KR100840157B1 - An amplifier apparatus for electro-stethoscope which can be removing frictional noise having great input signal level, efficiently - Google Patents

Abstract

An amplifier device for an electronic stethoscope to efficiently remove friction noise having a large input signal level according to the present invention includes an inverting input terminal to which an input signal is applied via a forward impedance, a non-inverting input terminal connected to a ground power source, and an output terminal. An amplifier, and a limiter provided between an inverting input terminal of the amplifier and an output terminal of the amplifier, wherein the limiter is connected between the input terminal of the limiter and the output terminal of the limiter in parallel with each other in parallel with each other in a reverse direction; And a resistor connected between an input terminal of the limiter and an output terminal of the limiter, wherein the electronic stethoscope amplifier device nonlinearly amplifies the large input signal and linearly amplifies the small input signal. Can be amplified.

Electronic stethoscope

Description

Electronic amplifier device for efficient removal of friction noise with high input signal level {AN AMPLIFIER APPARATUS FOR ELECTRO-STETHOSCOPE

1 is a diagram showing the amplitude of an amplifier input signal and a magnitude of an output signal for auscultation signals and friction noise when using a linear amplifier having a maximum output signal of ± 1.5V and performing 15 times amplification.

2 is a view showing the magnitude of the input signal versus the output signal of the amplifier when the limiter is installed in front of the linear amplifier,

3 is a diagram illustrating an input signal size versus an output signal size of an amplifier in which amplification ratio is changed by adjusting a limiter and a resistance value by a microprocessor;

4 is a circuit diagram of a basic amplifier device equipped with a limiter,

5a, b is a detailed configuration diagram of the limiter,

6 is a diagram illustrating an output signal of an amplifier when the input voltage levels of the friction noise and the acoustic signal are very small;

7 is a diagram showing an output signal of the amplifier when the output voltage level of the friction noise and the acoustic signal is within the saturation region of the amplifier;

8 is a diagram illustrating a signal saturated when the input voltage level of friction noise is large and an output signal of an amplifier according to the present invention;

9 is a configuration diagram of an amplifier device according to the present invention to adjust the feedback impedance and the number of stage limiters,

10 is a detailed configuration diagram of a feedback impedance block;

11 is a detailed block diagram of a block capable of adjusting the number of stages of the limiter.

The present invention provides an electronic stethoscope that electronicizes sound generated in the heart or lungs of the human body, filters and amplifies only the desired stethoscope signal sound, and transmits the signal to a doctor. And amplification is performed linearly at the input signal level of the closed sound, and nonlinear amplification is performed at the friction noise band having a large input signal level, thereby minimizing the friction noise generated at the time of auscultation while amplifying the heart sound and the lung sound to the maximum. The present invention relates to an electronic stethoscope amplifier device for efficiently eliminating friction noise having a large input signal level.

An electronic stethoscope converts sound from the heart (heart) or lungs (pulmonary) into an electrical signal, then amplifies the converted signal, passes a filter that passes only the heart or lungs, and converts it back to sound. It is a device that can provide high performance stethoscope information to doctors by delivering it to doctors.

However, when auscultating, the sound collecting part of the stethoscope touches the human body or clothes, and noise is generated. This is called friction noise. As such, when the sound from the heart or lungs is picked up, a noise is generated while the stethoscope touches a person's body or clothes, and the size of the friction noise is much larger than that of the heart or lung. Such friction noise is mainly received in the same frequency band as the heart sound or the closed sound at the moment when the heart sound or the lung sound is collected.

In general, when noise is input at a different time from the desired signal or at a different frequency than the desired signal, it can be easily removed by time processing or using a filter. However, if noise enters the same frequency band at the same time as the desired signal, a problem arises in removing it. In particular, the friction noise is received at a voltage greater than that of the heart sound or the closed sound. For example, when the heart sound or the closed sound is received at about 200 mV, the friction noise may be received up to about 1.2 V.

Here, the friction noise must be removed to the maximum to provide the doctor with high performance hearing information. In addition, since the friction noise that is not removed is transmitted to the doctor as it is, when the doctor examines using the stethoscope, the user needs to pay attention to the stethoscope more lightly through the friction noise.

