CN101309071A - Apparatus for inhibiting transient noise of audio power amplifier - Google Patents
Apparatus for inhibiting transient noise of audio power amplifier Download PDFInfo
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- CN101309071A CN101309071A CNA2007100408133A CN200710040813A CN101309071A CN 101309071 A CN101309071 A CN 101309071A CN A2007100408133 A CNA2007100408133 A CN A2007100408133A CN 200710040813 A CN200710040813 A CN 200710040813A CN 101309071 A CN101309071 A CN 101309071A
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Abstract
The invention discloses a device which can restrain the transient noise of an audio power amplifier and can reduce or eliminate the click noise generated in the loudspeaker when the audio power amplifier is switched on or off, or enters or exits the standby mode. The technique proposal of the invention is that the device includes a noise restraining control signal generation module and a noise restraining module. In the noise restraining control signal generation module, a first input terminal receives standby mode enable signal; a second input terminal receives the power supply voltage; a first output terminal is connected with the output of the audio power amplifier and outputs the standby signal to the output of the audio power amplifier; a second output terminal outputs time sequence control signal. In the noise restraining module, the input of the module is connected with the second output terminal of the noise restraining control signal generation module to receive the time sequence control signal; a first output terminal is connected between the audio power amplifier and a blocking capacitor; a second output terminal is connected between the loudspeaker and the blocking capacitor to restrain the transient noise in the loudspeaker, which is generated by the audio transient signal output from the audio power amplifier. The device of the invention can be applied in the audio playing field.
Description
Technical field
The present invention relates to audio frequency amplifier spare, relate in particular to the device that a kind of transient noise that audio-frequency power amplifier spare is produced is suppressed.
Background technology
Be used for driving the process that opens or closes of the single-power supply audio power amplifier of loud speaker (earphone or loudspeaker), the audio transients signal can produce " click clatter " sound or other strange transient noises in loud speaker.Along with the raising of people to the properties of product desired value, no transient state noise becomes the important indicator that people select product, thereby also is the crucial attraction of portable audio device.
The upward and downward electric process of general audio frequency apparatus can't be by repeatable operation, yet in portable use, reducing power consumption is to prolong the battery key of service time, when not needing some functional module work, generally can forbid these modules, this function might further be given prominence to this unfavorable factor of " click clatter " sound.In portable audio device, cause the factor of amplifier transition noise mainly to be divided into four kinds of situations of two big classes: category-A: to power on (energized) and cut off the power supply (turning off power supply); Category-B: withdraw from standby mode (powering up in the past) and make a forcible entry into standby mode (power supply on).
Usually, the noise when device enters standby mode is very little, and when still withdrawing from standby mode, the noise of hearing is but extremely obvious.This is caused by simultaneous two incidents: upwards be biased to the input of suitable level and the variation of output offset level.Because the output of single-power supply audio power amplifier has a Dc bias, need this direct voltage and loud speaker be separated with big capacity output coupling capacitor.Otherwise, just have a large amount of direct currents and flow into loud speaker, cause unnecessary power consumption, and may damage loud speaker and audio-frequency power amplifier.Output coupling capacitor is the main source that produces click and Pi puff sound.
When device was placed standby mode, the input and output bias voltage all can slowly descend, and fall often is a hundreds of millivolt or bigger.If device stand-by time long enough, even may drop to the degree that is equal to mutually with ground level.Yet when equipment returned operating state, the input and output bias voltage can be got back to its rated value rapidly, and input and output bias voltage and the gap between the rated value during standby are big more, and the instantaneous noise that produces when returning operating state is just big more.
Fig. 1 shows the structure chart that existing audio-frequency power amplifier is connected with loud speaker, referring to Fig. 1 switching on and shutting down click clatter generating noise process is described.Audio-frequency power amplifier 101 is connected with supply voltage VCC, comprises the negative input and the positive input of common mode reference voltage Vcm and the output Vx of output signal that are used for receiving inputted signal Vin.After audio-frequency power amplifier 101 is realized amplification or decay by feedback resistance R2 and 1 couple of input signal Vin of resistance R, the output signal Vx that obtains is connected on the capacitance Cout, to stop the DC component among the output signal Vx, the other end Vy of capacitance Cout is connected on the loud speaker 110.
