Magnetic element employing graphite laminate to enhance heat transfer and heat dissipation

Abstract

An air gap is formed in the magnetic core of the inductor, and heat is prevented from being transferred from the upper magnetic core to the lower magnetic core through the air gap. The cross section of the magnetic core is E-shaped, a wire is wound on the central column or the framework, and no wire is wound on the left supporting leg and the right supporting leg. The graphite flakes are coated with adhesives, and the graphite flakes are attached to the outer sides of the left supporting foot and the right supporting foot. The graphite adhesive laminate spans the air gap, enabling heat transfer through the air gap. The graphite flake is not attached to the skeleton. Thermally conductive particles, such as carbon nanotubes, may be added to the binder. A plurality of inductors may be laterally stacked together. The radiator connected to the lower magnetic core can conduct heat through the graphite flakes crossing the air gaps, and therefore heat generated by the upper magnetic core is dissipated.

Description

[Technical field]

[0001] The present invention relates to an inductor having a magnetic core, and more particularly to heat transfer across an air gap in the magnetic core of an inductor. [Background technology]

[0002] Magnetic components such as inductors and transformers are commonly used in power converters, such as switched-mode power supplies (SMPS).

[0003] Figure 1 shows an inductor with a magnetic core. The inductor has a long insulated wire wound around its core. A transformer is an inductor that has two or more windings on the core, such as a primary and a secondary, that are electrically isolated but magnetically coupled. Traditionally, the core is made of iron or ferrite and is cylindrical in shape.

[0004] A more advanced inductor has an E-shaped core or E-core. In FIG1 , a wire 120 is wound around a central column or skeleton 106 of the E-core. The E-core has an upper core 104 and a lower core 108, each of which has a cross-section that resembles the letter E. For example, the cross-section of the upper core 104 looks like the letter E rotated downward, while the cross-section of the lower core 108 looks like the letter E rotated upward ( FIG4 ).

[0005] The bobbin 106 is located at the center of the E-shaped cross section, while the sides of the upper core 104 and the lower core 108 partially surround the wire 120. In various different E-cores, the bobbin 106 can be square or round. The wire 120 is easier to wrap around the round bobbin 106 than the square bobbin 106. E-core inductors offer lower core losses even at higher temperatures; higher efficiency due to better magnetic coupling; lower manufacturing costs; compact design to overcome space limitations; and easier assembly for prototyping and testing.

[0006] The upper core 104 and the lower core 108 are separated by an air gap 100. The air gap 100 prevents saturation and allows for higher magnetic flux and energy storage.

[0007] FIG2 shows an inductor core. The wire 120 has been removed in FIG2 to show the upper core 104 and the lower core 108 in more detail. The skeleton 106 is not rectangular but cylindrical to better wind the wire 120 into a coil shape. There are air gaps 100 on both sides of the skeleton 106 and the upper core 104 and the lower core 108.

[0008] FIG3 shows an inductor mounted on a heat sink. The heat sink 112 may be directly connected to the bottom of the lower magnetic core 108 as shown, or may be indirectly connected to the bottom of the lower magnetic core 108 via a printed circuit board (PCB) having a metal heat pipe or other heat conducting component on the printed circuit board to conduct heat from the lower magnetic core 108 to the heat sink 112.

[0009] Note that the upper core 104 is not connected to any heat sink. High density power converters are usually narrow and do not allow for heat sinks to be mounted on both the upper and lower cores of the inductor.

[0010] FIG4 is a cross section of the inductor of FIG1-3. The upper magnetic core 104 is E-shaped and is separated from the E-shaped lower magnetic core 108 by an air gap 100. The skeleton 106 is also separated by the air gap 100. The wire 120 (not shown) is wound around the skeleton 106 and is located in the gap 116 between the skeleton 106 and the upper magnetic core 104 and the lower magnetic core 108.

[0011] The heat sink 112 is connected to the bottom of the lower magnetic core 108. The heat sink 112 can dissipate heat from the lower magnetic core 108. Airflow can be forced through the fins on the lower surface of the heat sink 112 to enhance the heat dissipation effect. However, since the air gap 100 hinders heat transfer, the heat generated in the upper magnetic core 104 cannot be easily transferred to the heat sink 112.

[0012] FIG5 illustrates heat transfer within the inductor of FIGS. 1-4. When current is passed through the wire 120, the wire 120 heats up due to the resistance in the long wire. In addition, when alternating current (AC) is applied to the wire 120, the magnetic flux reverses as the direction of the AC current changes. These flux reversals may have hysteresis, which can generate eddy currents within the upper core 104 and the lower core 108. The heat generated by these eddy currents is greatest in the skeleton 106 where the magnetic flux is most dense.

[0013] The heat generated by the resistance in the wire 120 and the magnetic flux reversal in the bobbin 106 may increase the temperature of the upper core 104 and the lower core 108. However, the heat of the lower core 108 may be transferred to the heat sink 112, thereby reducing the temperature of the lower core 108. However, the air gap 100 prevents or significantly reduces the heat transfer from the upper core 104 to the lower core 108. Therefore, the temperature of the upper core 104 may be higher than that of the lower core 108.

[0014] The temperature of the upper core 104 may be 40 degrees higher than that of the lower core 108. Such higher temperatures in the upper core 104 are undesirable because overheating can cause failure and shorten the useful life of the inductor and other nearby components.

[0015] An inductor with improved heat transfer is needed. An inductor with enhanced heat transfer across the air gap between the upper and lower E-cores is needed. An air gap inductor with a laminate coating is needed to transfer heat across the air gap.

Brief Description of the Drawings

[0016] Figure 1 shows an inductor with a magnetic core.

[0017] Figure 2 shows the inductor core.

[0018] Figure 3 shows the inductor mounted to a heat sink.

