Power module

Abstract

To suppress effects of noise without adding physical noise suppression components.SOLUTION: A power module 17-1 includes an upper arm switching element 1a, a lower arm switching element 2a, a first dielectric 1c, 2c provided between the upper arm switching element and the lower arm switching element, and a second dielectric 1d, 2d provided at a location other than between the upper arm switching element and the lower arm switching element, and a stray capacitance of the first dielectric is different from a stray capacitance of the second dielectric.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a power module. [Background Art]

[0002] Patent Document 1 discloses a technique for reducing common mode noise generated in a power module. Specifically, in the conventional technique disclosed in Patent Document 1, common mode noise (common mode current) is suppressed by arranging the collector surface and the emitter surface in reverse to reduce stray capacitance on the output side (see, for example, FIG. 4 of Patent Document 1). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2007-181351 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] However, the conventional technique does not take into account countermeasures against normal mode noise and common mode noise generated in devices other than the power module. Therefore, in order to prevent malfunction of peripheral devices of an inverter equipped with the power module, additional noise countermeasure components such as an X capacitor for suppressing normal mode noise and a Y capacitor for suppressing common mode noise may be required. As described above, the conventional technique has room for improvement in suppressing the influence of noise.

[0005] The present invention has been made in view of the above problems, and an object of the present invention is to provide a power module capable of suppressing the influence of noise without adding physical noise countermeasure components. [Means for Solving the Problem]

[0006] To achieve the above objective, the power module (17-1) of the present invention comprises an upper arm switching element (1a), a lower arm switching element (2a), a first dielectric (1c, 2c) provided between the upper arm switching element and the lower arm switching element, and a second dielectric (1d, 2d) provided at locations other than between the upper arm switching element and the lower arm switching element, wherein the stray capacitance of the first dielectric is different from the stray capacitance of the second dielectric.

[0007] According to this disclosure, normal mode noise can be suppressed without adding physical noise suppression components. Furthermore, in order to achieve perfect noise suppression, physical noise suppression components such as X capacitors and Y capacitors may be provided in the motor drive circuit path outside the power module, along with the module of the present invention, and the present invention does not exclude such embodiments. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows the configuration of a motor drive circuit equipped with the power module of this disclosure. [Figure 2] This is an external view of a power module according to the first embodiment of the present disclosure. [Figure 3] This figure shows the equivalent circuit of the power module according to the first embodiment. [Figure 4] This is a cross-sectional view of a power module according to the first embodiment. [Figure 5] This diagram illustrates the operation of a motor drive circuit equipped with a power module according to the first embodiment. [Figure 6] This is a diagram showing the configuration of a power module according to a second embodiment of the present disclosure. [Figure 7] This figure shows the equivalent circuit of the power module according to the second embodiment. [Figure 8] This is a cross-sectional view of a power module according to the second embodiment. [Figure 9]FIG. 10 is a diagram for explaining the operation of a motor drive circuit including the power module according to the second embodiment. [Figure 10] It is a configuration diagram of a power module according to a third embodiment of the present disclosure. [Figure 11] FIG. 12 is a diagram showing an equivalent circuit of the power module according to the third embodiment. [Figure 12] It is a cross-sectional view of the power module according to the third embodiment. [Figure 13] FIG. 14 is a diagram for explaining the operation of a motor drive circuit including the power module according to the third embodiment. [Figure 14] It is a configuration diagram of a power module according to a fourth embodiment of the present disclosure. [Figure 15] FIG. 16 is a diagram showing an equivalent circuit of the power module according to the fourth embodiment. [Figure 16] It is a cross-sectional view of the power module according to the fourth embodiment. [Figure 17] It is a cross-sectional view of the power module according to the fifth embodiment. [Figure 18] It is a cross-sectional view of the power module according to the sixth embodiment. [Figure 19] FIG. 20 is a diagram showing an equivalent circuit of the power module according to the seventh embodiment. [Figure 20] It is a cross-sectional view of the power module according to the seventh embodiment. MODES FOR CARRYING OUT THE INVENTION

[0009] Hereinafter, an embodiment of the present invention will be described.

[0010] (First Embodiment) Figure 1 shows the configuration of a motor drive circuit equipped with the power module of this disclosure. The motor drive circuit 10 is a circuit that drives a motor by converting DC power supplied from a DC power supply 11, which is a hybrid (HV) power supply, to AC power. A Line Impedance Stabilization Network (LISN) 12 is connected to the DC power supply 11. The Line Impedance Stabilization Network 12 stabilizes the impedance of the DC power supply as seen from the inverter 13. The inverter 13 is connected to the Line Impedance Stabilization Network 12 via a DC bus (PN line) 14.

