Low-inductance DC link having gel frame
Patent Information
- Authority / Receiving Office
- EP · EP
- Patent Type
- Applications
- Current Assignee / Owner
- Filing Date
- 2024-05-17
- Publication Date
- 2026-04-08
Smart Images
Figure EP2024063721_05122024_PF_FP_ABST
Abstract
Description
[0001] Description
[0002] title
[0003] Low-inductive intermediate circuit with gel frame
[0004] State of the art
[0005] The present invention relates to a low-inductance intermediate circuit and a power module with a low-inductance intermediate circuit.
[0006] Turning off a transistor can cause the voltage in power modules to rise sharply due to parasitic inductances. These voltage spikes can endanger the power switches, which is why their blocking voltage must be set accordingly high or their switching frequency reduced.
[0007] The demand in power electronics for high efficiencies while simultaneously increasing switching frequencies encounters the limitations of semiconductor components, especially at higher power levels. A key parameter here is parasitic inductances, the reduction of which reduces the risk of overloading the power switches and reduces switching losses.
[0008] Disclosure of the invention
[0009] The low-inductance intermediate circuit according to the invention with the features of claim 1 has the advantage that the creepage distances between a DC+ busbar and a DC- busbar are reduced by encapsulating the intermediate circuit with a gel. This enables the DC+ busbar and the DC- busbar to be guided closely to one another, whereby they can be designed with a small space requirement such that the current is guided through the busbars with particularly low inductance. The low inductance makes it possible to increase the switching frequencies of adjacent circuit breakers or to design the circuit breakers for a lower blocking voltage. This is achieved according to the invention with the features of claim 1 in that a low-inductance intermediate circuit between a circuit breaker and a passive electrical component comprises a DC+ busbar and a DC- busbar, which are separated from one another by an insulating film.The low-inductance intermediate circuit is also at least partially enclosed by a gel.
[0010] The gel is preferably poured in a liquid state over the low-inductance intermediate circuit under vacuum and then cross-linked, causing it to harden. The gel is preferably a silicone gel, which has good electrical insulation properties. Potting the low-inductance intermediate circuit with gel allows the DC+ and DC- rails to be routed with a small gap between them.
[0011] A low-inductance intermediate circuit is one that preferably has an inductance of less than or equal to 3 nH. The low-inductance intermediate circuit is preferably designed to transmit currents between 600 A and 900 A and voltages between 800 V and 1000 V. The low inductance of 3 nH or less enables fast switching frequencies even at high electrical voltages and currents.
[0012] The subclaims show preferred developments of the invention.
[0013] Preferably, the passive electrical component is a capacitor. In particular, the capacitor is a film capacitor. The capacitor allows for the storage of electrical energy near the power switches. This prevents negative effects on the inductance caused by an external power supply.
[0014] More preferably, the DC+ rail and the DC- rail are arranged parallel to each other. Parasitic inductances arise where the current encloses a certain area. The parallel and, in particular, flat current flow through the DC+ and DC- rails makes it possible to reduce the inductance of the intermediate circuit.
[0015] Particularly preferably, the DC+ rail and the DC- rail are arranged at least partially above one another along the low-inductance intermediate circuit. By routing the DC+ and DC- rails parallel to one another, a further reduction in inductance is possible.
[0016] The low-inductance intermediate circuit preferably comprises a first gel frame, which provides a boundary for the gel. The gel frame is designed to be manufactured by overmolding an edge region of the low-inductance intermediate circuit. The gel frame is preferably manufactured using an injection molding process. This enables leak-proof and reliable production of a gel-filled region around the low-inductance intermediate circuit, thereby reliably preventing leakage currents during operation.
[0017] Further preferably, the low-inductance intermediate circuit has a first connection region configured to form a material connection between the low-inductance intermediate circuit and the passive component. The material connection can be established, for example, by soldering or welding and enables a reduction in the electrical resistance of the low-inductance intermediate circuit.
[0018] In a preferred embodiment of the invention, the first connection region has a plurality of alternating DC+ contact areas on the DC+ rail and DC- contact areas on the DC- rail. The contact area is a significant source of parasitic inductances. The alternating arrangement of a plurality of DC+ and DC- contact areas results in a parallel connection of the inductances in the contact area, which can reduce the resulting total inductance of the low-inductance intermediate circuit. The close, alternating arrangement of the contact areas in a limited space is made possible by the high insulation properties of the intermediate circuit according to the invention with the aid of the gel.
