The present invention relates to a power transformer assembly for transforming electromagnetic power of an oscillating electromagnetic field into electric power of an electric current or available electric current for charging an electric storage device or energizing an electric toad. The power transformer assembly comprises a magnetic assembly for receiving the oscillating electromagnetic field and transforming it into an electric alternating current, and an electronic assembly for receiving the electric alternating current and transforming it into the electric current or available electric current. The power transformer assembly further comprises heat dissipation means for dissipating heat generated by the electronic assembly during their respective power transforming operation.

The power transformer assembly, also referred to as a wireless charger module, may be used for charging a high-voltage (HV) battery of a vehicle. Such a module, sometimes also referred to as car-pad module (CPM), can receive an oscillating magnetic field from an external transmitter, which is sometimes referred to as ground-pad module (GPM), and transform the oscillating electromagnetic, predominantly magnetic field, into an alternating current which is converted (typically rectified) into an electric current (typically a direct current) used for charging the HV battery.

Batteries of electric vehicles can be charged using alternating current (AC) or direct current (DC) energy transfer. DC energy transfer is typically provided using high- power converters which are placed at dedicated charging points. While DC charging is typically faster than AC charging, it is not convenient for the end user as DC charging points are typically placed in remote areas and not installed in houses or residential areas as the installation of a DC charging point is expensive and the preexisting network capacity in those areas is usually vulnerable.

AC charging on the other hand is very important for residential areas and (semi)public urban areas. Typical AC chargers are capable of providing a charging power of up to 22 kW. AC charging systems can be divided into wired charging systems and wireless charging systems, wherein wireless charging systems are mainly embodied as inductive charging systems (ICSs). Wired AC chargers are typically integrated in electric vehicles and are also referred to as on-board chargers. An ICS typically comprises two separate modules which are often referred to as ground-pad module (GPM) and car-pad module (CPM).

The GPM is installed outside the electric vehicle while the CPM is installed in the electric vehicle, usually at the botom side of the vehicle. Electromagnetic interaction between the GPM and the CPM enables energy transfer from the GPM to the CPM, and the CPM is in turn used for charging a batery of the electric vehicle. Wireless charging systems are often more convenient for a user as typically no manual intervention is required for starting the charging process of the batery other than parking and positioning the vehicle above the GPM. Wired charging systems on the other hand require the user to connect the electric vehicle to a utility grid via a cable.

When it comes to cooling, it is important to understand that a CPM has two regions of heat generation: (a) the electronic assembly (power electronics) generating a lot of heat, but relatively concentrated at specific locations (high density), and (b) the magnetic assembly (coil and ferrite) generating less and relatively well distributed heat (low density). Prior art cooling systems for such CPMs are not well tailored to these circumstances and are relatively difficult to manufacture and thus expensive.

Therefore, it is an object of the invention to provide a power transformer assembly with improved overall cooling and in particular with improved electronic assembly cooling.

This object is achieved by a power transformer assembly for transforming electromagnetic power of an oscillating electromagnetic field into electric power of an electric current or available electric current for charging an electric storage device or energizing an electric load, the power transformer assembly comprising: a magnetic assembly for receiving the oscillating electromagnetic field and transforming it into an electric alternating current; an electronic assembly for receiving the electric alternating current and transforming it into the electric current or available electric current; and heat dissipation means for dissipating heat generated by the electronic assembly during their respective power transforming operation, characterized in that the heat dissipation means comprises a first heat transfer portion associated to said electronic assembly.

This first heat transfer portion allows concentrated heat from specific locations of the electronic assembly to be removed from the electronic assembly.

Heat transfer from the electronic assembly may be a combination of (heat) radiation, (heat) conduction and (heat) convection.

Preferably, the first heat transfer portion is in thermal contact with the electronic assembly. As a result, heat transfer from the electronic assembly is due more to heat conduction than to heat radiation. Heat transferred by conduction can be better contained while being channeled away from the electronic assembly than heat transferred by radiation.

Typically, the electronic assembly comprises power electronics, preferably with several power electronics components such as diodes, thyristors and power transistors (MOSFETs and/or IGFTs).

In a preferred embodiment, an arrangement of electronic components of said electronic assembly extends along a first smoothened imaginary reference surface within a first volume defined by said first imaginary reference surface and a first imaginary thickness extending in a direction orthogonal to said first reference surface.

Preferably, said first smoothened imaginary reference surface comprises at least one of a planar surface portion, a surface portion with a one-dimensional curvature and a surface portion with a two-dimensional curvature, thus defining a plate-like and/or shell-like first volume having an edge-like circumferential periphery and comprising said electronic assembly.

With all the heat generated by said electronic assembly originating from this plate-like or shell-like first volume, the distance from any point within said first volume to a closest boundary point of said first volume is very short. The maximum such distance would be half the first volume thickness if either one of the two large boundary surfaces can be chosen for the boundary point. The maximum such distance would be one (entire) first volume thickness if only one of the two large boundary surfaces can be chosen for the boundary point. As a result, thermal resistance within the imaginary first volume around the electronic assembly is low, and heat generated by said electronic assembly is easily removed from said electronic assembly by heat conduction.

