CN107212877A - Variable gain mixer amplifier, biological signal collecting and process chip and system - Google Patents
Variable gain mixer amplifier, biological signal collecting and process chip and system Download PDFInfo
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Abstract
本发明涉及一种可变增益混频放大器、生物信号采集与处理芯片及系统。该芯片包括可变增益混频放大器11、本振信号产生电路12、能量获取单元13、第一电容C1和第一电阻R1；可变增益混频放大器11的生物信号输入端Vin接收生物信号，其电源输入端VDD电连接能量获取单元13，其本振信号输入端LO电连接本振信号产生电路12，其接地端GND用于获取外部供地信号，其输出端Vout电连接第一电容C1的第一端且第一电容C1的第二端用于输出经调制后的音频信号；本振信号产生电路12用于接收交流电信号并经处理后为可变增益混频放大器11提供本振信号；能量获取单元13用于接收交流电信号并经处理后为可变增益混频放大器11提供直流电源。
The invention relates to a variable gain mixing amplifier, a biological signal acquisition and processing chip and a system. The chip includes a variable gain mixing amplifier 11, a local oscillator signal generating circuit 12, an energy acquisition unit 13, a first capacitor C1 and a first resistor R1; the biological signal input terminal Vin of the variable gain mixing amplifier 11 receives biological signals, Its power input terminal VDD is electrically connected to the energy acquisition unit 13, its local oscillator signal input terminal LO is electrically connected to the local oscillator signal generating circuit 12, its ground terminal GND is used to obtain an external ground supply signal, and its output terminal Vout is electrically connected to the first capacitor C1 The first terminal of the first capacitor C1 and the second terminal of the first capacitor C1 are used to output the modulated audio signal; the local oscillator signal generating circuit 12 is used to receive the AC signal and provide a local oscillator for the variable gain mixing amplifier 11 after processing Signal; the energy acquisition unit 13 is used to receive the AC signal and provide DC power for the variable gain mixing amplifier 11 after processing.
Description
Technical Field
The invention belongs to the technical field of integrated circuit design, and particularly relates to a variable gain mixer amplifier, a biological signal acquisition and processing chip and a system.
Background
With the increasing demand for health and medical care, wearable and implantable medical devices based on Wireless Body Area Networks (WBANs) have attracted much attention. The medical equipment is convenient to use, can realize real-time monitoring of human body signals, and sends the human body signals to the intelligent terminal for data processing, and has important significance for prevention and monitoring of diseases. Common biological signals comprise Electrocardiosignals (ECG), electroencephalogram (EEG) signals, Electromyogram (EMG) signals and the like, the signals are very weak, typical values are in the micro-volt and millivolt magnitude, the frequency is low, and strict requirements are imposed on the low noise performance of an acquisition system. The chopper modulation technique is a noise reduction technique commonly used in biological signal amplifiers, and realizes the spectral separation of biological signals and low-frequency noise, thereby filtering the noise. The amplified signal is transmitted through the audio line, and the ADC (analog-to-digital converter) and the digital signal processing are completed by using the intelligent terminal, so that the structure of a front-stage circuit can be simplified. However, the conventional low-noise preamplifier and other chips are required to be adopted in the conventional audio modulation system using the chopping modulation technology, the problems of large circuit structure area and high power consumption caused by the redundant circuit exist in the chip, and the internal circuit of the chip cannot be changed due to the adoption of the conventional inherent chip structure, so that the circuit function expansion is greatly influenced.
Therefore, how to develop an audio modulation system and a chip structure with simple circuit structure, area saving and small power consumption becomes a hot problem of current research.
Disclosure of Invention
In order to solve the above problems in the prior art, the present invention provides a variable gain mixer amplifier, a biological signal collecting and processing chip and a system.
An embodiment of the present invention provides a biological signal collecting and processing chip 10, which includes a variable gain mixer amplifier 11, a local oscillator signal generating circuit 12, an energy obtaining unit 13, a first capacitor C1, and a first resistor R1; wherein,
a biological signal input terminal Vin of the variable gain mixer amplifier 11 receives a biological signal, a power input terminal VDD thereof is electrically connected to the energy obtaining unit 13, a local oscillator signal input terminal LO thereof is electrically connected to the local oscillator signal generating circuit 12, a ground terminal GND thereof is used for obtaining an external common ground signal, an output terminal Vout thereof is electrically connected to a first terminal of the first capacitor C1, and a second terminal of the first capacitor C1 is used for outputting a modulated audio signal;
the local oscillation signal generating circuit 12 is configured to receive an ac electrical signal and provide a local oscillation signal to the variable gain mixer amplifier 11 after processing the ac electrical signal;
the energy obtaining unit 13 is configured to receive an ac electrical signal and provide a dc power supply for the variable gain mixer amplifier 11 after processing the ac electrical signal;
the resistor R1 is connected in series between the ground GND of the variable gain mixer amplifier 11 and the second end of the first capacitor C1.
