Electrical component and method for grounding an electrical component

Abstract

The invention relates to an electrical component (1), wherein the electrical component (1) has a housing (5) in which the electrical components of the component (1) are arranged, wherein at least one component is connected to an internal ground (4), wherein the internal ground (4) can be connected to an external ground (7) outside the housing (5) via at least one connecting element (6), wherein a switching element (S1-S6) is arranged between the internal ground (4) and the at least one connecting element (6), wherein the electrical component (1) has at least one control unit (3) which is designed to control the at least one switching element (S1-S6) as a function of an operating point of the electrical component (1), and also to a method for connecting an electrical component to ground.

Description

[0001] The invention relates to an electrical component and a method for grounding such an electrical component.

[0002] Electrical components often generate electromagnetic interference, especially if they contain fast-switching transistors. Examples of such components include pulse-controlled inverters and DC / DC converters.

[0003] To improve EMC behavior, it is known that the components of the component are arranged in a housing, whereby the housing is electrically conductive and is made of metal, for example. This causes the housing to act like a Faraday cage. An internal ground of the electrical component is connected to an external ground. In a motor vehicle, this is typically the body or terminal 31. Screw connections are often used as connecting elements. In this case, capacitances can also be provided in the connecting line between the internal and external grounds in order to improve EMC behavior. However, it can also be intended that the connection simply has the lowest possible resistance. The type of connection depends on the respective component, whereby the most suitable connection is typically determined in advance through EMC tests.

[0004] The invention is based on the technical problem of creating an electrical component with improved EMC behavior and of providing a suitable method for grounding an electrical component.

[0005] The solution to the technical problem is provided by an electrical component having the features of claim 1 and a method having the features of claim 9. Further advantageous embodiments of the invention emerge from the subclaims.

[0006] The electrical component has a housing in which the electrical components of the component are arranged, wherein at least one component is connected to an internal ground. The internal ground can be connected to an external ground outside the housing via at least one connecting element. A switching element is arranged between the internal ground and the at least one connecting element, wherein the electrical component has at least one control unit which is designed to control the at least one switching element depending on an operating point of the electrical component. The basic idea of ​​the invention is that, depending on the operating points, it is possible to choose between at least two different ground connections.For example, a ground connection is fixed for a first operating point, whereas at the second operating point the switching element is closed, resulting in a different ground connection. This allows the EMC behavior to be adjusted for different operating points. For example, if a capacitor is provided in the fixed connection, this capacitor can be short-circuited at the second operating point by closing the switching element, resulting in a low-impedance ground connection.

[0007] In one embodiment, at least one capacitor and / or one resistor is connected in series with the at least one switching element. The capacitor and resistor can be connected in series or in parallel.

[0008] In a further embodiment, at least two switching elements are present, wherein the series circuits comprising switching element and capacitor and / or resistor are connected in parallel. It can also be provided that at least one switching element is not assigned a capacitor or resistor. It can also be provided that all ground connections are assigned at least one switching element, i.e. there is no fixed ground connection. If there are several switching elements, it can further be provided that for each operating point exactly one switching element is closed and the other switching elements are open. However, it is also possible for two or more switching elements to be closed for one operating point.

[0009] In a further embodiment, at least two connecting elements are connected, with the switching elements being connected to different connecting elements. This is based on the realization that, in addition to the components (capacitor and / or resistor), the EMC behavior also depends on the spatial location of the external ground connection.

[0010] In a further embodiment, the connecting elements are designed as screw connections.

[0011] In another embodiment, the electrical component is designed as a pulse-controlled inverter or DC / DC converter. The pulse-controlled inverter can be a pulse-controlled inverter for driving the traction network of an electric vehicle and / or an onboard charger. However, the electrical component can also be an EMC filter.

[0012] In a further embodiment, the switching elements are designed as transistors. It can further be provided that the switching elements are each formed by two MOSFETs connected in series in opposite directions, thus preventing parasitic currents through the intrinsic diodes.

[0013] With regard to the procedural design of the invention, reference is made in full to the preceding statements.

[0014] The invention is explained in more detail below using preferred embodiments. The figures show: Fig. 1 a schematic representation of an electrical component and Fig. 2 a schematic representation of a switching element in an embodiment with two oppositely connected MOSFETs.

