Abstract
A planar transformer including a planar first primary coil; a planar first secondary coil inductively coupled with the first primary coil; and a transformer magnetic core for guiding a magnetic flux generated by the first primary coil and/or the first secondary coil around at least a first opening of the transformer magnetic core. The first primary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening. The first primary coil and the first secondary coil are arranged on a first plane. The embodiments further refer to a battery charger including such a planar transformer.
Claims
1-24. (canceled)
25. A planar transformer, comprising: a planar first primary coil; a planar first secondary coil inductively coupled with the first primary coil; and a transformer magnetic core for guiding a magnetic flux generated by the first primary coil and/or the first secondary coil around at least a first opening of the transformer magnetic core; wherein the first primary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening; and wherein the first primary coil and the first secondary coil are arranged on a first plane.
26. The planar transformer of claim 25, wherein the first primary coil and the first secondary coil are concentric.
27. The planar transformer of claim 25, wherein the first primary coil is surrounded by the first secondary coil.
28. The planar transformer of claim 25, wherein the first primary coil and the first secondary coil are spaced apart in a radial direction; wherein a radial distance between the first primary coil and the first secondary coil is from 0.1 mm to 15 mm.
29. The planar transformer device of claim 25, further comprising one or more intercoil radial dielectric spacers extending in a radial direction between the first primary coil and the first secondary coil.
30. The planar transformer of any of claim 25, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in an axial direction by one or more axial dielectric spacers; and/or wherein the first primary coil and/or the first secondary coil (is separated from the transformer magnetic core in the axial direction by an axial dielectric spacer having a thickness in the axial direction from 0.1 mm to 3 mm.
31. The planar transformer of any of claim 25, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in a radial direction by one or more radial dielectric spacers; and/or wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in the radial direction by a radial dielectric spacer having a thickness in the radial direction from 0.5 mm to 2.5 mm.
32. The planar transformer device of claim 29, wherein any of said dielectric spacers comprises or is of a material having a dielectric constant smaller than 10.
33. The planar transformer of claim 25, wherein the first primary coil and/or the first secondary coil comprises from 1 to 30 coil turns; and/or wherein the first primary coil and/or the first secondary coil has an inductance in the range from 10 μH to 10 mH.
34. The planar transformer according to claim 25, wherein the transformer magnetic core is further configured for guiding the magnetic flux generated by the first primary coil and/or the first secondary coil around at least a second opening of the transformer magnetic core, wherein the first secondary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening and through the second opening.
35. The planar transformer according to claim 25, further comprising: a planar second primary coil; and a planar second secondary coil inductively coupled with the second primary coil; and wherein the second primary coil and the second secondary coil are coiled around the transformer magnetic core through the first opening; and wherein the second primary coil and the second secondary coil are arranged on a second plane parallel to the first plane and spaced apart from the first plane in the axial direction.
36. The planar transformer of claim 35, wherein at least one of the second primary coil and the second secondary coil is separated from the first primary coil and/or the first secondary coil in the axial direction by one or more intercoil axial dielectric spacers.
37. The planar transformer device of claim 25, further comprising a first inductor element comprising: a planar first induction coil electrically connected in series with the first primary coil, and a first induction magnetic core for guiding a magnetic flux generated by the first induction coil around at least a first opening of the first induction magnetic core, wherein the first inductor element is arranged over the transformer magnetic core.
38. The planar transformer device of claim 37, further comprising a second inductor element comprising: a planar second induction coil electrically connected in series with the first secondary coil, and a second induction magnetic core for guiding a magnetic flux generated by the second induction coil around at least a first opening of the second induction magnetic core, wherein the second inductor element is arranged below the transformer magnetic core or over the first inductor element.
39. The planar transformer of claim 37, wherein the first inductor element further comprises: a first induction auxiliary coil electrically connected in series with both the first induction coil and with the first primary coil, and wherein the first induction magnetic core is further configured for guiding a magnetic flux generated by the first auxiliary induction coil around the at least first opening of the first induction magnetic core, wherein the first induction coil and the first induction auxiliary coil are planar coils arranged on a same plane, and wherein the planar first induction coil and the planar first induction auxiliary coil are concentric.
40. The planar transformer of claim 37, wherein the second inductor element further comprises: a second induction auxiliary coil electrically connected in series with both the second induction coil and with the first secondary coil, and wherein the second induction magnetic core is further configured for guiding a magnetic flux generated by the second auxiliary induction coil around the at least first opening of the second induction magnetic core, wherein the second induction coil and the second induction auxiliary coil are planar coils arranged on a same plane, and wherein the planar second induction coil and the planar second induction auxiliary coil are concentric.
