CN201956976U - Switch-on control circuit for audio amplifier - Google Patents
Switch-on control circuit for audio amplifier Download PDFInfo
- Publication number
- CN201956976U CN201956976U CN2010206815465U CN201020681546U CN201956976U CN 201956976 U CN201956976 U CN 201956976U CN 2010206815465 U CN2010206815465 U CN 2010206815465U CN 201020681546 U CN201020681546 U CN 201020681546U CN 201956976 U CN201956976 U CN 201956976U
- Authority
- CN
- China
- Prior art keywords
- switching tube
- resistance
- control circuit
- potential
- ground
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
Images
Landscapes
- Amplifiers (AREA)
Abstract
The utility model relates to a switch-on control circuit for an audio amplifier. The switch-on control circuit comprises a first switching tube, a second switching tube, a third switching tube, a fourth switching tube, a first potential-divider network, a second potential-divider network, a comparator, a current mirror, a current source and a capacitor, wherein each switching tube is provided with a control end and two signal ends; one signal end of the first switching tube is connected with an external power source, the other signal end and the first potential-divider network are connected to earth; one signal end of the second switching tube is connected with the external power source, the other signal end and the second potential-divider network are connected to earth; the control ends of the first switching tube and the second switching tube are connected and used for receiving an external enable signal. The switch-on control circuit for the audio amplifier can conveniently control the switch-on process of class A and B audio amplifiers and effectively reduce transient noise occurred during switch-on process of class A and B audio amplifiers.
Description
Technical field
The utility model relates to integrated circuit, relates in particular to a kind of audio frequency amplifier open control circuit.
Background technology
As shown in Figure 1, the pseudo-differential bridge mode (BTL) of single-ended input both-end output is a kind of system architecture of the AB of being widely used in genus audio power amplifier circuit.Than other system architecture, the advantage of BTL is that power output is big, and has the ability of common-mode noise inhibition preferably.
Yet, in the single supply system, the input dc point of amplifier PA is generally half of supply voltage VDD, it is by resistance pressure-dividing network 1 ', be that resistance R 1 ', R2 ' and shunt capacitance Cb realize that this just requires input audio signal Audio In need be loaded into the input of amplifier PA by a capacitance Ci.Yet, because the existence of shunt capacitance Cb and capacitance Ci, can cause in opening process, producing an instantaneous potential pulse with the different of capacitance Ci charge rate at circuit output end owing to shunt capacitance Cb at amplifier circuit, when this instantaneous voltage pulse during greater than 15mV, audio system will produce similar " Pi ", " " the unlatching noise.
As shown in Figure 2, usually, solution to the problems described above is earlier by the input of a switch M with first order amplifier PA1 when amplifier circuit is opened, the output short circuit, constitute a voltage follower, accurately control the charging process of shunt capacitance Cb and the turn off process of above-mentioned switch M by an open control circuit 2 ' again, be implemented in the audio frequency amplifier initialization procedure with this, forward output and negative sense output end voltage can rise to about supply voltage near half synchronously slowly, so just can reduce the size of audio frequency amplifier output instantaneous voltage pulse in opening process as far as possible, avoid occurring " Pi ", " " sound.
Yet the process of above-mentioned this accurate control is more complicated often, needs for example more hardware resources such as current source, voltage comparator, counter, also needs strict sequencing control.Therefore, how reaching the startup that better simply control mode is finished audio-frequency amplifier circuit at lower cost, reduce to export transient noise as far as possible, is insider's urgent problem.
The utility model content
In order to solve the problem that above-mentioned prior art exists, the utility model aims to provide a kind of audio frequency amplifier open control circuit, to reach under the condition that consumes less hardware resource, and the purpose of the transient noise when effectively reducing the unlatching of AB genus audio power amplifier.
