A planar transformer and a signal isolator

Abstract

A planar transformer and a signal isolator, belonging to the technical field of transformers. A planar transformer includes a PCB board, and the PCB board includes a first board layer, a second board layer, and a third board layer; a first side coil assembly is arranged between the first board layer and the second board layer, and a second side coil assembly is arranged between the second board layer and the third board layer. The first side coil assembly includes a first copper-clad layer and a second copper-clad layer. A board-interlayer is arranged between the first copper-clad layer and the second copper-clad layer. The thickness of the board-interlayer is less than the thickness of the second board layer. The board-interlayer is provided with a via hole, and a conductive medium is arranged in the via hole. The conductive medium is electrically connected to the first copper-clad layer and the second copper-clad layer. By reducing the thickness of the PCB board in this application, the volume of the planar transformer can be reduced to solve the problem that it is difficult to miniaturize the signal isolator due to the large volume of the planar transformer.

Description

Technical Field

[0001] The present invention belongs to the technical field of transformers, and particularly relates to a planar transformer and a signal isolator. Background Art

[0002] A planar transformer is a transformer formed by stacking conductive foils such as copper foils on a multi-layer printed circuit board (PCB) as windings. Compared with traditional transformers, it has a smaller volume, so it is widely used in products such as communication, computers, industrial control, aerospace engineering, and medical equipment.

[0003] For example, Chinese Patent No. CN113808825A discloses a planar transformer. In its PCB wire package, the second electrical connection points of the PCB coils in odd order are connected through corresponding second through holes to form one of the secondary winding and the primary winding, and the second electrical connection points of the PCB coils in even order are connected through corresponding second through holes to form the other of the secondary winding and the primary winding.

[0004] In an industrial control system, when the cabinet space is tight, there is often a need to use ultra-thin and low-power signal isolators. Most of the existing signal isolators use traditional wound high-frequency transformers or magnetic ring transformers, and it is often difficult to meet the requirements in terms of volume and power consumption. Although some signal isolators use planar transformers, due to the still relatively large volume of the planar transformer, it brings certain difficulties to the miniaturization of the signal isolator.

[0005] Therefore, there is an urgent need to develop a planar transformer and a signal isolator to solve the problems in the prior art. Summary of the Invention

[0006] The purpose of the present invention is to provide a planar transformer and a signal isolator, which can reduce the volume of the planar transformer to solve the problem of difficulty in miniaturizing the signal isolator caused by the relatively large volume of the planar transformer as proposed in the above background art.

[0007] To solve the above technical problems, the specific technical solutions of the present invention are as follows:

[0008] A planar transformer includes a PCB board, which includes a first board layer, a second board layer, and a third board layer. A first side coil assembly is provided between the first board layer and the second board layer, and a second side coil assembly is provided between the second board layer and the third board layer. The first side coil assembly includes a first copper-clad layer and a second copper-clad layer. A board-interlayer is provided between the first copper-clad layer and the second copper-clad layer. The thickness of the board-interlayer is less than the thickness of the second board layer. The board-interlayer is provided with a via hole, and a conductive medium is provided in the via hole. The conductive medium is electrically connected to the first copper-clad layer and the second copper-clad layer.

[0009] In this application, the first copper-clad layer and the second copper-clad layer are used as two parts of the coil within the first-side coil assembly, and insulation isolation between the two parts of the coil is achieved through the interlayer between the boards. Also, since the insulation requirement between the coils on the same side in a planar transformer is lower than that between the coils on different sides, the thickness of the interlayer between the boards can be smaller than the thickness of the second board layer used to isolate the first-side coil assembly and the second-side coil assembly, thereby reducing the thickness of the PCB board and shrinking the volume of the planar transformer.

[0010] A signal isolator includes the aforementioned planar transformer.

[0011] In this application, setting one or more planar transformers with reduced volume within the signal isolator helps to further shrink the volume of the signal isolator.

