JP6372433B2 - Power converter - Google Patents

Description

  The present invention relates to a power conversion device.

  For example, an electric vehicle includes a power converter that converts electric power of a DC power source into electric power that drives a motor for traveling. The power conversion device includes a plurality of semiconductor elements for power conversion. A semiconductor element for power conversion generates a large amount of heat. For example, Patent Document 1 discloses a power conversion device having a structure for efficiently cooling a plurality of semiconductor elements that generate a large amount of heat. In the power conversion device, a plurality of semiconductor elements for power conversion are distributed and accommodated in a plurality of flat plate type power modules. The power converter includes a stacked unit in which a plurality of flat plate-shaped coolers are arranged in parallel, and the power module is sandwiched between adjacent coolers. Each power module is efficiently cooled by a cooler from both sides.

  On the other hand, in a power conversion apparatus that handles a large current, it is desirable that the inductance generated in the conductor connecting the semiconductor elements and the inductance generated in the conductor connecting the semiconductor element and other electronic components are small. In the power conversion device of Patent Document 1, not only the power module but also a capacitor connected to the semiconductor element in the power conversion circuit is stacked in the stacked unit. By adopting such a structure, the distance between the power module and the capacitor is shortened, and the length of the conductor connecting the semiconductor element accommodated in the power module and the capacitor is also shortened. Therefore, the inductance of the conductor connecting the semiconductor element and the capacitor is reduced. Hereinafter, for convenience of explanation, in this specification, a conductor connecting semiconductor elements and a conductor connecting a semiconductor element and other electronic components are referred to as a bus bar.

JP2013-121236A

  In addition to shortening the length of the bus bar, the method of reducing the inductance includes a method of arranging another metal plate in parallel with the flat bus bar (or the flat terminal extending from the power module). Are known. The magnetic field generated due to the current flowing through the bus bar (or terminal) is the cause of the inductance, but if a metal plate is placed parallel to the bus bar (or terminal), an eddy current is generated in the metal plate, and as a result. The magnetic field is reduced and the inductance is also reduced. The technology disclosed in the present specification provides a power conversion device having a compact inductance reduction structure using the structural features of the above-described laminated unit.

  The power conversion device disclosed in the present specification includes a flat plate type power module containing a semiconductor element and a stacked unit. In the laminated unit, a plurality of flat plate type coolers are arranged in parallel, and a power module is sandwiched between adjacent coolers. The power module extends in a direction orthogonal to the stacking direction of the coolers, and includes a flat terminal that is electrically connected to a semiconductor element inside the power module. And the cooler is provided with the metal plate extended so that the terminal may be opposed. The metal plate extends from the cooler along the terminal, and then curves in a U shape and extends toward the cooler. The part ahead of the U-shaped curve of the metal plate is close to the terminal.

  Originally, the cooler is disposed adjacent to the power module. In the power conversion device disclosed in the present specification, a metal plate for inductance reduction extending along the terminal is provided from the cooler. The metal plate is curved in a U shape, and a portion ahead of the curve is close to the terminal of the power module. The power conversion device disclosed in the present specification reduces inductance by extending a metal plate from a cooler disposed near a terminal extending from a power module. Since the distance between the cooler and the terminal is short, the metal plate can be short and the structure added for inductance reduction can be small. The U-shaped metal plate can be adjusted in shape and relative position with respect to the terminal (particularly, the shape and relative position of the part ahead of the curve) so as to effectively reduce the inductance. The technology disclosed in this specification relates to a power conversion device including a multilayer unit, and provides a compact inductance reduction structure. Details and further improvements of the technology disclosed in this specification will be described in the following “DETAILED DESCRIPTION”.

It is a block diagram of the electric vehicle including the power converter device of an Example. It is a typical perspective view of the power converter device of an Example. It is a front view of a lamination | stacking unit. It is sectional drawing of the lamination | stacking unit cut | disconnected by the IV-IV line of FIG.

  A power converter 2 according to an embodiment will be described with reference to the drawings. The power conversion device 2 according to the embodiment is mounted on the electric vehicle 100. The power conversion device 2 is a device that converts battery power into power for driving a traveling motor. FIG. 1 shows a block diagram of an electric vehicle 100 including the power conversion device 2.

  The electric vehicle 100 includes two motors 83a and 83b for traveling. The outputs of the two motors 83a and 83b are combined / distributed by the power distribution mechanism 85 and transmitted to the axle 86 (that is, drive wheels).