[0019] Preferably, the low-inductance intermediate circuit has a second connection region configured to be connected to the power switch by wire bonding. In particular, the second connection region is configured to be connected to the power switch by laser bonding, since laser bonding allows for lower inductances. Encapsulating the second connection region enables a close arrangement of the different electrical potentials of the second connection region relative to one another.
[0020] Particularly preferably, the second connection region has a plurality of alternating DC+ contact areas on the DC+ rail and DC- contact areas on the DC- rail. Thus, the parasitic inductance of the second connection region is divided into several parallel inductances, thereby reducing the total inductance of the low-inductance intermediate circuit. The encapsulated low-inductance intermediate circuit according to the invention enables secure, tight current conduction of different electrical potentials in the second connection region.
[0021] The first connection region preferably has a second gel frame, which provides a boundary for the gel. The first connection region is encapsulated with the gel. Furthermore, the second connection region preferably has the first gel frame, so that the second connection region is also encapsulated with the gel. Particularly preferably, the second gel frame is arranged on the opposite side of the first gel frame. This enables leak-proof and reliable encapsulation of the first connection region and / or second connection region in a first and second gel-filled region, whereby leakage currents can be reliably prevented during operation.
[0022] Further preferably, the first gel frame and the second gel frame are one-piece. Thus, they can be manufactured quickly and cost-effectively in a single production step.
[0023] The insulation film separating the DC+ rail and the DC- rail preferably has a width between 200 pm and 300 pm. In particular, the insulation film has a width of 250 pm. This allows the DC- and DC+ rails to be brought close together. The insulation film is designed to reliably prevent leakage currents or voltage flashovers between the DC- and DC+ rails. The insulation film can also be a ceramic substrate, for example. The invention further describes a power module comprising a power switch, an intermediate circuit according to the invention, and a passive electrical component. The passive component is, in particular, a capacitor.
[0024] Preferably, the power switch and the low-inductance intermediate circuit are arranged at least partially within the first gel frame and encapsulated in a gel. This allows the creepage distances within the power switch and the low-inductance intermediate circuit to be reduced simultaneously, enabling a compact design of the power module.
[0025] Short description of the drawings
[0026] A preferred embodiment of the invention will be described in detail below with reference to the accompanying drawings. In the drawing:
[0027] Figure 1 is an exemplary schematic view of a front side of a
[0028] Power module according to a preferred embodiment,
[0029] Figure 2 is an exemplary schematic view of a rear side of the
[0030] Power module from Figure 1 ,
[0031] Figure 3 is a schematic detailed view of a second
[0032] Connection area on the front of the power module from Figure 1 ,
[0033] Figure 4 is a schematic detailed view of a first
[0034] connection area on the back of the power module shown in Figure 2, and
[0035] Figure 5 is a schematic sectional view of the power module from
[0036] Figure 1.
[0037] Embodiment of the invention With reference to Figures 1 to 5, a power module
[0038] 6 with a low-inductance intermediate circuit 1 according to a preferred embodiment of the invention is described in detail.
[0039] Figure 1 shows the power module 6 from a front view. The power module 6 comprises a plurality of power switches 2, which are configured to convert a direct current from the low-inductance intermediate circuit 1 into a three-phase current on an alternating current side 7. For this purpose, the power switches 2 are assigned to three power switch modules 21, each of which converts the direct current from the low-inductance intermediate circuit 1 into one phase of the three-phase current on the alternating current side 7.
[0040] The low-inductance intermediate circuit 1 comprises a DC+ rail 11 and a DC- rail 12. The DC+ rail 11 has two DC+ contact areas 51 per circuit breaker module 21, which are each connected to the circuit breaker module 21 via three laser bonded connections 9. An insulating film 12 is arranged between the DC+ rail 11 and the DC- rail 12, or between the DC+ contact area 51 and the DC- contact area 52, which electrically insulates the DC+ rail 11 and the DC- rail 12 from one another.
