EMI filter circuit for EV / HEV battery charger

Abstract

A filter circuit (1) for a battery charger of an electric or hybrid vehicle comprises: a plurality of filters (2a, 2b) for electromagnetic interference connected in series with one another and provided with at least one coil (2a) comprising a ferromagnetic core (3) and at least one winding (4a, 4b) provided with an input (6) and an output (7); a plurality of line capacitors (2b); a printed circuit board (8) suitable for supporting the capacitors (2b) with each other; a plurality of connection elements (10) suitable for electrically connecting the coil (2a) to the printed circuit board (8); wherein, in addition to the last coil (2a), each output (7) of each coil (2a) is directly connected to the respective input (6) of the next coil (2a), and the outputs (7) are associated together with the respective input (6) to the same connection element (10).

Description

Technical Field

[0001] The present invention relates to a filter circuit for a battery charger of an electric vehicle or a hybrid vehicle. Background Art

[0002] As is well known, electric vehicles are powered by converting part of the chemical energy stored in one or more batteries into electrical energy and then transferring the latter to an engine.

[0003] In order to be able to charge the battery regularly, electric and hybrid vehicles are provided with special battery chargers (so-called "on-board chargers (OBC)"), which can be connected to the AC power supply line at the input end and to the vehicle battery at the output end. These battery chargers are suitable for converting the AC current at the input end into a corresponding, predetermined DC current and transmitting it to the battery for storage via the output end.

[0004] In this context, it should be mentioned that the above-mentioned conversions are performed in the battery charger by power supply units operating at high voltages and, as such, they may generate electromagnetic interferences which may propagate onto the supply lines.

[0005] To overcome this problem, battery chargers are provided with filtering circuits designed to filter these electromagnetic interferences coming from downstream.

[0006] Figure 1 An example of a known filter circuit is given.

[0007] It can be seen that the known filtering circuit C includes one or more filters F to protect against electromagnetic interference (such as filters of the electromagnetic interference (EMI) filter type), and the filter F includes a coil B mounted on a printed circuit board S and a plurality of capacitors CND.

[0008] Specifically, each coil B includes a ferromagnetic core N, for example, in the shape of a ring (such as Figure 1 and Figure 2 as shown) or elliptical, and four windings V, each winding being wound around a corresponding winding portion P of a ferromagnetic core N.

[0009] In detail, from Figure 2 As can be clearly seen in FIG. 1 , each winding V is provided with an input terminal IN and an output terminal OUT which are opposite to each other with respect to the winding portion P.

[0010] Specifically, a plurality of input terminals IN may be connected to three phases and a neutral line of a three-phase AC power supply line, and a plurality of output terminals OUT may be connected to a power supply unit.

[0011] It should be noted that in the known filter circuit C provided with a plurality of filters F, the connection between the filters is achieved directly on the printed circuit board S by using special connecting wires made of conductive material (eg copper) in parallel or in the middle layer.

[0012] Specifically, the connecting wires connect the input terminal IN of one filter F to the power supply line, connect the output terminal OUT of another filter to the power supply unit, and connect the remaining input terminals IN and output terminals OUT to each other to define multiple intermediate connections between the individual filters F.

[0013] Therefore, one filter F is directly connected to the power supply line at the input end, another filter F is directly connected to the power supply unit at the output end, and all filters F are connected in series with each other.

[0014] However, mounting the filter F directly on the printed circuit board S and connecting it via connecting wires is a technically expedient solution, but it is not without problems.

[0015] In this regard, it is worth considering that the width of the connecting wire must be proportional to the value of the current flowing through it, to ensure that there is no risk of overheating or even damage to the connecting wire.

[0016] With this in mind, it is not difficult to understand how the high currents mentioned earlier would necessitate the manufacture of connecting wires of inconvenient widths.

[0017] The larger the width of the wire is, the more conductive material needs to be used, which ultimately has a negative impact on the manufacturing cost of the filter circuit C.

[0018] Moreover, the fact that the connecting wires made of electrically conductive material are arranged side by side or superimposed on a plurality of layers results in considerable heat exchanges between them, which substantially increases their temperature.

