CN110798786A - Electret capacitor microphone with selectable sensitivity - Google Patents

Electret capacitor microphone with selectable sensitivity Download PDF

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Publication number
CN110798786A
CN110798786A CN201911303128.4A CN201911303128A CN110798786A CN 110798786 A CN110798786 A CN 110798786A CN 201911303128 A CN201911303128 A CN 201911303128A CN 110798786 A CN110798786 A CN 110798786A
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capacitor
resistor
field effect
filter circuit
microphone
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张树信
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Weifang Pinghe Electronic Co Ltd
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Weifang Pinghe Electronic Co Ltd
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R19/00—Electrostatic transducers
    • H04R19/01—Electrostatic transducers characterised by the use of electrets
    • H04R19/016—Electrostatic transducers characterised by the use of electrets for microphones

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Circuit For Audible Band Transducer (AREA)

Abstract

The invention discloses an electret condenser microphone with selectable sensitivity, which comprises a shell, a conductive copper ring and a circuit board assembly, wherein the circuit board assembly comprises at least two field effect transistors, each field effect transistor is respectively coupled with a filter circuit, and the circuit board outputs different sensitivities corresponding to bonding pads through Field Effect Transistors (FETs) with different amplification factors; a plurality of same FETs on the circuit board can be respectively coupled with different anti-interference, anti-static, filtering and other circuits according to requirements. A plurality of FET tube cores can be pasted according to the sizes of a circuit board and an electret capacitor electret microphone, only one microphone is needed to be adopted to carry out sensitivity conversion under the control of a selection switch, a user can conveniently select the microphone during testing when the sensitivity and the circuit of a product are shaped, and the proofing trial-manufacturing and testing time is greatly reduced.

