Integrated resonant capability of printed circuit boards for planar transformers

Abstract

1. A planar transformer comprising: a printed circuit board; a primary planar winding disposed within the printed circuit board; a secondary planar winding disposed within the printed circuit board; a magnetic material disposed within the printed circuit board between the primary and secondary planar windings, the magnetic material configured to generate a secondary magnetic flux path; and a magnetic core disposed around a periphery of the printed circuit board and magnetically coupled to the primary and secondary planar windings, the magnetic core configured to generate the primary magnetic flux path.

Description

Technical Field

[0001] The present disclosure relates to a planar power transformer having a magnetic material directly laminated within a printed circuit board winding so as to provide an alternative magnetic flux path and increase leakage inductance.

Background Art

[0002] A planar transformer is basically a transformer that typically uses planar windings on a printed circuit board (PCB). Instead of copper wire wound to form a coil, planar windings are utilized. The printed circuit board structure creates a form factor that provides several inherent advantages and some trade-offs

[0003] In power electronics, the demand for higher efficiency and power density is increasing ever more rapidly. Furthermore, high-frequency magnetic materials are desirably as small as possible and integrated with electronic circuits and devices. Thus, planar transformers have been increasingly used in industries that have conventionally used wound transformers. Power conversion by resonant switching is used in many applications, from data centers to automotive applications. Examples of end uses for planar transformers include both AC / DC and DC / DC switched-mode power supplies (SMPS), aerospace, avionics, household appliances industrial power systems radar power conversion use of wide-bandgap (WBG) devices in power electronics as well as resonant or quasi-resonant power converters.

[0004] However, the inherently low leakage inductance in planar transformers limits the use of zero-voltage or resonant switching techniques. The printed circuit board integrated resonance capability enables soft switching of transistors, thereby enhancing the efficiency and size, weight, and power improvement of the power system.

[0005] What is needed is a planar transformer that increases leakage inductance.

Summary of the Invention

[0006] According to this disclosure, the printed circuit board comprises a printed circuit board having a first layer and a second layer adjacent to the first layer; a first planar winding disposed in the first layer of the printed circuit board; a second planar winding disposed in the second layer of the printed circuit board; a magnetic material disposed between the first planar winding and the second planar winding within the printed circuit board; and a magnetic core that covers the printed circuit board and is magnetically coupled to the first planar winding and the second planar winding.

[0007] Further embodiments of any of the above embodiments may additionally and / or alternatively include the printed circuit board including a window height, the first and second planar windings including a winding width, and the ratio of the window height to the winding width being at least 1:1.

[0008] Further embodiments of any of the above embodiments may additionally and / or alternatively include the first planar winding comprising a primary planar winding and the second planar winding comprising a secondary planar winding.

[0009] Further embodiments of any of the above embodiments may additionally and / or alternatively include the use of a first planar winding instead of a first wound winding.

[0010] Further embodiments of any of the above embodiments may additionally and / or alternatively include a planar transformer further comprising an additional primary planar winding disposed in the printed circuit board adjacent to the second planar winding on the opposite side of the first planar winding, and an additional magnetic material disposed in the printed circuit board between the second planar winding and the additional primary planar winding.

[0011] Further embodiments of any of the above embodiments may additionally and / or alternatively include a first planar winding comprising a secondary planar winding, a second planar winding comprising a primary planar winding, and the planar transformer further comprising an additional secondary planar winding disposed on a printed circuit board adjacent to the primary planar winding on the opposite side of the first planar winding, and an additional magnetic material disposed within the printed circuit board between the primary planar winding and the additional secondary planar winding.

[0012] Further embodiments of any of the above embodiments may additionally and / or alternatively include incorporating the planar transformer described in claim 1 into a converter circuit for ultra-high density electronic equipment.

[0013] The present disclosure provides a planar transformer comprising a printed circuit board, a primary planar winding disposed within the printed circuit board, a secondary planar winding disposed within the printed circuit board, a magnetic material disposed within the printed circuit board between the primary and secondary planar windings, configured to generate a secondary magnetic flux path, and a magnetic core disposed around the entire perimeter of the printed circuit board and magnetically coupled to the primary and secondary planar windings, configured to generate a primary magnetic flux path.

[0014] Further embodiments of any of the above embodiments may additionally and / or alternatively include configuring the secondary flux path to increase the leakage inductance more significantly than the leakage inductance from the primary flux path of the magnetic core.

[0015] Further embodiments of any of the above embodiments may additionally and / or alternatively include interleaving the primary planar winding and the secondary planar winding.

[0016] Further embodiments of any of the above embodiments may additionally and / or alternatively include incorporating a planar transformer into a converter circuit for ultra-high-density electronic equipment.

