CN106935384B

CN106935384B - Coupled inductor array and related method

Info

Publication number: CN106935384B
Application number: CN201611170310.3A
Authority: CN
Inventors: 姚迪; A·伊克里亚尼科夫
Original assignee: Wal Tara Semiconductor Ltd
Current assignee: Wal Tara Semiconductor Ltd
Priority date: 2015-12-18
Filing date: 2016-12-16
Publication date: 2019-12-10
Anticipated expiration: 2036-12-16
Also published as: CN106935384A

Abstract

A coupled inductor array includes a monolithic magnetic core formed of a magnetic material with distributed gaps, first and second windings, and a low permeability magnetic structure. The first and second windings form respective first and second winding turns around a common winding axis extending in the height direction. A low permeability magnetic structure is embedded in the monolithic core and looped around the common winding axis. The low permeability magnetic structure separates the first and second winding turns in a height direction and is formed of a magnetic material having a lower permeability than the one or more magnetic materials forming the monolithic magnetic core. One possible application of the coupled inductor array is in a multi-phase switched power converter.

Description

Coupled inductor array and related method

RELATED APPLICATIONS

This application is a partial continuation of U.S. patent application serial No.14/199833, filed 3/6/2014, which is a partial continuation of U.S. patent application serial No.13/303062, filed 11/22/2011. Each of the above-mentioned applications is incorporated herein by reference.

Background

It is known to electrically couple a plurality of switched sub-converters in parallel to increase the switched power converter capacity and/or improve the switched power converter performance. Multi-phase switching power converters generally have better performance than single-phase switching power converters of otherwise similar design. In particular, out-of-phase switching in a multiphase converter causes ripple current cancellation at the converter output filter and allows the multiphase converter to have a better transient response than an otherwise similar single phase converter.

As taught by Schultz et al in U.S. patent No.6362986, which is incorporated herein by reference, the performance of a multiphase switching power converter can be improved by magnetically coupling two or more phases of energy storage inductors. Such magnetic coupling causes ripple current cancellation in the inductors and increases ripple switching frequency, thereby improving converter transient response, reducing input and output filtering requirements, and/or increasing converter efficiency relative to an otherwise equivalent converter without magnetically coupled inductors.

Two or more magnetically coupled inductors are often collectively referred to as "coupled inductors" and have associated leakage and magnetizing inductance values. The magnetizing inductance is related to the magnetic coupling between the windings; the larger the magnetizing inductance, the stronger the magnetic coupling between the windings. Leakage inductance, on the other hand, is associated with energy storage. Thus, the greater the leakage inductance, the more energy is stored in the inductance. As taught by Schultz et al, a larger magnetizing inductance is desirable to better realize the advantages of using coupled inductors instead of discrete inductors in a switched mode power converter. On the other hand, the leakage inductance must generally be within a relatively small range of values. Specifically, the leakage inductance must be large enough to avoid excessive ripple current amplitude, but not so large as to degrade converter transient response.

Disclosure of Invention

In an embodiment, a coupled inductor array includes a magnetic core and N windings, where N is an integer greater than one. The core has opposing first and second sides, with a linear separation distance between the first and second sides defining a length of the core. The N windings pass at least partially through the core in a length direction, and each of the N windings forms a loop in the core about a respective winding axis. Each winding axis is generally perpendicular to the length direction, and each winding axis may be parallel to but offset from each other winding axis. Each winding has opposite first and second ends extending at least towards the first and second sides of the magnetic core, respectively.

In an embodiment, a multiphase switched mode power converter includes a coupled inductor and N switching circuits, where N is an integer greater than one. The coupled inductor includes a magnetic core having opposing first and second sides, and a linear separation distance between the first and second sides defines a length of the magnetic core. The N windings pass at least partially through the magnetic core in a length direction, and each of the N windings forms a loop in the magnetic core about a respective winding axis. Each winding axis is generally perpendicular to the length direction and each winding axis is parallel to but offset from each other winding axis. Each winding has opposite first and second ends extending at least towards the first and second sides of the magnetic core, respectively. Each switching circuit is adapted to enable switching of the first end of a respective one of the N windings between at least two different voltage levels.

In an embodiment, an electronic device includes an integrated circuit package, a semiconductor die housed in the integrated circuit package, and a coupling inductor housed in the integrated circuit package and electrically coupled to the semiconductor die. The coupled inductor includes a magnetic core having opposing first and second sides, a linear separation distance between the first and second sides defining a length of the magnetic core. The coupled inductor further includes N windings passing at least partially through the magnetic core in a length direction, where N is an integer greater than one. Each of the N windings forms a loop in the magnetic core about a respective winding axis, and each winding axis is substantially perpendicular to the length direction, and each winding axis is parallel to but offset from each other winding axis. Each winding has opposite first and second ends extending at least towards the first and second sides of the magnetic core, respectively.

In an embodiment, a coupled inductor array has a length, a width, and a height. The coupled inductor array includes a monolithic magnetic core formed of a magnetic material having distributed gaps, and a plurality of windings embedded in the monolithic magnetic core. Each winding forms a respective winding loop of one or more turns around a respective winding axis, and each winding axis extends in the height direction. The area of the monolithic core surrounded by the winding loops may be larger than the area of the monolithic core outside the winding loops, as seen when the array of coupled inductors is viewed in cross-section in the height direction.

In an embodiment, a method for forming a coupled inductor array comprising a magnetic core having at least one non-magnetic structure embedded therein comprises the steps of: (1) disposing at least two conductor layers on the core portion in a height direction such that the conductor layers at least partially form at least two winding loops, as seen in the height direction; (2) disposing one or more non-magnetic structures on the core portion and outside the winding loops, as seen in a height direction; and (3) disposing a magnetic material on the core portion, the conductor layer, and the one or more non-magnetic structures.

In an embodiment, a coupled inductor array having a length, a width, and a height includes a monolithic magnetic core formed from one or more magnetic materials having distributed gaps, first and second windings, and a low permeability magnetic structure. The first and second windings form respective first and second winding turns around a common winding axis extending in a height direction, and each of the first and second winding turns is embedded in the monolithic magnetic core. A low permeability magnetic structure is embedded in the monolithic core and looped around a common winding axis. A low permeability magnetic structure separates the first and second winding turns in the height direction and is formed of a magnetic material having a lower permeability than the one or more magnetic materials forming the monolithic core.

In an embodiment, a coupled inductor array having a length, a width, and a height includes a monolithic magnetic core formed of one or more magnetic materials having a distributed gap, a first winding, and a second winding. The first winding is embedded in the monolithic core and forms one or more first winding turns around respective winding axes extending in the height direction. Each winding axis is offset in the width direction from each other winding axis. The second winding is embedded in the monolithic magnetic core, and the second winding forms a respective second winding turn for each of the one or more first winding turns. Each second winding turn and its respective first winding turn collectively enclose a respective common portion of the monolithic magnetic core as seen when the coupled inductor array is viewed through a cross-section in a height direction.

Drawings

Fig. 1 shows a perspective view of an array of coupled inductors, according to an embodiment.

Fig. 2 shows a perspective view of the coupled inductor array of fig. 1, wherein the magnetic core of the coupled inductor array is shown as transparent.

Fig. 3 shows a top plan view of the coupled inductor array of fig. 1 with the top plate removed.

Fig. 4 shows a top plan view of an alternative embodiment of the fig. 1 coupled inductor array with the top plate removed and with a longer winding loop than in the fig. 3 embodiment.

Fig. 5 shows a top plan view of an alternative embodiment of the fig. 1 coupled inductor array with the top plate removed and with a smaller winding loop than in the fig. 3 embodiment.

Fig. 6 shows a top plan view of an alternative embodiment of the fig. 1 coupled inductor array with the top plate removed and with a circular winding ring.

Fig. 7 shows a cross-sectional view of the coupled inductor array of fig. 1.

Fig. 8 shows a cross-sectional view of an alternative embodiment of the fig. 1 coupled inductor array including coupling teeth.

Fig. 9 shows a cross-sectional view of an alternative embodiment of the coupled inductor array of fig. 1 including both drain teeth (leakage teeth) and coupling teeth.

Fig. 10 shows a cross-sectional view of another alternative embodiment of the coupled inductor array of fig. 1 including both a drain tooth and a coupling tooth.

Fig. 11 shows a cross-sectional view of an alternative embodiment of the coupled inductor array of fig. 1 including a drain tooth, a coupling tooth, and a non-magnetic spacer separating the coupling tooth from the top plate.

Fig. 12 shows a schematic diagram of a three-phase buck converter including the coupled inductor array of fig. 1, according to an embodiment.

Fig. 13 illustrates one possible printed circuit board footprint for applying the coupled inductor array of fig. 1 in a multi-phase buck converter application, in accordance with an embodiment.

Fig. 14 shows a perspective view of an array of coupled inductors similar to the array of coupled inductors of fig. 1, but in which the winding second ends are electrically coupled to a common tongue, in accordance with an embodiment.

Fig. 15 illustrates one possible printed circuit board footprint for applying the coupled inductor array of fig. 14 in a multi-phase buck converter application, in accordance with an embodiment.

Fig. 16 shows a perspective view of a coupled inductor array similar to the coupled inductor array of fig. 1, but where the windings are wire windings having a substantially arc-shaped cross-section, in accordance with an embodiment.

Fig. 17 illustrates one possible printed circuit board footprint for applying the coupled inductor array of fig. 16 in a multi-phase buck converter application, in accordance with an embodiment.

Fig. 18 shows a perspective view of an array of coupled inductors similar to the array of coupled inductors of fig. 16, but with the winding ends extending from opposite core sides, in accordance with an embodiment.

Fig. 19 illustrates one possible printed circuit board footprint for applying the coupled inductor array of fig. 18 in a multi-phase buck converter application, in accordance with an embodiment.

fig. 20 shows a perspective view of a dual winding coupled inductor array according to an embodiment.

Fig. 21 shows a top plan view of an alternative embodiment of the fig. 20 coupled inductor array with the top plate removed and with a circular winding ring.

Fig. 22 shows a top plan view of an alternative embodiment of the fig. 20 coupled inductor array with the top plate removed and with the windings formed from the conductive film.

Fig. 23 shows a perspective view of a coupled inductor array similar to the coupled inductor array of fig. 1, but having solder tabs on both its top and bottom surfaces, in accordance with an embodiment.

Fig. 24 shows an electronic device according to an embodiment.

Fig. 25 shows another electronic device according to an embodiment.

Fig. 26 is a side elevational view of a prior art coupled inductor including a ladder core formed of ferrite magnetic material.

FIG. 27 shows a side cross-sectional view of a prior art magnetic device.

FIG. 28 shows a top cross-sectional view of the prior art magnetic device of FIG. 27.

FIG. 29 shows a top cross-sectional view of a magnetic device in which the windings are in close proximity.

Figure 30 is a top plan view of a coupled inductor array including a monolithic magnetic core formed of magnetic material with distributed gaps, under an embodiment.

Fig. 31 is a side elevational view of the fig. 30 coupled inductor array.

Fig. 32 is a cross-sectional view taken along line 30A-30A of fig. 30.

Fig. 33 is a cross-sectional view taken along line 31A-31A of fig. 31.

FIG. 34 is a cross-sectional view of a magnetic device.

FIG. 35 shows the magnetic device of FIG. 34 with an equivalent electrical model projected thereon.

FIG. 36 is an electrical model showing the magnetic flux flowing through the cross-section of the magnetic device of FIG. 34.

Fig. 37 is a graph showing relative magnetic flux density in a cross section of the magnetic device of fig. 34.

Fig. 38 is a top plan view of an array of coupled inductors including a multilayer film magnetic core including nonmagnetic structures included in a monolithic magnetic core, under an embodiment.

Fig. 39 is a side elevational view of the fig. 38 coupled inductor array.

Fig. 40 is a cross-sectional view of the coupled inductor array of fig. 38 taken along line 38A-38A of fig. 38.

Fig. 41 is a cross-sectional view of the coupled inductor array of fig. 38 taken along line 39A-39A of fig. 39.

Fig. 42 is a cross-sectional view of a coupled inductor array including a non-magnetic structure formed from a conductive material, according to an embodiment.

Figure 43 illustrates a method for forming a coupled inductor array including a magnetic core having a non-magnetic structure embedded therein, according to an embodiment.

Fig. 44 is a cross-sectional view of a coupled inductor array similar to the coupled inductor array of fig. 33, but with larger winding loops than the winding loops of the coupled inductor array of fig. 33, under an embodiment.

Fig. 45 is a reproduction of the cross-sectional view of fig. 33.

Fig. 46 shows a cross-sectional view of an array of coupled inductors without cross-bonding of windings, according to an embodiment.

Fig. 47 shows a top plan view of a coupled inductor array including interdigitation of windings according to an embodiment.

Fig. 48 shows a side elevation view of the fig. 47 coupled inductor array.

Fig. 49 shows a cross-sectional view of the coupled inductor array of fig. 47 taken along line 47A-47A of fig. 47.

Fig. 50 illustrates a cross-sectional view of the fig. 48 coupled inductor array taken along line 48A-48A of fig. 48.

Fig. 51 is a perspective view of a coupled inductor array including two vertically stacked windings according to an embodiment.

Fig. 52 is a top plan view of the fig. 51 coupled inductor array.

Fig. 53 is a side elevational view of the fig. 51 coupled inductor array.

Fig. 54 is a vertical cross-sectional view of the fig. 51 coupled inductor array.

Fig. 55 is a horizontal cross-sectional view of the fig. 51 coupled inductor array.

Fig. 56 shows the fig. 51 coupled inductor array without the magnetic core in an exploded view.

FIG. 57 is a vertical cross-sectional view similar to FIG. 54, except that the cross-sectional view shows an approximate flux path within the monolithic core.

Fig. 58 is a perspective view of an array of coupled inductors in which each winding forms a plurality of winding turns, according to an embodiment.

Fig. 59 is a top plan view of the fig. 58 coupled inductor array.

Fig. 60 is a side elevational view of the fig. 58 coupled inductor array.

Fig. 61 is a vertical cross-sectional view of the coupled inductor array of fig. 58.

Fig. 62 is another vertical cross-sectional view of the coupled inductor array of fig. 58.

fig. 63 is a horizontal cross-sectional view of the coupled inductor array of fig. 58.

Fig. 64 is another horizontal cross-sectional view of the coupled inductor array of fig. 58.

Fig. 65 shows the windings of the coupled inductor array of fig. 58 separated from the magnetic core of the coupled inductor array.

