CN114142814A - Noise suppression circuit and method in starting process of audio amplifier - Google Patents
Noise suppression circuit and method in starting process of audio amplifier Download PDFInfo
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- CN114142814A CN114142814A CN202010979683.5A CN202010979683A CN114142814A CN 114142814 A CN114142814 A CN 114142814A CN 202010979683 A CN202010979683 A CN 202010979683A CN 114142814 A CN114142814 A CN 114142814A
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Abstract
The invention provides a noise suppression circuit and a method in the starting process of an audio amplifier, wherein the noise suppression circuit in the starting process of the audio amplifier comprises the following steps: the state conversion module is used for switching between the starting state and the working state of the audio amplifier; the audio amplification module is connected with the state conversion module and used for following the starting voltage of the audio amplifier in the starting state or amplifying the audio input signal in the working state; and the volume modulation module is respectively connected with the state conversion module and the audio amplification module and is used for adjusting the audio input signal in the working state. The invention effectively inhibits the POP noise of the audio amplifier by controlling the output voltage in the starting and establishing process and controlling the slow rise of the reference voltage after starting.
Description
Technical Field
The invention belongs to the technical field of audio amplifiers, relates to a noise suppression circuit, and particularly relates to a noise suppression circuit and a suppression method in the starting process of an audio amplifier.
Background
The audio output circuit is used for amplifying an audio input signal and driving a post-stage circuit, for example, when the audio output circuit of an earphone or a loudspeaker is powered on (power on), powered off (power off), quitted from an off state (power is turned on in advance) and forcibly turned off (power is not turned off), output voltage can generate step or pulse, an objectionable transient signal which can be heard by human ears and audible POP noise (POP-noise) can be easily generated as an audio product, and the user experience can be greatly reduced.
Therefore, how to provide a noise suppression circuit and a suppression method in the start-up process of an audio amplifier to solve the defects that the prior art cannot effectively suppress POP noise and the like generated in the start-up process of the audio amplifier becomes a technical problem to be solved by those skilled in the art.
Disclosure of Invention
In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a noise suppression circuit and a suppression method during the start-up of an audio amplifier, which are used to solve the problem that the prior art cannot effectively suppress POP noise generated during the start-up of the audio amplifier.
To achieve the above and other related objects, an aspect of the present invention provides a noise suppression circuit during a start-up process of an audio amplifier, including: the state conversion module is used for switching between the starting state and the working state of the audio amplifier; the audio amplification module is connected with the state conversion module and used for following the starting voltage of the audio amplifier in the starting state or amplifying the audio input signal in the working state; the volume modulation module is respectively connected with the state conversion module and the audio amplification module and is used for adjusting the audio input signal in the working state; when the state conversion module is switched to a starting state, the state conversion module and the audio amplification module form a follower, so that the audio amplifier is started according to the starting voltage, and the starting voltage is in an ascending trend; when the state conversion module is switched to a working state, the audio input signal enters the audio amplification module through the volume modulation module to be amplified.
In an embodiment of the present invention, the state conversion module includes a first switch unit and a second switch unit; the first switch unit is used for being conducted in the starting state, so that the state conversion module and the audio amplification module form a follower, the output voltage is kept at 0V when the audio amplification module is started, and the starting voltage is enabled to start the audio amplifier in a curve rising mode after the audio amplification module is started; the second switch unit is used for being conducted in the working state, so that the audio input signal enters the audio amplification module through the volume modulation module to be subjected to signal amplification.
In an embodiment of the present invention, the audio amplifying module includes a first stage amplifying unit and a second stage amplifying unit; the first-stage amplification unit is connected with the second-stage amplification unit; the first-stage amplification unit is used for converting signals of a positive input end and a negative input end of the audio amplification module into two paths of modulation voltages; the second-stage amplifying unit is used for carrying out push-pull output on the two paths of modulation voltages.
In an embodiment of the invention, the first-stage amplifying unit is a folded cascode structure, and includes a common-source tube unit and a common-gate tube unit, the common-source tube unit is connected to the common-gate tube unit, and is configured to convert signals at a positive input end and a negative input end of the audio amplifying module into two current signals in a differential manner, and the common-gate tube unit is configured to convert the two current signals into two modulation voltages.
