Transformer with controllable leakage inductance

Abstract

A multi-leg transformer (10) includes a core (20, 22) having a plurality of center rods (24, 25, 26), a primary coil (40) wound on at least one of the center rods (24, 25, 26), a secondary coil (42) wound on at least one of the center rods (24, 25, 26) and spaced apart from the primary coil (40), and at least one magnetic shunt material (50) disposed in one or more selected regions between the primary coil (40) and the secondary coil (42).

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 63 / 344,819, filed on May 23, 2022, the contents of which are incorporated herein by reference. Technical Field

[0003] The disclosed concepts relate generally to electrical components and, more particularly, to transformers. Background Art

[0004] Transformers face many design challenges. For example, in high power transformer applications, cooling is a concern. As another example, in transformers used in LLC applications, the size of the core gap and fringing flux are concerns. In addition, the leakage inductance of the transformer affects the suitability of the transformer in certain applications and is compensated by using additional inductors.

[0005] There is still room for improvement in transformers. Summary of the invention

[0006] According to one aspect of the disclosed concept, a multi-leg transformer includes: a core having a plurality of center rods; a primary coil wound around at least one center rod; a secondary coil wound around at least one center rod and spaced apart from the primary coil; and at least one magnetic shunt material disposed in one or more selected regions between the primary coil and the secondary coil.

[0007] According to one aspect of the disclosed concept, a method of manufacturing a multi-leg transformer includes: providing a core having one or more core legs, a primary coil wound on at least one core leg, and a secondary coil wound on at least one core leg and spaced apart from the primary coil; determining a desired leakage inductance level for the multi-leg transformer; and adjusting the multi-leg transformer to the desired leakage inductance level by placing at least one magnetic shunt material in one or more selected regions between the primary coil and the secondary coil.

[0008] According to one aspect of the disclosed concept, a bobbin for a multi-leg transformer having a core including a plurality of center rods, a primary coil wound on at least one center rod, a secondary coil wound on at least one center rod and spaced apart from the primary coil, and at least one magnetic shunt material disposed in one or more selected areas between the primary coil and the secondary coil, the bobbin comprising: a plurality of center portions corresponding to the plurality of center rods, each center portion being configured to have a coil of a primary coil or a secondary coil wound thereon; at least one insulating barrier disposed between two of the plurality of center rods and configured to provide insulation between the coils of the primary coil or the secondary coil; and at least one capture feature configured to assist the primary coil or the secondary coil in maintaining a shape around the center rod. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The disclosed concepts can be best understood from the following description of the preferred embodiments when read in conjunction with the accompanying drawings, in which:

[0010] Figure 1A is an axonometric view of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0011] Figure 1B yes Figure 1A Top view of a multi-leg transformer;

[0012] Figure 1C yes Figure 1A A front view of a multi-leg transformer;

[0013] Figure 1D yes Figure 1A A side view of a multi-leg transformer;

[0014] Figure 2A is a top view of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0015] Figure 2B yes Figure 2A A cross-sectional view of a multi-leg transformer;

[0016] Figure 3 is an exploded front view of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0017] Figure 4 is an exploded axial side view of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0018] Figure 5A is an axial view of a lower core of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0019] Figure 5B yes Figure 5A A top view of the lower core;

[0020] Figure 5C yes Figure 5A A front view of a lower core;

[0021] Figure 5D yes Figure 5A A side view of a lower core;

[0022] Fig. 6A is an axial view of a bobbin of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0023] Figure 6B yes Fig. 6A Top view of the spool of thread;

[0024] Figure 6C yes Fig. 6A A front view of a spool;

[0025] Fig.6D yes Fig. 6A A side view of a spool;

[0026] Fig. 7A is an axial view of a winding of a multi-leg transformer according to an example embodiment of the disclosed concept;

[0027] Figure 7B yes Fig. 7A A front view of the winding; and

[0028] Figure 7C yes Fig. 7A Side view of the winding. DETAILED DESCRIPTION

[0029] Directional phrases used herein, such as left, right, front, rear, upper, lower and their derivatives, relate to the orientation of elements shown in the drawings and do not limit the claims unless explicitly recited therein.

