CN219497518U - Transformer - Google Patents

Abstract

The utility model discloses a transformer, comprising: at least two layers of PCB boards; the primary winding is arranged on the first layer of the PCB; the auxiliary winding is arranged on the PCB, and the auxiliary winding and the primary winding are positioned on the same layer of the PCB. According to the transformer disclosed by the utility model, the primary winding and the auxiliary winding are arranged on the same layer of PCB, so that the number of lamination layers of the PCB in the transformer is effectively reduced, and the manufacturing cost is saved. Meanwhile, the auxiliary winding and the primary winding are arranged in the same layer, so that the distance between the auxiliary winding and the magnetic field generated by the primary winding is guaranteed to be nearest, the auxiliary winding is convenient to induce magnetic field change, higher induction voltage is generated, and the performance of the transformer is improved.

Description

Transformer

Technical Field

The utility model relates to the technical field of transformer manufacturing, in particular to a transformer.

Background

In the transformer in the prior art, the auxiliary winding cannot be positioned on the same layer with other windings (such as a primary winding) in a PCB (PCB: printed Circuit Board, chinese name is printed circuit board, also called printed circuit board), and an additional layer of PCB is required to be arranged for placing the auxiliary winding, so that the number of layers of the required PCB is more, the primary winding and the auxiliary winding cannot be flexibly arranged, and the manufacturing cost is increased.

Disclosure of Invention

The utility model aims to provide a novel technical scheme of a transformer, which at least can solve the problems of more layers of a transformer PCB and the like in the prior art.

The utility model provides a transformer, comprising: at least two layers of PCB boards; the primary winding is arranged on the first layer of the PCB; the auxiliary winding is arranged on the PCB, and the auxiliary winding and the primary winding are positioned on the same layer of the PCB.

Optionally, the primary winding and the auxiliary winding are both wound in a ring shape, the outer diameter of the auxiliary winding is smaller than the inner diameter of the primary winding, and the auxiliary winding is arranged in an inner hollow area of the primary winding.

Optionally, the auxiliary winding is arranged concentric with the primary winding.

Optionally, the primary winding comprises a multi-turn primary coil, and the auxiliary winding comprises a multi-turn auxiliary coil, the auxiliary coil being located in the gap of each turn of the primary coil.

Optionally, the transformer further includes: the secondary winding is arranged on the second layer of the PCB board and is concentric with the primary winding.

Optionally, the secondary winding comprises a plurality of turns of secondary coil, and the number of turns of the secondary coil is greater than or equal to the number of turns of the primary coil.

Optionally, the number of turns of the secondary coil is no more than 5 times the number of turns of the primary coil.

Optionally, the calculation formula of the line width of the primary coil or the auxiliary coil is:

wherein S is _b R is the line width of the coil _i Is the inner diameter of the coil, r _a Is the outer diameter of the coil S _a And N is the number of turns of the coil.

Optionally, the primary coil has a first winding start end and a first winding end, the auxiliary coil has a second winding start end and a second winding end, the secondary coil has a third winding start end and a third winding end, a first input end, a second input end, a first output end and a second output end are arranged on the PCB board, a third input end and a third output end are arranged on the PCB board, the first input end is connected with the first winding start end, the first output end is connected with the first winding end, the second input end is connected with the second winding start end, the second output end is connected with the second winding end, the third input end is connected with the third winding start end, and the third output end is connected with the third winding end.

Optionally, the first input end, the second input end, the first output end and the second output end are located on the same side of the PCB board, the third input end and the third output end are arranged on the same side, and the third input end and the first input end are located on two radial sides of the primary winding.

According to the transformer disclosed by the utility model, the primary winding and the auxiliary winding are arranged on the same layer of PCB, so that the number of lamination layers of the PCB in the transformer is effectively reduced, and the manufacturing cost is saved. Meanwhile, the auxiliary winding and the primary winding are arranged in the same layer, so that the distance between the auxiliary winding and the magnetic field generated by the primary winding is guaranteed to be nearest, the auxiliary winding is convenient to induce magnetic field change, higher induction voltage is generated, and the performance of the transformer is improved.

