JP6500735B2 - Power converter - Google Patents

Description

  The present invention relates to a power converter. In particular, the present invention relates to a power conversion device including a plurality of semiconductor modules and a stacked cooling unit in which a plurality of coolers are disposed in parallel and sandwiching the respective semiconductor modules between adjacent coolers.

  A power converter such as a voltage converter or an inverter includes a plurality of switching elements that generate a large amount of heat. The plurality of switching elements are accommodated in the semiconductor module one by one or several. As a structure for efficiently cooling a plurality of semiconductor modules, a stacked cooling unit in which a plurality of coolers are arranged in parallel is known. The stacked cooling unit sandwiches each semiconductor module between adjacent coolers. For example, Patent Documents 1 to 4 disclose a power converter including such a stacked cooling unit.

  In the power conversion device through which a large amount of power flows, the terminals of the semiconductor module and other parts are connected by an elongated metal plate (an elongated metal rod) called a bus bar. With the increase in switching speed of switching elements, suppression of surge voltage has become an issue. The surge voltage can be suppressed by reducing the inductance of the conductive path conducted to the switching element. In Patent Documents 1 and 2, a technique for suppressing the inductance of the bus bar is also proposed. In the technology of Patent Document 1, a flat bus bar (positive bus bar) connected to the positive electrode terminal of each semiconductor module and a flat bus bar (negative bus bar) connected to the negative electrode terminal are opposed. Current flows in the opposite direction to the positive bus bar and the negative bus bar. The magnetic fields resulting from the current of the respective bus bars cancel each other, and the inductance is suppressed. In the technique of Patent Document 2, the positive bus bar is disposed so as to be connected to the positive electrode terminal after crossing without contacting the negative electrode terminal. Alternatively, the negative bus bar is disposed so as to be connected to the negative electrode terminal after crossing without contacting the positive electrode terminal. A closed loop for the high frequency component of the current is formed by the positive electrode terminal, the negative electrode terminal, the positive bus bar (negative bus bar), and the switching element in the semiconductor module body. By shortening the path of the high frequency component of the current, the inductance of the conductive path (bus bar and terminal) conducting to the switching element is reduced.

JP, 2015-139270, A JP, 2013-192403, A JP, 2014-110400, A JP, 2014-060304, A

  The technique of Patent Document 1 reduces the inductance by bringing the positive bus bar and the negative bus bar close to each other. The technique of Patent Document 2 reduces the inductance by bringing the positive electrode terminal and the negative bus bar (or the negative electrode terminal and the positive bus bar) close to each other. Both techniques approach conductive components (bus bars or terminals) of different polarity to reduce inductance. When conducting parts of different polarities are brought close, care must be taken to prevent short circuits. Between conductive parts of different polarity, a creepage distance corresponding to the voltage between them must be secured. The present specification provides a technique for reducing the inductance of a conductive path (bus bar and terminal) conducting to a switching element using conductive parts of the same polarity.

A power converter disclosed in the present specification includes a plurality of semiconductor modules, a stacked cooling unit that cools them, and a bus bar. Each semiconductor module includes a main body accommodating the switching element, and a flat plate-like terminal electrically connected to the switching element in the main body and extending out of the main body. In the stacked cooling unit, a plurality of coolers are arranged in parallel, and each semiconductor module is sandwiched between adjacent coolers. The bus bar is connected to the terminal of each semiconductor module. The bus bar includes a base plate, a connection portion, and an opposing portion. The base plate has a plurality of through holes and the terminals of the semiconductor modules pass through the through holes. The connection portion is conductive, extends from the edge of the through hole of the base plate, and is connected to the terminal. The facing portion extends from the edge of the through hole of the base plate in the opposite direction to the connecting portion, and faces the flat surface at a distance from the flat surface of the terminal . In this power conversion device, since the opposing part is electrically connected to the terminal through the bus bar, the opposing part and the bus bar have the same potential. However, the facing portion itself faces the terminal at a distance. Since the high frequency current has the property of being transmitted on the surface of the conductor, the current flows on the surfaces of the opposing terminal and the opposing portion. The magnetic fields resulting from those currents cancel each other, reducing the inductance of the bus bar and the terminals. The technology disclosed in the present specification reduces the inductance between the terminal of the same potential and the opposite portion by providing the bus bar connected to the terminal with the opposite portion facing the terminal. The technology disclosed in the present specification reduces the inductance of the conductive paths (bus bars and terminals) conducted to the switching elements without bringing the conductive members of different polarities close to each other.

  The details and further improvement of the technology disclosed in the present specification will be described in the following "Forms for Carrying Out the Invention".

