Power conversion device
The power conversion device addresses temperature rise in discharge circuits by arranging identical resistive elements with varying spacings to evenly distribute heat, ensuring consistent performance and cost-effectiveness.
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- MITSUBISHI ELECTRIC MOBILITY CORP
- Filing Date
- 2024-12-09
- Publication Date
- 2026-06-18
Smart Images
Figure JP2024043382_18062026_PF_FP_ABST
Abstract
Description
Power conversion device 【0001】 This application relates to a power conversion device. 【0002】 Power conversion devices are installed in electrified vehicles such as hybrid vehicles (HV), plug-in hybrid vehicles (PHV, PHEV), electric vehicles (EV), and fuel cell vehicles (FCV). The power conversion device is, for example, an inverter that drives a drive motor, converts the DC power of a DC power source insulated from the vehicle body into AC power, and supplies the converted AC power to the motor. In HV, PHV, and PHEV, since the power conversion device is installed in the engine room in addition to the engine, downsizing is one of the important performance indicators for recent vehicle power conversion devices. 【0003】 The power conversion device includes a semiconductor module having a power conversion circuit, a smoothing capacitor that smooths the voltage of the DC power source, a bus bar that electrically connects the semiconductor module and the smoothing capacitor, a discharge circuit that discharges the smoothing capacitor within a predetermined time, and a control circuit board that controls the operation of the semiconductor module. Since the discharge circuit is connected in parallel to the smoothing capacitor and a high voltage of 400 V to 800 V is constantly applied, heat generation due to loss in the resistor has become a problem. 【0004】 In order to suppress the temperature rise of the resistor in the discharge circuit, for example, in Patent Document 1, in an electronic device including a discharge circuit composed of at least three or more resistors connected in series, the resistance value of the resistor arranged other than both ends is smaller than the resistance value of the resistor arranged at both ends, and is set to decrease toward the center of the column. According to such a configuration, it is possible to increase the loss of the resistors at both ends that are easily heat-dissipated and reduce the loss of the resistors other than both ends that are likely to increase in temperature due to heat received from adjacent resistors, so that the temperature rise can be suppressed. 【0005】 Japanese Patent No. 5104923 【0006】However, when using two or more types of resistors, as in Patent Document 1, from the perspective of long-term reliability, each resistor will exhibit different resistance change behavior due to aging degradation, causing the loss distribution to change and resulting in an unexpected distribution, which may worsen the heat generation of the discharge circuit. In addition, increasing the number of types of resistors used leads to problems such as increased complexity in parts procurement and increased man-hours for inventory management. 【0007】 This application discloses technology to solve the above-mentioned problems, and aims to provide a power conversion device that can suppress the temperature rise of the discharge circuit while preventing the device from becoming larger. 【0008】 The power conversion device disclosed herein comprises a smoothing capacitor for smoothing the voltage of a DC power supply and a discharge circuit for discharging the charge stored in the smoothing capacitor, wherein the discharge circuit has a plurality of identical resistive elements spaced apart from each other on a mounting surface, and for at least some of the resistive elements, the spacing between adjacent resistive elements widens or narrows as it approaches a specific position. 【0009】 According to the power conversion device disclosed herein, in a discharge circuit having multiple identical resistive elements, the heat generated by the multiple resistive elements is dispersed and equalized by increasing or decreasing the spacing between adjacent resistive elements as one approaches a specific position. This makes it possible to suppress the temperature rise of the discharge circuit without increasing the size of the device. Furthermore, by using identical resistive elements, each resistive element exhibits the same resistance change behavior, so even after long-term use, the loss distribution does not change from the initial design, and the temperature rise of the discharge circuit can be suppressed over the long term. Other objectives, features, viewpoints, and effects of this application will become clearer from the following detailed description with reference to the drawings. 【0010】This is a circuit diagram of a power converter according to Embodiment 1. This diagram illustrates the arrangement method of resistive elements in the discharge circuit of a power converter according to Embodiment 1. This is a plan view showing an example of resistive element arrangement in the discharge circuit of a power converter according to Embodiment 1. This is a plan view showing the arrangement of resistive elements in the discharge circuit of a power converter according to a comparative example. This diagram shows specific examples of the temperature of resistive elements in the discharge circuits of Embodiment 1 and the comparative example. This diagram shows the maximum and minimum temperatures of resistive elements in the discharge circuits of Embodiment 1 and the comparative example. This diagram illustrates the arrangement method of resistive elements in the discharge circuit of a power converter according to Embodiment 2. This diagram illustrates the arrangement method of resistive elements in the discharge circuit of a power converter according to Embodiment 2. This is a plan view showing an example of resistive element arrangement in the discharge circuit of a power converter according to Embodiment 2. This diagram illustrates the arrangement method of resistive elements in the discharge circuit of a power converter according to Embodiment 3. This diagram illustrates the arrangement method of resistive elements in the discharge circuit of a power converter according to Embodiment 3. This is a plan view showing an example of resistive element arrangement in the discharge circuit of a power converter according to Embodiment 3. This is a plan view showing the first wiring layer and the layers below the second wiring layer of the multilayer wiring board of a power converter according to Embodiment 4. This is a cross-sectional view showing a multilayer wiring board of a power conversion device according to Embodiment 4. 