Double-back-pole push-pull output electret capacitor microphone

Abstract

The utility model discloses a double-back-pole push-pull output electret capacitor microphone, which comprises a pole head, and is characterized in that the pole head comprises an upper back pole, a lower back pole and a vibrating diaphragm arranged between the upper back pole and the lower back pole; a first gap is formed between the upper back pole and the vibrating diaphragm, and a second gap is formed between the lower back pole and the vibrating diaphragm; a first electret film layer is arranged on the lower surface of the upper back electrode, and a second electret film layer is arranged on the upper surface of the lower back electrode; the upper surface and the lower surface of the vibrating diaphragm are respectively provided with a metal layer. The upper back pole is provided with a sound inlet hole, and the lower back pole is provided with a sound balance hole. According to the electret capacitor microphone, the sensitivity is higher, and the output signal is stronger.

Description

Technical Field

[0001] The present application relates to the field of acoustic technology, and in particular to a dual back-pole push-pull output electret condenser microphone. Background Art

[0002] Electret condenser microphone (ECM), commonly known as microphone head, is an acoustic-to-electric conversion device, which belongs to the category of condenser microphone. The electret condenser microphone uses an electret material (commonly known as a permanent charge) that can store electric charge as the diaphragm or back electrode, so no external polarization power supply is required. Sensitivity refers to the acoustic-to-electric conversion efficiency of the microphone. In a free acoustic field, when a sound signal of a specific sound intensity is applied to the microphone, the open-circuit output of the microphone (in millivolts) is the sensitivity of the microphone. How to improve the sensitivity and output signal strength of the microphone is the direction of the industry's efforts. Summary of the invention

[0003] The main technical problem solved by the present application is to provide a dual back-pole push-pull output electret condenser microphone.

[0004] The present application proposes a dual back-pole push-pull output electret condenser microphone, comprising a pole head, wherein the pole head comprises:

[0005] An upper back pole, a lower back pole, and a diaphragm arranged between the upper back pole and the lower back pole;

[0006] There is a first gap between the upper back pole and the diaphragm, and there is a second gap between the lower back pole and the diaphragm;

[0007] The lower surface of the upper back electrode is provided with a first electret film layer, and the upper surface of the lower back electrode is provided with a second electret film layer;

[0008] The upper surface and the lower surface of the diaphragm are respectively provided with metal layers;

[0009] The upper back pole is provided with a sound inlet hole, and the lower back pole is provided with a sound balancing hole.

[0010] In some optional implementations, the dual back-pole push-pull output electret condenser microphone further includes:

[0011] A first impedance converter, electrically connected to the upper back electrode and the metal layer on the upper surface of the diaphragm, for performing impedance conversion on a first electrical signal output between the upper back electrode and the metal layer on the upper surface of the diaphragm to generate a first amplified signal;

[0012] The second impedance converter is electrically connected to the lower back pole and the metal layer on the lower surface of the diaphragm, and is used to perform impedance conversion on the second electrical signal output between the lower back pole and the metal layer on the lower surface of the diaphragm to generate a second amplified signal.

[0013] In some optional embodiments, the first electret film layer and the second electret film layer carry the same charge, and the first electrical signal and the second electrical signal have opposite phases; the dual back-pole push-pull output electret condenser microphone also includes: a phase converter, configured to convert the phase of the second electrical signal to be the same as the first electrical signal to generate a second conversion signal, or to convert the phase of the first electrical signal to be the same as the second electrical signal to generate a first conversion signal.

[0014] In some optional embodiments, the dual back-pole push-pull output electret condenser microphone further includes: a circuit board, carrying the first impedance converter, the second impedance converter and the phase converter, the circuit board also having an output terminal, the output terminal being used to output a combined signal of the first amplified signal and the second converted signal, or to output a combined signal of the second amplified signal and the first converted signal.

[0015] In some optional implementations, the dual back-pole push-pull output electret condenser microphone further includes:

[0016] A first conductive wire, used for connecting the upper back electrode and the first impedance converter;

[0017] A second wire, used for connecting the lower back electrode and the second impedance converter;

[0018] A third wire is used to connect the metal layer on the upper surface of the diaphragm to the first impedance converter, and to connect the metal layer on the lower surface of the diaphragm to the second impedance converter.

