Planar winding structure

Abstract

A planar winding structure is provided. The planar winding structure is used for the needs of main power transformers and / or auxiliary power supplies. A planar winding structure of printed circuit board type can limit electric fields by magnetic core potential control, creating a design without partial discharge for medium voltage applications. At the same time, the winding structure can be formed during printed circuit board manufacturing, creating a more modular and reliable structure, improving manufacturability. Techniques such as termination handling, primary and secondary winding placement can be used to control electric stress in medium voltage applications.

Description

Technical Field

[0001] This invention relates to a planar winding structure used in power transformers, and more particularly to a planar winding structure for medium-voltage power transformers. Background Technology

[0002] As medium-voltage power distribution becomes increasingly used in data centers, electric vehicle charging, and other emerging applications, its low conduction losses and potential smaller footprint are becoming increasingly desirable. In medium-voltage applications (e.g., around 4kV to around 13.8kV), the conventional approach requires a bulky line frequency transformer to step down medium-voltage alternating current (MVAC) power to low-voltage alternating current (AC) or direct current (DC) power for direct use by the load. To overcome the disadvantages of line frequency transformers, solid-state transformer (SST) technology has been developed to utilize the high-frequency operation of semiconductor elements to create high-frequency pulse width modulation (PWM) AC links. Among these, the much lower volt-seconds used can potentially reduce the footprint of passive transformers (see reference [1]). However, the size reduction of high-frequency passive transformers is not inversely proportional to the operating frequency because reliable insulation must be between the high-voltage and low-voltage windings (see reference [2]).

[0003] For the design of medium-voltage high-frequency transformers, the objectives can be summarized as follows: First, the medium-voltage transformer must be free of partial discharge (PD). Partial discharge is one of the most common causes of degradation during long-term operation, especially if the insulation material is made of polymer. Freedom of partial discharge ensures a long service life after deployment. Second, considering cost and ease of manufacturing, modular solutions and / or industry-recognized technologies are preferred. Third, the transformer needs higher efficiency and higher power density. High efficiency is a key performance indicator, especially when comparing solid-state solutions with traditional power frequency solutions. Furthermore, since most insulation materials have poor thermal conductivity, higher efficiency results in less thermal stress on the transformer, allowing heat to be easily removed.

[0004] Figure 1A schematic diagram of a publicly known solution for a stranded wire encapsulated transformer. See reference [3]. In a publicly known solution for a stranded wire encapsulated transformer, both the primary and secondary sides are made of Litz wire, i.e., stranded wire. Since stranded wire is composed of multiple electrically insulated strands, it is difficult to control the gaps and air bubbles between the strands during the potting process. Therefore, it is difficult to control the insulation quality of the stranded wire combined with the epoxy insulator. This is mainly because epoxy insulators usually have high viscosity, and it is inevitable that small gaps will form between the strands. Accordingly, one solution is to use two layers of insulating material applied in two steps. The manufacturing of the two-layer structure requires the use of a mold. Low-viscosity insulating materials, such as silicon-based insulators, can be used to form the first insulating layer. After the stranded wire is placed in the mold, the silicon-based insulator can be applied. Since the silicon-based insulator has low viscosity, it can fill the small gaps between different strands. Then, after the silicon-based insulator is cured, it is placed in the second mold to form an epoxy resin-based insulator. Epoxy-based insulators have higher viscosity and offer better breakdown strength. This approach eliminates concerns about potential voids forming within the epoxy insulator, as it does not contact the stranded wires. After the epoxy (main insulator) layer has cured on the test sample, an additional shielding layer can be applied to confine the electric field within the insulator. However, this solution is highly complex, requiring custom molds and multiple steps to complete the curing process. It also lacks modularity, making mass production difficult.

[0005] Figure 2 Another known transformer design is disclosed, which inserts a gap between the cores and divides the transformer into a low-voltage (LV) side and a high-voltage (HV) side. See reference [4]. In this solution, the primary and secondary windings are located on opposite sides of the transformer and separated by a gap and an insulator between them. The two separate parts of the core no longer share the same or similar potentials. Since the gap is intentionally placed between the cores, the insulation requirements between the high-voltage winding and the high-voltage core or between the low-voltage winding and the low-voltage core can be reduced. However, the resulting problems may negate the benefits of this solution. First, since this solution requires a gap structure to provide the main insulation, the electrical performance is related to the insulation performance in this design. However, in some resonant converter applications, the transformer's magnetic flux needs to be controlled within a predetermined range to achieve soft switching and maintain a small circulating energy. If the gap is too large, the magnetic flux may be too small, resulting in too much circulating energy and unnecessary conduction losses. Second, this solution cannot be implemented in some applications because the cores need to be grounded on both the high-voltage and low-voltage sides.

[0006] Figure 3A schematic diagram of a known solution using a coaxial structure to form the primary and secondary sides of a transformer is provided. See reference [5]. This solution has two advantages. First, it forms an insulation structure through the coaxial cable insulation layer, so the insulation performance can be well controlled on the cable side without the need for further processing with epoxy or silicon-based encapsulation. Second, there is another hollow space inside the inner conductive layer of the cable, so liquid cooling is possible. If needed, coolant can flow into the pipe to remove heat. However, this solution also faces some challenges. First, the inner tube of the cable is made of rigid metal. In order to form the winding, the metal must be bent. And under the condition of meeting the minimum bending ratio, it is also necessary to ensure that the insulation layer covering the conductor is free of cracks. This means that it is difficult to form a shape that meets the small bending ratio. Second, the coaxial structure is more suitable for a 1:1 turns ratio design, but it is difficult to realize the design that requires lowering or raising the voltage between the primary and secondary sides, which is common in medium voltage applications.