【0011】 Embodiment 1. The power conversion device according to Embodiment 1 will be described below with reference to the drawings. Figure 1 is a schematic circuit diagram of the power conversion device according to Embodiment 1, Figure 2 is a diagram illustrating the arrangement method of resistive elements in the discharge circuit of the power conversion device according to Embodiment 1, and Figure 3 is a plan view showing an example of the arrangement of resistive elements in the discharge circuit of the power conversion device according to Embodiment 1. In each figure, the same or corresponding parts are denoted by the same reference numerals. 【0012】As shown in Figure 1, the power conversion device 1 according to Embodiment 1 includes a DC power supply 100, a smoothing capacitor 200, a discharge circuit 300, a driver circuit 410, a three-phase inverter circuit including a U-phase leg 401, a V-phase leg 402, and a W-phase leg 403, and a three-phase AC motor 500. Note that the DC power supply 100, the driver circuit 410, and the three-phase AC motor 500 are the same as conventional ones and are not directly related to this disclosure, so their explanation is omitted here. 【0013】 The multilayer wiring board 2 is one of the components that make up the power conversion device 1, and is a board necessary for operating or assisting the power conversion device 1. The multilayer wiring board 2 has a driver circuit 410 that drives switching elements, a discharge circuit 300 that discharges the charge stored in the smoothing capacitor 200, and circuits such as a voltage sensor and a current sensor (not shown) mounted on it. 【0014】 A smoothing capacitor 200, which smooths the voltage of the DC power supply 100, is connected in parallel with the DC power supply 100. A three-phase inverter circuit, including a U-phase leg 401, a V-phase leg 402, and a W-phase leg 403, is connected downstream of the smoothing capacitor 200, and a three-phase AC motor 500 is connected downstream of that. The three-phase inverter circuit converts the high voltage smoothed by the smoothing capacitor 200 into a three-phase AC voltage and supplies it to the three-phase AC motor 500 for vehicle drive. 【0015】 The U-phase leg 401 has switching elements 401a and 401b as switching elements for the upper and lower arms. Similarly, the V-phase leg 402 has switching elements 402a and 402b, and the W-phase leg 403 has switching elements 403a and 403b. In each leg, the switching elements of the upper arm and the lower arm are connected in series. 【0016】Switching elements such as IGBTs (Insulated Gate Bipolar Transistors) or MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors) are used. In Figure 1, a MOSFET is shown. These switching elements are controlled to be turned on and off in a predetermined sequence to generate a three-phase alternating current, enabling the driving of the three-phase AC motor 500. 【0017】 The smoothing capacitor 200 accumulates charge when the power converter 1 is in operation, and remains charged even when not in operation. The charge accumulated in the smoothing capacitor 200 is discharged by the discharge circuit 300. The discharge of the smoothing capacitor 200 is carried out so as to be completed within a predetermined time. 【0018】 The discharge circuit 300 is composed of several to tens of resistive elements in multiple series and multiple parallel configurations, and a loss of approximately 0.1W is constantly occurring. The discharge circuit 300 according to this embodiment 1 has a plurality of identical resistive elements arranged at intervals from each other in the arrangement area on the arrangement surface 2a (see Figure 14) of the multilayer wiring board 2. Identical resistive elements 31 are, in other words, of the same type, shape, and size, and have the same characteristics. 【0019】 The basic arrangement method of resistive elements in the discharge circuit according to Embodiment 1 will be explained with reference to Figure 2. The discharge circuit has at least four identical resistive elements 31a, 31b, 31c, and 31d (collectively referred to as resistive elements 31), and these resistive elements 31 are connected in series or parallel by a wiring pattern (not shown) formed on the arrangement surface 2a. In the discharge circuit, the spacing between adjacent resistive elements 31 becomes wider or narrower as one approaches a specific position. 【0020】In this embodiment 1, the specific position is the center position of the arrangement region 3 of the resistive elements 31 (indicated as C in Figure 2), and the spacing between adjacent resistive elements 31 widens as you move from both ends 3e of the arrangement region 3 towards the center position C. When there are four resistive elements 31, the spacing between adjacent resistive elements 31 (S1, S2, S3 in Figure 2) is wider on the side of the center position C (S2) than on the sides of both ends 3e of the arrangement region 3 (S1, S3) (S1 < S2, S3 < S2). 【0021】 In this embodiment 1, the intervals S1, S2, and S3 between adjacent resistive elements 31 are determined so that the temperature difference between multiple resistive elements 31 is reduced compared to the case where resistive elements are arranged at equal intervals in an arrangement region 3 of the same area. 