CN102571009B - Feedforward automatic gain control circuit working in extremely low voltage current mode - Google Patents
Feedforward automatic gain control circuit working in extremely low voltage current mode Download PDFInfo
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Abstract
The invention provides a feedforward automatic gain control circuit working in an extremely low voltage current mode, and relates to the technology of sensors. The feedforward automatic gain control circuit comprises a fully differential operational amplification unit, a capacitive-resistance device, a resistor array, a control switch, rectifier, a filter, a controller, a digital reference table, a digital comparator and an add-subtract counter, wherein the fully differential operational amplification unit is used for correspondingly amplifying voltage signals of an output end of a microphone according to variation of the resistance array; the rectifier is used for converting the voltage signals into current signals and rectifying current; the filter is used for filtering the current output by the rectifier and carrying out envelop detection on input signals; the digital controller is used for comparing current output by the filter with the reference current to obtain digital control signals in the digital reference table; the digital comparator is used for comparing output of the add-subtract counter with the digital control signals, when the sound volume is in different levels, the amplifying multiple of the fully differential operational amplification unit is adjusted, so that the hearing of the auditorily handicapped is protected; when the sound volume is in a normal state, the amplifying multiple of the fully differential operational amplification unit is restored to the original value, so that the automatic gain control on the different sound volumes is realized.
Description
Technical field
The present invention relates to microphone sensor technical field, relate to the high-precision readout circuit chip that is applicable to micro-acoustic-electric system (MEMS) microphone sensor, is the automatic gain control circuit of digital deaf-aid microphone reading circuit chip.
Background technology
Along with the continuous progress of micro-acoustic-electric system (MEMS) technology, micro-acoustic-electric hearing aid microphone transducer arises at the historic moment, it has that volume is little, low in energy consumption, distortion is little and the advantage such as noise resisting ability is strong, and its corresponding reading circuit becomes the focus of industrial quarters research.
This transducer can be equivalent to a comparatively desirable voltage source conventionally: a very little resistance on desired voltage subject string.But the signal of microphone micro-electro-mechanical sensors output is very faint, generally only between μ V～mV magnitude, this design to reading circuit has proposed very harsh requirement.The noise level of reading circuit and precision have determined its minimum signal amplitude that can detect, and low noise and high-precision reading circuit are designed in order to realize high-precision key, especially in the extremely low supply voltage situation of digital microphone.
The Design of Automatic Gain Control of microphone reading circuit mainly can be divided into analog feedback control amplifier forward direction open-loop gain in the world at present, it is (the reference: Jones of analog feedback control amplifier bias current, Mario Martinez: " a kind of CMOS hearing aids ", analog integrated circuit and signal processing, 21,163-172 (1999); Bake: ' a kind of low-power consumption monocycle for artificial ear and the control of dicyclo automatic gain ', solid-state circuit, SC-41 (9), pp.1983-1996,2006) and (reference: Huo Man: " a kind of low noise CMOS automatic gain control ", solid-state circuit, SC-27 (7) of the gate source voltage of the controlled metal-oxide-semiconductor equivalent resistance of analog feedback control, pp.974-981,1992; Jin Shuyong: " a kind of efficient analog front end circuit of sub-1V digital deaf-aid ", solid-state circuit, SC-41 (4), pp.876-882,2006.) and current-mode FEEDBACK CONTROL metal-oxide-semiconductor mutual conductance (reference: lattice draw Leix: " low pressure subthreshold value index amplifies and automatic gain control ", circuit, device and system, Vol.152, No.1, Feb 2005) two schemes.And above automatic gain control circuit obtains application widely in simulation hearing aids field.But the former shortcoming is its linearity and can be subject to the restriction of technique and supply voltage, special in the situation that supply voltage is lower.The advantage of analog feedback is that its signal has stronger continuity.But the difficult point of analog feedback is the realization of the amplifier output accuracy of low-voltage.Conventionally the multiplication factor of amplifier has realized comparatively ideal precision under the control of analog feedback, and realize very high precision in integrated circuit, is extremely difficult, conventionally needs complicated compensating circuit or very large power consumption.The shortcoming of current-mode feedback system is that amplifier itself does not have negative feedback structure, thereby system is lower to the precision of signal processing.And digital deaf-aid requires reading circuit to have extraordinary reading accuracy, this has proposed challenge to the design of reading circuit.
