Low-inductance intermediate circuit with gel frame
By using gel casting and insulating film to separate the DC+ and DC- buses in the power module, and combining gel frame and laser bonding, the problem of voltage peak caused by parasitic inductance is solved, and fast switching frequency and low loss are achieved under high voltage and high current conditions.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-17
- Publication Date
- 2026-03-10
AI Technical Summary
In power modules, parasitic inductance causes voltage peaks to rise, which harms power switches and limits the improvement of switching frequency and efficiency, especially under high power conditions where the limits of semiconductor components are difficult to meet.
By using gel casting in the intermediate circuit, the DC+ bus and DC- bus are tightly guided and separated by an insulating film to form a low-inductance intermediate circuit. Combined with a gel frame and laser bonding connection, the inductance is reduced and the current conduction capability is improved.
It achieves fast switching frequency under high voltage and current conditions, reduces switching losses, and effectively reduces inductance in a compact space design, thereby improving the reliability and efficiency of power switches.
Smart Images
Figure CN121646860A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a low-inductance intermediate circuit and a power module having a low-inductance intermediate circuit. Background Technology
[0002] When the transistor is turned off, the voltage in the power module rises suddenly due to parasitic inductance. This voltage spike can damage the power switch, so its reverse voltage should be designed to be higher or its switching frequency must be reduced.
[0003] In power electronics, high efficiency is required while increasing switching frequency, a requirement that, especially at higher power levels, pushes the limits of semiconductor components. Here, a key parameter is parasitic inductance; reducing parasitic inductance minimizes the risk of overload in the power switch and lowers switching losses. Summary of the Invention
[0004] In contrast, the low-inductance intermediate circuit according to the invention, having the features of claim 1, has the advantage of reducing the creepage distance between the DC+ bus and the DC- bus by encapsulating the intermediate circuit with gel. This allows the DC+ and DC- buses to be guided relatively closely to each other, thus enabling them to be designed with limited space requirements, allowing current to be guided through the bus with particularly low inductance. The low inductance enables the increase of the switching frequency of adjacent power switches or the design of power switches for smaller reverse voltages. This is achieved according to the invention, with the features of claim 1, by comprising a low-inductance intermediate circuit between the power switch and passive electrical components, comprising DC+ and DC- buses separated from each other by an insulating film. Here, the low-inductance intermediate circuit is additionally at least partially surrounded by gel.
[0005] The gel is preferably cast in a vacuum in a liquid state onto a low-inductance intermediate circuit and subsequently cross-linked, thereby hardening the gel. The preferred gel is a silicone gel with good electrical insulating properties. Casting the gel onto the low-inductance intermediate circuit allows for the guidance of the DC+ and DC- buses with a relatively small spacing relative to each other.
[0006] A low-inductance intermediate circuit is understood to preferably have an inductance of 3 nH or less. Here, the low-inductance intermediate circuit is preferably designed to carry currents between 600 A and 900 A and voltages between 800 V and 1000 V. With an inductance of 3 nH or less, fast switching frequencies can be achieved even under high voltage and current conditions.
[0007] The dependent claims illustrate preferred improvements to the invention.
[0008] The preferred passive electrical component is the capacitor. Specifically, a film capacitor. Capacitors can store electrical energy near the power switch. Therefore, they can prevent the negative effects on the inductor caused by external power direction.
[0009] More preferably, the DC+ bus and the DC- bus are arranged parallel to each other. Parasitic inductance occurs where the current encloses a defined area. By means of the parallel and particularly flat current guidance achieved by the DC+ and DC- buses, the inductance of the intermediate circuit can be reduced.
[0010] It is particularly preferable that the DC+ bus and the DC- bus are arranged at least partially vertically relative to each other along a low-inductance intermediate circuit. By guiding the DC+ and DC- buses vertically and parallel to each other, inductance can be further reduced.
[0011] The preferred low-inductance intermediate circuit includes a first gel frame, which provides a defining portion for gelation. Here, the gel frame is configured for manufacturing by injection encapsulation of the edge region of the low-inductance intermediate circuit. Preferably, the gel frame is manufactured using an injection molding method. This allows for leak-proof and reliable manufacturing of the gel-filled region surrounding the low-inductance intermediate circuit, thereby reliably preventing leakage current during operation.
[0012] More preferably, the low-inductance intermediate circuit has a first connection region configured to construct a material-locked connection between the low-inductance intermediate circuit and the passive component. The material-locked connection can be manufactured, for example, by brazing or welding, and can reduce the resistance of the low-inductance intermediate circuit.