For convenience, the specified Dc bias of importing with output stage is set at VCC/2, i.e. Vcm=Vx=VCC/2.After being provided with like this, output signal Vx just can have higher output amplitude on forward and negative sense, and can not take place on one side by the situation of another side amplitude limit.Simultaneously with reference to figure 2, suppose the operating voltage VCC=5V of equipment, then when audio-frequency power amplifier powers on suddenly or is electric down, the maximum of the Dc bias of output signal end Vx changes will reach 2.5V, because the both end voltage of capacitance Cout can not be suddenlyd change, these voltages are uprushed and will be passed on the loud speaker 110, produce great instantaneous noise.The reason that this thing happens is that the variation of voltage is too fast, is the variation that direct current takes place to such an extent as to capacitance Cout is beyond recognition out this, therefore allows signal to pass through.As seen from Figure 2, the voltage of the Vy of capacitance end will produce a positive step when powering on, (the RL here is the resistance of loud speaker 110 with RL * Cout then, Cout is the capacitance of capacitance) carry out exponential damping for time constant, this process will be kept t1, same, following when electric noise with life period t2.
Input Dc bias Vcm and output Dc bias Vx obviously reduced and cause when the noise that produces on loud speaker 110 came from audio-frequency power amplifier 101 and enters standby mode.Traditional solution is all to force the input and output bias voltage to remain on the rated value when audio-frequency power amplifier 101 is in any state.Produce the scheme of a kind of simple possible of this specified bias voltage, in the input and output circuit, add a resitstance voltage divider exactly respectively, so that obtain bias voltage from supply voltage VCC, simultaneously, in order to prevent the influence of biasing resistor to input and output signal, needing increases extra control switch, makes when equipment is in normal operating conditions that this external source will be disconnected.Yet this is not a good solution.Because it requires two resistance for good and all are installed respectively on the input and output device end, this will cause extra power loss.In addition, do the problem that can only solve that audio-frequency power amplifier enters and produce click clatter noise when withdrawing from standby mode like this, it is the category-B problem, and for the category-A problem, be that equipment is in startup and shutdown, because cell voltage is difficult for continuous, ohmically specified dividing potential drop can not remain on the VCC/2, so still can produce click clatter noise, so usually in switching on and shutting down, need slowly charge for the capacitance Cout of loud speaker by a little current source, till the output Vx of audio-frequency power amplifier 101 reaches VCC/2.In order to prevent the inhibition of capacitance Cout to low-frequency audio signal, suppose that speaker resistor is 32 Ohm, generally the big electric capacity of needs employing 220uF just can reach and allow blanketing frequency drop to 20Hz with the insensitive infrasound frequency of servant's ear, and the time of discharging and recharging for this big capacitor C out is quite very long, with the insensitive limit of voltage jump behaviour ear below the 1mV on the loud speaker, the time that the electric capacity of giving 220uF so needs with constant current charge is with second-time.So, if do not consume power consumption when both having wished standby mode, wish circuit again when standby mode switches to normal mode of operation, the response speed of circuit is enough fast, just so traditional solution route seems outdated.
Summary of the invention
The objective of the invention is to address the above problem, a kind of device that suppresses transient noise of audio power amplifier is provided, the click clatter noise that in loud speaker, is produced in the time of reduction or elimination audio-frequency power amplifier power-on and power-off and entry and exit standby mode, simultaneously the circuit response speed is enough fast, and makes and do not consume extra power consumption when audio-frequency power amplifier enters standby mode.