41. The planar transformer of claim 37, wherein the first inductor element and the second inductor element are mutually separated by one or more intercore axial spacers and/or wherein the first inductor element and/or the second inductor element are separated from the transformer magnetic core by one or more intercore axial spacers.
42. The planar transformer of claim 37, wherein the first induction magnetic core and/or the second induction magnetic core comprises two superposed induction sub-cores separated in the axial direction by an intersub-core axial spacer.
43. The planar transformer of claim 25, wherein at least one of the first primary coil and the first secondary coil comprises or is of litz wire.
44. A battery charger for charging an electric battery comprising the planar transformer of claim 25.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 schematically illustrates a planar transformer according to embodiments of the invention. FIGS. 1a and 1b respectively illustrate a cross-sectional front view and a cross-sectional top view thereof. FIG. 1c corresponds to the view of FIG. 1a for the transformer magnetic core of the planar transformer.
[0044] FIG. 2 schematically illustrates a planar transformer according to embodiments of the invention. FIGS. 2a and 2b respectively illustrate a cross-sectional front view and a cross-sectional top view thereof. FIG. 2ec corresponds to the view of FIG. 2a for the transformer magnetic core of the planar transformer.
[0045] FIG. 3 schematically illustrates a transformer according to embodiments of the invention.
[0046] FIG. 4 is a schematic circuit diagram corresponding to the planar transformer of FIG. 3.
[0047] FIG. 5 schematically illustrates a planar transformer according to embodiments of the invention.
[0048] FIG. 6 is a schematic circuit diagram corresponding to the planar transformer of FIG. 5.
[0049] FIG. 7 schematically illustrates a planar transformer according to embodiments of the invention.
[0050] FIG. 8 schematically illustrates a transformer according to embodiments of the invention.
[0051] FIG. 9 schematically illustrates a planar transformer according to embodiments of the invention.
[0052] FIG. 10 schematically illustrates a top view of an inductor element according to embodiments of the invention.
DESCRIPTION OF DETAILED EMBODIMENTS OF THE INVENTION
[0053] FIG. 1 illustrates a planar transformer 10 according to embodiments of the first aspect of the present invention. FIG. 1a illustrates a cross-sectional front view of the planar transformer 10, while FIG. 1b illustrates a cross-sectional top view of the power transformer 10 at the cut plane A-A′ indicated in FIG. 1a win a dashed line. The planar transformer 10 comprises a planar first primary coil 12 and a planar first secondary coil 14. The turns of the first primary coil 12 and the turns of the first secondary coil 14 extend substantially in one plane, the “first plane”. For the sake of comprehensiveness, the turns of the coils have been schematically illustrated as independent turns, although each coil should be regarded as a spiral defining several turns.
[0054] The planar first secondary coil 14 is inductively coupled with the first primary coil 12. The power transformer 10 comprises a transformer magnetic core 18, an isolated cross-sectional view of which is provided in FIG. 1c, corresponding to the top view of FIG. 1a, with all other elements removed for illustrative purposes. In the embodiment shown, the transformer magnetic core 18 comprises a C-shaped sub-core 18a superposed on and I-shaped sub-core 18b. The lateral arms of the C-shaped sub-core 18a abut on the I-shaped sub-core 18b, thereby forming a first opening 16 between the sub-cores 18a and 18b of the transformer magnetic core 18. In the embodiment shown, the first opening 16 has a rectangular cross-section, as seen in FIG. 1c. In other embodiments, the first opening 16 can have a cross-section with other shapes.
[0055] The first primary coil 12 and the first secondary coil 14 are coiled around the transformer magnetic core 18 through the first opening 16. In particular, the first primary coil 12 and the first secondary coil 14 are coiled around the left lateral arm (as seen in FIG. 1) of the C-shaped sub-core 18a of the transformer magnetic core 18 traversing the opening 16. When an electric current flows through the first primary coil 12, the magnetic flux generated by the first primary coil 12 is guided by the transformer magnetic core 18 through the interior of the transformer magnetic core 18 and around the first opening 16. The magnetic flux generated by the first primary coil 12 induces an induced electric current in the first secondary coil 14. The transformer magnetic core 18 is a ferromagnetic core made of an iron compost.
