Coil assembly of planar transformer, planar transformer and switching power supply circuit

Abstract

The utility model discloses a coil assembly of a planar transformer, the planar transformer and a switching power supply circuit, and the coil assembly of the planar transformer comprises a plurality of circuit board layers and a plurality of coils, the plurality of circuit board layers comprise a first circuit board layer, a second circuit board layer and a plurality of middle layers located between the first circuit board layer and the second circuit board layer; the plurality of coils are arranged on the plurality of circuit board layers, the positions of the plurality of coils correspond to each other in the stacking direction of the plurality of circuit board layers, and at least one layer of circuit board is arranged between every two adjacent coils for separation; at least two of the coils form a primary winding, the rest of the coils form a secondary winding, the coils forming the primary winding are arranged on the first circuit board layer and the second circuit board layer respectively, and the coils forming the secondary winding are located on the multiple middle layers. The method is used for solving the problems that miniaturization design is difficult to achieve, technological processing difficulty is large, and parameter testing cannot be achieved.

Description

Technical Field

[0001] The utility model relates to the technical field of transformers, in particular to a coil component of a planar transformer, a planar transformer and a switching power supply circuit. Background Art

[0002] At present, transformers often use skeleton transformers or plate-type planar transformers. Skeleton transformers are large in size and difficult to meet the requirements of module miniaturization design. Therefore, planar transformers are often used to achieve miniaturization design. However, most existing planar transformers have the following problems:

[0003] First, due to the limited number of PCB layers, the number of winding coils is limited, which leads to a small air gap design and difficult processing. Problems such as large inductance deviation, easy saturation, and low efficiency often occur.

[0004] Secondly, since it is not designed independently from other circuits on the PCB, parameter testing cannot be performed, and the pass rate can only be improved by standardizing the appearance, structure or production process, but the improvement effect of using such methods is not ideal. Utility Model Content

[0005] The main purpose of the utility model is to provide a coil assembly of a planar transformer, a planar transformer and a switching power supply circuit, which are used to solve the problems of difficulty in miniaturization design, difficulty in process processing and inability to achieve parameter testing.

[0006] To achieve the above object, the utility model provides a coil assembly of a planar transformer, comprising:

[0007] A plurality of circuit board layers stacked in sequence, wherein the plurality of circuit board layers comprises a first circuit board layer, a second circuit board layer, and a plurality of intermediate layers located between the first circuit board layer and the second circuit board layer;

[0008] A plurality of coils are arranged on the multi-layer circuit board layer, and in the stacking direction of the multi-layer circuit board layer, the positions of the plurality of coils correspond to each other, and at least one layer of circuit board is separated between two adjacent coils;

[0009] At least two of the multiple coils constitute the primary winding, and the rest constitute the secondary winding. The coils constituting the primary winding are arranged on the first circuit board layer and the second circuit board layer, and the coils constituting the secondary winding are located in the multiple intermediate layers.

[0010] In one embodiment, a plurality of first welding points are provided on both sides of the circuit board layer, and the plurality of circuit board layers are connected and fixed to each other via the plurality of first welding points.

[0011] In one embodiment, the circuit board layer is provided with a magnetic core hole, the magnetic core hole is used for inserting an iron core, and the coil is arranged around the magnetic core hole.

[0012] In one embodiment, the circuit board layer is provided with a first electrical connection end and / or a second electrical connection end, the first electrical connection end is used for connecting the coil to an external circuit, and the second electrical connection end is used for connecting the coil to coils of other circuit board layers.

[0013] In one embodiment, the circuit board layer is provided with a first electrical connection end and a second electrical connection end, and the coil is spirally wound from the first electrical connection end to the second electrical connection end, or the coil is spirally wound from the second electrical connection end to the first electrical connection end.

[0014] In one embodiment, the second electrical connection end includes a first slot hole and a second slot hole, and the coil is spirally wound from the first slot hole to the second slot hole. The first slot hole is used for connecting the coil with the coil of the upper circuit board layer, and the second slot hole is used for connecting the coil with the coil of the lower circuit board layer. The coils connected to the same second electrical connection end have the same winding direction.

[0015] To achieve the above objectives, the utility model also provides a planar transformer, which includes a core assembly and a coil assembly of the planar transformer as described above, wherein the core assembly is provided with an iron core, and the iron core is inserted into a magnetic core hole of a multi-layer circuit board layer and passes through the multi-layer circuit board layers.

[0016] In one embodiment, the core assembly is provided with positioning grooves for placing and positioning the multi-layer circuit board layers.

[0017] In one embodiment, there are two core components, and the two core components are arranged opposite to each other along the stacking direction of the multiple circuit board layers. One of the two core components is arranged close to the first circuit board layer, and the other is arranged close to the second circuit board layer. The cores of the two core components are passed through the multiple circuit board layers and abut against each other.

[0018] To achieve the above object, the utility model further provides a switching power supply circuit, which includes the planar transformer as described above.

