KR101764603B1 - Bio signal Read-out Circuit - Google Patents

Abstract

A biological signal read-out circuit according to the present embodiment includes: an amplification part which receives and amplifies a bio signal and includes an impedance boosting capacitor which is connected in a positive feedback configuration between output and input; a variable gain amplification part for amplifying a signal outputted from the amplification part with a gain varying in accordance with the amplitude of the signal outputted by the amplification part; and an envelope signal forming part for receiving and detecting the signal outputted from the amplification part, and outputting an envelope to the variable gain amplification part. A characteristic deterioration due to motion artifact does not occur.

Description

Bio-signal read-out circuit [0002]

The present invention relates to a biological signal lead-out circuit.

Devices that monitor health conditions for 24 hours typically operate in contact with the wearer's body. The monitor devices detect electrical signals formed in the body, and provide electrical information about the wearer's body through electrical signal processing.

The monitor device must be able to sensitively receive electrical signals provided by the wearer's body, smoothly process the received signals, and provide motion artifacts formed by the wearer's motion, The performance deterioration due to the inflow of noise introduced from the input side should be small.

Japanese Patent Publication Patent Specification 2006-503279 (2006.1.26.)

The main object of the present embodiment is to provide a lead-out circuit for inputting a living body signal so as to satisfy the above object. The main object of the present embodiment is to provide a lead-out circuit that does not cause deterioration of characteristics due to motion artifacts formed by a user's motion in a monitor device operating in contact with the wearer's body.

One of the main goals of this embodiment is to provide a lead-out circuit that reduces the digital signal processing burden and performs smooth signal processing.

The biological signal lead-out circuit according to the present embodiment includes: an amplification unit including an impedance boosting capacitor connected to an output and an input in a positive feedback configuration to receive and amplify a living body signal; A variable gain amplifier section for amplifying a signal output from the amplification section with a gain varying in amplitude, an envelope signal forming section for receiving and detecting the signal output from the amplification section, and outputting an envelope to the variable gain amplifier section do.

The envelope signal forming unit according to the present embodiment is an envelope signal forming circuit that outputs an envelope of a living body signal. The envelope signal forming circuit includes a pair of differential circuits. The differential circuit includes a common source amplifier, A common gate amplifier for receiving an output of the common source amplifier and buffering and outputting it as a current signal; a common gate amplifier for receiving the current signal and for amplifying and outputting the current signal; And a capacitor that accumulates the current provided by the current mirror and the current mirror to form a voltage signal, the output node being connected to the input of each differential circuit pair in a negative feedback configuration.

According to this embodiment, even when the measurer moves, the effect of moving artifact can be reduced, and the envelope of the EMG signal can be detected at the analog terminal, thereby reducing the burden on the digital signal processing Advantages are provided.

1 is a block diagram showing the outline of a biological signal lead-out circuit according to the present embodiment.
Fig. 2 (a) is a diagram showing the opening of the electrocardiogram signal, and Fig. 2 (b) is a diagram showing the opening of the electromyogram signal.
3 is a schematic circuit diagram of an envelope signal forming unit.
5 is a diagram showing a result of measuring the electrocardiogram using the lead-out circuit according to the prior art and a result of measuring the electrocardiogram using the lead-out circuit according to the present embodiment.

The description of the present invention is merely an example for structural or functional explanation, and the scope of the present invention should not be construed as being limited by the embodiments described in the text. That is, the embodiments are to be construed as being variously embodied and having various forms, so that the scope of the present invention should be understood to include equivalents capable of realizing technical ideas.

Meanwhile, the meaning of the terms described in the present application should be understood as follows.

The terms "first "," second ", and the like are used to distinguish one element from another and should not be limited by these terms. For example, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

It is to be understood that when an element is referred to as being "on" or "on" another element, it may be directly on top of the other element, but other elements may be present in between. On the other hand, when an element is referred to as being "in contact" with another element, it should be understood that there are no other elements in between. On the other hand, other expressions that describe the relationship between components, such as "intervening" and "intervening", between "between" and "immediately" or "neighboring" Direct neighbors "should be interpreted similarly.