[0011] The inverter 13 includes a smoothing capacitor 16 for smoothing the current and a power module 17-1 for converting a DC voltage to an AC voltage. The power module 17-1 includes multiple switching elements.

[0012] Figure 2 is an external view of a power module according to a first embodiment of the present disclosure. The power module 17-1 comprises a first power card 1, a second power card 2, a first heatsink 3, and a second heatsink 4.

[0013] The first power card 1 comprises an upper arm switching element 1a, a housing 1b that surrounds the upper arm switching element 1a, a conductive input section A, and a conductive output section O. The first power card 1 is positioned adjacent to the second power card 2.

[0014] The second power card 2 comprises a lower arm switching element 2a, a housing 2b that surrounds the lower arm switching element, a conductive input section B, and a conductive output section O.

[0015] The first heatsink 3 is a cooling component provided on the first power card 1. The first heatsink 3 is positioned on the side of the first power card 1 opposite to the side facing the second power card 2. The second heatsink 4 is a cooling component provided on the second power card 2. The second heatsink 4 is positioned on the side of the second power card 2 opposite to the side facing the first power card 1. The first heatsink 3 and the second heatsink 4 are made of a conductive material such as aluminum or metal.

[0016] Next, the internal configuration of the power module 17-1 will be described with reference to Figures 3 and 4. Figure 3 is a diagram showing the equivalent circuit of the power module according to the first embodiment. Figure 4 is a cross-sectional view of the power module according to the first embodiment.

[0017] As shown in Figure 4, the first power card 1 comprises a first dielectric 1c and a second dielectric 1d.

[0018] The first dielectric 1c is provided between the input section A of the first power card 1 and the input section B of the second power card 2. The first dielectric 1c may be part of the housing 1b, or it may be a separate structure from the housing 1b.

[0019] The second dielectric 1d is provided between the output section O of the first power card 1 and the first heat sink 3. The second dielectric 1d can be interpreted as a dielectric provided in a location other than between the upper arm switching element 1a and the lower arm switching element 2a.

[0020] The first dielectric 1c and the second dielectric 1d include an insulating material. The insulating material may be an organic material, an inorganic material, or a combination of both. Inorganic materials include silicon oxide (SiO2), silicon nitride (Si3N4), silicon oxynitride (SiON), aluminum oxide (Al2O3), aluminum nitride (AlN), silicon carbide (SiC), silicon carbide nitride (SiCN), carbon-doped silicon oxide (SiCO), borosilicate glass, and quartz glass. Organic materials include polyimide, epoxy resin, benzocyclobutene resin, polyamide, phenolic resin, fluororesin, liquid crystal polymer, polyamide-imide, polybenzoxazole, cyanate resin, aramid resin, polyolefin, and polyester.

[0021] The second power card 2 comprises a first dielectric 2c and a second dielectric 2d. The first dielectric 2c is provided between the input section B of the second power card 2 and the input section A of the first power card 1. The second dielectric 2d is provided between the output section O of the second power card 2 and the second heat sink 4. The second dielectric 2d may be interpreted as a dielectric provided in a location other than between the upper arm switching element 1a and the lower arm switching element 2a. The first dielectric 2c and the second dielectric 2d, like the first dielectric 1c and the second dielectric 1d, contain an insulating material. The first dielectric 1c and the first dielectric 2c may be a single dielectric or separate dielectrics.

[0022] The first heat sink 3 is provided on the side of the upper arm switching element 1a opposite to the side facing the first dielectric 1c.

[0023] The second heatsink 4 is provided on the side of the lower arm switching element 2a opposite to the side facing the first dielectric 2c.

[0024] A first dielectric 1c and a first dielectric 2c are provided between input A and input B, thereby forming a stray capacitance (C) between input A and input B. The stray capacitance (C) may be defined by the following equation (1). In equation (1), ε0 represents the permittivity of vacuum. S represents the relative permittivity. In equation (1) below, S represents the area of ​​the dielectric surface that faces the switching element. In equation (1) below, d represents the thickness of the dielectric in the direction of the switching element arrangement. C=ε0ε S S / d····(1)

[0025] Due to this stray capacitance C, a capacitor Cx is formed between input A and input B, as shown in Figures 3 and 4. Capacitor Cx may be interpreted as a pseudo-X capacitor. A pseudo-X capacitor may be interpreted as a capacitor different from a physical X capacitor. "Pseudo" can be interpreted as a state in which a function equivalent to that of a physical X capacitor is generated by the capacitance formed by the dielectric of the power module 17-1, independently of the physical X capacitor. The X capacitor may be interpreted as an across-the-line capacitor that suppresses normal-mode noise.