[0019] Compared with the prior art, the utility model has the following beneficial effects:

[0020] The coil assembly of the planar transformer includes a plurality of circuit board layers stacked in sequence, and a plurality of coils are arranged on the plurality of circuit board layers. In the stacking direction of the plurality of circuit board layers, the positions of the plurality of coils correspond to each other, and there is at least one circuit board layer separating two adjacent coils, so that the plurality of circuit board layers provided with coils can be used as the coil assembly of the planar transformer, thereby solving the problem of large volume caused by the design of a skeleton structure, and effectively meeting the design requirements of module miniaturization. Compared with the plate-cut planar transformer, the surface mounting method can save the process of pressing the magnetic core in the production and manufacturing, and can also fundamentally reduce the risk of high production defect rate and improve the yield rate;

[0021] The multi-layer circuit board layer includes a first circuit board layer, a second circuit board layer and a plurality of intermediate layers located between the first circuit board layer and the second circuit board layer. At least two of the plurality of coils constitute a primary winding, and the rest constitute a secondary winding. The coils constituting the primary winding are arranged on the first circuit board layer and the second circuit board, and the coils constituting the secondary winding are located on the plurality of intermediate layers. This can realize independent circuit design, facilitate transformer testing, avoid the problem of being unable to perform parameter testing, and resulting in the problem of only being able to improve the pass rate by standardizing the appearance, structure or production process, effectively improve the yield rate, and facilitate production, testing and application;

[0022] The independent planar transformer design can also make transformer testing more convenient, save the production process of pressing the magnetic core during production, reduce production and processing costs, and improve production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0024] Figure 1 A circuit diagram of an embodiment of a planar transformer of the utility model;

[0025] Figure 2 It is a structural schematic diagram of an embodiment of a coil assembly of the utility model;

[0026] Figure 3 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0027] Figure 4 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0028] Figure 5It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0029] Figure 6 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0030] Figure 7 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0031] Figure 8 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0032] Fig. 9 It is a structural schematic diagram of another embodiment of the coil assembly of the utility model;

[0033] Fig.10 It is a structural schematic diagram of an embodiment of a planar transformer of the utility model;

[0034] Fig.11 It is an exploded view of an embodiment of a planar transformer of the present utility model.

[0035] Description of Figure Numbers:

[0036] Label name Label name 100 Circuit board layers 130 Core hole 101 First circuit board layer 200 Coil 102 Second PCB layer 310 Primary Winding 103 Middle Layer 320 Secondary Winding 104 Silkscreen circuit board layer 400 Core components 110 The first welding point 410 Iron Core 121 First electrical connection terminal 420 Positioning slot 122 Second electrical connection terminal 4201 Bottom of the tank 1221 First slot 430 Positioning parts 1222 Second slot

[0037] The realization of the purpose, functional features and advantages of the utility model will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments of the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0039] It should be noted that if all directional indications in the embodiments of the present invention are only used to explain the relative position relationship, movement status, etc. between the components in a certain specific posture, if the specific posture changes, the directional indication will also change accordingly.

[0040] If the description of "first", "second", etc. in the present utility model is only used for descriptive purposes, and cannot be understood as indicating or implying their relative importance, or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. If the description of "A and / or B" is involved in the present utility model, it means that it includes solution A or solution B, or includes solution A and solution B. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present utility model.

[0041] Generally, many analog input and output modules in the discrete control field require multiple voltage outputs on the field side. When there is only a 24V input voltage or other low input voltages, a flyback switching power supply is often used as the power supply for the field side circuit system. Conventional flyback switching power supplies require the use of PWM chips in conjunction with transformers. At present, this type of transformer often uses a skeleton transformer or a plate-section planar transformer. Due to its large size, skeleton transformers are difficult to meet the requirements of module miniaturization design, so planar transformers are often used to achieve miniaturization design. However, most of the existing planar transformers have the following problems:

[0042] First, due to the limited number of PCB layers, the number of winding coils is limited, which leads to a small air gap design and difficult processing. Problems such as large inductance deviation, easy saturation, and low efficiency often occur.

[0043] Secondly, since it is not designed independently from other circuits on the PCB, parameter testing cannot be performed, and the pass rate can only be improved by standardizing the appearance, structure or production process, but the improvement effect of using such methods is not ideal.

[0044] In order to solve the problems that existing technologies are difficult to achieve miniaturization design, difficult to process, and unable to achieve parameter testing, refer to Figures 1 to 11 , the present application provides a coil assembly of a planar transformer, a planar transformer and a switching power supply circuit.

[0045] Reference Figures 1 to 11 The coil assembly of the planar transformer includes a plurality of circuit board layers 100 and a plurality of coils 200 stacked in sequence.

[0046] The multi-layer circuit board layer 100 includes a first circuit board layer 101, a second circuit board layer 102, and a plurality of intermediate layers 103 located between the first circuit board layer 101 and the second circuit board layer 102. A plurality of coils 200 are arranged on the multi-layer circuit board layer 100. In the stacking direction of the multi-layer circuit board layer 100, the positions of the plurality of coils 200 correspond to each other, and there is at least one circuit board layer separating two adjacent coils 200.

[0047] With such an arrangement, the multi-layer circuit board layer 100 provided with the coil 200 can be used as a coil component of a planar transformer, thereby solving the problem of large volume caused by being designed as a skeleton structure, and effectively meeting the design requirements of module miniaturization. Compared with a plate-section planar transformer, the surface-mount mounting method can save the process of pressing the magnetic core in the production and manufacturing, and can also fundamentally reduce the risk of high production defective rate and improve the yield rate.