In an embodiment of the present invention, the common-source unit includes a first MOS transistor, a second MOS transistor, and a third MOS transistor; the second MOS tube and the third MOS tube form a current mirror, the first MOS tube provides bias current for the current mirror, and drain electrodes of the second MOS tube and the third MOS tube output the two paths of current signals; the common-gate tube unit is composed of at least two MOS tube pairs, and the MOS tube pairs are used for converting the two current signals into two voltage signals.
In an embodiment of the present invention, the second-stage amplifying unit is a push-pull output structure, and includes an on-off subunit, a potential control subunit, and a negative feedback output subunit; the on-off subunit is used for inputting the two paths of modulation voltages to the potential control subunit when the voltage is started, and the potential control subunit is used for enabling the negative feedback output subunit to output 0V when the on-off subunit is disconnected; and the negative feedback output subunit is used for reversely amplifying the two paths of modulation voltages when the on-off subunit is switched on so as to keep the output voltage of the second-stage amplification unit at 0V.
In an embodiment of the present invention, the on-off subunit includes a first voltage signal on-off control tube and a second voltage signal on-off control tube; the potential control subunit comprises a high potential control tube and a low potential control tube, the high potential control tube is used for controlling the output voltage of the second-stage amplification unit to be high potential, and the low potential control tube is used for controlling the output voltage of the second-stage amplification unit to be 0V.
In an embodiment of the present invention, the volume modulation module includes a first modulation unit and a second modulation unit, and the first modulation unit is connected to the second modulation unit; the first modulation unit and the second modulation unit realize resistance value adjustment through control signals so as to adjust the amplification proportion of the audio input signals.
The invention also provides a noise suppression method in the starting process of the audio amplifier, which comprises the following steps: sending a control instruction to the audio amplifier according to the starting and stopping state of audio playing so as to execute different switching states when the audio amplifier is opened; when the switching state is a starting state, starting the audio amplifier by using a starting voltage output by the follower, wherein the starting voltage is in an ascending trend; and when the switching state is a working state, performing signal amplification on the input audio input signal.
In an embodiment of the present invention, the follower is composed of a state conversion module and an audio amplification module; when the switching state is a starting state, the step of starting the starting voltage in a curve rising mode by using the follower comprises the following steps of: the audio amplifier comprises a folded cascode structure, a push-pull output structure, a starting voltage and a push-pull output structure, wherein the folded cascode structure is used for carrying out primary amplification on the starting voltage, the push-pull output structure is used for carrying out secondary amplification on a voltage signal after the primary amplification, so that the output voltage is kept at 0V when the audio amplification module is started, and the starting voltage is used for starting the audio amplifier in a curve rising mode after the audio amplification module is started.
As described above, the noise suppression circuit and the suppression method in the audio amplifier turn-on process according to the present invention have the following advantages:
the invention provides a circuit for suppressing POP noise in an audio amplifier. The circuit controls the output end voltage of the output stage of the audio amplifier to be 0V all the time in the starting and establishing process of the audio amplifier, eliminates voltage pulse generated in the establishing process of the audio amplifier, and accordingly eliminates POP noise in the starting and establishing process of the audio amplifier. After the audio amplifier circuit is started, the reference voltage connected with one end of the audio amplifier slowly and smoothly rises from an initial value to reach a reference voltage value for enabling the audio amplifier to normally work, and the reference voltage slowly and smoothly rises further and effectively prevents POP noise of the audio amplifier from being generated.
Drawings
Fig. 1 is a schematic diagram of a noise suppression circuit in an audio amplifier start-up process according to an embodiment of the present invention.
Fig. 2 is a schematic circuit diagram of a noise suppression circuit in an audio amplifier start-up process according to an embodiment of the invention.
Fig. 3 is an amplifying circuit diagram of the noise suppression circuit in the audio amplifier starting process according to an embodiment of the invention.
Fig. 4 is a schematic flow chart illustrating a method for suppressing noise during the start-up of an audio amplifier according to an embodiment of the present invention.
FIG. 5 is a timing diagram illustrating a noise suppression method during the turn-on process of an audio amplifier according to an embodiment of the present invention.
Fig. 6 is a schematic diagram illustrating the start-up voltage control of the noise suppression method during the start-up process of the audio amplifier according to an embodiment of the invention.