BRIEF DESCRIPTION OF THE DRAWINGS It is a block diagram of the electric power system of an electric vehicle containing the power converter device of an Example. It is a top view which shows the in-case layout of a power converter device (state which removed the cover). It is a perspective view of an assembly of a lamination | stacking unit, a smoothing capacitor unit, and a bus bar. It is a perspective view of a bus bar. It is sectional drawing of the connection part of a bus bar and a terminal. It is a perspective view of the assembly of the bus bar of a modification, a lamination | stacking unit, and a capacitor | condenser unit. It is a perspective view of the assembly of the bus bar of a modification, a lamination | stacking unit, and a capacitor | condenser unit (a bus bar is disassembled). It is an expansion perspective view of the bus bar of a modification. It is sectional drawing of the connection part of the bus bar of a modification, and a terminal. It is sectional drawing of the connection part of the bus bar of a modification, and a terminal (2nd modification). It is sectional drawing of the connection part of the bus bar of a modification, and a terminal (3rd modification). It is sectional drawing of the connection part of the bus bar of a modification, and a terminal (4th modification).

  A power converter according to an embodiment will be described with reference to the drawings. The power conversion device of the embodiment is mounted on an electric vehicle and outputs driving 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 power distribution mechanism 85 and transmitted to the axle 86 (ie, drive wheels).

  Power converter 2 is connected to battery 81 via system main relay 82. Power converter 2 includes a voltage converter circuit 12 for boosting the voltage of battery 81, and two sets of inverter circuits 13a and 13b for converting DC power after boosting to an alternating current.

  The voltage converter circuit 12 boosts the voltage applied to one terminal (low voltage terminal) and outputs it to the other terminal (high voltage terminal), and the voltage converter circuit 12 applies the other terminal (high voltage terminal) to the other terminal (high voltage terminal). It is a so-called bi-directional DC-DC converter capable of performing both of the step-down operation of stepping down the voltage and outputting it to one terminal (low voltage end). For convenience of explanation, the low voltage end is hereinafter referred to as the input end 18, and the high voltage end is referred to as the output end 19. 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 respectively referred to as an output positive electrode end 19a and an output negative electrode end 19b. The notations “input end 18” and “output end 19” are for convenience of explanation, and as described above, since the voltage converter circuit 12 is a bi-directional DC-DC converter, the output end Power may flow from 19 to the input end 18.

  The voltage converter circuit 12 is configured of a series circuit of two switching elements T7 and T8, a reactor 7, a filter capacitor 5, and diodes connected in anti-parallel to the respective switching elements. The high potential side of the series circuit is connected to the output positive terminal 19a, and the low potential side is connected to the output negative terminal 19b. One end of the reactor 7 is connected to the input positive end 18a, and the other end is connected to the middle point of the series circuit. The filter capacitor 5 is connected between the input positive end 18a and the input negative end 18b. The input negative electrode end 18 b is directly connected to the output negative electrode end 19 b.

  As mentioned above, the voltage converter circuit 12 can perform both the step-up operation and the step-down operation. The boosting operation of the voltage converter circuit 12 is an operation of boosting the voltage of the battery 81 and supplying it to the inverter circuits 13a and 13b. The step-down operation of the voltage converter circuit 12 is an operation to step-down DC power (regenerated power generated by the motor 83a or 83b) input from the inverter circuits 13a and 13b. The reduced regenerative power is used to charge the battery 81. The switching element T8 mainly contributes to the step-up operation, and the switching element T7 mainly contributes to the step-down operation. The voltage converter circuit 12 of FIG. 1 is well known and will not be described in detail. A circuit within a dashed-lined rectangle indicated by reference numeral 8g corresponds to a semiconductor module 8g described later. The reference numerals 25a and 25b indicate terminals extending from the semiconductor module 8g. The code | symbol 25a has shown the terminal (positive electrode terminal 25a) connected with the electrode by the side of high electric potential of the series circuit of switching element T7, T8. The code | symbol 25b represents the terminal (negative electrode terminal 25b) connected with the electrode by the side of the low electric potential of the series circuit of switching element T7, T8. As described below, the notation of the positive electrode terminal 25a and the negative electrode terminal 25b is also used in other semiconductor modules.

  The inverter circuit 13a has a configuration in which three series circuits of two switching elements are connected in parallel (T1 and T4, T2 and T5, T3 and T6). A diode is connected in reverse parallel to each switching element. The high potential 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 terminal (negative terminals 25b) of the three sets of series circuits is voltage The output negative terminal 19 b of the converter circuit 12 is connected. Three-phase alternating current (U phase, V phase, W phase) is output from the middle point of three sets of series circuits. Each of the three sets of series circuits corresponds to semiconductor modules 8a, 8b and 8c described later.