[0019] 4 is a cross-section of the inductor of FIGS. 1-3 .

[0020] FIG. 5 shows heat conduction within the inductor of FIG. 1-4 .

[0021] Figure 6 An E-core inductor is shown with a thermally conductive laminate attached to the outer surface of the core.

[0022] Figure 7 An E-core inductor is shown with a graphite bonded laminate attached to the outer surface of the E-core.

[0023] Figure 8 A cross section of an E-core inductor with graphite sheets attached to the outer surface to transfer heat across the air gap.

[0024] Fig. 9 The heat transfer across the graphite sheet and the air gap is highlighted.

[0025] Fig.10 The graphite laminate is shown also attached to the front and rear surfaces of the E-core side legs.

[0026] Fig.11 Shown is a graphite laminate attached to all exterior surfaces of an E-core.

[0027] Fig.12 More details of the graphite laminate are shown.

[0028] Figure 13 shows graphene layers in graphite.

[0029] Fig.14 The process of forming a bonding layer on a graphite sheet to form a graphite laminate is shown.

[0030] Fig.15 The graphite laminate is shown in more detail.

[0031] Figures 16A-16B A single graphite laminate is shown attached to the four outer sides of the inductor.

[0032] Fig.17The attachment of a single large graphite sheet to the upper core 32 and the lower core 34 is highlighted.

[0033] Fig.18 Shown are 3 inductor cores laminated together using laminated graphite sheets.

[0034] Fig.19 A stacked inductor is shown with graphite rings between the inductor cores.

[0035] Fig. 20 Shown is a stacked inductor connected to a heat sink.

[0036] Figures 21A-21B Different core types are shown.

[0037] Fig. 22 A stacked inductor with five cores is shown. [Specific implementation method]

[0038] The present invention relates to improvements in inductors. The following description is intended to enable one of ordinary skill in the art to make and use the invention in the context of a particular application and its requirements. Various modifications to the preferred embodiments will be apparent to those skilled in the art, and the general principles defined herein may also be applied to other embodiments. Therefore, the present invention is not intended to be limited to the specific embodiments shown and described, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0039] Figure 6 An E-core inductor is shown with a thermally conductive laminate attached to the outer surface of the core. Inductor 30 is an E-core inductor with an upper core and a lower core separated by an air gap 10. A long wire (not shown) is wound around the bobbin 106 of the inductor 30. The side legs of the upper and lower cores partially surround the coils wound around the bobbin 106.

[0040] The graphite sheets 22, 24, 26, 28 are laminated sheets, each of which has a graphite layer and an adhesive layer laminated together. The adhesive layer of the graphite sheet 22 is pressed on the outer surface of the right leg of the upper and lower magnetic cores. The adhesive layer of the graphite sheet 24 is pressed on the outer surface of the left leg of the upper and lower magnetic cores. The adhesive layer of the graphite sheet 26 is pressed on the outer top surface of the upper magnetic core, and the adhesive layer of the graphite sheet 28 is pressed on the outer top surface of the lower magnetic core.

[0041] Graphite sheet 22 spans across the air gap 10 that separates the right leg of the upper and lower cores. Similarly, graphite sheet 24 spans across the air gap 10 that separates the left leg of the upper and lower cores. The adhesive layer ensures that the graphite layer of the laminate adheres to the outer surface of the core.

[0042] Figure 7An E-core inductor is shown, in which the outer surface of the E-core is attached with a graphite bonded laminate. The four outer surfaces of the upper and lower E-cores of the inductor 30 are attached with graphite sheets 22, 24, 26, 28, respectively. Graphite has good thermal conductivity and can conduct heat from the upper core to the lower core through the air gap 10. The graphite sheet 22 passes through the air gap 10 on the right side of the E-core, and the graphite sheet 24 passes through the air gap 10 on the left side of the E-core.

[0043] Figure 8 1 is a cross-sectional view of an E-type core inductor having a graphite sheet attached to its outer surface for transferring heat across the air gap. The upper core 32 and the lower core 34 are E-type ferrite cores with a long wire (not shown) wound around their skeletons. The graphite sheet 22 is attached to the outer surface of the right leg of the upper core 32 and the lower core 34 so that the graphite sheet 22 covers the right side of the air gap 10. The graphite sheet 24 is attached to the outer surface of the left leg of the upper core 32 and the lower core 34 so that the graphite sheet 24 covers the left side of the air gap 10.

[0044] Graphite sheet 26 is attached to the top surface of upper core 32 by adhesive, while graphite sheet 28 is attached to the bottom surface of lower core 34 by adhesive. Heat sink 122 may be attached to graphite sheet 28 by another layer of adhesive, or may simply be pressed together and secured in place by connectors or fasteners such as screws or bolts.

[0045] Fig. 9 The heat conduction of the graphite sheet across the air gap is highlighted. During operation, the bobbins of the upper and lower cores 32, 34 heat up due to the eddy currents in the ferrite core and the resistive heating of the long wires wrapped around the bobbins. The heat from the bobbins flows outward through the upper core 32 to the left and right legs of the upper core 32. Some of the heat from the bobbins is also conducted to the graphite sheet 26 and then flows along the top of the inductor to the graphite sheets 22, 24 on both sides.

[0046] Part of the heat conducted along the top graphite sheet 26 and more heat conducted from the left leg of the upper magnetic core 32 is conducted to the left graphite sheet 24. The heat in the left graphite sheet 24 is conducted downward through the air gap 10 to the left leg of the lower magnetic core 34, or to the bottom graphite sheet 28 and the heat sink 112. Therefore, the heat of the upper magnetic core 32 skeleton is conducted to the heat sink 112 through the graphite sheets 26, 24, 28, and the heat sink can dissipate the heat into the air.

