TW201326830A - Bio-potential sensing circuit and method - Google Patents

Abstract

A bio-potential sensing circuit, comprising: a first electrode, receiving a first physiological signal and a first noise; a first capacitor, with one terminal electrically connecting to the first electrode; a first control unit, with one terminal electrically connecting to the other terminal of the first capacitor, and the other terminal electrically connecting to a voltage reference node; a second electrode, receiving a second physiological signal and a second noise; a second capacitor, with one terminal electrically connecting to the second electrode; a second control unit, with one terminal electrically connecting to the other terminal of the second capacitor, and the other terminal electrically connecting to the voltage reference node; an input matching circuit, electrically coupling to the other terminal of the first electrode and the other terminal of the second electrode, and generating a first control signal and/or a second control signal according to the first noise and the second noise, controlling the first control unit and the second control unit, to equalize amplitudes of the first noise and the second noise.

Description

Bioelectric signal sensing circuit and method

The present invention relates to a bioelectric signal sensing circuit and method, and more particularly to a bioelectric signal sensing circuit and method that can accommodate different electrode types.

With the rapid development of medical technology, the demand for medical products and the demand for quality have increased greatly, which makes the medical and health sensing products of medical care have considerable room for growth in the future. Currently used physiological signal measurement and electrode forms used include: wet electrodes, such as hospital electrocardiogram and electromyography measurement, with wet gel or saline contact with the skin, the electrode impedance is the lowest (about 100Ω~5kΩ), the signal measurement method uses differential amplifier circuit plus Driven Right Leg (DRL) for noise cancellation; dry electrode, such as stainless steel electrode or silver chloride electrode, directly with the skin Contact, because of its high impedance value (about 1kΩ~20kΩ), with differential amplifier circuit as measurement circuit; capacitive electrode with non-contact sensing characteristics, often using soft plastic electrode or fabric electrode and foil In close contact with the skin under insulation isolation (no substantial electrical contact), because the electrodes are insulated and isolated, the impedance is very high (about 100Ω~100MΩ, 10pF~100nF), and the signal measurement method is mainly The capacitor neutralization circuit plus the back-end differential amplifier circuit is mainly used. In the prior art, the sensing circuit of the low-impedance electrode (wet electrode) cannot apply the high-impedance electrode (dry electrode, capacitive electrode), and the high-impedance electrode (dry electrode, capacitive electrode) cannot apply the low-impedance electrode (wet type) Sensing circuit of the electrode). Furthermore, in practical applications, the impedance value of the electrode often changes due to changes in the measurement environment. For example, an athlete's heart rhythm is measured by a dry electrode. At first, the athlete's skin is dry and the impedance of the electrode is high, but when the athlete starts to sweat, the equivalent impedance of the electrode end is lowered. Therefore, there is a need for a bioelectric signal sensing circuit that can accommodate various types of electrodes and various measurement environments.

In view of the above, the present invention provides a bioelectric signal sensing circuit including a first electrode for receiving a first biosignal; the first biosignal includes a first physiological characteristic and a first noise; and a first capacitor One end is electrically connected to a first electrode; a first control unit has one end electrically connected to the other end of the first capacitor, the other end is electrically connected to a reference potential node; and a second electrode receives a second The second biological signal includes a second physiological characteristic and a second noise; a second capacitor is electrically connected at one end to a second electrode; and a second control unit is coupled to the second capacitor One end is electrically connected, and the other end is electrically connected to the reference potential node; an input balancing unit is respectively coupled to the other end of the first capacitor and the other end of the second capacitor, and according to the first biological signal and The second biosignal generates a first control signal and/or a second control signal to respectively control the first control unit and/or the second control unit to make the first noise and the second miscellaneous The amplitudes are equal; a differential amplifier is coupled to the other end of the first capacitor and the other end of the second capacitor to receive the first biosignal and the second biosignal and generate an output signal .

