CN101330277B - Circuit and method for eliminating horn popping when turning on and turning down power amplifier - Google Patents
Circuit and method for eliminating horn popping when turning on and turning down power amplifier Download PDFInfo
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- CN101330277B CN101330277B CN2007101112644A CN200710111264A CN101330277B CN 101330277 B CN101330277 B CN 101330277B CN 2007101112644 A CN2007101112644 A CN 2007101112644A CN 200710111264 A CN200710111264 A CN 200710111264A CN 101330277 B CN101330277 B CN 101330277B
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- circuit
- loudspeaker
- amplifier
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Abstract
The invention discloses a circuit and a method for eliminating horn popping when a power amplifier is started and closed down, and particularly relates to a circuit and a method for ensuring that by utilizing the charge and discharge characteristics of a capacitor, when the power amplifier is started and closed down, the popping is lower than an audible degree when a horn is started and closed down by utilizing charge characteristics of an input capacitance to replace the pre-charge of the input capacitance. The circuit not only has the advantages of low cost and simple design, but also can not limit the bandwidth in design.
Description
Technical field
The elimination circuit and the method for loudspeaker sonic boom when the present invention relates to a kind of power amplifier start and shutdown, particularly a kind of charging voltage of input capacitance of utilizing is come the precharge as output capacitance, lets horn switch machine sonic boom be lower than the degree that can hear.
Background technology
In digital world now, the utilization rate of loudspeaker is not less than any electronic component, and to any audio-visual devices, loudspeaker all are bound to use from computer, TV.More there is many people great achievement that spares no expense to promote horn system originally in the hope of having better tonequality.Yet the user usually can find to contain the appliance and electronic of loudspeaker, often in switching on and shutting down, all can have sonic boom to occur.Long-term sonic boom can damage the sense of hearing at some products incessantly, and loudspeaker itself also might damage.
The method of handling the start sonic boom traditionally is before start, lets amplifier be in closed condition and stablizes back amplifier output sound signal again up to relevant capacitor voltage.As shown in Figure 1, when power supply unit (Power Supply) started, power supply supply voltage can rise to V from no-voltage
CcDuring this section, output capacitance C
OutSee through two divider resistance R and begin charging, the formula of charging current does
I＝(Vcc/R)e
-t/0.5RCout
The wherein initial value of charging current, that is peak, I
Peak=V
Cc/ R, and charge constant is 0.5RC
OutBecause the value of charging resistor R is far longer than the value of loudspeaker load, is generally 4ohms or 8ohms, above formula is ignored the load of loudspeaker.
General audio frequency amplifier requires low frequency-3db frequency less than 20Hz, the impedance of low frequency-3db frequency and loudspeaker and output capacitance C
OutRelation be f
-3db=1/ (1/2 π R
SpkC
Out).R wherein
SpkRepresent the impedance (Speaker Impedance) of loudspeaker, for the loudspeaker of 4ohms under the requirement of 20Hz low frequency-3db C
Out=1/ (2 π R
Spkf
-3db)=1/ (2 π * 4 * 20)=2000uF.So, for frequency range problem, output capacitance C
OutValue needs big to 2000uF.
In order to reduce the peak current of charging, I
Peak=V
Cc/ R, the R value must be big as much as possible.If reduce peak current below 1mA and suppose that supply voltage is 5V, then R=V
Cc/ I
Peak=5V/1mA=5kohms.
The formula of electric capacity charging voltage does
V＝Vcc/2(1-e
-t/0.5RCout)，
As to fill full output capacitance C
OutVoltage to 99% of Vcc/2
(V
cc/2)×99％＝V
cc/2(1-e
-t/0.5RCout)，
Promptly
(5V/2)×0.99＝5V/2(1-e
-t/0.5RCout)，
Like this
t＝-0.5RC
out×1n(0.01)＝2.3RC
out
＝2.3×5k?ohms×2000uF
＝23seconds。
By can know with following formula as to reduce the sonic boom electric current to 1mA and charging voltage reach 99% stand-by period must be greater than 23 seconds.But reasonably the stand-by period needed less than 3～5 seconds, and so the sonic boom electric current need increase to 5～8mA nearly.So the designer must do compromise selection between the size of stand-by period and sonic boom.