Description of the element reference numerals
Noise suppression circuit in starting process of audio amplifier
11 state conversion module
12 audio frequency amplifying module
13 volume modulation module
S41-S43
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.
It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
The method for suppressing the noise in the starting process of the audio amplifier effectively suppresses the POP noise in the starting process of the audio amplifier by controlling the output voltage to be kept at 0V when the audio amplifier module is started and established and performing two stages that the starting voltage slowly rises to reach the normal working voltage when the whole audio amplifier is started.
The principle and implementation of the noise suppression circuit and the suppression method in the audio amplifier turn-on process of the present embodiment will be described in detail below with reference to fig. 1 to 6, so that those skilled in the art can understand the noise suppression circuit and the suppression method in the audio amplifier turn-on process of the present embodiment without creative efforts.
Fig. 1 is a schematic diagram of a noise suppression circuit in an audio amplifier start-up process according to an embodiment of the present invention. As shown in fig. 1, the noise suppression circuit 1 in the audio amplifier starting process includes: a state conversion module 11, an audio amplification module 12 and a volume modulation module 13.
The state transition module 11 is configured to switch between a start-up state and an operating state of the audio amplifier.
The audio amplification module 12 is connected to the state transition module 11, and is configured to follow a start voltage of the audio amplifier in the start state or amplify an audio input signal in the working state.
The volume modulation module 13 is respectively connected to the state conversion module and the audio amplification module, and is configured to adjust the audio input signal in the operating state.
When the state conversion module 11 is switched to a starting state, the state conversion module 11 and the audio amplification module 12 form a follower, so that the audio amplifier is started according to the starting voltage, and the starting voltage is in a rising trend; when the state switching module 11 is switched to the working state, the audio input signal enters the audio amplifying module 12 through the volume modulation module 13 for signal amplification.
Fig. 2 is a schematic circuit diagram of a noise suppression circuit in the audio amplifier start-up process according to an embodiment of the invention. As shown in fig. 2, the state transition module 11 includes a first switch unit SW1 and a second switch unit SW 2. It should be noted that, although SW1 and SW2 in fig. 2 are shown by switch symbols only, they do not represent a mechanical single-pole switch in practical application, but rather, the switch functions of SW1 and SW2 are realized by a circuit in which one or more MOS transistors are combined through a MOS transistor circuit controlled by a digital signal.
The first switch unit SW1 is configured to be turned on in the startup state, so that the state transition module and the audio amplification module PA _ OP form a follower, so that the output voltage of the audio amplification module PA _ OP is kept at 0V when the audio amplification module PA _ OP is started, and after the audio amplification module PA _ OP is started up, the start voltage PA _ VCMO starts up the audio amplifier in a curve-up manner. The starting voltage PA _ VCMO is a common-mode reference voltage of the audio amplifier in practical application.
The second switch unit SW2 is configured to be turned on IN the operating state, so that the audio input signal PA _ IN enters the audio amplification module PA _ OP through the volume modulation module for signal amplification.
In fig. 2, the volume modulation module 13 includes a first modulation unit R1 and a second modulation unit R2, and the first modulation unit R1 and the second modulation unit R2 are connected.
The first modulation unit R1 and the second modulation unit R2 realize resistance value adjustment through control signals so as to adjust the amplification ratio of the audio input signal PA _ IN.
It should be noted that R1 and R2 are digital signal controlled adjustable resistors, i.e., digital potentiometers or digitally controlled programmable resistors, and the adjustable resistors are enabled to reach preset resistance values by digital signals.
In fig. 2, the whole circuit of the state transition module 11, the audio amplification module 12 and the volume modulation module 13 constitutes an audio amplifier or a local circuit of the audio amplifier, and in practical applications, the circuit may further constitute the audio amplifier by adding other peripheral circuits for optimizing the audio amplifier. The switching process of the two states of the audio amplifier is as follows: in normal operation, SW2 is closed, SW1 is opened, and the ratio of R1 to R2 is adjusted, namely the gain of the audio amplifier is adjusted. When SW2 is opened and SW1 is closed, the audio amplifier becomes a buffer and a follower to start the audio amplifier.
