WO2024228115A1 - Filtering circuit for battery chargers of electric or hybrid vehicles - Google Patents

Abstract

Filtering circuit (1) for battery chargers of electric or hybrid vehicles, comprising at least one filter (2, 8) provided with: - a coil (2) comprising: - a ferromagnetic core (3) comprising: - a straight first stretch (3a) and second stretch (3b); and - a first connecting stretch (3c) and a second connecting stretch (3d) conformed curvilinear; - a first winding (4a), a second winding (4b), a third winding (4c) and a fourth winding (4d), each of which is provided with an input end (6) and with an output end (7); wherein the third winding (4c) and said fourth winding (4d) are wound on the first connecting stretch (3c) and on the second connecting stretch (3d) respectively, along the entire length of the latter.

Description

FILTERING CIRCUIT FOR BATTERY CHARGERS OF ELECTRIC OR HYBRID VEHICLES

Technical Field

The present invention relates to a filtering circuit for battery chargers of electric or hybrid vehicles.

Background Art

As is well known, electric vehicles use, for propulsion, the conversion of part of the chemical energy stored in one or more batteries into electrical energy and the subsequent transfer of the latter to the motorized unit.

For the purpose of enabling periodic recharging of batteries, electric and hybrid vehicles are provided with special battery chargers (so-called “on-board chargers”, OBCs), connectable at input to an AC power line and at output to the vehicle battery, adapted to convert the incoming AC current into a corresponding, predefined DC current to be sent at output to the battery for storage.

In this regard, it should be mentioned that the aforementioned conversions are carried out, in the battery charger, by a power unit operating at high voltages and that, due to this very fact, they can generate electromagnetic noise that are likely to be propagated to the power line.

In order to mitigate this problem, battery chargers are provided with filtering circuits deputed to filter such electromagnetic noise coming from downstream. An example of known filtering circuits is provided in Figures 1 through 3.

Specifically, as visible in Figure 1, these known filtering circuits C comprise one or more filters F for electromagnetic noise (e.g., of the EMI filter type) comprising a coil B and a plurality of line capacitors CND.

Specifically, the coil B comprises a ferromagnetic core N and four windings V, each wound around a respective winding portion P of the ferromagnetic core N. The coil B may have various and different conformations; it may, e.g., be toroidal (as shown in Figures 1 and 2), or it may be substantially oval (as shown in Figure 3), that is, composed of two straight stretches, parallel to each other, and of two curvilinear connecting stretches placed between the two straight stretches.

As for the windings V, each of them comprises an input end IN and an output end OUT opposite each other with respect to the winding portion P, where the input ends IN are connectable to the three phases and to the neutral of a three-phase AC power line and the output ends OUT are connectable to the power unit.

Specifically, in the case where the filtering circuit is provided with a single filter F, then it is possible to directly connect its four input ends IN and its four output ends OUT to the power line and to the power unit, respectively.

In this way, four input connections can be defined between the single filter F and the power line and four output connections between the single filter F and the power components.

The filtering circuit may alternatively comprise a plurality of filters F.

Specifically, if the filtering circuit comprises two filters F (as shown illustratively in Figure 2), then it is possible to connect the input ends IN of one of the two filters F to the power line, the output ends OUT of the other of the two filters F to the power unit, and to connect the two filters F to each other via the remaining input ends IN and output ends OUT to define, between them, four intermediate connections.

Thus, in this case, one of the two filters F is directly connected at input to the power line and is provided with the input connections, while the other of the two filters F is directly connected at output to the power unit and is provided with the output connections.

In all cases, the filtering circuits just described suffer from an important issue that makes them amenable to improvement.

It must, in fact, be specified that the connections defined by the input ends IN and by the output ends OUT are made by means of tracks made of conducting material, e.g., copper, side by side to each other, or positioned in intermediate layers, on a suitable insulating printed circuit board S.

This geometric feature results in capacitive coupling being created between the input connections and the output connections and, therefore, some of the electromagnetic noise coming from downstream, by coupling in a capacitive maimer to the input connections and to the output connections, is carried towards the power line. It is easy to appreciate, then, how such issues end up greatly reducing the effectiveness of known circuits against electromagnetic noise generated by high- voltage conversions.

