A loudspeaker module

Abstract

The application provides a loudspeaker module, which comprises a moving coil module and a MEMS module capable of respectively and independently emitting sound, the moving coil module is provided with a containing portion, the MEMS module is installed in the containing portion and electrically connected with the moving coil module, the moving coil module is provided with a first sound hole, the MEMS module is provided with a second sound hole, and the first sound hole and the second sound hole are located on the same side of the loudspeaker module. The loudspeaker module of the application adopts integrated design, organically combines the moving coil module and the MEMS module together, is compact in structure, realizes miniaturization, meets the demand of electronic products on the loudspeaker being more and more miniaturized, and the moving coil module and the MEMS module respectively and independently emit sound, effectively solves the problems of poor high-frequency sound quality of a single moving coil speaker and insufficient low frequency of a MEMS loudspeaker in a traditional TWS earphone, realizes full-band, especially high-quality sound output of high frequency and low frequency, and provides high-fidelity and rich-detail audio experience for users.

Description

Technical Field

[0001] This application relates to the field of acoustics, and in particular to a loudspeaker module. Background Technology

[0002] With the rapid development of the TWS (True Wireless Stereo) earphone market, consumers have placed higher demands on earphones in terms of sound quality, wearing comfort, and battery life. Regarding sound quality, users expect earphones to provide a superior listening experience, encompassing rich audio details and a wider frequency response range. Traditional TWS earphones mostly use dynamic drivers, which face numerous challenges in achieving high-fidelity sound. On the one hand, limited by the extremely confined space inside TWS earphones, traditional dynamic drivers struggle to deliver high-quality sound across the entire frequency range within a small size. For example, in high-frequency sound, the diaphragm material and structural characteristics of dynamic drivers result in less clear and transparent sound, with significant loss of detail, failing to meet the demands of high-fidelity audio. On the other hand, within the limited space inside TWS earphones, to improve battery life, the size of the speaker must become increasingly smaller.

[0003] Currently, the common sound output solutions for TWS earphones on the market mainly include: Single dynamic driver solution: Most TWS earphones use this solution. This solution performs poorly in the high-frequency range. The inertia of the diaphragm makes it difficult to respond quickly to high-frequency signals, resulting in blurry sound, loss of detail, and unclear and transparent sound quality.

[0004] Multi-balanced armature driver solution: Some high-end TWS earphones use multiple balanced armature drivers. Compared to dynamic drivers, balanced armature drivers perform better in the mid-to-high frequency range, with high sound resolution and the ability to clearly reproduce sound details. However, the disadvantage of balanced armature drivers is insufficient low-frequency performance. Multiple drivers are needed to cover a wider frequency range, which increases the design and manufacturing cost of the earphones, takes up more space, and makes tuning multiple drivers more difficult, which can easily lead to unnatural sound transitions.

[0005] The dynamic driver + balanced armature hybrid solution combines dynamic and balanced armature drivers, using the dynamic driver for low frequencies and the balanced armature for mid and high frequencies to achieve good sound performance across the entire frequency range. This solution improves sound quality to some extent, but it faces challenges in spatial layout and crossover design during integration, and its high cost hinders large-scale adoption.

[0006] While MEMS (Micro-Electro-Mechanical Systems) speakers have advantages such as small size and excellent high-frequency response, their low-frequency performance is weak when used alone, which cannot meet users' needs for a rich audio experience. Summary of the Invention

[0007] In view of this, this application proposes a speaker module with an integrated design of dynamic coil module and MEMS module.

[0008] This application provides a speaker module, including a dynamic coil module and a MEMS module that can emit sound independently. The dynamic coil module is provided with a receiving portion, and the MEMS module is installed in the receiving portion and electrically connected to the dynamic coil module. The dynamic coil module is provided with a first sound hole, and the MEMS module is provided with a second sound hole, and the first sound hole and the second sound hole are located on the same side of the speaker module.

[0009] In one embodiment, the moving coil module and the MEMS module are coaxially arranged.