Other features of the present utility model and its advantages will become apparent from the following detailed description of exemplary embodiments of the utility model, which proceeds with reference to the accompanying drawings.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the utility model and together with the description, serve to explain the principles of the utility model.

Fig. 1 is a schematic diagram of a coil winding of a transformer according to an embodiment of the present utility model.

FIG. 2 is a schematic diagram of a primary winding of a transformer according to an embodiment of the utility model;

FIG. 3 is a schematic diagram of a transformer according to an embodiment of the present utility model;

FIG. 4 is a schematic diagram of the routing of the primary and auxiliary coils of a transformer according to an embodiment of the utility model;

FIG. 5 is a schematic diagram of the routing of the secondary winding of a transformer according to an embodiment of the present utility model;

fig. 6 is a schematic diagram of a trace of a PCB board of a transformer according to an embodiment of the present utility model;

fig. 7 is another routing schematic of a PCB board of a transformer according to an embodiment of the present utility model.

Reference numerals:

a primary winding 10; a primary coil 11;

an auxiliary winding 20; an auxiliary coil 21;

a secondary winding 30; a secondary coil 31;

a first input 41; a first output 42; a second input 43; a second output 44; a third input 45; and a third output 46.

Detailed Description

Various exemplary embodiments of the present utility model will now be described in detail with reference to the accompanying drawings. It should be noted that: the relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present utility model unless it is specifically stated otherwise.

The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the utility model, its application, or uses.

Techniques, methods, and apparatus known to one of ordinary skill in the relevant art may not be discussed in detail, but are intended to be part of the specification where appropriate.

In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of exemplary embodiments may have different values.

It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

In the description and claims of the present utility model, the terms "first," "second," and the like, if any, may include one or more of those features, either explicitly or implicitly. In the description of the present utility model, unless otherwise indicated, the meaning of "a plurality" is two or more. Furthermore, in the description and claims, "and/or" means at least one of the connected objects, and the character "/", generally means that the associated object is an "or" relationship.

In the description of the present utility model, it should be understood that, if the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are referred to, the positional relationship indicated based on the drawings is merely for convenience of description and simplification of the description, and does not indicate or imply that the apparatus or element referred to must have a specific orientation, be configured and operated in a specific orientation, and therefore should not be construed as limiting the utility model.

In the description of the present utility model, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly, unless otherwise specifically defined and limited. For example, the connection can be fixed connection, detachable connection or integrated connection; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

A transformer according to an embodiment of the present utility model is described in detail below with reference to the accompanying drawings.

As shown in fig. 1, the transformer according to the embodiment of the present utility model includes at least two layers of PCB boards, a primary winding 10 and an auxiliary winding 20.

Specifically, the primary winding 10 is provided on a first layer of PCB board. The auxiliary winding 20 is arranged on the PCB, and the auxiliary winding 20 and the primary winding 10 are positioned on the same layer of PCB.

In other words, referring to fig. 1, the transformer according to the embodiment of the present utility model is mainly composed of at least two layers of PCB boards, a primary winding 10 and an auxiliary winding 20. The primary winding 10 is arranged on a first layer of PCB (PCB: printed Circuit Board, chinese name printed circuit board, also called printed circuit board). The auxiliary winding 20 is arranged on the PCB, and the auxiliary winding 20 and the primary winding 10 are positioned on the same layer of PCB, so that the lamination layer number of the PCB is effectively saved. When the auxiliary winding 20 and the primary winding 10 are positioned on the same layer of PCB, the distance between the auxiliary winding 20 and the magnetic field generated by the primary winding 10 is enabled to be nearest, the auxiliary winding 20 is convenient to induce magnetic field change, higher induction voltage is generated, and the performance of the transformer is facilitated to be improved.

According to the law of electromagnetic induction, when current is fed into the primary winding 10, a loop is formed by the magnetic field generated by the primary winding passing through the inner diameter of the coil, the auxiliary winding 20 is positioned at the nearest position generating the magnetic field, the magnetic field is strongest, and the generated induced voltage is superior to the induced voltage generated by the auxiliary winding 20 positioned on other layers of PCB boards.

