CN101764574A - Audio-frequency amplifier circuit with noise suppression - Google Patents
Audio-frequency amplifier circuit with noise suppression Download PDFInfo
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- CN101764574A CN101764574A CN200910216714A CN200910216714A CN101764574A CN 101764574 A CN101764574 A CN 101764574A CN 200910216714 A CN200910216714 A CN 200910216714A CN 200910216714 A CN200910216714 A CN 200910216714A CN 101764574 A CN101764574 A CN 101764574A
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- 230000001629 suppression Effects 0.000 title abstract 3
- 239000003990 capacitor Substances 0.000 claims abstract description 52
- 230000008878 coupling Effects 0.000 claims abstract description 21
- 238000010168 coupling process Methods 0.000 claims abstract description 21
- 238000005859 coupling reaction Methods 0.000 claims abstract description 21
- 238000007600 charging Methods 0.000 abstract description 24
- 238000000034 method Methods 0.000 abstract description 9
- 230000008901 benefit Effects 0.000 abstract description 2
- 238000001514 detection method Methods 0.000 abstract 1
- 230000010354 integration Effects 0.000 abstract 1
- 230000008569 process Effects 0.000 description 8
- 238000001914 filtration Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 230000005764 inhibitory process Effects 0.000 description 2
- 239000004065 semiconductor Substances 0.000 description 2
- 230000003321 amplification Effects 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 231100001261 hazardous Toxicity 0.000 description 1
- 230000008676 import Effects 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
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Abstract
The invention discloses an audio-frequency amplifier circuit with noise suppression, relating to the electronic technique and comprising an amplifier, a coupling capacitor and a decoupling capacitor. The invention is characterized in that the audio-frequency amplifier circuit with noise suppression also comprises a charging unit, a detecting unit and a control unit, wherein the charging unit is connected with the decoupling capacitor and is used for rapidly charging the decoupling capacitor; the detecting unit is connected with the control unit and is used for detecting the voltage of the decoupling capacitor; and the control unit is connected with the detecting unit and the charging unit and is used for controlling the working states of the amplifier and the charging unit according to the detection result of the detecting unit. The audio-frequency amplifier circuit can suppress the noises of the previous circuit. The rapid charging of the coupling capacitor and the decoupling capacitor can ensure that the voltage of the capacitor is as stable as the same bias voltage when the amplifier can be used. Compared with the traditional solution scheme, the audio-frequency amplifier circuit has the advantages of simplicity and easy integration and has no need of increasing the delay of the amplifier.
Description
Technical field
The present invention relates to electronic technology.
Background technology
A mistake! Do not find Reference source.Be depicted as conventional bridge-type audio amplifier circuit.Circuit is made up of two operational amplifiers 11 and 12 that oppositely amplify.A resistance 13 and a coupling capacitance 14 input that be connected to system of the reverse input end of first amplifier by series connection.The output of first amplifier 11 is connected to his reverse input end by a resistance 15.The reverse input end of second amplifier 12 is connected to the output of first amplifier 11 by a resistance 16, is connected to the output of oneself by a resistance 17.The output separately of first and second amplifiers is connected respectively to the port of load 18.Load 18 is generally a basis and flows through the loudspeaker that himself electric current is sounded.The positive input of first and second amplifiers is connected to a common point BP.Common point BP is connected to by being connected on two resistance 19 between power supply and the ground and the mid point of 20 voltage dividers of forming.A gate-controlled switch 21 that is generally metal-oxide-semiconductor is inserted between resistance 19 and the power supply.Bypass control signal SB controls the power supply of this switch and the one the second amplifiers.In bypass condition, bypass control signal makes the output of the one the second amplifiers place high-impedance state, and disconnects gate-controlled switch to significantly reduce power consumption.An electric capacity 22 is connected between common point and the ground, to filter out the noise that is produced by resistance and power supply.
The gain of first amplifier 11 is by the ratio decision of its input resistance 13 and feedback resistance 15.Second Amplifier Gain is usually by being set to identical being set to-1 with its input resistance 16 with feedback resistance 17.
The voltage of load is
V
L＝V
O1-V
O2＝-2(R
15/R
13)×(V
M-V
BP)
Wherein, R
15And R
13Be respectively the resistance value of the feedback resistance 15 and the input resistance 13 of first amplifier, V
O1, V
O2, V
BPAnd V
MBe respectively the output voltage of the one the second amplifiers, the voltage between common point voltage and the input coupling capacitance 14 and the first amplifier input resistance 13.The voltage of voltage divider common point is set to reference voltage so that the bias voltage of audio frequency amplifier to be set.For example, reference voltage can select to make voltage divider resistance identical and be half of supply voltage.During operate as normal, when system input E did not have signal, decoupling capacitor 22 had identical voltage with coupling capacitance 14, and voltage equals reference voltage, and load voltage is zero.When voltage of system input E input, input coupling capacitance 14 has suppressed the flip-flop of input voltage, and makes input voltage reality add the alternating component of input voltage for reference voltage.