Fig. 66 is a perspective view of a coupled inductor array similar to the coupled inductor array of fig. 58, but with a winding including a plurality of electrical conductors electrically coupled in parallel, in accordance with an embodiment.

Fig. 67 shows the windings of the coupled inductor array of fig. 66 separated from the magnetic core of the coupled inductor array.

Fig. 68 shows a perspective view of a coupled inductor array similar to the coupled inductor array of fig. 67, but with windings including interleaved electrical conductors, in accordance with an embodiment.

Fig. 69 shows the windings of the coupled inductor array of fig. 68 separated from the magnetic core of the coupled inductor array.

Fig. 70 is a perspective view of an array of coupled inductors similar to the array of coupled inductors of fig. 66, but with each winding forming only a single winding turn, in accordance with an embodiment.

Fig. 71 shows the windings of the coupled inductor array of fig. 70 separated from the magnetic core of the coupled inductor array.

Fig. 72 is a vertical cross-sectional view of the fig. 70 coupled inductor array.

Fig. 73 is a perspective view of an array of coupled inductors similar to the array of coupled inductors of fig. 68, but with each winding forming only a single winding turn, in accordance with an embodiment.

Fig. 74 shows the windings of the coupled inductor array of fig. 73 separated from the magnetic cores of the coupled inductor array.

Fig. 75 is a vertical cross-sectional view of the fig. 73 coupled inductor array.

Figure 76 is a cross-sectional view similar to the cross-sectional view of figure 62, except that the cross-sectional view illustrates a monolithic magnetic core divided into segments of a coupled inductor array, in accordance with an embodiment.

Fig. 77 is a cross-sectional view similar to that of fig. 72, but showing a monolithic magnetic core of a coupled inductor array divided into six layers, under an embodiment.

Fig. 78-83 are top plan views of layers 1-6, respectively, of the coupled inductor array of fig. 77.

FIG. 84 is a cross-sectional view similar to the cross-sectional view of FIG. 75, except that the cross-sectional view illustrates a monolithic magnetic core of a coupled inductor array divided into six layers, under an embodiment.

Fig. 85-90 are top plan views of layers 1-6, respectively, of the fig. 84 coupled inductor array.

Detailed Description

Coupled inductor arrays are disclosed herein that may be used, for example, as energy storage inductors in multiphase switched power converters. Such coupled inductors may achieve one or more significant advantages, as discussed below. For example, certain embodiments of these inductors achieve relatively strong magnetic coupling, relatively large leakage inductance values, and/or relatively low core losses within a small package size. As another example, leakage inductance and/or magnetization inductance may be easily adjusted during design and/or manufacturing of certain embodiments. Throughout the following disclosure, specific instances of an item may be referred to by using a number within parentheses (e.g., winding 118(1)), while a number without parentheses refers to any such item (e.g., winding 118).

Fig. 1 shows a perspective view of coupled inductor array 100. The array 100 includes a magnetic core 102 formed of a magnetic material, such as a ferrite material, a powdered iron material within a binder, or several layers of magnetic film. The magnetic core 102 includes a top plate 104 disposed on a bottom plate 106 and has opposing first and second sides 108, 110, the first and second sides 108, 110 being separated by a linear separation distance that defines a core length 112. Core 102 also has a width 114 perpendicular to length 112 and a height 116 perpendicular to both length 112 and width 114. Fig. 2 shows the array 100 with the magnetic core 102 shown as transparent. Fig. 3 shows a top plan view of the array 100 with the top plate 104 removed.

Coupled inductor array 100 also includes two or more windings 118 disposed in magnetic core 102 between top plate 104 and bottom plate 106. Although the figures of the present disclosure illustrate the array 100 as having three windings 118, it should be understood that such an array may be modified to have any number of windings greater than 1. In other words, the coupled inductor array disclosed herein may be adapted to have N windings, where N is any integer greater than one.

Each winding 118 passes through the core 102 in the length direction 112 and forms a loop 120 in the core 102. In the exemplary embodiment, ring 120 is substantially planar. Although the loop 120 is shown as forming a single turn, the loop 120 may alternatively form two or more turns to facilitate low flux density and associated low core loss. Opposite first and second ends 122, 124 of the winding 118 extend toward the first and second sides 108, 110 of the core, respectively. Each first end 122 forms a respective first welding tab 123 and each second end 124 forms a respective second welding tab 125. The solder tabs 123/125 are configured for surface mount attachment to a Printed Circuit Board (PCB).

Each loop 120 is wound around a respective winding axis 126, and each winding axis 126 is substantially parallel to, but offset from, each other winding axis 126 in the width direction 114. Accordingly, each loop surrounds a respective region 128 within the magnetic core 102, and each loop region 128 does not overlap with every other loop region 128 along the width 114 of the magnetic core. Such a configuration provides coupled inductor array 100 with "negative" or "reverse" magnetic coupling. The diamagnetic coupling is characterized in that the array 100 induces a current of increasing magnitude through the remaining windings 118 in a first direction, for example, by a current of increasing magnitude through one of the windings 118 in the first direction. For example, a current of increasing magnitude flowing into winding 118(2) from core first side 108 will induce a current of increasing magnitude flowing into windings 118(1), 118(3) from core first side 108.

The configuration of the array 100 promotes large values of magnetizing and leakage inductance, as well as low reluctance flux paths. Specifically, windings 118 are typically longer in length direction 112 than in width direction 114, such that a large portion of windings 118 are in close proximity and provide a wide path for magnetic flux coupling adjacent windings. The flux coupling adjacent windings is represented in fig. 3 by solid arrows 130, only some of which are labeled for clarity of illustration. Such a wide path provides a low reluctance path for the magnetic flux, thereby promoting strong magnetic coupling and low core loss between the windings.

Furthermore, the magnetic core 102 typically extends beyond the loops 120 such that each loop region 128 is smaller than the area of the magnetic core 102 in the same plane as the loops. As a result, magnetic core 102 provides a path for leakage flux around most or all of the perimeter of each ring 120, where leakage flux is the flux generated by varying the current flowing through one winding 118 that is not coupled to the remaining windings 118. The leakage flux is indicated in fig. 3 by dashed arrows 132, only some of which are labeled for clarity of illustration. As a result, each winding 118 has a relatively wide low reluctance leakage flux path, thereby promoting low core loss and large leakage inductance values associated with the windings 118.

The magnetizing inductance and leakage inductance can be individually controlled during design and/or manufacture of coupled inductor array 100 by controlling the size and/or shape of windings 118, and/or the extent to which magnetic core 102 extends outside of winding loop 120. Specifically, the magnetizing inductance may be increased by increasing the closely adjacent portions of the windings 118 and/or decreasing the spacing between the windings 118. For example, fig. 4 shows a top plan view similar to fig. 3 including an alternative embodiment of a winding ring 420 instead of the winding ring 120. The winding loop 420 is longer in the length direction 112 than the winding loop 120 of the embodiment of fig. 3. Accordingly, the embodiment of FIG. 4 will have a greater magnetizing inductance than the embodiment of FIG. 3, assuming otherwise equivalent. However, the relatively long length of winding loop 420 reduces the portion of core 102 available for coupling leakage flux. Thus, the embodiment of fig. 4 will have a smaller leakage inductance value than the embodiment of fig. 3, assuming otherwise equivalent.

As another example, fig. 5 shows a cross-sectional view similar to fig. 3 including an alternative embodiment of a winding ring 520 instead of the winding ring 120. The winding loop 520 is smaller than the winding loop 120 of the embodiment of fig. 3. Thus, in the embodiment of fig. 5 a larger portion of the magnetic core 102 is outside the winding loop than in the embodiment of fig. 3, so that a larger portion of the core is available for leakage flux in the embodiment of fig. 5. Thus, the embodiment of fig. 5 will have a larger leakage inductance value than the embodiment of fig. 3, assuming otherwise equivalent. However, the closely adjacent portions of the winding loops are smaller in the embodiment of fig. 5 than in the embodiment of fig. 3. Thus, the embodiment of FIG. 5 will have a smaller magnetizing inductance than the embodiment of FIG. 3, assuming otherwise equal.

The embodiments discussed above have rectangular winding loops that help maximize the closely adjacent portions of each loop, thereby promoting large magnetizing inductance values. However, the winding loops may have other shapes. For example, fig. 6 shows a cross-sectional view similar to fig. 3 of an alternative embodiment comprising a circular winding ring 620 instead of a rectangular winding ring 120. The circular shape reduces the length of the loop, thereby promoting low winding resistance. However, the circular shape also reduces the closely adjacent portions of winding ring 620, thereby reducing magnetizing inductance.

the configuration of core 102 may also be changed during design and/or manufacture of coupled inductor array 100 to control magnetizing inductance and/or leakage inductance. Fig. 7 shows a cross-sectional view of coupled inductor array 100 taken along line a-a of fig. 2. The portion 134 inside the winding loop 120 provides a path for both leakage flux and flux coupling the winding 118, while the portion 136 outside the winding loop 120 provides a path for leakage flux only. Both the magnetizing inductance and the leakage inductance are approximately proportional to the cross-sectional area of portion 134, and the leakage inductance is also approximately proportional to the cross-sectional area of portion 136. Thus, the magnetization inductance and leakage inductance can be adjusted by, for example, adjusting the width 135 of the portion 134, and the leakage inductance can be adjusted individually by, for example, adjusting the width 137 of the portion 136. Each instance of width 135 need not be the same, and each instance of width 137 need not be the same. For example, in some embodiments, one portion 136 has a greater width 137 than the other portion 136 to establish an asymmetric leakage inductance value.

The magnetizing inductance and leakage inductance can also be varied together by changing the spacing 139 between the top and bottom plates 104, 106. In general, the smaller the spacing 139, the larger the magnetizing inductance and leakage inductance.

In addition, the magnetization inductance and/or leakage inductance may be controlled by controlling the reluctance of portions 134 and/or 136. For example, the magnetizing inductance and leakage inductance may be increased by adding magnetic material to portion 134 to reduce the reluctance of the leakage flux path and the flux path of coupling winding 118. Similarly, leakage inductance may be increased by adding magnetic material to portion 136 to reduce the reluctance of the leakage flux path.

Fig. 8 shows a cross-sectional view similar to fig. 7 including an alternative embodiment of coupling teeth 838 disposed in the portion 134 within the windings 120 between the top plate 104 and the bottom plate 106. Coupling teeth 838, which are formed of a magnetic material, reduce the reluctance of the flux path in portion 134, thereby increasing the magnetizing inductance and leakage inductance. As another example, FIG. 9 shows a cross-sectional view similar to FIG. 7 including an alternative embodiment of coupling teeth 838 and drain teeth 940 in portion 134, with drain teeth 940 disposed in portion 136 between top plate 104 and bottom plate 106. The leakage tooth 940, also formed of a magnetic material, reduces the reluctance of the flux path in the portion 136, thereby increasing the leakage inductance value. Each of the leakage teeth 940(2), 940(3) is disposed between adjacent winding rings, while the leakage teeth 940(1), 940(4) are disposed at opposite ends of the rows of winding rings, respectively. The magnetic materials forming coupling tooth 838 and drain tooth 940 need not be the same and may be individually selected to achieve desired magnetization and leakage inductance values. For example, in some embodiments, the coupling teeth 838 are formed of a material having a higher magnetic permeability than the leakage teeth 940. Alternatively, the coupling tooth 838 and the drain tooth 940 may be formed of the same magnetic material to simplify the construction of the core 102, and both teeth may even be formed of the same material as the top and bottom plates 104, 106 to further simplify the core construction. In some embodiments, the magnetic material forming coupling teeth 838 and/or winding teeth 940 is non-homogenous.

One or more coupling teeth 838 may be spaced from the top plate 104 and/or the bottom plate 106 by a gap filled with a non-magnetic material to control magnetizing and leakage inductance and/or to help avoid magnetic saturation. For example, such gaps may be filled with air, plastic, paper, and/or adhesive. Similarly, one or more leakage teeth 940 may be spaced from the top plate 104 and/or bottom plate 106 by a gap filled with a non-magnetic material (e.g., air, plastic, paper, and/or adhesive) to control leakage inductance. For example, fig. 10 illustrates a cross-sectional view similar to fig. 7 including an alternative embodiment of the coupling teeth 1038 spaced from the top plate 104 by an air gap 1042. The embodiment of fig. 10 also includes a drain tooth 1040 separated from the top plate 104 by an air gap 1044. The thicknesses of the air gaps 1042 and 1044 are optionally optimized separately and need not be the same. As another example, FIG. 11 illustrates a cross-sectional view similar to FIG. 7 of an alternative embodiment in which each coupling tooth 1138 is spaced from top plate 104 by a spacer 1146 formed of a non-magnetic material, and each leakage tooth 1140 is spaced from top plate 104 by a respective air gap 1144 and spacer 1146. In certain embodiments, spacers 1146 are formed of the same material as an insulator (not shown) that separates overlapping portions of windings 118.

In certain embodiments, the magnetic core 102 is formed from a material having a distributed air gap (e.g., iron powder within a binder). In such embodiments, leakage inductance and/or magnetization inductance may also be adjusted by changing the material composition to change the distributed air gap properties.

One possible application of coupled inductor array 100 is a switched mode power converter application, including but not limited to a multi-phase buck converter, a multi-phase boost converter, or a multi-phase buck-boost converter. For example, fig. 12 shows one possible application of coupled inductor array 100 in a multi-phase buck converter. Specifically, fig. 12 shows a schematic diagram of a three-phase buck converter 1200 using coupled inductor array 100 as a coupled inductor. The first end 122 of each winding is electrically coupled to a respective switching node Vx, and the second end 124 of each winding is electrically coupled to the common output node Vo. A respective switching circuit 1248 is electrically coupled to each switching node Vx. Each switching circuit 1248 is electrically coupled to an input port 1250, and the input port 1250 is in turn electrically coupled to a power source 1252. Output port 1254 is electrically coupled to output node Vo. Each switching circuit 1248 and corresponding inductor are collectively referred to as a "phase" 1255 of the converter. Thus, the multi-phase buck converter 1200 is a three-phase converter.

Controller 1256 causes each switching circuit 1248 to repeatedly switch its respective winding first end 122 between power supply 1252 and ground, thereby switching its first end between two different voltage levels to transfer power from power supply 1252 to a load (not shown) electrically coupled across output port 1254. The controller 1256 typically causes the switching circuit 1248 to switch at a relatively high frequency (e.g., 100kHz or higher) to facilitate low ripple current amplitudes and fast transient response and to ensure that the switching-induced noise is at a frequency above the human-perceptible frequency.