[0017] Further embodiments of any of the above embodiments may additionally and / or alternatively include a planar transformer further comprising an additional primary planar winding disposed on a printed circuit board adjacent to a secondary planar winding on the opposite side of the primary planar winding, and an additional magnetic material disposed within the printed circuit board between the second planar winding and the additional primary planar winding.

[0018] Further embodiments of any of the above embodiments may additionally and / or alternatively include the printed circuit board including a window height, the first and second planar windings including a winding width, and the ratio of the window height to the winding width being at least 1:1.

[0019] The present disclosure provides a process for increasing the leakage inductance of a planar transformer, the process comprising: a printed circuit board; arranging a primary planar winding within the printed circuit board; arranging a secondary planar winding within the printed circuit board adjacent to the primary planar winding; arranging a magnetic material within the printed circuit board between the primary and secondary planar windings; generating a secondary magnetic flux path using the magnetic material; arranging a magnetic core around the entire perimeter of the printed circuit board; magnetically coupling the magnetic core to the primary and secondary planar windings; generating a primary magnetic flux path using the magnetic core; and increasing the leakage inductance of the planar transformer.

[0020] Further embodiments of any of the above embodiments may additionally and / or alternatively include the steps of locating an additional primary planar winding on a printed circuit board in proximity to a secondary planar winding on the opposite side of the primary planar winding, and locating additional magnetic material within the printed circuit board between the second planar winding and the additional primary planar winding.

[0021] Further embodiments of any of the embodiments described above may additionally and / or alternatively include a step of increasing the leakage inductance that includes a combination of a secondary flux path and a primary flux path of the magnetic core.

[0022] A further embodiment of any of the above embodiments may additionally and / or alternatively include the step of further integrating a planar transformer into a converter circuit for ultra-high density electronic devices.

[0023] A further embodiment of any of the above embodiments may additionally and / or alternatively include the step of further interleaving a primary planar winding and a secondary planar winding.

[0024] Other details of the planar transformer are described in the following detailed description and the accompanying drawings, in which like reference numerals indicate like elements.

Brief Description of the Drawings

[0025] [Figure 1] An isometric view of an exemplary planar transformer. [Figure 2] An exploded view of an exemplary planar transformer. [Figure 3] A cross-sectional view of an exemplary planar transformer. [Figure 4] A cross-sectional view of an alternative exemplary planar transformer. [Figure 5] A cross-sectional view of an alternative exemplary planar transformer. [Figure 6] A cross-sectional view of an alternative exemplary planar transformer. [Figure 7] An isometric view of an alternative exemplary planar transformer incorporated into a converter circuit for ultra-high density electronic devices.

Modes for Carrying Out the Invention

[0026] Referring here to Figures 1 and 2, a planar transformer 10 is shown. The planar transformer 10 includes a printed circuit board 12. The printed circuit board 12 includes planar windings 14. The planar windings 14 can be formed from a thin copper sheet or an etched spiral pattern, as shown in Figure 2. The printed circuit board 12 includes layers 16 that are laminated on the circuit board 12. A magnetic material 18 is laminated between the layers 16 of the printed circuit board 12. The magnetic material 18 may be integrated integrally with the material of the printed circuit board 12. The magnetic material 18 can be scattered throughout the material of the printed circuit board 12. The magnetic material 18 may include a magnetic thermoplastic laminate material such as a low-loss, high-resistance ceramic filler thermoplastic matrix material. An example of such a magnetic material 18 may include MAGTREX555®. The magnetic core 20 covers the printed circuit board 12 and is positioned close to the planar windings 14, thereby magnetically coupling the magnetic core 20 to the primary planar windings 28 and the secondary planar windings 32.

[0027] As shown in Figure 1, the average length of the winding turns 22 is equal to the leakage inductance (L lk This is shown as a schematic diagram related to ). See also Figure 3, which shows a cross-sectional view of the planar transformer 10. The leakage inductance is directly related to the window height 24 and inversely correlated with the width 26 of the printed circuit board 12. This relationship is L lk It can be expressed as αlh / w, L lk = leakage inductance, l = average length of winding turns, h = window height, w = winding width. A planar magnetic core 20 used with a small window height 24 and a wide winding width 26 together with a printed circuit board 12 can reduce leakage inductance. Exemplary ratios of core winding width 26 to window height 24 can include 1:1 or more, and ratios of 2:1 or even 3:1 in particular can offer technical advantages.

[0028] Figure 3 shows a printed circuit board 12 having a primary winding 28 adjacent to the first layer 30 and a secondary winding 32 adjacent to the second layer 34 on opposite sides. The magnetic material 18 is placed between the primary winding 28 and the secondary winding 32 within the material of the printed circuit board 12.

