CN206564689U - A kind of audio-frequency noise eliminates circuit - Google Patents

Abstract

The utility model embodiment discloses a kind of audio-frequency noise and eliminates circuit, it is characterised in that including：Audio input circuit, electric capacity and power amplifier, wherein audio input circuit are connected by electric capacity with power amplifier；Audio input circuit includes：Aerial drainage module, the first input resistance, the first feedback resistance and the first operational amplifier.It is different from prior art, a kind of audio-frequency noise that the utility model is provided eliminates circuit, by the PMOS and electric resistance partial pressure of diode-connected, providing grid voltage for NMOS tube can be by by the drain electrode of NMOS tube and source conduction, and by source ground by charge discharging resisting.And it is capable of the size of adaptive wide scope capacitance so that the main energy of noise signal of the leakage current of generation is in below 20Hz, outside the non-audible scope of human ear.Response quickly, using flexible, and output step and impulsive sound are small.

Description

A kind of audio-frequency noise eliminates circuit

Technical field

The utility model embodiment is related to analog electronics technique field, and more particularly to a kind of audio-frequency noise eliminates electricity Road.

Background technology

In audio processing chip system, audio output signal can typically give audio frequency power amplifier as input signal.In reality In the application of border, in order to save packaging pin number, the packaging pin output signal of the audio processing chip of chip is generally single-ended Signal.In this scheme, chip audio has capacitance between being output to power amplifier input.And in this type of application, some In the case of audio processing chip need save fall to control power amplifier MUTE pin.It is residual in these application scheme high-speed switch machines The electric charge stayed on capacitance, can cause to produce poop when chip output is set up to common mode electrical level.Refering to Fig. 1, Existing processing mode is usually output end one non-essential resistance of increase in chip, when chip is closed, The electric charge released using this resistance on capacitance.But, during the utility model embodiment is realized, invention human hair At least there is problems with existing correlation technique：

1. because the choosing value of resistance is related to capacitance size to control RC to release the time, it is built into chip internal Use dumb, it is necessary to which each capacitance scheme readjusts internal resistance size.

2. this resistance closes output in a flash in audio processing chip, a step response can be produced in the defeated of power amplifier Go out, its size is inversely proportional with bleeder resistor size, be directly proportional to the feedback resistance of power amplifier.A compromise is to produced, it is small Bleeder resistor leakage current speed is fast, and system can be set up faster, but the power amplifier output step and impulsive sound that produce can be got over Greatly.Otherwise it is very long that system setup time can be dragged.

3. the low frequency component of step response is relatively more, so the impulsive sound that power amplifier output is produced can be than larger.

Utility model content

The utility model embodiment eliminates circuit mainly solving the technical problems that providing a kind of audio-frequency noise, uses spirit Living, output step and impulsive sound are small.

In order to solve the above technical problems, the technical scheme that the utility model is used is：A kind of audio-frequency noise is provided to disappear Except circuit, including：Audio input circuit, electric capacity and power amplifier, wherein audio input circuit pass through electric capacity and power amplifier It is connected；Audio input circuit includes：Aerial drainage module, the first input resistance, the first feedback resistance and the first operational amplifier. Wherein, the first input resistance is connected to the input in the same direction of the first operational amplifier；First feedback resistance one end is connected to first The input in the same direction of operational amplifier, the other end is connected to the output end of the first operational amplifier；One end of aerial drainage module passes through It is connected with the first input resistance with the input in the same direction of the first operational amplifier, the other end is connected to the defeated of the first operational amplifier Go out end.

Wherein, the audio input circuit also includes：D/A converting circuit, first switch, second switch and the first electricity Stream source；D/A converting circuit is connected by first switch with the first input resistance, is connected by second switch with aerial drainage module；The Two switch one end are connected with aerial drainage module, and the other end is connected between D/A converting circuit and the first input resistance；Current source one End is connected to the reverse input end of the first operational amplifier, other end ground connection.

Wherein, aerial drainage module includes：Input, tie point, the second branch road, the 3rd branch road, the 4th branch road, bleeder circuit And the 3rd switch；Tie point, the second branch road, one end of the 3rd branch road and the 4th branch road are connected another termination with input Ground；Bleeder circuit is connected with the output end of the first operational amplifier；3rd switch one end is connected with input, other end ground connection.

Wherein, tie point includes：First PMOS, the second PMOS and first resistor；The source electrode of first PMOS It is connected with input, grid is connected after being connected with drain electrode with the source electrode of the second PMOS；The grid of second PMOS connects with drain electrode It is connected after connecing with first resistor；First resistor is grounded.