In addition, if the amplifier performs 15 times the amplification, the heart sound or the closed sound input with the maximum 200mV voltage can be maximized linearly in the amplifier with the maximum output signal range of 3V, but the friction of the input voltage is 1.2V maximum. An amplifier with a maximum output signal range of 18V is required to linearly amplify noise 15 times without distortion.In order to operate such an amplifier, a lot of power is consumed to increase battery consumption, which requires frequent battery replacement. Increases the inconvenience caused by battery replacement.

In addition, when an amplifier having a maximum output signal of 3V is used and a friction noise having an input voltage of 1.2V is input and 15 times linear amplification is performed, clipping occurs and high frequency components remain in the output signal. By the unpleasant sound is transmitted to the doctor.

That is, as shown in Fig. 1, when the maximum AC output signal without clipping is ± 1.5V, and an AC signal (solid line) of ± 0.1V is input to the amplifier for 15 times amplification, amplification without distortion is performed. On the other hand, when an AC signal (dotted line) having an input voltage of ± 0.6 V is input, clipping occurs to output a high frequency signal.

Therefore, in the present invention, an amplifier designed to linearly amplify a heart sound or a closed sound having a small input signal voltage and a nonlinear amplification at a small amplification ratio of a friction noise having a large input signal voltage is designed.

According to the present invention, a limiter is placed in front of the linear amplifier to non-linearly amplify a signal having a large input signal and linearly amplify a signal having a small input signal, thereby amplifying a small sound from the heart or lung. It is an object of the present invention to provide an amplifier device for an electronic stethoscope for efficiently eliminating friction noise having a large input signal level at which the clipping noise does not occur while amplifying the friction noise having a large input signal to a minimum.

Furthermore, the present invention allows the digital signal processor (DSP; or microprocessor) to continuously analyze the signal at the rear of the amplifier, so that the clipping phenomenon is not solved even with the configuration in which the limiter is installed, or the amplification rate itself is increased by the friction noise. By designing the amplifying stage so that the re-adjustment can be done, the input signal level can be amplified relatively large in the magnitude of the heart sound or the lung sound while minimizing the influence of the friction noise, which has a relatively large magnitude of the input signal compared to the heart sound or the lung sound. An object of the present invention is to provide an amplifier device for an electronic stethoscope to efficiently remove this large friction noise.

Electronic amplifier amplifier device for efficiently removing the friction noise with a large input signal level according to the present invention for achieving the above object is an inverted input terminal, grounded non-inverting input terminal, and output terminal, the input signal is applied via a forward impedance An amplifier having a; And a limiter provided between the inverting input terminal of the amplifier and the output terminal, wherein the limiter includes a first diode and a second diode connected in parallel to each other in parallel between the input terminal of the limiter and the output terminal of the limiter; And a resistor connected between the input terminal of the limiter and the output terminal of the limiter, wherein the electronic stethoscope amplifier device can nonlinearly amplify the large input signal and linearly amplify the small input signal. .

The electronic stethoscope amplifier device for efficiently removing friction noise having a large input signal level includes an amplifier having an inverted input terminal, a grounded non-inverting input terminal, and an output terminal to which an input signal is applied through a forward impedance, and the amplifier. And a limiter provided between the inverting input terminal and the output terminal, wherein the limiter includes a plurality of first diodes each connected in series in a forward direction between an input terminal of the limiter and an output terminal of the limiter; And a plurality of second diodes each connected in series in a reverse direction between the output terminal and the limiter, and resistors connected between an input terminal of each of the plurality of first diodes and an output terminal of the limiter, respectively. An input terminal of each of the plurality of first diodes and each of the plurality of second diodes The output stage are connected to each other, the plurality of first diodes each of the input terminals of each of said plurality of output terminals and the second diode corresponding to is characterized in that connected to each other.

In addition, the amplifier device for an electronic stethoscope according to the present invention is an amplifier having an inverted input terminal, a grounded non-inverting input terminal, and an output terminal to which the input signal is applied via a forward impedance, a feedback provided between the inverting input terminal and the output terminal of the amplifier. An impedance block, a limiter stage regulating block provided between the inverting input terminal of the amplifier and the output terminal, an A / D converter connected to the output terminal of the amplifier, and an output terminal of the A / D converter, and monitoring an output signal of the amplifier If a large input beyond the operating range of the amplifier is received as a result of the monitoring, the saturated output signal is monitored to calculate a value for adjusting the feedback impedance and the number of stages of the limiter, or the previously set value of the feedback impedance and the limiter stage. To control the feedback, the control signals for adjusting the feedback impedance And a digital signal processor configured to output an impedance block and output control signals for controlling the stage of the limiter to the limiter stage adjusting block.

