Transformer with high permeability material

Abstract

A transformer is provided, comprising a magnetic core, a primary winding, a secondary winding, and a high-permeability material. The magnetic core includes a magnetic post, with the primary and secondary windings wound on the magnetic post. The secondary winding is located on at least one side of the primary winding and has a first distance from it. The high-permeability material is disposed at a second distance from the primary winding, wherein the second distance is not greater than the first distance, and the first and second distances are in the arrangement direction of the primary and secondary windings. The permeability of the high-permeability material is higher than the permeability of the magnetic post.

Description

[Technical Field]

[0001] This invention relates to transformers, and more particularly to transformers that improve leakage inductance through high permeability materials. [Previous Technology]

[0002] Generally, the primary-side architecture of a resonant converter can be a half-bridge, a full-bridge, etc., while the secondary-side architecture can be a full-bridge, a center-tapped, etc. In a two-slot architecture, uneven current distribution during the positive and negative half-cycles may cause leakage inductance imbalance. While a three-slot architecture provides a solution to uneven current distribution during the positive and negative half-cycles, the leakage inductance value is limited by the distance between the primary and secondary circuits. [Summary of the Invention]

[0003] According to an embodiment of this disclosure, a transformer is provided, including a magnetic core, a primary winding, a secondary winding, and a high-permeability material. The magnetic core includes a magnetic post, the primary winding and the secondary winding are wound on the magnetic post, and the secondary winding is located on at least one side of the primary winding and has a first distance from the primary winding. The high-permeability material is disposed to have a second distance from the primary winding, wherein the second distance is not greater than the first distance, and the first distance and the second distance are in the arrangement direction of the primary winding and the secondary winding. The permeability of the high-permeability material is higher than the permeability of the magnetic post.

[0004] In one embodiment, the secondary winding and the high-permeability material overlap. The secondary winding further includes an output portion, such that the overlap ratio between the secondary winding and the high-permeability material is greater than 70%. In another embodiment, the magnetic post further includes an air gap in which the high-permeability material is disposed.

[0005] According to an embodiment of this disclosure, a transformer is provided, including a magnetic core, a primary winding, a secondary winding, and a high-permeability material. The magnetic core includes a magnetic post, the primary winding and the secondary winding are wound on the magnetic post, and the secondary winding is located on at least one side of the primary winding. The high-permeability material is disposed to cover the magnetic post, and the permeability of the high-permeability material is higher than the permeability of the magnetic post.

[0006] The high-permeability material is a nanocrystalline ribbon, comprising a protective film, a release film, and a nanocrystalline stack. The nanocrystalline stack has multiple nanocrystalline layers, and each nanocrystalline layer is connected to the others by double-sided adhesive. The nanocrystalline stack and the release film are also connected by double-sided adhesive. The nanocrystalline ribbon is made of an iron-based nanocrystalline alloy, composed of iron, silicon, boron, bismuth, copper, etc., while the magnetic pillar is made of manganese-zinc ferrite.

Implementation Method

[0008] Figure 1 is a circuit diagram of a resonant converter 10 according to an embodiment of the present disclosure. The resonant converter 10 includes a supply voltage Vin, a resonant capacitor Cr, a primary-side leakage inductance Llkp, a magnetizing inductance Lm, secondary-side leakage inductances Llks1 and Llks2, switches SR1 and SR2, and an output load (including load elements such as capacitors and resistors) for outputting an output voltage Vout. Referring to Figures 3A to 8B, the effect of the magnetic column of the transformer architecture provided in this disclosure combined with the primary-side coil corresponds to the magnetizing inductance Lm. By switching SR1 and SR2 on at different half-cycles, the leakage flux that escapes due to the incomplete coupling between the primary-side winding and the secondary-side winding can be improved by using a high-permeability material, thereby increasing the primary-side leakage inductance Llkp and the secondary-side leakage inductances Llks1 and Llks2.

[0009] In the resonant converter 10 that operates using a magnetizing inductor Lm, a resonant inductor (in this disclosure, the leakage inductance is used as the resonant inductor), and a resonant capacitor Cr, by using the primary-side leakage inductance Llkp as the resonant inductor, the space and other costs required for additional inductors are reduced (or replaced). However, the leakage inductance of the resonant converter 10 is affected by the relative position or distance between the primary-side winding and the secondary-side winding; when this distance is too close, the leakage inductance will decrease significantly. Therefore, by adding other high-permeability materials to the transformer architecture of the resonant converter 10, the leakage inductance can be increased without increasing the circuit size.

