CN103096216A - Audio processing circuit and earphone - Google Patents

Audio processing circuit and earphone Download PDF

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CN103096216A
CN103096216A CN2013100497274A CN201310049727A CN103096216A CN 103096216 A CN103096216 A CN 103096216A CN 2013100497274 A CN2013100497274 A CN 2013100497274A CN 201310049727 A CN201310049727 A CN 201310049727A CN 103096216 A CN103096216 A CN 103096216A
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audio frequency
resistance
processing circuit
audio
frequency processing
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CN103096216B (en
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韩盈盈
吴凡
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Qingdao Goertek Co Ltd
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Qingdao Goertek Co Ltd
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Abstract

The invention discloses an audio processing circuit which comprises an audio input port, a third resistance, a left sound track difference audio processing circuit and a right sound track difference audio processing circuit, wherein the third resistance is connected between a public end of the audio input port and a ground terminal of an audio processing circuit. The resistance value of the third resistance is far larger than the resistance value of an equivalent resistance of the audio signal wire. The left sound track difference audio processing circuit comprises a left difference audio amplifier and a left sound track signal processing circuit. The right sound track difference audio processing circuit comprises a right difference audio amplifier and a right sound track signal processing circuit. Correspondingly, the invention further discloses the earphone which comprises the audio processing circuit. The audio processing circuit and the earphone can effectively avoid that charging current produces interference on audio signals and obviously eliminates noise of the earphone.

Description

A kind of audio frequency processing circuit and earphone
Technical field
The present invention relates to the audio signal processing technique field, particularly a kind of audio frequency processing circuit and earphone.
Background technology
At present, the application of earphone is more and more general.A lot of wireless headsets not only can be in the situation that wireless the use, and has simultaneously line jack is arranged.This earphone both can come playback of audio information by wireless mode, can by line jack being arranged and being connected with the audio frequency apparatus of output function (as PC etc.), adopt the wired mode playback of audio information again.
Earphone generally all adopts rechargeable battery power supply, in the situation of the low electricity of battery, need to charge to battery, can be while charging playback of audio information.When same audio frequency apparatus of earphone connection carries out the broadcast of audio-frequency information and charges, under normal condition, charging current in earphone is back in audio frequency apparatus by the ground wire (PGND) of its charging circuit, voice-frequency signalling current is back in audio frequency apparatus by the ground wire (AGND) of its audio frequency processing circuit, does not disturb mutually.But, the reference potential that is PGND and audio frequency processing circuit due to the reference potential of charging circuit in earphone is that AGND is equipotentiality, the charging current that changes will some be back to the audio frequency apparatus the inside by AGND, like this, the charging current that changes will have influence on the output voltage of audio frequency processing circuit, produce drone current noise, have a strong impact on the result of broadcast of audio-frequency information.
For example; situation shown in Figure 1; the audio input end of earphone is connected to the audio output interface of a computer; its charging inlet connects on the charging inlet (as USB interface) of this computer simultaneously, and earphone is play the audio frequency of this computer and charged by this computer, in this case; will there be lasting drone noise in the audio frequency of playing in earphone; and drone noise will increase along with the increase of volume, suspend or play when switching playing, and this noise is all the more obvious.
Summary of the invention
A kind of audio frequency processing circuit provided by the invention and earphone are to solve existing earphone by connecting the problem that has noise when same audio frequency apparatus carries out audio-frequency information output and charging simultaneously.
The invention provides a kind of audio frequency processing circuit, described audio frequency processing circuit comprises audio input interface, the 3rd resistance, L channel difference audio frequency processing circuit, R channel difference audio frequency processing circuit; Wherein,
Described the 3rd resistance is connected between the common port and audio frequency processing circuit earth terminal of described audio input interface, and the resistance of described the 3rd resistance is far longer than the equivalent resistance of audio signal wire;
Described L channel difference audio frequency processing circuit comprises: left difference audio frequency amplifier, left channel signals treatment circuit, be connected with respectively resistance between the input of left difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of left difference audio frequency amplifier connects described left channel signals treatment circuit;
Described R channel difference audio frequency processing circuit comprises: right difference audio frequency amplifier, right-channel signals treatment circuit, be connected with respectively resistance between the input of right difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of right difference audio frequency amplifier connects described right-channel signals treatment circuit.