The feedback impedance block includes a plurality of resistors connected in series between the inverting input terminal of the amplifier and the ground power supply; And the plurality of first multiplexers in response to control signals for receiving a plurality of first multiplexer input voltages distributed by each of the plurality of resistors connected in series and for adjusting the feedback impedance output from the digital signal processor. A first multiplexer MUX1 outputs one of the multiplexer input voltages to an output terminal of the amplifier.

The limiter stage adjusting block may include a plurality of first diodes connected in series between an input terminal of the amplifier and the ground power supply; A plurality of second diodes each connected in a reverse direction and in parallel with each first diode corresponding thereto; A plurality of resistors each connected in parallel with each corresponding first diode; And the plurality of second multiplexers input in response to control signals for receiving a plurality of second multiplexer input voltages distributed by each of the plurality of resistors and for adjusting the number of stages of the limiter output from the digital signal processor. And a second multiplexer MUX2 for outputting one of the input voltages to the output terminal of the amplifier.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 and 3 will be described the operation according to the present invention.

2 corresponds to a configuration in which a limiter is provided in front of the amplifier, and the size of the amplifier output signal with respect to the magnitude of the input signal can be changed according to the configuration of the limiter.

In the case of FIG. 2, linear amplification is performed up to a predetermined input signal, and when the magnitude of the input signal exceeds a predetermined value, the amplification ratio of the input signal to the output signal is changed.

FIG. 3 shows the result after the microprocessor (or DSP) compares and analyzes the sound of the rear end of the amplifier when clipping does not continue even when the limiter is placed in front of the amplifier, or when the noise of the friction noise is not reduced. By varying the resistance value at the rear of the amplifier, the effect of the limiter can be achieved while the amplification factor of the amplifier itself is varied.

That is, as shown in FIG. 3, the microprocessor adjusts the amplification factor even for a signal having a low input signal level based on the signal analysis result. In this method, the amplification rate for a certain signal level or more can be adjusted lower than in the method of FIG. 2, so that even if the sound from the heart or lungs is not amplified at a maximum, the friction noise input above a certain signal level is further increased. There is an advantage that can be minimized.

In addition, in the amplification stage design of FIG. 3, the pass frequency band due to filtering may be changed, which may be designed to minimize the change in the frequency band in consideration of this when designing the resistance value in FIG. 11.

Hereinafter, an embodiment of a circuit for performing the operation according to the present invention as described above will be described in detail.

4 shows a circuit diagram of a basic amplifier device 1 according to the present invention with a limiter 2 in which the input signal Vin is connected to the inverting input terminal (-) of the amplifier 3 via a forward impedance Z1. The circuit diagram of the amplifier device 1 according to the present invention is applied, the limiter 2 is provided between the inverting input terminal (-) and the output terminal of the amplifier 3 and the non-inverting input terminal (+) of the amplifier 3 is grounded. to be.

5A and 5B are diagrams showing an example of a detailed configuration of the limiter 2 shown in FIG. 4, respectively.

FIG. 5A shows a configuration corresponding to one limiter 2, in which diodes D11 and D12 are reversed between the input terminal IN of the limiter 2 and the output terminal OUT of the limiter 2. Are connected in parallel with each other, and a resistor R1 is connected in parallel with each of the diodes D11 and D12.

The amplifier performance of the limiterless configuration is expressed as the ratio of the input signal size to the output signal size indicated by solid lines in FIG. 2, and a signal having a small signal size, such as a stethoscope, due to the addition of a limiter circuit as shown in FIG. Amplification is performed linearly without the influence of D11 or D12), but a signal with a large input size, such as friction noise, is passed through a diode (D11 or D12) so that relatively small amplification is performed and clipping after amplification Is prevented. The number of diodes is determined by the magnitude of the auscultation noise and the friction noise.

FIG. 5B illustrates a limiter 2 using a plurality of diodes, the diodes D11, D21,..., Dn1 connected in series between an input terminal IN and an output terminal OUT, and a diode connected in series. Each of D12, D22, ..., Dn2 is connected in parallel in opposite directions to each other, and resistors R1, R2, ..., Rn each of the diodes D11, D21, ..., Dn1. , D12, D22, ..., Dn2) are connected in parallel.