  Since the configuration of the inverter circuit 13b is the same as that of the inverter circuit 13a, the illustration of the specific circuit is omitted in FIG. Similar to the inverter circuit 13a, the inverter circuit 13b also has a configuration in which three series circuits of two switching elements are connected in parallel. The hardware corresponding to each series circuit is referred to as semiconductor modules 8d, 8e, 8f.

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

  The switching elements T1 to T8 are transistors, and are typically IGBTs (Insulated Gate Bipolar Transistors), but may be other transistors, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). Moreover, the switching element here is used for power conversion, and may be called a power semiconductor element.

  In FIG. 1, each of broken lines 8a to 8g corresponds to a semiconductor module. The power converter 2 includes seven sets of series circuits of two switching elements. As hardware, a series circuit of two switching elements and a diode associated therewith are accommodated in one semiconductor module. Hereinafter, any one of the semiconductor modules 8a to 8g will be denoted as the semiconductor module 8 when it is indicated without distinction.

  In FIG. 1, the conductive paths in the broken line indicated by reference numeral 30 correspond to bus bars (P bus bars) connecting the positive terminals 25 a of the plurality of semiconductor modules 8 and the smoothing capacitors 6. The conductive path in the broken line indicated by reference numeral 40 corresponds to a bus bar (N bus bar) connecting the plurality of negative terminals 25 b and the smoothing capacitor 6. The P bus bar 30 and the N bus bar 40 will be described later.

  Next, the hardware configuration of the power conversion device 2 will be described. The top view of the power converter device 2 is shown in FIG. FIG. 2 is a plan view of the power conversion device 2 with the cover removed, showing the layout of parts housed inside the case 90. As shown in FIG. In the case 90, the filter capacitor unit 105, the reactor unit 107, the laminated cooling unit 20, the smoothing capacitor unit 106, and the like are accommodated. The stacked cooling unit 20 accommodates a plurality of semiconductor modules 8. In addition to these parts, a circuit board is accommodated below the laminated cooling unit 20, although not shown. Although other parts are also accommodated in the case 90, their illustration and description will be omitted.

  In the filter capacitor unit 105, a capacitor element corresponding to the filter capacitor 5 shown in FIG. 1 is accommodated. In the reactor unit and 107, a reactor device corresponding to the reactor 7 shown in FIG. 1 is accommodated. In the smoothing capacitor unit 106, a capacitor element corresponding to the smoothing capacitor 6 described in FIG. 1 is accommodated. Since a large current flows in the filter capacitor 5, the smoothing capacitor 6, and the reactor 7, the size of the hardware corresponding to them is large.

  A laminated cooling unit 20 is disposed adjacent to the smoothing capacitor unit 106. The stacked cooling unit 20 is a unit in which a plurality of coolers 22 are arranged in parallel, and the respective semiconductor modules 8 are sandwiched between the adjacent coolers 22. In FIG. 2 and the subsequent drawings, only one of the plurality of semiconductor modules is given the reference numeral 8, and the reference numerals for the other semiconductor modules are omitted. The same applies to the cooler 22.

  Each semiconductor module 8 accommodates two switching elements (semiconductor elements). The stacked cooling unit 20 is inserted between a support wall 89 provided on the case 90 and two support columns 87. Although illustration is omitted, a plate spring is inserted between the support column 87 and the laminated cooling unit 20, and the laminated cooling unit 20 is pressed in the laminated direction by the plate spring to the case 90. Be supported. By the pressurization in the stacking direction, the adhesion between the semiconductor module 8 and the cooler 22 is enhanced, and the cooling performance is improved. Further, the refrigerant supply pipe 23 and the refrigerant discharge pipe 24 are connected to one end of the multi-layered cooling unit 20, and the tip of the pipe penetrates the case 90 and is opened to the outside of the case 90. The refrigerant supplied from the refrigerant supply pipe 23 is distributed to all the coolers 22. The refrigerant absorbs heat from the adjacent semiconductor module 8 while passing through the inside of the cooler 22. The refrigerant that has passed through the cooler 22 is discharged out of the power conversion device 2 through the refrigerant discharge pipe 24. The semiconductor modules 8 are flat type (card type), and the respective flat surfaces are cooled by the cooler 22. The lamination | stacking cooling unit 20 can cool efficiently the switching element accommodated in each semiconductor module 8 by the structure which clamps the semiconductor module 8 between adjacent coolers 22. As shown in FIG.

