Electronic power conversion appliance for electric or hybrid vehicles

Abstract

The electronic power conversion appliance (1) for electric or hybrid vehicles, comprises: a printed circuit board (2); a plurality of power components mounted on said printed circuit board (2) and comprising at least one MOSFET device (3); a heat sink body (5); an attachment portion (7) of the heat sink body (5) to the printed circuit board (2); wherein: the appliance ( 1) comprises at least one thermal pad (6) arranged in contact with each of the power components and with the heat sink body (5); the attachment portion (7) comprises a tolerance space (8) positioned between the printed circuit board (2) and the heat sink body (5); the appliance (1) comprises elastic means (9, 10) adapted to elastically bend to enable the attachment of the printed circuit board (2) to the heat sink body (5) so as to compensate for the dimensional tolerances of the printed circuit board (2), of the power components and / or of the heat sink body (5).

Description

[0001] ELECTRONIC POWER CONVERSION APPLIANCE FOR ELECTRIC OR HYBRID VEHICLES

[0002] Technical Field

[0003] The present invention relates to an electronic power conversion appliance for electric or hybrid vehicles.

[0004] Background Art

[0005] In order to enable periodic recharging of batteries, electric and hybrid vehicles are provided with special appliances (so-called on-board chargers, OBCs) connectable at input to an AC power line and at output to the battery of the vehicle.

[0006] Specifically, known appliances are provided with a printed circuit board on which a plurality of power components is mounted adapted to convert the incoming alternating current into a corresponding and predefined direct current to be sent out to the battery for storage.

[0007] Among the various power components, such appliances comprise one or more MOSFETs of the SMD or PTH (Passing Through Hole) top-cooled type, which consist of special transistors where the dissipation of the heat generated takes place by means of special heat sinks located where the portion of the MOSFETs opposite that associated with the printed circuit board is located.

[0008] A detail of a known appliance relating to the mounting of the aforementioned MOSFET and of the relevant heat sink is illustrated by way of example in Figures 1-6, where the detail of the appliance under consideration, the printed circuit board and the MOSFETs have been identified with the reference letters A, C and M, respectively.

[0009] The peculiar placement of the heat sink of the MOSFETs M makes it entirely unnecessary to provide special IMS circuit boards (Insulated Metal Substrate, i.e. printed circuit boards with insulated metal substrate for dissipation), thus reducing the total footprint of such appliances A and the manufacturing complexity thereof.

[0010] In order to expel heat externally to the appliance A, it becomes necessary to associate the heat sinks of the individual components with the heat sink D (which may be of the type of a liquid cooling circuit) of the appliance itself by means of the interposition between the two of one or more thermally conductive components.

[0011] Not only that, but appropriate electrical insulation must also be provided between the heat sink of the components and the heat sink D of the appliance in order to comply with current safety regulations.

[0012] In order to comply with these requirements, a first embodiment of known appliances A involves the presence of a gap filler G, i.e., a single- component / bicomponent layer made of electrically insulating material with high thermal conductivity, between the heat sink D and the MOSFETs M (Figures 1 and 2).

[0013] In the present case, the gap filler G is an elastic layer which is adapted to solidify as a result of the application thereof to the power components; therefore, the gap filler G can be squeezed during the assembly of the appliance A, fitting between the various power components and electrically insulating them.

[0014] It is important to explain, in this regard, that the distance between the MOSFETs M and the heat sink D must be strictly maintained above a minimum threshold value to ensure adequate electrical insulation of the MOSFETs M during the use of the appliance A.

[0015] It must, however, be considered that the dimensional tolerances of the various components of the appliance A, when added together, can cause the MOSFETs M to be at a potentially shorter distance from the heat sink D than expected, jeopardizing, in this case, the proper electrical insulation of the appliance A.

[0016] Another circumstance to keep in mind is related to the fact that gap fillers G frequently have bubbles therein, which are known to result in a significant reduction in the electrical insulation and thermal conductivity abilities of the gap filler G.

