Weak heart and lung sound signal pickup circuit, practical electronic stethoscope circuit and stethoscope head structure

Abstract

The utility model relates to the field of electronic stethoscopes, provides an electronic stethoscope circuit with a weak heart and lung sound signal pickup circuit and a structure, and aims to solve the problem that an existing electronic stethoscope can only realize listening, and cannot display waveforms in real time and record and store audio data. Weak heart and lung sound signals enter the signal processing circuit through two-stage filtering amplification of the pickup circuit and then are converted into digital signals for display and transmission, and the stethoscope head structure further comprises an auscultation film, a circuit board of the pickup circuit and a trumpet-shaped sound receiver. According to the negative voltage stabilizer disclosed by the utility model, a circuit is simplified, peripheral capacitors and resistors of the two stages of filter amplifiers respectively play a good filtering role and prevent direct current offset, correct signals are ensured to be amplified and output by a data line, and meanwhile, pickup, listening, recording, waveform real-time display, Bluetooth data transmission and audio coding are realized; and converting the sound signal into a WAV format for storage.

Description

Technical Field

[0001] The utility model relates to the technical field of electronic stethoscopes, and more specifically to an electronic stethoscope circuit and structure with a weak cardiopulmonary sound signal pickup circuit. Background Art

[0002] The stethoscope is an indispensable routine examination method for clinicians, which is of great help in diagnosing diseases. Experienced doctors can make effective predictions about the disease through auscultation, so as to provide more targeted treatment. However, the shortcomings of traditional mechanical stethoscopes are also obvious. For example, it is difficult to capture some weak but very important physiological sounds emitted by the human internal organs, and the accuracy is poor; the waveform cannot be displayed in real time while auscultating, and it is easily affected by the limitations of human hearing sensitivity and the subjective experience of the auscultator. These shortcomings ultimately lead to the doctor's inability to make a correct diagnosis in time. With the development of stethoscopes, some mechanical electronic stethoscopes with better sound effects have emerged, but they are expensive. There are also many styles of electronic stethoscopes, but most of them can only listen, and cannot display waveforms in real time and record and save audio data, which is not convenient for the analysis of the disease. With the improvement of public health awareness, both clinical and home use require a device with high accuracy, real-time waveform display, simplicity and ease of use, low cost and small size. Summary of the invention

[0003] Based on the weak signal of traditional stethoscopes and the unstable signal and voltage of common electronic auscultation, the purpose of this utility model is to provide an electronic stethoscope circuit and structure with a weak cardiopulmonary sound signal pickup circuit. The weak cardiopulmonary sound signal pickup circuit has a negative voltage regulator acting on the operational amplifier circuit, and uses the power management circuit to provide a stable 3.3V voltage to the entire circuit. At the same time, the voltage loop management module charges the lithium battery to ensure that the device continues to work without power failure. The STM32 chip is used to realize the digital-to-analog conversion of sound signals, screen display, Bluetooth data transmission, audio encoding, and audio file storage.

[0004] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0005] A weak cardiopulmonary sound signal pickup circuit comprises a sound signal collection circuit and a two-stage filter amplifier circuit, wherein the output end of the sound signal collection circuit is connected to the first-stage filter amplifier circuit, the output end of the first-stage filter amplifier circuit is connected to the input end of the second-stage filter amplifier circuit, and the output end of the second-stage filter amplifier circuit is filtered by a low-pass filter circuit and used as the output OUT of the pickup circuit, wherein: the sound signal collection circuit comprises a microphone MIC for collecting cardiopulmonary sounds, the microphone MIC converts the collected audio signal of the weak cardiopulmonary sounds into an electrical signal, a capacitor C9 for filtering out high-frequency signals in the audio signal collected by the microphone MIC is connected between the positive and negative electrodes of the microphone MIC, the positive electrode of the microphone MIC is connected to a power supply VCC through a pull-up resistor R4, and the electrical signal is coupled to the first-stage filter amplifier circuit through a capacitor C8.

