CN114373613A

CN114373613A - Planar transformer, power conversion circuit and adapter

Info

Publication number: CN114373613A
Application number: CN202111466811.7A
Authority: CN
Inventors: 方乐安; 李佳; 曹阅; 陈文洁; 张希俊; 李闯鹏
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2021-12-03
Filing date: 2021-12-03
Publication date: 2022-04-19
Also published as: WO2023098280A1

Abstract

A planar transformer, a power conversion circuit and an adapter are provided, the planar transformer comprises N groups of transformer substructures, each group of transformer substructures comprises a first magnetic core, a second magnetic core and a PCB winding board; the PCB winding board comprises a first composite winding layer and a second composite winding layer; the first composite winding layer comprises a first sub-winding layer and a second sub-winding layer; a second sub-winding layer is arranged between every two adjacent first sub-winding layers; the second composite winding layer comprises two third sub-winding layers and one fourth sub-winding layer; a fourth sub-winding layer is arranged between every two adjacent third sub-winding layers; the number of winding turns of the first sub-winding layer is the same as that of the third sub-winding layer; the second sub-winding layer and the fourth sub-winding layer have the same winding number and opposite winding directions. By using the planar transformer provided by the application, the primary winding and the secondary winding in the planar transformer are designed in a symmetrical cancellation mode, and a better common mode noise suppression effect can be achieved under a very small volume.

Description

Planar transformer, power conversion circuit and adapter

Technical Field

The application relates to the field of transformers, in particular to a planar transformer, a power conversion circuit and an adapter.

Background

Adapters are also known as switching power supplies, switching converters, and are widely used in various fields. The function of the adapter is to convert one type of input voltage into a voltage or current required by the user terminal through different types of architectures. The input of the adapter is an alternating current power supply (such as commercial power) or a direct current power supply, and the output is a device needing to use the direct current power supply.

The problem of the adapter suffering from noise interference during operation is very prominent, and the noise mainly includes: differential mode noise and common mode noise. In practical applications, common mode noise is often the main factor causing electromagnetic interference (EMI). Common mode noise mainly includes noise between the reference ground generated by interaction of devices in the power conversion circuit, and the common mode noise can be conducted and radiated to the electric equipment along the circuit network and cause the electric equipment to be subjected to EMI, so that the requirement of the adapter on noise suppression is very strict at present.

In order to reduce the interference caused by common mode noise, more filtering measures are often adopted to suppress EMI, such as increasing common mode inductance or increasing the capacitance between the primary and secondary circuits in the power conversion circuit, but these measures increase the cost and volume of the adapter. With the research of the technology of suppressing the noise of the planar transformer, the planar transformer is used in the adapter, and a good effect on suppressing the common mode noise can be achieved.

A planar transformer (planar transformer) is a transformer structure with high frequency, very low height and very high operating frequency. The greatest difference between planar transformers and conventional transformers is in the core and coil windings. The planar transformer adopts a small-size magnetic core, is made of high-frequency power ferrite materials, and has lower magnetic core loss at high frequency; the winding is formed by multilayer (PCB) iterative winding, and the winding or copper sheets are overlapped on the planar iron core to form a magnetic circuit of the transformer. The planar transformer has low direct current copper resistance, low leakage inductance and distributed capacitance. Referring to fig. 1A and 1B, a planar transformer with a zero-noise matching layer (zero-noise matching method) structure is commonly used, where fig. 1A is a schematic diagram of a planar transformer with a shielding winding structure, and fig. 1B is a schematic diagram of a planar transformer with a zero-noise matching layer structure.

With the increasing expectations for the power density and common mode noise suppression effect of the adapter, the planar transformer structure shown in fig. 1A and 1B is difficult to support the requirements of the current adapter for noise suppression for suppressing common mode noise. In view of the above, it is desirable to design a planar transformer structure with better common mode noise rejection than the existing structures.

Disclosure of Invention

The application provides a planar transformer, power conversion circuit and adapter adopts the mode of symmetry cancellation, can reach better common mode noise suppression effect under very little volume.

In a first aspect, the present application provides a planar transformer, which includes N groups of transformer substructures, each of the N groups of transformer substructures includes a first magnetic core, a second magnetic core and a PCB winding board, and N is a positive integer; the PCB winding board includes: the first composite winding layer is wound on the first magnetic core, and the second composite winding layer is wound on the second magnetic core; the first composite winding layer comprises at least one group of first sub-winding layers and at least one layer of second sub-winding layers; each group of first sub-winding layers comprises two adjacent layers of first sub-winding layers; at least one second sub-winding layer is arranged between two first sub-winding layers in each group of first composite winding layers; the second composite winding layer comprises at least one group of third sub-winding layers and at least one layer of fourth sub-winding layers; each group of third sub-winding layers comprises two adjacent layers of third sub-winding layers; at least one fourth sub-winding layer is arranged between two third sub-winding layers in each group of second composite winding layers; the total number of the at least two first sub-winding layers is the same as that of the at least two third sub-winding layers; the number of winding turns of each layer of the first sub-winding layer is the same as that of the third sub-winding layer; the total number of the at least one second sub-winding layer is the same as that of the at least one fourth sub-winding layer; and the number of winding turns of each layer of the second sub-winding layer is the same as that of the fourth sub-winding layer, and the winding directions are opposite.

The planar transformer structure provided by the application adopts a symmetrical cancellation mode, compared with the prior art, the common mode noise is obviously reduced on the premise of not increasing the volume, compared with the existing scheme of adding the shielding winding, at least more than two shielding layers can be reduced, the winding layer of the planar transformer is simpler to manufacture, and the loss is reduced; compared with a zero-noise matching layer scheme, the number of turns of adjacent layers of the original secondary side does not need to be consistent, so that the design of the winding is simple, and the EMI suffered by the circuit is reduced remarkably.

As a possible embodiment, each of the at least two first sub-winding layers is connected in series to form a first winding, each of the at least two second sub-winding layers is connected in series to form a second winding, each of the at least one third sub-winding layers is connected in series to form a third winding, and each of the at least one fourth sub-winding layers is connected in series to form a fourth winding. Each first sub-winding layer in the at least two layers of first sub-winding layers can be connected in series through the via hole on each layer of first sub-winding layer, each third sub-winding layer in the at least two layers of first sub-winding layers is connected in series through the via hole on each layer of first sub-winding layer, and a person skilled in the art can flexibly set the number of the via holes and the positions of the via holes according to actual engineering needs, so that the noise in the planar transformer can be offset better. As a possible embodiment, the first winding is connected in series with the third winding; the second winding is connected in series with the fourth winding.

