Motion artifact compensation front-end circuit for non-contact electrocardiogram monitoring and control method

Abstract

The invention discloses a motion artifact compensation front-end circuit for non-contact electrocardiogram monitoring and a control method. The circuit comprises a non-contact dry electrode, an electrocardiogram-impedance detection multiplexing module and a pulse width modulation module. The method comprises the following steps: acquiring electrode-skin interface impedance information and electrocardiosignals interfered by motion artifacts; carrying out impedance value calculation processing on the electrode-skin interface impedance information, and outputting an electrode-skin interface impedance measurement value; the electrode-skin interface impedance measurement value is adjusted and compared, and a PWM feedback signal is output; and dynamically compensating the electrocardiosignal interfered by the motion artifact in combination with the PWM feedback signal, and outputting the compensated electrocardiosignal. According to the embodiment of the invention, motion artifact interference caused by impedance fluctuation can be effectively compensated, and the accuracy of electrocardiosignal measurement is improved. The method can be widely applied to the technical field of analog integrated circuits.

Description

Technical Field

[0001] This application relates to the field of analog integrated circuit technology, and particularly to a front-end circuit and control method for motion artifact compensation in non-contact electrocardiogram monitoring. Background Art

[0002] In order to cope with the wide dynamic input range caused by motion artifacts, the existing traditional electrocardiogram monitoring front-end circuits based on voltage amplifiers must have ultra-high input impedance. However, the ultra-high input impedance also brings new problems, that is, the sensitivity to environmental noise increases significantly. Common environmental noises, such as 50Hz / 60Hz power frequency interference, may be coupled into the signal path through the contact impedance mismatch and amplified together with the biological signal, further reducing the signal quality.

[0003] In the field of medical health, in order to ensure the accuracy and reliability of electrocardiogram signals, it is necessary to reduce the interference of motion artifacts and environmental noises as much as possible; in the field of motion monitoring, in order to ensure the stability of signals in a dynamic environment, it is necessary to improve the anti-interference ability of the system. However, while the existing non-contact electrocardiogram monitoring front-end copes with motion artifacts, its ultra-high input impedance significantly increases the sensitivity to environmental noise, resulting in signal distortion and a decrease in signal-to-noise ratio, limiting its application in high-precision and high-reliability scenarios.

[0004] In summary, the technical problems existing in the related technologies need to be improved. Summary of the Invention

[0005] The main purpose of the embodiments of this application is to propose a front-end circuit and control method for motion artifact compensation in non-contact electrocardiogram monitoring, which can effectively compensate for the motion artifact interference caused by impedance fluctuations and improve the accuracy of electrocardiogram signal measurement.

[0006] To achieve the above object, on the one hand, an embodiment of this application proposes a front-end circuit for motion artifact compensation in non-contact electrocardiogram monitoring. The circuit includes a non-contact dry electrode, an electrocardiogram-impedance detection multiplexing module, and a pulse width modulation module. The non-contact dry electrode includes an electrode-skin interface impedance unit. The output end of the non-contact dry electrode is connected to the input end of the electrocardiogram-impedance detection multiplexing module, and the electrocardiogram-impedance detection multiplexing module is connected to the pulse width modulation module, where:

[0007] The non-contact dry electrode is used to obtain electrode-skin interface impedance information and electrocardiogram signals interfered by motion artifacts;

[0008] The electrocardiogram - impedance detection multiplexing module is used to calculate and process the impedance value of the electrode - skin interface impedance information, output the electrode - skin interface impedance measurement value, and dynamically compensate the electrocardiogram signal interfered by motion artifacts in combination with the PWM feedback signal, and output the compensated electrocardiogram signal;

[0009] The pulse - width modulation module is used to adjust and compare the electrode - skin interface impedance measurement value, and output the PWM feedback signal.

[0010] In some embodiments, the electrocardiogram - impedance detection multiplexing module includes an electrode - skin interface impedance monitoring module and an electrocardiogram signal acquisition module. The electrode - skin interface impedance monitoring module and the electrocardiogram signal acquisition module are electrically connected, where:

[0011] The electrode - skin interface impedance monitoring module is used to calculate and process the impedance value of the electrode - skin interface impedance information, and output the electrode - skin interface impedance measurement value;

[0012] The electrocardiogram signal acquisition module is used to dynamically compensate the electrocardiogram signal interfered by motion artifacts according to the PWM feedback signal, and output the compensated electrocardiogram signal.

[0013] In some embodiments, the electrode - skin interface impedance monitoring module includes an operational amplifier module, a first resistor, a second resistor, and a third resistor. Among them, the second end of the first resistor, the first end of the second resistor are connected to the electrode - skin interface impedance unit, the second end of the second resistor, the first end of the third resistor are connected to the inverting input terminal of the operational amplifier module, and the second end of the third resistor is connected to the output terminal of the operational amplifier module.

[0014] In some embodiments, the electrocardiogram signal acquisition module includes a common - mode feed - forward circuit, a charge amplifier, an RC low - pass filter, a buffer, a correlated double - sampling circuit, and a sample - and - hold circuit. The charge amplifier includes a first charge - amplifier unit and a second charge - amplifier unit. The common - mode feed - forward circuit, the charge amplifier, the RC low - pass filter, the buffer, the correlated double - sampling circuit, and the sample - and - hold circuit are connected in sequence, where:

[0015] The common - mode feed - forward circuit is used to suppress environmental noise of the electrocardiogram signal interfered by motion artifacts, and output a pre - processed electrocardiogram charge signal;

[0016] The charge amplifier is used to adjust the gain coefficient according to the PWM feedback signal, and perform conversion and amplification signal processing on the pre - processed electrocardiogram charge signal to obtain a pre - processed electrocardiogram voltage signal;

[0017] The RC low-pass filter is used to filter the preprocessed electrocardiogram voltage signal to obtain the filtered electrocardiogram signal;

[0018] The buffer is used to isolate the signal source of the filtered electrocardiogram signal to obtain the buffered electrocardiogram signal;

[0019] The correlated double sampling circuit is used to perform correlated double sampling on the buffered electrocardiogram signal to obtain the sampled electrocardiogram signal;

[0020] The sample and hold circuit is used to hold the stable signal value of the sampled electrocardiogram signal to obtain the compensated electrocardiogram signal.

[0021] In some embodiments, the common-mode feedforward circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first operational amplifier, the charge amplifier includes a first switch, a second switch, a first feedback capacitor, a second feedback capacitor, a second operational amplifier and a third operational amplifier, the RC low-pass filter includes an eighth resistor, a ninth resistor, a third feedback capacitor, a first capacitor and a second capacitor, the buffer includes a first buffer unit and a second buffer unit, the correlated double sampling circuit includes a third capacitor, a fourth capacitor, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a fourth feedback capacitor, a fifth feedback capacitor and a fourth operational amplifier, and the sample and hold circuit includes a ninth switch, a tenth switch, a fifth capacitor, a sixth capacitor and a seventh capacitor.

