CN101534463B - A noise elimination device - Google Patents
A noise elimination device Download PDFInfo
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- CN101534463B CN101534463B CN 200910130436 CN200910130436A CN101534463B CN 101534463 B CN101534463 B CN 101534463B CN 200910130436 CN200910130436 CN 200910130436 CN 200910130436 A CN200910130436 A CN 200910130436A CN 101534463 B CN101534463 B CN 101534463B
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Abstract
The invention provides a noise elimination device, which comprises a delay unit and a control unit; wherein the delay unit is connected between a power output end and a first load in series; under the control of the control unit, the delay unit distributes the current flowing to the first load to prolong the time for an audio circuit to construct a quiescent operating point; the control unit which is connected to the delay unit is used for controlling whether the delay unit works based on the received control signal. The device solves the problem of the prior art that noise is generated when the current rush passes the load at the moment of electrifying, thereby improving the user experience.
Description
Technical Field
The invention relates to the field of communication, in particular to a noise elimination device.
Background
With the development of electronic technology, miniaturized electronic products, such as MP3, MP4, PDA, Digital Camera (DC), home video camera (DV), and the like, are becoming more popular. The electronic products are mainly powered by batteries, and in order to enhance the cruising ability of the batteries, most electronic products adopt a strategy of 'power supply on demand', namely, when a user uses a certain function, the electronic product starts a power supply part corresponding to the function, so that unnecessary loss is reduced.
The above strategy is effective for reducing power consumption of electronic products, but for audio devices in electronic products, the strategy may cause the following problems: when a user uses an audio function, the electronic product starts a corresponding audio output circuit, and at the moment, the voltage rises instantly to generate impulse current, so that noise (which can be called POP) sound is generated, and the experience of the user is reduced.
FIG. 1 is a schematic circuit diagram of a power output part of an audio device loaded with R1, R2, and R in the related artLDiodes D1 and D2, and trios T1, T2 and T3, and capacitor C1, the specific connection of the components is shown in fig. 1. Based on the above strategy, when the audio function signal is used, the power supply of the power amplifier circuit corresponding to the audio function is started, i.e. Vcc shown in fig. 1 is turned on. Since the circuit needs to establish a quiescent operating point, the output coupling capacitor C1 is charged first, with the current flow from left to right through the load RL(RLTypically a headphone with a resistance of 32 omega or an 8 omega speaker) to ground. Since the human ear is very sensitive, a voltage of about 50mV is applied to RLThe sound generated at the two ends can be sensed by human ears, so that the noise (POP sound) generated at the moment of starting the circuit is sensed by a user, and the experience of the user is influenced.
In summary, the electronic product including the audio device has a problem that noise is generated due to the adoption of the power on demand strategy, so that the experience of the user is affected, and an effective solution is not provided at present.
Disclosure of Invention
The invention is provided aiming at the problem that the noise is generated by adopting the power supply on demand strategy, and the experience of a user is further influenced. To this end, the present invention aims to provide an improved noise cancellation solution to solve at least one of the above problems.
In order to achieve the above object, according to the present invention, there is provided a noise canceling device applied to a circuit including a power output terminal and a first load.
The noise canceling device according to the present invention includes: the delay unit is connected between the power output end and the first load in series and used for prolonging the time of the audio circuit for establishing a static working point by shunting current flowing to the first load under the control of the control unit; and the control unit is connected to the delay unit and used for controlling whether the delay unit works or not according to the received control signal.
Preferably, the delay unit is an integrating circuit.
Wherein, the delay unit comprises: the second load is connected between the power output end and the first load in series; and the capacitor is connected between the second load and the ground level in series.
The control unit includes: the control pin is used for receiving a control signal; the first switch is connected to the control pin, connected with the second load in parallel and used for short-circuiting the second load under the control of the control signal; the second switch is connected to the control pin and is connected between the capacitor and the ground level in series, and is used for enabling the current flowing through the capacitor to flow to the ground level under the control of the signal; wherein the first switch and the second switch are configured to: according to the control signal, the second switch opens the circuit between the capacitor and the ground level while the first switch short-circuits the second load; alternatively, the second switch allows a path between the capacitor and ground while the first switch operates the second load.
The control signal is used for representing the power-on condition of the audio circuit, wherein when the control signal represents that the power-on condition of the audio circuit is to be powered on, the first switch enables the second load to work, and the second switch enables a passage between the capacitor and the ground level; and under the condition that the control signal indicates that the power-on condition of the audio circuit is the power-on completion condition, the first switch enables the second load to be in short circuit, and the second switch enables the capacitor to be disconnected with the ground level.