[0012] Other features and advantages of the present invention will be disclosed in detail in the following specific embodiments and the drawings. Description of the Drawings

[0013] Figure 1 It is a schematic diagram of the overall structure of the planar transformer of the present invention;

[0014] Figure 2 It is an exploded view of the overall structure of the planar transformer of the present invention;

[0015] Figure 3 It is a cross-sectional view of the PCB board of the present invention;

[0016] Figure 4 It is a planar expansion view of the PCB board of the present invention;

[0017] Figure 5 It is a schematic diagram of the structure of the first copper-clad layer of the present invention;

[0018] Figure 6 It is a schematic diagram of the structure of the second copper-clad layer of the present invention;

[0019] Figure 7 It is a schematic diagram of the structure of the third copper-clad layer of the present invention;

[0020] Figure 8 It is a schematic diagram of the structure of the fourth copper-clad layer of the present invention;

[0021] Figure 9 It is a comparison schematic diagram before and after the PCB board of the present invention is flipped along the short axis.

[0022] Reference Numerals: 1. Housing; 11. First housing part; 12. Second housing part; 2. PCB board; 21. Core via hole; 22. Pad; 23. First board layer; 24. Second board layer; 25. Third board layer. Detailed Description of the Invention

[0023] A planar transformer, as shown in Figure 1 and Figure 2 shown, includes a housing 1 and a PCB board 2. The housing 1 includes a first housing part 11 and a second housing part 12. A first magnetic core part is fixedly connected to the first housing part 11, and a second magnetic core part is fixedly connected to the second housing part 12. A magnetic core through hole 21 for inserting and cooperating with the first magnetic core part and the second magnetic core part is provided in the middle of the PCB board 2. The PCB board 2 is centrosymmetric about the axis of the magnetic core through hole 21. Both the first housing part 11 and the second housing part 12 are provided with accommodation cavities for accommodating part of the PCB board.

[0024] As shown in Figure 3 and Figure 4 shown, the PCB board 2 includes a first board layer 23, a second board layer 24, and a third board layer 25. The first board layer 23, the second board layer 24, and the third board layer 25 are stacked in sequence along the thickness direction of the PCB board 2; the PCB board 2 further includes a first side coil assembly and a second side coil assembly. The first side coil assembly is located between the first board layer 23 and the second board layer 24, and the second side coil assembly is located between the second board layer 24 and the third board layer 25; both ends in the length direction of the PCB board 2 are provided with pads 22. The pads 22 include a first side pad and a second side pad. Both the first side pad and the second side pad include three pads for connecting the PCB board 2 to an external circuit; the first coil assembly is connected to the first side pad, and the second side pad is connected to the second coil assembly.

[0025] When welding the PCB board 2 to an external circuit, part or all of the first side pads and the second side pads are connected to the external circuit through solder, so as to connect the first side coil assembly and the second side coil assembly to the external circuit, realizing the functions of voltage transformation and / or signal isolation.

[0026] As shown in Figure 3 and Figure 4 shown, the first side coil assembly includes a first copper clad layer L1 and a second copper clad layer L2. The first copper clad layer L1 is located on the side of the first board layer 23 relatively closer to the second board layer 24, and the second copper clad layer L2 is located on the side of the second board layer 24 relatively closer to the first board layer 23. A board - to - board interlayer M1 is provided between the first copper clad layer L1 and the second copper clad layer L2; the second side coil assembly includes a third copper clad layer L3 and a fourth copper clad layer L4. The third copper clad layer L3 is located on the side of the second board layer 24 relatively closer to the third board layer 25, and the fourth copper clad layer L4 is located on the side of the third board layer 25 relatively closer to the second board layer 24. A board - to - board interlayer M2 is provided between the third copper clad layer L3 and the fourth copper clad layer L4. The thickness of the first board layer 23, the second board layer 24, and the third board layer 25 is H, and H satisfies the relationship: 0.8mm < H < 1.1mm. The thickness of the board - to - board interlayer M1 and the board - to - board interlayer M2 is h, and h satisfies the relationship: 0.15mm < h < 0.23mm.

[0027] The first-side coil assembly is composed of a first copper-clad layer L1 and a second copper-clad layer L2, and is insulated by an interlayer M1 between the boards. Since the first copper-clad layer L1 and the second copper-clad layer L2 are coils on the same side, the insulation distance required for the interlayer M1 of the coils on the same side for isolation is smaller than the insulation distance between coils on different sides. In the embodiment of the present application, the interlayer between the boards is made of prepreg commonly used in printed circuit boards, so as to reduce the thickness of the PCB board and the volume of the planar transformer.

