CN109616301B

CN109616301B - Low common mode noise transformer

Info

Publication number: CN109616301B
Application number: CN201811654710.0A
Authority: CN
Inventors: 陈成辉; 刘志成
Original assignee: Tonly Electronics Holdings Ltd
Current assignee: Tonly Electronics Holdings Ltd
Priority date: 2018-12-29
Filing date: 2018-12-29
Publication date: 2022-06-10
Anticipated expiration: 2038-12-29
Also published as: CN109616301A

Abstract

The invention discloses a transformer with low common mode noise, which comprises a magnetic core, a first primary winding, a first eliminating winding, a secondary winding and an auxiliary eliminating winding, wherein the first primary winding, the first eliminating winding and the secondary winding are sequentially wound on the magnetic core, the auxiliary eliminating winding is wound on any one of a winding post formed after the first primary winding is wound, a winding post formed after the first eliminating winding is wound, a winding post formed after the secondary winding is wound and the magnetic core, the first primary winding is provided with a primary dead point, a first end of the first eliminating winding is suspended, a second end of the first eliminating winding is connected with a first end of the auxiliary eliminating winding, and a second end of the auxiliary eliminating winding is connected with the primary dead point. Therefore, the technical problem that the winding of the low common mode noise transformer elimination layer needs to be debugged for many times in the prior art is solved.

Description

Low common mode noise transformer

Technical Field

The invention relates to the technical field of transformers, in particular to a low common mode noise transformer.

Background

Common mode noise of the low common mode noise transformer is usually a source of EMI (EMI, conduction interference ce (interference), radiation interference re (radiation interference), and harmonic) interference of the switching power supply, and in order to eliminate the common mode noise, an elimination winding is usually added when the low common mode noise transformer is wound, as shown in fig. 1 and 3, where E1 and E2 represent an elimination layer, and the first elimination winding E1 and the second elimination winding E2 shown in fig. 1 and 3 may be a winding layer or a copper skin layer. Since the elimination layer is not fully wound or the copper sheet width is smaller than the slot width, so that the primary and secondary windings form a parasitic capacitance Cps through the gap of the layer, the elimination layer is usually connected to the primary side, and forms a first interlayer capacitance Ces as shown in fig. 2 or a second interlayer capacitance Ces1 and a third interlayer capacitance Ces2 with the secondary winding as shown in fig. 4.

In the sequential winding method of fig. 1, the cross-sectional structure is as shown in fig. 2, and the voltage difference Δ Vps between the primary winding Np and the secondary winding Ns forms a common mode current Ips from the primary to the secondary direction on the interlayer capacitor Cps, which includes:

Ips＝Qps/t＝Cps*ΔVps/t

the voltage difference Δ Ves between the secondary winding Ns and the first cancel winding E1 forms a common mode current Ise in the primary direction from the secondary on the first interlayer capacitor Ces, and includes:

Ise＝Qse/t＝Ces*ΔVes/t

when Ips is equal to Ise, the transformer structure with low common mode noise achieves the purpose of eliminating common mode noise; therefore, we adjust Δ Ves by adjusting the number of turns of the erasing layer, and adjust Cps and Ces by adjusting the winding width or the copper sheet width of the erasing layer, and finally, Cps Δ Vps becomes Ces Δ Ves, thereby achieving Ips ═ Ise.

For the sandwich winding method of the low common mode noise transformer in fig. 3, the cross-sectional structure is as shown in fig. 4, the principle is the same, and the number of turns and the width of the eliminating layer are adjusted to make:

Cps*ΔVps＝Ces1*ΔVes1+Ces2*ΔVes2，

thereby achieving Ips-Ise

During practical application, because in order to reach the demand that reduces or even eliminate common mode noise, need adjust the number of turns or the width of eliminating the layer, because the influence of the miscellaneous parameter is scattered to actual coiling elasticity, device moreover, the number of turns and the width of eliminating the layer can't eliminate common mode noise through calculating accurate realization, consequently need adjustment and the test that does not stop among the designer's actual debugging just can reach best effect, waste time and energy very much.

Disclosure of Invention

The invention mainly aims to provide a low common mode noise transformer, and aims to solve the technical problem that the winding of a low common mode noise transformer elimination layer needs to be debugged for many times in the prior art.

In order to achieve the above object, the present invention provides a transformer with low common mode noise, which includes a magnetic core, a first primary winding, a first canceling winding, a secondary winding and an auxiliary canceling winding, wherein the first primary winding, the first canceling winding and the secondary winding are sequentially wound on the magnetic core, the auxiliary canceling winding is wound on any one of a winding post formed after the first primary winding is wound, a winding post formed after the first canceling winding is wound, a winding post formed after the secondary winding is wound, and the magnetic core, and the first primary winding has a primary quiescent point;

the first end of the first elimination winding is suspended, the second end of the first elimination winding is connected with the first end of the auxiliary elimination winding, and the second end of the auxiliary elimination winding is connected with the primary dead point.

Optionally, the first cancellation winding is a single layer winding.

Optionally, the magnetic core includes two vertical walls and a center pillar connecting the two vertical walls, a winding slot is formed between the two vertical walls and the center pillar, and the first primary winding, the first cancellation winding and the secondary winding are sequentially wound on the center pillar.