Each switching circuit 1248 includes a control switch 1258 that alternately switches between its conductive and non-conductive states under the command of the controller 1256. Each switching circuit 1248 further includes a freewheeling device 1260 adapted to provide a path for current flowing through its respective winding 118 when the control switching device 1258 of the switching circuit transitions from its conductive state to a non-conductive state. The freewheeling device 1260 may be a diode as shown to facilitate system simplification. However, in certain alternative embodiments, the freewheeling device 1260 may be supplemented or replaced by a switching device that operates under the command of the controller 1256 to improve converter performance. For example, a diode in the freewheeling device 1260 may be supplemented by a switching device to reduce the forward voltage drop of the freewheeling device 1260. 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.

The controller 1256 is optionally configured to control the switching circuit 1248 to adjust one or more parameters of the multi-phase buck converter 1200, such as input voltage, input current, input power, output voltage, output current, or output power. The buck converter 1200 typically includes one or more input capacitors 1262 electrically coupled across the input port 1250 for providing a ripple component of the input current of the switching circuit 1248. Additionally, one or more output capacitors 1264 are typically electrically coupled across the output port 1254 to shunt ripple current generated by the switching circuit 1248.

Buck converter 1200 can be modified to have a different number of phases and coupled inductor array 100 can be modified accordingly to have a corresponding number of windings 118. Further, the buck converter 1200 may be modified to incorporate two or more instances of the coupled inductor array 100. For example, an alternative embodiment of converter 1200 includes six phases 1255 and two instances of coupled inductor array 100. A first instance of the array 100 serves the first through third phases and a second instance of the array 100 serves the fourth through sixth phases. Buck converter 1200 may also be modified to have a different topology, for example, a topology with a multi-phase boost converter or a multi-phase buck-boost converter, or to have an isolated topology, such as a flyback converter or a forward converter.

Fig. 13 shows a Printed Circuit Board (PCB) footprint 1300, which is one possible footprint for applying coupled inductor array 100 to a multi-phase buck converter application, such as buck converter 1200 (fig. 12). Footprint 1300 includes a pad 1366 for coupling each first solder tab 123 to a respective switching node Vx and a pad 1368 for coupling each second solder tab 125 to a common output node Vo. Due to the anti-magnetic coupling of the array 100, all switching nodes Vx are on the first side 1308 of the coverage area 1300, which facilitates layout simplification of the PCB including the coverage area 1300.

In certain alternative embodiments, the second end 124 of each winding is electrically coupled to a common conductor, such as a common tongue, to provide a low impedance connection to an external circuit. For example, fig. 14 shows a perspective view of coupled inductor array 1400, array 1400 being identical to array 100 (fig. 1) except that second ends 124 of the windings are electrically coupled to a common tab 1470 rather than forming respective solder tabs. Tab 1470 is configured for surface mount attachment to a printed circuit board, for example. Fig. 15 shows a PCB footprint 1500, which is one possible footprint for applying coupled inductor array 1400 to a multi-phase buck converter application, such as buck converter 1200 (fig. 12). Footprint 1500 includes pads 1566 for coupling each first solder tab 123 to a respective switching node Vx, and pads 1568 for coupling common tab 1470 to common output node Vo. It can be appreciated from fig. 15 that the common tab 1470 provides a large surface area for connection to a PCB pad, thereby promoting a low impedance connection between the tab and the PCB and helping to cool the inductor 1400 and nearby components.

Although the magnetic core 102 is shown as including separate top and bottom plates 104, 106, the magnetic core 102 may have other configurations. For example, the top and bottom plates 104, 106 may alternatively be part of a single-piece magnetic element that optionally includes the coupling teeth 838 and/or the weep teeth 940. As another example, in some alternative embodiments, magnetic core 102 is a single-piece monolithic structure having windings 118 embedded therein, such as a core formed by molding a composition that includes a magnetic material in an adhesive. In such embodiments, there is no gap or spacing between individual core segments, and the magnetization and leakage inductances can be varied by changing the magnetic material composition and/or winding configuration, as discussed above. As yet another example, in certain alternative embodiments, magnetic core 102 is formed by providing multiple layers or films of magnetic material. In such embodiments, a non-magnetic material is optionally disposed in at least a portion of the portions 134 and/or 136 to establish a gap similar to the gaps 1042, 1044 in fig. 10. Furthermore, in some alternative embodiments, the core 102 completely surrounds the winding ring 120. In embodiments including coupling teeth 838 and/or leakage teeth 940, such teeth may be discrete magnetic elements and/or part of another piece of core 102. For example, in some embodiments, at least one of the coupling teeth 838 and/or the drain teeth 940 is part of the top plate 104 or the bottom plate 106.

for example, the windings 118 are formed separately from the core 102 and then disposed therein, for example, prior to joining the top and bottom plates 104, 106. In embodiments where the core 102 is formed by molding a composition including a magnetic material in a binder, for example, the windings 118 are formed separately and placed into the mold prior to adding the composition to the mold. The winding 118 may also be formed by applying a conductive film, for example by applying a thick film conductive material such as silver, to portions of the magnetic core 102 or to a substrate disposed on the magnetic core 102. An insulating film may be disposed between adjacent conductive film layers to avoid shorting different portions of the winding 118 together. In embodiments where one or more of windings 118 are multi-turn windings, the magnetic material optionally spaces two or more winding turns apart from each other to provide an additional path for leakage flux, thereby promoting a large leakage inductance value.

Arrays 100 and 1400 are shown with windings 118 being foil windings. The rectangular cross-section of the foil winding helps to reduce skin effect induced losses, thus promoting low winding resistance at high frequencies. However, the coupled inductor arrays disclosed herein are not limited to foil windings. For example, winding 118 may alternatively have an arcuate or square cross-section, or may alternatively be a cable formed from a plurality of wires. Further, although arrays 100 and 1400 are shown as including solder tabs configured for surface mount attachment to a PCB, the coupled inductor arrays disclosed herein may be modified to connect to external circuitry in other ways, such as by using through-hole connections or by coupling to a socket.

For example, fig. 16 shows a perspective view of an array 1600 of coupled inductors, the array 1600 being similar to coupled inductor 100 (fig. 1) except that foil windings 118 are replaced with wire windings 1618 having a generally arcuate cross-section. In fig. 16, the core 102 is shown as transparent to show the windings 1618. The opposing first and second ends 1622, 1624 of the winding 1618 form first and second via pins 1623, 1625, respectively, that extend through the bottom surface 1672 of the magnetic core 102. Fig. 17 shows PCB footprint 1700, which is one possible footprint for applying coupled inductor array 1600 to a multi-phase buck converter application, such as buck converter 1200 (fig. 12). Footprint 1700 includes vias 1766 for coupling each via pin 1623 to a respective switching node Vx and vias 1768 for coupling via pin 1625 to common output node Vo.

As another example, fig. 18 shows a perspective view of coupled inductor array 1800, which is similar to coupled inductor array 1600 (fig. 16), but includes wire windings 1818 having opposing first and second ends 1822, 1824, the first and second ends 1822, 1824 extending from core sides 108, 110, respectively, to form first and second via pins 1823, 1825. Fig. 19 shows PCB footprint 1900, which is one possible footprint for applying coupled inductor array 1800 to a multi-phase buck converter application, such as buck converter 1200 (fig. 12). Footprint 1900 includes vias 1966 for coupling each via pin 1823 to a respective switching node Vx and vias 1968 for coupling via pins 1825 to a common output node Vo. Because the windings of array 1800 extend from the sides of core 102, rather than from the bottom of core 102, array 1800 is generally not as mechanically robust as array 1600 (fig. 16). However, the fact that the via pins 1823, 1825 extend from the core sides 108, 110 may eliminate the need to route PCB conductive traces underneath the core 102, thereby shortening the trace length. Shortening the trace length in turn reduces the trace impedance and associated losses.

In embodiments with only two windings, the winding loops may at least partially overlap, thereby helping to minimize the inductor footprint size. For example, fig. 20 shows a perspective view of a dual winding coupled inductor array 2000 comprising at least partially overlapping winding loops. The coupled inductor array 2000 includes a magnetic core 2002, the magnetic core 2002 including top and bottom plates 2004, 2006. Magnetic core 2002 has opposing first and second sides 2008, 2010, which are spaced apart by a linear spacing distance that defines a core length 2012. Core 2002 also has a width 2014 perpendicular to length 2012 and a height 2016 perpendicular to both length 2012 and width 2014. In fig. 20, the magnetic core 2002 is shown as transparent.

The coupled inductor array 2000 also includes two windings 2018 disposed in the magnetic core 2002 between the top and bottom plates 2004, 2006. Although windings 2018(2) are shown by dashed lines to help an observer distinguish between windings 2018(1) and 2018(2), in reality both windings are generally of the same construction. Each winding 2018 passes through magnetic core 2002 in length direction 2012 and forms a loop 2020 in magnetic core 2002. In the exemplary embodiment, ring 2020 is generally planar. Although the loop 2020 is shown as forming a single turn, the loop 2020 may alternatively form two or more turns to facilitate low flux density and associated low core loss. The opposing first and second sides 2022, 2024 of the winding 2018 extend toward the first and second sides 2008, 2010 of the core, respectively. Each first end 2022 forms a respective first via pin 2023, and each second end 2024 forms a respective second via pin 2025. In certain alternative embodiments, the winding ends 2022, 2024 are adapted to be otherwise connected to external circuitry. For example, in some alternative embodiments, the winding ends 2022, 2024 form respective soldering tabs configured for surface mount attachment to a PCB.

Each ring 2020 is wound around a respective winding shaft 2026. The rings 2020 are wound in opposite directions to obtain a diamagnetic coupling. Such diamagnetic coupling is characterized by the array 2000 inducing increasingly larger magnitudes of current flowing from the first side 2008 of the core into the windings 2018(2), for example, by increasingly larger magnitudes of current flowing from the first side 2008 of the core into the windings 2018 (1). Each winding axis 2026 is substantially parallel to each other winding axis 2026 but offset in the width direction 2014. Two rings 2020 partially overlap such that the two rings surround a common region 2028 within the magnetic core 2002. The magnetizing inductance value and the leakage inductance value can be adjusted during design and/or manufacturing of the coupled inductor array 2000 by adjusting the degree of overlap of the winding loops 2020, or in other words by adjusting the size of the area 2028 enclosed by the two loops. Specifically, as the winding rings 2020 are separated from each other to reduce the size of the region 2028, the leakage inductance will increase and the magnetizing inductance will decrease. Conversely, as the winding rings 2020 are drawn closer together to increase the size of region 2028, the leakage inductance will decrease and the magnetizing inductance will increase.

Leakage inductance and/or magnetizing inductance may also be adjusted during design and/or manufacture of the inductor by adding one or more coupling teeth and/or one or more leakage teeth in a manner similar to that discussed above with respect to fig. 8-11. For example, the magnetizing inductance and leakage inductance may be increased by adding a leakage tooth connecting the top and bottom plates 2004, 2006 in the region 2028 surrounded by the two winding rings 2020. As another example, leakage inductance may be increased by adding coupling teeth connecting the top and bottom plates 2004, 2006 outside of the region 2028. Leakage inductance and/or magnetization inductance may also be varied during array design and/or manufacturing by using techniques similar to those discussed above with respect to array 100, for example, by varying the size of winding rings 2020, the geometry of winding rings 2020, the composition of magnetic core 2002, and/or the spacing between top and bottom plates 2004, 2006.

For example, fig. 21 shows a top plan view of coupled inductor array 2100 with the top plate removed. Array 2100 is similar to array 2000 of fig. 20, except that array 2100 has winding loops 2120 that are generally circular in shape, rather than generally rectangular in shape. The circular shape helps to reduce the length of the windings 2118, thereby reducing winding impedance. However, the circular shape reduces the overlap of the winding loops 2120, thereby reducing the magnetizing inductance and increasing the leakage inductance. Although windings 2118(2) are shown in dashed lines to help the viewer distinguish between windings 2118(1) and 2118(2), in practice, both windings typically have the same configuration. Array 2100 also differs from array 2000 in that the opposing winding ends 2122, 2124 are electrically coupled to respective soldering tabs 2123, 2125, rather than forming through-hole pins.

The configuration of the magnetic core 2002 (fig. 20) may be changed in a manner similar to that discussed above with respect to the array 1000. For example, the top and bottom plates 2004, 2006 may instead be part of a single piece magnetic element. As another example, in some alternative embodiments, magnetic core 2002 is a single-piece monolithic structure having windings 2018 embedded therein, such as a core formed by molding a composition that includes a magnetic material in an adhesive. As yet another example, in certain alternative embodiments, magnetic core 2002 is formed by providing multiple layers or films of magnetic material. Furthermore, in some alternative embodiments, magnetic core 2002 completely surrounds winding ring 2020.

Further, the configuration of the windings 2018 may also be varied. For example, the wire windings 2018 may be replaced with foil windings or conductive films. For example, fig. 22 shows a top plan view of coupled inductor array 2200 with the top plate removed. Array 2200 is similar to array 2000 of fig. 20, except that it includes windings 2218 formed from a conductive film. At least the overlapping portions of the windings 2218 are insulated from each other by, for example, an insulating film (not shown) disposed between the overlapping winding portions. In contrast to the array 2000, the winding ends 2222, 2224 are electrically coupled to the respective soldering tabs 2223, 2225, instead of forming through-hole pins.

The configuration of the coupled inductor array disclosed herein facilitates a low height of the array such that certain embodiments may be viewed as a "chip-type" coupled inductor array. For example, certain embodiments have a height 116 (FIG. 1) of 0.8 millimeters or less.