[0047] Additional heat conducted along the top graphite sheet 26 and more heat conducted from the right leg of the upper magnetic core 32 is conducted to the right graphite sheet 22. The heat in the right graphite sheet 22 is conducted downward through the air gap 10 to the right leg of the lower magnetic core 34, or to the bottom graphite sheet 28 and the heat sink 112. Therefore, the heat of the upper magnetic core 32 skeleton is also conducted through the graphite sheets 26, 22, 28 to the heat sink 112, and the heat sink can dissipate the heat into the air.

[0048] The graphite sheets 22, 24 act as a bridge across the air gap 10, allowing heat to be conducted from the upper core 32 to the lower core 34. Heat is more evenly distributed within the inductor, thereby reducing hot spots and thermal failures. The heat sink 112 can dissipate this heat when a fan forces air to flow over the fins on the heat sink 112.

[0049] Fig.10 The graphite laminate is also shown attached to the front and rear surfaces of the E-core side legs. The front graphite sheet 52 has a back adhesive layer that is pressed onto the front faces of the upper and lower cores 32, 34. The rear graphite sheet 54 has a front adhesive layer that is pressed onto the back faces of the upper and lower cores 32, 34. The front graphite sheet 52 and the rear graphite sheet 54 are not pressed onto the skeleton.

[0050] Fig.11 Graphite laminate is shown attached to all outer surfaces of the E-type core. Although the graphite laminate is not attached to the skeleton around which the long wire is wound, graphite sheets 22, 24, 26 are attached to the outer top and side surfaces of the upper core 32, and graphite sheets 22, 24, 28 are attached to the outer bottom and side surfaces of the lower core 34. The graphite sheets 22, 24 span the air gap.

[0051] The front graphite sheet 52 is a square ring attached to the front surface of the upper magnetic core 32 and the lower magnetic core 34. The rear graphite sheet 54 is a square ring attached to the rear surface or back surface of the upper magnetic core 32 and the lower magnetic core 34.

[0052] Fig.12 The graphite laminate is shown in more detail. The graphite sheet 22 is a laminate having a graphite layer 70 and an adhesive layer 74. The adhesive layer 74 may be an acrylic tape attached to the graphite layer 70. The thermal conductivity of the adhesive layer 74 may be enhanced by adding thermally conductive particles 76 to the adhesive layer 74. For example, the thermally conductive particles 76 may be carbon nanotubes.

[0053] FIG13 shows graphene layers in graphite. Graphite has multiple layers of graphene 102, which are stacked together like a stack of paper. However, the stacked blocks of graphene 102 may have different orientations. The carbon atoms of graphene 102 are in a planar hexagonal pattern. Graphite has good thermal conductivity and electrical conductivity.

[0054] Ferrite cores have good magnetic properties but are electrically insulating. If conductive graphite layers 22, 24 are placed in or between the air gaps, the magnetic flux across the air gap will be affected, reducing the effective saturation. Eddy currents may be generated in the conductors, resulting in higher power losses. When the graphite layers 22, 24 are located around or outside the air gap, the magnetic field is less disturbed and eddy current losses can be avoided. Since the core is usually made of a non-conductive material, such as ferrite, electrical conductors such as graphite layers 22, 24 across the air gap 10 will not cause any electrical shorts or problems.

[0055] Fig.14 The process of forming an adhesive layer on a graphite sheet to form a graphite laminate is shown. The graphite layer 70 may be a commercially available graphite sheet. When the graphite layer 70 is rolled by a conveyor belt or the like, a nozzle 77 sprays a liquid adhesive onto the upper surface of the graphite layer 70 to form an adhesive layer 74 on the upper surface of the graphite layer 70. Before the mixture is input to the nozzle 77, the thermally conductive particles 76 may be mixed with the liquid adhesive. The mechanical mixing may be supplemented with ultrasonic mixing to better disperse the thermally conductive particles 76 in the adhesive.

[0056] Therefore, the adhesive layer 74 contains thermally conductive particles 76 , which are randomly distributed in the adhesive layer 74 .

[0057] Fig.15 More details of the graphite laminate layers are shown. Adhesive layer 74 has been printed onto the upper surface of graphite layer 70. Microbumps 78 are provided on adhesive layer 74 to enhance adhesion. Microbumps 78 may be adhesive dots or bumps printed onto the upper surface of adhesive layer 74 by stenciling, special or 3D printing. Additional nozzle arrays may be used to print microbumps 78 onto adhesive layer 74.

[0058] Figures 16A-16B A single graphite laminate is shown glued to the four outer sides of the inductor. Fig.16A In the embodiment of the present invention, a single large graphite sheet coated with adhesive is folded on the dotted lines. Thus, folds are made between parts A, B, C, and D, which correspond to graphite sheets 24, 26, 22, and 28, respectively.

[0059] Cuts are made on the solid lines. Thus, cuts are made between the A2, B2, C2, and D2 portions of the rear graphite sheet 54. Cuts are also made between the A1, B1, C1, and D1 portions of the front graphite sheet 52.

[0060] exist Fig. 16B In the embodiment, after a single large graphite sheet is cut, the graphite sheet is applied to the outer surfaces of the upper magnetic core 32 and the lower magnetic core 34. The A portion forms the left graphite sheet 24, and the B portion forms the upper graphite sheet 26. The C portion forms the right graphite sheet 22, and the D portion forms the lower graphite sheet 28 (not shown).

[0061] Once portion A is applied to the left leg of upper and lower cores 32, 34, portion A1 may be folded over the left front edge of upper and lower cores 32, 34 and pressed against the front surface of upper and lower cores 32, 34 to form a portion of front graphite sheet 52. Portion C1 may be folded over the right front edge of upper and lower cores 32, 34 to form the right portion of front graphite sheet 52.

