ES2897005A1 - EMI stackable filter. (Machine-translation by Google Translate, not legally binding) - Google Patents

Abstract

An EMI filter comprising a main unit (115) that can be connected to a stackable complement (120), having the main unit with connectors (51, 52; 53, 54) to connect between a power supply and an electrical charge, Power conductors (42, 44) that can be electrically connected by the connectors between the power supply and the electrical charge, inductive elements (L1-L4) to block an unwanted interference signal superimposed at a supply voltage; Including the stacking complement an additional electrical circuit (20) on a printed circuit board (127), the printed circuit board (127) being electrically connected permanently to the power conductors (42, 44) by means of connection means Complementary (32, 34), according to which the stacking complement is configured so that it is stated in the main unit, according to which the printed circuit board, when stacked, joins the complementary connection means without interrupting The electrical continuity of the power conductors (42, 44). (Machine-translation by Google Translate, not legally binding)

Description

DESCRIPTION

STACKABLE EMI FILTER

technical domain

The present invention relates to filters against electromagnetic interference (EMI filters). The concept of an EMI filter overlaps with, and for the purpose of this discussion is synonymous with: electromagnetic compatibility filters (EMC filters), line filters, EMI/EMC chokes, and low-pass filters.

Related art

Most EMI filter applications involve passive modules that are inserted between a device and its power source, along supply conductors that could have a direct current (DC) supply, or an alternating current supply. (AC) with a utility frequency below 400 Hz, typically 50/60 Hz.

Low pass filters are found in almost an infinite variety of circuits, many of which are suitable for use as EMI filters. A single-phase AC or DC EMI filter typically has two line terminals and two load terminals that are internally connected by a low-resistance path comprising conductors and inductive elements. The filter also includes bypass elements, usually capacitive or resistive in nature, whereby the current supply will pass through the filter with little or no change, and electromagnetic interference occurring at a higher frequency is attenuated. to a large degree. Normally, the path between the line and load terminals is guaranteed by means of large gauge conductors or solid busbars, to minimize ohmic losses.

There are also multi-phase AC EMI filters, and the present invention applies to them as well. The number of line and load terminals on these devices corresponds to the number of phases, plus optionally a pair for a neutral conductor.

Although the ports of an EMI filter are conventionally designated as "line" and "load" or "in" and "out", many filters are in fact bidirectional and attenuate the interference in both directions. EMI filters are not limited to being inserted directly between a supply line and a load, but also find their place in more complex equipment, such as motorized drive units.

In addition to their electrical and filtering characteristics, EMI filters must also meet specifications for dimensions, heat dissipation, thermal resistance, vibration immunity, and many other parameters. In automotive applications, where electrical components are becoming more common, these specifications are especially strict. As a result, despite the apparent simplicity of the underlying electrical circuitry, EMI filters are complex products that are difficult to design and customize for all possible applications.

Brief statement of the invention

The present invention proposes a stackable filter that can be adapted to different applications by superimposing different complementary modules on a base unit.

According to the invention, these objects are achieved by the subject matter of the appended claims.

Brief description of the drawings

Exemplary embodiments of the invention are set forth in the description and illustrated by the drawings, in which:

Figure 1a schematically illustrates the electrical circuit of an EMI filter.

Figures 1b and 1c illustrate a filter with different electrical characteristics than those of figure 1a, thanks to the inclusion of additional components.

Figure 2 illustrates the stackable filter of the invention.

Examples of embodiments of the present invention

Figure 1a represents a DC or single-phase EMI filter 15. The present description will refer to this type of device for brevity, it being understood that the invention also includes multi-phase filters. The filter has line terminals 51, 52 for connection to a supply line, and load terminals 53, 54 for providing filtered power to a load not shown. Line and load are connected via bus bars 42, 44, or other suitable power conductors, with inductive elements L1-L4 interposed.

Capacitors C1, C2 shunt unwanted interference currents to ground. These are connected between the bus bars 41,42 and ground, or another suitably low impedance node at the frequencies where interference occurs.

The EMI filter 15 may be included in a filter base unit of the invention, as will be discussed below.

Figure 1b illustrates a filter having all of the filter elements 15 and additional bypass components 20. The bypass components include two additional bypass elements between the bus bar and ground: R2, C4, respectively R3, C5, and a line-to-line tap composed of R1 and C3.

In the example presented, each of the additional elements is made up of a capacitor and a resistor in series, to improve attenuation and damping, although this is not essential, and the invention is not limited thereby. In other variants not shown, the additional elements 20 can have the damping resistors in parallel with the reactive components, instead of in series as shown, or they are simply composed of damping resistors, connected between the lines or between the lines. and ground, electrically connected in parallel to the capacitors in the main circuit 15, or simply capacitors, between the lines and ground or between the lines. Additional components may also include an RLC network of any topology, and active elements.

The addition of the bypass components 20 to the filter 15 changes the transfer function of the filter and/or modifies its behavior, possibly improving the attenuation in some desired frequency band, suppressing a resonance or adding some function by means of active elements.

The additional elements 20 can be included in a stackable complement according to the invention, as will be explained later.