Optionally, the first cancellation winding is wound along the magnetic core counterclockwise and is fully wound by one layer;

the auxiliary eliminating winding is wound according to the following winding mode:

determining the number of coils of the secondary winding QNs and the number of coils of the first cancel winding QE 1;

calculating the number QNc of the auxiliary eliminating windings according to the number QNs of the secondary windings, the number QE1 of the first eliminating windings and a calculation formula QNc which is (QNs-QE 1)/2;

when the obtained number QNc of the auxiliary eliminating winding is calculated to be less than 0, the auxiliary eliminating winding is wound from a primary static point and is connected to the winding starting point of the first eliminating winding after being wound QNc circles clockwise along the magnetic core;

when the calculated coil number QNc >0 of the auxiliary eliminating winding, the auxiliary eliminating winding starts from a primary dead point and is wound along the magnetic core in a counterclockwise direction for QNc turns and then is connected to the winding start point of the first eliminating winding.

In order to achieve the above object, the present invention further provides a low common mode noise transformer, which includes a magnetic core, a first primary winding, a first cancellation winding, a secondary winding, a second primary winding, a second cancellation winding, and an auxiliary cancellation winding, wherein the first primary winding has a primary quiescent point;

The first primary winding, the first elimination winding, the secondary winding, the second elimination winding and the second primary winding are sequentially wound on the magnetic core in a layered manner, the auxiliary elimination winding is wound on any one of a winding post formed after the first primary winding is wound, a winding post formed after the first elimination winding is wound, a winding post formed after the secondary winding is wound, a winding post formed after the second primary winding is wound, a winding post formed after the second elimination winding is wound and the magnetic core;

the first end of the first eliminating winding and the first end of the second eliminating winding are respectively suspended, the second end of the first eliminating winding and the second end of the second eliminating winding are respectively connected with the first end of the auxiliary eliminating winding, and the second end of the auxiliary eliminating winding is connected with the primary dead point.

Optionally, the first cancel winding and the second cancel winding are single layer windings.

Optionally, the magnetic core includes two vertical walls and a central pillar connecting the two vertical walls, a winding slot is formed between the two vertical walls and the central pillar, and the first primary winding, the first cancel winding, the secondary winding, the second cancel winding and the second primary winding are sequentially wound on the central pillar in a layer-by-layer manner.

Optionally, the first elimination winding and the second elimination winding are wound counterclockwise from a winding starting point and are fully wound by one layer;

determining a number of coils QNs for the secondary winding and a number of coils QE1 for the first cancel winding;

calculating the number QNc of the auxiliary eliminating winding according to the number QNs of secondary winding coils, the number QE1 of the first eliminating winding coils and the calculation formula QNc which is (QNs-QE 1)/2;

when the number of the coils of the auxiliary eliminating winding is QNc <0, the auxiliary eliminating winding is wound from a primary static point, and after the auxiliary eliminating winding is wound for QNc circles clockwise, the auxiliary eliminating winding is connected to the winding starting point of the first eliminating winding and the winding starting point of the second eliminating winding;

when the number of the coils QNc of the auxiliary eliminating winding is larger than 0, the auxiliary eliminating winding is wound from a primary static point, and is connected to the winding starting point of the first eliminating winding and the winding starting point of the second eliminating winding after being wound for QNc circles anticlockwise.

determining a number of coils from a secondary winding QNs and the second cancel winding QE 2;

Calculating the number QNc of the auxiliary cancellation winding according to the number QNs of secondary winding coils, the number QE2 of the second cancellation winding coils and a calculation formula QNc which is (QNs-QE 2)/2;

when the number of the auxiliary eliminating winding is QNc <0, the auxiliary eliminating winding is wound from a primary static point, and after the auxiliary eliminating winding is wound for QNc circles clockwise, the auxiliary eliminating winding is connected to the winding starting point of the first eliminating winding and the winding starting point of the second eliminating winding;

The invention provides a transformer with low common mode noise, which comprises a magnetic core, a first primary winding, a secondary winding, a first eliminating winding and an auxiliary eliminating winding, wherein the first primary winding, the first eliminating winding and the secondary winding are sequentially wound on the magnetic core, the auxiliary eliminating winding is wound on any one of a winding column formed after the first primary winding is wound, a winding column formed after the first eliminating winding is wound, a winding column formed after the secondary winding is wound and the magnetic core, and the first primary winding is provided with a primary dead point. The first end of the first elimination winding is suspended, the second end of the first elimination winding is connected with the first end of the auxiliary elimination winding, and the second end of the auxiliary elimination winding is connected with the primary dead point. In this application first primary winding, first elimination winding and secondary winding in proper order the layer wind in on the magnetic core, first elimination winding keeps apart secondary winding with first primary winding to eliminate secondary winding and first primary winding's interlayer capacitance completely, at this moment, because of first elimination winding keeps apart secondary winding with first primary winding, and first elimination winding produces parasitic common mode capacitance with secondary winding, and secondary winding produces first electric current at parasitic common mode capacitance this moment, sets up supplementary elimination winding and produces the second electric current on common mode parasitic capacitance this moment, makes first electric current and second electric current offset, thereby realizes that the common mode electric current of low common mode noise transformer is zero purpose. Therefore, common mode noise can be eliminated without multiple times of debugging, the production procedure is simplified, and the technical problem that the winding of the low-common mode noise transformer eliminating layer needs multiple times of debugging in the prior art is solved.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.