[0041] The DC busbar 12 has three DC contact areas 52 per circuit breaker module 21, each with two laser bonded connections 9. The DC contact areas 52 are arranged alternately with the DC+ contact areas 51.
[0042] The low-inductance intermediate circuit 1, the power switches 2, and the AC side 7 are arranged within a first gel frame 41 in a first gel-filled region 44. The first gel frame 41 represents a boundary for a gel 4, with which the low-inductance intermediate circuit 1, the power switches 2, and the AC side 7 are encapsulated. The gel makes it possible to reduce creepage distances between different electrical potentials of the power module 6 and thus to reduce the distances between components with different electrical potentials and to reduce the inductance of the low-inductance intermediate circuit 1. 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 delimits the region in which the gel 4 can spread in the uncrosslinked state.
[0043] Figure 2 schematically illustrates a section of the rear side of the power module 6. On the rear side of the power module 6, a passive electrical component 3 is shown as a capacitor 31. The capacitor 31 is integrally connected to the low-inductance intermediate circuit 1 via a first connection area 5.
[0044] The first connection area 5 has six DC+ contact areas 51 and nine DC- contact areas 52, which are arranged alternately at short distances from one another. The insulating film 15 is arranged between the DC+ contact areas 51 and the DC- contact areas 52. The inductances of the DC+ contact areas 51 and the DC- contact areas 52 are connected in parallel, thereby reducing the total inductance of the power module 6 and the low-inductance intermediate circuit 1. Alternatively, a higher or lower number of DC+ and DC- contact areas 51, 52 can be provided in the first connection area 5.
[0045] A second gel frame 42 is arranged around the first contact area 5, which is encapsulated 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 in the same injection molding process as the first gel frame 41. Thus, the first gel frame 41 and the second gel frame 42 are one-piece.
[0046] Figure 3 shows a detailed view of the front of the power module 6 from Figure
[0047] I in the area of the second connection area 8. The DC+ rail 11 and the DC- rail 12 are arranged essentially parallel to each other in the second connection area 8, with the boundary area between the DC+ rail 11 and the DC- rail 12 being designed in a meandering manner. Thus, the DC+ rail
[0048] II and the DC- busbar 12 are interlocked in a “castellated” manner in the second connection area 8. The intermediate area between the DC+ busbar 11 and the DC- busbar 12 is filled with the insulation film 15. The meandering shape of the intermediate area results in alternating DC+ contact areas 51 and DC- contact areas 52, which are designed to be connected to the circuit breaker modules 21 via laser bond connections 9. In the exemplary embodiment, each DC+ contact area 51 has three laser bond connections 9. The DC- contact area 52 has either two laser bond connections 9, which connect the DC- contact area 52 to a circuit breaker module 21, or four laser bond connections 9, with two laser bond connections 9 connecting the DC- contact area 52 to a circuit breaker module 21 and the two further laser bond connections 9 connecting the DC contact area 52 to another circuit breaker module 21.
[0049] The first gel frame 41 borders the second connection area 8. Figure 41 shows a honeycomb structure of the first gel frame 51. The honeycomb structure enables an increase in the mechanical properties of the low-inductance intermediate circuit 1 and reduces the material requirements of the first gel frame 41.
[0050] Figure 4 shows a detailed view of the rear of the power module 6 from Figure 2. In Figure 4, the capacitor 31 is hidden. The DC rail 12 runs on the rear of the power module 6 and has cutouts in the first connection region 5, in which the DC+ contact region 51 is arranged. The DC+ contact region 51 is separated from the DC rail 12 on the circumference by the insulation film 15. Between the cutouts, the DC rail 12 has DC contact regions 52. The DC contact regions 52 and DC+ contact regions 51 of the first connection region 5 are designed to form a materially bonded connection with the passive electrical component 3.
[0051] The first contact area 5 is bounded by the second gel frame 42. The second gel frame 42 has a rectangular recess for the DC- contact areas 52 and the DC+ contact areas 51.
[0052] Figure 5 shows a schematic sectional view of the power module, according to the embodiment in Figure 1, in the area of the low-inductance intermediate circuit 1. The low-inductance intermediate circuit 1 comprises the DC+ rail 11 and the DC- rail 12, which contact the power switches 2 via a second connection area 8 and connect them to the capacitor 31 in a first connection area 5. The power switches 2, which are not shown in Figure 5, are connected to the low-inductance intermediate circuit 1 via laser bond connections 9.