[0013] In a preferred embodiment of the invention, the first connection region has a plurality of alternating DC+ contact regions at the DC+ bus and DC- contact regions at the DC- bus. Contact regions are a major source of parasitic inductance. By alternating the arrangement of the plurality of DC+ and DC- contact regions, a parallel circuit of inductance exists within the contact regions, thereby reducing the total inductance caused by the low-inductance intermediate circuit. The high insulation properties of the intermediate circuit according to the invention enable a close, alternating arrangement of the contact regions within a defined space via a gel.
[0014] The preferred low-inductance intermediate circuit has a second connection region configured for connection to a power switch via wire bonding. Specifically, the second connection region is configured for connection to the power switch via laser bonding, as laser bonding allows for even lower inductance. By casting the second connection region, a close arrangement of the different potentials of the second connection regions relative to each other can be achieved.
[0015] Particularly preferred is that the second connection region has multiple alternating DC+ contact regions at the DC+ bus and DC- contact regions at the DC- bus. Therefore, the parasitic inductance of the second connection region is distributed as multiple inductors in parallel, thereby reducing the total inductance of the low-inductance intermediate circuit. Here, the low-inductance intermediate circuit cast according to the invention enables reliable and tight current guidance for different potentials in the second connection region.
[0016] Preferably, the first connection region has a second gel frame, which provides a defining portion for gelling. Here, the first connection region is cast with gel. Furthermore, it is preferable that the second connection region has a first gel frame, such that the second connection region is also cast with gel. Particularly preferably, the second gel frame is arranged on the opposite side of the first gel frame. Therefore, leak-proof and reliable casting in the first and / or second gel-filled regions can be achieved for the first and / or second connection regions, thereby reliably preventing leakage current during operation.
[0017] More preferably, the first gel framework and the second gel framework are one-piece designs. Therefore, they can be manufactured quickly and cost-effectively in a single processing step.
[0018] Preferably, the insulating film separating the DC+ and DC- buses has a width between 200 µm and 300 µm. Specifically, the insulating film has a width of 250 µm. This allows the DC- and DC+ buses to be tightly assembled. The insulating film is designed in such a way that it reliably prevents leakage current or voltage breakdown between the DC- and DC+ buses. The insulating film can also be, for example, a ceramic substrate.
[0019] Furthermore, the present invention describes a power module comprising a power switch, an intermediate circuit according to the invention, and passive electrical components. Here, the passive components are, in particular, capacitors.
[0020] Preferably, the power switch and the low-inductance intermediate circuit are at least partially arranged within the first gel frame and encapsulated by gel casting. This simultaneously reduces the creepage distance within the power switch and the low-inductance intermediate circuit, thereby enabling a compact design of the power module. Attached Figure Description
[0021] Preferred embodiments of the invention will now be described in detail with reference to the accompanying drawings. In the drawings: Figure 1 An exemplary schematic view of the front of a power module according to a preferred embodiment is shown. Figure 2 Showing from Figure 1An exemplary schematic view of the back of the power module. Figure 3 Showing from Figure 1 A schematic detailed view of the second connection area on the front of the power module. Figure 4 Showing from Figure 2 A schematic detailed view of the first connection area on the back of the power module, and Figure 5 Showing from Figure 1 A schematic cross-sectional view of the power module. Detailed Implementation
[0022] Next reference Figures 1 to 5 The power module 6, which has a low-inductance intermediate circuit 1 according to a preferred embodiment of the present invention, is described in detail.
[0023] Figure 1 The power module 6 is shown from the front. The power module 6 includes multiple power switches 2 configured to convert direct current from the low-inductance intermediate circuit 1 into three-phase current on the AC side 7. For this purpose, the power switches 2 are associated with three power switch modules 21, which convert the direct current from the low-inductance intermediate circuit 1 into one phase of the three-phase current on the AC side 7.
[0024] The low-inductance intermediate circuit 1 includes a DC+ bus 11 and a DC- bus 12. The DC+ bus 11 has two DC+ contact areas 51 for each power switch module 21, and these DC+ contact areas are connected to the power switch module 21 via three laser bonding connections 9. An insulating film 12 is disposed between the DC+ bus 11 and the DC- bus 12, or between the DC+ contact areas 51 and the DC- contact areas 52, such that the DC+ bus 11 and the DC- bus 12 are electrically insulated from each other.