[0017] In this context, it is common practice to overdose the gap filler G between the MOSFETs M and the heat sink D so as to ensure proper electrical insulation of the MOSFETs themselves even in cases where the gap filler G had numerous bubbles therein and / or the distance between the MOSFETs M and the heat sink D was less than the aforementioned threshold value.

[0018] It is easy to appreciate, however, how this fact results in the use of high and often excessive amounts of gap filler G, leading to a waste of material and, therefore, to an increase in the overall costs to be incurred for the production of the appliance A.

[0019] A second embodiment of known appliances A (Figures 3 and 4) involves the use of special electrically insulating thermal plates (known, in the industry, as “thermal pads” and denoted, in Figures 2-6, by the reference letter P) in place of the gap filler G.

[0020] Such thermal pads P are made of thermally conductive paste and, therefore, are free from the formation of internal bubbles, thus remedying the problems caused by the presence of the latter.

[0021] Nonetheless, this second type of appliance A is still affected by drawbacks related to the fact that, in the absence of the gap filler G, it is necessary to use thermal pads P that are thick enough to be simultaneously in contact with the MOSFETs M and the heat sink D.

[0022] However, the high thickness of such thermal pads P results in a significant reduction in the thermal conductivity thereof and, therefore, a significant reduction in the capacity with which the appliance A is able to dissipate the heat produced by power components, resulting in undermining the proper operation of the appliance itself.

[0023] In addition, the greater compressive stiffness of such thermal pads P compared with the gap filler G makes it more difficult to position the printed circuit board C at the correct distance from the heat sink D, leading, in this respect, to considerable difficulties during the assembly phase.

[0024] A third embodiment of known appliances A, shown in Figures 5 and 6, involves the combined use of the thermal pads P and the gap filler G.

[0025] In this case, the thermal pads P are arranged in contact with each MOSFET M and the gap filler G is applied between the thermal pads P and the heat sink D so as to conduct the heat generated by the MOSFETs M to the latter.

[0026] It is important to appreciate that, due to the presence of the gap filler G, it is possible to use thermal pads P of reduced thickness, overcoming the drawbacks related to their reduced thermal conductivity shown for the previous embodiment. In spite of this, it is important to point out that the fact of providing both the gap filler G and the thermal pad P turns out to be a very costly technical solution from an economic point of view, ending up, therefore, severely penalizing company revenues.

[0027] Description of the Invention

[0028] The main aim of the present invention is to devise an electronic power conversion appliance for electric or hybrid vehicles which allows reducing material waste and overall costs compared with known appliances while ensuring adequate electrical insulation and effective disposal of the heat produced by the power components, particularly by MOSFETs.

[0029] Another object of the present invention is to devise an electronic power conversion appliance for 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 efficient to use as well as cost-effective solution. The aforementioned objects are achieved by this electronic power conversion appliance for electric or hybrid vehicles having the characteristics of claim 1. Brief Description of the Drawings

[0030] Other characteristics and advantages of the present invention will become more apparent from the description of a preferred, but not exclusive, embodiment of an electronic power conversion appliance for electric or hybrid vehicles, illustrated by way of an indicative, yet non-limiting example in the accompanying tables of drawings in which:

[0031] Figure 1 is an axonometric overall view of a first embodiment of a known appliance;

[0032] Figure 2 is a front, cross-sectional view of the known appliance in Figure 1;

[0033] Figure 3 is an axonometric overall view of a second embodiment of a known appliance;

[0034] Figure 4 is a front, cross-sectional view of the known appliance in Figure 3;

[0035] Figure 5 is an axonometric overall view of a third embodiment of a known appliance;

[0036] Figure 6 is a front, cross-sectional view of the known appliance in Figure 5;

[0037] Figure 7 is an axonometric overall view of a first embodiment of the appliance according to the invention;

[0038] Figure 8 is a front, cross-sectional view of the appliance in Figure 7;

[0039] Figure 9 shows from above some components of the appliance in Figure 7 and 8; Figures 10a, 10b and 10c are front views, from above, of a second embodiment of the appliance according to the invention.

