Output transformer and resonant inductor in a combined magnetic structure

Abstract

A magnetic assembly includes a single bobbin structure that supports a first coil and a second coil. A first E-core has a center leg positioned within the first coil. A second E-core has a center leg positioned within the second coil. An I-core is positioned between the first E-core and the second E-core. The I-core completes a first set of magnetic paths between the center leg and outer legs of the first E-core and also completes a second set of magnetic paths between the center leg and outer legs of the second E-core. The two E-cores and the I-core are stacked in a vertical E-I-E configuration with respect to a common set of pin rails. In one embodiment, the first coil and the first E-core are configured as a transformer; and the second coil and the second E-core are configured as an inductor.

Claims

1. A magnetic assembly comprising: a bobbin structure having a first flange, the first flange having a first outer flange surface, a second flange spaced apart from the first flange in a first direction, a third flange spaced apart from the second flange in the first direction, a fourth flange spaced apart from the third flange in the first direction, a first core passage extending between the first flange and the second flange, a second core passage extending between the third flange and the fourth flange, a third core passage, the third core passage positioned between the second flange and the third flange, the third core passage oriented perpendicular to the first core passage and the second core passage, a first pin rail and a second pin rail, the first pin rail and the second pin rail extending perpendicularly from the first flange in a second direction opposite the first direction, the first pin rail spaced apart from the second pin rail by a core channel on the outer surface of the first flange, the first core passage extending to the core channel; a first coil at least partially surrounding the first core passage; a second coil at least partially surrounding the second core passage; an I-core having at least a central portion positioned in the third core passage, the I-core having a first planar surface and a second planar surface; a first E-core having a main body positioned in the core channel between the first pin rail and the second pin rail, having a center leg positioned in the first core passage and having a first outer leg and a second outer leg, the first and second outer legs of the first E-core having respective end surfaces contacting the first planar surface of the I-core; and a second E-core having a center leg positioned in the second core passage and having a first outer leg and a second outer leg, the first and second outer legs and the center leg of the second E-core having respective end surfaces positioned proximate to and spaced apart from the second planar surface of the I-core.

2. The magnetic assembly of claim 1, wherein the center leg of the first E-core is shorter than the outer legs of the first E-core by a length difference such that an end surface of the center leg of the first E-core is spaced apart from the first planar surface of the I-core by a gap distance equal to the length difference.

3. The magnetic assembly of claim 1, further including a gap spacer positioned between the second planar surface of the I-core and the end surfaces of the first outer leg, the second outer leg and the center leg of the second E-core, the gap spacer having a thickness selected to provide a predetermined gap spacing between the end surfaces of the first outer leg, the second outer leg and the center leg of the second E-core and the second planar surface of the I-core.

4. The magnetic assembly of claim 1, wherein: the first coil, the first E-core and at least a first portion of the I-core comprise a first inductive device; and the second coil, the second E-core and at least a second portion of the I-core comprise a second inductive device.

5. The magnetic assembly of claim 4, wherein: the first inductive device is a transformer; and the second inductive device is an inductor.

6. A bobbin for a magnetic assembly, comprising: a first flange, a second flange, a third flange and a fourth flange, the second flange spaced apart from the first flange in a first direction, the third flange spaced apart from the second flange in the first direction, the fourth flange spaced apart from the third flange in the first direction, the first flange having an outer surface facing in a second direction, the second direction opposite the first direction; a first pin rail and a second pin rail, each pin rail extending perpendicularly from the first flange in the second direction, the first pin rail and the second pin rail spaced apart along the outer surface of the first flange by a core channel formed on the outer surface of the first flange; a first winding portion positioned between the first flange and the second flange; a second winding surface positioned between the third flange and the fourth flange; an I-core receiving passage positioned between the second flange and the third flange, the I-core receiving passage oriented in a third direction, the third direction perpendicular to the second direction; a first core leg receiving passage extending in the first direction from the core channel formed on the outer surface of the first flange to the second flange; and a second core leg receiving passage extending in the second direction from the fourth flange to the third flange.