After stand-by period or time of delay, the output of amplifier (Amplifier) can be unlocked, then a V
Cc/ 2 voltage is sent to C
OutIf fall short of this time of delay, second sonic boom can not appear in loudspeaker when promptly the voltage of Cout reached Vcc/2, because the V of amplifier output
Cc/ 2 voltages will force C
OutQuick charge is to V
Cc/ 2 and produce big momentary charge electric current.
Except the charging sonic boom of output capacitance, input capacitance also has the problem of charging sonic boom as shown in Figure 2, input capacitance C
InValue also be subject to-demand of 3db low frequency f
-3dbFrequency calculating formula is f
-3db=1/2 π R
InC
InBy MAXIM company (MAX9715 is proposed; Page8) and propose (TDA8932 by PhilipsSemiconductors; Page16) solution is all closed the output stage of amplifier; Open after all stablizing up to input charging circuit and output charging circuit, the basic principle of this method and preceding method roughly the same need the booting wait time again.
Summary of the invention
Main purpose of the present invention is circuit and the method in the elimination that a kind of loudspeaker start and close popping noise are provided, particularly through the mild precharge to output capacitance lets horn switch machine sonic boom be lower than the degree that can hear as input signal with the input capacitance charging voltage.
Circuit of the present invention mainly comprises control unit; Voltage through the detecting power supply comes guiding operation; Simultaneously send control signals to switching circuit and amplifier according to circuit requirements, wherein at least one switch receives the charge and discharge of electric capacity in this control signal and the charge control circuit; Amplifier exports low frequency LC filter to behind amplification input signal or the voltage.Filtered signal is resent to loudspeaker device.Therefore when start, control unit can transmit control signal and begin input capacitance Cin is charged to switch, and this charging signals directly amplifies and promotes loudspeaker.Because the charging voltage of input capacitance is the mild up voltage of going up, its charge constant is (Rs+Rin) x Cin.This goes up gently up voltage also is mild output voltage after amplifier amplifies, and this mild output voltage will carry out mild charging to output capacitance Cout, has replaced the precharge of peak value, I with mild charging
Peak=Vcc/R, and the start sonic boom is reduced.When this control signal detects when shutdown, the electric capacity that has charged is through the discharge of the discharge circuit in amplifier charging gently again when treating next time switch.
Equaling 20K ohms and input capacitance value with the input resistance value, to equal 1uF be example, input circuit-the 3db frequency be 1/ (2 π * 20k * 1u)=8Hz, in the case, as long as the little electric capacity of 1uF can reach the low frequency bandwidth of 8Hz.The frequency response of general loudspeaker and the sense of hearing of people's ear are probably more than 20Hz, if the electric capacity charge rate of output can show less than loudspeaker or people's ear can find the sensation that does not just have sonic boom.If produce a charging voltage then this charging promptly can not cause sonic boom with the frequency range of 8Hz.This kind charging modes need not waited until that all electric capacity are charged to and saturatedly just can import music signal in addition.The charging curve of input circuit does
V＝V
cc/2(1-e
-t/RinCin)，
Calculate charging voltage then with Rin=20k ohms and Cin=1uF
V＝5/2(1-e
-t/20kxlu)
＝2.5(1-e
-t/20m)，
If voltage is charged to V
Cc99%, then
5/2x99%=5/2 (1-e
-t/20m), promptly
0.99＝1-e
-t/20m，
Or t=-20m * 1n0.01
＝0.092seconds。
The charging voltage of this moment and the difference of Vcc/2 do
5V/2-5V/2×99％＝0.025V。
Usually the voltage gain of power amplifier is about 10 times, and then 0.025V will be enlarged into 0.025V * 10=0.25V.If input this moment music signal, so little voltage can not impact sound quality.Can know by above discussion that the stand-by period has only 0.1 second and do not have second sonic boom produces.