Description

Electret capacitor microphone with selectable sensitivity
Technical Field
The invention belongs to the technical field of electronics, and particularly relates to an electret capacitor microphone with selectable sensitivity.
Background
In recent years, along with the continuous development of intelligent technology, the innovation of man-machine communication and the continuous expansion of intelligent home, electroacoustic product microphones used for receiving human languages and sounds in various intelligent devices play an important role; the electret capacitor microphone becomes the first choice of the current microphone due to small volume and high stability.
In the course of implementing the present invention, the inventor finds that the current microphone has at least the following disadvantages: after the conventional electret capacitor microphone is manufactured at present, one product only has fixed sensitivity, different single filter circuits are required to be configured in the microphone for different matched applications, if the sensitivity is required to be adjusted, the adjustment can be only carried out through the adjustment of a post-stage amplification circuit of a user finished product, if different filter circuits are required, different microphones are required to be redesigned (the electret capacitor microphone needs different built-in filter, anti-interference and anti-static circuit elements in different fields, for example, the microphone for a television, the microphone for monitoring, the microphone for a telephone and the microphone filter circuit for a conference system are different), the design and the manufacture of a single circuit board are carried out according to different requirements, and the manufactured product can be only used in the field of single products.
If a certain product needs to be configured with microphones with different sensitivities according to the change of the pickup distance, the microphone with different sensitivities needs to be adopted to realize through a selection switch under the current situation, or the microphone with different sensitivities needs to adjust the post-stage output amplified sound to realize; the problems faced are then: the plurality of microphones have no too much place to place space, and the noise and the distortion degree of the body are increased after the post-stage amplification.
Disclosure of Invention
The invention aims to solve the technical problem of providing an electret capacitor microphone with selectable sensitivity, which overcomes the defects of the existing single electret capacitor microphone.
In order to solve the technical problems, the technical scheme of the invention is as follows: an electret condenser microphone with selectable sensitivity, which comprises a shell, a conductive copper ring and a circuit board assembly, and is characterized in that: the circuit board assembly comprises at least two field effect transistors, and each field effect transistor is respectively coupled with a filter circuit.
Further, the at least two field effect transistors are different in model or/and the same in filter circuit.
Further, the at least two field effect transistors are the same in model or/and different in filter circuit.
Further, the FET selects a junction N-channel FET here.
Furthermore, the grids of the at least two field effect transistors are respectively connected with the conductive copper ring, and the source electrodes and the shell of the field effect transistors are connected with the negative electrode.
Further, the filter circuit comprises a resistor R1, a capacitor C1, a capacitor C2 and a voltage dependent resistor V, one end of the resistor R1 is connected with the drain of the field effect transistor and one end of the capacitor C1, the other end of the resistor R1 is connected with one end of the capacitor C2, one end of the voltage dependent resistor V and the output end Term, and the other end of the capacitor C1, the other end of the capacitor C2 and the other end of the voltage dependent resistor V are connected with the negative electrode.
Further, the filter circuit comprises a resistor R1, a capacitor C1 and a capacitor C2, wherein the value of the resistor R1 is 0, one end of the resistor R1 is connected with the drain of the field effect transistor and one end of the capacitor C1, the other end of the resistor R1 is connected with one end and the output end Term of the capacitor C2, and the other end of the capacitor C1 and the other end of the capacitor C2 are connected with the negative electrode.
The filter circuit further comprises an L-shaped filter circuit consisting of a resistor R3 and a capacitor C3, one end of the resistor R2 is connected with the drain electrode of the field effect transistor, the other end of the resistor R2 is connected with one end of the capacitor C3 and the output end Term, and the other end of the capacitor C3 is connected with the negative electrode.
Furthermore, the filter circuit also comprises a pi-type filter circuit consisting of a resistor R3, a capacitor C4 and a capacitor C5, wherein one end of the resistor R3 is connected with the drain of the field effect transistor and one end of the capacitor C4, the other end of the resistor R3 is connected with one end of the capacitor C5 and the output end Term, and the other end of the capacitor C4 and the other end of the capacitor C5 are connected with the negative electrode.
Furthermore, the filter circuit also comprises an antistatic pi-type filter circuit consisting of a resistor R4, a capacitor C6, a capacitor C7 and a piezoresistor V, wherein one end of the resistor R4 is connected with the drain of the field effect transistor and one end of the capacitor C6, the other end of the resistor R4 is connected with one end of the capacitor C7, one end of the piezoresistor V and the output end Term, and the other end of the capacitor C6, the other end of the capacitor C7 and the other end of the piezoresistor V are connected with the negative electrode.
By adopting the technical scheme, compared with the prior art, the invention has the following advantages: the field effect transistors FET with different amplification factors are pasted on the circuit board, so that the corresponding bonding pads output different sensitivities.