[0019] In some optional embodiments, the dual back-pole push-pull output electret condenser microphone further includes: a metal shell for accommodating the pole head and the circuit board, the metal shell is connected to the third wire, and is connected to the first impedance converter and the second impedance converter via the circuit board.

[0020] In some optional embodiments, the upper back pole and the metal shell are insulated from each other, and the lower back pole and the metal shell are insulated from each other.

[0021] In some optional embodiments, the method further comprises:

[0022] The correction module is arranged on the circuit board and is configured to calculate the nonlinear distortion D according to the following formula: SE , according to the calculated D SE Performing compensation adjustment on the first amplified signal converted by the first impedance converter 12 or the second amplified signal converted by the second impedance converter 13;

[0023] DSE =|δ t | / (1+C t0 / C p );

[0024] In the formula, δ t represents the relative displacement of the diaphragm, C t0 represents the static capacitance between the diaphragm and the upper back electrode or the lower back electrode, C p Represents the fixed capacitance of the capacitor formed by the diaphragm and the upper backpole or the lower backpole.

[0025] In some optional embodiments, the dual back-pole push-pull output electret condenser microphone further includes: an insulating gasket disposed between the lower back-pole and the circuit board.

[0026] In some optional embodiments, the first electret film layer and the second electret film layer carry different charges, and the first electrical signal and the second electrical signal have the same phase.

[0027] In some optional embodiments, the pole head further includes a clamping ring for fixing the diaphragm, wherein the clamping ring forms the first gap between the diaphragm and the upper back pole, and the second gap between the diaphragm and the lower back pole.

[0028] It can be seen from the above technical solutions that the embodiments of the present application have the following advantages:

[0029] The dual back-pole push-pull output electret condenser microphone of the present application has a pole head composed of an upper back-pole and a lower back-pole and a diaphragm therebetween, forming two capacitors, and the two capacitors share a diaphragm, so that when converting sound signals into electrical signals, the two capacitors work together, and the push-pull addition of the two enhances the signal, thereby effectively utilizing the characteristics of the dual back-pole push-pull output, making the electret condenser microphone more sensitive and having a stronger output signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments and the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0031] Figure 1 It is a structural schematic diagram of an embodiment of a dual back-pole push-pull output electret condenser microphone of the present application;

[0032] Figure 2 It is a schematic diagram of a miniature condenser microphone whose diaphragm is made of flexible material.

[0033] Figure markings: 1-upper back pole; 2-small sound inlet hole; 3-large sound inlet hole; 4-first electret film layer; 5-clamp ring; 6-metal layer; 7-diaphragm; 8-lower back pole; 9-sound balance hole; 10-second electret film layer; 11-metal shell; 12-first impedance converter; 13-second impedance converter; 14-output terminal; 15-first wire; 16-second wire; 17-third wire; 18-circuit board; 19-insulating gasket. DETAILED DESCRIPTION

[0034] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only embodiments of a part of the present application, not all embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0035] The terms "first", "second", "third", etc. in the specification and claims of this application and the above-mentioned drawings are used to distinguish different objects, rather than to describe a specific order. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, system, product or device that includes a series of steps or units is not limited to the listed steps or units, but optionally includes steps or units that are not listed, or optionally includes other steps or units inherent to these processes, methods, products or devices.

[0036] The following describes the embodiments in detail.

[0037] refer to Figure 1 , Figure 1 FIG. 1 is a schematic diagram of the structure of an embodiment of a dual back-pole push-pull output electret condenser microphone of the present application. Figure 1 As shown, the dual back-pole push-pull output electret condenser microphone (hereinafter referred to as electret condenser microphone or microphone) of the present application includes a pole head for realizing acoustic-electric conversion.