[0026] Furthermore, since a second dielectric 1d is provided between the first heat sink 3 and the output section O, a stray capacitance is formed. Similarly, since a second dielectric 2d is provided between the second heat sink 4 and the output section O, a stray capacitance is formed.

[0027] In power module 17-1, the stray capacitance of the first dielectric 1c is different from that of the second dielectric 1d. Specifically, the stray capacitance of the first dielectric 1c is higher than that of the second dielectric 1d. The stray capacitance of the first dielectric 1c may be interpreted as the stray capacitance formed between input section A and input section B by the first dielectric 1c. The stray capacitance of the second dielectric 1d may be interpreted as the stray capacitance formed between the first heat sink 3 and output section O by the second dielectric 1d.

[0028] Similarly, in power module 17-1, the stray capacitance of the first dielectric 2c is different from the stray capacitance of the second dielectric 2d. Specifically, the stray capacitance of the first dielectric 2c is higher than that of the second dielectric 2d. The stray capacitance of the first dielectric 2c may be interpreted as the stray capacitance formed between input section A and input section B by the first dielectric 2c. The stray capacitance of the first dielectric 2c may also be interpreted as the stray capacitance formed between the second heat sink 4 and output section O by the second dielectric 2d.

[0029] Figure 5 is a diagram illustrating the operation of a motor drive circuit equipped with a power module according to the first embodiment. As shown in Figure 5, a capacitor Cx is formed between input A and input B. When the switching element of the motor drive circuit 10 in which capacitor Cx is formed switches, the DC voltage supplied from the DC power supply 11 is converted to an AC voltage and applied to the AC motor 15.

[0030] Here, the impedance of capacitor Cx is low in the high-frequency range. Also, since the stray capacitance of the first dielectric 1c and first dielectric 2c that form capacitor Cx is higher than the stray capacitance of the second dielectric 1d and second dielectric 2d, a path for high-frequency noise, which is normal mode noise, is formed between input A and input B. In other words, capacitor Cx acts as a path that bypasses high-frequency noise from input A to input B, or a path that bypasses high-frequency noise from input B to input A.

[0031] As a result, some of the normal-mode noise generated by the switching element flows into capacitor Cx, as indicated by the dashed arrow, and is collected within the power module 17-1. The normal-mode noise collected within the power module 17-1 is attenuated by the resistance components within the power module 17-1.

[0032] Therefore, normal mode noise can be suppressed without adding a physical X capacitor as a noise suppression component. As a result, malfunctions of peripheral equipment of the inverter 13 can be suppressed. In addition, since a physical X capacitor is not required, the configuration of the motor drive circuit 10 is simplified, which may improve the yield during manufacturing of the motor drive circuit 10. Furthermore, the simplification of the configuration of the motor drive circuit 10 may improve the reliability of the motor drive circuit 10.

[0033] (Second Embodiment) The second embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. The same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0034] Figure 6 is a configuration diagram of a power module according to a second embodiment of the present disclosure. The power module 17-2 according to the second embodiment includes a third heatsink 5 in addition to the configuration of the first embodiment. The third heatsink 5 is a cooling member provided between the first power card 1 and the second power card 2. More specifically, the third heatsink is a cooling member provided between the upper arm switching element 1a and the lower arm switching element 2a.

[0035] Next, the internal configuration of the power module according to the second embodiment will be described with reference to Figures 7 and 8. Figure 7 is a diagram showing the equivalent circuit of the power module according to the second embodiment. Figure 8 is a cross-sectional view of the power module according to the second embodiment.

[0036] As shown in Figure 8, the third heat sink 5 is provided between the first dielectric 1c and the first dielectric 2c. The third heat sink 5 can be interpreted as a cooling member provided between the upper arm switching element 1a and the lower arm switching element 2a. The third heat sink 5 is made of a conductive material such as aluminum or metal.

[0037] The first dielectric 1c is provided between the upper arm switching element 1a and the third heat sink 5. The first dielectric 2c is provided between the lower arm switching element 2a and the third heat sink 5.

[0038] In power module 17-2, the stray capacitance of the first dielectric 1c is higher than that of the second dielectric 1d. The stray capacitance of the first dielectric 1c may be interpreted as the stray capacitance formed between the third heat sink 5 and the input section A by the first dielectric 1c. Similarly, in power module 17-2, the stray capacitance of the first dielectric 2c is higher than that of the second dielectric 2d. The stray capacitance of the first dielectric 2c may be interpreted as the stray capacitance formed between the third heat sink 5 and the input section B by the first dielectric 2c.

