CN201127015Y

CN201127015Y - Audio power amplifier capable of reducing unwanted sound remarkably

Info

Publication number: CN201127015Y
Application number: CNU2007200485385U
Authority: CN
Inventors: 刘鉴明
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-02-12
Filing date: 2007-02-12
Publication date: 2008-10-01
Anticipated expiration: 2017-02-12

Abstract

The utility model discloses an audio power amplifier capable of remarkably reducing the noise; the audio power amplifier is composed of mutual electrical connection between an input signal detecting circuit (1), a power-on detecting circuit (2), a power-off detecting circuit (3), an input signal amplifying circuit (4), a noise filtering circuit (5), an electronic control sound-breaking circuit (6), a power amplifying circuit (7), an AC power source clean circuit (8), a rectifier filter DC circuit (9) and other functional circuits. Because the utility model adopts the measures of cleaning the mains supply, reducing the noise aiming at the frequency band of the noise, and breaking off the noise when no signal exist, the utility model has the advantages of greatly reducing the noise when has signal and making an idealized effort of completely breaking off the noise when does not have the signals. The utility model has the characters of simple structure and good effect of reducing noise; the utility model is widely popularized and used.

Description

Can significantly reduce the audio-frequency power amplifier of noise

Technical field:

The utility model relates to a kind of acoustics, specifically a kind of audio-frequency power amplifier that can significantly reduce noise.

Background technology:

The noise problem of audio-frequency power amplifier is one always and had not only allowed the people feel a very disagreeable while but also an old problem that is difficult to eliminate.Here said noise, broadly be meant all voice signals except that useful signal, so its sound that shows is diversified, wherein the noise of modal audio-frequency power amplifier mostly is " rustling " sound or " silk silk " sound or the more higher noise of shriek equifrequent, or be " drone " the low noise of sound or " pouncing on " " Ka Ka " sound equifrequent.Especially in recent years, the noise problem of these several respects is just more more obvious, the following factors of tracing it to its cause: the pollution that at first is the mains supply aspect is more and more serious, also be sinusoidal wave civil power basically before original more than ten years, in recent years, because increasing TV, computer, game machine, air-conditioning, VCD, DVD ... Switching Power Supply and controllable silicon etc. have mostly been used etc. various electrical equipment, add various electrical equipment such as increasing energy-saving daylight lamp, producing a large amount of non-sinusoidal waveforms all at all timesly, and caused serious electromagnetic pollution, and the frequency spectrum that this class nonsinusoidal wave electromagnetic pollutes is quite wide, wherein some is exactly within the audiorange that can hear, so its power pollution is just very big to the influence of audio-frequency power amplifier; Noise source be to consider inconsiderately aspect circuit design and the layout on the other hand, for example the leakage field of transformer does not shield too greatly again and too close preposition amplification, or the input of amplifier is designed to too high input impedance, thereby also very easily generates noise voltage; Noise also has from the source of sound itself that prime inserted, for example inserted if radio receiver signal, the noise carried secretly of its signal is just much so; Noise source is produced by not good enough its inside of electronic devices and components of quality, such as one piece of noise own with regard to amplifier bigger than normal, if allow it work in the input of complete machine signal, so, after the amplification through tens db, its noise also just can not have been seen certainly for a short time; In addition, the change of the impact during startup and shutdown electric current also can form unexpected and strong impact noise to loudspeaker ...More than all multifactor influences, all can encourage the generation of its noise source, thereby audio-frequency power amplifier be produced allow the very disagreeable noise of people.The noise-reduction method that past people adopts mostly is that automatic clamping is judged the method for bypass, that is to say that working as incoming signal level is lower than after a certain set point, just by automatically saturated triode by a big slightly electric capacity is gone into ground with the audio signal bypass, with upper frequency the high-frequency noise removal.But its effect is just often not as people's will, this is because so do not add whole high band all not to be decayed with differentiating, will make sound become dull unpleasant to hear, and this noise-reduction method is to but at a loss what to do fully by the noise that power pollution caused because of having lacked due high audio composition.