[0022] In some embodiments, in the electrocardiogram signal acquisition module, the first end of the fourth resistor is connected to the first end of the sixth resistor, the second end of the fourth resistor, the non-inverting input terminal of the first operational amplifier are connected to the first end of the fifth resistor, the second end of the fifth resistor is connected to the first end of the seventh resistor, the second end of the sixth resistor, the inverting input terminal of the second operational amplifier, the first end of the first switch are connected to the first end of the first feedback capacitor, the inverting input terminal of the first operational amplifier, the output terminal of the first operational amplifier, the non-inverting input terminal of the second operational amplifier are connected to the non-inverting input terminal of the third operational amplifier, the second end of the seventh resistor, the inverting input terminal of the third operational amplifier, the first end of the second switch are connected to the first end of the second feedback capacitor, the second end of the first switch, the second end of the first feedback capacitor are connected to the output terminal of the second operational amplifier through a third switch and the first end of the eighth resistor, the output terminal of the second operational amplifier, the second end of the second feedback capacitor are connected to the second end of the second switch through a fourth switch and the first end of the ninth resistor, the second end of the eighth resistor, the second end of the first capacitor, the first end of the third feedback capacitor are connected to the input terminal of the first buffer unit, the second end of the ninth resistor, the first end of the second capacitor, the second end of the third feedback capacitor are connected to the input terminal of the second buffer unit, the first end of the first capacitor and the second end of the second capacitor are both grounded, the output terminal of the first buffer unit is connected to the first end of the third capacitor, the output terminal of the second buffer unit is connected to the first end of the fourth capacitor, the second end of the third capacitor is connected to the first end of the fifth switch, the second end of the fourth capacitor is connected to the first end of the sixth switch, the second end of the fifth switch, the first end of the seventh switch, the first end of the fourth feedback capacitor are connected to the non-inverting input terminal of the fourth operational amplifier, the second end of the sixth switch, the first end of the eighth switch, the first end of the fifth feedback capacitor are connected to the inverting input terminal of the fourth operational amplifier, the second end of the seventh switch, the second end of the fourth feedback capacitor, the first output terminal of the fourth operational amplifier are connected to the first end of the ninth switch, the second end of the eighth switch, the second end of the fifth feedback capacitor, the second output terminal of the fourth operational amplifier are connected to the first end of the tenth switch, the second end of the ninth switch, the second end of the fifth capacitor are connected to the first end of the seventh capacitor, the second end of the tenth switch, the first end of the sixth capacitor are connected to the second end of the seventh capacitor, the first end of the fifth capacitor and the second end of the sixth capacitor are both grounded.

[0023] In some embodiments, the pulse width modulation module includes an analog-to-digital converter, a digital arithmetic unit, a programmable capacitor array, and a comparator. The analog-to-digital converter, the digital arithmetic unit, the programmable capacitor array, and the comparator are connected in sequence, where:

[0024] The analog-to-digital converter is configured to perform analog-to-digital conversion processing on the measured value of the electrode-skin interface impedance to obtain a digital signal of the measured value of the electrode-skin interface impedance;

[0025] The digital arithmetic unit is configured to perform weighted calculation on the digital signal of the measured value of the electrode-skin interface impedance to obtain a digital signal proportional to the electrode-skin interface impedance;

[0026] The programmable capacitor array is configured to perform pulse width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to a constant current source signal to obtain an adjusted electrode-skin interface impedance signal;

[0027] The comparator is configured to compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output the PWM feedback signal.

[0028] To achieve the above object, on the other hand, an embodiment of the present application proposes a control method for a front-end circuit for compensating motion artifacts in non-contact electrocardiogram monitoring. The control method includes the following steps:

[0029] Obtain electrode-skin interface impedance information and an electrocardiogram signal interfered by motion artifacts;

[0030] Perform impedance value calculation processing on the electrode-skin interface impedance information and output a measured value of the electrode-skin interface impedance;

[0031] Perform adjustment and comparison processing on the measured value of the electrode-skin interface impedance and output a PWM feedback signal;

[0032] Dynamically compensate the electrocardiogram signal interfered by motion artifacts in combination with the PWM feedback signal and output a compensated electrocardiogram signal.

[0033] In some embodiments, the performing adjustment and comparison processing on the measured value of the electrode-skin interface impedance and outputting a PWM feedback signal includes:

[0034] Perform analog-to-digital conversion processing on the measured value of the electrode-skin interface impedance to obtain a digital signal of the measured value of the electrode-skin interface impedance;

[0035] Perform weighted calculation on the digital signal of the measured value of the electrode-skin interface impedance to obtain a digital signal proportional to the electrode-skin interface impedance;

[0036] Perform pulse-width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to the constant current source signal to obtain an adjusted electrode-skin interface impedance signal;

[0037] Compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output the PWM feedback signal.

[0038] In some embodiments, dynamically compensating the electrocardiogram signal interfered by motion artifacts by combining the PWM feedback signal and outputting a compensated electrocardiogram signal includes:

[0039] Suppress environmental noise of the electrocardiogram signal interfered by motion artifacts and output a preprocessed electrocardiogram charge signal;

[0040] Perform gain coefficient adjustment processing according to the PWM feedback signal, and perform conversion and amplification signal processing on the preprocessed electrocardiogram charge signal to obtain a preprocessed electrocardiogram voltage signal;

[0041] Perform filtering processing on the preprocessed electrocardiogram voltage signal to obtain a filtered electrocardiogram signal;

[0042] Perform isolation signal source processing on the filtered electrocardiogram signal to obtain a buffered electrocardiogram signal;

[0043] Perform correlated double sampling processing on the buffered electrocardiogram signal to obtain a sampled electrocardiogram signal;

[0044] Keep the signal value of the sampled electrocardiogram signal stable to obtain the compensated electrocardiogram signal.