[0007] Figure 4 A publicly known solution for medium-voltage applications using printed circuit boards is described in reference [6]. In this solution, the primary and secondary windings are arranged in a regular spiral structure and stacked on top of each other to fill the window area of ​​the core. Reference [6] does not present any results regarding medium-voltage operation, but mentions that this solution can be immersed in a tank for potential high-voltage environments. However, dry-type transformers are easier to maintain in medium-voltage applications.

[0008] Therefore, there is a need to provide a modular and easy-to-manufacture power transformer solution for medium-voltage applications. This power transformer solution needs to be free of partial discharge, have higher efficiency and better heat dissipation, and enable low-noise coupling between the primary and secondary windings.

[0009] References:

[0010] 1.J.Wang, AQHuang, W.Sung, Y.Liu and BJBaliga, "Smart gridtechnologies," in IEEE Industrial Electronics Magazine, vol.3, no.2, pp.16-23, June 2009, doi:10.1109 / MIE.2009.932583.

[0011] 2.D.Rothmund,G.Ortiz,T.Guillod and J.W.Kolar,"10kV SiC-based isolatedDC-DC converter for medium voltage-connected Solid-State Transformers,"2015IEEE Applied Power Electronics Conference and Exposition(APEC),Charlotte,NC,USA,2015,pp.1096-1103,doi:10.1109 / APEC.2015.7104485.

[0012] 3.Q.Chen,etc"High Frequency Transformer Insulation in Medium VoltageSiC enabled Air-cooled Solid-State Transformers,"2018IEEE Energy ConversionCongress and Exposition(ECCE),Portland,OR,USA,2018,pp.2436-2443,doi:10.1109 / ECCE.2018.8557849.

[0013] 4.S.Zhao,Q.Li,F.C.Lee and B.Li,"High-Frequency Transformer Design forModular Power Conversion From Medium-Voltage AC to 400VDC,"in IEEETransactions on Power Electronics,vol.33,no.9,pp.7545-7557,Sept.2018,doi:10.1109 / TPEL.2017.2774440.

[0014] 5.L.Heinemann, "An actively cooled high power, high frequency transformer with high insulation capability," APEC.Seventeenth Annual IEEEApplied Power Electronics Conference and Exposition(Cat.No.02CH37335), Dallas, TX, USA, 2002, pp.352-357vol.1, doi:10.1109 / APEC.2002.989270.

[0015] 6. C. Loef, RWDe Doncker and B. Ackermann, "On high frequency highvoltage generators with planar transformers," 2014IEEE Applied PowerElectronics Conference and Exposition-APEC 2014, Fort Worth, TX, USA, 2014, pp.1936-1940, doi:10.1109 / APEC.2014.6803571. Summary of the Invention

[0016] The present invention aims to provide a planar winding structure comprising an insulating plate, multiple conductive layers, a first terminal and a second terminal, and a shielding layer. The insulating plate has a winding portion and a terminal portion, with a through-hole in the central portion of the winding portion. Multiple conductive layers are embedded within the winding portion of the insulating plate and electrically connected to each other through one or more embedded holes. The multiple conductive layers are patterned to form a transformer winding surrounding the through-hole. The first terminal and the second terminal are located in the terminal portion of the insulating plate, and each first terminal and second terminal is electrically connected to a corresponding conductive layer. A shielding layer is coated on the outer surface of the winding portion of the insulating plate.

[0017] In one embodiment, the planar winding structure further includes a shielding edge treatment layer located in the terminal portion between the shielding layer and the first terminal and the second terminal.

[0018] In one embodiment, the planar winding structure further includes an electrical bushing having a potting portion and a hollow portion, wherein the terminal portion of the insulating plate is accommodated within the potting portion.

[0019] In one embodiment, the electrical bushing further includes a terminal block located in the potting portion to electrically and mechanically support the first and second terminals.

[0020] In one embodiment, the planar winding structure further includes an equalizing ring structure embedded in the terminal portion of the insulating plate.

[0021] In one embodiment, the equalizing ring structure includes an outer grounding ring and an inner grounding ring. The outer grounding ring is located on an outer surface of the insulating plate, near the interface between the winding portion and the terminal portion. The inner grounding ring is embedded in the insulating plate and is electrically connected to the outer grounding ring through one or more blind holes.

[0022] In one embodiment, the equalizing ring structure includes a plurality of equalizing rings and at least one resistor. The plurality of equalizing rings are embedded in the terminal portion of the insulating plate and extend horizontally from the interface between the winding portion and the terminal portion. The at least one resistor is embedded in the terminal portion of the insulating plate and is electrically connected to an adjacent equalizing ring.

[0023] In one embodiment, the equalizing ring furthest from the interface is electrically connected to one of the first and second terminals.

[0024] In one embodiment, the planar winding structure further includes multiple electromagnetic interference shielding layers embedded in an insulating plate, wherein a conductive layer is embedded in the insulating plate and located between the multiple electromagnetic interference shielding layers.

[0025] In one embodiment, the shielding layer comprises a semiconductor material.

[0026] In one embodiment, the insulating plate comprises FR4 material.

[0027] Another object of the present invention is to provide a power transformer, the structure of which includes the aforementioned planar winding structure, magnetic core, and secondary winding structure. The secondary winding structure is magnetically coupled to the planar winding structure via the magnetic core.

[0028] In one embodiment, a portion of the magnetic core is disposed within a through-hole in an insulating plate.

[0029] In one embodiment, the secondary winding structure is electrically connected to the shielding layer of the planar winding structure.

[0030] Another object of the present invention is to provide a planar winding structure, which includes an insulating plate, a first winding group, and a second winding group. The central portion of the insulating plate has a through hole to accommodate a magnetic core. The first winding group is disposed on the insulating plate and surrounds the through hole and is close to its periphery. The second winding group is disposed on the insulating plate and surrounds the through hole. The second winding group is spaced from the periphery of the through hole by a first distance and from the edge of the planar winding structure by a second distance.