【0022】 For comparison, consider the temperature of each resistor 31 when four resistors 31 are arranged at equal intervals (S1=S2=S3) in the arrangement region 3 shown in Figure 2. The resistors 31a and 31d, which are placed on both ends 3e of the arrangement region 3, dissipate heat easily and their temperature rises relatively slowly. However, the resistors 31b and 31c, which are placed on the side of the center C, do not dissipate heat easily and their temperature rises easily due to heat absorption from adjacent resistors 31a and 31c (or 31b and 31d). 【0023】 Therefore, when the four resistive elements 31 are arranged at equal intervals, the temperatures of the resistive elements 31b and 31c located on the side of the center position C will be higher than the temperatures of the resistive elements 31a and 31d located on the sides of both ends 3e, resulting in a temperature difference (let's call this ΔT1) between the four resistive elements 31. 【0024】 Therefore, in this embodiment 1, the spacing S1, S2, and S3 between the resistive elements 31 are determined such that, compared to the case of equally spaced arrangement, the temperature of the resistive elements 31a and 31d on both ends 3e is higher, and the temperature of the resistive elements 31b and 31c on the center position C is lower. In other words, when the temperature difference between the four resistive elements 31 is ΔT2, the spacing S1, S2, and S3 between the resistive elements 31 are determined such that ΔT2 is smaller than ΔT1. 【0025】A specific example of the arrangement of resistive elements in the discharge circuit 300 according to Embodiment 1 will be explained with reference to Figure 3. Figure 4 shows the arrangement of resistive elements in the discharge circuit of a power converter according to a comparative example. In Figures 3 and 4, the Z direction indicates the thickness direction of the multilayer wiring board 2, and the arrangement area is on the XY plane. Also, in Figures 3 and 4, the vertical arrow A indicates the series direction, and the horizontal arrow B indicates the parallel direction. 【0026】 As shown in Figure 3, the discharge circuit 300 has a total of 40 resistor elements 301 to 340 arranged in 10 series and 4 parallel in the arrangement area 3. These resistor elements 301 to 340 are identical chip resistors ranging from a few kΩ to several tens of kΩ. The resistor elements 301 to 340 are arranged in four columns in the series direction indicated by arrow A and in ten rows in the parallel direction indicated by arrow B. 【0027】 For example, in Figure 3, the resistors 301 to 310 in the leftmost column are connected in series by a wiring pattern (not shown). Also, the resistors 303, 313, 323, and 333 in the third row from the top in Figure 3 are connected in parallel by a wiring pattern. The other rows and columns are similarly connected by wiring patterns. 【0028】 In the resistive elements 301 to 340, the spacing between adjacent resistive elements increases as you move from both ends of the arrangement region 3 towards the center position C. In Figure 3, both ends of the arrangement region 3 include both ends in the series direction and both ends in the parallel direction. 【0029】 Furthermore, the resistive elements 301 to 340 are arranged in a matrix, and the spacing between adjacent resistive elements in each column increases as you move from the ends of the column towards the center, and the spacing between adjacent resistive elements in each row increases as you move from the ends of the row towards the center. 【0030】Taking the rightmost column in Figure 3 as an example, the spacing between adjacent resistive elements gradually increases as you move from both ends of the column (top end E1, bottom end E2) towards the center C1 of the column. For resistive elements 335 to 340 included in the same column, if we let S4 be the spacing between resistive elements 335 and 336 closest to the center C1, S8 be the spacing between resistive element 340 closest to the bottom end E2 and its adjacent resistive element 339, and S5, S6, and S7 from top to bottom, then S4 > S5 > S6 > S7 > S8. Furthermore, similarly for resistive elements 331 to 335 included in the same column, the spacing between adjacent resistive elements gradually increases as you move from the top end E1 of the column towards the center C1. 【0031】 Furthermore, taking the third row from the top in Figure 3 as an example, if we let S10 be the distance between resistors 313 and 323 closest to the center C2 of the row, and S9 be the distance between resistor 303 closest to the left end E3 of the same row and the adjacent resistor 313, then S10 > S9. Similarly, if we let S11 be the distance between resistor 333 closest to the right end E4 of the same row and the adjacent resistor 323, then S10 > S11. 【0032】 As shown in Figure 4, the comparative example discharge circuit 350 has a total of 40 resistor elements 301 to 340 arranged in a configuration area 3 with the same area as the discharge circuit 300 according to Embodiment 1, with 10 in series and 4 in parallel. In the comparative example, adjacent resistor elements are arranged at equal intervals in each column and row. In Figure 4, the distance between adjacent resistor elements in each column is a constant interval S12, and the distance between adjacent resistor elements in each row is a constant interval S13. 【0033】Figure 5 shows the results of measuring the temperature of each resistive element in the discharge circuits according to Embodiment 1 and the Comparative Example, and Figure 6 is an excerpt of the maximum and minimum temperatures from Figure 5. The resistance value and power consumption of the resistive elements used here are 68 kΩ / element and 0.1 W / element, respectively, and the overall resistance value and power consumption of the discharge circuits 300 and 350 are 170 kΩ and 4 W, respectively. In Figure 5, resistance temperature (A) is the temperature of each resistive element in the discharge circuit 350 according to the Comparative Example (see Figure 4), resistance temperature (B) is the temperature of each resistive element in the discharge circuit 300 according to Embodiment 1 (see Figure 3), and effect (B-A) shows the temperature difference between them. 