[0006] Furthermore, the first-stage filtering and amplifying circuit includes an amplifier U2.2, a capacitor C6, a resistor R5 and a resistor R2. The output end of the sound signal acquisition circuit is connected to the reverse input end of the amplifier U2.2 through the resistor R5. The resistor R2 and the capacitor C6 are connected in parallel to the reverse input end and the output end of the amplifier U2.2.

[0007] Furthermore, the second-stage filter amplifier circuit includes an amplifier U2.1, a capacitor C7, a resistor R6 and a resistor R3. The output end of the first-stage filter amplifier circuit is connected to the reverse input end of the amplifier U2.1 through the resistor R6. The resistor R3 and the capacitor C7 are connected in parallel to the reverse input end and the output end of the amplifier U2.1. The output end of the amplifier U2.1 is grounded through a low-pass filter circuit composed of a resistor R7 and a capacitor C10.

[0008] A practical electronic stethoscope circuit comprises the above-mentioned weak cardiopulmonary sound pickup circuit, and also comprises a signal processing circuit, a power management circuit, an audio conversion circuit and an audio interface circuit. The output OUT of the pickup circuit is connected to the signal input end of the signal processing circuit. The signal processing circuit converts the analog signal inputted into the pickup circuit into a digital signal convenient for display and transmission. The power management circuit realizes battery charge and discharge management and 5V regulated voltage output. The audio conversion circuit converts the cardiopulmonary sound signal into a WAV audio format file. The audio interface circuit comprises a pickup interface, an earphone interface and a recording interface. The pickup interface is connected to the output OUT of the pickup circuit as the signal input end of the audio interface. The earphone interface and the recording interface are used for connecting the output ends of the audio signal to the earphone and the recording device respectively.

[0009] A practical electronic stethoscope head structure includes the above-mentioned practical electronic stethoscope circuit, and also includes a stethoscope membrane, a circuit board of a cardiopulmonary sound pickup circuit, and a horn-shaped receiver. The stethoscope membrane is connected to one side of a horn-shaped opening end of the horn-shaped receiver through a stethoscope membrane fixing ring, and the circuit board is placed on the other side of the horn-shaped receiver. The horn-shaped opening end is a conical structure, a sound receiving hole is provided in the center of the horn-shaped opening end, and a through hole for placing a microphone is provided on the side away from the horn-shaped opening end, and the sound receiving hole is connected to the through hole.

[0010] Furthermore, the aperture of the sound receiving hole is smaller than the aperture of the through hole.

[0011] Furthermore, an annular groove for accommodating a sealing rubber ring is provided on the edge of the trumpet-shaped opening end.

[0012] Furthermore, one side of the speaker-shaped receiver connection circuit board is fixedly connected to the back cover, and the back cover is provided with a round hole for the power line and the signal line to pass through.

[0013] In summary, the invention has the following beneficial effects:

[0014] (1) Negative voltage regulators can simplify circuits, provide reliable power supply for operational amplifiers, and extend battery life to ensure the safety and stability of electronic equipment.

[0015] (2) The external capacitors and resistors of the two-stage filter amplifier play a good filtering role and prevent DC offset, thereby ensuring correct signal amplification and output from the data line.

[0016] (3) It can simultaneously realize sound pickup, listening, recording, real-time waveform display, Bluetooth data transmission and audio encoding, and convert sound signals into WAV format for storage.

[0017] (4) The power management circuit can not only provide a stable 3.3V voltage for the entire circuit, but also charge the lithium battery. The circuit of the utility model has better reliability and better effect. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a negative voltage regulator circuit of the utility model;

[0019] Figure 2 The microphone of the utility model is a circuit that is amplified twice;

[0020] Figure 3 It is the STM32 chip and debugging port of the utility model;

[0021] Figure 4 The power management circuit of the utility model;

[0022] Figure 5It is the sound pickup, listening and recording headphone socket circuit of the utility model;

[0023] Figure 6 The memory, Bluetooth module and display screen interface circuit of the utility model;

[0024] Figure 7 It is the work flow chart of the utility model;

[0025] Figure 8 and Fig. 9 All of them are structural explosion diagrams of the utility model;

[0026] Fig.10 It is a cross-sectional structural diagram of the horn-shaped sound receiver of the present utility model.

