CN104703097B - Audio ground loop noise suppressing system and method - Google Patents
Audio ground loop noise suppressing system and method Download PDFInfo
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- CN104703097B CN104703097B CN201510095791.5A CN201510095791A CN104703097B CN 104703097 B CN104703097 B CN 104703097B CN 201510095791 A CN201510095791 A CN 201510095791A CN 104703097 B CN104703097 B CN 104703097B
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Abstract
The present invention provides a kind of audio ground loop noise suppressing system and methods, provide a kind of ground loop noise suppression circuit small in size and inexpensive.Including audio-frequence player device, audio reception device and tone frequency channel wire connecting the two；Audio reception device includes a noise-cancellation circuit and a balancing circuitry；Tone frequency channel wire includes the first audio signal wire and audio ground wire；First audio signal wire connects the first input end of noise-cancellation circuit, and audio ground wire connects the second input terminal of noise-cancellation circuit；Second input terminal of noise-cancellation circuit connects balancing circuitry over the ground；Balancing circuitry is based on the equivalent resistance of its own come the impedance on Balanced Audio ground wire, so that ground loop noise is converted into common-mode noise input noise bucking circuit, noise-cancellation circuit inhibits the common-mode noise, the audio signal without ground loop noise is exported, there are this high technical problems of volume great achievement when solving in the prior art using audio-frequency transformer elimination ground loop noise.
Description
Technical field
The present invention relates to audio-frequency noise technology for eliminating fields, and in particular to a kind of audio ground loop noise suppressing system and base
In the audio ground loop noise suppressing method of the audio ground loop noise suppressing system.
Background technique
In audio frequency broadcast system, usually there are the service condition interconnected between two audio frequency apparatuses by tone frequency channel wire, examples
Such as audio player connection earphone, audio frequency power amplifier connect speaker.
As shown in Figure 1, when audio frequency apparatus 1 and audio frequency apparatus 2 are interconnected by tone frequency channel wire 3, audio frequency apparatus 1 and audio frequency apparatus 2
Between ground potential there are problems that potential difference Vn；In tone frequency channel wire 3 between the two will superimposed noise electric current Inoise, this is made an uproar
Acoustoelectric current will form ground loop noise in audio frequency apparatus 2.
It is directed to the solution of ground loop noise in the prior art, as shown in Fig. 2, being usually to increase in audio frequency apparatus 2
Audio-frequency transformer T1；While audio-frequency transformer T1 realizes signal coupling using electromagnetic induction principle, and to audio frequency apparatus 1 and sound
Frequency equipment 2 has carried out isolation electrically, it can block the loop current in tone frequency channel wire, is effectively isolated ground loop noise.
But audio-frequency transformer is unable to get always popularization and application due to bulky and higher cost.
Summary of the invention
The embodiment of the present application by providing a kind of audio ground loop noise suppressing system and method, provide it is a kind of small in size and
The ground loop noise suppression circuit of low cost, body when solving to eliminate ground loop noise using audio-frequency transformer in the prior art
The big technical problem at high cost of product.
In order to solve the above technical problems, the present invention is achieved by the following scheme:
It is proposed a kind of audio ground loop noise suppressing system, including audio-frequence player device and audio reception device, the sound
The output end of frequency playback equipment is connect by tone frequency channel wire with the audio reception device；The tone frequency channel wire includes the first audio signal
Line and audio ground wire；The audio reception device includes a noise-cancellation circuit and a balancing circuitry；First audio signal
Line connects the first input end of the noise-cancellation circuit, and the audio ground wire connects the second input of the noise-cancellation circuit
End；The output end of the noise-cancellation circuit connects the audio signal input end of the audio reception device；The noise cancellation
Second input terminal of circuit connects the balancing circuitry over the ground；The balancing circuitry balances the impedance on the audio ground wire, with
Ground loop noise is set to be converted into common-mode noise；The noise-cancellation circuit inhibits the common-mode noise, exports without ground loop noise
Audio signal to the audio reception device audio signal input end.
Further, the balancing circuitry is a balance resistance.
Further, the tone frequency channel wire further includes the second audio signal wire；The noise-cancellation circuit further includes that third is defeated
Enter end；Second audio signal wire connects the third input terminal of the noise-cancellation circuit.
Further, the noise-cancellation circuit includes the first operational amplifier, first resistor, second resistance, third electricity
Resistance and the 4th resistance；One end of the first resistor is the first input end of the noise-cancellation circuit, the first resistor
The other end connects the inverting input terminal of first operational amplifier；Described second resistance one end is the noise-cancellation circuit
Second input terminal, the other end of the second resistance connect the non-inverting input terminal of first operational amplifier；The third electricity
Resistance one end connects the inverting input terminal of first operational amplifier, and the other end of the 3rd resistor connects first operation
The output end of amplifier；Described 4th resistance one end connects the non-inverting input terminal of first operational amplifier, the 4th electricity
The second end of resistance is grounded.
Further, is in series between first audio signal wire and the first input end of the noise-cancellation circuit
One capacitor；The second capacitor is in series between the audio ground wire and the second input terminal of the noise-cancellation circuit.