[0039] These stray capacitances may be defined by equation (1) above. Furthermore, these stray capacitances form a capacitor Cy between input A and ground (GND), as shown in Figure 7, and another capacitor Cy between input B and ground. These capacitors Cy may be interpreted as pseudo-Y capacitors. Pseudo-Y capacitors may be interpreted as capacitors different from physical Y capacitors. Pseudo means a state in which a function equivalent to that of a physical Y capacitor is generated by the capacitance formed by the dielectric material of the power module 17-2, independently of the physical Y capacitor. The Y capacitors may be interpreted as line bypass capacitors that suppress common-mode noise.

[0040] Figure 9 is a diagram illustrating the operation of a motor drive circuit equipped with a power module according to the second embodiment. As shown in Figure 9, a capacitor Cy is formed between input A and ground. A capacitor Cy is also formed between input B and ground. When the switching element of the motor drive circuit 10, in which capacitor Cy is formed, switches, the DC voltage supplied from the DC power supply 11 is converted to an AC voltage and applied to the AC motor 15.

[0041] Here, the impedance of capacitor Cy is low in the high-frequency range. Also, as mentioned above, the stray capacitance of the first dielectric 1c and the first dielectric 2c that form capacitor Cy is higher than the stray capacitance of the second dielectric 1d and the second dielectric 2d, so a common-mode noise path, which is high-frequency noise, is formed between input A and ground. Furthermore, a common-mode noise path is also formed between input B and ground. In other words, capacitor Cy acts as a path that bypasses high-frequency noise from ground to input A, or from ground to input B. Note that ground may be interpreted as the ground potential of the heat sink, or as the ground potential of the inverter 13's enclosure.

[0042] As a result, when the inverter 13 is driven, some of the common-mode noise transmitted to the inverter 13's casing, heat sink, etc., via the stray capacitance Ca of the AC motor 15 flows into the capacitor Cy, as shown by the dashed arrow, and is recovered within the power module 17-2. The common-mode noise recovered within the power module 17-2 is attenuated by the resistive components within the power module 17-2.

[0043] Therefore, common-mode noise can be suppressed without adding a physical Y-capacitor as a noise suppression component. As a result, malfunctions of peripheral equipment of the inverter 13 can be suppressed.

[0044] Furthermore, since a physical Y-capacitor is not required, the configuration of the motor drive circuit 10 is simplified, which may improve the yield during manufacturing of the motor drive circuit 10. In addition, the simplification of the configuration of the motor drive circuit 10 may improve the reliability of the motor drive circuit 10.

[0045] Furthermore, when the power module and heatsink are placed close together to improve the cooling performance of the power module, stray capacitance is generated between the power module and the heatsink, which can become a propagation path for common-mode noise. Power module 17-2 can effectively suppress such common-mode noise.

[0046] (Third embodiment) The third embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. The same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0047] Figure 10 is a configuration diagram of a power module according to a third embodiment of the present disclosure. The power module 17-3 according to the third embodiment includes a first power card 1 with its upper and lower surfaces inverted. In addition, the positions of the input section A and output section O of the first power card 1 and the second power card 2 of the power module 17-3 differ from those of the first embodiment.

[0048] Next, the internal configuration of the power module according to the third embodiment will be described with reference to Figures 11 and 12. Figure 11 is a diagram showing the equivalent circuit of the power module according to the third embodiment. Figure 12 is a cross-sectional view of the power module according to the third embodiment.

[0049] As shown in Figure 12, the first dielectric 1c and the first dielectric 2c are provided between the output section O of the upper arm switching element 1a and the input section B of the lower arm switching element 2a. Specifically, the first dielectric 1c is provided between the output section O of the upper arm switching element 1a and the second power card 2. The first dielectric 2c is provided between the input section B of the lower arm switching element 2a and the first power card 1.

[0050] In power module 17-3, similar to the first embodiment, the stray capacitance of the first dielectric 1c is higher than the stray capacitance of the second dielectric 1d. The stray capacitance of the first dielectric 1c may be interpreted as the stray capacitance formed by the first dielectric 1c between the output section O of the first power card 1 and the input section B of the second power card 2. The stray capacitance of the first dielectric 1c may also be interpreted as the stray capacitance formed by the first dielectric 1c between the emitter E1 of the first power card 1 and the emitter E2 of the second power card 2.

[0051] This stray capacitance may be defined by equation (1) mentioned above. Due to this stray capacitance, a capacitor C1 is formed between the output section O and ground, as shown in Figure 11. Capacitor C1 may be interpreted as a pseudo-snubber capacitor. A pseudo-snubber capacitor may be interpreted as a capacitor different from a physical snubber capacitor.

[0052] "Simulated" can be interpreted as a state in which the capacitance formed by the dielectric material of the power module 17-3 generates a function equivalent to that of a physical snubber capacitor. A snubber capacitor can be interpreted as a capacitor that absorbs high-frequency noise generated when the switching element is switched on or off.