The present invention further provides a method for measuring a bioelectric signal, comprising separately measuring a first biosignal and a second biosignal, wherein the first biosignal and the second biosignal respectively comprise a first noise and a first Second noise; determining whether the amplitude of the first noise and the second noise are equal; if the amplitude of the first noise is greater than the amplitude of the second noise, reducing the amplitude of the first noise or amplifying the first The amplitude of the second noise; if the amplitude of the first electrode noise is smaller than the amplitude of the second electrode noise, amplifying the amplitude of the first noise or reducing the amplitude of the second noise; repeating the above steps until the first electrode And the noise amplitude of the second electrode is equal; and differentially amplifying the physiological signals received from the first electrode and the second electrode.

FIG. 1 is a schematic structural view of a bioelectric signal sensing circuit 100 according to an embodiment of the present invention. Referring first to FIG. 1, the bioelectric signal sensing circuit 100 includes a first electrode P1 and a second electrode P2. In some embodiments, the first electrode P1 and the second electrode P2 may be dry electrodes, wet electrodes, or capacitive electrodes, but are not limited thereto. The first electrode P1 and the second electrode P2 may be the same type of electrodes or different types of electrodes.

The first electrode P1 and the second electrode P2 are in contact with the living organism or biological tissue to be measured to obtain the first bioelectric signal S1 and the second bioelectric signal S2, respectively, as shown in FIGS. 2A and 2B. The first bioelectric signal S1 and the second bioelectric signal S2 are voltage information generated by the muscle tissue, nervous system, organ or cell of the living being. In some embodiments, the first bioelectric signal S1 and the second bioelectric signal S2 may be an electroencephalogram (EEG), a skin potential response (GSR), an electrocardiogram (ECG), an electromyography (EMG), or Heart rate changes (HRV), etc., but are not limited to this. The first bioelectric signal S1 and the second bioelectric signal S2 respectively include first and second biopotentials V1, V2, first and second noises Q1, Q2, and first and second physiological features R1, R2. The first and second biopotentials V1, V2 and the first and second noises Q1, Q2 are the environmental potential and background noise of the organism itself, and the first and second physiological features R1, R2 are the muscle tissue of the living being, Changes in voltage produced by the nervous system, organs or cells.

Referring to FIG. 1 , the bioelectric signal sensing circuit 100 includes a first capacitor C1 and a second capacitor C2. One end is coupled to the first electrode P1 and the second electrode P2 to receive the first bioelectric signal S1 and the second. Bioelectric signal S2. The first capacitor C1 and the second capacitor C2 generally have a higher capacitance value (for example, greater than 1 μF) for coupling the front end physiological signals and filtering the biopotentials V1 and V2 of the direct current portion, and the first and second physiological characteristics R1 And R2 and the first and second noises Q1 and Q2 are passed. The other ends of the first capacitor C1 and the second capacitor C2 respectively output the first bioelectric signal S1' and the second bioelectric signal S2', wherein the first bioelectric signal S1' is different from the first bioelectric signal S1 received by the electrode. Only the biopotential V1 of the DC portion has been eliminated; the second bioelectric signal S2' differs from the second bioelectric signal S2 received by the electrode only in that the biopotential V2 of the DC portion has been eliminated.

As shown in FIG. 1, the bioelectric signal sensing circuit 100 further includes a first control unit M1 and a second control unit M2, voltage followers AMP1 and AMP2. One end of the first control unit M1 and the second control unit M2 are electrically coupled to the other ends of the first capacitor C1 and the second capacitor C2, respectively, and the other end is electrically coupled to a reference potential node GND; the voltage follower The input terminals of the AMP1 and the AMP2 are respectively coupled to the other ends of the first capacitor C1 and the second capacitor C2, and are used as impedance conversion of the weak input signal to transmit the first bioelectric signal S1' and the second bioelectric signal S2' to The output of the voltage follower AMP1 and AMP2. The outputs of the voltage followers AMP1 and AMP2 are connected to nodes n1 and n2, respectively. In some embodiments, the other ends of the first capacitor C1 and the second capacitor C2 are electrically connected to a circuit having impedance matching and electrostatic discharge protection functions (including the diodes D1 and D2) to add an extra electrostatic discharge. The voltage is introduced into the reference potential node GND to prevent damage to the bioelectric signal sensing circuit 100. In some embodiments, when the first electrode P1 or the second electrode P2 is a capacitive electrode, there are respectively an outer ring L1 and L2 (shown in FIG. 1 by dashed lines), which are electrically connected to the nodes n1 and n2, respectively. To maintain a very low voltage difference with the potential of the sensing electrode, this allows the tiny signal to easily escape from the threshold of the existing capacitor voltage into the voltage followers AMP1 and AMP2. In some embodiments, the feedback circuits of the voltage followers AMP1 and AMP2 further include passive components such as resistors and capacitors in series, which are not shown in FIG. 1 for the sake of simplicity.