[0029] The performance of the printed circuit board 12 may depend on the specific permeance P∝μA of the magnetic materials of the magnetic materials 18 pairs integrated into the printed circuit board 12 and the bulk magnetic core 20, where μ is the permeability and A is the cross-sectional area of ​​the magnetic material perpendicular to the path of the magnetic flux. The magnetic flux follows the path of higher permeance. Therefore, the permeance of the leakage path (or more) must be much lower than the permeance of the bulk core without becoming so low that the permeance does not have a significant effect on the magnetic performance. In the exemplary embodiment shown in Figure 3, a reasonable permeance range is P core >5x~100xP lk This may be the case. However, the effective permeance, including the effects of winding and core geometry, is difficult to determine analytically, and methods such as finite element analysis and prototyping are typically used to directly evaluate leakage inductance.

[0030] The magnetic core 20 surrounding the printed circuit board 12 provides a primary flux path 36, as shown in Figure 3. An additional / secondary flux path 38 is formed by the magnetic material 18 within the printed circuit board 12 by introducing a magnetic material 18 between the primary winding 28 and the secondary winding 32. The additional / secondary flux path 38 acts to increase the leakage inductance. The resulting leakage has low electromagnetic interference (EMI) and is located inside the magnetic core 20. The additional flux path 38 also helps to avoid harmful coupling to additional structures such as a base plate, enclosure, or nearby electronic equipment (not shown).

[0031] See also Figure 4, which shows an exemplary embodiment of the planar transformer 10. The printed circuit board 12 may include an array of interleaved / alternating planar windings 40. As shown in Figure 4, the first primary winding 42 is located adjacent to the secondary winding 44, and as shown in the figure, the second primary winding 46 is on the opposite side of the first primary winding 42. A first layer 48 of magnetic material may be placed between the first primary winding 43 and the secondary winding 44. A second layer 50 of magnetic material may be placed between the secondary winding 44 and the second primary winding 46.

[0032] See also Figure 5, which shows an exemplary embodiment of the planar transformer 10. The printed circuit board 12 may include an array of interleaved / alternating planar windings 40. As shown in Figure 5, the first secondary winding 52 may be located adjacent to the primary winding 54, and as shown in the figure, the second secondary winding 56 is on the opposite side of the first secondary winding 52. A first layer 48 of magnetic material may be placed between the first secondary winding 52 and the primary winding 54. A second layer 50 of magnetic material may be placed between the primary winding 54 and the second secondary winding 56. The interleaved array 40 can reduce winding losses and improve coupling between windings due to the effects caused by high frequencies.

[0033] Referring also to Figure 6, an exemplary embodiment using a hybrid planar transformer 60 is shown. The hybrid planar transformer 60 includes a printed circuit board 12 having an array of a primary winding 62 configured as a wound winding and a secondary winding 64 configured as a planar winding. A magnetic material layer 66 may be located between the primary winding 62 and the secondary winding 64. In another embodiment of the hybrid planar transformer 60 (not shown), the primary winding 62 is a planar winding and the secondary winding 64 is a wound winding, and a magnetic material layer 66 may be provided between the primary winding 62 and the secondary winding 64. Another alternative embodiment may include a multi-tap planar transformer or a multi-secondary planar transformer (not shown).

[0034] In an alternative embodiment, the disclosed planar transformer 10, having a magnetic material 18 laminated integrally with the printed circuit board 12 between windings 28 and 32, includes integrating the planar transformer 10 into a converter circuit for ultra-high-density electronic equipment, as shown in Figure 7. For example, the exemplary planar transformer 10 can be integrated into a converter so that the planar transformer is integrated with an additional converter circuit.

[0035] The technical advantages of the disclosed planar transformer include the use of magnetic materials that can be embedded in a circuit board, as a low permeability is utilized in the disclosed magnetic structure, which allows the use of materials at lower frequencies.

[0036] Another technical advantage of the disclosed planar transformer is its ability to utilize magnetic materials that can be embedded in circuit boards at frequencies below 1 MHz.

[0037] Another technical advantage of the disclosed planar transformer is that the permeability of the laminated magnetic material to the bulk magnetic core is 0.25 or less.

[0038] Another technical advantage of the disclosed planar transformer is that it offers approximately a tenfold increase in the percentage of leakage inductance compared to planar transformers without magnetic material lamination on the printed circuit board between the windings.

[0039] A planar transformer is provided. While the planar transformer has been described in the context of its particular embodiment, other unexpected alternative, modified, and variant forms will become apparent to those skilled in the art who have read the above description. Therefore, it is intended to encompass alternative, modified, and variant forms that fall within the broad scope of the appended claims.