[0030] As used herein, the term "number" shall mean one or an integer greater than one (ie, a plurality).

[0031] Figures 1A to 1D Various views of a multi-leg transformer 10 are shown in accordance with an example embodiment of the disclosed concept. Figure 2A-2B Additional views are shown, including a cross-sectional view of the multi-leg transformer 10, and Figure 3 and Figure 4 An exploded view of a multi-leg transformer 10 is shown.

[0032] The multi-leg transformer 10 includes upper and lower cores 20 and 22 , upper and lower bobbin portions 30 and 32 , primary and secondary coils 40 and 42 , and a shunt material 50 . Figures 6A-6DAdditional views of the lower core 22 are shown, Figures 6A-6D Additional views of the upper spool portion 30 are shown and Figures 7A-7C Additional views are shown of the primary coil 40. It should be appreciated that the upper and lower cores 20, 22 may be the same or similar, the upper and lower bobbin portions 30, 32 may be the same or similar, and the primary coil 40 and secondary coil 42 may be the same or similar.

[0033] In the exemplary embodiment of the multi-leg transformer 10, the upper core 20 and the lower core 22 form a multi-leg ee or eI core type structure (eg, Figures 5A-5D As shown). However, it should be understood that the core that can be used has any number of cores or center rods greater than one. It should also be understood that the center rods 24, 25, 26 can have any shape, such as but not limited to round, square, rectangular, rectangular or other shapes, without departing from the scope of the disclosed concept. The primary coil 40 is wound on the center rod of the upper core 20, and the secondary coil 42 is wound on the center rod of the lower core 22, but it should be understood that the primary coil 40 and the secondary coil 42 can be switched without departing from the scope of the disclosed concept. It should also be understood that the primary coil 40 and the secondary coil 42 can be wound on any number of center rods or outer rods without departing from the scope of the disclosed concept. The upper bobbin portion 30 and the lower bobbin portion 32 are constructed to facilitate the winding and placement of the primary coil 40 and the secondary coil 42 around their respective core rods.

[0034] In an exemplary embodiment, the multi-leg transformer 10 is constructed so that the primary coil 40 and the secondary coil 42 are spaced apart flat windings. However, it should be understood that the windings of the primary coil 40 and the secondary coil 42 can vary without departing from the scope of the disclosed concept. For example, but not by way of limitation, the windings can be single-layer or multi-layer. The primary coil 40 and / or the secondary coil 42 can each have a single or multiple windings. In an embodiment with multiple windings, the windings can be connected in series or in parallel to increase design flexibility. In addition, each winding can be any of a variety of conductor styles, such as but not limited to copper foil, LITZ wire, or any other suitable conductor style. It should also be understood that the windings can be single-strand or multi-strand without departing from the scope of the disclosed concept. In an exemplary embodiment of the disclosed concept, a shunt material 50 can be disposed in a selected portion of the space between the primary coil 40 and the secondary coil 42. The shunt material 50 can be a magnetic shunt material, such as but not limited to a ferrite material or a powdered iron alloy. In some exemplary embodiments, the shunt material 50 can be a material plate. Selected portions where the shunt material 50 is disposed may be selected to adjust characteristics of the multi-leg transformer 10, such as leakage inductance. That is, the shunt material 50 may be disposed in more or less of the volume between the primary coil 40 and the secondary coil 42 to adjust the leakage inductance of the multi-leg transformer 10 to a desired level. Adjustment of the leakage inductance is useful in transformer applications, such as, but not limited to, transformers used in LLC converters. Furthermore, by being able to adjust the leakage inductance via the shunt material 50, a separate resonant inductor is not required to control the leakage inductance element within the LLC circuit.