  The two switching elements accommodated in the main body 21 of each semiconductor module 8 are connected in series inside the main body 21. The main body 21 is a package made of resin. The high potential terminal (positive electrode terminal 25a), the low potential terminal (negative electrode terminal 25b), and the middle terminal (midpoint terminal 25c) of the series connection of the switching elements extend from the main body 21 in the Z direction. There is. The positive electrode terminal 25a, the negative electrode terminal 25b, and the middle point terminal 25c are all flat. The positive electrode terminal 25 a, the negative electrode terminal 25 b, and the middle point terminal 25 c are electrically connected to the switching element inside the main body 21 of the semiconductor module 8. The positive electrode terminal 25 a, the negative electrode terminal 25 b, and the middle point terminal 25 c extend outside the main body 21 of the semiconductor module 8. The positive electrode terminals 25 a of the plurality of semiconductor modules 8 are aligned in the stacking direction of the coolers 22 of the stacked cooling unit 20. The stacking direction is the X direction in the coordinate system of the figure. Likewise, the negative terminals 25b and the midpoint terminals 25c of the plurality of semiconductor modules 8 are arranged in the stacking direction (X direction).

  As described with reference to the circuit diagram of FIG. 1, one semiconductor module 8 is used for a booster circuit, and six semiconductor modules 8 are used for two sets of inverter circuits. As described with reference to FIG. 1, the positive electrode terminals 25 a of the plurality of semiconductor modules 8 are connected to one electrode of the smoothing capacitor 6 by the P bus bar 30, and the negative electrode terminal 25 b is the other of the smoothing capacitor 6 by the N bus bar 40. Connected to the Although a bus bar for transmitting AC output to the outside is connected to the middle point terminal 25c of the semiconductor module 8, the illustration of the bus bar and the connector terminal block connected to the tip of the bus bar is omitted. There is.

  As described above, the smoothing capacitor 6 is connected in parallel between the voltage converter circuit 12 and the inverter circuits 13a and 13b. The smoothing capacitor 6 is connected to all the semiconductor modules 8. The P bus bar 30 and the N bus bar 40 electrically connect the smoothing capacitor 6 (smoothing capacitor unit 106) and the plurality of semiconductor modules 8. The P bus bar 30 is composed of a base plate 31 and a plurality of branch portions 32. The structure of the P bus bar 30 will be described in detail later.

  Each semiconductor module 8 is provided with a control terminal on the opposite side of the terminals 25a, 25b, 25c of the main body 21, and the control terminal is connected to a circuit board (not shown). The control terminal is connected to the gate electrode of the switching element, and the circuit board generates a gate signal to be supplied to the switching element.

  The relationship between the smoothing capacitor unit 106, the laminated cooling unit 20, and the P bus bar 30 will be described with reference to FIG. 3 is a perspective view of the assembly of the smoothing capacitor unit 106, the laminated cooling unit 20, and the bus bar in the power conversion device 2. As shown in FIG. In FIG. 3, the illustration of the N bus bar 40 is omitted. Furthermore, FIG. 4 shows a perspective view of the P bus bar 30 in a portion exposed from the smoothing capacitor unit 106.

  The P bus bar 30 is divided into a base plate 31 and a plurality of branches 32 for convenience of explanation. The base plate 31 is a plate member extending from the smoothing capacitor unit 106 toward the laminated cooling unit 20 and extending in the XY plane in the coordinate system in the drawing. The plurality of branch portions 32 extend from the end of the base plate 31 close to the laminated cooling unit 20, and are bent halfway to be parallel to the YZ plane. The plurality of branches 32 are arranged in the X direction in the coordinate system in the drawing. The tips of the plurality of branch portions 32 are joined to the positive electrode terminal 25 a of the corresponding semiconductor module 8. In FIG. 4, positive terminals 25 a extending from the respective semiconductor modules 8 are drawn by imaginary lines. The positive electrode terminal 25 a is also flat, and its flat surface is connected to the tip of the branch portion 32 of the flat P-type bus bar 30.

  An opposing portion 33 extends from the tip of each branch portion 32 of the P bus bar 30. The facing portion 33 is provided to the positive electrode terminal 25 a of each semiconductor module 8. The opposing portion 33 is joined to the surface of the branch portion 32 opposite to the surface joined to the positive electrode terminal 25 a. The facing portion 33 extends from the P bus bar 30 toward the main body 21 of the semiconductor module 8 along the extending direction of the positive electrode terminal 25 a. The facing portion 33 is flat and is close to and opposed to the flat surface of the positive electrode terminal 25a. The facing portion 33 faces the flat surface at a distance from the flat surface of the positive electrode terminal 25a. The facing portion 33 is made of copper like the P bus bar 30 and is conductive. Therefore, the facing portion 33 is electrically connected to the positive electrode terminal 25a through the P bus bar 30, and has the same potential as the positive electrode terminal 25a. However, the facing portion 33 faces the positive electrode terminal 25a at a distance, and the facing portion 33 itself does not directly touch the positive electrode terminal 25a. Next, the function of the facing portion 33 will be described.

