CN111863410A - Composite inductor, DC-DC power converter and method for manufacturing composite inductor - Google Patents

Abstract

A composite inductor, a DC-DC power converter and a method of manufacturing a composite inductor. An example composite inductor includes a coil and a first hot-pressed magnetic powder. The coil is at least partially disposed within the first hot pressed magnetic powder to define a shield core. The shield core defines an opening through the first hot pressed magnetic powder and the coil. The composite inductor also includes a central core positioned in an opening through the first hot pressed magnetic powder and the coil. The central core includes a second magnetic powder. The second magnetic powder includes a magnetic material different from the first hot-pressed magnetic powder. The composite inductor also includes two or more terminals electrically coupled to the coil. Example methods of fabricating the composite inductor are also described.

Description

Composite inductor, DC-DC power converter and method for manufacturing composite inductor

Technical Field

The present disclosure relates generally to composite inductors and, in particular, to high current, high frequency, low loss composite inductors including different magnetic powders for a shielding core and a central core.

Background

This section provides background information related to the present disclosure, but not necessarily prior art.

High current, high frequency, low loss inductors increase power density for smaller sized power supplies and provide higher power for the same sized power supplies. For high frequency applications, the inductor may have a closed magnetic loop to reduce electromagnetic interference (EMI) and specified magnetic materials to reduce losses.

Some high density inductors are manufactured using cold pressing techniques to form molded inductors. Some other high density inductors are fabricated by injecting magnetic glue into an open loop inductor.

Disclosure of Invention

This section provides a general summary of the disclosure, but is not a comprehensive disclosure of its full scope or all of its features.

An example composite inductor, comprising: coil and first hot pressing magnetic powder. The coil is at least partially disposed within the first hot pressed magnetic powder to define a shield core. The shield core defines an opening through the first hot pressed magnetic powder and the coil. The composite inductor also includes a central core located in the opening through the first hot pressed magnetic powder and the coil. The central core includes a second magnetic powder. The second magnetic powder includes a magnetic material different from the first hot-pressed magnetic powder. The composite inductor also includes two or more terminals electrically coupled to the coil. Example methods of fabricating the composite inductor are also described.

Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.

Drawings

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

Fig. 1A illustrates a coil of a composite inductor according to an example embodiment of the present disclosure.

Fig. 1B illustrates a shielded core including the coil shown in fig. 1A.

Fig. 1C illustrates the central core of the composite inductor.

Fig. 1D illustrates a composite inductor including the shielded core shown in fig. 1B and the central core shown in fig. 1C.

Fig. 2A illustrates a top view of a composite inductor according to an example embodiment of the present disclosure.

Fig. 2B is a side view of the composite inductor shown in fig. 2A.

Fig. 2C is a bottom view of the composite inductor shown in fig. 2A.

Fig. 2D is a rotated side view of the composite inductor shown in fig. 2A.

Fig. 2E is an orthogonal view of the composite inductor shown in fig. 2A.

Fig. 3 is a flowchart illustrating a method of manufacturing a composite inductor according to an example embodiment of the present disclosure.

Fig. 4 is a line graph illustrating an example inductance in nanohenries (nH) versus current in amperes (a) for the central core of the composite inductor shown in fig. 1A-1D.

Fig. 5 is a line graph illustrating an example temperature rise in degrees celsius (° c) versus current in amperes (a) for the composite inductor shown in fig. 1A-1D.

Corresponding reference characters indicate corresponding, but not necessarily identical, parts throughout the several views of the drawings.

Detailed Description

Example embodiments will now be described more fully hereinafter with reference to the accompanying drawings.

High current, high frequency, low loss inductors increase power density for smaller sized power supplies and provide higher power for the same sized power supplies. For high frequency applications, the inductor may have a closed magnetic loop to reduce electromagnetic interference (EMI and specified magnetic materials to reduce losses).