In such scheme, described L channel difference audio frequency processing circuit comprises: the 4th resistance, the 5th resistance, the 6th resistance, the 11 resistance, left difference audio frequency amplifier and left channel signals treatment circuit; Wherein, first input end described the 4th resistance of serial connection of described left difference audio frequency amplifier also is connected on the left channel signals input interface of described audio input interface, also connect the audio frequency processing circuit earth terminal by serial connection the 11 resistance, the second input described the 5th resistance of serial connection also is connected on the common port of audio input interface, also connect the output of described left difference audio frequency amplifier by described the 6th resistance, the output of described left difference audio frequency amplifier connects the input of described left channel signals treatment circuit;
Described R channel difference audio frequency processing circuit comprises: the 7th resistance, the 8th resistance, the 9th resistance, the 12 resistance, right difference audio frequency amplifier and right-channel signals treatment circuit; Wherein, the second input described the 8th resistance of serial connection of described right difference audio frequency amplifier also is connected on the right-channel signals input interface of described audio input interface, also connect the audio frequency processing circuit earth terminal by serial connection the 12 resistance, first input end is connected in series described the 7th resistance and is connected to the common port of described audio input interface, also connect the output of described right difference audio frequency amplifier by described the 9th resistance, the output of described right difference audio frequency amplifier connects the input of described right-channel signals treatment circuit.
In such scheme, the resistance of described the 6th resistance, the 9th resistance, the 11 resistance and the 12 resistance is equal, and the resistance of described the 4th resistance, the 5th resistance, the 7th resistance and the 8th resistance equates.
In such scheme, described audio frequency processing circuit also comprises:
The first electric capacity is connected with described the 4th resistance, is serially connected between the left channel signals input interface of the input of described left difference audio frequency amplifier and described audio input interface;
And/or the second electric capacity is connected with described the 5th resistance, is serially connected between the audio frequency processing circuit earth terminal of the input of described left difference audio frequency amplifier and described audio input interface;
And/or the 11 electric capacity is serially connected between the input of the output of described left difference audio frequency amplifier and described left channel signals treatment circuit.
In such scheme, described audio frequency processing circuit also comprises:
The 3rd electric capacity is connected with described the 8th resistance, is serially connected between the left channel signals input interface of the input of described right difference audio frequency amplifier and described audio input interface;
And/or the 4th electric capacity is connected with described the 7th resistance, is serially connected between the audio frequency processing circuit earth terminal of the input of described right difference audio frequency amplifier and described audio input interface;
And/or the 12 electric capacity is serially connected between the input of the output of described right difference audio frequency amplifier and described right-channel signals treatment circuit.
The present invention also provides a kind of earphone, and described earphone comprises charging circuit, battery and above-mentioned audio frequency processing circuit;
Described charging circuit, charging inlet and the described battery of connection outer audio equipment are described battery charging; Described battery is described audio frequency processing circuit power supply;
The earth terminal of described charging circuit is identical with the current potential of described audio frequency processing circuit earth terminal.
In such scheme, described earphone is wireless headset.
In such scheme, described earphone is active wired earphone.
The beneficial effect of the embodiment of the present invention is: at first, adopt resistance to isolate between the common port of audio input interface and audio frequency processing circuit earth terminal, avoid charging current to produce interference to audio signal, effectively subdue the noise of earphone; Secondly, increase audio frequency amplifier in audio frequency processing circuit, by the mode that difference input, audio signal is processed, the earth terminal of offsetting audio frequency apparatus is different with the common-mode signal between earth terminal of powering, the impact of elimination earth terminal electrical potential difference on audio signal.Like this, charging current neither can have influence on audio signal, the interference signal of power supply on earth terminal can picked audio signal yet in, reached the purpose of eliminating noise.