[0056] As seen in FIG. 1, the first primary coil 12 and the first secondary coil 14 are arranged on a first plane, i.e. are coplanar. The first primary coil 12 and the first secondary coil 14, as illustrated in FIG. 1b, are concentric, i.e. are concentrically coiled around one of the lateral arms of the C-shaped sub-core 18a. The first primary coil is surrounded by the first secondary coil 14. Although only two turns 12a and 12b of the first primary coil 12 and two turns of 14a and 14b of the first secondary coil 14 are exemplarily illustrated in FIG. 1, the first primary coil 12 and the first secondary coil 14 can comprise a larger number of turns, which are not represented for illustrative simplicity. For example, the first primary coil 12 and the first secondary coil 14 may each comprise four turns coiled around the transformer magnetic core 18.
[0057] As illustrated in FIG. 1b, the first primary coil 12 and the first secondary coil 14 are spaced apart in a radial direction by a radial distance, which in the embodiment shown is of 2.5 mm. The first primary coil 12 is separated from the first secondary coil 14 in the radial direction by an intercoil radial dielectric spacer 20 that extends in the radial direction between the first primary coil 12 and the first secondary coil 14 having a thickness corresponding to the aforesaid radial distance. In the embodiment shown in FIG. 1, the first primary coil 12 and the first secondary coil 14, i.e. the turns thereof, have a circular cross-section.
[0058] In the embodiment shown in FIG. 1, the first primary coil 12 and the first secondary coil 14 are separated from the transformer magnetic core 18 in an axial direction—represented in FIG. 1a as direction “z”—by a first axial dielectric spacer 22a and a second axial dielectric spacer 22b. The first axial dielectric spacer 22a is arranged in the axial direction between the C-shaped sub-core 18a and the “first plane” on which the first primary coil 12 and the first secondary coil 14 are arranged, thus extending between the C-shaped sub-core 18a on one side and the first primary coil 12 and the first secondary coil 14 on the other side. The second axial dielectric spacer 22b is arranged in the axial direction between the I-shaped sub-core 18b and the “first plane”, extending in the axial direction z between the I-shaped sub-core 18b on one side and the first primary coil 12 and the first secondary coil 14 on the other side. In the embodiment shown, the axial dielectric spacers 22a and 22b have a thickness in the axial direction of 0.4 mm.
[0059] The first primary coil 12 is separated from the transformer magnetic core 18 in the radial direction, which in the cross-section represented in FIG. 1a corresponds to direction “x”, by a first radial dielectric spacer 24a and a second radial dielectric spacer 24b, which extend in the radial direction, on respective sides of the left hand side lateral arm of the C-shaped sub-core 18a, between the transformer core 18 and the first primary coil 12. The first secondary coil 14 is separated from the transformer magnetic core 18 in the radial direction by a third radial dielectric spacer 24c and extends in the radial direction between the right hand side lateral arm of the C-shaped sub-core 18a and the first secondary coil 14. In the embodiment shown, the first to third radial dielectric spacers 24a, 24b and 24e have a thickness in the radial direction of 1.5 mm.
[0060] The dielectric spacers 20, 22a, 22b, 24a, 24b, 24c, 24d and 24e are made of a material having a dielectric constant smaller than 2.5, for example polyurethane.
[0061] In the embodiment shown in FIG. 1, the first primary coil 12 and the first secondary coil 14 have approximately an inductance of 220 μH.
[0062] FIG. 2 illustrates a power transformer 10 according to a related embodiment of the invention. FIG. 2a illustrate a cross-sectional front view corresponding to the view of FIG. 1a. FIG. 2b illustrates a cross-sectional top view corresponding to the view of FIG. 1b. FIG. 2c illustrates the view of FIG. 2a with all elements but the transformer magnetic core 18 removed for illustrative purposes, corresponding to the view of FIG. 1c. The elements of the power transformer 10 that have already been described for the transformer 10 of FIG. 1 are indicated with the same reference numerals and are not described again in detail for brevity.
[0063] In the embodiment shown in FIG. 2, the first primary coil 12 and the first secondary coil 14 have a rectangular cross-section, as seen in FIG. 2a, instead of a circular cross-section. In other embodiments, the first primary coil 12 and the first secondary coil 14 can have different cross sections, and a cross-section of the first primary coil 12 can be different in shape from a cross-section of the first secondary coil 14. Although only one turn of each of the first primary coil 12 and the first secondary coil 14 is illustrated in FIG. 2, this is only for illustrative purposes. The first primary coil 12 and the first secondary coil 14 may comprise a larger number of turns, for example 4, 5 or 10 turns.
[0064] As seen in FIG. 2c, the transformer magnetic core 18 of these embodiment comprises an E-shaped sub-core 18a stacked on and I-shaped sub-core 18b, thereby forming a first opening 16a and a second opening 16b between the E-shaped sub-core 18a and the I-shaped sub-core 18b. The first primary coil 12 and the first secondary coil 14 are coiled around the transformer magnetic core 18, in particular around the central arm of the E-shaped sub-core 18a, through the first opening 16a and the second opening 16b. The transformer magnetic core 18 is configured for guiding a magnetic flux generated by the first primary coil 12, which induces an induced electric current in the first secondary coil 14, around the first opening 16a and the second opening 16b.
