A non-contact ECG monitoring circuit that can effectively suppress motion interference

Abstract

This invention discloses a non-contact ECG monitoring circuit that effectively suppresses motion interference. It includes a high-pass input stage circuit, a motion interference suppression stage circuit, a low-pass amplification stage circuit, a power frequency suppression stage circuit, and an output stage circuit. The high-pass input stage circuit includes a floating electrode, a low-bias current operational amplifier circuit A1, and an active low-pass feedback module. The motion interference suppression stage circuit is an inverting integrator circuit, and its output is connected to the reference level pin REF of the low-bias current operational amplifier circuit A1. The gain of the low-bias current operational amplifier circuit A1 is 10 to 100 times. This invention reduces human motion interference signals while ensuring the accuracy of ECG signal acquisition.

Description

[Technical field]

[0001] The invention belongs to the technical field of electrocardiogram monitoring circuits, and in particular relates to a non-contact electrocardiogram monitoring circuit capable of effectively suppressing motion interference. [Background technology]

[0002] Dynamic electrocardiogram is a commonly used screening method for cardiovascular diseases in clinical practice. By recording the ECG signals of suspected patients in their natural living state for more than 24 hours, arrhythmia events and abnormal ST segment changes that are not easy to be found in conventional ECG can be found, and important diagnostic evaluation basis can be obtained. The ECG signal acquisition electrodes used in traditional ECG measurement are Ag / AgCl wet electrodes with conductive glue. Before using this wet electrode, the skin needs to be cleaned with alcohol and the electrode should be pressed tightly against the human skin. This wet electrode is irritating and is not suitable for people with skin allergies. It cannot be reused and is not suitable for long-term dynamic monitoring of human ECG signals. Moreover, the cost of long-term monitoring is high and the implementation is complicated, so it is not suitable for daily ECG monitoring. In addition, the non-contact lead electrode only has the ECG signal acquisition function, and a separate right leg drive electrode is used to feedback the common mode signal. When using it, two lead electrodes need to be placed on the left and right chests, and a separate right leg drive electrode needs to be placed on the right abdomen, which is very inconvenient to use.

[0003] Contactless ECG monitoring equipment uses ECG electrodes that are not in direct contact with human skin to acquire ECG signals in real time, which can improve the comfort and compliance of ECG monitoring users. The electrodes of the capacitive coupling contactless ECG monitoring system do not come into direct contact with human skin, which reduces the skin cleaning steps and preparation time. The main disadvantages are that the ECG signal is severely attenuated, it is susceptible to noise and motion interference, and the ECG signal quality is poor. The relative movement between the capacitive coupling contactless ECG electrodes and the skin will produce motion artifacts, and the friction between the electrodes and the insulating layer will cause a large voltage offset at the electrode input. The impact of noise and motion interference on ECG signals is the key issue that makes it difficult for capacitive coupling contactless ECG monitoring systems to obtain ECGs that can be used for clinical diagnosis.

[0004] Therefore, it is necessary to provide a new non-contact ECG monitoring circuit that can effectively suppress motion interference to solve the above technical problems. [Summary of the invention]

[0005] The main purpose of the present invention is to provide a non-contact ECG monitoring circuit that can effectively suppress motion interference, thereby reducing human motion interference signals while ensuring the accuracy of ECG signal acquisition.

[0006] The present invention achieves the above-mentioned purpose through the following technical scheme: a non-contact ECG monitoring circuit that can effectively suppress motion interference, which includes a high-pass input stage circuit, a motion interference suppression stage circuit, a low-pass amplifier stage circuit, a power frequency suppression stage circuit and an output stage circuit; the high-pass input stage circuit includes a floating electrode, a low bias current operational amplifier circuit A1, and an active low-pass feedback module; the motion interference suppression stage circuit is an inverting integration circuit, and its output end is connected to the reference level pin REF of the low bias current operational amplifier circuit A1. The gain of the low bias current operational amplifier circuit A1 is 10 times to 100 times.