[0031] In one embodiment, the planar winding structure further includes a third winding group disposed on the insulating plate, and the third winding group surrounds the through hole and is close to the edge of the insulating plate.

[0032] In one embodiment, the first distance and the second distance are equal.

[0033] In one embodiment, the percentage difference between the first distance and the second distance is less than 20%.

[0034] Another object of the present invention is to provide a planar winding structure, the structure comprising an insulating plate, a first high-voltage winding, and a first low-voltage winding. The insulating plate has a first through-hole and a second through-hole for accommodating a magnetic core. The first high-voltage winding is disposed on the insulating plate. The first high-voltage winding surrounds the first through-hole and is close to its periphery. The first low-voltage winding is disposed on the insulating plate. The first low-voltage winding surrounds the second through-hole and is spaced from its periphery by a first distance.

[0035] In one embodiment, the planar winding structure further includes a second high-voltage winding and a second low-voltage winding. The second high-voltage winding is disposed on an insulating planar plate, surrounding the second through hole and close to its periphery. The second low-voltage winding is disposed on an insulating plate, surrounding the first through hole and spaced a second distance from its periphery.

[0036] In one embodiment, the first low-voltage winding and the second low-voltage winding are connected in series. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of a publicly known solution for a stranded wire encapsulated transformer.

[0038] Figure 2 To disclose another known transformer design, gaps are inserted between the magnetic cores, dividing the transformer into two parts: a low-voltage (LV) side and a high-voltage (HV) side.

[0039] Figure 3 A schematic diagram of a known solution for forming the primary and secondary sides of a transformer using a coaxial structure.

[0040] Figure 4 This provides publicly available solutions for medium-voltage applications using printed circuit boards.

[0041] Figure 5 This is a perspective view of a printed circuit board (PCB) type planar winding structure for a power transformer in an embodiment of the present invention.

[0042] Figure 6 For public Figure 5 A cross-sectional view of a PCB-type planar winding structure along line segment AA, which includes the shielding edge treatment layer of an embodiment of the present invention.

[0043] Figure 7 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure along the BB line segment.

[0044] Figure 8 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure along the CC line segment, which includes the equalizing ring structure of this embodiment.

[0045] Figure 9 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure along the DD line segment.

[0046] Figure 10 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure along line segment AA, which includes the embedded EMI shielding layer of the present invention.

[0047] Figure 11 For public Figure 10 Top view of each layer of a PCB-type planar winding structure.

[0048] Figure 12 For public Figure 10 Equivalent circuit diagram of a PCB-type planar winding structure.

[0049] Figure 13 This invention discloses the primary winding assembly structure comprising two identical planar winding modules in an embodiment of the present invention.

[0050] Figure 14 For public Figure 13 Equivalent circuit diagram of the primary winding assembly structure.

[0051] Figure 15 To disclose embodiments of the present invention, including Figure 13 The transformer assembly structure shown is a primary winding assembly structure.

[0052] Figure 16 To disclose the embodiments of the present invention used for maintaining Figure 13 The diagram shows a cross-sectional view of the integrated conductive frame of the primary winding assembly structure.

[0053] Figure 17 This is a top view of a planar winding structure that integrates high-voltage and low-voltage windings on the same PCB to achieve a smaller electric field, according to one embodiment of the present invention.

[0054] Figure 18 This is a cross-sectional view of a planar winding structure that integrates high-voltage and low-voltage windings on the same PCB to achieve a smaller electric field, according to one embodiment of the present invention.

[0055] Figure 19 This is a top view of a planar winding structure that integrates high-voltage and low-voltage windings on the same PCB to achieve a smaller electric field, in another embodiment of the present invention.

[0056] Figure 20 This is a cross-sectional view of a planar winding structure that integrates the high-voltage winding and the low-voltage winding on the same PCB to achieve a smaller electric field, in another embodiment of the present invention.

[0057] Figure 21 The above view shows a planar winding structure with a smaller electric field, in which the high-voltage winding and the low-voltage winding are integrated on the same PCB in another embodiment of the present invention.

[0058] Figure 22 This is a cross-sectional view of a planar winding structure that integrates the high-voltage winding and the low-voltage winding on the same PCB to achieve a smaller electric field, in another embodiment of the present invention.

[0059] Figure 23 The above view discloses a planar winding structure in which the high-voltage winding and the low-voltage winding are integrated on the same PCB to achieve a smaller electric field, in another embodiment of the present invention.

[0060] Figure 24 This is a cross-sectional view of a planar winding structure that integrates the high-voltage winding and the low-voltage winding on the same PCB to achieve a smaller electric field, in another embodiment of the present invention.

[0061] The attached figures are labeled as follows:

