EMI filter circuit for EV / HEV battery charger

Abstract

A filter circuit (1) for a battery charger of an electric or hybrid vehicle, comprising at least one electromagnetic interference filter (2, 8) provided with at least one coil (2), the coil (2) comprising: a ferromagnetic core (3); four windings (4a, 4b), each winding being wound around a respective winding portion (5a, 5b) of the ferromagnetic core (3), and each winding being provided with an input (6) and an output (7); at least one line capacitor (8); wherein each winding (4a, 4b) comprises: a first plurality of turns (4a) provided with an input (6) and wound around a respective first winding portion (5a) of the ferromagnetic core (3); and a second plurality of turns (4b) provided with an output (7) and wound around a corresponding second winding portion (5b) of the ferromagnetic core (3) opposite the first winding portion (5a).

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 a power supply unit operating at a high voltage and due to this fact 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] exist Figures 1 to 3 Examples of known filtering circuits are provided in .

[0007] Specifically, Figure 1 As shown, the known filter circuit C includes one or more filters F for electromagnetic interference (eg, filters of the electromagnetic interference (EMI) filter type), and the filter F includes a coil B and a plurality of line capacitors CND.

[0008] Specifically, the coil B includes a ferromagnetic core N and four windings V, each of which is wound around a corresponding winding portion P of the ferromagnetic core N, respectively.

[0009] Coil B can have a variety of different configurations; for example, it can be annular (such as Figure 1 and Figure 2 ), or it may be substantially elliptical (as shown Figure 3 , that is, it consists of two straight line segments parallel to each other and two curved connecting segments located between the two straight line segments.

[0010] As for the windings V, each of them includes input terminals IN and output terminals OUT opposite to each other relative to the winding portion P, wherein a plurality of input terminals IN can be connected to three phases and a neutral line of a three-phase AC power supply line, and a plurality of output terminals OUT can be connected to a power supply unit.

[0011] Specifically, in the case where the filter circuit is provided with a single filter F, the four input terminals IN of the filter and the four output terminals OUT of the filter may be directly connected to the power supply line and the power supply unit, respectively.

[0012] In this way, four input connections can be defined between a single filter F and the supply line, and four output connections can be defined between a single filter F and the power supply components.

[0013] Alternatively, the filtering circuit may include a plurality of filters F.

[0014] Specifically, if the filtering circuit includes two filters F (such as Figure 2 As shown in the example in ), the input terminal IN of one of the filters F can be connected to the power supply line, the output terminal OUT of the other filter F can be connected to the power supply unit, and the two filters F can be connected to each other via the remaining input terminal IN and output terminal OUT, thereby defining four intermediate connections between them.

[0015] In this case, therefore, one of the two filters F is connected directly to the supply line at the input end and is provided with an input connection, while the other of the two filters F is connected directly to the power supply unit at the output end and is provided with an output connection.

[0016] In all cases, known filter circuits suffer from a significant problem which makes them desirable for improvement.

[0017] In fact, it must be stated that the connection defined by the input IN and the output OUT is realized by conductors arranged side by side or located in an intermediate layer on a suitable insulating printed circuit board S, these conductors being made of a conductive material, for example copper.

[0018] This geometric characteristic causes capacitive coupling between the input connection and the output connection. Therefore, some electromagnetic interference from downstream is carried to the power supply line by capacitive coupling to the input connection and the output connection.

[0019] Therefore, it is not difficult to understand that these problems will eventually greatly reduce the effectiveness of the known filter circuit in suppressing the electromagnetic interference generated by high voltage conversion. Summary of the invention

[0020] The main object of the present invention is to devise a filtering circuit for a battery charger for an electric or hybrid vehicle which allows filtering electromagnetic interference coming from downstream in a more effective way than the above-mentioned prior art.

[0021] 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.

[0022] 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

[0023] 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:

[0024] Figure 1 is an overall isometric view of a filter circuit of a known type;

[0025] Figure 2 It is a schematic diagram of the details in the known filter circuit;

[0026] Figure 3 is a schematic diagram of details of a known filter circuit according to different embodiments;

[0027] Figure 4 is a schematic diagram of a filter circuit according to the present invention;

[0028] Figure 5 yes Figure 4 Detailed axonometric drawing of medium detail;

[0029] Figure 6 Shown along Figure 5 A cross-sectional view taken along section VI-VI. DETAILED DESCRIPTION

[0030] Specific reference Figures 4 to 6 , reference numeral 1 generally denotes a filter circuit for a battery charger of an electric vehicle or a hybrid vehicle.

[0031] 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.