[0007] Furthermore, the active low-pass feedback module includes a low bias current operational amplifier A2, a resistor R1, and a capacitor C1, and the floating electrode is divided into two paths respectively connected to the non-inverting input terminal of the low bias current operational amplifier circuit A1 and the non-inverting input terminal of the low bias current operational amplifier A2.

[0008] Furthermore, the output end of the low bias current operational amplifier A2 is electrically connected to the inverting input end; one end of the resistor R1 is connected to the output end of the low bias current operational amplifier A2, and the other end is respectively connected to the inverting input end of the low bias current operational amplifier circuit A1 and the capacitor C1; the other end of the capacitor C1 is grounded.

[0009] Furthermore, the motion interference suppression stage circuit includes an operational amplifier A3, a resistor R2, and a capacitor C2.

[0010] Furthermore, the output end of the low bias current operational amplifier circuit A1 is connected to the inverting input end of the operational amplifier A3, and the resistor R2 is arranged on the connection line; one end of the capacitor C2 is connected to the inverting input end of the operational amplifier A3, and the other end is connected to the output end of the operational amplifier A3; the non-inverting input end of the operational amplifier A3 is grounded, and the output end is connected to the reference level pin REF of the low bias current operational amplifier circuit A1.

[0011] Furthermore, the low-pass amplifier stage circuit is a low-pass filter amplifier circuit, which includes an operational amplifier A4, a resistor R3, a resistor R4 and a capacitor C3.

[0012] Furthermore, the output end of the low bias current operational amplifier circuit A1 is connected to the non-inverting input end of the operational amplifier A4; the resistor R4 and the capacitor C3 are connected in parallel between the inverting input end and the output end of the operational amplifier A4; the resistor R3 is connected in series with the resistor R4 and the capacitor C3, one end of the resistor R3 is grounded and the other end is connected to the inverting input end of the operational amplifier A4.

[0013] Furthermore, the power frequency suppression stage circuit is an active trap circuit.

[0014] Furthermore, the output stage circuit is a follower circuit.

[0015] Compared with the prior art, the non-contact ECG monitoring circuit of the present invention can effectively suppress motion interference and has the beneficial effects of: comprising a plurality of circuit stages, while reducing the interference signal caused by human motion, ensuring the collection of ECG signals; filtering out the interference signal generated by human motion through the motion interference suppression circuit, enabling the ECG monitoring device to perform ECG monitoring during human activities, greatly improving the applicability of the non-contact ECG monitoring device; at the same time, the combination of the high-pass input stage circuit and the low-pass amplifier stage circuit designed in the present scheme, while ensuring the reasonable transmission of the signal, retains the power of the ECG signal to the greatest extent, greatly improving the signal-to-noise ratio, and improving the monitoring accuracy and reliability.

Brief Description of the Drawings

[0016] Figure 1 It is a schematic structural diagram of an embodiment of the present invention. [Specific implementation method]

[0017] Embodiment 1:

[0018] Please refer to Figure 1 The present embodiment is a non-contact ECG monitoring circuit 100 that can effectively suppress motion interference, which includes a high-pass input stage circuit 1, a motion interference suppression stage circuit 2, a low-pass amplifier stage circuit 3, a power frequency suppression stage circuit 4 and an output stage circuit 5.

[0019] The high-pass input stage circuit 1 includes a floating electrode 11, a low bias current operational amplifier circuit A1, and an active low-pass feedback module, wherein the active low-pass feedback module includes a low bias current operational amplifier A2, a resistor R1, and a capacitor C1. The floating electrode 11 is divided into two paths, which are respectively connected to the non-inverting input terminal of the low bias current operational amplifier circuit A1 and the non-inverting input terminal of the low bias current operational amplifier A2. The output terminal of the low bias current operational amplifier A2 is electrically connected to the inverting input terminal; one end of the resistor R1 is connected to the output terminal of the low bias current operational amplifier A2, and the other end is respectively connected to the inverting input terminal of the low bias current operational amplifier circuit A1 and the capacitor C1; the other end of the capacitor C1 is grounded. The low bias current operational amplifier A2, the resistor R1 and the capacitor C1 form a low-pass filter, whose output enters the low bias current operational amplifier circuit A1, is subtracted from the ECG signal collected by the floating electrode 11, and is differentially amplified in the low bias current operational amplifier circuit A1, thereby achieving a high-pass effect. The typical value of the low-pass cut-off frequency is 0.1Hz to 1Hz.