FIG. 1 is a schematic circuit diagram of a conventional sequential winding method for a transformer;

FIG. 2 is a schematic cross-sectional view of a conventional transformer wound in sequence;

FIG. 3 is a schematic circuit diagram of a conventional transformer sandwich winding method;

FIG. 4 is a schematic cross-sectional view of a conventional transformer sandwich winding method;

FIG. 5 is a schematic circuit diagram of a sequential winding method for a low common mode noise transformer according to the present invention;

FIG. 6 is a schematic cross-sectional view of a sequential winding method for a low common mode noise transformer according to the present invention;

FIG. 7 is a schematic circuit diagram of a sandwich winding method of a low common mode noise transformer according to the present invention;

FIG. 8 is a schematic cross-sectional view of a sequential winding method for a low common mode noise transformer according to the present invention;

FIG. 9 is a schematic diagram of the flow of common mode current in the sequential winding of the low common mode noise transformer according to the present invention;

FIG. 10 is a schematic diagram showing the variation of common mode current in the sequential winding of the low common mode noise transformer according to the present invention;

FIG. 11 is a schematic diagram of the voltage variation of the first canceling winding and the secondary winding of the low common mode noise transformer according to the present invention;

FIG. 12 is a schematic diagram of the common mode voltage variation between the first cancel winding and the secondary winding of the sequential winding method of the low common mode noise transformer according to the present invention;

FIG. 13 is a schematic diagram illustrating the flow of common mode current in the sandwich winding method of the low common mode noise transformer of the present invention;

FIG. 14 is a schematic diagram illustrating the common mode current variation of the low common mode noise transformer by sandwich winding according to the present invention;

FIG. 15 is a schematic diagram of voltage variations of the first canceling winding, the second canceling winding, the first primary winding and the second primary winding of the low common mode noise transformer according to the sandwich winding method of the present invention;

fig. 16 is a schematic diagram of the common-mode voltage variation between the first cancellation winding and the secondary winding and the common-mode voltage variation between the second cancellation winding and the secondary winding of the low common-mode noise transformer according to the present invention.

The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It should be noted that, if directional indications (such as up, down, left, right, front, and back … …) are involved in the embodiment of the present invention, the directional indications are only used to explain the relative positional relationship between the components, the movement situation, and the like in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indications are changed accordingly.

In addition, if there is a description of "first", "second", etc. in an embodiment of the present invention, the description of "first", "second", etc. is for descriptive purposes only and is not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. The meaning of "and/or" appearing throughout is to include three technical solutions, exemplified by "a and/or B" including solution a, or solution B, or a solution where both a and B are satisfied. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.

The invention provides a low common mode noise transformer, which is used for solving the technical problem that the winding of a low common mode noise transformer elimination layer needs to be debugged for many times in the prior art.

In the exemplary technique, as shown in fig. 1 and 2, the secondary winding Ns is layered with the first primary winding Np1, and the first cancel winding E1 is located between the secondary winding Ns and the first primary winding Np1, at this time, due to the manufacturing process of the first cancel winding E1, a parasitic capacitance Cps is easily generated between the first primary winding Np1 and the secondary winding Ns, in the exemplary technique, multiple passes of the first cancel winding E1 are required, the number of layers of the first cancel winding E1 and the width of the first cancel winding E1 are varied, the current flowing through the first interlayer capacitor Ces between the first cancellation winding E1 and the secondary winding Ns is cancelled out by the current flowing through the parasitic capacitor Cps between the first primary winding Np1 and the secondary winding Ns, so that the effect of the first cancellation winding E1 in eliminating the common mode noise is the best, but a large amount of manpower and material resources are consumed for practical debugging.

In order to solve the above problems, in an embodiment of the present invention, as shown in fig. 5 and 6, the transformer with low common mode noise according to the present invention includes a magnetic core, a first primary winding Np1, a first cancel winding E1, a secondary winding Ns, and an auxiliary cancel winding Nc, wherein the first primary winding Np1, the first cancel winding E1, and the secondary winding Ns are sequentially wound on the magnetic core, the auxiliary cancel winding Nc is wound around any one of a winding pillar formed after the first primary winding Np1 is wound, a winding pillar formed after the first cancel winding E1 is wound, a winding pillar formed after the secondary winding Ns is wound, and the magnetic core, and the first primary winding Np1 has a primary dead point. A first end of the first cancel winding E1 is floating, a second end of the first cancel winding E1 is connected to a first end of the auxiliary cancel winding Nc, and a second end of the auxiliary cancel winding Nc is connected to the primary dead point.

In the above embodiment, the first cancel winding E1 is densely wound and has an area greater than or equal to the area of the first primary winding Np1 or the second primary winding Ns, so as to completely cancel the parasitic capacitance Cps of the second primary winding Ns and the first primary winding Np1, at this time, since the first cancel winding E1 is disposed to isolate the second primary winding Ns from the first primary winding Np1, the first cancel winding E1 and the second winding Ns generate the first interlayer capacitance Ces, the second winding Ns forms a first ac voltage linearly varying in the slot width direction on the first interlayer capacitance Ces, the first cancel winding E1 also forms a second ac voltage linearly varying in the slot width direction on the first interlayer capacitance Ces, the auxiliary cancel winding Nc is disposed to stabilize the voltage value of the first primary winding Np1 and the voltage value of the second winding Ns, so as to ensure that the average value of the voltage variation of the second winding is equal to the average value of the voltage variation of the first cancel winding E1, as shown in fig. 9 and 10, the common mode current on the first interlayer capacitor Ces is dynamically balanced, i.e., Ies1 is Ies2, so that the common mode current is zero, and thus, under the influence of external parameters such as any winding process, impregnation method, operating temperature, and the like, the good production quality is maintained, the EMC (electromagnetic Compatibility) performance of the product is improved, the production cost is saved, and the defective rate is reduced. Therefore, the common mode noise can be eliminated without multiple times of debugging, the production procedure is simplified, and the technical problem that the winding of the low-common mode noise transformer eliminating layer needs multiple times of debugging in the prior art is solved.