[0038] like Figure 1As shown, the pole head part includes an upper back pole 1, a lower back pole 8, and a diaphragm 7 arranged between the upper back pole 1 and the lower back pole 8. The lower surface of the upper back pole 1 is provided with a first electret film layer 4, and the upper surface of the lower back pole 8 is provided with a second electret film layer 10; the upper surface and the lower surface of the diaphragm 7 are provided with metal layers 6 respectively. The upper back pole 1 is provided with a sound inlet hole (the sound inlet hole may include a large sound inlet hole 3 located in the center of the upper back pole 1, and / or a small sound inlet hole 2 located around the upper back pole 1, and the small sound inlet hole 2 may be one or more), and the lower back pole 8 is provided with a sound balance hole 9. There is a first gap between the upper back pole 1 and the diaphragm 7, so that the upper back pole 1 and the diaphragm 7 constitute an upper capacitor; there is a second gap between the lower back pole 8 and the diaphragm 7, so that the lower back pole 8 and the diaphragm 7 constitute a lower capacitor, and the upper capacitor and the lower capacitor share the diaphragm 7. Among them, the first gap and the second gap can be substantially equal, or they can also be not completely equal.

[0039] Here, the first electret film layer 4 may be an electret film layer plated with a metal layer, that is, it may include a metal plated layer formed on the upper back electrode 1 and an electret film formed on the metal plated layer. Similarly, the second electret film layer 10 may be an electret film layer plated with a metal layer, that is, it may include a metal plated layer formed on the lower back electrode 8 and an electret film formed on the metal plated layer.

[0040] In some optional embodiments, the pole head may further include a clamp ring 5 for fixing the diaphragm 7, the clamp ring 5 forms a first gap between the diaphragm 7 and the upper back pole 1, and forms a second gap between the diaphragm 7 and the lower back pole 8. Optionally, the clamp ring 5 may include an upper clamp ring and a lower clamp ring, the edge of the diaphragm 7 is clamped between the upper clamp ring and the lower clamp ring, the upper clamp ring is located between the diaphragm 7 and the upper back pole 1, and the lower clamp ring is located between the diaphragm 7 and the lower back pole 8. The clamp ring may be made of non-conductive materials such as plastic.

[0041] In some optional embodiments, the microphone of the present application further includes:

[0042] The first impedance converter 12 is electrically connected to the upper back electrode 1 and the metal layer 6 on the upper surface of the diaphragm 7, and is used to perform impedance conversion on the first electrical signal output between the upper back electrode 1 and the metal layer 6 on the upper surface of the diaphragm 7 when the diaphragm 7 vibrates to change the capacitance of the upper capacitor, so as to generate a first amplified signal;

[0043] The second impedance converter 13 is electrically connected to the lower back pole 8 and the metal layer 6 on the lower surface of the diaphragm 7, and is used to perform impedance conversion on the second electrical signal output between the lower back pole 8 and the metal layer 6 on the lower surface of the diaphragm 7 when the diaphragm 7 vibrates so that the capacitance of the lower capacitor changes, thereby generating a second amplified signal.

[0044] Here, the first impedance converter 12 and the second impedance converter 13 may be preamplifiers, which may be implemented by field effect transistors. Field effect transistors generally include three electrodes, namely, a source (S), a gate (G) and a drain (D).

[0045] In some optional embodiments, the first electret film layer 4 and the second electret film layer 10 can carry the same charge, and the generated first electrical signal and the second electrical signal have opposite phases; in order to combine the first electrical signal and the second electrical signal for output (parallel output), the dual back-pole push-pull output electret condenser microphone of the present application also includes a phase converter (not shown in the figure), which is configured to convert the phase of the second electrical signal to be the same as the first electrical signal, generating a second conversion signal, so that the second conversion signal and the first amplified signal have the same phase, and can be combined for output. Alternatively, in some other optional embodiments, the phase converter can also be used to convert the phase of the first electrical signal to be the same as the second electrical signal, generating a first conversion signal, at which time the first conversion signal and the second amplified signal have the same phase, and the two can be combined for output.

[0046] In some optional implementations, the dual back-pole push-pull output electret condenser microphone of the present application further includes:

[0047] A circuit board (PCB) 18 carries the first impedance converter 12, the second impedance converter 13 and the phase converter. The circuit board 18 is also provided with an output terminal 14, which is used to output a combined signal of the first amplified signal and the second converted signal, or to output a combined signal of the second amplified signal and the first converted signal. The terminal 14 includes but is not limited to a solder point or a pad.