[0010] In one embodiment, the speaker module includes a housing, the dynamic coil module is disposed inside the housing and includes a magnetic cover, the housing has an open end, the magnetic cover is disposed at the open end, and the middle part of the magnetic cover is recessed into the housing to form a concave portion, the concave portion surrounds to form the receiving portion, the first sound hole is disposed in the area of ​​the magnetic cover located outside the concave portion, and the second sound hole is disposed on the side of the MEMS module opposite to the concave portion.

[0011] In one embodiment, the moving coil module includes a basin frame and a magnet. The basin frame is supported by the magnet on the side of the magnetic cover away from the opening end, and the basin frame, the magnet, and the magnetic cover together form a magnetic circuit system. The basin frame and the magnet are disposed on the periphery of the concave portion and form a magnetic gap with the concave portion. The first sound hole corresponds to the position of the magnetic gap.

[0012] In one embodiment, the moving coil module includes a vibration system, a cavity is formed between the magnetic circuit system and the housing, the vibration system is disposed in the cavity, and the magnetic gap is in communication with the cavity; the vibration system includes a diaphragm, a voice coil and a metal component, the diaphragm is supported on the frame by the metal component, one end of the voice coil is connected to the diaphragm and the other end extends into the magnetic gap.

[0013] In one embodiment, the recessed portion is provided with a first through hole on one side of the cavity, and the first through hole connects the cavity and the receiving portion.

[0014] In one embodiment, a second through hole is provided at the end of the outer shell opposite to the opening end, and the second through hole connects the cavity to the outside of the shell.

[0015] In one embodiment, a damping element is provided outside the second through hole.

[0016] In one embodiment, the speaker module includes a first circuit board and a second circuit board, the voice coil is electrically connected to the first circuit board, one end of the second circuit board is electrically connected to the MEMS module, and the other end is electrically connected to the first circuit board.

[0017] In one embodiment, a step is formed on the periphery of the outer casing at the end opposite to the opening, and the first circuit board is located outside the outer casing and disposed on the step; And / or, the second circuit board is a flexible circuit board, the magnetic cover and the outer shell together form an extension channel, the second circuit board is located in the extension channel, and one end of the second circuit board extends into the receiving portion and the other end extends to the first circuit board.

[0018] In summary, this application provides a speaker module, including a dynamic driver module and a MEMS module capable of independently producing sound. The dynamic driver module has a receiving portion, and the MEMS module is mounted in the receiving portion and electrically connected to the dynamic driver module. The dynamic driver module has a first sound hole, and the MEMS module has a second sound hole, with the first and second sound holes located on the same side of the speaker module. The speaker module of this application adopts an integrated design, organically combining the dynamic driver module and the MEMS module, resulting in a compact structure and miniaturization. This meets the increasingly smaller speaker requirements of electronic products. Furthermore, the dynamic driver module and the MEMS module produce sound independently, effectively solving the problems of poor high-frequency sound quality of traditional TWS earphones with a single dynamic driver and insufficient low-frequency sound of MEMS speakers. This achieves high-quality sound output across the entire frequency range, especially in the high and low frequencies, providing users with a high-fidelity, richly detailed audio experience. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of a speaker module at one angle in one embodiment of this application.

[0020] Figure 2 for Figure 1 A three-dimensional structural diagram of the speaker module from another angle.

[0021] Figure 3 for Figure 1 A cross-sectional view of the speaker module along one direction.

[0022] Attached image labels: a-Central axis; 10-Speaker module; 12-Dynamic coil module; 14-MEMS module; 16-Receiving part; 18-First sound hole; 20-Second sound hole; 22-Outer shell; 24-Opening end; 26-Bearing frame; 28-Magnet; 30-Magnetic cover; 32-Recessed part; 34-Magnetic gap; 36-Cavity; 38-Diaphragm; 40-Voice coil; 42-Metal part; 44-Intermediate bending section; 46-Outer extension section; 48-Inner extension section; 50-First cavity; 52-Second cavity; 54-First through hole; 56-Second through hole; 58-Damping element; 60-First circuit board; 62-Second circuit board; 64-Step; 66-Extension channel. Detailed Implementation