[0019] This negative impact necessitates, among other things, the use of more material for producing the connecting conductors and ultimately exacerbates the above-mentioned problems associated with the production costs of the known filter circuit C.

[0020] On top of that, having to use a specific size for the connecting wires also has an adverse effect on the final size of the filter itself, leading to inconvenience issues related to the overall size of the filter. Summary of the invention

[0021] The main object of the invention is to devise a filter circuit for a battery charger for an electric or hybrid vehicle which, compared with known filter circuits, allows to reduce the use of materials for its manufacture, thereby reducing the manufacturing costs.

[0022] Another object of the invention is to devise a filter circuit for a battery charger for an electric or hybrid vehicle which allows enhanced heat dissipation compared to the above-mentioned prior art.

[0023] Another object of the invention is to devise a filtering circuit for a battery charger for an electric or hybrid vehicle which allows overcoming the above-mentioned drawbacks of the prior art within the framework of a simple, rational, easy to use, effective and cost-effective solution.

[0024] The aforementioned object is achieved by a filter circuit for a battery charger of an electric vehicle or a hybrid vehicle having the features of claim 1 . BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Other features and advantages of the invention will become more apparent from the description of a preferred but not exclusive embodiment of a filter circuit for a battery charger for an electric or hybrid vehicle, illustrated by way of indicative but not limiting example in the accompanying diagrams, in which:

[0026] Figure 1 is an overall isometric view of a filter circuit of a known type;

[0027] Figure 2 yes Figure 1 A schematic diagram of a top view of a known circuit in ;

[0028] Figure 3 is an overall axonometric diagram of a filter circuit according to the present invention;

[0029] Figure 4 is an axonometric view of a detail in a filter circuit according to the present invention;

[0030] Figure 5 Shows Figure 4 A schematic diagram of the circuit viewed from above;

[0031] Figure 6 yes Figure 5 Axonometric drawing of medium detail;

[0032] Figure 7 Shown along Figure 6 A cross-sectional view taken along section VII-VII. DETAILED DESCRIPTION

[0033] Specific reference Figures 3 to 7 , reference numeral 1 generally denotes a filter circuit for a battery charger of an electric vehicle or a hybrid vehicle.

[0034] The filter circuit 1 for a battery charger for an electric vehicle or a hybrid vehicle may be installed in at least one battery charger of the electric vehicle or the hybrid vehicle provided with at least one power supply unit for converting alternating current into predetermined direct current.

[0035] Specifically, the circuit 1 includes a plurality of filters 2a, 2b for electromagnetic interference, which are connected in series with each other and are provided with at least one coil 2a, which includes:

[0036] - at least one ferromagnetic core 3;

[0037] - at least one winding 4a, 4b, wound on a respective winding portion 5a, 5b of the ferromagnetic core 3 and provided with at least one input 6 connectable to at least one AC power supply line and at least one output 7 connectable to a power supply unit.

[0038] In this respect, a circuit 1 may be provided which may be connected to a single-phase AC supply line and which is therefore provided with a coil 2a having a single winding 4a, 4b.

[0039] Alternatively, the circuit 1 may be connected to a three-phase AC power supply line.

[0040] In this case, if Figures 3 to 5 As shown, the coil 2a comprises four windings 4a, 4b.

[0041] Specifically, each winding 4a, 4b is wound around a corresponding winding portion 5a, 5b of the ferromagnetic core 3, and each winding is provided with a corresponding input terminal 6 connectable to one of the three phases or the neutral line of at least one three-phase AC power supply line, and a corresponding output terminal 7 connectable to a power supply unit.

[0042] In fact, referring to the use configuration of the circuit 1, wherein the circuit 1 is mounted on a battery charger and connected to the supply line and the power supply unit, three of the four input terminals 6 are respectively connected to one of the three phases, while the fourth input terminal 6 is connected to the neutral line.

[0043] When explaining the ferromagnetic core 3 in detail, it should first be stated that it is preferably made of a ferromagnetic metal (eg iron) or a ferromagnetic compound having low coercivity and low hysteresis properties.

[0044] In particular, the ferromagnetic core 3 is made of at least one amorphous alloy or nanocrystalline alloy.