Description of drawings
Fig. 1 is the prior art circuits sketch map;
Fig. 2 is another prior art circuits sketch map;
Fig. 3 is a circuit diagram of the present invention;
Fig. 4 is a circuit sequence sketch map of the present invention.
The figure number explanation:
1 signal source
2 signal resistance R
s
3 switching transistor NMOS2
4 input capacitance C
In
5 switching transistor NMOS1
6 input resistance R
In
7 amplifiers
8 control units
9 LC low-frequency filters
10 output capacitance C
Out
11 loudspeaker
Embodiment
Main purpose of the present invention is in the circuit and the method that provide a kind of sonic boom that loudspeaker are produced during in switching on and shutting down to eliminate, as input signal output capacitance is done mild precharge to reduce horn switch machine sonic boom to inaudible degree through the mild charging that utilizes input capacitance.As shown in Figure 3, the output of a signal source 1 is provided with a signal resistance R
s2, signal resistance R
s2 are connected to a switching transistor NMOS2 (3) and input capacitance C
In4.Because one of switching transistor NMOS2 (3) terminates to systematically (System Ground), therefore when switching transistor NMOS2 (3) starts, can be shorted to input signal systematically, thus the signal cut that offers loudspeaker 11.Input capacitance C
In4 snap into switching transistor NMOS1 (5) and input resistance R
In6, because the end of switching transistor NMOS1 (5) also is to receive systematically, therefore when switching transistor NMOS1 (5) starts, via input capacitance C
In4 voltage can direct short-circuit arrive systematically input resistance R
In6 inputs that snap into amplifier 7.(5) two of switching transistor NMOS2 (3) and switching transistor NMOS1 belong to metal-oxide semiconductor.In addition; Switching transistor NMOS1 (5), switching transistor NMOS2 (3) and amplifier 7 snap into a control unit 8 simultaneously, and control unit 8 comes guiding operation through the voltage of detecting power supply and sends control signal and come control switch transistor NMOS1 (5), switching transistor NMOS2 (3) and amplifier 7.The signal output part of amplifier 7 can further be linked a LC low-frequency filter 9, and the output of LC low-frequency filter 9 can be connected to an output capacitance C
Out10, output capacitance C
Out10 are connected to loudspeaker device 11.For the embodiment of the invention can be understood more in detail, below can pass through at input capacitance C
InThe change in voltage that the output C of the A point after 4, the B point of amplifier 7 outputs and low-frequency filter 9 is ordered is explained.
Fig. 4 is the circuit timing diagram of Fig. 3 of the present invention, and all signals all are in ground voltage before start.As supply voltage V
CcDuring rising, promptly between t1～t2, SW1 and SW2 control signal rise along with supply voltage, and just switching transistor NMOS2 (3) and switching transistor NMOS1 (5) keep conducting state, make input capacitance C
InThe voltage at 4 two ends maintains earth potential.When supply voltage rises to a certain magnitude of voltage, i.e. t2, the signal of SDNB transfers high voltage to start amplifier by ground voltage, and the signal of SW1 transfers ground voltage to off switch transistor NMOS1 (5) at the same time.So the amplifier builtin voltage is through input resistance R
In6 couples of input capacitance C
In4 chargings and the A point voltage is risen like icon.Amplifier as shown in Figure 4 is promptly exported PWM (Pulse Width Modulation, pulse width modulation) signal to the B point after the voltage that reception A is ordered.Because supply voltage is also rising, i.e. so t2～t3 is the also rising thereupon of the amplitude of the pulse voltage that B is ordered.In addition the A voltage of order be mild a last up voltage so it is low to B point PWM degree of regulation, it is a rising and pulse duration pwm signal of serving as reasons and broadening for a short time gently that these two factors cause the amplitude of B point voltage.This B point signal is after LC low-frequency filter 9, i.e. C point signal is that a mild up voltage of going up is with to output capacitance C
Out10 chargings, after charging is accomplished, i.e. t3, the signal of SW2 transfers ground voltage to turning off switching transistor NMOS2 (3) by high voltage, and is like this then signal signal source promptly passes through signal resistance R
s2, input capacitance C
In4 and input resistance R
In6 are sent to amplifier 7, and this moment, entire circuit got into normal operating state.To wait until not necessarily that by the time point of diagram t3 A point charging voltage is stable.