To remedy at least part of the aforementioned drawbacks, filtering circuits built in accordance with the teachings of patent document US2021152144A1 are known.

Such filtering circuits have components quite similar to those just illustrated for the previous filtering circuits, but differ from the latter in that they are provided with a ferromagnetic core having a rectangular conformation.

Even the filtering circuits according to US2021152144A1 do not, however, allow for an effective solution to the problems raised above, being themselves perfectible in order to ensure effective filtering of electromagnetic noise and consequently avert the latter from being carried towards the power line.

Description of the Invention

The main aim of the present invention is to devise a filtering circuit for battery chargers of electric or hybrid vehicles which allows filtering the electromagnetic noise coming from downstream more effectively than the prior art mentioned above.

Another object of the present invention is to devise a filtering circuit for battery chargers of electric or hybrid vehicles which allows the aforementioned drawbacks of the prior art to be overcome within the framework of a simple, rational, easy and effective to use as well as affordable solution.

The aforementioned objects are achieved by this filtering circuit for battery chargers of electric or hybrid vehicles having the characteristics of claim 1.

Brief Description of the Drawings

Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of a filtering circuit for battery chargers of electric or hybrid vehicles, illustrated by way of an indicative, yet non-limiting example, in the accompanying tables of drawings in which:

Figure 1 is an axonometric, overall view of a filtering circuit of known type; Figure 2 is a schematic view of a detail of the known filtering circuit;

Figure 3 is a schematic view of a detail of the known filtering circuit in a different embodiment;

Figure 4 is a schematic view of the filtering circuit according to the invention; Figure 5 is an axonometric, detailed view of a detail from Figure 4;

Figure 6 shows a section, along the VI-VI section plane, from Figure 5. Embodiments of the Invention

With particular reference to Figures 4 through 6, reference numeral 1 globally denotes a filtering circuit for battery chargers of electric or hybrid vehicles.

The filtering circuit 1 for battery chargers of electric or hybrid vehicles can be installed on at least a battery charger of electric or hybrid vehicles which is provided with at least one power unit for the conversion of alternating current into a predefined direct current.

As will be appreciated in the remainder of the disclosure, the circuit 1 is of the so-called “closed” type, that is, it has output currents of substantially the same value as the input currents.

In this case, the circuit 1 comprises at least one printed circuit board and at least one filter 2, 8 from electromagnetic noise associated with the printed circuit board.

In this case, the filter 2, 8 is provided with at least one coil 2 comprising: at least one ferromagnetic core 3; at least a first winding 4a, at least a second winding 4b, at least a third winding 4c and at least a fourth winding 4d, each of which is provided with at least one input end 6 connectable to one of the three phases or to the neutral of at least one AC power line and with at least one output end 7 connectable to the power unit.

In actual facts, referring to a configuration of use of the circuit 1 wherein it is installed on a battery charger and is connected to the power line and to the power unit, three of the four input ends 6 are each connected to one of the three phases, while the fourth input end 6 is connected to the neutral.

Going into details, as visible in Figure 5, each of the first winding 4a and the second winding 4b comprises a first plurality of turns 40 provided with the input end 6 and a second plurality of turns 41 provided with the output end 7.

By detailing the ferromagnetic core 3, it should first be said that it is preferably made of ferromagnetic metal (e.g., iron), or ferromagnetic compounds marked by low coercivity and low hysteresis.

In particular, the ferromagnetic core 3 is made of at least one amorphous or nanocrystalline alloy.

Such alloys do, in fact, offer excellent performance (e.g., saturation induction greater than 0.9 T, high relative magnetic permeability and excellent stability under varying temperature) for working frequencies on the order of a few tens of kHz and for applications under critical environmental conditions.

Specifically, the choice of an amorphous ferromagnetic core 3 is particularly suitable in the case of making a filter 2a, 2b of very compact size and traversed by high DC currents with small high-frequency components.