As a possible implementation manner, the potential dead point of the primary circuit of the power conversion circuit is connected to one end of the second winding and one end of the fourth winding, the potential dead point of the secondary circuit of the power conversion circuit is connected to one end of the first winding and one end of the third winding, and the power conversion circuit is configured to convert a voltage provided by an external power source into a voltage meeting a charging or power supply standard of the device to be charged, and charge or supply the device to be charged.

One end of the second winding and one end of the fourth winding may be connected to a primary switching tube of the primary circuit, the one end of the second winding may correspond to one end of a last layer of coils of the second winding, and the one end of the fourth winding may correspond to one end of a last layer of coils of the fourth winding. One end of the first winding and one end of the third winding may be connected to a secondary rectifier of the secondary circuit, the one end of the first winding may correspond to one end of the last coil of the first winding, and the one end of the third winding may correspond to one end of the last coil of the third winding.

As a possible implementation manner, the difference between the voltage flowing through the second winding and the set voltage is a first voltage, the difference between the voltage flowing through the fourth winding and the set voltage is a second voltage, and the first voltage and the second voltage are the same in magnitude and opposite in direction.

As a possible implementation manner, the potential static point of the primary circuit of the power conversion circuit is connected to one end of the first winding and one end of the third winding, the potential static point of the secondary circuit of the power conversion circuit is connected to one end of the second winding and one end of the fourth winding, and the power conversion circuit is configured to convert a voltage provided by an external power source into a voltage meeting a charging or power supply standard of the device to be charged, and charge or supply the device to be charged.

After the potential static point of the primary circuit of the power conversion circuit is connected with one end of the second winding and one end of the fourth winding, and the potential static point of the secondary circuit of the power conversion circuit is connected with one end of the first winding and one end of the third winding: the second winding and the fourth winding are connected in series to form a primary side/primary winding, and the first winding and the third winding are connected in series to form a secondary side/secondary winding. The potential quiescent point of the primary circuit of the power conversion circuit can be a node connecting the primary side/primary winding and the primary filter capacitor. Alternatively, the potential dead point of the primary circuit of the power conversion circuit may be a ground node of the primary circuit. The potential dead point of the secondary circuit of the power conversion circuit may be a node at which the secondary side/secondary winding is connected to the secondary filter capacitor. Alternatively, the potential dead point of the secondary circuit of the power supply conversion circuit may be a ground node of the secondary circuit.

One end of the second winding and one end of the fourth winding may be connected to a secondary rectifier of the secondary circuit, the one end of the second winding may correspond to one end of the last coil of the second winding, and the one end of the fourth winding may correspond to one end of the last coil of the fourth winding. One end of the first winding and one end of the third winding may be connected to a primary switching tube of the primary circuit, the one end of the first winding may correspond to one end of a last coil of the first winding, and the one end of the third winding may correspond to one end of a last coil of the third winding.

As a possible implementation manner, the difference between the voltage passing through the first winding and the set voltage is a third voltage, the difference between the voltage passing through the third winding and the set voltage is a fourth voltage, and the third voltage and the fourth voltage have the same magnitude and opposite directions.

As a possible implementation, the first magnetic core and the second magnetic core are arranged along a first direction, and the first direction is parallel to the PCB winding board. First magnetic core and second magnetic core of this application are arranged along first direction, and first direction is parallel with PCB winding board. The first magnetic cores and the second magnetic cores arranged along the first direction jointly form each group of the N groups of transformer substructures.

As a possible implementation manner, each of the N sets of transformer substructures is arranged along a first direction and/or a second direction, and the second direction is parallel to the PCB winding board and perpendicular to the first direction. In addition, when the transformer substructure in the planar transformer is actually ensured to have at least one symmetry axis or one symmetry mode for symmetry, the planar transformer can keep a good common-mode noise suppression effect.

As a possible implementation, the first composite winding layer includes at least one group of first composite winding layers, and each group of the at least one group of first composite winding layers includes two layers of first sub-winding layers and at least one layer of second sub-winding layers; at least one second sub-winding layer is arranged between two first sub-winding layers in the first composite winding layer; the second composite winding layer comprises at least one group of second composite winding layers, and each group of second composite winding layers in the at least one group of second composite winding layers comprises two layers of third sub-winding layers and at least one layer of fourth sub-winding layers; at least one fourth sub-winding layer is arranged between two third sub-winding layers in the second composite winding layer. Each composite winding layer may include multiple composite winding layers, and the multiple layers may be used to increase the common mode noise rejection effect.

As a possible implementation manner, each of the at least one second sub-winding layer has the same size as the first parasitic capacitance formed by the adjacent first sub-winding layer; each fourth sub-winding layer in the at least one layer of fourth sub-winding layers has the same size as the second parasitic capacitance formed by the adjacent third sub-winding layer; the first parasitic capacitance is the same as the second parasitic capacitance. The second condition of symmetry cancellation defined herein: the parasitic capacitance between adjacent winding layers is the same. The space between the winding layers and the overlapping coverage condition between the winding layers are indirectly defined through the limitation of the size of the parasitic capacitance.

As a possible implementation manner, in order to reduce the difficulty of manufacturing the planar capacitor, the first parasitic capacitance formed by each second sub-winding layer in the at least one second sub-winding layer and the adjacent first sub-winding layer is within the set capacitance range; each fourth sub-winding layer in the at least one layer of fourth sub-winding layers is within a set capacitance size interval formed by the adjacent third sub-winding layer.

As a possible embodiment, the first and second magnetic cores are of EE, EI or RM type structure.

In a second aspect, the present application provides a power conversion circuit, including: the planar transformer comprises a primary circuit, a secondary circuit and the planar transformer of the first aspect, wherein the planar transformer is arranged between the primary circuit and the secondary circuit, and the power conversion circuit is used for converting voltage provided by an external power supply into voltage meeting the charging or power supply standard of the equipment to be charged and charging or supplying power to the equipment to be charged.

In a third aspect, the present application provides an adapter, including the power conversion circuit of the second aspect, where the power conversion circuit is configured to convert a voltage provided by an external power source into a voltage that meets a charging or power supply standard of a device to be charged, and charge or power the device to be charged.

These and other aspects of the present application will be more readily apparent from the following description of the embodiments.

Drawings

FIG. 1A is a schematic diagram of a planar transformer with a shielded winding configuration;

FIG. 1B is a schematic diagram of a planar transformer with a zero-noise matching layer structure;

fig. 2 is a schematic view of an application scenario of a planar transformer;

FIG. 3 is a schematic diagram of a power conversion circuit;

fig. 4A is a schematic structural diagram and a schematic cross-sectional diagram of a planar transformer according to the present application;

FIG. 4B is a schematic cross-sectional view of a planar transformer of the present application;

fig. 5 is a schematic plan view of a first sub-winding layer in the planar transformer of the present application;

fig. 6 is a first schematic plan view illustrating a second sub-winding layer and a fourth sub-winding layer in the planar transformer of the present application;

fig. 7 is a second schematic plan view illustrating a second sub-winding layer and a fourth sub-winding layer in the planar transformer of the present application;

fig. 8 is a first schematic plan view of a planar transformer according to the present application;

fig. 9 is a schematic plan structure view of a transformer substructure in a planar transformer according to the present application;

fig. 10 is a second schematic plan view of the planar transformer of the present application;

fig. 11 is a schematic diagram of a possible arrangement of transformer substructures in a planar transformer.