During shutdown, power source voltage Vcc promptly begins to descend, i.e. t4～t5, this moment, amplifier 7 was in a lower operating voltage, thus pulse amplitude of its output signal B also along with reduction, the C point voltage through filtering after is decline thereupon also.When supply voltage is reduced to a certain low-voltage, i.e. t4, SDNB signal promptly transfer low-voltage to turn off amplifier 7 and to start the internal discharge circuit of amplifier 7 by high voltage, and the inner discharge circuit of amplifier this moment promptly discharges to the B point.SW2 also transfers high voltage to by low-voltage and opens switching transistor NMOS2 (3) and the signal of signal source is shorted to ground through signal resistance Rs 2 at the same time, makes input signal no longer be sent to amplifier 7.Because this moment, supply voltage was in low-voltage state, the minimizing that the discharging current that B point or C are ordered can be relative and the unlikely close popping noise that causes loudspeaker 11.Point at one time, i.e. t4, the SW1 signal also transfers high voltage to and actuating switch transistor NMOS1 (5) by low-voltage, makes A point voltage repid discharge to ground voltage A point voltage when next time starting shooting be in the initial value of ground voltage.Switching transistor NMOS1 (5) conducting causes a low-voltage input with pair amplifier 7, but this moment, amplifier 7 was closed so can not cause loudspeaker 11 sonic booms.Entire circuit is got back to ground voltage and this amplifier can be activated again again when t5.
More than explanation is an example with the D power-like amplifier, and the power amplifier of other type such as its operation of AB power-like amplifier or improvement principle also are identical.
In practical implementation, can also implement as follows:
The removing method of loudspeaker sonic boom when a kind of power amplifier start and shutdown comprises:
Control at least one switch through control unit, wherein said at least one ON-OFF control circuit comprises input and output capacitors; During start, first switch is controlled said input capacitance charging, and this charging voltage is after said amplifier amplifies; Directly to said output capacitance precharge; Set up second switch to be responsible for the signal of opening and closing said circuit signal source, during shutdown, said second switch cuts off the signal in circuit signal source; Said first switch discharges said input capacitance, and said amplifier is closed and discharge circuit discharges to said output capacitance simultaneously.
More than disclosedly be merely several specific embodiment of the present invention, still, the present invention is not limited thereto, any those skilled in the art can think variation all should fall into protection scope of the present invention.
Claims (5)
1. the elimination circuit of loudspeaker sonic boom is characterized in that when a power amplifier was started shooting and shut down, and comprising:
Control unit comes guiding operation through detecting sound signal source, and transmits control signal according to circuit requirements;
First switch receives the charge and discharge of the input and output capacitors in said control signal and the charge control circuit;
Second switch receives said control signal and is responsible for opening and closing said sound signal source;
Amplifier, amplification input signal; And
Low-frequency filter; The signal that average said amplifier is exported also sends filtered filtering signal to loudspeaker device; Said input capacitance is connected between signal resistance and switching transistor NMOS1 and the input resistance, and said output capacitance is connected between low-frequency filter and the loudspeaker; When said loudspeaker device was started shooting, said first switch was controlled said input capacitance charging, and this charging voltage is after said amplifier amplifies, directly to said output capacitance precharge; During this loudspeaker device shutdown, said second switch cuts off the sound signal source, and said first switch discharges said input capacitance, and said amplifier is closed and discharge circuit discharges to said output capacitance simultaneously.