[0020] The action interference suppression stage circuit 2 is an inverting integration circuit, and its output end is connected to the reference level pin REF of the low bias current operational amplifier circuit A1. The action interference suppression stage circuit 2 includes an operational amplifier A3, a resistor R2, and a capacitor C2. The output end of the low bias current operational amplifier circuit A1 is connected to the inverting input end of the operational amplifier A3, and the resistor R2 is arranged on the connection line; one end of the capacitor C2 is connected to the inverting input end of the operational amplifier A3, and the other end is connected to the output end of the operational amplifier A3; the same-direction input end of the operational amplifier A3 is grounded, and the output end is connected to the reference level pin REF of the low bias current operational amplifier circuit A1. The low bias current operational amplifier circuit A1 adopts a differential amplification structure, which mainly realizes two functions, one is to realize low bias current, and the other is to have a fixed gain of 10 times to 100 times. Multiple amplifiers can be used to form an instrument amplifier circuit structure, and a single-chip instrument amplifier can also be used to realize it. The bias current of the low bias current operational amplifier circuit A1 and the low bias current operational amplifier A2 is 10fA to 90fA.

[0021] The low-pass amplifier circuit 3 is a low-pass filter amplifier circuit, which includes an operational amplifier A4, a resistor R3, a resistor R4 and a capacitor C3. The output end of the low bias current operational amplifier circuit A1 is connected to the non-inverting input end of the operational amplifier A4; the resistor R4 and the capacitor C3 are connected in parallel between the inverting input end and the output end of the operational amplifier A4, the resistor R3 is connected in series with the resistor R4 and the capacitor C3, one end of the resistor R3 is grounded and the other end is connected to the inverting input end of the operational amplifier A4. The typical value of the low-pass cut-off frequency is several hundred Hz to 1kHz.

[0022] The power frequency suppression stage circuit 4 is an active trap circuit, such as a common double-T type 50 Hz power frequency trap circuit, which is a prior art, and its specific structure will not be described in detail in this embodiment.

[0023] The output stage circuit 5 is a follower circuit.

[0024] After the ECG signal is sensed by the suspension electrode 11, one path is input into the low bias current operational amplifier circuit A1, and the other path is input into the active low-pass feedback module. The low frequency and DC parts in the induced signal of the suspension electrode 11 are filtered out by the active low-pass feedback module, and the high frequency part is amplified and output by the low bias current operational amplifier circuit A1. When human body movements generate abnormal jitter signals, the jitter signals are tens or even hundreds of times stronger than the ECG signals. When the ECG signals are superimposed with jitter signals generated by abnormal human body movements, the output of the high-pass input stage circuit 1 rises sharply in positive or negative phase, and the output voltage of the corresponding motion interference suppression stage circuit 2 rises sharply in negative or positive direction. The output of the motion interference suppression stage circuit 2 is then fed back to the low bias current operational amplifier circuit A1 as a reference voltage, so that the output of the high-pass input stage circuit 1 tends to be stable, thereby suppressing the interference of the jitter signal caused by abnormal human body movements on the ECG signals. The signal after the high-pass input stage circuit 1 tends to be stable is amplified by the low-pass amplifier stage circuit 3 to filter out the noise outside the ECG signal frequency and improve the signal-to-noise ratio. The power frequency noise of the signal is then filtered out by the power frequency suppression stage circuit 4 to further improve the signal-to-noise ratio. The conditioned signal is output to the subsequent system through the output stage circuit 5 for processing.