In fact, in this case, the saturation induction level of the ferromagnetic core 3 enables the same to handle high currents effectively, limiting their losses in the face of their low ripple.

What’s more, a ferromagnetic core 3 made of nanocrystalline alloy has decidedly low losses not only due to limited current ripples, but also to considerable magnetic field variations.

Ultimately, making the ferromagnetic core 3 from amorphous or nanocrystalline alloy allows, for the same size and number of turns, much higher inductances to be achieved than using materials such as ferrite, thus enabling the filter 2, 8 to perform its function in a very efficient maimer.

As far as conformation is concerned, as clearly visible in Figure 6, the ferromagnetic core 3 comprises: at least a substantially straight first stretch 3 a defining a plurality of first winding portions 5a on each of which a respective first plurality of turns 40 is wound; at least a substantially straight second stretch 3b and side by side, in a substantially parallel manner, to the first stretch 3a, defining a plurality of second winding portions 5b, opposite the first winding portions 5a and on each of which a respective second plurality of turns 41 is wound.

Specifically, the first stretch 3a and the second stretch 3b have substantially coincident lengths.

Specifically, the turns belonging to the first plurality of turns 40 are all side by side on the first stretch 3 a and are aligned with each other along at least a first axis of winding Al.

Again, the turns belonging to the second plurality of turns 41 are all side by side on the second stretch 3 b and are aligned with each other along at least a second axis of winding A2 parallel to and separate from the first axis of winding Al (see Figures 6 and 7 in this regard).

In this sense, referring to the preferred embodiment, to state that the first winding portions 5a and the second winding portions 5b are opposite each other is to mean that they are arranged on two straight, separate and mutually parallel stretches of the ferromagnetic core 3.

In other words, to state this is to say that the first axis of winding Al and the second axis of winding A2 lie on the first stretch 3 a and on the second stretch 3b respectively, and are parallel to the latter.

Having a first plurality of turns 40 provided with the input end 6 and a second plurality of turns 41 provided with the output end 7 allows connecting the input ends 6 to the power line and the output ends 7 to the power unit while keeping the connections thus defined spaced apart from each other and, thus, avoiding the occurrence of capacitive coupling between any electromagnetic noise and the various connections of the circuit 1.

Conveniently, the first pluralities of turns 40 are wound around the first winding portions 5a with at least a first way of winding and the second pluralities of turns 41 are wound around the second winding portions 5b with at least a second way of winding opposite the first way of winding.

As is clearly visible in Figures 4 through 6, the first way of winding is clockwise and the second way of winding is counterclockwise.

The opposite case cannot however be ruled out wherein the first way of winding is counterclockwise and the second way of winding is clockwise.

In this regard, it should be pointed out that the way of winding in which the turns are wound determines the orientation of the electric current flowing through them and, consequently, the direction of the magnetic field generated by it.

Keeping this in mind it is, therefore, easy to appreciate that the special expedient of winding the first plurality of turns 40 and the second plurality of turns 41 with opposite ways of winding makes it possible to generate magnetic fields having equal directions to each other and, therefore, to sum their respective inductances, thus increasing the filtering effectiveness of the circuit 1.

In addition, the ferromagnetic core 3 also comprises a first connecting stretch 3c and a second connecting stretch 3d conformed substantially curvilinear and placed between the first stretch 3a and the second stretch 3b to connect the latter to each other so as to make a closed ferromagnetic core 3.

In this case, the connecting stretches 3c, 3d are substantially D-shaped.

In actual facts, the ferromagnetic core 3 is substantially oval-shaped.

Again, the ferromagnetic core 3 is made in a single body piece.

In other words, the first stretch 3a, the second stretch 3b and the connecting stretch 3c are connected to each other in a continuous maimer and without the interposition of any welding joints.

It should, in this regard, be borne in mind that it is precisely the particular oval shape of the ferromagnetic core 3 that allows the latter to be made as a single body piece and, therefore, to disregard the use of welding joints to connect the aforementioned stretches 3a, 3b, 3c.