The relatively low height of such an array may enable it to be housed in an integrated circuit package with, and optionally electrically coupled to, a semiconductor die or a semiconductor bar. For example, some embodiments of the array may be housed in a common integrated circuit package with the semiconductor die, but physically separated from the die within the package. Furthermore, certain other embodiments of the coupled inductor arrays disclosed herein are formed on a semiconductor die, for example, by disposing several layers of magnetic material and layers of conductive material on the semiconductor die to form a magnetic core and a winding, respectively. The semiconductor die and the array of coupling inductors are, in turn, optionally housed in a common integrated circuit package, and the coupling inductors are optionally electrically coupled to the semiconductor die. For example, fig. 24 shows an electronic device 2400 that includes an integrated circuit package 2402, a semiconductor die 2404 housed in the integrated circuit package 2402, and a coupled inductor 2406 housed in the integrated circuit package 2402. Coupled inductor 2406 is electrically coupled to semiconductor die 2404, as symbolically illustrated by dashed line 2408. As another example, fig. 25 shows an electronic device 2500 that includes an integrated circuit package 2502, a semiconductor die 2504 housed in the integrated circuit package 2502, and a coupled inductor 2506 housed in the integrated circuit package 2502, for example. Coupled inductor 2506 is disposed on semiconductor die 2504, and coupled inductor 2506 is electrically coupled to semiconductor die 2504, as symbolically illustrated by dashed line 2508.

The examples discussed above show the solder tabs disposed on the bottom surface of the coupled inductor array rather than the top surface of the array. Such a configuration may be advantageous in applications where it is desirable for the top surface of the array to be electrically isolated, for example where an optional heat sink is to be disposed on the top surface.

However, certain alternative embodiments include weld tabs on both the top and bottom surfaces of the array. For example, fig. 23 shows a perspective view of coupled inductor array 2300, array 2300 being similar to coupled inductor array 100 (fig. 1) except further including solder tabs 2374, 2376 disposed on top surface 2378 and solder tab 123 (not visible in the perspective view of fig. 23) disposed on bottom surface 2372.

Applicants have additionally discovered that in embodiments where the magnetic core is formed of a magnetic material having distributed gaps (e.g., a material comprising magnetic powder within a binder), great care must be taken with respect to winding geometry and relative winding position to ensure significant magnetic coupling of the windings. As discussed above and in the Schultz document, the windings must be given strong magnetic coupling in switched power converter applications to achieve the advantages of using coupled inductors instead of multiple discrete inductors.

To help recognize the special considerations that must be made when using a core formed of distributed gap magnetic material, consider first the prior art coupled inductor 2600 of fig. 26, which includes a core 2602 formed of ferrite material, rather than a core formed of magnetic material with a distributed air gap. Magnetic core 2602 is a "ladder" magnetic core that includes opposing ladder rails (rails) 2604, 2606 and three rungs 2608. A respective winding 2610 is wound around each rung 2608. As is known in the magnetic arts, ferrite magnetic materials have very high relative permeability, which tends to be in the range of 2000 to 3000, and thus ferrite magnetic materials have low magnetic resistance. As a result, the magnetic core 2602 has a low magnetic reluctance and the magnetic flux generated by the current flowing through the one or more windings 2610 will be almost entirely confined to the magnetic core 2602. For example, arrow 2612 in fig. 26 symbolically illustrates how magnetic flux generated by current flowing through windings 2610(2) will flow almost entirely within core 2602 to couple to windings 2610(1) and 2610 (3). Therefore, even if the pitch 2614 between adjacent rungs or the pitch 2616 between the ladder bars 2604 and 2606 is large, strong magnetic coupling can occur to the winding 2610.

Consider now prior art magnetic device 2700 shown in fig. 27 and 28 that includes monolithic magnetic core 2702 formed of magnetic material with a distributed gap. Fig. 27 shows a side cross-sectional view of magnetic device 2700, and fig. 28 shows a top cross-sectional view of magnetic device 2700. Three windings 2704 are embedded in a monolithic core 2702 and each winding 2704 forms a circular ring. The distributed gap magnetic material has a greater magnetic permeability than air. However, the distributed gap causes these magnetic materials to have a permeability that is much less than that of ferrite magnetic materials. As a result, magnetic core 2702 has a relatively large magnetic reluctance and the magnetic flux generated by current flowing through one winding 2704 will therefore flow very close to the winding and not significantly couple to the other winding 2704. For example, arrow 2706 in fig. 27 and symbol 2708 in fig. 28 symbolically illustrate how the magnetic flux generated by the current flowing through winding 2704(2) does not significantly couple to windings 2704(1) and 2704 (3). Accordingly, magnetic device 2700 is only a collection of three independent inductors where no significant magnetic coupling occurs, and magnetic device 2700 cannot be considered a coupled inductor array.

Furthermore, even if magnetic device 2700 is modified to bring windings 2704 together, windings 2704 do not experience significant magnetic coupling. For example, fig. 29 shows a top cross-sectional view of a magnetic device 2900 that is similar to the magnetic device 2700 of fig. 27 and 28, except that the windings 2704 are very close together in the width direction 2901. Symbol 2908 symbolically illustrates the path of magnetic flux generated by current flowing through windings 2704 (2). As shown, flux from winding 2704(2) couples very little to the remaining windings 2704(1) and 2704(3), even though windings 2704 are in close proximity. Thus, magnetic device 2900 is still only a collection of three independent inductors where no significant magnetic coupling occurs, and thus magnetic device 2900 cannot be considered a coupled inductor array.

However, the applicant has found that in an arrangement comprising a monolithic core with distributed gaps, both strong magnetic coupling and relatively large leakage inductance values can be achieved if (1) the winding is longer in the length direction than in the width direction (such as discussed in relation to fig. 1-4) such that the winding forms a winding loop that encloses a substantially rectangular loop region, and (2) the region enclosed by the winding loop is substantially larger than the region outside the winding loop in a given length direction by width direction cross-section of the core.

Fig. 30 to 33 show an example of a magnetic device that satisfies these requirements. Specifically, fig. 30 is a top plan view and fig. 31 is a side elevation view of coupled inductor array 3000 having a length 3002, a width 3004, and a height 3006. Fig. 32 is a sectional view taken along line 30A-30A of fig. 30, and fig. 33 is a sectional view taken along line 31A-31A of fig. 31. One possible application of coupled inductor array 3000 is in a switched power converter application, such as in three-phase buck converter 1200 of fig. 12.

Coupled inductor array 3000 includes a monolithic magnetic core 3008 formed of a magnetic material with distributed gaps. For example, in some embodiments, monolithic magnetic core 3008 is formed from a single piece of powdered magnetic material within an adhesive. As another example, in some other embodiments, monolithic magnetic core 3008 is formed from multiple magnetic film layers stacked together to form a monolithic magnetic core, wherein each magnetic film layer is formed from a powder of magnetic material in a binder. The distributed gap of monolithic core 3008 allows core 3008 to have a permeability that is much lower than the permeability of typical ferrite magnetic materials.

The coupled inductor array 3000 includes a plurality of windings 3010 embedded within a monolithic magnetic core 3008, wherein each winding forms a respective winding loop 3012 of one or more turns about a respective winding axis 3016, wherein each winding axis 3016 extends in a height direction. Each winding loop 3012 includes a plurality of conductor layers 3014 spaced apart from each other in the height direction, such that each winding loop 3012 has a thickness T in the height direction. Only some of conductor layers 3014 are labeled in fig. 32 to facilitate clarity of illustration. The conductor layers 3014 of each winding loop 3012 are electrically coupled in series by electrical connectors (not shown), e.g., conductive vias, that extend in the height direction between adjacent conductor layers 3014. Adjacent winding loops 3012 are spaced apart from one another by a widthwise spacing distance D.

Each winding loop 3012 surrounds a corresponding lengthwise-by-widthwise loop region Ain having a substantially rectangular shape elongated in the lengthwise direction (refer to fig. 33). The winding loop 3012 surrounds the magnetic core 3008 in a substantially larger area than the area of the magnetic core 3008 outside the winding loop 3012, as seen when the coupled inductor array 3000 is viewed through a cross-section in a height direction. In other words, in a given cross-sectional plane including the winding loop 3012 in the length direction by the width direction, the overall size of the core region Ain surrounded by the winding loop 3012 is significantly larger than the overall size of the core region Aout outside the winding loop 3012. This relationship between winding loop geometry, winding loop location, and the magnetic core 3008 allows the magnetic core 3008 to provide a low reluctance path between adjacent winding loops 3012 even though the magnetic core 3008 has a relatively low magnetic permeability. As a result, the winding loops 3012 are strongly magnetically coupled such that they are part of a coupled inductor array, rather than just part of a collection of individual inductors.

Furthermore, the fact that the magnetic core 3008 extends beyond the winding rings 3012 in the length-by-width direction enables the magnetic core 3008 to provide a path for leakage flux that substantially surrounds the entire respective perimeter of each winding ring 3012. Thus, the coupled inductor array 3000 has a wide or large cross-sectional area of the leakage flux path. The large cross-sectional area of the leakage flux path causes the path to have a low reluctance, thereby promoting low core losses and large leakage inductance values associated with the winding 3010. Accordingly, coupled inductor array 3000 achieves strong magnetic coupling of winding 3010 and significant leakage inductance values associated with winding 3010, even though magnetic core 3008 has a relatively low magnetic permeability.

Modifications to coupled inductor array 3000 may be made without departing from the scope of this document. For example, the number of windings 3010 may be varied as long as coupled inductor array 3000 includes at least two windings 3010. As another example, the number of conductor layers 3014 in each winding loop 3012 may vary as long as each winding loop 3012 includes at least one conductor layer 3014. Further, although magnetic core 3008 is shown as homogenous, magnetic core 3008 may alternatively be a composite magnetic core having two or more portions composed of different compositions, so long as a majority of the volume of magnetic core 3008 is formed of a magnetic material having distributed gaps. Further, although it is contemplated that coupled inductor array 3000 is typically symmetric, in some alternative embodiments coupled inductor array 3000 has an asymmetric configuration, for example, to achieve an asymmetric coupled inductor array.

Applicants have further determined that strong magnetic coupling and significant leakage inductance in distributed gap magnetic devices are facilitated if the width-wise winding loop spacing distance has some relationship to the winding loop height. To help recognize this relationship, consider the magnetic device 3400 shown in cross-section in FIG. 34. The magnetic device 3400 includes a rectangular monolithic magnetic core 3402 formed of magnetic material (e.g., powdered magnetic material within an adhesive) with distributed gaps. The magnetic device 3400 has a length 3404 and a height 3406, and the magnetic device 3400 includes a multi-turn winding loop 3408 embedded in a monolithic magnetic core 3402, wherein the winding loop 3408 has a height T.

Magnetic core 3402 may be modeled by dividing a length by height cross section into imaginary squares (e.g., length by height cross section 3410 includes squares 1-5). Although such a model is approximate and only a portion of monolithic core 3402 is considered, the model is illustrative in the sense of letting understand how fast the flux density decreases with increasing distance from winding loop 3408. Ignoring the boundary conditions and second order effects, the magnetoresistance between the vertices of squares can be modeled by an equivalent electrical model (as shown in fig. 35), where each resistor represents the normalized magnetoresistance between two vertices. For example, the reluctance of the path from point a to point B is about twice the reluctance of the path from point a to point C, as shown by resistor 3502 having twice the resistance of resistor 3504.

The magnetic flux through cross section 3410 can be approximately modeled as shown in fig. 36, where the total magnetic flux flowing through cross section 3410 is represented by current source 3602 having an amplitude of 1. When cross-section 3410 is approximated by discrete paths defined by the boundaries of squares 1-5, the current flowing through each electrical branch in fig. 36 represents the relative magnetic flux flowing through the corresponding path of magnetic core 3402. For example, approximately 55.7% of the total flux within cross-section 3410 flows between point A and point B, and only approximately 30.9% of the total flux flows between point C and point D. Fig. 37 is a graph 3700 of relative magnetic flux density in cross-section 3410 and is derived from fig. 36, where the area under curve 3702 represents the total magnetic flux within cross-section 3410. Horizontal axis 3704 represents which square (e.g., square 1) in cross-section 3410 the magnetic flux flows through, and vertical axis 3706 represents the estimated relative magnetic flux density within that square.

As shown in fig. 37, most of the magnetic flux flowing through the cross section 3410 flows in the square 1. As a result, any additional winding loops (not shown) must also be located within square 1 to enable strong magnetic coupling of the additional winding loops to winding loops 3408. If D is less than T, this constraint is satisfied in the coupled inductor array 3000 of FIGS. 30-33. Accordingly, in some embodiments of the coupled inductor array 3000, each width-wise spacing distance D is less than the thickness T of the winding loops 3012 to further enable strong magnetic coupling of the winding loops 3012.

Although strong magnetic coupling is required in the coupled inductor array, some leakage inductance is also necessary for energy storage. Thus, in typical embodiments, the separation distance D should be at least 10% of the winding loop thickness T to provide sufficient length-wise by width-wise cross-sectional area for leakage flux. Furthermore, the separation distance D should be large enough to avoid manufacturing difficulties associated with very small values of the separation distance D. For example, if the manufacturing process has a mechanical precision tolerance of +/-dD, then D should be at least twice dD to promote robust manufacturing. Accordingly, in some embodiments of the coupled inductor array 3000, D is less than T, and D is greater than the greater of 0.1 x T or 2 x D to achieve strong magnetic coupling, significant leakage inductance values, and robust manufacturing.

In some coupled inductor array applications, it may be desirable to have very strong magnetic coupling of the windings. Accordingly, applicants have developed additional techniques that facilitate strong magnetic coupling of windings in coupled inductor arrays having distributed gap cores by virtue of a tradeoff with increased leakage flux path reluctance.

In particular, applicants have discovered that blocking the flow of magnetic flux around a winding ring by embedding a non-magnetic structure in the magnetic core further enables strong magnetic coupling of the winding ring in a coupled inductor array with a distributed gap magnetic core. For example, fig. 38 is a top plan view and fig. 39 is a side plan view of coupled inductor array 3800 including a nonmagnetic structure embedded in a monolithic magnetic core. Coupled inductor array 3800 has a length 3802, a width 3804, and a height 3806. Fig. 40 is a sectional view taken along line 38A-38A of fig. 38, and fig. 41 is a sectional view taken along line 39A-39A of fig. 39. One possible application of coupled inductor array 3800 is in a switched mode power converter application, such as, for example, three-phase buck converter 1200 of fig. 12.

Coupled inductor array 3800 includes a monolithic magnetic core 3808 having a distributed gap. In the illustrated example, the monolithic magnetic core 3808 is formed from a plurality of magnetic film layers 3809 stacked in the height direction (see fig. 40), wherein each magnetic film layer is formed from a magnetic material (e.g., a powdered magnetic material within an adhesive) having distributed gaps. However, in some alternative embodiments, monolithic core 3808 is a bulk core formed from a distributed gap material (e.g., powdered magnetic material within an adhesive).