[0035] In some example embodiments, the multi-leg transformer 10 has a low profile, for example, with short core legs and flat windings. The low profile enables better cooling, for example, by providing a larger core surface area to achieve better cold plate cooling. The improved cooling is useful in high power applications. In some example embodiments, the multi-leg transformer 10 can be used for applications such as, but not limited to, 1-22kW, and in some example embodiments can be used for applications such as 4-7kW. In some example embodiments, the multi-leg transformer 10 can be used for LLC converters, but it should be understood that the multi-leg transformer 10 can be used for other applications, such as, but not limited to, battery charging applications, as a distribution transformer for stepping down in large-scale server applications, or for other applications.

[0036] In some example embodiments, the gap between the core legs is minimal so that any fringing flux is confined to a smaller area and only allows limited interaction with the windings of the primary coil 40 and the secondary coil 42 .

[0037] In some example embodiments, the windings of the primary coil 40 and the secondary coil 42 are flat windings such as, but not limited to, solid wire or LITZ wire. In some example embodiments, the flat windings minimize proximity effect losses and allow for good coupling between the primary coil 40 and the secondary coil 42. The windings can be made in series so that a winding around a core leg and an immediately adjacent winding around an adjacent core leg have current flowing in the same direction, such as Figure 7B denoted by the arrows representing current flow. Currents flowing in the same direction in adjacent windings will cause the magnetic flux generated by the currents to cancel each other out. In an exemplary embodiment, to encourage currents in adjacent windings to flow in the same direction, the transition from one winding to the adjacent winding will have a wire running from the outer edge of one winding to the inner edge of the adjacent winding, as shown in FIG. Figure 7B In some example embodiments, to facilitate isolation of winding transitions and prevent short circuits under high voltage conditions, the bobbin may include features to route and isolate wires transitioning from one winding to another from each other.

[0038] In some example embodiments, the primary coil 40 and the secondary coil 42 are wound in a similar manner, but it should be understood that they can be wound differently. It should be understood that the primary coil 40 and the secondary coil 42 can have the same or different number of turns. The primary coil 40 and the secondary coil 42 can be configured as a matrix so that the windings around each rod can be connected in series or in parallel depending on the voltage and current requirements. In some example embodiments, the primary coil 40 and the secondary coil 42 can also be configured as tapped windings to allow the use of switching devices with lower voltage ratings. In some example embodiments, the primary coil 40 and the secondary coil 42 may or may not be molded to allow better heat transfer and increased voltage isolation.

[0039] It should be understood that the bobbin can be formed of any number of parts without departing from the scope of the disclosed concepts. For example, while an upper bobbin portion 30 and a lower bobbin portion 32 are shown in the exemplary embodiment, it should be understood that the upper bobbin portion 30 and the lower bobbin portion 32 can be combined or further divided into any number of bobbin portions in various ways. The upper bobbin portion 30 and the lower bobbin portion 32 each include a central portion corresponding to the central rod 24, 25, 26. Each coil of the primary coil 40 and the secondary coil 42 is wound on one of the central portions.

[0040] In some example embodiments, the upper and lower bobbin portions 30, 32 may include one or more capture features that may assist in maintaining the primary and secondary coils 40, 42 flat and in a substantially helical shape around each rod. Figure 6CAn example of a capture feature 34 is shown in FIG. The capture feature 34 may be, for example, but not limited to, a shaped cutout.

[0041] In some example embodiments, the upper bobbin portion 30 and the lower bobbin portion 32 may also include an insulation barrier between the central coils to increase the turn-to-turn isolation voltage of the outermost turns in each coil.

[0042] In some example embodiments of the disclosed concept, the thickness, width and / or length of the shunt material 50 is variable to adjust the leakage inductance of the multi-leg transformer 10. The shunt material 50 may be located in any or all spaces between the core center bar and / or the outer sides of the core legs.

[0043] Although specific embodiments of the disclosed concepts have been described in detail, those skilled in the art will appreciate that various modifications and alternatives to these details may be developed based on the overall teachings of the present disclosure. Therefore, the specific arrangements disclosed are intended to be illustrative only and not to limit the scope of the disclosed concepts, which shall be given the full breadth of the appended claims and any and all equivalents thereof.