[0045] The embodiments of the present application at least include the following beneficial effects: The present application provides a front-end circuit and control method for motion artifact compensation in non-contact electrocardiogram monitoring. This solution obtains electrode-skin interface impedance information and electrocardiogram signals interfered by motion artifacts, performs impedance value calculation processing on the electrode-skin interface impedance information and adjustment comparison processing on the measured value of the electrode-skin interface impedance respectively, and finally combines the PWM feedback signal to dynamically compensate the electrocardiogram signals interfered by motion artifacts and outputs a compensated electrocardiogram signal. The gain coefficient of the charge amplifier is adjusted by the PWM feedback signal to dynamically compensate for motion artifacts caused by contact impedance fluctuations, realizing closed-loop real-time compensation. Through low-input impedance design and real-time detection of the electrode-skin interface impedance, motion artifact interference caused by impedance fluctuations is effectively compensated, realizing high-precision and high-reliability electrocardiogram signal measurement. Description of the Drawings

[0046] Figure 1 is a schematic structural diagram of a front-end circuit for motion artifact compensation in non-contact electrocardiogram monitoring provided by an embodiment of the present application;

[0047] Figure 2 It is a schematic flowchart of a control method for a front - end circuit for compensating motion artifacts in non - contact electrocardiogram monitoring provided by an embodiment of the present application;

[0048] Figure 3 It is a schematic circuit diagram of an electrode - skin interface impedance monitoring module provided by an embodiment of the present application;

[0049] Figure 4 It is a schematic circuit diagram of an electrocardiogram signal acquisition module provided by an embodiment of the present application;

[0050] Figure 5 It is a schematic circuit diagram of an electrocardiogram - impedance detection multiplexing module provided by an embodiment of the present application;

[0051] Figure 6 It is a timing schematic diagram of an electrocardiogram - impedance detection multiplexing module provided by an embodiment of the present application;

[0052] Figure 7 It is a schematic circuit diagram of a pulse - width modulation module provided by an embodiment of the present application.

[0053] Description of the drawings: 1. Non - contact dry electrode; 2. Electrocardiogram - impedance detection multiplexing module; 3. Pulse - width modulation module; 11. Common - mode feed - forward circuit; 121. First charge amplifier unit; 122. Second charge amplifier unit; 13. RC low - pass filter; 14. Buffer; 15. Correlated double - sampling circuit; 16. Sample - and - hold circuit; 21. Analog - to - digital converter; 22. Digital arithmetic unit; 23. Programmable capacitor array; 24. Comparator. Detailed implementation manners

[0054] In order to make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementation manners described in the following exemplary embodiments do not represent all implementation manners consistent with the embodiments of the present application. They are only examples of systems and methods that are consistent with some aspects of the embodiments of the present application detailed in the appended claims.

[0055] It will be appreciated that the terms "first", "second", etc. used in this application may be used herein to describe various concepts, but unless otherwise specified, these concepts are not limited by these terms. These terms are only used to distinguish one concept from another. For example, without departing from the scope of the embodiments of this application, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the words "if", "when" as used herein may be interpreted as "when...", "while...", or "in response to determining".

[0056] The terms "at least one", "a plurality of", "each", "any one", etc. used in this application, where at least one includes one, two or more than two, a plurality includes two or more than two, each refers to each of the corresponding plurality, and any one refers to any one of the plurality.

[0057] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of this application and are not intended to limit this application.

[0058] First of all, it should be noted that non-contact electrocardiogram monitoring technology realizes electrocardiogram measurement without direct contact with the skin, providing users with a convenient and non-invasive means of physiological signal monitoring. However, since there is no direct contact between the electrode and the skin, the interface impedance is significantly higher than that of traditional contact electrodes, and it is more vulnerable to factors such as human body movement and breathing, resulting in large fluctuations. This instability of the interface impedance will cause drastic changes in the signal amplitude and DC level, namely motion artifacts (Motion Artifact, MA). Compared with the amplitude of a typical electrocardiogram signal of about 1 mV, the amplitude of motion artifacts can reach 100 mV, seriously interfering with the accurate extraction and analysis of electrocardiogram signals.

[0059] In the related art, there are some deficiencies, such as serious environmental noise coupling and significant motion artifact interference caused by high input impedance in the existing non-contact electrocardiogram monitoring front-end circuit.

[0060] In view of this, an embodiment of this application provides a motion artifact compensation front-end circuit for non-contact electrocardiogram monitoring. By means of low input impedance design and real-time detection of the electrode-skin interface impedance, it effectively compensates for the motion artifact interference caused by impedance fluctuations, realizing high-precision and high-reliability electrocardiogram signal measurement, and is particularly suitable for the scenario of monitoring various physiological signals by wearable devices in a dynamic environment.

[0061] Refer to Figure 1 , Figure 1 is a flowchart of a motion artifact compensation front-end circuit for non-contact electrocardiogram monitoring provided by an embodiment of the present invention. Refer toFigure 1 , the circuit includes a non-contact dry electrode 1, an electrocardiogram-impedance detection multiplexing module 2, and a pulse width modulation module 3. The non-contact dry electrode includes an electrode-skin interface impedance unit. The output end of the non-contact dry electrode is connected to the input end of the electrocardiogram-impedance detection multiplexing module, and the electrocardiogram-impedance detection multiplexing module is interconnected with the pulse width modulation module.

[0062] The embodiment of the present invention includes an electrocardiogram-impedance detection multiplexing module and a pulse width modulation module. First, the input end of the electrocardiogram-impedance detection multiplexing module is connected to the non-contact dry electrode to obtain electrode-skin interface impedance information, and the output electrode-skin interface impedance measurement value is input to the pulse width modulation module. Further, the pulse width modulation module receives the electrode-skin interface impedance measurement value, generates a PWM feedback signal through an operation unit and a comparator, and feeds back the signal to the electrocardiogram-impedance detection multiplexing module. Finally, the input end of the electrocardiogram-impedance detection multiplexing module is connected to the non-contact dry electrode to obtain an electrocardiogram signal interfered by motion artifacts. The PWM feedback signal controls the gain coefficient of the charge amplifier of the electrocardiogram signal acquisition module, thereby dynamically compensating for the motion artifacts caused by the fluctuation of the contact impedance and outputting the compensated electrocardiogram signal.

[0063] The non-contact dry electrode is used to obtain electrode-skin interface impedance information and an electrocardiogram signal interfered by motion artifacts;

[0064] The differential input pair of the non-contact electrocardiogram monitoring front-end circuit is V ip and V in , and the differential output pair is V on and V op , where the differential input pair is respectively connected to two independent non-contact dry electrodes. The input end of the non-contact dry electrode forms an equivalent capacitor with the human body through an insulating dielectric layer. There is an air / clothing layer with a thickness of 0.1 to 1 mm between the electrode surface and the skin. Each electrode has an independent electrode-skin interface impedance Z ESI . The signals monitored by the two electrodes include a common-mode signal to be suppressed and a differential-mode signal V ECG to be extracted. The positive and negative input ends of the electrocardiogram-impedance detection multiplexing module are respectively connected to V ip and V in , and the positive and negative output ends are respectively connected to V on and V op ; the input end of the pulse width modulation module is connected to the impedance detection output voltage V Z of the electrocardiogram-impedance detection multiplexing module, and its output end V pwm controls the integration time of the charge amplifier of the electrocardiogram signal acquisition module.