Technical scheme of the present invention is: the present invention proposes a kind of device that suppresses transient noise of audio power amplifier, suppress to be used for to drive the transient noise that audio transients signal that the audio-frequency power amplifier of loud speaker exports produces at this loud speaker, link to each other by capacitance between this audio-frequency power amplifier and this loud speaker, this device comprises:
The noise suppressed control signal generating module, its first input end receives the standby enable signal, second input receives supply voltage, first output connects the output stage of this audio-frequency power amplifier, the standby signal that is produced by this standby enable signal with output is to the output stage of this audio-frequency power amplifier, second output output control timing signal;
Noise suppression module, its input connects second output of this noise suppressed control signal generating module to receive this control timing signal, first output is connected between this audio-frequency power amplifier and this capacitance, second output is connected between this loud speaker and this capacitance, suppresses the transient noise that audio transients signal that this audio-frequency power amplifier exports produces in this loud speaker.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, the output stage of this audio-frequency power amplifier further comprises:
Draw current source, the one end connects this power voltage terminal, and the other end is connected in the output of amplifier by power amplifier output stage first switch;
Irritate current source, one end ground connection, the other end is connected in the output of amplifier by power amplifier output stage second switch;
The folding of this power amplifier output stage first switch and this power amplifier output stage second switch is subjected to the control of this standby signal.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this draws current source, this filling current source, this power amplifier output stage first switch and this power amplifier output stage second switch is field effect transistor; Perhaps this power amplifier output stage first switch and this power amplifier output stage second switch are triodes; Perhaps the output stage of this power amplifier or power amplifier itself are triodes.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, the output stage of this audio-frequency power amplifier further comprises:
The one PMOS pipe, its grid connects the previous stage of amplifier, and drain electrode connects this power voltage terminal, and source electrode connects the output of amplifier;
The 2nd PMOS pipe is connected between the grid of a PMOS pipe and this power voltage terminal and the grid of the 2nd PMOS pipe connects this standby signal;
The one NMOS pipe, its grid connects the previous stage of this amplifier, grounded drain, source electrode connects the output of amplifier;
The 2nd NMOS pipe is connected between the grid of a NMOS pipe and the ground and the grid of the 2nd NMOS pipe connects this standby signal.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this noise suppression module comprises:
First switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between the output and this capacitance of this audio-frequency power amplifier, the 3rd end ground connection;
Second switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between this capacitance and this loud speaker, the 3rd end ground connection.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this first switch and second switch are field-effect transistor or triode.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this noise suppression module further comprises:
First current source, the one end connects common mode reference voltage, the other end is connected between this audio-frequency power amplifier and this capacitance by first switch, when this audio-frequency power amplifier powers on by this first switch of this control timing signal closes to realize the current drives of drawing to this loud speaker;
Second current source, one end are connected between this audio-frequency power amplifier and this capacitance, other end ground connection; And
Second switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between this capacitance and this loud speaker, the 3rd end ground connection.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this second current source is connected between this audio-frequency power amplifier and this capacitance by the 3rd switch, passes through this control timing signal closes the 3rd switch to realize the filling current drives to this loud speaker when this audio-frequency power amplifier outage.
The device of above-mentioned inhibition transient noise of audio power amplifier, wherein, this first switch, this second switch and the 3rd switch all are field effect transistor or triode.
The present invention contrasts prior art following beneficial effect: the present invention has reduced the voltage swing amplitude of capacitance Vy end by the control of noise control signal generation module and the effect of noise suppression module, has reduced time constant.The contrast prior art, the present invention has reduced the gross energy of noise and most of noise energy has been transferred to high band more than the 20KHz, has also accelerated the start-up course of circuit when weakening click clatter noise greatly.
Description of drawings
Fig. 1 is the structure chart that existing audio-frequency power amplifier connects loud speaker.
Fig. 2 is existing change in voltage schematic diagram.
Fig. 3 is the block diagram of the device of inhibition transient noise of audio power amplifier of the present invention.
Fig. 4 is the circuit diagram of first embodiment of the device of inhibition transient noise of audio power amplifier of the present invention.
Fig. 5 is the power up schematic diagram of the audio-frequency power amplifier of Fig. 4 embodiment.
Fig. 6 is the following electric process schematic diagram of the audio-frequency power amplifier of Fig. 4 embodiment.
Fig. 7 is the circuit diagram of second embodiment of the device of inhibition transient noise of audio power amplifier of the present invention.
Fig. 8 is the circuit diagram of first embodiment of the output stage of sound intermediate frequency power amplifier of the present invention.
Fig. 9 is the circuit diagram of second embodiment of the output stage of sound intermediate frequency power amplifier of the present invention.
Figure 10 is the schematic diagram of the control timing signal of Fig. 7 embodiment.
Figure 11 is the schematic diagram of power up of the audio-frequency power amplifier of Fig. 7 embodiment.