[0027] In the figure, 1-stethoscope membrane fixing ring, 2-stethoscope membrane, 3-horn-shaped receiver, 4-circuit board, 5-back cover, 31-horn-shaped opening end, 32-sound receiving hole, 33-through hole, 34-annular groove. DETAILED DESCRIPTION

[0028] The utility model is further described in detail below in conjunction with the accompanying drawings.

[0029] It should be noted that, for the sake of convenience, the directions described below are consistent with the directions of the drawings themselves, but do not limit the structure of the present invention.

[0030] like Figures 1 to 7 As shown, the utility model discloses a weak heart and lung sound signal pickup circuit, which collects the sound signal of the heartbeat and converts the sound signal into a stable electrical signal after filtering and amplification. The circuit has a voltage stabilizer, and only three capacitors are needed externally to establish a complete DC-DC charge pump inverter. The sound signal is collected by a microphone and passes through an operational amplifier, and finally output by a data line. The circuit includes a sound signal collection circuit and a two-stage filter amplifier circuit. The output end of the sound signal collection circuit is connected to the first-stage filter amplifier circuit, and the output end of the first-stage filter amplifier circuit is connected to the input end of the second-stage filter amplifier circuit. The output end of the second-stage filter amplifier circuit is filtered by a low-pass filter circuit and used as the output OUT of the pickup circuit, wherein:

[0031] The sound signal acquisition circuit includes a microphone MIC for collecting heart and lung sounds. The microphone MIC converts the collected audio signal of weak heart and lung sounds into an electrical signal. A capacitor C9 for filtering out high-frequency signals in the audio signal collected by the microphone MIC is connected between the positive and negative electrodes of the microphone MIC. The positive electrode of the microphone MIC is connected to the power supply VCC through the pull-up resistor R4, and the electrical signal is coupled to the first-stage filtering and amplifying circuit through the capacitor C8.

[0032] The first-stage filtering and amplifying circuit includes an amplifier U2.2, a capacitor C6, a resistor R5 and a resistor R2. The output end of the sound signal acquisition circuit is connected to the reverse input end of the amplifier U2.2 through the resistor R5. The resistor R2 and the capacitor C6 are connected in parallel to the reverse input end and the output end of the amplifier U2.2.

[0033] The second-stage filter amplifier circuit includes an amplifier U2.1, a capacitor C7, a resistor R6 and a resistor R3. The output end of the first-stage filter amplifier circuit is connected to the reverse input end of the amplifier U2.1 through the resistor R6. The resistor R3 and the capacitor C7 are connected in parallel to the reverse input end and the output end of the amplifier U2.1. The output end of the amplifier U2.1 is grounded through a low-pass filter circuit composed of a resistor R7 and a capacitor C10.

[0034] The utility model also discloses a practical electronic stethoscope circuit, including the above-mentioned weak heart and lung sound pickup circuit, and also includes a signal processing circuit, a power management circuit, an audio conversion circuit and an audio interface circuit. The output OUT of the pickup circuit is connected to the signal input end of the signal processing circuit. The signal processing circuit converts the analog signal of the input pickup circuit into a digital signal that is easy to display and send; the power management circuit realizes battery charge and discharge management and 5V voltage-regulated output, converts the battery voltage or other input voltage into the required negative voltage for use by the amplifier; the audio conversion circuit converts the heart and lung sound signal into a WAV audio format file; the audio interface circuit includes a pickup interface, a headphone interface and a recording interface. The pickup interface is connected to the output OUT of the pickup circuit as the signal input end of the audio interface, and the headphone interface and the recording interface are used to connect the headphone and the recording device respectively for the output end of the audio signal. There are three headphone sockets, namely, pickup, listening and recording. The pickup is used to receive the sound signal collected by the weak heart and lung sound signal pickup circuit. The doctor inserts the 3.5mm headphone cable into the listening headphone socket for auscultation, and the recording headphone socket is used to record the sound information into the doctor's or patient's mobile phone for preservation