[0015] In the Fig. 1 schematically shows an electrical component 1 designed as a pulse-controlled inverter. The pulse-controlled inverter 2 has three half-bridges, each having a high-side switch HS1-HS3 and a low-side switch LS1-LS3. The high-side switches HS1-HS3 and the low-side switches LS1-LS3 are preferably designed as transistors, although the high-side and low-side switches can also have more than one transistor. The electrical component 1 has a control unit 3 that controls the high-side switching elements HS1-HS3 and the low-side switching elements LS1-LS3. The control unit 3 can thus operate the pulse-controlled inverter 2 at different operating points. The low-side switching elements LS1-LS3 are connected to an internal ground 4. The electrical component 1 is arranged in an electrically conductive housing 5. The housing 5 is connected to an external ground 7 via connecting elements 6.The connecting elements 6 are preferably designed as a screw connection, i.e. a screw or bolt with a nut. The number of connecting elements 6 can also be greater than two. The left connecting element is connected to the internal ground 4 via a switching element S1 in series with a capacitor C1. In parallel with the series connection of the first switching element S1 and capacitor C1, a further switching element S2 is connected in series with a parallel connection of a resistor R2 and a capacitor C2. Also shown is a further switching element S3, which is connected in parallel to the two series connections. Corresponding switching elements S4-S6 are then arranged with capacitors C4, C5 and resistor R5 between the internal ground 4 and the right connecting element 6. The capacitors C1 and C4 and / or the capacitors C2 and C5 and the resistors R2 and R5 can be the same. However, they can also be different.This involves determining which ground connection results in the most optimal EMC behavior for various operating points of the pulse-controlled inverter 2. For example, the EMC behavior is best at a first operating point when the switching element S1 is closed. At a second operating point, the EMC behavior is best when the second switching element S2 is closed, and so on. It can also be provided that the EMC behavior is most optimal at an operating point when two or more switches S1-S6 are closed. The assignment of the operating point and the switching elements S1-S6 to be closed is stored in the control unit 3, which then sets the operating point by controlling the high- and low-side switching elements HS1-HS3, LS1-LS3 and controls the corresponding switching element(s) S1-S6. The operating points can differ, for example, in terms of frequency and / or power or the direction of energy flow.The switching elements S1-S6 can be implemented as relays or transistors. If the transistors are implemented as MOSFETs, they have an intrinsic diode, so that the current flow in the off state is not completely blocked in both directions, which can lead to unwanted feedback from the external ground 7.

[0016] Preferably, therefore, the switching element S1-S6 is formed by two oppositely connected MOSFETs T1, T2, which in Fig. 2 for the first switching element S1. List of reference symbols 1 component 2 pulse inverters 3 Control unit 4 internal mass 5 housings 6 Connecting element 7 external mass HS1-HS3 high-side switching elements LS1-LS3 low-side switching elements C1, C2, C4, C5 capacitors R2, R5 resistors S1-S6 switching elements T1, T2 MOSFETs

Claims

[1] Electrical component (1), wherein the electrical component (1) has a housing (5) in which the electrical components of the component (1) are arranged, wherein at least one component is connected to an internal ground (4), wherein the internal ground (4) can be connected to an external ground (7) outside the housing (5) via at least one connecting element (6), characterized by that a switching element (S1-S6) is arranged between the internal ground (4) and the at least one connecting element (6), wherein the electrical component (1) has at least one control unit (3) which is designed to control the at least one switching element (S1-S6) as a function of an operating point of the electrical component (1). [2] Electrical component according to claim 1, characterized by that at least one capacitor (C1, C2, C4, C5) and / or one resistor (R2, R5) is connected in series with the at least one switching element (S1, S2, S4, S5). [3] Electrical component according to claim 2, characterized by that at least two switching elements (S1-S6) are present, with the series circuits connected in parallel. [4] Electrical component according to claim 3, characterized by that at least two connecting elements (6) are present, wherein the switching elements (S1-S6) are connected to different connecting elements (6). [5] Electrical component according to one of the preceding claims, characterized by that the connecting element (6) is designed as a screw connection. [6] Electrical component according to one of the preceding claims, characterized by that the electrical component (1) is designed as a pulse inverter (2) or DC / DC converter. [7] Electrical component according to one of the preceding claims, characterized by that the switching elements (S1-S6) are designed as transistors (T1, T2). [8] Electrical component according to claim 7, characterized by that the switching elements (S1-S6) are each formed by two MOSFETs connected in series in opposite directions. [9] Method for grounding an electrical component (1), wherein the electrical component (1) has a housing (5) in which the electrical components of the component (1) are arranged, wherein at least one component is connected to an internal ground (4), wherein the internal ground (4) can be connected to an external ground (7) outside the housing (5) via at least one connecting element (6), wherein a switching element (S1-S6) is arranged between the internal ground (4) and the at least one connecting element (6), wherein the electrical component (1) has at least one control unit (3) which controls the at least one switching element (S1-S6) as a function of an operating point of the electrical component (1).

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