Summary of the invention
The object of the invention is open one and work in utmost point low supply voltage current-mode feedforward automatic gain control circuit, it is the microphone reading circuit of current-mode feedforward, to overcome the deficiencies in the prior art, not only can effectively realize the function of automatic gain control, more by the high accuracy that adopts passive resistance array to realize under utmost point low-voltage, read.Possess under low supply voltage work, along with the increase of volume, power consumption reduces thereupon simultaneously, reaches the function that power consumption rate is utilized.The present invention provides the automatic gain control reading circuit of a kind of high accuracy, low-voltage for digital deaf-aid microphone.
For achieving the above object, technical solution of the present invention is:
One works in utmost point low supply voltage current-mode feedforward automatic gain control circuit, for hearing aids; It comprises: Differential OPAMP unit, appearance resistance device, electric resistance array, antenna array control switch, rectifier, filter, digital reference table, digitial controller, digital comparator and forward-backward counter;
One Differential OPAMP unit, for the amplification to microphone output signal;
Two inputs of Differential OPAMP unit hold resistance device through two respectively and are connected with ground with microphone output, in order to form the high-pass filtering to input signal;
Two electric resistance arrays are connected across respectively between two outputs, two inputs of Differential OPAMP unit, in order to determine the yield value of Differential OPAMP to signal;
Two electric resistance array control switchs are connected to respectively two electric resistance array one sides, in order to control the yield value of Differential OPAMP unit;
One rectifier is for carrying out rectification to microphone output small-signal;
Rectifier and a filter form envelope detected circuit, obtain detecting the energy of microphone output signal in order to rectified signal is carried out to filtering;
One digitial controller, output valve and reference level to peak detection circuit compare;
One digital reference table, in order to search corresponding digital reference code;
One forward-backward counter, the compression in order to automatic gain control to signal and recovery;
One digital comparator, controls forward-backward counter and adds reducing, and it compares the enable logic with output squeezing and recovery by the output encoder of forward-backward counter and reference encoder.
Described current-mode feedforward automatic gain control circuit, its physical circuit is as follows: the first and second inputs of Differential OPAMP unit are connected with microphone output with ground through the first and second appearance resistance devices respectively, the first electric resistance array is connected across first input end and second output of Differential OPAMP unit, and the second electric resistance array is connected across the second input and first output of Differential OPAMP unit; The first electric resistance array control switch is connected across the first electric resistance array and Differential OPAMP unit one output, and the second electric resistance array control switch is connected across the second electric resistance array and another output of Differential OPAMP unit;
Rectifier input connects microphone output, rectifier order and low pass filter, digitial controller, digital reference table, digital comparator one input electrical connection, and another output of digitial controller is electrically connected with Differential OPAMP unit;
Forward-backward counter input is electrically connected with two clocks, digital comparator two outputs respectively, another input electrical connection of forward-backward counter output respectively with the first antenna array control switch, the second antenna array control switch, digital comparator.
Described current-mode feedforward automatic gain control circuit, Differential OPAMP unit described in it, according to the different adjustment bias current of multiplication factor, makes in the situation that volume is larger, amplifier power consumption to be reduced; Wherein, M1, M2MOS pipe works in sub-threshold region, makes constant bandwidth.
Described current-mode feedforward automatic gain control circuit, rectifier and filter described in it, under the utmost point low supply voltage of 0.8V, the small-signal more than 100uV of microphone output is carried out to rectification and filtering, and the signal transmission of rectifier and filter is current-mode signal; The M8 of filter circuit, M9MOS pipe works in sub-threshold region.
Described current-mode feedforward automatic gain control circuit, digitial controller described in it, under the utmost point low supply voltage of 0.8V, carries out logic control output to the small-signal more than 100uV of microphone output.