Preferably, the first switch is an audio analog switch.
Preferably, the second switch is a triode, wherein a base of the triode is connected with the control pin, a collector of the triode is connected with the capacitor in series, and an emitter of the triode is connected with the ground level.
Preferably, the apparatus further comprises: a first bias load connected in parallel with the capacitor; the second bias load is connected between the control pin and the base electrode of the triode in series; and the third bias load is connected between the base electrode of the triode and the ground level.
By means of at least one of the technical schemes, the delay unit for shunting the current flowing to the load is connected in series between the power output stage of the audio circuit and the load, so that the time for establishing the static working point of the audio circuit is prolonged, the problem of noise generated when the impulse current at the moment of power-on passes through the load in the prior art is solved, and the experience of a user is further improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the invention without limiting the invention. In the drawings:
fig. 1 is an audio circuit diagram of an audio device in the related art;
fig. 2 is a block diagram of an audio apparatus including a noise canceling device according to an embodiment of the present invention;
FIG. 3 is a block diagram of a preferred structure of a noise canceling device according to an embodiment of the present invention;
FIG. 4 is an audio circuit diagram including a noise canceling device according to an embodiment of the present invention;
fig. 5 is a circuit diagram of one configuration example of a shunt circuit in the noise canceling device shown in fig. 4;
FIG. 6 is a simulation diagram of a measured waveform at the moment of power-on at the input terminal of a coupling capacitor in the related art;
FIG. 7 is a simulation diagram of the measured waveform at the moment of power-on at the input end of the coupling capacitor after the noise canceling device according to the embodiment of the present invention is applied;
fig. 8 is a schematic circuit diagram of a simple circuit for applying the noise canceling device according to the embodiment of the present invention to an audio apparatus.
Detailed Description
Overview of the function
As described above, due to the adoption of the "power on demand" strategy in the related art, the impulse current generated by the audio circuit at the moment of power-on generates noise when passing through the load, thereby affecting the experience of the user. Based on this, the invention provides a noise elimination scheme, that is, by connecting a delay unit in series between the power output stage of the audio circuit and the load, the delay unit can shunt impulse current which is generated at the moment of power-on and flows to the load, so that the current which flows to the load is not enough to generate noise which affects the experience of the user, thereby effectively improving the user experience.
The present invention will be described in detail below with reference to the accompanying drawings in conjunction with embodiments. It should be noted that the embodiments and features of the embodiments in the present application may be combined with each other without conflict.
According to an embodiment of the present invention, there is provided a noise canceling device applied to an audio circuit including a power output terminal and a load. Fig. 2 is a block diagram of an audio apparatus including a noise removing device according to an embodiment of the present invention, as shown in fig. 2, the noise removing device including: delay unit 1 and control unit 2. The delay unit 1 is connected in series between the power output terminal and a load (i.e., the load 1 in the figure), and is used for prolonging the time of the audio circuit establishing a static operating point by shunting current flowing to the load 1 under the control of the control unit; and the control unit 2 is connected to the delay unit 1 and used for controlling whether the delay unit works or not according to the received control signal.
As can be seen from the above description, the delay unit 1 shunts the impulse current passing through the load 1, so that the time for the audio circuit to establish the quiescent operating point is prolonged, noise generated when the impulse current passes through the load 1 in the prior art is avoided, and the user experience is improved.
Preferably, the delay unit may be an integration circuit. The invention is further described below with a delay cell as the integrating circuit. Fig. 3 is a block diagram of a preferred structure of the noise canceling device according to the embodiment of the present invention, and as shown in fig. 3, the delay unit 1 includes: a load 12 and a capacitor 14; the control unit 2 includes: a control pin 20, a first switch 22, and a second switch 24, each of which is described in detail below.
A load 12 is connected in series between the power output terminal of the audio circuit and the load 1, and a capacitor 14 is connected in series between the load 12 and the ground level. Load 12 and capacitor 14 form an integrating circuit.
A control pin 20 for receiving a control signal; a first switch 22 connected to the control pin 20 and in parallel with the load 12 for short-circuiting the load 12 under control of a control signal; and a second switch 24 connected to the control pin 20 and connected in series between the capacitor 14 and the ground level for allowing the current flowing through the capacitor to flow to the ground level under the control of the signal.
The above-described first switch 22 and second switch 24 are configured to: in response to a control signal received at the control pin 20, the second switch 24 opens the circuit between the capacitor 14 and ground while the first switch 22 short-circuits the load 12; alternatively, the second switch 24 routes the capacitor 14 to ground while the first switch 22 operates the load 12.
