CN114157951A - Active noise reduction circuit and device - Google Patents
Active noise reduction circuit and device Download PDFInfo
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- CN114157951A CN114157951A CN202111427986.7A CN202111427986A CN114157951A CN 114157951 A CN114157951 A CN 114157951A CN 202111427986 A CN202111427986 A CN 202111427986A CN 114157951 A CN114157951 A CN 114157951A
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- 230000009467 reduction Effects 0.000 title claims abstract description 47
- 238000001914 filtration Methods 0.000 claims abstract description 141
- 239000003990 capacitor Substances 0.000 claims description 213
- 230000003321 amplification Effects 0.000 claims description 56
- 238000003199 nucleic acid amplification method Methods 0.000 claims description 56
- 238000013016 damping Methods 0.000 claims description 17
- 230000009977 dual effect Effects 0.000 claims description 5
- 238000010586 diagram Methods 0.000 description 14
- 230000000694 effects Effects 0.000 description 6
- 230000008859 change Effects 0.000 description 3
- 238000010587 phase diagram Methods 0.000 description 3
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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
- H04R1/00—Details of transducers, loudspeakers or microphones
- H04R1/10—Earpieces; Attachments therefor ; Earphones; Monophonic headphones
- H04R1/1083—Reduction of ambient noise
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- G—PHYSICS
- G10—MUSICAL INSTRUMENTS; ACOUSTICS
- G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
- G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
- G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
Abstract
The invention relates to the technical field of electronics, and discloses an active noise reduction circuit and device. According to the active noise reduction circuit, an input signal is filtered through a filtering module to obtain a filtered signal, the filtered signal is transmitted to a signal feedback module, the filtered signal is amplified through the signal feedback module, the amplified signal is transmitted to the filtering module to be filtered again, and the re-filtered signal is transmitted to the signal feedback module. According to the invention, the amplified signal is transmitted to the filtering module for re-filtering through the signal feedback module, a re-filtered signal in phase opposition to the amplified signal can be obtained, and then the filtered signal and the re-filtered signal are superposed through the signal feedback module, so that the filtered signal and the re-filtered signal in phase opposition to the filtered signal can be superposed, and thus, the signal noise can be effectively reduced.
Description
Technical Field
The invention relates to the technical field of electronics, in particular to an active noise reduction circuit and device.
Background
With the gradual diversification of functions of consumer electronics products, consumers have more and more demands on noise reduction products at a receiver end, namely active noise reduction earphones. The electronic filter design of the active noise reduction earphone needs to consider amplitude and phase control. The conventional shelf filter has a limited ability to control the amplitude, especially the phase, of the noise-lifting band, resulting in more noise-lifting and a reduced user experience. Therefore, how to effectively reduce the noise is an urgent technical problem to be solved.
The above is only for the purpose of assisting understanding of the technical aspects of the present invention, and does not represent an admission that the above is prior art.
Disclosure of Invention
The invention mainly aims to provide an active noise reduction circuit and an active noise reduction device, and aims to solve the technical problem that noise cannot be effectively reduced by using an active noise reduction earphone in the prior art.
To achieve the above object, the present invention provides an active noise reduction circuit, including: the device comprises a filtering module and a signal feedback module;
the filtering module is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module;
the signal feedback module is configured to amplify the filtered signal, transmit the amplified signal to the filtering module for re-filtering, and transmit the re-filtered signal to the signal feedback module;
the signal feedback module is further configured to superimpose the filtered signal and the re-filtered signal to implement signal noise reduction.
Optionally, the filtering module includes: a first filtering unit and a second filtering unit;
the first filtering unit is connected with the input end of the signal feedback module, the output end of the signal feedback module is connected with the input end of the second filtering unit, and the second filtering unit is connected with the input end of the signal feedback module;
the first filtering unit is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module;
the signal feedback module is configured to amplify the filtered signal to obtain an amplified signal, and transmit the amplified signal to the second filtering unit;
the second filtering unit is configured to perform re-filtering on the amplified signal to obtain a re-filtered signal, and transmit the re-filtered signal to the signal feedback module.
Optionally, the signal feedback module includes: an operational amplification unit;
the positive input end of the operational amplification unit is grounded, the reverse input end of the operational amplification unit is respectively connected with the output end of the first filtering unit and the output end of the second filtering unit, and the output end of the operational amplification unit is connected with the input end of the second filtering unit.
Optionally, the first filtering unit and/or the second filtering unit further include: at least one damping control unit;
the damping control unit is used for carrying out slope adjustment on the filtered signal and the re-filtered signal.
Optionally, the first filtering unit includes: a first T-type filter; the second filtering unit includes: a second T-type filter;
the first T-type filter includes: the circuit comprises a first resistor, a first capacitor, a second capacitor and a second resistor;
the first end of the first resistor is connected with the anode of the first capacitor, the cathode of the first capacitor is respectively connected with the first end of the second resistor and the anode of the second capacitor, the second end of the second resistor is grounded, and the cathode of the second capacitor and the second end of the first resistor are connected with the reverse input end of the operational amplification unit;
the second T-type filter includes: a third resistor, a third capacitor, a fourth capacitor and a fourth resistor;
the first end of the third resistor is connected with the reverse input end of the operational amplification unit and the anode of the third capacitor, the cathode of the third capacitor is connected with the first end of the fourth resistor and the anode of the fourth capacitor, the second end of the fourth resistor is grounded, and the cathode of the fourth capacitor and the second end of the third resistor are connected with the output end of the operational amplification unit.
