Patent Publication Number: US-11049643-B1

Title: Combined U-core magnetic structure

Description:
A portion of the disclosure of this patent document contains material that is subject to copyright protection. The copyright owner has no objection to the reproduction of the patent document or the patent disclosure, as it appears in the U.S. Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever. 
     CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims benefit of priority of U.S. Provisional Application No. 62/563,259 filed Sep. 26, 2017, entitled “Combined U Core Magnetic Structure,” which is incorporated by reference herein in its entirety. 
     FIELD OF THE INVENTION 
     The present disclosure relates generally to transformers and methods for making transformers. More particularly, the present disclosure relates to magnetic assemblies having multiple independent magnetic components. 
     BACKGROUND 
     In a conventional electronic system that includes magnetic components, each magnetic component comprises a respective core, a respective bobbin and at least one respective winding positioned on the bobbin. For example,  FIGS. 1A and 1B  illustrate a portion of a conventional printed circuit board  100  having a first magnetic assembly  110  and a second magnetic assembly  112 . Each magnetic assembly  110 ,  112  in  FIGS. 1A  and  1 B has respective E-shaped core halves. Each magnetic assembly may be a transformer, a choke (or inductor) or another type of magnetic component having a winding and a core. 
     The first magnetic assembly  110  comprises a bobbin  120 A having a first pin rail  122 A and a second pin rail  124 A. Each pin rail supports a plurality of terminal pins  126 A. At least two of the terminal pins are electrically connected to a winding  130 A, which is wound about a passageway  132 A having a first end  134 A and a second end  136 A. The first end of the passageway receives a middle leg  142 A of a first core half  140 A. A first outer leg  144 A of the first core half extends along a first side of the bobbin in parallel with the passageway. A second outer leg  146 A of the first core half extends along a second side of the bobbin in parallel with the passageway. The second end of the passageway receives a middle leg  152 A of a second core half  150 A. Respective ends (not shown) of the first middle legs of the first and second core halves are adjacent within the passageway. In certain embodiments, the ends are spaced apart by a selected distance to provide an air gap in the magnetic path formed by the two middle legs. A first outer leg  154 A of the second core half extends along the first side of the bobbin in parallel with the passageway. A second outer leg  156 A of the second core half extends along the second side of the bobbin in parallel with the passageway. In the illustrated embodiment, the respective ends of the corresponding outer legs along the sides of bobbin abut to form a continuous magnetic path from the middle legs and around the outside of the bobbin. 
     The second magnetic assembly  112  comprises a bobbin  120 B having a first pin rail  122 B and a second pin rail  124 B. Each pin rail supports a plurality of terminal pins  126 B. At least two of the terminal pins are electrically connected to a winding  130 B, which is wound about a passageway  132 B having a first end  134 B and a second end  136 B. The first end of the passageway receives a middle leg  142 B of a first core half  140 B. A first outer leg  144 B of the first core half extends along a first side of the bobbin in parallel with the passageway. A second outer leg  146 B of the first core half extends along a second side of the bobbin in parallel with the passageway. The second end of the passageway receives a middle leg  152 B of a second core half  150 B. Respective ends (not shown) of the first middle legs of the first and second core halves are adjacent within the passageway. In certain embodiments, the ends are spaced apart by a selected distance to provide an air gap in the magnetic path formed by the two middle legs. A first outer leg  154 B of the second core half extends along the first side of the bobbin in parallel with the passageway. A second outer leg  156 B of the second core half extends along the second side of the bobbin in parallel with the passageway. In the illustrated embodiment, the respective ends of the corresponding outer legs along the sides of bobbin abut to form a continuous magnetic path from the middle legs and around the outside of the bobbin. 
     As shown in  FIGS. 1A and 1B , each of the first magnetic assembly  110  and the second magnetic assembly  112  occupies a respective area on an upper surface  160  of the printed circuit board  100 . In addition to the minimum area required to accommodate the nominal peripheral dimensions of the respective magnetic assembly, additional space must be provided between each adjacent magnetic assembly to provide allowance for tolerances in the peripheral dimensions. Furthermore, in order to allow the magnetic assemblies to be automatically positioned on the printed circuit board (e.g., by using pick-and-place equipment), sufficient spaced must be provided between adjacent magnetic assemblies to allow the positioning equipment to engage the sides of the assemblies. 
     BRIEF SUMMARY 
     Accordingly, a need exists for a magnetic assembly that combines multiple magnetic components into a single component that can be positioned within a smaller surface area on a printed circuit board than the area occupied by the multiple magnetic components. 