  The facing portion 33 is provided for the purpose of reducing the inductance (parasitic inductance) of the P bus bar 30 and the positive electrode terminal 25a. In the facing portion 33, an eddy current is generated by the magnetic field generated by the current flowing through the adjacent positive electrode terminal 25a. The magnetic field resulting from the eddy current cancels out the magnetic field resulting from the current flowing through the positive electrode terminal 25a. This cancellation reduces the inductance. In addition to this, the magnetic field resulting from the current flowing on the surface of the facing portion 33 separates the magnetic field resulting from the current flowing on the surface of the positive electrode terminal 25a facing the facing portion 33 separately from the eddy current. Is reduced. FIG. 5 shows a cross section in the XZ plane of the positive electrode terminal 25a of one semiconductor module 8 and the P bus bar 30 (branch portion 32) connected thereto. It is known that the high frequency current generated due to the switching operation of the switching element travels on the surface of the conductor. Arrows shown in FIG. 5 indicate propagation paths of high frequency current. The high frequency current generated inside the main body 21 of the semiconductor module 8 is transmitted to the surface of the positive electrode terminal 25 a and transmitted to the surface of the facing portion 33 through the surface of the P bus bar 30. The high frequency current propagated to the surface of the facing portion 33 returns to the surface of the P bus bar 30 at the back side in the drawing, and is further transmitted to the smoothing capacitor 6. As shown by arrows A1 and A2 in FIG. 5, the direction A1 of the high frequency current transmitted on the surface of the positive electrode terminal 25a and the direction A2 of the high frequency current transmitted on the surface of the facing portion 33 are opposite to each other. Although the direction of the current also has a component in the direction perpendicular to the paper surface and a component returning from the facing portion 33 to the P bus bar 30, at least a part of the high frequency current is mutually different on the surface of the facing portion 33 and the surface of the positive electrode terminal 25a. It will be in the opposite direction. Since the currents are opposite to each other, the directions of the magnetic fields generated due to the currents are also opposite, and part of the magnetic field is canceled. By partially canceling the magnetic field generated due to the current, the inductance of P bus bar 30 and positive electrode terminal 25a is reduced. In other words, the facing portion 33 reduces the parasitic inductance of the conductive path (the P bus bar 30 and the positive electrode terminal 25 a) conducted to the switching element in the vicinity of the semiconductor module 8. The N bus bar 40 is also provided with a similar facing portion, and the above description of the P bus bar 30 also holds true for the N bus bar 40. The N bus bar 40 also has the same structure as the P bus bar 30 with regard to the configuration of the branches and the connection relationship with the smoothing capacitor unit 106.

  The inductance reduction effect due to the generation of the eddy current can be obtained even if the facing portion 33 and the positive electrode terminal 25a are not conducted. On the other hand, the inductance reduction effect obtained by the high frequency current generated due to the switching operation flowing through the surface of the positive electrode terminal 25a and the surface of the facing portion 33 is obtained by conduction between the positive electrode terminal 25a and the facing portion 33. .

  Next, a modification (first modification) of the bus bar will be described with reference to FIGS. FIG. 6 shows an assembly of the P bus bar 130, the N bus bar 140, the laminated cooling unit 20, and the smoothing capacitor unit 106 according to a modification. FIG. 7 shows an exploded view in which the P bus bar 130 and the N bus bar 140 of the modified example are separated from the laminated cooling unit 20 and the smoothing capacitor unit 106. Note that in FIG. 7, the electrode connection portion 139 of the P bus bar 130 and the electrode connection portion 149 of the N bus bar 140 are portions that are originally inserted into the smoothing capacitor unit 106. These electrode connection portions 139 and 149 are connected to the electrodes of the capacitor element in the smoothing capacitor unit 106. FIG. 8 is a partially enlarged view of the assembly. FIG. 9 is a cross-sectional view in which the positive electrode terminal 25 a and the periphery thereof are cut in a plane parallel to the XZ plane in the coordinate system in the drawing.