Optionally, the first filtering unit includes: a first T-type filter; the second filtering unit includes: a second T-type filter;
the first T-type filter includes: a fifth capacitor, a fifth resistor, a sixth capacitor, a seventh resistor and an eighth resistor;
the positive electrode of the fifth capacitor is connected with the first end of the fifth resistor, the second end of the fifth resistor is respectively connected with the first end of the sixth resistor and the positive electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected with the first end of the seventh resistor, the second end of the seventh resistor is grounded, the negative electrode of the fifth capacitor is respectively connected with the first end of the eighth resistor and the second end of the sixth resistor, and the second end of the eighth resistor is connected with the reverse input end of the operational amplification unit;
the second T-type filter includes: a ninth resistor, a seventh capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor and an eighth capacitor;
the first end of the ninth resistor is connected with the inverting input end of the operational amplification unit, the second end of the ninth resistor is respectively connected with the anode of the seventh capacitor and the first end of the eleventh resistor, the second end of the eleventh resistor is respectively connected with the first end of the twelfth resistor and the anode of the eighth capacitor, the cathode of the eighth capacitor is grounded, and the second end of the tenth resistor and the second end of the twelfth resistor are connected with the output end of the operational amplification unit.
Optionally, the first filtering unit includes: a first double-T filter; the second filtering unit includes: a second double T-type filter;
the first double-T filter includes: a thirteenth resistor, a fourteenth resistor, a ninth capacitor, a tenth capacitor, a fifteenth resistor, and an eleventh capacitor;
a first end of the thirteenth resistor is connected with an anode of the ninth capacitor, a cathode of the ninth capacitor is respectively connected with a first end of the fifteenth resistor and an anode of the tenth capacitor, a second end of the fifteenth resistor is grounded, a second end of the thirteenth resistor is respectively connected with an anode of the eleventh capacitor and a first end of the fourteenth resistor, a cathode of the eleventh capacitor is grounded, and a second end of the fourteenth resistor and a cathode of the tenth capacitor are connected with a reverse input end of the operational amplification unit;
the second dual T-type filter includes: a sixteenth resistor, a seventeenth resistor, a twelfth capacitor, a thirteenth capacitor, an eighteenth resistor and a fourteenth capacitor;
the first end of the sixteenth resistor and the positive electrode of the twelfth capacitor are connected with the reverse input end of the operational amplification unit, the negative electrode of the twelfth capacitor is respectively connected with the positive electrode of the thirteenth capacitor and the first end of the eighteenth resistor, the second end of the eighteenth resistor is grounded, the second end of the sixteenth resistor is respectively connected with the positive electrode of the fourteenth capacitor and the first end of the seventeenth resistor, the negative electrode of the fourteenth capacitor is grounded, and the second end of the seventeenth resistor and the negative electrode of the thirteenth capacitor are connected with the output end of the operational amplification unit.
Optionally, the first filtering unit includes: a first double-T filter; the second filtering unit includes: a second double T-type filter;
the first double-T filter includes: a nineteenth resistor, a twentieth resistor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a twenty-first resistor, an eighteenth capacitor and a twenty-second resistor;
a first end of the nineteenth resistor is connected with an anode of the fifteenth capacitor, a cathode of the fifteenth capacitor is respectively connected with a first end of the twenty-first resistor and an anode of the sixteenth capacitor, a second end of the twenty-first resistor is connected with an anode of the eighteenth capacitor, a cathode of the eighteenth capacitor is grounded, a second end of the nineteenth resistor is respectively connected with an anode of the seventeenth capacitor and a first end of the twentieth resistor, a cathode of the seventeenth capacitor is grounded, a second end of the twentieth resistor is respectively connected with a first end of the twenty-second resistor and a cathode of the sixteenth capacitor, and a second end of the twenty-second resistor is connected with a reverse input end of the operational amplification unit;
the second dual T-type filter includes: a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a nineteenth capacitor, a twentieth capacitor, a twenty-sixth resistor, a twenty-first capacitor and a twenty-seventh resistor;
the first end of the twenty-third resistor is connected with the reverse input end of the operational amplification unit, the second end of the twenty-third resistor is respectively connected with the first end of the twenty-fourth resistor and the anode of the nineteenth capacitor, the cathode of the nineteenth capacitor is respectively connected with the anode of the twentieth capacitor and the first end of the twenty-sixth resistor, the second end of the twenty-sixth resistor is grounded, the second end of the twenty-fourth resistor is respectively connected with the anode of the twenty-first capacitor and the first end of the twenty-fifth resistor, the cathode of the twenty-first capacitor is connected with the first end of the twenty-seventh resistor, the second end of the twenty-seventh resistor is grounded, and the second end of the twenty-fifth resistor and the cathode of the twenty-fifth capacitor are connected with the output end of the operational amplification unit.
Optionally, the active noise reduction circuit further comprises: a power amplification module;
the power amplification module is connected with the output end of the signal feedback module;
and the power amplification module is used for amplifying a target signal generated by superposing the filtered signal and the re-filtered signal to obtain an amplified signal.
To achieve the above object, the present invention further proposes an active noise reduction device, which includes the active noise reduction circuit as described above.