[0065] The electrocardiogram-impedance detection multiplexing module is used to calculate and process the impedance value of the electrode-skin interface impedance information, output the measured value of the electrode-skin interface impedance, and dynamically compensate the electrocardiogram signal disturbed by motion artifacts in combination with the PWM feedback signal, and output the compensated electrocardiogram signal;

[0066] Specifically, the electrocardiogram-impedance detection multiplexing module includes an electrode-skin interface impedance monitoring module and an electrocardiogram signal acquisition module. The electrode-skin interface impedance monitoring module and the electrocardiogram signal acquisition module are electrically connected. Among them, the electrode-skin interface impedance monitoring module is used to calculate and process the impedance value of the electrode-skin interface impedance information and output the measured value of the electrode-skin interface impedance; the electrocardiogram signal acquisition module is used to dynamically compensate the electrocardiogram signal disturbed by motion artifacts according to the PWM feedback signal and output the compensated electrocardiogram signal.

[0067] In this embodiment, the electrocardiogram-impedance detection multiplexing module is composed of an electrode-skin interface impedance monitoring module and an electrocardiogram signal acquisition module, integrating the functions of contact impedance detection and electrocardiogram signal acquisition, and realizing the alternating monitoring of the electrode-skin interface impedance change and the electrocardiogram characteristic waveform through switch control; the electrode-skin interface impedance monitoring module transmits the impedance measurement value to the pulse width modulation circuit; the pulse width modulation module receives the impedance measurement value and generates a PWM feedback signal; the electrocardiogram signal acquisition module adjusts the gain coefficient of the charge amplifier through the PWM feedback signal, dynamically compensates for the motion artifacts caused by the contact impedance fluctuation, and realizes closed-loop real-time compensation.

[0068] More specifically, the electrode-skin interface impedance monitoring module includes an operational amplifier module, a first resistor R1, a second resistor R2, and a third resistor R3. Among them, the second end of the first resistor, the first end of the second resistor are connected to the electrode-skin interface impedance unit, the second end of the second resistor, the first end of the third resistor are connected to the negative input terminal of the operational amplifier module, and the second end of the third resistor is connected to the output terminal of the operational amplifier module.

[0069] In this embodiment, the electrode-skin interface impedance monitoring module is composed of an operational amplifier OPA2 / OPA3 and three resistors R1, R2, R3; the non-inverting input terminal of the operational amplifier is connected to the common-mode voltage, and both ends of R1 are V cm +V ctrl and V x , both ends of R2 are V x and the inverting input terminal of the operational amplifier, both ends of R3 are the inverting input terminal and the output terminal of the operational amplifier, forming negative feedback; in the electrode-skin interface impedance monitoring module, R2 is connected in parallel with ZESI and then in series with R0 to form a voltage dividing circuit, V x is the equivalent impedance of R2 and ZESI connected in parallel, and V ctrlThe divided voltage is amplified by an inverting amplifier composed of R2, R3, and an operational amplifier to obtain V z 。

[0070] The electrocardiogram signal acquisition module includes a common-mode feedforward circuit 11, a charge amplifier, an RC low-pass filter 13, a buffer 14, a correlated double sampling circuit 15, and a sample and hold circuit 16. The charge amplifier includes a first charge amplifier unit 121 and a second charge amplifier unit 122. The common-mode feedforward circuit, the charge amplifier, the RC low-pass filter, the buffer, the correlated double sampling circuit, and the sample and hold circuit are connected in sequence. Among them, the common-mode feedforward circuit is used to suppress environmental noise for the electrocardiogram signal interfered by motion artifacts and output a preprocessed electrocardiogram charge signal; the charge amplifier is used to adjust the gain coefficient according to the PWM feedback signal and perform conversion and amplification signal processing on the preprocessed electrocardiogram charge signal to obtain a preprocessed electrocardiogram voltage signal; the RC low-pass filter is used to filter the preprocessed electrocardiogram voltage signal to obtain a filtered electrocardiogram signal; the buffer is used to isolate the signal source for the filtered electrocardiogram signal to obtain a buffered electrocardiogram signal; the correlated double sampling circuit is used to perform correlated double sampling processing on the buffered electrocardiogram signal to obtain a sampled electrocardiogram signal; the sample and hold circuit is used to hold a stable signal value for the sampled electrocardiogram signal to obtain a compensated electrocardiogram signal.

[0071] Among them, the common-mode feedforward circuit includes a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a seventh resistor R7 and a first operational amplifier OPA1. The charge amplifier includes a first switch S1, a second switch S2, a first feedback capacitor CF1, a second feedback capacitor CF2, a second operational amplifier OPA2 and a third operational amplifier OPA3. The RC low-pass filter includes an eighth resistor R8, a ninth resistor R9, a third feedback capacitor CF3, a first capacitor C1 and a second capacitor C2. The buffer includes a first buffer unit U1 and a second buffer unit U2. The correlated double sampling circuit includes a third capacitor C3, a fourth capacitor C4, a fifth switch S5, a sixth switch S6, a seventh switch S7, an eighth switch S8, a fourth feedback capacitor CF4, a fifth feedback capacitor CF5 and a fourth operational amplifier OPA4. The sample and hold circuit includes a ninth switch S9, a tenth switch S10, a fifth capacitor C5, a sixth capacitor C6 and a seventh capacitor C7. In the electrocardiogram signal acquisition module, the first end of the fourth resistor is connected to the first end of the sixth resistor. The second end of the fourth resistor, the positive input terminal of the first operational amplifier and the first end of the fifth resistor are connected. The second end of the fifth resistor is connected to the first end of the seventh resistor. The second end of the sixth resistor, the negative input terminal of the second operational amplifier, the first end of the first switch and the first end of the first feedback capacitor are connected. The negative input terminal of the first operational amplifier, the output terminal of the first operational amplifier, the positive input terminal of the second operational amplifier and the positive input terminal of the third operational amplifier are connected. The second end of the seventh resistor, the negative input terminal of the third operational amplifier, the first end of the second switch and the first end of the second feedback capacitor are connected. The second end of the first switch, the second end of the first feedback capacitor and the output terminal of the second operational amplifier are connected to the first end of the eighth resistor through a third switch. The output terminal of the second operational amplifier, the second end of the second feedback capacitor and the second end of the second switch are connected to the first end of the ninth resistor through a fourth switch. The second end of the eighth resistor, the second end of the first capacitor, the first end of the third feedback capacitor and the input terminal of the first buffer unit are connected. The second end of the ninth resistor, the first end of the second capacitor, the second end of the third feedback capacitor and the input terminal of the second buffer unit are connected. The first end of the first capacitor and the second end of the second capacitor are both grounded. The output terminal of the first buffer unit is connected to the first end of the third capacitor. The output terminal of the second buffer unit is connected to the first end of the fourth capacitor. The second end of the third capacitor is connected to the first end of the fifth switch. The second end of the fourth capacitor is connected to the first end of the sixth switch. The second end of the fifth switch, the first end of the seventh switch, the first end of the fourth feedback capacitor and the positive input terminal of the fourth operational amplifier are connected. The second end of the sixth switch, the first end of the eighth switch, the first end of the fifth feedback capacitor and the negative input terminal of the fourth operational amplifier are connected. The second end of the seventh switch, the second end of the fourth feedback capacitor, the first output terminal of the fourth operational amplifier and the first end of the ninth switch are connected.The second terminal of the eighth switch, the second terminal of the fifth feedback capacitor, the second output terminal of the fourth operational amplifier are connected to the first terminal of the tenth switch. The second terminal of the ninth switch, the second terminal of the fifth capacitor are connected to the first terminal of the seventh capacitor. The second terminal of the tenth switch, the first terminal of the sixth capacitor are connected to the second terminal of the seventh capacitor. The first terminal of the fifth capacitor and the second terminal of the sixth capacitor are both grounded.