In one embodiment of the present invention, the variable gain mixer amplifier 11 comprises a low noise pre-mixer amplifier 111, a programmable gain amplifier 112, a band-pass filter 113 and an output buffer 114; wherein,
the low-noise pre-mixer amplifier 111, the programmable gain amplifier 112, the band-pass filter 113 and the output buffer 114 are sequentially connected in series between the bio-signal input terminal Vin and the first capacitor C1, and the low-noise pre-mixer amplifier 111 is electrically connected to the local oscillator signal input terminal LO.
In one embodiment of the invention, the low noise pre-mixer amplifier 111 comprises an AM modulation module 1111 and a pre-amplifier module 1112; the AM modulation module 1111 and the preamplifier module 1112 are sequentially connected in series between the bio-signal input terminal Vin and the programmable gain amplifier 112, and the AM modulation module 1111 is electrically connected to the local oscillator signal input terminal LO.
In an embodiment of the present invention, the local oscillator signal generating circuit 12 includes a bias circuit 121 and a signal shaping circuit 122, the bias circuit 121 and the signal shaping circuit 122 are sequentially connected in series to the local oscillator signal input terminal LO of the variable gain mixer amplifier 11, and the input terminal of the bias circuit 121 receives the ac electrical signal.
In one embodiment of the present invention, the signal shaping circuit 122 includes: a fifth transistor M5, a sixth transistor M6, a seventh transistor M7, a first inverter INV1, a second inverter INV2, a third inverter INV3, a fourth inverter INV4, a second resistor R2, and a third resistor R3; wherein,
the second resistor R2, the fifth transistor M5 and the seventh transistor M7 are sequentially connected in series between a dc power supply and a ground terminal, a control terminal of the fifth transistor M5 is inputted with a coupling signal VSIN, and a control terminal of the seventh transistor M7 is inputted with a bias voltage VBIAS;
the third resistor R3 and the sixth transistor M6 are sequentially connected in series between the direct current power supply and a node G formed by connecting the fifth transistor M5 and the seventh transistor M7 in series, and the control end of the sixth transistor M6 is input with a reference voltage VREF;
the first inverter INV1 and the second inverter INV2 are sequentially connected in series to a node E formed by the second resistor R2 and the fifth transistor M5 in series, and an output end of the first inverter INV1 is electrically connected to a local oscillation signal input end LO of the variable gain mixer amplifier 11 to output a first local oscillation signal;
the fourth inverter INV4 and the third inverter INV3 are sequentially connected in series to a node F formed by the third resistor R3 and the sixth transistor M6 in series, and the fourth inverter INV4 is electrically connected to the local oscillation signal input terminal LO of the variable gain mixer amplifier 11 to output a second local oscillation signal.
In one embodiment of the present invention, the energy harvesting unit 13 includes a rectifier 131, an overvoltage protection circuit 132, and an LDO 133; the rectifier 131, the overvoltage protection circuit 132 and the LDO133 are sequentially connected in series to the power input terminal VDD of the variable gain mixer amplifier 11 to provide a dc power, and the rectifier 131 receives the ac electrical signal.
Another embodiment of the present invention provides a variable gain mixer amplifier 11, which includes a low noise pre-mixer amplifier 111, a programmable gain amplifier 112, a band-pass filter 113, and an output buffer 114 connected in series in sequence, and a first input terminal of the low noise pre-mixer amplifier 111 receives a biological signal and a second input terminal thereof receives a local oscillator signal.
In one embodiment of the present invention, the low noise pre-mixer amplifier 111 includes an AM modulation module 1111 and a pre-amplifier module 1112 connected in series in sequence; the signal input terminal of the AM modulation module 1111 receives the bio-signal and the local oscillator input terminal thereof receives the local oscillator signal, and the output terminal of the preamplifier module 1112 is electrically connected to the programmable gain amplifier 112.
In one embodiment of the present invention, the AM modulation module 1111 includes a first transistor M1, a second transistor M2, a third transistor M3 and a fourth transistor M4; the signal input end of the AM modulation module 1111 includes a first signal input end IN + and a second signal input end IN-, the local oscillator input end of the AM modulation module 1111 includes a first local oscillator input end LO + and a second local oscillator input end LO-, and the output end of the AM modulation module 1111 includes an IN-phase output end OUT + and an anti-phase output end OUT-; wherein,
the first transistor M1 is connected IN series between the first signal input terminal IN + and the IN-phase output terminal OUT +, and a control terminal thereof is electrically connected to the first local oscillator input terminal LO +;
the second transistor M2 is connected IN series between the first signal input terminal IN + and the inverted output terminal OUT-, and a control terminal thereof is electrically connected to the second local oscillator input terminal LO-;
the third transistor M3 is connected IN series between the second signal input terminal IN-and the IN-phase output terminal OUT +, and its control terminal is electrically connected to the second local oscillator input terminal LO-;
the fourth transistor M4 is connected IN series between the second signal input terminal IN-and the inverted output terminal OUT-, and has a control terminal electrically connected to the first local oscillator input terminal LO +.