One of the present invention works in utmost point low supply voltage current-mode feedforward automatic gain control circuit, can be for the automatic gain control reading circuit of the current-mode feedforward of digital deaf-aid, it is digital controlled signal that its mode by feedforward makes the power conversion of microphone output signal, thereby by digital control circuit controlling resistance array, the gain of amplifier is controlled, effectively solved the problem of its continuity and precision.Circuit of the present invention be applicable to very low operation supply voltage (as, 0.8V is following), it contributes to provide a kind of low-voltage, low-power consumption and the high-precision reading circuit that is used in portable digital hearing aids, realized the method for automatic ride gain digital feed forward and the circuit of working under low-voltage accordingly.
Accompanying drawing explanation
Fig. 1 is the utmost point low supply voltage current-mode feedforward automatic gain control circuit figure that works in of the present invention, wherein, and main element label declaration:
Differential OPAMP unit 1 first holds resistance device 2
Second holds resistance device 3 first electric resistance arrays 4
The second electric resistance array 5 first electric resistance array control switchs 6
The second electric resistance array control switch 7 rectifiers 8
Forward-backward counter 13;
Fig. 2 is the Differential OPAMP circuit diagram that works in utmost point low supply voltage in the present invention;
Fig. 3 is the rectifier circuit figure that works in utmost point low supply voltage in the present invention;
Fig. 4 is the filter circuit figure that works in utmost point low supply voltage in the present invention;
Fig. 5 is the digitial controller circuit diagram that works in utmost point low supply voltage in the present invention.
Embodiment
The present invention has provided one and has worked in utmost point low supply voltage current-mode feedforward automatic gain control circuit, by employing, work in the circuit module of low supply voltage, the mode of current-mode feedforward and Digital Circuit Control efficiently solves the nonlinear problem that prior art exists.
The present invention carries out high pass by holding 2,3 pairs of microphone direct current signals of resistance device, and filtering microphone direct current signal, reads microphone small-signal by Differential OPAMP circuit 1; The energy of the envelope detected electric circuit inspection microphone small-signal that rectifier 8 and filter 9 form simultaneously, digitial controller 11 is processed and is obtained digital controlled signal energy, digital reference table 10 is found corresponding gain control code according to digital controlled signal, be applied to digital comparator 12, obtain enable signal, realize the plus-minus counting function of forward-backward counter 13, realized the function of Signal Compression and recovery.Plus-minus counting is synchronous with clock 22 and 33 respectively.And gain control code corresponding to alternative sounds magnitude, final amplifier gain is realized by electric resistance array 4,5 and electric resistance array control switch 6,7 controlling resistance arrays 4,5 by gain control code.
This circuit can be read by wind signal owing to adopting the mode of electric resistance array to realize high-precision wheat under low supply voltage, and by current feed-forward, numerically controlled mode has realized the automatic gain control under low supply voltage simultaneously.
Fig. 1 is the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention.Automatic gain control circuit is divided into following components, comprising: Differential OPAMP unit 1, appearance resistance device, electric resistance array, antenna array control switch, rectifier 8, filter 9, digital reference table 10, digitial controller 11, digital comparator 12 forward-backward counters 13;
Differential OPAMP unit 1 first and second input is connected with microphone output with ground through the first and second appearance resistance devices 2,3 respectively, the first electric resistance array 4 is connected across Differential OPAMP unit 1 first input end and the second output, the second electric resistance array 5 is connected across Differential OPAMP unit 1 second input and the first output, the first electric resistance array control switch 6 is connected across the first electric resistance array 4 and Differential OPAMP unit 1 output, and the second electric resistance array control switch 7 is connected across the second electric resistance array unit 5 and Differential OPAMP unit 1 output.Rectifier 8 inputs connect microphone input, output order and low pass filter 9, digitial controller 11, digital reference table 10, digital comparator 12 input electrical connections, and digitial controller 11 another outputs are electrically connected with Differential OPAMP unit 1.Forward-backward counter 13 inputs are electrically connected with two clocks 22,33, digital comparator 12 outputs respectively, another input electrical connection of forward-backward counter 13 output respectively with the first antenna array control switches 6, the second antenna array control switch 7, digital comparator 12.