Therefore, according to the transformer provided by the embodiment of the utility model, the primary winding 10 and the auxiliary winding 20 are arranged on the same layer of PCB, so that the number of lamination layers of the PCB in the transformer is effectively reduced, and the manufacturing cost is saved. Meanwhile, the auxiliary winding 20 and the primary winding 10 are arranged in the same layer, so that the distance between the auxiliary winding 20 and the magnetic field generated by the primary winding 10 is ensured to be nearest, the auxiliary winding 20 is convenient to induce magnetic field change, higher induction voltage is generated, and the performance of the transformer is improved.

According to one embodiment of the present utility model, the primary winding 10 and the auxiliary winding 20 are each wound in a ring shape, the outer diameter of the auxiliary winding 20 is smaller than the inner diameter of the primary winding 10, and the auxiliary winding 20 is provided in an inner hollow region of the primary winding 10.

That is, as shown in fig. 1 and 3, the primary winding 10 and the auxiliary winding 20 are wound as ring windings, and the outer diameter of the auxiliary winding 20 is smaller than the inner diameter of the primary winding 10, so that the auxiliary winding 20 is disposed in an inner hollow region (inner region) of the primary winding 10. When the auxiliary winding 20 is located in the same layer as the primary winding 10, the auxiliary winding 20 is located in the inner diameter of the primary winding 10. According to the law of electromagnetic induction, when current is supplied to the primary winding 10, a loop is formed by the magnetic field generated by the primary winding passing through the inner diameter of the coil, the auxiliary winding 20 is positioned at the center of the generated magnetic field, the magnetic field is strongest, and the generated induced voltage is superior to the induced voltage generated by other layers of the auxiliary winding 20.

In the present utility model, as shown in fig. 1 and 3, the auxiliary winding 20 is concentrically arranged with the primary winding 10, when current is supplied to the primary winding 10, a loop is formed by the magnetic field generated by the primary winding passing through the inner diameter of the coil, the auxiliary winding 20 is located at the most central position of the generated magnetic field, the distance from the auxiliary winding 20 is closest to the primary winding 10, the magnetic field is strongest, and the generated induced voltage is superior to the induced voltage generated by the auxiliary winding 20 located at other layers.

In some embodiments of the utility model, the primary winding 10 comprises a multi-turn primary winding 11 and the auxiliary winding 20 comprises a multi-turn auxiliary winding 21, the auxiliary winding 21 being located in the gap of each turn of the primary winding 11.

When the auxiliary coil 21 and the primary coil 11 are positioned on the same layer, the number of turns of the auxiliary coil 21 is not limited by the inner diameter of the primary coil 11, the number of turns of the auxiliary coil 21 can be less than or equal to the number of turns of the primary coil 11, and the area of the auxiliary coil 21 is increased, thereby increasing the inductance thereof. Meanwhile, each turn of the auxiliary coil 21 can sense a magnetic field generated by current flowing into each turn of the primary coil 11, and larger output voltage is generated.

According to one embodiment of the utility model, the transformer further comprises: and a secondary winding 30, the secondary winding 30 being provided on the second layer PCB board, and the secondary winding 30 being provided concentrically with the primary winding 10.

In other words, as shown in fig. 3 and 5, the transformer may further include a secondary winding 30, the secondary winding 30 being disposed on the second layer PCB board, and the secondary winding 30 being disposed concentrically with the primary winding 10. The auxiliary winding 20 and the primary winding 10 in the transformer coil are positioned at the same layer, the secondary winding 30 and the primary winding 10 are positioned at different layers, the size of the auxiliary winding 20 is limited, the outer diameter of the auxiliary winding 20 is smaller than the inner diameter of the primary winding 10, so that the auxiliary winding 20 and the primary winding 10 can be positioned at the same layer, two layers of PCB boards where the primary winding 10 and the secondary winding 30 are positioned can be flexibly changed, and the lamination layer number and the manufacturing cost of the PCB boards are greatly saved.

In the utility model, because the auxiliary winding 20 has smaller size, can be placed in each layer and can not overlap with the wires of the primary winding 10 and the secondary winding 30, the distance between the primary winding 10 and the secondary winding 30 and the number of separated layers can be finely adjusted according to the voltage induced by the secondary winding 30, so that the PCB layers where the primary winding 10 and the secondary winding 30 are positioned are more flexible and changeable, and the lamination layers of the PCB are also greatly saved.