Specifically, before the audio amplifier is started, SW1 is closed and SW2 is opened in fig. 1, the audio amplifier becomes a buffer, and after PA _ OP is started, the voltage of PA _ OUT is equal to PA _ VCMO due to feedback. The PA _ VCMO initial voltage is 0V, and after PA _ OP is started, PA _ VCMO starts to slowly rise from 0V to the common mode reference voltage 0.5 VDD, and PA _ OUT will slowly rise from 0V to the common mode level VCMO following PA _ VCMO, and this slow rising process is to avoid POP noise, but at the time of PA _ OP start, the PA _ OP setup will bring a spike signal to PA _ OUT, and this pulse generates POP noise. To eliminate this pulse due to PA _ OP build-up, the present invention employs the two-stage amplification circuit configuration of fig. 3.
Fig. 3 is an amplifying circuit diagram of a noise suppression circuit in the audio amplifier starting process according to an embodiment of the invention. As shown in fig. 3, the audio amplifying module PA _ OP includes a first-STAGE amplifying unit STAGE1 and a second-STAGE amplifying unit STAGE 2; the first-STAGE amplifying unit STAGE1 and the second-STAGE amplifying unit STAGE2 are connected.
The first-STAGE amplifying unit STAGE1 is configured to convert signals of the positive input end INP and the negative input end INN of the audio amplifying module PA _ OP into two modulation voltages VON1 and VON 2.
The second-STAGE amplifying unit STAGE2 is configured to perform push-pull output on the two modulation voltages VON1 and VON 2.
In fig. 3, the first-STAGE amplifying unit STAGE1 is a folded cascode structure, and includes a common-source tube unit and a common-gate tube unit, where the common-source tube unit is connected to the common-gate tube unit, and is configured to convert signals at a positive input end and a negative input end of the audio amplifying module PA _ OP into two current signals (a drain current signal of PM11 and a drain current signal of PM 12) in a differential manner, and the common-gate tube unit is configured to convert the two current signals into two modulation voltages VON1 and VON 2.
In fig. 3, the common source unit includes a first MOS transistor PM13, a second MOS transistor PM11, and a third MOS transistor PM 12; the second MOS transistor PM11 and the third MOS transistor PM12 constitute a current mirror, the first MOS transistor PM13 provides a bias current for the current mirror, and the drains of the second MOS transistor PM11 and the third MOS transistor PM12 output the two current signals.
The common-gate tube unit is composed of at least two MOS tube pairs, and the MOS tube pairs are used for converting the two current signals into two voltage signals. In the practical application of fig. 3, the MOS transistors include a pair of MOS transistors (PM5-1 and PM5-2), a pair of MOS transistors (PM6 and PM8), a pair of MOS transistors (PM10, NM9 and NM8, PM9), a pair of MOS transistors (NM6 and NM4), and a pair of MOS transistors (NM7 and NM 5).
In fig. 3, the second-STAGE amplifying unit STAGE2 is a push-pull output structure, and includes an on-off sub-unit (NM2, PM3, PM4, NM3), a potential control sub-unit (PM2-1, PM2-2), and a negative feedback output sub-unit (PM1, NM 1).
The on-off subunit is used for inputting the two paths of modulation voltages to the potential control subunit when the voltage is started, and the potential control subunit is used for enabling the negative feedback output subunit to output 0V when the on-off subunit is disconnected; and the negative feedback output subunit is used for reversely amplifying the two paths of modulation voltages when the on-off subunit is switched on so as to keep the output voltage of the second-stage amplification unit at 0V.
In fig. 3, the on-off subunit includes first voltage signal on-off control tubes PM4, NM3 and second voltage signal on-off control tubes NM2, PM 3.
The potential control subunit comprises a high potential control tube PM2-1 and a low potential control tube PM2-2, the high potential control tube PM2-1 is used for controlling the output voltage OUT of the second-STAGE amplification unit STAGE2 to be at a high potential, and the low potential control tube PM2-2 is used for controlling the output voltage OUT of the second-STAGE amplification unit STAGE2 to be at 0V.