     One embodiment disclosed herein is a magnetic core for simultaneous use with two independent magnetic bobbins. The magnetic core comprises a first core half and a second core half. Each of the first core half and the second core half includes a main core body, a first outer leg, a second outer leg, and a middle leg. The main core body extends between a first end surface of the main core body and a second end surface of the main core body. The main core body has a main core outer surface, a first main core inner surface, and a second main core inner surface. The first and second main core inner surfaces are positioned opposite the main core outer surface. The first outer leg extends perpendicularly from the inner surface of the main core body. The first outer leg is positioned proximate to the first end surface of the main core body. The first outer leg has a first outer leg length defined between the first main core inner surface and a first outer leg end surface of the first outer leg. The first outer leg has a first outer leg cross-sectional profile which includes a first outer leg cross-sectional area. The second outer leg extends perpendicularly from the inner surface of the main core body. The second outer leg is positioned proximate to the second end surface of the main core body. The second outer leg has a second outer leg length defined between the second main core inner surface and a second outer leg end surface of the second outer leg. The second outer leg has a second outer leg cross-sectional profile which includes a second outer leg cross-sectional area. The middle leg extends perpendicularly from the inner surface of the main core body, the middle leg is positioned between the first outer leg and the second outer leg. The middle leg is spaced apart from the first outer leg by a first width and is spaced apart from the second outer leg by a second width. The middle leg has a middle leg end surface positioned at least as far as each of the first and second outer leg end surfaces are from the main core outer surface. The middle leg has a middle leg cross-sectional profile which includes a middle leg cross-sectional area. The middle leg cross-sectional area is at least as great as the sum of the first outer leg cross-sectional area and the second outer leg cross-sectional area. 
     In certain embodiments, the main core body has a first thickness and a second thickness. The first thickness is defined between the main core outer surface and the first main core inner surface. The second thickness is defined between the main core outer surface and the second main core inner surface. The first thickness is at least as great as the second thickness. 
     In certain embodiments, the main core body has a first main core body cross-sectional area and a second main core body cross-sectional area. The first main core body cross-sectional area is defined between the main core outer surface and the first main core inner surface. The first main core body cross-sectional area is greater than or equal to the first outer leg cross-sectional area. The second main core body cross-sectional area is defined between the man core outer surface and the second main core inner surface. The second main core body cross-sectional area is greater than or equal to the second outer leg cross-sectional area. 
     In certain embodiments, the first outer leg end surface of the first core half is spaced apart from the first outer leg end surface of the second core half by a first gap distance. 
     In certain embodiments, the second outer leg end surface of the first core half is spaced apart from the second outer leg end surface of the second core half by a second gap distance. 
     In certain embodiments, the first outer leg is configured to fit within a passageway of the first bobbin, and the second outer leg is configured to fit within a passageway of the second bobbin. 
     Another embodiment disclosed herein is a magnetic assembly having two independent magnetic components sharing a common core structure. The magnetic assembly comprises a first bobbin, a second bobbin, a first core half, and a second core half. The first bobbin includes a first winding configured to surround a respective passageway of the first bobbin. The first bobbin further includes a respective first end flange and a respective second end flange positioned at opposite ends of the passageway. The passageway of the first bobbin has a respective passageway length defined between a respective outer surface of the first end flange and a respective outer surface of the second end flange. The second bobbin includes a second winding configured to surround a respective passageway of the second bobbin. The second bobbin further includes a respective first end flange and a respective second end flange positioned at opposite ends of the passageway. The passageway of the second bobbin has a respective passageway length defined between a respective outer surface of the first end flange and a respective outer surface of the second end flange. Each of the first core half and the second core half includes a main core body, a first outer leg, a second outer leg, and a middle leg. The main core body extends between a first end surface of the main core body and a second end surface of the main core body. The first outer leg extends perpendicularly from an inner surface of the main core body and is positioned proximate to the first end surface of the main core body. The first outer leg has a first outer leg cross-sectional profile configured to fit within the passageway of the first bobbin. The first outer leg cross-sectional profile defines a first outer leg cross-sectional area. The second outer leg extends perpendicularly from the inner surface of the main core body and is positioned proximate to the second end surface of the main core body. The second outer leg has a second outer leg cross-sectional profile configured to fit within the passageway of the second bobbin. The second outer leg cross-sectional profile defines a second outer leg cross-sectional area. The middle leg extends perpendicularly from the inner surface of the main core body between the first outer leg and the second outer leg. The middle leg is spaced apart from the first outer leg by a first window width and is spaced apart from the second outer leg by a second window width. The middle leg has a middle leg end surface. The middle leg further has a middle leg cross-sectional profile which defines a middle leg cross-sectional area. The middle leg cross-sectional area is at least as great as the sum of the first outer leg cross-sectional area and the second outer leg cross-sectional area. 
     In certain embodiments, the first outer leg of each core half is configured to be inserted into the passageway of the first bobbin, and the second outer leg of each core half is configured to be inserted into the passageway of the second bobbin. The middle leg of each core half is configured to span between the first bobbin and the second bobbin with the middle led end surface of the first core half abutting the middle leg end surface of the second core half. 
