Abstract
A coil form with a low inter-winding capacitance is disclosed including a bobbin formed from an electrically insulating material and including a tube section shaped wall. A coil is mechanically supported by the bobbin and includes a first plurality of conductor windings on the outside of the wall and a second plurality of conductor windings on the inside of the wall. Furthermore, a transformer with such a coil form as any of its primary or secondary windings is disclosed.
Claims
1. A coil form, comprising: a bobbin made of an electrically insulating material and including a tube section shaped wall; and a coil mechanically supported by the bobbin and including a first plurality of conductor windings on an outside of the tube section shaped wall and a second plurality of conductor windings on an inside of the tube section shaped wall, wherein the first plurality of conductor windings and the second plurality of conductor windings are formed from a single continuous conductor section that passes the tube section shaped wall at one end of two ends of the bobbin.
2. The coil form of claim 1, further comprising a third plurality of conductor windings on the outside of the tube section shaped wall, wherein the first plurality of conductor windings, the second plurality of conductor windings and the third plurality of conductor windings are formed from the single continuous conductor section.
3. The coil form of claim 2, wherein the single continuous conductor section passes the tube section shaped wall at both ends of the bobbin.
4. The coil form of claim 2, wherein the first plurality of conductor windings and the third plurality of conductor windings are separated by a flange of the bobbin radially extending from the outside of the tube section shaped wall.
5. The coil form of claim 4, further comprising connection leads for electrically connecting both ends of the coil, wherein the connection leads are connected to the ends of the first and third pluralities of conductor windings on opposite sides of the flange of the bobbin.
6. The coil form of claim 5, wherein the connection leads are extending through separate channels of an insulating housing mechanically connected to the bobbin.
7. The coil form of claim 1, wherein the bobbin comprises an end flange radially extending from the outside of the tube section shaped wall at at least one of its ends, the end flange comprising a port through which the single continuous conductor section passes.
8. The coil form of claim 1, wherein the second plurality of conductor windings comprises one layer of conductor windings on the inside of the tube section shaped wall only.
9. The coil form of claim 1, wherein each plurality of conductor windings on the outside of the tube section shaped wall comprises one layer of conductor windings on the outside of the tube section shaped wall only.
10. A transformer comprising the coil form of claim 1 as any one of its primary or secondary windings.
11. The transformer of claim 10, wherein the other of the primary or secondary windings comprises a further coil of a plurality of conductor windings wound on the outside of a first tube section shaped wall of a further bobbin made of an electrically insulating material, wherein the further bobbin comprises a second tube section shaped wall enclosed by the first tube section shaped wall and supporting the coil form within the further coil.
12. The transformer of claim 11, wherein a gap remaining between the coil form and the first tube section shaped wall of the further bobbin is filled with a potting material.
13. The transformer of claim 12, wherein the potting material encloses the primary and secondary windings within a transformer housing.
14. The transformer of claim 11, wherein the second tube section shaped wall has a circular, oval, ellipsoidal, or rectangular cross-sectional profile.
15. The coil form of claim 4, wherein except for both ends of the single continuous conductor section, a winding layout of the coil form is mirror-symmetric with regard to a symmetry plane extending through the flange.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) In the following, the disclosure is further explained and described with respect to preferred exemplary embodiments illustrated in the drawings.
(2) FIG. 1 is a cross-section through a wall of a bobbin and pluralities of windings on the inside and outside of the wall of a coil form according to the present disclosure.
(3) FIG. 2 is a full perspective view of the coil form according to FIG. 1; and
(4) FIG. 3 is a perspective view of a transformer including the coil form according to FIGS. 1 and 2.
DETAILED DESCRIPTION
(5) In the coil form 1 according to FIGS. 1 and 2 a single continuous conductor section 2 formed from solid wire 3 is wound within and around a bobbin 4 made of electrically insulating material 5. The bobbin 4 comprises a tube section shaped wall 6, a center flange 7 made of the material 5 and radially extending from the outside of the wall 6 and two end flanges 8 and 9 also made of the material 5 and radially extending from the outside of the wall 6. Beginning at a start 10, the continuous conductor section 2 at first forms a first plurality 11 of conductor windings on the outside of the wall 6. Then, the continuous conductor section 2 passes a port 12 in the end flange 8. Next, the continuous conductor section 2 forms a second plurality 13 of conductor windings at the inside of the wall 6. Then, the continuous conductor section 2 passes a port in the end flange 9, before it finally forms a third plurality of conductor windings 14 up to an end 15. Except of connection terminals 16 and 17 at the start 10 and the end 15 of the continuous conductor section 2, the entire winding layout is mirror-symmetric with regard to a symmetry plane 18 extending through the center flange 7. All three pluralities 11, 13 and 14 of conductor windings only comprise one layer of windings. The first, second and third pluralities 11, 13 and 14 of conductor windings are separated from each other by the insulating material 5. Thus, the maximum voltage present between directly adjacent or neighboring conductor windings is reduced to 1/n of the voltage present between the connection terminals 16 and 17 with n conductor windings in the entire coil form 1. Further, the electrical resistance of the coil including all three pluralities 11, 13 and 14 of conductor windings is not affected by any solder joints between the individual pluralities 11, 13 and 14 of conductor windings.