This fact makes it possible to increase the magnetic properties (e.g., inductance) of the ferromagnetic core 3, consequently leading to even more effective current handling.

Conveniently, as visible in Figure 6, the input end 6 and the output end 7 of each of the windings 4a, 4b, 4c, 4d are substantially aligned with each other along respective directions of alignment LI, L2.

This fact operates in conjunction in further increasing the filtering effectiveness of the filtering circuit 1 over what has already been described since it allows the connections to be aligned with each other and, therefore, prevents the same from being side-by-side at certain stretches.

According to the invention, the third winding 4c and the fourth winding 4d are wound on the first connecting stretch 3c and on the second connecting stretch 3d respectively, along the entire length of the latter.

It is important to explain how this technical expedient proves to be very advantageous, enabling the drawbacks of the prior art complained of above to be overcome.

In fact, having curvilinear connecting stretches 3c, 3d along which to wind the third winding 4c and the fourth winding 4d allows maximizing the number of turns present on the ferromagnetic core 3, thus increasing even more the inductance of the filter 2, 8 and ensuring, by virtue of this, effective shielding of the electromagnetic noise generated by high-voltage conversions.

In other words, the technical expedient in question makes it possible to wind the turns of the windings 4a, 4b, 4c, 4d substantially along the entire perimeter of the ferromagnetic core 3 and to obtain, by virtue of this, a very high-performance filtering circuit 1.

It should be noted, in this regard, how this important feature is not achievable through the use of ferromagnetic cores having a rectangular conformation, since this particular shape does not allow the turns to be wrapped around the entire perimeter of the ferromagnetic core itself, thus limiting the maximum values of inductance achievable.

In this sense, it is easy to appreciate how the circuit 1 is marked by significantly higher inductances than the previously discussed circuits of the prior art, being considerably more efficient in filtering electromagnetic noise.

In this regard, the windings 4a, 4b, 4c, 4d are sized so as to have substantially equal values of inductance.

This fact proves very convenient since it allows avoiding the occurrence of undesirable saturation phenomena caused by currents flowing through the circuit 1.

In fact, a difference in inductance between the windings 4a, 4b, 4c, 4d would result in a non-zero sum of the respectively generated magnetic fields and, being the circuit 1 of the closed type, would lead to the saturation of the ferromagnetic core 3.

In addition, the filter 2, 8 comprises at least one line capacitor 8 connected to at least one of the input ends 6 or the output ends 7.

Specifically, the filter 2, 8 comprises a plurality of line capacitors 8.

In particular, some of the line capacitors 8 are connected to the input ends 6 while the others are connected to the output ends 7.

As visible in Figure 4, the line capacitors 8 are arranged between each phase and the neutral or between two phases.

The filter 2, 8 is substantially of the type of an EMI filter.

According to a first embodiment, the circuit 1 comprises a single filter 2, 8 and, consequently, a single coil 2.

In this case, the input ends 6 of the single coil 2 are directly connectable to the power line and, similarly, the output ends 7 of the single coil 2 are directly connectable to the power unit.

It is specified, in this regard, that by using the term “directly” with reference to the connection between the input ends 6 and the power line, it is intended to mean that no additional electrical component (such as, e.g., an additional coil 2) is positioned between these two.

Similar considerations apply when employing the above term in reference to the connection between the output ends 7 and the power unit.

Alternatively, in accordance with a second embodiment, the circuit 1 comprises a plurality of filters 2, 8 connected in series to each other and, consequently, a plurality of coils 2.

In this case, the input ends 6 of the first coil 2 and the output ends 7 of the last coil 2 are directly connectable to the power line and to the power components, respectively.

In addition, the output ends 7 of each coil 2 except for the last one are directly connected to the input ends 6 of each next coil 2 to define, between two next filters 2, 8 four intermediate connections parallel to each other. Keeping in mind the arrangement of the input ends 6 and of the output ends 7 previously described, it is easy to appreciate how, in this second embodiment, all connections (i.e., input connections, output connections and intermediate connections) are aligned along four lines parallel to each other (see Figure 4 in this regard).

