Discharge resistance circuit and power conversion device using the same

Abstract

To obtain a discharge resistance circuit that can discharge a smoothing capacitor within a predetermined time without damaging the smoothing capacitor while suppressing enlargement, and a power conversion device using the discharge resistance circuit.SOLUTION: A discharge resistance circuit includes a first connection part that is connected to a first electrode of a smoothing capacitor, a second connection part connected to a second electrode of the smoothing capacitor, and at least three or more resistor elements connected in series between the first connection part and the second connection part. One of or both the resistance element at a first end, which is the resistance element connected to the first connection part, and the resistance element at a second end, which is the resistance element connected to the second connection part, are particular resistor elements and a resistance value of the particular resistance elements is set smaller than an average of resistance values of the resistance elements other than the particular resistor element.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present application relates to a discharge resistor circuit and a power conversion device using the same. [Background technology]

[0002] Vehicles equipped with drive motors, such as hybrid vehicles (HVs), plug-in hybrid vehicles (PHVs, PHEVs), electric vehicles (EVs), and fuel cell vehicles (FCVs), are equipped with power conversion devices. A power conversion device is, for example, an inverter that converts DC power from a high-voltage (e.g., 400 V to 800 V) DC power source insulated from the vehicle body into AC power and supplies the converted AC power to the motor. The power conversion device includes a semiconductor module having a power conversion circuit, a smoothing capacitor that smooths the DC power, a bus bar that electrically connects the semiconductor module and the smoothing capacitor, a discharge resistor connected to the smoothing capacitor and discharging the smoothing capacitor within a predetermined time without damaging the smoothing capacitor, and a control circuit board that controls the operation of the semiconductor module. In HVs, PHVs, and PHEVs, a power conversion device is installed in the engine compartment in addition to the engine. Therefore, miniaturization has become an important performance indicator for power conversion devices for vehicles in recent years.

[0003] A discharge resistance circuit that is connected in parallel to a smoothing capacitor and discharges the charge stored in the smoothing capacitor has been disclosed (see, for example, Patent Document 1). In the discharge resistance circuit disclosed in Patent Document 1, a space is provided between the discharge resistor and the smoothing capacitor to protect the smoothing capacitor from heat generated by the discharge resistor that constitutes the discharge resistance circuit during discharge.

[0004] Also disclosed is a discharge resistor circuit configured by connecting in series a plurality of resistor elements (e.g., chip resistors) that are discharge resistors surface-mounted on a substrate (see, for example, Patent Document 2). Patent Document 2 describes, as a technique for suppressing heat generation from individual resistor elements, increasing the width of the substrate wiring that connects the resistor elements to each other to improve heat dissipation into the air, and setting large resistance values ​​for the resistor elements at both ends of the plurality of resistor elements connected in series so that losses are biased toward the resistor elements at both ends that are considered to have good heat dissipation properties. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 6919348 [Patent Document 2] Patent No. 5104923 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, a space is provided between the discharge resistor and the smoothing capacitor, thereby protecting the smoothing capacitor from heat generated by the discharge resistor. In Patent Document 2, the width of the board wiring is expanded to improve heat dissipation into the air, thereby suppressing heat generation by the discharge resistor and protecting the smoothing capacitor from heat generated by the discharge resistor. However, from the perspective of miniaturization, the discharge resistor is surface-mounted in an extremely limited area on the control circuit board, for example, as three or more chip resistors in series, and only very limited space can be secured between the control circuit board and the smoothing capacitor. Therefore, securing space as in Patent Document 1 and expanding the width of the board wiring as in Patent Document 2 pose a problem of increasing the size of the discharge resistor circuit and the power conversion device using it.

[0007] Furthermore, because a large alternating current frequently flows through the busbar connecting the semiconductor module and the smoothing capacitor during the power conversion process, the busbar itself becomes a heat source. The heat generated in the busbar is transferred to the discharge resistors electrically connected to the busbar and to the control circuit board. The discharge resistors most affected by the heat generated in the busbar are the ones closest to the busbar among the series-connected discharge resistors. Therefore, the technique disclosed in Patent Document 2 concentrates losses in the discharge resistor closest to the busbar among the multiple series-connected discharge resistors, making it difficult to protect the smoothing capacitor from the heat of the busbar and the discharge resistors.

[0008] Therefore, the present application aims to provide a discharge resistance circuit that can discharge a smoothing capacitor within a predetermined time without damaging the smoothing capacitor while suppressing an increase in size, and a power conversion device using the same. [Means for solving the problem]

[0009] The discharge resistance circuit disclosed in the present application comprises a first connection portion connected to a first electrode of a smoothing capacitor, a second connection portion connected to a second electrode of the smoothing capacitor, and at least three or more resistance elements connected in series between the first connection portion and the second connection portion, wherein one or both of the resistance element at the first end, which is the resistance element connected to the first connection portion, and the resistance element at the second end, which is the resistance element connected to the second connection portion, are designated as specific resistance elements, and the resistance value of the specific resistance element is set to be smaller than the average resistance value of the other resistance elements excluding the specific resistance element.

[0010] The power conversion device disclosed in the present application comprises a discharge resistance circuit disclosed in the present application and a smoothing capacitor connected to a first connection portion and a second connection portion, wherein the discharge resistance circuit has a substrate having a first connection portion and a second connection portion, a resistance element is provided on the substrate, at least one resistance element is provided on one side of the substrate, and the smoothing capacitor is arranged on the other side of the substrate. [Effects of the Invention]

[0011] The discharge resistance circuit disclosed in the present application comprises a first connection portion connected to a first electrode of the smoothing capacitor, a second connection portion connected to a second electrode of the smoothing capacitor, and at least three or more resistance elements connected in series between the first connection portion and the second connection portion, and one or both of the resistance element at the first end, which is the resistance element connected to the first connection portion, and the resistance element at the second end, which is the resistance element connected to the second connection portion, are designated as specific resistance elements, and the resistance value of the specific resistance element is set to be smaller than the average resistance value of the other resistance elements excluding the specific resistance element.This makes it possible to suppress the temperature rise of the specific resistance element caused by the current when discharging the smoothing capacitor, and eliminates the need for measures to protect the smoothing capacitor from the heat of the specific resistance element.As a result, a discharge resistance circuit can be obtained that can discharge the smoothing capacitor within a predetermined time while suppressing an increase in size and without damaging the smoothing capacitor.