The second switch 24 may control the operation or non-operation of the integration circuit according to the control signal. That is, if the second switch 24 opens the circuit between the capacitor 14 and the ground level, the integration circuit does not operate, and if the second switch 24 opens the circuit between the capacitor 14 and the ground level, the integration circuit operates.
The above-mentioned control signal is used for indicating the power-on condition of the audio circuit, wherein, in the case that the control signal indicates that the power-on condition of the audio circuit is to be powered on, the first switch 22 makes the load 12 work, and the second switch 24 makes the path between the capacitor 14 and the ground level; in the event that the control signal indicates that the power-up condition of the audio circuit is complete power-up, the first switch 22 short-circuits the load 12 and the second switch 24 opens the circuit between the capacitor 14 and ground level. For example, a control signal of 1 indicates that the power-on condition of the audio circuit is to be powered on, and a control signal of 0 indicates that the power-on condition of the audio circuit is complete power on.
The first switch 22 may be an audio analog switch and the second switch 24 may be a transistor. Wherein, the base of triode is connected with control pin 20, the collector of triode is connected with capacitor 14 in series, the emitter of triode is connected with ground level.
In a specific implementation process, the above modules may be integrated according to requirements, for example, the capacitor 14 and the second switch 24 may be integrated to form a shunt circuit.
Preferably, the noise cancellation device may further include 3 bias loads, where the first bias load is connected in parallel with the capacitor 14 to provide a current drainage channel for the capacitor 14; the second bias load is connected between the control pin 20 and the base electrode of the triode in series; and the third bias load is connected between the base electrode of the triode and the ground level. The second bias load and the third bias load are bias resistors of a transistor.
Based on the circuit shown in fig. 1, the following describes an embodiment of the present invention in detail by taking the shunt circuit formed by integrating the capacitor 14 and the second switch 24 as an example.
Fig. 4 is a circuit diagram of an audio circuit including a noise canceling device according to an embodiment of the present invention, as shown in fig. 4, using a device in a black box, i.e., a noise canceling device. The noise cancellation device comprises R3, an audio analog switch, a shunt circuit and a control pin Ctrl, wherein R3 is the load 12, the audio analog switch is the first switch 22, the shunt circuit is a circuit formed by the capacitor 14 and the second switch 24, and the control pin Ctrl is the control pin 20.
Before the power supply Vcc of the power amplifier circuit is turned on, the control pin Ctrl is first set to operate the noise cancellation device, that is, the control signal Ctrl received by the control pin is set to be at a high level, at this time, the audio analog switch is in an off state (non-conducting state), and at this time, the shunt circuit is in an on state (that is, the shunt circuit performs shunt). Then turning on the power supply Vcc of the power amplifier circuit, waiting for a period of time, where the period of time is the time for the circuit to establish a static operating point, generally 300ms to 500ms, and the shunt circuit is used for shunting current to the load R during the period of timeLThereby avoiding the load RLGeneration of noise. After the circuit establishes a static working point, the control pin Ctrl is set to be at a low level, the audio analog switch is in a pass state, the shunt circuit is short-circuited and has no current, so that the shunt circuit does not shunt at the moment, and the noise eliminating device does not work. When the noise eliminating device does not work, the noise eliminating device is equivalently disconnected from the original audio equipment circuit, and the normal work of the power amplifying circuit cannot be influenced.
Fig. 5 is a circuit diagram showing an example of the configuration of the shunt circuit in the noise canceling device shown in fig. 4, and as shown in fig. 5, the device in the black frame in the diagram is the shunt circuit shown in fig. 4, and the shunt circuit includes a transistor Tchg, a capacitor Cchg, and a resistor R4 (i.e., the first bias load), R5 (i.e., the second bias load), and R6 (i.e., the third bias load). The capacitor Cchg and the resistor R3 form an integration circuit, and the transistor Tchg is connected in series in the integration circuit. The triode Tchg is equivalent to an electronic switch by setting the triode to work in a saturation state and a cutoff state, so that the on/off (working/non-working) of the integrating circuit can be controlled. The resistors R5 and R6 are bias resistors of the triode Tchg; r4 is connected in parallel with capacitor Cchg to provide a current leakage path for capacitor Cchg. In order to reduce the impulse current at the moment of power-on as much as possible, the integration time is usually selected to be larger, so that the resistance value of the resistor R3 is also larger, the resistance value is generally selected to be about 300 Ω -1K Ω during actual debugging, and the corresponding RC time constant is about 100 mS-300 mS. The operating principle of the shunt circuit is described in detail below.