  The power conversion device 2 is connected to a battery 81 via a system main relay 82. The power conversion device 2 includes a converter circuit 87 that boosts the voltage of the battery 81 and two inverter circuits 88a and 88b that convert the boosted DC power into AC power. The inverter circuit 88a supplies power to the motor 83a, and the inverter circuit 88b supplies power to the motor 83b.

  The converter circuit 87 includes a series circuit of two switching elements T7 and T8, a reactor 97, a filter capacitor 95, and two diodes. Reactor 97 has one end connected to the midpoint of the series circuit and the other end connected to a high potential terminal on the input side (battery side). The filter capacitor 95 is connected between the high potential terminal and the low potential terminal on the input side.

  The converter circuit 87 boosts the voltage of the battery 81 and supplies it to the inverter circuits 88 a and 88 b (boost operation), and steps down the DC power (regenerative power) input from the inverter circuits 88 a and 88 b to the battery 81. Both supply operation (step-down operation) can be performed. Since the converter circuit 87 of FIG. 1 is well known, detailed description thereof is omitted. Note that the series circuit in the range of the broken-line rectangle indicated by the symbol PM7 corresponds to one of the plurality of power modules 20 described later.

  The inverter circuit 88a has a configuration in which three sets of series circuits of two switching elements are connected in parallel (T1 and T4, T2 and T5, T3 and T6). A diode is connected in antiparallel to each switching element. The high potential side of the three sets of series circuits PM1 to PM3 is connected to the output terminal on the high potential side of the converter circuit 87, and the low potential side of the three sets of series circuits is connected to the output terminal on the low potential side of the converter circuit 87. Has been. An alternating current (U phase, V phase, W phase) is output from the midpoint of each of the three sets of series circuits PM1 to PM3. Three sets of series circuits PM1 to PM3 correspond to three of a plurality of power modules 20 described later.

  Since the configuration of the inverter circuit 88b is the same as that of the inverter circuit 88a, a specific circuit is not shown in FIG. Similarly to the inverter circuit 88a, the inverter circuit 88b has a configuration in which three sets of series circuits of switching elements are connected in parallel. Three sets of series circuits PM4 to PM6 correspond to another three of a plurality of power modules 20 described later.

  A smoothing capacitor 96 is connected in parallel to the input terminals of the inverter circuits 88a and 88b. The smoothing capacitor 96 removes noise (current pulsation accompanying switching operation) superimposed on the direct current input to the inverter circuits 88a and 88b.

  The switching elements T1-T8 are transistors, typically IGBTs (Insulated Gate Bipolar Transistors), but may be other transistors, for example, MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). Alternatively, in the future, different types of switching elements may be used in the power conversion device. The switching element here is used to convert a large amount of electric power, and is sometimes called a power semiconductor element.

  In FIG. 2, the typical perspective view of the power converter device 2 is shown. 2 shows only the laminated unit 8 (details will be described later) among the components housed in the case 6 of the power conversion device 2, and other components such as the reactor 97 and the filter capacitor in FIG. 95, the smoothing capacitor 96, and the circuit board for controlling the switching elements T1 to T8 are not shown. In FIG. 2, the metal plate for reducing the inductor provided in the cooler 10 (described later in detail) is also omitted. Further, in FIG. 2, one power module 20 is drawn from the stacked unit 8 out of the plurality of power modules 20 included in the stacked unit 8 to help understanding.

  The plurality of switching elements T <b> 1 to T <b> 8 shown in FIG. 1 and diodes connected in antiparallel to each switching element are distributed in several power modules 20. Specifically, two switching elements and two diodes are accommodated in one power module 20. More specifically, the two switching elements and the two diodes are sealed in a resin package 21. The two switching elements are connected in series inside the package 21, and one diode is connected in antiparallel to each switching element. The package 21 (power module 20) is a flat plate type.

  A switching element for power conversion generates a large amount of heat. Therefore, the power module 20 includes heat radiation plates 23a and 23b on the surface of the package 21 that faces the cooler. Although not shown in FIG. 2, the heat radiating plate 23c is also exposed on the surface of the package 21 opposite to the heat radiating plates 23a and 23b. The heat sink 23c appears in FIG. Hereinafter, when the heat sinks 23a, 23b, and 23c are shown without distinction, they are referred to as the heat sink 23.

