WO2014075710A1 - Noyau magnétique plan - Google Patents

Noyau magnétique plan Download PDF

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Publication number
WO2014075710A1
WO2014075710A1 PCT/EP2012/072521 EP2012072521W WO2014075710A1 WO 2014075710 A1 WO2014075710 A1 WO 2014075710A1 EP 2012072521 W EP2012072521 W EP 2012072521W WO 2014075710 A1 WO2014075710 A1 WO 2014075710A1
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WO
WIPO (PCT)
Prior art keywords
base
core
wing
straight edge
pcb
Prior art date
Application number
PCT/EP2012/072521
Other languages
English (en)
Inventor
Oscar Persson
Martin ETSARE
Per Ferm
Magnus Karlsson
Igor PEREZ-URIA
Original Assignee
Telefonaktiebolaget L M Ericsson (Publ)
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Telefonaktiebolaget L M Ericsson (Publ) filed Critical Telefonaktiebolaget L M Ericsson (Publ)
Priority to PCT/EP2012/072521 priority Critical patent/WO2014075710A1/fr
Publication of WO2014075710A1 publication Critical patent/WO2014075710A1/fr

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/30—Fastening or clamping coils, windings, or parts thereof together; Fastening or mounting coils or windings on core, casing, or other support
    • H01F27/306—Fastening or mounting coils or windings on core, casing or other support
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/24—Magnetic cores
    • H01F27/26—Fastening parts of the core together; Fastening or mounting the core on casing or support
    • H01F27/263—Fastening parts of the core together
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2804—Printed windings
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01F—MAGNETS; INDUCTANCES; TRANSFORMERS; SELECTION OF MATERIALS FOR THEIR MAGNETIC PROPERTIES
    • H01F27/00—Details of transformers or inductances, in general
    • H01F27/28—Coils; Windings; Conductive connections
    • H01F27/2804—Printed windings
    • H01F2027/2819—Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit

Definitions

  • Embodiments disclosed herein relate to the field of magnetic cores for mounting on a printed circuit board, and, in particular, a magnetic core of a planar magnetic component.
  • a planar magnetic core consists of two pieces of magnetic material ⁇ usually referred to as “cores”, but sometimes referred to as "half-cores" which are used with a flat coil that is part of a printed circuit board (PCB) ; one core is positioned above the coil and the other core is positioned below the coil, with the cores being connected together through at least one hole in the printed circuit board .
  • FIG. 1 by way of example, the parts of of a planar magnetic component are shown unassembled.
  • An upper core 11 and a lower core 12 are provided respectively above and below a multi - layered PCB 13.
  • the types or cores 11, 12 shown are E-plane cores.
  • the PCB 13 comprises at least one hole, as shown in Figure 1, to allow a central part of each core to extend into the PCB 13.
  • the PCB 13 may also contain holes, not shown in Figure 1, to allow the outer wings of the "E" of each core to also extend into the PCB 13.
  • Printed tracks on layers of the PCB 13 provide coils round part of the core as well as input and output connections to the component.
  • the upper core 11 and the lower core 12 are attached to each other by the mechanical clip 14.
  • the mechanical clip 14 extends around the edges of the PCB 13 and the ends of the mechanical clip 14 attach to recesses 15, 16 in the top surface of the upper core 11.
  • two mechanical clips may alternatively have been used with separate clips attaching to respective ends of the upper and lower cores.
  • each piece of a planar magnetic core can be referred to as "cores” or “half-cores” .
  • cores the pieces of a planar magnetic core
  • half-cores the pieces of a planar magnetic core.
  • each piece will be referred to as a core.
  • the cores which are assembled to form a complete planar magnetic core may be identical ⁇ as shown in Figure 1) or may be different.
  • Known magnetic cores for use with planar magnetic components include the RM series .
  • the KM series of cores are made by a number of manufactures and conform to standards published by the International Electrotechnical Commission.
  • the RMS core is widely used in power electronics and is designed according to the International Standard IEC 62314-4.
  • An RMS core is shown in Figure 2 and the dimensions and tolerances of a RMS core are shown in Figure 3.