(6) The embodiment of the disclosure illustrated in FIG. 1 and FIG. 2 comprises only one layer of conductor windings within each of the pluralities 11, 13, 14 of conductor windings. In an alternative embodiment, at least one of all pluralities 11, 13, 14 of conductor windings, e.g. the first and the third plurality of conductor windings, comprises more than one layer of conductor windings. In order to still have an optimized symmetry with regard to the symmetry plane 18, the amounts of layers and conductor windings of the first and third pluralities 11, 14 of conductor windings have to be equal then. Another alternative embodiment not shown in in the drawings, only comprises two pluralities of conductor windings, wherein the first plurality 11 is located on the outside of the wall 6 and the second plurality 13 is located at the inside of the wall 6 of the bobbin 4. In this case it is also possible that at least one of the first and second pluralities 11, 13 of conductor windings comprises more than one layer of conductor windings. In that case, the first and second pluralities of conductor windings do not necessarily comprise the same amounts of layers and/or conductor windings. In this particular case it is also possible that the first and second pluralities 11, 13 of conductor windings comprise different amounts of layers and/or conductor windings, wherein the resulting coil form 1 may still provide a sufficiently uniform and balanced magnetic field distribution that narrows the leakage inductance spread and reduces the electromagnetic influence interference (EMI) when used in a transformer.
(7) In the transformer 19 depicted in FIG. 3, the coil form 1 according to FIGS. 1 and 2 provides a secondary winding 20 arranged within a coil 21, forming the primary winding 22 of the transformer 19. The coil 21 comprises a plurality of windings of a continuous conductor section 23 which is also formed from a solid wire 24, here. The coil 21 comprises a plurality of layers wound around a first tube section shaped wall 25 of a further bobbin 26 extending between end flanges 27 and 28. The further bobbin 26 also comprises a second tube section shaped wall 29 on which the coil form 1 according to FIGS. 1 and 2 is arranged to align it in a defined relative position with regard to the primary winding 22. The connection terminals 16 and 17 are connected by connection leads (not visible here) extending through separate channels 31 and 32 of an insulation housing 30 mechanically connected to the bobbin 4 of the coil form 1.
(8) The second tube section shaped wall 29 of the further bobbin 26, which—like the tube section shaped wall 6 of the bobbin 4—may be of various cross-sections including circular, oval, ellipsoid and rectangular cross-sections with or without rounded edges, defines a through-hole 33. The transformer 19 may comprise a magnetic core—not explicitly depicted in FIG. 3—which extends through a through-hole 33 and which may comprise any known core geometry, e.g. an U-I or an E-E core geometry. Advantageously a cross section of the magnetic core corresponds to the cross section of the through-hole 33 in order to provide a sufficient form fit between the magnetic core and the further bobbin 26 in the assembled status of the transformer 19.
(9) The transformer 19 depicted in FIG. 3 may be arranged in a transformer housing not explicitly illustrated in FIG. 3 for reason of clarity. The transformer housing may be made of metal and may be electrically grounded later on in order to act as an electromagnetic shielding which reduces the electromagnetic radiation generated by the transformer 19. Additionally or alternatively a metal sheet is provided as an electromagnetic shielding covering the outer conductor windings wound on the first tube section shaped wall 25 of the further bobbin 26. The remaining gap between the second tube section shaped wall 29—or rather the coil form 1—and the first tube section shaped wall 25 of the further bobbin 26 may be filled with potting material 34. In order to prevent an outflow of the potting material 34 out of the backside of that gap, the further bobbin 26 comprises a continuous wall section between the second tube section shaped wall 29 and the first tube section shaped wall 25 at one side of the further bobbin 26, e.g. at the side of the end flange 28. This offers the possibility to use that gap as a box for the potting material 34 and provide the potting material 34 only to the secondary (inner) winding 20 but not to the primary (outer) winding 22. This saves material and costs in applications the primary (outer) winding 22 do not require a coverage with potting material 34, e.g. due to its low voltages. Due to the lower amount of potting material 34 and its position within the transformer also thermal stresses applied to the magnetic core of the transformer is eliminated, at least reduced significantly. However it is optionally also possible, that the assembled transformer 19 within the transformer housing is as a whole—or at least at large—embedded in potting material 34 in order to fix the arrangement of the primary winding 22 and the secondary winding 20 as well as the arrangement of the transformer 19 within the transformer housing and to enhance the electrical insulation between the primary and secondary windings 22, 20 and between that windings and the transformer housing. Additionally, the closed continuous wall section between the second tube section shaped wall 29 and the first tube section shaped wall 25 at the one side of the further bobbin 26 ensures an optimized isolation between the magnetic core and the secondary winding 20 at that one side. Due to this isolation the magnetic core can be brought in direct contact with the continuous wall and therefore relatively close to—but electrically isolated from—the secondary winding. This is an advantage with regard to the overall building size of the transformer.