  A plurality of through holes 131 a are provided in the flat base plate 131 of the P bus bar 130. The positive electrode terminal 25a of each semiconductor module 8 penetrates through each through hole 131a. Connecting portions 132 extend from the edge of each through hole 131a. The connection portion 132 extends in the direction away from the main body 21 of the semiconductor module 8 along the positive electrode terminal 25 a. Each connection portion 132 of the P bus bar 130 is connected to the corresponding positive terminal 25a. Moreover, the opposing part 133 is extended from the edge of each through-hole 131a. The opposite portion 133 extends in the direction toward the main body 21 of the semiconductor module 8 opposite to the connection portion 132 (see FIG. 9). As well shown in FIG. 9, the opposing portion 133 is electrically connected to the positive electrode terminal 25a through the P bus bar 130, but the opposing portion 133 is opposed to the positive electrode terminal 25a at a distance, and the opposing portion 133 itself is not in direct contact with the positive electrode terminal 25a. The facing portion 133 is close to the flat surface of the positive electrode terminal 25a and is opposed thereto without being in direct contact with the positive electrode terminal 25a. Also in the layout of FIG. 9, the Z-direction component (terminal extension direction component) of the high-frequency current flowing on the surface of the positive electrode terminal 25a and the Z-direction component of the high-frequency current flowing on the surface of the facing portion 133 are opposite to each other. A portion of the magnetic field resulting from each high frequency current cancels out. As a result, the inductance of P bus bar 130 and positive electrode terminal 25a is reduced.

  The N bus bar 140 is also provided with the facing portion 143, and the role thereof is the same as that of the facing portion 133 of the P bus bar 130. The N bus bar 140 is outlined. The base plate 141 of the N bus bar 140 is provided with a plurality of through holes 141a, and the negative electrode terminals 25b of the semiconductor modules 8 pass through the through holes 141a. The structure around the through hole 141 a is the same as the structure around the through hole 131 a of the P bus bar 130. That is, the connection portion 142 extends from the edge of the through hole 141a, and the connection portion 132 is connected to the negative electrode terminal 25b. In addition, the facing portion 143 extends from the edge of the through hole 141a. The facing portion 143 extends toward the main body 21 of the semiconductor module 8 along the extending direction (the Z direction in the drawing) of the negative electrode terminal 25 b. The facing portion 143 is close to and opposed to the negative electrode terminal 25 b at a distance. Similar to the facing portion 133 of the P bus bar 130, the facing portion 143 of the N bus bar 140 also contributes to the reduction of the inductance of the N bus bar 140 and the negative electrode terminal 25b.

  As shown in FIG. 8 and FIG. 9, another through hole 141b is provided in the flat base plate 141 of the N bus bar 140, and the positive electrode terminal 25a penetrates the through hole 141b. The base plate 131 of the P bus bar 130 and the base plate 141 of the N bus bar 140 also face each other. Since currents in opposite directions flow through the P bus bar 130 and the N bus bar 140, the base plates 131 and 141 of the respective bus bars oppose each other, so that the magnetic fields resulting from the currents cancel each other. The fact that the base plates 131 and 141 of the respective bus bars face each other also contributes to the reduction of the inductance.

  Further, as described above, the connection portion 132 extends in the direction away from the main body 21 of the semiconductor module 8 along the positive electrode terminal 25 a, and the opposite portion 133 is directed to the main body 21 opposite to the connection portion 132. It extends in the direction (see FIG. 9). The connection part 132 and the positive electrode terminal 25a are connected by welding. The fact that the connecting portion 132 extends away from the main body 21 facilitates the work of welding the connecting portion 132 to the positive electrode terminal 25 a as compared with the case where the connecting portion 132 extends in the direction toward the main body 21. . Further, since the connecting portion 132 extends in the direction away from the main body 21 and the opposing portion 133 extends in the direction toward the main body 21, the opposing portion 133 does not disturb when welding the connecting portion 132.

  Still another modification of the bus bar will be described with reference to FIGS. 10 to 12 are cross-sectional views of the connection portion of the bus bar and the terminal. A modification (second modification) of FIG. 10 is obtained by adding an insulating layer 135 to the P bus bar 130 of FIG. The insulating layer 135 is sandwiched between the facing portion 133 and the positive electrode terminal 25a. The insulating layer 135 is inserted in order to keep the gap between the facing portion 133 and the positive electrode terminal 25a constant. As described above, although the opposing portion 133 and the positive electrode terminal 25a have the same potential, when the opposing portion 133 and the positive electrode terminal 25a are in direct contact, currents in opposite directions no longer flow on the respective surfaces. The inductance reduction effect is reduced. The insulating layer 135 is provided so as to face each other while maintaining a narrow gap without directly contacting the facing portion 133 and the positive electrode terminal 25a. An insulating layer may be sandwiched also between the facing portion of the N bus bar 140 and the negative electrode terminal.