[0053] Figure 13 is a diagram illustrating the operation of a motor drive circuit equipped with a power module according to the third embodiment. As shown in Figure 13, a capacitor C1 is formed between the output section O and ground. When the switching element of the motor drive circuit 10 in which capacitor C1 is formed switches, the DC voltage supplied from the DC power supply 11 is converted to an AC voltage and applied to the AC motor 15.

[0054] Here, the stray capacitance of the first dielectric 1c and the first dielectric 2c forming capacitor C1 is higher than the stray capacitance of the second dielectric 1d and the second dielectric 2d, so a high-frequency noise path is formed between the output section O and ground. In other words, capacitor C1 becomes a path that bypasses high-frequency noise between the output section O and ground.

[0055] As a result, some of the noise generated by the switching element flows into capacitor C1, as indicated by the dashed arrow, and is collected within the power module 17-3. The noise collected within the power module 17-3 is then attenuated within the power module 17-3. In addition, the high-frequency noise is attenuated due to the loss of capacitor C1, which absorbs the high-frequency noise.

[0056] Therefore, noise generated during the operation of the switching element can be suppressed without adding a physical snubber capacitor as a noise suppression component. As a result, malfunctions of peripheral equipment of the inverter 13 can be suppressed.

[0057] Furthermore, since a physical snubber capacitor is not required, the configuration of the motor drive circuit 10 is simplified, which may improve the yield during manufacturing of the motor drive circuit 10. In addition, the simplification of the configuration of the motor drive circuit 10 may improve the reliability of the motor drive circuit 10.

[0058] Furthermore, if a physical snubber capacitor is provided in the inverter 13, the snubber capacitor may become a thermal resistance of the inverter 13, thus requiring heat dissipation measures for the snubber capacitor. By providing a pseudo-snubber capacitor in the power module 17-3, heat can be dissipated by the heat sink of the power module 17-3, eliminating the need for heat dissipation measures for the physical snubber capacitor and simplifying the configuration of the motor drive circuit 10.

[0059] The capacitor C1 may also be formed on the upper arm switching element 1a. In other words, the capacitor C1 may be provided between the input section A and the output section O of the first power card 1 which is equipped with the upper arm switching element 1a.

[0060] (Fourth Embodiment) The fourth embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. The same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description. Figure 14 is a configuration diagram of a power module according to the fourth embodiment of this disclosure. The power module 17-4 according to the fourth embodiment comprises a first power card 1 with its upper and lower surfaces inverted and a second power card 2 with its upper and lower surfaces inverted.

[0061] Next, the internal configuration of the power module according to the fourth embodiment will be described with reference to Figures 15 and 16. Figure 15 is a diagram showing the equivalent circuit of the power module according to the fourth embodiment. Figure 16 is a cross-sectional view of the power module according to the fourth embodiment.

[0062] The difference from the first embodiment is that the second dielectric 1d is provided between the first heat sink 3 and the input A of the upper arm switching element 1a, and furthermore, the second dielectric 2d is provided between the second heat sink 4 and the input B of the lower arm switching element 2a.

[0063] Another difference from the first embodiment is that in the power module 17-4 according to the fourth embodiment, the stray capacitance of the second dielectric 1d is higher than the stray capacitance of the first dielectric 1c, and furthermore, the stray capacitance of the second dielectric 2d is higher than the stray capacitance of the first dielectric 2c.

[0064] This stray capacitance may be defined by equation (1) described above. Due to this stray capacitance, a capacitor Cy is formed between the first heatsink 3 and the input section A, and a capacitor Cy is formed between the second heatsink 4 and the input section B, as shown in Figure 16. These capacitors Cy may be interpreted as pseudo-Y capacitors, similar to the second embodiment.

[0065] Thus, with the power module 17-4, even without the third heatsink 5, a pseudo-Y capacitor is formed using the first heatsink 3 and the second heatsink 4. Therefore, the same effects as in the second embodiment can be obtained, and the configuration of the motor drive circuit 10 can be simplified. Furthermore, by simplifying the configuration of the motor drive circuit 10, the reliability of the motor drive circuit 10 can be improved.

[0066] (Fifth embodiment) The fifth embodiment has the same basic configuration as the first embodiment, so the differences will be explained below. The same reference numerals as in the first embodiment indicate the same components, and refer to the preceding description.

[0067] Figure 17 is a cross-sectional view of a power module according to the fifth embodiment. The difference from the first embodiment is that in the power module 17-5 according to the fifth embodiment, the thickness of the first dielectric in the direction of arrangement of the upper arm switching element 1a and the lower arm switching element 2a is thinner than the thickness of the second dielectric in the same arrangement direction.