It should be noted that, in this embodiment, the auxiliary cancel winding Nc is wound around the magnetic core and is located between the first primary winding Np1 and the magnetic core, or the auxiliary cancel winding Nc is wound around the winding post formed by winding the first primary winding Np1, or the auxiliary cancel winding Nc is wound around the winding post formed by winding the first cancel winding E1, or the auxiliary cancel winding Nc is wound around the winding post formed by winding the secondary winding Ns. The primary quiescent point is the point at which the voltage across the first primary winding Np1 does not change.

In the first mode, the auxiliary cancel winding Nc is wound around the magnetic core and located between the first primary winding Np1 and the magnetic core, so that a common mode current can be prevented from being formed between the auxiliary cancel winding Nc and the secondary winding Ns, and thus common mode noise interference can be eliminated.

In a second mode, the auxiliary cancel winding Nc is wound around a winding post formed after the first primary winding Np1 is wound, and the auxiliary cancel winding Nc is disposed between the first cancel winding E1 and the first primary winding Np1, so that a common mode current can be prevented from being formed between the auxiliary cancel winding Nc and the secondary winding Ns, and thus common mode noise interference can be eliminated.

In a third mode, the auxiliary cancellation winding Nc is disposed around a winding post formed after the secondary winding Ns is disposed, and a second parasitic capacitance Ccs is also formed between the auxiliary cancellation winding Nc and the secondary winding Ns at this time, and at this time, the number of strands and the wire diameter of the auxiliary cancellation winding Nc can be reduced as much as possible so as to reduce the second parasitic capacitance Ccs, so that a common mode current is not generated here, and an influence of the common mode current on the second parasitic capacitance Ccs between the auxiliary cancellation winding Nc and the secondary winding Ns on the common mode current of the total low common mode noise transformer is eliminated.

In a fourth mode, the auxiliary cancel winding Nc is wound around a winding leg formed by winding the first cancel winding E1. The auxiliary cancel winding Nc is disposed between the first cancel winding E1 and the secondary winding Ns, and a second parasitic capacitance Ccs is also formed between the auxiliary cancel winding Nc and the secondary winding Ns at this time, and at this time, the number of strands and the wire diameter of the auxiliary cancel winding Nc can be reduced as much as possible to reduce the second parasitic capacitance Ccs, so that a common mode current is not generated here, and the influence of the common mode current on the second parasitic capacitance Ccs between the auxiliary cancel winding Nc and the secondary winding Ns on the common mode current of the total low common mode noise transformer is eliminated.

Optionally, the first cancel winding E1 is a single layer winding.

The first elimination winding E1 is a single-layer winding, so that the first primary winding Np1 and the secondary winding Ns can be completely isolated, the parasitic capacitance Cps between the first primary winding and the secondary winding Ns approaches to infinity (approximately equals to zero), the consumable items of the windings can be saved on the basis of eliminating the parasitic capacitance Cps, the volume of the final low common mode noise transformer is reduced, and the production cost is saved.

Alternatively, as shown in fig. 6, the magnetic core includes two vertical walls 110 and a center pillar 111 connecting the two vertical walls 110, a winding slot is formed between the two vertical walls 110 and the center pillar 111, and the first primary winding Np1, the first cancel winding E1 and the secondary winding Ns are sequentially wound on the center pillar 111.

The structure of the two vertical walls 110 and the center pillar 111 connecting the two vertical walls 110 can facilitate the sequential layer winding of the first primary winding Np1, the first cancel winding E1 and the secondary winding Ns, and has better stability.

Optionally, the first elimination winding E1 is wound along the magnetic core counterclockwise and is wound by one layer;

wherein the direction of the first elimination winding E1 along the counterclockwise direction of the magnetic core is positive. The positive and negative values at this time are relatively simple, and are convenient to calculate and judge. In the present embodiment, clockwise and counterclockwise may be interchanged. The positive and negative may be interchanged, and the winding method of the auxiliary cancel winding Nc is determined below with the counterclockwise direction being positive and the clockwise direction being negative.

The auxiliary cancellation winding Nc is wound according to the following winding manner:

determining the number of coils QNs of the secondary winding Ns and the number of coils QE1 of the first cancel winding E1;

the number QNs of the secondary winding Ns is generally a fixed number, and the number QE1 of the first cancel winding E1 is determined by actual conditions and can be changed.

Calculating the number of coils QNc of the auxiliary cancel winding Nc according to the number of coils QNs of the secondary winding Ns, the number of coils QE1 of the first cancel winding E1, and a calculation formula QNc (QNs-QE 1)/2;

the number of coils QNs of the secondary winding Ns is generally a fixed number, the number of coils QE1 of the first cancel winding E1 is determined by the actual conditions and can be changed, the number of coils QNc of the auxiliary cancel winding Nc is known by the above formula and is changed with the change of the number of coils QE1 of the first cancel winding E1, the number of coils of the auxiliary cancel winding Nc can be directly determined by the above formula according to the number of coils of the secondary winding Ns and the number of coils of the first cancel winding E1, the number of coils of the auxiliary cancel winding Nc can be determined without debugging the width and the number of coils of the first cancel winding E1 for many times, and the time for debugging and testing the common mode noise of the low common mode noise transformer and adjusting the EMC (electromagnetic compatibility) can be shortened according to the above formula.