The alternating component that load voltage equals input voltage multiply by gain amplifier-2R
15/ R
13By selecting suitable resistance ratio, the voltage peak-to-peak value of load will have different range values.
When circuit powers on, because the charging of coupling capacitance 14 and decoupling capacitor 22 has the time difference.This makes first amplifier 11 be output as high voltage, and the output of second amplifier 12 still is zero.The load two ends had very big voltage when so huge difference caused powering on, and caused the unwelcome noise that can hear.
For addressing this problem, a lot of solutions has been proposed.For example, circuit is connected with load with a switch, when postponing time enough, the transient process of circuit behind the complete stability again with this switch closure.But such circuit is difficult to be used for mini-plants such as mobile phone and walkman because they often profile is very big and be difficult to integrated.
Another way is to revise circuit so that the charging interval long enough of coupling capacitance and decoupling capacitor.Like this, capacitance voltage will keep identical as far as possible in whole process.So then reduced load voltage, simultaneously noise has been reduced, even do not heard fully.But, just prolonged circuit thus greatly from time of delay that bypass condition starts.And to reach desirable effect, this time can reach 1～2 second time usually, and is normally unacceptable in most applications, particularly during phone application.
Moreover some solutions are utilized the compromise between time of delay and the Power Supply Rejection Ratio.Really, the minimum latency time is suitable for reducing to import the capacitance of coupling capacitance and the impedance of seeing into from power supply.This will change the ability of the possible supply voltage disturbance of circuit inhibition.
Summary of the invention
Technical problem to be solved by this invention is, a kind of audio-frequency amplifier circuit with noise suppressed is provided, and having only less when bypass or halted state start or do not having hazardous noise, is easy to integratedly, reduces start-up time.
The technical scheme that the present invention solve the technical problem employing is, the audio-frequency amplifier circuit of band noise suppressed, and the audio-frequency amplifier circuit of band noise suppressed comprises amplifier and coupling capacitance and decoupling capacitor, it is characterized in that, also comprises:
Charhing unit is connected with decoupling capacitor 22, is used for decoupling capacitor 22 quick charges;
Detecting unit is connected with control unit, is used to detect the voltage of decoupling capacitor 22;
Control unit is connected with detecting unit, charhing unit, according to the testing result control amplifier of detecting unit and the operating state of charhing unit.
Specifically, the present invention includes first amplifier and second amplifier of cascade, the reverse input end of first amplifier is by resistance and coupling capacitance connected system input, the reverse input end of first amplifier connects output by resistance, the output of first amplifier connects the reverse input end of second amplifier by resistance, and the positive input of first amplifier meets common point BP; The positive input of second amplifier meets common point BP, and the reverse input end of second amplifier connects output by resistance, and common point BP is by decoupling capacitor ground connection, and common point BP is connected to the output point of voltage divider; The gate-controlled switch that is subjected to bypass control signal SB control is arranged between voltage divider and the power supply, and bypass control signal SB control is the power supply of first, second amplifier also; Also comprise a comparator 60, the reverse input end of comparator 60 meets common point BP, positive input meets reference point BPC, reference point BPC is the opposite endpoint of the ground termination points of decoupling capacitor 22, reference point BPC is by being subjected to gate-controlled switch 39 ground connection of bypass control signal SB control, between common point BP and the decoupling capacitor 22 gate-controlled switch 32 is arranged, current source 51 meets reference point BPC by gate-controlled switch 31; Be parallel with a gate-controlled switch 36 with resistance 15, be parallel with the reverse input end of gate-controlled switch 37, the first amplifiers 11 by gate-controlled switch 38 ground connection that are subjected to bypass control signal SB control with resistance 17; The output signal control gate-controlled switch 31,32,36,37 of comparator 60.
The noise of circuit before the present invention can suppress.The quick charge of coupling capacitance and decoupling capacitor can guarantee that the voltage of electric capacity is stable at identical bias voltage when enabling amplifier.The present invention compares simpler with existing solution, and is easy to integratedly, does not need to increase the delay of amplifier.
The present invention can use bigger decoupling capacitor to suppress to obtain bigger power supply when obtaining above advantage.