     In certain embodiments, each of the first and second end flanges of the first bobbin include a first flange width defined between the passageway and a lateral outer periphery of the respective end flange. The first bobbin flange width is less than the first window width. Each of the first and second end flanges of the second bobbin includes a second bobbin flange width defined between the passageway and a lateral outer periphery of the respective end flange. The second bobbin flange width is less than the second window width. 
     In certain embodiments, the main core body, the first outer leg, the second outer leg, and the middle leg of each of the first and second core halves have a selected common height. 
     In certain embodiments, the first outer legs and the middle legs of the first and second core halves define a first winding window. The first winding window includes the first window width and a first window length. The first window length is defined between a respective first main core inner surface of the main core body of the first core half and a respective first main core inner surface of the main core body of the second core half when the first and second core halves are mated. A second winding window is defined between the middle legs and the second outer legs of the first and second core halves. The second winding window including the second window width and a second window length. The second window length is defined between a respective second main core inner surface of the main core body of the first core half and a respective second main core inner surface of the main core body of the second core half when the first and second core halves are mated. 
     In certain embodiments, the first window length is at least as great as the passageway length of the passageway of the first bobbin. Also, the second window length is at least as great as the passageway length of the passageway of the second bobbin. 
     In certain embodiments, the main core body of each of the first core half and second core half includes a main core outer surface, a first main core inner surface, and a second main core inner surface. The first and second main core inner surfaces are positioned opposite to the main core outer surface. The first main core inner surface is defined between the first outer leg and the middle leg. The second main core inner surface is defined between the middle leg and the second outer leg. The middle leg of each of the first and second core halves includes a middle leg end surface, a first common length, and a second common length. The first common length is defined between the first main core inner surface and the middle leg end surface. The second common length is defined between the second main core inner surface and the middle leg end surface. The first outer leg of each of the first and second core halves includes a first outer leg end surface and a third common length. The third common length is defined between the first main core inner surface and the first outer leg end surface. The second outer leg of each of the first and second core halves includes a second outer leg end surface and a fourth common length. The fourth common length is defined between the second main core inner surface and the second outer leg end surface. 
     In certain embodiments, the first common length is greater than the third common length by one-half of a first gap distance. The first gap distance is defined between the first outer leg end surface of the first core half and the first outer leg end surface of the second core half. 
     In certain embodiments, the second common length is greater than the fourth common length by one-half of a second gap distance. The second gap distance is defined between the second outer leg end surface of the first core half and the second outer leg end surface of the second core half. 
     Another embodiment disclosed herein is a method of assembling a magnetic assembly having two independent magnetic components sharing a common core structure. The method includes the step of providing a first bobbin and a second bobbin. Each bobbin has a respective passageway and at least one respective winding wound around the respective passageway. Each passageway has a respective first end and a respective second end. The passageway of the first bobbin is parallel to the passageway of the second bobbin. 
     The method further includes the step of engaging a first core half with the first bobbin and the second bobbin by positioning a first outer leg of the first core half into the first end of the passageway of the first bobbin, positioning a second outer leg of the first core half into the first end of the passageway of the second bobbin, and positioning the middle of the first core half between the first bobbin and the second bobbin. The first outer leg of the first core half has a respective first outer leg cross-sectional area. The second outer leg of the first core half has a respective second outer leg cross-sectional area. The middle leg of the first core half has a respective middle leg cross-sectional area. The middle leg cross-sectional area is at least as great as the sum of the first outer leg cross-sectional area of the first core half and the second outer leg cross-sectional area of the second core half. 
     The method further includes the step of engaging a second core half with the first bobbin and the second bobbin by positioning a first outer leg of the second core half into the second end of the passageway of the first bobbin, positioning a second outer leg of the second core half into the second end of the passageway of the second bobbin, and positioning the middle of the second core half between the first bobbin and the second bobbin. The first outer leg of the second core half has a respective first outer leg cross-sectional area that is substantially equal to the first outer leg cross-sectional area of the first core half. The second outer leg of the second core half has a respective second outer leg cross-sectional area that is substantially equal to the second outer leg cross-sectional area of the first core half. The middle leg of the second core half abuts the middle leg of the first core half. The middle leg of the second core half has a respective middle leg cross-sectional area that is substantially equal to the middle leg cross-sectional area of the first core half. 
     In certain embodiments, the method further includes the step of selecting a first common length of the middle leg of each of the first core half and the second core half. The combined first common lengths of the middle legs of the first core half and the second core half are at least as great as a passageway length of the passageway of the first bobbin. The method further includes the step of selecting a second common length of the middle leg of each of the first core half and the second core half. The combined second common lengths of the middle legs of the first core half and the second core half are at least as great as a passageway length of the passageway of the second bobbin. 
     In certain embodiments, the passageway length of the second bobbin differs from the passageway length of the first bobbin. 