[0035] like Figures 8 to 10As shown, the utility model also discloses a practical electronic stethoscope listening head structure, including the above-mentioned practical electronic stethoscope circuit, and also includes a stethoscope membrane 2, a circuit board 4 of a heart and lung sound pickup circuit, and a horn-shaped receiver 3. The stethoscope membrane 2 is connected to one side of the horn-shaped opening end 31 of the horn-shaped receiver 3 through a stethoscope membrane fixing ring 1, and the circuit board 4 is placed on the other side of the horn-shaped receiver 3. The horn-shaped opening end 31 is a conical structure, and a sound receiving hole 32 is provided at the center of the horn-shaped opening end 31. A through hole 33 for placing a microphone is provided on the side away from the horn-shaped opening end 31. The sound receiving hole 32 is connected to the through hole 33, and the aperture of the sound receiving hole 32 is smaller than the aperture of the through hole 33; an annular groove 34 for placing a sealing rubber ring is provided at the edge of the horn-shaped opening end 31. The side of the horn-shaped receiver 3 connected to the circuit board 4 is fixedly connected to the back cover 5, and the back cover 5 is provided with a round hole for the power line and the signal line to pass through. The power line and the ground signal output line are connected to the listening earphone seat on the heart and lung sound analog-to-digital conversion and transmission circuit.

[0036] In the embodiment shown in the accompanying drawings, three external capacitors and a negative voltage regulator TPS60400DBVR are used to establish a complete DC-DC charge pump inverter. On this basis, a filter capacitor is added to improve the system performance, so that the input positive voltage and the converted output negative voltage are used for the operational amplifier. At this time, the sound signal passes through the microphone through the filter capacitor and the coupling decoupling capacitor to reach the operational amplifier, so that the correct signal is amplified and output. The sound signal output by the cardiopulmonary sound signal pickup circuit is connected to the pickup earphone seat and converted to digital through STM32, so that the digital signal of the cardiopulmonary sound signal draws a heart rate image on the display screen, and the digital quantity is sent to the mobile phone end by Bluetooth. The sound signal is directly transmitted to the earphone through the earphone seat. 24C02 stores a small part of the audio data, while VS1053 performs audio encoding and then stores it with a TF card. The power management circuit provides a stable 3.3V voltage for the entire circuit.

[0037] The STM32 chip is used to convert the analog sound signal into a digital signal, and the heart rate waveform is displayed on the display screen. The serial port of the STM32 is used to transmit data via Bluetooth. The VS1053 and TF card are used to implement audio encoding and audio file storage. The FM3209F chip and AMS1117-3.3 chip in the power management circuit provide a stable 3.3V voltage for the entire circuit. A USB interface can be used to charge the lithium battery with the FM3209F and enable the system to work continuously without power failure.

[0038] like Figure 1 As shown, the utility model uses a negative voltage regulator U1, which forms a DC-DC charge pump inverter with capacitors C2, C3 and C5, and uses capacitors C1 and C4 for filtering. The input voltage is 3.3V provided by the battery, and the output negative voltage U2-4 is used Figure 2Negative power supply terminal of operational amplifier U2.2.

