Application circuits, printed circuit boards, microphones, and microphones for microphones.
By introducing field-effect transistors, capacitors, and low-pass filter circuits into the microphone, combined with TVS diodes and RC decoupling networks, the problem of microphone circuits being susceptible to electromagnetic interference is solved, achieving effective resistance to frequency bands such as 2.4G, 5G, and 6G, and improving anti-interference capabilities and electrostatic protection.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- DONGGUAN RUIQIN ELECTRONICS CO LTD
- Filing Date
- 2025-07-30
- Publication Date
- 2026-07-03
AI Technical Summary
Microphones' electronic circuits are susceptible to electromagnetic interference radiation, which can affect the quality of voice calls. Existing technologies are unable to effectively resist interference from frequency bands such as 2.4G, 5G, and 6G.
An application circuit consisting of field-effect transistors, capacitors, and low-pass filter circuits is designed with TVS diodes and RC decoupling networks to provide anti-interference printed circuit boards.
It significantly attenuates radio frequency interference, reduces radio frequency coupling caused by impedance mismatch, improves the microphone's anti-interference capability, meets the level 4 anti-static requirements, and effectively resists interference from frequency bands such as 2.4G, 5G, and 6G.
Smart Images
Figure CN224459943U_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of microphone technology, specifically to an application circuit, printed circuit board, microphone, and microphone. Background Technology
[0002] The application environment for microphones is becoming increasingly complex, and their electronic circuits are susceptible to electromagnetic interference, affecting the voice quality of the final call. To improve user experience, microphone products themselves must have excellent anti-interference capabilities, effectively resisting interference from the widely available 2.4G, 5G, and 6G frequency bands. Utility Model Content
[0003] The main technical problem addressed by this application is to provide an application circuit, printed circuit board, microphone, and microphone for use in order to help resist interference.
[0004] In a first aspect, this application provides an application circuit for a microphone, the application circuit including a field-effect transistor, a first capacitor, a second capacitor, and a low-pass filter circuit, wherein: the first capacitor is connected between the drain of the field-effect transistor and the ground terminal; the second capacitor is connected between the source of the field-effect transistor and the ground terminal; a first resistor and a third capacitor are connected in series between the drain of the field-effect transistor and the ground terminal to form the low-pass filter circuit.
[0005] In some alternative implementations, the application circuit further includes: a first TVS diode connected between the drain of the field-effect transistor and ground; and a second TVS diode connected between the source of the field-effect transistor and ground.
[0006] In some alternative implementations, the application circuit further includes a second resistor and a fourth capacitor, connected in series between the source of the field-effect transistor and ground.
[0007] In some alternative embodiments, the field-effect transistor is a junction field-effect transistor, the gate of the field-effect transistor is connected to the ground terminal via the acoustic-electric conversion unit, the drain of the field-effect transistor is connected to the operating voltage, and the source of the field-effect transistor is connected to the output terminal.
[0008] In some alternative implementations, a first end of the first resistor is connected to the drain of the field-effect transistor, a second end of the first resistor is connected to a first end of the third capacitor, and a second end of the third capacitor is connected to ground.
[0009] In some alternative implementations, the first end of the second resistor is connected to the source of the field-effect transistor, the second end of the second resistor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to ground.
[0010] In some alternative embodiments, the capacitance of the first capacitor is 8.2pF, the capacitance of the second capacitor is 8.2pF, the capacitance of the third capacitor is 6.8nF, and the resistance of the first resistor is 330Ω.
[0011] Secondly, this application provides a printed circuit board that includes application circuitry for a microphone as described in the first aspect.
[0012] Thirdly, this application provides a microphone, which is an electret condenser microphone, and the electret condenser microphone includes a printed circuit board, the printed circuit board including the application circuit for the microphone as described in the first aspect.
[0013] Fourthly, this application provides a microphone, said microphone including the microphone described in the third aspect.
