301 is folded back and has at least some portions that face each other, it is possible to effectively suppress an increase in wiring inductance. Although FIG. 7 illustrates the folded wiring portion 301 of the positive bus bar 201, the same applies to the other folded wiring portions 302 to 304 of the positive bus bar 201 and the folded wiring portions 305 to 308 of the negative bus bar 202.

[0045] <Reduction rate of wiring inductance> Using FIG. 8, the relationship between the width of the wiring in the folded wiring portion, the spacing between the opposing portions of the wiring in the folded wiring portion, and the reduction rate of the wiring inductance will be described. First, mutual inductance and combined inductance will be described. FIG. 8(b) is a plan view showing a simplified shape of the folded wiring portion in this embodiment. In the figure, the folded wiring portion 401 is folded back and has opposing portions 401a and 401b that are portions that face each other. The self-inductance of each of the opposing portions 401a and 401b is expressed as L 401a , L 401b Let's say. L 401a , L 401b When the coupling coefficient of is K, L 401a , L 401b The mutual inductance M is given by equation (2).

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[0046] From equation (2), it can be seen that the larger the coupling coefficient K, the larger the mutual inductance M. When currents flow in opposite directions through the opposing portions 401a and 401b, the magnetic fluxes generated in the adjacent wirings are cancelled out. The combined inductance L of the opposing portions 401a and 401b is 401a(M) and L 401b(M)is shown in equation (3) and equation (4).

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[0047] From equations (2), (3), and (4), the larger the coupling coefficient K, the larger the mutual inductance M and the larger the combined inductance L 401a(M) and L 401b(M) The combined inductance L 401a(M) and L 401b(M) Since the wiring inductance in the folded wiring portion 401 is reduced, the wiring inductance in the folded wiring portion 401 can be reduced.

[0048] In FIG. 8(b), the width of the wiring in the folded wiring portion 401 is a1 [mm], the distance between the opposing portions of the wiring in the folded wiring portion 401 is b1 [mm], and the length of the opposing portions of the wiring in the folded wiring portion 401 is c1 [mm]. FIG. 8(c) is a plan view showing the shape of a wiring portion that is not folded back and that extends in a straight line. The wiring shown in FIG. 8(c) is called the straight wiring portion 402. The straight wiring portion 402 has a width a1 [mm] that is the same as the width of the wiring in the folded wiring portion 401, and a length c1 [mm] that is the same as the length of the opposing portions of the wiring in the folded wiring portion 601.

[0049] 8(b) and 8(c), a current flows in the direction of the arrow, the width a1 [mm] and the length c1 [mm] are fixed values, and the interval b1 [mm] is a variable. 401(M) and the combined inductance L of the straight wiring section 402 402(M) The results of analytical calculations of the relationship between the ratios are shown in Figure 8(a). The horizontal axis of Figure 8(a) is the ratio of the spacing b1 [mm] to the width a1 [mm] shown in Figure 8(b), and the vertical axis is the combined inductance L 401(M) and L 402(M)According to equations (2), (3), and (4) and FIG. 8(a), the smaller the spacing b1 [mm], the larger the mutual inductance coupling coefficient K. Therefore, the combined inductance L 401(M) It can be seen that the

[0050] From Figure 8(a), if the ratio of the spacing b1 to the width a1 is set to 1, the combined inductance L 401(M) and L 402(M) The ratio of the above is 1 or less. In this embodiment, the width of the wiring in the folded wiring portion is a1, the distance between the opposing portions of the wiring in the folded wiring portion is b1, and they are set to b1≦a1. If b1≦a1 is set, the combined inductance L 402(M) Therefore, the combined inductance L 401(M) Therefore, an increase in the wiring inductance of the specific bus bar can be effectively suppressed.