  • the core 31 has a centrally positioned cylindrical centre pin 33 protruding from the middle of a base 32 and two wings 34, 35 protruding at each end of the base 32.
  • the core 31 is reflectively symmetric about a long axis and also reflectively symmetric about a short axis, the short axis being orthogonal to the long axis in the plane of the base 32 of the core 31.
  • the long and short axis are shown in Figure 3 and intersect each other at the centre of the centre pin 33.
  • the wings wrap around the centre pin 33 apart from the necessary gaps to allow access to the centre pin 33.
  • RMS cores 31 rather than E-plane cores 11, 12 in planar magnetic components, in particular for inductors and transformers.
  • Known planar magnetic components use two RMS cores 31 that are attached to each other through the PCB by one or more mechanical clips, such as the clip 14 shown for the cores in Figure 1.
  • Recesses, similar to the recesses 15, 16, 17 shown in Figure 1, are therefore provided in RMS cores 31 in order for the mechanical clips to be attached.
  • RMS cores 31 are widely used in planar magnetic components, the RMS core 31 was designed for use as a wire wound component , With a wire wound component , a core is mounted above the surface a PCB and a wire is wound, around the core with both ends of the wire connected to the surface of the PCB.
  • a number of problems are experienced by the known RM cores , such as the RMS core 31, when used as planar magnetic cores in which the cores are inserted into holes in the PCB and the coil is formed by printed tracks integrated within the PCB .
  • the RMS core 31 one problem experienced by the RMS core 31 is that the close proximity of the wings to the centre pin requires the printed tracks that provide the one or more windings around the core to be narrow. The use of narrow tracks increases the resistance of the tracks and increases the amount of heat dissipated within the device,
  • a further problem is that it is difficult to provide vias between the different layers of the PCB when the tracks are narrow.
  • the space available for inputs and outputs is narrow, resulting in the input and output tracks to the component also being narrow and the connection of the tracks to other components being obstructed.
  • Such a narrow space also makes it hard to transfer away heat dissipated within the device and so the temperature of the device increases .
  • a further problem is that it is difficult to use all of the available space on the PCB efficiently when known cores are arranged with other components.
  • RMS core 31 There are many other types of core that have a similar shape to the RMS core 31, with wings that wrap around a circular centre pin, but with different dimensions.
  • An example of such a core is the RM7 core.
  • a core for a planar magnetic component on a printed circuit board comprising a first wing, a second, wing, a centre pin and a base.
  • the first wing, second wing and centre pin all protrude from the same face of the base .
  • the base has a straight edge betv/een a first end of the base and a second end of the base.
  • the first wing has a straight edge and the first wing is arranged at the first end of the base with said straight edge of the first wing aligned, along said straight edge of the base.
  • the second wing has a straight edge and the second wing is arranged at the second end of the base with said straight, edge of the second wing aligned along said straight edge of the base.
  • the centre pin is positioned on said face of the base such that there is a gap on said face of the base between said straight edge of the base and the closest part of the centre pin to said straight edge of the base.
  • each of the first and second wings extend on said face of the base in a direction perpendicular to said straight edge of the base no further than the distance of the furthest part of the centre pin on said face of the base from said straight edge of the base.
  • the wings do not wrap around the core and any input and output connections are obstructed less by the wings ..
  • each of the first and second wings extend on said face of the base in a direction perpendicular to said straight edge of the base no further than the distance of the centre of the centre pin on said face of the base from said straight edge of the base .
  • the wings are even less of an obstruction to any input and output connections .
  • the cross-sectional area of the centre pin is substantially equal to the sum of the cross - sectional areas of the first and second wings.
  • the height of the base is preferably at least large enough to provide the same effective magnetic area in the base as that of the centre pin or the wings , and is further preferably set to the height that provides the same effective magnetic area as the centre pin or the wings , wherein the height of the base is the dimension of the base that is perpendicular to the face of the base and directed away from the protrusions on the face of the base .
  • the magnetic areas are no larger than necessary since the effective magnetic area of the core is set by the smallest magnetic area of the cross -sectional area of the centre pin, the combined cross -sectional areas of the wings and. the height of the base .