[0039] like Figure 2 As shown, VCC3.3V is used to power the microphone MIC and amplifier U2.2. The sound signal is collected by the microphone MIC and filtered by capacitor C9 to filter out the high-frequency signal of the microphone MIC. After coupling through capacitor C8, the weak AC signal of the microphone MIC is coupled as the input signal of the two-pole filter amplifier circuit for amplification. The amplification factor of the first-stage filter amplifier circuit is determined by resistor R5 and resistor R2. The functions of resistor R2 and capacitor C6 are mainly two: (1) It is an advance compensation circuit for the first-stage filter amplifier circuit to prevent the amplifier circuit from generating self-oscillation; (2) It constitutes a low-pass filter circuit to effectively block high-frequency noise signals and only amplify the cardiopulmonary sound signals within the preset low-frequency range. The functions of the corresponding components in the second-stage filter amplifier circuit are the same as those of the first-stage filter amplifier circuit. Capacitor C10 performs filtering to filter out high-frequency interference after the signal is amplified.

[0040] like Figures 3 to 6 As shown, the utility model discloses a cardiopulmonary sound analog-to-digital conversion and transmission circuit.

[0041] This embodiment uses the STM32F103C8T6 chip U3 to realize the AD conversion of the heart and lung sound signal and display the heart rate waveform image on the display screen.

[0042] The power management circuit of this embodiment adopts FM3209F chip U4, AMS1117-3.3 chip U5, lithium battery interface P1, power switch button P2, lithium battery charging port USB1, indicator light LED1 and indicator light LED2 are power indicator lights. When USB1 is connected, indicator light LED1 and indicator light LED2 light up at the same time. If only battery power is supplied, only indicator light LED2 lights up.

[0043] Capacitor C12 should be placed near the FM3209FPin4 pin to prevent the inductor from generating ripples that interfere with the chip; capacitor C14 needs to be placed close to the FM3209F Pin2 pin to prevent the inductor from generating ripples that interfere with the chip; capacitor C18 needs to be placed close to the FM3209F Pin6 and Pin7 pins; capacitors C21 and C22 must be placed close to the FM3209F Pin7 and Pin8 pins; capacitor C23 must be placed close to the FM3209F Pin9 pin; capacitor C15 must be placed close to the FM3209F Pin15 pin.

[0044] FM3209F has a constant current and constant voltage lithium battery charger with a synchronous switching structure. When the battery voltage is less than 3V, 100mA trickle charging is used; when the battery voltage is greater than 3V, constant current charging is entered; when the battery voltage is greater than 4.2V, constant voltage charging is entered. After charging is completed, if the battery voltage is lower than 4.1V, the battery charging is restarted. FM3209F has built-in adaptive power path management. The chip will automatically adjust the charging current according to the VIN voltage and is compatible with all adapters on the market. There is an overvoltage protection circuit inside the chip. When the input voltage is higher than 5.6V, the chip will shut down the charging system to protect the internal circuit from being damaged by high voltage. FM3209F supports charging and discharging at the same time, giving priority to powering external loads.

[0045] Figure 5 As shown, the corresponding interfaces of the utility model for sound pickup, listening and recording, the output OUT of the weak cardiopulmonary sound signal pickup circuit of the utility model is connected to the sound pickup port, the 3.5mm headphone line is connected to the listening port, and the recording port is connected to the mobile phone for recording through a 3.5mm data line with male connectors at both ends.

[0046] The utility model is used to convert audio data into a VS1053 chip in WAV format, and store the WAV audio file in a TF card through the VS1053 chip and STM32.

[0047] 24C02 is used to store a small amount of audio data, the Bluetooth module's interface P4 is used to send digital signals to the mobile phone, and the display interface Screen is used to display the heart rate waveform image to facilitate physician observation and diagnosis.

[0048] It is obvious to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential features of the present invention. Therefore, the embodiments should be regarded as exemplary and non-restrictive from any point of view, and the scope of the present invention is defined by the appended claims rather than the above description, and it is intended that all changes falling within the meaning and scope of the equivalent elements of the claims be included in the present invention. Any reference numeral in a claim should not be regarded as limiting the claim to which it relates.