Wherein, the second branch road includes：3rd PMOS, the 4th PMOS and second resistance；The source electrode of 3rd PMOS It is connected with input, grid is connected after being connected with drain electrode with the source electrode of the 4th PMOS；The grid of 4th PMOS connects with drain electrode It is connected after connecing with second resistance；Second resistance is grounded.

Wherein, the 3rd branch road includes：5th PMOS and 3rd resistor；The source electrode of 5th PMOS pipes connects with input Connect, grid is connected after being connected with drain electrode with 3rd resistor；3rd resistor is grounded.

Wherein, the 4th branch road includes：6th PMOS and the 4th resistance；The source electrode of 6th PMOS connects with input Connect, grid is connected after being connected with drain electrode with the 4th resistance；4th resistance eutral grounding.

Wherein, the bleeder circuit includes：First NMOS tube, the second NMOS tube, the 3rd NMOS tube, the 4th NMOS tube and 5th NMOS tube；The grid of first NMOS tube is connected with the drain electrode of the second PMOS, drain electrode and the output of the first operational amplifier End connection, source ground；The grid of second NMOS tube is connected with the drain electrode of the 4th PMOS, drain electrode and the first operational amplifier Output end is connected, source ground；The grid of 3rd NMOS tube is connected with the drain electrode of the 5th PMOS, drain electrode and the first operation amplifier The output end connection of device, source ground；The grid of 4th NMOS tube is connected with the drain electrode of the 6th PMOS, drain electrode and the first computing The output end connection of amplifier, source ground；The grid of 5th NMOS tube respectively with the first PMOS, the second PMOS, the 3rd PMOS, the 4th PMOS, the source electrode connection of the 5th PMOS, drain electrode are connected with the output end of the first operational amplifier, source electrode Ground connection.

Wherein, power amplifier includes：Second input resistance, the second feedback resistance and the second operational amplifier, wherein, the Two input resistance one end are connected and capacitance connection, and the other end is connected on the input in the same direction of the second operational amplifier, and second is anti- Feed resistance one end is connected to the in-phase input end of the second operational amplifier, and the other end is connected to the output of the second operational amplifier End.

In order to solve the above technical problems, another technical scheme that the utility model is used is：A kind of electronic installation is provided, It is characterised in that it includes：Circuit as described above.

Prior art is different from, a kind of audio-frequency noise that the utility model is provided eliminates circuit, passes through diode-connected PMOS and electric resistance partial pressure, providing grid voltage for NMOS tube can be by by the drain electrode of NMOS tube and source conduction, and passes through Source ground is by charge discharging resisting.And it is capable of the size of adaptive wide scope capacitance so that the leakage current of generation is made an uproar The main energy of message number is in below 20Hz, outside the non-audible scope of human ear.Response quickly, using flexible, and output rank Jump and impulsive sound are small.

Brief description of the drawings

Fig. 1 is that a kind of audio-frequency noise of prior art eliminates the structural representation of circuit；

Fig. 2 is the structural representation that a kind of audio-frequency noise that the utility model is provided eliminates circuit；

Fig. 3 is the structural representation of the aerial drainage module shown in Fig. 2.

Embodiment

For the ease of understanding the utility model, with reference to the accompanying drawings and detailed description, the utility model is carried out more Detailed description.It should be noted that when element is expressed " being fixed on " another element, it can be directly in another element There may be above or therebetween one or more elements placed in the middle.When an element is expressed " connection " another element, it can To be directly to another element or there may be one or more elements placed in the middle therebetween.This specification is used Term " vertical ", " level ", "left", "right" and similar statement for illustrative purposes only.

Unless otherwise defined, technology all used in this specification and scientific terminology are with belonging to skill of the present utility model The implication that the technical staff in art field is generally understood that is identical.In art used in the description of the present utility model in this specification Language is intended merely to describe the purpose of specific embodiment, is not intended to limit the utility model.Art used in this specification Language "and/or" includes the arbitrary and all combination of one or more related Listed Items.

Embodiment one

Refering to Fig. 2, a kind of audio-frequency noise that the utility model embodiment is provided eliminates circuit：Including：Audio input circuit 1st, electric capacity C1 and power amplifier 3, wherein audio input circuit 1 are connected by electric capacity C1 with power amplifier 3.