[0028] As Figures 4 to 8 shown, a fifth copper-clad layer L5 is further provided on the side of the first board layer 23 relatively far from the second board layer 24, and a sixth copper-clad layer is further provided on the side of the third board layer 25 relatively far from the second board layer 24. As Figures 3 to 7 shown, six terminals are provided on each of the first copper-clad layer L1, the second copper-clad layer L2, the third copper-clad layer L3, the fourth copper-clad layer L4, the fifth copper-clad layer L5, and the sixth copper-clad layer L6. The six terminals are respectively electrically connected to six pads. The six terminals include terminal 22a, terminal 22b, terminal 22c, terminal 22d, terminal 22e, and terminal 22f. Among them, terminal 22a, terminal 22b, and terminal 22c are located on the same side and arranged at equal intervals, and are electrically connected to the first-side pads at one end of the PCB board 2. Terminal 22d, terminal 22e, and terminal 22f are located on the same side and arranged at equal intervals, and are electrically connected to the second-side pads at the other end of the PCB board 2. The first-side pads and the second-side pads are symmetrically arranged.

[0029] By providing six terminals, namely terminal 22a, terminal 22b, terminal 22c, terminal 22d, terminal 22e, and terminal 22f, the electrical connection between the pads and the external circuit and the coil composed of four copper-clad layers can be realized.

[0030] As Figure 5 With Figure 6As shown, the first copper-clad layer L1 further includes a first side sub-coil 1A and a first side sub-coil 1B, and the first side sub-coil 1A and the first side sub-coil 1B are arranged in parallel in the same direction. One end of the first side sub-coil 1A relatively close to the pad is electrically connected to the terminal 22b, and one end of the first side sub-coil 1B relatively close to the pad is electrically connected to the terminal 22c. The second copper-clad layer further includes a first side sub-coil 1C and a first side sub-coil 1D, and the first side sub-coil 1C and the first side sub-coil 1D are arranged in parallel in the same direction. One end of the first side sub-coil 1C relatively close to the pad is electrically connected to the terminal 22a, and one end of the first side sub-coil 1D relatively close to the pad is electrically connected to the terminal 22b. The first side sub-coil 1A and the first side sub-coil 1C are arranged in opposite directions. In this embodiment, as shown, the first side sub-coil 1A and the first side sub-coil 1B are arranged in parallel in a counterclockwise direction, and the first side sub-coil 1C and the first side sub-coil 1D are arranged in parallel in a counterclockwise direction; via holes are provided in the interlayer M1 between the first copper-clad layer L1 and the second copper-clad layer L2, there are two via holes, and conductive media are provided in both of the two via holes. One end of the first side sub-coil 1A relatively far from the terminal 22b is electrically connected to one end of the first side sub-coil 1C relatively far from the terminal 22a through the conductive medium, and one end of the first side sub-coil 1B relatively far from the terminal 22c is electrically connected to one end of the first side sub-coil 1D relatively far from the terminal 22b through the conductive medium.

[0031] The external circuit is connected to the first side sub-coil 1A, the first side sub-coil 1B, the first side sub-coil 1C, and the first side sub-coil 1D connected to the terminals 22a, 22b, and 22c through the pad. Specifically, when the external circuit is connected to the terminals 22a and 22b through the pad 22, the current passes through the terminal 22a, the first side sub-coil 1C, the conductive medium, the first side sub-coil 1A, and the terminal 22b. When the external circuit is connected to the terminals 22b and 22c through the pad, the current passes through 22b, the first side sub-coil 1D, the conductive medium, the first side sub-coil 1B, and the terminal 22c. That is, when the external circuit is connected to two adjacent terminals among the terminals 22a, 22b, and 22c, the number of sub-coils connected to the external circuit is two; when the external circuit is connected to the terminals 22a and 22c through the pad 22, the current passes through the terminal 22a, the first side sub-coil 1C, the conductive medium, the first side sub-coil 1A, the terminal 22b, the first side sub-coil 1D, the conductive medium, the first side sub-coil 1B, and the terminal 22c. That is, when the external circuit is connected to the non-adjacent terminals 22a and 22c, the number of sub-coils connected to the external circuit is 4. Also, since the number of turns of the first side sub-coil 1A, the first side sub-coil 1B, the first side sub-coil 1C, and the first side sub-coil 1D is the same, the number of turns N1 when connected to adjacent terminals is half of the number of turns N2 when connected to non-adjacent terminals, and the turn ratio N1:N2 = 1:2.