[0040] Embodiments of the Invention

[0041] With particular reference to Figures 7-10, reference numeral 1 globally denotes an electronic power conversion appliance for electric or hybrid vehicles.

[0042] The electronic power conversion appliance 1 for electric or hybrid vehicles, which can be installed within an electric or hybrid vehicle and connectable to the battery of the vehicle comprises, first of all: at least one printed circuit board 2; and a plurality of power components configured for the conversion of an input current / voltage into a predefined output current / voltage to be sent to the battery, the power components being mounted on the printed circuit board 2 and comprising at least one MOSFET device 3 of the SMD or PTH topcooled type.

[0043] As mentioned above, the MOSFET device 3 is provided with a special heat dissipation element 4 adapted to dissipate the heat generated during the use of the appliance 1.

[0044] In this regard, the MOSFET device 3 is provided with two reference portions 3a, 3b, of which a first reference portion 3a faces the printed circuit board 2 and a second reference portion 3b, opposite the first reference portion 3a, faces the opposite side with respect to the printed circuit board 2.

[0045] In this sense, the heat dissipation element 4 is associated with the second reference portion 3b.

[0046] The appliance 1 then comprises at least one heat sink body 5 adapted to dissipate the heat generated by the power components, removing it from the appliance itself.

[0047] In particular, the heat sink body 5 may be of the type shown in the figures, the type of a water chamber or other types still known to the branch engineer.

[0048] According to the invention, the appliance 1 comprises at least one thermal pad 6 made of electrically insulating and thermally conductive material arranged in contact with each of the power components and with the heat sink body 5.

[0049] In other words, the thermal pad 6 is provided with at least a first surface 6a facing the MOSFET device 3 and with at least a second surface 6b opposite the first surface 6a.

[0050] In this sense, the heat sink body 5 is associated with the second surface 6b of the thermal pad 6.

[0051] Conveniently, the thermal pad 6 has a thickness of 200 pm or less.

[0052] Preferably, the thermal pad 6 has a thickness comprised between 100 pm and 200 pm.

[0053] Due to its small thickness, the thermal pad 6 is distinguished by high thermal conductivity, enabling it to effectively dissipate the heat produced by the power components.

[0054] This ensures proper operation of the appliance 1 while avoiding material waste due to the total absence of gap filler between the power components between the thermal pad 6 and the heat sink body 5.

[0055] In addition, the appliance 1 comprises at least one attachment portion 7 of the printed circuit board 2 to the heat sink body 5.

[0056] In this regard, according to the invention, the attachment portion 7 comprises at least one tolerance space 8 positioned between the printed circuit board 2 and the heat sink body 5 (Figure 8).

[0057] In other words, the printed circuit board 2 is placed at a distance from the heat sink body 5 where the attachment portion 7 is located to define the aforementioned space 8.

[0058] The special mutual positioning of the printed circuit board 2 and of the heat sink body 5 causes the size of the space 8 (i.e., the distance between the printed circuit board 2 and the heat sink body 5 where the attachment portion 7 is located) to vary according to the dimensional tolerances of the components of the appliance 1.

[0059] In other words, this distance is comprised between a maximum value and a minimum value for which the components of the appliance 1 have the minimum size and the maximum size allowed by their dimensional tolerances, respectively. In this regard, the appliance 1 comprises, according to the invention, elastic means 9, 10 associated with the printed circuit board 2 and adapted to elastically bend to enable the attachment of the printed circuit board 2 to the heat sink body 5.

[0060] Due to their elastic bending, the elastic means 9, 10 allow offsetting the dimensional tolerances of the printed circuit board 2, of the power components, and / or of the heat sink body 5.

[0061] This means that, in the case where the size of the space 8 is maximum, the elastic means 9, 10 bend elastically to a maximum extent to enable the attachment of the printed circuit board 2 to the heat sink body 5, and vice versa.

[0062] Before going into detail about the elastic means 9, 10 it is important to emphasize at the outset how they operate in conjunction with the thermal pad 6 in making an appliance 1 distinguished by adequate electrical insulation, effective dissipation of the heat produced by the power components and a significant reduction in the overall production costs.