Work(audio input circuit 1 includes：D/A converting circuit 11, switch SW0, switch SW1, aerial drainage module 12, resistance Rin1, resistance Rfb1, the operational amplifier 14 of current source 13 and first.Wherein, D/A converting circuit 11 is by switching SW0 and electricity Rin1 connections are hindered, resistance Rin1 is connected to the input in the same direction of the first operational amplifier 14.Resistance Rfb1 one end is connected to first The input in the same direction of operational amplifier 14, the other end is connected to the output end of the first operational amplifier 14.Switch SW1 and aerial drainage mould Block 12 is connected, and switch SW1 one end is connected between D/A converting circuit 11 and resistance Rin1, one end connection of aerial drainage module 12 In the output end of the first operational amplifier 14.The one end of current source 13 is connected to the reverse input end of the first operational amplifier 14, separately One end is grounded.

Power amplifier 3 includes：Resistance Rin2, resistance Rfb2 and the second operational amplifier 31, wherein, resistance Rin2 one end Connection is connected with electric capacity C1, and the other end is connected to the input in the same direction of the second operational amplifier 31, and resistance Rfb2 one end is connected to The in-phase input end of second operational amplifier 31, the other end is connected to the output end of the second operational amplifier 31.

Refering to Fig. 3, aerial drainage module 12 includes：Branch road I1, branch road I2, branch road I3, branch road I4, bleeder circuit 121 and open Close SW2.Branch road I1, I2, I3, I4 one end is connected other end ground connection with input PD_IN, and input PD_IN turns with digital-to-analogue Circuit 11 is changed to connect.Bleeder circuit 121 is connected with the output end of operational amplifier 14.

Wherein, branch road I1 includes：PMOS MP1, PMOS MP2 and resistance R1.PMOS MP1 source electrode and input PD_IN connections, grid is connected after being connected with drain electrode with PMOS MP2 source electrode.PMOS MP2 grid with drain electrode be connected after and Resistance R1 connections.Resistance R1 is grounded.

Branch road I2 includes：PMOS MP3, PMOS MP4 and resistance R2.PMOS MP3 source electrode and input PD_IN Connection, grid is connected after being connected with drain electrode with PMOS MP4 source electrode.PMOS MP4 grid with drain electrode be connected after with resistance R2 connections.Resistance R2 is grounded.

Branch road I3 includes：PMOS MP5 and resistance R3.PMOS MP5 source electrode is connected with input PD_IN, grid It is connected after being connected with drain electrode with resistance R3.Resistance R3 is grounded.

Branch road I4 includes：PMOS MP6 and resistance R4.PMOS MP6 source electrode is connected with input PD_IN, grid It is connected after being connected with drain electrode with resistance R4.Resistance R4 is grounded.

Bleeder circuit 121 includes：NMOS tube MN1, NMOS tube MN2, NMOS tube MN3, NMOS tube MN4 and NMOS tube MN5.

NMOS tube MN1 grid is connected with PMOS MP2 drain electrode, and drain electrode is connected with the output end of operational amplifier 14, Source ground.NMOS tube MN2 grid is connected with PMOS MP4 drain electrode, and drain electrode is connected with the output end of operational amplifier 14, Source ground.NMOS tube MN3 grid is connected with PMOS MP5 drain electrode, and drain electrode is connected with the output end of operational amplifier 14, Source ground.NMOS tube MN4 grid is connected with PMOS MP6 drain electrode, and drain electrode and the output end of operational amplifier 14 connect Connect, source ground.NMOS tube MN5 grid connects with PMOS MP1, MP3, MP5, MP6 source electrode and input PD_IN respectively Connect, drain electrode is connected with the output end of operational amplifier 14, source ground.

Switch SW2 one end is connected with the output end of operational amplifier 14, other end ground connection.

In above-mentioned PMOS, PMOS MP1, MP2, MP4, MP5 conducting threshold is 3.3v, and PMOS MP3, MP5 is led Logical threshold is 1.2v.

When aerial drainage module 12 works, input connection D/A converting circuit 11, the voltage warp that D/A converting circuit 11 is provided The PMOS and electric resistance partial pressure of diode-connected, grid voltage is provided for NMOS tube.Following V (DAC) represents digital-to-analogue conversion electricity The voltage that road 11 is provided, V (PMOS label) represents the voltage of corresponding PMOS.

Specifically, NMOS tube MN1 grid voltage is：V(DAC)-V(MP1)-V(MP2).

NMOS tube MN2 grid voltage is：V(DAC)-V(MP3)-V(MP4).

NMOS tube MN3 grid voltage is：V(DAC)-V(MP4).

NMOS tube MN4 grid voltage is：V(DAC)-V(MP5).

NMOS tube MN5 grid voltage is：V(DAC).