[0062] Portion B1 may then be folded onto the top front edge of upper core 32 and pressed onto the top front surface of upper core 32 to form a portion of front graphite sheet 52. Portion D1 may be folded onto the bottom front edge of lower core 34 to form the bottom portion of front graphite sheet 52.

[0063] Portions A2 and C2 may also be folded onto the back surfaces of the upper and lower cores 32 and 34, and then portion B2 may be folded onto the back surface of the upper core 32, and portion D2 may be folded onto the back surface of the lower core 34. Thus, a single graphite sheet may be folded, cut, and applied onto these outer surfaces of the upper and lower cores 32 and 34, thereby forming graphite sheets 22, 24, 26, 28, 52, 54 from a single graphite sheet.

[0064] Fig.17 The application of a single large graphite sheet to the upper and lower cores 32, 34 is highlighted. Part B is first pressed against the top surface of the upper core 32, such as with a pressure roller or a scraper. The applied pressure helps press the adhesive into the surface of the upper core 32, flatten the graphite sheet, and remove air bubbles. Then, after forming the top graphite sheet 26 using Part B, the large graphite sheet is folded over the left side surfaces of the upper and lower cores 32, 34, and this portion of the graphite sheet is then pressed against the left side surfaces of the upper and lower cores 32, 34 using a pressure roller or scraper to form the left graphite sheet 24.

[0065] Continuing to use the pressure roller or scraper, the right graphite sheet 22 and the bottom graphite sheet 28 can be formed. Then, the A1, B1, C1, and D1 parts are folded onto the front edges of the upper and lower magnetic cores 32 and 34 to form the front graphite sheet 52. Finally, the A2, B2, C2, and D2 parts are folded onto the rear edges of the upper and lower magnetic cores 32 and 34 to form the rear graphite sheet 54.

[0066] Fig.18 3 inductor cores are shown laminated together using laminated graphite sheets. Inductor 30 can be formed by pressing graphite adhesive sheets onto the outer surfaces of upper core 32 and lower core 34 to form right graphite sheet 22, left graphite sheet 24, upper graphite sheet 26, lower graphite sheet 28, front graphite sheet 52, and rear graphite sheet 54. Larger graphite sheets (such as Figures 16A-16B34 ) to wrap the inductor 30. All graphite sheets 22, 24, 26, 28, 52, 54 have adhesives attached to the inner surfaces facing the magnetic cores 32, 34, such as the front adhesive sheet 53 and the rear adhesive sheet 55.

[0067] Multiple components identical to inductor 30 may be constructed with graphite sheets 22, 24, 26, 28, 52, 54 attached thereto. As with inductor 30, the outer surfaces of front inductor 600 and rear inductor 602 are covered with graphite sheets.

[0068] Graphite sheets are attached to the right, left, top and bottom of the front inductor 600. The front inductor 600 also has a front graphite sheet 652 connected by a front bonding ring 653 and a rear graphite sheet 654 connected by a rear bonding ring 655.

[0069] The rear inductor 602 has right, left, top and bottom graphite sheets attached. The rear inductor 602 also has a front graphite sheet 752 connected by a front bonding ring 753 and a rear graphite sheet 754 connected by a rear bonding ring 755.

[0070] Lamination rings 690, 790 are adhesive rings that laminate the core components together. Lamination ring 690 has an adhesive that bonds the front inductor 600 to the front of the inductor 30, while lamination ring 790 bonds the rear inductor 602 to the rear of the inductor 30. More specifically, lamination ring 690 is sandwiched between the rear graphite sheet 654 and the front graphite sheet 52. Similarly, lamination ring 790 is sandwiched between the rear graphite sheet 54 and the front graphite sheet 752.

[0071] The front inductor 600 can be pressed onto the inductor 30, so that the adhesive of the lamination ring 690 is squeezed between the rear graphite sheet 654 and the front graphite sheet 52, forming a good bond with low contact resistance. Then, the assembly of the front inductor 600 and the inductor 30 is pressed onto the rear inductor 602, so that the adhesive in the lamination ring 790 is squeezed between the rear graphite sheet 52 and the front graphite sheet 752, forming a good bond with low contact resistance.

[0072] This compression may be performed by loosely fitting the inductor 30, front inductor 600, and back inductor 602 together with the lamination rings 690, 790 and then applying force to the entire sandwich and both ends of the inductor core.

[0073] Graphite ring 52 allows lateral heat conduction from the front end of inductor 30. Graphite ring 654 allows lateral heat conduction from the front inductor 600.

[0074] Likewise, graphite ring 54 allows lateral heat conduction from the rear end of inductor 30. Graphite ring 752 allows lateral heat conduction from rear inductor 602.

[0075] Thus, heat can be transferred laterally between the stacked inductor cores through the intermediate graphite rings 52 , 654 , 54 , 752 .

[0076] Fig.19 A stacked inductor is shown with graphite rings between the inductor cores. Stacked inductor 90 has three inductor cores laminated together.

[0077] The outer surfaces of the inductor 30, the front inductor 600 and the rear inductor 602 are all attached with graphite adhesive laminates, but not attached to the bobbin wound with the wire 92. The wire 92 is wound on all three bobbins at each winding.

[0078] Fig. 20 The stacked inductor connected to the heat sink is shown. There is a gap between the front inductor 600 and the inductor 30 in the stacked inductor 90 to expose the wire 92 for viewing, but usually the front inductor 600 will be pressed on the inductor 30 with the graphite ring 52 and its adhesive layer in between. All three of the inductor 30, the front inductor 600 and the rear inductor 602 are connected to the heat sink 112. The heat generated by the inductor 30 can be transmitted downward through the right graphite sheet 22 and the left graphite sheet 24, passing through the air gap between the upper magnetic core 32 and the lower magnetic core 34. This heat is then transferred to the bottom graphite sheet 28, and then transferred to the heat sink 112 to be dissipated through the air.