2. the elimination circuit of loudspeaker sonic boom is characterized in that said first switch is a metal-oxide semiconductor when power amplifier was started shooting and shut down according to claim 1.
3. the elimination circuit of loudspeaker sonic boom is characterized in that said second switch is a metal-oxide semiconductor when power amplifier was started shooting and shut down according to claim 1.
4. the removing method of loudspeaker sonic boom when a power amplifier is started shooting and shut down; Comprise: control first switch through control unit; And second switch; The charge and discharge of input and output capacitors in wherein said first ON-OFF control circuit, said input capacitance are connected between signal resistance and switching transistor NMOS1 and the input resistance, and said output capacitance is connected between low-frequency filter and the loudspeaker; When said loudspeaker device was started shooting, first switch was controlled said input capacitance charging, and this charging voltage is after amplifier amplifies; Directly to said output capacitance precharge; Wherein said second switch is responsible for the signal of unlatching and shut-off circuit signal source, and during shutdown, said second switch cuts off the signal in circuit signal source; Said first switch is discharged to ground voltage with said input capacitance, and said amplifier is closed and discharge circuit discharges to said output capacitance simultaneously.
5. the removing method of loudspeaker sonic boom is characterized in that said control unit is controlled said first switch and second switch through sending control signals to said first switch and second switch during like said power amplifier start of claim 4 and shutdown.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007101112644A CN101330277B (en) | 2007-06-20 | 2007-06-20 | Circuit and method for eliminating horn popping when turning on and turning down power amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2007101112644A CN101330277B (en) | 2007-06-20 | 2007-06-20 | Circuit and method for eliminating horn popping when turning on and turning down power amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN101330277A CN101330277A (en) | 2008-12-24 |
| CN101330277B true CN101330277B (en) | 2012-02-08 |
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ID=40205914
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2007101112644A Expired - Fee Related CN101330277B (en) | 2007-06-20 | 2007-06-20 | Circuit and method for eliminating horn popping when turning on and turning down power amplifier |
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| CN (1) | CN101330277B (en) |
Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101511046B (en) * | 2009-02-24 | 2013-10-09 | 华为终端有限公司 | Audio play apparatus and process capable of eliminating popping |
| CN101924969B (en) * | 2009-06-17 | 2017-03-22 | 晨星软件研发(深圳)有限公司 | Audio frequency controller capable of removing sonic booms and method for removing sonic booms |
| CN102629855B (en) * | 2012-04-13 | 2015-04-08 | 成都芯源系统有限公司 | Noise suppression circuit and control method thereof |
| CN107360505B (en) * | 2017-07-10 | 2021-06-08 | 林其亮 | High-efficiency automatic modulation booster circuit and control method |
| CN107911776B (en) * | 2017-11-30 | 2020-09-22 | 珠海亿智电子科技有限公司 | Method for eliminating POP sound on audio power amplifier |
| CN111263268B (en) * | 2020-01-15 | 2022-02-01 | 深圳创维数字技术有限公司 | Loudspeaker POP sound cancelling circuit and electronic product during outage |
| CN111510826B (en) * | 2020-05-21 | 2024-05-31 | 杭州国芯科技股份有限公司 | Circuit and method for eliminating shutdown pop sound of media playing device |
Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1862950A (en) * | 2005-05-09 | 2006-11-15 | 华硕电脑股份有限公司 | Shock-wave noise preventing circuit |
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Patent Citations (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN1862950A (en) * | 2005-05-09 | 2006-11-15 | 华硕电脑股份有限公司 | Shock-wave noise preventing circuit |
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|---|---|
| CN101330277A (en) | 2008-12-24 |
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Granted publication date: 20120208 Termination date: 20130620 |