Preferably, said heat dissipation means comprises a second heat transfer portion associated to said magnetic assembly.

This second heat transfer portion allows less and relatively well distributed heat (less concentrated heat) from specific locations of the magnetic assembly to be removed from the magnetic assembly.

Again, heat transfer from the magnetic assembly may be a combination of (heat) radiation, (heat) conduction and (heat) convection.

Preferably, the second heat transfer portion is in thermal contact with the magnetic assembly. Again, as a result, heat transfer from the magnetic assembly is due more to heat conduction than to heat radiation. Heat transferred by conduction can be beter contained while being channeled away from the magnetic assembly than heat transferred by radiation.

In a further preferred embodiment, a coil topology of the magnetic assembly extends along a second smoothened imaginary reference surface within a second volume defined by said second imaginary reference surface and a second imaginary thickness extending in a direction orthogonal to said second reference surface.

Preferably, said second smoothened imaginary reference surface comprises at least one of a planar surface portion, a surface portion with a one-dimensional curvature and a surface portion with a two-dimensional curvature, thus defining a plate-like and/or shell-like second volume having an edge-like circumferential periphery and comprising said magnetic assembly.

Again, with all the heat generated by said magnetic assembly originating from this plate-like or shell-like second volume, the distance from any point within said second volume to a closest boundary point of said second volume is very short. The maximum such distance would be half the second volume thickness if either one of the two large boundary surfaces can be chosen for the boundary point. The maximum such distance would be one (entire) second volume thickness if only one of the two large boundary surfaces can be chosen for the boundary point. As a result, thermal resistance within the imaginary second volume around the magnetic assembly is low, and heat generated by said magnetic assembly is easily removed from said magnetic assembly by heat conduction.

In a still further preferred embodiment, the heat dissipation means comprises a coolant circuit with said first heat transfer portion being a portion of said coolant circuit.

This coolant circuit allows concentrated heat, originating from said electronic assembly and removed form said electronic assembly primarily by conduction, to be further removed by forced convection, i.e. by a cooling fluid pumped through said coolant circuit.

Preferably, the electronic assembly and the first volume surrounding it is located adjacent to said edge-like circumferential periphery of said second volume comprising said magnetic assembly.

This first-volume/second volume edge-to-edge adjacent arrangement, i.e. nonstacked arrangement, of the electronic assembly and the magnetic assembly contributes to the overall small thickness of the entire power transformer assembly. As a result, a ground-pad module (GPM) comprising such power transformer assembly will also have a small thickness, thus keeping a low profile when fited to the bottom side of an electric vehicle.

Preferably, the coolant circuit extends along at least a portion of said edge-like circumferential periphery of said second volume comprising said magnetic assembly. This contributes to the compactness of a ground-pad module (GPM) comprising such power transformer assembly, again making it easier for a GPM to be fitted to the bottom side of an electric vehicle.

In an even further preferred embodiment, said first heat transfer portion extends along a third smoothened imaginary reference surface within a third volume defined by said third imaginary reference surface and a third imaginary thickness extending in a direction orthogonal to said third reference surface.

Preferably, said third smoothened imaginary reference surface comprises at least one of a planar surface portion, a surface portion with a one-dimensional curvature and a surface portion with a two-dimensional curvature, thus defining a plate-like and/or shell-like third volume having an edge-like circumferential periphery and comprising said first heat transfer portion.

With all the heat originating from said electronic assembly, i.e. from said first volume, and entering said first heat transfer portion, i.e. into said third volume, the distance from any point within said third volume to a closest boundary point of said third volume is very short. The maximum such distance would be half the second volume thickness if either one of the two large boundary surfaces can be chosen for the boundary point. The maximum such distance would be one (entire) second volume thickness if only one of the two large boundary surfaces can be chosen for the boundary point As a result, thermal resistance within the imaginary third volume around the first heat transfer portion is low, and heat generated by said electronic assembly is easily removed from said electronic assembly by heat conduction and forced convection within said first heat transfer portion, i.e. within said third volume.

In another preferred embodiment, a) said arrangement of electronic components of said electronic assembly extending within said first volume defined by said first imaginary reference surface and said first imaginary thickness orthogonal to said first reference surface, on the one hand, and b) said first heat transfer portion extending within said third volume defined by said third imaginary reference surface and said third imaginary thickness orthogonal to said third reference surface, on the other hand, are thermally associated to each other.

Preferably, a) said arrangement of electronic components of said electronic assembly and b) said first heat transfer portion are arranged in stacked relationship adjacent to each other with said first imaginary reference surface and said third imaginary reference surface close to each other.

The electronic assembly, corresponding to said first volume, and the first heat transfer portion, corresponding to said third volume, are stacked plates (planar) or stacked shells (curved).

Irrespective of their geometries (planar or curved), this compact stacked relationship of the electronic assembly and the first heat transfer portion improves the heat transfer between the electronic assembly and the first heat transfer portion which may be a portion of a coolant circuit.