【0034】 As shown in Figure 5, in the comparative example discharge circuit 350, the highest temperature was 91.8 degrees Celsius at the resistive element 316 located near the center of the arrangement region 3. In the first embodiment discharge circuit 300, the resistive element 316 was 89.8 degrees Celsius, which was 2.0 degrees lower than in the comparative example. Furthermore, the highest temperature in the discharge circuit 300 was 90.5 degrees Celsius at the resistive element 318, which was 1.3 degrees lower than the highest temperature in the comparative example. 【0035】 Furthermore, in the comparative example discharge circuit 350, the lowest temperature was 85.9 degrees Celsius at the resistive element 331 located near the corner of the arrangement area 3. In the first embodiment discharge circuit 300, the resistive element 331 was 86.5 degrees Celsius, which was 0.6 degrees higher than the comparative example. The lowest temperature in the discharge circuit 300 was 86.5 degrees Celsius at the resistive elements 331 and 340, which was 0.6 degrees higher than the lowest temperature in the comparative example. 【0036】 As in the comparative example discharge circuit 350, when resistive elements are arranged at equal intervals in each column (or row), the resistive elements near the center of each column (or row) tend to heat up more easily than the resistive elements at both ends, which dissipate heat more readily, because their heat interferes with each other. Therefore, in the discharge circuit 350, the temperature of the resistive elements increases as you move from both ends of each column (or row) towards the center. As shown in Figure 6, the difference between the highest and lowest temperatures (ΔT1) of the resistive elements in the discharge circuit 350 was 5.9 degrees. 【0037】In contrast, in the discharge circuit 300 according to Embodiment 1, the spacing between resistive elements near the center of each column (or row), where temperature rise is more likely, is widened, and the spacing between resistive elements near both ends is narrowed, so that the entire discharge circuit 300 generates heat evenly. As a result, as shown in Figure 6, the difference between the highest and lowest temperatures (ΔT2) of the resistive elements in the discharge circuit 300 was 4.0 degrees. 【0038】 Thus, in the discharge circuit 300 according to Embodiment 1, the maximum temperature of the resistive element is lower and the minimum temperature is higher compared to the discharge circuit 350 according to the comparative example. It was confirmed that the temperature difference ΔT2 between the maximum and minimum temperatures is 1.9 degrees lower than the temperature difference ΔT1 between the maximum and minimum temperatures in the comparative example. 【0039】 In Figure 3, for all the resistive elements 301 to 340 arranged in a matrix, the spacing between adjacent resistive elements widens as it approaches the center of each column (or row), which is a specific position. However, the arrangement of resistive elements in the discharge circuit 300 is not limited to this. It is sufficient that for at least some of the resistive elements, the spacing between adjacent resistive elements widens as it approaches the center of the arrangement area of some of the resistive elements. 【0040】 Furthermore, in Figure 3, for example, the resistors 331 to 335 and 336 to 340, which make up the rightmost column, are arranged symmetrically with respect to the column center C1, but they do not have to be symmetrical. Similarly, in Figure 3, the resistors 303, 313 and 323, 333, which make up the third row from the top, are arranged symmetrically with respect to the row center C2, but they do not have to be symmetrical. Also, the spacing between adjacent resistors may change gradually as shown in Figure 3, or it may change in steps, for example, S4 = S5 > S6 = S7 > S8. 【0041】As described above, according to the power conversion device 1 according to the first embodiment, in the discharge circuit 300 having a plurality of identical resistance elements arranged at intervals on the arrangement surface 2a, by widening or narrowing the interval between adjacent resistance elements as they approach a specific position, the heat generation of the plurality of resistance elements is dispersed and equalized. Therefore, without increasing the size of the discharge circuit 300, the temperature rise of the discharge circuit 300 can be suppressed. 【0042】 Further, by setting the specific position as the center position of the arrangement region of the resistance elements and widening the interval between adjacent resistance elements as they approach the center position from both ends of the arrangement region 3, the temperature difference between the resistance elements can be made smaller than when the resistance elements are arranged at equal intervals within the same arrangement region 3. Thereby, the heat generation of the plurality of resistance elements can be dispersed and equalized, and without increasing the size of the arrangement region 3, the temperature rise of the discharge circuit 300 can be suppressed. 【0043】 In addition, by using the same resistance elements, each resistance element exhibits the same resistance change behavior. Therefore, from the perspective of long-term reliability, the distribution of losses does not change from the initial design of suppressing the loss of the resistance elements in the central part and increasing the losses of the resistance elements at both ends, and the temperature rise of the discharge circuit 300 can be suppressed in the long term. 