A plurality of same FETs on the circuit board can be respectively coupled with different anti-interference, anti-static, filtering and other circuits according to requirements.
A plurality of FET tube cores, namely circuits with different sensitivities, can be pasted according to the sizes of a circuit board and the electret condenser electret microphone.
Only one microphone is needed to be adopted for sensitivity conversion under the control of the selection switch.
According to different FET models and single products integrating the amplification output number, the selection of any sensitivity of a user is facilitated;
when the user shapes the sensitivity and the circuit of the product, the user can conveniently select the product in the test, and the proofing and trial-manufacturing time and the testing time are greatly reduced.
Drawings
FIG. 1 is a schematic diagram of an electret condenser microphone with selectable sensitivity according to an embodiment of the invention;
FIG. 2 is a circuit diagram of different power FETs and filter circuits according to an embodiment of the present invention;
FIG. 3 is a circuit diagram of the same field effect transistor with amplification factor and filter circuit in an embodiment of the present invention;
in the figure, the position of the upper end of the main shaft,
the circuit board comprises a shell, a sound collecting hole, a dust screen, a vibrating diaphragm, an insulating gasket, a back plate, an insulating plastic ring, a conductive copper ring and a circuit board component, wherein the shell is 1, the sound collecting hole is 2, the dust screen is 3, the vibrating diaphragm is 4, the insulating gasket is 5, the back plate is 6, the insulating plastic ring is 7, the conductive copper ring is.
Detailed Description
In order to more clearly understand the technical features, objects and effects of the present invention, a wireless monitoring security camera is taken as an example, and the following detailed description of the present invention is described with reference to the accompanying drawings.
In an embodiment, as shown in fig. 1, an electret capacitor microphone with selectable sensitivity includes a housing 1, a sound pickup hole 2 is formed in the front of the housing 1, a dust screen 3 is formed outside the sound pickup hole 2, a diaphragm 4, an insulating spacer 5, a back plate 6, an insulating plastic ring 7 and a conductive copper ring 8 are arranged in the housing 1, a circuit board assembly 9 is arranged at the bottom of the housing 1, the back plate 6, the conductive copper ring 8 and the diaphragm 4 form a parallel plate capacitor, and the electret capacitor microphone is a conventional electret capacitor microphone structure, which is not an innovative point of the present invention.
As shown in fig. 2, the circuit board assembly 9 includes at least two FETs, each FET having a filter circuit coupled thereto.
The FET here selects a junction N-channel FET.
In this embodiment, four FETs and corresponding filter circuits are disposed on the circuit board assembly 9, the electret condenser microphone has a size of 9.7 mm by 4.5mm, the circuit board assembly 9 is disposed with four FETs, each FET is coupled with a filter circuit, and the four FETs and the filter circuits may be the same or different, and are identical and denoted by the same symbols for ease of description.
The FET1 and the corresponding filter circuit are used for explanation, the structures and connection relations of the remaining three FETs 1 and the filter circuits thereof are not described in detail, the gate of the FET1 is connected to the conductive copper ring 8, the source of the FET1 and the housing 1 are connected to the negative electrode, the filter circuit includes a resistor R1, a capacitor C1, a capacitor C2 and a varistor V, one end of the resistor R1 is connected to the drain of the FET and one end of the capacitor C1, the other end of the resistor R1 is connected to one end of the capacitor C2, one end of the varistor V and the output terminal Term, the other end of the capacitor C1, the other end of the capacitor C2 and the other end of the varistor V are connected to the negative electrode.
The electret condenser microphone also comprises an available external selection switch, the movable contact piece of the selection switch can be selectively connected with the output end, namely the other corner of the resistor R1, the selection switch is arranged outside the electret condenser microphone, and in order to reduce the volume of the microphone body, the selection switch can be welded through the corresponding welding point when in use.
In the circuit shown in fig. 2, the filter circuit may be a common filter circuit formed by a resistor R1, a capacitor C1 and a capacitor C2, and the resistor R1 is 0, and is used for a communication microphone such as a mobile phone.
The L-shaped filter circuit can also be formed by the resistor R1 and the capacitor C2 and is used for wireless transmission microphones such as Bluetooth and wifi.
The resistor R1, the capacitor C1 and the capacitor C2 can also be used to form a pi-type filter circuit for wireless transmission microphones such as Bluetooth and wifi.
In the pi-type filter circuit, a piezoresistor V can be added for a microphone with an antistatic requirement, so that the microphone is prevented from being failed due to electrostatic breakdown of a field effect tube.
And (3) testing: in order to make an actual electret condenser microphone have various sensitivities, the types of field effect transistors and the structure of a filter circuit or parameters of components may be different, and four different types of field effect transistors are described below in combination with the same filter circuit.
The filter circuit comprises a first field effect transistor FET1, a second field effect transistor FET2, a third field effect transistor FET3, a fourth field effect transistor FET4, a first filter circuit, a second filter circuit, a third filter circuit and a fourth filter circuit, wherein the circuit structures are not described in detail, a FET1 adopts RJN1123KB, a FET adopts RJN2123KB, a FET3 adopts RJN2123KC, and a FET4 adopts RJN5123 KB; in the circuit, capacitors C1, C3, C5 and C7 are 33PF, capacitors C2, C4, C6 and C8 are 10NF, and resistors R1, R2, R3 and R4 are 330 omega, so that a pi-shaped filter circuit is formed to enhance and filter interference signals of Bluetooth 2.4GHZ and interference signals of WIFI; on the basis of the filter circuit, V1, V2, V3 and V4 are added to select 100PF piezoresistors, so that the antistatic 4-level performance can be effectively enhanced.