[0023] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0025] Please also refer to Figure 1 and Figure 2 As shown, this application provides a speaker module 10, which can be applied to speakers in multimedia devices such as headphones, mobile phones, and audio equipment. The speaker module 10 includes a dynamic coil module 12 and a MEMS module 14, both capable of independent sound emission. The dynamic coil module 12 has a receiving portion 16, which may be, for example, a recessed structure. The MEMS module 14 is mounted in the receiving portion 16 and electrically connected to the dynamic coil module 12. The MEMS module 14 can be a finished product of an existing MEMS speaker. The dynamic coil module 12 has a first sound hole 18, and the MEMS module 14 has a second sound hole 20, with the first sound hole 18 and the second sound hole 20 located on the same side of the speaker module 10. The speaker module 10 of this application adopts an integrated design, organically combining the dynamic driver module 12 and the MEMS module 14. The structure is compact and miniaturized, meeting the increasingly smaller requirements of electronic products for speakers. Moreover, the dynamic driver module 12 and the MEMS module 14 emit sound independently, effectively solving the problems of poor high-frequency sound quality of traditional TWS earphones with single dynamic drivers and insufficient low-frequency sound of MEMS speakers. It achieves high-quality sound output across the entire frequency range, especially in the high and low frequencies, providing users with a high-fidelity and richly detailed audio experience.

[0026] In this embodiment, the speaker module 10 is designed as a cylindrical structure, that is, both the moving coil module 12 and the MEMS module 14 are cylindrical structures. In other embodiments, the speaker module 10 may also be designed as other shapes, and this application is not limited to this.

[0027] In a preferred embodiment, such as Figure 3 As shown, the moving coil module 12 and the MEMS module 14 are coaxially arranged. For example, the speaker module 10 has a central axis a, and the central axis of the moving coil module 12 and the central axis of the MEMS module 14 are respectively arranged to coincide with the central axis a, thereby realizing the coaxiality of the moving coil module 12 and the MEMS module 14.

[0028] The speaker module 10 of this application consists of a dynamic coil module 12 and a MEMS module 14, which are combined to form a composite speaker module. The dynamic coil module 12 is mainly responsible for low-frequency and mid-frequency sound output, while the MEMS module 14, embedded inside the magnetic cover of the dynamic coil module 12, serves as a tweeter and is mainly responsible for high-frequency sound output. The dynamic coil module 12 and the MEMS module 14 emit sound independently. The dynamic coil module 12 can fully utilize its own structural radiation area to achieve better acoustic performance. The MEMS module 14, embedded inside the magnetic cover, emits sound independently and does not need to occupy the vibration radiation area of ​​the dynamic coil module 12 to fully realize its acoustic performance, while also saving space in the overall unit.

[0029] Specifically, please also refer to Figure 3 As shown, the speaker module 10 includes a housing 22, which is a cylindrical structure. An installation space is formed inside the housing 22, within which both the dynamic coil module 12 and the MEMS module 14 are installed. The speaker module 10 of this application adopts an integrated design, organically combining the dynamic coil module 12 and the MEMS module 14 within a compact housing 22. The housing 22 can be made of lightweight, high-strength materials, such as aluminum alloy, stainless steel, or high-strength engineering plastics, which ensures structural stability while reducing the module's weight, meeting the lightweight requirements of TWS earphones.

[0030] The outer casing 22 has an open end 24 along the central axis a. The moving coil module 12 includes a magnetic circuit system and a vibration system. The magnetic circuit system is located inside the outer casing 22 on the side near the open end 24, and the vibration system is located on the side of the magnetic circuit system away from the open end 24. Specifically, the magnetic circuit system includes a frame 26, magnets 28, and a magnetic cover 30. The frame 26 and magnets 28 are both annular, and the magnetic cover 30 is circular and located at the open end 24. The frame 26, magnets 28, and magnetic cover 30 are all coaxially arranged along the central axis a. The center of the magnetic cover 30 is recessed into the mounting space inside the outer casing 22 to form a recess 32. The recess 32 encloses a receiving portion 16, in which the MEMS module 14 is fixedly installed. The frame 26 can be made of a magnetically conductive material such as cold-rolled steel, serving as a magnetically conductive plate above the magnets 28, forming a complete magnetic circuit with the magnets 28 and the magnetic cover 30. The design of the recessed portion 32 in the middle of the magnetic cover 30 forms a support surface at the top of the recessed portion 32, which is used to support the placement of the MEMS module 14.