It should be understood that the singular " include "or" have "are to be construed as including a stated feature, number, step, operation, component, It is to be understood that the combination is intended to specify that it is present and not to preclude the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

Each step may take place differently from the stated order unless explicitly stated in a specific order in the context. That is, each step may occur in the same order as described, may be performed substantially concurrently, or may be performed in reverse order.

The drawings referred to for explaining embodiments of the present disclosure are exaggerated in size, height, thickness, and the like intentionally for convenience of explanation and understanding, and are not enlarged or reduced in proportion. In addition, any of the components shown in the drawings may be intentionally reduced, and other components may be intentionally enlarged.

All terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Terms such as those defined in commonly used dictionaries should be interpreted to be consistent with the meanings in the context of the relevant art and can not be construed as having ideal or overly formal meaning unless explicitly defined in the present application .

1 is a block diagram showing the outline of a biological signal lead-out circuit according to the present embodiment. 1, the bio-signal lead-out circuit 1 according to the present embodiment includes impedance boosting capacitors Cfa and Cfb connected in a positive feedback configuration between an output and an input, A variable gain amplifier 200 for amplifying a signal output from the amplifier with different gains according to amplitudes of signals output from the amplifier 100 and an amplifier 100 And an envelope signal forming unit 300 for outputting an envelope and providing the envelope to the variable gain amplifier.

In one embodiment, the input signal provided to the lead-out circuit 1 includes an electrocardiogram (ECG) signal detected using a pad worn by the wearer, and an EMG signal detected by an EMG detection device mounted on the wearer can do. 2 (a) is a diagram showing the opening of an electrocardiogram signal. 2 (a), an electrocardiogram (ECG) signal is a signal obtained by detecting the activity current generated in the myocardium according to the heartbeat on the body surface, and includes a T wave, a P wave, and a QRS wave , And the QRS wave is formed when excitation is spread to the ventricle and ventricular contraction begins. The R wave with the largest amplitude may have a voltage value of approximately 0.5 mV to 1.5 mV, and the period of the R wave approximately coincides with the heartbeat period.

Fig. 2 (b) is a diagram showing the opening of the EMG signal. The EMG signal is an electrical signal generated from the skeletal muscle, which is formed by a potential difference generated when the muscle cell is activated electrically or neu- ratically. The electromyogram signal shown in FIG. 2 (b) is obtained when the muscle contracts, and it has a higher frequency than the electrocardiogram signal and has a peak voltage of 150 uV to 200 uV.

As shown in FIGS. 2 (a) and 2 (b), the EMG signal has a frequency higher than that of the electrocardiogram signal ECG, and the ECG signal has a peak It can be confirmed that the voltage is large. 2 (a) and 2 (b) illustrate only electrocardiogram signals and electromyogram signals, they are merely examples, and the lead-out circuit according to the present embodiment provides various electrical signals formed in the living body Can receive.

Referring again to FIG. 1, a biological signal such as an electrocardiogram signal, an electromyogram signal, and an EEG signal acquired from a wearer is provided as an input. In the embodiment illustrated in FIG. 1, the bio-electrical signal is converted into a differential signal by a patch (not shown) installed by the wearer for bio-signal measurement and provided to the lead-out circuit 1 according to the present embodiment do. According to another embodiment not shown, the biological signal may be provided as a single ended signal.

The coupling capacitor Cc interrupts the flow of the DC component from the bio-signal provided to the lead-out circuit 1, and provides the signal component to the input chopper circuit 412. The input chopper circuit 412 receives the input signal and performs switching at a predetermined frequency, a predetermined period, so that the provided input signal has a desired duty ratio, and outputs the result to the amplification unit 100.

The amplification unit 100 receives a signal output from the input chopper circuit 412, amplifies the signal, and outputs the amplified signal. 1, the amplifier 100 includes a capacitor Ca connected in parallel and a capacitor Cb connected between the inverting input and the non-inverting output of the operational amplifier and connected in parallel to the resistor Ra, The resistor Rb may be implemented as a differential integrator connected between the noninverting input and the inverting output of the operational amplifier.

In an embodiment not shown, the amplifier may be a capacitor connected in parallel and a single-ended integrator whose resistance is connected between the inverting input and the inverting output of the operational amplifier. In another embodiment not shown, the amplification section may be implemented with a low pass filter.

