Coupled Inductors for Low EMI

Abstract

A coupled inductor for low electromagnetic interference includes a plurality of coils and a composite magnetic core, wherein the composite magnetic core includes a coupled magnetic structure formed of a first magnetic material and a leakage magnetic structure formed of a second magnetic material with distributed gaps. The coupled magnetic structure magnetically couples the plurality of coils together, and the leakage magnetic structure provides a leakage magnetic flux path for the plurality of coils.

Description

[0001] This application is a divisional application of the Chinese patent application with the application date of August 18, 2017, application number 201710711277.9, and titled “Coupled Inductor for Low Electromagnetic Interference”.

[0002] Related applications

[0003] This application claims priority to U.S. Provisional Patent Application No. 62 / 377,455, filed on August 19, 2016, which is incorporated herein by reference. Background Art

[0004] It is known to electrically couple multiple switching subconverters in parallel to increase the capacity and / or improve the performance of a switching power converter. One type of switching power converter with multiple switching subconverters is a "multiphase" switching power converter, in which the subconverters, referred to as "phases," switch out of phase with each other. This out-of-phase switching results in ripple current cancellation at the converter output filter and enables the multiphase converter to have better transient response than an otherwise similar single-phase converter.

[0005] As taught in U.S. Patent No. 6,362,986 to Schultz et al. (which is incorporated herein by reference), the performance of a multiphase switching power converter can be improved by magnetically coupling the energy storage inductors of two or more phases. This magnetic coupling results in ripple current cancellation in the inductors and increases the ripple switching frequency relative to an otherwise identical converter without magnetically coupled inductors, thereby improving converter transient response, reducing input and output filtering requirements, and / or improving converter efficiency.

[0006] Two or more magnetically coupled inductors are often collectively referred to as "coupled inductors" and have associated leakage inductance and magnetizing inductance values. Magnetizing inductance is associated with the magnetic coupling between the coils; thus, the greater the magnetizing inductance, the stronger the magnetic coupling between the coils. Leakage inductance, on the other hand, is associated with energy storage. Thus, the greater the leakage inductance, the more energy stored in the inductor. Leakage inductance is generated by leakage magnetic flux generated by current flowing through one coil of the coupled inductor that is not coupled to the other coils of the inductor.

[0007] Figure 1FIG2 is a diagram of a prior art coupled inductor 100 that includes a magnetic core 102 that magnetically couples a plurality of coils 104 together. Magnetic core 102 is shown in a wire view, i.e., only its outline is shown, to illustrate the internal features of coupled inductor 100. Magnetic core 102 is typically formed of a ferrite magnetic material and includes a gap 106 in its leakage magnetic flux path. Gap 106 is typically formed of air or another non-magnetic material and provides energy storage within coupled inductor 100, thereby helping to prevent magnetic saturation of coupled inductor 100. During the design of coupled inductor 100, the leakage inductance value of coupled inductor 100 can be adjusted by adjusting the size of gap 106. Several examples of prior art coupled inductors similar to coupled inductor 100 are disclosed in U.S. Patent No. 8,237,530 to Ikriannikov, which is incorporated herein by reference. Summary of the Invention

[0008] (A1) A coupled inductor for low electromagnetic interference may include a plurality of coils and a composite magnetic core including a coupled magnetic structure formed of a first magnetic material and a leakage magnetic structure formed of a second magnetic material having distributed gaps. The coupled magnetic structure may magnetically couple the plurality of coils together, and the leakage magnetic structure may provide a leakage magnetic flux path for the plurality of coils.

[0009] (A2) In the coupled inductor described in A1, the first magnetic material may have a greater magnetic permeability than the second magnetic material.

[0010] (A3) In the coupled inductors described in A1 and A2, the first magnetic material may include a ferrite material, and the second magnetic material may include an iron powder material disposed within a binder.

[0011] (A4) In any of the coupled inductors described in A1 to A3, the leakage flux structure may at least partially cover the plurality of coils.

[0012] (A5) In any of the coupled inductors described in A1 to A4, the coupled magnetic structure may include (1) a first rail and a second rail separated from each other in a first direction and (2) a plurality of rungs. Each of the plurality of rungs may connect the first rail with the second rail in the first direction, and each of the plurality of coils may be at least partially wound around a corresponding one of the plurality of rungs.

[0013] (A6) In the coupled inductor described in A5, the composite magnetic core may be configured such that the leakage flux structure provides a path for leakage magnetic flux between the first ladder rod and the second ladder rod in the first direction.

[0014] (A7) In any of the coupled inductors described in A5 and A6, the magnetic flux leakage structure may be bounded by the first ladder rod and the second ladder rod in the first direction.

[0015] (A8) In any of the coupled inductors described in A5 to A7, the second ladder bar may be U-shaped as viewed in cross section along a second direction orthogonal to the first direction.

[0016] (A9) In any of the coupled inductors described in A5 to A6, the leakage flux structure may be U-shaped as viewed when the coupled inductor is viewed cross-sectionally along the first direction.

[0017] (A10) In the coupled inductor described in A9, the magnetic flux leakage structure is bounded by the first ladder rod and the second ladder rod in the first direction.

[0018] (A11) In the coupled inductor described in A5, the first ladder bar may include a plurality of first ladder bar sub-segments arranged in a row in a second direction orthogonal to the first direction, and the second ladder bar may include a plurality of second ladder bar sub-segments arranged in a row in the second direction.

[0019] (A12) In the coupled inductor described in A11, adjacent first ladder bar sub-segments may be separated from each other in the second direction, and adjacent second ladder bar sub-segments may be separated from each other in the second direction.

[0020] (A13) In any of the coupled inductors described in A11 and A12, the magnetic flux leakage structure may be bounded by the first ladder bar and the second ladder bar in the first direction.

[0021] (A14) In any of the coupled inductors described in A11 to A13, the leakage magnetic structure may include a plurality of leakage sub-segments connected in the second direction.

[0022] (A15) In any of the coupled inductors described in A11 to A13, the leakage magnetic structure may include a plurality of leakage sub-segments separated from each other in the second direction.

[0023] (A16) In any of the coupled inductors described in A1 to A15, the coupled inductor may be at least partially embedded in a magnetic flux leakage structure.

[0024] (A17) In any of the coupled inductors described in A1 to A16, the coupled inductor may further include one or more magnetic flux suppression structures embedded in the leakage flux structure.

[0025] (B1) A coupled inductor for low electromagnetic interference may include a plurality of coils and a coupled magnetic structure. The coupled magnetic structure may include (1) a first ladder bar comprising a plurality of first ladder bar segments arranged in a row in a first direction, (2) a second ladder bar separated from the first ladder bar in a second direction orthogonal to the first direction, the second ladder bar comprising a plurality of second ladder bar segments arranged in a row in the first direction, and (3) a plurality of rungs, each of the plurality of rungs connecting the first ladder bar with the second ladder bar in the second direction. Each of the plurality of coils may be at least partially wound around a corresponding one of the plurality of rungs. The leakage magnetic structure may include (1) one or more internal leakage plates, which are placed between the first ladder bar and the second ladder bar in the second direction, and (2) an external leakage plate, which bridges the first ladder bar and the second ladder bar in the second direction. The external leakage plate does not overlap with the first ladder bar and the second ladder bar as seen when the coupled inductor is viewed in a cross-section along the second direction.

[0026] (B2) In the coupled inductor described in B1, each inner drain plate can be separated from each of the first ladder bar and the second ladder bar in a second direction, and the outer drain plate can be separated from each of the first ladder bar and the second ladder bar in a third direction orthogonal to each of the first and second directions.

[0027] (B3) In any of the coupled inductors described in B1 and B2, each of the coupling magnetic structure and the leakage magnetic structure may be formed of one or more ferrite magnetic materials.