[0048] It can be understood that the plurality of coils 200 overlap along the projection direction of the multi-layer circuit board layer 100, and there is at least one circuit board layer 100 between two adjacent coils 200, and the coil can be optionally arranged on at least one side of the circuit board layer. The outer side of the outermost circuit board layer 100 of the coil assembly of the planar transformer can be optionally not designed for wiring, or a coil 200 can also be arranged. The multi-layer circuit board layer 100 has a first end and a second end opposite to each other along its stacking direction, the first circuit board layer 101 is arranged at the first end of the coil assembly or close to the first end of the coil assembly, and the second circuit board layer 102 is arranged at the second end of the coil assembly or close to the second end of the coil assembly. The first circuit board layer 101 includes at least one circuit board layer. When the first circuit board layer 101 is provided with a multi-layer circuit board layer 100, the multi-layer circuit board layers 100 are stacked in sequence; the second circuit board layer 102 is also the same. The middle layer 103 includes at least one circuit board layer 100. When the middle layer 103 is provided with a multi-layer circuit board layer 100, the multi-layer circuit board layers 100 are stacked in sequence and arranged between the first circuit board layer 101 and the second circuit board layer 102. The shapes and sizes of the multi-layer circuit board layers 100 may be the same or different; the number of turns, winding width, line spacing of the coils 200 arranged on different circuit board layers 100 and the copper foil thickness, dielectric layer thickness, etc. of the circuit board layers 100 may be the same or different; the specific settings may be based on actual conditions and are not limited here.

[0049] At least two of the multiple coils 200 constitute the primary winding 310 , and the rest constitute the secondary winding 320 . The coils 200 constituting the primary winding 310 are disposed on the first circuit board layer 101 and the second circuit board layer 102 , and the coils 200 constituting the secondary winding 320 are located on multiple intermediate layers 103 .

[0050] A plurality of coils 200 are arranged on a multi-layer circuit board layer 100, at least two of the plurality of coils 200 constitute a primary winding 310, and the coils 200 constituting the primary winding 310 are disposed on a first circuit board layer 101 and a second circuit board layer 102. Specifically, the coils 200 constituting the primary winding 310 may be disposed on at least one first circuit board layer 101 and at least one second circuit board layer 102. Other coils 200 of the plurality of coils 200 constitute at least one secondary winding 320, and the plurality of coils 200 constituting the secondary winding 320 are disposed on a plurality of middle layers 103, so that the coil assembly is arranged in a structure similar to a sandwich, with the primary winding 310 disposed on the outer layer and the secondary winding 320 disposed on the middle layer 103. In this way, independent circuit design can be realized, transformer testing is facilitated, and the problem that parameter testing cannot be performed, resulting in the problem that the qualified rate can only be improved by standardizing the appearance, structure or production process, is avoided, and the qualified rate is effectively improved, and production, testing and application are facilitated.

[0051] The independent design of the planar transformer is achieved through the improvement of the planar transformer coil assembly, which makes the transformer testing more convenient and saves the production process of pressing the magnetic core in the production process, reduces the production and processing costs, and improves production efficiency.

[0052] In one embodiment, a plurality of first welding points 110 are disposed on both sides of the circuit board layer 100 , and the multi-layer circuit board layers 100 are connected and fixed to each other via the plurality of first welding points 110 .

[0053] The design of the first welding point 110 can connect and fix the multi-layer circuit board layer 100, and can further reduce the occupied space of the planar transformer by reducing the volume of the coil assembly. In addition, the first welding point 110 can also be used as the first electrical connection end 121 of the coil assembly to achieve the connection of at least part of the circuit board layer 100 with the external circuit. Optionally, part of the multiple first welding points 110 on both sides of the circuit board layer 100 is designed to be used for connecting and fixing the multi-layer circuit board layer 100; the other parts of the multiple first welding points 110 are used for connecting the circuit board layer 100 with the external circuit or for electrically connecting at least two circuit board layers 100 arranged adjacently or spaced apart; the number of first welding points 110 arranged on both sides of the same circuit board layer 100 can be the same or different, and the number of first welding points 110 arranged on different circuit board layers 100 and the positions of the first welding points 110 can be the same or different; the specific settings can be based on actual conditions and are not limited here.

[0054] In one embodiment, the circuit board layer 100 is provided with a magnetic core hole 130 , and the magnetic core hole 130 is used for inserting the iron core 410 , and the coil 200 is disposed around the magnetic core hole 130 .

[0055] Specifically, the positions of the plurality of first welding points 110 of the multilayer circuit board layer 100 may be arranged to correspond to each other, the positions of the magnetic core holes 130 of the multilayer circuit board layer 100 may be arranged to correspond to each other, and the coil 200 may be arranged around the magnetic core holes 130. In order to further reduce the volume of the coil assembly and the planar transformer, the magnetic core holes 130 may be arranged in the middle of the circuit board layer 100 or close to the middle of the circuit board layer 100 to surround as many turns of the coil 200 as possible.