[0065] As seen in FIG. 2, the first primary coil 12 is separated from the central arm of the E-shaped sub-core 18a of the transformer magnetic core 18 in the radial direction (i.e. in the x-direction in FIG. 2a) by a radial dielectric spacer 24e that is arranged on the first plane, on which the first primary coil 12 and the first secondary coil 14 extend, surrounding the central arm of the E-shaped sub-core 18a extending between said central arm and the first primary coil 12 in the radial direction.
[0066] As in the embodiment illustrated in FIG. 1, the first primary coil 12 and the first secondary coil 14 are mutually separated in the radial direction by an inter-core radial dielectric spacer 20. Further, the first secondary coil 14 is separated from the left-hand side lateral arm of the E-shaped sub-core 18a by a first radial dielectric spacer 24d that is arranged around the left-hand side lateral arm of the E-shaped sub-core 18a extending in the radial direction between said lateral arm and the first secondary coil 14. Likewise, the first secondary coil 14 is separated from the right hand side lateral arm of the E-shaped sub-core 18a in the radial direction by a second radial dielectric spacer 24f that is arranged around the right-hand side lateral arm of the E-shaped sub-core 18a on the first plane and hence extends in the radial direction between the right-hand side lateral arm of the E-shaped sub-core 18a and the first secondary coil 14.
[0067] FIG. 3 illustrates a flat transformer 10 according to a related embodiment of the invention. Those elements of the planar transformer 10 that have been previously discussed for the planar transformers 10 of the embodiments illustrated in FIG. 1 and FIG. 2 are indicated with the same reference numerals and are not discussed again in detail for brevity.
[0068] In addition to the first primary coil 12 and the first secondary coil 14, the planar transformer 10 illustrated in FIG. 3 comprises a planar second primary coil 32 and a planar second secondary coil 34 that is inductively coupled with the second primary coil 32. The second primary coil 32 and the second secondary coil 34 are mutually coplanar and are arranged on a second plane that is parallel to the first plane, on which the first primary coil 12 and the first secondary coil 14 are arranged, and spaced from this first plane in the axial direction, which in FIG. 3 corresponds to the direction z. The second primary coil 32 is arranged below the first primary coil 12 parallel thereto. The second secondary coil 34 is arranged below the first secondary coil 14 parallel thereto.
[0069] The second primary coil 32 and the second secondary coil 34 are coiled around the transformer magnetic core 18 of the first opening 16a and through the second opening 16b of the transformer magnetic core 18, like the first primary coil 12 and the first secondary coil 14.
[0070] In the embodiment shown in FIG. 3, the transformer magnetic core 18 comprises a first E-shaped sub-core 18a stacked on a second E-shaped sub-core 18b, such that the arms of the first E-shaped sub-core 18a abut on the arms of the second E-shaped sub-core 18b, thereby forming the first opening 16a and the second opening 16be between the two E-shaped sub-cores 18a and 18b.
[0071] The first primary coil 12 is separated from the transformer magnetic core 18 in the radial direction, in particular from the central arm of the first E-shaped sub-core 18a by a radial dielectric spacer 24e that is arranged around the central arm of the E-shaped sub-core 18a extending between the transformer magnetic core 18 and the first primary coil 12 in the radial direction. The first primary coil 12 and the first secondary coil 14 are separated from each other in the radial direction by the intercoil radial dielectric spacer 20. The first secondary coil 14 is separated from the lateral arms of the first E-shaped sub-core 18a in the radial direction by a radial dielectric spacer 24d that is arranged surrounding the central arm of the first E-shaped sub-core 18a adjacent to the internal walls of the lateral arms of the first E-shaped sub-core 18a, as seen in FIG. 3. In the axial direction, the first primary coil 12 and the first secondary coil 14 are separated from the first E-shaped sub-core 18a by an axial dielectric spacer 22a having a configuration analogous to the configuration of the axial dielectric spacer 22a.