The output of the amplification unit 100 is provided to the output chopper circuit 414 and the output chopper circuit 414 outputs the output signal of the amplification unit 100 to a predetermined frequency so that the signal output from the amplification unit 100 has a desired duty ratio, Periodically.

In the embodiment shown in FIG. 1, the input chopper circuit 412 and the output chopper circuit 414 are disposed at the input of the amplification unit and the output chopper circuit 414, respectively. However, according to the embodiment, Only one of the input chopper circuit 412 and the output chopper circuit 414 can be connected.

The output of the output chopper circuit 414 is positively fed back to the input side of the amplifier 100 through the impedance boost capacitors Cfa and Cfb. In the embodiment illustrated in FIG. 1, the signal output from the non-inverting output of the amplifier 100 and through the output chopper circuit is connected to the non-inverting input of the amplifier 100 via the impedance boost capacitor Cfb. A signal output from the inverting output of the amplifying unit 100 and passed through the output chopper circuit is connected to the inverting input side of the amplifying unit 100 via the impedance boost capacitor Cfa.

There is provided an advantage that the input impedance characteristic of the readout circuit 1 can be improved by the positive feedback configuration using the impedance boost capacitors Cfa and Cfb of the amplifier unit 100. [ The input chopper circuit 412, the output chopper circuit 414, and the impedance boost capacitors Cfa and Cfb are also connected to the input chopper circuit 412, the output chopper circuit 414, and the impedance boost capacitor Cb when the wearer of the ECG measuring device and the EMG measuring device performs walking, There is provided an advantage that the motion artifact generated due to the movement of the wearer can be removed by the amplifying part 100 included therein.

In one embodiment, when the signal output from the output chopper circuit 414 is a signal obtained by amplifying an electrocardiogram (ECG) signal, the second switch SWb is cut off and the first switch SWa is turned on. Thus, the signal is provided to the variable gain amplifier 220 along the first path Pl. When the signal output from the output chopper circuit 414 is a signal obtained by amplifying the EMG signal, the first switch SWa is cut off and the second switch SWb is made conductive. Accordingly, the signal is provided to the envelope signal forming unit 300 along the second path P2.

In one embodiment, the first switch SWa and the second switch SWb can be controlled by the level detector 210 from the magnitude of the signal input to the level detector 210. [ As another example, the first switch SWa and the second switch SWb may be controlled by a control unit (not shown).

When the signal output from the output chopper circuit 414 is the amplified electrocardiogram signal ECG, the first switch SWa is turned on and supplied to the variable gain amplifier 220. [ The level detector 210 detects the amplitude magnitude of the input signal to control the gain of the variable gain amplifier 220, and the variable gain amplifier 220 amplifies the provided signal and provides the amplified signal to the analog-to-digital converter 300.

The first switch SWa is turned off and the second switch SWb is turned on to be provided to the envelope signal forming unit 300. When the output chopper circuit 414 outputs the amplified EMG signal EMG, The envelope signal forming unit 300 rectifies and detects the dense EMG signal at a high frequency to form an envelope signal of the EMG signal.

3 is a diagram schematically showing a circuit of the envelope signal forming unit 300 according to the present embodiment. Referring to FIG. 3, the envelope signal generator 300 includes M1 and M2 transistors forming a common source amplifier to receive the input signals V _INP and V _INN , a buffer for receiving an output signal of the common source amplifier, M3 and M4 transistors constituting a common gate amplifier for receiving and outputting the output signals of the buffer units B and B 'and the buffer units B and B' to output the current signals output from the common gate amplifiers, A capacitor Cext for accumulating the mirrored current into a voltage signal and a leakage current for adjusting a voltage formed in the capacitor Cext by forming a leakage current, Forming portion (I). The envelope detection of the near-infrared signal is performed by the capacitor Cext and the leakage current forming portion I. [

The M3 and M4 gates forming the common gate amplifier and the output node O are connected and the output is negatively fed back to the input. By the negative feedback configuration, the output signal Vout is the input signals V _INP and V _INN Which acts as a rectifier that follows the larger voltage.

The envelope signal forming unit 300 illustrated in FIG. 3 has a differential structure. The input signal V _INP And the V _INN signal and the circuits that operate accordingly operate complementarily. Hereinafter, for the sake of brevity and clarity, the operation of a circuit operated by one input signal V _INP of the differential pair will be described.