[0079] Likewise, the heat generated by the front inductor 600 and the rear inductor 602 can pass through the graphite sheets 622, 722 through their air gaps ( Fig.18 ), and then passes downward to the heat sink 112.

[0080] Graphite ring 52, 54 ( Fig.18 ) not only allows heat to transfer downward through the air gap, but also allows heat to transfer laterally from inductor 30 to the front inductor 600 and the rear inductor 602.

[0081] The inductor 30 located in the middle would normally retain more heat because it cannot dissipate heat laterally and can only dissipate heat downward to the heat sink. However, the graphite ring 52 allows the heat on the front surface of the inductor 30 to transfer laterally, through the front air gap, and then downward into the heat sink 112 below the inductor 30. Similarly, the graphite ring 54 allows the heat on the rear surface of the inductor 30 to transfer laterally, through the rear air gap, and then downward into the heat sink 112 below the inductor 30. Therefore, more heat can be effectively removed from the inductor 30.

[0082] Figures 21A-21B Different core types are shown. Fig.21AA conventional E-core is shown with a rectangular bobbin formed by the center legs of the upper core 32' and the lower core 34'. Such a rectangular bobbin or bobbin is undesirable because it is more difficult to wind wire around the square bobbin. In addition, the thickness of the bobbin is the same as the thickness of the side legs, which causes the wire wound around the bobbin to extend beyond the side legs.

[0083] There are many different E-cores available. Some E-cores have round bobbins, which makes it easier to wind the wire. Also, if the bobbin is round, the wire is less likely to break at the corners of the square bobbin. This improves reliability. The bobbin thickness can be reduced to allow the left and right legs to extend beyond the wire wound around the bobbin.

[0084] Fig.21B A PQ core is shown. The PQ core is a variation of the E core and can be considered a type of E core. In a PQ core, the shape of the upper core 32" and the lower core 34" are modified. The center post or bobbin is rounded to facilitate winding. The left and right legs are thicker than the bobbin. The shape of the PQ core can be optimized for a Switch Mode Power Supply (SMPS) or other AC application.

[0085] When a PQ core is used, the right graphite sheet 22 and the left graphite sheet 24 can be rectangular, but the top graphite sheet 26 and the bottom graphite sheet 28 may need to be cut to fit the top shape of the upper core 32" and the shape of the lower core 34". Alternatively, the top graphite sheet 26 and the bottom graphite sheet 28 can use a rectangular shape, and the graphite sheets can be larger or smaller than the top of the upper core 32". The front graphite sheet 52 and the rear graphite sheet 54 can be deleted or reduced in size, for example, only covering the left and right feet without covering the top and bottom near the skeleton.

[0086] Fig. 22 A stacked inductor with five cores is shown. Fig.18 Three inductor cores are shown connected laterally by two graphite rings, but more cores can be included in the stacked inductor 90'. In this example there are five cores with four graphite rings between them. The size of the heat sink 112 can be increased due to the additional heat and size of the five core stacked inductor 90'. [Alternative Embodiments]

[0087] The inventors have contemplated other embodiments. For example, the upper and lower magnetic cores can have multiple combinations and variations. In some embodiments, some of the graphite bonded laminates can be deleted, or they can be cut into different shapes.

[0088] Although E-type and PQ-type core variations have been described, the cores may also have a variety of variations, such as a pot-shaped core with the sides extended to more completely surround the skeleton 106, a U-shaped core lacking a second side leg, an E1-type core in which the upper core is an E-type core and the lower core is rectangular or l-shaped, an RM-type core, an RS-type core, a DS-type core, etc. Various extensions and hybrid shapes and combinations of the E-type core are possible, such as an EER-type core, an ETD-type core, an EP-type core, an EC-type core, an EFF-type core, an El-type core, etc. Since graphite sheets are highly flexible, the present invention can be applied to any core shape, size, and core material.

[0089] Although the core is shown with a bobbin, a left leg, and a right leg, the core may have only one leg and the bobbin. For a core rod, a graphite sheet is first attached to the core rod. Then, insulating tape is wrapped around the top of the graphite sheet. Finally, the coil is wrapped around the rod. The legs can extend toward each other and merge at the back to form a semicircle. An air gap can exist in the bobbin and in one leg but not in the other leg. The air gap can be located near the bottom instead of midway between the top and bottom. There can be other variations in the air gap. There can be multiple air gaps or more than two core sections in an inductor.

[0090] The core can be made of iron, iron oxide, ferrite, ferrite ceramic, silicon steel, amorphous steel, neodymium, iron powder, or other materials. Ceramics can also be used. Examples of ferromagnetic core materials include: silicon steel, powdered iron, nickel-iron alloys, amorphous metals, etc. Examples of non-ferromagnetic core materials include: manganese ferrite, non-magnetic ceramics, polymers. The core can be made of ferromagnetic or non-ferromagnetic materials. Ferrite is a general name that refers to a mixture of iron oxide and other metal oxides. Other materials may include different mixtures, such as amorphous.

[0091] The air gap in the core can have small shims at the corners to maintain the desired air gap thickness. These shims can be ceramic or other non-conductive materials. The air gap can be filled with dielectric materials or spacers that are non-electrical and magnetic conductors, such as PET tape or FR4. However, the air gap is usually filled with air.

[0092] The air gap can be located in the middle of the inductor as shown, or it can be off-center, such as closer to the bottom of the inductor rather than the top. The upper core can be larger than the lower core as the air gap moves downward. The air gap can be located at the bottom of the bobbin, and the lower core can be a bar shape rather than an E shape, such as an E1 core inductor.