[0048] In some optional implementations, the dual back-pole push-pull output electret condenser microphone of the present application further includes:

[0049] A first conductive wire 15, used to connect the upper back electrode 1 and the first impedance converter 12;

[0050] A second conductor 16, used for connecting the lower back electrode 8 and the second impedance converter 13;

[0051] The third wire 17 is used to connect the metal layer 6 on the upper surface of the diaphragm 7 to the first impedance converter 12 , and to connect the metal layer 6 on the lower surface of the diaphragm 7 to the second impedance converter 13 .

[0052] In some optional embodiments, the dual back-pole push-pull output electret condenser microphone of the present application further includes a metal shell 11, which is used to accommodate a pole head and a circuit board 18, and the pole head and the circuit board 18 are encapsulated in the metal shell 11. Optionally, the metal shell 11 has a bottom and an opening opposite to the bottom, the pole head can be set at the bottom, and the circuit board 18 can be blocked at the opening. Optionally, the bottom of the metal shell 11 can be provided with a sound inlet channel, and the circuit board 18 can be provided with a balancing hole for balancing the sound pressure.

[0053] In some optional embodiments, the metal shell 11 can be used as a part of the circuit in the microphone. For example, the third wire 17 can be connected to the metal shell, and the metal shell 11 is connected to the first impedance converter 12 and the second impedance converter 13 through the circuit on the circuit board. Optionally, the upper back pole 1 and the lower back pole 8 are insulated from the metal shell 11.

[0054] In some optional embodiments, the dual back-pole push-pull output electret condenser microphone of the present application further includes: an insulating gasket 19 disposed between the lower back-pole 8 and the circuit board 18 to separate the pole head portion from the circuit board 18 .

[0055] As described above, the embodiment of the present application proposes a dual back-pole push-pull output electret condenser microphone.

[0056] Its structural principle is:

[0057] There is a diaphragm 7 between the upper back pole 1 and the lower back pole 8. When an external sound signal enters through the sound inlet hole on the upper back pole 1 and drives the diaphragm 7 to vibrate, there is a change in capacitance between the upper back pole 1 and the diaphragm 7. In this way, the change in the sound signal is converted into a first electrical signal through the change in capacitance between the upper back pole 1 and the diaphragm 7, and then converted into a first amplified signal by the first impedance converter 12 and then output;

[0058] At the same time, when the external sound signal drives the diaphragm 7 to vibrate, there is also a change in capacitance between the lower back pole 8 and the diaphragm 7. The change in the sound signal is converted into a second electrical signal through the change in capacitance between the lower back pole 8 and the diaphragm 7, and then converted into a second amplified signal by the second impedance converter 13 and then output.

[0059] Since the electret film layers on the upper back pole 1 and the lower back pole 8 carry the same charge and the same potential (usually negative potential), the first electric signal converted by the capacitance change between the upper back pole 1 and the diaphragm 7 and the second electric signal converted by the capacitance change between the lower back pole 8 and the diaphragm 7 are opposite in phase. It is necessary to convert the second electric signal into a phase consistent with the first electric signal through a phase converter (or the first electric signal can also be converted to be consistent in phase with the second electric signal), and the two are pushed-pull added to output and the signal is strengthened.

[0060] The present application effectively utilizes the characteristics of dual back-pole push-pull output, so that the electret condenser microphone has higher sensitivity and stronger output signal.

[0061] In some optional implementations, the present application also provides another structure of a dual back-pole push-pull output electret condenser microphone, which is different from the dual back-pole push-pull output electret condenser microphone described above in that:

[0062] The first electret film layer 4 and the second electret film layer 10 may carry different charges, and the first electrical signal and the second electrical signal generated at this time have the same phase. In this case, the amplified first amplified signal and the second amplified signal may be directly combined and outputted without the need for a phase converter.