When the calculated number QNc <0 of the auxiliary cancel winding Nc is obtained, the auxiliary cancel winding Nc is wound from a primary static point and is connected to the winding start point of the first cancel winding E1 after being wound by QNc turns clockwise along the magnetic core;

when the obtained coil number QNc >0 of the auxiliary cancel winding Nc is calculated, the auxiliary cancel winding Nc is wound from a primary dead point and is connected to the winding point of the first cancel winding E1 after being wound by QNc circles counterclockwise along the magnetic core.

When the calculated coil number QNc of the auxiliary cancel winding Nc is 0, the winding start point of the first cancel winding E1 is directly connected to the primary dead point, and the auxiliary cancel winding Nc is not provided.

In the above embodiment, after the first cancellation winding E1 and the auxiliary cancellation winding Nc are subjected to the winding process, the specific implementation effect can be verified through the following process, taking the structure of the low common mode noise transformer as shown in fig. 5 and 6 as an example,

if the interlayer current I × t ═ C × Δ U between the secondary winding Ns and the first cancellation winding E1, then:

Ies∝Ces*(ΔVs_av-ΔVe1_av)

ies denotes the interlayer current, Ces denotes the first parasitic capacitance, Δ Vs _ av denotes the average voltage of the secondary winding Ns, and Δ Ve1_ av denotes the average voltage of the first cancel winding E1.

Analyzing the interlayer winding Δ U, the voltage of each layer can be equivalently linearly changed into schematic diagrams as shown in fig. 11 and 12 according to the relationship between the number of turns and the voltage of the low common mode noise transformer.

At this time, the voltage of the auxiliary cancel winding Nc is set through formula calculation, so that the voltage of the secondary winding Ns and the first cancel winding E1 are stabilized, and the purpose that the common-mode voltage of the low common-mode noise transformer is zero is achieved.

When the number of coils of the secondary winding Ns is 12Ts and the number of coils of the first cancel winding E1 is 16Ts, the number of coils of the auxiliary cancel winding Nc shown in fig. 6 is:

Nc＝(Ns-Ne1)/2＝(12-16)/2＝-3Ts

as shown in fig. 6, the auxiliary cancellation winding Nc is wound clockwise 3Ts from the fourth leg 4 on the primary side of the low common mode noise transformer, and then connected to the third leg 3 of the low common mode noise transformer. The voltage on the low common mode noise transformer winding is proportional to the number of turns, assuming that 1Ts is 1V, Vs in fig. 11 changes linearly from 12V to 0V from left to right, Ve1 changes linearly from 13V to-3V from left to right, and since Δ Ves (common mode voltage) is Ve1-Vs (secondary winding Ns voltage), the common mode voltage Δ Ves in fig. 12 changes linearly from +3V to-3V. The average common mode voltage Δ Ves _ av is 0, that is, Ies ∞ Ces Δ Ves _ av is 0, so as to achieve the purpose of eliminating the common mode noise. Since Δ Ves _ av is 0, as shown in fig. 9 and 10, the common mode current Ies1+ Ies2 is independent of the first parasitic capacitor Ces, and therefore, the common mode current Ies1+ Ies2 is zero regardless of the influence of external parameters such as a winding process, an impregnation method, and a working temperature on the value of the first parasitic capacitor Ces, so that the batch consistency of the common mode noise of the low common mode noise transformer is greatly improved, and the problem of difficulty in debugging is solved.

In another embodiment of the present invention, to achieve the above object, as shown in fig. 7 and 8, the present invention provides a low common mode noise transformer, which includes a magnetic core, a first primary winding Np1, a first cancellation winding E1, a secondary winding Ns, a second primary winding Np2, a second cancellation winding E2, and an auxiliary cancellation winding Nc, wherein the first primary winding Np1 has a primary dead point. The first primary winding Np1, the first eliminating winding E1, the secondary winding Ns, the second eliminating winding E2 and the second primary winding Np2 are sequentially wound on the magnetic core, the auxiliary elimination winding Nc is wound on any one of a winding post formed after the first primary winding Np1 is wound, a winding post formed after the first elimination winding E1 is wound, a winding post formed after the secondary winding Ns is wound, a winding post formed after the second primary winding Np2 is wound, a winding post formed after the second elimination winding E2 is wound and the magnetic core, the first end of the first cancel winding E1 and the first end of the second cancel winding E2 are respectively floating, a second end of the first cancel winding E1 and a second end of the second cancel winding E2 are connected to a first end of the auxiliary cancel winding Nc, respectively, and a second end of the auxiliary cancel winding Nc is connected to the primary dead point.