Description of drawings
Fig. 1 is the circuit diagram of existing skill wood.
Fig. 2 is a circuit diagram of the present invention.
Embodiment
Referring to Fig. 2.
The present invention proposes a kind of power amplification circuit, comprises first and second operational amplifiers of cascade, and first and second operational amplifiers each have first input end and accept a reference voltage that connects decoupling capacitor 22.They connect by a load 18 in output separately, and return second input separately, the input voltage that second input of first operational amplifier 11 need amplify by 14 inputs of a coupling capacitance.Amplifier must be respectively to coupling and decoupling capacitor charging from shutoff or bypass start-up the time.At least answer pair amplifier to suppress in the charging process respectively at this.
The present invention is charging respectively to coupling and decoupling capacitor when finishing, and the difference of coupling capacitance and decoupling capacitor voltage is compared and can be ignored with the imbalance of amplifier, and the voltage difference of two electric capacity is zero, and amplifier is enabled.
To being coupled 14 and decoupling capacitor 22 when charging respectively, coupling capacitance 14 will be charged to given reference voltage earlier than decoupling capacitor 22.Amplifier can be suppressed before decoupling capacitor 22 chargings reach reference voltage at least.
Decoupling capacitor 22 of the present invention is re-used.In charging process, decoupling capacitor 22 act as time-delay, after charging finishes, decoupling capacitor 22 act as filtering.
Specifically, circuit of the present invention is when bypass or off state start, the coupling capacitance 14 and the decoupling capacitor 22 of bridge joint operational amplifier charge respectively, and the inhibition operational amplifier.This charges respectively and remains to decoupling capacitor 22 at least and be charged to given reference voltage.
A mistake! Do not find Reference source.Be depicted as the amplifier circuit of a kind of specific implementation of the present invention.Circuit is made up of two operational amplifiers 11 and 12 that oppositely amplify.A resistance 13 and a coupling capacitance 14 input that be connected to system of the reverse input end of first amplifier 11 by series connection.The output of first amplifier 11 is connected to the reverse input end of oneself by a resistance 15.The reverse input end of second amplifier 12 is connected to the output of first amplifier 11 by a resistance 16, is connected to the output of oneself by a resistance 17.The output separately of first and second amplifiers is connected respectively to the port of load 18.Load 18 is generally a basis and flows through the loudspeaker that himself electric current is sounded.The positive input of first and second amplifiers is connected to a common point BP.
Amplifier circuit of the present invention comprises a kind of voltage structure that decoupling capacitor 22 can be quickly charged to predetermined voltage.
For example, this structure is series between power supply and the ground by current source 51, switch 31 and decoupling capacitor 22 and constitutes.Select the size of electric current, can adjust the time of quick charge.Switch can be a metal-oxide-semiconductor.Switch is controlled by control signal Ctr.
Amplifier circuit comprises a reference voltage network.Circuit is when bypass or off state start, and this network can fast and stable, output reference voltage.This network is made of the switch 21, first resistance 19 and second resistance 20 that are series between power supply and the ground.Switch is controlled by bypass control signal SB.Select the ratio of first resistance and second resistance, can determine the size of reference voltage.Usually, resistance 50 of series connection can improve power supply and suppresses between the intersection point of first and second resistance and reference voltage point BP.
Amplifier circuit of the present invention comprises that testing circuit detects the charging of decoupling capacitor, provides a control signal when the decoupling capacitor charging reaches reference voltage.Testing circuit is a comparator 60, and its first and second input is received the opposite endpoint BPC of the ground termination points of reference voltage common point BP and decoupling capacitor 22 respectively.Comparator is output as control voltage Ctr.
Amplifier circuit of the present invention comprises a control circuit, makes decoupling capacitor 22 can finish multiplexing function, promptly in charging process, decoupling capacitor 22 act as time-delay, after charging finishes, decoupling capacitor 22 act as filtering.According to a specific implementation of the present invention, this control circuit can only be made of a switch 32.The two ends of switch are received reference voltage common point BP and electric capacity end points BPC respectively, and switch is controlled by control signal Ctr.In charging process, the BPC of decoupling capacitor 22 end and reference voltage common point BP disconnect, decoupling capacitor act as time-delay, after charging finished, the BPC of decoupling capacitor 22 held and reference voltage common point BP conducting, decoupling capacitor act as filtering.