[0056] Optionally, the circuit board layer 100 shown has a wiring portion in the middle for winding the coil 200. The wiring portion can be specifically set to a circular shape, an elliptical shape or any shape suitable for actual use. The center of the magnetic core hole 130 coincides with the center point of the wiring portion, and extension portions are symmetrically provided on both sides of the wiring portion. The two extension portions and the wiring portion are an integrally formed structure, which are used to construct the circuit board layer 100 shown in this application. The direction of the two extension portions away from each other is taken as the length direction of the extension portion. The length direction of the two extension portions is parallel to the radial direction of the magnetic core hole 130, and the two extension portions are provided with a plurality of first welding points 110 at intervals along their length direction.

[0057] In one embodiment, the circuit board layer 100 is provided with a first electrical connection end 121 and / or a second electrical connection end 122, the first electrical connection end 121 is used for connecting the coil 200 to an external circuit, and the second electrical connection end 122 is used for connecting the coil 200 to the coil 200 of another layer of the circuit board layer 100.

[0058] Optionally, the first electrical connection end 121 is provided at the first welding point 110, or the first electrical connection end 121 is connected to the closest first welding point 110 for connection with an external circuit. The coil 200 is spirally wound from the first electrical connection end 121 to the second electrical connection end 122, and the coil 200 can be wound in a clockwise direction or in a counterclockwise direction. In addition, the second electrical connection end 122 shown can also be set as a second welding point, and a slot hole can be opened corresponding to the second welding point, so that the slot hole is provided on the circuit board layer 100 in the form of penetrating the thickness of the circuit board layer 100, and the specific setting can be based on actual conditions and is not limited here.

[0059] The second electrical connection end 122 is used for connecting the coil 200 with the coil 200 of the other circuit board layer 100. The other circuit board layer 100 can be stacked with the circuit board layer 100 as the upper circuit board layer 100 or the lower circuit board layer 100 of the circuit board layer 100, or the other circuit board layer 100 can also be arranged in other layers and spaced apart from the circuit board layer 100. When the circuit board layer 100 is provided with the second electrical connection end 122, the position of the second electrical connection end 122 of the circuit board layer 100 and the position of the second electrical connection end 122 of the other correspondingly connected circuit board layer 100 are adjacently arranged or at least partially overlapped in the stacking direction of the circuit board layer 100, so as to realize the connection between the coils 200 between the boards.

[0060] Optionally, the same circuit board layer 100 is only provided with a plurality of first electrical connection terminals 121 for connecting the coil 200 to an external circuit; or, the same circuit board layer 100 is only provided with a plurality of second electrical connection terminals 122 for connecting the coil 200 to an external circuit; or, the same circuit board layer 100 is provided with at least one electrical connection terminal for connecting the coil 200 to an external circuit and at least one second electrical connection terminal 122 for connecting the coil 200 to the coil 200 of other circuit board layers 100.

[0061] As an example, when the circuit board layer 100 is provided with a plurality of first electrical connection ends 121, the coil 200 is spirally wound from one of the first electrical connection ends 121 to another of the first electrical connection ends 121, so as to realize the connection between the coil 200 and the external circuit;

[0062] As another example, when the circuit board layer 100 is provided with a plurality of second electrical connection ends 122, the coil 200 is spirally wound from one of the second electrical connection ends 122 to another of the second electrical connection ends 122, so as to realize the connection of the coil 200 between the boards;

[0063] As another example, when the circuit board layer 100 is provided with both the first electrical connection end 121 and the second electrical connection end 122, the coil 200 is spirally wound from the first electrical connection end 121 to the second electrical connection end 122, or the coil 200 is spirally wound from the second electrical connection end 122 to the first electrical connection end 121;

[0064] The number of the first electrical connection terminals 121 and the second electrical connection terminals 122 and the positions of the first electrical connection terminals 121 and the second electrical connection terminals 122 may be set according to actual conditions, and are not limited herein.

[0065] In one embodiment, the second electrical connection end 122 includes a first slot 1221 and a second slot 1222. The coil 200 is spirally wound from the first slot 1221 to the second slot 1222. The first slot 1221 is used for connecting the coil 200 to the coil 200 of the upper circuit board layer 100, and the second slot 1222 is used for connecting the coil 200 to the coil 200 of the lower circuit board layer 100. The coils 200 connected to the same second electrical connection end 122 have the same winding direction.

[0066] It can be understood that the multi-layer circuit board layers 100 are stacked in sequence from top to bottom, and the stacking direction of the multi-layer circuit board layers 100 is from top to bottom. The upper circuit board layer 100 of any circuit board layer 100 is arranged on the upper side of the circuit board layer 100, and the lower circuit board layer 100 of any circuit board layer 100 is arranged on the lower side of the circuit board layer 100. The first slot 1221 is used for connecting the coil 200 arranged on the circuit board layer 100 with the coil 200 of the circuit board layer 100 arranged on the upper side of the circuit board layer 100, and the second slot 1222 is used for connecting the coil 200 arranged on the circuit board layer 100 with the coil 200 of the circuit board layer 100 arranged on the lower side of the circuit board layer 100. The embodiment in which the multi-layer circuit board layers 100 are stacked in sequence from bottom to top refers to the above-mentioned example in which the multi-layer circuit board layers 100 are stacked in sequence from top to bottom, and will not be repeated here.