【0044】 Furthermore, by using only the same resistance elements, the trouble in purchasing the resistance elements can be saved, and the man-hours for inventory management can also be reduced. Therefore, costs such as material costs and labor costs can be reduced. From these facts, according to the first embodiment, it is possible to provide at a low cost a power conversion device 1 that can suppress the temperature rise of the discharge circuit 300 while preventing the device from becoming larger. 【0045】 Embodiment 2. FIGS. 7 and 8 are diagrams for explaining a method of arranging resistance elements in a discharge circuit of a power conversion device according to the second embodiment, and FIG. 9 is a plan view showing an arrangement example of resistance elements in a discharge circuit of a power conversion device according to the second embodiment. 【0046】The power conversion device according to Embodiment 2 has the same configuration as the power conversion device 1 according to Embodiment 1 except for the arrangement of the resistance elements in the discharge circuit, and thus the description thereof is omitted here. Further, the discharge circuit 300A according to Embodiment 2 has the same configuration as the discharge circuit 300 according to Embodiment 1 except for the arrangement of the resistance elements, and thus only the differences will be described. 【0047】 The basic arrangement method of the resistance elements in the discharge circuit according to Embodiment 2 will be described with reference to FIGS. 7 and 8. In FIG. 7, arrow A indicates the series direction, and in FIG. 8, arrow B indicates the parallel direction. The discharge circuit has at least three or more identical resistance elements in the arrangement region on the arrangement surface 2a (see FIG. 14) of the multilayer wiring board 2. 【0048】 In the example shown in FIG. 7, three resistance elements 32a, 32b, and 32c (collectively referred to as resistance element 32) are connected in series by a wiring pattern (not shown) to form a column L1. Further, in the example shown in FIG. 8, three resistance elements 33a, 33b, and 33c (collectively referred to as resistance element 33) are connected in parallel by a wiring pattern to form a row R1. 【0049】 In the discharge circuit, the interval between adjacent resistance elements becomes wider or narrower as it approaches a specific position. In the present Embodiment 2, the power conversion device includes a heat-generating component 6 that is a heat source, and the specific position is the heat-generating component 6. The resistance element on the side closer to the heat-generating component 6 is likely to have its temperature increased due to heat received from the heat-generating component 6. Therefore, the interval between adjacent resistance elements becomes wider as it approaches the heat-generating component 6. The heat-generating component 6 is, for example, a smoothing capacitor 200. 【0050】 When there are three resistance elements, the interval between adjacent resistance elements is wider on the side closer to the heat-generating component 6 than on the side farther from the heat-generating component 6. In FIG. 7, three resistance elements 32 are arranged in the series direction. When the interval between the resistance element 32a arranged at the position closest to the heat-generating component 6 and the adjacent resistance element 32b is S20, and the interval between the resistance element 32c arranged at the position farthest from the heat-generating component 6 and the adjacent resistance element 32b is S21, then S20 > S21. 【0051】Furthermore, in Figure 8, three resistors 33 are arranged in parallel. When the distance between resistor 33a, which is located closest to the heat-generating component 6, and the adjacent resistor 33b is S22, and the distance between resistor 33c, which is located furthest from the heat-generating component 6, and the adjacent resistor 33b is S23, then S22 > S23. 【0052】 A specific example of the arrangement of resistive elements in the discharge circuit 300A according to Embodiment 2 will be explained with reference to Figure 9. In Figure 9, the Z direction indicates the thickness direction of the multilayer wiring board 2, and the arrangement area is on the XY plane. Also in Figure 9, the vertical arrow A indicates the series direction, and the horizontal arrow B indicates the parallel direction. The multilayer wiring board on which the discharge circuit 300A is mounted is assembled into the housing 7 of the power converter, and the heat-generating components 6 are located inside the housing 7. 【0053】 The discharge circuit 300A, like the discharge circuit 300 according to Embodiment 1 above, has a total of 40 resistive elements 301 to 340 arranged in a matrix. The resistive elements 301 to 340 form four columns in the series direction and ten rows in the parallel direction. The spacing between adjacent resistive elements in each column widens as it approaches the heat-generating component 6, and the spacing between adjacent resistive elements in each row widens as it approaches the heat-generating component 6. 【0054】 In Figure 9, for example, in the rightmost column, if the distance between resistors 335 and 336, which are located closest to the heat-generating component 6, is S24, and the distance between resistor 340, which is located closest to the heat-generating component 6, and the adjacent resistor 339 is S28, and the distances between resistors 336, 337, 338, and 339 in between are S25, S26, and S27, then S24 > S25 > S26 > S27 > S28. Also, for resistors 331 to 335 in the same column, the distance between adjacent resistors gradually increases as they get closer to the heat-generating component 6. The same applies to the other columns. 【0055】Furthermore, in Figure 9, for example, in the bottom row, if the distance between the resistor element 340 located closest to the heat-generating component 6 and the adjacent resistor element 330 is S29, the distance between the resistor element 310 located furthest from the heat-generating component 6 and the adjacent resistor element 320 is S31, and the distance between resistor elements 320 and 330 in between is S30, then S29 > S30 > S31. The same applies to the other rows. 