According to one embodiment of the present utility model, referring to fig. 1, 3 and 4, the secondary winding 30 includes a plurality of turns of the secondary coil 31, and the number of turns of the secondary coil 31 is equal to or greater than the number of turns of the primary coil 11. When the auxiliary coil 21 and the primary coil 11 are positioned on the same layer, the number of turns of the auxiliary coil 21 is not limited by the inner diameter of the primary coil 11 any more when the auxiliary coil 21 is positioned in the gap of each turn of the primary coil 11, the number of turns of the auxiliary coil 21 can be greater than or equal to the number of turns of the primary coil 11, the area of the auxiliary coil 21 can be increased to some extent, the inductance of the auxiliary coil 21 is increased, and meanwhile, each turn of the auxiliary coil 21 can sense a magnetic field generated by current flowing into each turn of the primary coil 11, so that a larger output voltage is generated.

According to an embodiment of the present utility model, the number of turns of the secondary coil 31 is not more than 5 times that of the primary coil 11, and alternatively, the ratio of the number of turns around which the auxiliary coil 21, the primary coil 11 and the secondary coil 31 are wound may be set to 1:2:3. For example, the number of turns of the auxiliary coil 21 may be set to 3 turns, the number of turns of the primary coil 11 may be set to 6 turns, and the number of turns of the secondary coil 31 may be set to 12 turns, forming 1:2:3. The primary coil 11 and the secondary coil 31 are separated by two PCB layers, the primary coil 11 may be located above the secondary coil 31, the primary coil 11 is placed on the top layer, the secondary coil 31 is placed on the bottom layer, and the auxiliary coil 21 is placed within the inner radius of the primary coil 11 on the top layer. The input end of the current is the end of the coil spiral winding, the output end of the primary current is the beginning end of the coil spiral winding, the effective electromagnetic fields are provided for the auxiliary coil 21 and the auxiliary coil 31 according to the right-hand spiral rule, the auxiliary coil 31 and the auxiliary coil 21 are not electrified with the current, and the voltage is formed by utilizing electromagnetic induction.

In some embodiments of the present utility model, the line width of the primary coil 11 or the auxiliary coil 21 is calculated as:

wherein S is _b R is the line width of the coil _i Is the inner diameter of the coil, r _a Is the outer diameter of the coil S _a And N is the number of turns of the coil.

In other words, the line width of the primary coil 11 or the auxiliary coil 21 can be calculated according to the following formula:

wherein S is _b R is the line width of the coil _i Is the inner diameter of the coil, r _a Is the outer diameter of the coil S _a And N is the number of turns of the coil.

In the utility model, the coil contained in the transformer is a transformer coil which is wound by copper film wires in a plane in a PCB board, the coil is spirally wound anticlockwise from inside to outside, and as shown in figure 2, the coil contains a coil inner diameter r _i Outer diameter r of coil _a Line width S _b Line spacing S _a The coil comprises a coil, a coil outer diameter, a coil end coil and a coil end coil, wherein the coil is arranged on the coil end coil, the coil inner diameter is the distance from the coil center to the coil start end coil near the center side, the coil outer diameter is the distance from the coil center to the coil end coil deviating from the center side, the coil end coil center is rotated N multiplied by 360 DEG to reach the coil end by the coil end coil, the coil outer diameter length comprises 1 coil inner diameter length, N coil copper wire interval lengths and N+1 coil copper wire width lengths.

The PCB of the utility model is an M layer plate, the coil comprises a primary coil 11, a secondary coil 31 and an auxiliary coil 21, the primary coil 11 and the secondary coil 31 are not in the same layer, the auxiliary coil 21 and the primary coil are in the same layer, the auxiliary coil 21 is spatially positioned in the inner circle of the primary coil 11, the outer diameter of the auxiliary coil 21 is smaller than or equal to the inner diameter of the primary coil 11, the inner diameters, the outer diameters and the circle centers of the secondary coil 31 and the primary coil 11 are the same, the line width and the line spacing of each type of coil are the same, and the line width is equal to the line widthThe input and output ends of the primary coil 11, the secondary coil 31 and the feedback coil are respectively connected to different ports through copper film wires, the wires connected to the different ports can not be crossed, the wires enter a layer without a coil through a through hole to be routed, and the primary coil 11, the secondary coil 31 and the auxiliary coil 21 form a transformer in a PCB.