[0032] like Figure 7 and Figure 8 As shown, the third copper clad layer L3 also includes a second side sub-coil 2A and a second side sub-coil 2B, and the second side sub-coil 2A and the second side sub-coil 2B are arranged in parallel and in the same direction. The end of the second side sub-coil 2A relatively close to the pad is electrically connected to the terminal 22d, and the end of the second side sub-coil 2B relatively close to the pad is electrically connected to the terminal 22e. The second copper clad layer also includes a second side sub-coil 2C and a second side sub-coil 2D, and the second side sub-coil 2C and the second side sub-coil 2D are arranged in parallel and in the same direction, and the end of the second side sub-coil 2C relatively close to the pad is electrically connected to the terminal 22e, and the end of the second side sub-coil 2D relatively close to the pad is electrically connected to the terminal 22f. The second side sub-coil 2A and the second side sub-coil 2C are arranged in opposite directions, and the first side sub-coil 1A and the second side sub-coil 2A are arranged in the same direction. In this embodiment, as shown in the figure, the second side sub-coil 2A and the first side sub-coil 1B are arranged in parallel in a counterclockwise direction, and the second side sub-coil 2C and the first side sub-coil 1D are arranged in parallel in a counterclockwise direction; the interlayer M2 between the third copper clad layer L3 and the fourth copper clad layer L4 also has two conducting holes, and conductive media are arranged in both conducting holes, and one end of the second side sub-coil 2A relatively away from the terminal 22d is electrically connected to the end of the second side sub-coil 2C relatively away from the terminal 22e through the conductive medium, and the end of the second side sub-coil 2B relatively away from the terminal 22e is electrically connected to the end of the second side sub-coil 2D relatively away from the terminal 22f through the conductive medium.

[0033] The external circuit is connected to the second-side sub-coils 2A, 2B, 2C, and 2D connected to the terminals 22d, 22e, and 22f through the pads. Specifically, when the external circuit is connected to the terminals 22d and 22e through the pad 22, the current passes through the terminal 22d, the second-side sub-coil 2A, the conductive medium, the second-side sub-coil 2C, and the terminal 22e. When the external circuit is connected to the terminals 22e and 22f through the pad, the current passes through 22e, the second-side sub-coil 2B, the conductive medium, the second-side sub-coil 2D, and the terminal 22f. That is, when the external circuit is connected to two adjacent terminals among the terminals 22a, 22b, and 22c, the number of sub-coils connected to the external circuit is two; when the external circuit is connected to the terminals 22a and 22c through the pad 22, the current passes through the terminal 22d, the second-side sub-coil 2A, the conductive medium, the second-side sub-coil 2C, the terminal 22b, the second-side sub-coil 2B, the conductive medium, the second-side sub-coil 2D, and the terminal 22f. That is, when the external circuit is connected to the non-adjacent terminals 22d and 22f, the number of sub-coils connected to the external circuit is four. Also, since the number of turns of the second-side sub-coils 2A, 2B, 2C, and 2D is the same, the number of turns N3 when connected to adjacent terminals is half of the number of turns N4 when connected to non-adjacent terminals, and the turn ratio N3:N4 = 1:2.

[0034] By providing the pads and the conductive medium, the electrical connection between the sub-coils on different layers can be realized, thus forming a closed loop. Moreover, the pads are electrically connected to the six terminals included in the fifth copper-clad layer and the sixth copper-clad layer, which can increase the area of the conductive material of the pads for connecting to the external circuit, thereby facilitating the use of this planar transformer.