[0068] Specifically, the thickness of the first dielectric 1c is thinner than the thickness of the second dielectric 1d in that arrangement direction. Also, the thickness of the first dielectric 2c is thinner than the thickness of the second dielectric 2d in that arrangement direction.

[0069] More specifically, the surface areas of the upper arm switching element 1a side faces of the first dielectric 1c and the second dielectric 1d are equal, and the relative permittivity ε of the first dielectric 1c and the second dielectric 1d is equal. S When they are equal to each other, the thickness of the first dielectric 1c is thinner than the thickness of the second dielectric 1d.

[0070] Furthermore, the surface areas of the faces of the first dielectric 2c and the second dielectric 2d on the lower arm switching element 2a side are equal to each other, and the relative permittivity ε of the first dielectric 2c and the second dielectric 2d is equal to each other. S When they are equal to each other, the thickness of the first dielectric 2c is thinner than the thickness of the second dielectric 2d.

[0071] As shown in equation (1) above, the stray capacitance (C) of the dielectric is given by "C = ε₀ S Since it is defined by "S / d", the thinner the thickness (d) of the first dielectric 1c, the larger the stray capacitance (C) of the first dielectric 1c becomes. The same applies to the first dielectric 2c.

[0072] In this way, by reducing the thickness of the first dielectric 1c and the first dielectric 2c, a capacitor Cx is formed between input A and input B in the power module 17-5, as shown in Figure 17. Capacitor Cx can be interpreted as a pseudo-X capacitor.

[0073] By providing capacitor Cx in this way, a portion of the normal-mode noise generated by the switching element flows into capacitor Cx and is collected within the power module 17-5. The normal-mode noise collected within the power module 17-5 is attenuated by the resistive components within the power module 17-5.

[0074] Therefore, normal mode noise can be suppressed without adding a physical X capacitor as a noise suppression component. As a result, malfunctions of peripheral equipment of the inverter 13 can be suppressed. In addition, since a physical X capacitor is not required, the configuration of the motor drive circuit 10 is simplified, which may improve the yield during manufacturing of the motor drive circuit 10. Furthermore, the simplification of the configuration of the motor drive circuit 10 may improve the reliability of the motor drive circuit 10.

[0075] Furthermore, in power module 17-5, a pseudo-X capacitor can be provided by making the thickness of the first dielectric 2c different from the thickness of the second dielectric 2d. Therefore, a specific relative permittivity ε S This is particularly useful when providing a first dielectric 1c, a first dielectric 2c, a second dielectric 1d, and a second dielectric 2d using a material having the properties of [the specified property].

[0076] (Sixth Embodiment) The sixth embodiment has the same basic configuration as the second embodiment, so the differences will be explained below. The same reference numerals as in the second embodiment indicate the same components, and refer to the preceding description.

[0077] Figure 18 is a cross-sectional view of a power module according to the sixth embodiment. The difference from the second embodiment is that in the power module 17-6 according to the sixth embodiment, the surface area of ​​the first dielectric facing the upper arm switching element 1a or the lower arm switching element 2a is larger than the surface area of ​​the second dielectric facing the upper arm switching element 1a or the lower arm switching element 2a.

[0078] Specifically, on the opposing surface 1c1 of the first dielectric 1c, an uneven portion 1c2 is formed when the first dielectric 1c is viewed from above. The opposing surface 1c1 may be interpreted as the surface of the first dielectric 1c that faces the upper arm switching element 1a, or it may be interpreted as the surface that faces the input portion A. The uneven portion 1c2 may be formed by forming a plurality of grooves on the first dielectric 1c, or by forming a plurality of protrusions on the first dielectric 1c.

[0079] Similarly, on the opposing surface 2c1 of the first dielectric 2c, an uneven surface 2c2 is formed when the first dielectric 2c is viewed from above. The opposing surface 2c1 may be interpreted as the surface of the first dielectric 2c that faces the lower arm switching element 2a, or it may be interpreted as the surface that faces the input section B. The uneven surface 2c2 may be formed by forming a plurality of grooves on the first dielectric 2c, or by forming a plurality of protrusions on the first dielectric 2c.

[0080] Furthermore, the first dielectric 1c may have an uneven surface formed on the surface facing the third heat sink 5. Similarly, the first dielectric 2c may have an uneven surface formed on the surface facing the third heat sink 5.

[0081] As shown in equation (1) above, the stray capacitance (C) of the dielectric is given by "C = ε₀ S Since it is defined by "S / d", the larger the area (S) of the opposing surface 1c1 of the first dielectric 1c, the larger the stray capacitance (C) of the first dielectric 1c. The same applies to the first dielectric 2c.