[0093] Although the graphite sheets are shown attached to all outer surfaces of the E-core, the graphite sheet 26 attached to the top surface of the upper magnetic core and the graphite sheet 28 attached to the lower surface of the lower magnetic core can be eliminated because the graphite sheets 26, 28 do not span the air gap 10. Although the graphite sheets 22, 24 are shown to completely cover the outer surfaces of the left and right legs of the E-core, the size of the graphite sheets 22, 24 can be reduced to only partially cover the sides of the E-core. The size of the graphite sheets 22, 24 can be reduced to only cover the air gap 10 and portions of the sides of the upper and lower E-cores. Heat will still be transferred through the air gap 10, although not as efficiently as the larger graphite sheets 22, 24 (which are attached to a larger surface area of ​​the sides of the E-core). The bottom graphite sheet 28 can be eliminated when good contact is made with the heat sink 112, such as through a connector.

[0094] The thermally conductive particles can be carbon nanotubes, ceramic powder, silicon carbide, aluminum oxide, boron oxide, magnesium oxide or other thermally conductive materials. The binder can provide a lower contact resistance for the graphite sheet, allowing the graphite sheet to better contact the surface of the inductor core, thereby providing better thermal conduction.

[0095] The outer edges of the upper magnetic core 32 and the lower magnetic core 34 can be rounded to allow a single large graphite sheet to better fit the corners ( Fig.17 ). Sharp edges can more easily crack or weaken the graphite laminate. After the graphite sheet is attached, a coating can be applied to the inductor to protect the graphite laminate from scratches, wear, or damage. Microbumps can be added to the adhesive ( Fig.15 ) to improve adhesion, or the microbumps can be removed to simplify the process. Many processing methods and variations are possible.

[0096] Although Fig.18 Two graphite rings 52, 654 are shown between the front inductor 602 and the inductor 30, but it can also be a single graphite sheet with adhesive on both sides.

[0097] Although graphite sheets have been shown to be thermally conductive, other thermally conductive materials can be substituted for graphite. Thermally conductive sheets can be any thermally conductive film such as copper, silicon, aluminum, etc., or a mixture of graphite and other materials. However, they may not be as effective as graphite sheets in improving thermal conductivity.

[0098] Terms such as up, down, above, below, horizontal, vertical, inside, outside, etc. are relative and depend on the viewing angle and are not meant to limit the invention to a particular viewing angle. The device can be rotated so that vertical is horizontal and horizontal is vertical, so these terms depend on the observer.

[0099] The background section of the present invention may contain background information about the problem or environment of the present invention, rather than describing the prior art of others. Therefore, the materials contained in the background section are not an admission by the applicant that the prior art is available.

[0100] Any method or process described herein is machine-implemented or computer-implemented, intended to be performed by a machine, computer or other device, and is not intended to be performed solely by humans without machine assistance. Tangible results produced may include reports or other machine-generated displays on display devices such as computer monitors, projection devices, audio generating devices, and related media devices, and may include hard copy printouts that are also machine-generated. Computer control of other machines is another tangible result.

[0101] Any advantages and benefits described do not necessarily apply to all embodiments of the invention. When the word "means" appears in a claim element, applicant intends that the claim element fall within 35 USC § 112(6). Typically, the word "means" is preceded by a label of one or more words. The one or more words preceding the word "means" are a label for the purpose of facilitating reference to the claim element and are not intended to express a structural limitation. Such a means-plus-function claim is intended to cover not only the structures described herein for performing the function and their structural equivalents, but also equivalent structures. For example, although a nail and a screw have different constructions, they are equivalent structures because they both perform the function of fastening. Claims that do not use the word "means" do not fall within 35 USC § 112(6). Signals are typically electronic signals, but can also be optical signals, such as those that can be transmitted over fiber optic lines.

[0102] The above description of the embodiments of the present invention is presented for the purpose of illustration and description. It is not intended to be exhaustive, nor is it intended to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of the above teachings. It is intended that the scope of the present invention is not limited by this detailed description, but rather by the limitations of the claims appended hereto.

Claims

1. An inductor, comprising: an upper magnetic core of magnetic material having a top, an upper leg extending downward from the top, and an upper frame extending downward from the top; a lower magnetic core of magnetic material having a bottom, a lower leg extending upward from the bottom, and a lower frame extending upward from the bottom; a frame air gap between the upper frame and the lower frame; a leg air gap between the upper leg and the lower leg; a graphite sheet laminate having an adhesive attached to an inner surface of the graphite sheet, the graphite sheet laminate being attached to an outer surface of the upper leg by the adhesive and to an outer surface of the lower leg by the adhesive, the graphite sheet laminate spanning the leg air gap; as well as A conductive wire is wound around the upper frame multiple times and wound around the lower frame multiple times; The heat generated on the upper frame is transferred to the upper leg through the top, and then to the graphite sheet laminate, and then to the lower leg of the lower magnetic core through the leg air gap. The graphite sheet laminate thereby transfers heat from the upper magnetic core to the lower magnetic core across the leg air gap.

2. The inductor according to claim 1, wherein the outer surface of the upper leg is a surface facing away from the upper frame; wherein the outer surface of the lower support leg is a surface facing away from the lower frame; wherein the graphite sheet laminate is attached to the outer surface; wherein the graphite sheet laminate is not attached to the inner surface of the upper leg facing the upper frame; The graphite sheet laminate is not attached to the inner surface of the lower leg facing the lower frame.