  • the base has a constant cross-sectional shape along the dimension of the base that is perpendicular to said face of the base and directed away from the protrusions on said face of the base .
  • the volume of base is maximised since there are no recesses in the base .
  • the centre pin has a circular cross -section with a radius of substantially 3.9mm.
  • each wing has a constant cross - section consisting of two straight edges, a concave edge and rounded portions between each edge and the concave edge is the closest edge to the centre pin.
  • the constant cross-section maximises the volume of the wings .
  • the shortest distance on the face of the base between the centre pin and either the first wing or the second wing is greater than or equal to said gap on said face of the base between said straight edge of the base and the closest part of the centre pin. to said straight edge of the base .
  • the maximum width of the tracks is set by the maximum allowed gap between the centre pin and the straight edge of the base .
  • a printed circuit board comprising a planar magnetic component with at least one of the above -described cores .
  • the PCB has a plurality of holes.
  • Each of the first wing, second wing and centre pin of the at least one core extend from the base of the core into a respective one of the plurality of holes in the PCB.
  • the at least one core is positioned on the PCB with the straight edge of the base of the core arranged along a straight edge of the PCB.
  • the planar magnetic component comprises two cores.
  • the bases of each core are mounted on opposite faces of the PCB and each of the first wing, second wing and centre pin of each core extend from the base of each core into the same plurality of holes in the PCB.
  • the two cores are glued to each other.
  • the PCB is a stacked arrangement of a plurality of printed circuit boards and one or more of the printed circuit boards have printed tracks that provide one or more windings of the inductor.
  • a switched mode power supply comprising the above described PCB.
  • Figure 1 is a diagram, showing unassembled parts of a known planar magnetic component ;
  • Figure 2 shows an RMS core
  • Figure 3 is a diagram showing the shape and dimensions of an RMS core
  • Figure 4 is a cross-sectional diagram showing the shape and dimensions of a core according to an embodiment
  • Figure 5 is a cross-sectional diagram showing the shape and dimensions of two cores positioned so as to provide a complete core of a planar magnetic component according to an embodiment ;
  • Figure 6 is a perspective diagram showing two cores positioned so as to provide a complete core of a planar magnetic component according to an embodiment ;
  • Figure 7a is a diagram showing the shape and dimensions of a new core for a transformer ;
  • Figure 7b shows a perspective view of a new core for a transformer ;
  • Figure 8 is a schematic diagram of part of the circuit of an isolated SMPS ;
  • Figure 9 is a diagram showing a printed circuit board layout designed for use with known RM core components.
  • Figure 10 is a diagram showing a printed circuit board layout designed for use with a component having a core according to an embodiment .
  • Embodiments provide a core 41 for a planar magnetic component that advantageously overcomes at least some of the problems experienced when a previously known core is used in a planar magnetic component, for example to form an inductor or transformer .
  • Figure 4 is a diagram showing a core 41 according to an embodiment.
  • Figures 5 and 6 show two such cores 41 positioned relative to each other as they would be when providing a complete core of a planar magnetic component.
  • the core 41 according to an embodiment is for inserting into holes in a PCB .
  • the PCB typically comprises a plurality of layers stacked on top of each other with printed tracks on one or more of the layers providing one or more windings around part of the core 41 as well as the input and output connections of the planar magnetic component.
  • the core 41 according the embodiments differs from known cores both in the shape of the core 41 and by how the core 41 is attached to the PCB.
  • Figure 4 shows a plan view of the shape and dimensions of the core 41, according to one embodiment .
  • the core 41 comprises a fiat base 42, a first wing 44 , a second wing 45 and a centre pin 43.
  • the shapes of these parts of the core 41 are described below.
  • the base 42 is planar and substantially elongate with a first straight edge 46 between two ends of the base 42 as the longest edge of the base .
  • a first end of the base 42 there is a curved section between the first straight edge 46 and a second straight edge 47 , The other end of the second straight edge 47 is connected to a third straight edge 48 via a curved section.