According to the active noise reduction circuit, an input signal is filtered through a filtering module to obtain a filtered signal, the filtered signal is transmitted to a signal feedback module, the filtered signal is amplified through the signal feedback module, the amplified signal is transmitted to the filtering module to be filtered again, and the re-filtered signal is transmitted to the signal feedback module. According to the invention, the amplified signal is transmitted to the filtering module for re-filtering through the signal feedback module, a re-filtered signal in phase opposition to the amplified signal can be obtained, and then the filtered signal and the re-filtered signal are superposed through the signal feedback module, so that the filtered signal and the re-filtered signal in phase opposition to the filtered signal can be superposed, and thus, the signal noise can be effectively reduced.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
FIG. 1 is a functional block diagram of a first embodiment of an active noise reduction circuit according to the present invention;
FIG. 2 is a functional block diagram of a second embodiment of an active noise reduction circuit according to the present invention;
fig. 3 is a schematic circuit diagram of a filtering module according to the present invention;
fig. 4 is a schematic circuit diagram of a filtering module according to the present invention;
fig. 5 is a schematic circuit diagram of a filtering module according to the present invention;
fig. 6 is a schematic circuit diagram of a filtering module according to the present invention;
fig. 7 is a schematic diagram of the signal amplitude and phase at the inverting input terminal of the signal amplifying unit according to the present invention.
The reference numbers illustrate:
| reference numerals | Name (R) | Reference numerals | Name (R) |
| 10 | |
1021 | Second T- |
| 20 | |
1012 | First double T-type filter |
| 30 | Power amplifying |
1022 | Second double |
| 101 | First filter unit | R1～R27 | First to twenty- |
| 102 | Second filter unit | C1～C21 | First to twenty- |
| 201 | Operational amplification unit | U | |
| 1011 | First T-type filter |
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention.
The invention provides an active noise reduction circuit.
Referring to fig. 1, fig. 1 is a functional block diagram of a first embodiment of an active noise reduction circuit according to the present invention.
In an embodiment of the present invention, the active noise reduction circuit includes: a filtering module 10 and a signal feedback module 20;
the filtering module 10 is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module 20;
it can be understood that the input signal may be collected by a microphone, and the collected input signal includes a noise signal.
In a specific implementation, the filtering module 10 may be configured to filter an input signal to obtain a filtered signal, where a waveform of the filtered signal is concave, and the filtering module may be a low-pass filter, a T-type filter, a double-T-type filter, and the like, which is not limited in this embodiment.
The signal feedback module 20 is configured to amplify the filtered signal, transmit the amplified signal to the filtering module 10 for re-filtering, and transmit the re-filtered signal to the signal feedback module;
it will be appreciated that the signal feedback module 20 may transmit the amplified signal to the filtering module 10 for re-filtering, i.e. negative feedback adjustment, so that a re-filtered signal in anti-phase with the amplified signal may be obtained, and the waveform of the re-filtered signal is convex.
The signal feedback module 20 is further configured to superimpose the filtered signal and the re-filtered signal to implement signal noise reduction.
In a specific implementation, the filtered signal and the re-filtered signal are superimposed, which is equivalent to superimposing the concave filtered signal and the convex re-filtered signal, so that noise in the input signal is reduced.
Further, the active noise reduction circuit further includes: a power amplification module 30;
the power amplification module 30 is connected with the output end of the signal feedback module 20;
the power amplifying module 30 is configured to amplify a target signal generated by superimposing the filtered signal and the re-filtered signal, so as to obtain an amplified signal.
It is understood that the target signal output by the signal feedback module 20 may be small, and therefore the target signal needs to be amplified to obtain an amplified signal.
In this embodiment, the active noise reduction circuit includes a filtering module and a signal feedback module, and in this embodiment, an input signal is filtered by the filtering module to obtain a filtered signal, and the filtered signal is transmitted to the signal feedback module, and then the filtered signal is amplified by the signal feedback module, and is transmitted to the filtering module for re-filtering, and then the re-filtered signal is transmitted to the signal feedback module. The embodiment transmits the amplified signal to the filtering module through the signal feedback module to perform re-filtering, can obtain a re-filtered signal in phase opposition to the amplified signal, then superimposes the filtered signal and the re-filtered signal through the signal feedback module, and can superimpose the filtered signal and the re-filtered signal in phase opposition to the filtered signal, thereby effectively reducing signal noise.
Further, referring to fig. 2, fig. 2 is a functional block diagram of a second embodiment of the active noise reduction circuit according to the present invention.
As shown in fig. 2, the filtering module 10 includes: a first filtering unit 101 and a second filtering unit 102;
the first filtering unit 101 is connected to an input end of the signal feedback module 20, an output end of the signal feedback module 20 is connected to an input end of the second filtering unit 102, and the second filtering unit 102 is connected to an input end of the signal feedback module 20;
the first filtering unit 101 is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module 20;
it is understood that the first filtering unit 101 can be used for filtering an input signal, and the first filtering unit 101 can be a low-pass filter, a T-type filter, a double-T-type filter, etc., which is not limited in this embodiment.
The signal feedback module 20 is configured to amplify the filtered signal to obtain an amplified signal, and transmit the amplified signal to the second filtering unit 102;
in a specific implementation, the signal feedback module 20 may be configured to amplify the filtered signal, and the signal feedback module 20 may be a component having a signal amplifying function and a negative feedback adjusting function, which is not limited in this embodiment.
Further, the signal feedback module 20 includes: an operational amplification unit 201;
the positive input end of the operational amplification unit 201 is grounded, the negative input end of the operational amplification unit 201 is connected to the output end of the first filtering unit 101 and the output end of the second filtering unit 102, respectively, and the output end of the operational amplification unit 201 is connected to the input end of the second filtering unit 102.
It is understood that the operational amplification unit 201 may be a component having a signal amplification function, such as: an operational amplifier, etc., and the present embodiment is not particularly limited thereto, and the operational amplifier will be described as an example.
The second filtering unit 102 is configured to re-filter the amplified signal to obtain a re-filtered signal, and transmit the re-filtered signal to the signal feedback module 20;
it is understood that the second filtering unit 102 can be used for filtering the amplified signal, and the second filtering unit 102 can be a high-pass filter, a T-type filter, a double-T-type filter, etc., which is not limited in this embodiment.