[0045] In fact, for operating frequencies of the order of tens of kHz and in applications under critical environmental conditions, this alloy does provide excellent properties (e.g., saturation induction greater than 0.9 T, high relative permeability, and excellent stability with temperature variations).

[0046] In particular, the selection of the amorphous ferromagnetic core 3 is particularly suitable for manufacturing filters 2a, 2b of extremely compact size, capable of passing high direct currents with small high-frequency components.

[0047] In fact, in this case, the saturation induction level of the ferromagnetic core 3 enables it to effectively control high currents, thus limiting its losses in the face of low ripples.

[0048] Furthermore, the ferromagnetic core 3 made of nanocrystalline alloy exhibits significantly low losses not only under limited current ripple but also under large changes in magnetic field, which makes it suitable for manufacturing switching transformers.

[0049] Finally, for the same dimensions and number of turns, a ferromagnetic core 3 made of an amorphous or nanocrystalline alloy allows obtaining a much higher inductance than using a material such as ferrite, thus enabling the filter 2a, 2b to perform its function in a particularly efficient manner.

[0050] In terms of configuration, Figure 7 As clearly shown in FIG. 1 , the ferromagnetic core 3 according to a preferred embodiment comprises:

[0051] - at least one first segment 3a, which is substantially rectilinear in shape;

[0052] - at least one second section 3b, which is substantially rectilinear in shape and is arranged substantially parallel to the first section 3a;

[0053] at least two connecting segments 3 c , which are substantially curvilinear in shape and are located between the first segment 3 a and the second segment 3 b to connect the first segment 3 a and the second segment 3 b to each other, thereby forming a closed ferromagnetic core 3 .

[0054] Specifically, the first section 3a and the second section 3b have substantially the same length.

[0055] Likewise, the connecting section 3c is substantially D-shaped.

[0056] In practice, the ferromagnetic core 3 is substantially elliptical.

[0057] However, a different configuration of the ferromagnetic core 3 , for example a substantially annular shape, cannot be excluded.

[0058] In this case, the winding portions 5a, 5b have a substantially curved configuration and the windings 4a, 4b are wound on the winding portions in a curvilinear manner.

[0059] Likewise, the ferromagnetic core 3 is made as a single piece.

[0060] In other words, the first segment 3a, the second segment 3b and the plurality of connecting segments 3c are continuously connected without interposing any welding joints.

[0061] In this respect, it should be remembered that it is the particular oval shape of the ferromagnetic core 3 that allows it to be made in a single piece, thereby eliminating the need to use welded joints to connect the aforementioned segments 3a, 3b, 3c.

[0062] This fact can significantly improve the magnetic properties (eg inductance) of the ferromagnetic core 3, thereby controlling the current more effectively.

[0063] Regarding more details of the single coil 2a, it should first be noted that each of the windings 4a, 4b provided with the single coil 2a includes a first plurality of turns 4a, which are provided with an input end 6 and are wound around a corresponding first winding portion 5a of the ferromagnetic core 3.

[0064] In particular, the turns belonging to the first plurality of turns 4a are all alongside each other and aligned with each other along at least the first winding axis A1 .

[0065] Similarly, the windings 4a, 4b also include a second plurality of turns 4b connected to the first plurality of turns 4a, the second plurality of turns 4b being provided with a plurality of output terminals 7, and the second plurality of turns 4b being wound around a corresponding second winding portion 5b of the ferromagnetic core 3, the corresponding second winding portion 5b being substantially opposite to the first winding portion 5a.

[0066] In particular, the turns belonging to the second plurality of turns 4b are all arranged side by side with one another and aligned with one another along at least a second winding axis A2 which is parallel to and separated from the first winding axis A1 (see in this respect Figure 6 and Figure 7 ).

[0067] Specifically, a first plurality of turns 4a of the winding 4a, 4b is wound on the first segment 3a, and a second plurality of turns 4b of the winding 4a, 4b is wound on the second segment 3b.

[0068] In this respect, with reference to the preferred embodiment, the first winding portion 5a, 5b and the second winding portion 5a, 5b opposite each other means that they are arranged on two straight, separate and mutually parallel sections of the ferromagnetic core 3.