Further, the noise-cancellation circuit further includes second operational amplifier, the 5th resistance, the 6th resistance, the 7th
Resistance and the 8th resistance；One end of 5th resistance is the third input terminal of the noise-cancellation circuit, the 5th resistance
The other end connect the inverting input terminal of the second operational amplifier；Described 6th resistance one end is the noise-cancellation circuit
The second input terminal, the other end of the 6th resistance connects the non-inverting input terminal of the second operational amplifier；Described 7th
Resistance one end connects the inverting input terminal of the second operational amplifier, the other end connection of the 7th resistance second fortune
Calculate the output end of amplifier；Described 8th resistance one end connects the non-inverting input terminal of the second operational amplifier, and the described 8th
The second end of resistance is grounded.
Further, the noise-cancellation circuit include third operational amplifier, four-operational amplifier, the 9th resistance,
Tenth resistance, eleventh resistor, twelfth resistor, thirteenth resistor, the 14th resistance and the 15th resistance；9th resistance
One end be the noise-cancellation circuit first input end, the other end of the 9th resistance connects the third operation amplifier
The inverting input terminal of device；One end of tenth resistance connects the inverting input terminal of the third operational amplifier, and the described tenth
The other end of resistance connects one end of the eleventh resistor, and the other end of the eleventh resistor connects the 4th operation and puts
The inverting input terminal of big device；One end of the twelfth resistor connects the inverting input terminal of the four-operational amplifier, described
The other end of twelfth resistor connects the output end of the four-operational amplifier；One end of the thirteenth resistor is described makes an uproar
Second input terminal of sound bucking circuit, the other end of the thirteenth resistor connect the anti-phase input of the four-operational amplifier
End；The non-inverting input terminal of the third operational amplifier connects the 14th resistance over the ground, the four-operational amplifier
Non-inverting input terminal connects the 15th resistance over the ground.
Further, the audio-frequence player device is audio player or audio-frequency power amplifier.
Further, the audio reception device is earphone or speaker.
A kind of audio ground loop noise suppressing method is proposed, in audio ground loop noise suppressing system, wherein described
Audio ground loop noise suppressing system includes audio-frequence player device and audio reception device, the output end of the audio-frequence player device
It is connect by tone frequency channel wire with the audio reception device；The tone frequency channel wire includes the first audio signal wire and audio ground wire；It is described
Audio reception device includes a noise-cancellation circuit and a balancing circuitry；First audio signal wire connects the noise cancellation
The first input end of circuit, the audio ground wire connect the second input terminal of the noise-cancellation circuit；The noise cancellation electricity
The output end on road connects the audio signal input end of the audio reception device；Second input terminal pair of the noise-cancellation circuit
Ground connects the balance resistance；It is specific the described method includes: equivalent output resistance based on the audio-frequence player device, described
The equivalent resistance of first audio signal wire, the equivalent resistance of the audio ground wire and the noise-cancellation circuit first input end
Internal resistance and the input internal resistance of the second input terminal are inputted, the equivalent resistance of the balancing circuitry is determined, so that the balancing circuitry
The impedance on the audio ground wire is balanced, converts common-mode noise for ground loop noise；So that the noise-cancellation circuit inhibits
The common-mode noise exports the audio signal input end of the audio reception device of the audio signal without ground loop noise.
Compared with prior art, the technical solution that the embodiment of the present application proposes, the technical effect or advantage having are: this Shen
Please embodiment propose audio ground loop noise suppressing system in, in audio reception device with the junction of audio ground wire increase
Balancing circuitry over the ground, and increase noise-cancellation circuit in audio reception device；When audio-frequence player device and audio receive
There are noise current and the shape on audio-frequence player device and tone frequency channel wire will be generated when potential difference, in system for the ground potential of equipment
At pressure drop, in the embodiment of the present application, by balancing circuitry, by reasonable resistors match, so that into noise-cancellation circuit
The noise voltage of first input end and the second input terminal is equal, then ground loop noise is converted into common-mode noise, becomes noise and supports
The common mode input signal on electric eliminating road, and the common-mode noise that noise-cancellation circuit is converted into effectively is inhibited, to realize
Inhibit the effect of ground loop noise；The effect of balancing circuitry is in the embodiment of the present application, according to the equivalent resistance of its own
Resistance in audio ground leg is matched, with adjust noise level in audio ground leg voltage distribution, and then make into
The noise voltage for entering two input terminals of noise-cancellation circuit keeps balance；As it can be seen that being balanced in the embodiment of the present application by one
Ground loop noise suppressing function can be realized in circuit and a noise-cancellation circuit, compared with the prior art used in audio become
Depressor, circuit structure is simple, therefore design volume is small, simple and at low cost using device, solves and uses in the prior art
There are this high technical problems of volume great achievement when audio-frequency transformer elimination ground loop noise.