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their repetitive description will be omitted. The words used in this application to describe positions and orientations are provided by way of example in the drawings and can be changed as desired and are intended to be encompassed by the present application. The drawings of the present application are for illustrating relative positional relationships only and do not represent true scale.

In order to make the objects, technical solutions and advantages of the present application more clear, the present application will be further described in detail with reference to the accompanying drawings. The particular methods of operation in the method embodiments may also be applied to apparatus embodiments or system embodiments. It is to be noted that "at least one" in the description of the present application means one or more, where a plurality means two or more. In view of this, the embodiments of the present invention may also be understood as "a plurality of" as "at least two". "and/or" describes the association relationship of the associated objects, meaning that there may be three relationships, e.g., a and/or B, which may mean: a exists alone, A and B exist simultaneously, and B exists alone. In addition, the character "/" generally indicates that the preceding and following related objects are in an "or" relationship, unless otherwise specified. In addition, it is to be understood that the terms first, second, etc. in the description of the present application are used for distinguishing between the descriptions and not necessarily for describing a sequential or chronological order.

To make the objects, features and advantages of the present application more comprehensible and to facilitate a full understanding of the technical solutions of the embodiments of the present application, first, technical terms or concepts related to the present application are introduced.

(1) A planar transformer: different from the traditional transformer structure, the magnetic core and the winding of the planar transformer are of a planar structure. The magnetic core generally adopts a small-sized E-shaped or square (RM) magnetic core structure, the winding is generally formed by winding a plurality of layers of printed circuit boards in an overlapping manner, and the design has small leakage inductance and distributed capacitance, small height and high working frequency.

(2) Flyback converter (flyback converter): the converter is widely applied to alternating current-to-direct current (AC-DC) and direct current-to-direct current (DC-DC) scenes, is a common low-power adapter converter, and has the advantages of simple structure and low cost. The core components of the power supply comprise a power switch tube, a transformer, a diode and a capacitor. The power switch tube is controlled by pulse width modulation, and high-frequency square wave signals are generated in a primary coil of the transformer by switching off and switching on and then are inductively coupled to a secondary coil of the transformer, so that energy transfer is realized. And stable direct current output is obtained at the output end through the filtering and rectifying action of a diode and a capacitor in a secondary circuit connected with the secondary coil.

(3) Common mode noise: common mode noise, also known as asymmetric noise or line-to-ground noise, which is present in electrical equipment using alternating current, flows in the same direction on the power line and remains in the same phase to ground and returns through the ground line. Common mode noise can be suppressed by using Y-capacitance between the common mode inductance or between the power line and ground.

(4) Differential mode noise: differential mode noise, also known as normal mode, symmetric noise or inter-line noise, exists in ac and neutral lines with a phase difference of 180 °. The current of the differential mode noise flows out along one alternating current line and returns along the other alternating current line, and no differential mode noise current exists in the ground line.

(5) Potential quiescent point: in a circuit network, the voltage potential amplitude at the nodes of the circuit network remains relatively constant during circuit operation without high frequency jumps or oscillations. Such as: the positive pole or the negative pole of the filter capacitor and the network node directly connected with the filter capacitor are potential quiescent points.

(6) Moving point of primary circuit: the primary circuit in the power conversion circuit is a circuit node or a network with voltage jump along with the on and off of the primary switch tube, such as a node of a primary power winding in the primary circuit connected with the switch tube.

(7) Moving point of secondary circuit: the secondary circuit in the power conversion circuit has a voltage jump to a circuit node or network along with the on and off of a secondary rectifier switching tube (including a diode), such as a node of a secondary power winding in the secondary circuit connected with a rectifier diode.

(8) An inductor-inductor-capacitor (LLC) circuit with a resonant inductor-inductor-capacitor combination: the LLC circuit comprises a resonance capacitor, a resonance inductor, a transformer excitation inductor, a transformer and a rectifier. LLC circuits include several types: a half-bridge (asymmetric) LLC and a full-bridge (symmetric) LLC. In terms of the topological structure, the primary side of the half-bridge topological structure is provided with two switching devices, and the primary side of the full-bridge topological structure is provided with four switching devices; secondly, from the voltage waveform of the input end of the resonant cavity network, the voltage waveform of the input end of the half-bridge LLC is a square wave with positive amplitude being bus voltage and negative amplitude being zero, and the voltage waveform of the input end of the full-bridge LLC is a square wave with positive and negative amplitudes being bus voltage values; finally, from the application analysis, the half-bridge type is suitable for small power occasions, while the full-bridge type is suitable for large power occasions.

The application provides a planar transformer, a power conversion circuit and an adapter. The planar transformer provided by the embodiment of the application can be arranged in a power conversion circuit, and the power conversion circuit can be arranged in an adapter.

In particular, the adapter may be applied in scenarios where a device is charged or powered. Referring to fig. 2, fig. 2 shows a possible application scenario of the embodiment of the present application. The application scenario includes an external power supply 20, an adapter 21, and a device to be charged 22. Illustratively, the device to be charged 22 may include, but is not limited to, a server device, a communication device, a cellular phone, a notebook computer, a mobile terminal, and the like. This is not limited by the present application. In general, the adapter 21 may be connected to the external power source 20, and the power conversion circuit included in the adapter 21 may be configured to convert the voltage provided by the external power source 20 into a voltage that conforms to a charging or power supply standard of the device to be charged 22 and to charge or power the device to be charged 223.

The planar transformer provided by the embodiment of the application can reduce noise interference generated by the adapter 21 or generated when a power conversion circuit in the adapter 21 works, and the noise interference generated when the power conversion circuit works can include common-mode noise. The power conversion circuit may also be referred to as an adapter converter. For example, the adapter converter may include, but is not limited to, a flyback converter. Common mode noise is generated by interaction between devices in the adapter circuit, which is mainly referred to as ground.