[0014] As can be seen from the above technical solutions, this application has the following advantages:
[0015] This application circuit for a microphone, by incorporating a first capacitor, a second capacitor, a first resistor, and a third capacitor, possesses excellent anti-interference capabilities. Specifically, the high-frequency bypass of the second capacitor significantly attenuates radio frequency interference coupled through the output line. The first resistor and the third capacitor reduce some radio frequency energy coupling through high-frequency bypass. The first capacitor reduces radio frequency coupling caused by impedance mismatch. In summary, this application circuit effectively resists interference from the widely prevalent 2.4G, 5G, and 6G frequency bands. Attached Figure Description
[0016] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the description of the embodiments and the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0017] Figure 1 This is a circuit diagram of the application circuit for a microphone according to Embodiment 1 of this application;
[0018] Figure 2 This is a circuit diagram of the application circuit for a microphone according to Embodiment 2 of this application;
[0019] Figure 3 This is a circuit diagram of the application circuit for a microphone according to Embodiment 3 of this application. Detailed Implementation
[0020] To enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present application, and not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present application.
[0021] The terms "first," "second," "third," etc., in the specification, claims, and accompanying drawings of this application are used to distinguish different objects, not to describe a specific order. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or apparatus that includes a series of steps or units is not limited to the listed steps or units, but may optionally include steps or units not listed, or may optionally include other steps or units inherent to these processes, methods, products, or apparatuses.
[0022] The following detailed descriptions will be provided through specific embodiments.
[0023]
Example 1
[0024] refer to Figure 1 This application provides an application circuit for a microphone. The microphone can be an electret condenser microphone, including a sound-to-electric conversion unit 10. Optionally, the sound-to-electric conversion unit 10 may include a diaphragm and metal plates separated by insulating spacers to form a parallel-plate capacitor, with the diaphragm and metal plates serving as the two electrodes of the capacitor. An electret is disposed on the diaphragm or the metal plates. The working principle of the sound-to-electric conversion unit 10 is as follows: when sound pressure is received, the diaphragm vibrates under the action of sound pressure, and the capacitance of the parallel-plate capacitor changes with the vibration of the diaphragm, thereby causing a voltage change and completing the sound-to-electric conversion. The capacitance between the diaphragm and the metal plates is relatively small, typically tens of pF. Therefore, the output impedance of the sound-to-electric conversion unit 10 is very high, approximately tens of megohms or more.
[0025] refer to Figure 1The microphone application circuit of this application structurally includes a field-effect transistor (FET) 10, a first capacitor C1, a second capacitor C2, and a low-pass filter circuit. It provides three external terminals: terminal 1 is connected to the operating voltage (Vs) 21; terminal 2 is connected to the output terminal (Output) 22; and terminal 3 is connected to the ground terminal 23. This application circuit can be mounted on a printed circuit board inside the microphone. The printed circuit board can be encapsulated by the microphone's housing (which can be a metal housing) and together with the housing forms a cavity. The cavity houses the electroacoustic conversion unit 10, and may also contain components such as metallization and insulating rings. This application circuit is connected to the electroacoustic conversion unit 10.
[0026] The field-effect transistor 11 is used to implement impedance transformation, reducing the output impedance of the voltage signal from the acoustic-to-electric conversion unit 10 to below several thousand ohms. Specifically, the field-effect transistor 11 can be a junction field-effect transistor (JFET). The JFET 11 includes three terminals: drain (D), source (S), and gate (G). The gate (G) is connected to one electrode of the acoustic-to-electric conversion unit 10, while the other electrode of the acoustic-to-electric conversion unit 10 is connected to ground terminal 23 via terminal 3. In other words, the gate (G) is connected to ground terminal 23 via the acoustic-to-electric conversion unit 10. The drain (D) is connected to terminal 1, which is connected to the operating voltage 21. The source (S) is connected to terminal 2, which is connected to the output terminal 22, outputting a voltage signal.
[0027] The connection relationships of the first capacitor C1, the second capacitor C2, and the low-pass filter circuit are as follows: the first capacitor C1 is connected between the drain (D) of the field-effect transistor 11 and the ground terminal 23; the second capacitor C2 is connected between the source (S) of the field-effect transistor 11 and the ground terminal 23; the first resistor R1 and the third capacitor C3 form a low-pass filter circuit, which is connected in series between the drain (D) of the field-effect transistor and the ground terminal 23. Specifically, the first end of the first resistor R1 is connected to the drain (D) of the field-effect transistor 11, the second end of the first resistor R1 is connected to terminal 1 and simultaneously connected to the first end of the third capacitor (C3), and the second end of the third capacitor C3 is connected to the ground terminal 23.