NMOS tube MN1, MN2, MN3, MN4, MN5 grid are controlled by above-mentioned voltage, make NMOS tube MN1, MN2, MN3, MN4, MN5 drain electrode and source conduction, are used as leakage pathway.

When a kind of audio-frequency noise eliminates circuit work, all switches of acquiescence and operational amplifier are all to close, switch SW2 closures ensure that input PD_IN pulled down to ground.Operational amplifier 14 is enabled, closure switch SW1 disconnects switch SW2, then exports a voltage with D/A converting circuit 11.The voltage that D/A converting circuit 11 is provided is through diode-connected PMOS and electric resistance partial pressure, grid voltage is provided for NMOS tube, makes NMOS tube MN1, MN2, MN3, MN4, MN5 drain electrode and source electrode Conducting, is finished so that the output end of operational amplifier 14 is output as 0, i.e., as leakage pathway and by charge discharging resisting on electric capacity C1 Ground level.It is again that operational amplifier 14 is whole to suitable gain afterwards, the amplification output of signal is carried out, is completed without on impulsive sound Electricity.

Prior art is different from, a kind of audio-frequency noise that the utility model is provided eliminates circuit, passes through diode-connected PMOS and electric resistance partial pressure, providing grid voltage for NMOS tube can be by by NMOS tube MN1, MN2, MN3, MN4, MN5 leakage Pole and source conduction, and by source ground by charge discharging resisting.And it is capable of adaptive wide scope capacitance C1 size, So that the main energy of noise signal of the leakage current produced is in below 20Hz, outside the non-audible scope of human ear.Response Quickly, using flexible, and output step and impulsive sound are small.

Embodiment two

The embodiment of the present application three provides a kind of electronic installation, disappears comprising a kind of audio-frequency noise described in above-mentioned implementation one Except circuit.

The electronic equipment of the present embodiment exists in a variety of forms, includes but is not limited to:

(1) mobile communication equipment:The characteristics of this kind equipment is that possess mobile communication function, and to provide speech, data Communicate as main target.This Terminal Type includes:Smart mobile phone (such as iPhone), multimedia handset, feature mobile phone, and it is low Hold mobile phone etc..

(2) super mobile personal computer equipment:This kind equipment belongs to the category of personal computer, there is calculating and processing work( Can, typically also possess mobile Internet access characteristic.This Terminal Type includes:PDA, MID and UMPC equipment etc., such as iPad.

(3) portable entertainment device:This kind equipment can show and play content of multimedia.The kind equipment includes:Audio, Video player (such as iPod), handheld device, e-book, and intelligent toy and portable car-mounted navigation equipment.

(4) other electronic installations for playing audio, sound or sounding.

During above-mentioned electronic device works, when a kind of audio-frequency noise in built-in embodiment one eliminates circuit work, acquiescence All switches and operational amplifier are all to close, and switch SW2 closures ensure that input PD_IN pulled down to ground.Make Can operational amplifier 14, closure switch SW1, disconnection switch SW2, then with one voltage of output of D/A converting circuit 11.Digital-to-analogue PMOS and electric resistance partial pressure of the voltage through diode-connected that change-over circuit 11 is provided, provide grid voltage for NMOS tube, make NMOS tube MN1, MN2, MN3, MN4, MN5 drain electrode and source conduction, it is as leakage pathway and charge discharging resisting on electric capacity C1 is complete Finish so that the output end of operational amplifier 14 is output as 0, i.e. ground level.It is again that operational amplifier 14 is whole to suitable increasing afterwards Benefit, carries out the amplification output of signal, completes without electric on impulsive sound.

Prior art is different from, a kind of electronic equipment that the utility model is provided passes through one kind in built-in embodiment one Audio-frequency noise eliminates circuit, by the PMOS and electric resistance partial pressure of diode-connected, and providing grid voltage for NMOS tube can be by Drain electrode and source conduction by NMOS tube MN1, MN2, MN3, MN4, MN5, and by source ground by charge discharging resisting.And Be capable of adaptive wide scope capacitance C1 size so that the main energy of noise signal of the leakage current of generation be in 20Hz with Under, outside the non-audible scope of human ear.Response quickly, using flexible, and output step and impulsive sound are small.

Of the present utility model preferably implement it should be noted that being given in specification of the present utility model and its accompanying drawing Mode, still, the utility model can be realized by many different forms, however it is not limited to the implementation described by this specification Mode, these embodiments are to make there is provided the purpose of these embodiments not as the extra limitation to the utility model content Understanding to disclosure of the present utility model is more thorough comprehensive.Also, above-mentioned each technical characteristic continues to be mutually combined, formed The various embodiments not being enumerated above, are accordingly to be regarded as the scope of the utility model specification record；Further, to this area For those of ordinary skill, it can according to the above description be improved or be converted, and all these modifications and variations should all belong to The protection domain of the utility model appended claims.