[0028] (C1) A coupled inductor for low electromagnetic interference may include (1) a plurality of coils, (2) a magnetic core that magnetically couples the plurality of coils together, the magnetic core forming a path in a leakage flux path of the coupled inductor, and (3) a metal shield that is placed on an outer surface of the magnetic core and at least partially covers the gap.

[0029] (C2) In the coupled inductor as described in C1, the magnetic core may include (1) a first ladder bar and a second ladder bar separated from each other in a first direction, (2) a plurality of coupling teeth, each of the coupling teeth being positioned between the first ladder bar and the second ladder bar in the first direction, each of the plurality of coils being at least partially wound around a corresponding one of the plurality of coupling teeth, and (3) a leakage plate bridging the first ladder bar and the second ladder bar in the first direction, the leakage plate forming a path in the leakage magnetic flux path.

[0030] (D1) A switching power converter may include any of the coupled inductors described according to A1 to A17, B1 to B3, C1 and D2. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a perspective view of a prior art coupled inductor.

[0032] Figure 2 is a perspective view of a coupled inductor for low electromagnetic interference according to an embodiment.

[0033] Figure 3 yes Figure 2 Exploded perspective view of a coupled inductor.

[0034] Figure 4 According to one embodiment Figure 2 A coupled inductor is similar to a perspective view of a coupled inductor for low electromagnetic interference, except that the coil ends are placed along the bottom surface of the leakage flux structure.

[0035] Figure 5 According to one embodiment Figure 2 Side view of a coupled inductor similar to that used for low EMI, but with the coil having additional turns and terminating in contacts located on the bottom surface of the leakage flux structure.

[0036] Figure 6 is a perspective view of a coupled inductor for low electromagnetic interference including a coupled magnetic structure with a leakage extension according to an embodiment.

[0037] Figure 7 yes Figure 6 Side view of the coupled magnetic structure of the coupled inductor.

[0038] Figure 8 is a perspective view of a coupled inductor for low electromagnetic interference with ladder bars including extensions according to an embodiment.

[0039] Figure 9 yes Figure 8 A perspective view of a leakage flux structure of a coupled inductor separated from the rest of the coupled inductor.

[0040] Figure 10 yes Figure 8 An exploded perspective view of the coupled magnetic structure of a coupled inductor.

[0041] Figure 11 is a perspective view of another coupled inductor for low electromagnetic interference according to an embodiment.

[0042] Figure 12 yes Figure 11 A perspective view of a leakage flux structure of a coupled inductor separated from the rest of the coupled inductor.

[0043] Figure 13 yes Figure 11 A perspective view of a coupled magnetic structure of a coupled inductor separated from the rest of the coupled inductor.

[0044] Figure 14 yes Figure 11 A perspective view of an example of a coil of a coupled inductor separated from the rest of the coupled inductor.

[0045] Figure 15 is a perspective view of a coupled inductor with extended ladder bars for low electromagnetic interference according to one embodiment.

[0046] Figure 16 yes Figure 15 A perspective view of a leakage flux structure of a coupled inductor separated from the rest of the coupled inductor.

[0047] Figure 17 is a perspective view of a coupled inductor for electromagnetic interference with a coupled magnetic structure having a reduced cross-sectional area according to one embodiment.

[0048] Figure 18 is a perspective view of a coupled inductor for electromagnetic interference according to an embodiment, the coupled inductor having coupled magnetic structures with different cross-sectional areas.

[0049] Figure 19 yes Figure 18 A perspective view of a leakage flux structure of a coupled inductor separated from the rest of the coupled inductor.

[0050] Figure 20 According to an embodiment Figure 6 A perspective view of three examples of coupled inductors connected together to effectively create a single coupled inductor with nine coils.

[0051] Figure 21 is a perspective view of a coupled inductor including two coils for low electromagnetic interference according to an embodiment.

[0052] Figure 22 is a perspective view of a coupled inductor for low electromagnetic interference, the coupled inductor including a magnetic flux impeding structure embedded in a leakage magnetic structure.

[0053] Figure 23 is a perspective view of a coupled inductor including a metal shield for low electromagnetic interference according to one embodiment.

[0054] Figure 24 yes Figure 23 Exploded perspective view of a coupled inductor in FIG. 1 , wherein the metal shield is separated from the rest of the coupled inductor.

[0055] Figure 25 yes Figure 23A perspective view of a coupled inductor in which the metal shield is omitted and the first ladder bar and the bushing are shown in line drawings to illustrate the internal features of the coupled inductor.

[0056] Figure 26 is a perspective view of another coupled inductor including a metal shield for low electromagnetic interference according to an embodiment.

[0057] Figure 27 An embodiment includes Figure 2 An example of a multiphase buck switching power converter with coupled inductors.

[0058] Figure 28 is a front view of a coupled inductor for low electromagnetic interference according to an embodiment, the coupled inductor including two drum core discrete inductors and a magnetic flux leakage structure.

[0059] Figure 29 yes Figure 28 A top plan view of a coupled inductor.

[0060] Figure 30 yes Figure 28 The coupled inductor along Figure 28 A cross-sectional view taken along line 30A-30A.

[0061] Figure 31 yes Figure 28 Side view of the coupled inductor.

[0062] Figure 32 is with Figure 28 Front view of an example of a drum core discrete inductor separated from the rest of the coupled inductor.

[0063] Figure 33 yes Figure 28 The coupled inductor is Figure 28 Front view of the coupled magnetic structure separated from the rest of the coupled inductor.

[0064] Figure 34 yes Figure 28 The coupled inductor is Figure 28 Front view of the leakage flux structure separated from the rest of the coupled inductor.

[0065] Figure 35 is a perspective view of another coupled inductor for low electromagnetic interference including two drum core discrete inductors according to one embodiment.

[0066] Figure 36 is with Figure 35A perspective view of an example of a drum core inductor and a portion of the leakage flux structure separated from the rest of the coupled inductor.

[0067] Figure 37 yes Figure 35 The coupled inductor is Figure 35 A top plan view of the coupled magnetic structure separated from the rest of the coupled inductor.

[0068] Figure 38 is a front view of yet another coupled inductor for low electromagnetic interference according to one embodiment, the yet another coupled inductor including two discrete drum core inductors.

[0069] Figure 39 yes Figure 38 A top plan view of a coupled inductor.

[0070] Figure 40 yes Figure 38 The coupled inductor along Figure 38 A cross-sectional view taken along line 40A-40A.

[0071] Figure 41 yes Figure 38 Side view of the coupled inductor.

[0072] Figure 42 is with Figure 38 Front view of an example of a drum core discrete inductor separated from the rest of the coupled inductor.

[0073] Figure 43 is with Figure 38 Front view of the coupled magnetic structure separated from the rest of the coupled inductor. DETAILED DESCRIPTION

[0074] Figure 1The prior art coupled inductor 100 achieves several advantages. For example, it has a small footprint, promotes strong magnetic coupling of the coils 104, and provides a short, balanced, and controllable leakage flux path. However, applicants have determined that coupled inductor 100, as well as other prior art coupled inductors, may not achieve adequate electromagnetic compatibility in applications requiring low electromagnetic interference, such as certain automotive, industrial control, and medical applications. For example, gap 106 must typically be relatively large to achieve the required energy storage performance, and this large gap can result in significant fringing flux, which is magnetic flux transmitted out of the magnetic core 102. This fringing flux can couple to adjacent electronic circuitry, potentially interfering with the operation of that circuitry. Furthermore, this fringing flux can induce eddy currents in adjacent metal inductors within and outside the coupled inductor 100, leading to heating of the metal inductors and associated power losses. Furthermore, coil 104 is partially exposed within coupled inductor 100 , which may cause undesirable capacitive coupling of coil 104 to adjacent components, particularly in switching power converter applications of coupled inductor 100 where coil 104 is subject to high voltage change rates.

