JP6690478B2 - Power converter - Google Patents

Description

  The technique disclosed in the present specification relates to a power conversion device. In particular, the present invention relates to a power converter having a stacked unit in which a plurality of coolers are arranged in parallel and a semiconductor module is sandwiched between adjacent coolers.

  For example, Patent Document 1 discloses a power conversion device including the above-described laminated unit. Each semiconductor module contains one to several switching elements. From the main body of the semiconductor module, a plurality of terminals (a positive electrode terminal and a negative electrode terminal) internally connected to the switching element extend. The terminals of the plurality of semiconductor modules are arranged in the stacking direction of the semiconductor module and the cooler as an example. The positive electrode terminal group and the negative electrode terminal group are arranged in two rows. A capacitor is arranged next to the laminated unit. The positive electrode terminal of each semiconductor module and one electrode of the capacitor are connected by a positive electrode bus bar, and the negative electrode terminal of each semiconductor module and the other electrode of the capacitor are connected by a negative electrode bus bar. Each of the positive electrode bus bar and the negative electrode bus bar has a plate-shaped flat plate portion (base portion), and a plurality of branch portions joined to the respective terminals extend from the flat plate portion. The flat plate portion of the positive electrode bus bar and the flat plate portion of the negative electrode bus bar are closely arranged to face each other. By arranging the two flat plate portions close to each other and facing each other, the inductance of the bus bar is reduced.

JP, 2014-110400, A

  The positive electrode bus bar has a plurality of branch portions extending from one flat plate portion. When the flat plate portion is deformed, the relative positions of the branch portions and the positive electrode terminal are varied, and the work of connecting the branch portions becomes difficult. The same applies to the negative electrode bus bar. The present specification relates to a power converter having a bus bar in which a plurality of branch portions extend from a flat plate portion, and provides a technique for suppressing deformation of the flat plate portion of the bus bar.

  The power conversion device disclosed in this specification includes a laminated unit, a capacitor unit, a positive electrode bus bar, and a negative electrode bus bar. The laminated unit is a device in which a plurality of coolers are arranged side by side, and a semiconductor module containing a switching element is sandwiched between adjacent coolers. The capacitor unit is arranged next to the laminated unit, contains the capacitor element, and is filled with a filler around the capacitor element. The positive electrode bus bar is joined to a positive electrode terminal extending from each side surface of the plurality of semiconductor modules, and is also connected to one electrode of the capacitor element. The negative electrode bus bar is joined to the negative electrode terminal extending from the side surface of each semiconductor module and is also connected to the other electrode of the capacitor element. The positive electrode terminals of the plurality of semiconductor modules are arranged in a row along the stacking direction of the cooler and the semiconductor module in the laminated unit, and the plurality of negative electrode terminals are arranged in a row in parallel with the row of the positive electrode terminals. The positive electrode bus bar includes a plate-shaped positive electrode bus bar flat plate portion extending from the capacitor unit along the side surface of the semiconductor module, and a plurality of positive electrode bus bar flat plate portions extending from the positive electrode bus bar flat plate portion toward the positive electrode terminals and connected to the positive electrode terminals. Of the positive electrode branch part. The negative electrode bus bar includes a plate-shaped negative electrode bus bar flat plate portion extending from the capacitor unit in parallel with the positive electrode bus bar flat plate portion, and a plurality of negative electrode bus bar flat plate portions extending from the negative electrode bus bar flat plate portion toward the negative electrode terminals and connected to the negative electrode terminals. The negative electrode branch portion of Both ends of the positive electrode bus bar flat plate portion and the negative electrode bus bar flat plate portion are bent at right angles in the stacking direction, and a part of the bent portion is embedded in the filler of the capacitor unit.

  In the above power conversion device, since both ends of the flat plate portion of the bus bar are bent at right angles, the rigidity of the flat plate portion is improved and it becomes difficult to deform. In addition, by embedding a part of the bent portion in the filling material of the capacitor unit, both ends of the flat plate portion are firmly held. This point also contributes to prevention of deformation of the flat plate portion. Details of the technology disclosed in the present specification and further improvements will be described in the following “Description of Embodiments”.

It is a block diagram of the electric power system of the electric vehicle including the power converter of an example. It is a perspective view of an assembly of a lamination unit, a bus bar, and a capacitor unit. It is an exploded perspective view of an assembly of a lamination unit, a bus bar, and a capacitor unit. FIG. 4 is a sectional view taken along line IV-IV of FIG. 2.

