Power conversion device

Abstract

A power conversion device (1) comprises: at least one circuit body (9) which performs power conversion; a relay bus bar (2) which connects a power source and the circuit body; a smoothing capacitor (8) which is connected in parallel to the circuit body and which smooths electric power that is supplied from the relay bus bar to the circuit body; a laminated bus bar (17) which connects the circuit body and the smoothing capacitor and which is formed by laminating a plurality of conductive members with an insulating layer (15) therebetween; and a cooling member (13, 14) which cools the circuit body and the laminated bus bar, wherein the laminated bus bar includes a first connection part (4) which is connected to the smoothing capacitor and a second connection part (5) which is connected to the relay bus bar, the first connection part is disposed on one side of the circuit body, and the second connection part is disposed on the other side of the circuit body.

Description

Power conversion device

[0001] The present invention relates to a power conversion device.

[0002] In Patent Document 1 below, the first current path between the power supply connection part and the terminal connection part connected to the power terminal of the semiconductor module is the second current path that is the current path between the power supply connection part and the element connection part connected to the capacitor element. It is characterized in that the thermal resistance is smaller, and the thermal resistance from the power supply connection part to the cooling pipe via the first current path is smaller than that of the second current path, thereby suppressing the temperature rise of the capacitor element. A configuration is disclosed.

[0003] Japanese Patent Application Laid-Open No. 2020-184810

[0004] In view of the technology described in Patent Document 1, an object of the present invention is to provide a power conversion device capable of reducing the heat received from the heat source in the smoothing capacitor.

[0005] The power conversion device includes at least one circuit body that performs power conversion, a relay bus bar that connects a power supply and the circuit body, a smoothing capacitor that is connected in parallel with the circuit body and smooths the power supplied from the relay bus bar to the circuit body, a laminated bus bar that connects the circuit body and the smoothing capacitor and is formed by laminating a plurality of conductive members via an insulating layer, and a cooling member that cools the circuit body and the laminated bus bar. The laminated bus bar has a first connection part connected to the smoothing capacitor and a second connection part connected to the relay bus bar. The first connection part is arranged on one side of the circuit body, and the second connection part is arranged on the other side of the circuit body.

[0006] A power conversion device capable of reducing the heat received by the smoothing capacitor can be provided.

[0007] An exploded perspective view of a power converter according to one embodiment of the present invention. A diagram illustrating the current path in a stacked busbar according to one embodiment of the present invention. A configuration diagram of a stacked busbar according to one embodiment of the present invention. A circuit diagram of a power converter according to one embodiment of the present invention. An exploded perspective view of a power converter according to a first modified example. A plan view of a power converter according to a first modified example. A configuration diagram of a stacked busbar according to a first modified example. A configuration diagram of a power converter and a smoothing capacitor according to a second modified example. A structural diagram of a cooling member in a power converter according to a third modified example.

[0008] Embodiments of the present invention will be described below with reference to the drawings. The following description and drawings are illustrative for illustrating the present invention, and have been omitted and simplified as appropriate for clarity of explanation. The present invention can also be carried out in various other forms. Unless otherwise specified, each component may be singular or plural.

[0009] The positions, sizes, shapes, and ranges of the components shown in the drawings may not represent their actual positions, sizes, shapes, and ranges in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the positions, sizes, shapes, and ranges disclosed in the drawings.

[0010] (One Embodiment and Overall Configuration) (Figure 1) The power converter 1 comprises an input relay busbar 2, an output busbar 3, a smoothing capacitor 8, a circuit body 9, a housing 10, and a laminated busbar 17. The housing 10 is preferably made of a conductor with high thermal conductivity, such as aluminum, but is not limited to this.

[0011] The housing 10 includes a cooling member 12, a refrigerant flow path 11, a refrigerant flow path inlet 11a, and a refrigerant flow path outlet 11b. Refrigerant flows through the refrigerant flow path 11, entering the housing 10 from the refrigerant flow path inlet 11a, and the cooling member 12 is indirectly cooled by the refrigerant. As a result, the housing 10 and the cooling member 12 can cool other components housed in the housing 10 by contact with them. The refrigerant that has flowed through the refrigerant flow path 11 flows out of the housing 10 from the refrigerant flow path outlet 11b. As shown in Figure 1, the refrigerant flow path inlet 11a and the refrigerant flow path outlet 11b are formed in the housing 10 from right to left in the drawing, but the order of the refrigerant flow path inlet 11a and the refrigerant flow path outlet 11b may be reversed.