[0072] In this embodiment, the ECG signal acquisition module includes a common-mode feedforward circuit, a charge amplifier, an RC low-pass filter, a buffer, a correlated double sampling circuit, and a sample-and-hold circuit. The common-mode feedforward circuit consists of voltage-dividing resistors R4, R5 and operational amplifier OPA1. R4 and R5 are identical fixed-value resistors, and their resistance values are much larger than R6, R7 and the electrode-skin interface impedance to prevent the integration current of the charge amplifier from flowing to R4 and R5. The common-mode voltages of V in and V ip are transmitted to the non-inverting input terminals of operational amplifiers OPA2 and OPA3 through the unity-gain negative feedback connection of OPA1. Through this connection, the voltage differences across R6 and R7 are V in -V ip and V ip -V in respectively. The currents flowing through R6 and R7 are proportional to the differential voltage of V in and V ip . The differential voltage of V in and V ip is the voltage obtained by R6 / R7 from VECG in the voltage-dividing circuit formed by the series connection of R6 / R7 and ZESIN / ZESIP, which is inversely proportional to the resistance value of ZESI and directly proportional to the voltage of VECG. The charge amplifier consists of operational amplifiers OPA2 / OPA3, switches Sres (S1 and S2), and feedback capacitors CF1 and CF2. The feedback capacitor CF is connected to the inverting input terminal and the output terminal of the operational amplifier to form negative feedback. The switch Sres is connected in parallel with CF and is used to control the integration time of the charge amplifier. The control signal of the switch Sres is the output V pwm; The gain coefficient of the charge amplifier is proportional to the integration time of the charge amplifier and inversely proportional to the size of CF. The input end of the RC low-pass filter is connected to the output end of the charge amplifier, and the output end is connected to the input end of the buffer to effectively suppress high-frequency noise. Both ends of the buffer are the RC low-pass filter and the correlated double sampling circuit to ensure the stability of signal transmission. The correlated double sampling circuit consists of switches S5 / S6, S7 / S8, capacitors C3 / C4, CF3 / CF4, and a fully differential operational amplifier OPA4; both ends of the capacitors C3 / C4 are respectively the output end of the buffer and the switches S5 / S6, and the other ends of the switches S5 / S6 are connected to the input end of the fully differential operational amplifier OPA4; both ends of the capacitors CF4 / CF5 are respectively the input end and the output end of the fully differential operational amplifier OPA4 to form negative feedback; the switches S7 / S8 are connected in parallel with the capacitors CF4 / CF5 to significantly reduce the low-frequency noise of the circuit through the correlated double sampling technology. The sample and hold circuit consists of switches S9 / S10 and capacitors C5 / C6. When the switches S9 / S10 are closed, the output of the correlated double sampling circuit is sampled and held.

[0073] The pulse width modulation module is used to adjust and compare the measured value of the electrode-skin interface impedance and output a PWM feedback signal.

[0074] Specifically, the pulse width modulation module includes an analog-to-digital converter 21, a digital arithmetic unit 22, a programmable capacitor array 23, and a comparator 24. The analog-to-digital converter, the digital arithmetic unit, the programmable capacitor array, and the comparator are connected in sequence. Among them, the analog-to-digital converter is used to perform analog-to-digital conversion processing on the measured value of the electrode-skin interface impedance to obtain the digital signal of the measured value of the electrode-skin interface impedance; the digital arithmetic unit is used to perform weighted calculation on the digital signal of the measured value of the electrode-skin interface impedance to obtain a digital signal proportional to the electrode-skin interface impedance; the programmable capacitor array is used to perform pulse width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to the constant current source signal to obtain the adjusted electrode-skin interface impedance signal; the comparator is used to compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output a PWM feedback signal.

[0075] In this embodiment, the pulse width modulation module includes an analog-to-digital converter, a digital arithmetic unit, a programmable capacitor array, and a comparator; the analog-to-digital converter is connected to the measured voltage Vz of the change in the electrode-skin interface impedance and converts it into a digital signal Dz. The digital arithmetic unit receives Dz and generates Dz2 proportional to the electrode-skin interface impedance. The programmable capacitor array is controlled by Dz2 and then uses a constant current source I ref to charge the programmable capacitor array. The slope of the charging curve is proportional to Dz2. The non-inverting input terminal of the comparator is connected to the output voltage Vcap of the programmable capacitor array, and the inverting input terminal is connected to the constant voltage source Vref are connected. By comparison, a PWM wave V with a corresponding duty cycle is generated pwm and the PWM wave is fed back to the electrocardiogram-impedance detection multiplexing module.

[0076] Please refer to Figure 2 . The embodiment of the present application also provides a control method for a front-end circuit for compensating motion artifacts in non-contact electrocardiogram monitoring, which can implement the above-mentioned front-end circuit for compensating motion artifacts in non-contact electrocardiogram monitoring. The system includes:

[0077] S100. Obtain the electrode-skin interface impedance information and the electrocardiogram signal interfered by motion artifacts;

[0078] S200. Perform impedance value calculation processing on the electrode-skin interface impedance information and output the electrode-skin interface impedance measurement value;

[0079] S300. Perform adjustment and comparison processing on the electrode-skin interface impedance measurement value and output a PWM feedback signal;

[0080] It should be noted that in some embodiments, step S300 may include: S310. Perform analog-to-digital conversion processing on the electrode-skin interface impedance measurement value to obtain a digital signal of the electrode-skin interface impedance measurement value; S320. Perform weighted calculation on the digital signal of the electrode-skin interface impedance measurement value to obtain a digital signal proportional to the electrode-skin interface impedance; S330. Perform pulse width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to the constant current source signal to obtain an adjusted electrode-skin interface impedance signal; S340. Compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output a PWM feedback signal.

