CN220001750U - PPG signal conditioning circuit - Google Patents
PPG signal conditioning circuit Download PDFInfo
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- CN220001750U CN220001750U CN202222946184.3U CN202222946184U CN220001750U CN 220001750 U CN220001750 U CN 220001750U CN 202222946184 U CN202222946184 U CN 202222946184U CN 220001750 U CN220001750 U CN 220001750U
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- 230000003750 conditioning effect Effects 0.000 title claims abstract description 24
- 238000013186 photoplethysmography Methods 0.000 abstract description 40
- 238000000034 method Methods 0.000 abstract description 8
- 239000008280 blood Substances 0.000 abstract description 3
- 210000004369 blood Anatomy 0.000 abstract description 3
- 230000008569 process Effects 0.000 abstract description 3
- 230000002401 inhibitory effect Effects 0.000 abstract description 2
- 230000000694 effects Effects 0.000 description 6
- 230000003321 amplification Effects 0.000 description 4
- 238000001914 filtration Methods 0.000 description 4
- 238000003199 nucleic acid amplification method Methods 0.000 description 4
- 238000012544 monitoring process Methods 0.000 description 3
- 210000004204 blood vessel Anatomy 0.000 description 2
- 239000003990 capacitor Substances 0.000 description 2
- 230000000747 cardiac effect Effects 0.000 description 2
- 230000009471 action Effects 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000036772 blood pressure Effects 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 230000008602 contraction Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 201000010099 disease Diseases 0.000 description 1
- 208000037265 diseases, disorders, signs and symptoms Diseases 0.000 description 1
- 238000002565 electrocardiography Methods 0.000 description 1
- 230000002996 emotional effect Effects 0.000 description 1
- 230000003862 health status Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
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Abstract
Photoplethysmography (PPG) is a non-invasive method of detecting blood volume by photoelectric means. The PPG signal generated using this method contains a variety of valuable biological information. The utility model provides a PPG signal conditioning circuit, which comprises an isolator circuit, a low-pass filter circuit, a high-pass filter circuit, a band-stop filter circuit, an in-phase proportion amplifying circuit, an inverter circuit and a bias circuit, wherein 7-stage circuits are sequentially connected in sequence, the original input signals are isolated and then filtered, the low-pass filter and the high-pass filter are equivalent to band-pass filters to extract PPG signals with the frequency of 0.5Hz to 5Hz, the band-stop filter is used for inhibiting power frequency interference generated by a power supply, the circuit can amplify the original signals by tens to hundreds of times, the signals are PPG signals with complete and clear waveforms and high signal-to-noise ratio, and finally, the PPG signals are added with direct current bias to enable the final output signals to be positive voltage after passing through the circuit, so that a subsequent microprocessor can conveniently process the signals, and biological information in the PPG signals is extracted.
Description
Technical Field
The utility model relates to the field of weak signal processing, in particular to a method for conditioning a tiny PPG signal and finally outputting a PPG signal with 0-5V meeting a standard voltage signal.
Background
Cardiac motion can reflect the health status, lifestyle, and even emotional state and disease information of an organism, and traditional monitoring of cardiac activity is accomplished by Electrocardiography (ECG), requiring electrodes connected to the body for monitoring. Photoplethysmography (PPG) is a method of non-invasively detecting changes in blood volume by means of electro-optical means, which uses heart beats to generate pressure waves acting on blood vessels, and the contraction and expansion of blood vessels each time the heart beats affects light transmission, becoming another method of monitoring heart activity. The PPG signal contains rich biological information, and the conditioning of the PPG signal can help people to conveniently and effectively acquire biological information such as blood pressure, blood oxygen and the like contained in the PPG signal.
Disclosure of Invention
The utility model provides a PPG signal conditioning circuit, which consists of 7 parts, namely an isolator circuit, a low-pass filter circuit, a high-pass filter circuit, a band-stop filter circuit, an in-phase proportional amplifying circuit, an inverter circuit and a bias circuit. The circuit filters the input weak PPG signal through a low-pass filter and a high-pass filter, and the action is equivalent to that of the band-pass filter, so that the PPG signal with the frequency of 0.5 Hz-5 Hz is extracted. The PPG signal is properly amplified through the gain-adjustable in-phase proportional amplifying circuit, and the direct current bias is added into the signal by the bias circuit, so that the conditioned PPG signal is a standard voltage signal, and a clear and complete PPG signal is obtained.