In a specific implementation, since the output end of the second filtering unit 102 is connected to the inverting input end of the operational amplifying unit 201, the operational amplifying unit 201 can perform a negative feedback adjustment function, and the obtained re-filtered signal is in an opposite phase to the amplified signal.
The signal feedback module 20 is further configured to superimpose the filtered signal and the re-filtered signal to implement signal noise reduction.
It can be understood that, after the signal feedback module 20 superimposes the filtered signal and the re-filtered signal, the input signal can be subjected to noise reduction, and the signal output by the signal feedback module 20 is the signal after the input signal is subjected to noise reduction processing.
Further, the first filtering unit 101 and/or the second filtering unit 102 further include: at least one damping control unit 103;
the damping control unit 103 is configured to perform slope adjustment on the filtered signal and the re-filtered signal.
It should be understood that damping means that the amplitude of vibration caused by external action gradually decreases, and the slope of the signal can be adjusted by the damping control unit 103 so that the slope of the signal increases.
In a specific implementation, the damping control unit 103 may include resistors, capacitors, and the like, and the number, the size of the resistors, and the size of the capacitors are not particularly limited, and the size and the number are related to the change of the signal slope.
Further, referring to fig. 3, fig. 3 is a schematic circuit structure diagram of a filtering module according to the present invention.
As shown in fig. 3, the first filtering unit 101 includes: a first T-type filter 1011; the second filtering unit 102 includes: a second T-type filter 1021;
the first T-type filter 1011 includes: the circuit comprises a first resistor R1, a first capacitor C1, a second capacitor C2 and a second resistor R2;
a first end of the first resistor R1 is connected to an anode of the first capacitor C1, a cathode of the first capacitor C1 is connected to a first end of the second resistor R2 and an anode of the second capacitor C2, respectively, a second end of the second resistor R2 is grounded, and a cathode of the second capacitor C2 and a second end of the first resistor R1 are connected to a reverse input terminal of the operational amplification unit 201;
the second T-type filter 1021 includes: a third resistor R3, a third capacitor C3, a fourth capacitor C4 and a fourth resistor R4;
a first end of the third resistor R3 is connected to the inverting input terminal of the operational amplification unit 201 and the anode of the third capacitor C3, a cathode of the third capacitor C3 is connected to the first end of the fourth resistor R4 and the anode of the fourth capacitor C4, a second end of the fourth resistor R4 is grounded, and a cathode of the fourth capacitor C4 and a second end of the third resistor R3 are connected to the output terminal of the operational amplification unit 201.
It is understood that the first T-type filter 1011 and the second T-type filter 1021 have the same structure and the same function, and both realize the filtering function. The capacitance values of the first capacitor C1 and the second capacitor C2 in the first T-type filter 1011 are the same, and the resistance values of the first resistor R1 and the second resistor R2 are the same; the capacitance values of the third capacitor C3 and the fourth capacitor C4 in the second T-type filter 1021 are the same, and the resistance values of the third resistor R3 and the fourth resistor R4 are the same.
In a specific implementation, the first filtering unit 101 may include a plurality of first T-type filters 1011, the second filtering unit 102 may also include a plurality of first T-type filters 1021, the larger the number of T-type filters is, the better the filtering effect is, the same or different the number of first T-type filters 1011 and the number of first T-type filters 1021 may be, but generally, the same, and the embodiment does not specifically limit this.
Further, referring to fig. 4, fig. 4 is a schematic circuit structure diagram of a filtering module according to the present invention.
As shown in fig. 4, the first filtering unit 101 includes: a first T-type filter 1011; the second filtering unit 102 includes: a second T-type filter 1021;
the first T-type filter 1011 includes: a fifth capacitor C5, a fifth resistor R5, a sixth resistor R6, a sixth capacitor C7, a seventh resistor R7 and an eighth resistor R8;
an anode of the fifth capacitor C5 is connected to a first end of the fifth resistor R5, a second end of the fifth resistor R5 is connected to a first end of the sixth resistor R6 and an anode of the sixth capacitor C6, respectively, a cathode of the sixth capacitor C6 is connected to a first end of the seventh resistor R7, a second end of the seventh resistor R7 is grounded, a cathode of the fifth capacitor C5 is connected to a first end of the eighth resistor R8 and a second end of the sixth resistor R6, respectively, and a second end of the eighth resistor R8 is connected to the inverting input terminal of the operational amplifier 201;
the second T-type filter 1021 includes: a ninth resistor R9, a seventh capacitor C7, a tenth resistor R10, an eleventh resistor R11, a twelfth resistor R12 and an eighth capacitor C8;
a first end of the ninth resistor R9 is connected to the inverting input terminal of the operational amplifier 201, a second end of the ninth resistor R9 is connected to the anode of the seventh capacitor C7 and the first end of the eleventh resistor R11, respectively, a second end of the eleventh resistor R11 is connected to the first end of the twelfth resistor R12 and the anode of the eighth capacitor C8, respectively, the cathode of the eighth capacitor C8 is grounded, and a second end of the tenth resistor R10 and the second end of the twelfth resistor R12 are connected to the output terminal of the operational amplifier 201.
It should be understood that the resistance and capacitance in the first T-type filter 1011 in fig. 4 and the first T-type filter 1011 in fig. 3 are reciprocal, and the resistance and capacitance in the first T-type filter 1021 in fig. 4 and the first T-type filter 1021 in fig. 3 are reciprocal, and the effects achieved are the same.