[0012] According to the power conversion device disclosed in the present application, the power conversion device comprises the discharge resistance circuit disclosed in the present application and a smoothing capacitor connected to a first connection portion and a second connection portion, wherein the discharge resistance circuit has a substrate having the first connection portion and the second connection portion provided thereon, and a resistive element is provided on the substrate, at least one resistive element is provided on one side of the substrate, and the smoothing capacitor is arranged on the other side of the substrate.Therefore, by providing the resistive element on the side of the substrate opposite to the side on which the smoothing capacitor is provided, the heat of the resistive element is less likely to be transmitted to the smoothing capacitor, and therefore the smoothing capacitor can be easily protected from the heat of the resistive element. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a configuration diagram showing an outline of a power conversion device according to a first embodiment. [Figure 2] 1 is a plan view showing an outline of a discharge resistance circuit of a power conversion device according to a first embodiment. [Figure 3] 3 is a diagram showing an example of the relationship between the position and resistance value of each resistor element in the discharge resistor circuit of the power converter according to the first embodiment. FIG. [Figure 4]5 is a diagram showing a specific example of the relationship between the resistance value of each resistor element and the temperature rise in the discharge resistor circuit of the power conversion device according to the first embodiment. FIG. [Figure 5] FIG. 10 is a plan view showing an outline of a discharge resistance circuit of a power conversion device according to a second embodiment. [Figure 6] 10 is a diagram showing an example of the relationship between the position and the resistance value of each resistor element in the discharge resistor circuit of the power converter according to the second embodiment. FIG. [Figure 7] FIG. 10 is a plan view showing an outline of a discharge resistance circuit of another power conversion device according to the second embodiment. [Figure 8] 8 is a cross-sectional view of another power converter taken along the line AA in FIG. 7. [Figure 9] FIG. 11 is a plan view showing an outline of a discharge resistance circuit of a power conversion device according to a third embodiment. [Figure 10] FIG. 10 is a plan view showing an outline of connections of the resistance elements of the discharge resistance circuit according to the fourth embodiment. [Figure 11] FIG. 10 is a diagram showing a specific example of the resistance value of each resistance element in the discharge resistance circuit according to the fourth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, a power conversion device according to an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same or equivalent members and parts are denoted by the same reference numerals.

[0015] Embodiment 1 Fig. 1 is a schematic configuration diagram of a power conversion device 1 according to embodiment 1, and is a side view with a portion of a housing 2 removed, Fig. 2 is a plan view showing an outline of a discharge resistance circuit 7 of the power conversion device 1, Fig. 3 is a diagram showing an example of the relationship between the position and resistance value of each resistance element in the discharge resistance circuit 7 of the power conversion device 1, and Fig. 4 is a diagram showing a specific example of the relationship between the resistance value and temperature rise of each resistance element in the discharge resistance circuit 7 of the power conversion device 1, together with a comparative example. The power conversion device 1 is a device that converts an input current from DC to AC, AC to DC, or an input voltage to a different voltage.

[0016] <Power conversion device 1> 1, the power conversion device 1 includes a semiconductor module 3 having a power conversion circuit, a smoothing capacitor 4 that smooths DC power and is connected in parallel to the semiconductor module 3, a pair of bus bars, namely a first bus bar 51 and a second bus bar 52, that electrically connect the semiconductor module 3 and the smoothing capacitor 4, a timing control unit 10 that is electrically connected to the semiconductor module 3 and is a control circuit that controls the operation of the semiconductor module 3, and a discharge resistance circuit 7 connected in parallel to the smoothing capacitor 4. The discharge resistance circuit 7 is connected to the first bus bar 51 and the second bus bar 52. The first bus bar 51 and the second bus bar 52 are made of, for example, copper, a metal material with low electrical resistivity and excellent conductivity. As shown in FIG. 2 , the discharge resistance circuit 7, the details of which will be described later, includes a first connection portion 81, a second connection portion 82, and at least three or more resistance elements connected in series between the first connection portion 81 and the second connection portion 82 (resistance elements 91, 92, 9N-1, and 9N are shown in FIG. 2 , but the resistance element between the resistance element 92 and the resistance element 9N-1 is omitted). In this embodiment, the discharge resistance circuit 7 includes a substrate 6 provided with the first connection portion 81 and the second connection portion 82, and the resistance elements are provided on the substrate 6. A timing control unit 10 is also provided on the substrate 6. A smoothing capacitor 4 is connected to the first connection portion 81 and the second connection portion 82. The power conversion device 1 in this embodiment is a device that converts DC power using a semiconductor module 3 and outputs AC power. Note that the configuration of the power conversion device 1 is not limited to this, and the power conversion device 1 may be a device that converts input current from AC to DC.

[0017] As shown in FIG. 1 , the power converter 1 further includes a housing 2 that houses a discharge resistor circuit 7, a smoothing capacitor 4, a semiconductor module 3, and a timing control unit 10, and a plurality of support posts 12 that are thermally connected to the housing 2 and that secure the substrate 6 to the housing 2. The housing 2 is an outer wall of the power converter 1 and functions to cool the entire power converter 1. The housing 2 is made of, for example, aluminum, which has excellent thermal conductivity, and has a cylindrical shape with a bottom. In this embodiment, the side of the housing 2 that opens from the bottom is defined as one side in the Z direction. The cooling function of the housing 2 is, for example, a flow path (not shown) through which a refrigerant flows, provided on the outside of the bottom surface of the housing 2. The cooling function is not limited to the refrigerant flow path, and may also be heat dissipation fins provided on the outer wall of the housing 2. The support posts 12 are made of, for example, stainless steel. While two support posts 12 are shown in FIG. 1 , at least five, typically ten, support posts 12 are provided to stably secure the substrate 6.

[0018] The timing control unit 10 controls the on / off of the semiconductor module 3. As shown in FIG. 2, in addition to the timing control unit 10, a power supply circuit unit 11 that generates an operating voltage for the timing control unit 10 is provided on the substrate 6. The timing control unit 10 and the power supply circuit unit 11 are arranged on the substrate 6 so as to surround the discharge resistance circuit 7 portion of the substrate 6. By providing the timing control unit 10 on the substrate 6, the timing control unit 10 is configured on the same substrate 6 as the discharge resistance circuit 7, thereby making it possible to reduce the size of the power conversion device 1. In this embodiment, the substrate 6 is arranged parallel to the X and Y directions shown in the figure. Note that FIG. 2 is a diagram showing the main parts of the substrate 6, and supports 12 that secure the substrate 6 are omitted.

[0019] <Comparative Example> Before describing the discharge resistance circuit 7, which is a main part of the present application, a comparative example of the discharge resistance circuit 7 will be described. The discharge resistance circuit of the comparative example is also connected to the first bus bar 51 and the second bus bar 52. In a typical discharge resistance circuit configuration, multiple resistance elements in the discharge resistance circuit are connected in series. The series-connected resistance elements are connected in parallel to a smoothing capacitor via the bus bar. A discharge current from the smoothing capacitor flows through the resistance element, and the charge accumulated in the smoothing capacitor is discharged. The smoothing capacitor is discharged within a predetermined time.

[0020] In the configuration of the comparative example of the present application, nine resistor elements, resistor element 91 to resistor element 99, are provided on the substrate, and the nine resistor elements are connected in series via the wiring pattern of the substrate. As shown in FIG. 4, all of the resistor elements have the same resistance value. Resistor element 91 is connected to the first bus bar 51 via the wiring pattern of the substrate, and resistor element 99 is connected to the second bus bar 52 via the wiring pattern of the substrate. Resistor element 91 is adjacent to the first bus bar 51, and resistor elements 92 and subsequent resistor elements are arranged in a row so as to be farther away from the first bus bar 51. Resistor element 99 is arranged furthest from the first bus bar 51 and the second bus bar 52. The arrangement of the resistor elements in the comparative example is the same as the arrangement of the resistor elements of the present application shown in FIG. 2.

[0021] The current discharging the smoothing capacitor 4 causes a uniform loss in all the resistance elements. Furthermore, losses occur in the first bus bar 51 due to the current flow associated with power conversion. These losses cause the temperature of each resistance element to rise slightly above the air temperature where the board is placed. Figure 4 shows the temperature rise values ​​for each resistance element. Comparing the magnitude of the temperature rise, the magnitude of the temperature rise is larger in resistance elements 91, 92, 93, and 94 adjacent to the first bus bar 51, which generates heat due to loss caused by current flow. The magnitude of the temperature rise is smaller in resistance elements 95 and after than in resistance elements 91, 92, 93, and 94.

