CN103441742A - Gain control circuit - Google Patents

Gain control circuit Download PDF

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Publication number
CN103441742A
CN103441742A CN2013103178872A CN201310317887A CN103441742A CN 103441742 A CN103441742 A CN 103441742A CN 2013103178872 A CN2013103178872 A CN 2013103178872A CN 201310317887 A CN201310317887 A CN 201310317887A CN 103441742 A CN103441742 A CN 103441742A
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output
resistance
control circuit
signal
phase
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CN103441742B (en
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陈友福
郑欣
周塔
罗建军
徐光煜
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SHANGHAI CHIPSTAR MICROELECTRONICS Ltd
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SHANGHAI CHIPSTAR MICROELECTRONICS Ltd
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Abstract

The invention relates to an electronic circuit, and discloses a gain control circuit. The gain control circuit comprises a pre-amplifying circuit, a switch and an integrator circuit. The pre-amplifying circuit is used for receiving a sound signal and outputting an amplified prime signal. The prime signal comprises a normal-phase prime signal and a reverse-phase prime signal. The pre-amplifying circuit comprises a normal-phase sound signal input end, a reverse-phase sound signal input end, a normal-phase prime signal output end and a reverse-phase prime signal output end. One end of the switch is connected with the normal-phase prime signal output end, and the other end of the switch is connected with the reverse-phase prime signal output end. The integrator circuit is used for receiving an output feedback signal and the prime signal output by the pre-amplifying circuit, the output feedback signal and the prime signal are shaped and filtered, the subtraction is carried out, and then the output feedback signal and the prime signal are output. An input resistor and a feedback resistor in the gain control circuit do not need to be sectioned, the problem of the wiring difficulty of an audio power amplifier chip is solved, and the clatter produced when the gain of the gain control circuit is adjusted is avoided.