     In certain embodiments, the method further includes the step of selecting a third common length of the first outer leg of each of the first core half and second core half. The third common length is less than the first common length. 
     In certain embodiments, the method further includes the step of selecting a fourth common length of the second outer leg of each of the first core half and second core half. The fourth common length is less than the second common length. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1A  illustrates a perspective view of a conventional printed circuit board with two independent magnetic assemblies positioned thereon. 
         FIG. 1B  illustrates a rear perspective view of the printed circuit board and the magnetic assemblies of  FIG. 1A . 
         FIG. 2  illustrates an upper front perspective view of a single magnetic assembly mounted on a printed circuit board wherein the single magnetic assembly comprises two independent magnetic components sharing a common core structure. 
         FIG. 3  illustrates an upper front perspective view of the single magnetic assembly of  FIG. 2  prior to installation on the printed circuit. 
         FIG. 4  illustrates an exploded upper front perspective view of the single magnetic assembly of  FIG. 3 . 
         FIG. 5  illustrates upper front perspective view of the first core half and the second core half of the core structure of the magnetic assembly of  FIG. 3 . 
         FIG. 6  illustrates an upper front perspective view of the first and second core halves juxtaposed to show the winding windows formed between the legs of the two core halves of the magnetic component of  FIG. 3  and further showing the gaps between the adjacent ends of the outer legs. 
         FIG. 7  illustrates a top plan view of the first and second core halves juxtaposed to show the common lengths of the legs of the two core halves of the magnetic component of  FIG. 3 . 
         FIG. 8  illustrates an upper front perspective view of the first bobbin of the leftmost magnetic component of  FIG. 3 . 
         FIG. 9  illustrates an upper front perspective view of the second bobbin of the rightmost magnetic component of  FIG. 3 . 
         FIG. 10  illustrates a top plan cross-sectional view of the magnetic assembly of  FIG. 3  taken along the line  10 - 10  of  FIG. 3  showing the gaps between the ends of the outer legs of the core structure positioned within the passageways of the first and second bobbins of the leftmost and the rightmost magnetic components. 
         FIG. 11  pictorially illustrates the flux paths within the bodies and the legs of the two core halves of the core structure of the single magnetic assemblies caused by the two independent magnetic components. 
         FIG. 12  pictorially compares the single magnetic assembly of  FIG. 2  with the two separate magnetic assembly of  FIGS. 1A and 1B . 
     
    
    
     DETAILED DESCRIPTION 
     In the following description, various dimensional and orientation words, such as height, width, length, longitudinal, horizontal, vertical, up, down, left, right, tall, low profile, and the like, may be used with respect to the illustrated drawings. Such words are used for ease of description with respect to the particular drawings and are not intended to limit the described embodiments to the orientations shown. It should be understood that the illustrated embodiments can be oriented at various angles and that the dimensional and orientation words should be considered relative to an implied base plane that would rotate with the embodiment to a revised selected orientation. 
     Reference will now be made in detail to embodiments of the present disclosure, one or more drawings of which are set forth herein. Each drawing is provided by way of explanation of the present disclosure and is not a limitation. It will be apparent to those skilled in the art that various modifications and variations can be made to the teachings of the present disclosure without departing from the scope of the disclosure. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. 
     It is intended that the present disclosure covers such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present disclosure are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present disclosure. 
       FIGS. 2-12  illustrate a single magnetic assembly  200  that includes a first (leftmost) magnetic component  210  and a second (rightmost) magnetic component  212  on a single core structure  214 . The single magnetic assembly is mounted on a printed circuit board (PCB)  216  in  FIG. 2 . The magnetic assembly is shown prior to mounting on the PCB in  FIGS. 3-11 . 
     As shown in  FIGS. 3 and 4 , for example, the magnetic assembly  200  comprises a first core half  220  and a second core half  222 . In the illustrated embodiment, the first core half and the second core half are identical or are substantially identical and are positioned in the single magnetic assembly in a mirrored orientation. Each of the first core half and the second core half of the single core structure has a general appearance similar to a conventional E-core half; however, the outer legs are inserted into two separate bobbins rather than surrounding a single bobbin, as further described below. 
     As shown in  FIGS. 4 and 5 , for example, the first core half  220  comprises a first core main half body portion  230  having a first end surface  232 , a second end surface  234 , an outer surface  236 , an inner surface  238 , a lower surface  240  and an upper surface  242 . The first core main half body portion  230  may also be referred to as a main core body  230  or a main body portion  230 . The inner surface  238  may be a single fixed distance from the outer surface  236 . In the illustrated embodiment, the inner surface  238  is divided into first and second inner surfaces  238 A,  238 B, respectively, as shown in  FIGS. 4-7 . The first inner surface  238 A is spaced apart from the outer surface  236  by a first distance D 1 . The first distance D 1  may be referred to as a first thickness D 1 . The second inner surface  238 B is spaced apart from the outer surface by a second distance D 2 . The second distance D 2  may be referred to as a second thickness D 2 . The first distance D 1  may be larger, smaller, or the same as the second distance D 2 . As illustrated, the first distance D 1  is greater than the second distance D 2 . 