3. The inductor of claim 2, wherein the upper magnetic core further comprises a second upper leg extending downward from the top portion, the second upper leg being located at a second end of the top portion, the second end of the top portion being opposite to a first end of the top portion, the first end having the upper leg extending downward; The lower magnetic core further includes a second lower leg extending upward from the bottom, the second lower leg is located at the second end of the bottom, the second end of the bottom is opposite to the first end of the bottom, and the first end of the bottom has the lower leg extending upward; wherein the upper frame is located between the upper support leg and the second upper support leg; The lower frame is located between the lower support leg and the second lower support leg.

4. The inductor according to claim 3, wherein the cross-section of the upper magnetic core is E-shaped; The cross section of the lower magnetic core is E-shaped; The inductor is an E-type magnetic core inductor.

5. The inductor according to claim 4, wherein the thickness of the upper skeleton is smaller than the thickness of the upper leg; The thickness of the lower frame is smaller than the thickness of the lower support leg. The inductor according to claim 5 , wherein the inductor is a PQ core inductor.

7. The inductor according to claim 4, further comprising: a heat sink attached to the lower magnetic core, the heat sink being used to forcibly dissipate heat into air surrounding the heat sink; wherein heat from the lower magnetic core is transferred to the heat sink; The heat from the upper magnetic core is transferred to the lower magnetic core through the graphite sheet laminate and then transferred to the heat sink.

8. The inductor according to claim 7, further comprising: A bottom graphite sheet laminate has an adhesive attached to an inner surface of the graphite sheet, the bottom graphite sheet laminate is attached to a bottom surface of the bottom of the lower magnetic core by the adhesive, and the bottom graphite sheet laminate is used to transfer heat from the lower magnetic core to the heat sink.

9. The inductor according to claim 8, further comprising: A top graphite sheet laminate having an adhesive attached to an inner surface of the graphite sheet, the top graphite sheet laminate being attached to a top surface of the top of the upper magnetic core by the adhesive.

10. The inductor according to claim 9, further comprising: a second leg air gap between the second upper leg and the second lower leg; a second graphite sheet laminate having an adhesive attached to an inner surface of the graphite sheet, the second graphite sheet laminate being attached to an outer surface of the second upper leg of the upper magnetic core by the adhesive, and the second graphite sheet laminate being also attached to an outer surface of the second lower leg of the lower magnetic core by the adhesive; wherein the second graphite sheet laminate spans the second leg air gap; The heat generated at the upper frame is transferred to the second upper leg through the top, and then to the second graphite sheet laminate, and then to the second lower leg of the lower magnetic core through the air gap of the second leg. Therefore, the second graphite sheet laminate also transfers heat from the upper magnetic core to the lower magnetic core through the second leg air gap.

11. The inductor according to claim 10, further comprising: a front graphite sheet laminate having an adhesive attached to the inner surface of the annular graphite sheet, the front graphite sheet laminate being attached to the front outer surfaces of the upper leg, the second upper leg, the top of the upper magnetic core, and the bottom of the lower magnetic core by the adhesive, the front graphite sheet laminate being not attached to the upper frame or the lower frame; A rear graphite sheet laminate having an adhesive attached to the inner surface of the annular graphite sheet, the rear graphite sheet laminate being attached to the rear outer surfaces of the upper leg, the second upper leg, the top of the upper magnetic core and the bottom of the lower magnetic core by the adhesive, the rear graphite sheet laminate being not attached to the upper frame or the lower frame.

12. The inductor of claim 11, wherein the binder is mixed with thermally conductive particles. The inductor of claim 12 , wherein the thermally conductive particles are carbon nanotubes.

14. The inductor according to claim 11, further comprising: The micro-bumps are formed on the adhesive, and are thicker areas of the adhesive, and are used to improve the adhesion between the graphite sheet and the surface of the upper magnetic core or the lower magnetic core.

15. The inductor of claim 11, wherein the graphite sheet laminate, the top graphite sheet laminate, the second graphite sheet laminate, the bottom graphite sheet laminate, the front graphite sheet laminate, and the back graphite sheet laminate are each part of a continuous graphite sheet laminate that is folded and cut to fit around the upper magnetic core and the lower magnetic core. 16 . The inductor of claim 15 , wherein the edge of the upper magnetic core and the edge of the lower magnetic core are rounded to prevent sharp edges from wearing the continuous graphite sheet laminate at the edge of the upper magnetic core and the edge of the lower magnetic core.

17. The inductor according to claim 11, wherein a second adhesive layer is further applied on the outer surface of the annular graphite sheet of the front graphite sheet laminate; Also includes: a front upper magnetic core having the same shape as the upper magnetic core, having a graphite sheet laminate attached to its outer surface, the front upper magnetic core being attached to the front graphite sheet laminate through the second adhesive layer; a front lower magnetic core having the same shape as the lower magnetic core, having a graphite sheet laminate attached to its outer surface, the front lower magnetic core being attached to the front graphite sheet laminate through the second adhesive layer; a front adhesive laminate ring applied between the front upper magnetic core and the upper magnetic core, the front adhesive laminate ring having a ring shape of the front graphite sheet laminate; a rear upper magnetic core having the same shape as the upper magnetic core and having a graphite sheet laminate attached to its outer surface, the rear upper magnetic core being attached to the rear graphite sheet laminate via a second rear adhesive layer; a rear lower magnetic core having the same shape as the lower magnetic core and having a graphite sheet laminate attached to its outer surface, the rear lower magnetic core being attached to the rear graphite sheet laminate through the second rear adhesive layer; and a rear adhesive laminate ring applied between the rear upper magnetic core and the upper magnetic core, the rear adhesive laminate ring having a ring shape of the rear graphite sheet laminate.