[0012] The input relay busbar 2 is a power connection section that electrically connects a DC power source, such as a battery (not shown), to the circuit body 9. The input relay busbar 2 may be configured as part of the power conversion device 1, or the input relay busbar 2 may not be used, and the second connection section 5 (described later) and the DC power source may be directly connected by a cable or the like.

[0013] The output busbar 3 is a busbar that electrically connects the AC busbar 16 (described later) to an AC load such as a motor. The output busbar 3 may be configured as part of the power converter 1, or the output busbar 3 may not be used, and the AC busbar 16 and the AC load may be directly connected by a cable or the like.

[0014] At least one circuit body 9 is cooled by being placed in a refrigerant flow path 11 formed within the housing 10. The laminated busbar 17 is formed by laminating conductive members, a positive DC wiring layer 6 and a negative DC wiring layer 7, with an insulating substrate layer (not shown) in between, and connects the circuit body 9 and the smoothing capacitor 8. The circuit body 9 has a semiconductor switching element and is connected to a control unit (not shown), the positive DC wiring layer 6, and the negative DC wiring layer 7, and converts DC power to AC power based on a signal from the control unit. Note that the order of lamination of the positive DC wiring layer 6 and the negative DC wiring layer 7 is not limited to that shown in Figure 1.

[0015] Since the circuit body 9 is mounted on the stacked busbar 17, the cooling member 12 does not need to form a complex cooling structure, making it easy to cool both the stacked busbar 17 and the circuit body 9 simultaneously. Furthermore, because the distance from the circuit body 9 and the semiconductor switching element to the stacked busbar 17 is short, the impedance can be reduced, thus reducing surges generated by switching.

[0016] The smoothing capacitor 8 is connected in parallel with the circuit body 9 (see Figure 4 below) and is, for example, a DC capacitor. In this way, the smoothing capacitor 8 smooths the DC power supplied from the DC power supply to the circuit body 9. In Figure 1, the circuit body 9 is shown as a group of three circuit bodies 9, each consisting of a pair of switching elements for the upper and lower arms. However, the upper and lower arms may be represented as separate circuit bodies 9, or there may be two or more circuit bodies 9 for each phase.

[0017] The cooling member 12 cools the laminated busbar 17 and the circuit body 9 mounted on the laminated busbar 17 by contacting the laminated busbar 17. The cooling member 12 only needs to be placed on at least one side of the circuit body 9 and the laminated busbar 17, but it may be placed on only one side or on both sides of the circuit body 9 and the laminated busbar 17.

[0018] (Figures 2 and 3) The laminated busbar 17 is formed by laminating a DC wiring layer and an insulating layer (not shown) onto each other. The DC wiring layer is formed by overlapping a positive DC wiring layer 6 and a negative DC wiring layer 7. The positive DC wiring layer 6 and the negative DC wiring layer 7 have a first connection part 4 connected to a smoothing capacitor 8 and a second connection part 5 connected to an input relay busbar 2.

[0019] Three circuit bodies 9 are mounted on the stacked busbar 17 between the first connection part 4 and the output busbar 3 (see Figure 1; only the symbols and arrows are shown in Figure 2). The terminals of the circuit bodies 9 are connected to the stacked busbar 17 via terminal connection parts 9a. The first connection part 4 is located on one side of the circuit body 9, and the second connection part 5 is located on the other side of the circuit body 9. The smoothing capacitor 8 is connected to the stacked busbar 17 via the first connection part 4. The smoothing capacitor 8 is located on the side of the first connection part 4 that is opposite to the side adjacent to the circuit body 9. As a result, heat transfer from the input relay busbar 2, which is a heat source, and heat generated by the semiconductor switching elements in the circuit body 9 are cooled by the cooling member 12 (Figure 1) at the location of the circuit body 9, thereby reducing the heat absorbed by the smoothing capacitor 8.

[0020] As shown in Figure 2, the laminated busbar 17 has a first current path 18 and a second current path 19. The first current path 18 is a path that electrically connects the second connection part 5 and the terminal connection part 9a connected to the circuit body 9 in the laminated busbar 17. The thermal path via this first current path 18 is from the input relay busbar 2 through the terminal connection part 9a and the circuit body 9 to the position where the cooling member 12 is provided. The second current path 19 is a path that electrically connects the second connection part 5 and the first connection part 4 connected to the terminal of the smoothing capacitor 8. The thermal path via this second current path 19 is from the input relay busbar 2 to the position where the smoothing capacitor 8 is provided. Therefore, the first current path 18 is a path that extends partway through the thermal path that starts from the input relay busbar 2 in the path of the second current path 19.