As the input signal V _INP is provided, the common source amplifier amplifies the input signal and provides an output signal to the drain electrode of the M1 transistor. The buffer unit B is supplied with the output signal of the common source amplifier to the gate electrode. The transistor of the buffer unit B is controlled to be turned on and off according to a signal supplied to the gate electrode to provide a current signal to the source electrode which is the input electrode of the common gate amplifier M3.

The common gate amplifier M3 performs the function of the current buffer. The common gate amplifier M3 buffers the input signal and outputs it to the current mirror M through the drain electrode of the M3 transistor. The current mirror mirrors the current signal output by the common gate amplifier M3 and provides it to the output node O through the transistor M7. The capacitor Cext accumulates the current signal to form the voltage signal V _OUT .

The gate electrode of the transistor M3 constituting the common gate amplifier and the gate electrode of the M4 transistor and the output node O are connected to form a negative feedback path. Therefore, the output signal Vout of the envelope detector 300 is input to the input signals V _INP and V _INN Which acts as a rectifier that follows the larger voltage.

The envelope detection is performed by the capacitor Cext connected to the output node O and the leakage current forming portion I. [ In one example, the leakage current forming portion I may include a plurality of diode-connected transistors connected by a cascode. As another example, the leakage current forming portion I may include a plurality of diodes connected in series.

In one embodiment, the envelope signal generator 300 may control the offset voltage of the output voltage by adjusting the sizes of the M3 and M4 transistors forming the common gate amplifier.

The envelope signal of the EMG signal output from the envelope signal forming unit 300 is provided to the variable gain amplifier 220 through the second switch SWb. The gain of the variable gain amplifier 220 is controlled by the level detector 210. Accordingly, the electrocardiogram signal having different amplitudes and the electromyogram signal can be amplified with different gains and amplified to match the input dynamic range of the analog-to-digital converter 500. Therefore, it can be converted into a digital signal having a sufficient resolution.

According to the envelope signal forming unit 300 according to the present embodiment, the envelope signal can be formed by sampling the electromyogram signal having a high frequency at a high frequency and detecting it in the analog domain without having to convert it into a digital signal. Therefore, there is provided an advantage that the burden of signal processing in the digital domain can be reduced.

The digital signal converted by the analog-to-digital converter 500 may be provided to the communication unit 600 and provided to an external circuit. In one embodiment, the communication unit 600 may include a wired communication module such as a serial communication interface (SPI). In another embodiment, the communication unit 600 may include a wireless communication module such as a zigbee, a Wi-fi, and a Bluetooth.

4 (a) to 4 () are diagrams showing an embodiment of the lead-out circuit 1 according to the present embodiment. Fig. 4A is a diagram schematically showing an upper surface of a lead-out circuit according to the present embodiment, and Fig. 4B is a diagram schematically showing a cross-section of a lead-out circuit according to this embodiment. Fig. 4 (c) is a view showing that the lead-out circuit is disposed on the flexible substrate S on which the lead-out circuit according to the present embodiment is formed. Referring to Figs. 4 (a) and 4 (b), the lead-out circuit 1 according to the present embodiment can be disposed on the flexible substrate S. The stretchable substrate S is formed of PDMS, for example, and can be compressed and stretched. As another example not shown, the lead-out circuit according to this embodiment can be disposed on a rigid substrate such as a printed circuit board (PCB).

According to the illustrated embodiment, the lead-out circuit 1 can be formed on the stretchable substrate S with the buffer layer BL interposed therebetween. The buffer layer BL prevents the lead-out circuit 1 and the substrate S from being separated from each other by an external force when an external force such as warping or bending of the flexible substrate is provided as shown in Fig. 4 (c) .

Comparative Example

5 is a diagram showing a result of measuring the electrocardiogram using the lead-out circuit according to the prior art and a result of measuring the electrocardiogram using the lead-out circuit according to the present embodiment. FIG. 5A is a diagram showing a state in which an electrocardiogram is measured using a lead-out circuit according to a related art. Referring to FIG. 5A, when the measurer is in a stationary state, It is possible to confirm periodic R waves, and it can be confirmed that a high frequency component influenced by a motion artifact is output without being intervened. However, in the moving state of the measurer, it can be confirmed that the high frequency component is formed to such an extent that the position of the R wave can not be confirmed by the motion artifact. The motion artifact, which is a high-frequency component, is actually formed by the movement of the measurer, not by the fact that the heart operates at a high frequency.