     A first outer leg  250  of the first core half  220  extends perpendicularly from the inner surface  238  of the main body portion  230  near the first end surface  232  of the main body portion. As shown in  FIG. 5 , the first outer leg has a first outer leg end surface  252 . The first outer leg has an outer lateral surface  254  and an inner lateral surface  256 . In the illustrated embodiment, the outer lateral surface of the first outer leg is coplanar with the first end surface  232  of the main body portion. The inner lateral surface of the first outer leg is parallel to the outer lateral surface of the first outer leg. The first outer leg further includes a first outer leg cross-sectional profile  258  defined by the first outer leg end surface  252 . The first outer leg cross-sectional profile has a first outer leg cross-sectional area. In the illustrated embodiment, the first outer leg has a lower surface coplanar with the lower surface  240  of the main body portion and has an upper surface coplanar with the upper surface  242  of the main body portion. The common upper and lower surfaces of the first outer leg and the other legs described in the following paragraphs are not numbered separately. 
     A second outer leg  260  of the first core half  220  extends perpendicularly from the inner surface  238  of the main body portion  230  near the second end surface  234  of the main body portion. The second outer leg has a second outer leg end surface  262 . The second outer leg has an outer lateral surface  264  and an inner lateral surface  266 . In the illustrated embodiment, the outer lateral surface of the second outer leg is coplanar with the second end surface  234  of the main body portion. The inner lateral surface of the second outer leg is parallel to the outer lateral surface of the second outer leg. The second outer leg further includes a second outer leg cross-sectional profile  268  defined by the second outer leg end surface  262 . The second outer leg cross-sectional profile has a second leg cross-sectional area. In the illustrated embodiment, the second outer leg has a lower surface coplanar with the lower surface  240  of the main body portion and has an upper surface coplanar with the upper surface  242  of the main body portion. 
     A middle leg  270  of the first core half  220  extends perpendicularly from the inner surface  238  of the main body portion  230  between the first end surface  232  and the second end surface  234  of the main body portion. The middle leg has a middle leg end surface  272 . The middle leg end surface may be positioned at least as far as each of the first and second outer leg end surfaces  252 ,  262  are from the outer surface  236  of the main body portion  230 . The middle outer leg has a first lateral surface  274  and a second lateral surface  276 . The first lateral surface faces toward the first end surface of the main body portion. The second lateral surface faces toward the second end surface of the main body portion. The first lateral surface and the second lateral surface are parallel to each other and parallel to the first and second end surfaces of the main body portion. The middle leg further includes a middle leg cross-sectional profile  278  defined by the middle leg end surface  272 . The middle leg cross-sectional profile has a middle leg cross-sectional area. The middle leg cross-sectional area is greater than or equal to a sum of the first outer leg cross-sectional area and the second outer leg cross-sectional area. In the illustrated embodiment, the middle leg has a lower surface coplanar with the lower surface  240  of the main body portion and has an upper surface coplanar with the upper surface  242  of the main body portion. 
     As further shown in  FIG. 6 , the second core half  222  is configured the same or substantially the same as the first core half  220 ; and the elements of the body portion and legs of the second core half are numbered the same as the corresponding elements of the first core half. In the illustrated embodiment, the first and second core halves are mirror images; and the end surface  252  of the first outer leg  250  of the first core half is juxtaposed with the end surface  252  of the first outer leg  250  of the second core half as shown. 
     When the two core halves  220 ,  222  of the core structure  216  are mated as shown in  FIGS. 6 and 7 , the respective end surfaces  252  of the first outer legs  250  of the two core halves are positioned adjacent to each other; the respective end surfaces  262  of the second outer legs  260  of the two core halves are positioned adjacent to each other; and the respective end surfaces  272  of the middle legs  270  of the two core halves are positioned adjacent to each other. As described below, the respective end surfaces of the respective middle legs are abutting. The respective end surfaces of the respective outer legs may be spaced apart. As illustrated, the respective end surfaces of the respective outer legs are spaced apart to form the gaps described above. 
     In the illustrated embodiment, the main body portion  230  and the three legs  250 ,  260 ,  270  extending from the main body portion of each core half  220 ,  222  have a common height H ( FIGS. 5 and 6 ). The main body portion includes a first main core body cross-sectional area and a second main core body cross-sectional area. The first main core body cross-sectional area is defined between the outer surface  236  and the first inner surface  238 A of the main body portion  230  of each core half. The first main core body cross-sectional area is substantially equal to the common height H multiplied by the first distance D 1 . The first main core body cross-sectional area is at least as great as the first outer leg cross-sectional area. The second main core body cross-sectional area is defined between the outer surface  236  and the second inner surface  238 B of the main body portion  230  of each core half. The second main core body cross-sectional area is substantially equal to the common height multiplied by the second distance D 2 . The second main core body cross-sectional area is at least as great as the second outer leg cross-sectional area. 