A kind of audio frequency amplifier open control circuit described in the utility model, it comprises first to fourth switching tube, first, second potential-divider network, a comparator, a current mirror, a current source and an electric capacity that all has a control end and two signal ends, wherein,
A signal end of described first switching tube is connected with an external power source, another signal end and described first potential-divider network are connected to ground, a signal end of described second switch pipe is connected with described external power source, another signal end and described second potential-divider network are connected to ground, described first, second control end of switching tube links to each other, and receives an outside enable signal;
The output of described first, second potential-divider network is connected respectively to the positive input and the reverse input end of described comparator, and the output of this comparator is connected respectively to described the 3rd, the 4th control end of switching tube;
A signal end of described the 3rd switching tube is connected with described external power source, another signal end is connected with a signal end of described the 4th switching tube, another signal end and the described current mirror of the 4th switching tube are connected to ground, and the continuous end of described the 3rd, the 4th switching tube is exported a control signal;
The input of described current source is connected with described external power source, and output and described current mirror are connected to ground;
One end of described electric capacity is connected the continuous end of described the 3rd, the 4th switching tube, other end ground connection.
In above-mentioned audio frequency amplifier open control circuit,
Described first potential-divider network comprises first resistance and second resistance that is connected on successively between described first switching tube and the ground, and the positive input of described comparator is connected between this first, second resistance;
Described second potential-divider network comprises the 3rd resistance and the 4th resistance that is connected on successively between described second switch pipe and the ground, and the reverse input end of described comparator is connected between the 3rd, the 4th resistance;
Described current mirror comprises first metal-oxide-semiconductor and second metal-oxide-semiconductor, and wherein, the drain electrode of described first metal-oxide-semiconductor is connected with the 4th switching tube, its source ground, its grid is connected with drain electrode with the grid of described second metal-oxide-semiconductor respectively, and the drain electrode of this second metal-oxide-semiconductor is connected its source ground with described current source.
In above-mentioned audio frequency amplifier open control circuit, described first resistance is identical with the resistance value of second resistance, and described the 3rd resistance is identical with the resistance value of the 4th resistance.
In above-mentioned audio frequency amplifier open control circuit, described first to fourth switching tube is respectively a MOS device, and the grid of described MOS device is control end, and its source electrode and drain electrode are signal end.
In above-mentioned audio frequency amplifier open control circuit, the source electrode of described first to the 3rd switching tube is connected with described external power source, and the source electrode of described the 4th switching tube is connected with the drain electrode of described first metal-oxide-semiconductor.
In above-mentioned audio frequency amplifier open control circuit, described first to the 3rd switching tube is the PMOS pipe, and described the 4th switching tube and first, second metal-oxide-semiconductor are the NMOS pipe.
Owing to adopted above-mentioned technical solution, the utility model constitutes the charging and discharging circuit of this shunt capacitance by adopting shunt capacitance in first potential-divider network and the external audio frequency amplifier, to realize accurate control to the shunt capacitance charging process, and this first potential-divider network is connected to the positive input of comparator, provide a reference level by second potential-divider network to the inverting input of comparator simultaneously, utilize the characteristic of the built-in input offset voltage of comparator, promptly when its positive input voltage is slightly less than but approaches reverse input end voltage, the level of its output just overturns, therefore, only need and after comparator is handled thus, the final control signal of exporting to be delivered to the switch on the first order amplifier in the external audio frequency amplifier, can realize accurate control this switch conduction and turn off process; In sum, the utility model can be realized the control to AB class audio amplifier opening process easily, and effectively reduces the transient noise that the AB class audio amplifier produces when opening.The utility model can be applied in any AB class audio amplifier circuit, especially is applied to some cheaply in the audio-frequency amplifier circuit.
Description of drawings
Fig. 1 is the structural representation of the pseudo-differential bridge mode audio frequency amplifier used always;
Fig. 2 has to suppress the circuit theory diagrams that audio frequency amplifier is opened the transient noise effect;
Fig. 3 is the structural representation of a kind of audio frequency amplifier open control circuit of the utility model;
Fig. 4 is the working waveform figure of a kind of audio frequency amplifier open control circuit of the utility model.
Embodiment
Below in conjunction with accompanying drawing, specific embodiment of the utility model is elaborated.
As shown in Figure 3, the utility model, it is a kind of audio frequency amplifier open control circuit, it comprises first to fourth switching tube P1, P2, P3, N1, first, second potential- divider network 1,2, a comparator A1, a current mirror 3, a current source Iref and a capacitor C e who all has a control end and two signal ends, wherein, first to fourth switching tube P1, P2, P3, N1 are respectively a MOS device, and their grid is control end, and its source electrode and drain electrode are signal end.