[0062] 500: Planar winding structure

[0063] 510: Winding Section

[0064] 511: PCB board

[0065] 512: Through hole

[0066] 513: Conductive layer

[0067] 514: Buried Hole

[0068] 515: Shielding layer

[0069] 520: Terminal section

[0070] 521: First terminal

[0071] 522: Second terminal

[0072] 523: Shielding edge

[0073] 524: Shielding edge treatment layer

[0074] 530: Terminal housing

[0075] 531: First Compartment

[0076] 532: Second compartment

[0077] 533: Insulating wall

[0078] 534, 535: Terminal blocks

[0079] 800: Equalizing ring structure

[0080] 810: External grounding ring

[0081] 820: Blind Hole

[0082] 830: Internal grounding ring

[0083] 840: Equalizing ring

[0084] 842: Upper Trace Line

[0085] 844: Lower Track

[0086] 846: Buried Hole

[0087] 850: Resistor

[0088] 1010, 1020: Shielding layer

[0089] 1300: Primary winding assembly structure

[0090] 1310, 1320: Planar winding modules

[0091] 1311, 1312: Terminal

[0092] 1313, 1323: Through holes

[0093] 1321, 1322: Terminal

[0094] 1400: Secondary winding

[0095] 1500: Transformer Assembly Structure

[0096] 1510: Magnetic core

[0097] 1520: Window area

[0098] 1600: Wireframe

[0099] 1700: Planar winding structure

[0100] 1701: First through hole

[0101] 1702: Second through hole

[0102] 1710: High-voltage winding

[0103] 1720: Low-voltage winding

[0104] 1730: PCB

[0105] 1800: Magnetic core

[0106] 1810, 1820: Magnet column

[0107] 1900: Planar winding structure

[0108] 1901: Through hole

[0109] 1910: High-voltage winding

[0110] 1920: Low-voltage winding

[0111] 1930: PCB

[0112] 2000: Magnetic Core

[0113] 2010: Central Magnetic Column

[0114] 2020: Side Magnetic Pillar

[0115] 2100: Planar winding structure

[0116] 2110: High-voltage winding

[0117] 2120: Low-voltage winding

[0118] 2130: PCB

[0119] 2200: Magnetic core

[0120] 2210: Central magnetic column

[0121] 2220: Side magnetic column

[0122] 2300: Planar winding structure

[0123] 2301: First through hole

[0124] 2302: Second through hole

[0125] 2310: High-voltage winding

[0126] 2320: Low-voltage winding

[0127] 2330: PCB

[0128] 2400: Magnetic core

[0129] 2410: First magnetic column

[0130] 2420: Second magnetic column

[0131] C PshEquivalent capacitance

[0132] C Gsh Equivalent capacitance

[0133] d1: First distance

[0134] d2: Second distance

[0135] d3: Third distance

[0136] d4: Distance

[0137] AA: line segment

[0138] BB: Line segment

[0139] CC: Line segment

[0140] DD: line segment

[0141] HV: High voltage

[0142] LV: Low pressure Detailed Implementation

[0143] High-frequency transformers are a key component in medium-voltage applications. Compared to traditional line-frequency transformers, high-frequency transformers can be made smaller and lighter due to their high-frequency operation of the power stage and smaller application volt-seconds. Furthermore, the insulation design of high-frequency transformers is crucial, and they must meet design goals such as no partial discharge, ease of manufacture, higher efficiency, and better thermal performance.

[0144] This invention provides a technique for printing circuit board (PCB) type planar transformers to form main power transformers and auxiliary power transformers. In embodiments of this invention, a confined electric field can be provided through core potential control, thereby creating a partial discharge (PD)-free design for medium voltage (MV) applications. Simultaneously, the winding structure can be formed through the PCB manufacturing process, creating a more modular and reliable structure, thereby improving manufacturability. Other techniques such as termination connection processing and primary and secondary winding arrangement can also be used to control electrical stress in medium voltage applications.

[0145] In medium-voltage applications, two types of transformers can be used. The first is the main power transformer. As mentioned above, the main power transformer is used in place of the traditional power frequency transformer. Therefore, all power supplied from the high-voltage (primary) side to the low-voltage (secondary) side needs to flow through the main power transformer. The second type of transformer is the auxiliary power transformer, used for auxiliary power applications on the high-voltage side. The high-voltage side can be, for example, but not limited to, gate driver power supplies, sensor power supplies, or other bias power supplies required by rectifier converters or DC-DC converters.

[0146] For main power transformers, high voltage is typically applied to the primary side. After a step-down function, the low-voltage output of the transformer is then connected to the secondary side. Therefore, the primary high-voltage winding needs to be designed for high voltage and low current, while the secondary winding needs to be designed for low voltage and high current. In this embodiment of the invention, a solution for a PCB-type high-voltage winding is provided.

[0147] Figure 5 This is a perspective view of a printed circuit board (PCB) type planar winding structure 500 for a power transformer according to an embodiment of the present invention. The PCB type planar winding structure 500 includes a winding portion 510 and a terminal portion 520.

[0148] See Figure 5 The winding portion 510 includes a PCB board 511, which is generally rectangular with rounded corners and has a thickness ranging from 1 mm to 6 mm. In some embodiments, the PCB board 511 further includes, for example, a through-hole 512 formed in the central portion of the PCB board 511 for accommodating a magnetic core. In this embodiment, a terminal portion 520 is formed, for example, on an extension of the PCB board 511, and its width is narrower than the width of the PCB board 511 of the winding portion 510, for example, about half the width of the PCB board 511 of the winding portion 510. The terminal portion 520 includes a first terminal 521 and a second terminal 522, respectively formed on the extension of the PCB board 511, for conducting and / or discharging current into and / or out of the planar winding structure 500. In one embodiment, the first terminal 521 and the second terminal 522, for example, pass through the PCB board 511 and are exposed on both surfaces of the PCB board 511. One or more conductive layers are embedded in the PCB board 511 and electrically connected to the first terminal 521 and the second terminal 522 to form a wound coil surrounding the through-hole 512. In one embodiment, the outer surface of the winding portion 510 is coated with a shielding layer, and has a shielding edge 523 at the interface where the PCB board 511 extends to the terminal portion 520. Understandably, the PCB board 511 and the through-hole 512 can be planar structures of any shape (e.g., rectangular, circular, elliptical, etc.) and any suitable size, depending on the design.