Description of drawings
Fig. 1 is the connection diagram of earphone and audio frequency apparatus in prior art;
Fig. 2 be earphone by same audio frequency apparatus charge and during audio signal output current noise produce principle schematic;
Fig. 3 is the circuit diagram of a kind of audio frequency processing circuit in the embodiment of the present invention;
Fig. 4 is earphone and charging and the circuit theory schematic diagram of audio signal when output noise reduction by same audio frequency apparatus in the embodiment of the present invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, embodiment of the present invention is described further in detail below in conjunction with accompanying drawing.
Being connected as shown in Figure 2 between earphone and audio frequency apparatus, wherein, the charging circuit of earphone is connected with the charging inlet of audio frequency apparatus, the audio frequency processing circuit of earphone is connected with the audio output interface of audio frequency apparatus, this earphone is used for the audio signal of this audio frequency apparatus of output, charges by this audio frequency apparatus simultaneously.
Wherein, earphone can comprise: charging circuit 21, battery 22 and audio frequency processing circuit 23, and wherein, charging circuit is used to the battery charging, and battery is used to other part power supplies, and audio frequency processing circuit is used for the audio signal of audio frequency apparatus is processed and exported.
Charging circuit 21 comprises: equivalent resistance the first resistance R 1 on charging process module 211, charge power supply line VBUS, charging ground wire PGND, each holding wire of charging circuit (VBUS and PGND).Wherein, the charging end U that connects successively charging inlet on audio frequency apparatus on charge power supply line VBUS CHG, the first resistance R 1, charging process module and battery, connect successively the charging ground end U of charging inlet on audio frequency apparatus on charging ground wire PGND G1, charging circuit earth terminal, charging process module 211 and battery 22.
Audio frequency processing circuit comprises: left channel signals treatment circuit A L, right-channel signals treatment circuit A R, equivalent resistance the second resistance R 2 on left channel loudspeaker L, right channel loudspeaker R, left channel signals line SPK_L, right-channel signals line SPK_R, audio frequency ground wire AGND, each holding wire of audio frequency processing circuit (SPK_L, SPK_R and AGND).Wherein, the left channel signals output interface U that connects successively audio output interface on audio frequency apparatus on left channel signals line SPK_L L, the second resistance R 2, left channel signals treatment circuit A LWith left channel loudspeaker L; The right-channel signals output interface U that connects successively audio output interface on audio frequency apparatus on right-channel signals line SPK_R R, the second resistance R 2, right-channel signals treatment circuit A RWith right channel loudspeaker R; Upper earth terminal UG1, the second resistance R 2 and the audio frequency processing circuit earth terminal GND2 that connects audio output interface on audio frequency apparatus of audio frequency ground wire AGND, left channel signals treatment circuit A L, right-channel signals treatment circuit A R, left channel loudspeaker L, right channel loudspeaker R also connect respectively described audio frequency processing circuit earth terminal GND2.
Wherein, the common port of the audio input interface of charging circuit earth terminal, audio frequency processing circuit earth terminal GND2 and audio frequency processing circuit is all same current potential, U G1Be the magnitude of voltage on the ground wire of charging inlet on audio frequency apparatus and audio output interface, the ground end of charging inlet and the earth terminal of audio output interface link together.
Charging current in charging circuit changes, and has periodic change under the impact of charging process module and battery.The constant portion of supposing charging current is I CHG, changing unit is Δ i, has the relation as shown in the formula (1), formula (2) to exist:
I CHG=I CHG1+I CHG2(1)
Δi=Δi 1+Δi 2(2)
Wherein, ICHG1 and Δ i1 are that charging current is at the backflow composition of charging ground wire PGND, I CHG2With Δ i2 be that charging current is at the backflow composition of audio frequency ground wire AGND, I CHG1And I CHG2And Δ i 1With Δ i 2Distribute according to the impedance relationship on the corresponding signal line respectively.