18. The inductor according to claim 17, wherein the conductive wire is wound on the upper skeletons of the front upper magnetic core, the upper magnetic core and the rear upper magnetic core for multiple times, wherein for each winding loop, the conductive wire is wound on the upper skeletons of the front upper magnetic core, the upper magnetic core and the rear upper magnetic core; The conductive wire is wound multiple times on the lower frames of the front lower magnetic core, the lower magnetic core and the rear lower magnetic core, wherein for each winding loop, the conductive wire is wound on the lower frames of the front lower magnetic core, the lower magnetic core and the rear lower magnetic core.

19. An inductor with improved thermal performance, comprising: An upper magnetic core made of ferrite or ferromagnetic material, comprising a top crossbar, an upper frame, a left upper leg and a right upper leg, wherein the upper crossbar is located in a top plane, the upper frame, the left upper leg and the right upper leg are located in a second plane perpendicular to the top plane, wherein the upper frame is located between the left upper leg and the right upper leg and is separated from the left upper leg and the right upper leg by an upper winding gap; A lower magnetic core made of ferrite or ferromagnetic material, comprising a bottom crossbar, a lower frame, a left lower leg and a right lower leg, wherein the bottom crossbar is located in a bottom plane parallel to the top plane, The lower frame, the left lower leg and the right lower leg are located in the second plane, wherein the lower frame is located between the left lower leg and the right lower leg and is separated from the left lower leg and the right lower leg by a lower winding gap; a left air gap located between a bottom of the upper left leg and a top of the lower left leg; a right air gap located between the bottom of the right upper leg and the top of the right lower leg; a frame air gap located between the bottom of the upper frame and the top of the lower frame; A wire, which is wound around the upper frame multiple times and around the lower frame multiple times, and the wire is wound in the upper winding gap and the lower winding gap; a left heat-conductive laminate applied to an outer surface of the left upper leg and to an outer surface of the left lower leg, the outer surface being a surface not facing the upper winding void or the lower winding void; wherein the left heat-conducting laminate plate spans the left air gap, and the left heat-conducting laminate plate is used to transfer heat from the upper magnetic core to the lower magnetic core through the left air gap; and a right heat-conductive laminate applied to an outer surface of the right upper leg and to an outer surface of the right lower leg, the outer surface being a surface not facing the upper winding void or the lower winding void; wherein the right heat-conducting laminate plate spans the right air gap, and the right heat-conducting laminate plate is used to transfer heat from the upper magnetic core to the lower magnetic core through the right air gap; wherein each heat-conducting laminate has an adhesive, the adhesive being applied on the surface of the heat-conducting layer facing the upper magnetic core or the lower magnetic core, the adhesive being used to reduce the contact resistance between the heat-conducting layer and the ferrite or ferromagnetic material of the upper magnetic core or the lower magnetic core; Thus, the left thermally conductive laminate increases heat transfer from the upper magnetic core to the lower magnetic core across the left air gap, and the right thermally conductive laminate increases heat transfer across the right air gap.

20. A laminated inductor with improved thermal performance, comprising a plurality of magnetic cores, each magnetic core comprising: An upper magnetic core made of ferrite or ferromagnetic material, comprising a top crossbar, an upper frame, a left upper leg and a right upper leg, wherein the top crossbar is located in a top plane, the upper frame, the left upper leg and the right upper leg are located in a second plane perpendicular to the top plane, wherein the upper frame is located between the left upper leg and the right upper leg and is separated from the left upper leg and the right upper leg by an upper winding gap; A lower magnetic core made of ferrite or ferromagnetic material, comprising a bottom crossbar, a lower frame, a left lower leg and a right lower leg, wherein the bottom crossbar is located in a bottom plane parallel to the top plane, the lower frame, the left lower leg and the right lower leg are located in the second plane, wherein the lower frame is located between the left lower leg and the right lower leg and is separated from the left lower leg and the right lower leg by a lower winding gap; a left air gap located between the bottom of the upper left leg and the top of the lower left leg; a right air gap located between the bottom of the right upper leg and the top of the right lower leg; A frame air gap, which is located between the bottom of the upper frame and the top of the lower frame; A wire, which is wound around the upper frame multiple times and around the lower frame multiple times, and the wire is wound in the upper winding gap and the lower winding gap; a left graphite laminate applied to an outer surface of the left upper leg and to an outer surface of the left lower leg, the outer surfaces being surfaces that do not face the upper winding void or the lower winding void; wherein the left graphite laminate spans the left air gap, and the left graphite laminate is used to transfer heat from the upper magnetic core to the lower magnetic core; and a right graphite laminate applied to an outer surface of the right upper leg and to an outer surface of the right lower leg, the outer surfaces being surfaces that do not face the upper winding void or the lower winding void; wherein the right graphite laminate plate spans the right air gap, and the right graphite laminate plate is used to transfer heat from the upper magnetic core to the lower magnetic core; wherein each graphite laminate has an adhesive, the adhesive being applied to the surface of the graphite layer facing the upper magnetic core or the lower magnetic core, the adhesive being used to reduce the contact resistance between the graphite layer and the ferrite or ferromagnetic material of the upper magnetic core or the lower magnetic core; Between a pair of adjacent magnetic cores among the plurality of magnetic cores, a front graphite laminate has adhesive on both surfaces of the graphite layer, the front graphite laminate being in a ring shape; wherein the front graphite laminate is attached to the front outer surfaces of the upper left leg, the upper right leg, the top crossbar of the upper magnetic core and the lower left leg, the lower right leg, the bottom crossbar of the lower magnetic core in the front magnetic core of the adjacent pair of magnetic cores by adhesive; wherein the front graphite laminate is attached to the rear outer surfaces of the upper left leg, the upper right leg, the top crossbar of the upper magnetic core and the lower left leg, the lower right leg, the bottom crossbar of the lower magnetic core in the back magnetic cores of the adjacent pair of magnetic cores by adhesive; Wherein, the front graphite laminate is not attached to the upper frame or the lower frame.

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