[0031] Preferably, the first sound hole 18 is disposed in the area of ​​the magnetic cover 30 located on the periphery of the recess 32. For example, multiple first sound holes 18 are disposed, and the multiple first sound holes 18 are evenly spaced along the circumference of the magnetic cover 30. The diameter of the first sound hole 18 is set to be greater than or equal to 0.5 mm, and the number of first sound holes 18 can be determined according to the air permeability requirements. The second sound hole 20 is disposed on the side of the MEMS module 14 opposite to the recess 32, so that the first sound hole 18 and the second sound hole 20 are located on the same side of the speaker module 10. Optionally, the second sound hole 20 is disposed in the middle of the MEMS module 14, that is, multiple first sound holes 18 and second sound holes 20 are coaxially arranged along the central axis a.

[0032] Furthermore, the basin frame 26 is supported by magnets 28 on the side of the magnetic cover 30 opposite to the opening end 24. The basin frame 26, magnets 28, and magnetic cover 30 together form a magnetic circuit system, and a magnetic loop is formed between the magnetic cover 30, the basin frame 26, and the magnets 28. For example, the basin frame 26 and magnets 28 are located on the periphery of the recess 32 and form a magnetic gap 34 between them. Multiple first sound holes 18 correspond to the positions of the magnetic gap 34, that is, the first sound holes 18 connect the magnetic gap 34 to the external environment. The radially outer ends of the basin frame 26, magnets 28, and magnetic cover 30 are respectively connected to the inner surface of the side wall of the outer casing 22, for example, by adhesive bonding or by other means, so that the magnetic circuit system is fixedly connected to the outer casing 22, achieving the installation stability of the magnetic circuit system.

[0033] In the illustrated embodiment, a cavity 36 is formed between the side of the magnetic circuit system away from the outlet end 24 and the outer shell 22. The vibration system is disposed within the cavity 36, and the magnetic gap 34 of the magnetic circuit system is connected to the cavity 36. Specifically, the vibration system includes a diaphragm 38, a voice coil 40, and a metal component 42, wherein the voice coil 40 and the metal component 42 are both annular, and the diaphragm 38 is circular. The diaphragm 38 is supported on the frame 26 by the metal component 42, and one end of the voice coil 40 is connected to the diaphragm 38, while the other end extends into the magnetic gap 34. The metal component 42 connects the diaphragm 38 and serves to support and guide the vibration. The diaphragm 38 can be made of a highly elastic material, such as a silicone membrane, and is bonded to the spherical top of the diaphragm 38 or integrally injection molded to drive the diaphragm 38 to produce sound. Preferably, the diaphragm 38, the voice coil 40, and the metal component 42 are all coaxially arranged around the central axis a.

[0034] Furthermore, the basin frame 26 has a three-section bending structure. For example, the basin frame 26 includes a middle bending section 44 extending along the central axis a, and an outer extension section 46 and an inner extension section 48 connected to both ends of the middle bending section 44 and extending radially. The end of the outer extension section 46 away from the middle bending section 44 is connected to the inner wall surface of the outer casing 22. The bottom surface of the inner extension section 48 is supported and connected to the top surface of the magnet 28, and the radial inner wall surface of the inner extension section 48 is flush with the radial inner wall surface of the magnet 28. The bottom surface of the metal part 42 is supported and connected to the top surface of the outer extension section 46, and the radial outer wall surface of the metal part 42 is connected to the inner surface of the side wall of the outer casing 22, for example, by adhesive bonding. The diaphragm 38 includes a spherical top, a folded surround connected to the outer edge of the spherical top, and a fixing part connected to the outer edge of the folded surround. The fixing part is fixedly connected to the top surface of the metal part 42, for example, by adhesive bonding. The top of the voice coil 40 is connected to the junction of the spherical top and the folded surround, for example, by adhesive bonding. This allows for the connection and fixation of the vibration system, the magnetic circuit system, and the housing 22, ensuring the stability of the vibration system installation. The design of the speaker module 10 in this application allows the diaphragm 38 to fully utilize the effective radiation area of ​​the overall device dimensions, without being affected by the design of the MEMS module 14.