[0053] In Figure 5, the laser bond connection 9 is connected to the DC rail 12 via the DC contact area 52. The capacitor 31 is connected to the DC+ rail 11 via the DC+ contact area 51.
[0054] Not shown in Figure 5 are laser bond connections 9 with the DC+ contact area 51 and connections between the capacitor 31 and the DC- contact area 51.
[0055] The DC+ rail 11 and the DC- rail 12 run parallel and superimposed between the first connection area 5 and the second connection area 8, flat relative to each other. This allows the inductance of the low-inductance intermediate circuit 1 to be kept to a minimum.
[0056] An insulating foil 15 is arranged between the DC+ rail 11 and the DC- rail 12.
[0057] On the layer of DC+ rail 11, DC- rail 12, and insulation foil 15, the first gel frame 41 is arranged on the front side, and the second gel frame 42 is arranged on the back side. The first gel frame 41 has a recess in the region of the second connection region 8, which recess is filled with gel 4. The second gel frame 42 has a recess in the region of the first connection region 5, which recess is also filled with gel 4. The recess is delimited in the first gel frame 41 and the second gel frame 42 by a wall region 43.
[0058] The capacitor 31 is arranged on the second gel frame 42.
Claims
Claims 1. Low-inductance intermediate circuit (1) between a circuit breaker (2) and a passive electrical component (3), comprising a DC+ rail (11), a DC- rail (12), and an insulation film (15) arranged between the DC+ rail (11) and the DC- rail (12), - wherein the low-inductance intermediate circuit (1) is at least partially encapsulated by a gel (4).
2. 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. Low-inductance intermediate circuit (1) according to claim 2, wherein the DC+ rail (11) and the DC- rail (12) are arranged parallel to each other.
4. Low-inductance intermediate circuit (1) according to claim 3, wherein the DC+ rail (11) and the DC- rail (12) are arranged at least partially one above the other along the low-inductance intermediate circuit (1).
5. Low-inductance intermediate circuit (1) according to one of the preceding claims, wherein the low-inductance intermediate circuit (1) comprises a first gel frame (41) which provides a boundary for the gel (4), wherein the first gel frame (41) is designed to be produced by overmolding an edge region of the low-inductance intermediate circuit (1).
6. Low-inductance intermediate circuit (1) according to one of the preceding claims, wherein the low-inductance intermediate circuit (1) has a first connection region (5) which is designed to form a material connection between the low-inductance intermediate circuit (1) and the passive component (3).
7. Low-inductance intermediate circuit (1) according to claim 6, wherein the first connection region (5) comprises a plurality of alternating DC+ contact regions (51) on the DC+ rail (11) and DC- contact areas (52) on the DC- rail (12).
8. Low-inductance intermediate circuit (1) according to one of the preceding claims, wherein the low-inductance intermediate circuit (1) has a second connection region (8) which is designed to be connected to the circuit breaker (2) by wire bonding.
9. Low-inductance intermediate circuit (1) according to claim 8, wherein the second Connection area has a plurality of alternating DC+ contact areas (51) on the DC+ rail (11) and DC- contact areas (52) on the DC- rail (12).
10. Low-inductance intermediate circuit (1) according to claim 5 to 9, wherein the first connection region (5) has a second gel frame (42) which provides a boundary for the gel (4), wherein the first connection region (5) is cast with the gel (4) and / or wherein the second connection region (8) has the first gel frame (41), wherein the second connection region (8) is cast with the gel (4).
11. 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. Low-inductance intermediate circuit (1) according to one of the preceding claims, wherein the insulation film (15) which separates the DC+ rail (11) and the DC- rail (12) from one another has a width between 200 pm and 300 pm, in particular of 250 pm. 13 Power module (6) comprising a power switch (2), an intermediate circuit (1) according to one of the preceding claims and a passive electrical component (3), in particular a capacitor (31). 14 Power module (6) according to claim 13, wherein the power switch (2) and the intermediate circuit (1) are arranged at least partially within the first gel frame (41) and are encapsulated by a gel (4).