[0149] See also Figure 5 In one embodiment, the terminal portion 520 further includes, for example, a terminal housing 530 having a first compartment 531 and a second compartment 532. The first compartment 531 and the second compartment 532 are separated, for example, by an insulating wall 533. Figure 5As shown, the first compartment 531 accommodates the first terminal 521 and the second terminal 522, and surrounds an extension of the PCB board 511. In one embodiment, the first compartment 531 is encapsulated with an insulating material such as epoxy resin to serve as a shielding edge treatment layer to smooth the electric field; details will be described further later. It should be understood that in this embodiment, the shielding edge 523 is completely covered by the insulating material in the first compartment 531.

[0150] In this embodiment, the second compartment 532 includes a hollow space providing the required creepage distance and an electrical conduit for connection to an external power source. Through-holes may be formed in the insulating wall 533 to allow the first terminal 521 and the second terminal 522 to be connected to the external power source. Terminal blocks 534 and 535, made of conductive materials such as metal, provide electrical and mechanical support for the connection between the external power source and the first and second terminals 521 and 522. In one embodiment, the insulating wall 533 and terminal blocks 534 and 535 are further penetrated, for example, by a metal screw (not shown). In some embodiments, when multiple PCBs such as Figure 15 As shown, when connected in series, the terminal housing 530 can be modified and applied to the transformer stage after multiple PCB boards are assembled.

[0151] Figure 6 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure 500 along line segment AA, which includes the shielding edge treatment layer of the present invention. Figure 7 For public Figure 5 Cross-sectional view of the 500-section planar winding structure along the BB line segment of the PCB type.

[0152] See Figure 6 and Figure 7 In this embodiment, the PCB-type planar winding structure 500 includes four conductive layers 513 (made of copper or other suitable metal material) connected in a cascaded manner and embedded in the PCB board 511. It is understood that, depending on the design choice, the planar winding structure 500 can use any suitable number of conductive layers 513. Figure 6 and Figure 7As shown, this embodiment utilizes only the inner layer as a high-voltage winding for conductivity. The conductive layers 513 are primarily insulated from each other by the PCB material of the PCB board 511 and electrically connected through buried vias 514. In other embodiments, the buried vias 514 may, for example, be filled with epoxy resin. In one embodiment, the PCB board 511 is made of an insulating material, such as FR4, to serve as the insulating layer between the conductive layers 513. Since FR4 material is widely used in related industries as power supply or control boards, the quality and void defects within FR4 or between FR4 and the inner copper layer can be well controlled, thus minimizing internal partial discharge (PD) or interlayer partial discharge defects.

[0153] In one embodiment, the outer surface of the PCB board 511 is coated with a shielding layer 515, which may be made of a semiconductor material such as a carbon conductive coating. The shielding layer 515 made of a semiconductor material may, for example, share the same potential as the low-voltage side. Thus, if the shielding layer 515 abruptly terminates at a shielding edge 523, high electrical stress will exist around the shielding edge 523. To avoid this strong electric field, in one embodiment, a shielding edge treatment layer 524 is used to smooth the electric field.

[0154] Figure 8 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure 500 along the CC line segment, which includes the equalizing ring structure 800 of this embodiment. Figure 9 For public Figure 5 Cross-sectional view of the 500-section planar winding structure of the PCB type along the DD line segment.

[0155] See Figure 8 and Figure 9 In this embodiment, a voltage equalization ring structure 800 is introduced between the conductive layer 513 and the shielding layer 515 to reduce electric field stress. It should be understood that the voltage equalization ring structure 800 can exist alone or in conjunction with... Figure 6 The shielding edge treatment layer 524 in the middle is combined to reduce electric field stress. Unlike Figure 6 The ground potential is terminated by shielding edge 523. In this embodiment, the ground potential can be extended into the internal PCB structure, for example, through an outer ground ring 810, a blind via 820, and an inner ground ring 830. The outer ground ring 810 is formed during PCB manufacturing and can be considered as an outer layer on the outer surface of the PCB board 511. When a shielding layer 515 is applied, the shielding layer 515 can cover the outer ground ring 810, thereby sharing the same ground potential. The blind via 820 further electrically connects the ground potential downward to the inner ground ring 830 embedded in the PCB board 511. Thus, strong electrical stress no longer exists on the shielding edge 523, but on the edge of the inner ground ring 830.

[0156] Because the internal grounding ring 830 is encased in a highly insulating material, the electric field exposed to the outside of the PCB board 511 can be mitigated. However, further reduction of the electric field may be necessary because the limited thickness of the insulating material (e.g., FR4) covering the internal grounding ring 830 may not bring the electric field below the air breakdown value. Therefore, it may be necessary to further extend the electric field in the horizontal direction. In one embodiment, multiple embedded equalizing rings 840 may be implemented between the internal grounding ring 830 and the first terminal 521 to provide a controlled potential between them. The equalizing rings 840 may initially be manufactured as a single piece and then etched into multiple equalizing rings 840. This allows the electric field to be significantly reduced from the vertical to the horizontal direction, thereby reducing the exposure stress on the outer surface of the PCB board 511. In one embodiment, the potential of each equalizing ring 840 can be controlled by embedded or buried resistors 850 connected respectively between adjacent equalizing rings 840. In some embodiments, the resistance of the buried resistor 850 is approximately 10 MΩ.

[0157] like Figure 9 As shown, each equalizing ring 840 includes an upper trace 842, a lower trace 844, and two buried vias 846, collectively forming a rectangular conductive ring surrounding the conductive layer 513. Resistors 850 between the equalizing rings 840 also have, for example, a rectangular ring shape. The upper trace 842, lower trace 844, and buried vias 846 can be manufactured during PCB manufacturing, thus requiring minimal additional labor. The resistors 850 between the equalizing rings 840 can also be manufactured during PCB manufacturing. In this embodiment, five equidistant equalizing rings 840 are included, each having a rectangular closed loop, and five of the aforementioned resistors 850. It should be understood that the equalizing ring structure 800 can be constructed of any suitable number and with any suitable shape and / or configuration of equalizing rings 840 and resistors 850. In one embodiment, the equalizing ring 840 furthest from the shielding edge 523 is, for example, electrically connected to one of the conductive layers 513 or one of the first terminal 521 and the second terminal 522.