Summary of the invention:

The purpose of this utility model just is to overcoming a kind of low noise audio-frequency power amplifier that above-described deficiency is researched and developed.It takes the following measure to remove to improve its noise: the one, set up the mains supply clean circuit, to reduce of the influence of its power pollution as far as possible to audio-frequency power amplifier.The 2nd, on circuit, add noise frequency range filtering circuit, because there are some researches show, to the bigger noise of people's sense of hearing influence, its frequency spectrum mostly concentrates between the 3.5KHz to 5.5KHz, as long as we carry out targetedly to this frequency range, and filtration just both can lower noise significantly, and don't can produce bigger influence to its tonequality.The 3rd, input audio signal is monitored automatically, all during no signal, the real-time noise elimination when promptly carrying out the input of absence of audio signal promptly is all during no signal, just synchronously with its signal transmission path direct short-circuit ground connection, do not allow its have that I guess the noisy sound of a wee bit release.Cut off the measure of making an uproar when cooperating the above audio defeat measure that audio signal when input arranged and no signal input, promptly multi-pronged quiet noise-reduction method, its effect is just even more ideal.

The utility model compared with prior art, owing to adopted the mains supply control techniques and cut off the measure of making an uproar during at the noise reduction measure of noise frequency range and at no signal specially, its useful result is: when it can accomplish signal, noise reduction significantly, the comparatively desirable noise reduction of then making an uproar fully extremely during no signal.

Description of drawings:

Fig. 1 is a square frame principle schematic diagram of the present utility model.Among the figure, the 1st, input signal detecting circuit, the 2nd, start detecting circuit, the 3rd, shutdown detecting circuit, the 4th, input signal amplifying circuit, the 5th, noise filtering circuit, the 6th, automatically controlled exhausted sound circuit, the 7th, power amplification circuit, the 8th, AC power clean circuit, the 9th, rectifying and wave-filtering DC circuit.AC among the figure is meant interchange, and DC is meant direct current, and IN is meant input, and OUT is meant output, and Y is meant loudspeaker.

Fig. 2 is an embodiment circuit theory schematic diagram of the present utility model, S among the figure is two tie-in line sockets, R is a resistance, C is an electric capacity, T is a transformer, and L is an inductance coil, and U1, U2, U3 all are low noise operational amplifiers, N1 and N2 all are not gate CMOS integrated circuits, Q1 and Q2 are triode transistors, and V+ is the positive power source terminal of DC power supply, and V-is the negative power end of DC power supply, B is the interchange three-plug connector of band earth connection, D is a diode, and Y is loudspeaker, and K is a mains switch, W is the potentiometer of adjustable resistance, and DP is foolproof low noise power amplifier module.

Embodiment:

The utility model will be further described below in conjunction with accompanying drawing:

Fig. 1 is the block diagram of a specific embodiment of the present utility model, among the figure, it is by input signal detecting circuit 1, start detecting circuit 2, shutdown detecting circuit 3, input signal amplifying circuit 4, noise filtering circuit 5, automatically controlled exhausted sound circuit 6, power amplification circuit 7, AC power clean circuit 8, the 9 mutual electric connections of rectifying and wave-filtering DC circuit form.Its interconnected relationship is: the signal input part of input signal amplifying circuit 4 is for external various source of sound usefulness, and its signal output part then is electrically connected with input signal detecting circuit 1 and noise filtering circuit 5 respectively mutually.The signal input part of automatically controlled exhausted sound circuit 6 then is electrically connected with input signal detecting circuit 1, start detecting circuit 2, shutdown detecting circuit 3 respectively mutually.The signal output part of automatically controlled exhausted sound circuit 6 then is electrically connected mutually with the signal input part of power amplification circuit 7.The signal output part of power amplification circuit 7 is used for the external loudspeaker playback.The input of AC power clean circuit 8 is for external electric main usefulness, and its output then low-voltage alternating-current output partly is electrically connected mutually with rectifying and wave-filtering DC circuit 9.The direct current output of rectifying and wave-filtering DC circuit 9 is made the work power supply for each functional circuit.