Figure 12 is the schematic diagram of following electric process of the audio-frequency power amplifier of Fig. 7 embodiment.
Embodiment
The invention will be further described below in conjunction with drawings and Examples.
Fig. 3 shows the principle frame of the device of inhibition transient noise of audio power amplifier of the present invention.See also Fig. 3, audio-frequency power amplifier 101 has the first input end, second input that is used to receive supply voltage VCC that are used to receive input audio signal Vin, is used to receive the 3rd input of standby signal and the output that is used to provide output audio signal, and output links together by pad 33 and loudspeaker module 111.Loudspeaker module 111 is made of capacitance Cout and loud speaker 110, wherein an end ground connection of loud speaker 110.
Noise suppressed control signal generating module 37 comprises the first input end pwrdn that receives the standby enable signal be used to produce standby signal, receives second input of supply voltage VCC and offers first output of audio-frequency power amplifier 101 standby signals and offer second output of noise suppression module 34 control timing signals.
Fig. 4 shows the physical circuit of first embodiment of the device of inhibition transient noise of audio power amplifier of the present invention.The output-stage circuit of audio-frequency power amplifier 101 comprises the current source 406,407 of two serial connections, and wherein current source 406 1 ends connect supply voltage VCC, and the other end connects switch S 1, and current source 407 1 ends connect switch S 2, other end ground connection.Switch S 1 and S2 are connected the output of audio-frequency power amplifier 101.The output stage of audio-frequency power amplifier 101 realizes the pull current and sink current of load loud speaker 110 is driven by current source 406 and current source 407 respectively, and switch S 1 and S2 are then in order to realize that audio-frequency power amplifier 101 enters or withdraw from standby mode.Noise suppression module is made up of two switch S 4, S5, wherein an end of switch S 4 connects the output and the end of the Vx between the capacitance Cout of audio-frequency power amplifier 101, other end ground connection, an end of switch S 5 connect the Vy end between capacitance Cout and the loud speaker RL, other end ground connection.Switch S 4 and S5 all receive the control timing signal from the noise suppressed control signal generating module, the folding condition of this clock signal control switch.Switch S 4 here and S5 can be field-effect transistor or triode.
Fig. 5 and Fig. 6 show powering on of Fig. 4 embodiment and following electric process respectively.Please be simultaneously referring to Fig. 4 and Fig. 5, in the audio frequency amplifier power up, energized at first, initial condition subaudio frequency power amplifier is output as 0, and switch S 1, S2, S4, S5 disconnect.Closing Switch S5 then, this moment, audio-frequency power amplifier output still was 0, switch S 5 closures, switch S 1, S2, S4 disconnect.Then Closing Switch S1, S2, the stand by tone audio amplifier is stable, this moment switch S 1, S2, S5 closure, switch S 4 disconnects.After audio-frequency power amplifier output reaches stable common-mode voltage Vcm, cut-off switch S5, last, switch S 1, S2 closure, switch S 4, S5 disconnect the audio frequency amplifier operate as normal.
Please be simultaneously referring to Fig. 4 and Fig. 6, in the electric process, audio-frequency power amplifier is output as Vcm during initial condition under audio frequency amplifier, switch S 1 and S2 closure, switch S 4 and S5 disconnect.Closing Switch S5 at first, this moment, audio-frequency power amplifier was output as common-mode voltage Vcm, switch S 1, S2, S5 closure, switch S 4 disconnects.Cut-off switch S1, S2 then, this moment, the voltage of Vx end still be Vcm, switch S 5 closures, S1, S2, S4 disconnection.Follow Closing Switch S4, Cout discharges to capacitance, at this moment, switch S 4, S5 closure, switch S 1, S2 disconnect.At last, the voltage of Vx end is discharged to zero by the time, then cut-off switch S4, S5, at this moment, switch S 1, S2, S4, S5 all disconnect, can cut off the whole audio-frequency amplifier system power supply of (comprising audio-frequency power amplifier and control circuit thereof etc.), have finished time electric process.
Because the conducting resistance of switch S 5 is also non-vanishing, when audio-frequency power amplifier draw current capacity very strong the time, still may bring out the click clatter noise of existing trace at loud speaker, so the above embodiments circuit can further be strengthened its function, main change is power up, and down electric process does not almost change, and Fig. 7 shows the physical circuit of second embodiment of the device of inhibition transient noise of audio power amplifier of the present invention.