[0158] The stray capacitance between the primary and secondary sides of the power transformer is determined by the high-voltage winding (conductive layer 513) relative to the shielding layer 515, which shares the same potential as the low-voltage side. Due to its relatively large footprint, the stray capacitance may not be negligible. Figure 10 For public Figure 5 A cross-sectional view of the PCB-type planar winding structure along line segment AA, including the embedded EMI shielding layers 1010 and 1020 of the present invention. Figure 11 For public Figure 10 Top view of each layer of the PCB-type planar winding structure 500.

[0159] Figure 10The PCB-type planar winding structure 500 shown is... Figure 5 The examples shown are essentially the same. In this embodiment, Figure 10 The planar winding structure 500 shown also includes a first embedded EMI shielding layer 1010 disposed above and insulated from the conductive layer 513, and a second embedded EMI shielding layer 1020 disposed below and insulated from the conductive layer 513. The first embedded EMI shielding layer 1010 and the second embedded EMI shielding layer 1020 are electrically coupled to the outside of the PCB board 511, for example, via a first EMI shielding terminal 1011 and a second EMI shielding terminal 1021, respectively. The first embedded EMI shielding layer 1010 and the second embedded EMI shielding layer 1020 inside the PCB board 511 provide a controlled EMI path for high-frequency electrical noise, thereby reducing the EMI level to the low-voltage side.

[0160] Figure 12 For public Figure 10 The equivalent circuit diagram of the PCB-type planar winding structure 500. The EMI shielding layers 1010 and 1020, together with the high-voltage winding (conductive layer 513), generate an equivalent capacitance C. Psh And it generates an equivalent capacitance C with the shielding layer 515. Gsh EMI shielding terminals 1011 and 1021 can be connected back to the primary ground terminal, allowing noise generated on the primary side to circulate back to the primary side, thereby reducing interaction with the transformer secondary side.

[0161] Figure 13 This invention discloses a primary winding assembly structure 1300 comprising two identical planar winding modules 1310 and 1320 in an embodiment of the present invention. Figure 14 For public Figure 13 Equivalent circuit diagram of the 1300 primary winding assembly structure. Figure 15 To disclose embodiments of the present invention, including Figure 13 The transformer assembly structure 1500 is shown as the primary winding assembly structure 1300.

[0162] See Figures 13 to 15 In one embodiment, planar winding module 1310 includes terminals 1311 and 1312, while planar winding module 1320 includes terminals 1321 and 1322. When planar winding modules 1310 and 1320 are combined to form primary winding assembly structure 1300, one of the planar winding modules 1310 and 1320 is rotated 180 degrees along its longitudinal axis, such that the planar winding modules 1310 and 1320 can be stacked on top of each other, with through-holes 1313 and 1323 aligned with each other, and terminals 1312 and 1322 aligned and electrically connected to each other. The planar winding modules 1310 and 1320 can be connected in series using external screws, and their equivalent circuit is as follows: Figure 14As shown. In this embodiment, the secondary winding 1400 can be made of stranded wire, and the primary winding can be made of two plates connected in series. The arrangement of the primary winding 1300 and the secondary winding 1400 can be, for example, as shown below. Figure 15 The side-by-side configuration shown, or the staggered configuration (i.e., secondary windings interleaved between primary windings), depends on the required leakage inductance. By using an external shielding layer, the potential of the shielding layer can be limited to a low voltage level, so the window area of ​​the core 1510 of the transformer assembly structure 1500 does not need to be filled with potting. The high-voltage winding is stacked with the low-voltage winding, even though the low-voltage winding is still a stranded wire.

[0163] Figure 16 To disclose the embodiments of the present invention used for maintaining Figure 13 The diagram shows a cross-sectional view of the integrated conductive frame 1600 of the primary winding assembly structure 1300. The frame 1600 is, for example, conductive or coated with a metal layer, allowing the shielding layer of the primary winding assembly structure 1300 to be grounded and share the same potential with the low-voltage side. Thus, potting is not required in the window region 1520 of the core 1510, and forced air cooling can directly remove the heat generated by the primary winding assembly structure 1300, resulting in excellent thermal efficiency.

[0164] As mentioned earlier, in addition to main power transformers, auxiliary power transformers are also widely used in medium-voltage applications. Auxiliary power transformers require a low profile (especially a small height) to fit within the power stage housing. For planar designs, the transformer height is typically determined by the core. Therefore, the potential between the core and the housing must be carefully controlled. Furthermore, these applications require minimal stray capacitance between the primary and secondary sides to reduce coupling from the power stage to the control stage. Moreover, most auxiliary power transformers do not handle high power, so the primary and secondary sides can be integrated into a single PCB.

[0165] Figure 17 The above-view diagram shows a planar winding structure 1700 that integrates a high-voltage (HV) winding 1710 and a low-voltage (LV) winding 1720 on the same PCB 1730 to achieve a smaller electric field, in an embodiment of the present invention. Figure 18 This is a cross-sectional view of a planar winding structure 1700 that integrates a high-voltage winding 1710 and a low-voltage winding 1720 on the same PCB 1730 to achieve a smaller electric field, according to one embodiment of the present invention. Figure 17 and Figure 18As shown, the planar winding structure 1700 includes a first through-hole 1701 and a second through-hole 1702, and can be used with a CC-type magnetic core 1800 to form a transformer. A high-voltage winding 1710 is wound around the first through-hole 1701 and the second through-hole 1702, and is very close to the two magnetic posts 1810 and 1820 of the magnetic core 1800. A low-voltage winding 1720 is wound around the first through-hole 1701 and the second through-hole 1702 in a similar manner to the high-voltage winding 1710, but relatively far from the magnetic posts 1810 and 1820, and the low-voltage winding 1720 is connected in series. The high-voltage winding 1710 and the low-voltage winding 1720 are separated from each other on the PCB 1730. Gaps can be formed between the high-voltage winding 1710 and the low-voltage winding 1720 and the top and bottom surfaces of the magnetic core 1800. Because the high-voltage winding 1710 is very close to the magnetic core 1800, the potential of the magnetic core 1800 can be controlled very close to the high-voltage side, which makes the electric field mainly concentrated in the central region from high voltage to low voltage.