Fig. 2 is an embodiment circuit theory schematic diagram of the present utility model, and " the input signal detecting circuit 1 " among the figure is by C14, C15, C16, C17, D1, D2, W2, R26, R16, R17, R18, D3, R19, form jointly with Q1." start detecting circuit 2 " is made of jointly D4, D5, R21, R22, R23, C18 NAND gate N1." shutdown detecting circuit 3 " is made of jointly D6, D7, C19, R24, R25 NAND gate N2., " input signal amplifying circuit 4 " is made of jointly two tie-in line socket S, resistance R 1, R2, R3, R4, capacitor C 1, C2 and low noise amplifier U1." noise filtering circuit 5 " by C3, C4, C5, C6,, C8, C9, C10, C12, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14 and low noise amplifier U2, U3 form jointly." automatically controlled exhausted sound circuit 6 " is by C12, R15, R20, form jointly with Q2." power amplification circuit 7 " is made of jointly W1 and DP." AC power clean circuit 8 " is made of jointly T1, T2, C20, C21, C22, C23, K, B." rectifying and wave-filtering DC circuit 9 " is made of jointly D8, D9, D10, D11, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33 and L1, L2, L3, L4.Selecting for use of its crux element of above circuit is as follows: low noise amplifier U1, U2, the ultra-low noise operational amplifier LM4562 that U3 can select for use the U.S. to release in recent years, the optional foolproof low noise power amplifier module DP60 of DP, not gate N1, two not gates among the optional general six not circuit CD4069 of N2, the rectifier diode D8 of big electric current, D9, D10, it is the 1N5401 of 3A 100V that D11 can select parameter for use, optional 1N4001 of all the other diodes or 1N4148, power transformer T2 optional elementary be 220V, secondary is 2 * 15V's, AC power purifies uses transformer T1, optional Peking University goes out that former to be used to do its turn ratio of power-supply filter be 1 to 1 transformer, inductance coil L1, L2, L3, L4 can be 10mH's with inductance value, triode Q1,9014 of the optional NPN type of Q2, the optional WH5-1 type of potentiometer W1, the adjustable resistance of the optional any model of W2, the optional single-pole double throw of mains switch K.

The operation principle of present embodiment is also uncomplicated, and it is as follows now to underdraw:

" the input signal amplifying circuit 4 " of present embodiment formed an in-phase amplification circuit jointly by two tie-in line socket S, resistance R 1, R2, R3, R4, capacitor C 1, C2 and low noise amplifier U1, its operation principle is identical with general in-phase amplifier, different only is the selected operational amplifier of present embodiment, it is the ultra-low noise dedicated pipe, the noise of itself low, near limit, this is that general amplifier is too far behind to catch up.Not much else, so do not repeat them here.

" noise filtering circuit 5 " of present embodiment by C3, C4, C5, C6, R5, R6, R7, R8, R9, with the T type band stop filter that low noise amplifier U2 forms jointly, C8, C9, C10, C12, R10, R11, R12, R13, R14 then form another T type band stop filter jointly with low noise amplifier U3; Each has stronger filtration to some noise frequencies these two T type band stop filters, and height is taken into account like this, thereby makes the noise signal after its output to descend more than the 12db significantly.