The coupled inductor array 3800 includes a plurality of windings 3810 embedded within a monolithic magnetic core 3808, wherein each winding forms a respective winding loop 3812 of one or more turns wound around a respective axis 3816, wherein each winding axis 3816 extends in a height direction. Each winding ring 3812 includes a plurality of conductor layers 3814 spaced apart from each other in the height direction such that each winding ring 3812 has a thickness T in the height direction. Only some of the conductor layers 3814 are labeled in fig. 40 to facilitate clarity of illustration. The conductor layers 3814 of each winding loop 3812 are electrically coupled in series by electrical connectors, such as conductive vias 3813 extending in the height direction between adjacent conductor layers 3814. The outline of the winding loop 3812 is partially shown in fig. 41 by dashed lines, wherein the conductor layer 3814 of the winding loop is not visible in the cross-sectional view of fig. 41. Adjacent winding loops 3812 are spaced apart from one another by a width-wise spacing distance D.

Each winding loop 3812 surrounds a corresponding length-by-width loop region Ain having a substantially rectangular shape elongated in the length direction (see fig. 41). The area of the magnetic core 3808 surrounded by the winding loops 3812 is substantially larger than the area of the magnetic core 3808 outside the winding loops 3812, as seen when the coupled inductor array 3800 is viewed through a cross-section in a height direction. In other words, in a given length by width cross-sectional plane that includes winding loop 3812, the overall size of loop region Ain is substantially greater than the overall size of region Aout of magnetic core 3808 that is outside of winding loop 3812. Thus, the winding loops 3812 are strongly magnetically coupled in a similar manner as discussed above with respect to fig. 30-33, such that the windings 3810 are part of an array of coupled inductors, rather than just a collection of individual inductors. Further, in some embodiments, D is less than T, and D is greater than the greater of 0.1 x T or 2 x D, to achieve strong magnetic coupling, significant leakage inductance values, and robust manufacturing in a manner similar to that discussed above.

A non-magnetic structure 3815 is embedded within the monolithic core and disposed outside the winding loops 3812 as seen through the cross-sectional view of the coupled inductor array 3800 in the height direction. Specifically, one or more non-magnetic structures 3815 are disposed adjacent to each winding loop 3812 in a common lengthwise-by-widthwise plane with the winding loops such that the lengthwise-by-widthwise area of the magnetic core 3808 outside of the winding loops 3812 is at least substantially covered by the non-magnetic structures 3815. The non-magnetic structure 3815 impedes the flow of magnetic flux outside the winding loop within the magnetic core 3808, thereby further facilitating strong magnetic coupling of the winding 3810. Although it is contemplated that nonmagnetic structure 3815 will typically cover substantially the entire lengthwise-by-widthwise area outside of winding loop 3812, as seen when coupling inductor array 3800 is viewed in a height direction through a cross-section, nonmagnetic structure 3815 may alternatively cover a smaller lengthwise-by-width area of magnetic core 3808 without departing from the scope of the present invention.

Modifications may be made to coupled inductor array 3800 without departing from the scope hereof. For example, the number of magnetic film layers 3809 may be changed. As another example, the number of nonmagnetic structures 3815 may be varied. For example, a given nonmagnetic structure 3815 may be divided into several smaller magnetic structures. As yet another example, the number of windings 3810 may be varied as long as the coupled inductor array 3800 includes at least two windings 3810. Furthermore, the number of conductor layers 3814 in each winding loop 3812 may vary, as long as each winding loop 3812 includes at least one conductor layer 3814. Further, although it is contemplated that coupled inductor array 3800 is generally symmetric, in some alternative embodiments coupled inductor array 3800 has an asymmetric configuration, e.g., to enable an asymmetric coupled inductor array.

The nonmagnetic structure 3815 is formed of a material having a lower magnetic permeability than the material forming the magnetic film layer 3809. In some embodiments, the non-magnetic structure 3815 is formed from a material having a relative magnetic permeability on the order of magnitude to maximize the flow of magnetic flux through the winding loop 3812. Ideally, the non-magnetic structure 3815 is formed of an electrically insulating material to avoid the flow of eddy currents within the non-magnetic structure 3815. However, using a different material for the non-magnetic structure 3815 than the material used for the conductor layer 3814 may complicate manufacturing. For example, in some embodiments, two different printing steps and associated masks are required to form the conductor layer 3814 and the non-magnetic structure 3815 with different respective materials. Thus, in some alternative embodiments, both the non-magnetic structure 3815 and the conductor layer 3814 are formed from a common conductive material, wherein the non-magnetic structure 3815 is electrically isolated from the winding 3810, and thus also from the winding loop 3812 and its constituent conductor layer 3814.

For example, fig. 42 is a cross-sectional view of coupled inductor array 4200 similar to the cross-sectional view of fig. 41. Coupled inductor array 4200 is an alternative embodiment of coupled inductor array 3800 in which coupled inductor array 4200 nonmagnetic structure 3815 is replaced with a nonmagnetic structure 4215 formed from a conductive material (e.g., the same type of conductive material that forms conductor layer 3814). One or more non-magnetic structures 4215 are disposed adjacent to each winding loop 3812 in a common lengthwise-by-widthwise plane with the winding loops such that a lengthwise-by-widthwise region of the magnetic core 3808 outside the winding loops 3812 is at least substantially covered by the non-magnetic structures 4215. The non-magnetic structure 4215 is electrically isolated from the windings 3810 and associated winding rings 3812. It is contemplated that a plurality of individual nonmagnetic structures 4215 will be disposed in a given width by length plane in place of a single nonmagnetic structure 4215 to reduce eddy current flow and facilitate manufacturability.

Fig. 43 illustrates a method 4300 for forming a coupled inductor array including a magnetic core having a non-magnetic structure embedded therein. In step 4302, at least two conductor layers are disposed on the core portion in a height direction such that the conductor layers at least partially form at least two winding loops as viewed in the height direction. In one example of step 4302, conductor layers 3814(1), 3814(4), and 3814(7) are printed onto magnetic film layer 3809(5) to partially form winding loops 3812(1), 3812(2), and 3812(3), respectively. (see FIG. 40). In step 4304, one or more non-magnetic structures are disposed on the core portion and outside the winding loops, as seen in a height direction. In one example of step 4304, non-magnetic structure 3815(1) is printed on magnetic film layer 3809(5) outside of winding loops 3812(1), (3812) (2), (3812) (3).

In step 4306, a magnetic material is disposed on the magnetic core portion, the conductor layer, and the non-magnetic structure. In one example of step 4306, a magnetic film layer 3809(6) is disposed on the magnetic film layer 3809(5), the conductor layer 3814(1), 3814(4), 3814(7), and the non-magnetic structure 3815 (1). Decision step 4308 determines whether additional conductor layers are needed. If so, steps 4302 through 4306 are repeated; otherwise the method 4300 ends.

It is also possible to increase the winding loop size to impede the flow of leakage flux, thereby increasing the magnetic coupling of the windings by means of a trade-off with increased leakage flux path reluctance. For example, fig. 44 is a cross-sectional view of a coupled inductor array 4400 having a length 4402 and a width 4404. The winding ring 4412 is embedded in a monolithic core 4408 formed of magnetic material with distributed gaps. Coupled inductor array 4400 is similar to coupled inductor array 3000 of fig. 30-33, but with larger winding loops. The cross-sectional view of coupled inductor array 3000 shown in fig. 33 is reproduced as fig. 45 to facilitate a comparison of coupled inductor arrays 3000 and 4400. As can be observed from a comparison of fig. 44 and 45, the lengthwise-by-widthwise portion of the magnetic core covered by the winding loops is larger in the coupled inductor array 4400 than in the coupled inductor array 3000. Thus, assuming otherwise equal, the coupled inductor array 4400 will have a stronger magnetic coupling of the windings by virtue of a tradeoff with increased leakage flux reluctance compared to the coupled inductor array 3000. Moreover, assuming otherwise equal, the increased size of the winding loops in coupled inductor array 4400 relative to coupled inductor array 3000 causes the windings in coupled inductor array 4400 to have a lower resistance than the corresponding windings in coupled inductor array 3000.

The applicant has also found that the interdigitation of the winding loops can promote strong magnetic coupling of the windings. To help recognize this finding, consider first a cross-bonded coupled inductor array 4600 without winding loops, as shown in the cross-sectional view of fig. 46. Coupled inductor array 4600 has a length 4602 and a width 4604. Coupled inductor array 4600 includes two winding rings 4612 embedded in a monolithic core 4608 formed of magnetic material with distributed gaps. The coupling and leakage magnetic fluxes are symbolically illustrated by arrows 4601 and 4603, respectively. Only leakage flux flows through the region 4605 between the winding rings 4612. Thus, region 4605 reduces magnetic coupling of winding ring 4612 by allowing magnetic flux to bypass winding ring 4612. It is not possible to eliminate the area 4605 because the winding rings 4612 must be spaced apart from each other in the width direction to avoid the winding rings being electrically shorted together.

Applicants have determined that interdigitation of the winding loops can reduce or eliminate the leakage flux path due to winding loop separation. For example, consider the coupled inductor array 4700 shown in the top view of fig. 47 and the side elevation view of fig. 48. Fig. 49 is a sectional view taken along line 47A-47A of fig. 47, and fig. 50 is a sectional view taken along line 48A-48A of fig. 48. Coupled inductor array 4700 has a length 4702, a width 4704, and a height 4706. One possible application of the coupled inductor array 4700 is in a switched power converter application, such as in a multi-phase buck converter similar to the three-phase buck converter 1200 of fig. 12.

Coupled inductor array 4700 includes monolithic magnetic core 4708 formed of magnetic material with distributed gaps. For example, in some embodiments, monolithic magnetic core 4708 is formed from a single piece of powdered magnetic material within an adhesive. As another example, in some other embodiments, monolithic magnetic core 4708 is formed from multiple layers of magnetic film that are stacked to form a monolithic magnetic core, wherein each layer of magnetic film is formed from a powder of magnetic material in an adhesive. The distributed gap of monolithic core 4708 allows monolithic core 4708 to have a permeability that is much lower than the permeability of typical ferrite magnetic materials.

Coupled inductor array 4700 includes windings 4710 embedded within a monolithic magnetic core 4708, wherein each winding forms a respective winding loop 4712 of one or more turns wound about a respective winding axis 4716, wherein each winding axis 4716 extends in a height direction. Each winding ring 4712 includes a plurality of conductor layers 4714 spaced apart from each other in the height direction such that each winding ring 4712 has a thickness T in the height direction. Only some of the conductor layers 4714 are labeled in fig. 49 to facilitate clarity of illustration. The conductor layers 4714 of each winding ring 4712 are electrically coupled in series by electrical connectors, such as conductive vias 4713, that extend in the height direction between adjacent conductor layers 4714. The outline of the winding ring 4712 is partially shown by dashed lines in fig. 50, wherein the conductor layer 4714 of the winding ring is not visible in the cross-sectional view of fig. 50.

Each winding ring 4712 surrounds a corresponding lengthwise-by-widthwise ring region Ain having a substantially rectangular shape elongated in the lengthwise direction (see fig. 50). The area of magnetic core 4708 surrounded by winding ring 4712 is substantially larger than the area of magnetic core 4708 outside of winding ring 4712, as seen when coupled inductor array 4700 is viewed in elevation through a cross-section. In other words, in a given length by width cross-sectional plane that includes winding ring 4712, the overall size of the core region Ain surrounded by winding ring 4712 is significantly greater than the overall size of the core region outside of winding ring 4712. Similar to that discussed above with respect to coupled inductor arrays 3000 and 3800, this relationship between winding loop geometry, winding loop position, and magnetic core 4708 allows magnetic core 4708 to provide a low reluctance path between adjacent winding loops 4712 even though magnetic core 4708 has a relatively low magnetic permeability.

Further, winding loops 4712 are interdigited in coupled inductor array 4700, or in other words, winding loops 4712 are partially overlapped, as seen when coupled inductor array 4700 is viewed in cross section in the height direction. This interdigitation of the winding rings 4712 causes the lengthwise by widthwise region 4705 between adjacent winding rings 4712 to be surrounded by both winding rings. As a result, region 4705 is a portion of the coupling flux path, not the leakage flux path. Thus, assuming otherwise equal, coupled inductor array 4700 has a stronger magnetic coupling of the windings than coupled inductor array 4600.

The fact that winding rings 4712 are interleaved requires that winding rings 4712 cross each other. Thus, it may be desirable to implement a given winding turn on two different layers to allow winding loops 4712 to cross over each other without electrically shorting together.

Modifications to coupled inductor array 4700 may be made without departing from the scope herein. For example, the number of windings 4710 may be varied as long as coupled inductor array 4700 includes at least two windings 4710. As another example, the number of conductor layers 4714 in each winding ring 4712 may be varied as long as each winding ring 4712 includes at least one conductor layer 4714. Further, although magnetic core 4708 is shown as homogenous, magnetic core 4708 may alternatively be a composite magnetic core having two or more portions composed of different compositions, so long as a majority of the volume of magnetic core 4708 is formed of a magnetic material having distributed gaps. Further, although it is contemplated that coupled inductor array 4700 is generally symmetrical, in some alternative embodiments, coupled inductor array 4700 has an asymmetrical configuration, e.g., to achieve an asymmetrical coupled inductor array.

Applicants have additionally developed a coupled inductor array comprising two vertically stacked windings with a strong magnetic coupling. The vertically stacked windings facilitate a small device footprint, which is particularly advantageous in applications where space for mounting components is limited.

Fig. 51-56 illustrate one example of such an array of coupled inductors. Specifically, fig. 51 is a perspective view of a coupled inductor array 5100 including two vertically stacked windings with strong magnetic coupling. The magnetic cores of the coupled inductor array 5100 are shown by line drawing in fig. 51, i.e., only the outline of the magnetic cores is shown to show the interior of the coupled inductor array. Fig. 52 is a top plan view of the coupled inductor array 5100, fig. 53 is a side elevation view of the coupled inductor array 5100, fig. 54 is a vertical cross-sectional view of the coupled inductor array 5100 taken along lines 52A-52A of fig. 52, and fig. 55 is a horizontal cross-sectional view of the coupled inductor array 5100 taken along lines 53A-53A of fig. 53. Fig. 56 shows the coupled inductor array 5100 without a magnetic core by way of an exploded view. The coupled inductor array 5100 has a length 5102, a width 5104, and a height 5106. One possible application of the coupled inductor array 5100 is in a switched power converter application, such as in a buck converter similar to the buck converter 1200 of fig. 12 but having only two phases 1255.