  A power converter according to an embodiment will be described with reference to the drawings. The power conversion device of the embodiment is a device that is mounted on an electric vehicle and that converts the power of a battery into the drive power of a traveling motor. FIG. 1 shows a block diagram of a power system of an electric vehicle 100 including the power conversion device 2. The electric vehicle 100 includes two traveling motors 83a and 83b. Therefore, the power conversion device 2 includes two sets of inverter circuits 13a and 13b. The outputs of the two motors 83a and 83b are combined / distributed by the gear box 85 and transmitted to the axle 86 (that is, the drive wheels).

  The power conversion device 2 is connected to the battery 81 via the system main relay 82. The power conversion device 2 includes a voltage converter circuit 12 that boosts the voltage of the battery 81 and two sets of inverter circuits 13a and 13b that convert the boosted DC power into AC.

  The voltage converter circuit 12 boosts the voltage applied to the terminal on the battery side and outputs it to the terminal on the inverter side, and lowers the voltage applied to the terminal on the inverter side and outputs it to the terminal on the battery side. It is a bidirectional DC-DC converter capable of performing both step-down operation. For convenience of description, the terminal on the battery side (low voltage side) is referred to as the input terminal 18, and the terminal on the inverter side (high voltage side) is referred to as the output terminal 19 below. Further, the positive electrode and the negative electrode of the input end 18 are referred to as an input positive electrode end 18a and an input negative electrode end 18b, respectively. The positive electrode and the negative electrode of the output end 19 are referred to as an output positive electrode end 19a and an output negative electrode end 19b, respectively. The expressions "input end 18" and "output end 19" are provided for the sake of convenience of description. As described above, the voltage converter circuit 12 is a bidirectional DC-DC converter. Power may flow from 19 to the input end 18.

  The voltage converter circuit 12 is composed of a series circuit of two switching elements 9a and 9b, a reactor 7, a filter capacitor 5, and a diode connected in antiparallel to each switching element. The reactor 7 has one end connected to the input positive electrode end 18a and the other end connected to the midpoint of the series circuit. The filter capacitor 5 is connected between the input positive electrode end 18a and the input negative electrode end 18b. The input negative electrode end 18b is directly connected to the output negative electrode end 19b. The switching element 9b is mainly involved in the step-up operation, and the switching element 9a is mainly involved in the step-down operation. The voltage converter circuit 12 shown in FIG. 1 is well known, and a detailed description thereof will be omitted. The circuit in the range of the broken line rectangle indicated by reference numeral 8a corresponds to the semiconductor module 8a described later. Reference numerals 25a and 25b indicate terminals extending from the semiconductor module 8a. Reference numeral 25a indicates a terminal (positive electrode terminal 25a) that is electrically connected to the high potential side of the series circuit of the switching elements 9a and 9b. Reference numeral 25b represents a terminal (negative electrode terminal 25b) that is electrically connected to the low potential side of the series circuit of the switching elements 9a and 9b. As described below, the notations of the positive electrode terminal 25a and the negative electrode terminal 25b are also used in other semiconductor modules.

  The inverter circuit 13a has a configuration in which three sets of series circuits of two switching elements are connected in parallel. The switching elements 9c and 9d, the switching elements 9e and 9f, and the switching elements 9g and 9h form series circuits, respectively. A diode is connected in antiparallel to each switching element. The high-potential side terminal (positive terminal 25a) of the three sets of series circuits is connected to the output positive terminal 19a of the voltage converter circuit 12, and the low-potential side terminal (negative terminal 25b) of the three sets of series circuit is the voltage. It is connected to the negative output terminal 19b of the converter circuit 12. Three-phase alternating current (U-phase, V-phase, W-phase) is output from the middle point of the three sets of series circuits. Each of the three sets of series circuits corresponds to semiconductor modules 8b, 8c, and 8d described later.

  Since the configuration of the inverter circuit 13b is the same as that of the inverter circuit 13a, the illustration of a specific circuit is omitted in FIG. Similarly to the inverter circuit 13a, the inverter circuit 13b also has a configuration in which three sets of series circuits of two switching elements are connected in parallel. The high potential side terminals of the three sets of series circuits are connected to the output positive terminal 19a of the voltage converter circuit 12, and the low potential side terminals of the three sets of series circuits are connected to the output negative terminal 19b of the voltage converter circuit 12. Has been done. The hardware corresponding to each series circuit is referred to as semiconductor modules 8e, 8f, 8g.