[0067] Optionally, the second electrical connection end 122 can be specifically configured as a second welding point, so that the first slot 1221 and the second slot 1222 are provided on the circuit board layer 100 as coil 200 connection vias that penetrate the thickness of the circuit board layer 100, and the coils 200 of adjacent circuit board layers 100 are electrically connected through the second electrical connection end 122 by welding, jumper connection, etc.

[0068] When the circuit board layer 100 is provided with a first slot hole 1221, the position of the first slot hole 1221 of the circuit board layer 100 at least partially overlaps with the position of the second slot hole 1222 of the previous circuit board layer 100 in the stacking direction of the circuit board layer 100, or the position of the first slot hole 1221 of the circuit board layer 100 and the position of the second slot hole 1222 of the previous circuit board layer 100 are adjacently arranged in the stacking direction of the circuit board layer 100, so that the coils 200 of the adjacent circuit board layers 100 are connected; when the circuit board layer 100 is provided with a second slot hole 1222, the position of the second slot hole 1222 of the circuit board layer 100 and the position of the first slot hole 1221 of the next circuit board layer 100 in the stacking direction of the circuit board layer 100 at least partially overlaps, or the position of the second slot hole 1222 of the circuit board layer 100 and the position of the first slot hole 1221 of the next circuit board layer 100 are adjacently arranged in the stacking direction of the circuit board layer 100, so that the coils 200 of the adjacent circuit board layers 100 are connected.

[0069] Reference Fig.10 , Fig.11 The present application also provides a planar transformer, which includes a coil assembly of a planar transformer as shown in the above example of the present application. Since the planar transformer adopts all the technical solutions of all the above embodiments, it has at least all the beneficial effects brought by the technical solutions of the above embodiments. The specific implementation method of this embodiment refers to the above embodiment, so it will not be repeated here one by one.

[0070] In one embodiment, the planar transformer further includes a core assembly 400 , wherein the core assembly 400 is provided with a core 410 , and the core 410 is inserted into the magnetic core hole 130 of the multi-layer circuit board layer 100 and is disposed through the multi-layer circuit board layer 100 .

[0071] The coil assembly of the planar transformer can be connected into a whole through the first welding points 110 on both sides after the stacking of the multi-layer circuit board layers 100 and the inter-board connection of the multiple coils 200 are completed, and as a whole, it can be sleeved outside the iron core 410 of the iron core assembly 400 through the middle magnetic core hole 130; or, the multi-layer circuit board layers 100 can be sleeved on the iron core 410 of the iron core assembly 400 in sequence, and the connection of the coils 200 of each layer of the circuit board layer 100 is completed in sequence during the sleeve process of the circuit board layers 100. After all the circuit board layers 100 are sleeved, the coil assembly is connected into a whole through the first welding points 110 on both sides of the multi-layer circuit board layers 100. The specific assembly method of the coil assembly and the iron core assembly 400 can be set according to the actual setting, which is not limited here.

[0072] In one embodiment, in order to position and install the coil assembly, the core assembly 400 is provided with a positioning groove 420 for the multi-layer circuit board layer 100 to be placed and positioned.

[0073] Optionally, the multi-layer circuit board layer 100 has the same shape and size, and the positioning groove 420 is snap-fitted with the multi-layer circuit board layer 100. In the assembled state, the groove wall of the positioning groove 420 fits with the outer peripheral wall of the multi-layer circuit board layer 100. The positioning groove 420 limits the circuit board layer 100 sleeved on the iron core 410, so that the multi-layer circuit board layer 100 is positioned and restricted in the positioning groove 420, thereby avoiding position displacement of the circuit board layer 100 and affecting the actual use effect.

[0074] In one embodiment, the core assembly 400 is provided with at least one positioning member 430 . The at least one positioning member 430 is arranged in a ring shape around the core assembly 400 to enclose a positioning groove 420 .

[0075] It can be understood that the positioning groove 420 is circled by the positioning member 430 to achieve the positioning of the circuit board layer 100. Specifically, multiple limiting members can be set along the periphery of the core assembly 400, or the limiting members can be set into an annular structure mounted on the core assembly 400 to enclose the positioning groove 420 shown.

[0076] Specifically, based on the above example, the inner peripheral wall of the positioning member 430 shown can be set to an arc shape corresponding to the wiring part of the circuit board layer 100, so that the inner peripheral wall of the positioning member 430 is set close to the outer peripheral wall of the wiring part of the circuit board layer 100. Each core assembly 400 is provided with two, three or other multiple positioning members 430, and multiple positioning members 430 of the same core assembly 400 are arranged at intervals, so that the extension of the circuit board layer 100 extends out of the core assembly 400 through the gap between the positioning members 430, and the side of the two extensions close to the wiring part and perpendicular to its length direction is used as the width of the extension. The spacing distance of multiple positioning members 430 is set corresponding to the width of the extension, so as to further position the coil assembly by limiting the displacement of the extension. In this way, the connection between the coil assembly and the external circuit can also be achieved to avoid blocking the first electrical connection end 121 and affecting the electrical connection.