  • the third straight edge 48 ends with a curved section that is at the widest part of the face of the base 42 in a direction perpendicular to the first straight edge 46 of the base 42.
  • the base 42 At a second end of the base 42, there is a curved section between the first straight edge 46 and a fourth straight edge 50, At the other end of the fourth straight edge 50 there is a curved section between the fourth straight edge 50 and a fifth straight edge 49, The other end of the fifth straight edge 49 is joined to the third straight edge 48 by said curved section that is at the widest part of the face of the base 42.
  • the second 47, third 48, fourth 50 and fifth 49 straight edges are all shorter than the first straight edge 46 between the two ends of the base 42.
  • the length of the second straight edge 47 is the same as the length of the fourth straight edge 50 and the length of the third straight edge 48 is the same as the length of the fifth straight edge 49.
  • the base 42 of the core 41 has a constant cross - section without there being any recesses in the base 42 for the attachments of one or more mechanical clips . This maximises the volume of the base 42 for a given cross - section.
  • a first wing 44 protrudes from the surface of the base 42 at the first end of the base 42 and a second wing 45 protrudes from the surface of the base 42 at a second end of the base 42.
  • the first wing 44 and the second wing 45 both protrude from the same face of the base 42.
  • the first wing 44 has a first straight edge that is aligned along the first straight edge 46 of the base .
  • the first wing 44 also has a second, straight edge 47 that is joined to the first straight edge of the first wing 44 via a curved section.
  • the second straight edge 47 and curved section of the first wing 44 are aligned along the second straight edge 47 and the curved section between the first straight edge 46 and second straight edge. 47 of the base 42.
  • the first wing 44 also has a concave section 51 that is joined to the other ends of first and second straight edges of the first wing 44 by curved sections .
  • the second wing 45 has a, first straight edge that is aligned along the first straight edge 46 of the base 42 ,
  • the second wing 45 also has a second straight edge 50 that is joined to the first straight edge of the second wing 45 via a curved section.
  • the second straight edge 50 and curved section of the second wing 45 are aligned along the fourth straight edge 50 and the curved section between the first straight edge 46 and the fourth straight edge 50 of the base 42 .
  • the second wing 45 also has a concave section 52 that is joined to the other ends of first and second straight edges of the second wing 45 by curved sections .
  • a centre pin 43 protrudes from the same face of the base as the first wing 44 and the second wing 5.
  • the centre pin 43 is cylindrical with a circular cross-section. Part of the circumference of the circular cross - section is aligned along said curved section that is at the widest part of the face of the base 42.
  • the diameter of the circular cross-section of the centre pin 43 is less than the width of the widest part of the face of the base , in a direction perpendicular to the first straight edge 46 of the base 42, and so there is a gap on said face of the base between the centre pin 43 and the first straight edge of the base 42.
  • the concave section of the first wing 44 and the concave section of the second wing 45 are both directed towards the centre pin 43 and are the closest parts of the first and second wings to the centre pin 43.
  • the gap between the centre pin 43 and the closest part of one of the wings is greater than or equal to the gap between the closest part of the centre pin 43 to the first straight edge of the base 42,
  • the maximum width of the tracks is set by the maximum allowed gap between the centre pin 43 and the first straight edge 46 of the base 42 and is not restricted by the location of the wings.
  • the shortest distance between the furthest part of the first and second wings from the first straight edge of the base 42 is less than or equal to the furthest distance of an edge of the centre pin 43 to the first straight edge of the base 42.
  • first and second wings do not extend on the face of the base further than the furthest part of the centre pin 43.
  • the distance that the first and second wings extend on said face of the base is less than or equal to the distance between the centre of the centre pin 43 on the face of the base and the first straight edge of the base 42.
  • each of the first wing 44, second wing 45 and centre pin 43 have a constant cross - section along the length of their protrusions above the face of the base 42.
  • the cross -sectional area of the centre pin 43 is preferably equal to the combined cross- sectional areas of the first and second wings.
  • the magnetic areas are no larger than necessary since the effective magnetic area is set by the smaller of the cross- sectional area of the centre pin 43 and the combined cross-sectional areas of the wings.