7. A magnetic assembly, comprising: a bobbin structure, the bobbin structure including: a first flange; a second flange parallel to the first flange and displaced away from the first flange in a first direction; a first core passage extending from the first flange to the second flange, the first core passage perpendicular to the first flange and the second flange; a first winding surface surrounding the first core passage between the first flange and the second flange; a third flange parallel to the second flange and displaced away from the second flange in the first direction, the third flange coupled to the second flange by at least one spacer wall to define an I-core receiving slot between the second flange and the third flange; a fourth flange parallel to the third flange and displaced away from the third flange in the first direction; a second core passage extending from the third flange to the fourth flange, the second core passage perpendicular to the third flange and the fourth flange; a second winding surface surrounding the second core passage between third flange and the fourth flange; a first pin rail and a second pin rail, the first pin rail and the second pin rail extending perpendicularly from the first flange in a second direction opposite the first direction, the first pin rail spaced apart from the second pin rail by a core channel, the first core passage extending to the core channel; at least a first coil wound around the first winding surface; at least a second coil wound around the second winding surface; a first E-core having a core body, and having a respective first outer leg, a respective second outer leg and a respective center leg, each leg having a respective end surface, the core body of the first E-core inserted into the core channel and the center leg of the first E-core inserted into the first core passage with the end surface of the center leg positioned proximate to the second flange; a second E-core having a respective first outer leg, a respective second outer leg and a respective center leg, each leg having a respective end surface, the center leg of the second E-core inserted into the second core passage with the end surface of the center leg positioned proximate to the third flange; and an I-core positioned in the I-core receiving slot, the I-core having a first planar side positioned against the end surfaces of the first outer leg and the second outer leg of the first E-core, the I-core having a second planar side positioned proximate to and spaced apart from the end surfaces of the first outer leg, the second outer leg and the center leg of the second E-core.

8. The magnetic assembly of claim 7, wherein the center leg of the first E-core is shorter than the outer legs of the first E-core by a length difference such that an end surface of the center leg of the first E-core is spaced apart from the first planar surface of the I-core by a gap distance equal to the length difference.

9. The magnetic assembly of claim 7, wherein: the first coil, the first E-core and at least a first portion of the I-core comprise a first inductive device; and the second coil, the second E-core and at least a second portion of the I-core comprise a second inductive device.

10. The magnetic assembly of claim 9, wherein: the first inductive device is a transformer; and the second inductive device is an inductor.

11. The magnetic assembly of claim 7, further including a gap spacer positioned between the second planar side of the I-core and the end surfaces of the first outer leg, the second outer leg and the center leg of the second E-core, the gap spacer having a thickness selected to provide a predetermined gap spacing between the end surfaces of the first outer leg, the second outer leg and the center leg of the second E-core and the second planar side of the I-core.

12. The magnetic assembly of claim 11, wherein the gap spacer comprises a polyester film material having a thickness selected to provide the predetermined gap.

13. The magnetic assembly of claim 12, wherein the thickness of the gap spacer is in a range between 0.0025 inch and 0.0200 inch.

14. The magnetic assembly of claim 11, wherein the gap spacer comprises a polyethylene terephthalate (PET) film.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

(1) FIG. 1 illustrates a circuit diagram showing a DC-DC converter as conventionally known in the art.

(2) FIG. 2 illustrates a perspective view of a conventional inductor.

(3) FIG. 3 illustrates an exploded perspective view of the inductor of FIG. 2.

(4) FIG. 4 illustrates a perspective view of a conventional output transformer.

(5) FIG. 5 illustrates an exploded perspective view of the transformer of FIG. 2.

(6) FIG. 6 illustrates a plan view of the inductor of FIG. 2 and the output transformer of FIG. 4 positioned on a printed circuit board in a longitudinal relationship.

(7) FIG. 7 illustrates a plan view of the inductor of FIG. 2 and the output transformer of FIG. 4 positioned on a printed circuit board in a lateral relationship.

(8) FIG. 8 illustrates a perspective view of a combined magnetic assembly with an inductor and an output transformer sharing a single bobbin, the view referenced to X-, Y-, and Z-axes.

(9) FIG. 9 illustrates the combined magnetic assembly of FIG. 8; the view flipped 180 degrees about the X-axis and then rotated 90 degrees about the Y-axis to show the surfaces hidden in FIG. 8.