Fig. 3 shows a schematic diagram of a power conversion circuit, wherein the power conversion circuit 30 generally includes a primary circuit 31, a secondary circuit 32 and a transformer 33. Referring to fig. 3, the primary circuit 31 may include, but is not limited to, a primary switch tube, a primary resonant inductor, a primary resonant capacitor, and the like. Further, the primary circuit 31 may further include a rectifying circuit. The primary switch tube can also be called a primary power switch tube. The secondary circuit 32 typically includes a secondary rectifier tube, a secondary resonant inductor, a secondary resonant capacitor, and the like. The transformer 33 includes a primary winding, a magnetic core, and a secondary winding. The primary winding can be connected with the primary switching tube, the primary resonant inductor and the primary resonant capacitor, and the secondary winding can be connected with the secondary rectifier tube, the secondary resonant inductor and the secondary resonant capacitor.

In general, a node connected to any one of both ends of the primary resonance capacitor is a potential dead point of the primary circuit 31, or a ground node of the primary circuit 31 may be a potential dead point of the primary circuit 31. The node connected to either one of the two ends of the secondary resonance capacitor is a potential quiescent point of the secondary circuit 32, or the ground node of the secondary circuit 32 may be a potential quiescent point of the secondary circuit 32.

The generation of common mode noise and the manner of transmission will be briefly described below with reference to fig. 2 and 3. Specifically, when the power conversion circuit 30 is in operation, the external power supply 20 rectifies and filters the input ac power through the primary circuit 31, and then converts the rectified and filtered ac power into a stable dc power, which is input to the primary winding of the transformer 33. And a primary switching tube connected with the primary winding couples the voltage on the primary winding to the secondary winding by switching the on state and the off state at high frequency. The voltage coupled to the secondary winding, after being rectified and filtered by the secondary circuit 32, outputs a direct current to the device 22 to be charged, which charges or powers the device 22 to be charged. During the operation of the power conversion circuit 30, the primary switch tube in the primary circuit 31 generates a jump voltage V due to the switching between the on state and the off state of the high frequency_pThe secondary rectifier tube can generate jump voltage V due to the switching of the on state and the off state of the high frequency_s. The primary switch tube and the secondary rectifier tube in the above embodiments may be one or more of various types of switch devices such as a relay, a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), a Bipolar Junction Transistor (BJT), an Insulated Gate Bipolar Transistor (IGBT), a silicon carbide (SiC) power tube, and the like, which are not listed in the embodiments of the present application.

The voltage V is stepped due to parasitic capacitance formed between the primary winding and the secondary winding of the transformer 33_pAnd V_sCommon mode noise is generated in the power conversion circuit 30 by the parasitic capacitance formed between the primary winding and the secondary winding. Specifically, the parasitic capacitor includes a parasitic capacitor C formed by the primary winding to the secondary winding_psAnd parasitic capacitance C of the secondary winding to the primary winding_sp. Jump voltage V in primary circuit 31_pThrough C_psGenerating a noise current I to ground_psVoltage jump V in secondary circuit 32_sThrough C_spGenerating a noise current I to ground_sp. The above noise current I_psAnd noise current I_spI.e. common mode noise.

It should be noted that the power conversion circuit 30 in fig. 3 may further include a Line Impedance Stabilization Network (LISN) circuit (not shown in fig. 3). The LISN circuit is a test circuit for detecting the total amount of common mode noise current flowing into the ground when the power conversion circuit 30 works, in other words, it can be considered that the ground current detected by the LISN circuit can be equivalent to the common mode noise generated by the power conversion circuit 30 after the power conversion circuit 30 flows into the LISN circuit.

Referring to fig. 1A and fig. 1B, fig. 1A is a schematic diagram of a planar transformer with a shielding winding structure, and fig. 1B is a schematic diagram of a planar transformer with a zero-noise matching layer structure. In the planar transformer structure shown in fig. 1A, an additional shielding winding is required to be added at the overlapping position of the primary and secondary windings, so that the number of layers of the PCB winding board is increased by at least 2 layers, and thus the loss caused by the increased number of layers is also increased. In the planar transformer structure shown in fig. 1B, it is necessary to ensure that the number of turns of the winding at the overlapping position of the primary winding and the secondary winding is completely the same, so that the design difficulty of the planar transformer is increased, and the loss caused by the design difficulty is also increased.

Due to the continuous improvement of the power density and common mode noise suppression effect of the current adapter, the high power density and high efficiency requirements of the current adapter are still difficult to support by the conventional planar transformer structure for suppressing the common mode noise. It is therefore desirable to design a planar transformer structure that has a better common mode noise rejection than existing structures.

In view of the above problems, embodiments of the present application provide a planar transformer capable of effectively suppressing common mode noise, and a power conversion circuit or an adapter using the planar transformer can have a higher common mode noise suppression performance. In addition, the embodiment of the application also provides a power conversion circuit applying the planar transformer and an adapter applying the power conversion circuit. Specifically, for the power conversion circuit and the adapter, reference may be made to descriptions in fig. 2 and fig. 3, which are not described herein again.

The planar transformer provided in the embodiment of the application mainly comprises a magnetic core and a winding coil, wherein the winding coil can be formed by firing a traditional copper (high-conductivity material) wire or etching a plurality of layers of PCBs. The transformer obtained by etching the multilayer PCB is flattened compared with the transformer obtained by the traditional winding, so the transformer is called a planar transformer. Fig. 4A shows a schematic structural diagram and a schematic cross-sectional diagram of a planar transformer according to an embodiment of the present application, and referring to fig. 4A, the planar transformer 40 includes N groups of transformer substructures 41 (one group is shown in fig. 4A), each of the N groups of transformer substructures 41 includes a first magnetic core 42, a second magnetic core 43 and a PCB winding board 44, and N is a positive integer.

The PCB winding board 44 includes: a first composite winding layer 441 and a second composite winding layer 442, wherein the first composite winding layer 441 is wound on the first magnetic core 42, and the second composite winding layer 442 is wound on the second magnetic core 43.

The first composite winding layer 441 includes at least one set of first sub-winding layers and at least one second sub-winding layer 46; wherein each group of first sub-winding layers comprises two adjacent layers of first sub-winding layers 45; at least one second sub-winding layer 46 is arranged between two first sub-winding layers 45 in each set of first sub-winding layers.

The second composite winding layer 442 includes at least one third sub-winding layer and at least one fourth sub-winding layer 48; wherein each group of the third sub-winding layers includes two adjacent layers of the third sub-winding layers 47; at least one fourth sub-winding layer 48 is arranged between two third sub-winding layers 47 in each set of second composite winding layers.

The total number of the at least two first sub-winding layers 45 is the same as the total number of the at least two third sub-winding layers 47; the number of winding turns of each layer of the first sub-winding layer 45 is the same as that of each layer of the third sub-winding layer 47; the total number of the at least one second sub-winding layer 46 is the same as the total number of the at least one fourth sub-winding layer 48; each layer of the second sub-winding layer 46 and each layer of the fourth sub-winding layer 48 are wound for the same number of turns in the opposite direction.