[0072] Likewise, the second primary coil 32 is separated from the central arm of the second E-shaped sub-core 18b in the radial direction by a radial dielectric spacer 44e having a configuration analogous to the configuration of the radial dielectric spacer 24b. The second primary coil 32 and the second secondary coil 34 are mutually separated in the radial direction by a second intercoil radial dielectric spacer 20′, which has a configuration analogous to the configuration of the intercoil radial dielectric spacer 20. The second secondary coil 34 is separated from the second E-shaped sub-core 18b in the radial direction by a radial dielectric spacer 44d that has a configuration analogous to the configuration of the radial dielectric spacer 24d. Further, the second primary coil 32 and the second secondary coil 34 are separated from the second E-shaped sub-core 18b in the axial direction by an axial dielectric spacer 22b.
[0073] In addition, the second primary coil 32 and the second secondary coil 34 are separated from the first primary coil 12 and the first secondary coil 14 in the axial direction by an intercoil axial dielectric spacer 40 that extends in the radial direction between the first plane, on which the first primary coil 12 and the first secondary coil 14 are arranged, and the second plane, on which the second primary coil 32 and the second secondary coil 34 are arranged. The intercoil axial dielectric spacer 40 is arranged around the central arms of the first E-shaped sub-core 18a and the second E-shaped sub-core 18b, as seen in FIG. 3.
[0074] The planar transformer 10 of FIG. 3 further comprises a first inductor element 50 that is arranged over the transformer magnetic core 18. In the embodiment shown, the first inductor element 50 is arranged directly on a back side of the first E-shaped sub-core 18a facing away from the first opening 16a and the second opening 16b. The first inductor element 50 comprises a planar first induction coil 52 that is electrically connected in series with the first primary coil 12, as illustrated in the circuit diagram of FIG. 4, which corresponds to the basic connection structure of the planar transformer device 10 represented in FIG. 3.
[0075] The first inductor element 50 further comprises a first induction magnetic core 58, which in the embodiment shown comprises a first E-shaped sub-core 58a and an I-shaped sub-core 58b mutually superposed forming a first opening 56a and a second opening 56b therebetween. In the embodiment shown, the E-shaped induction sub-core 58a is separated from the I-shaped induction sub-core 58b in the axial direction by an inter-sub-core axial dielectric spacer 72.
[0076] The first induction coil 52 is coiled around the first induction magnetic core 58, in particular around the central arm of the E-shaped induction sub-core 58a, such that the first induction magnetic core 58 is configured for guiding a magnetic flux generated by the first induction coil 52 around the first opening 56a and the second opening 56b of the first induction magnetic core 58.
[0077] The power transformer device 10 represented in FIG. 3 further comprises a second inductor element 60 comprising a second induction coil 62 that is electrically connected in series with the first secondary coil 14, as illustrated in FIG. 4, and a second induction magnetic core 68 for guiding a magnetic flux generated by the second induction coil 62 around corresponding openings 66a and 66b of the second induction magnetic core 68. In the embodiment shown, the second inductor element 16 is arranged over the first inductor element 50. The second inductor element 60 has a structure and configuration analogous to the structure and configuration of the first inductor element 50 but for the different orientation. The I-shaped inductor sub-core 58b of the first induction magnetic core 58 is arranged adjacent to the I shaped induction sub-core 68b of the second induction magnetic core 68. Consequently, lines of magnetic flux that are respectively created by the first induction coil 52 and guided by the first induction magnetic core 58 and created by the second induction coil 62 and guided by the second induction magnetic core 68, which are represented in FIG. 3 as closed dashed lines, can cancel each other.
[0078] In the embodiment illustrated in FIG. 3, the first induction coil 52 is separated from the central arm of the E-shaped induction sub-core 58a in the radial direction by a radial dielectric spacer 86e and the second induction coil 62 is separated from the central arm of the E-shaped induction sub-core 68a in the radial direction by a radial dielectric spacer 84e. The radial dielectric spacers 86e, 84e are respectively arranged around the central arm of the E-shaped induction sub-core 58a and around the central arm of the E-shaped induction sub-core 68a and have a configuration and arrangement analogous to the configuration and arrangement of the radial dielectric spacers 24e and 44e.
[0079] Likewise, the first induction coil 52 is separated in the radial direction from the lateral arms of the I-shaped induction sub-core 58b by a radial dielectric spacer 86d and is separated in the axial direction from the E-shaped induction sub-core 58a by an axial dielectric spacer 88b and from the inter-sub-core axial dielectric spacer 72 by an axial dielectric spacer 88a. The second induction coil 62 is separated in the radial direction from the lateral arms of the E-shaped induction sub-core 68a by a radial dielectric spacer 84d, and is separated in the axial direction from the E-shaped induction sub-core 68a by an axial dielectric spacer 82a and is separated in the axial direction from the inter-sub-core axial dielectric spacer 72 by an axial dielectric spacer 82b.