[0035] When using this planar transformer, the first-side pads and the second-side pads of the planar transformer are usually used as the input terminal and the output terminal respectively. For example, in an external circuit, the two pads connected to terminals 22a and 22b in the first-side pads are used as the input terminal, and the pads connected to terminals 22d and 22f in the second-side pads are used as the output terminal. Further, the pad connected to terminal 22a is used as the positive pole of the input terminal, and the pad connected to terminal 22b is used as the negative pole of the input terminal. When the external circuit supplies power to this planar transformer, the current enters from terminal 22a, passes through the first-side sub-coil 1C, the conductive medium, and the first-side sub-coil 1A, and flows out from 22b. The current direction in the coil is clockwise, and a magnetic field is generated around the coil. The second-side coil assembly generates an induced current under the action of the magnetic field. At this time, the current direction of the induced current should also be clockwise, that is, the current flows in from terminal 22f, successively passes through the second-side sub-coil 2D, the conductive medium, the second-side sub-coil 2B, terminal 22e, the second-side sub-coil 22C, the conductive medium, and the second-side sub-coil 22A, and flows out from terminal 22d. The above is the situation of the current in the planar transformer when the planar transformer is correctly welded in this external circuit. Since the appearance of this planar transformer is highly symmetrical, it may be installed and connected incorrectly during installation. One case of incorrect installation is as follows: Taking the relatively short axis of symmetry of the planar transformer as the axis of rotation, the planar transformer is flipped. After flipping, the comparison of the first copper-clad layer L1, the second copper-clad layer L2, the third copper-clad layer L3, and the fourth copper-clad layer L4 with that before flipping is Figure 9 , after connecting the reversed planar transformer to the original external circuit, at this time, the positive pole of the input terminal is the pad connected to terminal 22d, and the negative pole of the input terminal is the pad connected to terminal 22e. The current direction is clockwise, and successively passes through terminal 22d, the second sub-coil 2A, the conductive medium, the second sub-coil 2C, and terminal 22e. At the same time, an induced current is generated in the first-side coil assembly. Specifically, the current direction is clockwise, and successively passes through terminal 22c, the first-side sub-coil 1B, the conductive medium, the first-side sub-coil 1D, terminal 22b, the first-side sub-coil 1A, the conductive medium, the first-side sub-coil 1C, and terminal 22a. At this time, the positive pole of the output terminal is the pad connected to terminal 22c, and the negative pole of the output terminal is the pad connected to terminal 22a. It can be found from this that the actual effect of the symmetrically flipped planar transformer is the same as that before flipping, and after the planar transformer is flipped around its longer axis of symmetry or rotated around its center point, the same effect can be maintained, that is, this planar transformer also has good fault tolerance. Even if the situation of flipping the planar transformer and installing it in the external circuit occurs, this planar transformer can still work with the same effect as in normal installation, reducing the probability of malfunction or damage to the external circuit caused by incorrect installation.

[0036] A signal isolator includes a planar transformer.

[0037] Example 2

[0038] The difference from Example 1 is that the vias located in the interlayer M1 between the plates also penetrate the first plate layer 23, and the vias located in the interlayer M2 between the plates penetrate the third plate layer 25.

[0039] Example 3

[0040] The differences from Examples 1 and 2 are that all the vias penetrate the interlayer M1 between the plates, the interlayer M2 between the plates, the first plate layer 23, the second plate layer 24, and the third plate layer 25.

[0041] It can be understood that the present invention is described by means of some examples. Those skilled in the art know that, without departing from the spirit and scope of the present invention, various changes or equivalent replacements can be made to these features and examples. In addition, under the teaching of the present invention, these features and examples can be modified to adapt to specific situations and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific examples disclosed herein, and all examples falling within the scope of the claims of this application belong to the scope protected by the present invention.