It can be understood that the capacitance values of the fifth capacitor C5 and the sixth capacitor C6 in the first T-type filter 1011 are the same, and the resistance values of the fifth resistor R5 and the sixth resistor R6 are the same; the capacitance values of the seventh capacitor C7 and the eighth capacitor C8 in the second T-type filter 1021 are the same, and the resistance values of the eleventh resistor R11 and the twelfth resistor R12 are the same.
In a specific implementation, damping control may be performed by only adding the seventh resistor R7 and the tenth resistor R10, so as to improve the slope change speed of the filter, and damping control may be performed by adding the eighth resistor R8 and the ninth resistor R9, where a specific resistance value may be set according to an actual situation, and in this embodiment, damping control may be performed by adding a resistor, and damping control may also be performed by adding a capacitor, and a specific number of resistors and a specific number of capacitors may also be set according to an actual situation, which is not limited in this embodiment.
Similarly, the first filtering unit 101 may include a plurality of first T-type filters 1011, the second filtering unit 102 may also include a plurality of first T-type filters 1021, the larger the number of T-type filters is, the better the filtering effect is, the same or different the number of first T-type filters 1011 and the number of first T-type filters 1021 may be, but generally, the same, and the embodiment does not specifically limit this.
Further, referring to fig. 5, fig. 5 is a schematic circuit structure diagram of a filtering module according to the present invention.
As shown in fig. 5, the first filtering unit 101 includes: a first double-T filter 1012; the second filtering unit 102 includes: a second double-T filter 1022;
the first double-T filter 1012 includes: a thirteenth resistor R13, a fourteenth resistor R14, a ninth capacitor C9, a tenth capacitor C10, a fifteenth resistor R15 and an eleventh capacitor C11;
a first end of the thirteenth resistor R13 is connected to the anode of the ninth capacitor C9, the cathodes of the ninth capacitor C9 are connected to the first end of the fifteenth resistor R15 and the anode of the tenth capacitor C10, respectively, a second end of the fifteenth resistor R15 is grounded, a second end of the thirteenth resistor R13 is connected to the anode of the eleventh capacitor C11 and the first end of the fourteenth resistor R14, the cathode of the eleventh capacitor C11 is grounded, and the second end of the fourteenth resistor R14 and the cathode of the tenth capacitor C10 are connected to the inverting input terminal of the operational amplification unit 201;
the second double T-type filter 1022 includes: a sixteenth resistor R16, a seventeenth resistor R17, a twelfth capacitor C12, a thirteenth capacitor C13, an eighteenth resistor R18 and a fourteenth capacitor C14;
a first end of the sixteenth resistor R16 and a positive electrode of the twelfth capacitor C12 are connected to the inverting input terminal of the operational amplification unit 201, a negative electrode of the twelfth capacitor C12 is connected to a positive electrode of the thirteenth capacitor C13 and a first end of the eighteenth resistor R18, respectively, a second end of the eighteenth resistor R18 is grounded, a second end of the sixteenth resistor R16 is connected to a positive electrode of the fourteenth capacitor C14 and a first end of the seventeenth resistor R17, a negative electrode of the fourteenth capacitor C14 is grounded, and a second end of the seventeenth resistor R17 and a negative electrode of the thirteenth capacitor C13 are connected to the output terminal of the operational amplification unit 201.
It can be understood that the capacitance values of the ninth capacitor C9, the tenth capacitor C10 and the eleventh capacitor C11 in the first double T-type filter 1012 are the same, and the resistances of the thirteenth resistor R13, the fourteenth resistor R14 and the fifteenth resistor R15 are the same; the capacitance values of the twelfth capacitor C12, the thirteenth capacitor C13 and the fourteenth capacitor C14 of the second double-T filter 1022 are the same, and the resistance values of the sixteenth resistor R16, the seventeenth resistor R17 and the eighteenth resistor R18 are the same.
In a specific implementation, the first filtering unit 101 may include a plurality of first double-T filters 1012, and the second filtering unit 102 may also include a plurality of first double-T filters 1022, where the larger the number of double-T filters is, the better the filtering effect is, and the number of first double-T filters 1012 and the number of first double-T filters 1022 may be the same or may not be the same, but generally the same, and this embodiment does not specifically limit this.
Further, referring to fig. 6, fig. 6 is a schematic circuit structure diagram of a filtering module according to the present invention.
As shown in fig. 6, the first filtering unit 101 includes: a first double-T filter 1012; the second filtering unit 102 includes: a second double-T filter 1022;
the first double-T filter 1012 includes: a nineteenth resistor R19, a twentieth resistor R20, a fifteenth capacitor C15, a sixteenth capacitor C16, a seventeenth capacitor C17, a twenty-first resistor R21, an eighteenth capacitor C18 and a twenty-second resistor R22;
a first end of the nineteenth resistor R19 is connected to an anode of the fifteenth capacitor C15, cathodes of the fifteenth capacitor C15 are connected to a first end of the twenty-first resistor R21 and an anode of the sixteenth capacitor C16, respectively, a second end of the twenty-first resistor R21 is connected to an anode of the eighteenth capacitor C18, a cathode of the eighteenth capacitor C18 is grounded, a second end of the nineteenth resistor R19 is connected to an anode of the seventeenth capacitor C17 and a first end of the twentieth resistor R20, a cathode of the seventeenth capacitor C17 is grounded, a second end of the twentieth resistor R20 is connected to a first end of the twenty-second resistor R22 and a cathode of the sixteenth capacitor C16, respectively, and a second end of the twenty-second resistor R22 is connected to the inverting input terminal of the operational amplification unit 201;
the second double T-type filter 1022 includes: a twenty-third resistor R23, a twenty-fourth resistor R24, a twenty-fifth resistor R25, a nineteenth capacitor C19, a twentieth capacitor C20, a twenty-sixth resistor C26, a twenty-first capacitor C21, and a twenty-seventh resistor R27;
a first end of the twenty-third resistor R23 is connected to the inverting input terminal of the operational amplification unit 201, a second end of the twenty-third resistor R23 is respectively connected with a first end of the twenty-fourth resistor R24 and a positive electrode of the nineteenth capacitor C19, the cathode of the nineteenth capacitor C19 is respectively connected with the anode of the twentieth capacitor C20 and the first end of the twenty-sixth resistor R26, a second end of the twenty-sixth resistor R26 is grounded, a second end of the twenty-fourth resistor R24 is respectively connected with an anode of the twenty-first capacitor C21 and a first end of the twenty-fifth resistor R25, the negative electrode of the twenty-first capacitor C21 is connected with the first end of the twenty-seventh resistor R27, a second end of the twenty-seventh resistor R27 is grounded, and a second end of the twenty-fifth resistor R25 and a negative electrode of the twentieth capacitor C20 are connected to the output end of the operational amplification unit 201.