With reference to figure 2, in actual applications, consider under lower supply voltage and lower power consumption, the bias current of Differential OPAMP unit 1 is designed to programmable offset current source 14, it is controlled by digitial controller 11, and difference is inputted M1, and M2MOS pipe is operated in sub-threshold region 15, has adopted the circuit topological structure of cascade simultaneously.This circuit possesses common mode output detection circuit simultaneously, common mode input detecting circuit and the function in the situation that volume is larger, amplifier power consumption being reduced.In order to prevent due to the too high common-mode input range that causes input common mode electrical level to exceed amplifier of common mode output level transient state output, in Fig. 2, by M6, M7, M8, M12, the input common mode testing circuit that M13MOS pipe forms follows the tracks of the input common mode electrical level beginning track that makes Differential OPAMP in output common mode level.And output common mode level is by M9, M10, M11, M14, the output common mode feedback control loop that M16MOS pipe forms is determined.When level of sound volume is different, digitial controller is to by M3, M4, and M5, M6, the programmable offset current source that M11MOS pipe forms reduces or increases, thereby reaches the object with high efficiency Differential OPAMP, and its gain bandwidth is:
ω
AGC＝β
iω
OTA＝β
ig
m/C
comp
Wherein β
ifor fully differential feedback factor, by feedback loop, determined g
m, C
compfor M1, the mutual conductance of M2MOS pipe and Differential OPAMP building-out capacitor.Due to M1, M2MOS pipe works in sub-threshold region, can realize the Linear Control of mutual conductance is realized to constant-gain bandwidth under different gains.
The output signal of microphone is carried out rectification by rectifier to it simultaneously, with reference to figure 3.Consider that this rectifier is operated in low supply voltage state, this rectifier adopts current-Mode Circuits cascade form, adopts capacitance-resistance C, and it is electric current that R makes voltage transitions, respectively forward current and the negative current of conversion is carried out to rectification with two cascade feedback control loops simultaneously.Its pipe all works in saturation region, can bear minimum operating voltage to be:
V
DD-MIN＝2
VGS-V
TH
Wherein V
gSfor metal-oxide-semiconductor gate source voltage, V
tHfor metal-oxide-semiconductor threshold voltage.
In Fig. 3, the feedback control loop that forward current is carried out to rectification is by M1, M2, and M3, M4MOS manages formation, and it is that voltage-to-current is degenerative across resistance amplifier structure, and object is the input resistance reducing across resistance amplifier, and electric current can be flowed into.Should can be determined by formula below across input impedance of resistance amplifier:
G in formula
md, g
mgbe respectively the grid mutual conductance of pipe, leak mutual conductance, C
compfor building-out capacitor.
The feedback control loop that negative current is carried out to rectification is by M5, M6, and M7, M8MOS manages formation, and when electric current is negative current, signal will carry out rectification, C to negative current by forward current feedback loop cascade negative current feedback loop
comp1for the building-out capacitor of negative current feedback loop.For the response time that makes forward current rectification equated with the response time of negative current rectification, C
compwith C
comp1relation can be determined by formula below:
I in formula
biaswith I be respectively M4, the bias current of M5MOS pipe.The filtered device filtering of this rectified signal subsequently obtains the energy signal of input current.This filter has adopted the filtering mode of current-voltage-electric current to carry out filtering to this rectified current signal, with reference to figure 4.M6, M7, M8, M9, M10MOS pipe forms the core circuit of filter, and it is similar to traditional active amplifier filter circuit, and different is, the M8 of this circuit, M9MOS pipe works in sub-threshold region. and for the electric current of accurate mirror image M1 and M2, in circuit, add the pass of buffer 1. its input and output to be
Wherein I is the parameter that control capacittance C discharges and recharges.
In Fig. 4, M1, M2MOS pipe plays respectively the function of current-voltage and Voltage-current conversion.M1, M2MOS pipe works in sub-threshold region.In conjunction with relational expression above, can obtain overall filter-the cut-off frequency expression formula of 3dB is
Obtain after the energy of filtered circuit, in order to wait until digital control reference code, can by digitial controller, relatively obtain with reference level.