[0166] In one embodiment, the magnetic core 1800 and the planar winding structure 1700 may be potted with epoxy resin or other insulating materials to provide mechanical support and prevent partial discharge. Because there are no stranded wires, high-viscosity potting materials can be used. Simultaneously, since the core potential is well controlled, the height of the potted shell can be very close to the core height, as there is no strong electric field around the top or bottom of the core.

[0167] Figure 19 To disclose another embodiment of the present invention, a top view of a planar winding structure 1900 in which a high-voltage winding 1910 and a low-voltage winding 1920 are integrated on the same PCB 1930 to achieve a smaller electric field is provided. Figure 20 To disclose another embodiment of the present invention, a cross-sectional view of a planar winding structure 1900 with a smaller electric field, in which the high-voltage winding 1910 and the low-voltage winding 1920 are integrated on the same PCB 1930, is provided. Figure 19 and Figure 20 As shown, the planar winding structure 1900 includes a through-hole 1901 and is used in conjunction with an EE-type magnetic core 2000 to form a transformer. A high-voltage winding 1910 is wound adjacent to the central magnetic post 2010 of the magnetic core 2000. A low-voltage winding 1920 is wound around the central magnetic post 2010 of the magnetic core 2000, forming a first distance d1 with the periphery of the through-hole 1901 (or with the central magnetic post 2010 of the magnetic core 2000), and a second distance d2 with the edge of the planar winding structure 1900 (or with the side magnetic posts 2020 of the magnetic core 2000). In various embodiments, the first distance d1 and the second distance d2 may be the same or slightly different (e.g., the percentage difference between the first distance d1 and the second distance d2 is less than 20%). Additionally, a third distance d3 may be formed between the high-voltage winding 1910 and the low-voltage winding 1920 and the top or bottom surface of the window area of ​​the magnetic core 2000.

[0168] Figure 21 To disclose a top view of a planar winding structure 2100 with a smaller electric field, in another embodiment of the present invention, the high-voltage winding 2110 and the low-voltage winding 2120 are integrated on the same PCB 2130. Figure 22 To disclose a further embodiment of the present invention, a cross-sectional view of a planar winding structure 2100 with a smaller electric field is provided, in which the high-voltage winding 2110 and the low-voltage winding 2120 are integrated on the same PCB 2130. (See figure) Figure 21 and Figure 22 As shown, the planar winding structure 2100 and the EE-type magnetic core 2200 together form a transformer. Figure 21 and Figure 22 The planar winding structure 2100 shown is... Figure 19 and Figure 20 The planar winding structure 1900 shown is essentially the same. In this embodiment, the planar winding structure 2100 further includes two sets of high-voltage windings 2110, wherein the first set of high-voltage windings 2110 is wound close to the central magnetic post 2210 of the magnetic core 2200, while the second set of high-voltage windings 2110 is adjacent to the side magnetic posts 2220 of the magnetic core 2200. The low-voltage winding 2120 is wound around the central magnetic post 2010 of the magnetic core 2200, forming a first distance d1 with the periphery of the through hole 2101 (or with the central magnetic post 2210), and forming a second distance d2 with the edge of the planar winding structure 2100 (or with the side magnetic post 2220). In one embodiment, the first distance d1 and the second distance d2 may be the same or slightly different (e.g., the percentage difference between the first distance d1 and the second distance d2 is less than 20%). A third gap d3 is formed between the top or bottom surface of the window area of ​​the high voltage winding 2110 and the low voltage winding 2120 and the magnetic core 2200.

[0169] Figure 23 To disclose a top view of a planar winding structure 2300 with a smaller electric field, in another embodiment of the present invention, the high-voltage winding 2310 and the low-voltage winding 2320 are integrated on the same PCB 2330. Figure 24 This document discloses a cross-sectional view of a planar winding structure 2300 with a smaller electric field, in which the high-voltage winding 2310 and the low-voltage winding 2320 are integrated on the same PCB 2330. (See cross-sectional view for another embodiment of the invention.) Figure 23 and Figure 24As shown, the planar winding structure 2300 includes a first through-hole 2301 and a second through-hole 2302, and the planar winding structure 2300 is used in conjunction with the CC-type magnetic core 2400 to form a transformer. The high-voltage winding 2310 is wound around the first through-hole 2301 and is very close to the periphery of the first through-hole 2301 or the first magnetic post 2410 of the magnetic core 2400. The low-voltage winding 2320 is wound around the second through-hole 2302 and forms a distance d4 with the second magnetic post 2420 of the magnetic core 2400. A third distance d3 is formed between the top or bottom surface of the window area of ​​the high-voltage winding 2310 and the low-voltage winding 2320 and the magnetic core 2400.

[0170] For purposes of illustration and definition of the invention, it should be noted that terms of degree (e.g., “substantially,” “slightly,” “approximately,” “comparatively,” etc.) are used herein to indicate an inherent degree of uncertainty that can be attributed to any quantitative comparison, value, measurement, or other representation. Such terms of degree may also be used herein to indicate a quantity different from the stated reference (e.g., a difference of about 10% or less) without altering the essential function of the subject matter. Unless otherwise stated herein, any numerical values ​​appearing herein may be modified by terms of degree (e.g., “approximately”) to reflect their inherent degree of uncertainty.