(10) FIG. 10 illustrates a front cross-sectional view of the combined magnetic assembly of FIG. 8 taken along the line 10-10 in FIG. 8.

(11) FIG. 11 illustrates an exploded perspective view of the combined magnetic assembly of FIG. 8.

(12) FIG. 12 illustrates a perspective view of the inductor E-core of the magnetic assembly as oriented in FIG. 8, the view referenced to the X-, Y-, and Z-axes of FIG. 8.

(13) FIG. 13 illustrates the inductor E-core of FIG. 12 flipped 180 degrees about the X-axis and then rotated 90 degrees about the Z-axis to show the surfaces hidden in FIG. 12.

(14) FIG. 14 illustrates a perspective view of the transformer E-core of the magnetic assembly as oriented in FIG. 8, the view referenced to the X-, Y-, and Z-axes of FIG. 8.

(15) FIG. 15 illustrates the transformer E-core of FIG. 14 flipped 180 degrees about the X-axis and then rotated 90 degrees about the Z-axis to show the surfaces hidden in FIG. 14.

(16) FIG. 16 illustrates a perspective view of the I-core of the magnetic assembly as oriented in FIG. 8, the view referenced to the X-, Y-, and Z-axes of FIG. 8.

(17) FIG. 17 illustrates the I-core of FIG. 21 flipped 180 degrees about the X-axis and then rotated 90 degrees about the Z-axis to show the surfaces hidden in FIG. 16.

(18) FIG. 18 illustrates a perspective view of the bobbin of the combined magnetic assembly of FIG. 8 prior to installation of the coils and prior to insertion of the cores, the view referenced to the X-, Y-, and Z-axes of FIG. 8.

(19) FIG. 19 illustrates a perspective view of the bobbin of FIG. 18 flipped 180 degrees about the X-axis and then rotated 180 degrees about the Z-axis with respect to the view in FIG. 18.

(20) FIG. 20 illustrates a front elevational view of the bobbin of FIG. 18.

(21) FIG. 21 illustrates a right elevational view of the bobbin of FIG. 18.

(22) FIG. 22 illustrates a top plan view of the bobbin of FIG. 18.

(23) FIG. 23 illustrates a bottom plan view of the bobbin of FIG. 18.

(24) FIG. 24 illustrates a schematic representation of the front cross-sectional view of the combined magnetic assembly in accordance with FIG. 11, the view annotated to illustrate the flux pattern in the resonant inductor E-core in dash-dot lines, the flux pattern in the output transformer E-core in dash-dot-dot lines, and the shared flux pattern in the common I-core in dashed lines.

DETAILED DESCRIPTION OF THE INVENTION

(25) An exemplary invention to the problem disclosed in FIGS. 1-7 is illustrated by a combined magnetic assembly 500 in FIGS. 8-24.

(26) FIGS. 8-11 illustrate views of the combined magnetic assembly 500 with a resonant inductor 510 and an output transformer 520 sharing a single bobbin 530. In the drawings, the X-axis, Y-axis and Z-axis are shown for reference to assist in visualizing the orientations of the structures.

(27) The inductor 510 and the transformer 520 are installed in the bobbin 530 with the inductor “stacked” on top of the transformer. The inductor includes an inductor coil 540 positioned around a first (upper) portion of the bobbin. The inductor further includes an inductor E-core 542 positioned with respect to the inductor coil. The transformer includes a transformer coil 550 positioned around a second (lower) portion of the bobbin. The transformer further includes a transformer E-core 552 positioned with respect to the transformer coil. The inductor and the transformer share a common I-core 560 positioned between the two E-cores as described below. The two E-cores and the I-core comprise a suitable ferromagnetic material such as, for example, silicon steel, a ferrite material, or other suitable material. In the illustrated embodiment, a gap spacer 570 is positioned between the I-core and the inductor E-core.