[0051] In the present embodiment, the switching element has been described as a MOSFET. The MOSFET may be made of a wide bandgap semiconductor element such as SiC or GaN, which can be driven at high frequency, has a fast switching speed (dv / dt, di / dt), and can reduce loss. A fast switching speed (di / dt) increases the surge voltage. In other words, if the power converter 1 described in this embodiment is configured using a wide bandgap semiconductor element, the surge voltage and heat generation of the wide bandgap semiconductor element can be suppressed, thereby further realizing a more compact and efficient power converter 1.

[0052] As described above, power converter 1 according to the first embodiment includes smoothing capacitor 102 having a first electrode and a second electrode, and a specific busbar connected to a specific electrode that is one or both of the first electrode and the second electrode, wherein the specific busbar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode, so that a portion of the wiring before being folded back in the folded wiring portion faces a portion of the wiring after being folded back, and currents flow in opposite directions in the facing wiring portions, thereby canceling magnetic fluxes generated by the currents flowing in the folded wiring portion. This effectively suppresses an increase in wiring inductance in the folded wiring portion connected to smoothing capacitor 102. Furthermore, in portions of positive busbar 201 and negative busbar 202 that are the specific busbars other than the folded wiring portions, currents flow in opposite directions in adjacent portions, thereby effectively suppressing an increase in wiring inductance in positive busbar 201 and negative busbar 202 connected to smoothing capacitor 102.

[0053] When the width of the wiring in the folded wiring portion is a1 and the distance between the opposing portions of the wiring in the folded wiring portion is b1, and b1 is set to be less than a1, the combined inductance in the folded wiring portion can be reduced compared to the combined inductance in the linear wiring portion when the wiring is linear. Because the combined inductance in the folded wiring portion is reduced, an increase in the wiring inductance of the specific bus bar can be effectively suppressed. Furthermore, when the folded wiring portion is connected to the specific electrode only at the end of the folded wiring portion, the number of contact points between the folded wiring portion and the specific electrode can be minimized, thereby preventing thermal interference between the positive bus bar 201 and the negative bus bar 202 having the folded wiring portion and the smoothing capacitors 102a to 102d having the specific electrode.

[0054] When a smoothing capacitor is provided on one side in the first direction of the main body portion of the specific busbar, a folded wiring portion is provided on one side in the first direction of the main body portion of the specific busbar, the folded wiring portion extends from the main body portion of the specific busbar to one side in the first direction and then folded back to extend to the other side in the first direction, and the end of the folded back wiring portion on the other side in the first direction is connected to the specific electrode, the length of the wiring in the folded wiring portion is minimized and the opposing portion can be provided with sufficient overlap, thereby more effectively suppressing an increase in wiring inductance of the folded wiring portion 301.

[0055] When the power converter 1 includes a plurality of smoothing capacitors 102a-102d, the main body of a specific busbar extends in a second direction perpendicular to the first direction, the plurality of smoothing capacitors 102a-102d are arranged side by side in the second direction on one side of the main body of the specific busbar in the first direction, and the specific busbar has a plurality of folded wiring portions, each of which is connected to a specific electrode of each of the plurality of smoothing capacitors 102a-102d, the plurality of smoothing capacitors 102a-102d are arranged side by side in the second direction on one side of the main body of the specific busbar in the first direction, thereby enabling the miniaturization of the power converter 1. Furthermore, because all of the smoothing capacitors 102a-102d are connected to the specific busbar by the folded wiring portions 301-308, an increase in wiring inductance of the specific busbar can be effectively suppressed.

[0056] The power converter 1 is equipped with a switching circuit 101 connected to a smoothing capacitor 102 and having a semiconductor element that converts the DC voltage applied to the smoothing capacitor 102 into power by switching, and if the semiconductor element is a wide bandgap semiconductor element, surge voltage and heat generation of the wide bandgap semiconductor element can be suppressed, thereby further realizing miniaturization and high efficiency of the power converter 1.