It can be understood that the capacitance values of the fifteenth capacitor C15, the sixteenth capacitor C16 and the seventeenth capacitor C17 in the first double T-type filter 1012 are the same, and the resistances of the nineteenth resistor R19, the twentieth resistor R20 and the twenty-first resistor R21 are the same; the capacitance values of the nineteenth capacitor C19, the twentieth capacitor C20 and the twenty-first capacitor C21 in the second dual T-type filter 1021 are the same, and the resistance values of the twenty-fourth resistor R24, the twenty-fifth resistor R25 and the twenty-sixth resistor R26 are the same.
Similarly, the first filtering unit 101 may include a plurality of first double-T filters 1012, and the second filtering unit 102 may also include a plurality of second double-T filters 1022, where the larger the number of double-T filters, the better the filtering effect, and the number of the first double-T filters 1012 and the number of the second double-T filters 1022 may be the same or different, but they are generally the same, and this embodiment does not specifically limit this.
It should be understood that damping control may be performed by only adding the twenty-second resistor R22 and the twenty-third resistor R23, so as to increase the slope change speed of the filter, and damping control may be performed by adding the eighteenth capacitor C18 and the twenty-seventh resistor R27, and the specific capacitance value and the resistance value may be set according to the actual situation, and in this embodiment, damping control may be performed by adding a resistor, damping control may also be performed by adding a capacitor, and the specific resistance number and the capacitance number may also be set according to the actual situation, which is not limited in this embodiment.
Further, referring to fig. 7, fig. 7 is a schematic diagram of signal amplitude and phase at the inverting input terminal of the signal amplifying unit according to the present invention.
As shown in fig. 7, the solid line represents a signal amplitude and phase diagram of the inverting input terminal of the signal amplifying unit of the circuit in fig. 3, the dotted line represents a signal amplitude and phase diagram of the inverting input terminal of the signal amplifying unit of the circuit in fig. 4, and the dotted line represents a signal amplitude and phase diagram of the inverting input terminal of the signal amplifying unit of the circuit in fig. 5. As can be seen from fig. 7, the dotted line has the largest amplitude and phase variation, and the noise reduction effect is also the best.
In a specific implementation, the first filtering unit 101 may include a plurality of T-type filters, and in this case, the second filtering unit 102 may include a plurality of double T-type filters; or the first filtering unit 101 may include a plurality of double T-type filters, in which case the second filtering unit 102 may include a plurality of T-type filters; or the first filtering unit 101 may include a plurality of T-type filters and a plurality of double T-type filters, in which case the second filtering unit 102 may include a plurality of T-type filters and a plurality of double T-type filters. The setting condition and the number of the specific filters can be set according to the actual situation, and this embodiment is not particularly limited thereto.
In this embodiment, the filtering module includes a first filtering unit and a second filtering unit, in this embodiment, the first filtering unit filters an input signal to obtain a filtered signal, and transmits the filtered signal to the signal feedback module, and then amplifies the filtered signal by the signal feedback module to obtain an amplified signal, and transmits the amplified signal to the second filtering unit, and then re-filters the amplified signal by the second filtering unit to obtain a re-filtered signal, and transmits the re-filtered signal to the feedback module, and then the signal feedback module superimposes the filtered signal and the re-filtered signal to implement signal noise reduction. The embodiment performs re-filtering on the amplified signal through the second filtering unit, can obtain a re-filtered signal in phase opposite to the amplified signal, and then superimposes the filtered signal and the re-filtered signal through the signal feedback module, and can superimpose the filtered signal and the re-filtered signal in phase opposite to the filtered signal, thereby effectively reducing signal noise.
In order to achieve the above object, the present invention further provides an active noise reduction apparatus, which includes the active noise reduction circuit as described above. The specific structure of the active noise reduction circuit refers to the above embodiments, and since the active noise reduction device adopts all technical solutions of all the above embodiments, at least all the beneficial effects brought by the technical solutions of the above embodiments are achieved, and no further description is given here.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (10)
1. An active noise reduction circuit, comprising: the device comprises a filtering module and a signal feedback module;
the filtering module is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module;
the signal feedback module is configured to amplify the filtered signal, transmit the amplified signal to the filtering module for re-filtering, and transmit the re-filtered signal to the signal feedback module;
the signal feedback module is further configured to superimpose the filtered signal and the re-filtered signal to implement signal noise reduction.