The bioelectric signal sensing circuit 100 further includes an input balancing unit 10 having input terminals a1 and a2 connected to nodes n1' and n2', respectively. The nodes n1' and n2' are electrically coupled to the nodes n1 and n2, respectively, to receive the first bioelectric signal S1' and the second bioelectric signal S2' from the outputs of the voltage followers AMP1 and AMP2. In some embodiments, between the nodes n1 and n1', and between the nodes n2 and n2', there are active elements such as passive components such as resistors and capacitors or active filters. For the sake of simplicity, the passive components are not shown in FIG. 1; the balancing unit 10 further includes output terminals f1 and f2 coupled to the first control unit M1 and the second control unit M2, respectively. The input balancing unit 10 reads the first bioelectric signal S1' and the second bioelectric signal S2' from the input terminals a1 and a2 for analysis, and outputs the first control voltage and/or the second from the output terminals f1 and f2 according to the analysis result. The voltage is controlled to adjust the resistance values of the first control unit M1 and/or the second control unit M2, respectively, so that the noise amplitudes of the first bioelectric signal S1 and the second bioelectric signal S2 are balanced. In a preferred embodiment, the input balancing unit 10 reads the first and second physiological features R1 and R2 when the biological tissue to be tested does not generate (for example, muscle relaxation does not produce myoelectric signals), and the input terminals a1 and a2 read The first bioelectric signal S1' and the second bioelectric signal S2' are the first noise Q1 and the second noise Q2. In some embodiments, the input balancing unit 10 further transmits the balanced first noise Q1 and the second noise Q2 to the opposite phase by the feedback circuit DRL and the third electrode P3. The human body to eliminate the effects of noise.

As shown in FIG. 1, in the embodiment, the first control unit M1 and the second control unit M2 are field effect transistors (FETs) having a first gate and a second gate, respectively. Therefore, the first control unit M1 and the second control unit M2 are hereinafter referred to as a first transistor M1 and a second transistor M2; the output terminals f1 and f2 of the input balancing unit 10 are electrically coupled to the first transistor M1, respectively. And the first gate and the second gate of the second transistor M2, and outputting the first control voltage and/or the second control voltage to control the first gate and/or the second gate to adjust the first control unit The resistance value of M1 and/or the second control unit M2. In other embodiments, the first control unit M1 and the second control unit M2 may be any type of voltage-controlled impedance variable element, and the first control unit M1 is adjusted according to the output signals of the output terminals f1 and f2. The resistance value of the second control unit M2.

The bioelectric signal sensing circuit 100 further includes a differential amplifier DIF, and the input ends thereof are electrically coupled to the other ends of the input terminals a1 and a2, the first capacitor C1 and the second capacitor C2, respectively, and the noise amplitude is balanced. A bioelectric signal S1' and a second bioelectric signal S2' are differentially processed to generate an output signal, which is output from the output terminal OUT.

Figure 3 is a flow chart showing the bioelectric signal balancing method of the input balancing unit 10 in the embodiment of Fig. 1. First, in step 12, the input terminals a1 and a2 of the input balancing unit 10 receive the first and second noises Q1 and Q2 from the first and second electrodes P1 and P2, respectively. Next, in step 14, the input balancing unit 10 determines whether the amplitudes w1 and w2 (shown in FIG. 2) of the first and second noises Q1 and Q2 are the same. If they are the same, the process proceeds directly to step 16 to complete the balance; Then, proceed to step 18 to compare the magnitudes of the amplitudes w1 and w2.