【0056】 In Figure 9, for example, the resistors 331 to 335 and 336 to 340 in the rightmost column are arranged symmetrically with respect to the center of the column, but they do not have to be symmetrical. Also, the spacing between adjacent resistors may change gradually as shown in Figure 9, or it may change in steps, for example, S24 = S25 > S26 = S27 > S28. 【0057】 Furthermore, in Figure 9, for all the resistive elements 301 to 340 arranged in a matrix, the spacing between adjacent resistive elements widens as they approach the heat-generating component 6, which is a specific location. However, the arrangement of resistive elements in the discharge circuit 300A is not limited to this. It is sufficient that for at least some of the resistive elements, the spacing between adjacent resistive elements widens as they approach the heat-generating component 6. 【0058】 According to the power conversion device of Embodiment 2, by designating a specific location as the heat-generating component 6 and increasing the spacing between adjacent resistive elements in the discharge circuit 300A as it approaches the heat-generating component 6, the temperature rise of resistive elements near the heat-generating component 6, which are prone to temperature rise, can be suppressed. This allows for the dispersion and equalization of heat generation from multiple resistive elements, making it possible to suppress the temperature rise of the discharge circuit 300A without increasing the size of the device. 【0059】 Embodiment 3. Figures 10 and 11 illustrate the arrangement method of resistive elements in the discharge circuit of the power conversion device according to Embodiment 3, and Figure 12 is a plan view showing an example of the arrangement of resistive elements in the discharge circuit of the power conversion device according to Embodiment 3. 【0060】The power conversion device according to Embodiment 3 has the same configuration as the power conversion device 1 according to Embodiment 1, except for the arrangement of the resistive elements in the discharge circuit, so its description will be omitted here. Furthermore, the discharge circuit 300B according to Embodiment 3 has the same configuration as the discharge circuit 300 according to Embodiment 1, except for the arrangement of the resistive elements, so only the differences will be explained. 【0061】 The basic arrangement method of resistive elements in the discharge circuit according to Embodiment 3 will be explained using Figures 10 and 11. In Figure 10, arrow A indicates the series direction, and in Figure 11, arrow B indicates the parallel direction. The discharge circuit has at least three or more identical resistive elements in the arrangement area on the arrangement surface 2a (see Figure 14) of the multilayer wiring board 2. 【0062】 In the example shown in Figure 10, three resistors 34a, 34b, and 34c (collectively referred to as resistors 34) are connected in series by a wiring pattern (not shown) to form a row L1. In the example shown in Figure 11, three resistors 35a, 35b, and 35c (collectively referred to as resistors 35) are connected in parallel by a wiring pattern to form a row R1. 【0063】 In a discharge circuit, the spacing between adjacent resistive elements widens or narrows as one approaches a specific location. In this embodiment 3, the power converter is equipped with a heat dissipation component 8 that serves as a cooling source, and the specific location is the heat dissipation component 8. The resistive elements closer to the heat dissipation component 8 are cooled by the heat dissipation component 8, so their temperature does not rise easily. For this reason, the spacing between adjacent resistive elements narrows as one approaches the heat dissipation component 8. The heat dissipation component 8 is, for example, a water channel for cooling the power converter, a heat sink, etc. 【0064】 When there are three resistive elements, the spacing between adjacent resistive elements is narrower on the side closer to the heat dissipation component 8 than on the side further away from the heat dissipation component 8. In Figure 10, three resistive elements 34 are arranged in series. When the spacing between the resistive element 34a, which is closest to the heat dissipation component 8, and the adjacent resistive element 34b is S32, and the spacing between the resistive element 34c, which is furthest from the heat dissipation component 8, and the adjacent resistive element 34b is S33, S32 < S33. 【0065】Furthermore, in Figure 11, three resistors 35 are arranged in parallel. When S34 is the distance between resistor 35a, which is located closest to the heat dissipation component 8, and the adjacent resistor 35b, and S35 is the distance between resistor 35c, which is located furthest from the heat dissipation component 8, and the adjacent resistor 35b, S34 < S35. 【0066】 A specific example of the arrangement of resistive elements in the discharge circuit 300B according to Embodiment 3 will be explained using Figure 12. In Figure 12, the Z direction indicates the thickness direction of the multilayer wiring board 2, and the arrangement area is on the XY plane. Also in Figure 12, the vertical arrow A indicates the series direction, and the horizontal arrow B indicates the parallel direction. The multilayer wiring board on which the discharge circuit 300B is mounted is assembled into the housing 7 of the power converter, and the heat dissipation component 8 is arranged inside the housing 7. 