Preferably, said first heat transfer portion is a duct portion of said coolant circuit.

As already mentioned above, this allows heat from the electronic assembly to be efficiently removed by conduction and forced convection.

Preferably, said duct portion comprises a plurality of protrusions extending in a direction transverse to a main coolant flow direction within said duct portion. Preferably, said plurality of protrusions are rooted in a first inner wall of said duct portion and extend towards a second inner wall, opposite to said first inner wall, of said duct portion.

Preferably, said plurality of protrusions are pin-like formations.

All this contributes to increased surface area for the coolant / duct portion interface, thus increasing heat flow across this interface, i.e. from the electronic assembly to the duct portion and to the coolant within said duct portion.

Preferably, said protrusions each have a protrusion axis, wherein the protrusion axes of all protrusions are parallel to each other.

Preferably, said protrusions each are tapered with their cross section diminishing along a protrusion axis from a greater cross section at a protrusion root portion to a smaller cross section at a protrusion tip portion.

The tapered protrusions may be truncated cones (frusto-conical shape) or truncated pyramids (frusto-pyramidal shape).

All this contributes to improved demoldability of molded parts if such parts of the protrusion-equipped duct portion are made by molding such as injection molding or die casting.

Preferably, a protrusion of said plurality of protrusions has a cross section selected from at least one of circular, oval, elliptical and polygonal.

Preferably, said cross section is a regular hexagon or a lozenge (diamond).

All these cross-sectional shapes help prevent dead zones from forming within the coolant flow. Again, this contributes to increased surface area for the coolant / duct portion interface, thus increasing heat flow across this interface, i.e. from the electronic assembly to the duct portion and to the coolant within said duct portion. Preferably, said plurality of protrusions comprises protrusions having different shapes and/or different sizes.

This allows free spaces between larger protrusions to be partially filled by smaller protrusions which again increases surface area for the coolant / duct portion interface, but also reduces the effective duct cross section for coolant flow. As a result, both cooling performance and coolant pressure drop along the duct portion can be adjusted by changing at least one of protrusion size, protrusion shape and protrusion packing density.

Preferably, said plurality of protrusions are staggered with respect to said main flow direction.

This helps prevent dead zones from forming within the coolant flow and, in addition, prevents short-circuiting with the coolant flow pattern.

Preferably, a) a first plurality of protrusions of said plurality of protrusions are rooted in a first inner wall of said duct portion and extend towards a second inner wall, opposite to said first inner wall, of said duct portion; and b) a second plurality of protrusions of said plurality of protrusions are rooted in said second inner wall of said duct portion and extend towards said first inner wall, opposite to said second inner wall, of said duct portion.

Again, this helps prevent dead zones from forming within the coolant flow and, in addition, prevents short-circuiting with the coolant flow pattern.

Also, if the duct portion or the entire coolant circuit with the duct portion are made by molding, this allows the duct portion or the entire coolant circuit to be made from two identical parts or “halves” which can be fitted together to obtain the duct portion or the coolant circuit.

Preferably, a length of each of said protrusions along said protrusion axis is smaller than a duct width along said protrusions axis between said first inner wall and said opposite second inner wall.

This allows for manufacturing tolerance compensation, thus preventing any of the protrusions from being too long and which may block the fiting together of two complementary molded parts of the duct portion or the entire coolant circuit. Preferably, said protrusions are hollow.

This not only reduces the weight of the duct portion or the entire coolant circuit, but also reduces the amount of material required for making the duct portion or the entire coolant circuit. In addition, the hollow spaces of the hollow protrusions lend themselves to providing fixing means such as fixing screws or bolts extending within the hollow protrusions, preferably along a protrusion axis and through a hole at the tip of said protrusion.

Preferably, said coolant circuit with said first heat transfer portion is made by forming (shaping) a material in a mold.

Preferably, said coolant circuit with said first heat transfer portion is made by molding (casting, injecting) a moldable material within or into said mold.

Preferably, said coolant circuit with said first heat transfer portion is made by sintering a sinterable material within said mold.

Preferably, said coolant circuit with said first heat transfer portion is made by crosslinking a cross-linkable material within said mold.

Preferably, said coolant circuit with said first heat transfer portion is made additively in a layer-by-layer fashion.

Figures 1 to 5 show an embodiment of the power transformer assembly according to the invention.

Fig. 1 shows a top view of a cut-away portion of a power transformer assembly according to the invention.

Fig. 2 shows a perspective view of a first part (botom part comprising protrusions) of the cut-away portion of the power transformer assembly of Fig. 1.

Fig. 3 shows a perspective view of a second part (top part without protrusions) of the cut-away portion of the power transformer assembly of Fig. 1.

Fig. 4 shows a first cross section, perpendicular to a coolant main flow direction, of the cut-away portion of the power transformer assembly of Fig. 1.

Fig. 5 shows a first cross section, perpendicular to a coolant main flow direction, of the cut-away portion of the power transformer assembly of Fig. 1 .