[0081] In some specific embodiments, as Figure 3 shown, the embodiment of the electrode-skin interface impedance monitoring module is composed of an operational amplifier OPA2 / OPA3 and three resistors R1, R2, and R3. The positive input terminal of the operational amplifier is connected to the common-mode voltage. Both ends of R1 are V cm +V ctrl and V x , both ends of R2 are V x and the negative input terminal of the operational amplifier, and both ends of R3 are the negative input terminal and the output terminal of the operational amplifier, forming negative feedback. In the electrode-skin interface impedance monitoring module, R2 is connected in parallel with ZESI and then connected in series with R1 to form a voltage dividing circuit. V x is the voltage divided from V ctrl by the equivalent impedance of the parallel connection of R2 and ZESI. After being amplified by the inverting amplifier composed of R2, R3, and the operational amplifier, V z is obtained.

[0082] As Figure 5 shown, the embodiment of the electrocardiogram-impedance detection multiplexing module consists of an electrode-skin interface impedance monitoring module and an electrocardiogram signal acquisition module, integrating the functions of contact impedance detection and electrocardiogram signal acquisition. The alternating monitoring of the electrode-skin interface impedance change and the electrocardiogram characteristic waveform is realized through switch control. The electrode-skin interface impedance monitoring module transmits the impedance measurement value to the pulse width modulation module; the pulse width modulation module receives the impedance measurement value and generates a PWM feedback signal; the electrocardiogram signal acquisition module adjusts the gain coefficient of the charge amplifier through the PWM feedback signal to dynamically compensate for the motion artifacts caused by the contact impedance fluctuation and realize closed-loop real-time compensation.

[0083] S400. Dynamically compensate the electrocardiogram signal interfered by motion artifacts and output the compensated electrocardiogram signal;

[0084] It should be noted that in some embodiments, step S400 may include: S410. Suppress the environmental noise of the electrocardiogram signal interfered by motion artifacts and output the preprocessed electrocardiogram charge signal; S420. Perform gain coefficient adjustment processing according to the PWM feedback signal, and perform conversion and amplification signal processing on the preprocessed electrocardiogram charge signal to obtain the preprocessed electrocardiogram voltage signal; S430. Perform filtering processing on the preprocessed electrocardiogram voltage signal to obtain the filtered electrocardiogram signal; S440. Perform isolation signal source processing on the filtered electrocardiogram signal to obtain the buffered electrocardiogram signal; S450. Perform correlated double sampling processing on the buffered electrocardiogram signal to obtain the sampled electrocardiogram signal; S460. Keep the signal value of the sampled electrocardiogram signal stable to obtain the compensated electrocardiogram signal.

[0085] In this embodiment, as Figure 4 shown, it includes a common-mode feedforward circuit, a charge amplifier, an RC low-pass filter, a buffer, a correlated double sampling circuit, and a sample and hold circuit. The common-mode feedforward circuit consists of voltage-dividing resistors R4, R5, and an operational amplifier OPA1. R4 and R5 are the same fixed-value resistors, and their resistance values are much larger than R6, R7, and the electrode-skin interface impedance to prevent the integration current of the charge amplifier from flowing to R4 and R5. The common-mode voltages of V in and V ip are transmitted to the non-inverting inputs of operational amplifiers OPA2 and OPA3 through the unity-gain negative feedback connection of OPA1. Through this connection, the voltage differences across R6 and R7 are V in -V ip and V ip -V in respectively. The currents flowing through R6 and R7 are proportional to the differential voltage of V in and V ip . V in and Vip The difference voltage is the circuit formed by R6 / R7 and ZESIN / ZESIP in series, R6 / R7 from V ECG The voltage divided by the resistor is inversely proportional to the resistance of ZESI and V ECG The charge amplifier consists of an operational amplifier OPA2 / OPA3, a switch Sres and a feedback capacitor CF. The feedback capacitor CF is connected to the negative electrode and the output of the operational amplifier to form a negative feedback. The switch Sres is connected in parallel with CF to control the integration time of the charge amplifier. The control signal of the switch Sres is the output V of the pulse width modulation module. pwm , the gain coefficient of the charge amplifier is proportional to the integration time and inversely proportional to the size of CF. The input of the RC low-pass filter is connected to the output of the charge amplifier, and the output is connected to the input of the buffer to effectively suppress high-frequency noise. The two ends of the buffer are RC low-pass filters and correlated double sampling circuits to ensure the stability of signal transmission. The correlated double sampling circuit consists of switches S5 / S6, S7 / S8, capacitors C3 / C4, CF4 / CF5 and a fully differential operational amplifier OPA4; the two ends of the capacitor C3 / C4 are the output of the buffer and the switch S5 / S6, respectively, and the other end of the switch S5 / S6 is connected to the input of the fully differential operational amplifier OPA4; the two ends of the capacitor CF4 / CF5 are the input and output of the fully differential operational amplifier OPA4, respectively, forming a negative feedback; the switch S7 / S8 is connected in parallel with the capacitor CF4 / CF5, and the low-frequency noise of the circuit is significantly reduced through the correlated double sampling technology. The sample-and-hold circuit is composed of switches S9 / S10 and capacitors C5 / C6. When the switches S9 / S10 are closed, the output of the correlated double sampling circuit is sampled and held.

[0086] like Figure 6As shown, in the φ1 time period, the ECG-impedance detection multiplexing module embodiment is equivalent to the ECG signal acquisition module, switches S11, S12, S33, S34, S41, S44, S3, S4 are closed, switches S21, S22, S31, S32, S42, S43 are opened, and when the switch Sres changes from closed to open, the charge amplifier starts to integrate. After a period of time, switches S7 and S8 are in a closed state, switches S5 and S6 change from closed to open, and the correlated double sampling circuit completes the first sampling. After a period of time, switches S7 and S8 are in an open state, switches S5 and S6 change from open to closed, and the correlated double sampling circuit completes the second sampling. Subsequently, switch Sres is closed, the charge amplifier enters a reset state, and integration ends. Switches S9 and S10 are closed, and the output of the ECG signal acquisition module is sampled and held. In the φ2 time period, the ECG-impedance detection multiplexing module embodiment is equivalent to the electrode-skin interface impedance monitoring module, switches S11, S12, S33, S34, S41, S44, S3, S4 are disconnected, switches S21, S22, S31, S32, S42, S43 are closed, and switch Sres is in the disconnected state.

