OR HYBRID VEHICLES

Technical Field

The present invention relates to a power conversion electronic appliance.

Background Art

In order to enable periodic charging of batteries, electric and hybrid vehicles are provided with special appliances (so-called “on-board chargers”, OBCs) which can be connected at input to an AC power line and at output to the vehicle battery.

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

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 heat generated is by means of special heat sinks positioned where a portion opposite the portion of the MOSFET is located which is associable with the printed circuit board.

One detail of a known appliance related to the assembly of the aforementioned MOSFET and of the relevant heat sink is shown in Figure 1 by way of example, wherein the detail of the appliance under consideration, the printed circuit board and the MOSFET have been identified with the reference letters A, C and M, respectively.

The aforementioned peculiar placement of the heat sink of the MOSFET M makes it completely unnecessary to provide special Insulated Metal Substrate (IMS) circuits for dissipation, thus reducing the overall dimensions of such appliances A and the manufacturing complexity thereof.

To enable heat to be expelled externally from the appliance A, the heat sinks of the individual components are associated with the heat sink D of the appliance itself, which may be of the type of a liquid cooling circuit.

Nevertheless, appropriate electrical insulation must be achieved between the heat sinks of the components and the heat sink D of the appliance in order to comply with current safety regulations; for this purpose, the appliance A provides for a gap filler G, which is a one- or two-component layer made of electrically insulating material with high thermal conductivity.

In the present case, the gap filler G is an elastic two-component layer adapted to solidify following its application onto the power components.

Therefore, the gap filler G can be squeezed during the assembly of the appliance A by fitting between the various power components and electrically insulating the latter.

Having said all this, it is important to specify at this point that monitoring the working temperature of MOSFETs M plays a major role in ensuring that they do not experience any dangerous overheating during the use of the appliance A. For this very reason, the appliance A comprises a plurality of temperature sensors S, each associated with one or more MOSFETs M and configured to detect the working temperature thereof.

In the specific case of the known appliances A under consideration, the temperature sensor S is placed in close proximity to the respective MOSFET M at a minimum distance; in this way, the gap filler G can fit between one and the other as a result of its own squeezing, and the heat generated by the MOSFETs M can thus be transferred to the respective temperature sensors S.

That said, it is important to point out that the methodology discussed so far is by no means without drawbacks.

First of all, it should be understood that the size of the temperature sensors S is, in general, considerably smaller than that of the MOSFETs M and thus forces an overdose of the amount of gap fillers G to be provided to ensure that the latter goes adequately between each MOSFET M and the respective temperature sensor S.

Even using smaller MOSFETs M, however, the placement of the gap filler G between the MOSFETs M and the temperature sensors S is, nevertheless, marked by very low accuracy and repeatability.

In this regard, it must, in fact, be considered that the squeezing of the gap filler G is, in itself, an operation of highly imprecise execution; this means that, even if repeated in a seemingly identical manner, this operation does not always return the same final result.

It is easy to appreciate that the lack of repeatability of an industrial process is a rather inconvenient circumstance since it can be a reason for uncertainties and problems, in the long run, on the products placed on the market.

Another drawback is that the placement of the temperature sensor S causes it to detect not only the temperature of the MOSFET M, but also that of the heat sink D of the appliance A since, as mentioned, both of the latter are thermally connected to the temperature sensor S by means of the gap filler G.

Description of the Invention

The main aim of the present invention is to devise a power conversion electronic appliance for electric or hybrid vehicles which enables thermal coupling between the MOSFET and the relevant temperature sensor which is accurate and repeatable for all manufactured products.

Another object of the present invention is to devise a power conversion electronic appliance for electric or hybrid vehicles which can overcome the aforementioned drawbacks of the prior art within the framework of a simple, rational, easy and effective to use as well as low cost solution.

The aforementioned objects are achieved by this power conversion electronic appliance for 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 power conversion electronic appliance for 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 overall axonometric view of a detail of a known appliance relating to the assembly of a MOSFET of the SMD top-cooled type;

Figure 2 is an axonometric view of a detail of the appliance according to the invention in accordance with a first embodiment; Figure 3 is an exploded view of a detail from Figure 2;

Figure 4 is an axonometric view of a detail of the appliance according to the invention in accordance with a second embodiment;

Figure 5 is an exploded view of a detail from Figure 4;

Figure 6 is a cutaway view of a detail of the appliance according to the invention in accordance with a third embodiment.

Embodiments of the Invention

With particular reference to these figures, reference numeral 1 globally denotes a power conversion electronic appliance for electric or hybrid vehicles.

The power conversion electronic appliance 1 for electric or hybrid vehicles can be installed inside at least one electric or hybrid vehicle and connectable to at least one battery of the vehicle comprises: at least one printed circuit board 2 provided with at least one first face 2a and at least one second face 2b opposite each other; a plurality of power components configured for the conversion of at least one input current/voltage to at least one predefined output current/voltage to be sent to the battery, the power components being mounted on the printed circuit board 2 and being arranged on one of either the first face 2a or the second face 2b.