[0022] If the temperature rise exceeds the heat resistance temperature of the resin that is the material of the board surface, it will be necessary to take measures such as reviewing the cooling structure of the first bus bar 51, increasing the mounting area of ​​the resistive element, and limiting the discharge current. In some cases, it will be necessary to take measures to protect the smoothing capacitor 4 from the heat of the first bus bar 51 and the resistive element. Taking these measures in the power conversion device 1 will increase the size of the power conversion device 1 and reduce the discharge performance of the smoothing capacitor 4.

[0023] <Discharge resistance circuit 7> The discharge resistance circuit 7, a key component of the present invention, will be described with reference to FIG. 2. The smoothing capacitor 4 shown in this embodiment is sealed with a resin material. As indicated by the dashed lines in FIG. 1, the smoothing capacitor 4 has a first electrode 4b and a second electrode 4c on both sides of its main body 4a. The discharge resistance circuit 7 includes a first connection portion 81 connected to the first electrode 4b of the smoothing capacitor 4, a second connection portion 82 connected to the second electrode 4c of the smoothing capacitor 4, and at least three or more resistor elements N (N is a natural number) connected in series between the first connection portion 81 and the second connection portion 82. The resistor element connected to the first connection portion 81 is referred to as the resistor element at the first end, and the resistor element connected to the second connection portion 82 is referred to as the resistor element at the second end. In FIG. 2, resistor elements 91 and 92 are designated in order from the closest to the first connection portion 81, and resistor elements 9N-1 and 9N are designated as the resistor elements furthest from the first connection portion 81. In FIG. 2, the resistive element 91 is the resistive element at the first end, and the resistive element 9N is the resistive element at the second end.

[0024] In this embodiment, the discharge resistor circuit 7 includes a substrate 6 having a first connection portion 81 and a second connection portion 82, and the resistor element is provided on the substrate 6. The resistor element at the first end and the first connection portion 81, the resistor elements, and the resistor element at the second end and the second connection portion 82 are connected by wiring patterns 13 provided on the substrate 6. The configuration is not limited to providing the resistor elements on the substrate 6, and the resistor elements may be connected by wires. When the resistor elements are provided on the substrate 6, the resistor element at the first end and the first connection portion 81, the resistor elements, and the resistor element at the second end and the second connection portion 82 can be easily connected by the wiring patterns 13, thereby improving the productivity of the discharge resistor circuit 7.

[0025] In this embodiment, the first connection portion 81 and the second connection portion 82 are through-holes that penetrate the substrate 6. The first bus bar 51 electrically connects the first electrode 4b of the smoothing capacitor 4 to a first through-hole, which is a through-hole in which the first connection portion 81 is formed. The second bus bar 52 electrically connects the second electrode 4c of the smoothing capacitor 4 to a second through-hole, which is a through-hole in which the second connection portion 82 is formed. The first connection portion 81 and the second connection portion 82 are not limited to through-holes and may be connectors provided on the substrate 6. By using through-holes for the first connection portion 81 and the second connection portion 82, the number of components in the discharge resistance circuit 7 can be reduced, thereby improving the productivity of the discharge resistance circuit 7. Furthermore, the discharge resistance circuit 7 can be made smaller.

[0026] In this embodiment, as shown in FIG. 1 , the first bus bar 51 has a first extension portion 51a extending from a main body of the first bus bar 51 in the thickness direction of the substrate 6. The second bus bar 52 has a second extension portion 52a extending from a main body of the second bus bar 52 in the thickness direction of the substrate 6. Since the substrate 6 is arranged parallel to the X and Y directions, the thickness direction of the substrate 6 corresponds to the Z direction. The first extension portion 51a and the second extension portion 52a extend in the Z direction. An end of the first extension portion 51a is electrically connected to the first through-hole, and an end of the second extension portion 52a is electrically connected to the second through-hole. The first extension portion 51a is formed, for example, by bending a portion of the first bus bar 51 in the Z direction, and the second extension portion 52a is formed, for example, by bending a portion of the second bus bar 52 in the Z direction. The method of electrically connecting the smoothing capacitor 4 and the resistor element does not necessarily need to be particularly limited. The connection between the smoothing capacitor 4 and the resistive element is not limited to the above-described configuration, and may be, for example, a connection using a connector and a harness. By electrically connecting the smoothing capacitor 4 and the resistive element using an extension extending in the thickness direction of the substrate 6 and a through-hole, the distance between the smoothing capacitor 4 and the resistive element is shortened, which makes it possible to prevent the power conversion device 1 from becoming larger.

[0027] At least one resistive element is provided on one surface of the substrate 6, and the smoothing capacitor 4 connected in parallel to the first connecting portion 81 and the second connecting portion 82 is disposed on the other surface of the substrate 6. In this embodiment, one surface of the substrate 6 is one surface of the substrate 6 in the Z direction, and the other surface of the substrate 6 is the other surface of the substrate 6 in the Z direction. In this embodiment, all resistive elements are provided on one surface of the substrate 6. By providing the resistive elements on the surface of the substrate 6 opposite to the side on which the smoothing capacitor 4 is provided, heat from the resistive elements is less likely to be transmitted to the smoothing capacitor 4, and therefore the smoothing capacitor 4 can be easily protected from the heat of the resistive elements.

[0028] In this embodiment, each of the resistive elements is a chip resistor of the same shape. The resistance value of each of the resistive elements is set by the resistance value of the corresponding chip resistor. The resistive elements are not limited to chip resistors of the same shape, but may be resistive elements having leads connected to the wiring pattern on the substrate 6. By using chip resistors of the same shape for the resistive elements, the substrate 6 can be made smaller, and therefore the discharge resistor circuit 7 can be made smaller. Furthermore, since the resistance value of each of the resistive elements is set by the resistance value of the corresponding chip resistor, the resistance value of the resistive element can be easily adjusted by replacing the chip resistor without changing the wiring pattern on the substrate 6.

[0029] One or both of the resistive element at the first end connected to the first connecting portion 81 and the resistive element at the second end connected to the second connecting portion 82 are designated as specific resistive elements, and the resistance value of the specific resistive element is set to be smaller than the average resistance value of the other resistive elements excluding the specific resistive element. The resistive element at the first end is connected to the first bus bar 51, and the resistive element at the second end is connected to the second bus bar 52. Therefore, the resistive element at the first end is easily affected by the heat of the first bus bar 51, which generates heat, and the resistive element at the second end is easily affected by the heat of the second bus bar 52, which generates heat. By designating one or both of the resistive element at the first end and the resistive element at the second end as specific resistive elements and setting the resistance value of the specific resistive element to be smaller than the average resistance value of the other resistive elements excluding the specific resistive element, it is possible to suppress a temperature rise in the specific resistive element caused by a current when the smoothing capacitor is discharged. Since measures to protect the smoothing capacitor 4 from the heat of the first bus bar 51, the second bus bar 52, and specific resistance elements are no longer necessary, a discharge resistance circuit 7 can be obtained that can discharge the smoothing capacitor 4 within a predetermined time without damaging the smoothing capacitor 4 while suppressing an increase in size.