[0080] The radial dielectric spacers of the first inductor element 50 and of the second inductor element have a configuration and arrangement analogous to the configuration and arrangement of the radial dielectric spacers 24e and 24d respectively. The radial dielectric spacers of the second inductor element 60 and of the second inductor element have a configuration and arrangement analogous to the configuration and arrangement of the axial dielectric spacers 22a and 22b respectively.
[0081] In the embodiment shown in FIG. 3, the axial dielectric spacer 66a has a thickness in the axial direction (i.e. in the z direction as seen in FIG. 3) of 0.3 mm, the radial dielectric spacers 84d and 84e have a thickness in the radial direction of 1.5 mm, the axial dielectric spacer 82b has a thickness in the axial direction of 0.6 mm. The inter-sub-core axial dielectric spacers 72 have a thickness in the axial direction of 0.5 millimetres. The axial dielectric spacer 88a has a thickness in the axial direction (i.e. in the z direction as seen in FIG. 3) of 0.6 mm, the radial dielectric spacers 86d and 86e have a thickness in the radial direction of 1.5 mm, the axial dielectric spacer 88b has a thickness in the axial direction of 0.3 mm.
[0082] The axial dielectric spacers 22a and 22b have a thickness in the axial direction of 0.4 mm. The radial dielectric spacers 24e, 24d, 44e and 44d have a thickness in the radial direction of 1.5 mm. The intercoil radial dielectric spacers 20 and 20′ have a thickness in the radial direction of 2.5 mm. The intercoil axial dielectric spacer 40 has a thickness in the axial direction of 3 mm.
[0083] In the embodiment shown in FIG. 3, the first primary coil 12 and the first secondary coil 14 have approximately an inductance of 220 μH, and each of the first inductor coil 52 and the second inductor coil 62 have approximately an inductance of 10 μH.
[0084] Although it is not illustrated in detail in FIG. 3, the first primary coil 12, the first secondary coil 14, the second primary coil 32 and the second secondary coil 34 are coils of litz wire comprising a plurality of interleaved coated sub-wires.
[0085] FIG. 5 illustrates a flat transformer 10 according to a related embodiment of the invention. Those elements of the planar transformer 10 that have been previously discussed for the planar transformers 10 of the embodiments illustrated in FIG. 1 to FIG. 4 are indicated with the same reference numerals and are not discussed again in detail for brevity.
[0086] In addition, the first inductor element 50 of the flat transformer 10 of FIG. 5 further comprises a first induction auxiliary coil 53 electrically connected in series with both the first induction coil 52 and with the first primary coil 12, as illustrated in FIG. 6. The first induction auxiliary coil 53 is coiled around the first induction magnetic core 58, in particular around the central arm of the E-shaped induction sub-core 58a, such that the first induction magnetic core 58 is configured for guiding a magnetic flux generated by the first induction auxiliary coil 53 around the first opening 56a and the second opening 56b of the first induction magnetic core 58.
[0087] As illustrated in FIG. 5, the first induction coil 52 and the first induction auxiliary coil 53 are spaced apart in a radial direction by a radial distance, which in the embodiment shown is of 2.5 mm. The first induction coil 52 is separated from the first induction auxiliary coil 53 in the radial direction by an intercoil radial dielectric spacer 87 that extends in the radial direction between the first induction coil 52 and the first induction auxiliary coil 53 having a thickness corresponding to the aforesaid radial distance.
[0088] In the particular embodiment of FIG. 5, the first induction coil 52 and the first induction auxiliary coil 53 are planar and concentric coils arranged on a same plane.
[0089] In addition, the second inductor element 60 of the flat transformer 10 of FIG. 5 further comprises a second induction auxiliary coil 63 electrically connected in series with both the second induction coil 62 and with the first secondary coil 14, as illustrated in FIG. 6. The second induction auxiliary coil 63 is coiled around the second induction magnetic core 68, in particular around the central arm of the E-shaped induction sub-core 68a, such that the second induction magnetic core 68 is configured for guiding a magnetic flux generated by the second induction auxiliary coil 63 around the first opening 66a and the second opening 66b of the first induction magnetic core 68.
[0090] As illustrated in FIG. 5, the second induction coil 62 and the second induction auxiliary coil 63 are spaced apart in a radial direction by a radial distance, which in the embodiment shown is of 2.5 mm. The second induction coil 62 is separated from the second induction auxiliary coil 63 in the radial direction by an intercoil radial dielectric spacer 85 that extends in the radial direction between the second induction coil 62 and the second induction auxiliary coil 63 having a thickness corresponding to the aforesaid radial distance.