(28) As shown in FIGS. 12 and 13, the E-core 542 of the inductor 510 includes a main body 600, a first outer leg 602, a second outer leg 604 and a center leg 606. The main body has an outer surface 610 and an inner surface 612. As illustrated, the outer surface has a length L (in a direction parallel to the Z-axis) and a width W1 (in a direction parallel to the X-axis). The main body has a thickness T (in a direction parallel to the Y-axis) between the inner surface and the outer surface. The three legs extend perpendicularly from the inner surface. The main body and the three legs have a first (front) common side surface 614 and a second (rear) common side surface 616.

(29) The first outer leg 602 of the inductor E-core 542 extends from the inner surface 612 of the main body 600 of the E-core to a first outer leg end surface 620. The first outer leg has an outer lateral surface 622 and an inner lateral surface 624. The first outer leg has a width W2 between the two lateral surfaces.

(30) The second outer leg 604 of the inductor E-core 542 extends from the inner surface 612 of the main body 600 of the E-core to a second outer leg end surface 630. The second outer leg has an outer lateral surface 632 and an inner lateral surface 634. In the illustrated embodiment, the second outer leg also has the width W2 between the two lateral surfaces corresponding to the width of the first outer leg 602.

(31) The center leg 606 of the inductor E-core 542 extends from the inner surface 612 of the main body 600 of the E-core to a center leg end surface 640. The center leg has a first lateral surface 642 that faces the inner lateral surface 624 of the first outer leg 602 and has a second lateral surface 644 that faces the inner lateral surface 634 of the second outer leg 604. The center leg has a width W3 between the two lateral surfaces. In the illustrated embodiment, the width W3 of the center leg may be approximately twice the width W2 of the two outer legs.

(32) In the illustrated embodiment, the center leg 606 of the inductor E-core 542 has substantially the same length as the lengths of the two outer legs 602, 604 of the inductor E-core with respect to the inner surface 612 of the main body 600 of the inductor E core such that the respective end surfaces of the three legs are aligned. The alignment is indicated by a dashed line 646 that passes through the edges of the three end surfaces. The end surfaces of the three legs are spaced apart from the inner surface of the main body of the inductor E-core by a first height H1.

(33) As shown in FIGS. 14 and 15, the E-core 552 of the transformer 520 includes a main body 650, a first outer leg 652, a second outer leg 654 and a center leg 656. The main body has an outer surface 660 and an inner surface 662. As illustrated, the outer surface has the length L and the width W1 corresponding to the length and width of the outer surface 610 of the main body 600 of the inductor E-core 542. In the illustrated embodiment, the main body of the transformer E-core may have the same thickness T between the inner surface and the outer surface as the thickness of the main body of the inductor E-core. The three legs extend perpendicularly from the inner surface. The main body and the three legs of the transformer E-core have a first (front) common side surface 664 and a second (rear) common side surface 666.

(34) The first outer leg 652 of the transformer E-core 552 extends from the inner surface 662 of the main body 650 to a first outer leg end surface 670. The first outer leg has an outer lateral surface 672 and an inner lateral surface 674. In the illustrated embodiment, the first outer leg has the width W2 between the two lateral surfaces corresponding to the width of the first outer leg 602 of the inductor E-core 510.

(35) The second outer leg 654 of the transformer E-core 552 extends from the inner surface 662 of the main body 650 of the E-core to a second outer leg end surface 680. The second outer leg has an outer lateral surface 682 and an inner lateral surface 684. In the illustrated embodiment, the second outer leg also has the width W2 between the two lateral surfaces corresponding to the width of the first outer leg 652.

(36) The center leg 656 of the transformer E-core 552 extends from the inner surface 662 of the main body 650 of the E-core to a center leg end surface 690. The center leg has a first lateral surface 692 that faces the inner lateral surface 674 of the first outer leg 652 and has a second lateral surface 694 that faces the inner lateral surface 684 of the second outer leg 654. In the illustrated embodiment, the center leg has the width W3 between the two lateral surfaces corresponding to the width of the center leg 606 of the inductor E-core 510.

(37) In the illustrated embodiment, the lengths of the two outer legs 652, 654 of the transformer E-core 552 with respect to the inner surface 662 of the main body 650 of the transformer E-core are substantially the same such that the respective end surfaces of the two outer legs are aligned as indicated by a first dashed line 696 that passes through the edges of the two end surfaces. Thus, the end surfaces of the two outer legs are spaced apart from the inner surface of the main body of the transformer E-core by a second height H2.