When the outer diameter of the primary coil 11 and the secondary coil 31 is 7.9mm, the inner diameter is 2.8mm, the line spacing is 8mi (0.2032 mm), and the formula is givenThe line width 0.5544mm of the primary coil 11 can be calculated. When the line width of the secondary coil 31 is 0.2047mm, the auxiliary coilThe outer diameter of the auxiliary coil 21 was 2.8mm, the inner diameter was 1mm, and the line width of the auxiliary coil 21 was 0.2976mm.

According to an embodiment of the present utility model, as shown in fig. 3, the primary winding 11 has a first winding start end and a first winding end, the auxiliary winding 21 has a second winding start end and a second winding end, the secondary winding 31 has a third winding start end and a third winding end, the PCB board is provided with a first input end 41, a second input end 43, a first output end 42 and a second output end 44, and the second layer PCB board is further provided with a third input end 45 and a third output end 46, wherein the first input end 41, the second input end 43, the first output end 42, the second output end 44, the third input end 45 and the third output end 46 are through holes penetrating through all layers of the PCB board.

The first input end 41 is connected to a first winding start end, the first output end 42 is connected to a first winding end, the second input end 43 is connected to a second winding start end, the second output end 44 is connected to a second winding end, the third input end 45 is connected to a third winding start end, and the third output end 46 is connected to a third winding end. The first input end 41, the second input end 43, the first output end 42 and the second output end 44 are located on the same side of the PCB board, the third input end 45 and the third output end 46 are arranged on the same side, and the third input end 45 and the first input end 41 are located on two radial sides of the primary winding 10.

In the present utility model, referring to fig. 3 to 7, in order to facilitate placement of the through holes, the spiral start ends (the first winding start end, the second winding start end and the third winding start end) and the spiral end ends (the first winding end, the second winding end and the third winding end) of the primary coil 11, the auxiliary coil 21 and the secondary coil 31 may be located at the same side, and at this time, the magnetic field generated by each turn of the primary coil 11 may be induced by the secondary coil 31 approximately two turns, so that the voltage induced by the secondary coil 31 may be effectively increased, and then the primary coil 11 and the secondary coil 31 may be kept stationary, and the auxiliary coil 21 may be rotated clockwise around the circle center by 90 ° so that the auxiliary coil 21 and the thin film wire of the primary coil 11 may be staggered without contact. At this time, the auxiliary coil 21 is already located at the center of the magnetic field generated by the primary coil 11, and the maximum magnetic field can be sensed, so that the auxiliary coil 21 is rotated by 90 degrees, and the influence on the magnetic field sensed by the auxiliary coil 21 is not great.

Because the auxiliary coil 21 and the wiring of the primary coil 11 are both positioned on the same layer, the auxiliary coil 21 is positioned in the inner circle of the coil with the same center as the primary coil 11, so that the wiring of the inner circle of the coil can be led out to the outside of the coil through the through hole by placing the through hole, and the input and output sides are conveniently connected.

Referring to fig. 3 to 7, the spiral winding start end (first winding start end) of the primary coil 11 is connected to H126 (first input end 41) as an input end of the current of the primary coil 11, and the spiral winding start end of the primary coil 11 is routed to the second layer PCB board through the through hole 1 and connected to H125 (first output end 42) as an output end of the current of the primary coil 11. According to the right hand screw rule, the magnetic field direction should be from top to bottom, since the transformer coil in this example is used in flyback transformer topologies, both the secondary coil 31 and the auxiliary coil 21 can develop voltages by electromagnetic induction in the switching of the field effect transistor. In the conventional flyback transformer, the winding mode of the secondary winding 31 and the auxiliary winding 21 is opposite to that of the primary winding 11, so that when the H126 of the transformer is input as the primary winding 11, the spiral winding end side (third winding end) of the secondary winding 31 should be connected with the H130 (third output end 46) as the input of the secondary side, the input of the secondary side is connected with the anode of the diode, and the spiral winding start side of the secondary winding 31 should be routed from the bottom layer to the third layer through the through hole 4 and connected with the H129 (third input end 45). The auxiliary winding 21 should be located at the same layer as the primary winding 11, so that the end side of the spiral winding (second winding end) and H128 (second output 44) can be connected as auxiliary inputs, the auxiliary input side should be connected to the anode of the auxiliary side diode, the spiral winding end side of the auxiliary winding 21 is connected to H128 from the top layer through the through hole 2, and the spiral winding start side (second winding start) of the auxiliary winding 21 is connected to H127 (second input 43) from the top layer through the through hole 3.