  The heat dissipation plate 23 a is connected to one electrode (drain electrode) of one switching element inside the package 21. The heat sink 23 b is connected to one electrode (source electrode) of another switching element inside the package 21. The heat radiating plate 23 c is connected to the other electrode (source electrode) of one switching element and the other electrode (drain electrode) of another switching element inside the package 21. That is, the heat sink 23c plays the role of a conductor that connects two switching elements in series. In other words, the three heat sinks 23a, 23b, and 23c are respectively connected to the high-potential side electrode, the midpoint electrode, and the low-potential side electrode of the series connection of the two switching elements. Yes. Since the heat radiating plate 23 is connected to the electrodes of the switching element, the heat radiating plate 23 conducts heat of the switching element well.

  Further, each of the three heat radiating plates 23 is connected to each of the three power terminals 26 a, 26 b, 26 c extending from one side surface of the package 21. The three power terminals 26a, 26b, and 26c correspond to a high-potential side terminal, a midpoint terminal, and a low-potential side terminal of two switching elements in the package connected in series. The three power terminals 26a, 26b, and 26c are flat plate types. This is because the internal resistance of the terminal is lowered to suppress power transmission loss and to suppress heat generation due to the flowing current. The three power terminals 26a, 26b, and 26c are connected to a bus bar (not shown), and are connected to terminals of other power modules or another device such as a reactor. Hereinafter, when any one of the three power terminals 26a, 26b, and 26c is shown without distinction, it is referred to as a power terminal 26.

  A gate terminal 29 extends from another side surface of the package 21. The gate terminal 29 is connected to the gate electrodes of the two switching elements inside the package 21.

  As shown in FIG. 2, the plurality of power modules 20 are stacked with the plurality of coolers 10. Each cooler 10 is made of metal (aluminum). Each cooler 10 is a flat plate type. Hereinafter, a stacked body of the plurality of power modules 20 and the plurality of coolers 10 is referred to as a stacked unit 8. The plurality of power modules 20 and the plurality of coolers 10 are alternately stacked one by one. In other words, the laminated unit 8 is a device in which a plurality of metal flat plate-like coolers 10 are arranged in parallel and the power module 20 is sandwiched between adjacent coolers 10. In the coordinate system shown in FIG. 2, the X axis corresponds to the stacking direction of the plurality of power modules 20 and the plurality of coolers 10. 3 and 4 referred later, the X axis corresponds to the stacking direction.

  The cooler 10 and the power module 20 are both flat plate types and are laminated so that their flat surfaces face each other. In the present embodiment, the seven coolers 10 are arranged for the six power modules 20 so that the coolers 10 are positioned at both ends in the stacking direction (X-axis direction). In the block diagram of FIG. 1, seven sets of series circuits of two switching elements are depicted, and the stacked unit 8 of FIG. 2 originally requires seven power modules, but in FIG. An illustration of one power module and a corresponding cooler is omitted.

  The heat radiation plate 23 electrically connected to the electrodes of the switching element is exposed on both surfaces of the power module 20, and the cooler 10 is made of metal. Insulating plate 30 is sandwiched between power module 20 and cooler 10 in order to insulate between heat sink 23 and cooler 10. Grease is applied to both surfaces of the insulating plate 30. The grease fills the microscopic gap between the power module 20 and the insulating plate 30 and the microscopic gap between the cooler 10 and the insulating plate 30, and heat transfer efficiency from the power module 20 to the cooler 10. To increase.

  The plurality of coolers 10 are connected by connecting pipes 4a and 4b. A refrigerant supply pipe 3 a and a refrigerant discharge pipe 3 b are connected to the cooler 10 at one end in the stacking direction (X-axis direction) of the power module 20 and the cooler 10. The refrigerant supplied through the refrigerant supply pipe 3a is distributed to all the coolers 10 through the connection pipe 4a. The cooler 10 is a hollow flat plate type, and the refrigerant passes through the internal space. The refrigerant passing through the cooler 10 absorbs heat from the power module 20 adjacent to the cooler 10. The refrigerant passing through each cooler 10 passes through the connection pipe 4b and is discharged from the refrigerant discharge pipe 3b. The refrigerant is a liquid, typically water.