The specific working process of PA _ OP in fig. 3 is: before PA _ OP is started, PDN is 0(PDN is a starting control signal, all BIAS biases in the circuit are controlled by the PDN, specifically, when the PDN signal is 0, a PDN signal is used for controlling MOS tubes additionally connected to gates where VBP1 and VBP2 are located, VBP1 and VBP2 are pulled to a power supply voltage through the connected MOS tubes to be in an off state, the PDN signal is used for controlling MOS tubes additionally connected to the gates where VBN1, VBN2 and VBN3 are located, VBN1, VBN2 and VBN3 are pulled to a ground potential through the connected MOS tubes to be in an off state, when the PDN signal is in a high potential, the MOS tubes for controlling VBP1, VBP2, VBN1, VBN2 and VBN 5 are connected to a low potential, the PDN signal is connected to a low potential, and the PDN signal is connected to an external voltage, so that the PDN signal is connected to a high potential, a low potential, a voltage and a voltage feedback signal feedback, a feedback signal, a feedback signal, and a feedback signal, wherein the feedback circuit, and a feedback circuit are respectively comprise a feedback circuit, wherein the feedback circuit, and a feedback circuit, wherein the feedback circuit are respectively comprise a feedback circuit, and a feedback circuit, wherein the feedback circuit, and a feedback circuit, wherein the feedback circuit are respectively comprise a feedback circuit, and a feedback circuit, wherein before the feedback circuit are respectively comprise a feedback circuit, before the feedback circuit, and a feedback circuit, before the feedback circuit, and a feedback circuit are respectively comprise a feedback circuit, and a feedback circuit, before the feedback circuit, and the feedback circuit, before the feedback circuit, wherein before the feedback circuit, and the feedback circuit, before the feedback circuit, and the feedback circuit.
Then, PA _ OP is started, PDN is made equal to VDD, DOWN is made equal to 0V, so that OUT is always kept equal to 0V, INP is made equal to 0V, and after station 1 is established, SW is turned high and SW is turned low, so that NM2, PM3, NM3, and PM4 are turned on, and then DOWN is released and turned high, so that voltages of VON2 and VON1 can be ensured to keep OUT at 0V, which avoids generating sharp pulses with large amplitude. After PA _ OP is started, PA _ VCMO in fig. 2 is slowly raised, and PA _ OUT also slowly rises following PA _ VCMO due to the follower feedback.
Please refer to fig. 4, which is a schematic flowchart illustrating a method for suppressing noise during the start-up of an audio amplifier according to an embodiment of the present invention. As shown in fig. 4, the noise suppression method in the audio amplifier starting process specifically includes the following steps:
and S41, sending a control instruction to the audio amplifier according to the start-stop state of audio playing so as to execute different switching states when the audio amplifier is opened. Specifically, when the sound is to be played, the upper computer sends an opening control instruction to open the audio amplifier, and when the playing is finished, the upper computer sends a closing control instruction to close the audio amplifier. And when the audio amplifier is turned on, controlling the noise suppression circuit in the turn-on process of the audio amplifier according to the preset time sequence of each signal so as to eliminate POP sound.
And S42, when the switching state is a starting state, starting the audio amplifier by using the starting voltage output by the follower, wherein the starting voltage is in an ascending trend.
In this embodiment, the follower is composed of a state conversion module and an audio amplification module.
Specifically, the starting voltage is subjected to primary amplification through a folded cascode structure, a voltage signal subjected to the primary amplification is subjected to secondary amplification through a push-pull output structure, so that the output voltage is kept at 0V when the audio amplification module is started, and the starting voltage is subjected to starting of the audio amplifier in a curve rising manner after the audio amplification module is started.
Specifically, the audio amplifier is of a two-stage operational amplifier structure, and is connected into a follower type in the process of establishing the audio amplifier, and the initial input reference voltage is 0V. The output stage of the audio amplifier is then disconnected from the previous stage and the input of the output stage is controlled to clamp the output voltage to 0V. The audio amplifier circuit is then enabled. The output of the audio amplifier is always 0V at this time. No step or pulse is generated. When the audio amplifier connected into a follower type is established, the connection between the input stage and the output stage of the audio amplifier is conducted, and the output of the first stage is very close to the input voltage of the second stage, so that the fluctuation of the output voltage of the second stage is very small, and the human ears can hardly hear the fluctuation.