【0067】 The discharge circuit 300B, like the discharge circuit 300 according to Embodiment 1 above, has a total of 40 resistive elements 301 to 340 arranged in a matrix. The resistive elements 301 to 340 form four columns in the series direction and ten rows in the parallel direction. The spacing between adjacent resistive elements in each column narrows as it approaches the heat dissipation component 8, and the spacing between adjacent resistive elements in each row narrows as it approaches the heat dissipation component 8. 【0068】 In Figure 12, for example, in the rightmost column, if the distance between resistors 335 and 336, which are located closest to the center of the heat dissipation component 8, is S32, and the distance between resistor 340, which is located furthest from the heat dissipation component 8, and the adjacent resistor 339 is S36, and the distances between resistors 336, 337, 338, and 339 in between are S33, S34, and S35, then S32 < S33 < S34 < S35 < S36. Also, for resistors 331 to 335 in the same column, the distance between adjacent resistors gradually narrows as they get closer to the heat dissipation component 8. The same applies to the other columns. 【0069】Furthermore, in Figure 12, for example, in the bottom row, if the distance between the resistor element 310, which is located closest to the heat dissipation component 8, and the adjacent resistor element 320 is S37, the distance between the resistor element 340, which is located furthest from the heat dissipation component 8, and the adjacent resistor element 330 is S39, and the distance between the resistor elements 320 and 330 in between is S38, then S37 < S38 < S39. The same applies to the other rows. 【0070】 In Figure 12, the resistors 331 to 335 and 336 to 340 in the rightmost column are arranged symmetrically with respect to the center of the column, but this arrangement does not have to be symmetrical. Also, the spacing between adjacent resistors may change gradually or in steps. 【0071】 Furthermore, in Figure 12, for all the resistive elements 301 to 340 arranged in a matrix, the spacing between adjacent resistive elements narrows as they approach the heat dissipation component 8, which is a specific location. However, the arrangement of resistive elements in the discharge circuit 300B is not limited to this. It is sufficient that for at least some of the resistive elements, the spacing between adjacent resistive elements narrows as they approach the heat dissipation component 8. 【0072】 According to the power conversion device of Embodiment 3, a specific location is designated as a heat dissipation component 8, and the spacing between adjacent resistive elements in the discharge circuit 300B is narrowed as it approaches the heat dissipation component 8. This allows the heat dissipation component 8 to cool areas where the spacing between resistive elements is narrow and where temperature rises easily. As a result, the heat generated by multiple resistive elements can be dispersed and equalized, making it possible to suppress the temperature rise of the discharge circuit 300B without increasing the size of the device. 【0073】 Embodiment 4. Figure 13 is a plan view showing a multilayer wiring board of a power conversion device according to Embodiment 4, where (a) shows the first wiring layer and (b) shows the layers from the second wiring layer onwards. Figure 14 is a cross-sectional view showing a multilayer wiring board of a power conversion device according to Embodiment 4. In Figures 13 and 14, the Z direction indicates the thickness direction of the multilayer wiring board 2, and the arrangement area is on the XY plane. 【0074】The power conversion device according to this fourth embodiment comprises a multilayer wiring board 2 on which one of the discharge circuits 300, 300A, or 300B according to the first to third embodiments is mounted, and a housing 7 that houses the multilayer wiring board 2. The multilayer wiring board 2 has a solid heat plane pattern 9 directly below the surface on which the discharge circuit is placed. In Figures 13(a) and 14, the discharge circuit 300 is mounted on the multilayer wiring board 2, and in Figure 13(b), the projected resistive elements are shown by dotted lines. 【0075】 As shown in Figure 13(a), the multilayer wiring board 2 has a discharge circuit 300 mounted on the first wiring layer, which is the mounting surface 2a, and has multiple identical resistive elements 301 to 340. Also, as shown in Figure 13(b), a solid pattern 9, indicated by the shaded area, is arranged on the layers from the second wiring layer downwards. The solid pattern 9 is provided so as to overlap all the resistive elements of the discharge circuit 300 in the Z direction. 【0076】 Furthermore, as shown in Figure 14, the ground plane 9 is connected to the housing 7, and the heat generated in the discharge circuit 300 is dissipated from the housing 7 via the ground plane 9. For example, the ground plane 9 and the housing 7 are connected by grounding the multilayer wiring board 2 to the housing 7 using bosses for assembling the multilayer wiring board 2. In the example shown in Figure 14, the multilayer wiring board 2 and the housing 7 are grounded at one point, but multiple points may be used. 【0077】 According to Embodiment 4, in a power conversion device equipped with a multilayer wiring board 2 on which any of the discharge circuits according to Embodiments 1 to 3 is mounted, a heat-dissipating solid pattern 9 is provided directly below the surface 2a where the discharge circuit is located, thereby suppressing the temperature rise of the discharge circuit at low cost. Furthermore, by connecting the solid pattern 9 to the housing 7, the heat dissipation effect of the solid pattern 9 is further enhanced. In addition, by connecting the solid pattern 9 to the housing 7 at multiple locations, the temperature rise of the discharge circuit can be further suppressed, making it possible to miniaturize the power conversion device. 【0078】As described above, the power conversion devices according to Embodiments 1 to 4 disperse and equalize the heat generated by multiple resistive elements by widening or narrowing the spacing between adjacent resistive elements in the discharge circuit as one approaches a specific location. The specific location is shown as the center position C of the resistive element arrangement area, the heat-generating component 6, and the heat-dissipating component 8, but there is not necessarily only one specific location. 