[0075] Therefore, the applicant has developed coupled inductors for low electromagnetic interference that at least partially overcome one or more of the above-mentioned problems. These coupled inductors include a composite magnetic core that includes a coupling magnetic structure and a leakage magnetic structure. In some embodiments, the coupling magnetic structure is at least partially embedded in the leakage magnetic structure. The coupling magnetic structure is formed of a magnetic material with relatively high magnetic permeability (such as a ferrite material), and the coupling magnetic structure magnetically couples multiple coils of the coupled inductor together. The leakage magnetic structure is formed of a magnetic material with relatively low magnetic permeability and having distributed gaps (such as iron powder molded or placed in a binder as a film in multiple layers). The leakage magnetic structure at least partially provides a leakage magnetic flux path for the coil, and the distributed gaps of the leakage magnetic structure eliminate the need for discrete gaps (such as Figure 1 In some embodiments, the coupled magnetic structure at least partially shields the coil of the coupled inductor from external components, thereby helping to minimize capacitive coupling between the coil and external components.

[0076] Disclosed below are several examples of these coupled inductors for low electromagnetic interference. However, it should be understood that variations of these embodiments are possible and within the scope of the present disclosure.

[0077] Figure 22 is a perspective view of a coupled inductor 200 for low electromagnetic interference having a length 202, a width 204, and a height 206. Coupled inductor 200 includes a composite magnetic core 208 including a coupled magnetic structure 210 at least partially embedded in a leakage magnetic structure 212. Leakage magnetic structure 212 is shown in line drawing so that an interior portion of coupled inductor 200 is visible, and Figure 3 FIG is an exploded perspective view of the coupled inductor 200, wherein the leakage flux structure 212 is separated from the rest of the coupled inductor 200. Figure 3 Only the outer contour of the magnetic flux leakage structure 212 is shown in order to improve the clarity of the description.

[0078] The coupling magnetic structure 210 is a stepped magnetic core comprising a first ladder bar 216, a second ladder bar 218, and a plurality of coupling teeth 220. The first ladder bar 216 and the second ladder bar 218 are separated in the height 206 direction, and each coupling tooth 220 is positioned between the first ladder bar 216 and the second ladder bar 218 in the height 206 direction. Although not required, it is contemplated that the coupling magnetic structure 210 will typically form one or more small gaps (e.g., a small gap associated with each coupling tooth 220) to control the magnetizing inductance of the coupled inductor 200. A corresponding coil 222 forms one or more turns around each coupling tooth 220. The coupling magnetic structure 210 magnetically couples the coils 222 together and is formed from a first magnetic material having a relatively high magnetic permeability (e.g., a ferrite material) to promote strong magnetic coupling of the coils 222.

[0079] The leakage structure 212 is formed from a second magnetic material with distributed gaps (e.g., iron powder molded or deposited in a binder in multiple film layers). The leakage structure 212 provides a path for leakage flux between the first ladder bar 216 and the second ladder bar 218 in the height 206 direction. Furthermore, in embodiments where the leakage structure 212 significantly extends beyond the coupling magnetic structure 210 in one of the length 202 direction, the width 204 direction, or the height 206 direction, the leakage structure 212 also provides a path for leakage flux outside the coupling magnetic structure 210. The second magnetic material forming the leakage structure 212 typically has a lower magnetic permeability than the first magnetic material forming the coupling magnetic structure 210 because it is generally desirable for the magnetizing inductance of the coupled inductor 200 to be significantly greater than the leakage inductance of the coupled inductor 200. The desired leakage inductance value is achieved by varying the magnetic permeability of the second magnetic material and / or the cross-sectional area of ​​the leakage structure 212 during the design of the coupled inductor 200.

[0080] It should be appreciated that there are no exposed gaps in composite magnetic core 208. Consequently, minimal fringing flux and associated electromagnetic interference and power losses are generated. Thus, coupled magnetic structure 210 acts as a shield, i.e., it separates coil 222 from external components, thereby helping to minimize capacitive coupling between coil 222 and external components.

[0081] The number of coupling teeth 220 and associated coils 222 may be varied without departing from the scope of the present invention, as long as the coupled inductor 200 includes at least two coupling teeth 220 and associated coils 222. In addition, the configuration of the coils 222 may be varied. For example, the coils 222 may be formed to be larger than Figure 2 and Figure 3 . In addition, although coil 222 is shown as a wound wire, coil 222 may be a foil coil or a spiral coil. Furthermore, coil 222 may terminate on a side of coupled inductor 200 other than that shown, and / or coil 222 may terminate in a manner other than that shown, such as at contacts for surface mount connection to a printed circuit board.

[0082] For example, Figure 4 is with Figure 2 A perspective view of a coupled inductor 400 for low electromagnetic interference is similar to the coupled inductor 200, except that the ends of the coil 222 are placed along the bottom surface 402 of the leakage flux structure 212 to form solderable contacts. As another example, Figure 5 is with Figure 2 A side view of a coupled inductor 500 for low electromagnetic interference similar to coupled inductor 200 of FIG. 2 , except that coil 222 is replaced by a coil 522 having additional turns and terminating in a contact 502 located on a bottom surface 504 of the leakage flux structure 212. Figure 2 and Figure 3 , the leakage magnetic structure 212 is Figure 4 and Figure 5 It is shown in a line diagram to illustrate the internal features of the coupled inductor.

[0083] The first ladder bar 216 and the second ladder bar 218 may be extended along the length 202 to form an extension of the coupled magnetic structure 210, thereby potentially reducing losses in the leakage flux path and increasing the mechanical strength of the coupled inductor. Figure 6 FIG is a perspective view of a coupled inductor 600 for low electromagnetic interference having a length 602, a width 604, and a height 606. The coupled inductor 600 has a composite magnetic core 608 and is connected to a Figure 22 is similar to coupled inductor 200 , except that core 608 includes a coupled magnetic structure 610 with first and second ladder bars 616 , 618 extending beyond outer coupling teeth 620 along length 602 to form drain extensions 624 . Figure 7 FIG is a side view of the coupled magnetic structure 610 separated from the rest of the coupled inductor 600. A respective coil 622 is wound around each coupling tooth 620. The leakage magnetic structure 612 is placed between the first ladder bar 616 and the second ladder bar 618 along the height 606. The leakage magnetic structure 612 is located at Figure 6 6 is shown in line diagram form to illustrate the internal features of coupled inductor 600.

[0084] The coupling magnetic structure 610 is formed from a first magnetic material, and the leakage magnetic structure 612 is formed from a second magnetic material with distributed gaps. The magnetic permeability of the first magnetic material is generally greater than the magnetic permeability of the second magnetic material, resulting in a higher magnetizing inductance than the leakage inductance. The leakage magnetic structure 612 provides a path for leakage magnetic flux between the first ladder bar 616 and the second ladder bar 618 along the height 606. The leakage extension 624 reduces the magnetic resistance of the leakage magnetic flux path at the outer edge of the coupled inductor 600. The leakage extension 624 can reduce losses in embodiments where the first magnetic material with relatively high magnetic permeability forming the coupling magnetic structure 610 has lower losses than the second magnetic material with relatively low magnetic permeability forming the leakage magnetic structure 612. In addition, the coupling magnetic structure 610 constrains the leakage magnetic structure 612 along the height 606, which improves the mechanical strength of the coupled inductor 600.

[0085] In a manner similar to the other coupled inductors discussed above, the number of coupling teeth 620 and associated coils 622 may be varied without departing from the scope thereof, so long as coupled inductor 600 includes at least two coupling teeth 620 and associated coils 622. Additionally, the configuration and / or termination of coils 622 may be varied. For example, coils 622 may be foil coils or spiral coils rather than wire wound coils. As another example, coils 622 may terminate on different sides of coupled inductor 600 and / or at different locations. Figure 6 Terminate as shown.