[0069] In other words, this means that the first winding axis A1 and the second winding axis A2 are located on the first section 3a and the second section 3b, respectively, and the first winding axis A1 is parallel to the second winding axis A2.

[0070] from Figure 4It can be seen that the input 6 and the output 7 of each winding 4a, 4b are substantially aligned with each other on the first section 3a and the second section 3b, respectively.

[0071] As will become clearer in the remainder of the present disclosure, this fact proves to be particularly advantageous since it allows the dissipation of the heat present in the circuit 1 to be enhanced, thus improving the thermal management of the circuit.

[0072] Conveniently, the first plurality of turns 4a are wound around the first winding portions 5a, 5b in at least a first winding direction and the second plurality of turns 4b are wound around the second winding portions 5a, 5b in at least a second winding direction opposite to the first winding direction. Figures 5 to 7 It can be clearly seen that the first winding direction is clockwise and the second winding direction is counterclockwise.

[0073] However, the opposite situation cannot be excluded, ie the first winding direction is counterclockwise and the second winding direction is clockwise.

[0074] In this regard, it should be noted that the winding direction of the turns determines the direction of the current flowing through the turns and thus the direction of the magnetic field generated by the turns.

[0075] In view of this, it is not difficult to understand that the special method of winding the first plurality of turns 4a and the second plurality of turns 4b in opposite winding directions can generate magnetic fields with consistent directions, thereby superimposing their respective inductances, thereby improving the filtering efficiency of the circuit 1.

[0076] Furthermore, the filter 2 a , 2 b comprises a plurality of line capacitors 2 b , each of which is connected to at least one input 6 or at least one output 7 .

[0077] Specifically, the line capacitor 2b is arranged between each phase and the neutral line or between two phases.

[0078] Considering what has been described so far, it is not difficult to understand that, in fact, the filters 2a, 2b are EMI type filters.

[0079] According to the invention, the circuit 1 comprises at least one printed circuit board 8 suitable for supporting the capacitors 2b and connecting the capacitors 2b to each other.

[0080] In this respect, the printed circuit board 8 comprises a plurality of connecting wires (not shown in the figure for the sake of simplicity) made of an electrically conductive material, which are suitable for electrically connecting the capacitors 2b to one another.

[0081] In other words, the capacitors 2b are mounted on the printed circuit board 8 and are electrically connected to each other on the printed circuit board body through connecting wires.

[0082] According to a preferred embodiment, the circuit 1 comprises at least one support 9 on which the coil 2 a is mounted, the support 9 being associated with a printed circuit board 8 .

[0083] Conveniently, the support body 9 comprises a plurality of housing cavities 9a obtained therethrough, wherein each housing cavity 9a is suitable for housing at least one respective coil 2a therein.

[0084] Specifically, the number of the accommodating chambers 9a is equal to the number of the coils 2a.

[0085] Specifically, Figure 4 As shown, the receiving chamber 9a has a substantially rectangular configuration.

[0086] The housing cavities 9a are positioned side by side on the support body 9, so that their number determines the length of the support body (ie defines the dimension developing in the longitudinal direction).

[0087] In order to electrically connect the coil 2 a to the printed circuit board 8 , the circuit 1 according to the invention comprises a plurality of connection elements 10 associated with each input 6 and each output 7 .

[0088] In particular, the support body 9 is provided with connecting elements 10 .

[0089] According to a preferred embodiment, the connecting element 10 is of pin type.

[0090] In this case, therefore, the printed circuit board 8 is provided with a plurality of sockets 11 (as is known in this technical term), in which the connecting elements 10 are arranged.

[0091] In fact, when the connection element 10 and the socket 11 are inserted into each other, they form a form coupling which allows the printed circuit board 8 and the support body 9 to be electrically connected.

[0092] At this point, it should be added that, except for the last coil, each output terminal 7 of each coil 2 a is directly connected to the corresponding input terminal 6 of the next coil 2 a and each output terminal 7 is associated with the same connection element 10 together with the corresponding input terminal 6 .

[0093] In practice, this means that, with the exception of the last coil, each output terminal 7 of each coil 2a and each corresponding input terminal 6 of the next coil 2a share the same connection element 10.

[0094] In this context, therefore, the statement that an output 7 is directly connected to a corresponding input 6 means that they are associated with the same connection element 10 .