[0057] Embodiment 2 A power converter 1 according to embodiment 2 will be described. Fig. 9 is a plan view of a main part of a capacitor module 100 of the power converter 1, showing a part equivalent to that in Fig. 6, Fig. 10 is a plan view of a main part of another capacitor module 100 of the power converter 1, showing a part equivalent to that in Fig. 6, and Fig. 11 is a plan view of a main part of another capacitor module 100 of the power converter 1, showing a part equivalent to that in Fig. 6. The capacitor module 100 of the power converter 1 according to embodiment 2 is configured such that a specific bus bar has an additional wiring section.

[0058] The specific busbar has an additional wiring portion disposed on the specific electrode, and an end of the additional wiring portion is connected to the specific electrode. The additional wiring portion has a facing portion facing a facing portion that is part of the folded wiring portion, and the current direction in the facing portion of the additional wiring portion is opposite to that in the facing portion of the folded wiring portion. By including the additional wiring portion in addition to the folded wiring portion in the specific busbar, the number of wiring paths is increased, thereby reducing wiring inductance in the specific busbar. Furthermore, because the current direction in the facing portion of the additional wiring portion is opposite to that in the facing portion of the folded wiring portion, magnetic fluxes generated by currents flowing in the facing portion and the facing portion are canceled out, effectively suppressing an increase in wiring inductance in the folded wiring portion and the additional wiring portion connected to the smoothing capacitor 102. Below, an example of a specific configuration of the additional wiring portion is described.

[0059] First, a case will be described in which the additional wiring portion 502 is folded back on the positive electrode 207a, which is a specific electrode, and has portions facing each other. As shown in FIG. 9 , the positive bus bar 201, which is a specific bus bar, has the folded back wiring portion 501 and the additional wiring portion 502. In this embodiment, the folded back wiring portion 501 and the additional wiring portion 502 have the same shape and are arranged side by side in the second direction. In this embodiment, the folded back wiring portion 501 and the additional wiring portion 502 extend from the main body portion 201a of the positive bus bar 201 to one side in the first direction, then are folded back to extend to the other side in the first direction, and are connected to the positive electrode 207a via the connecting member 206 at the end portions on the other side in the first direction of the folded back wiring portion 501 and the additional wiring portion 502. The portion of folded wiring portion 501 that is connected to positive electrode 207a relative to the folded point is the facing portion, and the portion of additional wiring portion 502 that is on the opposite side of the folded point from the side that is connected to positive electrode 207a is the facing portion. The dashed arrows in Figure 9 indicate the direction of current when a surge voltage occurs.

[0060] With this configuration, the folded wiring section 501 and the additional wiring section 502 each have wiring portions facing each other, and currents flow in opposite directions in each of the facing wiring portions, so that magnetic fluxes generated due to currents flowing in the folded wiring section 501 and the additional wiring section 502 are canceled, thereby effectively suppressing an increase in wiring inductance in the folded wiring section 501 and the additional wiring section 502 connected to the smoothing capacitor 102a. Furthermore, because the current direction in the facing section of the additional wiring section 502 and the current direction in the faced section of the folded wiring section 501 are opposite to each other, magnetic fluxes generated due to currents flowing in the facing section and the faced section are canceled, thereby more effectively suppressing an increase in wiring inductance in the folded wiring section 501 and the additional wiring section 502 connected to the smoothing capacitor 102a. Although Figure 9 illustrates the use of the folded wiring portion 501 and the additional wiring portion 502 of the positive bus bar 201, the same effect can be obtained by arranging additional wiring portions side by side for the other folded wiring portions of the positive bus bar 201 and the folded wiring portion of the negative bus bar 202.

[0061] In this embodiment, additional wiring portion 502 is connected to positive electrode 207a only at the end of additional wiring portion 502. Since the number of contact points between additional wiring portion 502 and positive electrode 207a can be minimized, it is possible to prevent thermal interference between positive bus bar 201 having additional wiring portion 502 and smoothing capacitor 102 having positive electrode 207a.