(38) In the illustrated embodiment, the center leg 656 of the transformer E-core 552 is shorter than the two outer legs 652, 654 with respect to the inner surface 662 of the main body 650 of the transformer E-core as illustrated by a second dashed line 698 that passes through the edge of the end surface of the center leg. The second dashed line is offset from the first dashed line by a gap G. The difference in length (e.g., the gap G) may be exaggerated in FIGS. 14 and 15 for the purpose of illustrating the difference. For example, the gap may range from 0.001 inch to 0.05 inch).

(39) In the illustrated embodiment, the outer legs 602, 604 of the inductor E-core 542 are shorter than the outer legs 652, 654 of the transformer E-core 552; however, in other embodiments, the outer legs of the inductor E-core may be as long as or may be longer than the outer legs of the transformer E-core. The lengths of the outer legs of the E-cores of the inductor and the transformer are determined in part by the lengths of the respective coil windings.

(40) In the illustrated embodiment, the center legs 606, 656 of the two E-cores 542, 552 have rectangular cross sections; however, in other embodiments, the center legs may be configured to have other cross sections (e.g., circular cross sections).

(41) As illustrated in FIGS. 16 and 17, the I-core 560 is a regular parallelepiped having a first (upper) major planar surface 700 and a second (lower) major planar surface 702. The two major surfaces have the length L and the width W1 corresponding to the lengths and the widths of the outer surfaces 610, 660, respectively, of the inductor E-core 542 and the transformer E-core 552. The two major surfaces are spaced apart by a height H3 to form a first (front) lateral surface 704 and a second (rear) lateral surface 706 along the width of the two major surfaces and to form a first end surface 710 and a second end surface 712 along the length of the two major surfaces. In the illustrated embodiment, the height H3 of the I-core is similar to the thickness T of the main bodies 600, 650 of the two E-cores; however, the thickness of the I-core may be greater or less than the main body thicknesses in other embodiments.

(42) As shown in the exploded view of FIG. 11, the gap spacer 570 includes a relatively thin material having planar surfaces (one shown) generally corresponding to the shape and size of the two planar surfaces 700, 702 of the I-core 560. For example, in one embodiment, the gap spacer comprise a polyester film material (e.g., a Mylar® polyethylene terephthalate (PET) film) having a thickness of between 0.0025 inch to 0.0200 inch). As discussed below, the thickness of the gap spacer is selected to provide a desired gap distance between the legs 602, 604, 606 of the inductor E-core 542 and the upper planar surface 700 of the I-core.

(43) As shown in FIGS. 19-23, the bobbin 530 includes a first (lower) flange 800. The first flange has a lowermost surface 802 and an uppermost surface 804. The first flange supports a first pin rail 810 and a second pin rail 812. Each pin rail has a plurality of pins 814 extending downward from the respective pin rail perpendicular to the first flange. The first pin rail includes a first lower channel wall 816 that extends from the lowermost surface of the first flange. The second pin rail includes a second lower channel wall 818 that also extends from the lowermost surface of the first flange. In the illustrated embodiment, each lower channel wall extends downward from the lowermost surface of the first flange by a height H4. The height is selected to be at least as great as the thickness T of the main body 650 of the transformer E-core 552. The channel walls also serve as standoffs. When the magnetic assembly 500 is installed on a printed circuit board (not shown), only a lowermost portion of each pin is inserted into through-holes in the printed circuit board. Thus, an uppermost portion of each pin is available to receive wiring without interfering with the later installation of the magnetic assembly.

(44) For the purposes of the following discussion the first pin rail 610 is located at the front of the bobbin 530 and extends from the left side to the right side of the bobbin as positioned in FIGS. 18 and 20. The second pin rail 612 is located at the rear of the bobbin and is parallel to the first pin rail.