[0082] In this way, by increasing the area of ​​the opposing surface 1c1 of the first dielectric 1c and the opposing surface 2c1 of the first dielectric 2c, the capacitance of the capacitor Cy shown in Figure 18 can be increased in the power module 17-6. Therefore, the same effects as in the second embodiment can be obtained, and furthermore, the impact of common-mode noise on peripheral equipment can be reduced even more.

[0083] Furthermore, by changing the uneven shape of the first dielectric 1c and the first dielectric 2c, that is, by adjusting the area of ​​the first dielectric 1c and the first dielectric 2c, the optimal stray capacitance can be set according to the frequency band of the common-mode noise. Therefore, the power module 17-6 can be applied to various devices.

[0084] (Seventh Embodiment) The seventh embodiment has the same basic configuration as the third embodiment, so the differences will be explained below. The same reference numerals as in the third embodiment indicate the same components, and refer to the preceding description.

[0085] Figure 19 is a diagram showing the equivalent circuit of the power module according to the seventh embodiment. Figure 20 is a cross-sectional view of the power module according to the seventh embodiment. The difference from the third embodiment is that in the power module 17-7 according to the seventh embodiment, a pseudo-resistor R is connected in series with the snubber capacitor C1.

[0086] As shown in Figure 20, the pseudo-resistance R is formed by the conductive member 6 provided between the upper arm switching element 1a and the lower arm switching element 2a. The pseudo-resistance R can be interpreted as a resistance different from the physical snubber resistance.

[0087] "Simulated" can be interpreted as a state in which the capacitance formed by the dielectric material of the power module 17-3 generates a function equivalent to that of a physical snubber resistor. The snubber resistor can be interpreted as a resistor that absorbs high-frequency noise generated when the switching element is switched on or off.

[0088] The conductive member 6 is provided adjacent to the first dielectric 1c and the first dielectric 2c. Specifically, the conductive member 6 is provided between the first dielectric 1c and the first dielectric 2c. The conductivity of the conductive member 6 is lower than the conductivity of input section A, input section B, or output section O. Specifically, examples of materials for input section A, input section B, or output section O include copper, gold, and silver. Examples of materials for the conductive member 6 include bronze, chromium, stainless steel, and lead.

[0089] According to the seventh embodiment of the power module 17-7, a portion of the noise generated by the switching element flows into the capacitor C1 and resistor R, is collected within the power module 17-7, and is attenuated within the power module 17-7 by the resistor R. High-frequency noise is attenuated due to the loss in the resistor R.

[0090] Therefore, noise generated during the operation of the switching element can be suppressed without adding a physical snubber resistor as a noise suppression component. As a result, malfunctions of peripheral equipment of the inverter 13 can be further suppressed.

[0091] Furthermore, since a physical snubber resistor is not required, the configuration of the motor drive circuit 10 is simplified, which may improve the yield during manufacturing of the motor drive circuit 10. In addition, the simplification of the configuration of the motor drive circuit 10 may improve the reliability of the motor drive circuit 10.

[0092] Furthermore, if a physical snubber resistor is provided in the inverter 13, this snubber resistor may become a thermal resistance of the inverter 13, requiring heat dissipation measures for the snubber resistor. By providing a pseudo-resistor R in the power module 17-7, heat can be dissipated by the heat sink of the power module 17-7, thus eliminating the need for thermal measures for the physical snubber resistor and simplifying the configuration of the motor drive circuit 10.

[0093] In this disclosure, the upper arm switching element 1a and the lower arm switching element 2a are provided as examples, which are IGBTs (Insulated Gate Bipolar Transistors). However, the upper arm switching element 1a and the lower arm switching element 2a may be transistors other than IGBTs.

[0094] The power modules according to each of the above embodiments are applicable to inverters with relatively high switching speeds, such as those installed in EVs (Electric Vehicles) and railway vehicles. Furthermore, the power modules according to each of the above embodiments are also applicable to power conversion devices other than inverters, such as buck-boost converters and forward discharge converters (FDCs).

[0095] It should be noted that the power modules according to the above embodiments are not limited to a structure in which multiple power cards are stacked. For example, a structure in which the dielectric and switching elements of each power card are provided on one or more planes can be applied to the power modules according to the above embodiments.