Detailed description of the invention
Fig. 1 is audio ground loop the formation of noise schematic diagram；
Fig. 2 is the circuit structure diagram for inhibiting ground loop noise in the prior art；
Fig. 3 is the audio ground loop noise suppressing system block diagram that the embodiment of the present application proposes；
A kind of audio ground loop noise suppressing system block diagram that this embodiment of the present application of Fig. 4 proposes；
Fig. 5 is a kind of audio ground loop for dual-channel audio line using respective individual screen that the embodiment of the present application proposes
Noise suppressing system block diagram；
Fig. 6 is the circuit diagram for the specific audio ground loop noise suppressing system that the embodiment of the present application proposes；
Fig. 7 is the circuit diagram for the another specific audio ground loop noise suppressing system that the embodiment of the present application proposes；
Fig. 8 is the circuit diagram for the another specific audio ground loop noise suppressing system that the embodiment of the present application proposes；
Fig. 9 is the system block diagram for the another audio ground loop noise suppressing system that the embodiment of the present application proposes；
Figure 10 is the method flow diagram for the audio ground loop noise suppressing method that the embodiment of the present application proposes.
Specific embodiment
The embodiment of the present application by providing a kind of audio ground loop noise suppressing system and method, provide it is a kind of small in size and
The ground loop noise suppression circuit of low cost, body when solving to eliminate ground loop noise using audio-frequency transformer in the prior art
The big technical problem at high cost of product.
In order to better understand the above technical scheme, in conjunction with appended figures and specific embodiments, it is right
Above-mentioned technical proposal is described in detail.
As shown in figure 3, the system block diagram of the audio ground loop noise suppressing system proposed for the embodiment of the present application, the system
Including audio-frequence player device 4, audio reception device 5 and tone frequency channel wire 3；It include that a balancing circuitry 7 and one is made an uproar in audio reception device 5
Sound bucking circuit 6；The output end of audio-frequence player device 4 is connect by tone frequency channel wire 3 with audio reception device 5；Tone frequency channel wire 3 includes the
One audio signal wire 31 and audio ground wire 32；First audio signal wire 31 connects the first input end 61 of noise-cancellation circuit 6, sound
Second input terminal 62 of the connection noise-cancellation circuit 6 of frequency ground wire 32；The output end 63 of noise-cancellation circuit connects audio reception and sets
Standby 5 audio signal input end；Second input terminal 62 of noise-cancellation circuit 6 connects the balancing circuitry 7 over the ground.
Wherein, balancing circuitry 7, using its equivalent impedance, impedance on Balanced Audio ground wire 32, so that ground loop noise
It is converted into common-mode noise, noise-cancellation circuit 6 inhibits the common-mode noise, audio letter of the output of output end 63 without ground loop noise
Number.Specifically, will be generated in system when the ground potential of audio-frequence player device 4 and audio reception device 5 is there are when potential difference Vn
Noise current Inoise then makes an uproar since audio-frequence player device 4 and tone frequency channel wire 3 have equivalent output resistance and equivalent resistance respectively
Acoustoelectric current Inoise can form pressure drop on audio-frequence player device 4 and tone frequency channel wire 3, then can be first specific on tone frequency channel wire 3
It is respectively formed pressure drop in audio signal branch road where audio signal wire 31 and the audio ground leg where audio ground wire 32, and
Due to audio signal branch and equivalent resistance in audio ground leg and not identical, then the pressure drop generated on the road Liang Gezhi is not yet
Together, it is based on this phenomenon, in the embodiment of the present application, by balancing circuitry 7, by reasonable resistors match, so that supporting into noise
The noise voltage of the first input end 61 on electric eliminating road 6 and the second input terminal 62 is equal, then ground loop noise is converted into common mode and makes an uproar
Sound becomes the common mode input signal of noise-cancellation circuit 6, and the common-mode noise that noise-cancellation circuit 6 is converted into carries out effectively
Inhibition, thus realize inhibit ground loop noise effect.
The effect of balancing circuitry 7 is in the embodiment of the present application, based on the equivalent impedance of its own, to audio ground leg
On resistance matched, with adjust noise level in audio ground leg voltage distribution, and then make enter noise cancellation electricity
The noise voltage of two input terminals on road keeps balance；As it can be seen that being made an uproar in the embodiment of the present application by a balancing circuitry and one
Ground loop noise suppressing function can be realized in sound bucking circuit, compared with the prior art used in audio-frequency transformer, circuit
Structure is simple, therefore design volume is small, simple and at low cost using device, solves and is disappeared in the prior art using audio-frequency transformer
There are this high technical problems of volume great achievement when except ground loop noise.
It is preferable to use a balance resistance Rb to realize for balancing circuitry 7, as shown in Figure 4；The problems such as to eliminate EMI electromagnetic interference,
Peripheral circuit, such as the both ends shunt capacitance etc. in balance resistance can be increased for balance resistance.