The reference potential of supposing audio frequency apparatus end earth terminal GND1 is 0V.
When audio frequency apparatus does not have audio signal output, charging current only is provided, suppose that charging voltage is 5V, have this moment: U L=U R=0, I L=I R=0, U CHG=5V.Wherein, U LBe respectively the upper left channel audio output voltage of audio frequency apparatus and right audio channel output voltage, U with UR CHGBe charging inlet output voltage on audio frequency apparatus.
According to Ohm's law, the voltage U on audio input circuit earth terminal GND2 G2Can be obtained by following formula (3):
U G2=(I CHG+Δi)*(R1//R2)=I CHG*(R1//R2)+Δi*(R1//R2)=I CHG*(R1//R2)+ΔU(3)
Wherein, R1 is the equivalent resistance of each holding wire on charging circuit, and R2 is the equivalent resistance of each holding wire on audio frequency processing circuit, and Δ U=Δ i* (R1//R2) is the voltage variety on GND2.
For loud speaker, owing to there is no audio signal output, the voltage variety in audio frequency processing circuit on the upper high potential U3 of left channel loudspeaker L is 0, and the voltage variety of its electronegative potential U4 is Δ U; Voltage variety in audio frequency processing circuit on the upper high potential U5 of right channel loudspeaker R is 0, and the voltage variety of its electronegative potential U6 is Δ U; According to following formula (4) and formula (5), can obtain input voltage U on two loud speakers SPK_L, U SPK_RVariation delta USPK_L, Δ USPK_R be-Δ U, at this moment, the variable quantity of this input voltage produces noise for-Δ U will cause loud speaker.
ΔU SPK_L=ΔU3-ΔU4=-ΔU≠0(4)
ΔU SPK_R=ΔU6-ΔU5=-ΔU≠0(5)
When the audio frequency apparatus output audio signal, it is Δ U that two voltage varieties on the loud speaker electronegative potential are arranged, the voltage variety Δ U3=I on left channel loudspeaker L high potential L* R2=Δ U L, the voltage variety Δ U6=I on right channel loudspeaker R high potential R* R2=Δ U R, Δ U L, Δ U RBe useful signal.
According to following formula (6) and formula (7), can obtain the variable quantity of input voltage on two loud speakers
Δ U SPK_L, Δ U SPK_RBe respectively Δ U L-Δ U, Δ U R-Δ U, as seen, Δ U can be added on audio signal, still can have noise.
ΔU SPK_L=ΔU3-ΔU4=ΔU L-ΔU(6)
ΔU SPK_R=ΔU6-ΔU5=ΔU R-ΔU(7)
In summary, be connected to when carrying out audio signal output and charging on same audio frequency apparatus at earphone, noise be due to charging circuit with audio frequency processing circuit altogether the time output of the charging current interference tones signal of variation produce.
If disconnect between the ground wire with the ground wire of charging circuit and audio frequency processing circuit, need to adopt electrical equipment isolating device such as the circuit such as audio frequency transformer, photoelectric isolating device of load, and these circuit also can produce to the audio signal of earphone output interference, and can increase area and the volume of complete machine, increase cost, increase exploitation debugging difficulty etc.
basic thought of the present invention is, the earphone that a kind of audio frequency processing circuit is provided and comprises this audio frequency processing circuit, be serially connected with a resistance between the common port of described audio frequency processing circuit sound intermediate frequency input interface and audio frequency processing circuit earth terminal, increase simultaneously Differential input circuit in audio frequency processing circuit, by the mode that difference is inputted, audio signal is processed, like this, make the earth terminal (identical with the charging circuit earth terminal) of audio frequency processing circuit separated by this resistance with the audio input interface common port, avoid in charging circuit charging current to flow in audio signal, eliminated the interference of charging current to audio signal, the mode of inputting by difference is simultaneously processed the different of common-mode signal between the earth terminal of the earth terminal of offsetting audio frequency apparatus and this earphone to audio signal, eliminate the earth terminal electrical potential difference to the impact of audio signal, reach the purpose of eliminating noise.