In the above embodiment, the first cancel winding E1 at this time is densely wound and has an area greater than or equal to the area of the first primary winding Np1 or the secondary winding Ns, and the second cancel winding E2 is densely wound and has an area greater than or equal to the area of the second primary winding Np2 or the secondary winding Ns. As shown in fig. 8, the second primary winding Np2 and the first primary winding Np1 are disposed with the secondary winding Ns in between, the second cancel winding E2 is disposed between the second primary winding Np2 and the secondary winding Ns, and the first cancel winding E1 is disposed between the first primary winding Np1 and the secondary winding Ns, which are formed by a sandwich winding method of the low common mode noise transformer, at this time, both the second end of the first cancel winding E1 and the second end of the second cancel winding E2 are connected to the first end of the auxiliary cancel winding Nc. At this time, the first eliminating winding E1 isolates the first primary winding Np1 from the secondary winding Ns, at this time, the first eliminating winding E1 is densely wound and has an area greater than or equal to the area of the first primary winding Np1 or the secondary winding Ns, the second eliminating winding E2 isolates the second primary winding Np2 from the secondary winding Ns, at this time, the first eliminating winding E1 is densely wound and has an area greater than or equal to the area of the second primary winding Np2 or the secondary winding Ns, so that the position between the first primary winding Np1 and the secondary winding Ns and the second primary winding Np2 and the secondary winding Ns do not generate parasitic capacitances Cps, thereby achieving a good effect of reducing the common mode noise of the low common mode noise transformer. At this time, since the first cancel winding E1 is disposed to isolate the secondary winding Ns from the first primary winding Np1, the first cancel winding E1 and the secondary winding Ns generate a second interlayer capacitor Ces1, the secondary winding Ns forms a first ac voltage linearly changing in the slot width direction on the second interlayer capacitor Ces1, the first cancel winding E1 also forms a second ac voltage linearly changing in the slot width direction on the second interlayer capacitor Ces1, and the auxiliary cancel winding Nc is disposed to stabilize the voltage value of the first primary winding Np1 and the voltage value of the secondary winding Ns, so as to ensure that the average value of the voltage change of the secondary winding Ns is equal to the average value of the voltage change of the first cancel winding E1, as shown in fig. 13 and 14, the common mode current on the second interlayer capacitor Ces1 is dynamically balanced, so that the common mode current is zero, that is Ies1 equal to Ies 2. In addition, since the second cancel winding E2 is provided to isolate the secondary winding Ns from the second primary winding Np2, the second cancel winding E2 and the secondary winding Ns generate a third inter-layer capacitor Ces2, the secondary winding Ns forms a third ac voltage linearly changing in the slot width direction on the third inter-layer capacitor Ces3, the second cancel winding E2 also forms a fourth ac voltage linearly changing in the slot width direction on the second inter-layer capacitor Ces1, and the auxiliary cancel winding Nc is provided to stabilize the voltage value of the second primary winding Np2 and the voltage value of the secondary winding Ns, so as to ensure that the voltage variation average value of the secondary winding Ns is equal to the voltage variation average value of the second cancel winding E2, and the common mode current on the third inter-layer capacitor Ces2 is balanced dynamically, that is Ies3 ═ Ies4, so that the common mode current is zero. Therefore, common mode noise can be eliminated without multiple times of debugging, the production procedure is simplified, and the technical problem that the winding of the low-common mode noise transformer eliminating layer needs multiple times of debugging in the prior art is solved. The sandwich winding method of the low common mode noise transformer can be provided with a plurality of primary windings and secondary windings Ns, so that a plurality of eliminating windings can be oppositely arranged, and the effect of reducing the common mode noise of the common mode noise transformer can be realized. The method can keep good production quality no matter what winding process, impregnation mode, working temperature and other external parameters influence, improve the EMC (Electro Magnetic Compatibility) performance of the common mode noise transformer, save production cost and reduce defective rate.

In the above embodiment, it is noted that the auxiliary cancel winding Nc is wound around the winding post formed after the first primary winding Np1 is wound, or the auxiliary cancel winding Nc is wound around the winding post formed after the first cancel winding E1 is wound, or the auxiliary cancel winding Nc is wound around the winding post formed after the secondary winding Ns is wound, or the auxiliary cancel winding Nc is wound around the winding post formed after the second primary winding Np2 is wound, or the auxiliary cancel winding Nc is wound around the winding post formed after the second cancel winding E2 is wound, or the auxiliary cancel winding Nc is wound around the magnetic core.

In the first mode, the auxiliary cancel winding Nc is wound around the winding leg formed after the first primary winding Np1 is wound, and the auxiliary cancel winding Nc is disposed between the first primary winding Np1 and the first cancel winding E1. At this time, the auxiliary cancellation winding Nc may be dynamically balanced by the common mode current of the third interlayer capacitor Ces2 and the second interlayer capacitor Ces1, so as to achieve the purpose of canceling the common mode noise.

In the second mode, the auxiliary cancel winding Nc is wound around the winding leg formed after the winding of the first cancel winding E1, and the auxiliary cancel winding Nc is disposed between the first cancel winding E1 and the secondary winding Ns. The auxiliary cancellation winding Nc can be dynamically balanced by the common mode current of the third interlayer capacitor Ces2 and the second interlayer capacitor Ces1, so that the purpose of eliminating common mode noise is achieved.

In a third mode, the auxiliary cancel winding Nc is wound around the winding post formed after the winding of the secondary winding Ns, and the auxiliary cancel winding Nc is disposed between the secondary winding Ns and the second secondary winding Ns. The auxiliary cancellation winding Nc can be dynamically balanced by the common mode current of the third interlayer capacitor Ces2 and the second interlayer capacitor Ces1, so that the purpose of eliminating common mode noise is achieved.

In the fourth mode, the auxiliary cancel winding Nc is wound around the winding post formed after the winding of the second secondary winding Ns, and the auxiliary cancel winding Nc is disposed between the second secondary winding Ns and the second primary winding Np 2. The auxiliary cancellation winding Nc can dynamically balance the common mode current of the third interlayer capacitor Ces2 and the second interlayer capacitor Ces1, so that the purpose of eliminating the common mode noise is achieved.

In a fifth mode, as shown in fig. 8, the auxiliary cancel winding Nc is wound around the winding leg formed after the second primary winding Np2 is wound, so as to avoid forming other types of micro-capacitance with other windings, and to eliminate common mode noise to the maximum extent.