Before turning on a power supply Vcc of a power amplification circuit, firstly setting a control pin Ctrl to be a high level, and at the moment, turning on a triode Tchg; then, a power supply Vcc of the power amplification circuit is turned on, and an impulse current at the electrifying moment is shunted by using an integral circuit formed by Tchg and a resistor R3 so as to prolong the time of establishing a static working point at the output end of the power amplification circuit. Therefore, only a very small impulse current flows through the load R via the coupling capacitor C1LThus, POP sound (namely the noise) generated at the moment of power-on of the original power amplifier circuit is eliminated.
Fig. 6 is a diagram showing a simulation of an actually measured waveform at the moment of power-on of the input terminal of the coupling capacitor in the related art, and fig. 7 is a diagram showing a simulation of an actually measured waveform at the moment of power-on of the input terminal of the coupling capacitor after the noise canceling device according to the embodiment of the present invention is applied.
As shown in fig. 6, when the power is turned on, a very high impulse voltage appears at the output terminal of the power amplifier circuit, and it is this impulse voltage that enters the load R after passing through the coupling capacitor C1LResulting in a powered-up POP tone. Comparing fig. 6 with fig. 7, it can be seen that, after the noise canceling device of the embodiment of the present invention is applied, the establishment of the quiescent operating point of the power amplifier circuit is changed from a fast step-up process to a slow integral-up process, so that the load R is increasedLThe POP sound generated at the moment of power-on can not occur.
When the power amplifier circuit normally works, the control pin Ctrl is set to be at a low level, at the moment, the triode Tchg is closed, the shunt circuit is disconnected, and the normal audio output signal can be prevented from being shunted. In addition, due to the load RLGenerally, the earphone is 32 Ω or the speaker is 8 Ω, so after the establishment of the quiescent operating point, the resistor R3 will seriously affect the normal operation of the power amplifier circuit. Therefore, the resistor R3 must be bypassed when the power amplifier is operating properly. This function will be easily implemented by the control pin Ctrl. At the moment of power-on, the control pin Ctrl is at a high level,the analog switch is turned off, and an impulse current flows from R3; when the power amplifier circuit normally works, the control pin Ctrl is at low level, and the analog switch is turned on, so that the R3 is short-circuited, and the normal output of the audio signal is not influenced.
In a default state (i.e., no setting is made to the control pin Ctrl), the noise cancellation device may be disabled by using the shunt circuit's own ground pin (corresponding to R6 in fig. 5). At this moment, the noise eliminating device is equivalently disconnected from the whole circuit, and the original function of the power amplifying circuit is not influenced.
As can be seen from the above description, the control functions of the signal received by the control pin Ctrl on the shunt circuit and the audio analog switch are exactly complementary, that is, when the audio analog switch works, the shunt circuit does not work; when the shunt circuit works, the audio frequency analog switch does not work. Therefore, the invention can be compatible with most of the existing audio power amplifier circuits.
Fig. 8 is a schematic Circuit diagram illustrating an application of the noise canceling device according to the embodiment of the present invention to an audio device, as shown in fig. 8, wherein the noise canceling device includes "audiocircuit" and a control pin Ctrl, one end of the "audiocircuit" is connected to an output terminal (i.e., a power output terminal) of the "AudioAmplifier", the other end of the "audiocircuit" is connected to a capacitor C1, and Ctrl (i.e., the control pin 20 described above) is used to control the operation or non-operation of the audiocircuit ".
As can be seen from fig. 8, the noise cancellation device provided in the embodiment of the present invention may be embedded in the power amplifier circuit as a separate module, that is, the noise cancellation device may be integrated into the power amplifier chip, and used as a part of the power amplifier chip or separately form a chip having a function of canceling the power-on POP sound. This represents a convenient integration feature of the present invention.
In summary, the noise cancellation device provided in the embodiment of the present invention slows down the establishment time of the static operating point by shunting the impulse current at the power-on instant, so as to eliminate the POP noise, thereby improving the user experience. After the static working point is established, the noise eliminating device can be disconnected from the system, so that the original function of the power amplifying circuit is not influenced. In addition, the use mode of the noise elimination device provided by the embodiment of the invention is quite simple, and the noise elimination device can be independently controlled, namely, when the POP noise needs to be eliminated, the noise elimination device is turned on in advance, and then turned off after a short time.
It should be noted that the noise cancellation device provided in the embodiment of the present invention can also be applied to an IC (integrated circuit) as a single functional module in the IC, so as to improve the performance of the IC.