Figure 1c shows how the additional elements 20 can be added to the original filter 15 without compromising the continuity of the busbars 22, 24. The additional elements 20 and the original filter 15 can conveniently be kept at different levels, and the connection is ensured by two conductive elements 32, 34 connecting the bus bars 42, 44 to suitable nodes of the additional circuit 20. The conductors 32, 34 should have a low impedance at the frequency at which the interference occurs, although they are not crossed by charging current at low or DC frequency and do not contribute appreciably to power losses. The electrical continuity between the ground points of the original circuit 15 and of the additional element 20 is implicit.

Figure 2 illustrates the stackable filter of the invention with a base element 15 comprising connectors for the line and load terminals, the bus bars, the inductive elements and possibly the bypass elements and the complementary element 120 stackable on the main element, with an electrical circuit comprising an additional electrical component mounted on a PCB 127, such as, for example, the additional circuit 20 shown above. The assembly also comprises two conductive elements 132, 134 which are connected to the bus bars or to the connectors on the side of the base element 15, and meet the printed circuit board of the stackable complementary element. A third electrical connection for ground can be obtained using dedicated conductors or a metal chassis of the base element 115. In the example shown, the ground connectors 138 are soldered by means of solder to the corresponding holes 128 of the PCB 127, and are screwed. to a suitable grounded point on the main filter unit 115.

Contact elements 134, 132 may be an integral part of the busbar construction (come from the same piece of copper) or separate elements welded to, soldered to, or attached to the busbar. by interference and friction (press fit). The contact elements can also be a separate piece that is pressed against the bus bar. Contact between elements 134, 132 and the corresponding tracks on the board Circuit board 127 is preferably soldered by soldering or press fit. The example in Figure 2 has holes 122, 124 on PCB 127 to accept and solder contact elements 134, 132.

The main unit in Figure 2 is a cable-mounted EMI filter for automotive applications, configured to mate with a pair of pigtails on either the load side or the line side. The conductors pass through the central hole of the magnetic core 137 and are fixed to screw terminals (not visible in the figure) of the main unit 115. The main unit 115 has openings 139 for inserting a screwdriver, or other tool. properly, and tighten the screw terminals. Similarly, the PCB of the stackable accessory 120 has the openings 129 aligned with the corresponding access openings 139 of the main unit 115 to allow insertion of the screwdriver.

The stackable filter depicted in Figure 2 is a very compact and integrated device and redesigning it to change its behavior would be difficult. The present invention provides a range of filters with different behaviors, in the same package or in compatible packages, by combining the same base unit with different stackable accessories.

Also, the addition of the stackable add-on 120 enhances the features of the base unit 115 in a desirable way without influencing the busbar design, mechanical interfaces, connectors, and magnet core design. Therefore, the invention allows to improve the behaviors of EMI filters and to provide customized filters with less design and engineering efforts.

Reference symbols in the figures

15 main circuit

20 additional circuit

32 driver

34 driver

42 bus bar

44 bus bar

51 terminal line

52 line terminal

load terminal

load terminal

main unit

stackable plugin

PCB hole

PCB hole

Printed circuit board

PCB hole

access openings for screwdriver driver, connecting pin

conductor, connecting pin

magnetic core

grounded conductor

access openings for screwdriver

Claims (8)

1. An EMI filter comprising a main unit (115) connectable with a stackable plug-in (120), the main unit having connectors (51, 52; 53, 54) for connecting between a power supply and a load power, power conductors (42, 44) that can be electrically connected via the connectors between the power supply and the electrical load, inductive elements (L1-L4) to block an unwanted interfering signal superimposed on a voltage of supply; the stackable complement comprising an additional electrical circuit (20) on a printed circuit board (127), the printed circuit board (127) being permanently electrically connected to the power conductors (42, 44) by means of connection means add-ons (32, 34), whereby the stackable add-on is configured to stack on the main unit, whereby the printed circuit board, when stacked, joins the add-on connecting means without interrupting the electrical continuity of the power conductors (42, 44). 2. The EMI filter of claim 1, wherein the power conductors are solid bus bars. 3. The EMI filter of claim 2, wherein the complementary connection means are conductive pins that rise from the bus bars in electrical contact with them. 4. The EMI filter of claim 3, wherein the complementary connection means is integrally formed with the busbars, or is soldered to the busbars, or is welded to the busbar, or is fixed by fit pressurized to the busbar or pressed against the busbars. 5. The EMI filter of claim 1, wherein the additional electrical circuit (20) modifies the behavior of the main unit, or improves the attenuation in a given frequency band, or suppresses a resonance or adds a function. 6. The EMI filter of claim 1, wherein the additional electrical circuitry (20) includes a capacitor between the supply lines and ground, and/or a capacitor between the lines, and/or snubber resistors, and/or RLC networks, and/or active elements. 7. The EMI filter of claim 1, wherein the main unit is a single-phase AC or DC unit with a pair of bus bars as power conductors, comprising magnetic cores magnetically coupled with the power bus bars as inductive elements, and line-to-ground capacitors to bypass an unwanted interfering component, and the stackable add-on unit includes additional line-to-ground and line-to-line capacitors and snubber resistors in series or parallel. 8. The EMI filter of claim 7, wherein the main unit is a cable mounted filter configured to be mounted on a pair of cable conductors on the load side or on the line side, where the conductors flexible cables are magnetically coupled with, and inserted into, a magnetic core of the EMI filter.