Description

Gain control circuit
Technical field
The present invention relates to electronic circuit, particularly a kind of gain control circuit of audio frequency power amplifier chip.
Background technology
In audio power amplification system, gain is a key parameter index, is defined as the ratio of output signal and input signal.The precision of gain and the consistency between sample are one of standards of weighing power discharging IC (integrated circuit, Integrated Circuit) quality, and it is an important component part in whole audio power amplification system that gain is controlled.During design system, for the accurately gain of control system, usually the ratio by the resistance of closed-loop system realizes, that is, and and A=R f/ R iN.Wherein, A is the gain of system, R fthe feedback resistance of system, R iNit is the input resistance of signal.
Fig. 1 is the structural representation of the gain control circuit of a comparatively general audio frequency power amplifier chip.Wherein, input resistance R i, feedback resistance R fwith the preamplifying circuit of difference transport and placing device composition power amplifier chips, input resistance R icomprise resistance R i1, resistance R i2, resistance R i1, resistance R i2resistance equates, feedback resistance R fcomprise resistance R f1, resistance R f2, resistance R f1, resistance R f2resistance equates.Audio signal V ipass through resistance R i, R fcircuit network obtains prime signal V after amplifying o1, audio signal V ithe gain A of amplifying vby resistance R i, R fratio set, A v=V o1/ V i=R f/ R i.Resistance R 1, resistance R 2, capacitor C 1, capacitor C 2form integrator circuit with the difference transport and placing device.Prime signal V o1with output feedback signal VF 1pass through the integrator circuit shaping filter and complete and subtract each other.In power amplifier application, because the amplitude of signal source is inconsistent, need gain on the conditioning signal path to realize the comfort level of power amplifier output volume.
Present stage, gain-adjusted is that power discharging IC needs an integrated basic function, and general way is to change resistance R by segmentation fand resistance R iNresistance complete, as shown in Figure 2.Wherein, resistance R fand resistance R ibe processed into the series connection of multistage resistance: R n1, R n2, R n3..., R nn-1, R nn, R nn+1, the resistance of these resistance is that the gain curve needed according to system comes reconnaissance to set.The condition of setting according to the user is chosen gain and is controlled tap net 1, net 2, net 3... net n-1, net n.For example, when choosing net2, signal gain is:
But this by the technical scheme of resistor section, in the physics realization process, the installation work of the resistance of gain control circuit will be very difficult, and the waste chip area.Because resistance is segmentation in proportion, need to be by input resistance R iwith feedback resistance R fbe divided into multiple resistance.Because the physical size of the resistance of different value is also different, the progression that gain is controlled is more, and system needs the resistance kind of resistance also more.
Simultaneously, in the power amplifier application facet, voltage jump is exaggerated at power take-off, and the user can hear and be unwilling to hear " click clatter " sound.Owing to being that there is larger difference in the resistance between resistance by resistance segmentation in proportion, even if 64 stage gains commonly used are controlled, be also like this.In gain change process, the variation of voltage signal is sufficiently oily, has the variation of moment.
Summary of the invention
The object of the present invention is to provide a kind of gain control circuit, make and avoid, by input resistance and feedback resistance segmentation, having solved audio frequency power amplifier chip wiring difficulty, " click clatter " sound while having avoided regulating the gain control circuit gain.
For solving the problems of the technologies described above, the invention provides a kind of gain control circuit, comprise: preamplifying circuit, switch sum-product intergrator circuit;
Described preamplifying circuit is for the prime signal of received audio signal output amplification; Described audio signal comprises positive audio signal and anti-phase audio signal; Described prime signal comprises positive prime signal and anti-phase prime signal; Described preamplifying circuit comprises two inputs and two outputs, described two inputs are respectively positive audio signal input end, anti-phase audio signal input end, and described two outputs are respectively positive prime signal output part, anti-phase prime signal output part;
One end of described switch and described positive prime signal output part join, and the other end and described anti-phase prime signal output part join;
Described integrator circuit is for receiving the prime signal of output feedback signal and described preamplifying circuit output, and by described output feedback signal and prime signal shaping and filtering and subtract each other laggard line output; Wherein, described output feedback signal comprises positive output feedback signal and anti-phase output feedback signal;
Described integrator circuit comprises positive output feedback signal input, anti-phase output feedback signal input, the first output and the second output; Described positive output feedback signal input and described positive prime signal output part join, described anti-phase output feedback signal input and described anti-phase prime signal output part join, and described the first output and the second output are by described shaping filter and the output of the signal that subtracts each other.