The input end of the current is the end of the coil spiral winding, the output end of the primary current is the beginning end of the coil spiral winding, the effective electromagnetic fields are provided for the auxiliary coil 21 and the auxiliary coil 31 according to the right-hand spiral rule, the auxiliary coil 31 and the auxiliary coil 21 are not electrified with the current, and the voltage is formed by utilizing electromagnetic induction.

Of course, other structures of the transformer and its working principle are understood and can be implemented by those skilled in the art, and detailed description thereof is omitted herein.

In summary, according to the transformer of the embodiment of the utility model, the primary winding 10 and the auxiliary winding 20 are arranged on the same layer of PCB, so that the lamination layer number of the PCB in the transformer is effectively saved, and the manufacturing cost is saved. Meanwhile, the auxiliary winding 20 and the primary winding 10 are arranged in the same layer, so that the distance between the auxiliary winding 20 and the magnetic field generated by the primary winding 10 is ensured to be nearest, the auxiliary winding 20 is convenient to induce magnetic field change, higher induction voltage is generated, and the performance of the transformer is improved.

While certain specific embodiments of the utility model have been described in detail by way of example, it will be appreciated by those skilled in the art that the above examples are for illustration only and are not intended to limit the scope of the utility model. It will be appreciated by those skilled in the art that modifications may be made to the above embodiments without departing from the scope and spirit of the utility model. The scope of the utility model is defined by the appended claims.

Claims (10)

1. A transformer, comprising:

at least two layers of PCB boards;

the primary winding is arranged on the first layer of the PCB;

the auxiliary winding is arranged on the PCB, and the auxiliary winding and the primary winding are positioned on the same layer of the PCB.

2. The transformer of claim 1, wherein the primary winding and the auxiliary winding are each wound in a ring shape, an outer diameter of the auxiliary winding is smaller than an inner diameter of the primary winding, and the auxiliary winding is disposed in an inner hollow region of the primary winding.

3. The transformer of claim 2, wherein the auxiliary winding is disposed concentric with the primary winding.

4. The transformer of claim 1, wherein the primary winding comprises a multi-turn primary coil and the auxiliary winding comprises a multi-turn auxiliary coil positioned within the gap of each turn of the primary coil.

5. The transformer of claim 4, further comprising: the secondary winding is arranged on the second layer of the PCB board and is concentric with the primary winding.

6. The transformer of claim 5, wherein the secondary winding comprises a plurality of turns of secondary winding, and the number of turns of the secondary winding is greater than or equal to the number of turns of the primary winding.

7. The transformer of claim 6, wherein the number of turns of the secondary winding is no more than 5 times the number of turns of the primary winding.

8. The transformer of claim 6, wherein the line width of the primary coil or the auxiliary coil is calculated by:

wherein S is _b R is the line width of the coil _i Is the inner diameter of the coil, r _a Is the outer diameter of the coil S _a And N is the number of turns of the coil.

9. The transformer of claim 6, wherein the primary winding has a first winding start end and a first winding end, the auxiliary winding has a second winding start end and a second winding end, the secondary winding has a third winding start end and a third winding end, the PCB board is further provided with a first input end, a second input end, a first output end and a second output end, the PCB board is further provided with a third input end and a third output end, the first input end is connected with the first winding start end, the first output end is connected with the first winding end, the second input end is connected with the second winding start end, the second output end is connected with the second winding end, the third input end is connected with the third winding start end, and the third output end is connected with the third winding end.

10. The transformer of claim 9, wherein the first input, the second input, the first output, and the second output are on the same side of the PCB, the third input and the third output are on the same side, and the third input is on both radial sides of the primary winding as the first input.