Some high density inductors are manufactured using cold pressing techniques to form molded inductors, while some other high density inductors are manufactured by injecting magnetic glue into open loop inductors. Some cold-pressed molded inductors have thickness limitations and may have difficulty in reducing Direct Current Resistance (DCR). Due to the limited maximum relative permeability (e.g., less than 15ui, etc.), an injected magnetic glue inductor may have a limited inductance value and may be costly.

Disclosed herein are exemplary embodiments of a composite inductor and methods of manufacturing a composite inductor that may provide higher inductance values, may provide lower DCR (e.g., as compared to other inductors having the same number of winding turns, etc.), may have improved roll-off curves due to the composite material used in the inductor, etc.

For example, a composite inductor may include a coil and a first hot-pressed magnetic powder. The coil is at least partially disposed within the first hot pressed magnetic powder to define a shield core. The shield core defines an opening through the first hot pressed magnetic powder and the coil.

The example composite inductor also includes a central core positioned in an opening through the first hot pressed magnetic powder and the coil. The central core includes a second magnetic powder (e.g., a second hot pressed magnetic powder, a second cold pressed magnetic powder, etc.). The second magnetic powder includes a magnetic material different from the first hot-pressed magnetic powder. The composite inductor also includes two or more terminals electrically coupled to the coil.

Accordingly, example embodiments disclosed herein may include a composite inductor that includes a hot-pressed core having filled holes or openings and/or which is located in another core formed from a different material than the hot-pressed core.

Example methods of fabricating the composite inductor are also described herein. For example, hot press molding may be used to mold the coil with carbonyl (carbonyl) iron powder (CIP), other magnetic powder, or the like to form the shielded inductor. In forming the shield inductor, a portion (e.g., a central portion, an opening, etc.) of the inductor may be removed. During hot press molding or the like, the portion may be removed using a specially designed tool device.

Another magnetic powder, such as a silicon iron (FeSi) powder, a silicon iron aluminum (fesai) powder, a nickel silicide (NiSi) powder, etc., is formed (e.g., hot press molding, cold press molding, etc.) into an R-shaped core. The R-shaped core may comprise any suitable core shape, such as a cylinder or rod having a circular cross-section, a square cross-section with rounded corners, or the like.

The shield inductor and the R-shaped core may then be assembled by inserting the R-shaped core into the removed portion of the shield inductor. An adhesive or glue may be applied to adhere the shield inductor and the R-shaped core to each other, and then the assembly may be cured with the terminals electrically coupled to the coil (e.g., to the exposed ends of the coil, as integral parts of the ends of the coil, etc.).

The example composite inductors described herein may provide a relative magnetic permeability (ui) of at least 50% (or better) and a saturation magnetic flux density of the same or better than some other types of inductors. For example, a cold-pressed molded inductor may have a maximum relative permeability of 25ui and a saturation flux density of 1000 millitesla (mT), and an induction magnetic glue inductor may have a maximum relative permeability of 15ui and a saturation flux density of 1000 mT. Some example embodiments herein may provide a relative permeability of up to 34 μ (or more) and a saturation magnetic flux density of up to 1200mT (or more).

In some embodiments, the hot press molding technique can result in an edge thickness of 0.6mm (or even thinner), which is at least 0.2mm thinner than cold press molding techniques that require an edge thickness of at least 0.8 mm. The reduced edge thickness of some example embodiments herein may allow for increased coil (e.g., copper, etc.) width and height to reduce DCR, thereby reducing power loss.

Some example embodiments may have a lower or lowest stress effect during assembly compared to injecting magnetic glue into an open loop inductor, and therefore, the performance of the R-shaped core is not affected. The relative permeability of the R-shaped core can be 160ui or even higher, which provides higher inductance and improved saturation flux density.

Referring to the drawings, fig. 1A-1D illustrate a composite inductor 100 according to some aspects of the present disclosure. As shown in fig. 1A, composite inductor 100 includes a coil 104 having an end 102.

As shown in fig. 1B, the composite inductor 100 includes a first hot-pressed magnetic powder 106. The coil 104 is at least partially disposed within the first hot pressed magnetic powder 106 to provide a shielded core 108 (e.g., a shielded inductor, etc.). The shield core 108 defines an opening 110 through the first hot pressed magnetic powder 106 and the coil 104.