[0021] In this invention, the thermal resistance of the heat path related to the first current path 18 is smaller than the thermal resistance of the heat path related to the second current path 19. Furthermore, the circuit body 9 is positioned midway along the second current path 19 that connects the second connection part 5 and the first connection part 4 connected to the smoothing capacitor 8, and the circuit body 9 and the second current path 19 are cooled by contact with the cooling member 12. As a result, the heat generated from the power supply connection part always passes through the region cooled by contact with the cooling member 12 and does not go directly to the smoothing capacitor 8. Moreover, the heat transferred from the input relay busbar 2 to the cooling member 12 is relatively larger than the heat transferred from the input relay busbar 2 to the smoothing capacitor 8, so the heat flowing into the smoothing capacitor 8 can be further suppressed, and the temperature rise of the smoothing capacitor 8 can be suppressed.

[0022] The positive DC wiring layer 6 and the negative DC wiring layer 7 each have at least one relay section 22 between the first connection section 4 and the second connection section 5. The relay section 22 is a current path and a heat path formed between the first connection section 4 and the second connection section 5. By forming multiple relay sections 22, there are multiple heat paths from the relay section 22 to the smoothing capacitor 8, allowing the heat paths to be distributed. Since the multiple relay sections 22 are cooled by contact with the cooling member 12, heat is less likely to be transferred to the smoothing capacitor 8, and the temperature rise of the smoothing capacitor 8 can be suppressed. In addition, the electrical resistance of the laminated busbar 17 is reduced, so the self-heating of the laminated busbar 17 can be reduced.

[0023] Furthermore, as shown in Figure 3, when three relay sections 22 are formed in the positive DC wiring layer 6 and the negative DC wiring layer 7, if the relay sections 22 closest to the input relay busbar 2 are designated as the first relay section 22a, the second relay section 22b, and the third relay section 22c, then the first relay section 22a has a smaller surface area and cross-sectional area than the second connection section 5. As a result, heat conducted from the second connection section 5 side is more likely to flow into the second relay section 22b and the third relay section 22c without being biased towards the first relay section 22a, thus suppressing the occurrence of a biased temperature rise in the smoothing capacitor 8 that would occur if heat were to flow only into the first relay section 22 and become biased. In addition, the contact area between the second connection section 5 and the cooling members 13 and 14 increases, which increases the amount of heat dissipated and suppresses heat transfer to the smoothing capacitor 8.

[0024] In this embodiment, the laminated busbar 17 is made of a thick copper substrate, and in a structure where the cooling member 12 and the laminated busbar 17 are in contact with an insulating material (such as a heat dissipation sheet) in between, the portion of the laminated busbar 17 in contact with the cooling member 12 will be approximately the same temperature as the water temperature of the cooling member 12. This suppresses the transfer of heat from the input relay busbar 2 to the smoothing capacitor 8, reducing the heat absorbed by the smoothing capacitor 8, which has a low heat resistance temperature, and thus suppressing the temperature rise. Furthermore, since the thermal margin of the smoothing capacitor 8 can be increased, the current specifications of the power converter 1 can be expanded. In addition, the overall heat dissipation of the power converter 1 can be improved.

[0025] Furthermore, as shown in Figure 1 above, the smoothing capacitor 8 is housed in the housing 10, so that the smoothing capacitor 8 and the housing 10 are in contact via a resin or the like (not shown). As a result, the cooling member 12 can cool the smoothing capacitor 8, thus suppressing the temperature rise of the smoothing capacitor 8. Note that the region where the laminated busbar 17 and the circuit body 9 are cooled simultaneously may be configured to allow simultaneous cooling by changing the refrigerant flow path structure of the housing 10, or an elastic heat dissipation sheet or the like may be placed between the housing 10 and the laminated busbar 17.

[0026] (Figure 4) The power converter 1 is connected to a DC power source 21 such as a battery via an input relay busbar 2. The input relay busbar 2 is connected to the second connection part 5 of the power converter 1, thereby supplying DC power output from the DC power source 21 to each circuit body 9. Each circuit body 9 is electrically connected to a smoothing capacitor 8 via a first connection part 4, thereby smoothing the DC power supplied to each circuit body 9 from the input relay busbar 2. Each circuit body 9 is connected to a motor 20, which is an AC load, via an output busbar 3, so that the AC power obtained by converting the DC power can be output to the motor 20. Although MOSFETs are shown as an example of semiconductor switching elements in the circuit body 9, IGBTs or other switching elements may also be used.