Still another embodiment of the present invention provides a biological signal collecting and processing system 1, which comprises a biological signal collecting and processing chip 10, an earphone interface 20, a biological electrode 30 and a terminal 40, wherein the biological signal collecting and processing chip 10 is electrically connected to the biological electrode 30 and sends the collected and modulated biological signal to the terminal 40 through the earphone interface 20; the biological signal collecting and processing chip 10 is the biological signal collecting and processing chip 10 provided in any of the above embodiments.
Through the above embodiment, the whole signal acquisition and processing chip of the invention is integrated in one IC chip, and can complete modulation, amplification and transmission of biological signals. In addition, the chip combines the audio AM modulation and the chopping technology, so that two times of redundant modulation in the modulation-demodulation-remodulation process are omitted, the signal can be modulated to the audio frequency only through one-time modulation, the spectrum separation of the signal and the noise is realized through the modulation, the noise is reduced through a post-stage filter, and the effect of chopping modulation is achieved. Because the gain of the variable gain mixing amplifier is adjustable, the chip can collect and process different biological signals (electrocardiosignals, electroencephalogram signals, electromyogram signals and the like). In addition, this biological signal gathers and two sound channels of processing system make full use of 3.5mm earphone cord, provides mains voltage and stable local oscillator signal for the system.
Drawings
Fig. 1 is a schematic circuit diagram of a biological signal collecting and processing system according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a circuit structure of a biological signal collecting and processing chip according to an embodiment of the present invention;
fig. 3 is a schematic circuit diagram of a variable gain mixer amplifier according to an embodiment of the present invention;
fig. 4 is a schematic circuit diagram of a low-noise pre-mixer amplifier according to an embodiment of the present invention;
fig. 5 is a schematic diagram comparing circuit structures of a variable gain mixer amplifier according to an embodiment of the present invention;
fig. 6 is a schematic circuit diagram of an AM modulation module according to an embodiment of the present invention;
fig. 7 is a schematic circuit structure diagram of a local oscillator signal generating circuit according to an embodiment of the present invention;
fig. 8 is a circuit diagram of a signal shaping circuit according to an embodiment of the present invention;
fig. 9 is a schematic circuit diagram of an energy harvesting unit according to an embodiment of the present invention;
fig. 10 is a schematic circuit diagram of a rectifier according to an embodiment of the present invention;
fig. 11 is a circuit schematic diagram of an overvoltage protection circuit according to an embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to specific examples, but the embodiments of the present invention are not limited thereto.
Example one
Referring to fig. 1, fig. 1 is a schematic circuit structure diagram of a biological signal collecting and processing system according to an embodiment of the present invention. The biological signal collecting and processing system 1 may include a biological signal collecting and processing chip 10, an earphone interface 20, a biological electrode 30 and a terminal 40. The biological signal collecting and processing chip 10 is electrically connected to the biological electrode 30 and sends the collected and modulated biological signal to the terminal 40 through the earphone interface 20. The system 1 can collect and process different kinds of biological signals (such as electrocardiosignals, electroencephalogram signals, electromyogram signals and the like).
Specifically, the bio-electrode 30 is attached to a to-be-collected portion of a living body (e.g., a human body) to collect a bio-signal, the collected bio-signal is modulated and amplified by the bio-signal collection and processing chip 10, i.e., the bio-signal is modulated into an audio signal, spectrum separation of the signal and noise is realized, and the noise is reduced, then the bio-signal collection and processing chip 10 transmits the bio-signal forming the audio to the terminal 40 (e.g., a smart phone) through the earphone interface 20, and the APP on the terminal 40 performs data reprocessing to show the user for viewing the collected bio-signal condition.
The earphone interface 20 is, for example, a 3.5mm earphone interface, and includes a left channel data interface, a right channel data interface, a common ground interface, and an MIC interface.
Referring to fig. 2, fig. 2 is a schematic circuit structure diagram of a biological signal collecting and processing chip according to an embodiment of the present invention. The chip 10 may include a variable gain mixer amplifier 11, a local oscillator signal generating circuit 12, an energy obtaining unit 13, a first capacitor C1, and a first resistor R1. A biological signal input terminal Vin of the variable gain mixer amplifier 11 receives a biological signal, a power input terminal VDD thereof is electrically connected to the energy obtaining unit 13, a local oscillator signal input terminal LO thereof is electrically connected to the local oscillator signal generating circuit 12, a ground terminal GND thereof is used for obtaining an external common ground signal, an output terminal Vout thereof is electrically connected to a first terminal of the first capacitor C1, and a second terminal of the first capacitor C1 is used for outputting a modulated audio signal; the local oscillation signal generating circuit 12 is configured to receive an ac electrical signal and provide a local oscillation signal to the variable gain mixer amplifier 11 after processing the ac electrical signal; the energy obtaining unit 13 is configured to receive an ac electrical signal and provide a dc power supply for the variable gain mixer amplifier 11 after processing the ac electrical signal; the resistor R1 is connected in series between the ground GND of the variable gain mixer amplifier 11 and the second end of the first capacitor C1.