Embodiment of the present invention in terms of existing technologies, realized the amplification of audio signal by preamplifying circuit, the decay of controlling the prime amplifying signal by conducting or the shutoff of switch, carried out output feedback signal and prime amplifying signal shaping filter and subtract each other laggard line output by integrator.Carry out the gain of ride gain control circuit by the control switch ON time, in this gain control circuit, do not need input resistance and feedback resistance segmentation in proportion, solved audio frequency power amplifier chip wiring difficulty, " click clatter " sound while having avoided regulating the gain control circuit gain.
In addition, switch is controlled by control circuit of duty ratio.Recently regulate the gain of described gain control circuit by the by-pass cock duty, can realize the step-less adjustment gain in certain limit, have more applicability.
In addition, this gain control circuit comprises the 3rd resistance R 3, the 4th resistance R 4; Described resistance R 3be connected between an end and described positive prime signal output part of switch; Described resistance R 4be connected between the other end and described anti-phase prime signal output part of switch.Described resistance R 3, R 4electric current while being used for the limit switch conducting, the protection preamplifying circuit.
In addition, the gain of preamplifying circuit is by input resistance R i, feedback resistance R fdetermine, and be set as the maximum of gain control circuit place system, to guarantee described gain control circuit, there is wide in range adjustable range.Because preamplifying circuit is existing mature technology, guaranteed the feasibility of embodiment of the present invention.
The accompanying drawing explanation
Fig. 1 is the structural representation of gain control circuit of the prior art;
Fig. 2 is the structural representation of the resistor network in gain control circuit of the prior art;
Fig. 3 is the structural representation according to the gain control circuit of first embodiment of the invention;
Fig. 4 is the control circuit of duty ratio according to first embodiment of the invention;
Fig. 5 is the structural representation according to the gain control circuit of second embodiment of the invention.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with accompanying drawing, the embodiments of the present invention are explained in detail.Yet, persons of ordinary skill in the art may appreciate that in each execution mode of the present invention, in order to make the reader understand the application better, many ins and outs have been proposed.But, even without these ins and outs and the many variations based on following each execution mode and modification, also can realize each claim of the application technical scheme required for protection.
The first execution mode of the present invention relates to a kind of gain control circuit, and as shown in Figure 3, this gain control circuit comprises the first resistance R 1, the second resistance R 2, the 5th resistance R i1, the 6th resistance R f1, the 7th resistance R i2, the 8th resistance R f2, the first capacitor C 1, the second capacitor C 2, the second difference transport and placing device, the 3rd difference transport and placing device and switch SW 1.
Wherein, the 5th resistance R i1, the 6th resistance R f1, the 7th resistance R i2, the 8th resistance R f2formed preamplifying circuit with the second difference transport and placing device, the prime signal that received audio signal output are amplified.Described audio signal comprises positive audio signal V iwith anti-phase audio signal-V i; Described prime signal comprises positive prime signal V o1with anti-phase prime signal-V o1.Described preamplifying circuit comprises two inputs and two outputs, described two inputs are respectively positive audio signal input end, anti-phase audio signal input end, and described two outputs are respectively positive prime signal output part, anti-phase prime signal output part.
Specifically, the 5th resistance R i1, the 7th resistance R i2for input resistance, the 6th resistance R f1, the 8th resistance R f2for feedback resistance; The second difference transport and placing device comprises an electrode input end, negative input, the first output and second output.The 5th resistance R i1one end is connected to described positive audio signal input end, and the other end is connected to the negative input of the second difference transport and placing device; The 6th resistance R f1one end is connected to the negative input of the second difference transport and placing device, and the other end is connected to the first output of the second difference transport and placing device; The 7th resistance R i2one end is connected to described anti-phase audio signal input end, and the other end is connected to the electrode input end of the second difference transport and placing device; The 8th resistance R f2one end is connected to the electrode input end of the second difference transport and placing device, and the other end is connected to the second output of the second difference transport and placing device.
In the present embodiment, the first resistance R 1, the second resistance R 2, the first capacitor C 1, the second capacitor C 2form integrator circuit with the 3rd difference transport and placing device, received the prime signal of output feedback signal and the output of described preamplifying circuit, and by output feedback signal and prime signal shaping and filtering and subtract each other laggard line output.Output feedback signal comprises positive output feedback signal VF 1with anti-phase output feedback signal-VF 1.Integrator circuit comprises positive output feedback signal input, anti-phase output feedback signal input, the first output and the second output; Described positive output feedback signal input and described positive prime signal output part join, described anti-phase output feedback signal input and described anti-phase prime signal output part join, and described the first output and the second output are by described shaping filter and the output of the signal that subtracts each other.