Digitial controller is with reference to figure 5, and what it utilized the output of prime current-mode and reference current I1-8 relatively obtains logic control level, then by encoder 16, obtains the control code 18 for the control code 17 of digital circuit and the adjusting of Differential OPAMP bias current.And reference current is obtained by identical rectifier 8 and filter 9.Its objective is in order to prevent the impact of process corner (PVT) on reference stream.Simultaneously in order to prevent that digitial controller 11 from vibrating in critical condition, uses I
0as the sluggish electric current of digitial controller 11, to guarantee the steady operation of digitial controller 11.
Digital comparator provides the enable signal of forward-backward counter plus-minus.And forward-backward counter provides the control coding signal of controlling amplifier electric resistance array.When volume is become when high-grade by inferior grade, when automatic gain control circuit compresses signal, counter is for subtracting counting operation, and while reducing to the reference encoder of appointment, digital circuit will make counter stop subtracting counting by digital comparator output enable signal; When volume is become when high-grade by high-grade, automatic gain control circuit will recover or remain to initial value signal.Concrete enforcement can make counter stop adding by digital comparator output enable signal to have counted.
Known from the above description, the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention is connected the output of microphone with automatic gain Control loop amplifier input, microphone output is connected with the input of rectifier simultaneously.The ratio of the output voltage of microphone being pressed to electric resistance array by Differential OPAMP is realized the amplification to it.Simultaneously in order to obtain different digital controlled signals corresponding to different volume ranks, microphone output signal need be carried out to quantification treatment, first by rectifier, microphone output voltage signal is carried out to rectification, its rectification output signal carries out to it input signal energy that filtering obtains by filter.Energy signal compares processing by digitial controller and reference level, obtains digital controlled signal, is found out other digital reference of diaphone magnitude encode by digital controlled signal on digital reference table.When volume is normal quantity rank, counter is not worked, and signal normally amplifies; When from amount of bass rank toward the transition of louder volume rank, counter is for subtracting counting, and counter subtracts by a upper encoding state this reference encoder state now that count down to, and the multiplication factor of Differential OPAMP from large to small, realizes the compression to signal.When from louder volume rank toward amount of bass level transition, counter is for adding counting, and counter is added and count down to this reference encoder state now by a upper encoding state, and the multiplication factor of Differential OPAMP is changed from small to big, and realizes the recovery of signal is amplified.When counter output encoder and digital reference, encode when identical, stop adding counting and subtracting counting of counter.The yield value of automatic gain control is determined by the digital reference coding in digital reference table, realize volume and encode at the different digital reference of different brackets correspondence: this realizes the function of automatic gain control according to the rank of volume with regard to having realized microphone reading circuit.
More than to the utmost point low supply voltage current-mode feedforward automatic gain control circuit that works in of the present invention, make microphone work in the description of the execution mode of utmost point low supply voltage current-mode feedforward automatic gain control, to one skilled in the art, some advantage that has obtained this circuit is apparent.Also should be appreciated that in scope and spirit of the present invention and can carry out various changes, modification and alternative embodiment.The protection range that protection scope of the present invention delimited by claims is completely boundary.
Claims (5)
1. work in a utmost point low supply voltage current-mode feedforward automatic gain control circuit, for hearing aids; It is characterized in that, comprising: Differential OPAMP unit, appearance resistance device, electric resistance array, antenna array control switch, rectifier, filter, digital reference table, digitial controller, digital comparator and forward-backward counter;
One Differential OPAMP unit, for the amplification to microphone output signal;
Two inputs of Differential OPAMP unit hold resistance device through two respectively and are connected with ground with microphone output, in order to form the high-pass filtering to input signal;
Two electric resistance arrays are connected across respectively between two outputs, two inputs of Differential OPAMP unit, in order to determine the yield value of Differential OPAMP to signal;
Two electric resistance array control switchs are connected to respectively two electric resistance array one sides, in order to control the yield value of Differential OPAMP unit;
One rectifier is for carrying out rectification to microphone output small-signal;
Rectifier and a filter form envelope detected circuit, obtain detecting the energy of microphone output signal in order to rectified signal is carried out to filtering;
One digitial controller, output valve and reference level to envelope detected circuit compare;
One digital reference table, in order to search corresponding digital reference code;
One forward-backward counter, the compression in order to automatic gain control to signal and recovery;
One digital comparator, controls forward-backward counter and adds reducing, and it compares the enable logic with output squeezing and recovery by the output encoder of forward-backward counter and reference encoder.