[0063] In particular, the appliance 1 in question allows for the effective dissipation of the heat generated by the power components as well as for the adequate insulation of these components regardless of the tolerances and, therefore, of the actual dimensions of the various components of the appliance itself.

[0064] This makes the appliance 1 particularly reliable, functional and, at the same time, cheap compared with the appliances previously described in the state of the art. Conveniently, the printed circuit board 2 is provided with a plurality of attachment holes 11 each of which is adapted to allow the insertion of an attachment element therein.

[0065] For example, the attachment element is at least partly threaded (e.g., a screw or similar component). In this regard, in accordance with a first embodiment, the elastic means 9, 10 comprise at least one elastic portion 10 associated with the printed circuit board 2, provided with a respective attachment hole 11 and adapted to allow the attachment hole 11 to move close to / away from the heat sink body 5 as a result of its own elastic bending (Figure 9).

[0066] In other words, depending on the size of the space 8, the elastic portion 9 can bend elastically towards the heat sink body 5, allowing the relevant attachment hole 11 to move close to the heat sink body, or it can bend elastically in the opposite direction from the heat sink body 5, allowing the relevant attachment hole 11 to move away from the heat sink body.

[0067] As already anticipated, the bending of the elastic portion 9 allows the printed circuit board 2 to be effectively attached to the heat sink body 5 regardless of the size of the space 8 and, therefore, of the actual size of the components of the appliance 1, thus, giving the latter considerable practicality and versatility of use. Conveniently, the printed circuit board 2 is provided with at least one pair of slots 12 cut at the sides of the respective attachment hole 11, the elastic portion 9 being formed into the printed circuit board 2 and being positioned between the slots 12. In actual facts, the presence of the slots 12 makes it possible to define a portion of the printed circuit board 2 characterized by lower stiffness and coinciding, therefore, with the elastic portion 9.

[0068] Different embodiments of the elastic portion 9 cannot however be ruled out, wherein e.g. the printed circuit board 2 may be without the slots 12 and the elastic portion 9 may be associated with the printed circuit board 2 so as to overhang with respect to the latter.

[0069] Preferably, the elastic means 9, 10 comprise a plurality of elastic portions 9 arranged along at least one side of the printed circuit board 2 substantially by its entire extent.

[0070] As visible in Figure 9, the elastic means 9, 10 comprise a first plurality of elastic portions 9 arranged along a first side of the printed circuit board 2 and a second plurality of elastic portions 9 arranged along a second side of the printed circuit board 2. In particular, the first side and the second side are substantially parallel to each other.

[0071] Advantageously, the printed circuit board 2 comprises at least one recessed portion 13, shown in Figure 9.

[0072] In this regard, in accordance with a second embodiment, the elastic means 9, 10 comprise at least one attachment device 10 comprising: at least one supporting body 14 arranged where the recessed portion 13 is located, provided with at least one opening 14a passable through by the attachment element and defining at least one stop surface 14b of the attachment element; and at least one pair of fins 15, each having a first end associated with the supporting body 14 and a second end associated with the printed circuit board 2, the fins 15 being adapted to elastically bend to move the supporting body 14 close to / away from the heat sink body 5.

[0073] Preferably, the supporting body 14 is conformed like a washer.

[0074] Usefully, as visible in the aforementioned figure, the fins 15 are arranged opposite the supporting body 14.

[0075] In this regard, the attachment device 10 comprises two fins 15; it is easy to appreciate, however, how the number of fins 15 may vary from the one just provided and be, e.g., higher.

[0076] In all cases, the fact of bending the fins 15 allows the opening 14a (and, therefore, the attachment element) to be moved close to / away from the heat sink body 5, allowing the printed circuit board 2 to be attached to the heat sink body regardless of the dimensional tolerances of the components of the appliance 1 and thus achieving the same advantages as described above regarding the elastic portion 9.