It is important to specify that the power components comprise at least one MOSFET device 3 of the SMD or PTH (Passing Through Hole) top-cooled type.

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

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

In this sense, the heat dissipation element 4 is associated with the second reference portion 3b. In addition, the appliance 1 comprises at least one sensor device 5 which is operationally associated with the MOSFET device 3 and is adapted to sense therefrom at least one temperature value.

Specifically, the expression “temperature value” relates to the working temperature of the MOSFET device 3, i.e., the temperature the latter has during the use of appliance 1.

The MOSFET device 3 is, in fact, traversed by high currents, making the measurement of its working temperature essential to ward off any overheating of the device and, in so doing, to prevent the appliance 1 from damaging.

Again, the appliance 1 comprises at least one layer 6 of electrically insulating and thermally conductive material arranged in contact with each of the power components.

Indeed, the high voltages applied to the power components require that the same be electrically insulated properly.

In this regard, the layer 6 is elastically deformable and can, therefore, be squeezed (e.g., during the assembly phase of the appliance 1), inserting itself at least partly between one power component and another and electrically insulating the latter in doing so.

Preferably, the layer 6 is of the type of a one- or two-component which is adapted to solidify after being applied to the appliance 1 (known in technical jargon as “gap filler”).

Again, the appliance 1 comprises at least one heat sink body 7 (which may be of the type shown in the figures or of the type of a water chamber) associated with the layer 6 and adapted to dissipate the heat generated by the power components, removing it from the appliance itself.

In this regard, it should be specified that the layer 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.

In this sense, the heat sink body 7 is associated with the second surface 6b.

According to the invention, the appliance 1 comprises thermal connection means 8 between the MOSFET device 3 and the sensor device 5 comprising at least one pad 9 made of thermally conductive material and placed between the MOSFET device 3 and the sensor device 5.

The pad 9 substantially consists of a plate-shaped element associated with the MOSFET device 3 and with the sensor device 5.

The pad 9 is at least partly made of copper, but the possibility of making it, at least partly, of different thermally conductive materials such as, e.g., of a different metallic material (e.g., steel, nickel...), or of other thermally conductive materials still known to the expert in the field cannot be ruled out.

It is important to specify, however, that the special expedient of thermally connecting the MOSFET device 3 to the sensor device 5 by means of the pad 9 allows achieving significant technical advantages, set forth below and in the remainder of this disclosure, which remedy the drawbacks of the prior art previously complained of.

First of all, it should be considered that the transmission of heat from the MOSFET device 3 to the sensor device 5 is, thanks to this expedient, completely unrelated to the presence of the layer 6 and, therefore, to the proper squeezing of the latter between the various power components.

In other words, this expedient allows heat to be conducted from the MOSFET device 3 to the sensor device 5 in a totally repeatable manner between one product and another and independently, therefore, of the presence of the layer 6 between the MOSFET device 3 and the sensor device 5.

The measurement of the sensor device 5 is, by the way, absolutely accurate because the temperature of the heat sink body 7 cannot be detected by the pad 9 in any way, averting the possibility of obtaining incorrect temperature values.

What’s more, since it does not intervene in the thermal coupling between the MOSFET device 3 and the sensor device 5, the layer 6 does not require any overdosing; it is easy to appreciate how this fact exerts a highly positive effect on the reduction of the production costs of the appliance 1.

According to a first embodiment of the appliance 1, shown in Figures 2 and 3, the MOSFET device 3 and the sensor device 5 are arranged on the first face 2a of the printed circuit board 2 and the pad 9 is mounted between the MOSFET device 3 and the sensor device 5 on the first face 2a.

In actual facts, the MOSFET device 3 and the sensor device 5 are arranged in contact with the pad 9, which is placed between the latter and allows heat transmission from the former to the latter.

The pad 9 can be of the type of an external element applied onto the printed circuit board 2, or it can be directly obtained from the printed circuit board itself.

As can be seen, the MOSFET device 3 and the sensor device 5 are arranged side by side on the first face 2a close together, so as to make the use of a small-sized pad 9 sufficient to thermally connect them together.

Specifically, in this first embodiment the thermal connection means 8 comprise a single pad 9, arranged in contact with the MOSFET device 3 and with the sensor device 5 on the first face 2a.

From what has been described so far, it is evident to appreciate that such a first embodiment achieves the aforementioned advantages through a simple and functional technical solution and simplifies the complexity of the appliance 1, while still ensuring effective heat transfer from the MOSFET device 3 and the sensor device 5.

It is important to add that the thermal connection means 8 comprise at least one thermal connection element 10 which is positioned between the MOSFET device 3 and the pad 9 and is adapted to facilitate the transfer of heat from the MOSFET device 3 to the pad 9.