The source electrode of the first switching tube P1 is connected with an external power source VDD, and its drain electrode is connected to ground GND with first potential-divider network 1; The source electrode of second switch pipe P2 is connected with external power source VDD, and its drain electrode is connected to ground with second potential-divider network 2, and the grid of first, second switching tube P1, P2 links to each other, and receives an outside enable signal SD;
First potential-divider network 1 comprises first resistance R 1 and second resistance R 2 that is connected on successively between the first switching tube P1 and the ground GND, and first resistance R 1 is identical with the resistance value of second resistance R 2; Second potential-divider network 2 comprises the 3rd resistance R 3 and the 4th resistance R 3 that is connected on successively between second switch pipe P2 and the ground GND, and the 3rd resistance R 3 is identical with the resistance value of the 4th resistance R 4;
The positive input of comparator A1 is connected between this first, second resistance R 1, the R2, and its reverse input end is connected between the 3rd, the 4th resistance R 3, the R4, and its output is connected respectively to the grid of the 3rd, the 4th switching tube P3, N1;
The source electrode of the 3rd switching tube P3 is connected with external power source VDD, and its drain electrode is connected with the drain electrode of the 4th switching tube N1, and the source electrode of the 4th switching tube N1 and current mirror 3 are connected to ground GND, and the continuous end of the 3rd, the 4th switching tube P3, N1 is exported a control signal ENB;
Current mirror Iref comprises the first metal-oxide-semiconductor N2 and the second metal-oxide-semiconductor N3, wherein, the drain electrode of the first metal-oxide-semiconductor N2 is connected with the 4th switching tube N1, its source ground GND, its grid is connected with drain electrode with the grid of the second metal-oxide-semiconductor N3 respectively, and the drain electrode of this second metal-oxide-semiconductor N3 is connected with the output of current source Iref, its source ground GND, and the input of current source Iref is connected with external power source VDD;
The end of capacitor C e is connected the continuous end of the 3rd, the 4th switching tube P3, P4, other end ground connection GND.
In the utility model, first to the 3rd switching tube P1 to P3 is the PMOS pipe, and the 4th switching tube N1 and first, second metal-oxide-semiconductor N2, N3 are the NMOS pipe.
Please in conjunction with Fig. 2 to Fig. 4, operation principle of the present utility model is as follows:
Second potential-divider network 2 provides comparator A1 the reference level Vref of reverse input end, owing to the 3rd, the 4th resistance R 3, R4 resistance equate, so reference level Vref is about the external power source vdd voltage half; The first shunt capacitance Cb of potential-divider network 1 in external audio frequency amplifier that first, second resistance R 1, the R2 that is equated by resistance constitutes constitutes its charging and discharging circuit, is connected to the positive input of comparator A1 simultaneously; First, second potential- divider network 1,2 is opened under the control of external enable signal SD and is turn-offed by first, second switching tube P1, P2 respectively; The output of comparator A1 is connected to the grid of the 3rd, the 4th switching tube P3, N1, and control capacitance Ce discharges and recharges, and the 3rd switching tube P3 provides the charging current of capacitor C e, and the source electrode of the 4th switching tube N1 connects current mirror 3, constitutes the discharge loop of capacitor C e; The reference input current of current mirror 3 is provided by current source Iref; The ratio of the breadth length ratio of first, second metal-oxide-semiconductor N1, N2 and the size of current source Iref have determined the size of capacitor C e discharging current jointly.