The coupled inductor array 5100 includes a monolithic core 5108 formed from a magnetic material having distributed gaps. For example, in some embodiments, monolithic core 5108 is formed from a single piece of powdered magnetic material within an adhesive. As another example, in some other embodiments, monolithic magnetic core 5108 is formed from multiple layers of magnetic film stacked in a direction of height 5106 to form a monolithic magnetic core, wherein each layer of magnetic film is formed from a powder of magnetic material in an adhesive. The distributed gap of the monolithic core 5108 is such that the monolithic core 5108 has a much lower permeability than that of typical ferrite magnetic materials. In some embodiments, the monolithic core 5108 includes one or more layers of non-magnetic material (not shown), such as one or more substrates for supporting features of the coupled inductor array 5800 during fabrication of the coupled inductor array and for providing dielectric insulation within the coupled inductor array.

The coupled inductor array 5100 includes a first winding 5110 and a second winding 5112. The first winding 5110 forms a first winding turn 5114 embedded in the monolithic core 5108 and the second winding 5112 forms a second winding turn 5116 embedded in the monolithic core (see fig. 51, 54, and 56). Each of the first and second winding turns 5114 and 5116 are wound about a common winding axis 5118 that extends in the direction of height 5106. Although each of the first and second winding turns 5114 and 5116 are shown as forming a single turn, one or more of these winding turns may form multiple turns. The first and second windings 5110, 5112 are optionally electrically isolated from each other within the monolithic core 5108.

The opposing ends 5120 and 5122 of the first winding 5110 terminate adjacent a first side 5124 of the monolithic magnetic core 5108, and the opposing ends 5126 and 5128 of the second winding 5112 terminate adjacent an opposing second side 5130 of the monolithic magnetic core 5108 (see fig. 51 and 56). The first and second sides 5124 and 5130 of the monolithic magnetic core 5108 are spaced apart from each other in the direction of the length 5102. Although the winding ends 5120, 5122, 5126, and 5128 are shown as forming respective solder tabs for surface mount soldering to a circuit board, one or more of these winding ends may form another type of connector, such as a through-hole pin, without departing from the scope hereof.

The coupled inductor array 5100 also includes a low permeability magnetic structure 5132 formed of a magnetic material having a lower permeability than the one or more magnetic materials forming the monolithic core 5108. A low permeability magnetic structure 5132 is embedded in the monolithic core 5108 and separates the first winding turn 5114 from the second winding turn 5116 in the direction of height 5106. The low permeability magnetic structure 5132 forms a loop around the common winding axis 5118 such that the low permeability magnetic structure 5132 forms an aperture 5134 aligned with the common winding axis 5118 (see fig. 51 and 54-56). Accordingly, the first winding turn 5114, the second winding turn 5116, and the low permeability magnetic structure 5132 collectively surround a first portion 5136 of the monolithic magnetic core 5108 as seen when the coupled inductor array 5100 is viewed through a cross-section in the direction of height 5106. In some embodiments, the first winding turn 5114, the second winding turn 5116, and the low permeability magnetic structure 5132 are rectangular such that the first portion 5136 of the monolithic magnetic core 5108 has a rectangular shape as seen when the coupled inductor array 5100 is viewed in cross-section in the direction of height 5106 to facilitate strong magnetic coupling of the first and second windings 5110, 5112.

The inclusion of the low permeability magnetic structure 5132 between the first and second winding turns 5114 and 5116 advantageously facilitates strong magnetic coupling of the first and second windings 5110 and 5112 while still providing a path for leakage flux to achieve significant leakage inductance values. To help appreciate these features, consider fig. 57, which is a vertical cross-sectional view similar to fig. 54, but showing an approximate coupling flux 5138 path and leakage flux 5140 path. The coupling flux 5138 links both the first and second winding turns 5114 and 5116, and thus the coupling flux 5138 flows through the first portion 5136 of the monolithic magnetic core 5108 and flows around the outside of the first and second winding turns. On the other hand, the leakage flux 5140 links only one of the winding turns 5114 and 5116, and therefore the leakage flux 5140 must flow through the low permeability magnetic structure 5132.

The magnetic material forming the first portion 5136 of the monolithic magnetic core 5108 has a permeability that is higher than the permeability of the low permeability magnetic structure 5132. Thus, the reluctance of the flux path through the first portion 5136 will be lower than the reluctance of the flux path through the low permeability magnetic structure 5132 such that a majority of the flux flowing through the first and second winding turns 5114 and 5116 is coupled flux, which facilitates strong magnetic coupling of the first and second windings 5110 and 5112. If the low permeability magnetic structure 5132 were not present and instead the first and second winding turns 5114 and 5116 were separated by the relatively high permeability material of the monolithic core 5108, the reluctance of the leakage flux path would be relatively low. As a result, relatively little of the magnetic flux flowing through the first and second winding turns 5114 and 5116 is coupling magnetic flux, resulting in relatively weak magnetic coupling of the first and second windings 5110 and 5112.

It is important to note that while the magnetic material forming the low permeability magnetic structure 5132 has a lower permeability than the magnetic material forming the first portion 5136 of the monolithic magnetic core 5108, the material forming the low permeability magnetic structure 5132 must be a magnetic material that is capable of achieving significant leakage inductance values. If the low permeability magnetic structure 5132 is instead formed of a non-magnetic material, it is difficult or even impossible to obtain the significant leakage inductance values required in typical switched power converter applications.

The leakage inductance value may be varied during design and/or fabrication of the coupled inductor array 5100 by adjusting the composition of the low permeability magnetic structure 5132 and/or by adjusting the thickness of the low permeability magnetic structure 5132 in the direction of the height 5106. For example, the leakage inductance value may be increased by increasing the thickness of the low permeability magnetic structure 5132 or by increasing the permeability of the low permeability magnetic structure 5132.

Modifications to the coupled inductor array 5100 may be made without departing from the scope hereof. For example, the first and second windings 5110 and 5112 can be modified such that their ends 5120, 5122, 5126, and 5128 terminate at different portions of the monolithic magnetic core 5108. For example, in an alternative embodiment, the first and second windings 5110 and 5112 are replaced with windings that are wound in opposite directions and have ends that terminate on opposite core sides (e.g., similar to the windings shown in fig. 22). Further, although the magnetic core 5108 is shown as homogenous, the monolithic magnetic core 5108 may alternatively be a composite magnetic core having two or more portions composed of different compositions, so long as a majority of the volume of the monolithic magnetic core 5108 is formed from a magnetic material having distributed gaps.

Applicants have also developed coupled inductor arrays in which each winding forms a plurality of winding turns, and each winding turn of a given winding is wound around a different winding axis to promote strong magnetic coupling of the windings and low height of the coupled inductor array. For example, fig. 58 is a perspective view of a coupled inductor array 5800 with each winding forming a plurality of winding turns. The magnetic core of the coupled inductor array 5800 is shown by a line drawing in fig. 58, i.e., only the outline of the magnetic core is shown to show the interior of the coupled inductor array. Fig. 59 is a top plan view of coupled inductor array 5800, fig. 60 is a side elevational view of coupled inductor array 5800, fig. 61 is a vertical cross-sectional view of coupled inductor array 5800 taken along line 59A-59A of fig. 59, fig. 62 is a vertical cross-sectional view of coupled inductor array 5800 taken along line 59B-59B of fig. 59, fig. 63 is a horizontal cross-sectional view of coupled inductor array 5800 taken along line 60A-60A of fig. 60, and fig. 64 is a horizontal cross-sectional view of coupled inductor array 5800 taken along line 60B-60B of fig. 60. Fig. 65 is a perspective view of the windings of coupled inductor array 5800 spaced from the magnetic core of the array. Coupled inductor array 5800 has a length 5802, a width 5804, and a height 5806. One possible application of coupled inductor array 5800 is in a switched mode power converter application, such as in a buck converter similar to buck converter 1200 of fig. 12 but with only two phases 1255.

Coupled inductor array 5800 includes a monolithic core 5808 formed of a magnetic material with distributed gaps. For example, in some embodiments, monolithic core 5808 is formed from a single piece of powdered magnetic material within an adhesive. As another example, in some other embodiments, monolithic core 5808 is formed from multiple magnetic film layers stacked in the height 5806 direction to form a monolithic core, where each magnetic film layer is formed from a powdered magnetic material within an adhesive. The distributed gap of monolithic core 5808 allows monolithic core 5808 to have a permeability that is much lower than the permeability of typical ferrite magnetic materials. In some embodiments, monolithic core 5808 includes one or more layers of non-magnetic material (not shown), such as one or more substrates for supporting features of coupled inductor array 5800 during fabrication of the coupled inductor array and for providing dielectric insulation within the coupled inductor array.

Coupled inductor array 5800 includes a first winding 5810 and a second winding 5812. The first winding 5810 forms a plurality of first winding turns 5814 embedded in a monolithic core 5808. Each first winding turn is formed about a respective winding axis 5816 extending in a height 5806 direction, and each winding axis 5816 is offset from each other winding axis 5816 in a width 5804 direction (see fig. 58, 61, 64, 65). As a result, the first winding turns 5814 are offset from each other in the width 5804 direction. The secondary winding 5812 forms a plurality of secondary winding turns 5818 embedded in a monolithic core 5808. Each second winding turn 5818 is formed about a respective one of the winding axes 5816 such that each second winding turn 5818 is coaxial with a respective first winding turn 5814 (see fig. 58, 61, 63, 65). As a result, each second winding turn 5818 and a corresponding one of the first winding turns 5814 collectively enclose a corresponding common portion 5819 of the monolithic core 5808, as seen when the coupled inductor array 5800 is viewed in cross-section in the height 5806 direction (see fig. 58). The first and second windings 5810 and 5812 are optionally electrically isolated from each other within the monolithic core 5808 by, for example, insulation on the windings or one or more dielectric substrates embedded within the monolithic core 5808.

The first and second windings 5810, 5812 are formed such that the first winding turn 5814 is wound in a first direction about a winding axis 5816, and the second winding turn 5818 is wound in a second direction, opposite the first direction, about the winding axis 5816, as seen when the coupled inductor array 5800 is viewed in cross-section in the height 5806 direction, to achieve diamagnetic coupling of the first and second windings 5810 and 5812. This diamagnetic coupling is characterized by the coupled inductor array 5800 inducing an increasingly larger magnitude current flowing from the first side 5820 into the second winding 5812 (see fig. 58), for example, by an increasingly larger magnitude current flowing from the first side 5820 into the first winding 5810 of the coupled inductor array.

The plurality of first winding turns 5814 are coaxial with corresponding second winding turns 5818, which provides multiple paths for the coupled magnetic flux in the monolithic core 5808, thereby facilitating strong magnetic coupling of the first and second windings 5810 and 5812. Furthermore, the fact that first winding turns 5814 are offset from each other in the width 5804 direction, and second winding turns 5818 are offset from each other in the width 5804 direction, facilitates a low height 5806 of coupled inductor array 5800. Some embodiments of the coupled inductor array 5800 further include a low permeability magnetic structure (not shown) that, similar to the low permeability magnetic structure of the coupled inductor array 5100 discussed above, spaces the first winding turn 5814 from the second winding turn 5818 in the height 5806 direction to further facilitate strong magnetic coupling of the first and second windings 5810 and 5812 while providing a path for leakage flux.

Modifications to coupled inductor array 5800 may be made without departing from the scope hereof. For example, the coupled inductor array 5800 may be modified to have additional windings offset from the first and second windings 5810 and 5812 in the lengthwise by widthwise direction. As another example, the first and second winding turns 5814 and 5818 may be modified to have different shapes, such as circular shapes instead of rectangular shapes. Furthermore, in some alternative embodiments of the coupled inductor array 5800, the first winding turn 5814 is offset from the second winding turn 5818 in one or more of the length 5802 direction or the width 5804 direction to provide an additional path for leakage flux by virtue of a tradeoff between weaker magnetic coupling with the first and second windings 5810 and 5812, and thereby promote large leakage inductance values. In these alternative embodiments, second winding turn 5818 is not coaxial with first winding turn 5814. In contrast, the second winding turns 5818 are wound around respective winding axes extending in the height direction, and the first winding axes 5814 are wound around different respective winding axes extending in the height 5806 direction.

The coupled inductor array 5800 can also be modified such that the first winding 5810 and the second winding 5812 each include a plurality of electrical conductors electrically coupled in parallel to facilitate low impedance of the windings. For example, fig. 66 is a perspective view of coupled inductor array 6600, which is similar to coupled inductor array 5800 of fig. 58, except that each winding includes two electrical conductors electrically coupled in parallel.

Coupled inductor array 6600 has a length 6602, a width 6604, and a height 6606, and coupled inductor array 6600 includes a monolithic magnetic core 6608, a first winding 6610, and a second winding 6612. The one-piece magnetic core 6608 is shown by a line drawing in fig. 66, i.e., only the outline of the magnetic core is shown. Fig. 67 is a perspective view of the first and second windings 6610, 6612 spaced apart from the monolithic core 6608. The first winding 6610 forms a plurality of first winding turns 6614 embedded in the monolithic core 6608, and each first winding turn 6614 is formed around a respective winding axis 6616 that extends in a direction of height 6606. The second winding 6612 forms a plurality of second winding turns 6618 embedded in a monolithic core 6608. Each second winding turn 6618 is formed around a respective one of the winding axes 6616 such that each second winding turn 6618 is coaxial with a respective first winding turn 6614. Only some examples of first winding turn 6614, shaft 6616, and second winding turn 6618 are labeled in fig. 66 to facilitate clarity of the description. The first winding 6610 includes two first electrical conductors 6630 electrically coupled in parallel, and the second winding 6612 includes two second electrical conductors 6632 electrically coupled in parallel. The second electrical conductor 6632 is stacked on the first electrical conductor 6630 in the height 6606 direction. One or more of the first winding 6610 and the second winding 6612 may be modified to include additional electrical conductors without departing from the scope herein.