Claims (10)

1. a kind of audio-frequency noise eliminates circuit, it is characterised in that including：Audio input circuit, electric capacity and power amplifier, wherein Audio input circuit is connected by electric capacity with power amplifier；Audio input circuit includes：Aerial drainage module, the first input resistance, First feedback resistance and the first operational amplifier, wherein, the first input resistance is connected to the in the same direction defeated of the first operational amplifier Enter end；First feedback resistance one end is connected to the input in the same direction of the first operational amplifier, and the other end is connected to the first computing and put The output end of big device；One end of aerial drainage module with the input in the same direction of the first input resistance and the first operational amplifier by connecting Connect, the other end is connected to the output end of the first operational amplifier.

2. circuit according to claim 1, it is characterised in that the audio input circuit also includes：D/A converting circuit, First switch, second switch and the first current source；D/A converting circuit is connected by first switch with the first input resistance, is led to Second switch is crossed to be connected with aerial drainage module；Second switch one end is connected with aerial drainage module, and the other end is connected to D/A converting circuit Between the first input resistance；Current source one end is connected to the reverse input end of the first operational amplifier, other end ground connection.

3. circuit according to claim 1, it is characterised in that aerial drainage module includes：Input, tie point, second Road, the 3rd branch road, the 4th branch road, bleeder circuit and the 3rd switch；Tie point, the second branch road, the 3rd branch road and the 4th The one end on road is connected other end ground connection with input；Bleeder circuit is connected with the output end of the first operational amplifier；3rd switch One end is connected with input, other end ground connection.

4. circuit according to claim 3, it is characterised in that tie point includes：First PMOS, the second PMOS with And first resistor；The source electrode of first PMOS is connected with input, grid be connected with drain electrode after with the source electrode of the second PMOS company Connect；The grid of second PMOS is connected after being connected with drain electrode with first resistor；First resistor is grounded.

5. circuit according to claim 4, it is characterised in that the second branch road includes：3rd PMOS, the 4th PMOS with And second resistance；The source electrode of 3rd PMOS is connected with input, grid be connected with drain electrode after with the source electrode of the 4th PMOS company Connect；The grid of 4th PMOS is connected after being connected with drain electrode with second resistance；Second resistance is grounded.

6. circuit according to claim 5, it is characterised in that the 3rd branch road includes：5th PMOS and the 3rd electricity Resistance；The source electrode of 5th PMOS is connected with input, and grid is connected after being connected with drain electrode with 3rd resistor；3rd resistor is grounded.

7. the circuit according to any one of claim 3-6 claim, it is characterised in that the 4th branch road includes：6th PMOS and the 4th resistance；The source electrode of 6th PMOS is connected with input, and grid connects after being connected with drain electrode with the 4th resistance Connect；4th resistance eutral grounding.

8. circuit according to claim 7, it is characterised in that the bleeder circuit includes：First NMOS tube, the 2nd NMOS Pipe, the 3rd NMOS tube, the 4th NMOS tube and the 5th NMOS tube；The drain electrode of the grid of first NMOS tube and the second PMOS connects Connect, drain electrode is connected with the output end of the first operational amplifier, source ground；The leakage of the grid of second NMOS tube and the 4th PMOS Pole is connected, and drain electrode is connected with the output end of the first operational amplifier, source ground；The grid and the 5th PMOS of 3rd NMOS tube Drain electrode connection, drain electrode be connected with the output end of the first operational amplifier, source ground；The grid and the 6th of 4th NMOS tube The drain electrode connection of PMOS, drain electrode is connected with the output end of the first operational amplifier, source ground；The grid of 5th NMOS tube point Source electrode not with the first PMOS, the second PMOS, the 3rd PMOS, the 4th PMOS, the 5th PMOS is connected, drain electrode and the The output end connection of one operational amplifier, source ground.

9. circuit according to claim 1 or 2, it is characterised in that power amplifier includes：It is second input resistance, second anti- Feed resistance and the second operational amplifier, wherein, the connection of second input resistance one end and capacitance connection, the other end are connected to second On the input in the same direction of operational amplifier, second feedback resistance one end is connected to the in-phase input end of the second operational amplifier, separately One end is connected to the output end of the second operational amplifier.

10. a kind of electronic installation, it is characterised in that including：Circuit described in claim any one of 1-9.