The composite inductor 100 also includes a central core 112 positioned in an opening 110, the opening 110 passing through the first hot pressed magnetic powder 106 and the coil 104. The central core 112 includes a second magnetic powder 114 (e.g., a second hot pressed magnetic powder, a second cold pressed magnetic powder, etc.). The second magnetic powder 114 includes a different magnetic material from the first hot-pressed magnetic powder 106. The composite inductor 100 also includes two or more terminals 116 electrically coupled to the coil 104.

The first hot pressed magnetic powder 106 may comprise any suitable magnetic material (e.g., metal alloy powder, etc.) capable of being hot pressed around the coil 104 to form the shielded core 108. For example, in some embodiments, the first hot press magnet powder 106 may include Carbonyl Iron Powder (CIP).

As mentioned above, the material of the second magnetic powder 114 is different from the material of the first hot-pressed magnetic powder 106. The second magnetic powder 114 may comprise any suitable magnetic powder that can be formed (e.g., hot pressed, cold pressed, etc.) into an R-shaped core. For example, the second magnetic powder 114 may include silicon iron (FeSi), silicon aluminum (fesai), nickel silicide (NiSi), or the like.

Using a different material for the shielding core 108 than the material used for the central core 112 may allow for the use of a first magnetic powder 106 that is more suitable for surrounding the coil 104, while the use of a second magnetic powder 114 is more suitable for providing improved electrical characteristics in the central core 112 of the composite inductor 100.

As shown in fig. 1B and 1D, the coil 104 is positioned within a first hot pressed magnetic powder 106 to form a shielded core 108. The coil 104 may be positioned in the composite inductor 100 to form a closed magnetic loop.

Coil 104 and end 102 may include any suitable wires, conductors, or the like for conducting current in composite inductor 100. For example, the coil 104 may comprise copper, may be flat, round, etc. In some embodiments, the coil 104 may be enameled (e.g., include a dielectric coating, etc.) to provide electrical insulation, etc., between the coil 104 and the first hot-pressed magnetic powder 106.

Fig. 1C illustrates the central core 112 as a cylindrical rod having a circular cross-section, which may be considered an R-shaped core. In other embodiments, the R-shaped core may have a square cross-section, a square cross-section with rounded corners, or any other suitable core shape.

As shown in fig. 1D, central core 112 is inserted into opening 110 of shielded core 108. Therefore, the central core 112 passes through the first hot-pressed magnetic powder 106 inside defined by the coil 104, but the central core 112 does not necessarily have to be located at the center of the hot-pressed magnetic powder 106, the center of an opening defined by the coil 104, or the like.

The terminals 116 are electrically coupled to the coil 104 to allow the coil 104 to be connected to other circuit components and the like. The terminals 116 may be integral with the coil 104, may be connected to the coil 104 via solder, may contact the ends of the coil 104, etc., as shown in FIG. 1D.

In the example embodiment shown in fig. 1B and 1D, when the shield core 108 is formed, the end 102 of the coil 104 extends out of the first hot pressed magnetic powder 106. The extended end 102 of the coil 104 is then bent around the outer surface of the shield core 108 to form the terminal 116.

Fig. 2A illustrates a top view of composite inductor 100. Composite inductor 100 is illustrated as approximately square (e.g., approximately 6.60 millimeters by 6.75 millimeters, etc.), but other embodiments may have other suitable shapes and sizes. Referring to fig. 2B, composite inductor 100 may have a height (e.g., thickness, etc.) of approximately 3.30mm, although other embodiments may have other suitable heights.

As described above, the composite inductor 100 includes two terminals 116 spaced apart from each other. Referring to fig. 2C and 2D, the terminals 116 are spaced apart from each other by 2.70mm ± 0.20mm, and each terminal has a length of 5.50mm ± 0.15mm on the bottom side of the composite inductor 100.