In general, tone frequency channel wire uses single (a corresponding voice-grade channel) or twin-core (corresponding two voice-grade channels) shielding line,
Audio ground wire is usually the shielded layer of tone frequency channel wire.Be above using monophonic audio ground loop noise suppressing system as embodiment,
In stereo double channel or multi-channel system, if the audio signal of each sound channel transmission when use it is independent
Above-mentioned audio ground loop noise suppressing system can be respectively adopted in shielded layer or shielding line in each sound channel when then designing,
As shown in figure 5, for using the audio system of the tone frequency channel wire of the shielded layer or shielding line independent of two-channel, audio broadcasting is set
Standby includes that audio-frequence player device 41(corresponds to L channel) right channel is corresponded to audio-frequence player device 42(), then it corresponds to each audio and broadcasts
It puts equipment and designs an audio ground loop noise suppressing system.
Embodiment one
Below by taking Fig. 6 as an example, monophonic audio ground loop noise suppressing system is illustrated.In the system, noise
Bucking circuit is a differential amplifier circuit, specifically includes the first operational amplifier U1, first resistor R1, second resistance R2, third
Resistance R3 and the 4th resistance R4；In conjunction with Fig. 4, one end of first resistor R1 is first input end 61(Fig. 6 of noise-cancellation circuit 6
Middle A point), the other end of first resistor R1 connects the inverting input terminal of the first operational amplifier U1；The one end second resistance R2 is to make an uproar
B point in second input terminal 62(Fig. 6 of sound bucking circuit 6), the other end of second resistance R2 connects the first operational amplifier U1's
Non-inverting input terminal；The one end 3rd resistor R3 connects the inverting input terminal of the first operational amplifier U1, the other end of 3rd resistor R3
Connect the output end vo ut of the first operational amplifier U1；4th one end resistance R4 connects the homophase input of the first operational amplifier U1
End, the second end ground connection of the 4th resistance R4.
In conjunction with Fig. 4 and Fig. 6, the audio signal that audio-frequence player device 4 exports is transmitted to rear class differential amplification electricity through tone frequency channel wire 3
Two input terminals on road 6, wherein the first audio signal wire 31 is connected to the inverting input terminal A of differential amplifier circuit, audio ground wire 32
It is connected to the non-inverting input terminal B of differential amplifier circuit.R0 be audio-frequence player device 4 equivalent output resistance, usually tens ohm
(when audio-frequence player device is power amplifier) is between several thousand ohms (when audio-frequence player device is amplifier)；RL and RG is respectively
The equivalent resistance of one audio signal wire 31 and audio ground wire 32, between 0.1-2 ohm；R1 and R2 is respectively that noise supports
The input resistance (namely two input terminals of differential amplifier circuit) of the first input end 61 on electric eliminating road 6 and the second input terminal 62,
Between 10k-100k ohm；R3 is the feedback resistance of the first operational amplifier U1, and R4 is the first operational amplifier
The biasing resistor of U1, R3 and R4 are generally between 10k-100k ohm.
When the ground potential between audio-frequence player device 4 and audio reception device 5 is there are when potential difference Vn, i.e. ground loop noise
Source will generate noise current Inoise in system, and the noise current is respectively in audio signal branch (audio-frequence player device and
On one audio signal wire) and audio ground leg (on audio-frequence player device and audio ground wire) generation pressure drop, theoretically, if noise
Noise voltage of the source Vn after the equivalent resistance circuit of two branches partial pressure in A, B two o'clock is equal, i.e. VA=VB, then noise is just
It is transformed to the common mode input noise signal of audio reception device, and differential amplifier circuit inhibits the common mode input noise, output
Audio signal without ground loop noise.
In system, on audio signal branch road, the current potential at A point is the equivalent output resistance R0 of audio-frequence player device 4,
The result of one audio signal wire equivalent resistance RL and first resistor R1 partial pressure；In audio ground leg, if not considering that access is flat
Weigh resistance Rb, and the current potential at B point is audio ground wire equivalent resistance RG and second resistance R2 partial pressure result；Since R1/ (R0+RL) is remote
Less than R2/RG, therefore the noise voltage at A point is far below the noise voltage at B point.Balance resistance is added in the embodiment of the present application
Rb, effect are exactly to match to the resistance in audio ground leg, adjust noise level Vn whereby on audio signal branch road
Voltage distribution so that noise voltage keeps balancing at noise voltage and A point at B point, namely make R1/ (R0+RL)=[Rb//
(R2+R4)]/RG, among these, " // " represent resistor coupled in parallel, and R0 is according to actual measurement acquisition or can consult device or chip
Specifications obtain, and RL and RG are obtained by actual measurement, and R1, R2 and R4 are it is known that obtain required balance resistance so as to calculate
The resistance value of Rb.
As shown in fig. 7, the audio of the tone frequency channel wire to use public shielded layer or shielding line for stereo double channel
Loop noise inhibits system embodiment；The embodiment is by dual-channel audio line (twin-core shielding line), audio-frequence player device, balance electricity
The noise cancellation of resistance and two differential amplifier circuits composition including the first differential amplifier circuit and the second differential amplifier circuit
Circuit composition.The audio ground loop noise suppressing system of stereo multichannel is similar.