A kind of audio frequency processing circuit that the embodiment of the present invention provides comprises audio input interface, the 3rd resistance, L channel difference audio frequency processing circuit, R channel difference audio frequency processing circuit; Wherein, described the 3rd resistance is connected between the common port and audio frequency processing circuit earth terminal of described audio input interface, and the resistance of described the 3rd resistance is far longer than the equivalent resistance of audio signal wire;
Described L channel difference audio frequency processing circuit comprises: left difference audio frequency amplifier, left channel signals treatment circuit, be connected with respectively resistance between the input of left difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of left difference audio frequency amplifier connects described left channel signals treatment circuit;
Described R channel difference audio frequency processing circuit comprises: right difference audio frequency amplifier, right-channel signals treatment circuit, be connected with respectively resistance between the input of right difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of right difference audio frequency amplifier connects described right-channel signals treatment circuit.
Concrete, with reference to shown in Figure 3, embodiment of the present invention sound intermediate frequency treatment circuit mainly can comprise: audio input interface 31, the 4th resistance R 4, the 5th resistance R 5, the 6th resistance R 6, left difference audio frequency amplifier A 1, the 7th resistance R 7, the 8th resistance R 8, the 9th resistance R 9, the 11 resistance R 11, the 12 resistance R 12, right difference audio frequency amplifier A 2, left channel signals treatment circuit A L, right-channel signals treatment circuit A R, left channel loudspeaker L, right channel loudspeaker R and the 3rd resistance R 3.
Wherein, described audio input interface 31 comprises three interfaces, it is respectively first interface 1, the second interface 2 and the 3rd interface 3, wherein, the 3rd interface 3 is as the left channel signals input interface, first interface 1 is the right-channel signals input interface as public terminal GND 3, the second interfaces 2 of audio input interface.
As shown in Figure 3, be serially connected with the 3rd resistance R 3 between the first interface 1 of audio input interface 31 and audio frequency processing circuit earth terminal GND2.The resistance of the 3rd resistance R 3 is far longer than the resistance of the equivalent resistance of the equivalent resistance of charging signals line and audio signal wire.In general, the resistance of the equivalent resistance of charging signals line and the equivalent resistance of audio signal wire is about several milliohms, and therefore, the resistance of the 3rd resistance R 3 is between 100 Ω and 100K Ω, and the resistance of preferred the 3rd resistance R 3 is 100 Ω.Like this, R3 can keep apart GND2 and GND3, avoids the charging current in charging circuit to flow in audio frequency processing circuit, can effectively subdue the noise that charging current interference tones signal causes.
As shown in Figure 3, left difference audio frequency amplifier A 1First input end serial connection the 4th resistance R 4 and be connected on the 3rd interface 3 of audio input interface 31, also connect audio frequency processing circuit earth terminal GND3 by serial connection the 11 resistance R 11, the second input serial connection the 5th resistance R 5 also is connected on the first interface 1 of audio input interface 31, the second input also connects output, left difference audio frequency amplifier A by the 6th resistance R 6 1Output connect left channel signals treatment circuit A LInput, left channel signals treatment circuit A LOutput connect the input of left channel loudspeaker L.
Right difference audio frequency amplifier A 2First input end serial connection the 7th resistance R 7 and be connected on the first interface 1 of audio input interface 31, also connect output by the 9th resistance R 9, the second input serial connection the 8th resistance R 8 also is connected on the second interface 2 of audio input interface 31, also connect audio frequency processing circuit earth terminal GND3 by serial connection the 12 resistance R 12, the output of right difference audio frequency amplifier A2 connects right-channel signals treatment circuit A RInput, right-channel signals treatment circuit A ROutput connect the input of right channel loudspeaker R.