Specifically, the 3rd difference transport and placing device comprises an electrode input end, negative input, the first output and second output; The first capacitor C 1one end is connected to described positive output feedback signal input, and the other end is connected to the first output of integrator; The second capacitor C 2one end is connected to described anti-phase output feedback signal input, and the other end is connected to the second output of integrator; The negative input of the 3rd difference transport and placing device is connected to described positive output feedback signal input, the electrode input end of the 3rd difference transport and placing device is connected to described anti-phase output feedback signal input, the first output that the first output of the 3rd difference transport and placing device is described integrator, the second output that the second output of the 3rd difference transport and placing device is integrator.
In the present embodiment, switch SW 1an end and described positive prime signal output part join, the other end and described anti-phase prime signal output part join.Switch SW 1conducting or turn-off to control the decay of prime amplifying signal.By control switch SW 1oN time is carried out the gain of ride gain control circuit.Therefore, do not need, by input resistance and feedback resistance segmentation in proportion, to have solved audio frequency power amplifier chip wiring difficulty " click clatter " sound while having avoided described adjusting gain control circuit gain in this gain control circuit.
In the present embodiment, switch SW 1by control circuit of duty ratio, controlled, described control circuit of duty ratio is for controlling described switch SW 1conducting or shutoff, as shown in Figure 4, control circuit of duty ratio comprises buffer circuit and comparator.Buffer circuit is the first difference transport and placing device; The positive pole of the just very buffer circuit of the first difference transport and placing device, the negative pole that the negative pole of the first difference transport and placing device is buffer circuit, the output that the output of the first difference transport and placing device is buffer circuit.Buffer circuit receives outside regulation voltage V dand export the buffering signals of this outside regulation voltage; Comparator receives the sawtooth waveforms V of fixed frequency sAWwith the buffering signals from described buffer circuit output.The output signal that the output signal of control circuit of duty ratio is comparator.By by outside regulation voltage V dwith sawtooth waveforms V sAWcompare, work as V dv sAWthe time, V sAWfor low level; Otherwise, work as V d<V sAWthe time, V sAWfor high level, the reasonable disposition switch SW 1turn-on and turn-off, can realize that the required duty ratio of gain control circuit place system decay gain controls.By by-pass cock SW 1duty is recently controlled the degree of decay of prime amplifying signal, thereby realizes the adjusting to described gain control circuit gain.On the one hand, in described gain control circuit, do not need, by input resistance and feedback resistance segmentation in proportion, to have solved the audio frequency power amplifier chip wiring difficulty in the physics realization process.On the other hand, described gain control circuit adopts the regulative mode of duty ratio, can realize the step-less adjustment gain in certain limit, has avoided the appearance of " click clatter " sound.
Therefore, in the present embodiment, by connecting valve SW between positive prime signal output part and anti-phase prime signal output part 1, and by control circuit of duty ratio control switch SW 1duty is recently realized the gain of ride gain control circuit, makes and avoids, by input resistance and feedback resistance segmentation, having solved audio frequency power amplifier chip wiring difficulty, " click clatter " sound while having avoided regulating described gain control circuit gain.
And the preamplifying circuit sum-product intergrator is existing mature technology, guaranteed the feasibility of embodiment of the present invention.
In addition, it should be noted that, the gain of preamplifying circuit is by input resistance, feedback resistance decision, in the present embodiment, the maximum that is described gain control circuit place system by the gain setting of preamplifying circuit, have wide in range adjustable range to guarantee described gain control circuit.
It is worth mentioning that, the duty cycle circuit in present embodiment, be a kind of concrete implementation, in actual applications, also can adopt other equivalent circuit structures, at this, do not repeat one by one.
The second execution mode of the present invention relates to a kind of gain control circuit.The second execution mode has been done further improvement on the basis of the first execution mode, and main improvements are, in second embodiment of the invention, also comprise the 3rd resistance R 3, the 4th resistance R 4, as shown in Figure 5.
In the present embodiment, resistance R 3be connected on switch SW 1an end and described positive prime signal output part between; Resistance R 4be connected on switch SW 1the other end and described anti-phase prime signal output part between.Resistance R 3, R 4be used for limit switch SW 1electric current during conducting, the protection preamplifying circuit.
Persons of ordinary skill in the art may appreciate that the respective embodiments described above are to realize specific embodiments of the invention, and in actual applications, can do various changes to it in the form and details, and without departing from the spirit and scope of the present invention.