[0086] Figure 8 is with Figure 6600 is a perspective view of coupled inductor 800 for low electromagnetic interference, except that second ladder bar 618 is replaced by second ladder bar 818, which includes extensions 826 and 828 extending toward first ladder bar 616 in the direction of height 606. When viewed in a cross-section along length 602, second ladder bar 818 has a U-shape. Extensions 826 and 828 reduce the impedance of the leakage magnetic flux path along height 606, thereby promoting a large leakage inductance value and / or low losses in the leakage path. Figure 6 The leakage magnetic structure 612 is also Figure 8 The magnetic flux leakage structure 812 is replaced by the magnetic flux leakage structure 812 in order to accommodate the U-shape of the second ladder bar 818. Figure 9 is a perspective view of the flux leakage structure 812 separated from the rest of the coupled inductor 800, and Figure 10 FIG is an exploded perspective view of the coupled magnetic structure 810. The leakage magnetic structure 812 is Figure 8 and Figure 9 Each of the figures is shown in line drawings and is Figure 9 Only the outline of the leakage flux structure 812 is shown.

[0087] The applicant has also developed a coupled inductor for low electromagnetic interference, in which the leakage flux path is mainly located outside the coupled magnetic structure. For example, Figure 11 FIG1 is a perspective view of a coupled inductor 1100 for low electromagnetic interference, wherein the coupled inductor 1100 has a length 1102, a width 1104, and a height 1106. The coupled inductor 1100 includes a composite magnetic core 1108, which includes a coupled magnetic structure 1110 and a leakage magnetic structure 1112. The leakage magnetic structure 1112 is formed at a Figure 11 1100 is shown in line drawing form so that internal features of coupled inductor 1100 are visible. Figure 12 is a perspective view of the leakage flux structure 1112 separated from the rest of the coupled inductor 1100, and Figure 13 is a perspective view of coupled magnetic structure 1110 separated from the rest of coupled inductor 1100 .

[0088] The coupled magnetic structure 1110 is a stepped magnetic core that includes a first ladder bar 1116, a second ladder bar 1118, and a plurality of coupling teeth 1120. The first ladder bar 1116 and the second ladder bar 1118 are separated in the width 1104 direction, and each coupling tooth 1120 is positioned between the first ladder bar 1116 and the second ladder bar 1118 along the width 1104 direction. Although not required, it is contemplated that the coupled magnetic structure 1110 will typically form one or more small gaps (e.g., a small gap associated with each coupling tooth 1120) to control the magnetizing inductance of the coupled inductor 1100. Each coil 1122 forms one or more turns around each coupling tooth 1120. Figure 14 1 is a perspective view of one example of coil 1122 separated from the rest of coupled inductor 1100. Coupling magnetic structure 1110 magnetically couples coils 1122 together, and coupling magnetic structure 1110 is formed of a first magnetic material (e.g., a ferrite material) having a relatively high magnetic permeability to promote strong magnetic coupling of coils 1122.

[0089] The coupling teeth 1120 are positioned close together along the length 1102 to promote a small footprint for the coupled inductor 1100 and strong magnetic coupling between the coils 1122. Consequently, the leakage flux path within the coupled magnetic structure 1110 has a minimal cross-sectional area. However, the leakage magnetic structure 1112, which partially surrounds the top, left, and right sides of the coupled magnetic structure 1110, provides a relatively large cross-sectional area for the leakage magnetic flux between the first ladder bar 1116 and the second ladder bar 1118. The leakage magnetic structure 1112 is formed from a second magnetic material with distributed gaps (e.g., iron powder molded or disposed in a binder in multiple film layers). The second magnetic material forming the leakage magnetic structure 1112 typically has a lower magnetic permeability than the first magnetic material forming the coupled magnetic structure 1110 because it is generally desirable for the magnetizing inductance of the coupled inductor 1100 to be significantly greater than the leakage inductance of the coupled inductor 1100. The desired leakage inductance value is achieved by changing the magnetic permeability of the second magnetic material and / or the cross-sectional area of ​​the leakage magnetic structure 1112 during the design process of the coupled inductor 1100 .

[0090] Composite core 1108 does not have exposed air gaps, thereby helping to generate minimal fringing flux. Additionally, leakage flux structure 1112 acts as a shield, ie, it separates coil 1122 from external components, thereby helping to minimize capacitive coupling between coil 1122 and external components.

[0091] The number of coupling teeth 1120 and associated coils 1122 may be varied without departing from the scope hereof. Furthermore, the configuration of the coils 1122 (e.g., the number of turns formed by the coils 1122 and / or the material forming the coils 1122) may also be varied without departing from the scope hereof. Figure 15-19 Several possible variations of the composite magnetic core of coupled inductor 1100 are shown.

[0092] In particular, Figure 15 is a perspective view of a coupled inductor 1500 for low electromagnetic interference having a length 1502, a width 1504, and a height 1506. Coupled inductor 1500 is similar to Figure 11 The coupled inductor 1100 is shown in FIG. 1 , except that the first ladder bar 1116 and the second ladder bar 1118 are replaced by an extended first ladder bar 1516 and an extended second ladder bar 1518 , respectively. Figure 11The leakage magnetic structure 1112 is also replaced by the leakage magnetic structure 1512, which is smaller than the leakage magnetic structure 1112 in the width 1504 direction. Figure 15 are shown with lines to illustrate internal features of coupled inductor 1500, and Figure 16 is a perspective view of leakage flux structure 1512 separated from the rest of coupled inductor 1500 . Figure 15 The first ladder bar 1516 and the second ladder bar 1518 are higher than the first ladder bar 1516 and the second ladder bar 1518 in the height 1506 direction. Figure 11 The first ladder bar 1116 and the second ladder bar 1118 extend further so that Figure 15 In the embodiment, Figure 11 Compared with the embodiment of FIG, a larger part of the leakage flux path is occupied by the magnetic material with high magnetic permeability. Therefore, assuming that all other things are the same, Figure 15 The coupled inductor 1500 with Figure 11 The coupled inductor 1100 will have a larger leakage inductance value. In addition, the first ladder bar 1516 and the second ladder bar 1518 partially constrain the leakage magnetic structure 1512 in the width 1504 direction, which improves the mechanical strength of the coupled inductor 1500.

[0093] Figure 17 is a perspective view of a coupled inductor 1700 for low electromagnetic interference having a length 1702, a width 1704, and a height 1706. Coupled inductor 1700 is similar to Figure 15 The coupled inductor 1500 is different in that the leakage magnetic structure 1512 is replaced by the leakage magnetic structure 1712. Figure 17 1700 is shown in a line drawing to illustrate the internal portion of the coupled inductor 1700. Figure 15 Compared with the leakage magnetic structure 1512, Figure 17 The leakage magnetic structure 1712 has a smaller cross-sectional area in the plane defined by the width 1702 and the height 1706. As a result, the coupled inductor 1700 will have a smaller leakage inductance value than the coupled inductor 1500, assuming all other factors are the same. Figure 17 1700 is shown in line diagram form to illustrate the internal features of coupled inductor 1700.

[0094] Figure 18 is a perspective view of coupled inductor 1800 having length 1802, width 1804, and height 1806. Coupled inductor 1800 is similar to Figure 15The coupled inductor 1500 is different in that the leakage magnetic structure 1512 is replaced by the leakage magnetic structure 1812. The first ladder bar 1516 and the second ladder bar 1518 are also replaced by the first ladder bar 1816 and the second ladder bar 1818 to correspond to the leakage magnetic structure 1812. Figure 18 1800 is shown in a line drawing to illustrate the internal features of the coupled inductor 1800, and Figure 19 FIG1 is a perspective view of a magnetic flux leakage structure 1812 separated from the rest of the coupled inductor 1800. The magnetic flux leakage structure 1812 has different cross-sectional areas in a plane defined by the length 1802 direction and the height 1806 direction. In particular, the magnetic flux leakage structure 1812 has a relatively small cross-sectional area in a top region 1826 above the coupling teeth 1120, and the magnetic flux leakage structure 1812 has a relatively large cross-sectional area at the end regions 1828 and 1830 of the coupled inductor 1800 (see FIG1 ). Figure 19 ). Therefore, leakage flux primarily flows through leakage structure 1812 at end regions 1828 and 1830, and the leakage inductance value can be adjusted during the design of coupled inductor 1800, for example, by varying the cross-sectional areas of end regions 1828 and 1830. Top region 1826 of leakage structure 1812 primarily serves as a shield, separating coil 1122 from external components. However, top region 1826 also provides a relatively high-impedance path for magnetic flux passing through leakage structure 1812.