[0032] In this case, the circuit 1 comprises at least one printed circuit board and at least one filter 2, 8 for eliminating electromagnetic interference associated with the printed circuit board.

[0033] In the present case, the filter 2, 8 has at least one coil 2 comprising:

[0034] - at least one ferromagnetic core 3;

[0035] - at least four windings 4a, 4b, each wound around a respective winding portion 5a, 5b of the ferromagnetic core 3 and each provided with at least one input terminal 6 connectable to one of the three phases or to the neutral conductor of at least one AC power supply line, and at least one output terminal 7 connectable to a power supply unit.

[0036] 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.

[0037] 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.

[0038] In particular, the ferromagnetic core 3 is made of at least one amorphous alloy or nanocrystalline alloy.

[0039] 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).

[0040] In particular, the selection of the amorphous ferromagnetic core 3 is particularly suitable for manufacturing filters 2, 8 of extremely compact size, capable of passing high direct currents with small high-frequency components.

[0041] In fact, in this case, the saturation induction level of the ferromagnetic core 3 enables it to effectively control large currents, thus limiting its losses in the face of low ripples.

[0042] 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.

[0043] 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 2 , 8 to perform its function in a particularly efficient manner.

[0044] In terms of configuration, Figure 6 As clearly shown in FIG. 1 , the ferromagnetic core 3 according to a preferred embodiment comprises:

[0045] - at least one first segment 3a, which is substantially rectilinear in shape;

[0046] - at least one second section 3b, which is substantially rectilinear in shape and is arranged substantially parallel to the first section 3a;

[0047] 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 .

[0048] Specifically, the first section 3a and the second section 3b have substantially the same length.

[0049] Likewise, the connecting section 3c is substantially D-shaped.

[0050] In practice, the ferromagnetic core 3 is substantially elliptical.

[0051] However, a different configuration of the ferromagnetic core 3 , for example a substantially annular shape, cannot be excluded.

[0052] 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.

[0053] Likewise, the ferromagnetic core 3 is made as a single piece.

[0054] 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.

[0055] 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.

[0056] This fact can significantly improve the magnetic properties (eg inductance) of the ferromagnetic core 3, thereby controlling the current more effectively.

[0057] Furthermore, the filter 2 , 8 comprises at least one line capacitor 8 which is connected to at least one of the plurality of inputs 6 or the plurality of outputs 7 .

[0058] In particular, the filter 2 , 8 comprises a plurality of line capacitors 8 .

[0059] Specifically, some of the line capacitors 8 are connected to the plurality of input terminals 6 , whereas other line capacitors 8 are connected to the plurality of output terminals 7 .

[0060] like Figure 4 As shown, a line capacitor 8 is arranged between each phase and the neutral conductor or between two phases.

[0061] The filters 2, 8 are essentially EMI type filters.

[0062] According to the invention, each winding 4a, 4b comprises a first plurality of turns 4a provided with a plurality of input terminals 6 and wound around a respective first winding portion 5a of the ferromagnetic core 3.

[0063] 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 .

[0064] 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.

[0065] 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 5 and Figure 6 ).

[0066] It is important to emphasize at this point that providing a first plurality of turns 4a provided with a plurality of input terminals 6 and a second plurality of turns 4b provided with a plurality of output terminals 7 allows a plurality of input terminals 6 to be connected to a power supply line and a plurality of output terminals 7 to be connected to a power supply unit while keeping the connections thus defined spaced apart from each other.

[0067] This fact avoids the risk of capacitive coupling that could occur between the input and output connections; the circuit 1 therefore effectively filters the electromagnetic interferences generated by the high voltage conversion, preventing these from entering the network.

[0068] 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.

[0069] In this respect, with reference to the preferred embodiment, the first winding portion 5a and the second winding portion 5b are opposite to each other in the sense that they are arranged on two straight, separate and mutually parallel sections of the ferromagnetic core 3 .

[0070] 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.

[0071] Conveniently, the first plurality of turns 4a is wound around the first winding portion 5a in at least a first winding direction and the second plurality of turns 4b is wound around the second winding portion 5b in at least a second winding direction opposite to the first winding direction.

[0072] from Figures 4 to 6 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] Conveniently, the input 6 and output 7 of each winding 4a, 4b are substantially aligned with each other on the first section 3a and the second section 3b respectively.

[0077] This fact in combination with what has already been described further improves the filtering efficiency of the filter circuit 1, since it allows the connections to be aligned with each other, thereby preventing the connections from being side by side in certain sections.

[0078] According to a first embodiment, the circuit 1 comprises only one filter 2 , 8 and therefore only one coil 2 .