The utility model is realized by the following technical scheme. The PPG signal conditioning circuit comprises an isolator circuit, a low-pass filter circuit, a high-pass filter circuit, a band-stop filter circuit, an in-phase proportional amplifying circuit, an inverter circuit and a bias circuit, wherein 7-stage circuits are sequentially connected. The signal amplitude and the signal-to-noise ratio are improved by amplifying, filtering and the like the original signal.
Furthermore, the isolator circuit is a voltage follower, mainly plays an isolating role, and facilitates the subsequent processing of amplifying, filtering and the like of signals by the circuit.
Furthermore, the low-pass filter and the high-pass filter circuit of the utility model mainly have the effects of extracting the PPG signal of 0.5 Hz-5 Hz in the signal source, filtering high-frequency interference and improving the signal-to-noise ratio of the signal. The band-stop filter with the stop band being near 50Hz is used for inhibiting the power frequency interference generated by the power supply, and further improving the signal-to-noise ratio of the signal.
Furthermore, the in-phase proportional amplifying circuit is an adjustable gain in-phase proportional amplifying circuit, proper amplification factor can be selected according to specific input signals, the peak value of the amplified signal is controlled within 5V, and the signal can be changed into a standard voltage signal after bias is added.
Furthermore, the phase of the filtered and amplified PPG signal is adjusted to be the same as the phase of the initial signal by the inverter circuit.
Furthermore, the bias circuit adds direct current bias into the PPG signal, and the bias PPG signal does not contain negative voltage and is difficult to process, and the bias voltage is required to be added to ensure that the whole output PPG signal is positive voltage, so that a complete and clear PPG signal is obtained.
Drawings
The utility model will be further described with reference to the drawings and examples.
Fig. 1 is an isolator circuit in accordance with the present utility model.
Fig. 2 is a low pass filter circuit of the present utility model.
Fig. 3 is a high pass filter circuit of the present utility model.
Fig. 4 is a band reject filter circuit of the present utility model.
Fig. 5 is an in-phase proportional amplifying circuit in the present utility model.
Fig. 6 is an inverter circuit in accordance with the present utility model.
Fig. 7 is a bias circuit in the present utility model.
Detailed Description
The PPG signal conditioning circuit is composed of 7 stages of circuits, and the specific stages of circuits sequentially comprise an isolator circuit, a low-pass filter circuit, a high-pass filter circuit, a band-stop filter circuit, an in-phase proportional amplifying circuit, an inverter circuit and a biasing circuit. The conditioning circuit filters, amplifies, adds bias and the like to the signal source, so that the output signal is a PPG signal with clear and good waveform, high signal to noise ratio and easy acquisition and processing.
The isolator circuit in the PPG signal conditioning circuit is shown in fig. 1. The isolator circuit main body is an integrated operational amplifier in the LM358 chip, the LM358 chip adopts positive and negative 5V voltage to supply power, and other LM358 chips in the conditioning circuit also adopt the mode to supply power. The output end of the operational amplifier is connected with the negative input end of the operational amplifier to form a voltage follower, the voltage follower has ideal input and output impedance, the isolation function is achieved, the influence of a front-stage circuit on signals is reduced, and the conditioning circuit can better process the input PPG signals.
The filtering circuit in the PPG signal conditioning circuit is shown in fig. 2, 3 and 4. Fig. 2 is a diagram showing the components of low-pass filter circuits R1, R2, C1 and C2 and an integrated op-amp, the lower limit cut-off frequency of the circuit is 0.5Hz, capacitors C3, C4, C5 and C6 filter the power supply, so as to further reduce interference, and meanwhile, the resistance value of the resistor R3 is the same as that of R4, which indicates that the circuit has 2 times of amplification effect on signals. Fig. 3 is a high-pass filter circuit, which has a structure similar to that of a low-pass filter circuit, and is mainly different in positions of a resistor and a capacitor, so that fig. 3 is an active second-order high-pass filter circuit, which has a 2-fold amplification effect on a signal, similar to the low-pass filter circuit. FIG. 4 is a band stop filter with a stop band frequency near 50Hz, which is mainly used for suppressing power frequency interference generated by a power supply and improving the signal-to-noise ratio of an output signal.