Amplifier of the present invention comprises a control circuit, can rejective amplifier work before decoupling capacitor 22 chargings reach reference voltage.This circuit can be made of a switch.For example, constitute by the output that connects first amplifier 11 and the switch 36 of second input, switch 36 simultaneously also with feedback resistance 15 parallel connections of first amplifier 11.Switch 36 is controlled by control signal Ctr, in charging process, and switch conduction, amplifier is suppressed, and output is irrelevant with the input E of system.After charging finished, switch disconnected.In like manner, between the output and second of second amplifier 12 is exported, a switch 37 is arranged.When switch 36 and 37 disconnected, their input was depended in amplifier 11 and 12 output.
When circuit being turn-offed or bypass, signal Ctr control amplifier is in high-impedance state, and its input also will be conducting to ground by switch 38.These switches are identical switch, and are disconnected or conducting by bypass control signal SB control.When the circuit bypass, switch 39 conductings, electric capacity 22 repid discharges.When circuit is reworked, circuit will repeat aforesaid process.
Claims (2)
1. the audio-frequency amplifier circuit of band noise suppressed comprises amplifier and coupling capacitance and decoupling capacitor, it is characterized in that, also comprises:
Charhing unit is connected with decoupling capacitor (22), is used for decoupling capacitor (22) quick charge;
Detecting unit is connected with control unit, is used to detect the voltage of decoupling capacitor (22);
Control unit is connected with detecting unit, charhing unit, according to the testing result control amplifier of detecting unit and the operating state of charhing unit.
2. the audio-frequency amplifier circuit of band noise suppressed as claimed in claim 1, it is characterized in that, first amplifier (11) and second amplifier (12) that comprise cascade, the reverse input end of first amplifier (11) is by resistance (13) and coupling capacitance (14) connected system input, the reverse input end of first amplifier (11) connects output by resistance (15), the output of first amplifier (11) connects the reverse input end of second amplifier (12) by resistance (16), and the positive input of first amplifier (11) meets common point BP; The positive input of second amplifier (12) meets common point BP, and the reverse input end of second amplifier connects output by resistance (17), and common point BP is by decoupling capacitor (22) ground connection, and common point BP is connected to the output point of voltage divider; Gate-controlled switch (21) is arranged, the power supply of bypass control signal SB control gate-controlled switch (21) and first, second amplifier between voltage divider and the power supply;
Also comprise a comparator (60), the reverse input end of comparator (60) meets common point BP, positive input meets reference point BPC, reference point BPC is the opposite endpoint of the ground termination points of decoupling capacitor (22), reference point BPC is by being subjected to gate-controlled switch (39) ground connection of bypass control signal SB control, gate-controlled switch (32) is arranged between common point BP and the decoupling capacitor (22), and current source (51) meets reference point BPC by gate-controlled switch (31); Be parallel with a gate-controlled switch (36) with resistance (15), be parallel with a gate-controlled switch (37) with resistance (17), the reverse input end of first amplifier (11) is by gate-controlled switch (a 38) ground connection that is subjected to bypass control signal SB control; The output signal control gate-controlled switch (31) of comparator (60), (32), (36), (37).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009102167145A CN101764574B (en) | 2009-12-11 | 2009-12-11 | Audio-frequency amplifier circuit with noise suppression |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009102167145A CN101764574B (en) | 2009-12-11 | 2009-12-11 | Audio-frequency amplifier circuit with noise suppression |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101764574A true CN101764574A (en) | 2010-06-30 |
| CN101764574B CN101764574B (en) | 2011-11-09 |
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ID=42495590
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009102167145A Expired - Fee Related CN101764574B (en) | 2009-12-11 | 2009-12-11 | Audio-frequency amplifier circuit with noise suppression |
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| Country | Link |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102035482A (en) * | 2010-12-13 | 2011-04-27 | 成都成电硅海科技股份有限公司 | EMI (Electro-Magnetic Interference) suppression circuit of D type power amplifier |
| CN107229447A (en) * | 2017-05-31 | 2017-10-03 | 深圳市邦华电子有限公司 | The removing method and device of audio noise |
-
2009
- 2009-12-11 CN CN2009102167145A patent/CN101764574B/en not_active Expired - Fee Related
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102035482A (en) * | 2010-12-13 | 2011-04-27 | 成都成电硅海科技股份有限公司 | EMI (Electro-Magnetic Interference) suppression circuit of D type power amplifier |
| CN107229447A (en) * | 2017-05-31 | 2017-10-03 | 深圳市邦华电子有限公司 | The removing method and device of audio noise |
| CN107229447B (en) * | 2017-05-31 | 2020-04-03 | 深圳市邦华电子有限公司 | Audio noise elimination method and device |
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| Publication number | Publication date |
|---|---|
| CN101764574B (en) | 2011-11-09 |
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