[0077] The core assembly 400 shown in the present application has at least one, and the core 410 shown is arranged in the middle of the positioning groove 420, so that the overall cross-section of the core assembly 400 is any one of C-type, E-type, F-type, H-type, I-type, L-type, T-type, and U-type, or a combination of multiple types. Specifically, the core 410 that can be independently arranged can be used as a core assembly 400, so that the overall cross-section of the core assembly 400 is I-type; or, the core assembly 400 is provided with at least one connecting plate along the axial direction of the core 410, and the connecting plate is arranged at at least one end of the core assembly 400, so that the overall cross-section of the core assembly 400 is C-type, L-type, T-type, U-type, or H-type; or, a positioning plate is additionally arranged in the middle of the core 410 of the core assembly 400 along the axial direction thereof, so that the overall cross-section of the core assembly 400 is E-type or F-type, so as to further restrict the multi-layer circuit board layer 100 and prevent the circuit board layer 100 from positional displacement. Multiple positioning members 430 are arranged on the connecting plate, so that the positioning groove 420 is formed in an open state between the inner walls of the multiple positioning members 430 and the connecting plate, and the groove bottom 4201 of the positioning groove 420 is formed on a side of the connecting plate close to the positioning member 430 to achieve the limitation of the coil assembly.

[0078] In one embodiment, the multi-layer circuit board layer 100 further includes a silk-screen circuit board layer 104, which is stacked outside the first circuit board layer 101 and arranged against the bottom 4201 of the positioning groove 420, and / or, the silk-screen circuit board layer 104 is stacked outside the second circuit board layer 102 and arranged against the bottom 4201 of the positioning groove 420. The silk-screen circuit board layer 104 is used for silk-screening logos or as a board layer of the multi-layer circuit board layer that can effectively place components without wiring on the silk-screen circuit board layer 104. The silk-screen circuit board layer 104 is arranged on the outermost layer of the multi-layer circuit board layer 100, and can be arranged outside the first circuit board layer 101 and / or outside the second circuit board layer 102 according to actual conditions, so that the silk-screen circuit board layer 104 is close to the bottom 4201 of the positioning groove 420 of the core assembly 400 in the assembled state, that is, the silk-screen circuit board layer 104 is close to the connection plate of the core assembly 400 in the assembled state, so that further limiting of the coil assembly can be achieved.

[0079] In one embodiment, for the convenience of assembly and connection, there are two core components 400, and the two core components 400 are arranged opposite to each other along the stacking direction of the multi-layer circuit board layer 100, one of the two core components 400 is arranged close to the first circuit board layer 101, and the other is arranged close to the second circuit board layer 102, and the cores 410 of the two core components 400 are penetrated through the multi-layer circuit board layer 100 and abut against each other. In this way, the coil component can be confined between the two core components 400, and the outermost circuit board layer 100 of the coil component is respectively arranged against the groove bottom 4201 of the positioning groove 420 of the two core components 400.

[0080] Optionally, at least one of the two core assemblies 400 is provided with an iron core 410, and at least one is provided with a positioning piece 430 for enclosing the above-mentioned positioning groove 420. When one of the two core assemblies 400 is provided with an iron core 410, in the assembled state, the iron core 410 is passed through the multi-layer circuit board layer 100 of the coil assembly and abuts against the other core assembly 400; when both core assemblies 400 are provided with an iron core 410, in the assembled state, the iron cores 410 of the two core assemblies 400 are passed through the multi-layer circuit board layer 100 of the coil assembly and abut against each other; the two core assemblies 400 are optionally provided with a positioning piece 430 or are not provided with a positioning piece 430. When at least one of the two core assemblies 400 is provided with a positioning piece 430, the positioning piece 430 is optionally configured to abut against The other core assembly 400 is in contact with or not in contact with the other core assembly 400, that is, the positioning piece 430 is vertically arranged on the connecting plate of the core assembly 400, the height of the positioning piece 430 is perpendicular to the connecting plate of the core assembly 400, and the overlapping length of the height of the positioning pieces 430 of the two core assemblies 400 is not greater than the stacking thickness of the multi-layer circuit board layer 100 of the coil assembly; in addition, when both core assemblies 400 are provided with positioning pieces 430, the positioning pieces 430 of the two core assemblies 400 can also be arranged into a snap-fitting and adaptable structure; the specific settings can be made according to the actual situation, which will not be elaborated here.

[0081] Without limiting the planar transformer shown in the present application, the lengths of the cores 410 of the two core assemblies 400 can be optionally set so that the lengths of the two core assemblies 400 are the same or different; alternatively, one of the two core assemblies 400 shown in the present application can be set to any one of F-type, H-type, I-type, L-type, T-type, and U-type, and the other can be set to a straight shape with only one connecting plate, so as to limit the coil assembly between the two core assemblies 400; alternatively; one of the two core assemblies 400 shown in the present application can be set to a C-type or other shape with two connecting plates set at intervals, and the other can be set to an I-type with only one core 410, the I-type core 410 passes through the magnetic core hole 130 of the multi-layer circuit board layer 100 of the coil assembly and its two ends are respectively connected to the two connecting plates of the other core assembly 400, so as to limit the coil assembly between the two core assemblies 400; the specific method of assembling the core assembly 400 and the core assembly 400 and the coil assembly can be set according to the actual setting, which is not limited here.