In a sixth mode, the auxiliary cancel winding Nc is wound around the magnetic core, and the auxiliary cancel winding Nc is disposed between the first primary winding Np1 and the magnetic core. The auxiliary cancellation winding Nc can be dynamically balanced by the common mode current of the third interlayer capacitor Ces2 and the second interlayer capacitor Ces1, so that the purpose of eliminating common mode noise is achieved.

In the above-described embodiment, the auxiliary cancel winding Nc is provided at any position to play a role of canceling the common mode noise.

Optionally, the first and second cancel windings E1 and E2 are single layer windings.

Alternatively, as shown in fig. 8, the magnetic core includes two vertical walls 110 and a center pillar 111 connecting the two vertical walls 110, a winding slot is formed between the two vertical walls 110 and the center pillar 111, and the first primary winding Np1, the first cancel winding E1, the secondary winding Ns, the second primary winding Np2 and the second cancel winding E2 are sequentially wound on the center pillar 111.

The structure of the two vertical walls 110 and the center pillar 111 connecting the two vertical walls 110 can facilitate the sequential layer winding of the first primary winding Np1, the first cancellation winding E1, the secondary winding Ns, the second primary winding Np2 and the second cancellation winding E2, and has better stability.

Optionally, the first elimination winding E1 and the second elimination winding E2 are wound counterclockwise from the winding starting point and are wound by one layer;

calculating the number of coils QNc of the auxiliary cancel winding Nc according to the number of coils QNs of the secondary winding Ns, the number of coils QE1 of the first cancel winding E1, and a calculation formula QNc ═ QNs-QE 1)/2;

in the above embodiment, the number of coils of the auxiliary cancel winding Nc can be directly determined by the above formula based on the number of coils QNs of the secondary winding Ns and the number of coils of the first cancel winding E1, and the number of coils of the auxiliary cancel winding Nc can be determined without performing a plurality of times of debugging on the width and the number of coils of the first cancel winding E1.

When the number of the coils of the auxiliary cancel winding Nc is QNc <0, the auxiliary cancel winding Nc is wound from a primary dead point, and after the auxiliary cancel winding Nc is wound for QNc turns clockwise, the auxiliary cancel winding Nc is connected to the winding start point of the first cancel winding E1 and the winding start point of the second cancel winding E2;

when the number of the coils QNc of the auxiliary cancel winding Nc is >0, the auxiliary cancel winding Nc is wound from the primary dead point, and is wound in a counter-clockwise QNc turns, and then is connected to the winding start point of the first cancel winding E1 and the winding start point of the second cancel winding E2.

Determining the number of coils QNs of the secondary winding Ns and the number of coils QE2 of the second cancel winding E2;

calculating the number of coils QNc of the first cancel winding E1 according to the number of coils QNs of the secondary winding Ns, the number of coils QE2 of the second cancel winding E2, and a calculation formula QNc ═ QNs-QE 2)/2;

when the number of the coils QNc of the auxiliary cancel winding Nc is greater than 0, the auxiliary cancel winding Nc is wound from a primary dead point, and is connected to the winding start point of the first cancel winding E1 and the winding start point of the second cancel winding E2 after being wound for QNc circles counterclockwise;

when the number of coils QNc of the auxiliary cancel winding Nc is 0, the winding start point of the first cancel winding E1 and the winding start point of the second cancel winding E2 are directly connected to the primary dead point, and the auxiliary cancel winding Nc is not required.

In the two embodiments, the sequential winding structure of the low common mode noise transformer is cancelled as shown in fig. 8, the first cancellation winding E1 is tightly wound and fully wound by one layer, completely isolating the first primary winding Np1 and the secondary winding Ns, and the second cancellation winding E2 is tightly wound and fully wound by one layer, completely isolating the second primary winding Np2 and the secondary winding Ns, so that the parasitic capacitance between the first primary winding Np1 and the secondary winding Ns and the parasitic capacitance between the second primary winding Np2 and the secondary winding Ns are approximately equal to zero. Meanwhile, new first and second parasitic common-mode capacitances are formed between the first and second cancel windings E1 and E2 and the secondary winding Ns, as shown in fig. 15 and 16, the secondary winding Ns forms an alternating voltage varying linearly in the slot width direction on the first and second parasitic common-mode capacitances, the first and second cancel windings E1 and E2 also form an alternating voltage varying linearly in the slot width direction on the first and second parasitic common-mode capacitances, respectively, when the average value Δ Vs _ av of the voltage variation of the secondary winding Ns is equal to the average value Δ Ve2_ av of the voltage variation of the first and second cancel windings E1 Δ Ve1_ av and E2, the common-mode currents on the first and second parasitic common-mode capacitances Ces1 and Ces2 are dynamically balanced, as shown in fig. 13 and 14, that is Ies1 ═ Ies2, 6853 ═ Ies4, the total common mode current Icm is 0. It is worth noting that the time for a designer to debug and test the common mode noise of the transformer with low common mode noise and to modify EMC can be shortened by using the formula to calculate the parameters

Taking the structure of the low common mode noise transformer in fig. 8 as an example, the interlayer current I × t ═ C × Δ U includes:

Ies∝Ces1*(ΔVs_av-ΔVe1_av)+Ces2*(ΔVs_av-ΔVe2_av)

ies is interlayer current, Ces1 is a first parasitic common mode capacitor Ces1, Ces2 is a second parasitic common mode capacitor Ces2

Δ Vs _ av is the average voltage of the secondary winding Ns, and Δ Ve1_ av is the average voltage of the first cancel winding E1.

