CN101330277A - 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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- CN101330277A CN101330277A CNA2007101112644A CN200710111264A CN101330277A CN 101330277 A CN101330277 A CN 101330277A CN A2007101112644 A CNA2007101112644 A CN A2007101112644A CN 200710111264 A CN200710111264 A CN 200710111264A CN 101330277 A CN101330277 A CN 101330277A
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- loudspeaker
- power amplifier
- circuit
- voltage
- sonic boom
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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 next precharge as output capacitance of charging voltage that utilizes input capacitance allows 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 all can have sonic boom to occur in switching on and shutting down.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, allows 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 is
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
OutThe pass 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 is
V＝V
cc/2(1-e
-t/0.5RCout)，
As filling 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×ln(0.01)＝2.3RC
out
＝2.3×5k?ohms×2000uF
＝23seconds。
By with following formula as can be known 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 have the charging sonic boom problem 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, page 8) and proposed by PhilipsSemiconductors that (TDA 8932, page 16) solution all the output stage of amplifier is closed, open after all stablizing up to input charging circuit and output charging circuit, the basic principle and the preceding method of this 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 by the mild precharge to output capacitance allows 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 by 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) xCin.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 does not need by the time all electric capacity to be charged to saturatedly just can to import music signal in addition.The charging curve of input circuit is
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
5/2x 99%=5/2 (1-e
-t/20m), promptly
0.99＝1-e
-t/20m，
Or t=-20m * ln 0.01
＝0.092seconds。
The charging voltage of this moment and the difference of Vcc/2 are
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.Stand-by period has only 0.1 second and does not have the generation of second sonic boom as can be known by above discussion.
Description of drawings
Fig. 1 is the prior art circuits schematic diagram;
Fig. 2 is another prior art circuits schematic diagram;
Fig. 3 is a circuit diagram of the present invention;
Fig. 4 is a circuit sequence schematic diagram 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
The 9LC low-frequency filter
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 by 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 by 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.In order to allow the embodiment of the invention understand by more detailed quilt, 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 as icon.Amplifier is promptly exported PWM (Pulse Width Modulation, pulse width modulation) signal to the B point after the voltage that reception A is ordered as shown in Figure 4.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 finished, 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 entered 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 the 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 this moment, the discharge circuit of amplifier inside promptly discharged to the B point.At the same time SW2 also transfer high voltage to by low-voltage and open switching transistor NMOS2 (3) and with the signal of signal source through signal resistance R
s2 are shorted to ground, make 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 also is identical as its operation of AB power-like amplifier or improvement principle.
More than disclosed only be 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 (12)
- The elimination circuit of loudspeaker sonic boom is characterized in that when 1, a kind of power amplifier was started shooting and shut down, and comprising:Control unit comes guiding operation by the voltage of detecting power supply, and transmits control signal according to circuit requirements;First switch receives the charge and discharge of electric capacity in described control signal and the charge control circuit;Amplifier, amplification input signal; AndLow-frequency filter, signal that average described amplifier is exported or voltage also send filtered signal to loudspeaker device.
- The elimination circuit of loudspeaker sonic boom is characterized in that described electric capacity comprises input and output capacitors when 2, power amplifier was started shooting and shut down according to claim 1.
- The elimination circuit of loudspeaker sonic boom when 3, power amplifier is started shooting and shut down according to claim 1, it is characterized in that when described loudspeaker device was started shooting, described first switch was controlled described input capacitance charging, this charging voltage is after described amplifier amplifies, directly to described output capacitance precharge.
- The elimination circuit of loudspeaker sonic boom is characterized in that when 4, power amplifier was started shooting and shut down according to claim 1, further comprised second switch, and described second switch receives described control signal and is responsible for opening and closing the signal of described circuit sound signal source.
- The elimination circuit of loudspeaker sonic boom when 5, power amplifier is started shooting and shut down according to claim 1, it is characterized in that, when described loudspeaker device shuts down, the signal in described second switch shutoff signal source, described first switch discharges described input capacitance, and described amplifier is closed and discharge circuit discharges to described output capacitance simultaneously.
- The elimination circuit of loudspeaker sonic boom is characterized in that described first switch is a metal-oxide semiconductor when 6, power amplifier was started shooting and shut down according to claim 1.
- 7, as the elimination circuit of loudspeaker sonic boom when power amplifier start and shutdown as described in the claim 4, it is characterized in that described second switch is a metal-oxide semiconductor.
- The removing method of loudspeaker sonic boom when 8, a kind of power amplifier is started shooting and shut down comprises:Control at least one switch by control unit, the charge and discharge of electric capacity in wherein said at least one ON-OFF control circuit; AndDuring start, the electric capacity in the charging can drive loudspeaker and come precharge; The capacitor discharge that charges during shutdown is to ground voltage.
- 9, as the removing method of loudspeaker sonic boom when power amplifier start and shutdown as described in the claim 8, it is characterized in that described control unit is controlled described switch by sending control signals to described switch.
- 10, as the removing method of loudspeaker sonic boom when power amplifier start and shutdown as described in the claim 8, it is characterized in that described control unit comes guiding operation by the voltage of detecting power supply.
- 11, as the removing method of loudspeaker sonic boom when power amplifier start and shutdown as described in the claim 8, it is characterized in that, further comprise and set up another switch to be responsible for open and close circuit signal source.
- 12, as the removing method of loudspeaker sonic boom when power amplifier start and shutdown as described in the claim 8, it is characterized in that described electric capacity comprises input capacitance and output capacitance.
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 true CN101330277A (en) | 2008-12-24 |
| CN101330277B CN101330277B (en) | 2012-02-08 |
Family
ID=40205914
Family Applications (1)
| 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 |
Country Status (1)
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| CN101924969A (en) * | 2009-06-17 | 2010-12-22 | 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 |
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| CN111263268A (en) * | 2020-01-15 | 2020-06-09 | 深圳市创维群欣安防科技股份有限公司 | Loudspeaker POP sound cancelling circuit and electronic product during outage |
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| CN100417016C (en) * | 2005-05-09 | 2008-09-03 | 华硕电脑股份有限公司 | Shock-wave noise preventing circuit |
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- 2007-06-20 CN CN2007101112644A patent/CN101330277B/en not_active Expired - Fee Related
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| 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 |
| CN101924969A (en) * | 2009-06-17 | 2010-12-22 | 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 |
| CN102629855A (en) * | 2012-04-13 | 2012-08-08 | 成都芯源***有限公司 | Noise suppression circuit and control method thereof |
| CN102629855B (en) * | 2012-04-13 | 2015-04-08 | 成都芯源***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 |
| CN107360505A (en) * | 2017-07-10 | 2017-11-17 | 深圳市中移联半导体科技有限公司 | A kind of high-effect automatic modulation booster circuit and control method |
| WO2019010967A1 (en) * | 2017-07-10 | 2019-01-17 | 深圳市中移联半导体科技有限公司 | High efficiency automatic modulation voltage boost circuit and control method |
| CN107911776A (en) * | 2017-11-30 | 2018-04-13 | 珠海亿智电子科技有限公司 | A kind of method for eliminating audio frequency power amplifier and powering on POP sound |
| 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 |
| CN111263268A (en) * | 2020-01-15 | 2020-06-09 | 深圳市创维群欣安防科技股份有限公司 | Loudspeaker POP sound cancelling circuit and electronic product during outage |
| CN111510826A (en) * | 2020-05-21 | 2020-08-07 | 杭州国芯科技股份有限公司 | Circuit and method for eliminating shutdown popping of media playing equipment |
| 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 |
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Granted publication date: 20120208 Termination date: 20130620 |