[0077] In accordance with a second embodiment of the appliance 1, shown in Figures 10a, 10b and 10c, the printed circuit board 2 comprises at least one flexible portion 16 with which the MOSFET device 3 is associated and which is adapted to bend elastically to move the MOSFET device 3 close to / away from the heat sink body 5. Thus, in this case, the appliance 1 lacks the space 8 between the attachment portion 7 and the heat sink body 5 since the bending of the flexible portion 16 and, therefore, of the MOSFET device 3 associated therewith allows the dimensional tolerances of the components of the appliance to be offset.

[0078] In detail, the printed circuit board 2 comprises: at least one basic portion 17; at least one breaking line 18 adapted to peripherally bound the flexible portion 16 and comprising at least one breaking stretch 18a located between the basic portion 17 and the flexible portion 16; and at least one connecting portion 19 between the basic portion 17 and the flexible portion 16.

[0079] Specifically, the basic portion 17 is arranged to surround the flexible portion 16. As visible in Figure 10a, the printed circuit board 2 can be provided with only one breaking stretch 18a and, therefore, with only one connecting portion 19.

[0080] In this case, the breaking stretch 18a preferably has an open-break shape.

[0081] In detail, the breaking stretch 18a has a “C” conformation.

[0082] The possibility of making the breaking stretch 18a with a different conformation, such as an open circle, cannot however be ruled out.

[0083] Alternatively, the breaking line 18 comprises a plurality of breaking stretches 18a disjointed from each other and the printed circuit board 2 comprises a plurality of connecting portions 19, each arranged between two respective breaking stretches 18a.

[0084] In other words, the breaking stretches 18a are separated from each other by a respective connecting portion 19.

[0085] Specifically, the breaking line 18 comprises at least one pair of breaking stretches 18a and the printed circuit board 2 comprises at least one pair of connecting portions 19.

[0086] As visible in Figure 10b, the breaking line 18 may comprise two breaking stretches 18a.

[0087] In this case, the printed circuit board 2 comprises two connecting portions 19.

[0088] In particular, the connecting portions 19 are arranged at opposite positions to each other with respect to the MOSFET device 3.

[0089] In the present case, as in the previous case, each breaking stretch 18a preferably has an open-break conformation.

[0090] In detail, each breaking stretches 18a has a “C” conformation.

[0091] In this sense, the breaking stretches 18a face each other.

[0092] Alternatively, as visible in Figure 10c, the breaking line 18 may comprise four breaking stretches 18a and, therefore, the printed circuit board 2 may comprise four connecting portions 19.

[0093] Specifically, the breaking stretches 18a have, in this case, a rectilinear conformation.

[0094] More specifically, the breaking stretches 18a visible in Figure 10c define a breaking line 18 having a substantially square / rectangular conformation.

[0095] In any case, the special expedient of providing a flexible portion 16 makes it possible to arrange the MOSFET device 3 at the correct distance from the heat sink body 5 regardless of the actual dimensions of the various components of the appliance 1, thus ensuring adequate electrical insulation, appropriate dissipation of the heat generated and, therefore, proper operation of the appliance itself.

[0096] It has in practice been ascertained that the described invention achieves the intended objects.

[0097] In particular, the fact is emphasized that the appliance in question makes it possible to reduce material waste and overall costs compared with known appliances while ensuring adequate electrical insulation and effective dissipation of the heat produced by the power components, particularly the MOSFETs.