[0095] In some embodiments of the coupled inductors discussed above, the coupling magnetic structure extends to the outer surface of the coupled inductor. Multiple examples of these embodiments can be linked together to effectively form a single coupled inductor having multiple coils. For example, Figure 20 Shown Figure 6 Three examples of coupled inductors 600 are shown, which are linked together to effectively form a single coupled inductor having nine coils 622. As is known in the art, multiple phases facilitate ripple current cancellation and fast transient response in multi-phase switching power converter applications. However, manufacturing a coupled inductor having multiple coils may be impractical. Linking multiple examples of the present coupled inductor advantageously enables multiple coils without having to manufacture a coupled inductor having multiple coils.

[0096] The coupled inductors discussed above have a "stepped" coupled magnetic structure that is advantageously scalable to accommodate any desired number of coils. However, the concepts disclosed herein may also be used with other configurations of coupled magnetic structures.

[0097] For example, Figure 21FIG2 is a perspective view of a coupled inductor 2100 for low electromagnetic interference, the coupled inductor 2100 having a length 2102, a width 2104, and a height 2106. The coupled inductor 2100 includes a composite magnetic core 2108 including a coupled magnetic structure 2110 embedded in a leakage magnetic structure 2112. The leakage magnetic structure 2112 is formed in a plurality of layers. Figure 21 The coupling magnetic structure 2110 forms a channel 2114 in the width 2104 direction, and the two coils 2122 extend through the channel 2114 in the width 2104 direction. The coupling magnetic structure 2110 is formed of a magnetic material with relatively high magnetic permeability (e.g., ferrite material) to promote strong magnetic coupling of the coils 2122.

[0098] The leakage magnetic structure 2112 is formed from a second magnetic material having distributed gaps (e.g., iron powder molded or deposited in a binder in multiple film layers). The second magnetic material forming the leakage magnetic structure 2112 typically has a lower magnetic permeability than the first magnetic material forming the coupled magnetic structure 2110. This is because it is generally desirable that the magnetizing inductance of the coupled inductor 2100 be significantly greater than the leakage inductance of the coupled inductor 2100. The desired leakage inductance value can be achieved by varying the magnetic permeability of the second magnetic material, the cross-sectional area of ​​the leakage magnetic structure 2112, and / or the configuration of the channel 2114 during the design of the coupled inductor 2100.

[0099] Composite core 2108 does not have exposed air gaps, thereby helping to generate minimal fringing flux. Additionally, leakage flux structure 2112 acts as a shield, ie, it separates coil 2122 from external components, thereby helping to minimize capacitive coupling between coil 2122 and external components.

[0100] As discussed above, in the current embodiment, the leakage inductance value can be adjusted by changing the magnetic permeability of the magnetic material forming the leakage magnetic structure and / or by changing the cross-sectional area of ​​the leakage magnetic structure. In addition, the leakage inductance value can be reduced by embedding flux suppression structures within the leakage magnetic structure. These flux suppression structures have a lower magnetic permeability than the magnetic material forming the leakage magnetic structure, and therefore, the flux suppression structures suppress the flow of leakage magnetic flux. The flux suppression structures can optionally be formed of a non-conductive material to prevent eddy currents from circulating therein. Desirably, the flux suppression structures do not extend to the outer surface of the leakage magnetic structure to prevent the generation of fringing flux.

[0101] Figure 22 An example of how the flux suppression structure can be used in the current embodiment is shown. In particular, Figure 22 FIG. 2 is a side view of a coupled inductor 2200 for low electromagnetic interference, which is similar to FIG. Figure 5The coupled inductor 500 is different in that it further includes a magnetic flux suppression structure 2202 embedded in the leakage magnetic structure 212. The magnetic flux suppression structure 2202 suppresses the flow of leakage magnetic flux through the leakage magnetic structure 212, thereby reducing the leakage inductance value of the coil 522.

[0102] The flux leakage structures disclosed herein can be formed using either a "cold pressing" method or a "hot pressing" method. Cold pressing involves pressing magnetic materials together at ambient temperature and under high pressure to solidify and mold the magnetic material. The high pressure pushes the magnetic particles together, and thus, cold pressing can achieve relatively high magnetic permeability. However, cold pressing also exerts considerable pressure on the coils within the magnetic material, requiring care to avoid damaging the coils, particularly in embodiments where the coils include dielectric insulation.

[0103] On the other hand, hot pressing involves curing the magnetic material at an elevated temperature without requiring substantial pressure. A relatively large amount of adhesive is required to compensate for the lack of pressure, and the adhesive limits the concentration of the magnetic particles. As a result, hot pressing generally cannot achieve as high a permeability as cold pressing. However, the leakage magnetic structure of the current embodiment may not require a high permeability because it is generally desirable that the leakage inductance value should be relatively low to ensure that the magnetizing inductance is greater than the leakage inductance. In addition, the lack of pressure when forming the leakage magnetic structure reduces the likelihood of coil damage. Therefore, when forming the leakage magnetic structure, the use of hot pressing may be preferred over cold pressing.

[0104] Applicants have also determined that low electromagnetic interference (EMI) can be achieved in coupled inductors by placing a metal shield over gaps in the leakage flux path of the magnetic core, or over any other source of alternating current (AC) magnetic fields in the coupled inductor. Any AC magnetic field near the metal shield generates eddy currents in the metal shield that oppose the AC magnetic field, thereby helping to minimize the potential for EMI from the AC magnetic field. Metal shields can be less expensive and simpler than composite magnetic cores, and they can help conduct heat away from the coupled inductor. However, the eddy currents circulating in the metal shield can consume considerable power during operation of the coupled inductor.

[0105] Figure 23-25 An example of a coupled inductor for low electromagnetic interference is shown that includes a metal shield instead of a composite magnetic core. In particular, Figure 23 is a perspective view of a coupled inductor 2300 for low electromagnetic interference having a length 2302, a width 2304, and a height 2306. The coupled inductor 2300 includes a metal shield 2324 covering the top, left, and right sides of the coupled inductor. Figure 2423 is an exploded perspective view of coupled inductor 2300, wherein metal shield 2324 is separated from the rest of the coupled inductor. Coupled inductor 2300 further includes a stepped magnetic core 2308, which includes a first ladder bar 2316 and a second ladder bar 2318 separated from each other in the width 2304 direction, and a plurality of coupling teeth 2320 (see FIG. 23) disposed between first ladder bar 2316 and second ladder bar 2318 in the width 2304 direction. Figure 25 ). Each coil 2322 is wound around each coupling tooth 2320, and the magnetic core 2308 magnetically couples the coils 2322 together. In some embodiments, the coils 2322 are similar to Figure 14 1122. Magnetic core 2308 also includes a drain plate 2326 that bridges first ladder bar 2316 and second ladder bar 2318 in the width 2304 direction. Drain plate 2326 forms a gap 2328 to provide energy storage and help prevent magnetic saturation of coupled inductor 2300. A metal shield 2324 covers gap 2328 and thereby helps prevent fringing magnetic flux generated by gap 2328 from coupling to external components. Figure 25 23 is a perspective view of coupled inductor 2300, wherein metal shield 2324 is omitted and first ladder bar 2316 and bushing 2326 are shown in line drawings to illustrate internal features of coupled inductor 2300. Magnetic core 2308 is formed of, for example, a magnetic material with high magnetic permeability (e.g., ferrite material).