See also Fig. 7, the anode of capacitance Cout, i.e. an end that links to each other with the output Vx of audio-frequency power amplifier 101, the upper end connects current source 402 by switch S 3, and the lower end connects current source 404 by switch S 4.One termination Vcm voltage of current source 402, an end ground connection of current source 404.The negative terminal of capacitance Cout, an end Vy who promptly links to each other with loud speaker 110 connects switch S 5, the other end ground connection of switch S 5.The output stage of audio-frequency power amplifier 101 comprises the current source 406,407 of two serial connections, and wherein current source 406 1 ends connect supply voltage VCC, and the other end connects switch S 1, and current source 407 1 ends connect switch S 2, other end ground connection.Switch S 1 and S2 are connected the output of audio-frequency power amplifier 101.The output stage of audio-frequency power amplifier 101 realizes the pull current and sink current of load loud speaker 110 is driven by current source 406 and current source 407 respectively, and switch S 1 and S2 are then in order to realize that audio-frequency power amplifier 101 enters or withdraw from standby mode.Switch S 1～S5 can adopt field-effect transistor (MOSFET) to realize, also can be triode (BJT), realizes with metal-oxide-semiconductor in the present embodiment.
Should be understood that present embodiment has several variations, for example audio-frequency power amplifier 101 can adopt input Vin to insert the forward amplification mode of amplifier anode.Switch S 1 in the foregoing description and S2 can adopt MOSFET to be connected in the output-stage circuit.See also Fig. 8, switch S 1, S2 are respectively pmos pipe 81 and nmos pipe 82, respectively control timing signal Pb and the P control that is provided by the noise suppressed control signal generating module.Pmos pipe 85 and nmos pipe 86 are respectively the current sources 406 and 407 in the foregoing description.Pmos pipe 85 is connected the previous stage circuit of amplifier with the grid of nmos pipe 86.Certainly, the output-stage circuit of this audio-frequency power amplifier also can be applicable among Fig. 4 embodiment.
See also Fig. 9, the grid of PMOS pipe 85 ' connects the previous stage circuit of amplifier, and drain electrode connects supply voltage VCC, and source electrode connects the output Vx of amplifier.The grid of NMOS pipe 86 ' connects the previous stage circuit of amplifier, grounded drain, and source electrode connects the output Vx of amplifier.PMOS pipe 81 ' is connected between the grid and supply voltage VCC of PMOS pipe 85 ', and grid connects control timing signal Pb.NMOS pipe 82 ' is connected between the grid and ground of NMOS pipe 86 ', and grid connects control timing signal P.Similarly, this output-stage circuit also can be applicable among Fig. 4 embodiment.
Principle of the present invention is the high band of when reducing the noise gross energy most of noise energy being transferred to more than the 20KHz.Therefore the noise suppression circuit among the present invention can be realized the operate as normal of circuit in the ms magnitude, has accelerated the start-up course of circuit greatly.Because start-up course is quite fast, thus adopt the noise suppression circuit of this structure no longer to need to distinguish standby mode and switching on and shutting down pattern, all according to the switching on and shutting down mode treatment of outage, spending that can more effective saving power consumption.
Figure 10 is the schematic diagram of control timing signal.See also Figure 10, be audio-frequency power amplifier when in upward and downward electric process, operating, the sequential logic situation of change of the switch controlling signal S1～S5 of audio-frequency power amplifier, capacitance Cout input Vx and loud speaker output Vy signal shown in the figure.Figure 11 and Figure 12 show audio-frequency power amplifier respectively and are powering on and the flow process of following electric process.The branch amplifier powers on and descends two stages of electricity that the principle of device is described below.