In practical applications, due to the characteristics and principles of the winding, the number of turns of the coil per sub-winding layer may be an integer or not, for example, the number of turns of the coil may be 2.5 turns, 3.8 turns, and the like, but the embodiment of the present application is not limited thereto.

Wherein the PCB winding board 44 in the planar transformer 40 is disposed on the multi-layer PCB assembly. The multilayer PCB assembly may be a printed circuit board based on an epoxy fiberglass cloth substrate, a composite substrate, a ceramic-based substrate, a metal-based substrate, or a thermoplastic substrate.

In the embodiment of the present application, the material of the first core 42 and the second core 43 is not limited. The first core 42 and the second core 43 may have EE, EI, or RM structures. The winding posts of the first and

second cores

42 and 43 may be provided with windings formed of a multilayer circuit board.

Specifically, a schematic of a cross-section of the PCB winding board 44 is shown below fig. 4A. As an example, the cross-section may lie in a ZR plane formed by a Z-axis and an R-axis, wherein the Z-axis is perpendicular to a plane (may be referred to as a first plane) in which the surface of the PCB winding board 44 lies, and the R-axis is perpendicular to the Z-axis and directed toward the center of the PCB winding board 44. At least two first sub-winding layers 45 and at least one second sub-winding layer 46 of the first composite winding layer 441 and at least one fourth sub-winding layer 48 of the second composite winding layer 442 including at least two third sub-winding layers 47 are located in the above cross section.

With continued reference to fig. 4A, the coils disposed on each of the first sub-winding layers 45 and the second sub-winding layers 46 in the first composite winding layer 441 may be connected in series with each other.

When the first sub-winding layer 45 is connected to the primary circuit 31 in the power conversion circuit 30 after being connected in series with each other, the second sub-winding layer 46 is connected to the secondary circuit 32 in the power conversion circuit 30 after being connected in series with each other. If the first sub-winding layer 45 is connected to the secondary circuit 32 of the power conversion circuit 30 after being connected in series, the second sub-winding layer is connected in seriesThe bank layer 46 is connected to the primary circuit 31 in the power conversion circuit 30. The sub-winding connected to the primary circuit 31 in the power conversion circuit 30 may be referred to as a primary side/primary sub-winding layer, and hereinafter may be denoted by P, or may be denoted by P₁、P₂…P_nAnd (4) showing. The sub-winding connected to the secondary circuit 32 in the power conversion circuit 30 may be referred to as a secondary/secondary sub-winding layer, and hereinafter, may be denoted by S, or may be denoted by S₁、S₂…S_nAnd (4) showing.

The coils disposed on each of the third sub-winding layers 47 in the second composite winding layers 442 may be connected in series with each other, and the coils disposed on each of the fourth sub-winding layers 48 in the second composite winding layers 442 may be connected in series with each other.

When the third sub-winding layer 47 is connected to the primary circuit 31 in the power conversion circuit 30 after being connected in series with each other, the fourth sub-winding layer 48 is connected to the secondary circuit 32 in the power conversion circuit 30 after being connected in series with each other. When the third sub-winding layer 47 is connected to the secondary circuit 32 in the power conversion circuit 30 after being connected in series with each other, the fourth sub-winding layer 48 is connected to the primary circuit 31 in the power conversion circuit 30 after being connected in series with each other. Among them, the sub-winding connected to the primary circuit 31 in the power conversion circuit 30 may be referred to as a primary side/primary sub-winding layer. The sub-windings connected to the secondary circuit 32 in the power conversion circuit 30 may be referred to as secondary side/secondary sub-winding layers.

Referring to fig. 4B as a possible implementation, fig. 4B shows a schematic cross-sectional view of a planar transformer according to an embodiment of the present application; the first composite winding layer 441 includes at least one set of first composite winding laminations 4411 therein, each set of first composite winding laminations 4411 of the at least one set of first composite winding laminations 4411 including: two adjacent layers of the first sub-winding layer 45 and at least one layer of the second sub-winding layer 46 disposed therebetween.

The second composite winding layer 442 includes at least one second composite winding layer 4421, and each of the at least one second composite winding layers 4421 includes: two adjacent layers of the third sub-winding layer 47 and at least one layer of the fourth sub-winding layer 48 disposed therebetween.

For example, when the first composite winding layer 441 includes only two first sub-winding layers 45 and one second sub-winding layer 45, if the first sub-winding layer 45 is connected to the secondary circuit 32 in the power conversion circuit 30 and the second sub-winding layer 46 is connected to the primary circuit 31 in the power conversion circuit 30, the structure of the first composite winding layer 441 is the first sub-winding layer 45-the second sub-winding layer 46-the first sub-winding layer 45 (i.e., P-S-P structure); when the first sub-winding layer 45 is connected to the primary circuit 31 in the power conversion circuit 30 and the first sub-winding layer 45 is connected to the secondary circuit 32 in the power conversion circuit 30, the structure of the first composite winding layer 441 is the first sub-winding layer 45-the second sub-winding layer 46-the first sub-winding layer 45 (i.e., S-P-S structure).

When the first composite winding layer 441 includes at least two first sub-winding layers 45 and at least one second sub-winding layer 45, if the at least two first sub-winding layers 45 are connected to the secondary circuit 32 in the power conversion circuit 30 after being connected in series, and the at least one second sub-winding layer 46 is connected to the primary circuit 31 in the power conversion circuit 30 after being connected in series, the structure of the first composite winding layer 441 is the first sub-winding layer 45-the second sub-winding layer 46-the first sub-winding layer 45 … -the first sub-winding layer 45-the second sub-winding layer 46-the first sub-winding layer 45 (i.e., P-S-P … P-S-P structure). If the at least two first sub-winding layers 45 are connected to the primary circuit 31 of the power conversion circuit 30 after being connected in series, and the at least one second sub-winding layer 46 is connected to the secondary circuit 32 of the power conversion circuit 30 after being connected in series, the first composite winding layer 441 has a structure of first sub-winding layer 45-second sub-winding layer 46-first sub-winding layer 45 … -first sub-winding layer 45-second sub-winding layer 46-first sub-winding layer 45 (i.e., S-P-S … S-P-S).

When the second composite winding layer 442 includes only two third sub-winding layers 47 and one fourth sub-winding layer 48, if the third sub-winding layer 47 is connected to the secondary circuit 32 in the power conversion circuit 30 and the fourth sub-winding layer 48 is connected to the primary circuit 31 in the power conversion circuit 30, the structure of the second composite winding layer 442 is the third sub-winding layer 47-fourth sub-winding layer 48-third sub-winding layer 47 (i.e., P-S-P structure); when the third sub-winding layer 47 is connected to the primary circuit 31 in the power conversion circuit 30 and the third sub-winding layer 47 is connected to the secondary circuit 32 in the power conversion circuit 30, the structure of the second composite winding layer 442 is the third sub-winding layer 47-the fourth sub-winding layer 48-the third sub-winding layer 47 (i.e., S-P-S structure).