     In the illustrated embodiment, the middle leg  270  of each core half  220 ,  222  has a first common selected length L 1  ( FIG. 7 ) such that when the two core halves are mated as shown in  FIGS. 6 and 7 , the respective end surfaces  272  of the middle legs of the two core halves touch (e.g., abut). The first common selected length L 1  is defined along the first lateral surface  274  ( FIG. 5 ) of the middle leg  270  of each core half  220 ,  222  and measured between the end surface  272  and the first inner surface  238 A. The middle leg of each core half has a second common selected length L 2  ( FIG. 7 ) defined along the second lateral surface  276  ( FIG. 5 ) of the middle leg  270  of each core half  220 ,  222  and measured between the end surface  272  and the second inner surface  238 B. 
     In the illustrated embodiment, the first outer legs  250  of the two core halves  220 ,  222  have a third common selected length L 3  ( FIG. 7 ) that is shorter than the first common selected length L 1 . The third common selected length L 3  is defined along the inner lateral surface  256  ( FIG. 5 ) of the first outer leg  250  of each core half  220 ,  222  and is measured between the end surface  252  and the first inner surface  238 A. The third common selected length L 3  is selected relative to the first common selected length L 1  such that when the two core halves are mated as shown in  FIGS. 6 and 7 , the respective end surfaces  252  of the first outer legs are spaced apart from each other by a first gap  300  that is determined by the sum of the leg length differences. For example, if the first common selected length is L 1  and the third common selected length is L 3 , a gap width G 1  of the first gap  300  is calculated as G 1 =2×(L 1 −L 3 ). The gap width G 1  may be referred to as a first gap distance G 1 . The first common selected length is greater than the third common selected length by one-half of the first gap distance G 1 . 
     In the illustrated embodiment, the second outer legs  260  of the two core halves  220 ,  222  have a fourth common selected length L 4  ( FIG. 7 ) that is shorter than the second common selected length L 2 . The fourth common selected length L 4  is defined along the inner lateral surface  266  ( FIG. 5 ) of the second outer leg  200  of each core half  220 ,  222  and is measured between the end surface  262  and the second inner surface  238 B. The fourth common selected length L 4  is selected relative to the second common selected length L 2  such that when the two core halves are mated as shown in  FIGS. 6 and 7 , the respective end surfaces  262  of the second outer legs are spaced apart from each other by a second gap  310  that is determined by the sum of the leg length differences. For example, if the second common selected length is L 2  and the fourth common selected length is L 4 , a gap width G 2  of the first gap  310  is calculated as G 2 =2−(L 2 −L 4 ). The gap width G 2  may be referred to as a second gap distance G 2 . The second common selected length is greater than the fourth common selected length by one-half of the second gap distance G 2 . 
     In the illustrated embodiment, the gap width G 1  of the first gap  300  and the gap width G 2  of the second gap  310  are shown as being approximately the same width; however, the first, second, third, and fourth common lengths may be selected such that the gap widths are different. For example, in one embodiment, the difference between the first common selected length of the middle legs  270  and the third common selected length of the first outer legs  250  may differ from the difference between the second common length of the middle legs  270  and the fourth common selected length of the second outer legs  260  such that the first gap width G 1  and the second gap width G 2  may be different. The first gap width G 1  may be greater or smaller than the second gap width G 2 . Alternatively, the difference between the first common selected length of the middle legs  270  and the third common selected length of the first outer legs  250  may be equal to the difference between the second common length of the middle legs  270  and the fourth common selected length of the second outer legs  260  such that the first gap width G 1  and the second gap width G 2  may be the same. It should be understood that the gap widths illustrated in the figures may be exaggerated so that the gaps may be visualized. In certain embodiments, the gap widths may be a small percentage of the lengths of the respective legs. For example, a gap may have a width of less than 0.001 inch or may have a width of more than 0.01 inch. 
     As further shown in  FIGS. 6 and 7 , the juxtaposition of the end surfaces of the three legs forms two winding windows in the core structure  214 . A first winding window  350  is formed between the juxtaposed first outer legs  250  and the juxtaposed middle legs  270 . The first winding window has a width W 1  determined by the leg spacing between the respective inner lateral surfaces  256  of the first outer legs and the respective first lateral surfaces  274  of the middle legs. The first winding window has a respective length determined by two times the first common length L 1 . 