[0027] (First Modified Example) (Figures 5-7) The same configuration as the embodiment described above will not be explained below. As shown in Figure 7, the laminated busbar 17 is formed by laminating DC wiring layers 6 and 7, AC wiring layer 23, and an insulating layer (not shown) onto each other. The AC wiring layer 23 has a first connection part 4 and a second connection part 5, similar to the DC wiring layers 6 and 7, and further has an AC busbar 16. As shown in Figure 5, the circuit body 9 is shown as having two circuit bodies per arm, but it is sufficient to have one or more circuit bodies per arm. The circuit body 9 is mounted on an insulating substrate layer 15.

[0028] The laminated busbar 17 is cooled by being sandwiched between the upper cooling member 13 and the lower cooling member 14. In other words, the upper cooling member 13 and the lower cooling member 14 are arranged on both sides of the circuit body 9, the relay section 22, the first connection section 4, and the second connection section 5, respectively. Although not shown in the figures, heat-dissipating insulating members may be provided in the gaps between the upper cooling member 13 and the circuit body 9 and laminated busbar 17, and between the lower cooling member 14 and the circuit body 9 and laminated busbar 17. By using this double-sided cooling configuration, the contact area between the circuit body 9 and laminated busbar 17 and the cooling members 13 and 14 is increased, thus improving the cooling effect of the power converter 1 compared to the single-sided cooling case shown in the above embodiment.

[0029] (Second Modification) (Figure 8) The smoothing capacitor 8 may be positioned on the upper cooling member 13 or the lower cooling member 14 on the side opposite to the side that contacts the circuit body 9. In other words, the smoothing capacitor 8 is positioned on the cooling member 13 on the side opposite to the side that faces the circuit body 9, and is in contact with the cooling member 13. In this case, the terminals 8a of the smoothing capacitor 8 and the laminated busbar 17 are connected to each other at the first connection part 4 in an external region not sandwiched between the upper cooling member 13 and the lower cooling member 14. In this way, even with a configuration that cools on both sides, the smoothing capacitor 8 can be directly cooled by bringing it into contact with either one of the cooling members, thus improving cooling performance.

[0030] (Third Modification) (Figure 9) The upper cooling member 13 and the lower cooling member 14 have an extended portion 13a. The extended portion 13a is at the same potential as the housing of the power converter 1 and is arranged on both sides of the laminated busbar 17 with a heat-dissipating insulating member (not shown) in between in the stacking direction. When the laminated busbar 17 is stacked in the order of positive DC wiring layer 6, AC wiring layer 23, and negative DC wiring layer 7, a Y capacitor is formed by arranging cooling members 13 and 14, which are widely formed in the planar direction and have an extended portion 13a in between the insulating member, on both sides, and the capacitance of the Y capacitor is increased, thus enabling noise countermeasures. In addition, since the laminated busbar 17 is in contact with the cooling members 13 and 14 on both sides and the contact area is increased, the cooling effect of the laminated busbar 17 is improved and the temperature rise of the laminated busbar 17 can be suppressed.

[0031] According to the embodiments of the present invention described above, the following effects and advantages are achieved.

[0032] (1) The power conversion device 1 comprises at least one circuit body 9 that performs power conversion, a relay bus bar 2 that connects the power source and the circuit body 9, a smoothing capacitor 8 connected in parallel with the circuit body 9 and smoothing the power supplied from the relay bus bar 2 to the circuit body 9, a laminated bus bar 17 that connects the circuit body 9 and the smoothing capacitor 8 and is formed by laminating a plurality of conductive members with an insulating layer in between, and a cooling member 12 that cools the circuit body 9 and the laminated bus bar 17. The laminated bus bar 17 has a first connection part 4 that is connected to the smoothing capacitor 8 and a second connection part 5 that is connected to the relay bus bar 2. The first connection part 4 is located on one side of the circuit body 9 and the second connection part 5 is located on the other side of the circuit body 9. In this way, a power conversion device 1 can be provided that can reduce the heat absorbed by the smoothing capacitor 8.

[0033] (2) The thermal resistance from the relay busbar 2 to the cooling member 12 is smaller than the thermal resistance from the relay busbar 2 to the smoothing capacitor 8. This prevents heat from the relay busbar 2 from flowing into the smoothing capacitor 8.

[0034] (3) In the laminated busbar 17, DC wiring layers 6 and 7 including the first connection part 4 and the second connection part 5, AC wiring layer 23 and insulating layer are stacked on top of each other, and the circuit body 9 is mounted on the laminated busbar 17. This makes it easy to cool the laminated busbar 17 and the circuit body 9 simultaneously, and reduces surges generated in the circuit body 9 during switching.