[0030] A specific example of the setting of the specific resistive element will be described. The specific resistive element is the resistive element at the first end or the resistive element at the second end, which corresponds to the shorter of the length of the connection path from the first connection portion 81 to the resistive element at the first end and the length of the connection path from the second connection portion 82 to the resistive element at the second end. In FIG. 2, the length of the wiring pattern 13, which is the connection path from the first connection portion 81 to the resistive element at the first end, is shorter than the length of the wiring pattern 13, which is the connection path from the second connection portion 82 to the resistive element at the second end. In FIG. 2, the resistive element 91, which is the resistive element at the first end, is the specific resistive element. As shown in FIG. 3(d), the resistance value of the resistive element 91 is set to be smaller than the average resistance value of the other resistive elements (resistive element 92 to resistive element 9N) excluding the resistive element 91. The area surrounded by the dashed line in the figure indicates the average resistance value of all the resistive elements from the resistive element 92 to the resistive element 9N.

[0031] This configuration allows the resistance value of the resistor element 91 connected by a short wiring pattern 13, starting from the position of the through hole connected to the first bus bar 51 that generates heat, to be relatively smaller than the resistance value of the resistor element 9N connected by a long wiring pattern 13. This reduces loss in the resistor element 91 adjacent to the first bus bar 51 that generates heat, thereby suppressing the extent of temperature rise in the resistor element 91 located in a position most affected by the heat generated by the first bus bar 51. Meanwhile, because the wiring pattern 13 is long, the resistor element 9N is separated from the second bus bar 52 that generates heat, making the resistor element 9N less susceptible to the heat generated by the second bus bar 52. This eliminates the need for measures to protect the smoothing capacitor 4 from the heat of the first bus bar 51 and the resistor element 91. This eliminates the need for measures to protect the smoothing capacitor 4 from the heat of the first bus bar 51 and the resistor element 91, thereby achieving a discharge resistor circuit 7 that can discharge the smoothing capacitor 4 within a predetermined time without damaging the smoothing capacitor 4, while minimizing size. Furthermore, the use of a single specific resistor element makes it easier to set the resistance value of the specific resistor element, improving the productivity of the discharge resistor circuit 7.

[0032] An example of setting the resistance values ​​of each resistor element will be described. The resistance values ​​of each of the other resistor elements increase stepwise or continuously as the shortest connection path from a specific resistor element to the other resistor elements increases in length. In FIG. 3(a), the resistance values ​​of each of the other resistor elements increase continuously. In FIGS. 3(b) and 3(c), the resistance values ​​of each of the other resistor elements increase stepwise. This configuration can suppress the temperature rise of each resistor element caused by the current when discharging the smoothing capacitor 4 stepwise or continuously, thereby reliably protecting the smoothing capacitor 4 from the heat of the resistor elements. In either configuration, the combined resistance of all resistor elements, i.e., the total resistance value of resistor elements 91 to 9N, must be equal to or less than that when all resistor elements are configured with the same resistance value. When discharging the charge stored in the smoothing capacitor 4 using resistor elements connected in parallel to the smoothing capacitor 4, the discharge time is shorter if the resistance value of the resistor element is small, and conversely, the discharge time is longer if the resistance value of the resistor element is large. Therefore, for example, unless the resistance value is set to be equal to or less than the combined resistance value of the resistance elements shown in the comparative example, the configuration of the present application will not be able to complete discharge within the specified time determined in the comparative example.

[0033] 3(b), the resistor elements connected in series between the side with the shortest wiring pattern 13 to the first connection portion 81 and the side with the longest wiring pattern 13 to the second connection portion 82 are divided in half, and the resistance value of the resistor element on the side with the shortest wiring pattern 13 to the first connection portion 81 is set low, while the resistance value of the resistor element on the side with the longest wiring pattern 13 to the second connection portion 82 is set high. For example, the resistance value of the resistor element on the side with the shortest wiring pattern 13 to the first connection portion 81 is set 20% lower than the average resistance value of all the resistor elements, and the resistance value of the resistor element on the side with the longest wiring pattern 13 to the second connection portion 82 is set 20% higher than the average resistance value of all the resistor elements. Also, the example of FIG. 3(c) is set such that the resistance value of resistor element 91 with the shortest wiring pattern 13 to the first connection portion 81 is set lower than the average resistance value of all the resistor elements, and the resistance value of resistor element 9N with the longest wiring pattern 13 to the second connection portion 82 is set higher than the average resistance value of all the resistor elements.

[0034] 3(a) to 3(c), the resistance value configuration shown in FIG. 3(d) is achieved. Therefore, the loss generated in a specific resistive element having a short wiring pattern 13 between the first connecting portion 81 connected to the heat-generating first bus bar 51 can be made relatively smaller than the loss generated in resistive elements other than the specific resistive element. Examples of setting the resistance value of each resistive element are not limited to the configurations shown in FIGS. 3(a) to 3(c), and other configurations may be used as long as the resistance value configuration shown in FIG. 3(d) is achieved.

[0035] Based on the configuration of the first embodiment, a case where the temperature rise of each resistor element when nine resistor elements are connected in series is actually observed will be described with reference to FIG. 4 . The resistance values ​​of the nine resistor elements in the comparative example are all 33 kΩ. The resistance values ​​of the resistor elements in the example are 27 kΩ and 33 kΩ, which are approximately 20% smaller than 33 kΩ, and 39 kΩ, which is approximately 20% larger than 33 kΩ. Resistance element 91 is a specific resistor element, and the resistance values ​​of resistor elements 91, 92, and 93 are 27 kΩ, the resistance values ​​of resistor elements 94, 95, and 96 are 33 kΩ, and the resistance values ​​of resistor elements 97, 98, and 99 are 39 kΩ. The range of temperature rise is particularly small in resistor elements 91, 92, and 93 adjacent to first bus bar 51, where heat is generated due to loss caused by current flow. When the range of temperature rise is compared between the comparative example and the example, the range of temperature rise in the example is reduced by approximately 2 degrees.

[0036] On the other hand, the temperature rise increased in the resistor elements 97, 98, and 99, which are located farther from the first bus bar 51 that generates heat. Comparing the temperature rise in the comparative example and the example, the temperature rise increased by approximately 2 degrees in the example. This is due to the larger resistance values ​​of the resistor elements 97, 98, and 99. The temperature rise of the resistor elements 97, 98, and 99 is smaller than that of the resistor elements 91, 92, and 93, so this is not a problem. Looking only at the temperature rise in the example, the resistor elements 91, 92, and 93 are still about 3 to 4 degrees larger than the resistor elements 97, 98, and 99. Therefore, it is acceptable to adjust the resistance values ​​so that the resistance value relationship is greater and the temperature rise is similar for each resistor element. If the resistor elements are chip resistors of the same shape, this type of post-adjustment of the resistance value is easily possible, which has the advantage of eliminating the need to redesign the substrate 6.