[0062] The width of the wiring in the additional wiring portion 502 is a2, and the distance between the opposing portions of the wiring in the additional wiring portion 502 is b2, and b2≦a 2 With this configuration, the combined inductance in additional wiring portion 502 can be reduced to be lower than the combined inductance in the linear wiring portion when wiring is linear. Because the combined inductance in additional wiring portion 502 is reduced, an increase in the wiring inductance of positive bus bar 201 can be effectively suppressed.

[0063] 9, the folded wiring portion 501 is arranged on one side in the second direction, and the additional wiring portion 502 is arranged on the other side in the second direction. The arrangement of the folded wiring portion 501 and the additional wiring portion 502 is not limited to this, and as shown in FIG. 10, the folded wiring portion 501 may be arranged on the other side in the second direction, and the additional wiring portion 502 may be arranged on one side in the second direction. When the folded wiring portion 501 and the additional wiring portion 502 are arranged in this manner, the portion of the folded wiring portion 501 opposite the side connected to the positive electrode 207a from the folded point is the facing portion, and the portion of the additional wiring portion 502 connected to the positive electrode 207a from the folded point is the facing portion. Even with this configuration, the current direction in the opposing part of the additional wiring part 502 and the current direction in the opposed part of the folded wiring part 501 are opposite to each other, so the magnetic flux generated due to the current flowing in the opposing part and the opposed part is canceled, and the increase in wiring inductance in the folded wiring part 501 and the additional wiring part 502 connected to the smoothing capacitor 102a can be more effectively suppressed.

[0064] Next, a case will be described in which the additional wiring portion 602 has a portion that extends linearly on the positive electrode 207a, which is a specific electrode. As shown in FIG. 11 , the positive bus bar 201, which is a specific bus bar, has a folded wiring portion 601 and an additional wiring portion 602. In this embodiment, the folded wiring portion 601 and the additional wiring portion 602 have different shapes and are arranged side by side in the second direction, with the folded wiring portion 601 on one side in the second direction and the additional wiring portion 602 on the other side in the second direction. In this embodiment, the folded wiring portion 601 extends from the main body portion 201a of the positive bus bar 201 to one side in the first direction, then is folded back to extend to the other side in the first direction, and is connected to the positive electrode 207a via the connecting member 206 at the end of the folded wiring portion 601 on the other side in the first direction. Additional wiring portion 602 extends from main body portion 201a of positive bus bar 201 to one side in the first direction, and is connected to positive electrode 207a via connection member 206 at an end of the extended portion of additional wiring portion 602 on one side in the first direction. The portion of folded wiring portion 601 on the side connected to positive electrode 207a relative to the folded-back point is the faced portion, and the portion of additional wiring portion 602 facing the faced portion is the facing portion. The dashed arrow in FIG. 10 indicates the direction of current when a surge voltage occurs.

[0065] With this configuration, the folded wiring portion 601 has wiring portions that face each other, and currents flow in opposite directions in each of the facing wiring portions. This cancels out magnetic fluxes generated due to the currents flowing in the folded wiring portion 601, thereby effectively suppressing an increase in wiring inductance in the folded wiring portion 601 connected to the smoothing capacitor 102a. Furthermore, the current directions in the facing portion of the additional wiring portion 602 and the facing portion of the folded wiring portion 601 are opposite to each other, so magnetic fluxes generated due to the currents flowing in the facing portion and the facing portion are canceled out, thereby effectively suppressing an increase in wiring inductance in the folded wiring portion 601 and the additional wiring portion 602 connected to the smoothing capacitor 102a. Furthermore, because the additional wiring portion 602 is formed linearly, the additional wiring portion 602 can be easily manufactured, thereby improving the productivity of a specific busbar having the additional wiring portion 602. Although Figure 10 illustrates the use of the folded wiring portion 601 and the additional wiring portion 602 of the positive bus bar 201, the same effect can be obtained by arranging additional wiring portions side by side for the other folded wiring portions of the positive bus bar 201 and the folded wiring portion of the negative bus bar 202.