Wherein the bio-signal is provided by bio-electrode 30; the alternating current signal received by the energy obtaining unit 13 can be obtained from the terminal 40 through the left channel interface of the earphone interface 20; the ac signal of the local oscillation signal generating circuit may be obtained from the terminal 40 through the right channel interface of the headphone interface 20; the audio signal output through the first capacitor C1 may be transmitted to the terminal 40 through the MIC interface of the headset interface 20; the common ground signal of the ground GND can be obtained from the terminal 40 through the common ground interface of the headphone interface 20.
Specifically, the variable gain mixer amplifier 11 modulates the biological signals collected by the biological electrodes to audio frequency (e.g., 5kHz), and then amplifies the signals according to suitable gain according to different types of biological signals for post-processing. Wherein, the local oscillator signal generating circuit 12 electrically connected to the local oscillator signal input terminal lo (local oscillator) of the variable gain mixer amplifier 11 is used for generating a stable local oscillator oscillation signal by the local oscillator signal generating circuit 12 for AM modulation; a power input end VDD of the variable gain mixer amplifier 11 is electrically connected with the energy acquisition unit 13 so that the energy acquisition unit 13 provides direct current voltage to supply power to the chip 10; the first end of the first capacitor C1 electrically connected to the output terminal Vout of the variable gain mixer amplifier 11 is coupled to the high frequency modulation signal by the first capacitor C1; the second terminal of the first capacitor C1 is connected to a first resistor R1 to sense the low impedance input of the MIC by the first resistor R1, so that the modulated audio signal is coupled into the terminal 40 through the MIC interface.
In this embodiment, the input of the local oscillator signal generating circuit 12 and the input of the energy obtaining unit 13 are respectively connected to the right channel and the left channel of the external 3.5mm headphone cable, the energy obtaining unit converts the fixed frequency sinusoidal signal output by the left channel into a direct current voltage to provide a power supply for the chip through an internal rectifier, the local oscillator signal generating circuit shapes the sinusoidal signal output by the right channel into a square wave signal to provide a local oscillator signal, the variable gain mixer amplifier 11 modulates and amplifies the input biological signal, and couples the signal to the output end (MIC input end of the 3.5mm headphone cable) through a coupling capacitor C1.
Example two
Referring to fig. 3 to fig. 6, fig. 3 is a schematic circuit diagram of a variable gain mixer amplifier according to an embodiment of the present invention; fig. 4 is a schematic diagram of a low-noise pre-mixer amplifier according to an embodiment of the present invention; fig. 5 is a schematic diagram comparing circuit structures of a variable gain mixer amplifier according to an embodiment of the present invention; fig. 6 is a schematic circuit diagram of an AM modulation module according to an embodiment of the present invention. In this embodiment, a circuit of a variable gain mixer amplifier will be described in detail based on the above embodiments.
Referring to fig. 3, the variable gain mixer amplifier 11 may include a low noise pre-mixer amplifier 111, a programmable gain amplifier 112, a band-pass filter 113, and an output buffer 114; the low-noise pre-mixer amplifier 111, the programmable gain amplifier 112, the band-pass filter 113 and the output buffer 114 are sequentially connected in series between the bio-signal input terminal Vin and the first capacitor C1, and the low-noise pre-mixer amplifier 111 is electrically connected to the local oscillator signal input terminal LO.
Note that, since the common ground signal connected to the ground terminal GND of the variable gain mixer amplifier 11 and the dc power supply connected to the power supply input terminal VDD are used for the low noise pre-mixer amplifier 111, the programmable gain amplifier 112, the band pass filter 113, and the output buffer 114, they are not shown for simplicity of illustration.
Specifically, the low-noise pre-mixer amplifier 111 modulates the biological signal collected by the biological electrode to audio frequency under the condition of ensuring that very small noise is introduced, and then performs first-stage amplification, and the gain of the programmable gain amplifier 112 is adjustable, so that an appropriate gain can be selected according to the strength of the amplified biological signal, so as to avoid saturation of the amplifier due to too large output signal or difficulty in detection due to too small output signal. Since the AM-modulated bio-signal is at audio frequency (e.g. 5kHz) and the modulation generates high frequency harmonics, while the 1/f noise and offset of the amplifier are not modulated and are at low frequency, the band-pass filter 113 is used to filter out the high frequency harmonics and the offset and noise at low frequency, resulting in a cleaner modulation signal. In order to improve the interference rejection capability, the low noise pre-mixer amplifier 111, the programmable gain amplifier 112, and the band pass filter 113 all use differential inputs and differential outputs. The output buffer 114 is used to convert the differential signal into a single-ended output signal and drive a load.
Referring to fig. 4, the low noise pre-mixer amplifier 111 may include an AM modulation module 1111 and a pre-amplifier module 1112; the AM modulation module 1111 and the preamplifier module 1112 are sequentially connected in series between the bio-signal input terminal Vin and the programmable gain amplifier 112, and the AM modulation module 1111 is electrically connected to the local oscillator signal input terminal LO.