[0091] In the particular embodiment of FIG. 5, the second induction coil 62 and the second induction auxiliary coil 63 are planar and concentric coils arranged on a same plane.
[0092] FIG. 7 illustrates a planar transformer 10′ according to embodiments of the second aspect of the invention described above. The planar transformer 10′ illustrated in FIG. 7 has the same components as the planar transformer 10 illustrated in FIG. 1. However, the first primary coil 12 and the first secondary coil 14 are not arranged on the same plane. Instead, the first primary coil 12 is arranged over the first secondary coil 14, such that the first primary coil 12 and the first secondary coil 14 are mutually spaced in the axial direction (which in the cross-section illustrated in FIG. 7 corresponds to the z direction), namely in a direction perpendicular to the plane of the first primary coil 12 and to the plane of the first secondary coil 14.
[0093] Instead of being separated in the radial direction by the intercoil radial dielectric spacer 20 shown in FIG. 1, in the embodiment illustrated in FIG. 7, the first primary coil 12 and the first secondary coil 14 are mutually separated in the axial direction by an intercoil axial dielectric spacer 40, which in the embodiment shown is made of polyurethane and has a thickness in the axial direction of 3 mm.
[0094] In the embodiment shown in FIG. 7, the transformer magnetic core 18 comprises a first C-shaped sub-core 18a and a second C-shaped sub-core 18b, which are superposed facing each other such as to form a first opening 16 of the transformer magnetic for 18 therebetween. The first primary coil 12, the first secondary coil 14 and the intercoil axial dielectric spacer 40 are coiled or wound around the transformer magnetic core through the first opening 16.
[0095] FIG. 8 illustrates a related embodiment of the invention in which the transformer magnetic core 18 comprises a first E-shaped sub-core 18a and a second E-shaped sub-core 18b. A first opening 16a and a second opening 16b are hence formed between the first E-shaped sub-core 18a and the second E-shaped sub-core 18b. The first primary coil 12 and the first secondary coil 14 are coiled around the central arms of the E-shaped sub-cores 18a and 18b through the first opening 16a and through the second opening 16b of the transformer magnetic core 18. The transformer magnetic core 18 is configured for guiding a magnetic flux generated by the first primary coil 12 around the first opening 16a and around the second opening 16b of the transformer magnetic core 18.
[0096] The first primary coil 12 and the second primary coil 14 have specifications corresponding to the specifications of the first primary coil 12 and the first secondary coil 14 previously described for the embodiments illustrated in FIGS. 1 to 7. In the embodiment shown, the first primary coil and the first secondary coil 14 are coils of litz wire comprising a plurality of interleaved coated sub-wires. Further, the specifications of the dielectric spacers 22a, 22b, 24a, 24b, 24c, 24d, and 24e respectively correspond to the specifications of the corresponding dielectric spacers of the embodiments of the invention described above with reference to FIGS. 1 to 7.
[0097] FIG. 9 illustrates a related embodiment of the second aspect of the invention in which the planar transformer 10′ further comprises a first inductor element 50 corresponding to the first inductor element described for the embodiment illustrated in FIG. 3, and a second inductor element 60 corresponding to the inductor element 60 described for the embodiment illustrated in FIG. 3. In the embodiment illustrated in FIG. 9, there is no inter-sub-core axial dielectric spacer between the sub-cores 58a and 58b of the first induction magnetic core 58 or between the sub-cores 68a and 68b of the second induction magnetic core 68. Instead of being stacked on the first inductor element 50 and over the transformer magnetic core 18, the second inductor element 60 is arranged in this embodiment below the transformer magnetic core 18, while the first inductor element 50 is arranged over the transformer magnetic core 18. Thus, the first inductor element 50 and the second inductor element 60 are arranged on opposite sides of the transformer magnetic core 18 in the axial direction z.
[0098] In the embodiment shown in FIG. 9, the first inductor element is separated from the transformer magnetic core 18 in the axial direction by a first intercore axial dielectric spacer 70 and the second inductor element 60 is separated from the transformer magnetic core 18 by a second intercore axial dielectric spacer 70. The intercore axial dielectric spacers 70 each have a thickness in the axial direction of 0.5 mm and are of polypropylene.
[0099] FIG. 10 illustrates a cross-sectional top view of the first inductor element 50 at the cut plane CC′ indicated in FIG. 9 by a dashed line. As seen in FIG. 10, the first induction coil 52 is coiled around the first induction magnetic core 58, in particular around the central arm of the E-shaped sub-core 58a of the first induction magnetic core 58. The second inductor element 60 has an analogous structure in a corresponding plane.