[0035] The diaphragm 38 divides the cavity 36 into a first cavity 50 near the magnetic circuit system and a second cavity 52 away from the magnetic circuit system. A recessed portion 32 is located on one side of the cavity 36; specifically, a first through-hole 54 is provided at the center of the top wall of the recessed portion 32. The first through-hole 54 connects the first cavity 50 with the receiving portion 16 and serves as a vent, allowing ventilation for the rear cavity of the MEMS module 14. A second through-hole 56 is provided at the center of the end of the outer shell 22 opposite to the opening end 24. The second through-hole 56 connects the second cavity 52 with the outside of the outer shell 22 and serves as a vent, allowing ventilation for the cavity 36 of the moving coil module 12. Preferably, the first through-hole 54 and the second through-hole 56 are coaxially arranged around the central axis a.

[0036] Optionally, a damping element 58 is also provided outside the second through hole 56. The damping element 58 is, for example, a filter screen, used to adjust the air permeability of the cavity 36. For example, the damping element 58 is attached to the outer wall surface of the outer shell 22 corresponding to the second through hole 56, and the damping element 58 covers the second through hole 56.

[0037] In the illustrated embodiment, the speaker module 10 includes a first circuit board 60 and a second circuit board 62, which are, for example, strip structures. The voice coil 40 is electrically connected to the first circuit board 60, and the MEMS module 14 is electrically connected to the first circuit board 60 through the second circuit board 62. For example, one end of the second circuit board 62 is electrically connected to the MEMS module 14, and the other end is electrically connected to the first circuit board 60.

[0038] Specifically, the first circuit board 60 is disposed on the outside of the housing 22. For example, a step 64 is formed by recessing the outer periphery of the housing 22 at the end opposite to the opening end 24 into the housing 22, and the first circuit board 60 is fixedly disposed on the step 64. Disposing the first circuit board 60 on the back side of the speaker module 10 away from the first sound hole 18 facilitates assembly of the entire device. The second circuit board 62 is preferably a flexible circuit board. The magnetic cover 30 and the housing 22 together form an extension channel 66. For example, the magnetic cover 30 and the housing 22 are respectively provided with notch structures, and the two notch structures are connected to form the extension channel 66. The second circuit board 62 is located in the extension channel 66, and one end of the second circuit board 62 extends into the receiving part 16 and is electrically connected to the MEMS module 14, and the other end extends to the first circuit board 60 and is electrically connected to it. Optionally, one end of the second circuit board 62 extends along one side wall and top wall of the receiving portion 16, the portion of the second circuit board 62 located at the top of the MEMS module 14 is soldered to the pads of the MEMS module 14, and the end of the second circuit board 62 extending onto the first circuit board 60 is externally soldered to the pads of the first circuit board 60.

[0039] This application fully utilizes the magnetic circuit space of the dynamic coil module 12 and integrates the MEMS module 14 within the magnetic circuit of the dynamic coil module 12 through a specific design. This results in a compact structure that allows the dynamic coil module 12 and the MEMS module 14 to be rationally arranged within the limited internal space of electronic products such as TWS earphones, without affecting the normal installation and use of other components. The MEMS module 14 is integrated inside the magnetic circuit of the dynamic coil module 12, and both emit sound independently, separated by a specially designed acoustic isolation structure to reduce mutual acoustic interference. The opening at the bottom of the magnetic cover 30 (first sound hole 18) serves as the sound outlet of the dynamic coil module 12, while the MEMS module 14 emits sound through its own front sound outlet (second sound hole 20). This allows the dynamic coil module 12 and the MEMS module 14 to emit sound independently, effectively utilizing the mid-low frequency performance of the dynamic coil module 12 and the high frequency performance of the MEMS module 14.