[0063] Exemplarily, the first electret film layer 4 carries a negative charge (negative potential), and the second electret film layer 10 carries a positive charge (positive potential); or, the first electret film layer 4 carries a positive charge (positive potential), and the second electret film layer 10 carries a negative charge (negative potential).

[0064] The structural principle of the electret condenser microphone of another structure of this embodiment is as follows:

[0065] There is a diaphragm 7 between the upper back pole 1 and the lower back pole 8. When an external sound signal enters through the sound inlet hole on the upper back pole 1 and drives the diaphragm 7 to vibrate, there is a change in capacitance between the upper back pole 1 and the diaphragm 7. In this way, the change in the sound signal is converted into a first electrical signal through the change in capacitance between the upper back pole 1 and the diaphragm 7, and then converted into a first amplified signal by the first impedance converter 12 and then output;

[0066] At the same time, when the external sound signal drives the diaphragm 7 to vibrate, there is also a change in capacitance between the lower back pole 8 and the diaphragm 7. The change in the sound signal is converted into a second electrical signal through the change in capacitance between the lower back pole 8 and the diaphragm 7, and then converted into a second amplified signal by the second impedance converter 13 and then output.

[0067] Since the electret film layers on the upper back pole 1 and the lower back pole 8 carry different charges, the first electric signal converted from the acoustic signal through the capacitance change between the upper back pole 1 and the diaphragm 7 and the second electric signal converted from the acoustic signal through the capacitance change between the lower back pole 8 and the diaphragm 7 have the same phase. At this time, there is no need for a phase converter, and the second electric signal and the first electric signal can be directly push-pull added and output to enhance the signal.

[0068] To facilitate the understanding and implementation of the technical solution of the present application, the following is an analysis of the effect of diaphragm vibration on the calculation of the pole capacitance and nonlinear distortion during diaphragm deformation. This is of great significance to the design and manufacture of excellent electret condenser microphones, and can make the electret condenser microphones more accurate, especially for large-sized, high-precision, and high-sensitivity electret condenser microphones.

[0069] The basic working principle of the electret condenser microphone (ECM) is that sound waves drive the diaphragm (i.e., the diaphragm) to vibrate, and the distance between the diaphragm and the back electrode parallel to it changes, thereby causing the capacitance between them to change accordingly. Ultimately, the output voltage changes with the change of sound pressure, thus achieving the purpose of sound-to-electricity conversion.

[0070] The capacitance of the ECM (Electret Condenser Microphone) capsule is a very important parameter for miniature condenser microphone capsules. However, the common calculation of the ECM capsule capacitance is only considered as a simple change in the distance between the plates of an air capacitor, which is obviously inappropriate.

[0071] This application introduces the diaphragms commonly used in electret condenser microphones, all of which are made of flexible materials. The calculation process is as follows. Figure 2 , Figure 2 It is a schematic diagram of a miniature condenser microphone whose diaphragm is made of flexible material.

[0072] When sound pressure acts on the flexible diaphragm of the condenser microphone, the diaphragm is transformed into a spherical surface with a radius of R by the sound pressure, so that the capacitance of the condenser microphone changes from the initial C0 to C1, (C0 = ε0πa 2 / d, d is the distance between the two plates, a is the radius of the diaphragm, ε0 is the dielectric constant), to calculate the deformed capacitance C1, we regard the deformed capacitor as a parallel connection of countless annular narrow-band parallel plate capacitors with a radius of: r, and r (0<r<a), a width of dr, and a spacing of d-y (y is the distance between the position of the annular band after deformation and the position before deformation). Assume that the capacitance of any annular parallel plate capacitor is dC1, then the capacitor parallel connection formula is:

[0073]

[0074] Because the diaphragm deformation is very small, y is much smaller than d, so

[0075] then

[0076]

[0077] like Figure 2 As shown, the variable y changes with r, and there is

[0078]

[0079] r<a<<R, so

[0080] thus

[0081]

[0082] then

[0083]

[0084]

[0085] Assume the diaphragm tension is f and the sound pressure is P, then

[0086] Pπa 2 =f2πa Sinθ = f2πa a / R, so

[0087] R=2f / p

[0088]

[0089] From this we can see that C0 and △C are two very important parameters for condenser microphones.