As shown in Figure 3, the voltage on the 3rd interface 3 is U L, left difference audio frequency amplifier A 1The voltage of output is UO1, and the voltage on the second interface 2 is U R, right difference audio frequency amplifier A 2The voltage of output is UO2, and the voltage on first interface 1 is that the voltage of GND3 is U G3, the voltage of audio frequency processing circuit earth terminal GND2 is UG2, the L channel audio frequency is processed and is formed subtraction circuit by R1, R4, R5, R6 and A1; Right audio channel is processed and is formed subtraction circuit by R2, R7, R8, R9 and A2, and its output is respectively:
U O 1 = ( 1 + R 6 R 5 ) × ( R 11 R 11 + R 4 ) × U L - R 6 R 5 U G 3
U O 2 = ( 1 + R 9 R 7 ) × ( R 12 R 12 + R 8 ) × U R - R 9 R 7 × U G 3
Work as R11=R6=R12=R9=Rf, during R4=R5=R7=R8=R, have
U O 1 = R f R ( U L - U G 3 )
U O 2 = R f R ( U R - U G 3 )
So the gain of left and right sound channels treatment circuit is:
Figure BDA00002831778900085
Here, in practical application, can adjust the gain that subtraction circuit brings under A1 by the resistance value of adjusting R11, R4, R5, R6, adjust by the resistance value of adjusting R12, R7, R8, R9 the gain that subtraction circuit brings under A2.But require R11=R6=R12=R9, R4=R5=R7=R8 is identical to guarantee the left and right acoustic channels gain.For example, when making R11=R6=R4=R5=R12=R9=R7=R8=4.7K Ω, this circuit gain is 1; Make R11=R6=R12=R9=10K Ω, during R4=R5=R7=R8=5K Ω, this circuit gain is 2.
Left difference audio frequency amplifier A 1With right difference audio frequency amplifier A 2Mainly play the function that differential signal turns single-ended signal, except also having in addition amplifying signal, improving the effects such as input impedance, reinforcing band load capacity.
In practical application, left difference audio frequency amplifier A 1, left channel signals treatment circuit A L, left channel loudspeaker L the power supply earth terminal GND2 of another input frames connecting with headphone; Right difference audio frequency amplifier A 2, right-channel signals treatment circuit A R, right channel loudspeaker R the also power supply earth terminal GND2 of frames connecting with headphone of another input.
In addition, left difference audio frequency amplifier A 1First input end and the 3rd interface 3 of audio input interface 31 between can also be serially connected with between the first interface 1 of the first capacitor C 1, the second input and audio input interface 31 and can also be connected in series the second capacitor C 2, output and left channel signals treatment circuit A LInput between can also be serially connected with the 12 capacitor C 12.Right difference audio frequency amplifier A 2The second interface 2 of the second input and audio input interface 31 between can also be connected in series the 4th capacitor C 4, can also be connected in series the 3rd capacitor C 3, output and right-channel signals treatment circuit A between the first interface 1 of first input end and audio input interface 31 RInput between can also be serially connected with the 11 capacitor C 11.Wherein, the first capacitor C 1, the second capacitor C 2, the 12 capacitor C 12, the 3rd capacitor C 3, the 4th capacitor C 4, the 11 capacitor C 11 are the input coupling capacitance, and capacitance is preferably 10 μ F, is used for the flip-flop on the erasure signal line.
The embodiment of the present invention also provides a kind of earphone, this earphone includes above-mentioned audio frequency processing circuit, concrete, as shown in Figure 4, described earphone can comprise: charging circuit 41, battery 42 and above-mentioned audio frequency processing circuit 43, wherein, charging circuit 41 connects charging inlet and the described battery 42 of audio frequency apparatus, is battery 42 chargings; Audio frequency processing circuit 43 connects the audio output interface of audio frequency apparatus, and the audio signal of audio frequency apparatus is processed and exported; Battery 42 is for powering with audio frequency processing circuit 43.Especially, described earphone can be wireless headset or active wired earphone.