[0095] More precisely, if Figure 5As shown schematically, the output 7 of each coil 2a and the corresponding input 6 of the next coil 2a are connected to the same connection element 10, thus defining an intermediate connection between two adjacent coils 2a parallel to each other.

[0096] Conveniently, the connection elements 10 are arranged along a plurality of parallel rows of connection elements 10 on the support 9 .

[0097] Specifically, each coil 2 a on the support body 9 is located between two rows of connecting elements 10 .

[0098] It follows that the connecting elements 10 are arranged in a number of rows equal to the number of coils 2 a plus one, and that each row of connecting elements 10 is provided with four connecting elements 10 .

[0099] At this point, it is important to emphasize that providing a printed circuit board 8 having only capacitors 2b mounted thereon and connecting coils 2a in series to connecting element 10 via their respective output terminals 7 and input terminals 6 can significantly reduce the amount of conductive material used in the manufacture of circuit 1.

[0100] In fact, in this case, the current mainly flows through the coil 2 a , and only a small amount of current flows through the capacitor 2 b on the printed circuit board 8 .

[0101] Therefore, a connecting wire made of a conductive material is necessary, and in this case, only the capacitor 2b needs to be connected instead of the coil 2a.

[0102] Therefore, since they do not need to be traversed by large currents, the connecting conductors can advantageously have a smaller width than in the prior art; this fact obviously has a certain positive impact on the material procurement costs, thus reducing the manufacturing expenses of the circuit 1 and its dimensions.

[0103] It is also worth emphasizing that this same connection configuration enables the circuit 1 to effectively dissipate the heat generated by the flow of current, thereby helping to reduce the amount of conductive material required to manufacture the circuit.

[0104] In this respect, the fact that the input terminals 6 and the output terminals 7 are substantially aligned greatly assists thermal management of the circuit 1 , since it allows the connections defined by the aforementioned terminals to be kept appropriately spaced from each other.

[0105] According to the preferred embodiment shown in the figure, the circuit 1 comprises three filters 2a, 2b connected in series, wherein:

[0106] - a plurality of input terminals 6 of the first filter 2a, 2b are directly connected to the power supply line;

[0107] - a plurality of output terminals 7 of the third filter 2a, 2b are directly connected to the power supply unit;

[0108] - The outputs 7 of the first and second filters 2a, 2b are directly connected to the inputs 6 of the second and third filters 2a, 2b, 2a, 2b, respectively.

[0109] In this respect, it is to be noted that by using the term “directly” to denote the connection between the input terminal 6 and the power supply line, it is meant that no additional magnetic components (eg an additional coil 2 a ) are interposed therebetween.

[0110] The same considerations apply when using the aforementioned terms to refer to the connection between the output terminal 7 and the power supply unit.

[0111] Therefore, the circuit 1 according to the preferred embodiment defines four input connections to the power supply lines, four output connections to the power supply unit and eight intermediate connections between multiple filters 2a, 2b connected in series (i.e., four between the first filter 2a, 2b and the second filter 2a, 2b and another four between the second filter 2a, 2b and the third filter 2a, 2b).

[0112] This means therefore that, in this case, the support body 9 is provided with sixteen connecting elements 10 , which are arranged along four rows of four connecting elements 10 .

[0113] However, it cannot be excluded that the circuit 1 may be provided with a different number of filters 2a, 2b, for example two filters 2a, 2b connected in series, or a different number of filters 2a, 2b, for example a greater number of filters 2a, 2b.

[0114] The described invention has in fact been determined to achieve the intended purpose.

[0115] Particular emphasis should be placed on the fact that the amount of conductive material used can be reduced considerably by providing a printed circuit board on which only the capacitors are mounted and by a special design that connects the coils directly to one another via their respective output and input terminals.

[0116] In fact, in this case, the connecting wires made of conductive material become only necessary to connect the capacitors to one another and, for this reason, they can have a smaller width than in the prior art, which has a positive effect on material procurement and manufacturing costs.

[0117] Finally, it is important to emphasize that this same connection configuration also enables the circuit to effectively dissipate the heat generated by the flow of current; this helps to further reduce the amount of conductive material required to manufacture the circuit.