[0090] The above calculation is applicable to the capacitance change of the lower back electrode of the present application.

[0091] The capacitance change of the upper back pole can also be deduced from the above calculation. The capacitance C0 of the upper back pole does not change, while the capacitance between the upper back pole and the diaphragm after deformation, named C2, becomes smaller because the distance between them becomes larger, while the change △C remains the same. Therefore, C0 and △C are two very important parameters for the design of electret condenser microphones.

[0092] For condenser microphones and electret condenser microphones, to improve their quality, the focus should be on the issue of nonlinear distortion. As we all know, the nonlinear distortion of condenser microphones and electret condenser microphones is generated by two parts: sound-to-electric transduction (pole) and electrical signal amplification (impedance transformation). Here we mainly discuss the part generated by sound-to-electric transduction. The capacitance of a capacitor should include two parts: one part is the capacitance formed between the diaphragm and the rear plate. This capacitance changes due to the action of sound waves on the diaphragm, which is called "variable capacitance" and is recorded as C. t (i.e., △C discussed above); the other part is unrelated to the action of the sound wave, called "fixed capacitance", denoted by C p (i.e. C0 in the previous discussion), including the device capacitance between the wire and the housing and the input capacitance of the subsequent circuit. There are two parts that should be considered. One part is Cs1 is the stray capacitance between the diaphragm and the back electrode through the gasket, C s2 C is the stray capacitance between the conductive ring outside the insulating tube and the grounded shell. s3 The stray capacitance between the insulating tube in the conductive ring and the grounded shell through the PCB board; the other part is for the electret condenser microphone, which will increase after the electret is polarized. e , then the total capacitance value C should be:

[0093] Total capacitance C = variable capacitance + fixed capacitance. Fixed capacitance C p for:

[0094] C p =C s1 +C s2 +C s3 +C e

[0095] Assume that C is not considered s1 +C s2 +C s3 The contributions of three parts.

[0096] If the relative displacement of the diaphragm is δ t , the equivalent displacement of the diaphragm under the action of sound waves is X, and the static distance between the diaphragm and the back electrode is d0, then δ t =X / d0. The output potential generated on the capacitor is U, then: U≈(Q0 / C t0 )×[δ t / (1+C p / C t0 ) 2 ]+(Q0 / C t0 )×[δ t 2 / (1+C p / C t0 ) 2 (1+C p / C t0 )]

[0097] Among them, C t0 : represents the static capacitance between the diaphragm and the back electrode, Q0: represents the charge stored in the capacitor in static state (when there is no sound wave). The first term here is the normal signal potential difference, which is related to the relative displacement of the diaphragm δ t The second term is proportional to the relative displacement of the diaphragm δ t 2 Proportional to the nonlinear distortion term U D .Right now:

[0098] U D =(Q0 / C t0 )×[δt 2 / (1+C p / C t0 ) 2 (1+C p / C t0 )]

[0099] If the nonlinear distortion in the acoustic-electric conversion of a capacitor microphone is defined as D SE , then D SE =|U D / U|.

[0100] D SE =|U D / U|=|δ t | / (1+C t0 / C p )

[0101] It can be seen that there are two ways to reduce the nonlinearity of the sound-to-electric conversion of the capacitor microphone:

[0102] ①Reduce the relative displacement of the diaphragm δ t , but this contradicts the sensitivity of the microphone;

[0103] ② Increase (1+C t0 / C p ) value, so we need to increase C t0 Value or reduce C p The value of C t0 To reduce the value, it is necessary to increase the effective area of ​​the capacitor or reduce the distance between the diaphragm and the back electrode, which involves the overall structure and size of the capacitor. p As for the numerical values ​​of , the design parameters can be optimized based on the previous discussion.

[0104] At present, the industry has not paid enough attention to the problem of nonlinear distortion of capacitor microphones, especially the increase of (1+C t0 / C p ), and no in-depth work has been done on the numerical values ​​of ), so what is shown is that excellent electret condenser microphones are very rare, and general products have large nonlinear distortion at high sound pressure levels. These products are not suitable for working at high sound pressure levels and are not suitable for close-range sound pickup.