  • the core 41 is reflectively symmetric about a plane that is perpendicular to the first straight edge of the base 42 and bisects the mid-point of the first straight edge of the base 42.
  • Figures 5 and 6 show two cores 41 according to an embodiment .
  • the two cores 41 are shown positioned relative to each other as they would be when providing a complete core of a planar magnetic component.
  • Figure 5 is a cross- section of a side on view of two of the cores 41.
  • the first wing 44, second wing 45 and centre pin 43 of a core 41 all protrude from the face of the base 42 by the same distance and the distance is set by the thickness of the PCB being used.
  • Advantages of the core 41 design according to embodiments are described below .
  • the first straight edge of the base 42, the alignment of straight edges of the wings of the core 41 along the first straight edge of the base 42 and the gap between the centre pin 43 and the first straight edge of the base 42 allow the core 41 to be positioned along a straight edge of a PCB.
  • the holes for the wings are short and do not extend far in to the PCB. This is less of a compromise of the mechanical stability of the PCB than if longer holes are made and cracks are less likely to be caused by vibrations or temperature cycling.
  • the core 41 also allows wider tracks to be used than with an RMS core since it has a larger gap between the centre pin 43 and both the wings and the straight edge of the core 41 , Electrical losses and heat dissipation within the device are therefore reduced.
  • a further advantage of the core 41 is that the wings are not symmetric about the longest axis of the core 41. This design feature follows from, the inventors discovery that any increase in flux leakage from the wings of the core 41 not wrapping around the centre pin 43 was not a significant problem, and components using the core 41 according to embodiments still performed well .
  • the lack of symmetry about the longest axis of the core 41 allows more room for input and output connections of the component and easier connections to other components .
  • the wider input and output connections also greatly improve the temperature characteristics since it is easier ⁇ to conduct heat away from the component .
  • Another advantage of positioning the core 41 at the edge of the PCB is that the space on the PCB can be used more efficiently and the packing of the components on the PCB is improved .
  • the two cores 41 are glued to each other and/ or the PCB .
  • one or more mechanical clips are not used to hold the two cores in place and so there are no recesses in the base 42 of each core 41 for allowing clips to be attached.
  • the previously described problems, experienced by RM designs of core, of recesses creating a bottleneck in the back of the core, requiring the core to be larger and reducing the effective area of the core are therefore avoided.
  • Not having recesses in the core allows the flux to be supported, with improved efficiency and for the core to be smaller .
  • a further advantage of gluing the two cores together is that holes made in the PCB need only be made large enough to accommodate the parts of the core 41 that extend through the PCB and there is also no requirement for the holes to be larger in order to allow clips to be used .
  • FIG. 7a and 7b Before an example of a PCB layout is provided that demonstrates advantages of the core 41 design according to embodiments , a description will be made of a new type of core , shown in Figures 7a and 7b, that that has also been designed by the present inventors for use in a component to be provided on the PCB with a component made from, cores 41.
  • the new type of core is described herein for use as a core of a planar magnetic transformer. However, it may also be used as the core of other planar magnetic components.
  • the new core shown in Figures 7a and 7b is an improvement over the known transformer core designs RM7 and RM10.
  • RM7 and RM10 cores are typically used for transformers.
  • the RM7 and RM10 cores were designed for use as a wire wound component. ' It therefore experiences the same earlier described problems as the RMS core when such components are used as planar magnetic components.
  • Figure 7a shows a preferable shape and preferable dimensions of the new core design.
  • Figure 7b shows a perspective view of the new core design.
  • the new core differs from known core designs by having wings that do not extend as far round the centre pin and are wider .
  • the increased width of the wings of the new core preferably results in each wing having the same cross -sectional area as a wing of, for example, an RM7 core so that the magnetic area of each wing and the centre pin of the new core is unchanged from that of the RM7 core.
  • the wings of the new core do not wrap around the centre pin as much as the wings for the RM7 core, it is easier provide the input and output connections to the component .
  • the gap between each wing and the centre pin of the new core is also greater and so wider tracks may be used.