[0010] Figure 3A is a side view of a transformer 100 shown according to an embodiment of the present disclosure, and Figure 3B is an isometric view of the transformer 100 shown in Figure 3A. The transformer 100 includes a magnetic core 102, a primary winding 106, and a secondary winding 108, wherein the magnetic core 102 further includes a magnetic post 104, and the secondary winding 108 further includes secondary windings 108a and 108b. As shown in Figure 3A, the transformer 100 further includes a high-permeability material 110 disposed between the secondary winding 108 and the primary winding 106. In Figure 3A, the secondary windings 108a and 108b are respectively disposed on opposite sides of the primary winding. The high-permeability material 110 is disposed between the secondary winding 108a and the primary winding 106, and between the secondary winding 108b and the primary winding 106.

[0011] The secondary windings 108a and 108b are respectively separated from the primary winding 106 by a distance D1, while the high-permeability material 110 is separated from the primary winding 106 by a distance D2, and distance D2 is not greater than distance D1. Since the high-permeability material 110 concentrates the magnetic flux of the transformer 100, the distances of the high-permeability material 110 relative to the secondary windings 108a and 108b and the primary winding 106 (i.e., the ratio of distance D2 to distance D1) have different degrees of influence on the leakage inductance of the transformer 100. For example, the closer the high-permeability material 110 is to the primary winding 106 (i.e., the smaller the distance D2), the greater the leakage inductance of the transformer 100. Conversely, the closer the high-permeability material 110 is to the secondary winding 108 (i.e., the larger the distance D2), the smaller the leakage inductance of the transformer 100. In some embodiments, distance D2 is no greater than 50%, 30%, 5% or other proportions of distance D1, as shown in Figure 2. The horizontal axis represents the ratio of distances D1 to D2 (e.g., 0% represents distance D2 being 0% of distance D1, while 100% represents distances D1 and D2 being equal), and the vertical axis represents the leakage inductance value generated by transformer 100.

[0012] Furthermore, when the high-permeability material 110 is disposed between the primary winding 106 and the secondary winding 108, considering that the copper wires (or other materials used as windings) of the windings need to extend to the outside of the transformer core to connect to other electronic components, the high-permeability material 110 does not completely cover the secondary winding 108. For example, in order to output voltage, the secondary winding 108 includes a lead-out portion, and the high-permeability material 110 does not cover this lead-out portion. In one embodiment, the lead-out portion occupies less than 30% of the lateral surface of the secondary winding 108 (i.e., the surface perpendicular to the stacking direction of the primary winding 106 and the secondary winding 108). That is, in this embodiment, the overlap ratio of the lateral surfaces of the high-permeability material 110 and the secondary winding 108 is greater than 70%. The higher the overlap ratio of the lateral surfaces of the high-permeability material 110 and the secondary winding 108, the greater the increase in leakage inductance.

[0013] The high-permeability material 110 has a higher permeability than the magnetic pillar 104 (e.g., including nanocrystalline ribbons). For example, the permeability of the nanocrystalline ribbon can be more than 10 times that of the magnetic pillar 104. The high-permeability material 110, realized from nanocrystalline ribbons, has a multilayer structure, including a protective film, a release film, and nanocrystalline stacks, which are stacked along a fixed direction. Referring to Figure 3A, the stacking direction of the high-permeability material 110 is the direction in which the magnetic pillar 104 extends. The two outermost layers of the high-permeability material 110 are the protective film and the release film, and the nanocrystalline stack is located between the protective film and the release film, and is connected to the release film by double-sided adhesive. The nanocrystalline stack is composed of multiple nanocrystalline layers stacked together, and any two nanocrystalline layers are connected by double-sided adhesive.

[0014] Since the nanocrystalline ribbon is an iron-based nanocrystalline alloy (e.g., composed of elements such as iron, silicon, boron, bismuth, and copper), the quantity (or thickness) of the nanocrystalline ribbon, as well as its relative position to the primary winding 106, the secondary winding 108, or the magnetic post 104, will affect the leakage inductance of the transformer 100. This will be explained in detail below through different embodiments.