[0105] Therefore, through the above analysis, the present application can design the structure so that (1+C t0 / C p ) is greater than a preset value, thereby reducing the nonlinear distortion of the microphone, which is meaningful for the manufacture of excellent electret condenser microphones.

[0106] In some optional implementations, based on the above analysis of nonlinear distortion, the dual back-pole push-pull output electret condenser microphone of the present application may further include:

[0107] The correction module is configured to calculate the nonlinear distortion D according to the following formula SE , according to the calculated D SE Performing compensation adjustment on the first amplified signal converted by the first impedance converter 12 or the second amplified signal converted by the second impedance converter 13, and combining the compensated and adjusted signals and inputting them into the output terminal;

[0108] D SE =|δ t | / (1+C t0 / C p );

[0109] In the formula, δ t Represents the relative displacement of the diaphragm, C t0 Represents the static capacitance between the diaphragm and the upper back electrode or the lower back electrode, C p It indicates the fixed capacitance of the capacitor composed of the diaphragm and the upper back electrode or the lower back electrode (fixed capacitance that is not related to the action of sound waves);

[0110] Among them, a first nonlinear distortion D can be calculated SE , the first amplified signal is compensated and adjusted. At this time, C in the formula t0 Represents the static capacitance between the diaphragm and the upper back electrode, C p It indicates the fixed capacitance of the capacitor composed of the diaphragm and the upper back electrode (fixed capacitance that has nothing to do with the action of sound waves);

[0111] And, a second nonlinear distortion D can be calculated SE , the second amplified signal is compensated and adjusted. At this time, C in the formula t0 Represents the static capacitance between the diaphragm and the lower back electrode, C p It represents the fixed capacitance of the capacitor composed of the diaphragm and the lower back electrode (fixed capacitance that is not related to the action of sound waves).

[0112] C p =C s1 +C s2 +C s3 +C e

[0113] C s1 It is the stray capacitance between the diaphragm through the gasket and the back electrode (upper back electrode or lower back electrode);

[0114] C s2 It is the stray capacitance between the conductive ring outside the insulating tube and the grounded shell;

[0115] C s3 It is the stray capacitance between the insulating tube in the conductive ring, the PCB board and the grounded shell;

[0116] C e This is for electret condenser microphones. After the electret is polarized, the part C e.

[0117] The correction module may be, for example, a chip or a hardware circuit arranged on a circuit board.

[0118] The compensation adjustment may be, for example, generating a nonlinear distortion D SE The opposite signal is used to make it different from the nonlinear distortion D in the first amplified signal and the second amplified signal. SE Offset each other.

[0119] The structure and distance of the dual back-pole push-pull output electret condenser microphone (ECM) of the embodiment of the present application are introduced above, and the calculation of the counter-diaphragm vibration counter-pole capacitance and the nonlinear distortion are also analyzed.

[0120] The basic working principle of the electret condenser microphone (ECM) of the present application is that the diaphragm is driven to vibrate by sound waves, and the distance between the diaphragm and the back electrode parallel to it changes, so that the capacitance between them changes accordingly, and finally the output voltage changes with the change of sound pressure to achieve the purpose of sound-to-electric conversion. However, it is different from the conventional electret condenser microphone in that two back electrodes and one diaphragm constitute two capacitors, which generate two electrical signals and push-pull and add them to output to strengthen the signal.

[0121] The capacitance of the pole head of an electret condenser microphone (ECM) is a very important parameter for the pole head of a miniature condenser microphone. However, in the common calculation of the pole head capacitance of an electret condenser microphone, it is only regarded as a simple change in the distance between the plates of an air capacitor, which is obviously inappropriate. This application is about the electret condenser microphone. When the sound pressure acts on the flexible material diaphragm of the condenser microphone, the diaphragm is transformed into a spherical surface with a radius of R by the sound pressure, thereby changing the capacitance of the condenser microphone. This patent analyzes the effect of the vibration of the diaphragm on the pole head capacitance calculation and nonlinear distortion in the electret condenser microphone. For condenser microphones and electret condenser microphones, in order to improve their quality, the focus should be on discussing the problem of their nonlinear distortion. The relevant discussion in the content of this application is for optimizing the design parameters. This is of great significance to the design and manufacture of excellent electret condenser microphones.