Claims (8)

1. a gain control circuit, is characterized in that, comprises: preamplifying circuit, switch sum-product intergrator circuit;
Described preamplifying circuit is for the prime signal of received audio signal output amplification; Described audio signal comprises positive audio signal and anti-phase audio signal; Described prime signal comprises positive prime signal and anti-phase prime signal; Described preamplifying circuit comprises two inputs and two outputs, described two inputs are respectively positive audio signal input end, anti-phase audio signal input end, and described two outputs are respectively positive prime signal output part, anti-phase prime signal output part;
One end of described switch and described positive prime signal output part join, and the other end and described anti-phase prime signal output part join;
Described integrator circuit is for receiving the prime signal of output feedback signal and described preamplifying circuit output, and by described output feedback signal and prime signal shaping and filtering and subtract each other laggard line output; Wherein, described output feedback signal comprises positive output feedback signal and anti-phase output feedback signal;
Described integrator circuit comprises positive output feedback signal input, anti-phase output feedback signal input, the first output and the second output; Described positive output feedback signal input and described positive prime signal output part join, described anti-phase output feedback signal input and described anti-phase prime signal output part join, and described the first output and the second output are by described shaping filter and the output of the signal that subtracts each other.
2. gain control circuit according to claim 1, is characterized in that, described gain control circuit also comprises the 3rd resistance and the 4th resistance;
Described the 3rd resistance is connected between an end and described positive prime signal output part of described switch;
Described the 4th resistance is connected between the other end and described anti-phase prime signal output part of described switch.
3. gain control circuit according to claim 1, is characterized in that, described gain control circuit comprises control circuit of duty ratio;
Described control circuit of duty ratio is for controlling conducting or the shutoff of described switch.
4. gain control circuit according to claim 3, is characterized in that, described control circuit of duty ratio comprises buffer circuit and comparator;
Described buffer circuit receives outside regulation voltage V dand export the buffering signals of this outside regulation voltage;
Described comparator receives the sawtooth waveforms V of fixed frequency sAWwith the buffering signals from described buffer circuit output;
The positive pole input external voltage of described buffer circuit, the negative pole of this buffer circuit directly is connected with the output of this buffer circuit, and the output of this buffer circuit directly is connected with the negative pole of described comparator, and the positive pole of described comparator is inputted described sawtooth waveforms V sAW;
The output signal that the output signal of described control circuit of duty ratio is described comparator.
5. gain control circuit according to claim 4, is characterized in that, described buffer circuit is the first difference transport and placing device;
The positive pole of the just very described buffer circuit of described the first difference transport and placing device, the negative pole that the negative pole of described the first difference transport and placing device is described buffer circuit, the output that the output of described the first difference transport and placing device is described buffer circuit.
6. gain control circuit according to claim 1, is characterized in that, described preamplifying circuit comprises the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance and the second difference transport and placing device;
Described the second difference transport and placing device comprises an electrode input end, negative input, the first output and second output;
Described the 5th resistance one end is connected to described positive audio signal input end, and the other end is connected to the negative input of described the second difference transport and placing device; Described the 6th resistance one end is connected to the negative input of described the second difference transport and placing device, and the other end is connected to the first output of described the second difference transport and placing device; Described the 7th resistance one end is connected to described anti-phase audio signal input end, and the other end is connected to the electrode input end of described the second difference transport and placing device; Described the 8th resistance one end is connected to the electrode input end of described the second difference transport and placing device, and the other end is connected to the second output of described the second difference transport and placing device.
7. according to the described gain control circuit of any one in claim 1 to 6, it is characterized in that the maximum that the gain setting of described preamplifying circuit is described gain control circuit place system.
8. gain control circuit according to claim 1, is characterized in that, described integrator circuit comprises the first resistance, the second resistance, the first electric capacity, the second electric capacity and the 3rd difference transport and placing device;
Described the first resistance is connected between an end and described positive output feedback signal input of described switch;
Described the second resistance is connected between the other end and described anti-phase output feedback signal input of described switch; Described the 3rd difference transport and placing device comprises an electrode input end, negative input, the first output and second output;
Described the first electric capacity one end is connected to described positive output feedback signal input, and the other end is connected to the first output of described integrator; Described the second electric capacity one end is connected to described anti-phase output feedback signal input, and the other end is connected to the second output of described integrator;
The negative input of described the 3rd difference transport and placing device is connected to described positive output feedback signal input, the electrode input end of described the 3rd difference transport and placing device is connected to described anti-phase output feedback signal input, the first output that the first output of described the 3rd difference transport and placing device is described integrator, the second output that the second output of described the 3rd difference transport and placing device is described integrator.
CN201310317887.2A 2013-07-25 2013-07-25 Gain control circuit Active CN103441742B (en)

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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101340244A (en) * 2008-08-08 2009-01-07 宁波环球广电科技有限公司 Optical receiving module
US20120169420A1 (en) * 2010-12-29 2012-07-05 Stmicroelectronics (Shenzhen) R&D Co. Ltd. Circuit and method for amplifying a digital signal
CN203590168U (en) * 2013-07-25 2014-05-07 上海智浦欣微电子有限公司 Gain control circuit

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN101340244A (en) * 2008-08-08 2009-01-07 宁波环球广电科技有限公司 Optical receiving module
US20120169420A1 (en) * 2010-12-29 2012-07-05 Stmicroelectronics (Shenzhen) R&D Co. Ltd. Circuit and method for amplifying a digital signal
CN203590168U (en) * 2013-07-25 2014-05-07 上海智浦欣微电子有限公司 Gain control circuit

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