[0106] The number of coupling teeth 2320 and corresponding coils 2322, as well as the configuration of the coils 2322, may be varied without departing from the scope of the present invention. Additionally, the metal shield 2324 may be varied as long as it at least substantially covers the gap 2328. For example, Figure 26 is a perspective view of a coupled inductor 2600 for low electromagnetic interference, which is similar to Figure 23 The coupled inductor 2300 is different in that the metal shield 2624 only covers the portions of the magnetic core 2308 near the gap 2328 (in Figure 26 is not visible in the ).

[0107] One possible application of the coupled inductors disclosed herein for low electromagnetic interference is in multi-phase switching power converter applications, including but not limited to multi-phase boost converter applications, multi-phase step-up converter applications, or multi-phase buck-boost converter applications. For example, Figure 27 The coupled inductor 200 ( Figure 2 ) is a possible use in a multi-phase buck converter 2700. Each coil 222 is electrically coupled to a corresponding switching node V x Shared output node V oA corresponding switching circuit 2702 is electrically coupled to each switching node V x Each switching circuit 2702 is electrically coupled to an input port 2704, which is electrically coupled to a power supply 2706. An output port 2708 is electrically coupled to an output node V o Each switching circuit 2702 and corresponding inductor are collectively referred to as a "phase" 2710 of the converter. Thus, the multi-phase buck converter 2700 is a three-phase converter.

[0108] Controller (CTRL) 2712 causes each switching circuit 2702 to repeatedly switch its corresponding coil end between power source 2706 and ground, thereby switching its coil end between two different voltage levels, in order to transfer power from power source 2706 to a load (not shown) electrically coupled across output port 2708. Controller 2712 typically causes switching circuit 2702 to switch at a relatively high frequency (e.g., 100 kHz or higher) to promote low ripple current amplitude and fast transient response, and to ensure that switching-induced noise is above a frequency at which it would be perceived by humans. Furthermore, in certain embodiments, controller 2712 causes switching circuit 2702 to switch out of phase with respect to each other in the time domain in order to improve transient response and promote ripple current cancellation in output capacitor 2704.

[0109] Each switching circuit 2702 includes a control switching device 2716 that alternately switches between its conductive state and its non-conductive state under the command of the controller 2712. Each switching circuit 2702 also includes a freewheeling device 2718 that is suitable for providing a path for current through its corresponding coil 222 when the control switching device 2716 of the switching circuit transitions from its conductive state to its non-conductive state. The freewheeling device 2718 can be a diode, as shown, to improve system simplicity. However, in certain alternative embodiments, the freewheeling device 2718 can be supplemented or replaced by a switching device that operates under the command of the controller 2712 to improve converter performance. For example, the diode in the freewheeling device 2718 can be supplemented by the switching device to reduce the forward voltage drop of the freewheeling device 2718. In the context of the present disclosure, a switching device includes, but is not limited to, a bipolar junction transistor, a field effect transistor (e.g., an N-channel or P-channel metal oxide semiconductor field effect transistor, a junction field effect transistor, a metal semiconductor field effect transistor), an insulated gate bipolar junction transistor, a thyristor, or a silicon controlled rectifier.

[0110] The controller 2712 is optionally configured to control the switching circuit 2702 to regulate one or more parameters of the multi-phase buck converter 2700, such as input voltage, input current, input power, output voltage, output current, or output power. The buck converter 2700 typically includes one or more input capacitors 2702, one or more input capacitors 2720 electrically coupled across an input port 2704 to provide input current to a ripple component of the switching circuit 2702. In addition, one or more output capacitors 2714 are typically electrically coupled across an output port 2708 to shunt ripple current generated by the switching circuit 2702.

[0111] Buck converter 2700 can be modified to have a different number of phases. For example, converter 2700 can be modified to have four phases and use Figure 11 Buck converter 2700 may also be modified to use one of the other coupled inductors disclosed herein, such as coupled inductors 400, 500, 600, 800, 1500, 1700, 1800, 2100, 2200, 2300, 2600, 2800 (discussed below), 3500 (discussed below), or 3800 (discussed below). Furthermore, buck converter 2700 may also be modified to have different multiphase switching power converter schemes (e.g., a multiphase buck converter or a multiphase buck-boost converter scheme) or isolation schemes (e.g., a flyback or forward converter) without departing from its scope.

[0112] Additionally, applicants have determined that multiple discrete inductors (e.g., multiple drum core discrete inductors) can be used with a magnetic flux leakage structure to form a coupled inductor for low electromagnetic interference. For example, Figure 28 2 is a front view of a coupled inductor 2800 for low electromagnetic interference, which includes two drum core discrete inductors 2801 and a leakage magnetic structure 2812. The coupled inductor 2800 has a length 2802, a width 2804, and a height 2806. Figure 29 is a top plan view of the coupled inductor 2800, Figure 30 is the edge of the coupled inductor 2800 Figure 28 A cross-sectional view taken along line 30A-30A, Figure 31 is a side view of coupled inductor 2800, and Figure 32 is a front view of an example of a drum core discrete inductor 2801 separated from the rest of the coupled inductor 2800.

[0113] The drum core discrete inductors 2801 are connected along the length 2802. The leakage magnetic structure 2812 and several elements of the drum core discrete inductors 2801 together form a composite magnetic core 2808, which includes a coupled magnetic structure 2810 and a leakage magnetic structure 2812. Figure 33 is a front view of coupled magnetic structure 2810 separated from the rest of coupled inductor 2800, and Figure 34 28 is a front view of a leakage flux structure 2812 separated from the rest of the coupled inductor 2800. The coupled magnetic structure 2810 formed by the elements of the two instances of the drum core discrete inductor 2801 is a stepped magnetic core comprising a first ladder bar 2816, a second ladder bar 2818, and a plurality of coupling teeth 2820. The first ladder bar 2816 is separated from the second ladder bar 2818 in the height 2806 direction, and each coupling tooth 2820 is positioned between the first ladder bar 2816 and the second ladder bar 2818 in the height 2806 direction. The first ladder bar 2816 includes a plurality of first ladder bar sub-segments 2817 arranged in a row along the length 2802 direction, wherein each first ladder bar sub-segment 2817 is part of a corresponding instance of the drum core discrete inductor 2801. Likewise, second ladder bar 2818 includes a plurality of second ladder bar sub-segments 2819 arranged in a row along length 2802, wherein each second ladder bar sub-segment 2819 is part of a corresponding instance of drum core discrete inductor 2801. In some embodiments, adjacent first ladder bar sub-segments 2817 are separated from one another along length 2802 by corresponding gaps 2826, and adjacent second ladder bar sub-segments 2819 are separated from one another along length 2802 by corresponding gaps 2828.

[0114] The magnetic flux leakage structure 2812 includes a plurality of leakage sub-segments 2813, each of which is positioned between a first ladder bar 2816 and a second ladder bar 2818 in height 2806. In some embodiments, all instances of leakage sub-segments 2813 are separated from one another in length 2802, while in some embodiments, at least two instances of leakage sub-segments 2813 are connected in length 2802. In a specific embodiment, the magnetic flux leakage structure 2812 is bounded in height 2806 by a first ladder bar 2816 and a second ladder bar 2818, as shown. The number of leakage sub-segments 2813 can vary without departing from the scope of this disclosure. For example, in an alternative embodiment, the leakage sub-segments 2813 at the ends of the coupled inductor 2800 are omitted.

[0115] Each coil 2822 forms one or more turns around each coupling tooth 2820. The coupling magnetic structure 2810 magnetically couples the coils 2822 together and is formed of a first magnetic material with relatively high magnetic permeability (eg, ferrite material) to promote strong magnetic coupling of the coils 2822.