When tone frequency channel wire is twin-core shielding line, as shown in fig. 7, corresponding further includes the second audio signal wire 33, noise cancellation
Then correspondence further includes C point in third input terminal 64(figure to circuit), the second audio signal wire 33 connects the third of noise-cancellation circuit
Input terminal 64.In noise-cancellation circuit 6, by the first operational amplifier U1, first resistor R1, second resistance R2,3rd resistor R3
The first differential amplifier circuit is formed with the 4th resistance R4, further includes by second operational amplifier U2, the 5th resistance R5, the 6th resistance
The second differential amplifier circuit of R6, the 7th resistance R7 and the 8th resistance R8 composition；One end of 5th resistance R5 is noise cancellation electricity
The third input terminal 64 on road 6, the inverting input terminal of the other end connection second operational amplifier U2 of the 5th resistance R5；6th resistance
The one end R6 is B point in the second input terminal 62(figure of noise-cancellation circuit 6), the other end of the 6th resistance R6 connects the second operation and puts
The non-inverting input terminal of big device U2；7th one end resistance R7 connects the inverting input terminal of second operational amplifier U2, the 7th resistance R7
The other end connection second operational amplifier U2 output end 63；8th one end resistance R8 connects the same of second operational amplifier U2
Phase input terminal, the second end ground connection of the 8th resistance R8.
In conjunction with Fig. 5 and Fig. 7, the audio signal of audio-frequence player device output is transmitted to rear class Double deference amplification electricity through tone frequency channel wire
Three input terminals on road, wherein the first audio signal (corresponding L channel) 31 is connected to the inverting input terminal of the first differential amplifier circuit
A, the second audio signal (corresponding right channel) 33 are connected to the inverting input terminal C of the second differential amplifier circuit；Audio ground wire 32 is distinguished
It is connected to the non-inverting input terminal B of the first differential amplifier circuit and the second differential amplifier circuit.R0 and R01 is respectively audio-frequence player device
The L channel equivalent output resistance and right channel equivalent output resistance of A, usually tens ohm (when audio-frequence player device is power amplifier
When) between several thousand ohms (when audio-frequence player device is amplifier)；RL, RR and RG are respectively the first audio signal wire 31,
The equivalent resistance of two audio signal wires 33 and audio ground wire 32, between 0.1-2 ohm, 31 He of the first audio signal wire
The equivalent resistance usually with similar resistance of second audio signal wire 33；R1, R2 are respectively the first difference channel two inputs
The input resistance (first input end 61 and the second input terminal 62 of corresponding noise-cancellation circuit 6) at end, generally between 10k-100k
Between ohm；R5, R6 are respectively the input resistance (third of corresponding noise-cancellation circuit 6 of second two input terminals of difference channel
Input terminal 63 and the second input terminal 62), between 10k-100k ohm；The feedback electricity that R3 is the first operational amplifier U1
Resistance, and R4 is the biasing resistor of the first operational amplifier U1, R3 and R4 are generally between 10k-100k ohm；R7 is the second fortune
The feedback resistance of amplifier U2 is calculated, and R8 is the biasing resistor of second operational amplifier U2, R7 and R8 are generally between 10k-100k
Between ohm.
When the ground potential between audio-frequence player device 4 and audio reception device 5 is there are when potential difference Vn, i.e. ground loop noise
Source will generate noise current Inoise in system, and the noise current is respectively in two audio signal branch (audio-frequence player devices
With on the first audio signal wire and audio-frequence player device on the second audio signal wire) with audio ground leg (audio broadcasting set
It is standby on audio ground wire) generate pressure drop, theoretically, if noise source Vn after the equivalent resistance circuit of three branches partial pressure A,
B and 3 points of C of noise voltage are equal, i.e. VA=VB=VC, then VA, VB are relative to corresponding first difference of the first audio signal 31
Common mode input noise is transformed into for amplifying circuit, similarly, VC, VB are poor relative to the second audio signal 33 corresponding second
Common mode input noise has been also transformed into for point amplifying circuit, and the first differential amplifier circuit and the second differential amplifier circuit inhibit
Two groups of common mode input noises export the binaural audio signal without ground loop noise.
In system, for L channel, the current potential at A point is the L channel equivalent output resistance R0 of audio-frequence player device 4,
The result of one audio signal wire equivalent resistance RL and first resistor R1 partial pressure；If not considering access balance resistance Rb, at B point
Current potential is audio ground wire equivalent resistance RG and second resistance R2 partial pressure result；Since R1/ (R0+RL) is much smaller than R2/RG, A
Noise voltage at point is far below the noise voltage at B point.For right channel, the current potential at C point is the right side of audio-frequence player device 4
The result of sound channel equivalent output resistance R01, the second audio signal wire equivalent resistance RR and the 5th resistance R5 partial pressure；If do not considered
Balance resistance Rb is accessed, the current potential at B point is the partial pressure result of audio ground wire equivalent resistance RG and the 6th resistance R6；Due to R5/
(R01+RR) it is much smaller than R6/RG, therefore the noise voltage at C point is far below the noise voltage at B point.Add in the embodiment of the present application
Enter balance resistance Rb, effect is exactly to match to the resistance in two audio ground legs, adjusts noise level Vn whereby and exists
The voltage distribution of two audio signal branch roads, so that noise voltage keeps balancing with noise voltage at A point and C point at B point,
I.e. so that R1/ (R0+RL)=R5/ (R01+RR)=[Rb//(R2+R4) // (R6+R8)]/RG, among these, " // " represents electricity
Resistance is in parallel, and R0 and R01 are obtained according to the specifications that obtains or can consult device or chip are surveyed, and RL, RR and RG are passed through
Cross actual measurement obtain, R1, R2 and R4 it is known that R5, R6 and R8 it is known that so as to calculate the resistance value for obtaining required balance resistance Rb.