[0028] In some alternative implementations, the capacitance of the first capacitor is 8.2pF, the capacitance of the second capacitor is 8.2pF, the capacitance of the third capacitor is 6.8nF, the resistance of the first resistor is 330Ω, and the voltage of the operating voltage (Vs) 21 can be between 1V and 10V, for example, 5V.
[0029] In some optional embodiments, when the microphone of this application is working, a capacitor C0 and a resistor RL can also be connected between its output terminal 22 and ground terminal 23. Specifically, the first end of the capacitor C0 is connected to the source (S) of the field-effect transistor 11 and to the first end of the resistor RL, the second end of the capacitor C0 is connected to the output terminal 22, and the second end of the resistor RL is connected to the ground terminal 23. Here, the resistor RL is a pull-down resistor, which can provide a stable low-level default state for the gate (G) to prevent false triggering due to floating; at the same time, it releases the charge accumulated on the gate to avoid electrostatic breakdown. Here, the capacitor C0 constitutes an output filter capacitor, which can filter out high-frequency noise in the output signal, stabilize the voltage, reduce ripple; and provide charge compensation during load transient changes to improve dynamic response.
[0030] In the application circuit of this application, the first resistor R1 and the third capacitor C3 constitute a low-pass filter circuit, which allows low-frequency signals to pass through while blocking high-frequency signals. This low-pass filter circuit is connected in series between the drain (D) of the field-effect transistor and ground terminal 23. Compared to connecting it between the source (S) and ground terminal 23, the filtering target is the power supply circuit, mainly filtering out power supply noise and high-frequency spurious signals from the FET itself. It does not affect the output impedance of the source (S), thus retaining the advantage of low output impedance while effectively suppressing power supply noise. If the low-pass filter circuit were connected in series between the source (S) of the field-effect transistor and ground terminal 23, it would increase the output impedance and would not effectively suppress power supply noise.
[0031] In the application circuit of this application, the first capacitor C1, the second capacitor C2, the first resistor R1, and the third capacitor C3 also provide anti-interference capabilities. Specifically, the high-frequency bypass of the second capacitor C2 can significantly attenuate RF interference coupled through the output line. The first resistor R1 and the third capacitor C3 can reduce some RF energy coupling through high-frequency bypass. The first capacitor C can reduce RF coupling caused by impedance mismatch. In summary, this application circuit can effectively resist interference from the widely available 2.4G, 5G, and 6G frequency bands.
[0032]
Example 2
[0033] refer to Figure 2 This application provides an application circuit for a microphone. Figure 2 The application circuit shown is Figure 1 The application circuit shown differs in that, Figure 2 The application circuit shown further includes:
[0034] The first TVS transistor 31 is connected between the drain (D) of the field-effect transistor 11 and the ground terminal 23;
[0035] The second TVS transistor 32 is connected between the source (S) of the field-effect transistor 11 and the ground terminal 23.
[0036] Here, TVS diode refers to a transient voltage suppression diode. TVS diodes utilize avalanche breakdown characteristics to clamp transient overvoltages such as electrostatic discharge (ESD) or surges to a safe level in a very short time, thereby protecting sensitive components inside the microphone, such as the field-effect transistor 11. Therefore, by adding a first TVS diode 31 and a second TVS diode 32 inside the microphone, the anti-static problem can be better solved; for example, it can meet the level 4 anti-static requirement.
[0037]
Example 3
[0038] refer to Figure 3 This application provides an application circuit for a microphone. Figure 3 The application circuit shown is Figure 3 The application circuit shown differs in that, Figure 3 The application circuit shown further includes:
[0039] The second resistor R2 and the fourth capacitor C4 are connected in series between the source (S) of the field-effect transistor 11 and the ground terminal 23. Specifically, the first end of the second resistor R2 is connected to the source (S) of the field-effect transistor 11, the second end of the second resistor R2 is connected to the output terminal 22 through the connection terminal 2, and the second end of the second resistor R2 is connected to the first end of the fourth capacitor C4, and the second end of the fourth capacitor C4 is connected to the ground terminal 23.