[0096] <Note> The features of this invention are as follows. (Note 1) A power module (17-1) comprising an upper arm switching element (1a), a lower arm switching element (2a), a first dielectric (1c, 2c) provided between the upper arm switching element and the lower arm switching element, and a second dielectric (1d, 2d) provided at locations other than between the upper arm switching element and the lower arm switching element, wherein the stray capacitance of the first dielectric is different from that of the second dielectric. (Note 2) The power module described in Appendix 1, wherein the stray capacitance of the first dielectric is higher than the stray capacitance of the second dielectric. (Note 3) The second dielectric is a power module as described in Appendix 1 or 2, provided between the cooling member (3, 4) provided on the side of the upper arm switching element or the lower arm switching element opposite to the side of the first dielectric, and the upper arm switching element or the lower arm switching element. (Note 4) A cooling member (5) is provided between the upper arm switching element and the lower arm switching element, and the first dielectric is provided between the upper arm switching element or the lower arm switching element and the cooling member, as described in any one of the appendices 1 to 3. (Note 5) The power module described in any one of the appendices 1 to 4, wherein the stray capacitance of the second dielectric is higher than that of the first dielectric. (Note 6) The second dielectric is a power module as described in any one of the appendices 1 to 5, provided between the cooling member (3, 4) provided on the side of the upper arm switching element or the lower arm switching element opposite to the side of the first dielectric, and the upper arm switching element or the lower arm switching element. (Note 7) The power module according to any one of the appendices 1 to 6, wherein the thickness of the first dielectric in the direction of arrangement of the upper arm switching element and the lower arm switching element is thinner than the thickness of the second dielectric in the direction of arrangement. (Note 8) The power module according to any one of the appendices 1 to 7, wherein the surface area of ​​the first dielectric facing the upper arm switching element or the lower arm switching element is larger than the surface area of ​​the second dielectric facing the upper arm switching element or the lower arm switching element. (Note 9) The power module according to any one of the appendices 1 to 8, wherein the surface of the first dielectric facing the upper arm switching element or the lower arm switching element has irregularities (1c2, 2c2) when the first dielectric is viewed in plan view. (Note 10) The first dielectric is provided between an output section (O) that outputs power from the upper arm switching element and an input section (A, B) that inputs power to the lower arm switching element, as described in any one of the appendices 1 to 9 of the power module. (Note 11) A power module according to any one of the appendices 1 to 10, wherein a conductive member (6) is provided adjacent to the first dielectric, and the conductivity of the conductive member is lower than the conductivity of the input section or the output section.

[0097] Although one embodiment of the present invention has been described above, it goes without saying that the present invention is not limited to the above, and can be implemented in various ways without departing from the spirit of the invention. [Explanation of Symbols]

[0098] 1 First power card, 1a Upper arm switching element, 1b Housing, 1c First dielectric, 1c1 Opposite surface, 1c2 Rough part, 1d Second dielectric, 2 Second power card, 2a Lower arm switching element, 2b Housing, 2c First dielectric, 2c2 Rough part, 2c1 Opposite surface, 2d Second dielectric, 3 First heat sink, 4 Second heat sink, 5 Third heat sink, 6 Conductive material, 10 Motor drive circuit, 11 DC power supply, 12 Power impedance stabilization network, 13 Inverter, 15 AC motor, 16 Smoothing capacitor, 17-1 Power module, 17-2 Power module, 17-3 Power module, 17-4 Power module, 17-5 Power module, 17-6 Power module, 17-7 Power module.

Claims

1. An upper arm switching element (1a) having a first input section (A) for inputting power and a first output section (O) for outputting power, A lower arm switching element (2a) having a second input section (B) for receiving power and a second output section (O) for outputting power, Cooling members (3, 4) provided on the upper arm switching element or the lower arm switching element, A first dielectric (1c, 2c) is provided between the first input section and the second input section, A second dielectric (1d, 2d) is provided between the first output unit and the cooling member, or between the second output unit and the cooling member, Equipped with, A power module (17-1) wherein the stray capacitance formed between the first input section and the second input section by the first dielectric is higher than the stray capacitance formed between the first output section and the cooling member, or between the second output section and the cooling member, by the second dielectric.

2. The power module according to claim 1, wherein the cooling members (3, 4) are provided on the side of the upper arm switching element or the lower arm switching element opposite to the first dielectric side.

3. A cooling member (5) is provided between the first input unit and the second input unit. The power module according to claim 1, wherein the first dielectric is provided between the first input section or the second input section and the other cooling member.

4. The power module according to claim 1, wherein the thickness of the first dielectric in the direction of arrangement of the upper arm switching element and the lower arm switching element is thinner than the thickness of the second dielectric in the direction of arrangement.

5. The power module according to claim 1, wherein the surface area of ​​the first dielectric facing the first input unit or the second input unit is larger than the surface area of ​​the second dielectric facing the first output unit or the second output unit.

6. The power module according to claim 5, wherein the surface of the first dielectric facing the first input portion or the second input portion has uneven surfaces (1c2, 2c2) when the first dielectric is viewed in plan view.

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