The drain electrode of the field effect transistor FET1 is electrically connected with terminal.1 of the bonding pad through a metallization hole process of the circuit board;
the drain electrode of the field effect transistor FET2 is electrically connected with terminal.2 of the bonding pad through a metallization hole process of the circuit board;
the drain electrode of the field effect transistor FET3 is electrically connected with terminal.3 of the bonding pad through a metallization hole process of the circuit board;
the drain electrode of the field effect transistor FET4 is electrically connected with terminal.4 of the bonding pad through a metallization hole process of the circuit board;
the sources of the FETs 1, 2, 3 and 4 are connected with each other and conducted with terminal.5 of the pad through the metallization hole process of the circuit board.
During detection, a working input direct current voltage positive electrode VS + of the field effect tube is connected with a working voltage positive electrode through a bias resistor R, and the working input direct current voltage positive electrode VS + is respectively connected with a Term.1, a Term.2, a Term.3 and a Term.4 through the bias resistor R, and the Term.1, the Term.2, the Term.3 and the Term.4 are positive electrode output positive electrodes of alternating current signals output through a direct current isolating capacitor C;
term.5 is connected with a negative electrode grounding end group;
in a professional tester, usually, VS + (selected by a toggle switch according to different voltages), a bias resistor R (selected by a toggle switch according to different resistances) and a dc blocking capacitor C are respectively connected to a circuit and a negative electrode grounding terminal in the machine, that is, the output positive electrode and the output negative electrode of a microphone are respectively connected in a "+" and "-" pole input mode.
The following are the sensitivities respectively detected by selecting 2.2K omega from VS + selection 2V, R, connecting term.1, term.2, term.3 and term.4 with positive input electrodes and connecting term.5 with negative input electrodes of HY6162 in a test instrument, and the results are as follows:
Figure 524960DEST_PATH_IMAGE001
the output sensitivity of the output corresponding to the bonding pad is different on the circuit board through the field effect transistor FETs with different amplification factors;
different numbers of FET chip dies (namely, the number of different sensitivities and the number of different circuits) can be designed according to different sizes of the circuit board and the electret condenser electret microphone;
only one microphone is needed to be adopted for sensitivity conversion under the control of the selection switch.
According to different FET models and single products integrating the amplification output number, the selection of any sensitivity of a user is facilitated;
according to different FET models and single products integrating the amplification output number, a user can select any sensitivity conveniently by adopting a selection switch;
when the user shapes the sensitivity and the circuit of the product, the user can conveniently select the product in the test, and the proofing and trial-manufacturing time and the testing time are greatly reduced.
As shown in fig. 3, the FET filter includes a first FET1, a second FET2, a third FET3, a fourth FET4, and first, second, third, and fourth filter circuits. The first FET1, the second FET2, the third FET3, and the fourth FET4 are of the same type.
The resistor R1, the capacitor C1 and the capacitor C2 form a common filter circuit which is a first filter circuit, and the value of the resistor R1 is 0, so that the common filter circuit is used for a mobile phone microphone.
The resistor R2 and the capacitor C3 form an L-shaped filter circuit which is a second filter circuit and used for Bluetooth and wifi microphones.
The resistor R3, the capacitor C4 and the capacitor C5 form a pi-type filter circuit which is a third filter circuit and is used for Bluetooth and wifi microphones.
The fourth filter circuit is an antistatic pi-shaped filter circuit formed by the resistor R4, the capacitor C6, the capacitor C7 and the piezoresistor V, and is used for preventing the breakdown of a field effect transistor and the failure of a microphone.
Different anti-interference, anti-static, filtering circuits and the like can be respectively designed for the same FET on the circuit board according to requirements;
the same FET type needs different anti-interference, filtering, antistatic circuits and other circuits on an integrated single product, so that the selection of a user is facilitated;
the integrated single product of different anti-interference, filtering, antistatic circuits and the like is required according to the same FET type, so that a user can conveniently select the integrated single product by adopting a selection switch;
when the user shapes the sensitivity and the circuit of the product, the user can conveniently select the product in the test, and the proofing and trial-manufacturing time and the testing time are greatly reduced.
The product is based on the common electret condenser microphone, and designs a plurality of circuits and a plurality of tube cores on a circuit board, so that the manufactured electret condenser microphone can select different sensitivity, anti-interference and filter circuits according to the requirement.
The foregoing is illustrative of the best mode of the invention and details not described herein are within the common general knowledge of a person of ordinary skill in the art. The scope of the present invention is defined by the appended claims, and any equivalent modifications based on the technical teaching of the present invention are also within the scope of the present invention.