For multi-channel audio system, if sound channel all in tone frequency channel wire all by the same shielded layer or shielding line (i.e.
Audio ground wire) it is shielded, then it can be each channel configuration differential amplifier circuit all the way that above-described embodiment is equally applicable at this time,
Public audio ground wire is connected to the non-inverting input terminal (as shown in the B point in figure) of each differential amplifier circuit simultaneously, and is put down
Weighing apparatus resistance Rb resistance value must calculate the non-inverting input terminal resistance of all differential amplifier circuits according to parallel connection, not superfluous herein
It states.
Embodiment two
As shown in figure 8, for the another concrete application embodiment of noise-cancellation circuit in the embodiment of the present application, the noise cancellation
Circuit 6 includes third operational amplifier U3, four-operational amplifier U4, the 9th resistance R9, the tenth resistance R10, eleventh resistor
R11, twelfth resistor R12, thirteenth resistor R13, the 14th resistance R14 and the 15th resistance R15；One end of 9th resistance R9
For A point in the first input end 61(figure of noise-cancellation circuit 6), the other end of the 9th resistance R9 connects third operational amplifier U3
Inverting input terminal；The inverting input terminal of one end connection third operational amplifier U3 of tenth resistance R10, the tenth resistance R10's
The other end connects one end of eleventh resistor R11, the reverse phase of the other end connection four-operational amplifier U4 of eleventh resistor R11
Input terminal；The inverting input terminal of one end connection four-operational amplifier U4 of twelfth resistor R12, twelfth resistor R12's is another
The output end vo ut of one end connection four-operational amplifier U4；One end of thirteenth resistor R13 is the second of noise-cancellation circuit 6
B point in input terminal 62(figure), the inverting input terminal of the other end connection four-operational amplifier U4 of thirteenth resistor R13；Third
The non-inverting input terminal of operational amplifier U3 connects the 14th resistance R14, the non-inverting input terminal pair of four-operational amplifier U4 over the ground
Ground connects the 15th resistance R15.
In the embodiment of the noise-cancellation circuit, first input end A point and the second input terminal B point are realized by resistors match
After the noise voltage at place is equal, reversely exported by third operational amplifier U3 to comprising noisy audio signal, then
Include noisy audio signal and audio Earth noise after reversed to third operational amplifier U3 by four-operational amplifier U4
Signal summation, due to audio ground noise signal with by noise signal of the third operational amplifier U3 after reversed it is equal in magnitude,
It is contrary, therefore the noise signal after summation is cancelled, and makes the output end vo ut output signal of four-operational amplifier U4
Audio signal without ground loop noise.For two-channel and multi-channel audio system, two-channel is directed to using with embodiment one kind
Mentality of designing identical with multi-channel audio system, it will not go into details herein.
In above-described embodiment, the operational amplifier being related to can may be based on single supply power supply based on dual power supply, with
Meet different design requirements.No matter dual power supply is powered or used using single supply, the input terminal of differential amplifier circuit,
Namely the output end of tone frequency channel wire can be in series with capacitance.It is specific as shown in figure 9, by taking monophonic audio system as an example, the
First capacitor C1 is in series between one audio signal wire 31 and the first input end 61 of noise-cancellation circuit；Audio ground wire 32 with
The second capacitor C2 is in series between second input terminal 62 of noise-cancellation circuit.
In addition, the problems such as being pre- EMI suppression, EMC, or in order to meet the adjustment requirement of different performance, the embodiment of the present application
Necessary protection circuit and filter circuit etc. can also be added in circuit, it will not go into details herein.
The application implement in audio-frequence player device 4 can be audio player (including monophonic, two-channel and more sound
Road) or audio-frequency power amplifier；Audio reception device 5 is earphone (transmitter portion containing wireless headset) or speaker.
Based on above-mentioned audio ground loop noise suppressing system, the embodiment of the present application also proposes a kind of audio ground loop noise
Suppressing method, as shown in Figure 10 the following steps are included:
Step S1: the equivalent output resistance of audio-frequence player device is determined.
The equivalent output resistance of audio-frequence player device is obtained according to actual measurement, either consults device or the specifications of chip obtain
?.
Step S2: the equivalent resistance of the first audio signal wire and the equivalent resistance of audio ground wire are determined.