2. The active noise reduction circuit of claim 1, wherein the filtering module comprises: a first filtering unit and a second filtering unit;
the first filtering unit is connected with the input end of the signal feedback module, the output end of the signal feedback module is connected with the input end of the second filtering unit, and the second filtering unit is connected with the input end of the signal feedback module;
the first filtering unit is configured to filter an input signal to obtain a filtered signal, and transmit the filtered signal to the signal feedback module;
the signal feedback module is configured to amplify the filtered signal to obtain an amplified signal, and transmit the amplified signal to the second filtering unit;
the second filtering unit is configured to perform re-filtering on the amplified signal to obtain a re-filtered signal, and transmit the re-filtered signal to the signal feedback module.
3. The active noise reduction circuit of claim 2, wherein the signal feedback module comprises: an operational amplification unit;
the positive input end of the operational amplification unit is grounded, the reverse input end of the operational amplification unit is respectively connected with the output end of the first filtering unit and the output end of the second filtering unit, and the output end of the operational amplification unit is connected with the input end of the second filtering unit.
4. The active noise reduction circuit of claim 2, wherein the first filtering unit and/or the second filtering unit further comprises: at least one damping control unit;
the damping control unit is used for carrying out slope adjustment on the filtered signal and the re-filtered signal.
5. The active noise reduction circuit of claim 3 or 4, wherein the first filtering unit comprises: a first T-type filter; the second filtering unit includes: a second T-type filter;
the first T-type filter includes: the circuit comprises a first resistor, a first capacitor, a second capacitor and a second resistor;
the first end of the first resistor is connected with the anode of the first capacitor, the cathode of the first capacitor is respectively connected with the first end of the second resistor and the anode of the second capacitor, the second end of the second resistor is grounded, and the cathode of the second capacitor and the second end of the first resistor are connected with the reverse input end of the operational amplification unit;
the second T-type filter includes: a third resistor, a third capacitor, a fourth capacitor and a fourth resistor;
the first end of the third resistor is connected with the reverse input end of the operational amplification unit and the anode of the third capacitor, the cathode of the third capacitor is connected with the first end of the fourth resistor and the anode of the fourth capacitor, the second end of the fourth resistor is grounded, and the cathode of the fourth capacitor and the second end of the third resistor are connected with the output end of the operational amplification unit.
6. The active noise reduction circuit of claim 3 or 4, wherein the first filtering unit comprises: a first T-type filter; the second filtering unit includes: a second T-type filter;
the first T-type filter includes: a fifth capacitor, a fifth resistor, a sixth capacitor, a seventh resistor and an eighth resistor;
the positive electrode of the fifth capacitor is connected with the first end of the fifth resistor, the second end of the fifth resistor is respectively connected with the first end of the sixth resistor and the positive electrode of the sixth capacitor, the negative electrode of the sixth capacitor is connected with the first end of the seventh resistor, the second end of the seventh resistor is grounded, the negative electrode of the fifth capacitor is respectively connected with the first end of the eighth resistor and the second end of the sixth resistor, and the second end of the eighth resistor is connected with the reverse input end of the operational amplification unit;
the second T-type filter includes: a ninth resistor, a seventh capacitor, a tenth resistor, an eleventh resistor, a twelfth resistor and an eighth capacitor;
the first end of the ninth resistor is connected with the inverting input end of the operational amplification unit, the second end of the ninth resistor is respectively connected with the anode of the seventh capacitor and the first end of the eleventh resistor, the second end of the eleventh resistor is respectively connected with the first end of the twelfth resistor and the anode of the eighth capacitor, the cathode of the eighth capacitor is grounded, and the second end of the tenth resistor and the second end of the twelfth resistor are connected with the output end of the operational amplification unit.
7. The active noise reduction circuit of claim 3 or 4, wherein the first filtering unit comprises: a first double-T filter; the second filtering unit includes: a second double T-type filter;
the first double-T filter includes: a thirteenth resistor, a fourteenth resistor, a ninth capacitor, a tenth capacitor, a fifteenth resistor, and an eleventh capacitor;
a first end of the thirteenth resistor is connected with an anode of the ninth capacitor, a cathode of the ninth capacitor is respectively connected with a first end of the fifteenth resistor and an anode of the tenth capacitor, a second end of the fifteenth resistor is grounded, a second end of the thirteenth resistor is respectively connected with an anode of the eleventh capacitor and a first end of the fourteenth resistor, a cathode of the eleventh capacitor is grounded, and a second end of the fourteenth resistor and a cathode of the tenth capacitor are connected with a reverse input end of the operational amplification unit;
the second dual T-type filter includes: a sixteenth resistor, a seventeenth resistor, a twelfth capacitor, a thirteenth capacitor, an eighteenth resistor and a fourteenth capacitor;
the first end of the sixteenth resistor and the positive electrode of the twelfth capacitor are connected with the reverse input end of the operational amplification unit, the negative electrode of the twelfth capacitor is respectively connected with the positive electrode of the thirteenth capacitor and the first end of the eighteenth resistor, the second end of the eighteenth resistor is grounded, the second end of the sixteenth resistor is respectively connected with the positive electrode of the fourteenth capacitor and the first end of the seventeenth resistor, the negative electrode of the fourteenth capacitor is grounded, and the second end of the seventeenth resistor and the negative electrode of the thirteenth capacitor are connected with the output end of the operational amplification unit.