[0079] In this case, the plurality of input terminals 6 of the coil 2 may be directly connected to the power supply line, and similarly, the plurality of output terminals 7 of the coil 2 may be directly connected to the power supply unit.

[0080] 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 there are no additional electrical components (eg an additional coil 2 ) in between.

[0081] The same considerations apply when using the aforementioned terms to refer to the connection between the output terminal 7 and the power supply unit.

[0082] Alternatively, according to a second embodiment, the circuit 1 comprises a plurality of filters 2 , 8 , and therefore also a plurality of coils 2 , connected in series with one another.

[0083] In this case, the plurality of input terminals 6 of the first coil 2 and the plurality of output terminals 7 of the last coil 2 can be directly connected to the power supply line and the power supply component, respectively.

[0084] Furthermore, the output terminals 7 of each coil 2, except for the last one, are directly connected to the input terminals 6 of the next coil 2, so as to define four intermediate connections between two consecutive filters 2, 8, which are parallel to each other.

[0085] Keeping in mind the previously described arrangement of the plurality of input terminals 6 and the plurality of output terminals 7, it is not difficult to understand how, in the second embodiment, all the connections (i.e., the input connections, the output connections and the intermediate connections) are aligned along four lines parallel to each other (see in this respect Figure 4 ).

[0086] Preferably, the circuit 1 comprises three filters 2, 8 connected in series.

[0087] In this case, the circuit 1 is therefore provided with four input connections to the power supply lines, four output connections to the power supply unit, and eight intermediate connections between multiple filters 2, 8 connected in series (i.e. four between the first filter 2, 8 and the second filter 2, 8 and a further four between the second filter 2, 8 and the third filter 2, 8).

[0088] However, it cannot be excluded that the circuit 1 may have a different number of filters 2 , 8 , for example two filters 2 , 8 connected in series, or a different number of filters 2 , 8 , for example a greater number of filters 2 , 8 .

[0089] The described invention has in fact been determined to achieve the intended purpose.

[0090] Particularly emphasised is the fact that providing a first plurality of turns provided with inputs and a second plurality of turns provided with outputs allows connecting the inputs and outputs to the supply line and the power supply unit while keeping the connections thus defined spaced apart from each other.

[0091] This fact avoids the risk of possible capacitive coupling between the input and output connections; in this way, the filter circuit effectively filters the electromagnetic interference generated by the high voltage conversion and prevents these from entering the network.

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 a predetermined direct current, the filter circuit (1) comprising at least one electromagnetic interference filter (2, 8), the electromagnetic interference filter being provided with: At least one coil (2) comprising: at least one ferromagnetic core (3); at least four windings (4a, 4b), each winding being wound around a corresponding winding portion (5a, 5b) of the ferromagnetic core (3), and each winding being provided with at least one input terminal (6) and at least one output terminal (7), the input terminal (6) being connectable to one of the three phases of an AC power supply line or a neutral line, and the output terminal (7) being connectable to the power supply unit; at least one line capacitor (8) connected to at least one input terminal (6) or at least one output terminal (7); It is characterized in that each of the windings (4a, 4b) includes a first plurality of turns (4a) provided with the input end (6) and a second plurality of turns (4b) provided with the output end (7), the first plurality of turns (4a) being wound around a corresponding first winding portion (5a) of the ferromagnetic core (3), the second plurality of turns (4b) being connected to the first plurality of turns (4a), the second plurality of turns (4b) being 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).

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

3. The circuit (1) according to claim 2, 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.

4. Circuit (1) according to one or more of the preceding claims, characterized in that The first plurality of turns (4a) are wound around the first winding portion (5a) in at least a first winding direction, and the second plurality of turns (4b) are wound around the second winding portion (5b) in at least a second winding direction, the second winding direction being opposite to the first winding direction.

5. Circuit (1) according to one or more of the preceding claims, characterized in that The circuit (1) comprises a single filter (2, 8), the input end (6) of a single coil (2) can be directly connected to the power supply line, and the output end (7) of a single coil (2) can be directly connected to the power supply unit.

6. Circuit (1) according to one or more of claims 1 to 4, characterized in that The circuit (1) comprises a plurality of filters (2, 8) connected in series with each other, wherein: - the input end (6) of the first coil (2) and the output end (7) of the last coil (2) can be directly connected to the power supply line and the power supply unit respectively; The output terminals (7) of each coil (2), except the last coil (2), are directly connected to the input terminals (6) of the next coil (2) to define four intermediate connections parallel to each other between two consecutive filters (2, 8).

7. The circuit (1) according to claim 6, characterized in that The circuit (1) comprises three filters (2, 8) connected in series.

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