Claims

1. A filter circuit (1) for a battery charger of an electric vehicle or a hybrid vehicle, the filter circuit (1) being installable in at least one battery charger of the electric vehicle or the hybrid vehicle, the battery charger being provided with at least one power supply unit for converting alternating current into predetermined direct current, the filter circuit (1) comprising: - a plurality of filters (2a, 2b) for electromagnetic interference, connected in series with each other, and provided with: - at least one coil (2a) comprising: - at least one ferromagnetic core (3); - at least one winding (4a, 4b), which is wound around a respective winding portion (5a, 5b) of the ferromagnetic core (3) and is provided with at least one input terminal (6) connectable to at least one AC power supply line and at least one output terminal (7) connectable to the power supply unit; - a plurality of line capacitors (2b), each line capacitor being connected to at least one input terminal (6) or at least one output terminal (7); Features: - the filter circuit (1) comprises at least one printed circuit board (8) suitable for supporting the capacitors (2b) and connecting the capacitors (2b) to each other; - the filter circuit (1) comprises a plurality of connection elements (10) associated with each input terminal (6) and each output terminal (7), and the connection elements (10) are suitable for electrically connecting the coil (2a) to the printed circuit board (8); - With the exception of the last coil (2a), each output terminal (7) of each of said coils (2a) is directly connected to the corresponding input terminal (6) of the next coil (2a), and the output terminal (7) and the corresponding input terminal (6) are associated together to the same connection element (10).

2. The circuit (1) according to claim 1, characterized in that It comprises at least one support body (9) on which the coil (2a) is mounted, the support body being associated with the printed circuit board (8) and provided with the connecting element (10).

3. The circuit (1) according to claim 2, characterized in that The connecting element (10) is pin-shaped, and the printed circuit board (8) is provided with a plurality of sockets (11), in which the connecting element (10) is placed.

4. Circuit (1) according to one or more of the preceding claims, characterized in that The coil (2a) comprises four windings (4a, 4b), wherein each winding (4a, 4b) is wound around the corresponding winding portion (5a, 5b) of the ferromagnetic core (3), and each winding (4a, 4b) is provided with a corresponding input end (6) and a corresponding output end (7), wherein the input end (6) can be connected to one of the three phases or the neutral line of at least one three-phase AC power supply line, and the output end (7) can be connected to the power supply unit.

5. Circuit (1) according to one or more of the preceding claims, characterized in that The invention comprises three filters (2a, 2b) connected in series, wherein: - a plurality of input terminals (6) of the first filter (2a, 2b) are directly connected to the power supply line; - a plurality of output terminals (7) of the third filter (2a, 2b) are directly connected to the power supply unit; - The plurality of output ends (7) of the first filter (2a, 2b) and the plurality of output ends (7) of the second filter (2a, 2b) are directly connected to the plurality of input ends (6) of the second filter (2a, 2b) and the third filter (2a, 2b), respectively.

6. Circuit (1) according to one or more of the preceding claims, characterized in that Each of the windings (4a, 4b) comprises: a first plurality of turns (4a) provided with said input end (6) and wound around a respective first winding portion (5a) of said ferromagnetic core (3); and - a second plurality of turns (4b) connected to the first plurality of turns (4a), provided with the output terminal (7), and wound around a corresponding second winding portion (5b) of the ferromagnetic core (3), the second winding portion (5b) being opposite to the first winding portion (5a).

7. The circuit (1) according to claim 6, characterized in that The ferromagnetic core (3) comprises: - at least one first section (3a) having a substantially rectilinear shape, on which a first plurality of turns (4a) of said winding (4a, 4b) are wound; - at least one second section (3b) having a substantially rectilinear shape and arranged substantially parallel to said first section (3a), on which a second plurality of turns (4b) of said winding (4a, 4b) are wound; - at least two connecting segments (3c) of substantially curvilinear shape and positioned between said first segment (3a) and said second segment (3b) in order to connect the latter to each other.

8. The circuit (1) according to claim 7, characterized in that The input end (6) and the output end (7) of each winding (4a, 4b) are substantially aligned with each other on the first section (3a) and the second section (3b), respectively.

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