Claims

1. A multi-leg transformer (10), include: A core (20, 22) having a plurality of center rods (24, 25, 26); A primary coil (40) is wound around at least one of the center rods (24, 25, 26); A secondary coil (42) wound on at least one of the central rods (24, 25, 26) and spaced apart from the primary coil (40); as well as At least one magnetic shunt material (50) is disposed in one or more selected regions between the primary coil (40) and the secondary coil (42).

2. The multi-leg transformer (10) of claim 1, wherein the at least one magnetic shunt material (50) comprises a plurality of pieces of magnetic shunt material.

3. The multi-leg transformer (10) of claim 2, wherein the plurality of pieces of shunt material comprise different types of magnetic shunt material.

4. The multi-leg transformer (10) of claim 1, wherein the at least one magnetic shunt material (50) is comprised of at least one of a ferrite material and an iron alloy.

5. The multi-leg transformer (10) of claim 1, wherein the one or more selected regions are selected to adjust a leakage inductance of the multi-leg transformer.

6. The multi-leg transformer (10) of claim 1, wherein the core (20, 22) is a multi-component core.

7. The multi-leg transformer (10) of claim 6, wherein the multi-component core comprises an upper core (20) and a lower core (22), wherein one of the primary coil (40) and the secondary coil (42) is wound on a center rod (24, 25, 26) of the upper core (40), and wherein the other of the primary coil (40) and the secondary coil (42) is wound on a center rod (24, 25, 26) of the lower core (22).

8. The multi-leg transformer (10) according to claim 1, further comprising: include: a first bobbin (30) configured to facilitate winding and placement of a primary coil (40); and The second bobbin (32) is configured to facilitate the winding and placement of the secondary coil (42).

9. The multi-leg transformer (10) of claim 8, wherein at least one of the upper bobbin (30) and the lower bobbin (32) includes at least one capture feature (34) configured to assist the primary coil (40) or the secondary coil (42) in retaining a shape around the center rod (24, 25, 26).

10. The multi-leg transformer (10) of claim 8, wherein at least one of the upper bobbin (30) and the lower bobbin (32) includes an insulation barrier configured to provide insulation between coils of the primary coil (40) or the secondary coil (42).

11. The multi-leg transformer (10) of claim 1, wherein at least one of the primary coil (40) and the secondary coil (42) has a flat winding.

12. The multi-leg transformer (10) of claim 1, wherein at least one of the primary coil (40) and the secondary coil (42) has a winding that is constructed so that a current flowing through a first winding around a first center pole (24) and a current flowing through an immediately adjacent winding around an adjacent second center pole (25) are in the same direction.

13. The multi-leg transformer (10) of claim 1, wherein at least one of the primary coil (40) and the secondary coil (42) has a winding of solid wire or LITZ wire.

14. A method for manufacturing a multi-leg transformer (10), the method include: Providing a core (20, 22) having one or more core legs, a primary coil (40) wound on at least one of the core legs, and a secondary coil (42) wound on at least one of the core legs and spaced apart from the primary coil; determining a desired leakage inductance level for a multi-leg transformer (10); as well as The multi-leg transformer (10) is tuned to the desired leakage inductance level by placing at least one magnetic shunting material (50) in one or more selected regions between the primary coil (40) and the secondary coil (42).

15. A bobbin (30, 32) for a multi-leg transformer (10), the multi-leg transformer having a core (20, 22) including a plurality of center rods (24, 25, 26), a primary coil (40) wound on at least one of the center rods (24, 25, 26), a secondary coil (42) wound on at least one of the center rods (24, 25, 26) and spaced apart from the primary coil (40), and at least one magnetic shunt material (50) disposed in one or more selected areas between the primary coil (40) and the secondary coil (42), the bobbin (30, 32) include: a plurality of center portions, corresponding to the plurality of center rods (24, 25, 26), each center portion being configured as a coil having a primary coil (40) or a secondary coil (42) wound thereon; at least one insulating barrier disposed between two of the plurality of center rods (24, 25, 26) and configured to provide insulation between coils of the primary coil (40) or the secondary coil (42); as well as At least one capture feature (34) is configured to assist the primary coil (40) or the secondary coil (42) in maintaining a shape around the central rod (24, 25, 26).

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