  The contrast with a structure in which conductive members having different polarities face each other to reduce the inductance will be described. Now, it is assumed that the positive electrode terminal 25a and a conductive member having a different polarity, for example, a facing portion extending from the N bus bar 140, face the positive electrode terminal 25a with the insulating layer therebetween. Since the insulating layer is separated, the opposing portion of the positive electrode terminal 25a and the N bus bar 140 does not short circuit. However, when members having different polarities are disposed close to each other, a creeping distance corresponding to the potential difference between the two must be secured between them. In the case of the power conversion device of the embodiment, members having the same potential are brought close to each other, so that there is an advantage that the creeping distance may not be taken into consideration.

  The P bus bar 230 of the modification (third modification) of FIG. 11 is different from the P bus bar 130 of the first modification in the structure of the facing portion 233. The P bus bar 230 has a base plate 131. The base plate 131 is provided with a plurality of through holes 131a, and the positive electrode terminals 25a of the semiconductor modules 8 are in communication with the through holes 131a. Connecting portions 132 extend from the edge of each through hole 131a. The connection portion 132 extends in a direction away from the main body 21 of the semiconductor module 8. Moreover, the opposing part 233 is extended from the edge of each through-hole 131a. The facing portion 233 extends from the base plate 131 of the P bus bar 230 toward the main body 21 along the extending direction of the positive electrode terminal 25 a. The facing portion 233 faces the positive electrode terminal 25a at a distance without being in direct contact with the positive electrode terminal 25a.

  Similarly to the facing portion 133 of the first modification, the facing portion 233 also reduces the inductance. The facing portion 233 is formed by bending a part of the portion closing the through hole 131 a of the base plate 131. The through hole 131 a and the facing portion 233 are formed by pressing a metal plate which is a material of the base plate 131. Since the through hole 131a and the facing portion 233 can be formed by a single pressing process, the P bus bar 230 of the third modification can be manufactured at low cost. Although illustration is omitted, the opposite portion of the N bus bar 140 is also made in the same manner.

  The P bus bar 330 of the modification (fourth modification) of FIG. 12 is different from the P bus bar 130 of the first modification in the structure of the facing portion 333. The P bus bar 330 has a base plate 131. The base plate 131 is provided with a plurality of through holes 131 a, and the positive electrode terminals 25 a of the semiconductor modules 8 pass through the through holes 131 a. Connecting portions 132 extend from the edge of each through hole 131a. The connection portion 132 extends in a direction away from the main body 21 of the semiconductor module 8. Moreover, the opposing part 333 is extended from the edge of each through-hole 131a. The facing portion 333 extends along the extending direction of the positive electrode terminal 25a. Unlike the first modification, the facing portion 333 extends away from the main body 21 of the semiconductor module 8. The opposing portion 333 is adjacent to the positive electrode terminal 25a at a distance and opposed to the positive electrode terminal 25a without being in direct contact with the positive electrode terminal 25a.

  As mentioned earlier, high frequency current propagates on the surface of the conductor. The component of a part of the high frequency current flowing on the surface of the facing portion 333 facing the positive electrode terminal 25a is different from the direction of the high frequency current propagating on the surface of the positive electrode terminal 25a. Some of the magnetic fields generated by currents of different directions cancel out. By partially offsetting the magnetic field generated due to the current, the inductance of positive electrode terminal 25a and P bus bar 330 is reduced. Although the facing portion 333 extending in the direction away from the main body 21 of the semiconductor module 8 is not as large as the facing portion in the first to third embodiments, an inductance reduction effect can be expected. Although illustration is omitted, the opposite portion of the N bus bar 140 is also made in the same manner.

  Some of the features of the structures described in the examples are listed. The facing portion 33 (133-333) may extend toward the main body 21 of the semiconductor module 8 along the extending direction of the positive electrode terminal 25a. The high frequency component of the current is transmitted from the main body 21 toward the tip on the surface of the positive electrode terminal 25a. On the other hand, the high frequency component of the current flows in the direction toward the main body 21 on the surface of the facing portion 33 (133-333) facing the positive electrode terminal 25a. That is, the direction of the current transmitted on the surface of the positive electrode terminal 25a and the direction of the current transmitted on the surface of the facing portion 33 (133-333) are opposite to each other. Therefore, the magnetic field due to the current transmitted on the terminal surface and the current due to the current transmitted on the surface of the opposite part effectively cancel each other, reducing the inductance. The same applies to the opposite part and the negative electrode terminal provided in the N bus bar.