Please be simultaneously referring to Figure 10 and Figure 11, in the power up of audio-frequency power amplifier, initial condition subaudio frequency power amplifier is output as 0V, and switch S 1～S5 all disconnects.After connecting the power supply of entire equipment, the control timing signal is Closing Switch S5 at first, makes the end Vy ground connection that capacitance Cout links to each other with loud speaker 110.Control timing signal closes switch S3 behind time t3, capacitance Cout is charged with a constant electric current by current source 402, behind the duration t4, till the Vx of capacitance Cout end reaches the specified bias voltage Vcm of audio power output stage.Because be constant current charge, so the output voltage of Vx is a ramp function, and switch S 5 is because adopt MOSFET to realize, and nonideal zero resistance switch, though compare resistance with loud speaker 110 little a lot, be equivalent to loud speaker 110 short circuits, but still can produce a forward square wave step at loud speaker output Vy.But because the amplitude of this step is very little, so the click clatter noise people ear that produces audible not.Follow cut-off switch S3, Closing Switch S1 and S2 behind time t5 wait for that audio-frequency power amplifier is stable.Because capacitance Cout has maintained a voltage identical with the rated output voltage of audio-frequency power amplifier,, promptly reach Vcm so Vx can reach stable in the very short time.The bias voltage that should be understood that input and output also can be selected the value between voltage VCC and ground GND arbitrarily except VCC/2, represents with Vcm in the present embodiment.After elapsed time t6 treats that the output of audio-frequency power amplifier is stable, cut-off switch S5, useful audio signal is transported to the output of loud speaker 110 after that time, and audio-frequency power amplifier begins operate as normal.
Please be simultaneously referring to Figure 10 and Figure 12, in the following electric process of audio-frequency power amplifier, the output voltage of initial condition subaudio frequency power amplifier is Vcm, be Vx=Vcm, the internal switch S1 and the S2 of audio power output stage are in closure state, and the switch S 3～S5 of noise suppression module then is in off-state.Still earlier by control timing signal closes switch S5, make the end ground connection that capacitance Cout links to each other with loud speaker 110.Disconnect the switch S 1 and the S2 of audio power output stage behind time t7, an end Vx who makes capacitance Cout link to each other with the output of audio-frequency power amplifier is in suspended state.This moment is path because the electric charge on the capacitance Cout is not released, so will maintain the specified output offset voltage of Vcm.After this elapsed time t8 Closing Switch S4,404 couples of capacitance Cout discharge with constant current source, and be t9 discharge time, till the Vx end is released ground level.The change in voltage that shows at capacitance Cout input Vx is a ramp function.Because capacitance Cout two ends charge conservation, so the end Vy that capacitance Cout links to each other with loud speaker 110 can become negative voltage, then by switch S 5, positive charge flows out the negative terminal that flows into capacitance from ground level, the electric charge at last capacitance two ends is drained, and remains zero level.Because the conducting resistance of switch S 5 is quite little,, promptly transmits the click clatter noise that comes out and still do not discovered by people's ear so the negative sense step voltage amplitude that produces on loud speaker 110 is also very little.At last after capacitance Cout both end voltage is zero, at this moment cut-off switch S4 and S5 disconnect the supply power voltage of audio-frequency power amplifier again, finish the following electric process of equipment.
Should be understood that and to omit switch S 4 among the embodiment in addition.If there is not the anode of 4 couples of capacitance Cout of switch S to discharge, then capacitor C out can be by any one the forward PN junction that is attached thereto, with release the fast forward conduction voltage VBE of PN junction of the Vcm voltage of storage on it, the audio frequency click clatter noise that can be discovered by people's ear in the generation of loud speaker output so still.The embodiment that omits switch S 4 is to avoiding the not influence of click clatter noise in the device power process.
Inventive point of the present invention is, has adopted following two kinds of means to avoid the generation of audio frequency click clatter noise: the change in voltage amplitude that reduces capacitance Vy end; Reduce time constant by the resistance that reduces the loud speaker end.
The foregoing description provides to those of ordinary skills and realizes or use of the present invention; those of ordinary skills can be under the situation that does not break away from invention thought of the present invention; the foregoing description is made various modifications or variation; thereby protection scope of the present invention do not limit by the foregoing description, and should be the maximum magnitude that meets the inventive features that claims mention.