It will be apparent to those skilled in the art that the modules or steps of the present invention described above may be implemented by a general purpose computing device, they may be centralized on a single computing device or distributed across a network of multiple computing devices, and they may alternatively be implemented by program code executable by a computing device, such that they may be stored in a storage device and executed by a computing device, or fabricated separately as individual integrated circuit modules, or fabricated as a single integrated circuit module from multiple modules or steps. Thus, the present invention is not limited to any specific combination of hardware and software.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (6)
1. A noise cancellation arrangement for use in a circuit comprising a power output and a first load, the arrangement comprising:
the delay unit is connected between the power output end and the first load in series and used for prolonging the time of the audio circuit for establishing a static working point by shunting current flowing to the first load under the control of the control unit;
the control unit is connected to the delay unit and used for controlling whether the delay unit works or not according to the received control signal,
the delay unit includes:
a second load connected in series between the power output terminal and the first load;
a capacitor connected in series between the second load and a ground level; wherein,
the control unit includes:
the control pin is used for receiving the control signal;
a first switch connected to the control pin and connected in parallel with the second load for short-circuiting the second load under the control of the control signal;
the second switch is connected to the control pin and is connected between the capacitor and the ground level in series, and is used for enabling the current flowing through the capacitor to flow to the ground level under the control of the signal;
wherein the first switch and the second switch are configured to: according to the control signal, the second switch opens the circuit between the capacitor and the ground level while the first switch short-circuits the second load; alternatively, the second switch allows a path between the capacitor and a ground level while the first switch operates the second load.
2. The apparatus of claim 1, wherein the delay unit is an integrating circuit.
3. The apparatus of claim 1, wherein the control signal is used to indicate a power-up condition of the audio circuit, wherein the first switch operates the second load and the second switch opens the path between the capacitor and ground level when the control signal indicates that the power-up condition of the audio circuit is to be powered up; and when the control signal indicates that the power-on condition of the audio circuit is the power-on completion condition, the first switch enables the second load to be in short circuit, and the second switch enables the capacitor to be disconnected with the ground level.
4. The apparatus of claim 1, wherein the first switch is an audio analog switch.
5. The apparatus of claim 1, wherein the second switch is a transistor, wherein a base of the transistor is connected to the control pin, a collector of the transistor is connected in series with the capacitor, and an emitter of the transistor is connected to ground.
6. The apparatus of claim 5, further comprising:
a first bias load connected in parallel with the capacitor;
the second bias load is connected between the control pin and the base electrode of the triode in series;
and the third biasing load is connected between the base electrode of the triode and the ground level.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910130436 CN101534463B (en) | 2009-04-07 | 2009-04-07 | A noise elimination device |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 200910130436 CN101534463B (en) | 2009-04-07 | 2009-04-07 | A noise elimination device |
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| CN101534463A CN101534463A (en) | 2009-09-16 |
| CN101534463B true CN101534463B (en) | 2013-09-11 |
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| CN 200910130436 Expired - Fee Related CN101534463B (en) | 2009-04-07 | 2009-04-07 | A noise elimination device |
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Families Citing this family (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN102325288B (en) * | 2011-09-02 | 2014-04-16 | 惠州Tcl移动通信有限公司 | De-noising device and method for audio circuit of mobile terminal earphone |
| CN104363547B (en) * | 2014-12-04 | 2017-09-26 | 青岛歌尔声学科技有限公司 | Audio frequency processing circuit and line control earphone for eliminating headset plugging noise |
Citations (3)
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| CN101005279A (en) * | 2006-01-16 | 2007-07-25 | 中华映管股份有限公司 | Acoustic Noise Suppression Circuit |
| CN101087130A (en) * | 2006-06-07 | 2007-12-12 | 英业达股份有限公司 | Audio device protection system |
| CN101325401A (en) * | 2007-06-12 | 2008-12-17 | 上海沙丘微电子有限公司 | Circuit for restraining start-up and closedown noise of whole difference audio power amplifier |
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2009
- 2009-04-07 CN CN 200910130436 patent/CN101534463B/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101005279A (en) * | 2006-01-16 | 2007-07-25 | 中华映管股份有限公司 | Acoustic Noise Suppression Circuit |
| CN101087130A (en) * | 2006-06-07 | 2007-12-12 | 英业达股份有限公司 | Audio device protection system |
| CN101325401A (en) * | 2007-06-12 | 2008-12-17 | 上海沙丘微电子有限公司 | Circuit for restraining start-up and closedown noise of whole difference audio power amplifier |
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| Title |
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| JP特开平11-112239A 1999.04.23 |
| MAXIM.具有旁路模式的杂音抑制器.《MAX9892》.2008, * |
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