Analyzing the interlayer winding Δ U, according to the direct proportion relationship between the number of turns of the low common mode noise transformer and the voltage, the voltage of each layer can be equivalently changed linearly, as shown in fig. 15 and 16:

when the number of turns of the secondary winding Ns is 12Ts, and the number of turns of the first cancel winding E1 and the second cancel winding E2 is 16Ts, the number of turns of the auxiliary cancel winding Nc shown in fig. 8 is:

Nc＝(Ns-Ne1)/2＝(QNs-QE2)/2＝(12-16)/2＝-3Ts

the auxiliary cancel winding Nc winding is wound from the fifth leg of the primary side ground of the low common mode noise transformer, is wound by 3Ts, and is then connected to the fourth leg of the low common mode noise transformer. The voltage on the low common mode noise transformer winding is proportional to the number of turns, and assuming that 1Ts is 1V, Vs in fig. 12 changes linearly from 12V to 0V from left to right, Ve1 changes linearly from 13V to-3V from left to right, and Ve2 changes linearly from 13V to-3V from left to right. Since Δ Ves1 ═ Ve1-Vs, the common mode voltage Δ Ves1 varied linearly from +3V to-3V; since Δ Ves2 ═ Ve2-Vs, the common mode voltage Δ Ves2 also varied linearly from +3V to-3V. The average common mode voltage Δ Ves _ av is 0, that is, Ies ∞ Ces Δ Ves _ av is 0, so as to achieve the purpose of eliminating the common mode noise.

Optionally, the auxiliary cancel winding Nc is disposed adjacent to the second primary winding Np 2.

The auxiliary cancel winding Nc of the sandwich winding method is adjacent to the second primary winding Np2, and no common mode current is generated on the primary side, so that the winding diameter and number of the winding are not required. Therefore, the influence of the change of the interlayer capacitance Cps on the common-mode noise is eliminated, and the mass production consistency of the common-mode noise of the low common-mode noise transformer is improved.

The above description is only a preferred embodiment of the present invention, and not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.

Claims

1. A transformer with low common mode noise is characterized in that the transformer with low common mode noise comprises a magnetic core, a first primary winding, a first eliminating winding, a secondary winding and an auxiliary eliminating winding,

the first primary winding, the first eliminating winding and the secondary winding are sequentially wound on the magnetic core, the auxiliary eliminating winding is wound on any one of a winding column formed after the first primary winding is wound, a winding column formed after the first eliminating winding is wound, a winding column formed after the secondary winding is wound and the magnetic core, and the first primary winding is provided with a primary quiescent point;

The first end of the first elimination winding is suspended, the second end of the first elimination winding is connected with the first end of the auxiliary elimination winding, and the second end of the auxiliary elimination winding is connected with the primary dead point;

the first eliminating winding is wound along the magnetic core anticlockwise and is fully wound by one layer;

determining the number of coils QNs of the secondary winding and the number of coils QE1 of the first cancellation winding;

2. The low common mode noise transformer of claim 1, wherein the first cancellation winding is a single layer winding.

3. The transformer of claim 1, wherein the core comprises two vertical walls and a center pillar connecting the two vertical walls, a winding slot is formed between the two vertical walls and the center pillar, and the first primary winding, the first cancel winding and the secondary winding are sequentially wound on the center pillar.

4. A low common mode noise transformer, characterized in that, the low common mode noise transformer comprises a magnetic core, a first primary winding, a first eliminating winding, a secondary winding, a second primary winding, a second eliminating winding and an auxiliary eliminating winding, the first primary winding has a primary dead point;

the first end of the first elimination winding and the first end of the second elimination winding are respectively suspended, the second end of the first elimination winding and the second end of the second elimination winding are respectively connected with the first end of the auxiliary elimination winding, and the second end of the auxiliary elimination winding is connected with the primary dead point;

The first elimination winding and the second elimination winding are wound anticlockwise from a winding starting point and are fully wound by one layer;

5. The low common mode noise transformer of claim 4, wherein the first cancellation winding and the second cancellation winding are single layer windings.

6. The transformer of claim 4, wherein the core comprises two vertical walls and a center pillar connecting the two vertical walls, a winding slot is formed between the two vertical walls and the center pillar, and the first primary winding, the first cancellation winding, the secondary winding, the second cancellation winding, and the second primary winding are sequentially wound on the center pillar.

7. A low common mode noise transformer, characterized in that the low common mode noise transformer comprises a magnetic core, a first primary winding, a first cancellation winding, a secondary winding, a second primary winding, a second cancellation winding and an auxiliary cancellation winding, wherein the first primary winding has a primary dead point;

the first primary winding, the first eliminating winding, the secondary winding, the second eliminating winding and the second primary winding are sequentially wound on the magnetic core in a layer-by-layer manner, the auxiliary eliminating winding is wound on any one of a winding column formed after the first primary winding is wound, a winding column formed after the first eliminating winding is wound, a winding column formed after the secondary winding is wound, a winding column formed after the second primary winding is wound, a winding column formed after the second eliminating winding is wound and the magnetic core;

a first end of the first cancellation winding and a first end of the second cancellation winding are respectively suspended, a second end of the first cancellation winding and a second end of the second cancellation winding are respectively connected with a first end of the auxiliary cancellation winding, and a second end of the auxiliary cancellation winding is connected with the primary dead point;

determining a number of coils QE2 according to a number of coils QNs of the secondary winding and the second cancel winding;

calculating the number QNc of the auxiliary eliminating winding according to the number QNs of secondary winding coils, the number QE2 of the second eliminating winding coils and the calculation formula QNc which is (QNs-QE 2)/2;