[0015] Figure 4 is a side view of a transformer 200 shown according to an embodiment of the present disclosure. Similar to transformer 100, transformer 200 has a magnetic core 102 including a magnetic column 104, a primary winding 106, and a secondary winding 108. The difference in transformer 200 is that the high-permeability material 110 is disposed on and covers the magnetic column 104 instead of being disposed between the primary winding 106 and the secondary winding 108. Since the magnetic flux in the air (e.g., released by transformer 200) is concentrated around the high-permeability material 110, the magnetic flux of the magnetic column 104 is reduced when the high-permeability material covers the magnetic column 104.

[0016] Furthermore, compared to a transformer architecture without the high-permeability material 110, the leakage inductance of transformer 200 is higher. However, since the high-permeability material 110 is not disposed between the primary winding 106 and the secondary winding 108, the increase in leakage inductance of transformer 200 is less than that of transformer 100.

[0017] Figure 5A is a side view of a transformer 300 shown according to an embodiment of the present disclosure, and Figure 5B is an isometric view of the transformer 300 shown in Figure 5A. Similar to transformer 100, transformer 300 has a magnetic core 102 including magnetic pillars 104, a primary winding 106, and a secondary winding 108. The difference in transformer 300 is that a high-permeability material 110 is instead provided to cover the primary winding 106. Referring to Figure 5B, in this embodiment, the high-permeability material 110 covers the primary winding 106.

[0018] Figure 6 is a side view of a transformer 400 shown according to an embodiment of the present disclosure. Similar to transformer 100, transformer 400 has a magnetic core 102 including magnetic pillars 104, a primary winding 106, and a secondary winding 108. The difference in transformer 400 is that a high-permeability material 110 is disposed in the air gap. For example, as shown in Figure 6, the high-permeability material 110 covers the transverse plane of the magnetic pillars 104 forming the air gap. Compared to transformers 100, 200, and 300, transformer 400 has the least amount of high-permeability material 110 disposed between the primary winding 106 and the secondary winding 108. However, since the high-permeability material 110 still has the effect of concentrating magnetic flux, transformer 400 still has a higher leakage inductance value and can reduce the total loss compared to transformer structures without high-permeability material 110.

[0019] Figure 7A is a side view of a transformer 500 shown according to an embodiment of the present disclosure, and Figure 7B is a partial schematic diagram of the transformer 500 shown in Figure 7A. In Figure 7B, the magnetic core 102 (and the magnetic column 104) are not drawn to clearly show the relative positions of the primary winding 106, the secondary winding 108, and the high-permeability material 110. Similar to transformer 100, transformer 500 has a magnetic core 102 including the magnetic column 104, a primary winding 106, and a secondary winding 108. The difference in transformer 500 is that the secondary windings 108a and 108b are disposed on the same side of the primary winding 106, while the high-permeability material 110 is disposed between the secondary winding 108b and the primary winding 106. In this embodiment, since the high permeability material 110 of the transformer 500 is disposed between the primary winding 106 and the secondary winding 108, the transformer 500 has a higher leakage inductance value compared to an architecture that does not have the high permeability material 110 disposed between the primary and secondary windings.

[0020] Figure 8A is a side view of a transformer 600 shown according to an embodiment of the present disclosure, and Figure 8B is a partial schematic diagram of the transformer 600 shown in Figure 8A. In Figure 8B, to clearly show the relative positions of the primary winding 106, the secondary winding 108, and the high-permeability material 110, the magnetic core 102 (and the magnetic post 104) are not drawn. Similar to transformer 500, transformer 600 has a magnetic core 102 including the magnetic post 104, a primary winding 106, and a secondary winding 108, with secondary windings 108a and 108b disposed on the same side of the primary winding 106, and the high-permeability material 110 disposed between the secondary winding 108b and the primary winding 106.

[0021] The difference in transformer 600 lies in the alternating arrangement of secondary windings 108a and 108b. Specifically, referring to figures 8A and 8B, the first turn of secondary winding 108a is positioned furthest from the primary winding 106; then, the first turn of secondary winding 108b is positioned between the first and second turns of secondary winding 108a; then, the second turn of secondary winding 108a is positioned between the first and second turns of secondary winding 108b, and so on, until the third turn of secondary winding 108b is positioned closest to the primary winding 106. Similarly, the secondary windings 108a and 108b of transformer 600 can also be arranged in the opposite manner. That is, the first turn of the secondary winding 108b is set to be furthest from the primary winding 106, and the remaining secondary windings 108a and 108b are alternately set until the third turn of the secondary winding 108a is set to be closest to the primary winding 106.