The operation principle of " the AC power clean circuit 8 " of present embodiment is: when the power turn-on K switch, the primary coil of power transformer T2 is switched on via T1, since be used as T1 that power purification uses aspect total number of turns and core area all than much smaller times of power transformer T2, and be to use relatively than the heavy gauge wire coiled, the number of turn of primary and secondary all is again identical, so it concerning the electric main of 50 all low frequencies, can regard as straight-through.But concerning scurrying into the High-frequency Interference noise pulse signal that is superimposed on the mains supply, the electric capacity that really is connected to the earth lead-in wire that is connected in the three pin plug by two lines directly inserted the earth before this, make noise signal be subjected to serious decay, another electric capacity that is connected to line-to-line in addition also can present lower impedance to it and by short circuit, and even the interfering noise signal of slipping through the net is arranged and by T1's, also can be by T1 the time because of it, its magnetic line of force that is produced effect of cancelling out each other of electric current of passing through because of two lines of coming in and going out, add of the short circuit effect of the filter capacitor of back in addition, and decayed significantly once more high-frequency signal.Thereby the influence that will be caused by the various interference noise pulse signals that AC power is introduced is reduced to minimum significantly.

The operation principle of " the rectifying and wave-filtering DC circuit 9 " of present embodiment is: in the power turn-on K switch, power transformer T2 secondary promptly induces corresponding low-voltage AC, and this low-voltage AC obtains comparatively straight each functional circuit of direct voltage confession on the one hand and makes the work power supply behind the common rectifying and wave-filtering of forming such as D8, D9, D10, D11, C24, C25, C26, C27, C28, C29, C30, C31, C32, C33 and L1, L2, L3, L4.

The operation principle of " the automatically controlled exhausted sound circuit 6 " of present embodiment is: the signal input part that the collector electrode of triode Q2 is connected to volume potentiometer also is the right of output signal current-limiting protection resistance R 15; and the base stage of Q2 only is connected on the R20 that joins with ground; and do not establish the last biasing resistance of directly receiving positive supply; so; it is in cut-off state at ordinary times, to the work of complete machine and volume all without any influence.But as D5, R23 in D3, R19 in " the input signal detecting circuit 1 " that be connected with its base stage or " the start detecting circuit 2 " or D7, the R24 in " shutdown detecting circuit 3 ", when any one among them is output as high level, Q2 will enter conducting state, thereby the direct ground connection of the signal input part of volume potentiometer is played the effect of making an uproar extremely, owing to be with all direct ground connection of signal, so its quiet noise reduction can reach more than the 90db.

The operation principle of " the start detecting circuit 2 " of present embodiment is: in the power turn-on K switch, by secondary low-voltage AC of inducting, become alternating current and charge to C18 through the D4 rectification through R21, because during C18 underfill electricity is electronegative potential, so in the power turn-on K switch, because C18 is in electronegative potential, be the equal of to low level of not gate N1 input, so not gate N1 promptly exports high level as the start detecting signal, this start detects high level through D5, R23 arrives the base stage of triode Q2, will make Q2 enter conducting state, thereby the signal input part of volume potentiometer is shorted to ground, thereby realize the exhausted sound function of start.The exhausted sound function of this start will be waited until when capacitor C 18 is full of electricity and just can automatically terminate.

And the operation principle of " shutdown detecting circuit 3 " of present embodiment is such: at the mains switch K closure duration of work of promptly starting shooting, the input of not gate is being kept high level by the direct voltage of D6 input, so at the start duration of work, not gate N2 output low level, not conducting of D7 can not start exhausted sound circuit.And when disconnecting power switch K, because the capacity of filter capacitor C19 is less, the electricity that capacitor C 19 is filled during shutdown also can become low level thereupon disappearing, therefore not gate N2 also can export high level immediately, this high level makes Q2 enter conducting state and the exhausted sound function of realizing shutting down through D7, R24, thereby has avoided the shutdown noise that still still can form because of the electric weight of being stored after shutdown because of rectifying and wave-filtering electric capacity.