Claims (9)
1 one kinds of devices that suppress transient noise of audio power amplifier, suppress to be used for to drive the transient noise that audio transients signal that the audio-frequency power amplifier of loud speaker exports produces at this loud speaker, link to each other by capacitance between this audio-frequency power amplifier and this loud speaker, this device comprises:
The noise suppressed control signal generating module, its first input end receives the standby enable signal, second input receives supply voltage, first output connects the output stage of this audio-frequency power amplifier, the standby signal that is produced by this standby enable signal with output is to the output stage of this audio-frequency power amplifier, second output output control timing signal;
Noise suppression module, its input connects second output of this noise suppressed control signal generating module to receive this control timing signal, first output is connected between this audio-frequency power amplifier and this capacitance, second output is connected between this loud speaker and this capacitance, suppresses the transient noise that audio transients signal that this audio-frequency power amplifier exports produces in this loud speaker.
The device of 2 inhibition transient noise of audio power amplifier according to claim 1 is characterized in that, the output stage of this audio-frequency power amplifier further comprises:
Draw current source, the one end connects this power voltage terminal, and the other end is connected in the output of amplifier by power amplifier output stage first switch;
Irritate current source, one end ground connection, the other end is connected in the output of amplifier by power amplifier output stage second switch;
The folding of this power amplifier output stage first switch and this power amplifier output stage second switch is subjected to the control of this standby signal.
The device of 3 inhibition transient noise of audio power amplifier according to claim 2 is characterized in that, this draws current source, this filling current source, this power amplifier output stage first switch and this power amplifier output stage second switch is field effect transistor; Perhaps this power amplifier output stage first switch and this power amplifier output stage second switch are triodes; Perhaps the output stage of this power amplifier or power amplifier itself are triodes.
The device of 4 inhibition transient noise of audio power amplifier according to claim 1 is characterized in that, the output stage of this audio-frequency power amplifier further comprises:
The one PMOS pipe, its grid connects the previous stage of amplifier, and drain electrode connects this power voltage terminal, and source electrode connects the output of amplifier;
The 2nd PMOS pipe is connected between the grid of a PMOS pipe and this power voltage terminal and the grid of the 2nd PMOS pipe connects this standby signal;
The one NMOS pipe, its grid connects the previous stage of this amplifier, grounded drain, source electrode connects the output of amplifier;
The 2nd NMOS pipe is connected between the grid of a NMOS pipe and the ground and the grid of the 2nd NMOS pipe connects this standby signal.
5 devices according to each described inhibition transient noise of audio power amplifier in the claim 2～4 is characterized in that this noise suppression module comprises:
First switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between the output and this capacitance of this audio-frequency power amplifier, the 3rd end ground connection;
Second switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between this capacitance and this loud speaker, the 3rd end ground connection.
The device of 6 inhibition transient noise of audio power amplifier according to claim 5 is characterized in that, this first switch and second switch are field-effect transistor or triode.
7 devices according to each described inhibition transient noise of audio power amplifier in the claim 2～4 is characterized in that this noise suppression module further comprises:
First current source, the one end connects common mode reference voltage, the other end is connected between this audio-frequency power amplifier and this capacitance by first switch, when this audio-frequency power amplifier powers on by this first switch of this control timing signal closes to realize the current drives of drawing to this loud speaker;
Second current source, one end are connected between this audio-frequency power amplifier and this capacitance, other end ground connection; And
Second switch, its first end connect the output of this noise suppressed control signal generating module to receive this control timing signal, and second end is connected between this capacitance and this loud speaker, the 3rd end ground connection.
The device of 8 inhibition transient noise of audio power amplifier according to claim 7, it is characterized in that, this second current source is connected between this audio-frequency power amplifier and this capacitance by the 3rd switch, passes through this control timing signal closes the 3rd switch to realize the filling current drives to this loud speaker when this audio-frequency power amplifier outage.
The device of 9 inhibition transient noise of audio power amplifier according to claim 8 is characterized in that, this first switch, this second switch and the 3rd switch all are field effect transistor or triode.
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Cited By (18)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102231867A (en) * | 2011-02-12 | 2011-11-02 | 北京昆腾微电子有限公司 | Audio circuit and method for eliminating noise of earphone by the audio circuit |
| CN102572642A (en) * | 2010-12-14 | 2012-07-11 | 联芯科技有限公司 | Audio POP sound elimination method and earphone audio circuit |
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| JP2005143079A (en) * | 2003-10-14 | 2005-06-02 | Matsushita Electric Ind Co Ltd | High-frequency power amplifier |
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