[0022] The embodiments described above illustrate different methods of setting the high-permeability material 110. In other embodiments, these different methods can be combined to achieve a better leakage inductance improvement and minimize losses caused by the nanocrystalline ribbon. For example, since setting the high-permeability material 110 between the primary winding 106 and the secondary winding 108 results in the greatest improvement in leakage inductance, embodiments in which the high-permeability material 110 is not or only partially set between the primary and secondary windings can be combined. For example, by combining the methods of setting the high-permeability material 110 in transformers 100 and 300, the nanocrystalline ribbon is placed between the lateral planes of the primary winding 106 and the secondary winding 108 while covering the primary winding 106. In this way, compared to transformer 300 where only the primary winding 106 is covered by the high-permeability material 110, the amount of high-permeability material 110 placed between the primary winding 106 and the secondary winding 108 will increase. Furthermore, compared to a transformer 100 that only places the high-permeability material 110 between the primary and secondary windings, the total amount of high-permeability material 110 used (or the ability to concentrate magnetic flux) is higher, thereby achieving a better leakage inductance improvement effect.

[0023] In another embodiment, the material originally used for winding can be replaced with other wires with lower losses. For example, the primary winding 106 and / or the secondary winding 108 can be replaced with Litz wire instead of the original copper wire (e.g., flat copper sheet). The Litz wire reduces the circuit impedance by utilizing the characteristic that it is made of multiple sets of insulated wires twisted together, thereby reducing losses and increasing leakage inductance.

[0024] In yet another embodiment, the transformer architecture combines placing a high-permeability material 110 between the primary winding 106 and the secondary winding 108, covering the primary winding with the high-permeability material 110, and changing the wires of the primary winding 106 and the secondary winding 108 to Litz wire, so that while the leakage inductance value is greatly increased, the copper loss and / or iron loss increased due to the addition of the high-permeability material 110 can be minimized as much as possible.

[0025] In addition to combining the high-permeability material 110 placement method of transformers 100 and 300, other embodiments of the high-permeability material 110 placement method can also be combined, while simultaneously modifying the winding wire. For example, the placement method of transformer 300 can be combined with transformer 500 or 600, so that the primary winding 106 of transformer 500 or 600 is also covered with high-permeability material 110. At the same time, the primary winding 106 and the secondary winding 108 are replaced with Litz wire, thereby enabling transformer 500 or 600 to simultaneously possess the feature of placing high-permeability material 110 between the primary and secondary windings and covering the primary winding, and the wire loss can be reduced by replacing the winding wire with Litz wire.

[0026] Furthermore, as described above with reference to Figures 3A and 3B, for the high-permeability material 110 with nanocrystalline ribbon, the thickness (e.g., the number of layers), the overlap area between the high-permeability material 110 and the winding, as well as the relative distance and position between the material and the winding, all affect the magnitude of the increase in leakage inductance. For example, the greater the thickness (e.g., changing from a single layer to multiple layers as shown in the figures), the greater the increase in leakage inductance. Furthermore, the greater the overlap area between the high-permeability material 110 and the winding, the greater the increase in leakage inductance. Moreover, the increase in leakage inductance is greatest when the high-permeability material 110 is disposed between the primary and secondary windings. Furthermore, the closer the high-permeability material 110 is to the primary winding 106, the greater the increase in leakage inductance.

[0027] Therefore, in order to maximize the increase in leakage inductance while minimizing the increase in losses caused by the high-permeability material 110, a multilayer (e.g., two-layer, three-layer, etc.) nanocrystalline strip can be placed between the primary winding 106 and the secondary winding 108, and placed as close as possible to the primary winding 106 (i.e., close to the low-current side). At the same time, the nanocrystalline strip covers the primary winding 106, minimizing the area ratio that cannot be covered by the nanocrystalline strip to avoid the winding's output portion, and the wires of the primary winding 106 and the secondary winding 108 are replaced with Litz wire, which has lower losses. In this way, compared to a transformer architecture without the high-permeability material 110, the transformer architecture proposed in this disclosure can maximize the increase in leakage inductance while minimizing the transformer's own losses (e.g., copper losses, iron losses, etc.). [Simplified Explanation of the Diagram]