The equivalent resistance of first audio signal wire and the equivalent resistance of audio ground wire are obtained by actual measurement.
Step S3: it determines in the input internal resistance and the input of the second input terminal of the first input end of noise-cancellation circuit
Resistance.
The input internal resistance of the input internal resistance and the second input terminal of the first input end of noise-cancellation circuit, is by known circuit
Resistance in design calculates equivalent internal resistance after in parallel or in series.
Step S4: the equivalent resistance of equivalent output resistance, the first audio signal wire based on audio-frequence player device, audio
The input internal resistance and the input internal resistance of the second input terminal of the equivalent resistance and noise-cancellation circuit first input end of line determine flat
The equivalent resistance of weighing apparatus circuit, so that the impedance on balancing circuitry Balanced Audio ground wire, converts common-mode noise for ground loop noise；
So that noise-cancellation circuit inhibits the common-mode noise, the audio of audio signal of the output without ground loop noise to audio reception device
Signal input part.
Wherein, above step S1 is not limited to step S3 and is executed sequence.
The audio ground loop noise suppressing system that the embodiment of the present application proposes and the audio ground loop noise based on the system
In suppressing method, increase balancing circuitry over the ground, such as balance resistance with the junction of audio ground wire in audio reception device
Rb will generate noise current in system when the ground potential of audio-frequence player device and audio reception device is there are when potential difference, by
Have equivalent output resistance and equivalent resistance respectively in audio-frequence player device and tone frequency channel wire, then the noise current is set in audio broadcasting
Pressure drop can be formed on standby and tone frequency channel wire accordingly, thinking provided by the embodiments of the present application is, by balance resistance Rb, passes through
Reasonable resistors match, so that it is equal into the first input end of noise-cancellation circuit and the noise voltage of the second input terminal, it will
The ground loop noise that the noise current as caused by potential difference is formed is converted into common-mode noise, becomes the common mode of noise-cancellation circuit
Input signal, and the common-mode noise that noise-cancellation circuit is converted into effectively is inhibited, to realize inhibition ground loop
The effect of noise.By the design of a balance resistance and a noise-cancellation circuit, ground loop noise suppressing function is realized,
Audio-frequency transformer used in compared with the prior art, circuit structure is simple, therefore design volume is small, it is simple using device and
It is at low cost, solve in the prior art using audio-frequency transformer eliminate ground loop noise when there are volume great achievement this high technology is asked
Topic.
In the prior art, audio-frequency transformer there are problems that influencing sound quality sometimes, and the embodiment of the present application is used to propose
Audio ground loop noise suppressing system, audio performance is not influenced substantially, is realized preferable with simple circuit design
The effect for inhibiting ground loop noise maintains the low noise performance of audio system.After actual measurement, the system that the embodiment of the present application proposes
The rejection ability of loop noise is up to 30DB or more over the ground, also, the matching precision of balance resistance is higher, and inhibitory effect is brighter
Aobvious, therefore, the system is not only at low cost, performance is stablized, and also has no adverse effect to sound quality, be suitably applied such as speaker, earphone,
In the products such as home theater.
It should be pointed out that the above description is not a limitation of the present invention, the present invention is also not limited to the example above,
Variation, modification, addition or the replacement that those skilled in the art are made within the essential scope of the present invention, are also answered
It belongs to the scope of protection of the present invention.
Claims (9)
1. audio ground loop noise suppressing system, including audio-frequence player device and audio reception device, the audio-frequence player device
Output end connect with the audio reception device by tone frequency channel wire；The tone frequency channel wire is including the first audio signal wire and audio
Line；It is characterized in that, the audio reception device includes a noise-cancellation circuit and a balancing circuitry；First audio signal
Line connects the first input end of the noise-cancellation circuit, and the audio ground wire connects the second input of the noise-cancellation circuit
End；The output end of the noise-cancellation circuit connects the audio signal input end of the audio reception device；The noise cancellation
Second input terminal of circuit connects the balancing circuitry over the ground；The balancing circuitry balances the impedance on the audio ground wire, with
Ground loop noise is set to be converted into common-mode noise；The noise-cancellation circuit inhibits the common-mode noise, exports without ground loop noise
Audio signal to the audio reception device audio signal input end;The balancing circuitry is balance resistance；The balance
The both ends shunt capacitance of resistance.
2. audio ground loop noise suppressing system according to claim 1, which is characterized in that the tone frequency channel wire further includes
Two audio signal wires；The noise-cancellation circuit further includes third input terminal；Second audio signal wire connects the noise
The third input terminal of bucking circuit.
3. audio ground loop noise suppressing system described in any one of -2 according to claim 1, which is characterized in that the noise
Bucking circuit includes the first operational amplifier, first resistor, second resistance, 3rd resistor and the 4th resistance；The first resistor
One end be the noise-cancellation circuit first input end, the other end of the first resistor connects first operation amplifier
The inverting input terminal of device；Described second resistance one end is the second input terminal of the noise-cancellation circuit, the second resistance
The other end connects the non-inverting input terminal of first operational amplifier；Described 3rd resistor one end connects first operation amplifier
The inverting input terminal of device, the other end of the 3rd resistor connect the output end of first operational amplifier；4th electricity
Resistance one end connects the non-inverting input terminal of first operational amplifier, the second end ground connection of the 4th resistance.