[0037] The effects of this embodiment will be further described. The internal temperature of the on-board power conversion device 1, i.e., the temperature of the environment in which the board 6 is installed, can reach 100 degrees due to the vehicle's environment and heat generated by the semiconductor module 3. Printed circuit boards, which are widely used in on-board products and made of epoxy resin, have a heat resistance temperature of 125 degrees. Therefore, the allowable temperature rise for printed circuit boards is 20 to 25 degrees. Therefore, for components such as resistor elements that constantly generate heat at approximately 20 degrees, a technology that suppresses a temperature rise of 1 to 2 degrees is a factor that ultimately determines the quality of the power conversion device 1. In this embodiment, the resistance value of a specific resistor element is set smaller than the average resistance value of the other resistor elements excluding the specific resistor element. This allows for a discharge resistor circuit 7 that can discharge the smoothing capacitor 4 within a predetermined time, similar to the comparative example, while suppressing an increase in size and without damaging the smoothing capacitor 4.

[0038] As described above, the discharge resistance circuit 7 according to the first embodiment includes the first connection portion 81 connected to the first electrode 4b of the smoothing capacitor 4, the second connection portion 82 connected to the second electrode 4c of the smoothing capacitor 4, and at least three or more resistive elements connected in series between the first connection portion 81 and the second connection portion 82, where one or both of the resistive element at the first end, which is the resistive element connected to the first connection portion 81, and the resistive element at the second end, which is the resistive element connected to the second connection portion 82, are designated as specific resistive elements, and the resistance value of the specific resistive element is set to be smaller than the average resistance value of the other resistive elements excluding the specific resistive element. This makes it possible to suppress a temperature rise in the specific resistive element caused by a current when discharging the smoothing capacitor 4. Because a temperature rise in the specific resistive element caused by a current when discharging the smoothing capacitor 4 can be suppressed, measures to protect the smoothing capacitor 4 from the heat of the specific resistive element are not required. This makes it possible to obtain a discharge resistance circuit 7 that can discharge the smoothing capacitor 4 within a predetermined time while suppressing an increase in size and without damaging the smoothing capacitor 4.

[0039] When the specific resistive element is the first end resistive element or the second end resistive element corresponding to the shorter of the length of the connection path from the first connecting portion 81 to the first end resistive element and the length of the connection path from the second connecting portion 82 to the second end resistive element, since there is only one specific resistive element, it is easy to set the resistance value of the specific resistive element, thereby improving the productivity of the discharge resistor circuit 7. Furthermore, when the resistance values ​​of the other resistive elements increase stepwise or continuously as the shortest connection path from the specific resistive element to the other resistive elements increases, it is possible to suppress stepwise or continuously the temperature rise of each resistive element caused by the current when discharging the smoothing capacitor, and therefore it is possible to reliably protect the smoothing capacitor 4 from the heat of the resistive elements.

[0040] If each of the resistive elements is a chip resistor of the same shape and the resistance value of each of the resistive elements is set by the resistance value of the chip resistor, the substrate 6 can be made smaller, and therefore the discharge resistor circuit 7 can be made smaller. Furthermore, the resistance value of the resistive element can be easily adjusted by replacing the chip resistor without changing the wiring pattern of the substrate 6. Furthermore, if the discharge resistor circuit 7 includes a substrate 6 having a first connecting portion 81 and a second connecting portion 82, the resistive elements are provided on the substrate 6, and the first connecting portion 81 and the second connecting portion 82 are through-holes that penetrate the substrate 6, the number of components of the discharge resistor circuit 7 can be reduced, thereby improving the productivity of the discharge resistor circuit 7. Furthermore, the discharge resistor circuit 7 can be made smaller.

[0041] In the power conversion device 1 according to embodiment 1, which is equipped with the discharge resistance circuit disclosed in the present application and a smoothing capacitor 4 connected to the first connection portion 81 and the second connection portion 82, and in which at least one resistive element is provided on one side of the substrate 6 and the smoothing capacitor 4 is arranged on the other side of the substrate 6, by providing the resistive element on the side of the substrate 6 opposite to the side on which the smoothing capacitor 4 is provided, the heat of the resistive element is less likely to be transmitted to the smoothing capacitor 4, and therefore the smoothing capacitor 4 can be easily protected from the heat of the resistive element.

[0042] When the power conversion device 1 includes a first bus bar 51 electrically connecting the first electrode 4b and the first through hole and a second bus bar 52 electrically connecting the second electrode 4c and the second through hole, the first bus bar 51 has a first extension portion 51a extending from the main body of the first bus bar 51 in the thickness direction of the substrate 6, and the second bus bar 52 has a second extension portion 52a extending from the main body of the second bus bar 52 in the thickness direction of the substrate 6, and the end of the first extension portion 51a is electrically connected to the first through hole and the end of the second extension portion 52a is electrically connected to the second through hole, the distance between the smoothing capacitor 4 and the resistive element is shortened, thereby preventing the power conversion device 1 from becoming larger. Furthermore, when the power conversion device 1 includes a semiconductor module 3 having a power conversion circuit and a timing control unit 10 that controls the operation of the semiconductor module 3, the smoothing capacitor 4 is connected in parallel to the semiconductor module 3, and the timing control unit 10 is provided on the substrate 6, the timing control unit 10 is configured on the same substrate 6 as the discharge resistance circuit 7, so the power conversion device 1 can be made smaller.

[0043] Embodiment 2 A discharge resistance circuit 7 and a power conversion device 1 according to embodiment 2 will be described. Fig. 5 is a plan view showing an outline of the discharge resistance circuit 7 of the power conversion device 1 according to embodiment 2, Fig. 6 is a diagram showing an example of the relationship between the position and resistance value of each resistance element in the discharge resistance circuit 7 of the power conversion device 1, Fig. 7 is a plan view showing an outline of the discharge resistance circuit 7 of another power conversion device 1 according to embodiment 2, and Fig. 8 is a cross-sectional view of another power conversion device 1 taken at the AA cross section position in Fig. 7. The discharge resistance circuit 7 of the power conversion device 1 according to embodiment 2 is configured such that both the resistance element at the first end and the resistance element at the second end are specific resistance elements.

[0044] In the first embodiment, the specific resistor element is the resistor element at the first end or the resistor element at the second end, whichever corresponds to the shorter of the length of the connection path from the first connection portion 81 to the resistor element at the first end and the length of the connection path from the second connection portion 82 to the resistor element at the second end. This is because the configuration of the first embodiment has the first connection portion 81 and the second connection portion 82 arranged adjacent to each other, and there is a significant difference in the length of the connection path from the first connection portion 81 to the resistor element at the first end and the length of the connection path from the second connection portion 82 to the resistor element at the second end. The first connection portion 81 and the second connection portion 82 are not necessarily arranged adjacent to each other. For example, as shown in FIG. 5, the first connection portion 81 and the second connection portion 82 may be spaced apart, and the first connection portion 81, the second connection portion 82, and the resistor element of the chip resistor may be arranged in a row. If there are restrictions on the arrangement of each component on the substrate 6 and it is not possible to provide a long wiring pattern 13 as shown in Figure 2 between the resistive element 9N, which is the resistive element at the second end, and the second connection portion 82, the arrangement will be as shown in Figure 5.