2. current-mode feedforward automatic gain control circuit as claimed in claim 1; it is characterized in that; physical circuit is as follows: the first and second inputs of Differential OPAMP unit are connected with microphone output with ground through the first and second appearance resistance devices respectively; the first electric resistance array is connected across first input end and second output of Differential OPAMP unit, and the second electric resistance array is connected across the second input and first output of Differential OPAMP unit; The first electric resistance array control switch is connected across the first electric resistance array and Differential OPAMP unit one output, and the second electric resistance array control switch is connected across the second electric resistance array and another output of Differential OPAMP unit;
Rectifier input connects microphone output, rectifier order and low pass filter, digitial controller, digital reference table, digital comparator one input electrical connection, and another output of digitial controller is electrically connected with Differential OPAMP unit;
Forward-backward counter input is electrically connected with two clocks, digital comparator two outputs respectively, another input electrical connection of forward-backward counter output respectively with the first antenna array control switch, the second antenna array control switch, digital comparator.
3. current-mode feedforward automatic gain control circuit as claimed in claim 1, is characterized in that described Differential OPAMP unit, according to the different adjustment bias current of multiplication factor, makes in the situation that volume is larger, amplifier power consumption to be reduced; Wherein, the input difference of Differential OPAMP works in sub-threshold region to pipe (Ml, M2).
4. current-mode feedforward automatic gain control circuit as claimed in claim 1, it is characterized in that, described rectifier and filter, under the utmost point low supply voltage of 0.8V, the small-signal more than 1OOuV of microphone output is carried out to rectification and filtering, and the signal transmission of rectifier and filter is current-mode signal.
5. current-mode feedforward automatic gain control circuit as claimed in claim 1, is characterized in that described digitial controller, under the utmost point low supply voltage of 0.8V, carries out logic control output to the small-signal more than 1OOuV of microphone output.
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| CN104183241B (en) * | 2013-05-28 | 2017-09-29 | 无锡华润矽科微电子有限公司 | Improve the control circuit and method of audio signal volume regulation |
| EP3262849B1 (en) * | 2015-02-27 | 2019-07-03 | TDK Corporation | Integrated circuit arrangement for a microphone, microphone system and method for adjusting one or more circuit parameters of the microphone system |
| CN104660194B (en) * | 2015-03-06 | 2017-05-31 | 东南大学 | A kind of four input trsanscondutance amplifiers for fully differential Gm C wave filters |
| US10627430B2 (en) * | 2016-05-24 | 2020-04-21 | Texas Instruments Incorporated | Fast current-based envelope detector |
| CN105915192A (en) * | 2016-05-25 | 2016-08-31 | 东南大学 | Stepping-type automatic gain control system |
| CN106533276B (en) * | 2016-12-07 | 2019-09-06 | 芯愿景软件有限公司 | A kind of method and circuit of servo motor position detection |
| CN107317563B (en) * | 2017-08-21 | 2024-02-13 | 四川西南交大铁路发展股份有限公司 | Differential selection filter circuit and method |
| CN111490739B (en) * | 2019-01-25 | 2023-09-26 | 杭州海康威视数字技术股份有限公司 | Device and equipment for amplifying audio signal |
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| CN101102097A (en) * | 2006-07-07 | 2008-01-09 | 美国凹凸微系有限公司 | Fixed gain amplifier for automatic gain control and variable gain amplifier |
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| US5061900A (en) * | 1989-06-19 | 1991-10-29 | Raytheon Company | Self-zeroing amplifier |
| CN101171745A (en) * | 2005-03-10 | 2008-04-30 | Nxp股份有限公司 | Receiver having a gain-controllable input amplifier |
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