As shown in Figure 4, charging circuit 41 comprises equivalent resistance the first resistance R 1 on charging process module 411 and each holding wire of charging circuit (VBUS and PGND).The input of wherein, charging process module 411 connects the charging inlet U of audio frequency apparatus by charge power supply line VBUS CHG, output connects battery 42, and the earth terminal of battery 42 connects the earth terminal GND1 of audio frequency apparatus as power supply earth terminal GND2 by charging ground wire PGND, and this power supply earth terminal GND2 is the earth terminal of charging circuit 41.Wherein, charging process module 411 can be specifically a kind of chip for charging process, can be for example that Texas Instrument's model is the chip of BQ24040.
In audio frequency processing circuit 43, the left difference audio frequency amplifier A during L channel is processed 1, left channel signals treatment circuit A L, left channel loudspeaker L connects and connects the L channel output interface U of audio output interface on audio frequency apparatus by left channel signals line SPK_L L, the right difference audio frequency amplifier A during R channel is processed 2, right-channel signals treatment circuit A R, right channel loudspeaker R connects by right-channel signals line SPK_R, and connects the R channel output interface U of audio output interface on audio frequency apparatus RLeft difference audio frequency amplifier A 1, right difference audio frequency amplifier A 2The earth terminal GND3 that also connects audio frequency processing circuit 43; Left channel signals treatment circuit A L, left channel loudspeaker L, right-channel signals treatment circuit A R, right channel loudspeaker R also connects power supply earth terminal GND2; The earth terminal GND3 of audio frequency processing circuit 43 is connected with the earth terminal GND1 of audio frequency apparatus by audio frequency ground wire AGND, and connects power supply earth terminal GND2 by the 3rd resistance R 3.Equivalent resistance on each holding wire of audio frequency processing circuit (SPK_L, SPK_R and AGND) is the second resistance R 2.
In the embodiment of the present invention, R3 is far longer than R1.So: R3+R2〉R1, according to Ohm's law, be back to the charging current variation delta i in audio frequency processing circuit 2=R1/ (R1+R2+R3) * Δ i ≈ 0, Δ i is the variable quantity of charging current in charging circuit, so, the reference voltage U on audio frequency processing circuit earth terminal GND3 G3Variation delta U G3=R2* Δ i 2≈ 0, like this, the variable quantity that changes the loud speaker input voltage that produces due to charging current is also almost nil, charging current is almost nil to the interference of audio frequency processing circuit sound intermediate frequency signal, be connected to when carrying out audio signal output and charging on same audio frequency apparatus at earphone, just be difficult to tell current noise for people's ear.
In the embodiment of the present invention, at first, adopt resistance to isolate between the common port of audio input interface and audio input circuit earth terminal, also just come by resistive isolation between the earth terminal with the common port of audio input interface and charging circuit, avoid charging current to be back in audio frequency processing circuit audio signal is produced interference, effectively subdue the noise of earphone; Secondly, increase audio frequency amplifier in audio frequency processing circuit, by the mode that difference input, audio signal is processed, the earth terminal of offsetting audio frequency apparatus is different with the common-mode signal between earth terminal of powering, the impact of elimination earth terminal electrical potential difference on audio signal.Like this, charging current neither can have influence on audio signal, the interference signal on the earphone earth terminal can picked audio signal yet in, reached the purpose of eliminating noise.
The above is only preferred embodiment of the present invention, is not for limiting protection scope of the present invention.All any modifications of doing within the spirit and principles in the present invention, be equal to replacement, improvement etc., all be included in protection scope of the present invention.

Claims (8)

1. an audio frequency processing circuit, is characterized in that, described audio frequency processing circuit comprises audio input interface, the 3rd resistance, L channel difference audio frequency processing circuit, R channel difference audio frequency processing circuit; Wherein,
Described the 3rd resistance is connected between the common port and audio frequency processing circuit earth terminal of described audio input interface, and the resistance of described the 3rd resistance is far longer than the equivalent resistance of audio signal wire;
Described L channel difference audio frequency processing circuit comprises: left difference audio frequency amplifier, left channel signals treatment circuit, be connected with respectively resistance between the input of left difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of left difference audio frequency amplifier connects described left channel signals treatment circuit;
Described R channel difference audio frequency processing circuit comprises: right difference audio frequency amplifier, right-channel signals treatment circuit, be connected with respectively resistance between the input of right difference audio frequency amplifier and described audio input interface, audio frequency processing circuit earth terminal, the output of right difference audio frequency amplifier connects described right-channel signals treatment circuit.