     A second winding window  360  is formed between the juxtaposed second outer legs  260  and the juxtaposed middle legs  270 . The second winding window has a width W 2  determined by the leg spacing between the respective inner lateral surfaces  266  of the second outer legs and the respective second lateral surfaces  376  of the middle legs. The second winding window has a respective length determined by two times the second common length L 2 . 
     In the illustrated embodiment, the main body portion  230  of each core half  220 ,  222 , has a width from the first end  232  to the second end  234  of approximately 1.128 inches. The main body portion and the three legs  250 ,  260 ,  270  extending from the main body portion have a common height from the lower surface  240  to the upper surface  242  of approximately 0.283 inch. The first outer leg  250  has a width of approximately 0.229 inch and the second outer leg  260  has a width of approximately 0.175 inch. The middle leg  270  has a width of approximately 0.404 inch. The width of the middle is equal to at least the sum of the width of the first outer leg and the width of the second outer leg. 
     The inner lateral surface  256  of the first outer leg  250  and the first lateral surface  274  of the middle leg  270  are spaced apart by a leg spacing of approximately 0.21 inch, which corresponds to the width W 1  of the first winding window  350 . The inner lateral surface  266  of the second outer leg  260  and the second lateral surface  276  of the middle leg  270  are spaced apart by a leg spacing of approximately 0.11 inch, which corresponds to the width W 2  of the second winding window  360 . In the illustrated embodiment, the two winding window widths differ; however, in other embodiments, the widths of the two winding windows may be the same or substantially the same. 
     Each of the core halves  220 ,  222  has a maximum length from the outer surface  236  of the main core body  230  to the end surface  272  of the middle leg  270 . In the illustrated embodiment, the maximum length is approximately 0.493 inch. 
     The main body portion  230  has a thickness from the outer surface  236  to the inner surface  238  that differs in accordance with the location. In the illustrated embodiment, the main body portion has a thickness of approximately 0.229 inch in a first region between the inner lateral surface  256  of the first outer leg  250  and the first lateral surface  274  of the middle leg  270 , which corresponds to the first winding window  350 . The main body portion has a thickness of approximately 0.175 inch in a second region between the second lateral surface  276  of the middle leg and the inner lateral surface  266  of the second outer leg  260 , which corresponds to the second winding window  360 . 
     When the first core half  220  and the second core half  222  are mated as illustrated in  FIGS. 6 and 7 , the respective end surfaces  272  of the middle legs  270  of the two core halves abut. In the illustrated embodiment, the first winding window  350  has a length of approximately 0.528 inch determined by twice the difference between the overall length of each core section (e.g., 0.493 inch in the illustrated embodiment) and the thickness of the main body portion  230  in the first region as described above (e.g., 0.229 inch in the illustrated embodiment). In the illustrated embodiment, the second winding window  360  has a length of approximately 0.636 inch determined by twice the difference between the overall length of each core section (e.g., 0.493 inch in the illustrated embodiment) and the thickness of the main body portion  230  in the second region as described above (e.g., 0.175 inch in the illustrated embodiment). 
     As shown in  FIG. 3 , the first (leftmost) magnetic component  210  comprises a first bobbin  400  having a first winding  410 . The first bobbin is shown in more detail in  FIG. 8  with the winding removed. The first bobbin includes a first end flange  420  and a second end flange  422 . A coil winding surface  424  extends between the first end flange and the second end flange. The coil winding surface surrounds a core leg receiving passageway  426 . As shown in  FIG. 10 , the passageway  426  has a passageway length  428  defined between an outer surface  421  of the first end flange  420  and an outer surface  423  of the second end flange  422 . The outer surfaces of the first end flange and the second end flange of the first bobbin are spaced apart by the passageway length which is selected to be less than the length of the first winding window  350  of the mated core halves  220 ,  222  as shown in  FIG. 10 . Each flange has a width FW 1  between the passageway and a lateral outer periphery of the flange that is selected to be no more than the width of the first winding window. 
     A first pin (or terminal) rail  430  extends from the first end flange  420 . A second pin (or terminal) rail  432  extends from the second end flange  422 . Each pin rail supports a plurality of pins (or terminals)  434 . Selected ones of the pins are electrically connected to the first winding  410  ( FIGS. 3 and 10 ) by conductors (not shown) in a conventional manner. 
     As shown, for example, in the cross-sectional view in  FIG. 10 , the passageway  426  of the first bobbin  400  has a shape and a size configured to receive the first outer legs  250  of the first and second core halves  220 ,  222  such that the first gap  300  formed by the juxtaposed end surfaces  252  of the first outer legs is positioned approximately in the middle of the passageway between the first end flange  420  and the second end flange  422 . As such, the first outer leg cross-sectional profile  258  is configured to fit with the passageway of the first bobbin  400 . When positioned as shown in  FIG. 3  (facing the first end flange  420 ), the respective rightmost portions of the flanges and the rightmost portion of the winding  410  fit within the first winding window  350  ( FIG. 10 ). 