【0079】 For example, various situations can be considered, such as when both heat-generating components 6 and heat-dissipating components 8 are present, or when there are multiple instances of each. In such cases, by freely combining the arrangements shown in Embodiments 1 to 3, it is possible to equalize the heat generation of multiple resistive elements and suppress the temperature rise of the entire discharge circuit. 【0080】 Specifically, the type of heat-generating component 6 or heat-dissipating component 8, their distance from each other, and their positional relationship are taken into consideration to determine the overall arrangement of the multiple resistive elements. For example, the arrangement of Embodiment 2 can be applied to some resistive elements located in areas where the heat-generating component 6 has a significant impact, while the arrangement of Embodiment 3 can be applied to other resistive elements located in areas where the cooling effect of the heat-dissipating component 8 is significant. Furthermore, the arrangement of Embodiment 1 may be partially modified to take into account the influence of the heat-generating component 6 or heat-dissipating component 8. 【0081】 Furthermore, while Embodiments 1 to 4 described the arrangement of resistive elements in the discharge circuit of a power conversion device, the method of arranging resistive elements in this disclosure is not limited to discharge circuits, but can be applied to any circuit having multiple identical resistive elements, such as a snubber circuit. 【0082】While this disclosure describes various exemplary embodiments and examples, the various features, aspects, and functions described in one or more embodiments are not limited to the application of a particular embodiment, but are applicable individually or in various combinations to the embodiments. Accordingly, countless variations not illustrated are envisioned within the scope of the technology disclosed herein. For example, these include modifying, adding or omitting at least one component, or extracting at least one component and combining it with a component from another embodiment. 【0083】 1 Power converter, 2 Multilayer wiring board, 2a Placement surface, 3 Placement area, 3e Both ends, 6 Heat-generating component, 7 Housing, 8 Heat dissipation component, 9 Ground plane, 31a, 31b, 31c, 31d, 32a, 32b, 32c, 33a, 33b, 33c, 34a, 34b, 34c, 35a, 35b, 35c, 301, 340 Resistor element, 100 DC power supply, 200 Smoothing capacitor, 300, 300A, 300B, 350 Discharge circuit, 401 U-phase leg, 402 V-phase leg, 403 W-phase leg, 401a, 401b, 402a, 402b, 403a, 403b Switching element, 410 Driver circuit, 500 Three-phase AC motor
Claims
1. A power conversion device comprising a smoothing capacitor for smoothing the voltage of a DC power supply, and a discharge circuit for discharging the charge stored in the smoothing capacitor, wherein the discharge circuit has a plurality of identical resistive elements arranged at intervals from each other on a mounting surface, and for at least some of the resistive elements, the spacing between adjacent resistive elements widens or narrows as it approaches a specific position.
2. The power conversion device according to claim 1, characterized in that the specific position is the center position of the arrangement region of the resistive elements, and the spacing between adjacent resistive elements widens as it approaches the center position from both ends of the arrangement region.
3. The power conversion device according to claim 2, characterized in that the plurality of resistive elements are arranged in a matrix, the spacing between adjacent resistive elements in each column widens as you move from both ends of the column towards the center, and the spacing between adjacent resistive elements in each row widens as you move from both ends of the row towards the center.
4. The power conversion device according to claim 1, characterized in that it is equipped with a heat-generating component that serves as a heat source, the specified position is the heat-generating component, and the distance between adjacent resistive elements widens as it approaches the heat-generating component.
5. The power conversion device according to claim 4, characterized in that the plurality of resistive elements are arranged in a matrix, the spacing between adjacent resistive elements in each column increases as they approach the heat-generating component, and the spacing between adjacent resistive elements in each row increases as they approach the heat-generating component.
6. The power conversion device according to claim 1, characterized in that it is equipped with a heat dissipation component that serves as a cooling and heating source, the specified position is the heat dissipation component, and the distance between adjacent resistive elements narrows as it approaches the heat dissipation component.
7. The power conversion device according to claim 6, characterized in that the plurality of resistive elements are arranged in a matrix, the spacing between adjacent resistive elements in each column narrows as it approaches the heat dissipation component, and the spacing between adjacent resistive elements in each row narrows as it approaches the heat dissipation component.
8. The power conversion device according to any one of claims 1 to 7, comprising a multilayer wiring board on which the discharge circuit is mounted, wherein the multilayer wiring board has a solid heat dissipation pattern directly below the surface on which the discharge circuit is mounted.
9. The power conversion device according to claim 8, comprising a housing for housing the multilayer wiring board, wherein the solid pattern is connected to the housing.