2. audio frequency processing circuit according to claim 1, is characterized in that,
Described L channel difference audio frequency processing circuit comprises: the 4th resistance, the 5th resistance, the 6th resistance, the 11 resistance, left difference audio frequency amplifier and left channel signals treatment circuit; Wherein, first input end described the 4th resistance of serial connection of described left difference audio frequency amplifier also is connected on the left channel signals input interface of described audio input interface, also connect the audio frequency processing circuit earth terminal by serial connection the 11 resistance, the second input described the 5th resistance of serial connection also is connected on the common port of audio input interface, also connect the output of described left difference audio frequency amplifier by described the 6th resistance, the output of described left difference audio frequency amplifier connects the input of described left channel signals treatment circuit;
Described R channel difference audio frequency processing circuit comprises: the 7th resistance, the 8th resistance, the 9th resistance, the 12 resistance, right difference audio frequency amplifier and right-channel signals treatment circuit; Wherein, the second input described the 8th resistance of serial connection of described right difference audio frequency amplifier also is connected on the right-channel signals input interface of described audio input interface, also connect the audio frequency processing circuit earth terminal by serial connection the 12 resistance, first input end is connected in series described the 7th resistance and is connected to the common port of described audio input interface, also connect the output of described right difference audio frequency amplifier by described the 9th resistance, the output of described right difference audio frequency amplifier connects the input of described right-channel signals treatment circuit.
3. audio frequency processing circuit according to claim 2, is characterized in that, the resistance of described the 6th resistance, the 9th resistance, the 11 resistance and the 12 resistance is equal, and the resistance of described the 4th resistance, the 5th resistance, the 7th resistance and the 8th resistance equates.
4. audio frequency processing circuit according to claim 2, is characterized in that, described audio frequency processing circuit also comprises:
The first electric capacity is connected with described the 4th resistance, is serially connected between the left channel signals input interface of the input of described left difference audio frequency amplifier and described audio input interface;
And/or the second electric capacity is connected with described the 5th resistance, is serially connected between the audio frequency processing circuit earth terminal of the input of described left difference audio frequency amplifier and described audio input interface;
And/or the 11 electric capacity is serially connected between the input of the output of described left difference audio frequency amplifier and described left channel signals treatment circuit.
5. audio frequency processing circuit according to claim 2, is characterized in that, described audio frequency processing circuit also comprises:
The 3rd electric capacity is connected with described the 8th resistance, is serially connected between the left channel signals input interface of the input of described right difference audio frequency amplifier and described audio input interface;
And/or the 4th electric capacity is connected with described the 7th resistance, is serially connected between the audio frequency processing circuit earth terminal of the input of described right difference audio frequency amplifier and described audio input interface;
And/or the 12 electric capacity is serially connected between the input of the output of described right difference audio frequency amplifier and described right-channel signals treatment circuit.
6. an earphone, is characterized in that, described earphone comprises charging circuit, battery and audio frequency processing circuit as described in claim 1 to 5 any one;
Described charging circuit, charging inlet and the described battery of connection outer audio equipment are described battery charging; Described battery is described audio frequency processing circuit power supply;
The earth terminal of described charging circuit is identical with the current potential of described audio frequency processing circuit earth terminal.
7. earphone according to claim 6, is characterized in that, described earphone is wireless headset.
8. earphone according to claim 6, is characterized in that, described earphone is active wired earphone.
CN201310049727.4A 2013-02-07 2013-02-07 Audio processing circuit and earphone Active CN103096216B (en)

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