[0116] The leakage magnetic structure 2812 is formed from a second magnetic material with distributed gaps (e.g., iron powder molded or placed in a binder in multiple film layers). The leakage magnetic structure 2812 provides a path for leakage magnetic flux between the first ladder bar 2816 and the second ladder bar 2818 in the height 2806 direction. The second magnetic material forming the leakage magnetic structure 2812 typically has a lower magnetic permeability than the first magnetic material forming the coupled magnetic structure 2810. This is because it is generally desirable that the magnetizing inductance of the coupled inductor 2800 is significantly greater than the leakage inductance of the coupled inductor 2800. The desired leakage inductance value is achieved by varying the magnetic permeability of the second magnetic material and / or the cross-sectional area of ​​the leakage magnetic structure 2812 during the design of the coupled inductor 2800.

[0117] Coupled inductor 2800 can be modified to include one or more additional instances of drum core discrete inductors 2801 connected in the direction of length 2802. For example, an alternative embodiment of coupled inductor 2800 includes three instances of drum core discrete inductors 2801 connected in the direction of length 2802 to obtain a three-coil coupled inductor. Furthermore, the configuration of coil 2822 can be varied. For example, coil 2822 can be formed with fewer or more turns than shown. Furthermore, while coil 2822 is shown as a foil coil, coil 2822 can instead be a wire wound or spiral coil. Furthermore, coil 2822 can terminate on a different side of coupled inductor 2800 than shown, and / or coil 2822 can terminate in a manner different from that shown, such as with contacts for surface mount connection to a printed circuit board.

[0118] Figures 35-37 Another example of a coupled inductor for low electromagnetic interference is shown, which is formed by multiple discrete inductors and a leakage magnetic structure. In particular, Figure 35 35 is a perspective view of a coupled inductor 3500 for low electromagnetic interference, which includes two drum core discrete inductors 3501 and a leakage magnetic structure 3512. Figure 36 An example of a drum core discrete inductor 3501 and a portion of a leakage flux structure 3512 separated from the rest of the coupled inductor 3500. The coupled inductor 3500 has a length 3502, a width 3504, and a height 3506. The drum core discrete inductors 3501 are connected along the length 3502.

[0119] The leakage flux structure 3512 and several elements of the drum core discrete inductor 3501 together form a composite magnetic core 3508 , which includes a coupled magnetic structure 3510 and a leakage flux structure 3512 . Figure 37FIG3 is a top plan view of coupled magnetic structure 3510 separated from the rest of coupled inductor 3500. Coupled magnetic structure 3510, formed by elements of two examples of drum core discrete inductor 3501, is a stepped magnetic core comprising a first ladder bar 3516, a second ladder bar 3518, and a plurality of coupling teeth 3520. First ladder bar 3516 is separated from second ladder bar 3518 in width 3504, and each coupling tooth 3520 is positioned between first ladder bar 3516 and second ladder bar 3518 in width 3504. First ladder bar 3516 comprises a plurality of first ladder bar sub-segments 3517 arranged in a row along length 3502, wherein each first ladder bar sub-segment 3517 is part of a corresponding example of drum core discrete inductor 3501. Likewise, second ladder bar 3518 includes a plurality of second ladder bar sub-segments 3519 arranged in a row along length 3502, wherein each second ladder bar sub-segment 3519 is part of a corresponding instance of drum core discrete inductor 3501. In some embodiments, adjacent first ladder bar sub-segments 3517 are separated from one another along length 3502 by corresponding gaps 3526, and adjacent second ladder bar sub-segments 3519 are separated from one another along length 3502 by corresponding gaps 3528.

[0120] The leakage magnetic structure 3512 includes a plurality of leakage sub-segments 3513, wherein each leakage sub-segment 3513 is positioned between a first ladder bar 3516 and a second ladder bar 3518 in the width 3504 direction. In some embodiments, all leakage sub-segment 3513 instances are separated from each other in the length 3502 direction, as shown, while in some other embodiments, at least two leakage sub-segment 3513 instances are connected in the length 3502 direction. In a specific embodiment, the leakage magnetic structure 3512 is bounded by a first ladder bar 3516 and a second ladder bar 3518 in the width 3504 direction, as shown. The number and configuration of the leakage sub-segments 3513 may be varied without departing from the scope hereof. For example, alternative embodiments of the coupled inductor 3500 also include a Figure 35 The corresponding drain sub-segment 3513 below each coupling tooth 3510 shown in FIG. Figure 35 35. Although the drain segment 3513 is shown as being arcuate, the shape of the drain segment 3513 can be changed without departing from its scope. For example, in some embodiments, the drain segment 3513 is rectangular.

[0121] The corresponding coil 3522 forms one or more turns around each coupling tooth 3520. Figure 35Only one coil 3522 is visible in the perspective view of FIG. The coupling magnetic structure 3510 magnetically couples the coils 3522 together, and the front magnetic structure 3510 is formed of a first magnetic material (e.g., a ferrite material) with relatively high magnetic permeability to promote strong magnetic coupling of the coils 3522.

[0122] The leakage magnetic structure 3512 is formed from a second magnetic material with distributed gaps (e.g., iron powder molded or placed in a binder in multiple film layers). The leakage magnetic structure 3512 provides a path for leakage magnetic flux between the first ladder bar 3516 and the second ladder bar 3518 in the width 3504 direction. The second magnetic material forming the leakage magnetic structure 3512 typically has a lower magnetic permeability than the first magnetic material forming the coupled magnetic structure 3510 because it is generally desirable that the magnetizing inductance of the coupled inductor 3500 is significantly greater than the leakage inductance of the coupled inductor 3500. The desired leakage inductance value is achieved by varying the magnetic permeability of the second magnetic material and / or the cross-sectional area of ​​the leakage magnetic structure 3512 during the design of the coupled inductor 3500.

[0123] Coupled inductor 3500 can be modified to include one or more additional instances of drum core discrete inductors 3501 connected along length 3502. For example, an alternative embodiment of coupled inductor 3500 includes three instances of drum core discrete inductors 3501 connected along length 3502 to create a three-coil coupled inductor. Furthermore, the configuration of coil 3522 can be varied. For example, coil 3522 can be formed with fewer or more turns than shown. Furthermore, while coil 3522 is shown as a foil coil, coil 3522 can alternatively be a wire wound or spiral coil. Furthermore, coil 3522 can terminate on a different side of coupled inductor 3500 than shown, and / or coil 3522 can terminate in a manner different from that shown, such as with contacts for surface mount connection to a printed circuit board.

[0124] Figures 38-43 Another example of a coupled inductor for low electromagnetic interference is shown, the coupled inductor being formed of a plurality of discrete inductors. In particular, Figure 38 FIG. 3 is a front view of a coupled inductor 3800 for low electromagnetic interference, which includes two drum core discrete inductors 3801 . Figure 39 is a top plan view of the coupled inductor 3800, Figure 40 is the edge of the coupled inductor 3800 Figure 38 A cross-sectional view taken along line 40A-40A, Figure 41 is a side view of coupled inductor 3800, and Figure 4238 is a front view of an example of a drum core discrete inductor 3801 separated from the rest of coupled inductor 3800. Coupled inductor 3800 has a length 3802, a width 3804, and a height 3806. Drum core discrete inductors 3801 are connected along length 3802.