Please refer to fig. 5, which is a timing signal diagram illustrating a noise suppression method in the audio amplifier start-up process according to an embodiment of the present invention. As shown in fig. 5, PDN is an on control signal of the audio amplifier, 0 is off, and 1 is on. SW and _ SW are signals that control switching between two stages of the audio amplifier. And _ DOWN is the control signal output by the pull-DOWN audio amplifier. The PA _ VCMO _ RAMP _ PD low level is used to turn on the PA _ VCMO signal to RAMP slowly. The MUTE high level is used for controlling the SW1 to be turned on and the SW2 to be turned off in the figure 2, so that the audio amplifier is connected into a buffer form, and the high level is changed into the low level after the voltage climbs for 200ms, so that the SW2 is turned on, and the SW1 is turned off to enter a normal operation mode.
Specifically, PDN is first 0, SW is 0, _ SW is 1, so that STAGE1 and STAGE2 of PA _ OP are disconnected, _ DOWN is first 0, so that PM2 is on, NM1 is on, and OUT output is 0V of VSSA, and then PDN is high, SW is 1, _ SW is 0, so that STAGE1 and STAGE2 of PA _ OP are communicated, and _ DOWN is 1, so that OUT output is kept at 0V due to the negative feedback effect of the negative feedback output subunit; then, in the follower mode where MUTE is 1, SW1 is turned on, and SW2 is turned off, PA _ VCMO _ RAMP _ PD becomes 0, so that the PA _ VCMO signal slowly rises.
And S43, when the switching state is the working state, performing signal amplification on the input audio input signal.
Therefore, the technology for eliminating the POP noise mainly comprises three technologies: firstly, the output of the audio amplifier is controlled to slowly rise to the common-mode voltage after being started, and the step jump of the output voltage is avoided. And secondly, the driving capability of the output of the audio amplifier is controlled, the driving capability of the output stage is limited in the starting and establishing process of the audio amplifier, and the normal driving capability of the output stage is recovered after the establishment is finished. Thirdly, the output voltage control of the audio amplifier in the starting and establishing process is added on the basis of combining the two points, so that the POP noise caused by sharp pulse generation of the output voltage due to the fact that the circuit feedback is not completely established is avoided.
Fig. 6 is a schematic diagram illustrating a start-up voltage control of the noise suppression method in the start-up process of the audio amplifier according to an embodiment of the invention. As shown in fig. 6, a is the spike V _ pulse appearing in the prior art, and b is the graph of the starting voltage VCMO in the suppression circuit or the suppression method of the present invention, so that the present invention effectively eliminates POP noise caused by the spike.
The protection scope of the noise suppression method in the audio amplifier starting process according to the present invention is not limited to the execution sequence of the steps listed in this embodiment, and all the schemes of adding, subtracting, and replacing steps in the prior art according to the principle of the present invention are included in the protection scope of the present invention.
In summary, the noise suppression circuit and method for audio amplifier turn-on process of the present invention provides a circuit for suppressing POP noise in an audio amplifier. The circuit controls the output end voltage of the output stage of the audio amplifier to be 0V all the time in the starting and establishing process of the audio amplifier, eliminates voltage pulse generated in the establishing process of the audio amplifier, and accordingly eliminates POP noise in the starting and establishing process of the audio amplifier. After the audio amplifier circuit is started, the reference voltage connected with one end of the audio amplifier slowly and smoothly rises from an initial value to reach a reference voltage value for enabling the audio amplifier to normally work, and the reference voltage slowly and smoothly rises further and effectively prevents POP noise of the audio amplifier from being generated. The invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A circuit for suppressing noise during start-up of an audio amplifier, the circuit comprising:
the state conversion module is used for switching between the starting state and the working state of the audio amplifier;
the audio amplification module is connected with the state conversion module and used for following the starting voltage of the audio amplifier in the starting state or amplifying the audio input signal in the working state;
the volume modulation module is respectively connected with the state conversion module and the audio amplification module and is used for adjusting the audio input signal in the working state;
when the state conversion module is switched to a starting state, the state conversion module and the audio amplification module form a follower, so that the audio amplifier is started according to the starting voltage, and the starting voltage is in an ascending trend; when the state conversion module is switched to a working state, the audio input signal enters the audio amplification module through the volume modulation module to be amplified.