Claims

1. A circuit for picking up weak heart and lung sound signals, characterized in that: It includes a sound signal collection circuit and a two-stage filter amplifier circuit. The output end of the sound signal collection circuit is connected to the first-stage filter amplifier circuit. The output end of the first-stage filter amplifier circuit is connected to the input end of the second-stage filter amplifier circuit. The output end of the second-stage filter amplifier circuit is filtered by a low-pass filter circuit and used as the output OUT of the pickup circuit. The sound signal acquisition circuit includes a microphone MIC for collecting heart and lung sounds. The microphone MIC converts the collected audio signal of weak heart and lung sounds into an electrical signal. A capacitor C9 for filtering out high-frequency signals in the audio signal collected by the microphone MIC is connected between the positive and negative electrodes of the microphone MIC. The positive electrode of the microphone MIC is connected to a power supply VCC through a pull-up resistor R4, and the electrical signal is coupled to the first-stage filtering and amplifying circuit through a capacitor C8.

2. The weak heart and lung sound signal pickup circuit according to claim 1, characterized in that: The first-stage filtering and amplifying circuit includes an amplifier U2.2, a capacitor C6, a resistor R5 and a resistor R2. The output end of the sound signal acquisition circuit is connected to the reverse input end of the amplifier U2.2 through the resistor R5. The resistor R2 and the capacitor C6 are connected in parallel to the reverse input end and the output end of the amplifier U2.

2.

3. The weak heart and lung sound signal pickup circuit according to claim 1, characterized in that: The second-stage filter amplifier circuit includes an amplifier U2.1, a capacitor C7, a resistor R6 and a resistor R3. The output end of the first-stage filter amplifier circuit is connected to the reverse input end of the amplifier U2.1 through the resistor R6. The resistor R3 and the capacitor C7 are connected in parallel to the reverse input end and the output end of the amplifier U2.

1. The output end of the amplifier U2.1 is grounded through a low-pass filter circuit composed of a resistor R7 and a capacitor C10.

4. A practical electronic stethoscope circuit, comprising the weak heart and lung sound pickup circuit according to any one of claims 1 to 3, characterized in that: It also includes a signal processing circuit, a power management circuit, an audio conversion circuit and an audio interface circuit. The output OUT of the pickup circuit is connected to the signal input end of the signal processing circuit. The signal processing circuit converts the analog signal input to the pickup circuit into a digital signal that is easy to display and send; the power management circuit realizes battery charge and discharge management and 5V regulated output; the audio conversion circuit converts the cardiopulmonary sound signal into a WAV audio format file; the audio interface circuit includes a pickup interface, a headphone interface and a recording interface. The pickup interface is connected to the output OUT of the pickup circuit as the signal input end of the audio interface. The headphone interface and the recording interface are used to connect the output ends of the audio signal to the headphone and the recording device respectively.

5. A practical electronic stethoscope head structure, comprising the practical electronic stethoscope circuit according to claim 4, characterized in that: The invention also comprises an auscultatory membrane (2), a circuit board (4) of a heart and lung sound pickup circuit, and a horn-shaped sound receiver (3). The auscultatory membrane (2) is connected to one side of a horn-shaped opening end (31) of the horn-shaped sound receiver (3) through an auscultatory membrane fixing ring (1). The circuit board (4) is arranged on the other side of the horn-shaped sound receiver (3). The horn-shaped opening end (31) is in a conical structure. A sound receiving hole (32) is arranged at the center of the horn-shaped opening end (31). A through hole (33) for placing a microphone is arranged on a side away from the horn-shaped opening end (31). The sound receiving hole (32) is connected to the through hole (33).

6. The practical electronic stethoscope head structure according to claim 5, characterized in that: The aperture of the sound receiving hole (32) is smaller than the aperture of the through hole (33).

7. The practical electronic stethoscope head structure according to claim 5, characterized in that: An annular groove (34) for accommodating a sealing rubber ring is provided at the edge of the trumpet-shaped opening end (31).

8. The practical electronic stethoscope head structure according to claim 5, characterized in that: One side of the horn-shaped receiver (3) connected to the circuit board (4) is fixedly connected to the back cover (5), and the back cover (5) is provided with a circular hole for the power line and the signal line to pass through.

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