4. audio ground loop noise suppressing system described in any one of -2 according to claim 1, which is characterized in that described first
First capacitor is in series between audio signal wire and the first input end of the noise-cancellation circuit；The audio ground wire with it is described
The second capacitor is in series between second input terminal of noise-cancellation circuit.
5. audio ground loop noise suppressing system according to claim 3, which is characterized in that the noise-cancellation circuit is also
Including second operational amplifier, the 5th resistance, the 6th resistance, the 7th resistance and the 8th resistance；One end of 5th resistance is
The other end of the third input terminal of the noise-cancellation circuit, the 5th resistance connects the reverse phase of the second operational amplifier
Input terminal；Described 6th resistance one end is the second input terminal of the noise-cancellation circuit, and the other end of the 6th resistance connects
Connect the non-inverting input terminal of the second operational amplifier；Described 7th resistance one end connects the reverse phase of the second operational amplifier
The other end of input terminal, the 7th resistance connects the output end of the second operational amplifier；Described 8th resistance one end connects
Connect the non-inverting input terminal of the second operational amplifier, the second end ground connection of the 8th resistance.
6. audio ground loop noise suppressing system according to claim 1, which is characterized in that the noise-cancellation circuit packet
Include third operational amplifier, four-operational amplifier, the 9th resistance, the tenth resistance, eleventh resistor, twelfth resistor, the tenth
Three resistance, the 14th resistance and the 15th resistance；One end of 9th resistance is the first input of the noise-cancellation circuit
End, the other end of the 9th resistance connect the inverting input terminal of the third operational amplifier；One end of tenth resistance
The inverting input terminal of the third operational amplifier is connected, the other end of the tenth resistance connects the one of the eleventh resistor
End, the other end of the eleventh resistor connect the inverting input terminal of the four-operational amplifier；The twelfth resistor
One end connects the inverting input terminal of the four-operational amplifier, and the other end of the twelfth resistor connects the 4th operation
The output end of amplifier；One end of the thirteenth resistor be the noise-cancellation circuit the second input terminal, the described 13rd
The other end of resistance connects the inverting input terminal of the four-operational amplifier；The non-inverting input terminal of the third operational amplifier
The 14th resistance is connected over the ground, and the non-inverting input terminal of the four-operational amplifier connects the 15th resistance over the ground.
7. audio ground loop noise suppressing system according to claim 1, which is characterized in that the audio-frequence player device is
Audio player or audio-frequency power amplifier.
8. audio ground loop noise suppressing system according to claim 1, which is characterized in that the audio reception device is
Earphone.
9. audio ground loop noise suppressing method, in audio ground loop noise suppressing system, which is characterized in that the audio
Ground loop noise suppressing system includes audio-frequence player device and audio reception device；The output end of the audio-frequence player device passes through
Tone frequency channel wire is connect with the audio reception device；The tone frequency channel wire includes the first audio signal wire and audio ground wire；The audio
Receiving device includes a noise-cancellation circuit and a balancing circuitry；First audio signal wire connects the noise-cancellation circuit
First input end, the audio ground wire connects the second input terminal of the noise-cancellation circuit；The noise-cancellation circuit
Output end connects the audio signal input end of the audio reception device；Second input terminal of the noise-cancellation circuit connects over the ground
Connect the balancing circuitry；The balancing circuitry is balance resistance；The both ends shunt capacitance of the balance resistance；The method packet
It includes:
Equivalent output resistance, the equivalent resistance of first audio signal wire, the audio based on the audio-frequence player device
The input internal resistance and the input internal resistance of the second input terminal of the equivalent resistance of ground wire and the noise-cancellation circuit first input end,
The equivalent resistance of the balancing circuitry is determined, so that the balancing circuitry balances the impedance on the audio ground wire, by ground loop
Noise is converted into common-mode noise；So that the noise-cancellation circuit inhibits the common-mode noise, the sound without ground loop noise is exported
Frequency signal to the audio reception device audio signal input end.
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| Publication number | Priority date | Publication date | Assignee | Title |
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| CN104703098B (en) * | 2015-03-04 | 2019-01-29 | 青岛歌尔声学科技有限公司 | Speaker ground loop noise suppressing system and method |
| CN106102311B (en) * | 2016-08-18 | 2018-10-19 | 浪潮电子信息产业股份有限公司 | The method that signal circuit and promotion receiving terminal receive the quality of signal |
| CN113132860B (en) * | 2019-12-30 | 2022-08-05 | 杭州海康威视数字技术股份有限公司 | Circuit and system for resisting noise of ground loop and unbalanced audio equipment |
| CN114245272B (en) * | 2021-12-22 | 2024-06-18 | 锐捷网络股份有限公司 | Noise elimination circuit, device and audio playing equipment |
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