  • a shorter overall length of each wing results in shorter holes being required in the PCB .
  • the shorter holes of the new core reduce the mechanical stability and strength of a PCB less than the longer holes of the known cores do.
  • the RM7 and RM10 cores are similar to the RMS core 31 in that they each comprise recesses to allow two of the cores to be connected to each other by mechanical clips.
  • the new core design shown in Figures 7a and 7b does not have such recesses since the two halves of the core are glued together and clips are not used.
  • Figure 8 is an exemplary circuit diagram with a transformer and an inductor directly connected to each other .
  • the circuit in Figure 8 may be part of the circuit of an isolated SMPS , for example , When a planar transformer and a planar inductor are directly connected to each other, the most convenient positioning of the cores of the transformer and inductor on the PCB is at right angles to each other .
  • Figure 9 shows an example of a track and component layout design for a layer of a PCB that comprises a planar transformer and a planar inductor directly connected to each other .
  • a planar inductor with an RMS core 31 is positioned towards the top right corner of the PCB .
  • the wings and centre pin of the RMS core 31 would extend through the shown holes in the PCB .
  • a planar transformer with an RM7 core is positioned on the left side of the PCB at a right angle to the RMS core 31.
  • the holes in the PCB for the centre pin and wings of the RM7 core are shown.
  • a serious problem experienced when such known RM designs of core are used is that it is very difficult to conduct heat away from the device and so the temperature of the device is relatively high for a given current which reduces the efficiency of the device .
  • the close positioning of the holes for the centre pin and wings of each core causes these parts of the PCB to be weak and have a low mechanical stability.
  • a further problem caused by the close positioning of each core to its wings is that the tracks between the core and wings are required to be narrow. This increases the resistance of the tracks and the heat dissipation within the device .
  • the mechanical strength of the PCB is low because the hole in the PCB for the left wing of the RMS core 31 is positioned close to the hole in the PCB for the top wing of the RM7 core .
  • the holes in the PCB required to accommodate the wings also make it difficult to directly connect the tracks of the inductor and the transformer .
  • the holes for the wings are clearly obstructing the input and output connections of the components and this requires the tracks to be narrow and long .
  • Another problem is that due to the space on the PCB used by the cores of the components, it is difficult: to use the top left area of the PCB, The packing of the components on the PCB is therefore poor.
  • Figure 9 shows a PCB layout with RMS and RM7 cores .
  • cores with similar shapes, such as the RM10 core, and the problems identified with the above - described PCB layout could alternatively have been described with different known core designs being used.
  • Figure 10 shows a track and component layout for a circuit on a PCB that has a planar transformer directly connected to a planar inductor.
  • the circuit has been designed using the core 41 according to embodiments as a core of the inductor and the new transformer core as described above .
  • the inductor core 41 is positioned in the top right part of the PCB.
  • the holes in the PCB for the wings and centre pin 43 of the core 41 are no larger than that required for the wings and centre pin 43 to be inserted through them.
  • the holes for the wings have been cut out from the side of the PCB so that first straight edge of the core 41 is positioned along a straight edge of the PCB.
  • the new transformer core is positioned left of the inductor core , approximately in the middle of the PCB, and at right angles to the inductor core.
  • the holes cut out in the PCB for the centre pin and wings of the of the new transformer core are no larger than they need to be in order for these parts of the core to pass through the PCB.
  • wider tracks may be used around the core 41.
  • the heat dissipation within the device is reduced.
  • the straight edge of the core 41 allows the core 41 to be positioned along the top edge of the PCB. A previously unused area along the top edge of the PCB can therefore be utilised, making maximum use of the area of the PCB . The packing of the components on the PCB is therefore improved.
  • Temperature Characteristics The temperature characteristics of an electrical component are a very important performance measure. Typically, the electrical resistance of printed tracks on a PCB will increase by 0.39% for every 1°C increase in its temperature. The efficiency of a device is therefore greatly improved if its temperature does not increase to relatively high values.