If the limiter circuit 2 is configured using a plurality of diodes as shown in FIG. 5B, as the number of diodes increases, the effect of lowering the amplification factor for a signal of a higher level than in FIG. 2 can be obtained. .

Hereinafter, the case where there is a limiter and the case where there is no limiter will be described based on experiments.

The operation of the general amplifier without the limiter structure will be described with reference to FIG.

In Fig. 6, the signal input near 0V is a friction noise and a stethoscope signal input to the microphone. As shown in FIG. 6, even if the input voltage of the friction noise or the stethoscope signal is small and amplified by the amplifier, the signal does not become saturated but is amplified and output cleanly.

Fig. 7 shows a stethoscope signal and friction noise at the amplifier input and a stethoscope signal and friction noise at the amplifier output when the signal level input to the microphone is increased.

In FIG. 7, a line including a square is a stethoscope signal, a line including a triangle is friction noise, and two signals at the bottom represent an input signal of an amplifier and two signals represent an output signal of an amplifier, respectively.

The reason why the output signal of the amplifier exists around 1.5V is because the allowable range of the amplifier used in the experiment for the present invention is 0 to 3V.

As shown in FIG. 7, when the voltage of the amplifier output signal is within 3V, the output of the amplifier is amplified and output without being saturated.

However, when friction noise with a large input signal voltage is input as shown in FIG. 8, the signal indicated by triangles and solid lines in FIG. 8 is an output signal of the amplifier when a linear amplifier is used, and this signal is the allowable voltage of the amplifier. Since it is higher than the saturation phenomenon can be seen. In addition, when the signal changes to a square wave due to this saturation state, the high frequency component increases, so when the doctor listens to the stethoscope by ear, an unpleasant noise is heard together.

However, when the limiter 2 is placed in front of the amplifier as shown in Fig. 4, the original waveform is output without large distortion, such as the signal component indicated by the square and solid line of Fig. 8, resulting in unpleasant noise due to the high frequency signal component. It can be seen that this is removed.

9 shows a configuration in which the number of stages of the limiter and the feedback impedance of the amplifier can be adjusted, and configured to control the feedback impedance in the feedback impedance block Z2, and the stage of the limiter in the limiter stage adjustment block Z3. It is configured to be. The feedback impedance block Z2 and the limiter stage adjusting block Z3 are connected in parallel with the amplifier 3 between the inverting input terminal and the output terminal of the amplifier 3 as in FIG.

Therefore, in this configuration, the output of desired amplification is possible according to the magnitude of the input signal. That is, the output signal Vout of the amplifier 3 is input using the A / D converter 4 (or codec) and is input by the digital signal processor 5 (DSP) (or microprocessor). The output signal Vout of the input amplifier 3 is continuously monitored.

As a result of the monitoring, when a large input beyond the operating range of the amplifier 3 is received, the digital signal processor 5 (or DSP) monitors the saturated output signal to adjust the feedback impedance and the number of stages of the limiter. You can calculate the value or adjust the feedback impedance and the number of stages of the limiter to a value already set.

At this time, the digital signal processor 5 (or DSP) (or microprocessor) outputs control signals (Z2 Control n-1, ..., Z2 Control 0) to adjust the feedback impedance, and sets the number of stage limiters. The control signals (Z3 Control n-1, ..., Z3 Control 0) are outputted for adjustment. As a result, the performance as shown in FIG. 3 can be obtained using the circuit of FIG.

10 and 11 show the detailed configurations of the feedback impedance block Z2 and the limiter stage regulating block Z3, respectively.

Referring to the configuration of the feedback impedance block Z2 illustrated in FIG. 10, n control signals Z2 Control n-1,..., Z2 output from the digital signal processor 5 (or DSP) (or a microprocessor) may be described. It consists of a multiplexer (MUX1) that can receive one of 2 ⁿ outputs by receiving Control 0) and 2 ⁿ array resistors (R (2 ⁿ -1), ..., R0).

In addition, as shown in FIG. 10, the block Z3 to adjust the number of stages of the limiter shown in FIG. 11 also has n control signals Z3 Control n outputted from the digital signal processor 5 (or DSP) (or a microprocessor). -1, ..., Z3 Control 0) is composed of a multiplexer (MUX2) that can select one of 2 ⁿ outputs by the output, and the multiple configuration limiter circuit shown in Figure 5b.