Referring to fig. 5, in the prior art, because the biological signal is very weak, the noise of the preamplifier is usually reduced by using a chopper modulation technique. The traditional structure of amplifying before modulating needs to use three modulation modules (chopper modulation, chopper demodulation and AM modulation) and two low-pass filters, wherein the chopper modulation and the chopper demodulation realize the spectrum separation of signals and noise, and the first low-pass filter is used for filtering 1/f noise and imbalance modulated to high frequency; AM modulation is used to modulate the amplified signal to audio and a second low pass filter is used to filter out high frequency harmonics. The signal goes through the process of modulation-demodulation-remodulation and the output signal is high frequency, so the latter two modulations are redundant. After simplification, the structure of the invention only needs to modulate once before the preamplifier, which not only can modulate the signal to audio frequency (such as 5kHz), but also can realize the frequency spectrum separation of the signal and noise, and plays the role of chopping modulation, and the unmodulated low-frequency noise and the detuning and the high-frequency harmonic wave generated by modulation are filtered by a band-pass filter of the later stage. That is, the output of the AM modulation module 1111 is connected to the input of the preamplifier 1112, the AM modulation module 1111 is configured to modulate the biological signal collected by the biological electrode to audio, and meanwhile, similar to the concept of chopper modulation, since the offset and the 1/f noise are not modulated, the spectrum separation of the signal and the noise is realized, and the low-frequency offset, the noise and the high-frequency harmonic are filtered by the band-pass filter of the subsequent stage, so as to reduce the noise of the whole low-noise pre-mixing amplifier 111. The preamplifier 1112 is configured to perform a first stage amplification on the bio-signal.
Specifically, referring to fig. 6, the AM modulation module 1111 may include a first transistor M1, a second transistor M2, a third transistor M3 and a fourth transistor M4; the signal input end of the AM modulation module 1111 includes a first signal input end IN + and a second signal input end IN-, the local oscillator input end of the AM modulation module 1111 includes a first local oscillator input end LO + and a second local oscillator input end LO-, and the output end of the AM modulation module 1111 includes an IN-phase output end OUT + and an anti-phase output end OUT-; the first transistor M1 is connected IN series between the first signal input terminal IN + and the IN-phase output terminal OUT +, and its control terminal is electrically connected to the first local oscillator input terminal LO +; the second transistor M2 is connected IN series between the first signal input terminal IN + and the inverted output terminal OUT-, and a control terminal thereof is electrically connected to the second local oscillator input terminal LO-; the third transistor M3 is connected IN series between the second signal input terminal IN-and the IN-phase output terminal OUT +, and its control terminal is electrically connected to the second local oscillator input terminal LO-; the fourth transistor M4 is connected IN series between the second signal input terminal IN-and the inverted output terminal OUT-, and has a control terminal electrically connected to the first local oscillator input terminal LO +. Wherein the substrate terminals of the transistors are not connected to a common ground signal for simplicity of illustration.
LO + and LO-are two square wave signals with opposite phases generated by local oscillation signals, IN + and IN-are connected with the differential output of the bioelectrode, when LO + is at high level and LO-is at low level, the switching transistors M1 and M4 are turned on, M2 and M3 are turned off, at this time, the IN + input signal is transmitted to OUT + through M1, the IN-input signal is transmitted to OUT + through M4, when the local oscillation signals are inverted, LO + jumps to low level and LO-jumps to high level, at this time, the switching transistors M2 and M3 are turned on, M1 and M4 are turned off, at this time, the IN + input signal is transmitted to OUT + through M2, and the IN-signal is transmitted to OUT + through M3. Because the input path and the output path are switched back and forth along with the local oscillation signal, the frequency mixing of the low-frequency biological signal and the high-frequency local oscillation signal, namely AM modulation, is realized.
In the embodiment, the variable gain mixer amplifier modulates the biological signal to the audio frequency, simultaneously utilizes the chopping principle to reduce noise, omits the last two redundant modulation modules in modulation-demodulation-remodulation, and the modulated and amplified signal is input to the intelligent terminal equipment through the earphone interface so as to transmit the biological signal modulated to the audio frequency by the chip with very low loss and distortion.
EXAMPLE III
Referring to fig. 7 and 8, fig. 7 is a schematic circuit structure diagram of a local oscillator signal generating circuit according to an embodiment of the present invention; fig. 8 is a circuit diagram of a signal shaping circuit according to an embodiment of the present invention. The present embodiment describes the local oscillation signal generating circuit in detail on the basis of the above-described embodiments.
Referring to fig. 7, the local oscillator signal generating circuit 12 may include a bias circuit 121 and a signal shaping circuit 122, the bias circuit 121 and the signal shaping circuit 122 are sequentially connected in series to the local oscillator signal input terminal LO of the variable gain mixer amplifier 11, and the input terminal of the bias circuit 121 receives the ac electrical signal. The input of the bias circuit 121 is connected to the right channel input signal, the output thereof is connected to the input of the signal shaping circuit 122, and the output thereof is connected to the local oscillation signal input terminal LO of the variable gain mixer amplifier 11. Since the sinusoidal signal common mode level of the right channel output cannot be determined, the biasing circuit 121 is used to couple the right channel output signal and determine the input common mode level (close to VDD/2) of the signal shaping circuit 122, which signal shaping circuit 122 is used to shape the sinusoidal signal into a square wave signal.