When the second composite winding layer 442 includes at least two third sub-winding layers 47 and at least one fourth sub-winding layer 48, if the at least two third sub-winding layers 47 are connected to the secondary circuit 32 in the power conversion circuit 30 after being connected in series, and the at least one fourth sub-winding layer 48 is connected to the primary circuit 31 in the power conversion circuit 30 after being connected in series, the structure of the second composite winding layer 442 is the third sub-winding layer 47-fourth sub-winding layer 48-third sub-winding layer 47 …, third sub-winding layer 47-fourth sub-winding layer 48-third sub-winding layer 47 (i.e., P-S-P … P-S-P structure). If the at least two third sub-winding layers 47 are connected to the primary circuit 31 of the power conversion circuit 30 after being connected in series, and the at least one fourth sub-winding layer 48 is connected to the secondary circuit 32 of the power conversion circuit 30 after being connected in series, the structure of the second composite winding layer 442 is that the third sub-winding layer 47-the fourth sub-winding layer 48-the third sub-winding layer 45 … -the third sub-winding layer 47-the fourth sub-winding layer 48-the third sub-winding layer 47 (i.e., S-P-S … S-P-S).

Because the secondary/secondary sub-winding layers are arranged on the two sides of the primary/secondary sub-winding layer, or the primary/secondary sub-winding layers are arranged on the secondary/secondary sub-winding layers, the first composite winding layer 441 and the second composite winding layer 442 have smaller leakage inductance, so that the loss of the planar transformer 40 can be reduced, wherein the leakage inductance refers to the magnetic flux leaked out of the planar transformer 40.

Referring to fig. 5, fig. 5 illustrates a schematic plan view of a first sub-winding layer in a planar transformer according to an embodiment of the present application, where the first sub-winding layer 45 in fig. 5 may be any one of the at least two first sub-winding layers 45 in the first composite winding layer 441. Further, those skilled in the art can flexibly set the number of layers and the number of turns of the first sub-winding layer 45 according to actual engineering requirements, so as to cancel the common mode noise in the planar transformer. In addition, the planar structure of the third sub-winding layer 47 in the planar transformer 40 is based on the same concept as the first sub-winding layer 45, and is not repeatedly shown here.

As a possible implementation, each of the first sub-winding layers 45 of the at least two layers of first sub-winding layers 45 is connected in series to constitute the first winding, and each of the third sub-winding layers of the at least two layers of third sub-winding layers is connected in series to constitute the third winding. Specifically, each first sub-winding layer 45 in the at least two first sub-winding layers 45 may be connected in series through a via hole on each first sub-winding layer 45 (not shown in fig. 5), and each third sub-winding layer 47 in the at least two first sub-winding layers 47 is connected in series through a via hole on each first sub-winding layer 47, and specifically, a person skilled in the art may flexibly set the number of via holes and the positions of the via holes according to actual engineering needs, so as to better achieve cancellation of noise in the planar transformer.

Referring to fig. 6, fig. 6 illustrates a first schematic plan view of a second sub-winding layer and a fourth sub-winding layer in the planar transformer according to the embodiment of the present invention, where the second sub-winding layer 46 in fig. 6 may be any one of the at least one first sub-winding layer 45 in the first composite winding layer 441. The fourth sub-winding layer 48 in fig. 6 may be any one of the at least one fourth sub-winding layer 48 in the second composite winding layer 442. Here, the second sub-winding layer 46 may be connected in series with the fourth sub-winding layer 48, and as shown in fig. 6, when the second sub-winding layer 46 and the fourth sub-winding layer 48 are printed, the second sub-winding layer 46 and the fourth sub-winding layer 48 may be directly printed on the same PCB, so that the second sub-winding layer 46 and the fourth sub-winding layer 48 are connected in series. In addition, the second sub-winding layer 46 and the fourth sub-winding layer 48 may be connected in series through vias (not shown in fig. 6), and those skilled in the art should understand that the details are not described herein.

Referring to fig. 7, fig. 7 is a schematic plan view illustrating a second sub-winding layer and a fourth sub-winding layer in the planar transformer according to the embodiment of the present invention. As can be seen from fig. 7, the skilled person can flexibly set the number of turns of the second sub-winding layer 46 and the fourth sub-winding layer 48 according to the actual engineering requirement to achieve the cancellation of the noise in the planar transformer.

As a possible implementation, each of the second sub-winding layers 46 of the at least one layer is connected in series to form the second winding, and each of the fourth sub-winding layers of the at least one layer is connected in series to form the fourth winding. Specifically, each first sub-winding layer 46 in the at least one second sub-winding layer 46 may be connected in series through a via hole on each first sub-winding layer 46 (not shown in fig. 6 and 7), and each third sub-winding layer 47 in the at least one first sub-winding layer 47 is connected in series through a via hole on each third sub-winding layer 47, and specifically, a person skilled in the art may flexibly set the number of via holes and the positions of the via holes according to actual engineering needs, so as to better achieve cancellation of noise in the planar transformer.

As a possible embodiment, the potential of the primary circuit 31 of the power conversion circuit 30 is connected to the second winding end and the fourth winding end, and the potential of the secondary circuit 32 of the power conversion circuit 30 is connected to the first winding end and the third winding end.

The second winding end and the fourth winding end may be connected to the primary switching tube of the primary circuit 31, the second winding end may correspond to an end of the last coil of the second winding, and the fourth winding end may correspond to an end of the last coil of the fourth winding. The first winding end and the third winding end may be connected to a secondary rectifier of the secondary circuit 32, the first winding end may correspond to an end of the last coil of the first winding, and the third winding end may correspond to an end of the last coil of the third winding.

Specifically, after the potential dead point of the primary circuit 31 of the power conversion circuit 30 is connected to one end of the second winding and one end of the fourth winding, and the potential dead point of the secondary circuit of the power conversion circuit is connected to one end of the first winding and one end of the third winding: the second winding and the fourth winding are connected in series to form a primary side/primary winding, and the first winding and the third winding are connected in series to form a secondary side/secondary winding. The potential quiescent point of the primary circuit 31 of the power conversion circuit 30 may be a node where the primary side/primary winding is connected to the primary filter capacitor. Alternatively, the potential dead point of the primary circuit 31 of the power conversion circuit 30 may be a ground node of the primary circuit 31. The potential dead point of the secondary circuit 32 of the power conversion circuit 30 may be a node where the secondary side/secondary winding is connected to the secondary filter capacitor. Alternatively, the potential dead point of the secondary circuit 32 of the power supply conversion circuit 30 may be a ground node of the secondary circuit 32.