If the amplitude w1 is smaller than the amplitude w2, the step 20 is performed, and the input balancing unit 10 increases the second control voltage of the output terminal f2 to open the gate of the second transistor M2, thereby reducing the resistance value of the second transistor M2. At this time, the first physiological characteristic R2 of the other end of the first capacitor C2 is reduced together with the first noise Q2; the input balancing unit 10 can also lower the first control voltage of the output terminal f1 to make the gate of the first transistor M1 Closed, increasing the resistance of the first transistor M1. At this time, the first physiological characteristic R1 of the other end of the first capacitor C1 is amplified together with the first noise Q1. In some embodiments, the input balancing unit 10 can simultaneously increase the second control voltage of the output terminal f2 and reduce the first control voltage of the output terminal f1 to reduce the first physiological characteristic R2 and the first noise Q2 and simultaneously amplify the first Physiological feature R1 and first noise Q1. Then, step 12 is repeated until the amplitudes w1 and w2 of the first and second noises Q1 and Q2 are the same, and the noise amplitude balance between the two is completed.

If the amplitude w1 is greater than the amplitude w2, the step 22 is performed, and the input balancing unit 10 lowers the second control voltage of the output terminal f2 to close the gate of the second transistor M2, thereby increasing the resistance value of the second transistor M2. At this time, the second physiological characteristic R2 of the other end of the second capacitor C2 is amplified together with the second noise Q2; the input balancing unit 10 can also increase the first control voltage of the output terminal f1 to make the gate of the first transistor M1 It is turned on to lower the resistance value of the first transistor M1. At this time, the first physiological characteristic R1 of the other end of the first capacitor C1 is reduced together with the first noise Q1. In some embodiments, the input balancing unit 10 can simultaneously reduce the second control voltage of the output terminal f2 and increase the first control voltage of the output terminal f1 to amplify the second physiological characteristic R2 and the second noise Q2 and simultaneously reduce the first Physiological feature R1 and first noise Q1. Then, step 12 is repeated until the amplitudes w1 and w2 of the first and second noises Q1 and Q2 are the same, and the noise amplitude balance between the two is completed.

The bioelectric signal sensing circuit provided by the invention can adapt to various types of electrodes, including dry electrodes, wet electrodes, and capacitive electrodes; and can accept the influence of changes in the measurement environment on the impedance of the electrodes, and increase the sensing circuit. The scope of application is timely and the integration and versatility of different measurement requirements are improved.

10. . . Input balance unit

100. . . Bioelectric signal sensing circuit

12, 14, 16, 18, 20, 22. . . step

A1. . . First input

A2. . . Second input

AMP1, AMP2. . . Voltage follower

C1. . . First capacitor

C2. . . Second capacitor

D1. . . Dipole

D2. . . Dipole

DRL. . . Right foot feedback circuit

F1, f2. . . Output

GND. . . Reference potential node

L1, L2. . . Outer ring

M1. . . First control unit

M2. . . Second control unit

N1, n1', n2, n2'. . . node

OUT. . . Output

P1-P3. . . electrode

Q1, Q2. . . First and second noise

R1, R2. . . First and second physiological characteristics

S1, S1’. . . First bioelectric signal

S2, S2’. . . Second bioelectric signal

W1, w2. . . First and second noises

V1, V2. . . First and second physiological potentials

1 is a schematic structural diagram of a bioelectric signal sensing circuit 100 according to an embodiment of the present invention;

2a is a schematic diagram showing the waveform of the bioelectric signal S1 in an embodiment of the present invention;

2b is a schematic diagram showing the waveform of the bioelectric signal S2 in an embodiment of the present invention;

Figure 3 is a flow chart showing the method of balancing the input balancing unit 10 in the embodiment of Figure 1 of the present invention.