Specifically, referring to fig. 8, the signal shaping circuit 122 includes: a fifth transistor M5, a sixth transistor M6, a seventh transistor M7, a first inverter INV1, a second inverter INV2, a third inverter INV3, a fourth inverter INV4, a second resistor R2, and a third resistor R3; the second resistor R2, the fifth transistor M5 and the seventh transistor M7 are sequentially connected in series between a dc power supply and a ground terminal, a control terminal of the fifth transistor M5 is inputted with a coupling signal VSIN, and a control terminal of the seventh transistor M7 is inputted with a bias voltage VBIAS; the third resistor R3 and the sixth transistor M6 are sequentially connected in series between the direct current power supply and a node G formed by connecting the fifth transistor M5 and the seventh transistor M7 in series, and the control end of the sixth transistor M6 is input with a reference voltage VREF; the first inverter INV1 and the second inverter INV2 are sequentially connected in series to a node E formed by the second resistor R2 and the fifth transistor M5 in series, and an output end of the first inverter INV1 is electrically connected to a local oscillation signal input end LO of the variable gain mixer amplifier 11 to output a first local oscillation signal; the fourth inverter INV4 and the third inverter INV3 are sequentially connected in series to a node F formed by the third resistor R3 and the sixth transistor M6 in series, and the fourth inverter INV4 is electrically connected to the local oscillation signal input terminal LO of the variable gain mixer amplifier 11 to output a second local oscillation signal. That is, the gate of the seventh transistor M7 is connected to the bias voltage VBIAS, the source is grounded, the drain is connected to the sources of the fifth transistor M5 and the sixth transistor M6, the gate of the fifth transistor M5 is connected to the right channel coupling signal VSIN, the drain is connected to the negative terminal of the load resistor R2 and is connected to the first local oscillation signal LO "through the inverters INV2 and INV1, the gate of the sixth transistor M6 is connected to the reference voltage VREF, the drain is connected to the negative terminal of the load resistor R3 and is connected to the second local oscillation signal LO + through the inverters INV3 and INV4, and the positive terminals of the load resistors R2 and R3 are connected to VDD.
The signal shaping circuit 122 is implemented like a comparator, the amplifier is used in an open loop, one end of the differential input is connected to the right channel coupling signal VSIN, the other end is connected to the reference voltage VREF (close to VDD/2), the sine signal edge is steepened through the shaping action of the amplifier, two square wave signals (LO + and LO-) with opposite phases are formed at the differential output end, it can be seen in the figure that LO + is in phase with the input sine signal, LO-is in phase opposition to the input sine signal, the second resistor R2 and the third resistor R3 are used to set the gain of the amplifier, the larger the gain, the steeper the output signal edge, the more desirable the obtained square wave, and the inverter is used to further shape the square wave signal.
Example four
Please refer to fig. 9 to 11; fig. 9 is a schematic circuit diagram of an energy harvesting unit according to an embodiment of the present invention; fig. 10 is a schematic circuit diagram of a rectifier according to an embodiment of the present invention; fig. 11 is a circuit schematic diagram of an overvoltage protection circuit according to an embodiment of the present invention. The present embodiment describes the energy acquisition unit in detail on the basis of the above-described embodiments.
The energy obtaining unit 13 may include a rectifier 131, an overvoltage protection circuit 132, and an LDO (low dropout regulator) 133, where the rectifier 131, the overvoltage protection circuit 132, and the LDO133 are sequentially connected in series to a power input terminal VDD of the variable gain mixer amplifier 11 to provide a dc power, and the rectifier 131 receives the ac electrical signal. The rectifier 131 and the overvoltage protection circuit 132 implement an AC-DC converter function, rectify a sinusoidal signal output by the left channel, and output a stable DC voltage through the LDO133 to supply power to the subsequent stage.
Referring to fig. 10, the rectifier 131 includes a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, an eighth transistor M8, a ninth transistor M9, a tenth transistor M10, an eleventh transistor M11, a first comparator COMP1, a second comparator COMP2, a third comparator COMP3, and a fourth comparator COMP 4; a source electrode of the eighth transistor M8 is electrically connected to a non-inverting input end of the first comparator COMP1, a drain electrode of the eighth transistor M8 is electrically connected to an inverting input end of the first comparator COMP1, and a gate electrode of the eighth transistor M8 is electrically connected to an output end of the first comparator COMP 1; the source of the ninth transistor M9 is electrically connected to the non-inverting input terminal of the second comparator COMP2, the drain is electrically connected to the inverting input terminal of the second comparator COMP2, and the gate is electrically connected to the output terminal of the second comparator COMP 2; the source of the tenth transistor M10 is electrically connected to the non-inverting input terminal of the third comparator COMP3, the drain is electrically connected to the inverting input terminal of the third comparator COMP3, and the gate is electrically connected to the output terminal of the third comparator COMP 3; the source of the eleventh transistor M11 is electrically connected to the non-inverting input terminal of the fourth comparator COMP4, the drain is electrically connected to the inverting input terminal of the fourth comparator COMP4, and the gate is electrically connected to the output terminal of the fourth comparator COMP 4; an input end VIN 'is electrically connected to the positive ends of the second capacitor C2 and the third capacitor C3, the negative end of the second capacitor C2 is electrically connected to the drain of the eighth transistor M8 and to the source of the ninth transistor M9, the drain of the ninth transistor M9 is electrically connected to the positive end of the fourth capacitor C4 and to the source of the tenth transistor M10, the drain of the tenth transistor M10 is electrically connected to the negative end of the third capacitor C3 and to the source of the eleventh transistor M11, the drain of the eleventh transistor M11 is electrically connected to the positive end of the fifth capacitor C5 and to the output end VOUT', and the negative ends of the fourth capacitor C4 and the fifth capacitor C5 are grounded.