Claims

CLAIMS1) Electronic power conversion appliance (1) for electric or hybrid vehicles, which can be installed within an electric or hybrid vehicle and connectable to the battery of said vehicle, comprising: at least one printed circuit board (2); a plurality of power components configured for the conversion of an input current / voltage into a predefined output current / voltage to be sent to said battery, said power components being mounted on said printed circuit board (2) and comprising at least one MOSFET device (3) of the SMD or PTH top-cooled type; at least one heat sink body (5) adapted to dissipate the heat generated by said power components; at least one attachment portion (7) of said heat sink body (5) to said printed circuit board (2); characterized by the fact that: it comprises at least one thermal pad (6) made of electrically insulating and thermally conductive material arranged in contact with each of said power components and with said heat sink body (5); said attachment portion (7) comprises at least one tolerance space (8) positioned between said printed circuit board (2) and said heat sink body (5); and by the fact that it comprises elastic means (9, 10) associated with said printed circuit board (2) and adapted to elastically bend to enable the attachment of said printed circuit board (2) to said heat sink body (5) so as to compensate for the dimensional tolerances of said printed circuit board (2), of said power components and / or of said heat sink body (5).2) Appliance (1) according to claim 1, characterized by the fact that: said printed circuit board (2) is provided with a plurality of attachment holes (11) each of which is adapted to allow the insertion of an attachment element therein; and that said elastic means (9, 10) comprise at least one elastic portion (9) associated with said printed circuit board (2), provided with a respective saidattachment hole (11) and adapted to allow said attachment hole (11) to move close to / away from said heat sink body (5) as a result of its own elastic bending.3) Appliance (1) according to claim 2, characterized by the fact that said printed circuit board (2) is provided with at least one pair of slots (12) cut into the sides of said respective attachment hole (11) and by the fact that said elastic portion (9) is cut into said printed circuit board (2) and is positioned between said slots (12).4) Appliance (1) according to claim 2 or 3, characterized by the fact that said elastic means (9, 10) comprise a plurality of said elastic portions (9) arranged along at least one side of said printed circuit board (2) substantially by its entire extent.5) Appliance (1) according to one or more of the preceding claims, characterized by the fact that said printed circuit board (2) comprises at least one recessed portion (13) and by the fact that said elastic means (9, 10) comprise at least one attachment device (10) comprising: at least one supporting body (14) arranged where said recessed portion (13) is located, provided with at least one opening (14a) passable through by said attachment element and defining at least one stop surface (14b) of said attachment element; and at least one pair of fins (15), each having a first end associated with said supporting body (14) and a second end associated with said printed circuit board (2), said fins (15) being adapted to elastically bend to move said supporting body (14) close to / away from said heat sink body (5).6) Appliance (1) according to claim 5, characterized by the fact that said supporting body (14) is conformed like a washer.7) Appliance (1) according to one or more of the preceding claims, characterized by the fact that said thermal pad (6) has thickness of 200 pm or less.8) Appliance (1) according to claim 7, characterized by the fact that said thermal pad (6) has thickness comprised between 100 pm and 200 pm.9) Electronic power conversion appliance (1) for electric or hybrid vehicles, which can be installed within an electric or hybrid vehicle and connected to the battery of said vehicle, comprising: at least one printed circuit board (2); a plurality of power components configured for the conversion of an input current / voltage into a predefined output current / voltage to be sent to said battery, said power components being mounted on said printed circuit board (2) and comprising at least one MOSFET device (3) of the SMD or PTH top-cooled type; at least one heat sink body (5) adapted to dissipate the heat generated by said power components; at least one attachment portion (7) of said heat sink body (5) to said printed circuit board (2); characterized by the fact that: it comprises at least one thermal pad (6) made of electrically insulating and thermally conductive material arranged in contact with each of said power components and with said heat sink body (5); said printed circuit board (2) comprises at least one flexible portion (16) with which said MOSFET device (3) is associated and which is adapted to elastically bend to move said MOSFET device (3) close to / away from said heat sink body (5).10) Appliance (1) according to claim 9, characterized by the fact that said printed circuit board (2) comprises: at least one basic portion (17); at least one breaking line (18) adapted to peripherally bound said flexible portion (16) and comprising at least one breaking stretch (18a) located between said basic portion (17) and said flexible portion (16); and at least one connecting portion (19) between said basic portion (17) and said flexible portion (16).11) Appliance (1) according to claim 10, characterized by the fact that said breaking line (18) comprises a plurality of said breaking stretches (18a) disjointed from each other and by the fact that said printed circuit board (2) comprises aplurality of said connecting portions (19), each arranged between two of said adjacent breaking stretches (18a).

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