The terminal 116 is spaced approximately 0.45mm from the edge of the composite inductor, the width of the terminal 116 is 1.2mm + -0.10 mm, and the thickness of the terminal 116 is approximately 0.25 mm. These dimensions are provided as examples, and other embodiments may include more or fewer terminals having different lengths, widths, thicknesses, pitch locations, tolerances, and the like.

Fig. 2C and 2E illustrate that terminals 116 are located at the bottom and sides of shielded core 108 and may exit shielded core 108 from one or more openings (e.g., electrically connected to coil 104, etc.). Terminals 116 may reach different heights on the sides of shielded core 108 as shown in fig. 2E.

Fig. 3 illustrates a flow chart of a method 301 for manufacturing a composite inductor according to an example embodiment of the present disclosure. The method 301 comprises the steps of: a first magnetic powder is placed around a pre-wound coil while maintaining an opening through the first magnetic powder and the coil.

Then, at 305, the first magnetic powder is hot-pressed to form a shield core including a coil and an opening passing through the first magnetic powder and the coil.

The hot pressing may include any suitable technique for forming a molded inductor using hot pressing. For example, using a heating temperature between 60 degrees Celsius (C.) and 200℃ can help mold magnetic powders of higher density, higher permeability, higher flux density, and the like. The hot pressing can avoid ultra high temperature curing compared to cold pressing, which uses normal temperature molding and does not generate heat during pressing.

At 307, a central core is formed using (e.g., hot pressing, cold pressing, etc.) a second magnetic powder. The second magnetic powder includes a magnetic material different from the first magnetic powder. At 309, a central core is inserted into an opening through the first magnetic powder and the coil.

Hot pressing the first and/or second magnetic powder may produce a hot pressing residue (e.g., a residue of hot pressing the first magnetic powder, a residue of the second magnetic powder, etc.) in some example embodiments. The hot press residue may be located with, external to, etc. the central core and/or the shield core, and may indicate that the central core and/or the shield core are formed using a hot press technique.

The method 301 may include applying an adhesive or glue between the central core and the shielding core, and curing the adhesive or glue to secure the central core to the shielding core. Two or more terminals may be connected with the coil, which may include one or more wire portions extending from the coil to define the terminals, etc. After assembly, the composite inductor may be coated to make the appearance uniform, etc.

In some embodiments, the first magnetic powder comprises carbonyl iron powder and the second magnetic powder comprises at least one of silicon iron (FeSi), silicon aluminum (fesai), and nickel silicide (NiSi). The pre-wound coil may comprise flat or round copper wire and the copper wire is enameled for electrical insulation. In other embodiments, other magnetic powder materials may be used, other coil configurations may be used, and the like.

In method 301, the central core may have any suitable shape, such as an R-shaped core (e.g., a rod-shaped core, etc.). The R-shaped core may be cylindrical, may have a circular cross-section, a square cross-section with rounded corners, etc.

Fig. 4 illustrates test data for the inductance 411 and roll-off 413 of the central core 112 of the composite inductor 100 versus DC current (Idc). For the test data shown in fig. 4, the relative permeability of the central core 112 is 40 μ i.

As shown in fig. 4, the inductance drops only from 553.5nH at an Idc value of zero amperes (a), to 414nH at an Idc value of 30A (i.e., a roll-off of 25.2% of the zero a inductance value) and to 386nH at an Idc value of 35A (i.e., a roll-off of 30.26% of the zero a inductance value). The composite inductor 100 may cause the Idc value to be 20.69% higher before a roll-off value of 30% occurs, as compared to some other inductors.

The composite inductor 100 used for testing may have a DCR value of 2.53m Ω (although composite inductors in other embodiments may have higher or lower DCR values). The composite inductor 100 may allow a 15.94% reduction in DCR compared to some other inductors.

The composite inductor 100 used for testing may have dimensions of approximately 6.36mm by 6.34mm by 2.30mm (although composite inductors in other embodiments may have different dimensions). The composite inductor 100 may allow a height reduction of 23% compared to some other inductors.