[0040] It is understandable that the directional terms "up," "down," "bottom," and "top" used above are all based on... Figure 3 The orientation of the speaker module 10 is used to define the positioning.

[0041] In summary, this application provides a speaker module, including a dynamic driver module and a MEMS module capable of independently emitting sound. The dynamic driver module has a receiving portion, and the MEMS module is mounted in the receiving portion and electrically connected to the dynamic driver module. The dynamic driver module has a first sound hole, and the MEMS module has a second sound hole, with the first and second sound holes located on the same side of the speaker module. The speaker module of this application adopts an integrated design, organically combining the dynamic driver module and the MEMS module, resulting in a compact structure and miniaturization. Furthermore, the dynamic driver module and the MEMS module emit sound independently, effectively solving the problems of poor high-frequency sound quality of traditional TWS earphones with a single dynamic driver and insufficient low-frequency sound of MEMS speakers. This achieves high-quality sound output across the entire frequency range, especially in the high and low frequencies, providing users with a high-fidelity, richly detailed audio experience.

[0042] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0043] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features of the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this invention.

[0044] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A speaker module, characterized in that, The speaker module includes a dynamic coil module and a MEMS module that can produce sound independently. The dynamic coil module is provided with a receiving part, and the MEMS module is installed in the receiving part and electrically connected to the dynamic coil module. The dynamic coil module is provided with a first sound hole, and the MEMS module is provided with a second sound hole. The first sound hole and the second sound hole are located on the same side of the speaker module.

2. The speaker module as described in claim 1, characterized in that, The moving coil module and the MEMS module are coaxially arranged.

3. The speaker module as described in claim 1, characterized in that, The speaker module includes a housing, the dynamic coil module is disposed inside the housing and includes a magnetic cover, the housing has an open end, the magnetic cover is disposed at the open end, and the middle part of the magnetic cover is recessed into the housing to form a concave portion, the concave portion surrounds to form the receiving portion, the first sound hole is disposed in the area of ​​the magnetic cover located outside the concave portion, and the second sound hole is disposed on the side of the MEMS module opposite to the concave portion.

4. The speaker module as described in claim 3, characterized in that, The moving coil module includes a basin frame and a magnet. The basin frame is supported by the magnet on the side of the magnetic cover away from the opening end, and the basin frame, the magnet and the magnetic cover together form a magnetic circuit system. The basin frame and the magnet are located on the periphery of the concave portion and form a magnetic gap with the concave portion. The first sound hole corresponds to the position of the magnetic gap.

5. The speaker module as described in claim 4, characterized in that, The moving coil module includes a vibration system, and a cavity is formed between the magnetic circuit system and the outer shell. The vibration system is disposed in the cavity, and the magnetic gap is connected to the cavity. The vibration system includes a diaphragm, a voice coil, and a metal component. The diaphragm is supported on the frame by the metal component, and one end of the voice coil is connected to the diaphragm, while the other end extends into the magnetic gap.

6. The speaker module as described in claim 5, characterized in that, The recessed portion is provided with a first through hole on one side of the cavity, and the first through hole connects the cavity and the receiving portion.

7. The speaker module as described in claim 5, characterized in that, The outer shell has a second through hole at one end opposite to the opening end, and the second through hole connects the cavity to the outside of the outer shell.

8. The speaker module as described in claim 7, characterized in that, A damping element is provided outside the second through hole.

9. The speaker module as described in claim 5, characterized in that, The speaker module includes a first circuit board and a second circuit board. The voice coil is electrically connected to the first circuit board. One end of the second circuit board is electrically connected to the MEMS module, and the other end is electrically connected to the first circuit board.

10. The speaker module as described in claim 9, characterized in that, The outer periphery of the outer casing and the opposite end of the opening is formed with a step, and the first circuit board is located outside the outer casing and disposed on the step; And / or, the second circuit board is a flexible circuit board, the magnetic cover and the outer shell together form an extension channel, the second circuit board is located in the extension channel, and one end of the second circuit board extends into the receiving portion and the other end extends to the first circuit board.

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