The operation principle of " the input signal detecting circuit " of present embodiment is: when the amplifier U1 in " input signal amplifying circuit 4 " has audio signal voltage output, this audio signal voltage is incorporated into C14, C15 through R26, its effect of the C14 of its medium and small capacitance is that needle pattern noise signal with upper frequency is directly with its ground connection, to avoid it to this " input signal detecting circuit " action that makes the mistake.And normal audio signal is delivered to the current rectifying and wave filtering circuit of being made up of D1, D2, C16, W2 through C15 and is changed direct voltage into, this direct voltage is regulated after R16 delivers to Q1 by adjustable resistance W2, and make Q1 be in the saturation conduction state, this moment, two utmost point D3 were in the back-pressure state, so can not exert an influence to be made of " automatically controlled exhausted sound circuit " Q2 and R20.But when the amplifier U1 in " input signal amplifying circuit 4 " does not have audio signal voltage output, the current rectifying and wave filtering circuit of being made up of D1, D2, C16, W2 does not have direct voltage output, thereby cause Q1 to enter cut-off state, so V+ voltage is sent to the Q2 base stage in " automatically controlled exhausted sound circuit " through R18, D3, R19, Q2 is saturated with the direct ground connection of all input signals, thereby makes " automatically controlled exhausted sound circuit " play exhausted sound effect.

Present embodiment is owing to finally reached remarkable reduction anti noise by above measures.

Claims

1. audio-frequency power amplifier that can significantly reduce noise, it is by input signal detecting circuit (1), start detecting circuit (2), shutdown detecting circuit (3), input signal amplifying circuit (4), noise filtering circuit (5), automatically controlled exhausted sound circuit (6), power amplification circuit (7), AC power clean circuit (8), the mutual electric connection of each functional circuit of rectifying and wave-filtering DC circuit (9) forms; It is characterized in that: it is provided with input signal detecting circuit (1), start detecting circuit (2), shutdown detecting circuit (3), noise filtering circuit (5), automatically controlled exhausted sound circuit (6), AC power clean circuit (8); More than the interconnected relationship of each functional circuit be: the signal input part of input signal amplifying circuit (4) is used for external various sources of sound, its signal output part then is electrically connected with input signal detecting circuit (1) and noise filtering circuit (5) respectively mutually, the signal input part of automatically controlled exhausted sound circuit (6) then respectively with input signal detecting circuit (1), start detecting circuit (2), shutdown detecting circuit (3) is electrically connected mutually, the signal output part of automatically controlled exhausted sound circuit (6) then is electrically connected mutually with the signal input part of power amplification circuit (7), the signal output part of power amplification circuit (7) is used for the external loudspeaker playback, the input of AC power clean circuit (8) is used for external electric main, its output then low-voltage alternating-current output partly is electrically connected mutually with rectifying and wave-filtering DC circuit (9), and the direct current output of rectifying and wave-filtering DC circuit (9) is made the work power supply for each functional circuit.

2. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said input signal detecting circuit (1) is interconnected by C14, C15, C16, C17, D1, D2, W2, R26, R16, R17, R18, D3, R19, Q1 to be formed; Its interconnected relationship is: the end of C15 is connected with the positive pole of D2 and the negative pole of D1 respectively, the other end of C15 is connected with the end of C14 and the end of R26, the other end ground connection of C14, the negative pole of D2 is connected with the end of C16 and the hot junction of W2 respectively, the other end ground connection of C16, the cold junction of W2 is connected with ground, the scalable end of W2 is connected with the end of R16, the other end of R16 is connected with the base stage of Q1 and the end of R17 respectively, the other end ground connection of R17, the emitter of Q1 is connected with ground, the collector electrode of Q1 respectively with the positive pole of D3, the end of R18 and the end of C17 are connected, the other end of C17 is connected with ground, and the negative pole of D3 is connected with the end of R19.

3. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said start detecting circuit (2) is interconnected and is formed by D4, D5, R21, R22, R23, C18, not gate N1; Its interconnected relationship is: the end of R21 is connected with the negative pole of D4, the other end of R21 is connected with an end and the end of C18 and the input of N1 of R22 respectively, the other end of R22 and the equal ground connection of the other end of C18, the positive pole of D5 is connected with the output of N1, and the negative pole of D5 is connected with the end of R23.

4. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said shutdown detecting circuit (3) is interconnected and is formed by D6, D7, C19, R24, R25, not gate N2; Its interconnected relationship is: the input of N2 is connected with the negative pole of D6, the end of C19 and the end of R25 respectively, the other end of C19 and the equal ground connection of the other end of R25, and the output of N2 is connected with the positive pole of D7, and the negative pole of D7 is connected with the end of R24.

5. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said input signal amplifying circuit (4) interconnects the ultra-low noise audio frequency amplifier of forming by two tie-in line socket S, R1, R2, R3, R4, C1, C2, amplifier U1; Its interconnected relationship is: the tie-in line end ground connection of two tie-in line socket S, another of two tie-in line socket S inserts line end and is connected with the end of C1 and the end of R1 respectively, the other end ground connection of R1, the other end of C1 is connected with the end of R2 and the positive input terminal of U1 respectively, the other end of R2 is connected with ground, the negative input end of U1 is connected with the end of R3 and the end of R4 respectively, the other end of R4 is connected with the end of C2, the other end ground connection of C2, the other end of R3 is connected with the output of U1.

6. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said noise filtering circuit (5) is interconnected two T type band stop filters forming by C3, C4, C5, C6, C8, C9, C10, C12, R5, R6, R7, R8, R9, R10, R11, R12, R13, R14, amplifier U2, U3; Its interconnected relationship is: the end of C4 is connected with the end of C3 and the end of R5 respectively, and the other end of C4 is connected in series mutually with the end of C5 and be connected in series the end that point inserts R7 at it, the other end of R7 respectively with the output of U2 and the end of R9, the end of R10, the end of C8 is connected, the other end of R5 is connected in series and inserts at its serial connection point the end of C6 mutually with the end of R6, the other end ground connection of C6, the other end of R6 is connected with the negative input end of U2 and the other end of C5 respectively, the positive input terminal of U2 is connected with the other end of R9 and the end of R8 respectively, the other end ground connection of R8, the other end of C8 is connected in series and inserts at its serial connection point the end of R12 mutually with the end of C9, the other end of R12 respectively with the output of U3 and the end of R14, the end of C12 is connected, the negative input end of U3 is connected with the other end of C9 and the end of R11 respectively, the other end of R11 is connected in series and inserts at its serial connection point the end of C10 mutually with the other end of R10, the other end ground connection of C10, the positive input terminal of U3 is connected with the other end of R14 and the end of R13 respectively, the other end ground connection of R13.

7. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said automatically controlled exhausted sound circuit (6) is interconnected by C12, R15, R20, Q2 to be formed; Its interconnected relationship is: the end of R15 is connected in series mutually with C12, and the other end of R15 is connected with the last stiff end of the collector electrode of Q2 and W1, the grounded emitter of Q2, and the end of R20 is connected with the base stage of Q2, the other end ground connection of R20.

8. the audio-frequency power amplifier that can significantly reduce noise according to claim 1 is characterized in that: wherein said AC power clean circuit (8) is interconnected by T1, T2, C20, C21, C22, C23, K, B to be formed; Its interconnected relationship is: C20 is connected in series mutually and will be connected in series with C21 a little to draw to be connected to and connects the earth lead end among the three-way ac plug B, C20 with after C21 is connected in series mutually end to end two draw line end respectively with the two ends of C22 mutually and connect, and the two ends of C22 are connected with secondary coil end lead-in wire of the same name with the primary coil end lead-in wire of the same name of T1 respectively, and two lead ends in addition of the primary coil of T1 and secondary coil are connected with C23 two ends and the elementary of T2 respectively; Among the non-two other that connects the earth lead end among the three-way ac plug B goes between, article one, be connected by non-the earth that end that goes between that connects of K switch and C20, non-among the three-way ac plug B connects among the two other lead-in wire of the earth lead end another and then is connected with non-that end that connects the earth lead-in wire of C21.