  The smoothing capacitor 6 is connected in parallel to the input terminals of the inverter circuits 13a and 13b. In other words, the smoothing capacitor 6 is connected in parallel to the output terminal 19 of the voltage converter circuit 12. The smoothing capacitor 6 removes the pulsation of the output current of the voltage converter circuit 12.

  The switching elements 9a-9h are transistors, typically IGBTs (Insulated Gate Bipolar Transistors), but may be other transistors, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). The switching element here is used for power conversion and is sometimes called a power semiconductor element.

  In FIG. 1, each of broken lines 8a-8g corresponds to a semiconductor module. The power conversion device 2 includes seven sets of series circuits of two switching elements. As hardware, two switching elements forming a series circuit and a diode connected in antiparallel to each switching element are housed in one package. In the following, when any one of the semiconductor modules 8a to 8g is shown without distinction, it is referred to as a semiconductor module 8.

  The high potential side terminal (positive electrode terminal 25a) of the seven semiconductor modules (seven sets of series circuits) is connected to the positive electrode of the smoothing capacitor 6, and the low potential side terminal (negative electrode terminal 25b) is the negative electrode of the smoothing capacitor 6. Connected to the electrodes. In FIG. 1, the conductive path within the broken line indicated by reference numeral 30 corresponds to a bus bar (positive electrode bus bar) that connects the positive electrode terminals 25a of the plurality of semiconductor modules 8 and the positive electrode of the smoothing capacitor 6 to each other. The conductive path in the broken line indicated by reference numeral 40 corresponds to a bus bar (negative electrode bus bar) that connects the plurality of negative electrode terminals 25b and the negative electrode of the smoothing capacitor 6 to each other. Next, the structures of the plurality of semiconductor modules 8, the positive electrode bus bar 30, and the negative electrode bus bar 40 will be described.

  FIG. 2 shows a perspective view of the hardware of the power conversion device 2. Note that, in FIG. 2, the housing of the power conversion device 2 and a part of the components are not shown. The plurality of semiconductor modules 8 (8a-8g) form a laminated unit 20 together with the plurality of coolers 22. Since all of the semiconductor modules 8a to 8g have the same shape, in FIG. 2 and FIG. 3 described later, only the leftmost semiconductor module is represented by the reference numeral 8 and the other semiconductor modules are omitted. Further, in FIG. 2 and FIG. 3 described later, the reference numeral 22 is attached only to the two leftmost coolers, and the reference numerals are omitted for the other coolers.

  Although FIG. 2 is a perspective view of the power conversion device 2, only the assembly of the laminated unit 20, the positive electrode bus bar 30, the negative electrode bus bar 40, and the capacitor unit 60 is drawn, and other parts are omitted. The laminated unit 20 is a device in which a plurality of card-type coolers 22 are arranged in parallel and a card-type semiconductor module 8 is sandwiched between adjacent coolers 22. The card-type semiconductor module 8 is stacked with its wide surface facing the cooler 22. Three terminals (a positive electrode terminal 25a, a negative electrode terminal 25b, a midpoint terminal 25c) extend from one side surface 80a of each semiconductor module 8. In FIG. 2 and FIG. 3 described later, reference numerals 25a, 25b, and 25c are attached only to the terminals of the semiconductor module 8 located at the left end of the laminated unit 20, and the remaining semiconductor modules 8 are omitted from the reference numerals indicating the terminals.

  As described above, the positive electrode terminal 25a and the negative electrode terminal 25b are the high potential side terminal and the low potential side terminal of the series circuit housed in the semiconductor module 8. The midpoint terminal 25c is a terminal that is electrically connected to the midpoint of the series circuit. In other words, all of the three terminals 25a-25c are electrically connected to the switching elements inside the semiconductor module 8. The three terminals 25a-25c extend from one side surface 80a intersecting the wide surface of the semiconductor module 8 in the Z-axis positive direction in the drawing. A plurality of control terminals extend in the Z-axis negative direction in the figure from the side surface opposite to the one side surface 80a. The control terminals are, for example, a gate terminal electrically connected to a gate electrode of a switching element built in the semiconductor module 8 and a signal terminal electrically connected to a temperature sensor or a current sensor built in the semiconductor module 8. .