(45) A second flange 820 is spaced apart vertically from the first flange 800. The second flange has a lowermost surface 822 that faces the first flange and has an uppermost surface 824 that faces away from the first flange (e.g., upward when the bobbin is positioned as shown in the drawings). A first winding portion 830 is defined between the uppermost surface 804 of the first flange and the lowermost surface of the second flange. In the illustrated embodiment, the first winding portion is defined by four rectangular outer surfaces 832. Corresponding inner surfaces 834 define a first passage 840 (FIG. 19) between the lowermost surface of the first flange and the uppermost surface of the second flange. The outer surfaces define the base of the first winding portion onto which the first layer of the transformer coil 550 is wound. In the illustrated embodiment, the first passage has a rectangular profile to match the profile of the center leg 656 of the transformer E-core 552 described above; however, in other embodiments, the passage may have a different profile (e.g., circular) to match a different profile of the center leg of the transformer E-core. In the illustrated embodiment, the first passage has a width slightly greater than the width W3 of the center leg of the transformer E-core and has a length slightly greater than the length L of the transformer E-core such that the center leg of the transformer E-core fits snugly within the passage when inserted into the passage.

(46) The first passage 840 has a height between the lowermost surface 802 of the first flange 800 to the uppermost surface 824 of the second flange 820 that is substantially the same as the height H2 of the outer legs 652, 654 of the transformer E-core 552 such that when the inner surface 662 of the main body 660 of the transformer E-core is positioned against the lowermost surface of the first flange, the exposed ends of the outer legs are substantially coincident with the uppermost surface of the second flange. To assure a continuous magnetic path between the end surfaces 670, 680 of the first and second outer legs of the transformer E-core and the second (lower) planar surface 702 of the I-core 560, the height of the passage may be slightly shorter than the height H2 of the two outer legs so that at least a short length of each outer leg extends beyond the uppermost surface of the second flange.

(47) A first spacer wall 850 (FIGS. 20 and 21) extends perpendicularly upward from the uppermost surface 824 of second flange 820 along the front of the bobbin 530. A second spacer wall 852 (FIG. 21) also extends perpendicularly upward from the uppermost surface of the second flange along the rear of the bobbin. The first and second spacer walls are parallel to each other and are spaced apart from each other across the length of the first passage 840 such that respective inner surfaces of the spacer walls are coincident with the inner surfaces 834 that define the passage. In the illustrated embodiment, each spacer wall has a width approximately the same as the width of the first passage. Each spacer wall has a common spacer wall height.

(48) The first spacer wall 850 and the second spacer wall 852 extend to a lowermost surface 862 of a third flange 860. The third flange has an uppermost surface 864. The sides of the bobbin between the first spacer wall and the second spacer wall are open to define a horizontally disposed I-core receiving passage (or slot) 866 (FIG. 2) between the two spacer walls and between the second flange 840 and the third flange. The spacer wall height between the second flange and the third flange is slightly greater than the height H3 of the I-core 560 such that the I-core receiving passage accommodates the combined height of the I-core and thickness of the gap spacer 570.

(49) A fourth flange 870 is spaced apart vertically from the third flange 860. The fourth flange has a lowermost surface 872 that faces the third flange and has an uppermost surface 874 that faces away from the third flange (e.g., upward when the bobbin is positioned as shown in FIG. 18). A second winding portion 880 is defined between the uppermost surface of the third flange and the lowermost surface of the fourth flange. In the illustrated embodiment, the second winding portion is defined by four rectangular outer surfaces 882 (one outer surface is shown in each of FIGS. 20 and 21). Corresponding rectangular inner surfaces 884 define a second passage 890 between the lowermost surface of the third flange and the uppermost surface of the fourth flange. The outer surfaces define the base of the second winding portion onto which the first layer of the inductor coil 540 is wound.

(50) The second passage 890 extends through the third flange 860 and the fourth flange 870 from the lowermost surface 862 of the third flange to the uppermost surface 874 of the fourth flange. The second passage is sized to receive the center leg 606 of the inductor E-core 542. In the illustrated embodiment, the second passage has a length in the direction from the front of the bobbin 530 to the rear of the bobbin that is slightly greater than the length L of the center leg of the inductor E-core. The second passage has width in the direction from the left side to the right side of the bobbin that is slightly greater than the width W3 of the center leg of the inductor E-core. If the center leg of the inductor E-core has a different cross section (e.g., a circular cross section), the second passage may be configured to have a corresponding different cross section. If, for example, the second passage has a circular cross section, the second winding surface may be configured to be cylindrical.