[0125] Several elements of drum core discrete inductor 3801 form a coupled magnetic structure 3810 , and coupled inductor 3800 additionally includes a leakage magnetic structure 3812 . Figure 43 3800 is a front view of coupled magnetic structure 3810 separated from the rest of coupled inductor 3800. Coupled magnetic structure 3810, formed by elements of two instances of drum core discrete inductor 3801, is a stepped magnetic core comprising a first ladder bar 3816, a second ladder bar 3818, and a plurality of coupling teeth 3820. First ladder bar 3816 is separated from second ladder bar 3818 in height 3806, and each coupling tooth 3820 is positioned between first ladder bar 3816 and second ladder bar 3818 in height 3806. First ladder bar 3816 includes a plurality of first ladder bar sub-segments 3817 arranged in a row along length 3802, wherein each first ladder bar sub-segment 3817 is part of a corresponding instance of drum core discrete inductor 3801. Likewise, second ladder bar 3818 includes a plurality of second ladder bar sub-segments 3819 arranged in a row along length 3802, wherein each second ladder bar sub-segment 3819 is part of a corresponding instance of drum core discrete inductor 3801. In some embodiments, adjacent first ladder bar sub-segments 3817 are separated from one another along length 3802 by corresponding gaps 3826, and adjacent second ladder bar sub-segments 3819 are separated from one another along length 3802 by corresponding gaps 3828.

[0126] Magnetic flux leakage structure 3812 includes one or more inner leakage plates 3813 and outer leakage plates 3830. Each inner leakage plate 3813 is positioned between a first rung 3816 and a second rung 3818 in height 3806. The outer leakage plates 3830 bridge the first rung 3816 and the second rung 3818 in height 3806 and, when coupled inductor 3800 is viewed in cross-section in height 3806, do not overlap the first rung 3816 and the second rung 3818. The outer leakage plates 3830 can optionally be separated from the first rung 3816 and the second rung 3818 in width 3804, for example, by non-magnetic spacers 3832, as shown. Each inner leakage plate 3813 can optionally be spaced apart from the first rung 3816 and the second rung 3818 by respective gaps 3834 and 3836. Only one example of each of gaps 3834 and 3836 is identified to promote clarity of illustration.The number and configuration of internal bushings 3813 may vary without departing from the scope hereof.

[0127] Each coil 3822 forms one or more turns around each coupling tooth 3820. The coupling magnetic structure 3810 magnetically couples the coils 3822 together, and the leakage magnetic structure 3812 provides a path for leakage magnetic flux between the first ladder bar 3816 and the second ladder bar 3818 in the height 3806 direction. In some embodiments, each of the coupling magnetic structure 3810 and the leakage magnetic structure 3812 is formed of a first magnetic material with relatively high magnetic permeability (e.g., a ferrite material).

[0128] Coupled inductor 3800 can be modified to include one or more additional instances of drum core discrete inductors 3801 connected along length 3802. For example, an alternative embodiment of coupled inductor 3800 includes three instances of drum core discrete inductors 3801 connected along length 3802 to create a three-coil coupled inductor. Furthermore, the configuration of coil 3822 can be varied. For example, coil 3822 can be formed with fewer or more turns than shown. Furthermore, while coil 3822 is shown as a foil coil, coil 3822 can alternatively be a wire wound or spiral coil. Furthermore, coil 3822 can terminate on a different side of coupled inductor 3800 than shown, and / or coil 3822 can terminate in a manner different from that shown, such as with contacts for surface mount connection to a printed circuit board.

[0129] Applicants have determined that forming a coupled inductor for low electromagnetic interference from a plurality of discrete inductors offers significant advantages. For example, forming a coupled inductor from a plurality of discrete inductors improves scalability by enabling different numbers of coils to be realized simply by varying the number of discrete inductors connected together. Furthermore, forming a coupled inductor from a plurality of discrete inductors improves manufacturing ease. In particular, conventional coupled inductor cores typically have complex shapes, and assembling coils on such complex cores is difficult. In contrast, discrete inductor cores typically have relatively simple shapes (e.g., drum shapes), and therefore, assembling coils on discrete inductor cores is typically simpler than on coupled inductor cores. Forming a coupled inductor from a plurality of discrete inductors improves manufacturing ease by enabling coils to be assembled on relatively simple discrete inductor cores.

[0130] Furthermore, when forming small coupled inductors, forming the coupled inductor from multiple discrete inductors improves manufacturing simplicity and achieves high manufacturing yields. In particular, conventional coupled inductor magnetic cores often have complex shapes, as described above, and small magnetic cores with complex shapes are susceptible to breakage during manufacturing. However, magnetic cores used for discrete inductors often have relatively simple shapes, as described above. Therefore, forming the coupled inductor from multiple discrete inductors improves manufacturing simplicity and achieves high manufacturing yields by reducing or even eliminating the need to work with small, complex-shaped magnetic cores during manufacturing.

[0131] Changes may be made in the above-described coupled inductors, systems, and methods without departing from their scope. For example, although the ladder bars and coupling teeth are shown as rectangular, the shapes of these elements may be varied. It should be noted, therefore, that the matter contained in the foregoing description and shown in the accompanying drawings is to be construed as illustrative and not limiting. The appended claims are intended to cover the generic and subordinate features described herein and all statements of the scope of the present apparatus, methods, and systems that, as a matter of language, might be said to fall therein.

Claims

1. A coupled inductor for low electromagnetic interference, comprising: Multiple coils; and a composite magnetic core, the composite magnetic core comprising a coupling magnetic structure formed of a first magnetic material, the coupling magnetic structure being at least partially embedded in a leakage magnetic structure formed of a second magnetic material, the coupling magnetic structure magnetically coupling the plurality of coils together and having (a) a first ladder bar and a second ladder bar separated from each other in a first direction and (b) a coupling tooth connected between the first ladder bar and the second ladder bar in a second direction, the coupling tooth forming a small gap in series with the coupling magnetic structure to control the magnetizing inductance of the coupled inductor, the first ladder bar and the second ladder bar extending beyond the coupling teeth in the second direction and being longer than the coupling teeth in a third direction orthogonal to the first direction and the second direction, the plurality of coils at least partially winding around the coupling teeth, the leakage magnetic structure enclosing the coupling teeth between the first ladder bar and the second ladder bar and providing a path for leakage magnetic flux on the outside of the coupling magnetic structure.

2. The coupled inductor according to claim 1, wherein: The first magnetic material has a greater magnetic permeability than the second magnetic material.

3. The coupled inductor according to claim 2, wherein: The first magnetic material includes a ferrite material and the second magnetic material includes iron powder in a binder.

4. The coupled inductor according to claim 1, wherein: The magnetic flux leakage structure at least partially covers the plurality of coils.

5. The coupled inductor according to claim 1, wherein: The magnetic flux leakage structure provides a path for magnetic flux leakage in the first direction between the first ladder bar and the second ladder bar.

6. The coupled inductor according to claim 1, wherein: The magnetic flux leakage structure is defined by the first ladder bars and the second ladder bars in the first direction.

7. The coupled inductor according to claim 1, wherein: The magnetic flux leakage structure is defined by the first ladder bars and the second ladder bars in the second direction.

8. The coupled inductor according to claim 1, wherein: The magnetic flux leakage structure is defined by the first ladder rod and the second ladder rod in the third direction.

9. The coupled inductor according to claim 1, wherein: The coupling teeth are rectangular.

10. The coupled inductor according to claim 1, wherein: The plurality of coils terminate at an end of the third direction opposite to the magnetic flux leakage structure.

11. The coupled inductor of claim 1, wherein: The coupled inductor also includes solder contacts at ends of the plurality of coils.

12. The coupled inductor according to claim 1, wherein: The coupling magnetic structure and the leakage magnetic structure include one or more ferrite magnetic materials.

13. The coupled inductor of claim 1, wherein: The coupling teeth consist of four coupling teeth, and the plurality of coils consist of four coils.

14. The coupled inductor of claim 1, wherein: The magnetic flux leakage structure forms a distributed gap.

15. The coupled inductor of claim 14, wherein: The magnetic flux leakage structure is molded in multiple film layers.

16. The coupled inductor of claim 1, wherein: The composite magnetic core has no exposed air gap.

17. The coupled inductor of claim 1, wherein: The magnetic flux leakage structure shields the plurality of coils from an external circuit.

18. The coupled inductor of claim 1, wherein: The plurality of coils comprises a foil.

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