[0040] Here, by adding a second resistor R2 and a fourth capacitor C4, a high-frequency RC decoupling network is formed, which can further suppress high-frequency noise and radio frequency interference. Furthermore, the high-frequency RC decoupling network formed by the second resistor R2 and the fourth capacitor C4, together with the low-pass filter circuit formed by the first resistor R1 and the third capacitor C3, forms a drain-source dual π-type circuit, achieving better radio frequency anti-interference capability and providing more effective resistance to interference from 2.4G, 5G, and 6G frequency bands.
[0041]
Example 4
[0042] This application also provides a printed circuit board, which may include application circuitry for a microphone as provided in any of embodiments 1-3.
[0043]
Example 5
[0044] This application also provides an electret condenser microphone, which includes a printed circuit board that may include application circuitry for the microphone as provided in any of embodiments 1-3.
[0045]
Example 6
[0046] This application also provides a microphone, which may include an electret condenser microphone as provided in Embodiment 5.
[0047] The technical solution of this application has been described in detail above through specific embodiments. In the above embodiments, the descriptions of each embodiment have their own emphasis, and for parts not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments.
[0048] It should be understood that the above embodiments are only used to illustrate the technical solutions of this application, and not to limit them. Those skilled in the art can modify the technical solutions described in the above embodiments, or make equivalent substitutions for some of the technical features; however, these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and protection scope of the technical solutions of the embodiments of this application.
Claims
1. An application circuit for a microphone, characterized in that, The application circuit includes a field-effect transistor, a first capacitor, a second capacitor, and a low-pass filter circuit, wherein: The first capacitor is connected between the drain of the field-effect transistor and the ground terminal; The second capacitor is connected between the source of the field-effect transistor and the ground terminal; The first resistor and the third capacitor are connected in series between the drain of the field-effect transistor and the ground terminal to form the low-pass filter circuit.
2. The application circuit for a microphone as defined in claim 1, wherein, Further includes: The first TVS diode is connected between the drain of the field-effect transistor and the ground terminal; The second TVS diode is connected between the source of the field-effect transistor and the ground terminal.
3. The application circuit for a microphone as defined in claim 2, wherein, Further includes: The second resistor and the fourth capacitor are connected in series between the source of the field-effect transistor and the ground terminal.
4. The application circuit for a microphone as defined in claim 1, wherein, The field-effect transistor is a junction field-effect transistor. The gate of the field-effect transistor is connected to the ground terminal via the acoustic-to-electric conversion unit of the microphone. The drain of the field-effect transistor is connected to the operating voltage, and the source of the field-effect transistor is connected to the output terminal.
5. The application circuit for a microphone as defined in claim 1, wherein, The first end of the first resistor is connected to the drain of the field-effect transistor, the second end of the first resistor is connected to the first end of the third capacitor, and the second end of the third capacitor is connected to the ground terminal.
6. The application circuit for a microphone as described in claim 3, characterized in that, The first end of the second resistor is connected to the source of the field-effect transistor, the second end of the second resistor is connected to the first end of the fourth capacitor, and the second end of the fourth capacitor is connected to the ground terminal.
7. The application circuit for a microphone as defined in claim 1, wherein The first capacitor has a capacitance of 8.2pF, the second capacitor has a capacitance of 8.2pF, the third capacitor has a capacitance of 6.8nF, and the first resistor has a resistance of 330Ω.
8. A printed circuit board, characterized by The printed circuit board includes application circuitry for a microphone as described in any one of claims 1-7.
9. A microphone, said microphone being an electret condenser microphone, said electret condenser microphone comprising a printed circuit board, characterized in that, The printed circuit board includes application circuitry for a microphone as described in any one of claims 1-7.
10. A microphone, characterized by The microphone includes the microphone as described in claim 9.