[0122] In the above, the technical solution of the present application is described in detail through specific embodiments. In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0123] It should be understood that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. A person skilled in the art may modify the technical solutions described in the above embodiments, or replace some of the technical features therein by equivalents; and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and protection scope of the technical solutions of the embodiments of the present application.

Claims

1. A dual back-pole push-pull output electret condenser microphone, comprising a pole head, characterized in that: The pole head comprises: an upper back pole, a lower back pole, and a diaphragm arranged between the upper back pole and the lower back pole; There is a first gap between the upper back pole and the diaphragm, and there is a second gap between the lower back pole and the diaphragm; The lower surface of the upper back electrode is provided with a first electret film layer, and the upper surface of the lower back electrode is provided with a second electret film layer; The upper surface and the lower surface of the diaphragm are respectively provided with metal layers; The upper back pole is provided with a sound inlet hole, and the lower back pole is provided with a sound balancing hole.

2. The dual back-pole push-pull output electret condenser microphone according to claim 1, characterized in that: Also includes: A first impedance converter, electrically connected to the upper back electrode and the metal layer on the upper surface of the diaphragm, for performing impedance conversion on a first electrical signal output between the upper back electrode and the metal layer on the upper surface of the diaphragm to generate a first amplified signal; The second impedance converter is electrically connected to the lower back pole and the metal layer on the lower surface of the diaphragm, and is used to perform impedance conversion on the second electrical signal output between the lower back pole and the metal layer on the lower surface of the diaphragm to generate a second amplified signal.

3. The dual back-pole push-pull output electret condenser microphone according to claim 2, characterized in that: The first electret film layer and the second electret film layer carry the same charge, and the first electrical signal and the second electrical signal have opposite phases; the dual back-pole push-pull output electret condenser microphone also includes: The phase converter is configured to convert the phase of the second electrical signal to be the same as the first electrical signal to generate a second conversion signal, or to convert the phase of the first electrical signal to be the same as the second electrical signal to generate a first conversion signal.

4. The dual back-pole push-pull output electret condenser microphone according to claim 3, characterized in that: Also includes: A circuit board carries the first impedance converter, the second impedance converter and the phase converter, and an output terminal is also provided on the circuit board, and the output terminal is used to output a combined signal of the first amplified signal and the second converted signal, or to output a combined signal of the second amplified signal and the first converted signal.

5. The dual back-pole push-pull output electret condenser microphone according to claim 4, characterized in that: Also includes: A first conductive wire, used for connecting the upper back electrode and the first impedance converter; A second wire, used for connecting the lower back electrode and the second impedance converter; A third wire is used to connect the metal layer on the upper surface of the diaphragm to the first impedance converter, and to connect the metal layer on the lower surface of the diaphragm to the second impedance converter.

6. The dual back-pole push-pull output electret condenser microphone according to claim 5, characterized in that: Also includes: The metal shell is used to accommodate the pole head and the circuit board. The metal shell is connected to the third wire and is connected to the first impedance converter and the second impedance converter via the circuit board.

7. The dual back-pole push-pull output electret condenser microphone according to claim 6, characterized in that: The upper back pole and the metal shell are insulated from each other, and the lower back pole and the metal shell are insulated from each other.

8. The dual back-pole push-pull output electret condenser microphone according to claim 4, characterized in that: Also includes: An insulating gasket is arranged between the lower back pole and the circuit board.

9. The dual back-pole push-pull output electret condenser microphone according to claim 2, characterized in that: The first electret film layer and the second electret film layer carry different charges, and the first electrical signal and the second electrical signal have the same phase.

10. The dual back-pole push-pull output electret condenser microphone according to any one of claims 1 to 9, characterized in that: The pole head also includes a clamp ring for fixing the diaphragm, wherein the clamp ring forms the first gap between the diaphragm and the upper back pole, and the second gap between the diaphragm and the lower back pole.

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