Claims

1. A planar transformer, characterized in that: A PCB board is included, wherein the PCB board includes a first board layer, a second board layer and a third board layer; a first side coil component is arranged between the first board layer and the second board layer, a second side coil component is arranged between the second board layer and the third board layer, the first side coil component includes a first copper clad layer and a second copper clad layer, an inter-board interlayer is arranged between the first copper clad layer and the second copper clad layer, the thickness of the inter-board interlayer is less than the thickness of the second board layer, a via hole is opened in the inter-board interlayer, a conductive medium is arranged in the via hole, and the conductive medium is electrically connected to the first copper clad layer and the second copper clad layer; The first copper clad layer includes a first side sub-coil 1A and a first side sub-coil 1B, and the first side sub-coil 1A and the first side sub-coil 1B are arranged in parallel and in the same direction; the second copper clad layer includes a first side sub-coil 1C and a first side sub-coil 1D, and the first side sub-coil 1C and the first side sub-coil 1D are arranged in parallel and in the same direction; the first side sub-coil 1A and the first side sub-coil 1C are arranged in opposite directions; an end of the first side sub-coil 1A relatively close to the inner side of the coil is electrically connected to an end of the first side sub-coil 1C relatively close to the inner side of the coil through a conductive medium, and an end of the first side sub-coil 1B relatively close to the inner side of the coil is electrically connected to an end of the first side sub-coil 1D relatively close to the inner side of the coil through a conductive medium; The second side coil component includes a third copper clad layer and a fourth copper clad layer, the third copper clad layer includes a second side sub-coil 2A and a second side sub-coil 2B, the second side sub-coil 2A and the second side sub-coil 2B are arranged in parallel and in the same direction; the fourth copper clad layer includes a second side sub-coil 2C and a second side sub-coil 2D, the second side sub-coil 2C and the second side sub-coil 2D are arranged in parallel and in the same direction; the second side sub-coil 2A and the second side sub-coil 2C are arranged in opposite directions; an inter-board interlayer is also provided between the third copper clad layer and the fourth copper clad layer, and the inter-board interlayer between the third copper clad layer and the fourth copper clad layer is also provided with two conducting holes, and a conductive medium is also provided in the two conducting holes, an end of the second side sub-coil 2A relatively close to the inner side of the coil is electrically connected to an end of the second side sub-coil 2C relatively close to the inner side of the coil through the conductive medium, and an end of the second side sub-coil 2B relatively close to the inner side of the coil is electrically connected to an end of the second side sub-coil 2D relatively close to the inner side of the coil through the conductive medium; The thickness of the first board layer, the second board layer and the third board layer is H, the thickness of the interlayer between the boards is h, and H and h satisfy the relationship: 0.8 mm <H<1.1mm,0.15mm<h<0.23mm。 2. The planar transformer according to claim 1, characterized in that: The PCB board also includes a first side solder pad, which is located on the end surface of the PCB board. There are three first side solder pads, which are electrically connected to the first side coil assembly. The first copper clad layer and the second copper clad layer both include terminals 22a, 22b and 22c, which are electrically connected to the three first side solder pads respectively. One end of the first side sub-coil 1A relatively close to the solder pad is electrically connected to the terminal 22b, one end of the first side sub-coil 1B relatively close to the solder pad is electrically connected to the terminal 22c, one end of the first side sub-coil 1C relatively close to the solder pad is electrically connected to the terminal 22a, and one end of the first side sub-coil 1D relatively close to the solder pad is electrically connected to the terminal 22b.

3. The planar transformer according to claim 1, characterized in that: The second side sub-coil 2A and the first side sub-coil 1A are arranged in the same direction; the PCB board also includes a first side solder pad and a second side solder pad, the first side solder pad and the second side solder pad are respectively located at two opposite end surfaces of the PCB board, three first side solder pads and three second side solder pads are respectively provided, the first side solder pad is electrically connected to the first side coil component, and the second side solder pad is electrically connected to the second side coil component, the first copper clad layer, the second copper clad layer, the third copper clad layer and the fourth copper clad layer all include terminals 22a, 22b, 22c, 22d, 22e and 22f, the terminals 22a, 22b and 22c are respectively electrically connected to the three first side solder pads; the terminals 22d, 22e and 22f are respectively electrically connected to the three second side solder pads; One end of the first side sub-coil 1A relatively close to the pad is electrically connected to the terminal 22b, one end of the first side sub-coil 1B relatively close to the pad is electrically connected to the terminal 22c, one end of the first side sub-coil 1C relatively close to the pad is electrically connected to the terminal 22a, and one end of the first side sub-coil 1D relatively close to the pad is electrically connected to the terminal 22b; One end of the second side sub-coil 2A relatively close to the pad is electrically connected to the terminal 22d, one end of the second side sub-coil 2B relatively close to the pad is electrically connected to the terminal 22e, one end of the second side sub-coil 2C relatively close to the pad is electrically connected to the terminal 22e, and one end of the second side sub-coil 2D relatively close to the pad is electrically connected to the terminal 22f.

4. The planar transformer according to any one of claims 1 to 3, characterized in that: The PCB board is provided with a through hole, the through hole passes through the PCB board, and the PCB board is symmetrical about the axis center of the through hole.

5. The planar transformer according to claim 4, characterized in that: It also includes a magnetic core, which is arranged in the through hole and is plug-fitted with the PCB board.

6. The planar transformer according to claim 5, characterized in that: It also includes a shell, which includes a first shell part and a second shell part, and the first shell part and the second shell part are both provided with a receiving cavity for receiving at least part of a PCB board, and the magnetic core includes a first magnetic core part and a second magnetic core part, the first shell part is fixedly connected to the first magnetic core part or is an integral part, and the second shell part is fixedly connected to the second magnetic core part or is an integral part.

7. A signal isolator, comprising the planar transformer according to any one of claims 1 to 6.

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