[0082] The planar transformer shown in the present application can be applied to a flyback switching power supply. As a specific embodiment of the present application, refer to Figure 1 The circuit schematic diagram of the planar transformer shown in the figure takes the selected magnetic core model EC13A as an example. When the magnetic core air gap size Igas, transformer inductance Lpri, primary side maximum impulse current Ipk, and magnetic core effective cross-sectional area Ae are known, the formula The maximum magnetic flux density Bmax is derived, and the number of winding turns on the primary side and the secondary side is further calculated according to the obtained maximum magnetic flux density Bmax to determine the number of coil turns of the primary winding 310 and the secondary winding 320 .

[0083] Specifically, the design core air gap size Igas is determined to be 90um. In addition, based on the output power consumption and the PWM chip, the transformer inductance Lpri is determined to be 35uH, the maximum impulse current Ipk on the primary side is determined to be 1A, and the effective cross-sectional area Ae of the core is determined to be 20.8mm2.

[0084] Substitute into the formula:

[0085] get:

[0086] The maximum magnetic flux density Bmax is calculated to be 1435G.

[0087] Furthermore, the number of winding turns on the primary side and the secondary side is calculated according to the following primary side winding turn calculation formula and secondary side winding turn calculation formula. Specifically:

[0088] Substitute the known parameters into the primary winding turns calculation formula:

[0089] get: By calculating Figure 1 The number of turns of the coil N3 shown is 10, that is, the number of turns of the coil of the primary winding 310 is 10.

[0090] Substitute the known parameters into the secondary winding turns calculation formula:

[0091] get:

[0092]

[0093]

[0094] By calculating Figure 1 The number of turns of the N1 coil shown is 8, and the number of turns of the N2 coil is 3. Figure 1 The N4 coil shown is shared by the N2 coil. Subtracting the shared part, we get Figure 1 The number of turns of the N4 coil shown is 5.

[0095] In summary, the primary winding N3 has 10 turns, and the secondary winding 320 includes a first secondary winding N1, a second secondary winding N2, and a third secondary winding N4. The first secondary winding N1 has 8 turns, the second secondary winding N2 has 3 turns, and the third secondary winding N4 has 5 turns.

[0096] According to the limited size of the core assembly 400 and the circuit board layer 100 actually designed, the multi-layer circuit board layer 100 of the coil assembly is designed as follows: Figures 2 to 11 The structure shown in the figure can be designed according to actual needs and processing requirements, with a winding width of 10 to 25 mil, a line spacing of 5 to 7 mil, a copper foil thickness of 0.8 to 1.5 oz, and a dielectric layer thickness of 0.08 to 1.2 mm. A plurality of first welding points 110 are respectively arranged on both sides of the circuit board layer 100 to form pins 1 to 11, so as to Figures 2 to 9 The circuit board layers 100 shown in the figure are sequentially used as the first to eighth circuit board layers 100, and according to Figure 1 The circuit shown is a coil 200 .

[0097] The coil N3 is used as the primary side, that is, the primary winding 310 is wound from pin 1 to pin 4. The coils N1, N2, and N4 are used as the secondary side 1 outputs, that is, the first secondary winding N1 is wound from pin 7 to pin 8; the second secondary winding N2 is wound from pin 6 to pin 7; the third secondary winding N4 is wound from pin 5 to pin 6. The remaining pins 2, 3, 9, 10, and 11 are used as fixed pins, that is, after the winding of the coil 200, the stacking design of the multi-layer circuit board layer 100, and the winding of the coil 200 are completed, each circuit board layer 100 is welded and fixed by the remaining pins 2, 3, 9, 10, and 11, so that the coil assembly is connected and fixed into a whole.

[0098] Reference Figure 2 The circuit board layer shown is a silk-screen circuit board layer 104, which serves as the first layer (TOP layer) of the multi-layer circuit board layer of the coil assembly. This circuit board layer is not wired and is tightly attached to the bottom 4201 of the positioning groove 420 of the core assembly 400 during installation.

[0099] by Figure 3 , Figure 4 The circuit board layers shown are respectively used as the second layer and the third layer of the multi-layer circuit board layer. Specifically, with respect to the coil assembly shown in the present application, the second and third circuit board layers are used as the first circuit board layer 101 of the multi-layer circuit board layer. The coil of the second circuit board layer starts from the first electrical connection end A, is wound 3 times, and is connected to the first slot C of the third circuit board layer through the second slot B; the coil of the third circuit board layer is connected to the second slot B of the second circuit board layer through the first slot C, and the coil of the third circuit board layer starts from the first slot C, is wound 3 times, and is connected to the first slot C of the third circuit board layer through the second slot D. Fig.10 The eighth circuit board layer is shown.