[0066] Furthermore, although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are conceivable within the scope of the technology disclosed in the present specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0067] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) a capacitor having a first electrode and a second electrode; a specific bus bar connected to a specific electrode that is one or both of the first electrode and the second electrode, The specific busbar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode. (Appendix 2) the specific bus bar has an additional wiring portion disposed on the specific electrode, and an end of the additional wiring portion is connected to the specific electrode; 2. The power converter according to claim 1, wherein the additional wiring portion has a facing portion facing a faced portion that is a part of the folded wiring portion, and a current direction in the facing portion of the additional wiring portion and a current direction in the faced portion of the folded wiring portion are opposite to each other. (Appendix 3) the additional wiring portion has portions that are folded back and opposed to each other on the specific electrode, a portion of the folded wiring portion on the side connected to the specific electrode relative to the folded portion is a facing portion, and a portion of the additional wiring portion on the opposite side to the side connected to the specific electrode relative to the folded portion is a facing portion. Alternatively, the power converter according to Appendix 2, wherein a portion of the folded wiring portion on the opposite side of the folded point from the side connected to the specific electrode is a facing portion, and a portion of the additional wiring portion on the side connected to the specific electrode from the folded point is a facing portion. (Appendix 4) the additional wiring portion has a portion that extends linearly on the specific electrode, 3. The power converter according to claim 2, wherein a portion of the folded wiring portion connected to the specific electrode from the folded point is a facing portion, and a portion of the additional wiring portion facing the facing portion is a facing portion. (Appendix 5) 5. The power converter according to claim 1, wherein a width of the wiring in the folded wiring portion is a1, a distance between opposing portions of the wiring in the folded wiring portion is b1, and b1≦a1 is satisfied. (Appendix 6) The width of the wiring in the additional wiring portion is a2, the distance between the opposing portions of the wiring in the additional wiring portion is b2, and b2≦a 2 4. The power converter of claim 3, wherein (Appendix 7) 7. The power converter according to claim 1, wherein the folded wiring portion is connected to the specific electrode only at an end of the folded wiring portion. (Appendix 8) 5. The power converter according to claim 2, wherein the additional wiring portion is connected to the specific electrode only at an end of the additional wiring portion. (Appendix 9) the capacitor is provided on one side of the main body portion of the specific bus bar in the first direction, the folded wiring portion is provided on one side of the main body portion of the specific bus bar in the first direction, the folded wiring portion extends from a main body portion of the specific busbar to one side in a first direction, is folded back to extend to the other side in the first direction, and is connected to the specific electrode at an end of the folded back wiring portion on the other side in the first direction. (Appendix 10) a plurality of the capacitors; a main body portion of the specific bus bar extends in a second direction perpendicular to the first direction; the plurality of capacitors are arranged side by side in the second direction on one side of the main body portion of the specific bus bar in the first direction, the specific bus bar has a plurality of the folded wiring portions, 10. The power converter according to claim 9, wherein each of the plurality of folded wiring portions is connected to the specific electrode of each of the plurality of capacitors. (Appendix 11) a switching circuit connected to the capacitor and having a semiconductor element that converts a DC voltage applied to the capacitor into power by switching; 11. The power converter according to any one of appendices 1 to 10, wherein the semiconductor element is a wide bandgap semiconductor element. [Explanation of symbols]

[0068] 1 power converter, 2 DC power supply, 3 three-phase AC motor, 100 capacitor module, 101 switching circuit, 102, 102a, 102b, 102c, 102d smoothing capacitor, 103a, 103b U-phase switching element, 104a, 104b V-phase switching element, 105a, 105b W-phase switching element, 106 specific bus bar, 107, 108 wiring inductance, 109 inductance load, 201 positive bus bar, 201a main body portion, 202 negative bus bar, 202a main body portion, 203a, 204a power supply connection terminal, 203b, 203c, 203d, 204b, 204c, 204d switching circuit connection terminal, 205 mold resin, 206 connection member, 207a, 207b, 207c, 207d Positive electrodes 208a, 208b, 208c, 208d Negative electrodes 301, 302, 303, 304, 305, 306, 307, 308 Folded wiring section 401 Folded wiring section 401a, 401b Opposing section 402 Straight wiring section 501 Folded wiring section 502 Additional wiring section 601 Folded wiring section 602 Additional wiring section

Claims

1. a capacitor having a first electrode and a second electrode; a specific bus bar connected to a specific electrode that is one or both of the first electrode and the second electrode, The specific busbar has a main body portion and a folded wiring portion that is provided on the main body portion and is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode.