[0087] like Figure 7 As shown, the pulse width modulation module embodiment includes an analog-to-digital converter, a digital operation unit, a programmable capacitor array circuit and a comparator, and the analog-to-digital converter and the electrode-skin interface impedance change measurement voltage V z The digital operation unit receives Dz and generates Dz2 which is proportional to the electrode-skin interface impedance. The programmable capacitor array is controlled by Dz2 and then a constant current source I is used. ref The programmable capacitor array is charged. The slope of the charging curve is proportional to Dz2. The comparator non-inverting input terminal is proportional to the output voltage V cap connected, the inverting input terminal is connected to the constant voltage source V ref Connected, by comparison, generate a PWM wave V with corresponding duty cycle pwm And feed back the PWM wave to the ECG-impedance detection multiplexing module.

[0088] In some specific embodiments, a cardiac-impedance detection multiplexing module and a pulse width modulation module are included. The differential input pair of the non-contact cardiac monitoring front-end circuit is V ip and V in , the differential output pair is V on and V op , where the differential input pair is connected to two independent non-contact dry electrodes, each electrode has an independent electrode-skin interface impedance ZESI, and the signals monitored by the two electrodes include the common-mode signal to be suppressed and the differential-mode signal V to be extracted ECG ; The positive and negative input terminals of the ECG-Impedance Detection Multiplexing Module are connected to Vip and V in , the positive and negative output terminals are respectively connected to V on and V op ; the input terminal of the pulse width modulation module is connected to the impedance detection output voltage V z of the electrocardiogram-impedance detection multiplexing module, and its output terminal V pwm controls the integration time of the charge amplifier of the electrocardiogram-impedance detection timing multiplexing module.

[0089] In summary, an embodiment of the present invention provides a non-contact electrocardiogram monitoring front-end circuit with low input impedance characteristics and a motion artifact compensation mechanism, including an electrocardiogram-impedance detection multiplexing module and a pulse width modulation module. The electrocardiogram-impedance detection multiplexing module is composed of an electrode-skin interface impedance monitoring module and an electrocardiogram signal acquisition module, and is used for high-frequency alternating monitoring of the electrode-skin interface impedance change and the electrocardiogram characteristic waveform; the electrode-skin interface impedance monitoring module includes an operational amplifier and three resistors, and is used for real-time monitoring of the interface impedance change; the electrocardiogram signal acquisition module is composed of a common-mode feedforward circuit, a charge amplifier, an RC low-pass filter, a buffer, a correlated double sampling circuit and a sample and hold circuit, and is used for high-precision acquisition of electrocardiogram signals and realization of motion artifact compensation. The pulse width modulation module is composed of an analog-to-digital converter, a digital arithmetic unit, a programmable capacitor array circuit and a comparator, and is used for generating a control signal for motion artifact compensation. The present invention effectively compensates for the motion artifact interference caused by impedance fluctuations through a low input impedance design and real-time detection of the electrode-skin interface impedance, realizes high-precision and high-reliability electrocardiogram signal measurement, and is particularly suitable for the scenario of monitoring various physiological signals by wearable devices in a dynamic environment.

[0090] It can be understood that the content in the above method embodiment is applicable to this circuit embodiment, and the functions specifically implemented by this circuit embodiment are the same as those in the above method embodiment, and the beneficial effects achieved are also the same as those in the above method embodiment.

[0091] The preferred embodiments of the embodiments of the present application have been described above with reference to the accompanying drawings, but this does not limit the scope of rights of the embodiments of the present application. Any modifications, equivalent replacements, and improvements made by those skilled in the art without departing from the scope and essence of the embodiments of the present application shall be within the scope of rights of the embodiments of the present application.

Claims

1. A front-end circuit for compensating motion artifacts in non-contact electrocardiogram monitoring, characterized in that, The circuit includes a non-contact dry electrode, an electrocardiogram-impedance detection multiplexing module, and a pulse width modulation module. The non-contact dry electrode includes an electrode-skin interface impedance unit. The output end of the non-contact dry electrode is connected to the input end of the electrocardiogram-impedance detection multiplexing module, and the electrocardiogram-impedance detection multiplexing module is interconnected with the pulse width modulation module, where: The non-contact dry electrode is used to acquire electrode-skin interface impedance information and an electrocardiogram signal interfered by motion artifacts; The electrocardiogram-impedance detection multiplexing module is used to calculate and process the impedance value of the electrode-skin interface impedance information, output the electrode-skin interface impedance measurement value, and dynamically compensate the electrocardiogram signal interfered by motion artifacts in combination with the PWM feedback signal, and output the compensated electrocardiogram signal; The pulse width modulation module is used to adjust and compare the electrode-skin interface impedance measurement value, and output the PWM feedback signal.

2. The circuit according to claim 1, wherein The electrocardiogram-impedance detection multiplexing module includes an electrode-skin interface impedance monitoring module and an electrocardiogram signal acquisition module. The electrode-skin interface impedance monitoring module is electrically connected to the electrocardiogram signal acquisition module, where: The electrode-skin interface impedance monitoring module is used to calculate and process the impedance value of the electrode-skin interface impedance information, and output the electrode-skin interface impedance measurement value; The electrocardiogram signal acquisition module is used to dynamically compensate the electrocardiogram signal interfered by motion artifacts according to the PWM feedback signal, and output the compensated electrocardiogram signal.

3. The circuit according to claim 2, characterized in that, The electrode-skin interface impedance monitoring module includes an operational amplifier module, a first resistor, a second resistor, and a third resistor. Wherein, the second end of the first resistor, the first end of the second resistor are connected to the electrode-skin interface impedance unit, the second end of the second resistor, the first end of the third resistor are connected to the negative input terminal of the operational amplifier module, and the second end of the third resistor is connected to the output terminal of the operational amplifier module.

4. The circuit according to claim 2, wherein The electrocardiogram signal acquisition module includes a common-mode feedforward circuit, a charge amplifier, an RC low-pass filter, a buffer, a correlated double sampling circuit, and a sample and hold circuit. The charge amplifier includes a first charge amplifier unit and a second charge amplifier unit. The common-mode feedforward circuit, the charge amplifier, the RC low-pass filter, the buffer, the correlated double sampling circuit, and the sample and hold circuit are connected in sequence, where: The common-mode feedforward circuit is used to suppress environmental noise of the electrocardiogram signal interfered by motion artifacts, and output a preprocessed electrocardiogram charge signal; The charge amplifier is used to adjust the gain coefficient according to the PWM feedback signal, and perform conversion and amplification signal processing on the preprocessed electrocardiogram charge signal to obtain a preprocessed electrocardiogram voltage signal; The RC low-pass filter is used to filter the preprocessed electrocardiogram voltage signal to obtain a filtered electrocardiogram signal; The buffer is used to isolate the signal source of the filtered electrocardiogram signal to obtain a buffered electrocardiogram signal; The related correlated double sampling circuit is used to perform correlated double sampling processing on the buffered electrocardiogram signal to obtain the sampled electrocardiogram signal; The sample and hold circuit is used to hold the stable signal value of the sampled electrocardiogram signal to obtain the compensated electrocardiogram signal.