  When the stacked unit 8 is accommodated in the case 6, the leaf spring 7 is inserted into one end side in the stacking direction (X-axis direction). A predetermined load is applied to the cooler 10, the power module 20, and the insulating plate 30 from both sides in the stacking direction by the leaf spring 7. The total pressure (load) applied to the laminated unit 8 is, for example, 3 [kN]. As described above, grease is applied to both surfaces of the insulating plate 30. The grease is thinly stretched by a high load of 3 [kN], thereby further improving the heat transfer efficiency (heat diffusion efficiency) from the power module 20 to the cooler 10.

  FIG. 3 shows a front view of the laminated unit 8. FIG. 4 shows a cross-sectional view of the laminated unit 8 cut along line IV-IV in FIG. FIG. 4 shows only one power module 20 and the coolers 10 on both sides thereof. It should be noted that the power module 20 and the cooler 10 continue alternately on the right side and the left side of FIG. As shown in FIG. 4, the cooler 10 is made by laminating two outer plates 16 with an intermediate plate 15 interposed therebetween. The outer plate 16 has a tray shape whose peripheral edge is bent at a right angle, and a space is formed between the middle plate 15 and each outer plate 16. A corrugated fin plate 19 is accommodated in the space. A space between the middle plate 15 and the outer plate 16 becomes a flow path through which the refrigerant passes. The outer plate 16 is made by pressing an aluminum plate. The intermediate plate 15 and the fin plate 19 are also made by pressing aluminum.

  The joint between the middle plate 15 and the outer plates 16 on both sides forms a flange 17 that goes around the outer periphery of the cooler 10. A metal plate 31 for reducing inductance is attached to the flange. As described above, the power module 20 extends in the direction (Z direction) orthogonal to the stacking direction with the cooler 10 and is in the form of a flat plate that is electrically connected to the switching element inside the power module 20. Power terminal 26 is provided. Each metal plate 31 extends from the cooler 10 so as to face each power terminal 26. As shown in FIG. 4, the metal plate 31 extends from the flange 17 of the cooler 10 along the power terminal 26, and then extends so as to be bent into a U shape and return toward the cooler 10. ing. A portion 31 a extending toward the cooler 10 is parallel to and close to the power terminal 26. Metal plates 31 extend from the coolers 10 on both sides of the power module 20, and portions 31 a ahead of the curvature of the metal plates 31 are close to the flat power terminals 26 on both sides. The metal plate 31 is made of the same aluminum as the material of the cooler 10. The metal plate 31 does not touch the power terminal 26, and both are in an insulated state.

  The internal structure of the power module 20 will be described with reference to FIG. The power module 20 is a device in which a semiconductor chip 41 is sealed with a resin package 21. The semiconductor chip 41 includes one switching element and a diode, and the switching element and the diode are connected in antiparallel within the chip. The semiconductor chip 41 in FIG. 4 corresponds to one of the switching elements T1 to T8 in FIG. 1 and a diode connected in antiparallel to the switching element. The semiconductor chip 41 has electrodes on both sides, one electrode is directly joined to the heat sink 23 b, and the other electrode is electrically connected to the heat sink 23 c through a conductive spacer 42. The heat sink 23b is also continuous with the power terminal 26c and forms a part of a terminal for connecting the electrode of the semiconductor chip 41 and an external device. Although not shown in the figure, the heat sink 23c is connected to another power terminal. A gate electrode is exposed on one surface of the semiconductor chip 41, and the gate electrode and the gate terminal 29 are connected by a wire. Two semiconductor chips are sealed in the package 21, and another semiconductor chip is sandwiched between the heat radiating plate 23a and the heat radiating plate 23c in a cross section different from the cross section of FIG. The structural relationship between another semiconductor chip and the heat sinks 23a and 23c is the same as the structural relationship between the semiconductor chip 41 and the heat sinks 23b and 23c shown in FIG.

  The function of the metal plate 31 will be described. The metal plate 31 reduces inductance when a current flows through the power terminal 26. Although not shown, a bus bar is bonded to the tip of the power terminal 26, and the semiconductor chip 41 is electrically connected to another device or another switching element via the power terminal 26 and the bus bar. When a current flows through the power terminal 26, a magnetic field is generated around the power terminal 26 due to the current. The larger the magnetic field, the greater the inductance. The metal plate 31 extends in parallel with the flat power terminal 26, and an eddy current is generated inside the metal plate 31 by the magnetic field generated by the power terminal 26. Generation of this eddy current weakens the magnetic field. That is, the inductance of the power terminal 26 can be reduced by arranging the metal plate 31 so as to be close to and parallel to the power terminal 26.