2. The circuit of claim 1, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the state conversion module comprises a first switch unit and a second switch unit;
the first switch unit is used for being conducted in the starting state, so that the state conversion module and the audio amplification module form a follower, the output voltage is kept at 0V when the audio amplification module is started, and the starting voltage is enabled to start the audio amplifier in a curve rising mode after the audio amplification module is started;
the second switch unit is used for being conducted in the working state, so that the audio input signal enters the audio amplification module through the volume modulation module to be subjected to signal amplification.
3. The circuit of claim 1, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the audio amplification module comprises a first-stage amplification unit and a second-stage amplification unit; the first-stage amplification unit is connected with the second-stage amplification unit;
the first-stage amplification unit is used for converting signals of a positive input end and a negative input end of the audio amplification module into two paths of modulation voltages;
the second-stage amplifying unit is used for carrying out push-pull output on the two paths of modulation voltages.
4. The circuit of claim 3, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the first-stage amplification unit is of a folding cascode structure and comprises a cascode unit and a common-gate tube unit, the cascode unit is connected with the common-gate tube unit and is used for converting signals of a positive input end and a negative input end of the audio amplification module into two current signals in a differential mode, and the common-gate tube unit is used for converting the two current signals into two modulation voltages.
5. The circuit of claim 4, wherein the noise suppression circuit during the turn-on of the audio amplifier comprises:
the common source unit comprises a first MOS tube, a second MOS tube and a third MOS tube; the second MOS tube and the third MOS tube form a current mirror, the first MOS tube provides bias current for the current mirror, and drain electrodes of the second MOS tube and the third MOS tube output the two paths of current signals;
the common-gate tube unit is composed of at least two MOS tube pairs, and the MOS tube pairs are used for converting the two current signals into two voltage signals.
6. The circuit of claim 3, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the second-stage amplification unit is of a push-pull output structure and comprises a switching sub-unit, a potential control sub-unit and a negative feedback output sub-unit;
the on-off subunit is used for inputting the two paths of modulation voltages to the potential control subunit when the voltage is started, and the potential control subunit is used for enabling the negative feedback output subunit to output 0V when the on-off subunit is disconnected; and the negative feedback output subunit is used for reversely amplifying the two paths of modulation voltages when the on-off subunit is switched on so as to keep the output voltage of the second-stage amplification unit at 0V.
7. The circuit of claim 6, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the on-off subunit comprises a first voltage signal on-off control tube and a second voltage signal on-off control tube;
the potential control subunit comprises a high potential control tube and a low potential control tube, the high potential control tube is used for controlling the output voltage of the second-stage amplification unit to be high potential, and the low potential control tube is used for controlling the output voltage of the second-stage amplification unit to be 0V.
8. The circuit of claim 1, wherein the noise suppression circuit during turn-on of the audio amplifier comprises:
the volume modulation module comprises a first modulation unit and a second modulation unit, and the first modulation unit is connected with the second modulation unit;
the first modulation unit and the second modulation unit realize resistance value adjustment through control signals so as to adjust the amplification proportion of the audio input signals.
9. A method for suppressing noise during the starting process of an audio amplifier is characterized in that the method for suppressing noise during the starting process of the audio amplifier comprises the following steps:
sending a control instruction to the audio amplifier according to the starting and stopping state of audio playing so as to execute different switching states when the audio amplifier is opened;
when the switching state is a starting state, starting the audio amplifier by using a starting voltage output by the follower, wherein the starting voltage is in an ascending trend;
and when the switching state is a working state, performing signal amplification on the input audio input signal.
10. The method of claim 9, wherein the follower comprises a state conversion module and an audio amplification module; when the switching state is a starting state, the step of starting the starting voltage in a curve rising mode by using the follower comprises the following steps of:
the audio amplifier comprises a folded cascode structure, a push-pull output structure, a starting voltage and a push-pull output structure, wherein the folded cascode structure is used for carrying out primary amplification on the starting voltage, the push-pull output structure is used for carrying out secondary amplification on a voltage signal after the primary amplification, so that the output voltage is kept at 0V when the audio amplification module is started, and the starting voltage is used for starting the audio amplifier in a curve rising mode after the audio amplification module is started.
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