Claims

1. It is a planar transformer, A printed circuit board having a first layer and a second layer adjacent to the first layer, A first planar winding disposed within the first layer of the printed circuit board, A second planar winding disposed within the second layer of the printed circuit board, A magnetic material disposed between the first planar winding and the second planar winding within the printed circuit board, A magnetic core is arranged to cover the printed circuit board and is magnetically coupled to the first planar winding and the second planar winding, Equipped with, A planar transformer wherein the magnetic core includes a window height, and the first planar winding and the second planar winding include a width in the direction along the surface of the printed circuit board that is represented by one winding width × number of turns + winding spacing × (number of turns - 1), and the ratio of the window height to the width is 2:1 or 3:

1.

2. The planar transformer according to claim 1, wherein the first planar winding includes a primary planar winding, and the second planar winding includes a secondary planar winding.

3. The planar transformer according to claim 2, wherein the first planar winding is used in place of the first wound winding.

4. An additional primary planar winding is arranged on the printed circuit board adjacent to the secondary planar winding on the opposite side of the first planar winding, An additional magnetic material disposed within the printed circuit board between the second planar winding and the additional primary planar winding, A planar transformer according to claim 2, further comprising:

5. The first planar winding includes a secondary planar winding, the second planar winding includes a primary planar winding, and the planar transformer is An additional secondary planar winding is arranged on the printed circuit board adjacent to the primary planar winding on the opposite side of the first planar winding, An additional magnetic material disposed within the printed circuit board between the primary planar winding and the additional secondary planar winding, A planar transformer according to claim 1, further comprising:

6. The planar transformer according to claim 1, wherein the planar transformer is incorporated into a converter circuit for ultra-high-density electronic equipment.

7. It is a planar transformer, Printed circuit board and A primary planar winding arranged within the printed circuit board, A secondary planar winding arranged within the aforementioned printed circuit board, A magnetic material disposed within the printed circuit board between the primary planar winding and the secondary planar winding, wherein the magnetic material is configured to generate a secondary magnetic flux path, A magnetic core is arranged around the entire periphery of the printed circuit board and is magnetically coupled to the primary planar winding and the secondary planar winding, and is configured to generate a primary magnetic flux path. Equipped with, A planar transformer wherein the magnetic core includes a window height, the primary planar winding and the secondary planar winding include a width in the direction along the surface of the printed circuit board that is represented by one winding width × number of turns + winding spacing × (number of turns - 1), and the ratio of the window height to the width is 2:1 or 3:

1.

8. The planar transformer according to claim 7, wherein the secondary magnetic flux path is configured to increase the leakage inductance by a larger amount than the leakage inductance from the primary magnetic flux path of the magnetic core.

9. The planar transformer according to claim 8, wherein the primary planar winding and the secondary planar winding are interleaved.

10. The planar transformer according to claim 8, wherein the planar transformer is incorporated into a converter circuit for ultra-high-density electronic equipment.

11. An additional primary planar winding is arranged on the printed circuit board, adjacent to the secondary planar winding on the opposite side of the primary planar winding, An additional magnetic material disposed within the printed circuit board between the secondary planar winding and the additional primary planar winding, A planar transformer according to claim 7, further comprising:

12. A process for increasing the leakage inductance in a planar transformer, Printed circuit board and The primary planar winding is placed within the aforementioned printed circuit board, The secondary planar winding is arranged in close proximity to the primary planar winding within the printed circuit board, The magnetic material is placed within the printed circuit board between the primary planar winding and the secondary planar winding. To generate a secondary magnetic flux path using the aforementioned magnetic material, The magnetic core is arranged around the entire perimeter of the printed circuit board, The magnetic core is magnetically coupled to the primary planar winding and the secondary planar winding, The primary magnetic flux path is generated using the aforementioned magnetic core, To increase the leakage inductance in the planar transformer, Includes, The process is as follows: The magnetic core includes a window height, and the primary planar winding and the secondary planar winding include a width in the direction along the surface of the printed circuit board that is represented by the winding width × number of turns + winding spacing × (number of turns - 1), and the ratio of the window height to the width is 2:1 or 3:

1.

13. An additional primary planar winding is placed on the printed circuit board adjacent to the secondary planar winding on the opposite side of the primary planar winding. Placing additional magnetic material within the printed circuit board between the secondary planar winding and the additional primary planar winding, The step according to claim 12, further comprising:

14. The step of increasing the leakage inductance includes a combination of the secondary flux path and the primary flux path of the magnetic core, according to claim 12.

15. The step according to claim 12, further comprising integrating the planar transformer into a converter circuit for ultra-high-density electronic equipment.

16. Interleaving the primary planar winding and the secondary planar winding, The step according to claim 12, further comprising:

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