When external enable signal SD became low level, the utility model was started working.At this moment, first, second switching tube P1, P2 conducting are started working by first, second potential- divider network 1,2, and reference level Vref rises to rapidly near half of supply voltage VDD, and because the existence of external shunt capacitance Cb, the voltage of BYPASS end As time goes on index rises; In the regular hour, the size greater than the BYPASS terminal voltage of reference level Vref, the level Vc of comparator A1 output is a low level, so the 3rd switching tube P3 conducting, the 4th switching tube N1 turn-offs, capacitor C e charges to rapidly near the supply voltage VDD by the 3rd switching tube P3, and control signal ENB is output as high level.In this course, control signal ENB control is connected across the switch M conducting on the audio frequency amplifier first order amplifier PA1, becomes a voltage follower; At this moment, audio-frequency amplifier circuit is in making state just, and its forward, inverse output terminal voltage rise synchronously, and therefore the instantaneous voltage difference that produces in output loading is very little, can not produce " Pi ", " " sound;
As time goes on, the BYPASS terminal voltage rise to supply voltage VDD half near, at this moment, comparator A1 overturns, the level Vc of output is a high level.So the 3rd switching tube P3 turn-offs, the 4th switching tube N1 conducting, capacitor C e is by the 4th switching tube N1 and first metal-oxide-semiconductor N2 discharge, because the size of this discharging current is a fixed value, so this discharge process is a linear process by current mirror 3 controls.Along with continuing of discharge process, the voltage linear of the control signal ENB of capacitor C e output diminishes, and makes the switch M conducting resistance that is connected across on the audio frequency amplifier first order amplifier PA1 strengthen gradually, and final the shutoff; Because said process is a slow asymptotic process, thus can reduce the size of the transient voltage pulse of audio frequency amplifier output greatly, can not cause exporting excessive " Pi ", " " noise;
After this, audio frequency amplifier enters normal operating conditions.
Obviously, for open control circuit described in the utility model, the opening time of whole AB class audio amplifier is by two aspect factor decisions, the one, by the charging interval of external shunt capacitance Cb by first, second resistance R 1, R2, the 2nd, capacitor C e is by the discharge time of the 4th switching tube N1, the first metal-oxide-semiconductor N2.
In sum, the utility model can be realized the control to AB class audio amplifier opening process easily, and effectively reduces the transient noise that the AB class audio amplifier produces when opening.The utility model can be applied in any AB class audio amplifier circuit, especially is applied to some cheaply in the audio-frequency amplifier circuit.
Below embodiment has been described in detail the utility model in conjunction with the accompanying drawings, and those skilled in the art can make the many variations example to the utility model according to the above description.Thereby some details among the embodiment should not constitute qualification of the present utility model, and the scope that the utility model will define with appended claims is as protection range of the present utility model.
Claims (6)
1. audio frequency amplifier open control circuit, it is characterized in that, described control circuit comprises first to fourth switching tube, first, second potential-divider network, a comparator, a current mirror, a current source and an electric capacity that all has a control end and two signal ends, wherein
A signal end of described first switching tube is connected with an external power source, another signal end and described first potential-divider network are connected to ground, a signal end of described second switch pipe is connected with described external power source, another signal end and described second potential-divider network are connected to ground, described first, second control end of switching tube links to each other, and receives an outside enable signal;
The output of described first, second potential-divider network is connected respectively to the positive input and the reverse input end of described comparator, and the output of this comparator is connected respectively to described the 3rd, the 4th control end of switching tube;
A signal end of described the 3rd switching tube is connected with described external power source, another signal end is connected with a signal end of described the 4th switching tube, another signal end and the described current mirror of the 4th switching tube are connected to ground, and the continuous end of described the 3rd, the 4th switching tube is exported a control signal;
The input of described current source is connected with described external power source, and output and described current mirror are connected to ground;
One end of described electric capacity is connected the continuous end of described the 3rd, the 4th switching tube, other end ground connection.
2. audio frequency amplifier open control circuit according to claim 1 is characterized in that,
Described first potential-divider network comprises first resistance and second resistance that is connected on successively between described first switching tube and the ground, and the positive input of described comparator is connected between this first, second resistance;
Described second potential-divider network comprises the 3rd resistance and the 4th resistance that is connected on successively between described second switch pipe and the ground, and the reverse input end of described comparator is connected between the 3rd, the 4th resistance;
Described current mirror comprises first metal-oxide-semiconductor and second metal-oxide-semiconductor, and wherein, the drain electrode of described first metal-oxide-semiconductor is connected with the 4th switching tube, its source ground, its grid is connected with drain electrode with the grid of described second metal-oxide-semiconductor respectively, and the drain electrode of this second metal-oxide-semiconductor is connected its source ground with described current source.