[0171] This invention may be modified in various ways by those skilled in the art, but all such modifications shall not depart from the protection sought by the appended claims.

Claims

1. A planar winding structure, comprising: An insulating plate having a winding portion and a terminal portion, wherein the central portion of the winding portion has a through hole; Multiple conductive layers are embedded in the winding portion of the insulating plate and electrically connected to each other through one or more vias, wherein the multiple conductive layers are patterned to form a transformer winding around the via. A first terminal and a second terminal are located at the terminal portion of the insulating plate, and each of the first terminal and the second terminal is electrically connected to one of the corresponding plurality of conductive layers; A shielding layer is coated on an outer surface of the winding portion of the insulating plate; and An equalizing ring structure is embedded in the terminal portion of the insulating plate and shares the same potential with the shielding layer.

2. The planar winding structure as claimed in claim 1 further includes a shielding edge treatment layer located in the terminal portion between the shielding layer and the first terminal and the second terminal.

3. The planar winding structure as claimed in claim 1 further includes an electrical bushing having a potting portion and a hollow portion, wherein the terminal portion of the insulating plate is accommodated within the potting portion.

4. The planar winding structure as claimed in claim 3, wherein the electrical bushing further includes a terminal block located in the potting portion to electrically and mechanically support the first terminal and the second terminal.

5. The planar winding structure as claimed in claim 1, wherein the equalizing ring structure includes an external grounding ring and an internal grounding ring, wherein the external grounding ring is located on an outer surface of the insulating plate, near an interface between the winding portion and the terminal portion, wherein the internal grounding ring is embedded in the insulating plate and electrically connected to the external grounding ring through one or more blind holes.

6. The planar winding structure as claimed in claim 1, wherein the equalizing ring structure includes a plurality of equalizing rings and at least one resistor, the plurality of equalizing rings being embedded in the terminal portion of the insulating plate and extending horizontally from an interface between the winding portion and the terminal portion, wherein the at least one resistor is embedded in the terminal portion of the insulating plate and electrically connected to the adjacent plurality of equalizing rings.

7. The planar winding structure as claimed in claim 6, wherein the one of the plurality of equalizing rings furthest from the interface is electrically connected to one of the first terminal and the second terminal.

8. The planar winding structure as described in claim 1 further includes a plurality of electromagnetic interference shielding layers embedded in the insulating plate, wherein the conductive layer is embedded in the insulating plate and located between the plurality of electromagnetic interference shielding layers.

9. The planar winding structure of claim 1, wherein the shielding layer comprises a semiconductor material.

10. The planar winding structure of claim 1, wherein the insulating plate comprises an FR4 material.

11. A power transformer, comprising: A planar winding structure, including: An insulating plate having a winding portion and a terminal portion, wherein the central portion of the winding portion has a through hole; Multiple conductive layers are embedded in the winding portion of the insulating plate and electrically connected to each other through one or more vias, wherein the multiple conductive layers are patterned to form a transformer winding around the via. A first terminal and a second terminal are located at the terminal portion of the insulating plate, and each of the first terminal and the second terminal is electrically connected to one of the corresponding plurality of conductive layers; A shielding layer is coated on an outer surface of the winding portion of the insulating plate; and An equalizing ring structure is embedded in the terminal portion of the insulating plate and shares the same potential with the shielding layer; One magnetic core; and A primary winding structure, wherein the secondary winding structure is magnetically coupled to the planar winding structure through the magnetic core.

12. The power transformer of claim 11, wherein a portion of the magnetic core is disposed within the through hole of the insulating plate.

13. The power transformer of claim 11, wherein the secondary winding structure is electrically connected to the shielding layer of the planar winding structure.

14. A planar winding structure, comprising: An insulating plate, wherein the central portion of the insulating plate has a through hole for accommodating a magnetic core; A first winding assembly is disposed on the insulating plate, and the first winding assembly surrounds the through hole and is close to a portion of the through hole; and A second winding assembly is disposed on the insulating plate and surrounds the through hole, wherein the second winding assembly is separated from the periphery of the through hole by a first distance and from an edge of the planar winding structure by a second distance, wherein the distance between the first winding assembly and the periphery of the through hole is less than the first distance.

15. The planar winding structure as described in claim 14 further includes a third winding group disposed on the insulating plate, the third winding group surrounding the through hole and close to the edge of the insulating plate.

16. The planar winding structure of claim 14, wherein the first distance and the second distance are equal.

17. The planar winding structure of claim 14, wherein the percentage difference between the first distance and the second distance is less than 20%.

18. A planar winding structure, comprising: An insulating plate having a first through hole and a second through hole for accommodating a magnetic core; A first high-voltage winding is disposed on the insulating plate, wherein the first high-voltage winding surrounds the first through hole and is close to a periphery of the first through hole; and A first low-voltage winding is disposed on the insulating plate, wherein the first low-voltage winding surrounds the second through hole and is separated from the periphery of the second through hole by a first distance, wherein the distance between the first high-voltage winding and the periphery of the first through hole is less than the first distance.

19. The planar winding structure as described in claim 18, further comprising: A second high-voltage winding is disposed on the insulating plane plate, wherein the second high-voltage winding surrounds the second through hole and is close to the periphery of the second through hole; and A second low-voltage winding is disposed on the insulating plate, wherein the second low-voltage winding surrounds the first through hole and is separated from the periphery of the first through hole by a second distance.

20. The planar winding structure of claim 19, wherein the first low-voltage winding and the second low-voltage winding are connected in series.

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