The in-phase proportional amplifying circuit in the PPG signal conditioning circuit is shown in fig. 5. R17 is a potentiometer, and signals are input from the positive end of the integrated operational amplifier, so the circuit is an adjustable gain in-phase proportional amplifying circuit, the signals can be amplified in several times to tens times, and the specific amplification factor of the signals is determined by the resistance values of R16 and R17 according to the requirements.
The inverter circuit in the PPG signal conditioning circuit is shown in fig. 6. The resistance of the resistor R18 is the same as that of the resistor R19, signals are input from the negative end of the integrated operational amplifier to form an inverting proportion amplifying circuit, the whole amplifying circuit amplifies by-1 times, and the effect is to adjust the phase of the filtered and amplified PPG signal to be the same as that of the initial signal.
The bias circuit in the PPG signal conditioning circuit is shown in fig. 7. The potentiometer R20 and the resistor R22 divide the voltage, the voltage in the middle of the potentiometer R20 and the resistor R22 is the bias voltage added into the signal, the resistance of the potentiometer R20 is regulated according to specific needs, and the proper bias voltage is added to enable the output PPG signal to be a standard voltage signal, so that the signal can be conveniently collected and processed subsequently. The circuit has certain amplifying capability to signals, the resistance values of the resistors R23 and R24 are the same, and the circuit amplifies the input PPG signals by 2 times.
The foregoing has shown and described the basic principles and main features of the present utility model and the advantages of the present utility model. It will be understood by those skilled in the art that the present utility model is not limited to the embodiments described above, and that the above embodiments and descriptions are merely illustrative of the principles of the present utility model, and various changes and modifications may be made without departing from the spirit and scope of the utility model, which is defined in the appended claims. The scope of the utility model is defined by the appended claims and equivalents thereof.
Claims (7)
1. A PPG signal conditioning circuit, characterized by: the signal conditioning circuit consists of an isolator circuit, a low-pass filter circuit, a high-pass filter circuit, a band-stop filter circuit, an in-phase proportional amplifying circuit, an inverter circuit and a bias circuit.
2. A PPG signal conditioning circuit according to claim 1, wherein: the original signal firstly passes through the isolator circuit, so that the influence of the circuit on the original signal is reduced.
3. A PPG signal conditioning circuit according to claim 1, wherein: the frequency of the PPG signal is 0.5 Hz-5 Hz, the signal passing through the isolator passes through a low-pass filter circuit with the lower limit cutoff frequency of 0.5Hz and a high-pass filter circuit with the upper limit cutoff frequency of 5Hz, the two are equivalent to a band-pass filter circuit, the PPG signal with the lower limit cutoff frequency of 0.5 Hz-5 Hz is extracted from the signal, and the interference signal is filtered.
4. A PPG signal conditioning circuit according to claim 1, wherein: the signal is passed through 50Hz band-stop filter to inhibit the power frequency interference caused by power supply, so as to raise signal-to-noise ratio.
5. A PPG signal conditioning circuit according to claim 1, wherein: the filtered signals are reasonably amplified by an adjustable gain in-phase proportional amplifying circuit.
6. A PPG signal conditioning circuit according to claim 1, wherein: the filtered PPG signal phase is 180 ° out of phase with the original signal phase, and the inverter circuit adjusts the signal phase to be the same as the original signal.
7. A PPG signal conditioning circuit according to claim 1, wherein: and adding direct current bias into the amplified PPG signal through a bias circuit to enable the final output of the PPG signal to be 0-5V and complete and clear.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222946184.3U CN220001750U (en) | 2022-11-05 | 2022-11-05 | PPG signal conditioning circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202222946184.3U CN220001750U (en) | 2022-11-05 | 2022-11-05 | PPG signal conditioning circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN220001750U true CN220001750U (en) | 2023-11-14 |
Family
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202222946184.3U Active CN220001750U (en) | 2022-11-05 | 2022-11-05 | PPG signal conditioning circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN220001750U (en) |
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2022
- 2022-11-05 CN CN202222946184.3U patent/CN220001750U/en active Active
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