  • An important advantage of the core according to embodiments is that, because the wings are not symmetric about the longest axis of the core 41 , there is more space for input and output connections to the component on the PCB . This allows wide tracks for thermally conducting heat away from the component, for example to a heat sink or the output pins, to be used . Conducting heat away from the component is an important and effective cooling mechanism.
  • the asymmetrical ferrite body of the core provides a higher thermal conductive integrity than that of known cores.
  • a first part of the PCB winding is covered by ferrite where conductivity is around 10 to 15W/mk .
  • a second part of the winding is free to be covered by a base plate or alike. This improves the thermo-- conductive integrity of the device .
  • the core according to embodiments has more space for tracks around the centre pin 43 and so wider tracks may be used that have a lower resistance . This reduces the amount of heat dissipated in the component and thereby reduces the increase in temperature of the device .
  • Figure 11 is a thermal image showing the temperature of a PCB comprising two RMS cores of an. inductor and a transformer with a current of 5OA flowing through the inductor. A maximum temperature of 129°C was recorded.
  • an RM7 core was used as the inductor core instead of an
  • the core according to embodiments, as well as the new transformer core disclosed herein allow higher currents to be used for a given temperature.
  • the above advantage is further demonstrated in Figure 12 that shows thermal images for PCBs with different currents flowing through the inductors of each circuit.
  • the top row in Figure 12 shows four thermal images of a PCB comprising the core according to an embodiment and a known transformer core .
  • the first, second , third and fourth columns respectively show thermal images when currents of 7OA, 8OA, 90A and 100A flow through the inductor.
  • the bottom row in Figure 12 shows four thermal images of a PCB comprising the core according to an embodiment and the new transformer core.
  • the first , second, third and fourth columns respectively show thermal images when currents of 7OA, 8OA, .9OA and 10OA flow through the inductor .
  • Figure 12 clearly shows that the use of the core according to an embodiment results in the maximum temperature being relatively low and only increasing to a temperature higher than 100°C when the current through the inductor is above 8 OA. Performance is further improved when the new transformer core is also used and this allows an inductor current of about 30A before the temperature increases to 100 °C.
  • the new core according to the embodiments described herein, as well as the new transformer core, therefore provide planar magnetic components with improved temperature characteristics over known designs.
  • the core 41 may be used as the core of any planar magnetic component and not just as inductor as described with reference to Figure 12.
  • the first and second wings of the core 41 are substantially triangular. Different shapes of wing may also be used that may, for example, result in an increased length of the first straight edge of the base 2 but the wing extending less into the face of the base. The amount of space available for input and output connections would therefore be increased.
  • the centre pin 43 is not restricted to having a circular cross-section and the cross -section may be oval or any other shape .
  • base 42 may have a substantially rectangular cross - section .
  • each core 41 may also be increased to ensure that the magnetic volume is unchanged by the smaller cross- section.
  • each core with the disclosed cross-section, may also be increased to increase the magnetic volume of the core .
  • designs with a lower height of core 41 may be used to allow for a thinner construction.
  • the core 41 may alternatively be designed with a centre pin 43 that protrudes from said face of the base 42 by a slightly shorter distance than the first and second wings protrude from the base.
  • an air gap would therefore be provided in the core 41.
  • Another alternative would be for one or both of the first and second wings to protrude above the face of the base 42 by a distance that is less than the distance that the centre pin 43 protrudes by so that an air gap is introduced in one or both of the wings .
  • Another alternative would be use a material with a distributed air gap between the cores .
  • the gap would be provided between metal powder and metal powder rather than as a physical gap .
  • FIG. 7 and 8 the cores have been described as glued together .
  • other techniques may also be used to hold the cores in place that also avoid the problem of recesses in the core being required for mechanical clips .
  • a casing may be positioned over the PCB that hold the cores in position.
  • An alternative arrangement for providing a complete core of a planar magnetic component is for a single core to extend through the PCB and a closed magnetic loop to be formed by a part positioned across the ends of the core without extending into the PCB.