The rectifier of the embodiment adopts a topological structure of a charge pump rectifier based on an active diode, wherein the integrated active diode can realize conduction voltage drop of dozens of millivolts. The number of rectifier stages is adjusted to meet the requirements according to different input signal amplitude ranges and the required power supply voltage of the system. For example, when a smart phone with an earphone channel output voltage peak-to-peak value larger than 0.7V is used as an input source, and the power voltage of the audio-modulated biological signal acquisition and processing chip is as low as 1.2V, theoretically, a two-stage rectifier can meet the requirement (assuming that the minimum drop-off voltage of the LDO is 200 mV).
Referring to fig. 11, the overvoltage protection circuit 132 may include a sixth capacitor C6, a first diode D1, a second diode D2, and a third diode D3; the signal input end VIN ″ is electrically connected with the positive end of the sixth capacitor C6 and is electrically connected with the positive electrode of the first diode D1, the negative end of the sixth capacitor C6 is grounded, the negative electrode of the first diode D1 is electrically connected with the positive electrode of the second diode D2, the negative electrode of the second diode D2 is electrically connected with the positive electrode of the third diode D3, the negative electrode of the third diode D3 is grounded, and the output end VOUT ″ is electrically connected with the positive electrode of the first diode D1.
The overvoltage protection circuit of the embodiment is used for preventing the transistors from being broken down due to overhigh voltage, because the peak-peak voltage output by different earphone sound channels of the smart phone is different (hundreds of millivolts to several volts), the possible amplitude of signals after rectification and boosting is very large, the highest voltage allowed by different processes is different, the highest voltage can be limited to the sum of the conduction voltage drops of the diodes (three times of the conduction voltage drop of the diodes in fig. 11, about 1.8V) by connecting a plurality of diodes in series to the ground at the positive end of the energy storage capacitor (C6), and once the voltage on the energy storage capacitor is higher than the maximum value, the diodes are all conducted, and the voltage on the energy storage capacitor is discharged to the limit value.
In summary, the principle and embodiments of the present invention are described herein by using specific examples, and the above descriptions of the examples are only used to help understanding the method and the core idea of the present invention; meanwhile, for a person skilled in the art, according to the idea of the present invention, there may be variations in the specific embodiments and the application scope, and in summary, the content of the present specification should not be construed as a limitation to the present invention, and the scope of the present invention should be subject to the appended claims.
Claims (10)
1. A biological signal acquisition and processing chip (10) is characterized by comprising a variable gain mixer amplifier (11), a local oscillator signal generating circuit (12), an energy acquisition unit (13), a first capacitor (C1) and a first resistor (R1); wherein,
a biological signal input end (Vin) of the variable gain mixer amplifier (11) receives a biological signal, a power supply input end (VDD) of the variable gain mixer amplifier is electrically connected with the energy acquisition unit (13), a local oscillator signal input end (LO) of the variable gain mixer amplifier is electrically connected with the local oscillator signal generation circuit (12), a ground end (GND) of the variable gain mixer amplifier is used for acquiring an external common ground signal, an output end (Vout) of the variable gain mixer amplifier is electrically connected with a first end of the first capacitor (C1) and a second end of the first capacitor (C1) is used for outputting a modulated audio signal;
the local oscillation signal generating circuit (12) is used for receiving an alternating current signal and providing a local oscillation signal for the variable gain mixer amplifier (11) after processing;
the energy acquisition unit (13) is used for receiving an alternating current signal and providing a direct current power supply for the variable gain mixer amplifier (11) after processing the alternating current signal;
the resistor R1 is connected in series between the Ground (GND) of the variable gain mixer amplifier (11) and the second end of the first capacitor (C1).
2. The chip (10) of claim 1, wherein the variable gain mixer amplifier (11) comprises a low noise pre-mixer amplifier (111), a programmable gain amplifier (112), a band pass filter (113), and an output buffer (114); wherein,
the low-noise pre-mixer amplifier (111), the programmable gain amplifier (112), the band-pass filter (113) and the output buffer (114) are sequentially connected in series between the biological signal input end (Vin) and the first capacitor (C1), and the low-noise pre-mixer amplifier (111) is electrically connected with the local oscillator signal input end (LO).
3. The chip (10) of claim 2, wherein the low noise pre-mixer amplifier (111) comprises an AM modulation module (1111) and a preamplifier module (1112); wherein the AM modulation module (1111) and the preamplifier module (1112) are sequentially connected in series between the bio-signal input terminal (Vin) and the programmable gain amplifier (112), and the AM modulation module (1111) is electrically connected to the local oscillator signal input terminal (LO).