  Hereinafter, for convenience of description, the stacking direction of the cooler 22 and the semiconductor module 8 in the stacking unit 20 will be simply referred to as the “stacking direction”. The X direction in the figure corresponds to the stacking direction.

  A coolant supply port 28 and a coolant discharge port 29 are provided in the cooler 22 at the right end in the figure. Adjacent coolers 22 are connected to each other by two connecting pipes. One of the connecting pipes is positioned so as to overlap the refrigerant supply port 28 when viewed in the stacking direction. The other connecting pipe is located so as to overlap with the refrigerant discharge port 29 when viewed in the stacking direction. A refrigerant circulating device (not shown) is connected to the refrigerant supply port 28 and the refrigerant discharge port 29. The refrigerant supplied from the refrigerant supply port 28 is distributed to all the coolers 22 through one connecting pipe. The coolant absorbs heat from the adjacent semiconductor module 8 while passing through the cooler 22. The refrigerant that has absorbed the heat is discharged from the laminated unit 20 through the other connecting pipe and the refrigerant discharge port 29. Since each semiconductor module 8 is cooled from both sides thereof, the laminated unit 20 has high cooling performance.

  Each of the three terminals 25a to 25c of each semiconductor module 8 has a flat plate shape. The positive electrode terminals 25a of the plurality of semiconductor modules 8 are arranged in a line in the stacking direction so as to face the flat surfaces of the positive electrode terminals 25a of the adjacent semiconductor modules 8. The negative electrode terminals 25b of the plurality of semiconductor modules 8 are also arranged in a line in the stacking direction so as to face the flat surfaces of the negative electrode terminals 25b of the adjacent semiconductor modules 8. The same applies to the midpoint terminals 25c of the plurality of semiconductor modules 8. The positive electrode terminals 25a, the negative electrode terminals 25b, and the midpoint terminals 25c of the plurality of semiconductor modules 8 are arranged in three rows.

  A capacitor unit 60 is arranged next to the laminated unit 20. The capacitor unit 60 is long in the stacking direction of the cooler 22 of the stacking unit 20 and the semiconductor module 8 (X direction in the drawing), and is aligned with the stacking unit in a direction intersecting the stacking direction. Two capacitor elements 61 (described later) are accommodated in the case of the capacitor unit 60. The positive electrode bus bar 30 is a conductor that connects the positive electrode terminals 25a of the plurality of semiconductor modules 8 and the capacitor element in the capacitor unit 60, and the negative electrode bus bar 40 is the negative electrode terminals 25b of the plurality of semiconductor modules 8. It is a conductor for connecting the capacitor element in the capacitor unit 60.

  FIG. 3 shows an exploded perspective view of an assembly of the positive electrode bus bar 30, the negative electrode bus bar 40, the laminated unit 20, and the capacitor element 61 (capacitor unit 60). The capacitor unit 60 of FIG. 2 accommodates two capacitor elements 61. In FIG. 3, the case of the capacitor unit 60 is omitted and the internal capacitor element 61 is drawn. As will be described later in detail, the periphery of the capacitor element 61 in the case of the capacitor unit 60 is filled with a filler. The capacitor element 61 corresponds to the smoothing capacitor 6 in FIG.

  The positive electrode terminals 25a of the plurality of semiconductor modules 8 and the positive electrode electrode 61a of the capacitor element 61 are connected by the positive electrode bus bar 30, and the plurality of negative electrode terminals 25b and the negative electrode electrode 61b of the capacitor element 61 are connected by the negative electrode bus bar 40.

  The positive electrode bus bar 30 includes a plate-shaped electrode portion 39, a plate-shaped flat plate portion 31, a plurality of positive electrode terminal holes 32, and a plurality of branch portions 33. The electrode portion 39 is connected to the positive electrode 61a of the capacitor element 61. The flat plate portion 31 of the positive electrode bus bar 30 is provided with a plurality of positive electrode terminal holes 32, and a branch portion 33 extends from the edge of each positive electrode terminal hole 32 in the Z direction. The positive electrode terminal 25a of each semiconductor module 8 passes through each positive electrode terminal hole 32, and the positive electrode terminal 25a and the branch portion 33 are joined by welding.