[0025] The DC-bus 12 has three DC-contact areas 52 for each power switch module 21, each having two laser-bonded connections 9. Here, the DC-contact areas 52 are arranged alternately with respect to the DC+contact areas 51.
[0026] The low-inductance intermediate circuit 1, power switch 2, and AC side 7 are arranged within a first gel frame 41 in a first gel filling region 44. The first gel frame 41 serves as a defining portion for the gel 4, into which the low-inductance intermediate circuit 1, power switch 2, and AC side 7 are cast. The gel allows for a reduction in creepage distance between different potentials of the power module 6, thereby reducing the spacing between components with different potentials and lowering the inductance of the low-inductance intermediate circuit 1.
[0027] The first gel frame 41 is an injection-molded component having a wall region 43. The wall region 43 is arranged perpendicular to the surface of the power module 6 and defines a region in which the gel 4 can diffuse in an uncrosslinked state.
[0028] Figure 2 A partial view of the back of the power module 6 is schematically shown. On the back of the power module 6, the passive electrical component 3 is represented as a capacitor 31. The capacitor 31 is connected to the low-inductance intermediate circuit 1 via a first connection region 5.
[0029] The first connection region 5 has six DC+ contact regions 51 and nine DC- contact regions 52, which are arranged alternately with a small spacing relative to each other. An insulating film 15 is disposed between the DC+ contact regions 51 and the DC- contact regions 52, respectively. The inductances of the DC+ contact regions 51 and the DC- contact regions 52 are connected in parallel, thereby reducing the total inductance of the power module 6 and the low-inductance intermediate circuit 1. Alternatively, a larger or smaller number of DC+ and DC- contact regions 51 and 52 can also be provided in the first connection region 5.
[0030] A second gel frame 42 is arranged around the first contact area 5. The second gel frame is cast with gel 4 and thus forms a second gel-filled area 45. The second gel frame 42 is connected to the first gel frame and is manufactured together with the first gel frame 41 in its own injection molding process. Therefore, the first gel frame 41 and the second gel frame 42 are integral.
[0031] Figure 3 Showing from Figure 1 A detailed view of the front of the power module 6 within the region of the second connection area 8. The DC+ bus 11 and DC- bus 12 are arranged substantially parallel to each other in the second connection area 8, wherein the limiting region between the DC+ bus 11 and DC- bus 12 is constructed in a meandering manner. Therefore, the DC+ bus 11 and DC- bus 12 are interlocked with each other in a "fortified" manner in the second connection area 8. The intermediate region between the DC+ bus 11 and DC- bus 12 is filled by an insulating film 15.
[0032] The DC+ contact area 51 and DC- contact area 52 are alternately formed by the meandering shape of the intermediate region. They are configured for connection to the power switch module 21 via laser bonding connections 9. Here, in this embodiment, each DC+ contact area 51 has three laser bonding connections 9. The DC- contact area 52 either has two laser bonding connections 9 connecting the DC- contact area 52 to the power switch module 21, or it has four laser bonding connections 9, wherein two laser bonding connections 9 connect the DC- contact area 52 to the power switch module 21 respectively, and two additional laser bonding connections 9 connect the DC- contact area 52 to another power switch module 21.
[0033] The first gel frame 41 is adjacent to the second connection region 8. Figure 41 shows the honeycomb structure of the first gel frame 51. The honeycomb structure enables improved mechanical properties of the low-inductance intermediate circuit 1 and reduces the material requirements of the first gel frame 41.
[0034] Figure 4 Showing from Figure 2 A detailed view of the rear of power module 6. Here, in Figure 4 The capacitor 31 is omitted. A DC-bus 12 extends on the back of the power module 6, and has a gap in the first connection area 5, in which a DC+ contact area 51 is arranged. The DC+ contact area 51 is separated from the DC-bus 12 on its peripheral side by an insulating film 15. Between the gaps, the DC-bus 12 has a DC-contact area 52. The DC-contact area 52 and the DC+ contact area 51 of the first connection area 5 are configured to form a material-locking connection with the passive electrical components 3.
[0035] The first contact area 5 is defined by a second gel frame 42. The second gel frame 42 has rectangular openings for the DC- contact area 52 and the DC+ contact area 51.
[0036] according to Figure 1 In the embodiments, Figure 5 A schematic cross-sectional view of the power module is shown in the region of the low-inductance intermediate circuit 1.
[0037] The low-inductance intermediate circuit 1 includes a DC+ bus 11 and a DC- bus 12, which contact the power switch 2 through the second connection region 8 and are connected to the capacitor 31 in the first connection region 5. Here, in Figure 5 The power switch 2, which is not shown, is connected to the low-inductance intermediate circuit 1 via laser bonding connection 9.