5 (b) is a diagram showing a state in which an electrocardiogram is measured using the lead-out circuit according to the present embodiment. 5 (b) shows the case where the electrocardiogram is measured while the measurer is in the stationary state, and the figure at the bottom of FIG. 5 (b) shows the case where the measurer measures the electrocardiogram It is one case. 5 (b) and FIG. 5 (b), it can be seen that even if the measurer moves, it is possible to grasp the periodic R waves and to improve the characteristic of eliminating moving artifacts have.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of illustration, It will be appreciated that other embodiments are possible. Accordingly, the true scope of the present invention should be determined by the appended claims.

100: amplification unit 200: variable gain amplification unit
300: envelope signal forming unit 412: input chopper circuit
414: output chopper circuit 500: analog-to-digital converter
600:

Claims (14)

A biological signal readout circuit, wherein the lead-out circuit comprises:
An amplifying unit including an impedance boosting capacitor that receives and amplifies the bio-electrical signal and is connected in a positive feedback configuration between an output and an input;
A variable gain amplifier for amplifying a signal output from the amplifier with different gains according to amplitudes of signals output from the amplifier;
And an envelope signal forming unit for receiving and detecting the signal output from the amplifying unit and outputting an envelope to the variable gain amplifying unit,
Wherein the lead-
Further comprising at least one chopper circuit,
Wherein at least one chopper circuit is connected to at least one of an input of the amplifier and an output of the amplifier. The method according to claim 1,
Wherein the biological signal is a signal measurable by the readout circuit,
The bio-
A first living body signal, and a second living body signal,
The first bio-signal is an electrocardiogram (ECG) signal,
And the second biometric signal is an electromyography (EMG) signal. 3. The method of claim 2,
The electromyogram (EMG) signal is provided to the envelope signal forming unit,
Wherein the envelope signal forming unit detects an envelope of the EMG signal and outputs the envelope. The method according to claim 1,
Wherein the impedance boosting capacitor increases the magnitude of the input impedance. The method according to claim 1,
Wherein the variable gain amplifier comprises:
An amplitude detector for detecting an amplitude of a signal provided to the variable gain amplifier;
And a variable gain amplifier whose gain is controlled in accordance with the detection result of the amplitude detector. The method according to claim 1,
Wherein the lead-out circuit is formed on a stretchable substrate. The method according to claim 1,
The envelope signal forming unit includes:
A buffer for receiving and buffering the input,
A common gate amplifier for amplifying the buffered signal,
And a current mirror for receiving and mirroring an output of the common gate amplifier,
And a capacitor for detecting an envelope of the bio-signal. 8. The method of claim 7,
The envelope signal forming unit includes:
And a diode-connected transistor that receives the mirrored current to form a leakage current to detect an envelope. delete The method according to claim 1,
Wherein the lead-
An analog-to-digital converter (ADC) that receives the output of the variable gain amplifier and converts the output to a digital signal and outputs the digital signal;
And a communication unit for outputting the digital-converted signal so as to be aligned with the communication protocol. An envelope signal forming circuit for outputting an envelope of a biological signal, the envelope signal forming circuit including a differential circuit pair, the differential circuit comprising:
A common source amplifier receiving the biological signal;
A buffer unit receiving the output of the common source amplifier and buffering and outputting it as a current signal;
A common gate amplifier receiving the current signal, amplifying the current signal, and outputting the amplified current signal;
A current mirror for receiving the output of the common gate amplifier, for mirroring and providing the output to the output node, and
And a capacitor for accumulating the current provided by the current mirror to form a voltage signal,
And the output node is connected to an input of each differential circuit pair in a negative feedback configuration. 12. The method of claim 11,
Wherein the envelope signal forming circuit further comprises a leakage current forming section that forms a leakage current at the output node. 13. The method of claim 12,
The leakage current forming unit includes:
An envelope signal forming circuit including any one of a diode-connected transistor and a diode. 12. The method of claim 11,
Wherein the bio-signal is an electromyogram signal.

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