Coupled inductor array 6600 can be modified to interleave first electrical conductor 6630 with second electrical conductor 6632 in the height 6606 direction to further facilitate strong magnetic coupling of first and second windings 6610 and 6612. For example, fig. 68 is a perspective view of coupled inductor array 6800 having a length 6802, a width 6804, and a height 6806. Coupled inductor array 6800 is similar to coupled inductor array 6600 of fig. 66, except that first and second windings 6810 and 6812 are included in place of first and second windings 6610 and 6612. Figure 69 is a perspective view of the first and second windings 6810 and 6812 spaced apart from the monolithic core 6608. The first winding 6810 includes two first electrical conductors 6830 electrically coupled in parallel, and the second winding 6812 includes two second electrical conductors 6832 electrically coupled in parallel. The second electrical conductor 6832 is interleaved with the first electrical conductor 6830 in the direction of the height 6806 to facilitate strong magnetic coupling of the first and second windings 6810 and 6812. The one-piece magnetic core 6608 is shown by a line drawing in fig. 68, i.e. only the outline of the magnetic core is shown.

Each of the coupled inductor arrays 5800, 6600, and 6800 can be modified such that each winding forms only a single winding turn to minimize coupled inductor array size and cost by virtue of a tradeoff with reduced magnetic coupling to the windings. For example, figure 70 is a perspective view of coupled inductor array 7000 having length 7002, width 7004, and height 7006. Coupled inductor array 7000 is similar to coupled inductor array 6600 of fig. 66 except that each winding forms only a single winding turn. Coupled inductor array 7000 includes monolithic magnetic core 7008, first winding 7010, and second winding 7012. The monolithic magnetic core 7008 is shown by a line drawing in fig. 70, i.e., only the outline of the magnetic core is shown. Fig. 71 is a perspective view of first and second windings 7010 and 7012 spaced from monolithic magnetic core 7008, and fig. 72 is a vertical cross-sectional view of coupled inductor array 7000 taken along line 70A-70A of fig. 70.

A first winding 7010 forms a first winding turn 7014 embedded in the monolithic magnetic core 7008 and formed around a winding axis 7016 extending in the direction of height 7006. A second winding 7012 forms a second winding turn 7018 embedded in the monolithic magnetic core 7008. The second winding turn 7018 is formed around the winding axis 7016 such that the second winding turn 7018 is coaxial with the first winding turn 7014. The first winding 7010 includes two first electrical conductors 7030 electrically coupled in parallel, and the second winding 7012 includes two second electrical conductors 7032 electrically coupled in parallel. The second electrical conductor 7032 is stacked on the first electrical conductor 7030 in the height direction. One or more of the first and second windings 7010, 7012 may be modified to include additional electrical conductors without departing from the scope hereof.

Fig. 73 shows another coupled inductor array in which each winding forms only a single turn. Specifically, fig. 73 is a perspective view of coupled inductor array 7300 having a length 7302, a width 7304, and a height 7306. Coupled inductor array 7300 is similar to coupled inductor array 6800 of fig. 68 except that each winding forms only a single winding turn. Coupled inductor array 7300 includes a monolithic magnetic core 7308, a first winding 7310, and a second winding 7312. A monolithic magnetic core 7308 is shown by a line drawing in fig. 73, i.e., only the outline of the magnetic core is shown. Fig. 74 is a perspective view of first and second windings 7310 and 7312 spaced apart from monolithic magnetic core 7308, and fig. 75 is a vertical cross-sectional view of coupled inductor array 7300 taken along line 73A-73A of fig. 73.

First winding 7310 forms first winding turn 7314, which is embedded in monolithic magnetic core 7308 and formed around winding axis 7316 extending in the direction of height 7306. Second winding 7312 forms second winding turns 7318 embedded in monolithic core 7308. The second winding turn 7318 is formed around the winding axis 7316 such that the second winding turn 7318 is coaxial with the first winding turn 7314. The first winding 7310 includes two first electrical conductors 7330 electrically coupled in parallel, and the second winding 7312 includes two second electrical conductors 7332 electrically coupled in parallel. The second electrical conductors 7332 are interleaved with the first electrical conductors 7330 in the height 7306 direction. One or more of the first and second windings 7310, 7312 may be modified to include additional electrical conductors without departing from the scope hereof.

The monolithic magnetic core in each of coupled inductor arrays 5800, 6600, 6800, 7000, and 7300 is optionally a composite magnetic core formed from at least two different types of magnetic materials to achieve the desired properties of the coupled inductor arrays. For example, in some embodiments of the coupled inductor array 5800 of fig. 58, each of the first and second windings 5810 and 5812 terminate on a common outer surface of the monolithic core 5808 such that the first and second windings 5810 and 5812 have unequal lengths. These unequal winding lengths cause the first and second windings 5810 and 5812 to default to having asymmetric leakage inductance values. However, if symmetric leakage inductance values are desired, the monolithic core 5808 may be implemented as a composite core to compensate for differences in winding lengths. For example, the portion of monolithic core 5808 surrounding the leakage path of the longer winding may have a smaller relative permeability than the portion of monolithic core 5808 surrounding the shorter winding to provide equal reluctance for the respective leakage inductance paths of the two windings, thereby providing the windings with symmetrical leakage inductance values.

As another example, the relative permeability of the magnetic material forming the monolithic core 5808 may be varied along the dimensions of the monolithic core 5808 to achieve a desired tradeoff between the magnetic coupling of the first and second windings 5810 and 5812 and the leakage inductance values of the windings. For example, FIG. 76 is a cross-sectional view similar to that of FIG. 62, but showing a single-piece magnetic core 5808 divided into several sections 7602-7628, wherein the magnetic permeability of the single-piece magnetic core 5808 varies between the sections. The following are several examples of possible configurations of the section 7602-7628 for obtaining various tradeoffs between magnetic coupling and leakage inductance values of the windings. However, it should be appreciated that the configuration of the one-piece magnetic core 5808 is not limited to these examples.

Example 1-coupled inductor array with composite magnetic core 5800.

Section 7602-7628 has the relative permeability shown in table 1 below. The portion of monolithic core 5808 within first and second winding turns 5814 and 5818 is formed from a magnetic material having a magnetic permeability greater than the magnetic permeability of at least some portions of monolithic core 5808 outside of the first and second winding turns, as seen when coupled inductor array 5800 is viewed in cross-section in a height 5806 direction. This configuration facilitates strong magnetic coupling of the first and second windings 5810 and 5812 by providing a low reluctance path along the winding axis 5816. However, the leakage inductance value is relatively small.

Segment of	Relative magnetic permeability
		7602	Is low in
7604	Height of
		7606	Is low in
7608	Is low in
		7610	Height of
7612	Is low in
		7614	Is low in
7616	Is low in
		7618	Is low in
7620	Height of
		7622	Is low in
7624	Is low in
		7626	Height of
7628	Is low in

TABLE 1

Example 2-coupled inductor array 5800 with another composite magnetic core.

Section 7602-7628 has the relative permeability shown in table 2 below. This configuration facilitates a larger leakage inductance value by reducing the reluctance of the leakage inductance path by means of a tradeoff with reduced magnetic coupling of the first and second windings 5810 and 5812, as compared to the configuration of example 1.

TABLE 2

Example 3-coupled inductor array with yet another composite magnetic core 5800.

Section 7602-7628 has the relative permeability shown in table 3 below. This configuration facilitates a larger leakage inductance value by further reducing the reluctance of the leakage inductance path by means of a tradeoff between further reduction of magnetic coupling with the first and second windings 5810 and 5812, as compared to the configuration of example 2. This configuration also facilitates balanced leakage inductance values for the first and second windings 5810 and 5812, provided that the windings terminate on the bottom outer surface of the monolithic core 5808.

TABLE 3

Example 4-coupled inductor array with composite magnetic core 7000.

Fig. 77-83 illustrate an embodiment of coupled inductor array 7000 (fig. 70) where monolithic core 7008 is a composite core. Specifically, fig. 77 is a cross-sectional view similar to that of fig. 72, but showing monolithic core 7008 divided into vertically stacked layers 1-6. Fig. 78-83 are top plan views of layers 1-6, respectively. As shown in FIGS. 78-83, layers 1-6 are divided into segments 7702-7768. Table 4 below lists the relative permeability of these different sections in one exemplary embodiment. The configuration of table 4 advantageously facilitates strong magnetic coupling of the first and second windings 7010 and 7012, as well as balanced leakage inductance values of the structurally asymmetric windings.

TABLE 4

Example 5-coupled inductor array 7300 with composite magnetic core.

Fig. 84-90 illustrate an embodiment of a coupled inductor array 7300 (fig. 73) in which monolithic core 7308 is a composite core. Specifically, fig. 84 is a cross-sectional view similar to that of fig. 75, but showing a monolithic magnetic core 7308 divided into vertically stacked layers 1-6. Fig. 85-90 are top plan views of layers 1-6, respectively. As shown in FIGS. 85-90, layers 1-6 are divided into sections 8402 and 8468. Table 5 below lists the relative permeability of these different sections in one exemplary embodiment. The configuration of table 5 advantageously facilitates strong magnetic coupling of the first and second windings 7310 and 7312, as well as balanced leakage inductance values of the structurally asymmetric windings.

TABLE 5

Combinations of features

The features described above as well as those claimed below may be combined in various ways without departing from the scope of the present disclosure. The following examples illustrate some possible combinations:

(A1) The coupled inductor array may include a magnetic core and N windings, where N is an integer greater than 1. The core may have opposing first and second sides, with a linear separation distance between the first and second sides defining a length of the core. The N windings may pass at least partially through the magnetic core in a length direction. Each of the N windings may be looped in the magnetic core about a respective winding axis, and each winding axis may be substantially perpendicular to the length direction, and each winding axis is parallel to but offset from each other winding axis. Each winding may have opposite first and second ends extending at least towards the first and second sides of the magnetic core, respectively.

(A2) In the coupled inductor array labeled (a1), each loop may surround a respective first region within the core, where each first region within the core is at least partially non-overlapping with each other first region in a width direction perpendicular to the length direction.

(A3) In the coupled inductor array labeled (a2), each first region may be completely non-overlapping with each other first region in the width direction.

(A4) In any of the coupled inductor arrays labeled (a2) or (A3), each loop may be substantially planar, and each first region may be smaller than a core region between the first and second sides within the plane of the respective first region.

(A5) In any of the coupled inductor arrays labeled (a2) through (a4), each winding axis may be offset from each other winding axis in the width direction within the magnetic core.

(A6) In any of the coupled inductor arrays labeled (a1) through (a5), the magnetic core may include a top plate and a bottom plate, and each loop may be disposed between the top plate and the bottom plate.

(A7) In the coupled inductor array labeled (a6), the magnetic core may further include N coupling teeth disposed between the top plate and the bottom plate, and each of the N windings may be wound around a respective one of the N coupling teeth.

(A8) In any of the coupled inductor arrays labeled (a6) or (a7), the magnetic core may further comprise at least one leakage tooth disposed between the top plate and the bottom plate, wherein the at least one leakage tooth is disposed between two adjacent ones of the respective rings.

(A9) In the coupled inductor array labeled (A8), at least one of the N coupling teeth may be formed of a different magnetic material than at least one instance of the at least one drain tooth.

(A10) Any of the coupled inductor arrays labeled (a7) through (a9) may further include a non-magnetic spacer disposed between at least one of the N coupled teeth and one of the top and bottom plates.

(A11) In any of the coupled inductor arrays labeled (a1) through (a5), the magnetic core may be a single-piece magnetic core, wherein each of the loops is embedded within the single-piece magnetic core.

(A12) In any of the coupled inductor arrays labeled (a1) through (a11), the N windings may be arranged within the magnetic core such that an increasingly larger magnitude of current flowing into a first winding of the N windings from a first side of the magnetic core induces an increasingly larger magnitude of current flowing into another winding of the N windings from the first side of the magnetic core.

(A13) In any of the coupled inductor arrays labeled (a1) through (a12), N may be an integer greater than 2.

(A14) In any of the coupled inductor arrays labeled (a1) through (a13), each loop may be disposed substantially within a common plane in the magnetic core.

(A15) In any of the coupled inductor arrays labeled (a1) through (a14), each of the loops may be longer in the length direction than in the width direction.

(A16) In any of the coupled inductor arrays labeled (a1) through (a15), each of the loops may have a substantially rectangular shape.

(A17) In any of the coupled inductor arrays labeled (a1) through (a14), each ring may have a substantially circular shape.

(A18) Any of the coupled inductor arrays labeled (a1) through (a17) may further include a common conductor electrically coupling at least two of the second ends of the N windings.

(A19) In the coupled inductor array labeled (a18), the common conductor may form a solder tab configured for surface mount attachment to a printed circuit board.

(A20) In any of the coupled inductor arrays labeled (a1) through (a19), at least one of the N windings may form a plurality of turns.

(A21) Any of the coupled inductor arrays labeled (a1) through (a20) may be co-packaged with the semiconductor die.

(A22) Any of the coupled inductor arrays labeled (a1) through (a20) may be disposed on a semiconductor die.

(A23) Any of the coupled inductor arrays labeled (a1) through (a20) may be disposed on a semiconductor die and packaged with the semiconductor die in a common integrated circuit package.

(A24) Any of the coupled inductor arrays labeled (a1) through (a20) may be co-packaged with and electrically coupled to a semiconductor die.

(A25) Any of the coupled inductor arrays labeled (a1) through (a20) may be disposed on and electrically coupled to a semiconductor die.

(A26) Any of the coupled inductor arrays labeled (a1) through (a20) may be disposed on and electrically coupled to a semiconductor die and packaged with the semiconductor die in a common integrated circuit package.

(B1) The multiphase switched mode power converter may include a coupled inductor and N switching circuits, where N is an integer greater than 1. The coupled inductor may include a magnetic core and N windings. The core may have opposing first and second sides, with a linear separation distance between the first and second sides defining a length of the core. The N windings may pass at least partially lengthwise through the magnetic core, and each of the N windings may form a loop in the magnetic core around a respective winding axis. Each winding axis may be substantially perpendicular to the length direction and each winding axis may be parallel to but offset from each other winding axis. Each winding may have opposing first and second ends extending at least toward the first and second sides of the magnetic core, respectively. Each switching circuit may be adapted to enable switching of the first end of a respective one of the N windings between at least two different voltage levels.

(B2) The multiphase switched mode power converter, designated (B1), may further include a controller adapted to control the N switching circuits to enable each of the N switching circuits to switch to a different phase relative to at least one other of the N switching circuits.

(B3) In any of the multi-phase switched power converters labeled (B1) or (B2), each ring may surround a respective first region within the core, wherein each first region within the core is at least partially non-overlapping with each other first region in a width direction perpendicular to the length direction.

(B4) In the multiphase switching power converter denoted as (B3), each first region may be completely non-overlapping with each other first region in the width direction.