(51) The second passage 890 has a height between the lowermost surface 862 of the third flange 860 to the uppermost surface 874 of the fourth flange 870 that is about the same as the height H1 of the three legs 602, 604, 606 of the inductor E-core 542 such that when the inner surface 612 of the main body 600 of the inductor E-core is positioned against the uppermost surface of the fourth flange, the exposed end surfaces 620, 630, 640 of the three legs of the inductor E-core are substantially coincident with the lowermost surface of the third flange. The height of the passage may be slightly less than the height of the three legs to assure that the end surfaces of the three legs are positioned against the gap spacer 570 when the center leg 606 is fully inserted into the passage.

(52) A first inductor core channel wall 900 and a second inductor core channel wall 902 extend perpendicularly from the uppermost surface 874 of the fourth flange 870. In the illustrated embodiment, the first inductor core channel wall is aligned with the first spacer wall 850. The second inductor core channel wall is aligned with the second spacer wall 852. Accordingly, the two inductor core channel walls are mutually parallel with each other and are spaced apart across the length of the second passage 890 by a length generally corresponding to the common length L of the main body 600 and the legs 602, 604, 606 of the inductor E-core. In the illustrated embodiment, the two inductor core channels have a common height. As illustrated, the common height of the two inductor core channels may be approximately half the thickness T of the inductor core main body; however, the height may be varied.

(53) Each of the third flange 860 and the fourth flange 870 includes a plurality of wiring slots 920 (e.g., four in each flange). Two of the wiring slots of each flange are positioned at the front of the bobbin 530, and two of the wiring slots are positioned at the rear of the bobbin. The fourth flange further includes a plurality of wiring guide posts 922 (e.g., four posts) that extend vertically upward from the uppermost surface 874 of the fourth flange. One of the posts is positioned at each of the four corners of the fourth flange. The third flange further includes a plurality of wiring notches 924 (e.g., four notches) positioned near the four corners of the third flange. The second flange 820 also includes a plurality of wiring notches 926 (e.g., four notches) positioned near the four corners of the second flange. In the illustrated embodiment, the wiring notches of the second flange are in substantial alignment with the wiring notches of the third flange.

(54) The first flange 800 includes a plurality of wiring notches 930 (e.g., six notches). Three of the wiring notches are positioned along the front of the bobbin 530; and three of the wiring notches are positioned along the rear of the bobbin. The three front wiring notches extend vertically from the uppermost surface 804 of the first flange through the first pin rail 810. The three rear wiring notches extend vertically from the uppermost surface of the first flange through the second pin rail 812.

(55) The transformer coil 550 is wound around the first winding portion 830 in a conventional manner. The coil includes the primary and secondary windings of the transformer 520. As shown in FIG. 9, terminal ends 950 of the windings of the transformer coil pass through selected notches 930 and are connected to selected pins 814 of the first (front) pin rail 810, the second (rear) pin rail 812, or both pin rails. In the illustrated example, four of the terminal ends are connected to pins in the second pin rail and two of the terminal ends are connected to pins in the first pin rail.

(56) As further shown in FIGS. 9 and 11, the inductor coil 540 is wound around the second winding portion 880 in a conventional manner. In the illustrated embodiment, each of two terminal ends 960 of the winding in the inductor coil passes through a respective winding slot 920 of the fourth flanges 870; wraps around a respective winding post 922; passes through a respective wiring notch 924 of the third flange; passes through a respective wiring notch 926 of the second flange 820; passes through a respective wiring notch 930 of the first flange 800; and is connected to a respective pin 814 of the first pin rail 810. Other wire routing configurations and pin selections can also be used.

(57) The combined magnetic assembly 500 is completed by inserting the transformer E-core 552, the inductor E-core 542, the I-core 560 and the gap spacer 570 into the bobbin 530. The I-core and the gap spacer are inserted into the I-core receiving passage 866 with the second (lower) planar surface 702 of the I-core facing downward toward the upper surface 824 of the second flange 820. The gap spacer is positioned between the first (upper) planar surface 700 of the I-core and the lowermost surface 862 of the third flange 860.