5. The circuit according to claim 4, wherein The common mode feedforward circuit includes a fourth resistor, a fifth resistor, a sixth resistor, a seventh resistor and a first operational amplifier. The charge amplifier includes a first switch, a second switch, a first feedback capacitor, a second feedback capacitor, a second operational amplifier and a third operational amplifier. The RC low-pass filter includes an eighth resistor, a ninth resistor, a third feedback capacitor, a first capacitor and a second capacitor. The buffer includes a first buffer unit and a second buffer unit. The related correlated double sampling circuit includes a third capacitor, a fourth capacitor, a fifth switch, a sixth switch, a seventh switch, an eighth switch, a fourth feedback capacitor, a fifth feedback capacitor and a fourth operational amplifier. The sample and hold circuit includes a ninth switch, a tenth switch, a fifth capacitor, a sixth capacitor and a seventh capacitor.

6. The circuit according to claim 5, wherein In the electrocardiogram signal acquisition module, the first end of the fourth resistor is connected to the first end of the sixth resistor, the second end of the fourth resistor, the positive input terminal of the first operational amplifier, and the first end of the fifth resistor are connected, the second end of the fifth resistor is connected to the first end of the seventh resistor, the second end of the sixth resistor, the negative input terminal of the second operational amplifier, the first end of the first switch, and the first end of the first feedback capacitor are connected, the negative input terminal of the first operational amplifier, the output terminal of the first operational amplifier, the positive input terminal of the second operational amplifier, and the positive input terminal of the third operational amplifier are connected, the second end of the seventh resistor, the negative input terminal of the third operational amplifier, the first end of the second switch, and the first end of the second feedback capacitor are connected, the second end of the first switch, the second end of the first feedback capacitor, and the output terminal of the second operational amplifier are connected to the first end of the eighth resistor through a third switch, the output terminal of the second operational amplifier, the second end of the second feedback capacitor, and the second end of the second switch are connected to the first end of the ninth resistor through a fourth switch, the second end of the eighth resistor, the second end of the first capacitor, and the first end of the third feedback capacitor are connected to the input terminal of the first buffer unit, the second end of the ninth resistor, the first end of the second capacitor, and the second end of the third feedback capacitor are connected to the input terminal of the second buffer unit, the first end of the first capacitor and the second end of the second capacitor are both grounded, the output terminal of the first buffer unit is connected to the first end of the third capacitor, the output terminal of the second buffer unit is connected to the first end of the fourth capacitor, the second end of the third capacitor is connected to the first end of the fifth switch, the second end of the fourth capacitor is connected to the first end of the sixth switch, the second end of the fifth switch, the first end of the seventh switch, and the first end of the fourth feedback capacitor are connected to the positive input terminal of the fourth operational amplifier, the second end of the sixth switch, the first end of the eighth switch, and the first end of the fifth feedback capacitor are connected to the negative input terminal of the fourth operational amplifier, the second end of the seventh switch, the second end of the fourth feedback capacitor, and the first output terminal of the fourth operational amplifier are connected to the first end of the ninth switch, the second end of the eighth switch, the second end of the fifth feedback capacitor, and the second output terminal of the fourth operational amplifier are connected to the first end of the tenth switch, the second end of the ninth switch, the second end of the fifth capacitor, and the first end of the seventh capacitor are connected, the second end of the tenth switch, the first end of the sixth capacitor, and the second end of the seventh capacitor are connected, the first end of the fifth capacitor and the second end of the sixth capacitor are both grounded.

7. The circuit according to claim 1, characterized in that, The pulse width modulation module includes an analog-to-digital converter, a digital arithmetic unit, a programmable capacitor array, and a comparator, and the analog-to-digital converter, the digital arithmetic unit, the programmable capacitor array, and the comparator are connected in sequence, where: The analog-to-digital converter is used to perform analog-to-digital conversion processing on the measured value of the electrode-skin interface impedance to obtain a digital signal of the measured value of the electrode-skin interface impedance; The digital arithmetic unit is used to perform weighted calculation on the digital signal of the measured value of the electrode-skin interface impedance to obtain a digital signal proportional to the electrode-skin interface impedance; The programmable capacitor array is used to perform pulse width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to the constant current source signal to obtain an adjusted electrode-skin interface impedance signal; The comparator is used to compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output the PWM feedback signal.

8. A control method for a front-end circuit for compensating motion artifacts in non-contact electrocardiogram monitoring, characterized in that, The control method includes the following steps: Obtain the electrode-skin interface impedance information and the electrocardiogram signal interfered by motion artifacts; Perform impedance value calculation processing on the electrode-skin interface impedance information and output the measured value of the electrode-skin interface impedance; Perform adjustment and comparison processing on the measured value of the electrode-skin interface impedance and output the PWM feedback signal; Combine the PWM feedback signal to perform dynamic compensation on the electrocardiogram signal interfered by motion artifacts and output the compensated electrocardiogram signal.

9. The method according to claim 8, characterized in that, The performing adjustment and comparison processing on the measured value of the electrode-skin interface impedance and outputting the PWM feedback signal includes: Perform analog-to-digital conversion processing on the measured value of the electrode-skin interface impedance to obtain a digital signal of the measured value of the electrode-skin interface impedance; Perform weighted calculation on the digital signal of the measured value of the electrode-skin interface impedance to obtain a digital signal proportional to the electrode-skin interface impedance; Perform pulse width adjustment processing on the digital signal proportional to the electrode-skin interface impedance according to the constant current source signal to obtain an adjusted electrode-skin interface impedance signal; Compare the constant voltage source signal with the adjusted electrode-skin interface impedance signal and output the PWM feedback signal.

10. The method according to claim 8, wherein The combining the PWM feedback signal to perform dynamic compensation on the electrocardiogram signal interfered by motion artifacts and outputting the compensated electrocardiogram signal includes: Suppress the environmental noise of the electrocardiogram signal interfered by motion artifacts and output a preprocessed electrocardiogram charge signal; Perform gain coefficient adjustment processing according to the PWM feedback signal, and perform conversion and amplification signal processing on the preprocessed electrocardiogram charge signal to obtain a preprocessed electrocardiogram voltage signal; Perform filtering processing on the preprocessed electrocardiogram voltage signal to obtain a filtered electrocardiogram signal; Perform isolation signal source processing on the filtered electrocardiogram signal to obtain a buffered electrocardiogram signal; Perform correlated double sampling processing on the buffered electrocardiogram signal to obtain a sampled electrocardiogram signal; Perform signal value holding stability on the sampled electrocardiogram signal to obtain the compensated electrocardiogram signal.

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