[0035] (4) The laminated busbar 17 has at least one relay section 22 that connects the first connection section 4 and the second connection section 5. This allows the heat path to be dispersed and the temperature rise of the smoothing capacitor 8 to be suppressed. It also reduces the self-heating of the laminated busbar 17.

[0036] (5) The relay section 22 has a smaller surface area and cross-sectional area than the second connection section 5 in at least one of these respects. This makes it possible to suppress the temperature rise of the smoothing capacitor 8.

[0037] (6) The cooling member 12 is positioned on at least one surface of the circuit body 9 and the laminated busbar 17. This improves the cooling effect.

[0038] (7) The smoothing capacitor 8 is positioned on the side opposite to the side adjacent to the circuit body 9 in the first connection section 4. This arrangement reduces the effect of heat generation from the semiconductor switching elements and the laminated busbar 17 in the circuit body 9 on the smoothing capacitor 8.

[0039] (8) The smoothing capacitor 8 is positioned on the side of the cooling member 12 opposite to the side facing the circuit body 9. This arrangement allows the smoothing capacitor 8 to be thermally separated from the circuit body 9 and actively cooled by contacting the cooling member 13, thereby suppressing temperature rise.

[0040] (9) The cooling member 12 is arranged on both sides of the circuit body 9, the relay section 22, the first connection section 4, and the second connection section 5. This increases the capacitance of the Y capacitor, which helps to reduce noise and suppress the temperature rise of the laminated busbar 17 and the circuit body 9.

[0041] It should be noted that the present invention is not limited to the embodiments described above, and various modifications and combinations of other configurations can be made without departing from the spirit of the invention. Furthermore, the present invention is not limited to having all the configurations described in the embodiments described above, and may also include configurations in which some of those configurations are omitted.

[0042] 1 Power converter 2 Input relay busbar 3 Output busbar 4 First connection section 5 Second connection section 6 Positive DC wiring layer 7 Negative DC wiring layer 8 Smoothing capacitor 8a Terminal 9 Circuit body 9a Circuit body terminal connection section 10 Housing 11 Refrigerant flow path 11a Refrigerant flow path inlet 11b Refrigerant flow path outlet 12 Cooling member 13 Upper cooling member 13a Extension section 14 Lower cooling member 15 Insulating substrate layer 16 AC busbar 17 Laminated busbar 18 First current path 19 Second current path 20 Motor 21 DC power supply 22 Relay section 22a First relay section 22b Second relay section 22c Third relay section 23 AC wiring layer

Claims

1. A power conversion device comprising: at least one circuit body that performs power conversion; a relay busbar connecting a power source and the circuit body; a smoothing capacitor connected in parallel with the circuit body and smoothing the power supplied from the relay busbar to the circuit body; a laminated busbar connecting the circuit body and the smoothing capacitor, formed by laminating a plurality of conductive members with an insulating layer in between; and a cooling member for cooling the circuit body and the laminated busbar, wherein the laminated busbar has a first connection portion connected to the smoothing capacitor and a second connection portion connected to the relay busbar, the first connection portion being located on one side of the circuit body and the second connection portion being located on the other side of the circuit body.

2. The power conversion device according to claim 1, wherein the thermal resistance from the relay busbar to the cooling member is smaller than the thermal resistance from the relay busbar to the smoothing capacitor.

3. The power conversion device according to claim 2, wherein in the laminated busbar, a DC wiring layer including the first connection portion and the second connection portion, an AC wiring layer, and the insulating layer are laminated together, and the circuit body is mounted on the laminated busbar.

4. The power conversion device according to claim 3, wherein the stacked busbar has at least one relay portion connecting the first connection portion and the second connection portion.

5. The power conversion device according to claim 4, wherein the relay portion has a surface area and cross-sectional area smaller than that of the second connection portion.

6. The power conversion device according to claim 3, wherein the cooling member is arranged on at least one surface of the circuit body and the laminated busbar.

7. The power conversion device according to claim 3, wherein the smoothing capacitor is located on the side opposite to the side adjacent to the circuit body in the first connection portion.

8. The power conversion device according to claim 3, wherein the smoothing capacitor is arranged on the cooling member on the side opposite to the side facing the circuit body.

9. The power conversion device according to claim 4, wherein the cooling member is arranged on both sides of the circuit body, the relay section, the first connection section, and the second connection section, respectively.

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