After the conditions that the displacement currents on the primary side/primary winding and the secondary side/secondary winding are the same in magnitude and opposite in direction are met, the common mode noise can be eliminated. The embodiments of the present application may be applied to a symmetric LLC circuit, for example, in the symmetric LLC circuit, the resonant inductor and the resonant capacitor are divided into two symmetrically disposed on two sides of the planar transformer. Or in other words, the embodiment of the present application can be applied to any scene where a quiet point symmetric topology exists.

Through the symmetrical arrangement design of the planar transformer 40, the displacement current on the first magnetic core 42 and the displacement current on the second magnetic core 43 on the planar transformer 40 can be ensured to be mutually offset, the windings with the same potential (dv/dt) distribution of the primary side/primary winding and the secondary side/secondary winding are reasonably staggered, and 0 common-mode noise can be approximately realized, so that the common-mode noise of the planar transformer is reduced, and meanwhile, the staggered design of the windings can also bring about the reduction of the winding loss.

Specifically, the common mode noise mainly includes two noise current sources, one is the jump voltage V in the primary circuit 31_pThrough C_psGenerating a noise current I to ground_psAnd the other is the jump voltage V in the secondary circuit 32_sThrough C_spGenerating a noise current I to ground_sp. The above noise current I_psNoise and harmingAcoustic current I_spI.e. common mode noise.

For example, referring to fig. 8, fig. 8 is a schematic plan view of a planar transformer, assuming that the end point of the first sub-winding layer 45 is c1-d1, the end point of the second sub-winding layer 46(1) -46(2) is b1-a1, the second sub-winding layer 46(1) is the first turn of the second sub-winding layer 46, the second sub-winding layer 46(2) is the second turn of the second sub-winding layer 46, the end point of the third sub-winding layer 47 is c2-d2, the end point of the fourth sub-winding layer 48(1) -48(2) is b2-a2, the fourth sub-winding layer 48(1) is the first turn of the second sub-winding layer 48, and the second sub-winding layer 48(2) is the second turn of the second sub-winding layer 48. Where point a is the primary side/primary side high voltage trip point end point, and point c is the secondary side/secondary side high voltage trip point end point, I between the first sub-winding layer 45 and the second sub-winding layer 46(1) -46(2)_CM1The magnitude of the displacement current is:

and I between the third sub-winding layer 47 and the fourth sub-winding layer 48(1) -48(2)_CM2The magnitude of the displacement current is:

therefore, if it is ensured that the displacement currents on the primary/primary winding and the secondary/secondary winding are the same in magnitude and opposite in direction, i.e., I is ensured_CM1＝I_CM2。

If it can be determined that the following two conditions are satisfied, I can be guaranteed_CM1＝I_CM2：

(1) The voltage jump points of the primary side/primary side high voltage jump point end point and the secondary side/secondary side high voltage jump point end point are consistent in size and opposite in direction. Namely, the following conditions are satisfied:

and

(2) the parasitic capacitances formed by adjacent sub-winding layers are the same in magnitude. Namely, the following conditions are satisfied: c_a1c1＝C_a2c2、C_a1d1＝C_a2d2、C_b1c1＝C_b2c2And C_b1d1＝C_b2d2。

Therefore, based on the condition (1), as a possible implementation manner, the difference between the voltage passing through the second winding and the set voltage is a first voltage, and the difference between the voltage passing through the fourth winding and the set voltage is a second voltage, and the first voltage and the second voltage have the same magnitude and opposite directions. The set voltage may be 0, or may be a value with another magnitude, and those skilled in the art may determine the magnitude according to the magnitude of the quiescent point voltage of the primary circuit 31 in the power conversion circuit 30, for example, the quiescent point voltage may be equal to half of the bus voltage.

Based on the above condition (2), as a possible implementation, each second sub-winding layer 46 of the at least one second sub-winding layer 46 forms the same magnitude of first parasitic capacitance with the adjacent first sub-winding layer 45; each fourth sub-winding layer 48 of the at least one fourth sub-winding layer 48 forms a second parasitic capacitance with the adjacent third sub-winding layer 47 with the same magnitude; the first parasitic capacitance is the same as the second parasitic capacitance in size.

In order to reduce the difficulty of manufacturing the planar capacitor, as a possible implementation manner, each second sub-winding layer 46 of the at least one second sub-winding layer 46 and the adjacent first sub-winding layer 45 form a first parasitic capacitance magnitude within a set capacitance magnitude interval; each fourth sub-winding layer 48 of the at least one fourth sub-winding layer 48 is within a set capacitance size interval formed with the adjacent third sub-winding layer 47.

It should be noted that, in the embodiment of the present application, two winding layers are adjacent to each other, which means that there is no other winding layer between the two winding layers. For example, each second sub-winding layer 46 of the at least one second sub-winding layer 46 and the adjacent first sub-winding layer 45 means that there are no other winding layers between the second sub-winding layer 46 and the first sub-winding layer 45.

The planar transformer provided by the embodiment of the application is based on the principle of symmetrical cancellation, and the noise index of the planar transformer is far superior to that of the schemes shown in fig. 1A and 1B. Illustratively, when the switching frequency of the switching device in the power conversion circuit 30 is 500KHz, the common mode noise is reduced by 22dB compared with the zero-noise matching layer scheme of fig. 1B, and the common mode noise is also significantly reduced at other switching frequencies, and the loss of the planar transformer provided in the embodiment of the present application is reduced by about 20% compared with the loss of the existing planar transformer.

The number of the transformer substructures 41 in the planar transformer 40 may be N (e.g., one, two, or more), which is not limited in the embodiment of the present application. When there is one transformer substructure 41 in the planar transformer 40, as a possible implementation, referring to fig. 9, fig. 9 is a schematic plan structure diagram of a transformer substructure in a planar transformer; the first magnetic core 42 and the second magnetic core 43 are arranged in a first direction, which is parallel to the PCB winding board. Specifically, the first magnetic core 42 and the second magnetic core 43 arranged along the first direction together form each of the N sets of transformer substructures 41.

When the number of the transformer substructures 41 in the planar transformer 40 is greater than or equal to two, as a possible implementation, refer to fig. 10, where fig. 10 is a schematic plan structure diagram of a planar transformer; each of the N groups of transformer substructures 41 is arranged along the first direction and/or the second direction, and the second direction is parallel to the PCB winding board 44 and perpendicular to the first direction.