3. audio frequency amplifier open control circuit according to claim 2 is characterized in that, described first resistance is identical with the resistance value of second resistance, and described the 3rd resistance is identical with the resistance value of the 4th resistance.
4. audio frequency amplifier open control circuit according to claim 1 and 2 is characterized in that, described first to fourth switching tube is respectively a MOS device, and the grid of described MOS device is control end, and its source electrode and drain electrode are signal end.
5. audio frequency amplifier open control circuit according to claim 4 is characterized in that, the source electrode of described first to the 3rd switching tube is connected with described external power source, and the source electrode of described the 4th switching tube is connected with the drain electrode of described first metal-oxide-semiconductor.
6. audio frequency amplifier open control circuit according to claim 5 is characterized in that, described first to the 3rd switching tube is the PMOS pipe, and described the 4th switching tube and first, second metal-oxide-semiconductor are the NMOS pipe.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010206815465U CN201956976U (en) | 2010-12-27 | 2010-12-27 | Switch-on control circuit for audio amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010206815465U CN201956976U (en) | 2010-12-27 | 2010-12-27 | Switch-on control circuit for audio amplifier |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201956976U true CN201956976U (en) | 2011-08-31 |
Family
ID=44501077
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010206815465U Expired - Lifetime CN201956976U (en) | 2010-12-27 | 2010-12-27 | Switch-on control circuit for audio amplifier |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN201956976U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102006018A (en) * | 2010-12-27 | 2011-04-06 | 上海贝岭股份有限公司 | Opening control circuit used for AB class audio amplifier |
-
2010
- 2010-12-27 CN CN2010206815465U patent/CN201956976U/en not_active Expired - Lifetime
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102006018A (en) * | 2010-12-27 | 2011-04-06 | 上海贝岭股份有限公司 | Opening control circuit used for AB class audio amplifier |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| CN103178813B (en) | Low-offset full-motion comparator | |
| CN102006018B (en) | Opening control circuit used for AB class audio amplifier | |
| CN101943925A (en) | Discharge circuit for voltage regulators | |
| CN108508951A (en) | The LDO regulator circuit of capacitance outside a kind of no piece | |
| CN104158516B (en) | voltage comparator | |
| CN103023463B (en) | A kind of ramp signal generative circuit and ramp signal generator | |
| CN103018588B (en) | Low-power-consumption anti-interference three-state input detection circuit | |
| CN102983825B (en) | A kind of category D amplifier chip | |
| CN203984244U (en) | The slope compensation circuit of Switching Power Supply | |
| CN101860331A (en) | Grid voltage control circuit of TDD radio-frequency amplifier | |
| CN102931931B (en) | Anti-sound break circuit for D-class power amplifier chip | |
| CN104092374A (en) | Slope compensation circuit and method for switching power supply | |
| CN103279162A (en) | Low-power-consumption reference voltage buffer based on assembly line ADC | |
| CN201956976U (en) | Switch-on control circuit for audio amplifier | |
| CN102572642B (en) | Audio POP sound elimination method and earphone audio circuit | |
| CN103107791A (en) | Gain linear variable gain amplifier with constant bandwidth | |
| CN201623690U (en) | TDD (Time Division Duplex) radio-frequency amplifier gate voltage control circuit | |
| CN105553023A (en) | Multi-loop composite switch type battery charging converter circuit | |
| CN203368322U (en) | Low-loss series capacitor voltage-sharing device | |
| CN202906845U (en) | Anti-cracking voice circuit for D-class power amplifier chip | |
| CN209014942U (en) | A kind of lower electric sequential control circuit and power circuit | |
| CN201266921Y (en) | Pulsewidth suppressing circuit and audio power amplifier | |
| CN208078642U (en) | Inhibit the control device of output surge current | |
| CN101764575B (en) | Audio power amplifier start-up charging circuit | |
| CN102186130A (en) | Slew rate control driving circuit |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| AV01 | Patent right actively abandoned |
Granted publication date: 20110831 Effective date of abandoning: 20130424 |
|
| RGAV | Abandon patent right to avoid regrant |