10. . . Input balance unit

100. . . Bioelectric signal sensing circuit

A1. . . First input

A2. . . Second input

AMP1, AMP2. . . Voltage follower

C1. . . First capacitor

C2. . . Second capacitor

D1. . . Dipole

D2. . . Dipole

DRL. . . Right foot feedback circuit

F1, f2. . . Output

GND. . . Reference potential node

L1, L2. . . Outer ring

M1. . . First control unit

M2. . . Second control unit

N1, n1', n2, n2'. . . node

OUT. . . Output

P1-P3. . . electrode

S1, S1’. . . First bioelectric signal

S2, S2’. . . Second bioelectric signal

Claims (12)

A bioelectric signal sensing circuit includes: a first electrode receiving a first bioelectric signal; the first bioelectric signal including a first physiological characteristic and a first noise; a first capacitor, one end and one The first electrode is electrically connected; a first control unit, one end is electrically connected to the other end of the first capacitor, the other end is electrically connected to a reference potential node; and a second electrode receives a second bioelectric signal; The second bioelectric signal includes a second physiological characteristic and a second noise; a second capacitor is electrically connected at one end to a second electrode; and a second control unit is electrically connected to one end of the second capacitor The other end is electrically connected to the reference potential node; an input balancing unit includes two input ends respectively coupled to the other end of the first capacitor and the other end of the second capacitor, and according to the first Generating a first control signal and/or a second control signal to control the first control unit and/or the second control unit to enable the first noise and The amplitude of the second noise is equal; and a differential amplifier, wherein the input end is coupled to the other end of the first capacitor and the other end of the second capacitor to differentially amplify the first bio-electric signal and the first The second bioelectric signal generates an output signal. The bioelectric signal sensing circuit of claim 1, wherein the capacitance of the first capacitor and the second capacitor is greater than 1 μF. The bioelectrical signal sensing circuit of claim 1, wherein the input balancing unit compares the amplitude of the first noise and the amplitude of the second noise, when the amplitude of the first noise is greater than the second noise The amplitude of the first control unit is decreased by the first control signal or the resistance of the second control unit is increased by the second control signal. The bioelectrical signal sensing circuit of claim 1, wherein the input balancing unit compares the amplitude of the first noise and the amplitude of the second noise, when the amplitude of the first noise is less than the second noise. The amplitude of the first control unit is increased by the first control signal or the resistance of the second control unit is decreased by the second control signal. The bioelectric signal sensing circuit of claim 1, wherein the first electrode and the second electrode are any of the following: a dry electrode, a wet electrode, and a capacitive electrode. The bioelectric signal sensing circuit of claim 1, further comprising a first voltage follower and a second voltage follower, wherein the first voltage follower input and the first The other end of the capacitor is electrically connected, and the output end is electrically connected to one input end of the input balance unit; the second end of the second voltage follower is electrically connected to the other end of the second capacitor, and the output end is The other input end of the input balancing unit is electrically connected. The bioelectric signal sensing circuit of claim 6, wherein the first electrode and the second electrode further comprise an outer ring respectively, and the output of the first voltage follower and the second voltage follower The end is coupled. The bioelectric signal sensing circuit of claim 1, wherein the first control unit and the second control unit are field effect transistors. The bioelectric signal sensing circuit of claim 1, further comprising an electrostatic protection circuit, the other end of the first capacitor and the other end of the second capacitor being coupled to the reference potential node. The bioelectric signal sensing circuit of claim 1, wherein the input balancing unit further comprises feeding back the balanced first noise or the second noise to the living organism to be tested. A bioelectric signal sensing method includes: measuring a first bioelectric signal and a second bioelectric signal, wherein the first biosignal and the second biosignal respectively comprise a first noise and a second Detecting whether the amplitude of the first noise and the second noise are equal; if the amplitude of the first noise is greater than the amplitude of the second noise, reducing the amplitude of the first noise or amplifying the second impurity The amplitude of the signal; if the amplitude of the first electrode noise is less than the amplitude of the second electrode noise, amplifying the amplitude of the first noise or reducing the amplitude of the second noise; repeating the above steps until the first noise and The amplitude of the second noise is equal; and the first bioelectric signal and the second bioelectric signal are differentially amplified. The bioelectric signal sensing method according to claim 11 of the patent application can be applied to a dry electrode, a wet electrode, and a capacitive electrode.