  Since the metal plate 31 is originally attached to the cooler 10 adjacent to the power module 20, the length thereof can be short. By providing the metal plate 31 for reducing the inductance in the cooler 10 of the laminated unit 8, the structure for reducing the inductance can be realized in a compact manner.

  The metal plate 31 is curved in a U shape. By changing the degree of bending, the shape of the metal plate 31 and the relative position with respect to the power terminal 26 (particularly, the portion 31a ahead of the bending) can be easily adjusted. For example, the bus bar is joined to the upper end of the power terminal 26, but curved so that the portion 31 a ahead of the curvature of the metal plate 31 extends in parallel with the power terminal 26 to the point where the power terminal 26 and the bus bar are joined. Can be adjusted. By doing so, the area of the metal plate 31 adjacent to the power terminal 26 (the portion 31a ahead of the curve) can be made as large as possible. In the metal plate 31, the inductance reduction effect is greater when the area of the portion adjacent to the power terminal 26 (the portion 31a ahead of the curve) is larger. Further, by adjusting the degree of bending, the portion 31 a ahead of the bending of the metal plate 31 can be brought closer to the power terminal 26. The shorter the distance from the power terminal 26 in the metal plate 31, the greater the inductance reduction effect. In this way, by bending the metal plate 31 in a U shape, the shape and position can be easily adjusted so that the inductance reduction effect is increased.

  As described above, an eddy current is generated in the metal plate 31. The temperature of the metal plate 31 rises due to the generation of eddy current. Since the metal plate 31 is attached to the cooler 10, the temperature rise of the metal plate 31 is suppressed by the cooler 10.

  Points to be noted regarding the technology described in the embodiments will be described. Although one metal plate 31 has been described in FIG. 4, one cooler 10 includes six metal plates 31, and each metal plate 31 has the structure and advantages described with reference to FIG. 4. doing. The metal plate 31 is joined to the flange 17 of the cooler 10 by welding or brazing. Alternatively, the metal plate 31 may be integrated with the outer plate 16 of the cooler 10. That is, the metal plate 31 may be configured to continue from the edge of the outer plate 16 of the cooler 10. Further, the U-shaped curved shape of the metal plate 31 shown in FIG. 4 is an example, and the metal plate 31 may have a curved shape different from that in FIG. The metal plate 31 may extend from the cooler 10 along the power terminal 26 and then be bent so as to return toward the cooler 10. For example, the metal plate may be curved in a U shape close to a V shape.

  In the embodiment, a metal plate 31 is provided for each of the three power terminals 26. A single wide metal plate that overlaps with the three power terminals 26 when viewed from the X direction (stacking direction) may be provided in the cooler 10. The semiconductor chip 41 of the embodiment corresponds to an example of a semiconductor element in the claims. The three power terminals 26 correspond to an example of terminals in the claims.

  Specific examples of the present invention have been described in detail above, 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 this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings can achieve a plurality of objects at the same time, and has technical usefulness by achieving one of the objects.

2: Power conversion device 6: Case 7: Leaf spring 8: Laminated unit 10: Cooler 15: Middle plate 16: Outer plate 17: Flange 19: Fin plate 20: Power module 21: Packages 23, 23a, 23b, 23c: Radiator 26, 26a, 26b, 26c: Power terminal 30: Insulating plate 31: Metal plate 31a: Part ahead of curve 41: Semiconductor chip (semiconductor element)
42: Spacer 81: Battery 100: Electric vehicle

Claims (3)

A flat power module containing a semiconductor element;
A plurality of flat plate-type coolers are arranged in parallel, and a laminated unit in which the power module is sandwiched between adjacent coolers;
With
The power module,
A planar power terminal extending in a direction perpendicular to the stacking direction of the cooler and electrically connected to a semiconductor element inside the power module ;
A gate terminal in conduction with the semiconductor element;
With
The cooler includes a metal plate extending to face the power terminal ,
The metal plate extends from the cooler along the power terminal , subsequently curves in a U-shape and extends toward the cooler, and a portion ahead of the U-shape is connected to the power terminal . A power converter characterized by being close to each other. The power module includes a resin package for sealing the semiconductor element;
The power terminal extends from one side of the package;
The gate terminal extends from a side surface of the package different from the one side surface;
The power conversion device according to claim 1. The power converter according to claim 1 or 2, wherein the portion of the metal plate ahead of the U-shaped curve extends in parallel to the power terminal.

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