Optionally, the arrangement of each transformer substructure of the N groups of transformer substructures 41 in the embodiment of the present application is not limited to the arrangement defined in the above embodiment, and referring to fig. 11, fig. 11 is a possible arrangement of transformer substructures in several planar transformers. In fig. 11, the planar transformer 40 includes 4 transformer substructures 41 as an example, and all of (a), (B), (C), and (D) in fig. 11 can be possible arrangements of the transformer substructures 41 in the planar transformer 40, but the present application is not limited to the above arrangement. In other words, the planar transformer 40 can maintain a good common mode noise suppression effect while ensuring that the transformer substructure 41 in the planar transformer 40 can have at least one symmetry axis or be symmetrical in a symmetrical manner.

By utilizing the planar transformer structure provided by the embodiment of the application, a symmetrical cancellation mode is adopted, so that the common mode noise is obviously reduced on the premise of not increasing the volume compared with the prior art, at least more than two shielding layers can be reduced compared with the existing scheme of increasing the shielding winding, the winding layers of the planar transformer are simpler to manufacture, and the loss is reduced; compared with a zero-noise matching layer scheme, the number of turns of adjacent layers of the original secondary side does not need to be consistent, so that the design of the winding is simple, and the EMI suffered by the circuit is reduced remarkably.

The embodiment of the present application further provides a power conversion circuit, which includes: the planar transformer 40 is arranged between the primary circuit and the secondary circuit, and the power conversion circuit is used for converting a voltage provided by an external power supply into a voltage meeting a charging or power supply standard of a device to be charged and charging or supplying power to the device to be charged.

Further, an embodiment of the present application further provides an adapter, where the adapter includes the power conversion circuit described in the foregoing embodiment.

As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.

The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.

These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.

It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the spirit and scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.

Claims

1. A planar transformer is characterized by comprising N groups of transformer substructures, wherein each group of transformer substructures in the N groups of transformer substructures comprises a first magnetic core, a second magnetic core and a Printed Circuit Board (PCB) winding board, and N is a positive integer;

the PCB winding board includes: the first composite winding layer is wound on the first magnetic core, and the second composite winding layer is wound on the second magnetic core;

the first composite winding layer comprises at least one group of first sub-winding layers and at least one layer of second sub-winding layers; each group of first sub-winding layers comprises two adjacent layers of first sub-winding layers; at least one second sub-winding layer is arranged between two first sub-winding layers in each group of first composite winding layers;

the second composite winding layer comprises at least one group of third sub-winding layers and at least one layer of fourth sub-winding layers; each group of third sub-winding layers comprises two adjacent layers of third sub-winding layers; at least one fourth sub-winding layer is arranged between two third sub-winding layers in each group of second composite winding layers;

the total number of the at least two first sub-winding layers is the same as that of the at least two third sub-winding layers; the number of winding turns of each layer of the first sub-winding layer is the same as that of the third sub-winding layer; the total number of the at least one second sub-winding layer is the same as that of the at least one fourth sub-winding layer; and the number of winding turns of each layer of the second sub-winding layer is the same as that of the fourth sub-winding layer, and the winding directions are opposite.

2. The planar transformer according to claim 1, wherein each of the first sub-winding layers of the first at least two layers is connected in series to form the first winding, each of the second sub-winding layers of the second at least one layer is connected in series to form the second winding, each of the third sub-winding layers of the third at least two layers is connected in series to form the third winding, and each of the fourth sub-winding layers of the fourth at least one layer is connected in series to form the fourth winding.

3. The planar transformer according to claim 2, wherein the first winding is connected in series with the third winding; the second winding is connected in series with the fourth winding.

4. The planar transformer according to claim 2 or 3, wherein a potential dead point of a primary circuit of a power conversion circuit is connected to one end of the second winding and one end of the fourth winding, a potential dead point of a secondary circuit of the power conversion circuit is connected to one end of the first winding and one end of the third winding, and the power conversion circuit is configured to convert a voltage provided by an external power source into a voltage meeting a charging or power supply standard of a device to be charged and charge or supply the device to be charged.

5. The planar transformer of claim 4, wherein the difference between the voltage flowing through the second winding and the set voltage is a first voltage, and the difference between the voltage flowing through the fourth winding and the set voltage is a second voltage, and the first voltage and the second voltage are the same in magnitude and opposite in direction.

6. The planar transformer according to claim 2 or 3, wherein a potential dead point of a primary circuit of a power conversion circuit is connected to one end of the first winding and one end of the third winding, a potential dead point of a secondary circuit of the power conversion circuit is connected to one end of the second winding and one end of the fourth winding, and the power conversion circuit is configured to convert a voltage provided by an external power source into a voltage meeting a charging or power supply standard of a device to be charged and charge or supply the device to be charged.

7. The planar transformer of claim 6, wherein the difference between the voltage across the first winding and the set voltage is a third voltage, and the difference between the voltage across the third winding and the set voltage is a fourth voltage, and the third voltage and the fourth voltage are the same in magnitude and opposite in direction.

8. The planar transformer according to any one of claims 1 to 7, wherein said first core and said second core are arranged along a first direction, said first direction being parallel to said PCB winding board.

9. The planar transformer according to claim 8, wherein each of the N sets of transformer substructures is arranged along the first direction and/or the second direction; the second direction is parallel to the PCB winding board and perpendicular to the first direction.

10. The planar transformer according to any of claims 1 to 9, wherein the first composite winding layer comprises at least one set of first composite winding layers, each set of the at least one set of first composite winding layers comprising: two adjacent layers of first sub-winding layers and at least one layer of second sub-winding layers arranged between the two adjacent layers;

the second composite winding layer comprises at least one group of second composite winding layers, and each group of the at least one group of second composite winding layers comprises: two adjacent layers of the third sub-winding layer and at least one layer of the fourth sub-winding layer arranged between the two adjacent layers.

11. The planar transformer according to any one of claims 1 to 10, wherein each of the at least one second sub-winding layer has the same magnitude of the first parasitic capacitance as the adjacent first sub-winding layer; each fourth sub-winding layer in the at least one fourth sub-winding layer has the same size as the second parasitic capacitance formed by the adjacent third sub-winding layer; the first parasitic capacitance is the same as the second parasitic capacitance in size.

12. The planar transformer according to any of claims 1 to 11, wherein said first and second magnetic cores are of EE-, EI-or RM-type construction.

13. A power conversion circuit, comprising: a primary circuit, a secondary circuit and a planar transformer as claimed in any one of claims 1 to 12, the planar transformer being arranged between the primary circuit and the secondary circuit, the power conversion circuit being configured to convert a voltage provided by an external power source into a voltage that meets a charging or power supply standard of a device to be charged and to charge or power the device to be charged.

14. An adapter, characterized by comprising the power conversion circuit according to claim 13, which is used for converting the voltage provided by the external power supply into the voltage conforming to the charging or power supply standard of the device to be charged and charging or supplying power to the device to be charged.