4. The chip (10) according to claim 1, wherein the local oscillator signal generating circuit (12) comprises a bias circuit (121) and a signal shaping circuit (122), the bias circuit (121) and the signal shaping circuit (122) are sequentially connected in series to a local oscillator signal input terminal (LO) of the variable gain mixer amplifier (11), and an input terminal of the bias circuit (121) receives the ac electrical signal.
5. The chip (10) of claim 4, wherein the signal shaping circuit (122) comprises: a fifth transistor (M5), a sixth transistor (M6), a seventh transistor (M7), a first inverter (INV1), a second inverter (INV2), a third inverter (INV3), a fourth inverter (INV4), a second resistor (R2), and a third resistor (R3); wherein,
the second resistor (R2), the fifth transistor (M5) and the seventh transistor (M7) are sequentially connected in series between a direct current power supply and a ground terminal, a control terminal of the fifth transistor (M5) is input with a coupling signal (VSIN), and a control terminal of the seventh transistor (M7) is input with a bias Voltage (VBIAS);
the third resistor (R3) and the sixth transistor (M6) are sequentially connected in series between the direct current power supply and a node (G) formed by connecting the fifth transistor (M5) and the seventh transistor (M7) in series, and the control end of the sixth transistor (M6) is input with a reference Voltage (VREF);
the first inverter (INV1) and the second inverter (INV2) are sequentially connected in series to a node (E) formed by connecting the second resistor (R2) and the fifth transistor (M5) in series, and the output end of the first inverter (INV1) is electrically connected to the local oscillation signal input end (LO) of the variable gain mixer amplifier (11) to output a first local oscillation signal;
the fourth inverter (INV4) and the third inverter (INV3) are sequentially connected in series to a node (F) formed by connecting the third resistor (R3) and the sixth transistor (M6) in series, and the fourth inverter (INV4) is electrically connected to the local oscillation signal input end (LO) of the variable gain mixer amplifier (11) to output a second local oscillation signal.
6. The chip (10) according to claim 1, wherein the energy harvesting unit (13) comprises a rectifier (131), an overvoltage protection circuit (132) and an LDO (133); the rectifier (131), the overvoltage protection circuit (132) and the LDO (133) are sequentially connected in series to a power input end (VDD) of the variable gain mixer amplifier (11) to provide a direct current power supply, and the rectifier (131) receives the alternating current signal.
7. A variable gain mixer amplifier (11) is characterized by comprising a low noise pre-mixer amplifier (111), a programmable gain amplifier (112), a band-pass filter (113) and an output buffer (114) which are sequentially connected in series, wherein a first input end of the low noise pre-mixer amplifier (111) receives a biological signal and a second input end thereof receives a local oscillator signal.
8. Variable gain mixer amplifier (11) according to claim 7, characterized in that the low noise pre-mixer amplifier (111) comprises an AM modulation module (1111) and a pre-amplifier module (1112) in series in sequence; the signal input end of the AM modulation module (1111) receives the biological signal and the local oscillation input end thereof receives the local oscillation signal, and the output end of the preamplifier module (1112) is electrically connected with the programmable gain amplifier (112).
9. The variable gain mixer amplifier (11) of claim 8, wherein the AM modulation module (1111) comprises a first transistor (M1), a second transistor (M2), a third transistor (M3) and a fourth transistor (M4); the signal input end of the AM modulation module (1111) comprises a first signal input end (IN +) and a second signal input end (IN-), the local oscillator input end of the AM modulation module (1111) comprises a first local oscillator input end (LO +) and a second local oscillator input end (LO-), and the output end of the AM modulation module (1111) comprises an IN-phase output end (OUT +) and an anti-phase output end (OUT-); wherein,
the first transistor (M1) is connected IN series between the first signal input terminal (IN +) and the IN-phase output terminal (OUT +), and a control terminal thereof is electrically connected to the first local oscillator input terminal (LO +);
the second transistor (M2) is connected IN series between the first signal input end (IN +) and the inverted output end (OUT-), and the control end of the second transistor is electrically connected to the second local oscillator input end (LO-);
the third transistor (M3) is connected IN series between the second signal input terminal (IN-) and the IN-phase output terminal (OUT +), and the control terminal thereof is electrically connected to the second local oscillator input terminal (LO-);
the fourth transistor (M4) is connected IN series between the second signal input terminal (IN-) and the inverted output terminal (OUT-) and has its control terminal electrically connected to the first local oscillator input terminal (LO +).
10. A biological signal acquisition and processing system (1) is characterized by comprising a biological signal acquisition and processing chip (10), an earphone interface (20), a biological electrode (30) and a terminal (40), wherein the biological signal acquisition and processing chip (10) is electrically connected with the biological electrode (30) and sends acquired and modulated biological signals to the terminal (40) through the earphone interface (20); wherein, the biological signal collecting and processing chip (10) is the biological signal collecting and processing chip (10) according to any one of claims 1 to 6.
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