[0100] The present disclosure further refers to the following examples:
Examples
[0101] 1. A planar transformer comprising: [0102] a planar first primary coil; [0103] a planar first secondary coil inductively coupled with the first primary coil; and [0104] a transformer magnetic core for guiding a magnetic flux generated by the first primary coil and/or the first secondary coil around at least a first opening of the transformer magnetic core; [0105] wherein the first primary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening. [0106] 2. The planar transformer of example 1, wherein the first primary coil is arranged over the first secondary coil, such that the first primary coil and the first secondary coil are mutually spaced in an direction perpendicular to the plane of the first primary coil and to the plane of the first secondary coil. [0107] 3. The planar transformer of any of the preceding examples, wherein the first primary coil and the first secondary coil are spaced apart in an axial direction. [0108] 4. The planar transformer of example 3, wherein an axial distance between the first primary coil and the first secondary coil is from 0.1 mm to 15 mm, preferably from 1 mm to 10 mm, more preferably from 2 mm to 4 mm [0109] 5. The planar transformer device of any of the preceding examples, further comprising one or more intercoil axial dielectric spacers extending in an axial direction between the first primary coil and the first secondary coil, wherein the first primary coil and the first secondary coil are mutually separated in the axial direction by the one or more intercoil axial dielectric spacers. [0110] 6. The planar transformer of any of the preceding examples, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in an axial direction by one or more axial dielectric spacers. [0111] 7. The planar transformer of any of the preceding example, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in the axial direction by an axial dielectric spacer having a thickness in the axial direction from 0.1 mm to 3 mm, preferably from 0.2 mm to 1.5 mm, more preferably from 0.3 mm to 1.0 mm or 0.3 to 0.6 mm [0112] 8. The planar transformer of any of the preceding examples, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in a radial direction by one or more radial dielectric spacers. [0113] 9. The planar transformer of any of the preceding examples, wherein the first primary coil and/or the first secondary coil is separated from the transformer magnetic core in the radial direction by a radial dielectric spacer having a thickness in the radial direction from 0.5 mm to 2.5 mm, preferably from 1.0 mm to 2.0 mm, more preferably from 1.25 mm to 1.75 mm [0114] 10. The planar transformer device of any of examples 6 to 10, wherein any of said dielectric spacers comprises or is of a material having a dielectric constant smaller than 10, preferably smaller than 5, more preferably smaller than 2.5. [0115] 11. The planar transformer of any of the preceding examples, wherein the first primary coil and/or the first secondary coil comprises from 1 to 30 coil turns, preferably from 1 to 10, more preferably from 1 to 5. [0116] 12. The planar transformer of any of the preceding examples, wherein the first primary coil and/or the first secondary coil has an inductance in the range from 10 μH to 10 mH, preferably from 50 μH to 1 mH, more preferably from 200 μH to 500 μH. [0117] 13. The planar transformer according to any of the preceding examples, wherein the transformer magnetic core is further configured for guiding the magnetic flux generated by the first primary coil and/or the first secondary coil around at least a second opening of the transformer magnetic core, wherein the first secondary coil and the first secondary coil are coiled around the transformer magnetic core through the first opening and through the second opening. [0118] 14. The planar transformer device of any of the preceding examples, further comprising a first inductor element comprising: [0119] a planar first induction coil electrically connected in series with the first primary coil, and [0120] a first induction magnetic core for guiding a magnetic flux generated by the first induction coil around at least a first opening of the first induction magnetic core, [0121] wherein the first inductor element is arranged over the transformer magnetic core. [0122] 15. The planar transformer device of example 14, further comprising a second inductor element comprising: [0123] a planar second induction coil electrically connected in series with the first secondary coil, and [0124] a second induction magnetic core for guiding a magnetic flux generated by the second induction coil around at least a first opening of the second induction magnetic core, [0125] wherein the second inductor element is arranged below the transformer magnetic core or over the first inductor element.
[0126] 16. The planar transformer of example 17 or 18, wherein the first inductor element and the second inductor element are mutually separated by one or more intercore axial dielectric spacers and/or wherein the first inductor element and/or the second inductor element are separated from the transformer magnetic core by one or more intercore axial dielectric spacers.
[0127] 17. The planar transformer of any of examples 17 to 19, wherein the first induction magnetic core and/or the second induction magnetic core comprises two superposed induction sub-cores separated in the axial direction by an intersub-core axial dielectric spacer.
[0128] 18. The planar transformer of any of the preceding examples, wherein at least one of the first primary coil and the first secondary coil comprises or is of litz wire.
[0129] 21. A battery charger for charging an electric battery comprising the planar transformer of any of the preceding examples.