[0007] Figure 1 is a circuit diagram of a resonant converter according to an embodiment of the present disclosure. Figure 2 is a line graph showing the effect of the distance between the high-permeability material and the primary winding on the leakage inductance value according to an embodiment of the present disclosure. Figure 3A is a side view of a transformer according to an embodiment of the present disclosure. Figure 3B is an isometric view of the transformer shown in Figure 3A. Figure 4 is a side view of a transformer according to an embodiment of the present disclosure. Figure 5A is a side view of a transformer according to an embodiment of the present disclosure. Figure 5B is an isometric view of the transformer shown in Figure 5A. Figure 6 is a side view of a transformer according to an embodiment of the present disclosure. Figure 7A is a side view of a transformer according to an embodiment of the present disclosure. Figure 7B is a partial schematic diagram of the transformer shown in Figure 7A. Figure 8A is a side view of a transformer according to an embodiment of the present disclosure. Figure 8B is a partial schematic diagram of the transformer shown in Figure 8A.

Claims

1. A transformer, comprising: A magnetic core includes a magnetic post; a primary winding wound on the magnetic post; a secondary winding wound on the magnetic post and located on at least one side of the primary winding, and having a first distance from the primary winding; and a high-permeability material disposed at a second distance from the primary winding, wherein the second distance is not greater than the first distance, and the first distance and the second distance are in the arrangement direction of the primary winding and the secondary winding, wherein the permeability of the high-permeability material is higher than the permeability of the magnetic post.

2. The transformer as described in claim 1, wherein the high-permeability material and the secondary winding overlap.

3. The transformer as claimed in claim 1, wherein the magnetic column includes an air gap, and the high-permeability material is disposed in the air gap.

4. The transformer as described in claim 1, wherein the overlap area between the secondary winding and the high-permeability material is greater than 70%.

5. The transformer as claimed in claim 1, wherein the high-permeability material does not completely overlap a lead portion of the secondary winding.

6. The transformer as described in claim 1, wherein the high-permeability material is a nanocrystalline ribbon.

7. The transformer as described in claim 6, wherein the nanocrystalline ribbon comprises: A protective film and a release film; And a nanocrystal stack having a plurality of nanocrystal layers, wherein each of the nanocrystal layers is connected to the other by double-sided adhesive, and the nanocrystal stack and the release film are connected by double-sided adhesive.

8. The transformer as described in claim 6, wherein the nanocrystalline ribbon is made of an iron-based nanocrystalline alloy composed of iron, silicon, boron, bismuth, copper, etc., and the magnetic column is made of manganese-zinc ferrite.

9. The transformer as described in claim 1, wherein the second distance is less than half of the first distance.

10. The transformer as claimed in claim 1, wherein the second distance is less than 30% of the first distance.

11. The transformer as described in claim 1, wherein the second distance is less than 5% of the first distance.

12. The transformer as claimed in claim 1, wherein the secondary winding includes a first secondary winding and a second secondary winding, and the first secondary winding and the second secondary winding are disposed on the same side of the primary winding.

13. The transformer as described in claim 12, wherein the first secondary winding and the second secondary winding are alternately arranged.

14. The transformer as claimed in claim 1, wherein the secondary winding includes a first secondary winding and a second secondary winding, and the first secondary winding and the second secondary winding are respectively disposed on opposite sides of the primary winding.

15. The transformer as claimed in claim 14, wherein the high-permeability material is disposed between the primary winding and the first secondary winding, or between the primary winding and the second secondary winding.

16. The transformer as claimed in claim 15, wherein the high-permeability material further covers the primary winding.

17. The transformer as claimed in claim 1, wherein the permeability of the high-permeability material is not less than 10 times the permeability of the magnetic column.

18. The transformer as claimed in claim 1, wherein the primary winding is made of copper wire and the secondary winding is made of Litz wire.

19. The transformer as claimed in claim 1, wherein the primary winding and the secondary winding are Litz wire.

20. A transformer, comprising: A magnetic core, comprising a magnetic post; and a primary winding wound on the magnetic post; A primary and secondary windings are wound on the magnetic post and located on at least one side of the primary winding; and a high-permeability material is disposed to cover the magnetic post, wherein the permeability of the high-permeability material is higher than the permeability of the magnetic post.

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