[0038] exist Figure 5In the process, laser bonding connection 9 is connected to DC- bus 12 via DC- contact area 52. Capacitor 31 is connected to DC+ bus 11 via DC+ contact area 51.
[0039] exist Figure 5 The laser bonding connection 9 to the DC+ contact area 51 and the connection between the capacitor 31 and the DC- contact area 51 are not shown.
[0040] DC+ bus 11 and DC- bus 12 extend parallel to each other between the first connection region 5 and the second connection region 8 and are arranged vertically relative to each other in a flat manner. Therefore, the inductance of the low-inductance intermediate circuit 1 can be kept to a minimum.
[0041] An insulating film 15 is arranged between the DC+ bus 11 and the DC- bus 12.
[0042] On a layer composed of DC+ busbar 11, DC- busbar 12, and insulating film 15, a first gel frame 41 is arranged on the front side and a second gel frame 42 is arranged on the back side. The first gel frame 41 has a void in the region of the second connection area 8, which is filled with gel 4. The second gel frame 42 also has a void in the region of the first connection area 5, which is also filled with gel 4. The voids in the first gel frame 41 and the second gel frame 42 are defined by wall regions 43.
[0043] A capacitor 31 is arranged on the second gel frame 42.
Claims
1. Low-inductive intermediate circuit (1) between a power switch (2) and a passive electrical component (3), the low-inductive intermediate circuit comprising: - a DC+ busbar (11), - a DC- busbar (12), and - an insulation film (15) arranged between the DC+ busbar (11) and the DC- busbar (12), - wherein the low-inductive intermediate circuit (1) is at least partially casted by a gel (4).
2. The low- inductance intermediate circuit (1) according to claim 1, wherein The passive electrical component (3) is a capacitor (31), in particular a film capacitor.
3. The low- inductance intermediate circuit (1) of claim 2, wherein The DC+ busbar (11) and the DC- busbar (12) are arranged parallel to each other.
4. The low- inductance intermediate circuit (1) of claim 3, wherein The DC+ busbar (11) and the DC- busbar (12) are arranged at least partially on top of each other along the low-inductive intermediate circuit (1).
5. The low- inductance intermediate circuit (1) according to any one of the preceding claims, wherein The low-inductive intermediate circuit (1) comprises a first gel frame (41) providing a defined portion for the gel (4), wherein the first gel frame (41) is provided for manufacturing by injection encapsulation of edge regions of the low-inductive intermediate circuit (1).
6. The low- inductance intermediate circuit (1) according to any one of the preceding claims, wherein The low-inductive intermediate circuit (1) has a first connection area (5) provided for a material-locking connection between the low-inductive intermediate circuit (1) and the passive component (3).
7. The low- inductance intermediate circuit (1) of claim 6, wherein The first connection area (5) has a plurality of alternating DC+ contact areas (51) at the DC+ busbar (11) and DC- contact areas (52) at the DC- busbar (12).
8. The low- inductance dc link (1) according to any one of the preceding claims, wherein The low-inductive intermediate circuit (1) has a second connection area (8) provided for a connection to the power switch (2) by wire bonding.
9. The low- inductance intermediate circuit (1) of claim 8, wherein The second connection area has a plurality of alternating DC+ contact areas (51) at the DC+ busbar (11) and DC- contact areas (52) at the DC- busbar (12).
10. The low- inductance intermediate circuit (1) according to claims 5 to 9, wherein The first connection area (5) has a second gel frame (42) providing a defined portion for the gel (4), wherein the first connection area (5) is casted with the gel (4) and / or wherein the second connection area (8) has the first gel frame (41), wherein the second connection area (8) is casted with the gel (4).
11. The low- inductance intermediate circuit (1) according to claim 10, wherein The first gel frame (41) and the second gel frame (42) are one piece.
12. The low- inductance dc link (1) according to any one of the preceding claims, wherein The insulation film (15) separating the DC+ busbar (11) and the DC- busbar (12) from each other has a width of between 200 pm and 300 pm, in particular 250 pm.
13. Power module (6) comprising a power switch (2), an intermediate circuit (1) according to any one of the preceding claims and a passive electrical component (3), in particular a capacitor (31).
14. The power module (6) according to claim 13, wherein The power switch (2) and the intermediate circuit (1) are at least partially arranged within the first gel frame (41) and encapsulated by a gel (4).