Specifically, in the first embodiment, the thermal connection element 10 is positioned between the MOSFET device 3 and the single pad 9.

Preferably, the thermal connection element 10 is of the type of a thermally conductive paste.

In this regard, it should be specified that the thermal connection element 10 is applied between the pad 9 and the MOSFET device 3 during the assembly phase of the various components in a totally automatic manner, i.e., without requiring any intervention by operators or skilled workers.

In this sense, after the appliance 1 has been assembled, the MOSFET device 3 squeezes the thermal connection element 10, thus allowing the latter to expand radially and to ensure, by virtue of this very expansion, the proper transfer of heat from the MOSFET device 3 to the sensor device 5.

In actual facts, after being squeezed, the thermal connection element 10 defines a large thermally conductive bearing surface of the MOSFET device 3 on the pad 9, thus ensuring that the heat transfer from the former to the latter occurs, for each product, in an appropriate manner.

So, the special expedient of providing a thermal connection element 10 operates in conjunction with the pad 9 in ensuring a thermal coupling of the MOSFET device 3 with the sensor device 5 which is absolutely precise and repeatable for all manufactured products.

Having described this first embodiment, it is important to reiterate that arranging the sensor device 5 and the MOSFET device 3 in close proximity on the first face 2a allows the temperature measurement of the latter to be carried out in a decidedly precise manner.

The aforementioned proximity does, however, mean that the sensor device 5 must also be electrically insulated, along with the power components, by means of the layer 6.

In this regard, in accordance with a second embodiment shown in Figures 4 and 5, the MOSFET device 3 is arranged on the first face 2a and the sensor device 5 is arranged on the second face 2b.

In actual facts, the MOSFET device 3 and the sensor device 5 are, in this second embodiment, opposite each other on the printed circuit board 2.

Such an arrangement of the sensor device 5 has, in addition to those already listed, the additional advantage of making the electrical insulation of the sensor device 5 completely unnecessary since the latter and the MOSFET device 3 are, in the aforementioned second embodiment, placed on different faces 2a, 2b of the printed circuit board.

To connect the MOSFET device 3 and the sensor device 5 to each other, the thermal connection means 8 comprise, in the second embodiment, two pads 9, of which: at least one first pad 9a positioned between the MOSFET device 3 and the first face 2a; and at least one second pad 9b, thermally connected to the first pad 9a, which is positioned between the second face 2b and the sensor device 5.

For the purpose of allowing the thermal connection between the first pad 9a and the second pad 9b, the thermal connection means 8 comprise at least one thermal connection hole 11 (known in technical jargon as “vias”) formed passing through the printed circuit board 2 and adapted to thermally connect the first pad 9a and the second pad 9b to each other.

Specifically, the thermal connection hole 11 is of the type of a metalized hole.

In more detail, the thermal connection means 8 comprise a plurality of thermal connection holes 11 visible in Figures 4 and 5.

Specifically, the thermal connection holes 11 pass through the printed circuit board 2, the first pad 9a and the second pad 9b.

These thermal connection holes 11 are lined with thermally conductive material so that the heat can be transmitted from the first pad 9a to the second pad 9b.

Preferably, the thermal connection holes 11 are lined with copper, but the possibility of lining them with different thermally conductive materials such as, e.g., with other types of metallic materials cannot be ruled out.

It is important to specify that this second embodiment achieves an additional and important technical result, namely, that of making the temperature measurement of the MOSFET device 3 by the sensor device 5 considerably faster.

Being, in fact, arranged on a face 2a, 2b of the printed circuit board 2 opposite that of the MOSFET device 3, the sensor device 5 is not affected in any way by any proximity or distance between the same and the MOSFET device 3, reacting readily to the junction temperature (i.e., the temperature of the MOSFET device 3 and, therefore, of the pads 9 during the operation of the appliance 1).

It is also specified that, in this second embodiment, the thermal connection element 10 is positioned between the MOSFET device 3 and the first pad 9a. In this regard, to further increase the conductive effectiveness of the thermal connection element 10, the thermal connection means 8 comprise, in a third embodiment of the appliance 1 shown in Figure 6, at least one thermal connection opening 12 formed passing through the first pad 9a, the printed circuit board 2 and the second pad 9b.

In actual facts, the third embodiment of the appliance 1 is in all respects identical to the second embodiment except for the fact of providing for the thermal connection opening 12 and the related expedients.

Precisely in this regard, the thermal connection opening 12 is formed with sufficient size to allow the at least partial insertion of the thermal connection element 10 inside it.

Thus, in this third embodiment, the thermal connection element 10 is positioned between the MOSFET device 3 and the sensor device 5, further and smoothly improving the thermal coupling between the latter.

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

In particular, the fact is emphasized that the special expedient of providing one or more pads made of thermally conductive material and placed between the MOSFET device and the sensor device makes it possible to achieve an absolutely precise and repeatable thermal coupling between them for all manufactured products.