Preferably, the circuit 1 comprises three filters 2, 8 connected in series.

In this case, the circuit 1 is therefore provided with four input connections with the power line, four output connections with the power unit and eight intermediate connections between the various filters 2, 8 in series (i.e., four between the first filter and the second filter 2, 8 and another four between the second filter and the third filter 2, 8).

It cannot, however, be ruled out that the circuit 1 may be provided with a different number of filters 2, 8, e.g. two filters 2, 8 connected in series or with a different and, e.g., larger number of filters 2, 8.

It has in practice been ascertained that the described invention achieves the intended objects.

In particular, the fact is emphasized that by providing two curvilinear stretches of the ferromagnetic core around which the third winding and the fourth winding are wound allows maximizing the inductance of the circuit according to the invention and, therefore, shielding the electromagnetic noise generated by high-voltage conversions in a particularly efficient maimer, avoiding their input to the grid.

Claims

1) Filtering circuit (1) for battery chargers of electric or hybrid vehicles, which can be installed on at least one battery charger of electric or hybrid vehicles which is provided with at least one power unit for the conversion of alternating current into a predefined direct current, comprising at least one filter (2, 8) from electromagnetic noise provided with: at least one coil (2) comprising: at least one ferromagnetic core (3); at least a first winding (4a), at least a second winding (4b), at least a third winding (4c) and at least a fourth winding (4d), each of which is provided with at least one input end (6) connectable to one of the three phases or to the neutral of at least one AC power line and with at least one output end (7) connectable to said power unit;

- at least one line capacitor (8) connected to at least one of said input ends (6) and said output ends (7); wherein each of said first winding (4a) and said second winding (4b) comprises a first plurality of turns (40) provided with said input end (6) and a second plurality of turns (41) provided with said output end (7), and wherein said ferromagnetic core (3) comprises: at least a substantially straight first stretch (3a) defining a plurality of first winding portions (5a) on each of which a respective said first plurality of turns (40) is wound; at least a substantially straight second stretch (3b) and parallel to said first stretch (3 a) defining a plurality of second winding portions (5b), opposite said first winding portions (5a), on each of which a respective said second plurality of turns (41) is wound; and a first connecting stretch (3c) and a second connecting stretch (3d) conformed substantially curvilinear and placed between said first stretch (3a) and said second stretch (3b) to connect the latter to each other; characterized by the fact that said third winding (4c) and said fourth winding (4d) are wound on said first connecting stretch (3 c) and on said second connecting stretch (3d) respectively, along the entire length of the latter.

2) Circuit (1) according to claim 1, characterized by the fact that said input ends

(6) and said output ends (7) are substantially aligned with each other along respective directions of alignment (LI, L2).

3) Circuit (1) according to one or more of the preceding claims, characterized by the fact that said first pluralities of turns (40) are wound around said first winding portions (5a) with at least a first way of winding and that said second pluralities of turns (41) are wound around said second winding portions (5b) with at least a second way of winding opposite said first way of winding.

4) Circuit (1) according to one or more of the preceding claims, characterized by the fact that it comprises a single said filter (2, 8), said input ends (6) of said single coil (2) being directly connectable to said power line and said output ends

(7) of said single coil (2) being directly connectable to said power unit.

5) Circuit (1) according to one or more of claims 1 to 3, characterized by the fact that it comprises a plurality of said filters (2, 8) connected in series to each other, wherein:

- said input ends (6) of the first of said coils (2) and said output ends (7) of the last of said coils (2) are directly connectable to said power line and to said power components, respectively;

- said output ends (7) of each said coil (2) except for the last one are directly connected to said input ends (6) of each said next coil (2) to define, between two of said next filters (2, 8), four intermediate connections parallel to each other.

6) Circuit (1) according to claim 5, characterized by the fact that it comprises three of said filters (2, 8) connected in series.

7) Circuit (1) according to one or more of the preceding claims, characterized by the fact that said windings (4a, 4b, 4c, 4d) are sized so as to have substantially equal values of inductance.