8. The active noise reduction circuit of claim 3 or 4, wherein the first filtering unit comprises: a first double-T filter; the second filtering unit includes: a second double T-type filter;
the first double-T filter includes: a nineteenth resistor, a twentieth resistor, a fifteenth capacitor, a sixteenth capacitor, a seventeenth capacitor, a twenty-first resistor, an eighteenth capacitor and a twenty-second resistor;
a first end of the nineteenth resistor is connected with an anode of the fifteenth capacitor, a cathode of the fifteenth capacitor is respectively connected with a first end of the twenty-first resistor and an anode of the sixteenth capacitor, a second end of the twenty-first resistor is connected with an anode of the eighteenth capacitor, a cathode of the eighteenth capacitor is grounded, a second end of the nineteenth resistor is respectively connected with an anode of the seventeenth capacitor and a first end of the twentieth resistor, a cathode of the seventeenth capacitor is grounded, a second end of the twentieth resistor is respectively connected with a first end of the twenty-second resistor and a cathode of the sixteenth capacitor, and a second end of the twenty-second resistor is connected with a reverse input end of the operational amplification unit;
the second dual T-type filter includes: a twenty-third resistor, a twenty-fourth resistor, a twenty-fifth resistor, a nineteenth capacitor, a twentieth capacitor, a twenty-sixth resistor, a twenty-first capacitor and a twenty-seventh resistor;
the first end of the twenty-third resistor is connected with the reverse input end of the operational amplification unit, the second end of the twenty-third resistor is respectively connected with the first end of the twenty-fourth resistor and the anode of the nineteenth capacitor, the cathode of the nineteenth capacitor is respectively connected with the anode of the twentieth capacitor and the first end of the twenty-sixth resistor, the second end of the twenty-sixth resistor is grounded, the second end of the twenty-fourth resistor is respectively connected with the anode of the twenty-first capacitor and the first end of the twenty-fifth resistor, the cathode of the twenty-first capacitor is connected with the first end of the twenty-seventh resistor, the second end of the twenty-seventh resistor is grounded, and the second end of the twenty-fifth resistor and the cathode of the twenty-fifth capacitor are connected with the output end of the operational amplification unit.
9. The active noise reduction circuit of any of claims 1-4, further comprising: a power amplification module;
the power amplification module is connected with the output end of the signal feedback module;
and the power amplification module is used for amplifying a target signal generated by superposing the filtered signal and the re-filtered signal to obtain an amplified signal.
10. An active noise reduction device, characterized in that it comprises an active noise reduction circuit according to any of claims 1 to 9.
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| CN202111427986.7A CN114157951A (en) | 2021-11-26 | 2021-11-26 | Active noise reduction circuit and device |
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101263734A (en) * | 2005-09-02 | 2008-09-10 | 丰田自动车株式会社 | Post-filter for microphone array |
| JP2009260452A (en) * | 2008-04-14 | 2009-11-05 | Sony Corp | Noise canceling apparatus |
| CN203596865U (en) * | 2013-11-28 | 2014-05-14 | 深圳Tcl新技术有限公司 | Audio signal high-frequency compensation circuit |
| US9941860B1 (en) * | 2016-10-21 | 2018-04-10 | Shenzhen Shengyuan Tech Ltd. | Filter circuit for noise cancellation earphones |
| CN109451398A (en) * | 2018-11-16 | 2019-03-08 | 珠海市杰理科技股份有限公司 | Equipment, acoustic feedback removing method, audio processing system are eliminated in acoustic feedback |
| CN109481146A (en) * | 2018-10-29 | 2019-03-19 | 南京航空航天大学 | It is a kind of with the active noise reduction earmuff and method of fitting different physics sound-insulating structures |
| US20200349916A1 (en) * | 2017-11-16 | 2020-11-05 | Ams Ag | Noise cancellation filter structure, noise cancellation system and signal processing method |
| US10950213B1 (en) * | 2020-05-31 | 2021-03-16 | Shenzhen GOODIX Technology Co., Ltd. | Hybrid active noise cancellation filter adaptation |
| CN113613120A (en) * | 2021-01-20 | 2021-11-05 | 深圳市冠旭电子股份有限公司 | Mixed feedback noise reduction circuit, mixed feedback noise reduction device and noise reduction earphone |
-
2021
- 2021-11-26 CN CN202111427986.7A patent/CN114157951A/en active Pending
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101263734A (en) * | 2005-09-02 | 2008-09-10 | 丰田自动车株式会社 | Post-filter for microphone array |
| JP2009260452A (en) * | 2008-04-14 | 2009-11-05 | Sony Corp | Noise canceling apparatus |
| CN203596865U (en) * | 2013-11-28 | 2014-05-14 | 深圳Tcl新技术有限公司 | Audio signal high-frequency compensation circuit |
| US9941860B1 (en) * | 2016-10-21 | 2018-04-10 | Shenzhen Shengyuan Tech Ltd. | Filter circuit for noise cancellation earphones |
| US20200349916A1 (en) * | 2017-11-16 | 2020-11-05 | Ams Ag | Noise cancellation filter structure, noise cancellation system and signal processing method |
| CN109481146A (en) * | 2018-10-29 | 2019-03-19 | 南京航空航天大学 | It is a kind of with the active noise reduction earmuff and method of fitting different physics sound-insulating structures |
| CN109451398A (en) * | 2018-11-16 | 2019-03-08 | 珠海市杰理科技股份有限公司 | Equipment, acoustic feedback removing method, audio processing system are eliminated in acoustic feedback |
| US10950213B1 (en) * | 2020-05-31 | 2021-03-16 | Shenzhen GOODIX Technology Co., Ltd. | Hybrid active noise cancellation filter adaptation |
| CN113613120A (en) * | 2021-01-20 | 2021-11-05 | 深圳市冠旭电子股份有限公司 | Mixed feedback noise reduction circuit, mixed feedback noise reduction device and noise reduction earphone |
Non-Patent Citations (1)
| Title |
|---|
| 陈振东;杨飞帆;: "自适应滤波器的设计与制作", 大学物理实验, no. 06, 26 December 2019 (2019-12-26) * |
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