Fig. 5 illustrates test data for the temperature rise versus DC current (Idc) for the composite inductor 100. As shown at 415 in fig. 5, the temperature rise in the composite inductor 100 reaches about 20 degrees celsius (° c) and the Idc value is about 27A. The composite inductor 100 can achieve a 20 ℃ temperature rise compared to some other inductors, with an Idc value 10A higher, corresponding to a 58.8% improvement (although the composite inductors in other embodiments can have different temperature rise characteristics).

The temperature rise in the composite inductor 100 reaches approximately 40 degrees celsius (° c) and the Idc value is approximately 32A. The composite inductor 100 can achieve a temperature rise of 40 ℃ with an Idc value 5A higher, corresponding to a 22.73% improvement, compared to some other inductors.

Table 1 below illustrates test parameters for composite inductor 100. These test parameters are provided for illustrative purposes only, and composite inductors in other embodiments may have other electrical parameters.

Electrical specification @25 deg.C

Electrical characteristics	MIN	NOM	MAX
				OCL@100khz,0.1V(nH)	448	560	672
DCR(mΩ)	-	2.5	3.0
				Temperature rise current Irms (A)	-	32	-
Saturated Current Isat (A)	-	35	-

TABLE 1

Example embodiments described herein may provide one or more (or none) of the following advantages: higher current, higher inductance, improved DC bias performance, lower DCR (e.g., lower power loss), fewer coil turns, wider copper width in the coil, central core relative permeability of up to 160ui or more, shielding core relative permeability of up to 35ui or more, etc. The composite inductor may be used in any suitable application, such as a DC-DC power converter or the like.

The example embodiments are provided so that this disclosure will be thorough and will fully convey the scope of the disclosure to those skilled in the art. Numerous specific details are set forth, such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms and that should not be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. Additionally, the advantages and improvements that may be realized by one or more exemplary embodiments of the present disclosure are provided for illustration only and do not limit the scope of the present disclosure, as the exemplary embodiments disclosed herein may provide all or none of the above advantages and improvements while remaining within the scope of the present disclosure.

Specific dimensions, specific materials, and/or specific shapes disclosed herein are exemplary in nature and do not limit the scope of the disclosure. The disclosure herein of particular values and particular value ranges for a given parameter does not preclude other values or value ranges that may be useful in one or more examples disclosed herein. Moreover, it is contemplated that any two particular values for a particular parameter described herein may specify endpoints that are applicable to a range of values for the given parameter (i.e., the disclosure of a first value and a second value for the given parameter is to be interpreted as disclosing any value between the first value and the second value that is also applicable to the given parameter). For example, if parameter X is exemplified herein as having a value a, and is also exemplified as having a value Z, it is foreseeable that parameter X may have a range of values from about a to about Z. Similarly, it is contemplated that the disclosure of two or more ranges of values for a parameter (whether nested, overlapping, or distinct) encompasses all possible combinations of the ranges of values that may be claimed using the endpoints of the disclosed ranges. For example, if parameter X is exemplified herein as having a value in the range of 1-10 or 2-9 or 3-8, it is also contemplated that parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9.

The term "about" when applied to a value means that some minor inaccuracy in the calculation or measurement of the value is allowed (the value is close to exact; about approximate or reasonable; nearly). Otherwise, if for some reason the imprecision provided by "about" is not otherwise understood in the art with this ordinary meaning, then "about" as used herein at least indicates a variation that may result from ordinary methods of measuring or using such parameters. For example, the terms "approximately", "about" and "substantially" may be used herein to mean within manufacturing tolerances.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, a description in the singular may be intended to include the plural unless the context clearly indicates otherwise. The terms "comprises," "comprising," and "having" are intended to be inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein do not have to be performed in the particular order discussed or illustrated herein, unless an order of performance is specifically indicated. It will also be appreciated that additional or alternative steps may be employed. When a component or layer is referred to as being "on," "engaged to," "connected to" or "coupled to" another component or layer,

It may be directly on, joined, connected, or coupled to the other component or layer, or intervening components or layers may be present. In contrast, when an element is referred to as being "directly on … …", "directly engaged to", "directly connected to", or "directly coupled to" another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between components should also be construed accordingly (e.g., "between" and "directly between … …," "adjacent" and "directly adjacent"), etc. As used herein, the term "and/or" includes any one or more of the associated items and all combinations thereof.

Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as "first," "second," and other numerical terms used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first component, region, layer or section discussed below could be termed a second component, region, layer or section without departing from the teachings of the example embodiments.

The foregoing description of the embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual components, intended or described uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, may be interchanged and used in a selected embodiment (even if not specifically shown or described). These embodiments may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims (17)

1. A composite inductor, comprising:

a coil;

a first hot pressed magnetic powder, the coil being at least partially disposed within the first hot pressed magnetic powder to define a shield core, the shield core defining an opening through the first hot pressed magnetic powder and the coil;

a central core located in the opening through the first hot pressed magnetic powder and the coil, the central core comprising a second magnetic powder comprising a different magnetic material than the first hot pressed magnetic powder; and

two or more terminals electrically coupled with the coil.

2. The composite inductor of claim 1 wherein:

the first hot-pressed magnetic powder comprises carbonyl iron powder; and is

The second magnetic powder comprises at least one of ferrosilicon FeSi powder, ferrosilicon aluminum FeSiAl powder and nickel silicide NiSi powder.

3. The composite inductor of claim 1, wherein the coil is positioned within the first hot pressed magnetic powder to define a closed magnetic loop.

4. The composite inductor of claim 1 wherein:

the coil comprises a flat copper wire or a round copper wire; and/or

For electrical insulation, the coils are enameled.

5. The composite inductor of claim 1, wherein the central core comprises an R-shaped core having a circular cross-section, a square cross-section, or a square cross-section with rounded corners.

6. The composite inductor of claim 1, wherein the first hot pressed magnetic powder has an edge thickness of less than or equal to 0.6 millimeters.

7. The composite inductor of claim 1 wherein:

the central core has a relative magnetic permeability of 160ui or more, and/or

The shielding core has a relative permeability of 35ui or more, and/or

The composite inductor has a saturation flux density of up to 1200 millitesla or more.

8. The composite inductor of claim 1, wherein the central core is adhered to the shielding core via a cured adhesive.

9. The composite inductor of claim 1, wherein the shield core comprises a thermocompression residue.

10. The composite inductor of claim 1, wherein the second magnetic powder of the shielding core comprises a second hot pressed magnetic powder or a second cold pressed magnetic powder.

11. A DC-DC power converter comprising a composite inductor according to any preceding claim.

12. A method of manufacturing a composite inductor, the method comprising the steps of:

placing a first magnetic powder around a pre-wound coil while maintaining an opening through the first magnetic powder and the coil;

hot-pressing the first magnetic powder to form a shield core including the coil and the opening passing through the first magnetic powder and the coil;

forming a central core using a second magnetic powder comprising a different magnetic material than the first magnetic powder; and

inserting the central core into the opening through the first magnetic powder and the coil.

13. The method of claim 12, further comprising the steps of:

applying an adhesive between the central core and the shield core; and

curing the adhesive to secure the central core to the shielding core.

14. The method of claim 12, further comprising the steps of: two or more terminals are electrically connected with the coil.

15. The method of claim 12, wherein:

the coil comprises flat copper wires or round copper wires, and the copper wires are enameled for electrical insulation; and/or

The central core comprises an R-shaped core having a circular cross-section, a square cross-section, or a square cross-section with rounded corners.

16. The method of claim 12, wherein the step of forming a central core using a second magnetic powder comprises: hot or cold pressing the second magnetic powder to form the central core.

17. The method of any of claims 12 to 16, wherein:

the first magnetic powder comprises carbonyl iron powder; and is

The second magnetic powder comprises at least one of ferrosilicon FeSi powder, ferrosilicon aluminum FeSiAl powder and nickel silicide NiSi powder.

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