[0045] In the arrangement shown in FIG. 5 , the first connection portion 81 is close to the resistor element 91, which is the resistor element at the first end, but the second connection portion 82 is far away. Conversely, the second connection portion 82 is close to the resistor element 9N, but the first connection portion 81 is far away. In this configuration, there is no significant difference between the length of the connection path from the first connection portion 81 to the resistor element at the first end and the length of the connection path from the second connection portion 82 to the resistor element at the second end. An example of no significant difference is when the difference in the lengths of the two connection paths is within 10%. In this case, both the resistor element at the first end and the resistor element at the second end are designated as specific resistor elements. By designating both the resistor element at the first end and the resistor element at the second end as specific resistor elements and setting the resistance value of the specific resistor element to be smaller than the average resistance value of the other resistor elements excluding the specific resistor element, it is possible to suppress the temperature rise of the specific resistor element caused by the current when discharging the smoothing capacitor. Since measures to protect the smoothing capacitor 4 from the heat of the first bus bar 51, the second bus bar 52, and specific resistance elements are no longer necessary, a discharge resistance circuit 7 can be obtained that can discharge the smoothing capacitor 4 within a predetermined time without damaging the smoothing capacitor 4 while suppressing an increase in size.

[0046] An example of setting a specific resistive element will be described. FIG. 6(a) shows an example of setting resistance values ​​when N, the number of resistive elements, is an even number of 8. Because resistive elements 91 to 94 are close to the first connection portion 81, the resistance value of resistive element 91, which is a specific resistive element, is set to be smaller than the average resistance value of resistive elements 92 to 94. The area surrounded by a dashed line on the left side of FIG. 6(a) shows the average resistance value of all resistive elements 92 to 94. Because resistive elements 95 to 98 are close to the second connection portion 82, the resistance value of resistive element 98, which is a specific resistive element, is set to be smaller than the average resistance value of resistive elements 95 to 97. The area surrounded by a dashed line on the right side of FIG. 6(a) shows the average resistance value of all resistive elements 95 to 97. The resistance values ​​of the other resistive elements, which are the resistive elements in the area surrounded by the dashed line, increase stepwise or continuously, for example, as the shortest connection path from the specific resistive element to the other resistive elements becomes longer.

[0047] FIG. 6(b) shows an example of setting resistance values ​​when N, the number of resistor elements, is an odd number of 9. Because N is an odd number, resistor element 95, located in the center, is located at the farthest position from both first connection portion 81 and second connection portion 82. Therefore, resistor elements 91 to 95 are close to first connection portion 81, so the resistance value of resistor element 91, which is a specific resistor element, is set to be smaller than the average resistance value of resistor elements 92 to 95. Because resistor elements 95 to 99 are close to second connection portion 82, the resistance value of resistor element 99, which is a specific resistor element, is set to be smaller than the average resistance value of resistor elements 95 to 98. The area surrounded by a dashed line on the left side of FIG. 6(b) indicates the average value of all resistance values ​​of resistor elements 92 to 95, and the area surrounded by a dashed line on the right side of FIG. 6(b) indicates the average value of all resistance values ​​of resistor elements 95 to 98. The resistance values ​​of the other resistive elements in the area surrounded by the dashed line increase stepwise or continuously, for example, as the shortest connection path from a specific resistive element to the other resistive elements increases in length. In this case, the resistance value of resistive element 95 is the largest.

[0048] The resistive elements 94 and 95 in the configuration shown in FIG. 6(a) and the resistive element 95 in the configuration shown in FIG. 6(b) are located at positions farthest from the first connecting portion 81 and the second connecting portion 82. However, these resistive elements are subject to considerable thermal interference from both the first connecting portion 81 and the second connecting portion 82. Furthermore, the resistance values ​​of these resistive elements may be set to have the largest resistance values ​​among the other resistive elements. In such cases, these resistive elements are likely to experience the largest losses. The temperature rise of these resistive elements may be greater than the temperature rise of a specific resistive element to which a heat-generating bus bar is connected.

[0049] A configuration for reducing the temperature rise of a resistor element located far from both the first connection portion 81 and the second connection portion 82 will be described. The substrate 6 is fixed to the housing 2 by a plurality of support columns 12. Heat generated by the timing control portion 10 and the power supply circuit portion 11 provided on the substrate 6 is dissipated to the housing 2, which has a cooling function, via several support columns 12. At least one of the support columns 12 is an adjacent support column 12a disposed adjacent to a distant resistor element, which is a resistor element having the smallest difference between the length of the connection path from the first connection portion 81 and the length of the connection path from the second connection portion 82. In FIG. 5, the distant resistor element is 9N / 2. This configuration allows the heat of the distant resistor element, whose temperature rise may be larger than that of a specific resistor element, to be efficiently dissipated to the housing 2 via the adjacent support column 12a.

[0050] A configuration for further reducing the temperature rise of the resistor element located farthest from the first connection portion 81 and the second connection portion 82 will be described with reference to FIGS. 7 and 8. The substrate 6 is a multilayer substrate. The multilayer substrate has an additional wiring pattern 14 that is insulated from the resistor element and electrically connected to the adjacent support 12a. The additional wiring pattern 14 is provided on one or both of the outer surface and inner layer of the multilayer substrate and is arranged around the spaced-apart resistor element. In FIGS. 8 and 9, the resistor element 9N / 2 is the spaced-apart resistor element. As shown in FIG. 8, in this embodiment, the additional wiring pattern 14 is provided on both the outer surface and inner layer of the multilayer substrate. When the additional wiring pattern 14 is provided on both the outer surface and inner layer of the multilayer substrate, the two additional wiring patterns 14 are electrically and thermally connected by via holes 15. The potential of the adjacent support 12a and the additional wiring pattern 14 is ground. With this configuration, heat from the spaced-apart resistor element can be more efficiently dissipated to the housing 2 via the additional wiring pattern 14 and the adjacent support 12a.

[0051] The first bus bar 51 is disposed on the other side in the Z direction of the first connection portion 81, and the second bus bar 52 is disposed on the other side in the Z direction of the second connection portion 82. Furthermore, the smoothing capacitor 4 and the semiconductor module 3 are provided on the other side in the Z direction of the substrate 6. Therefore, there is little freedom in arranging the support posts 12, and it is often difficult to promote heat dissipation from the first bus bar 51 and the second bus bar 52 by arranging the support posts 12 around the first connection portion 81 and the second connection portion 82. When it is difficult to arrange the support posts 12, the technology of reducing loss in a specific resistance element, which is a feature of the present application, is particularly useful.

[0052] Embodiment 3 The discharge resistance circuit 7 of the power conversion device 1 according to embodiment 3 will be described. Fig. 9 is a plan view showing an outline of the discharge resistance circuit 7 of the power conversion device 1 according to embodiment 3. The discharge resistance circuit 7 of the power conversion device 1 according to embodiment 3 is configured such that both the resistance element at the first end and the resistance element at the second end are specific resistance elements.

[0053] In the configuration of the discharge resistance circuit 7 shown in FIG. 9, the first connection portion 81 and the second connection portion 82 are arranged adjacent to each other. The wiring pattern 13 is arranged in a U-shape, and multiple resistance elements are arranged along the wiring pattern 13 except for the bottom portion of the U. There is no significant difference in the length of the connection path from the first connection portion 81 to the resistance element at the first end and the length of the connection path from the second connection portion 82 to the resistance element at the second end. In such a case, as in the second embodiment, both the resistance element at the first end and the resistance element at the second end are designated as specific resistance elements.