  • Such a part may be, for example, a bar or a planar part with the same cross -section as the base of the core but with no protruding parts from its surface.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Coils Or Transformers For Communication (AREA)

Abstract

La présente invention concerne un noyau destiné à un composant magnétique plan sur une carte de circuits imprimés, le noyau comprenant une première aile, une seconde aile, une broche centrale et une base. La première aile, la seconde aile et la broche centrale dépassent toutes de la même face de la base. La base possède un bord droit entre une première extrémité de la base et une seconde extrémité de la base. La première aile possède un bord droit et la première aile est agencée au niveau de la première extrémité de la base, ledit bord droit de la première aile étant aligné le long dudit bord droit de la base. La seconde aile possède un bord droit et la seconde aile est agencée au niveau de la seconde extrémité de la base, ledit bord droit de la seconde aile étant aligné le long dudit bord droit de la base. La broche centrale est positionnée sur ladite face de la base de sorte qu'il existe un espace sur ladite face de la base entre ledit bord droit de la base et la partie la plus proche de la broche centrale par rapport audit bord droit de la base. Avantageusement, le noyau peut être positionné le long d'un bord droit d'une carte de circuits imprimés, PCB, et cela permet que l'espace disponible sur la PCB soit utilisé plus efficacement et qu'il soit plus facile de connecter un composant magnétique plan à l'aide du noyau à d'autres composants. Des applications comprennent des blocs d'alimentation à mode de commutation et d'autres dispositifs qui utilisent des composants magnétiques plans.
PCT/EP2012/072521 2012-11-13 2012-11-13 Noyau magnétique plan WO2014075710A1 (fr)

Priority Applications (1)

Application Number Priority Date Filing Date Title
PCT/EP2012/072521 WO2014075710A1 (fr) 2012-11-13 2012-11-13 Noyau magnétique plan

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Application Number Priority Date Filing Date Title
PCT/EP2012/072521 WO2014075710A1 (fr) 2012-11-13 2012-11-13 Noyau magnétique plan

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WO2014075710A1 true WO2014075710A1 (fr) 2014-05-22

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Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0068745A1 (fr) * 1981-06-19 1983-01-05 TDK Corporation Noyaux de fer et dispositifs les utilisant
US5903134A (en) * 1998-03-30 1999-05-11 Nippon Electric Industry Co., Ltd. Inductive battery charger
US6084381A (en) * 1998-01-16 2000-07-04 Kabushiki Kaisha Toyoda Jidoshokki Seisakusho Inductive charger coupling
EP1279651A2 (fr) * 2001-07-17 2003-01-29 TDK Corporation Noyau magnétique pour transformateur, composition de ferrite fondée sur Mn-Zn et sa procédé de production
EP1717825A2 (fr) * 2005-04-28 2006-11-02 TDK Corporation Noyau de ferrite et transformateur l'utilisant
US20090115564A1 (en) * 2007-11-05 2009-05-07 Schweitzer Engineering Laboratories, Inc. Systems and Methods for Forming an Isolated Transformer
US20110115600A1 (en) * 2009-11-17 2011-05-19 Delta Electronics, Inc. Magnetic core and transformer having the same

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0068745A1 (fr) * 1981-06-19 1983-01-05 TDK Corporation Noyaux de fer et dispositifs les utilisant
US6084381A (en) * 1998-01-16 2000-07-04 Kabushiki Kaisha Toyoda Jidoshokki Seisakusho Inductive charger coupling
US5903134A (en) * 1998-03-30 1999-05-11 Nippon Electric Industry Co., Ltd. Inductive battery charger
EP1279651A2 (fr) * 2001-07-17 2003-01-29 TDK Corporation Noyau magnétique pour transformateur, composition de ferrite fondée sur Mn-Zn et sa procédé de production
EP1717825A2 (fr) * 2005-04-28 2006-11-02 TDK Corporation Noyau de ferrite et transformateur l'utilisant
US20090115564A1 (en) * 2007-11-05 2009-05-07 Schweitzer Engineering Laboratories, Inc. Systems and Methods for Forming an Isolated Transformer
US20110115600A1 (en) * 2009-11-17 2011-05-19 Delta Electronics, Inc. Magnetic core and transformer having the same

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