2. A capacitor having a first electrode and a second electrode; a specific bus bar connected to a specific electrode that is one or both of the first electrode and the second electrode, the specific bus bar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode; the specific bus bar has an additional wiring portion disposed on the specific electrode, and an end of the additional wiring portion is connected to the specific electrode; The additional wiring portion has an opposing portion that faces an opposed portion that is part of the folded wiring portion, and the current direction of the opposing portion of the additional wiring portion and the current direction of the opposed portion of the folded wiring portion are opposite to each other.

3. the additional wiring portion has portions that are folded back and opposed to each other on the specific electrode, a portion of the folded wiring portion on the side connected to the specific electrode relative to the folded portion is a facing portion, and a portion of the additional wiring portion on the opposite side to the side connected to the specific electrode relative to the folded portion is a facing portion. Alternatively, the power converter according to claim 2, wherein a portion of the folded wiring portion on the opposite side of the folded point from the side connected to the specific electrode is a facing portion, and a portion of the additional wiring portion on the side connected to the specific electrode from the folded point is a facing portion.

4. the additional wiring portion has a portion that extends linearly on the specific electrode, 3. The power converter according to claim 2, wherein a portion of the folded wiring portion connected to the specific electrode from the folded point is a facing portion, and a portion of the additional wiring portion facing the facing portion is a facing portion.

5. A capacitor having a first electrode and a second electrode; a specific bus bar connected to a specific electrode that is one or both of the first electrode and the second electrode, the specific bus bar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode; The power converter has a width a1 of the wiring in the folded wiring portion, a distance b1 between opposing portions of the wiring in the folded wiring portion, and b1≦a1.

6. 4. The power converter according to claim 3, wherein a width of the wiring in the additional wiring portion is a2, a distance between opposing portions of the wiring in the additional wiring portion is b2, and b2≦a2 is satisfied.

7. 6. The power converter according to claim 1, wherein the folded wiring portion is connected to the specific electrode only at an end of the folded wiring portion.

8. The power converter according to claim 2 , wherein the additional wiring portion is connected to the specific electrode only at an end of the additional wiring portion.

9. A capacitor having a first electrode and a second electrode; a specific bus bar connected to a specific electrode that is one or both of the first electrode and the second electrode, the specific bus bar has a folded wiring portion that is folded back on the specific electrode and has portions that face each other, and an end of the folded wiring portion is connected to the specific electrode; the capacitor is provided on one side of the main body portion of the specific bus bar in the first direction, the folded wiring portion is provided on one side of the main body portion of the specific bus bar in the first direction, the folded wiring portion extends from a main body portion of the specific busbar to one side in a first direction, then folds back to extend to the other side in the first direction, and the end of the folded wiring portion on the other side in the first direction after being folded back is connected to the specific electrode.

10. a plurality of the capacitors; a main body portion of the specific bus bar extends in a second direction perpendicular to the first direction; the plurality of capacitors are arranged side by side in the second direction on one side of the main body portion of the specific bus bar in the first direction, the specific bus bar has a plurality of the folded wiring portions, The power converter according to claim 9 , wherein each of the plurality of folded wiring portions is connected to the specific electrode of each of the plurality of capacitors.

11. a switching circuit connected to the capacitor and having a semiconductor element that converts a DC voltage applied to the capacitor into power by switching; 10. The power converter according to claim 1, wherein the semiconductor element is a wide bandgap semiconductor element.

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