  The negative electrode bus bar 40 includes a plate-shaped electrode portion 49, a plate-shaped flat plate portion 41, a plurality of negative electrode terminal holes 42, and a plurality of branch portions 43. The electrode portion 49 is connected to the negative electrode 61b of the capacitor element 61. The flat plate portion 41 of the negative electrode bus bar 40 is provided with a plurality of negative electrode terminal holes 42, and a branch portion 43 extends in the Z direction from the edge of each negative electrode terminal hole 42. The negative electrode terminal 25b of each semiconductor module 8 passes through each negative electrode terminal hole 42, and the negative electrode terminal 25b and the branch part 43 are joined.

  The negative electrode bus bar 40 is located on the opposite side of the positive electrode bus bar 30 from the laminated unit 20. A plurality of positive electrode terminal holes 45 are provided in the negative electrode bus bar 40, and the positive electrode terminal 25 a of the semiconductor module 8 and the branch portion 33 of the positive electrode bus bar 30 pass through each positive electrode terminal hole 45. The flat plate portion 31 of the positive electrode bus bar 30 and the flat plate portion 41 of the negative electrode bus bar 40 are both plate-shaped, and closely face each other. When a current flows through one of the bus bars, a magnetic field is generated around the bus bar due to the current. There is a positive correlation between the magnitude of the magnetic field and the inductance of the bus bar (the larger the magnetic field, the larger the inductance). When the flat plate portions of the positive electrode bus bar 30 and the negative electrode bus bar 40 face each other, an eddy current is generated in the other bus bar by the magnetic field of one bus bar. The generation of the eddy current weakens the magnetic field of one bus bar. The weakening of the magnetic field means that the inductance becomes small. By arranging the flat plate portions 31 and 41 of the bus bar close to each other, the inductance of the bus bar can be reduced.

  Both ends of the flat plate portion 31 of the positive electrode bus bar 30 in the stacking direction (X direction) are bent at right angles. The portions bent at right angles are called reinforcing ribs 37 and 38. Both ends of the flat plate portion 41 of the negative electrode bus bar 40 in the stacking direction (X direction) are also bent at right angles. The portions bent at right angles are called reinforcing ribs 47 and 48. As described above, the capacitor element 61 is housed in the case 68 (see FIG. 4) and is embedded in the filler in the case 68. Therefore, part of the positive electrode bus bar 30 and part of the negative electrode bus bar 40 are also embedded in the filler in the case 68 of the capacitor unit 60. Naturally, the electrode parts 39 and 49 are embedded in the filling material. Part 31a of the flat plate portion 31 of the positive electrode bus bar 30 is also embedded in the filling material, and part 41a of the flat plate portion 41 of the negative electrode bus bar 40 is also embedded in the filling material. The portions indicated by reference numerals 31b and 41b are exposed portions of the flat plate portions 31 and 41 that are exposed from the capacitor unit 60.

  Part 37a, 38a, 47a, 48a of the reinforcing ribs 37, 38, 47, 48 is also embedded in the filling material. FIG. 4 shows a sectional view taken along the line II-II in FIG. The cross-sectional view of FIG. 4 is a cross-section of the capacitor unit 60 cut in front of the laminated unit 20 in the laminating direction. In FIG. 4, illustration of a part of the semiconductor module 8 (laminated unit 20) is omitted. As shown in FIG. 4, parts 37 a and 47 a of the reinforcing ribs 37 and 47 are embedded in the filling material 69. Although not visible in FIG. 4, parts 38 a and 48 a of the reinforcing ribs 37 and 48 on the opposite side are also embedded in the filling material 69. The gray fill indicates the filler material 69. The filler 69 is, for example, a potting material containing silicon.