[0100] by Figures 5 to 8The circuit board layers shown are respectively used as the fourth, fifth, sixth and seventh layers of the multi-layer circuit board layer. Specifically, in the coil assembly shown in the present application, the fourth, fifth, sixth and seventh circuit board layers are used as the middle layer 103 of the multi-layer circuit board layer. The coil of the fourth circuit board layer starts from the first electrical connection end E, is wound 4 times, and is connected to the first slot G of the fifth circuit board layer through a via at the second slot F; the coil of the fifth circuit board layer is connected to the second slot F of the fourth circuit board layer from the first slot G, and the coil of the fifth circuit board layer starts from the first slot G and is wound. After being wound 4 turns, it is connected at the first electrical connection terminal H, and is constructed into a first secondary winding N1 through the coils of the fourth and fifth circuit board layers; the coil of the sixth circuit board layer starts from the first electrical connection terminal I, is wound 5 turns, and then passes through the via hole at the second slot J to the seventh circuit board layer, so as to construct a third secondary winding N4; the first slot K of the seventh circuit board layer is connected to the second slot J of the sixth layer, and the coil of the seventh circuit board layer starts from the first slot K, is wound 3 turns, and is connected to the first electrical connection terminal L, so as to construct a second secondary winding N2.

[0101] by Fig. 9 The circuit board layer shown serves as the eighth layer of the multi-layer circuit board layer. Specifically, with respect to the coil assembly shown in the present application, the eighth circuit board layer serves as the second circuit board layer 102 of the multi-layer circuit board layer. The eighth circuit board layer is connected to the second slot D of the third circuit layer through the first slot M. The coil of the eighth circuit board layer starts from the first slot M, is wound four times, and is connected to the first electrical connection terminal N. The primary winding N3 is constructed by the coils of the first, second, and eighth circuit board layers.

[0102] When the winding connection pins are determined, the stacking order of each circuit board layer, the number of coils provided on each circuit board layer, etc. can be adjusted according to actual conditions, which are not limited here.

[0103] In one embodiment, the present application also provides a switching power supply circuit, which includes a planar transformer as in any of the above embodiments, and has the technical features of the planar transformer in the above embodiments, and can at least achieve the beneficial effects of the above-mentioned planar transformer implementation. To avoid repetition, it will not be repeated here.

[0104] The above description is only an optional embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A coil assembly of a planar transformer, characterized in that: include: A plurality of circuit board layers stacked in sequence, wherein the plurality of circuit board layers comprises a first circuit board layer, a second circuit board layer, and a plurality of intermediate layers located between the first circuit board layer and the second circuit board layer; A plurality of coils are arranged on the multi-layer circuit board layer, and in the stacking direction of the multi-layer circuit board layer, the positions of the plurality of coils correspond to each other, and at least one layer of circuit board is separated between two adjacent coils; At least two of the multiple coils constitute the primary winding, and the rest constitute the secondary winding. The coils constituting the primary winding are arranged on the first circuit board layer and the second circuit board layer, and the coils constituting the secondary winding are located in the multiple intermediate layers.

2. The coil assembly of the planar transformer according to claim 1, characterized in that: A plurality of first welding points are arranged on both sides of the circuit board layer, and the multiple circuit board layers are connected and fixed to each other through the plurality of first welding points.

3. The coil assembly of the planar transformer according to claim 1, characterized in that: The circuit board layer is provided with a magnetic core hole, the magnetic core hole is used for inserting an iron core, and the coil is arranged around the magnetic core hole.

4. The coil assembly of the planar transformer according to any one of claims 1 to 3, characterized in that: The circuit board layer is provided with a first electrical connection end and / or a second electrical connection end, the first electrical connection end is used for connecting the coil with an external circuit, and the second electrical connection end is used for connecting the coil with coils of other circuit board layers.

5. The coil assembly of the planar transformer according to claim 4, characterized in that: The circuit board layer is provided with a first electrical connection end and a second electrical connection end, and the coil is spirally wound from the first electrical connection end to the second electrical connection end, or the coil is spirally wound from the second electrical connection end to the first electrical connection end.

6. The coil assembly of the planar transformer according to claim 4, characterized in that: The second electrical connection end includes a first slot hole and a second slot hole. The coil is spirally wound from the first slot hole to the second slot hole. The first slot hole is used for connecting the coil with the coil of the upper circuit board layer, and the second slot hole is used for connecting the coil with the coil of the lower circuit board layer. The coils connected to the same second electrical connection end have the same winding direction.

7. A planar transformer, characterized in that: It comprises an iron core component and a coil component of a planar transformer as described in any one of claims 1 to 6, wherein the iron core component is provided with an iron core, the iron core is inserted into a magnetic core hole of a multi-layer circuit board layer and penetrates the multi-layer circuit board layer.

8. The planar transformer according to claim 7, characterized in that: The core assembly is provided with positioning grooves for placing and positioning the multi-layer circuit board layers.

9. The planar transformer according to any one of claims 7 to 8, characterized in that: There are two core components, which are arranged opposite to each other along the stacking direction of the multiple circuit board layers. One of the two core components is arranged close to the first circuit board layer, and the other is arranged close to the second circuit board layer. The cores of the two core components are passed through the multiple circuit board layers and abut against each other.

10. A switching power supply circuit, characterized in that: Comprising the planar transformer as claimed in any one of claims 7 to 9.

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