(58) The center leg 656 of the transformer E-core 552 is inserted into the first passage 840 of the bobbin 530 from the bottom of the bobbin. The transformer E-core is fully inserted with the inner surface 662 of the main body 650 of the transformer E-core adjacent to the lowermost surface 822 of the first flange 800. The end surfaces 670, 680 of the outer legs 652, 654 of the transformer E-core extend so that the end surfaces are at least flush with the uppermost surface 624 of the second flange 620 and may extend slightly beyond the uppermost surface to assure solid contact with second (lower) planar surface 702 of the I-core 570. The main body 650 of the transformer E-core fits snugly between the inner surface of the channel wall 816 of the first pin rail 810 and the inner surface of the channel wall 818 of the second pin rail 812. As described above, the heights of the pin rails with respect to the lowermost surface 802 of the first flange are selected to be at least as great as thickness T of the main body of the E-core such that the main body of the E-core does not extend below the channel walls. Thus, the mail body of the E-core does not interfere with the insertion of the pins 814 into a printed circuit board (not shown).

(59) The center leg 606 of the inductor E-core 542 is inserted into the second passage 890 of the bobbin 530 from the top of the bobbin. The inductor E-core is fully inserted with the inner surface 612 of the main body 600 of the inductor E-core adjacent to the uppermost surface 874 of the fourth flange 870. When fully inserted, the end surface 640 of the center leg and the end surfaces 620, 630 of the two outer legs 602, 604 of the inductor E-core are at least substantially flush with the lowermost surface 862 of the third flange 860. The end surfaces may extend slightly beyond the lowermost surface to assure that the end surfaces contact the gap spacer 570 and are thus spaced apart from the I-core by no more than the gap distance provided by the gap spacer. The main body of the inductor E-core fits snugly between the inner surfaces of the first inductor core channel 900 and the second inductor core channel 902.

(60) The gap spacer 570 provides an equal gap between the first planar surface 700 of the I-core 560 and the end surfaces 620, 630, 640 of the three legs 602, 604, 606 of the inductor E-core 542. The equal gap reduces the flux interference between the transformer 520 and the inductor 510. The gap spacer also aids in forcing the second (lower) planar side 702 of the I-core against the end surfaces 670, 680 of the outer legs 652, 654 of the transformer E-core 552 so that no gap is formed between the outer legs of the transformer E-core and the I-core. As discussed above, the center leg 656 of the transformer E-core is shorter than the outer legs of the transformer E-core such that a single gap (G) is formed between the end surface 690 of the center leg of the transformer E-core and the second planar surface of the I-core.

(61) The effect of the foregoing construction is illustrated in FIG. 24, which is a schematic representation of the front elevational view of the combined magnetic assembly 500. The schematic representation shows a flux pattern 990 in the inductor E-core in dash-dot lines; shows a flux pattern 992 in the transformer E-core in dash-dot-dot lines; and shows a flux pattern 994 in the common I-core in dashed lines. As illustrated, the inductor and the transformer produce a shared flux pattern in the I-core.

(62) As described above, the combined magnetic assembly 500 integrates the functions of the resonant inductor 510 and the output transformer 520 into a single assembly with a smaller printed circuit footprint than two separate devices. The resonant inductor and the output transformer are stacked to provide the reduced footprint. A single bobbin 530 is used for both the resonant inductor and the output transformer. The combined magnetic assembly shares the common I-core 560 positioned between the ends of the legs of the two E-cores 542, 552 within the I-core receiving passage 866 in the bobbin. The two E-cores and the common I-core form an “E-I-E” structure with the I-core providing a shared flux path for each of the E-cores. The combined magnetic assembly reduces the printed circuit board area needed for the two functions (resonant inductor and output transformer). By requiring only two E-cores and one shared I-core, the overall volume of core material is reduced. By using only a single bobbin for both functions, the overall costs of material are reduced.

(63) The previous detailed description has been provided for the purposes of illustration and description. Thus, although there have been described particular embodiments of the present invention of a new and useful “Output Transformer and Resonant Inductor in a Combined Magnetic Structure,” 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.