  The effect of the reinforcing ribs 37 and 38 of the positive electrode bus bar 30 will be described. As shown in FIG. 3, the positive electrode bus bar 30 includes a single flat plate portion 31 and a plurality of branch portions 33 extending in a line. The positive terminal 25a of each semiconductor module 8 is connected to each branch 33. When the flat plate portion 31 is deformed, the relative positions of the branch portions 33 and the positive electrode terminals 25a vary, and the cost required for the work of joining the branch portions 33 and the positive electrode terminals 25a increases. Further, each branch portion 33 and each positive electrode terminal 25a are sandwiched by a chuck at the time of joining, but if the relative positions of each branch portion 33 and each positive electrode terminal 25a are varied, all the positive electrode terminals 25a and the branch portions 33 are combined. As a result of being sandwiched by the chucks, the flat plate portion 31 is greatly deformed. Due to the deformation of the flat plate portion 31, when a part of the flat plate portion 31 approaches the main body of the semiconductor module 8, the insulation performance between the bus bar and the semiconductor module deteriorates. The reinforcing ribs 37 and 38 of the positive electrode bus bar 30 increase the rigidity of the flat plate portion 31 and reduce the deformation of the flat plate portion 31. The fact that the reinforcing ribs 37, 38 are partly embedded in the filling material 69 of the capacitor unit 60 also means that the reinforcing ribs 37, 38 are firmly fixed, which contributes to increasing the rigidity of the flat plate portion 31. To do. Similar advantages can be obtained with the reinforcing ribs 47 and 48 of the flat plate portion 41 of the negative electrode bus bar 40.

  Points to be noted regarding the technique described in the embodiment will be described. The flat plate portion 31 and the branch portion 33 of the positive electrode bus bar 30 of the embodiment correspond to an example of the “positive electrode bus bar flat portion” and the “positive electrode branch portion” of the claims, respectively. The flat plate portion 41 and the branch portion 43 of the negative electrode bus bar 40 of the embodiment correspond to an example of the “negative electrode bus bar flat portion” and the “negative electrode branch portion” of the claims, respectively.

  Specific examples of the present invention have been described above in detail, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above. The technical elements described in the present specification or the drawings exert technical utility alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technique illustrated in the present specification or the drawings can simultaneously achieve a plurality of objects, and achieving the one object among them has technical utility.

2: Power converter 5: Filter capacitor 6: Smoothing capacitor 7: Reactor 8, 8a-8g: Semiconductor module 9a-9h: Switching element 12: Voltage converter circuit 13a, 13b: Inverter circuit 20: Laminated unit 22: Cooler 25a : Positive electrode terminal 25b: Negative electrode terminal 25c: Midpoint terminal 30: Positive electrode bus bar 31, 41: Flat plate portion 32, 45: Positive electrode terminal hole 33, 43: Branch portion 39, 49: Electrode portion 40: Negative electrode bus bar 42: Negative electrode terminal hole 60: Capacitor unit 61: Capacitor element 61a: Positive electrode 61b: Negative electrode 68: Case 69: Filler 81: Battery 82: System main relays 83a and 83b: Motor 85: Gear box 100: Electric vehicle

Claims (1)

A plurality of coolers are arranged side by side, between adjacent coolers, a laminated unit in which a semiconductor module containing a switching element is sandwiched,
A capacitor unit, which is arranged next to the laminated unit, contains a capacitor element and is filled with a filler around the capacitor element,
A positive electrode bus bar joined to a positive electrode terminal extending from each side surface of the plurality of semiconductor modules and connected to one electrode of the capacitor element,
A negative electrode bus bar connected to the negative electrode terminal extending from the side surface of each of the semiconductor modules and connected to the other electrode of the capacitor element,
Is equipped with
The positive electrode terminals of the plurality of semiconductor modules are arranged in a row along a stacking direction of the cooler and the semiconductor module, and the plurality of negative electrode terminals are arranged in a row in parallel with the row of the positive electrode terminals. ,
The positive electrode bus bar has a plate-shaped positive electrode bus bar flat plate portion extending from the capacitor unit along the side surface of the semiconductor module, and the positive electrode bus bar flat plate portion extending from the positive electrode bus bar flat plate portion toward the positive electrode terminals and the positive electrodes. A plurality of positive electrode branch portions connected to the terminals,
The negative electrode bus bar is a plate-shaped negative electrode bus bar flat plate portion extending from the capacitor unit in parallel with the positive electrode bus bar flat plate portion, and the negative electrode bus bar flat plate portion extends from the negative electrode bus bar flat plate portion toward the negative electrode terminals and the negative electrode terminals. And a plurality of negative electrode branch portions connected to
The positive electrode bus bar flat plate portion and the negative electrode bus bar flat plate portion are each bent at right angles at both ends in the stacking direction, and a part of the bent portion is embedded in the filler of the capacitor unit. Converter.