[0025] The present embodiment provides a non-contact ECG monitoring circuit 100 that can effectively suppress motion interference. It is a non-contact ECG monitoring circuit that includes multiple stages of circuits. It reduces interference signals caused by human motion while ensuring the collection of ECG signals. The motion interference suppression stage circuit filters out interference signals generated by human motion, thereby enabling the ECG monitoring device to perform ECG monitoring during human activities, greatly improving the applicability of the non-contact ECG monitoring device. At the same time, the combination of the high-pass input stage circuit and the low-pass amplifier stage circuit designed in the present solution retains the power of the ECG signal to the greatest extent while ensuring reasonable signal transmission, thereby greatly improving the signal-to-noise ratio and improving the monitoring accuracy and reliability.

[0026] The above are only some embodiments of the present invention. For those skilled in the art, several modifications and improvements can be made without departing from the creative concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A non-contact ECG monitoring circuit capable of effectively suppressing motion interference, characterized in that: It includes a high-pass input stage circuit, an action interference suppression stage circuit, a low-pass amplifier stage circuit, an industrial frequency suppression stage circuit and an output stage circuit; the high-pass input stage circuit includes a floating electrode, a low bias current operational amplifier circuit A1, and an active low-pass feedback module; the action interference suppression stage circuit is an inverting integration circuit, and its output end is connected to the reference level pin REF of the low bias current operational amplifier circuit A1, and the gain of the low bias current operational amplifier circuit A1 is 10 times to 100 times; the active low-pass feedback module includes a low bias current operational amplifier A2, a resistor R1, and a capacitor C1, the floating electrode is divided into two paths, which are respectively connected to the in-phase input end of the low bias current operational amplifier circuit A1 and the in-phase input end of the low bias current operational amplifier A2; the output end of the low bias current operational amplifier A2 The resistor R1 is electrically connected to the inverting input terminal; one end of the resistor R1 is connected to the output terminal of the low bias current operational amplifier A2, and the other end is respectively connected to the inverting input terminal of the low bias current operational amplifier A1 and the capacitor C1; the other end of the capacitor C1 is grounded; the action interference suppression stage circuit includes an operational amplifier A3, a resistor R2, and a capacitor C2; the output terminal of the low bias current operational amplifier A1 is connected to the inverting input terminal of the operational amplifier A3, and the resistor R2 is arranged on the connection line; one end of the capacitor C2 is connected to the inverting input terminal of the operational amplifier A3, and the other end is connected to the output terminal of the operational amplifier A3; the non-inverting input terminal of the operational amplifier A3 is grounded, and the output terminal is connected to the reference level pin REF of the low bias current operational amplifier A1.

2. The non-contact ECG monitoring circuit capable of effectively suppressing motion interference as claimed in claim 1, characterized in that: The low-pass amplifier stage circuit is a low-pass filter amplifier circuit, which includes an operational amplifier A4, a resistor R3, a resistor R4 and a capacitor C3.

3. The non-contact ECG monitoring circuit capable of effectively suppressing motion interference as claimed in claim 2, characterized in that: The output end of the low bias current operational amplifier circuit A1 is connected to the non-inverting input end of the operational amplifier A4; the resistor R4 and the capacitor C3 are connected in parallel between the inverting input end and the output end of the operational amplifier A4; the resistor R3 is connected in series with the resistor R4 and the capacitor C3, one end of the resistor R3 is grounded and the other end is connected to the inverting input end of the operational amplifier A4.

4. The non-contact ECG monitoring circuit capable of effectively suppressing motion interference as claimed in claim 1, characterized in that: The power frequency suppression stage circuit is an active trap circuit.

5. The non-contact ECG monitoring circuit capable of effectively suppressing motion interference as claimed in claim 1, characterized in that: The output stage circuit is a follower circuit.

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