[0054] This type of arrangement is used, for example, when the DC power supply connected to the smoothing capacitor 4 becomes even higher in voltage, and the number of resistor elements connected in series must be increased to reduce the voltage applied to each resistor element. This type of arrangement is also used when the board does not have enough area to arrange multiple resistor elements in a straight line. Even with this arrangement, it is possible to use specific resistor elements for both the resistor element at the first end and the resistor element at the second end. Because resistor elements 91 to 9N / 2 are close to the first connection 81, the resistance value of the specific resistor element, resistor element 91, is set to be smaller than the average resistance value of resistor elements 92 to 9N / 2. Because resistor elements 9N / 2+1 to 9N are close to the second connection 82, the resistance value of the specific resistor element, resistor element 9N, is set to be smaller than the average resistance value of resistor elements 9N / 2+1 to 9N-1.

[0055] In the configuration shown in FIG. 9 , all resistive elements are arranged only on one surface of the substrate 6 in the Z direction. The arrangement of the resistive elements is not limited to this; resistive elements may be arranged on both surfaces of the substrate 6. For example, resistive elements 91 to 9N / 2 may be arranged on one surface of the substrate 6 in the Z direction, and resistive elements 9N / 2+1 to 9N may be arranged on the other surface of the substrate 6 in the Z direction, with the bottom of the U-shape connected using via holes. However, with this arrangement, there is no shield between the resistive elements mounted on the side where the smoothing capacitor 4 is provided and the first and second bus bars to block the radiant heat from both. This makes it easier for the temperature of the resistive elements mounted on the side where the smoothing capacitor 4 is provided to rise. Therefore, as shown in FIG. 6 , it is desirable to arrange resistive elements only on one surface of the substrate 6 in the Z direction, not on the side where the smoothing capacitor 4 is provided.

[0056] Embodiment 4 The discharge resistance circuit 7 of the power conversion device 1 according to embodiment 4 will be described. Fig. 10 is a plan view showing an outline of the connection of each resistance element of the discharge resistance circuit 7 according to embodiment 4, with the first connection part and the second connection part omitted, and Fig. 11 is a diagram showing specific examples of the resistance value of each resistance element in the discharge resistance circuit 7 together with a comparative example. The discharge resistance circuit 7 of the power conversion device 1 according to embodiment 4 is configured such that each resistance element is a single chip resistor or a plurality of chip resistors connected in parallel.

[0057] In the above-described embodiment, the resistance value of each resistive element is set by changing the resistance value of the resistive element mounted on the substrate 6, and the range of temperature rise at each resistance value is controlled. In the present embodiment, chip resistors having the same resistance value are used, and the resistance value of each resistive element is set by the number of chip resistors.

[0058] Each resistive element is a single chip resistor or multiple chip resistors connected in parallel. Each of the multiple chip resistors has the same resistance value. The resistance value of a resistive element is set according to the number of chip resistors. Hereinafter, each resistive element consisting of multiple chip resistors will be referred to as a resistor set.

[0059] A comparative example of a discharge resistor circuit 7, in which each resistor set has the same resistance value, will be described using FIG. 10(b). One resistor set is composed of M chip resistors connected in parallel. N resistor sets are connected in series to form the discharge resistor circuit 7. In FIG. 10(b), each resistor set is connected in series in the Y direction. The resistance values ​​of each of resistor sets 101 to 10N are calculated using a synthesis formula for the M chip resistors. Therefore, if the resistance value of one chip resistor is R, the resistance value of each resistor set is R / M, and the synthesis resistance of the discharge resistor circuit 7 is expressed as N×R / M.

[0060] An example of the configuration of the discharge resistor circuit 7 of the present application will be described with reference to FIG. 10(a). In the configuration shown in FIG. 10(a), the chip resistor that was in the Mth row of the resistor set 10N in the configuration shown in FIG. 10(b) has been moved to the (M+1)th row of the resistor set 101. With this configuration, the resistance value of the resistor set 101 becomes R / (M+1), which is smaller than the resistance value R / M of the resistor set 101 of the comparative example. Furthermore, the resistance value of the resistor set 10N becomes R / (M-1), which is larger than the combined resistance of the resistor sets 10N of the comparative example. In FIG. 10(a), the minimum number of chip resistors in one resistor set is M-1, but the minimum number of chip resistors in one resistor set may be just one.

[0061] In the manufacturing process of a power converter, it is generally considered better to use fewer types of components in the power converter for ease of management. The configuration shown in this embodiment makes it possible to obtain a discharge resistor circuit 7 that can discharge the smoothing capacitor 4 within a predetermined time without increasing the total number of chip resistors, using chip resistors of one type of resistance value, while suppressing size increase and without damaging the smoothing capacitor 4. Furthermore, since the resistance value of the chip resistors is one type, management of the chip resistors is easy, thereby improving the productivity of the discharge resistor circuit 7 and the power converter 1. The configuration shown in this embodiment can thus be said to be a highly practical embodiment.

[0062] The resistance values ​​of each resistor set (hereinafter referred to as "set resistance values") when nine resistor sets are connected in series for the example of the fourth embodiment and the comparative example will be described with reference to FIG. 11. The resistance value of one chip resistor in the comparative example is 36 kΩ, and the resistance value of one chip resistor in the example of the fourth embodiment is 33 kΩ. This is to make the overall resistance value of the discharge resistor circuit 7 uniform. The number of chip resistors in each resistor set in the comparative example is three. The example of the fourth embodiment is configured by moving the third column of resistor sets 107 to 109 in the comparative example to the fourth column of resistor sets 101 to 103. With this configuration, the set resistance values ​​of resistor sets 101 to 103 in the example of the fourth embodiment are approximately 30% smaller than the set resistance values ​​in the comparative example. Furthermore, the set resistance values ​​of resistor sets 107 to 109 in the example of the fourth embodiment are approximately 40% larger than the set resistance values ​​in the comparative example. Therefore, in the example of the fourth embodiment, the loss from resistor set 101 to resistor set 103 becomes smaller, and accordingly the range of temperature rise from resistor set 101 to resistor set 103 becomes smaller.

[0063] Furthermore, although the present application describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to application to a particular embodiment, but may be applied to the embodiments alone or in various combinations. Therefore, countless variations not illustrated are conceivable within the scope of the technology disclosed in the present specification, including, for example, cases where at least one component is modified, added, or omitted, and cases where at least one component is extracted and combined with components of another embodiment.