  Furthermore, the P bus bar 230 has the following structure. The P bus bar 230 includes a base plate 131 and a connection portion 132. The base plate 131 has a plurality of through holes 131 a and the positive electrode terminal 25 a passes through each through hole. The connection portion 132 extends from the edge of each through hole along the positive electrode terminal 25 a in a direction away from the main body 21 and is connected to the positive electrode terminal 25 a. The facing portion 233 extends from the edge of the through hole toward the main body along the extending direction of the terminal. The opposing portion 233 is formed by bending a portion which blocks the through hole of the base plate. This structure has an advantage that the facing portion can be realized at low cost.

  Points to be noted regarding the technology of the embodiment and its modification will be described. The power conversion device of the embodiment uses the opposing portion 33 (133-333) having the same potential as the positive electrode terminal 25a (negative electrode terminal 25b) of the semiconductor module 8 and the inductance (parasitic inductance) of the bus bar and the positive electrode terminal 25a (negative electrode terminal 25b) Reduce). When reducing the inductance by bringing a conductor of a potential different from the positive terminal (or P bus bar) close to reduce the inductance, it is necessary to take care that the positive terminal (or P bus bar) does not contact the conductor. is there. The technology disclosed herein uses a conductor (opposite portion) having the same potential as the positive electrode terminal (or P bus bar). Therefore, even if contact is made, the inductance reduction effect is reduced, but short-circuiting of members with different polarities does not occur. The technology disclosed in the present specification is easy to implement as compared to the technology of reducing the inductance by using a conductor of a potential different from that of the positive electrode terminal (or P bus bar).

  In addition, the technology disclosed in the present specification can be realized with a simple structure of extending the opposite part from the bus bar. The structure can be realized in a narrow space. Therefore, the technology disclosed in the present specification is a technology suitable for a power conversion device having a stacked cooling unit in which the gap between the terminals of adjacent semiconductor modules is narrow.

  In the bus bar of the first to fourth modifications, the connecting portion extends from the edge of the through hole provided in the base plate, and the opposite portion extends from the edge opposite to the edge where the connecting portion extends. The opposite part may extend from the edge on the same side as the connection.

  In the embodiment, the description of the bus bar connected to the midpoint terminal 25c is omitted. An opposing portion may be provided on the bus bar connected to the midpoint terminal 25c.

  As mentioned above, although the specific example of this invention was described in detail, these are only an illustration and do not limit a claim. The art set forth in the claims includes various variations and modifications of the specific examples illustrated above. The technical elements described in the present specification or the drawings exhibit technical usefulness singly or in various combinations, and are not limited to the combinations described in the claims at the time of application. In addition, the techniques exemplified in the present specification or the drawings can simultaneously achieve a plurality of purposes, and achieving one of the purposes itself has technical utility.

2: Power converter 5: Filter capacitor 6: Smoothing capacitor 7: Reactor 8, 8a-8g: Semiconductor module 12: Voltage converter circuit 13a, 13b: Inverter circuit 20: Multilayer cooling unit 21: Main body 22: Cooler 25a: Positive electrode Terminal 25b: negative electrode terminal 25c: middle point terminal 30, 130, 230, 330: P bus bar 31, 131: base plate 32: branch portion 33, 133, 143, 233, 333: opposing portion 40, 140: N bus bar 100: Electric car 105: filter capacitor unit 106: smoothing capacitor unit 107: reactor unit 131a: through hole 132, 142: connection portion 135: insulating layer 139, 149: electrode connection portion 141: base plate 141a, 141b: through hole T1-T8 : Switching element

Claims (3)

A main body containing a switching element, and a plurality of semiconductor modules each including a flat plate-like terminal electrically connected to the switching element in the main body and extending to the outside of the main body;
A stacked cooling unit in which a plurality of coolers are arranged in parallel and sandwiching the semiconductor module between adjacent coolers;
A bus bar connected to the terminals of each of the semiconductor modules;
Equipped with
The bus bar is
A base plate having a plurality of through holes and through which the terminals of each semiconductor module pass through each through hole;
A connecting portion extending from an edge of the through hole and connected to the terminal;
A conductive counter portion extending from the edge of the through hole in the opposite direction to the connection portion and facing the flat surface at a distance from the flat surface of the terminal ;
A power converter device. The connecting portion extends in a direction away from the body along the extending direction of the terminal, the facing portion extends toward the front Stories body along the extending direction, to claim 1 Power converter as described. Before SL facing portion, said a said through-hole was not blocked portion is folded portion of the base plate, power converter according to claim 2.

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