Accordingly, the output signal of the amplifier input from the digital signal processor (DSP) (or microprocessor) is analyzed to control the feedback impedance and the number of diodes in the limiter, whereby the amplification degree of the amplifier due to the magnitude of the input signal is Is determined.

As described above, according to the present invention, by using an amplifier composed of a feedback circuit of an amplifier and a limiter circuit composed of a diode and a resistor, a stethoscope such as a heart sound or a lung sound of a human body is used in the use of an electronic stethoscope than a desired stethoscope sound. In addition, a large level of friction when rubbed on the skin is amplified as it is, which effectively removes signal components that may cause discomfort and discomfort to the ear of a medical doctor using a stethoscope.

In addition, it is possible to provide a high-quality stethoscope sound without the hassle of designing a material or a material that is resistant to friction noise.

Claims (4)

An amplifier including an inverting input terminal, a grounded non-inverting input terminal, and an output terminal to which an input signal is applied through a forward impedance; And A limiter disposed between the inverting input terminal of the amplifier and the output terminal of the amplifier, The limiter is, A first diode connected between the inverting input terminal of the amplifier and the output terminal of the amplifier; A second diode connected between an inverting input terminal of the amplifier and an output terminal of the amplifier and connected in a reverse direction to the first diode; And A resistor connected between the inverting input terminal of the amplifier and the output terminal of the amplifier, The electronic stethoscope amplifier device can efficiently amplify the large input signal nonlinearly and linearly amplify the small input signal. Amplifier device for electronic stethoscope. An electronic stethoscope amplifier device for efficiently removing friction noise having a large input signal level, An amplifier having an inverting input stage, a grounded non-inverting input stage, and an output stage to which the input signal is applied via a forward impedance; And And a limiter provided between the inverting input terminal of the amplifier and the output terminal of the amplifier, The limiter is, A plurality of first diodes each connected in series in a forward direction between an input terminal of the limiter and an output terminal of the limiter; A plurality of second diodes each connected in series in a reverse direction between an input terminal of the limiter and an output terminal of the limiter; And Resistors connected between an input terminal of each of the plurality of first diodes and an output terminal of the limiter, An output terminal of each of the plurality of second diodes corresponding to an input terminal of each of the plurality of first diodes is connected to each other, and each of the plurality of second diodes corresponding to an output terminal of each of the plurality of first diodes is connected. And an input stage is connected to each other, and an amplifier device for an electronic stethoscope to efficiently remove friction noise having a large input signal level. An amplifier including an inverting input terminal to which an input signal is applied via a forward impedance, a non-inverting input terminal connected to a ground power source, and an output terminal; A feedback impedance block disposed between the inverting input terminal of the amplifier and the output terminal of the amplifier; A limiter stage adjusting block disposed between the inverting input terminal of the amplifier and the output terminal of the amplifier; An A / D converter connected to the output of the amplifier; And Connected to the output terminal of the A / D converter and monitoring the output signal of the amplifier, and when a large input beyond the operating range of the amplifier is received, the saturated output signal is monitored to adjust the feedback impedance and the number of stages of the limiter. A control signal for outputting control signals for adjusting the feedback impedance to the feedback impedance block and for adjusting the number of stages of the limiter to calculate a value or to adjust the feedback impedance and the stage of the limiter to a value already set. And a digital signal processor for outputting them to the limiter stage adjusting block. The method of claim 3, wherein the feedback impedance block, A plurality of resistors connected in series between the inverting input terminal of the amplifier and the ground power supply; And The plurality of first multiplexers in response to control signals for receiving a plurality of first multiplexer input voltages distributed by each of the plurality of resistors connected in series and for adjusting the feedback impedance output from the digital signal processor. A first multiplexer configured to output one input voltage selected from among input voltages to an output terminal of the amplifier, The limiter stage adjustment block, A plurality of first diodes connected in series between an input terminal of the amplifier and the ground power source; A plurality of second diodes each connected in a reverse direction and in parallel with each first diode corresponding thereto; A plurality of resistors each connected in parallel with each corresponding first diode; And The plurality of second multiplexers input in response to control signals for receiving a plurality of second multiplexer input voltages distributed by each of the plurality of resistors and for adjusting the number of stages of the limiter output from the digital signal processor. And a second multiplexer for outputting one input voltage selected from among input voltages to an output terminal of the amplifier. The amplifier apparatus for an electronic stethoscope for efficiently removing friction noise having a large input signal level.

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