     As shown in  FIG. 3 , the second (rightmost) magnetic component  212  comprises a second bobbin  450  having a second winding  460 . The second bobbin is shown in more detail in  FIG. 9  with the winding removed. The second bobbin includes a first end flange  470  and a second end flange  472 . A coil winding surface  474  extends between the first end flange and the second end flange. The coil winding surface surrounds a core leg receiving passageway  476 . As shown in  FIG. 10 , the passageway  476  has a passageway length  478  defined between an outer surface  471  of the first end flange  470  and an outer surface  473  of the second end flange  472 . The outer surfaces of the first end flange and the second end flange of the second bobbin are spaced apart by the passageway length, which is selected to be less than the length of the second winding window  360  of the mated core halves  220 ,  222  as shown in  FIG. 10 . Each flange has a width FW 2  between the passageway and a lateral outer periphery of the flange that is selected to be no more than the width of the second winding window. 
     A first pin (or terminal) rail  480  extends from the first end flange  470 . A second pin (or terminal) rail  482  extends from the second end flange  472 . Each pin rail supports a plurality of pins (or terminals)  484 . Selected ones of the pins are electrically connected to the second winding  460  ( FIGS. 3 and 10 ) by conductors (not shown) in a conventional manner. 
     As shown, for example, in the cross-sectional view in  FIG. 10 , the passageway  476  of the second bobbin  450  has a shape and a size configured to receive the second outer legs  260  of the first and second core halves  220 ,  222  such that the second gap  310  formed by the juxtaposed end surfaces  252  of the first outer legs is positioned approximately in the middle of the passageway between the first end flange  470  and the second end flange  472 . As such, the second outer leg cross-sectional profile  268  is configured to fit with the passageway of the second bobbin  450 . When positioned as shown in  FIG. 3  (facing the first end flange  470 ), the respective leftmost portions of the flanges and the leftmost portion of the winding  460  fit within the second winding window  360  ( FIG. 10 ). 
     As further shown in  FIG. 10 , the middle leg  270  of each core half  220 ,  222 , is configured to span between the first bobbin  400  and the second bobbin  450 . 
       FIG. 11  pictorially represents the flux paths through the core structure  216  generated by the respective windings  410 ,  460  of the magnetic components  210 ,  212 . As shown, the flux generated by the first winding  410  follows a first flux path  500 , which passes through the first outer legs  250  positioned within the passageway  426  of the first bobbin  400  onto which the first winding is wound, including the first gap  300 . The first flux path passes through a region of the main body portion  230  of the first core half  220  to the middle legs  270 ; passes through the middle legs  270 ; passes through a region of the main body portion  230  of the second core half  222 ; and passes back to the first outer legs positioned within the first winding. Accordingly, the first flux path encompasses the first winding window  350 . 
     Similarly, the flux generated by the second winding  460  follows a second flux path  510 , which passes through the second outer legs  260  positioned within the passageway  476  of the second bobbin  450  onto which the second winding is wound, including the second gap  310 . The second flux path passes through a region of the body portion  230  of the first core half  220  to the middle legs  270 ; passes through the middle legs; passes through a region of the body portion  230  of the second core half  222 ; and passes back to the second outer legs positioned within the second winding. Accordingly, the second flux path encompasses the second winding window  360 . 
     As illustrated in  FIG. 11 , the flux generated by the first winding  410  passes along the first flux path  500  through the middle legs  270  with the flux from the second winding  460 . The cross-sectional areas of the middle legs are selected to be sufficiently great such that the middle legs are able to accommodate the flux generated by the two windings without exceeding a desired flux density. As stated above, the cross-sectional area of the middle leg is equal to at least the cross-sectional area of the first outer leg  250  plus the cross-sectional area of the second outer leg  260 . As further illustrated in  FIG. 11 , the flux generated by two sources pass through the middle leg along independent flux paths within separate portions of the middle leg and do not interact. 
     One benefit of the magnetic assembly  200  disclosed herein is illustrated pictorially in  FIG. 12 , which shows the first magnetic assembly  110  and the second magnetic assembly  112  of  FIGS. 1A and 1B  replaced with the single magnetic assembly  200  of  FIG. 2 . As illustrated, a structural gap  600  between the first magnetic assembly and the second magnetic assembly is eliminated by the improved single core structure. Furthermore, the new core structure eliminates the first outer legs  144 A,  154 A of the E-cores of the first magnetic assembly and the second outer legs  146 C,  156 C of the E-cores of the second magnetic assembly. Thus, the overall structure requires less area on a printed circuit board. Furthermore, the installation steps are reduced by having to install only a single magnetic component instead of three magnetic components. 
     The previous detailed description has been provided for the purposes of illustration and description. Thus, although there have been described particular embodiments of a new and useful invention, it is not intended that such references be construed as limitations upon the scope of this invention except as set forth in the following claims.