Claims (10)

1. An electret condenser microphone with selectable sensitivity, comprising a housing (1), a conductive copper ring (8) and a circuit board assembly (9), characterized in that: the circuit board assembly (9) comprises at least two field effect transistors, and each field effect transistor is respectively coupled with a filter circuit.
2. A sensitivity selectable electret condenser microphone as claimed in claim 1, wherein: the at least two field effect transistors are different in type or/and the same in filter circuit.
3. A sensitivity selectable electret condenser microphone as claimed in claim 1, wherein: the at least two field effect transistors are the same in type or/and different in filter circuit.
4. A sensitivity selectable electret condenser microphone as claimed in claim 3 wherein: the FET here selects a junction N-channel FET.
5. A sensitivity selectable electret condenser microphone as claimed in claim 2, wherein: the grids of the at least two field effect tubes are respectively connected with the conductive copper ring (8), and the source electrodes of the field effect tubes and the shell (1) are connected with the negative electrode.
6. The electret condenser microphone of claim 5 wherein: the filter circuit comprises a resistor R1, a capacitor C1, a capacitor C2 and a piezoresistor V, one end of the resistor R1 is connected with the drain of the field effect transistor and one end of the capacitor C1, the other end of the resistor R1 is connected with one end of the capacitor C2, one end of the piezoresistor V and an output end Term, and the other end of the capacitor C1, the other end of the capacitor C2 and the other end of the piezoresistor V are connected with the negative electrode.
7. A sensitivity selectable electret condenser microphone as claimed in claim 3 wherein: the filter circuit comprises a resistor R1, a capacitor C1 and a capacitor C2, wherein the value of the resistor R1 is 0, one end of the resistor R1 is connected with the drain of the field effect transistor and one end of the capacitor C1, the other end of the resistor R1 is connected with one end of the capacitor C2 and the output end Term, and the other end of the capacitor C1 and the other end of the capacitor C2 are connected with the negative electrode.
8. A sensitivity selectable electret condenser microphone as claimed in claim 3 wherein: the filter circuit further comprises an L-shaped filter circuit consisting of a resistor R3 and a capacitor C3, one end of the resistor R2 is connected with the drain electrode of the field effect transistor, the other end of the resistor R2 is connected with one end of the capacitor C3 and the output end Term, and the other end of the capacitor C3 is connected with the negative electrode.
9. A sensitivity selectable electret condenser microphone as claimed in claim 3 wherein: the filter circuit further comprises a pi-type filter circuit consisting of a resistor R3, a capacitor C4 and a capacitor C5, one end of the resistor R3 is connected with the drain of the field effect transistor and one end of the capacitor C4, the other end of the resistor R3 is connected with one end of the capacitor C5 and the output end Term, and the other end of the capacitor C4 and the other end of the capacitor C5 are connected with the negative electrode.
10. A sensitivity selectable electret condenser microphone as claimed in claim 3 wherein: the filter circuit further comprises an antistatic pi-shaped filter circuit consisting of a resistor R4, a capacitor C6, a capacitor C7 and a piezoresistor V, wherein one end of the resistor R4 is connected with the drain electrode of the field effect transistor and one end of the capacitor C6, the other end of the resistor R4 is connected with one end of the capacitor C7, one end of the piezoresistor V and the output end Term, and the other end of the capacitor C6, the other end of the capacitor C7 and the other end of the piezoresistor V are connected with the negative electrode.
CN201911303128.4A 2019-12-17 2019-12-17 Electret capacitor microphone with selectable sensitivity Pending CN110798786A (en)

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CN201911303128.4A CN110798786A (en) 2019-12-17 2019-12-17 Electret capacitor microphone with selectable sensitivity

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CN110798786A true CN110798786A (en) 2020-02-14

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