[0064] Various aspects of the present disclosure are summarized below as appendices. (Appendix 1) a first connection part connected to a first electrode of a smoothing capacitor, and a second connection part connected to a second electrode of the smoothing capacitor; at least three resistor elements connected in series between the first connection portion and the second connection portion, A discharge resistance circuit in which one or both of the resistance element at the first end, which is the resistance element connected to the first connection part, and the resistance element at the second end, which is the resistance element connected to the second connection part, are set as specific resistance elements, and the resistance value of the specific resistance element is set to be smaller than the average resistance value of the other resistance elements excluding the specific resistance element. (Appendix 2) The specific resistive element is the resistive element at the first end or the resistive element at the second end, which corresponds to the shorter of the length of the connection path from the first connection portion to the resistive element at the first end and the length of the connection path from the second connection portion to the resistive element at the second end. (Appendix 3) 3. The discharge resistance circuit according to claim 1, wherein the resistance value of each of the other resistance elements increases stepwise or continuously as the shortest connection path from the specific resistance element to the other resistance element becomes longer. (Appendix 4) each of the resistor elements is a chip resistor of the same shape; 4. The discharge resistance circuit according to claim 1, wherein the resistance value of each of the resistor elements is set by the resistance value of each of the chip resistors. (Appendix 5) Each of the resistive elements is a single chip resistor or a plurality of chip resistors connected in parallel, each of the plurality of chip resistors has the same resistance value; 4. The discharge resistor circuit according to claim 1, wherein the resistance value of the resistor element is set depending on the number of the chip resistors. (Appendix 6) a substrate having the first connection portion and the second connection portion; the resistor element is provided on the substrate, the resistor element at the first end and the first connection portion, the resistor elements, and the resistor element at the second end and the second connection portion are connected by wiring patterns provided on the substrate; 6. The discharge resistor circuit according to claim 1, wherein the first connection portion and the second connection portion are through holes that penetrate the substrate. (Appendix 7) A discharge resistor circuit according to any one of appendices 1 to 5; a smoothing capacitor connected to the first connection portion and the second connection portion, the discharge resistance circuit includes a substrate on which the first connection portion and the second connection portion are provided, the resistor element is provided on the substrate, At least one of the resistor elements is provided on one surface of the substrate, The smoothing capacitor is disposed on the other surface of the substrate. (Appendix 8) A discharge resistor circuit as described in Appendix 6; A smoothing capacitor; a first bus bar electrically connecting a first electrode of the smoothing capacitor and a first through-hole that is the through-hole forming the first connection portion; a second bus bar electrically connecting a second electrode of the smoothing capacitor and a second through-hole that is the through-hole forming the second connection portion, the first bus bar has a first extension portion that extends from a main body portion of the first bus bar in a thickness direction of the substrate, the second bus bar has a second extension portion that extends from a main body portion of the second bus bar in a thickness direction of the substrate, A power conversion device in which an end of the first extension portion and the first through hole are electrically connected, and an end of the second extension portion and the second through hole are electrically connected. (Appendix 9) a semiconductor module having a power conversion circuit; a control circuit for controlling the operation of the semiconductor module; the smoothing capacitor is connected in parallel to the semiconductor module; 9. The power conversion device according to claim 7, wherein the control circuit is provided on the substrate. (Appendix 10) a housing that accommodates the discharge resistance circuit, the smoothing capacitor, the semiconductor module, and the control circuit; a plurality of support posts thermally connected to the housing and fixing the substrate to the housing; The power conversion device described in Appendix 9, wherein at least one of the pillars is an adjacent pillar arranged adjacent to a separation resistance element, which is the resistance element for which the difference between the length of the connection path from the first connection portion and the length of the connection path from the second connection portion is smallest. (Appendix 11) the substrate is a multilayer substrate, the multilayer substrate has an additional wiring pattern insulated from the resistor element and electrically connected to the adjacent support pillars; 11. The power conversion device according to claim 10, wherein the additional wiring pattern is provided on one or both of an outer surface and an inner layer of the multilayer substrate and is arranged around the spacing resistive element. [Explanation of symbols]

[0065] REFERENCE SIGNS LIST 1 power conversion device, 2 housing, 3 semiconductor module, 4 smoothing capacitor, 4a main body, 4b first electrode, 4c second electrode, 51 first bus bar, 51a first extension, 52 second bus bar, 52a second extension, 6 substrate, 7 discharge resistor circuit, 81 first connection portion, 82 second connection portion, 91, 92, 94, 95, 97, 98, 99, 9N / 2, 9N-1, 9N resistor element, 10 timing control section, 11 power supply circuit section, 12 support, 12a adjacent support, 13 wiring pattern, 14 additional wiring pattern, 15 via hole, 101, 103, 107, 109, 10N resistor set

Claims

1. a first connection part connected to a first electrode of a smoothing capacitor, and a second connection part connected to a second electrode of the smoothing capacitor; at least three resistor elements connected in series between the first connection portion and the second connection portion, A discharge resistance circuit in which one or both of the resistance element at the first end, which is the resistance element connected to the first connection portion, and the resistance element at the second end, which is the resistance element connected to the second connection portion, are set as specific resistance elements, and the resistance value of the specific resistance element is set to be smaller than the average resistance value of the other resistance elements excluding the specific resistance element.

2. 2. The discharge resistor circuit according to claim 1, wherein the specific resistor element is the resistor element at the first end or the resistor element at the second end, which corresponds to the shorter of the length of the connection path from the first connection portion to the resistor element at the first end and the length of the connection path from the second connection portion to the resistor element at the second end.

3. 3. The discharge resistance circuit according to claim 2, wherein the resistance value of each of the other resistance elements increases stepwise or continuously as the shortest connection path from the specific resistance element to the other resistance element increases in length.

4. each of the resistor elements is a chip resistor of the same shape; 2. The discharge resistor circuit according to claim 1, wherein the resistance value of each of the resistor elements is set by the resistance value of each of the chip resistors.

5. Each of the resistive elements is a single chip resistor or a plurality of chip resistors connected in parallel, each of the plurality of chip resistors has the same resistance value; 2. The discharge resistor circuit according to claim 1, wherein the resistance value of the resistor element is set depending on the number of the chip resistors.

6. a substrate having the first connection portion and the second connection portion; the resistor element is provided on the substrate, the resistor element at the first end and the first connection portion, the resistor elements, and the resistor element at the second end and the second connection portion are connected by wiring patterns provided on the substrate; The discharge resistor circuit according to claim 1 , wherein the first connection portion and the second connection portion are through holes that penetrate the substrate.

7. a discharge resistor circuit according to claim 1; a smoothing capacitor connected to the first connection portion and the second connection portion, the discharge resistance circuit includes a substrate on which the first connection portion and the second connection portion are provided, the resistor element is provided on the substrate, At least one of the resistor elements is provided on one surface of the substrate, The smoothing capacitor is disposed on the other surface of the substrate.

8. a discharge resistor circuit according to claim 6; A smoothing capacitor; a first bus bar electrically connecting a first electrode of the smoothing capacitor and a first through-hole that is the through-hole forming the first connection portion; a second bus bar electrically connecting a second electrode of the smoothing capacitor and a second through-hole that is the through-hole in which the second connection portion is formed, the first bus bar has a first extension portion that extends from a main body portion of the first bus bar in a thickness direction of the substrate, the second bus bar has a second extension portion that extends from a main body portion of the second bus bar in a thickness direction of the substrate, A power conversion device in which an end of the first extension portion and the first through hole are electrically connected, and an end of the second extension portion and the second through hole are electrically connected.

9. a semiconductor module having a power conversion circuit; a control circuit for controlling the operation of the semiconductor module; the smoothing capacitor is connected in parallel to the semiconductor module; The power conversion device according to claim 7 , wherein the control circuit is provided on the substrate.

10. a housing that accommodates the discharge resistance circuit, the smoothing capacitor, the semiconductor module, and the control circuit; a plurality of support posts thermally connected to the housing and fixing the substrate to the housing; 10. The power conversion device according to claim 9, wherein at least one of the pillars is an adjacent pillar arranged adjacent to a separation resistance element, which is the resistance element for which the difference between the length of the connection path from the first connection portion and the length of the connection path from the second connection portion is smallest.

11. the substrate is a multilayer substrate, the multilayer substrate has an additional wiring pattern insulated from the resistor element and electrically connected to the adjacent support pillars; The power conversion device according to claim 10 , wherein the additional wiring pattern is provided on one or both of an outer surface and an inner layer of the multilayer substrate, and is arranged around the spacing resistive element.

Images