(B5) In any of the multiphase switched mode power converters labeled (B3) or (B4), each ring may be substantially planar, and each first region may be smaller than a magnetic core region between the first and second sides in the plane of the respective first region.

(B6) in any of the multi-phase switched power converters labeled (B1) through (B5), each winding axis may be offset from each other winding axis in the width direction within the magnetic core.

(B7) In any of the multi-phase switched power converters labeled (B1) through (B6), the magnetic core may include a top plate and a bottom plate, and each ring may be disposed between the top plate and the bottom plate.

(B8) In the multi-phase switching power converter labeled (B7), the magnetic core may further include N coupling teeth disposed between the top plate and the bottom plate, and each of the N windings may be wound around a respective one of the N coupling teeth.

(B9) In any of the multiphase switched mode power converters labeled (B7) or (B8), the magnetic core may further include at least one drain tooth disposed between the top plate and the bottom plate, wherein the at least one drain tooth is disposed between two adjacent ones of the respective rings.

(B10) In the multi-phase switching power converter, designated (B9), at least one of the N coupling teeth may be formed of a different magnetic material than at least one instance of the at least one drain tooth.

(B11) Any of the multi-phase switched power converters designated (B8) through (B10) may further include a non-magnetic spacer disposed between at least one of the N coupling teeth and one of the top and bottom plates.

(B12) In any of the multi-phase switched power converters labeled (B1) through (B6), the magnetic core may be a single-piece magnetic core, wherein each of the rings is embedded within the single-piece magnetic core.

(B13) In any of the multi-phase switched power converters labeled (B1) through (B12), the multi-phase switched power converter may include at least one of a multi-phase buck converter, a multi-phase boost converter, and a multi-phase buck-boost converter.

(B14) In any of the multi-phase switched power converters labeled (B1) through (B13), the N windings may be arranged within the magnetic core such that an increasingly larger magnitude of current flowing into a first winding of the N windings from the first side of the magnetic core is capable of inducing an increasingly larger magnitude of current flowing into another winding of the N windings from the first side of the magnetic core.

(B15) In any of the multi-phase switched power converters labeled (B1) through (B14), N may be an integer greater than 2.

(B16) In any of the multi-phase switched power converters labeled (B1) through (B15), each ring may be disposed substantially within a common plane in the magnetic core.

(B17) In any of the multi-phase switched power converters labeled (B1) through (B16), each of the loops may be longer in the length direction than in the width direction.

(B18) In any of the multi-phase switched power converters labeled (B1) through (B17), each of the rings may have a substantially rectangular shape.

(B19) In any of the multi-phase switched power converters labeled (B1) through (B16), each ring may have a substantially circular shape.

(B20) Any of the multi-phase switched power converters labeled (B1) through (B19) may further include a common conductor electrically coupling at least two of the second ends of the N windings.

(B21) In the multiphase switched power converter labeled (B20), the common conductor may form a solder tab configured for surface mount attachment to a printed circuit board.

(B22) In any of the multi-phase switched power converters labeled (B1) through (B21), at least one of the N windings may form a plurality of turns.

(C1) A coupled inductor array having a length, a width, and a height may include a monolithic magnetic core formed of a magnetic material having a distributed gap and a plurality of windings embedded in the monolithic magnetic core. Each winding may form a respective winding loop of one or more turns around a respective winding axis, wherein each winding axis extends in height direction. The area of the monolithic core surrounded by the winding loops may be larger than the area of the monolithic core outside the winding loops, as seen when viewing the array of coupled inductors through a cross-section in a height direction.

(C2) In the coupled inductor array labeled (C1): the winding loops may be spaced apart from each other in the width direction, and each winding loop may surround a respective loop region elongated in the length direction.

(C3) in the coupled inductor array labeled (C2), each loop region may have a substantially rectangular shape.

(C4) In any of the coupled inductor arrays labeled (C1) through (C3): (1) each winding loop may have a thickness T in the height direction, (2) adjacent winding loops may be spaced apart from each other by a width-wise spacing distance D, and (3) D may be less than T.

(C5) In the coupled inductor array labeled (C4), D may be greater than 0.1 × T.

(C6) Any of the coupled inductor arrays labeled (C1) through (C5) may further include one or more non-magnetic structures embedded in the monolithic core, wherein the one or more non-magnetic structures are disposed outside the winding loops as seen when the coupled inductor array is viewed in elevation through a cross-section.

(C7) In the coupled inductor array labeled (C6), the one or more non-magnetic structures may include at least one non-magnetic structure disposed adjacent to each winding loop and in a common lengthwise by widthwise plane with the winding loop.

(C8) In any of the coupled inductor arrays labeled (C6) or (C7), the one or more non-magnetic structures may have a magnetic permeability that is lower than a magnetic permeability of a magnetic material having a distributed gap.

(C9) In any of the coupled inductor arrays labeled (C6) through (C8), the one or more non-magnetic structures may be formed of a conductive material, and the one or more non-magnetic structures may be electrically isolated from the plurality of windings.

(C10) In the coupled inductor array, labeled (C9), the one or more non-magnetic structures and the plurality of windings may be formed from a common material.

(C11) In the coupled inductor array, designated as (C1), at least two of the winding loops may overlap each other as seen when the coupled inductor array is viewed through a cross-section in a height direction.

(C12) In the coupled inductor array labeled (C11), two of the winding loops may surround a common lengthwise by widthwise region within the monolithic core.

(C13) In any of the coupled inductor arrays labeled (C11) or (C12), each winding loop may surround a respective loop region elongated in the length direction.

(C14) In the coupled inductor array labeled (C13), each loop region may have a substantially rectangular shape.

(C15) In any of the coupled inductor arrays labeled (C1) through (C14), the magnetic material having a distributed gap may comprise a powdered magnetic material within a binder.

(C16) In the coupled inductor array labeled (C15), the monolithic core may be a bulk core.

(C17) In the coupled inductor array labeled (C15), the monolithic magnetic core may include a plurality of magnetic film layers stacked in a height direction.

(D1) A method for forming a coupled inductor array including a magnetic core having at least one nonmagnetic structure embedded therein may include the steps of: (1) disposing at least two conductor layers on a core portion in a height direction such that the at least two conductor layers at least partially form at least two winding loops, as viewed in the height direction, (2) disposing one or more non-magnetic structures on the core portion and outside the at least two winding loops, as viewed in the height direction, and (3) disposing magnetic material on the core portion, the at least two conductor layers, and the one or more non-magnetic structures.

(D2) In the method labeled (D1), the non-magnetic structure may have a permeability that is lower than a permeability of a magnetic material disposed on the core portion.

(D3) In any of the methods labeled (D1) or (D2), the one or more non-magnetic structures may be formed of an electrically conductive material, and the one or more non-magnetic structures may be electrically isolated from the at least two winding loops.

(D4) In the method labeled (D3), the one or more non-magnetic structures and the at least two conductor layers may be formed from a common material.

(E1) A coupled inductor array having a length, a width, and a height may include a monolithic magnetic core formed from one or more magnetic materials having distributed gaps, first and second windings, and a low permeability magnetic structure. The first and second windings may form respective first and second winding turns around a common winding axis extending in a height direction, and each of the first and second winding turns may be embedded in the monolithic magnetic core. The low permeability magnetic structure may be embedded in the monolithic core and looped around a common winding axis. The low permeability magnetic structure may separate the first and second winding turns in a height direction, and the low permeability magnetic structure may be formed of a magnetic material having a lower permeability than the one or more magnetic materials forming the monolithic core.

(E2) In the coupled inductor array labeled (E1), the first and second winding turns and the low permeability magnetic structure may collectively surround a first portion of the monolithic magnetic core as seen when the coupled inductor array is viewed through a cross-section in a height direction.

(E3) In the coupled inductor array labeled (E2), the first portion of the monolithic core may be formed of a magnetic material having a higher permeability than the magnetic material forming the low permeability magnetic structure.

(E4) In any of the coupled inductor arrays labeled (E2) or (E3), the first portion of the monolithic magnetic core may have a substantially rectangular shape as seen when the coupled inductor array is viewed through a cross-section in a height direction.

(E5) In any of the coupled inductor arrays labeled (E1) through (E4), each of the first and second windings may be electrically isolated from each other within the monolithic core.

(E6) In any of the coupled inductor arrays labeled (E1) through (E5), the one or more magnetic materials forming the monolithic magnetic core may include powdered magnetic material within an adhesive.

(E7) In any of the coupled inductor arrays labeled (E1) through (E6), the monolithic core may be a bulk core.

(E8) In any of the coupled inductor arrays labeled (E1) through (E6), the monolithic magnetic core may include a plurality of magnetic film layers stacked in a height direction.

(F1) A coupled inductor array having a length, a width, and a height may include a monolithic magnetic core formed of one or more magnetic materials having distributed gaps, a first winding, and a second winding. The first winding may be embedded in the monolithic magnetic core and the first winding may form one or more first winding turns around respective winding axes extending in the height direction. Each winding axis may be offset in the width direction from each other winding axis. The second winding may be embedded in the monolithic magnetic core, and the second winding may form a respective second winding turn for each of the one or more first winding turns. Each second winding turn and its respective first winding turn may together enclose a respective common portion of the monolithic magnetic core as seen when the coupled inductor array is viewed through a cross-section in a height direction.

(F2) In the coupled inductor array labeled (F1), each second winding turn may be formed around a respective one of the winding axes such that each second winding turn is coaxial with a respective one of the plurality of first winding turns.

(F3) In any of the coupled inductor arrays labeled (F1) or (F2), the first winding may include a plurality of first electrical conductors electrically coupled in parallel, the second winding may include a plurality of second electrical conductors electrically coupled in parallel, and the plurality of second electrical conductors may be stacked on the plurality of first electrical conductors in the height direction.

(F4) In any of the coupled inductor arrays labeled (F1) or (F2), the first winding may include a plurality of first electrical conductors electrically coupled in parallel, the second winding may include a plurality of second electrical conductors electrically coupled in parallel, and the plurality of second electrical conductors may be interleaved with the plurality of first electrical conductors in the elevation direction.

(F5) In any of the coupled inductor arrays labeled (F1) through (F4), each first winding turn may be wound in a first direction and each second winding turn may be wound in a second direction opposite the first direction, as seen when the coupled inductor array is viewed through a cross-section in the elevation direction.

(F6) In any of the coupled inductor arrays labeled (F1) through (F5), the monolithic magnetic core may be formed of at least two different magnetic materials.

(F7) In the coupled inductor array labeled (F5), the portion of the monolithic core within the winding turns may be formed of a magnetic material having a higher magnetic permeability than at least some portions of the core outside of the first and second winding turns, as seen when the coupled inductor array is viewed through a cross-section in a height direction.

(F8) In any of the coupled inductor arrays labeled (F1) through (F7), each of the first and second windings may be electrically isolated from each other within the monolithic core.

(F9) In any of the coupled inductor arrays labeled (F1) through (F8), the one or more magnetic materials forming the monolithic magnetic core may include powdered magnetic material within an adhesive.

(F10) In the coupled inductor array labeled (F9), the monolithic core may be a bulk core.

(F11) In the coupled inductor array labeled (F9), the monolithic magnetic core may include a plurality of magnetic film layers stacked in a height direction.

Changes may be made in the above methods and systems without departing from the scope hereof. For example, the number of windings in each array may be varied. It is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.

Claims

1. A coupled inductor array having a length, a width, and a height, the coupled inductor array comprising:

A monolithic magnetic core formed of one or more magnetic materials with a distributed gap, the monolithic magnetic core having opposing first and second sides separated from each other in a width direction;

A first winding embedded in the monolithic magnetic core and having two opposing ends terminating at the first side and the second side of the monolithic magnetic core, respectively, the first winding forming N first winding turns about respective winding axes extending in a height direction, each winding axis being offset in a width direction from each other winding axis, N being an integer greater than one; and

A second winding embedded in the monolithic magnetic core and having two opposing ends terminating at the first side and the second side of the monolithic magnetic core, respectively, the second winding forming N second winding turns,

Each of the N first winding turns and each of the N second winding turns are fully embedded in the monolithic magnetic core,

Each of the N second winding turns overlaps a respective first winding turn of the N first winding turns in the height direction, an

The N first winding turns and the N second winding turns are configured such that an increasingly larger magnitude of current flowing into the first winding at the first side of the monolithic core induces an increasingly larger magnitude of current flowing into the second winding at the first side of the monolithic core.

2. The coupled inductor array of claim 1, each of the N second winding turns formed about a respective one of the winding axes such that each of the N second winding turns is coaxial with a respective one of the N first winding turns.

3. The coupled inductor array of claim 2, the first winding comprising a plurality of first electrical conductors electrically coupled in parallel with each other and the second winding comprising a plurality of second electrical conductors electrically coupled in parallel with each other, the plurality of first electrical conductors stacked on each other in the height direction, the plurality of second electrical conductors stacked on each other in the height direction, and the plurality of second electrical conductors stacked on the plurality of first electrical conductors in the height direction.

4. The coupled inductor array of claim 2, the first winding comprising a plurality of first electrical conductors electrically coupled in parallel with each other, and the second winding comprising a plurality of second electrical conductors electrically coupled in parallel with each other, the plurality of second electrical conductors interleaved with the plurality of first electrical conductors in the height direction.

5. The coupled inductor array of claim 1, each of the N first winding turns wound in a first direction and each of the N second winding turns wound in a second direction opposite the first direction, as seen when the coupled inductor array is viewed in cross-section in the elevation direction.

6. The coupled inductor array of claim 1, the monolithic magnetic core being formed of at least two different magnetic materials.

7. The array of coupled inductors of claim 6, portions of the monolithic core within the N first winding turns and the N second winding turns being formed of a magnetic material having a higher magnetic permeability than at least some portions of the monolithic core outside the N first winding turns and the N second winding turns, as seen when the array of coupled inductors is viewed in cross-section in the elevational direction.

8. The array of coupled inductors of claim 1, each of the first and second windings being electrically isolated from each other within the monolithic core.

9. The coupled inductor array of claim 1, the one or more magnetic materials forming the monolithic magnetic core comprising powdered magnetic material within an adhesive.

10. The coupled inductor array of claim 9, the monolithic magnetic core being a bulk magnetic core.

11. The coupled inductor array of claim 9, the monolithic magnetic core comprising a plurality of magnetic film layers stacked in the height direction.

12. The coupled inductor array of claim 1, wherein N is greater than two, and the monolithic magnetic core is configured to magnetically couple each of the N first winding turns with each of the N second winding turns.