An invasive blood pressure monitor lead-off detection circuit

Abstract

This invention provides a lead detachment detection circuit for an invasive blood pressure monitor. The circuit includes a power supply circuit and a lead detachment detection circuit electrically connected to each other. The power supply circuit acquires the state of the invasive blood pressure monitor leads and converts the state into a detachment voltage signal, which is then transmitted to the lead detachment detection circuit. The lead detachment detection circuit includes an instrument operational amplifier unit and a comparator unit electrically connected in sequence. The instrument operational amplifier unit removes common-mode interference from the detachment voltage signal and then performs differential voltage amplification to obtain a differential amplified voltage signal. The comparator unit compares the differential amplified voltage signal with a detachment reference voltage and outputs a logic level signal. The lead detachment detection circuit for an invasive blood pressure monitor provided by this invention improves the detection range across a wider voltage range and overcomes the shortcomings of existing technologies, such as complex circuitry and high accuracy requirements due to AC coupling.

Description

Technical Field

[0001] The invention relates to the technical field of electronic circuits, and in particular to a lead-off detection circuit for an invasive sphygmomanometer. Background Art

[0002] Blood pressure is one of the essential parameters for monitoring electrophysiological signals of the human body. In critically ill patients such as shock patients, some heart surgeries and other major surgeries, real-time monitoring of blood pressure changes has important clinical value, which requires the use of invasive blood pressure monitoring technology.

[0003] Since the invasive sphygmomanometer belongs to the isolated application part, most power supply solutions use isolated power supply directly or step down the voltage through voltage regulator chip. Conventional invasive sphygmomanometer lead detachment detection is mostly implemented by AC coupling, which is mainly to directly add AC signal to the electrode input end. Since the amplifier circuit of the invasive sphygmomanometer adopts bipolar differential amplification, the added AC signal is common-mode offset at the end of the amplifier, and another bypass is used to amplify and filter the tiny AC signal to determine the current electrode detachment status.

[0004] However, the use of AC coupling to detect the detachment of the electrode of the invasive blood pressure monitor not only adds an AC input excitation circuit at the input end, which increases the burden of filtering processing for the entire amplification trunk; the detachment detection circuit performed by the bypass requires continuous amplification and filtering, which increases the chip cost, and the detection accuracy is easily affected by environmental interference, affecting the judgment effect; furthermore, the isolated power supply has a large ripple, requiring the analog circuit to have a higher power supply rejection ratio, and the use of a voltage regulator chip increases the circuit power consumption.

[0005] Therefore, providing a simple and effective wide voltage electrode detachment detection method to overcome the shortcomings of the prior art such as complex circuits and high precision requirements due to the AC coupling method has become a technical problem that needs to be solved urgently. Summary of the invention

[0006] The embodiment of the present invention provides an invasive blood pressure monitor lead-off detection circuit to solve the shortcomings of the prior art, such as complex circuits in an AC coupling mode and low precision of the lead-off detection circuit.

[0007] An embodiment of the present invention provides a lead-off detection circuit for an invasive blood pressure monitor, comprising: a power supply circuit and a lead-off detection circuit electrically connected to each other, wherein:

[0008] The power supply circuit is used to obtain the state of the lead of the invasive blood pressure monitor, and convert the state into a lead-off voltage signal to be transmitted to the lead-off detection circuit;

[0009] The lead-off detection circuit includes an instrument operational amplifier unit and a comparison unit which are electrically connected in sequence, wherein the instrument operational amplifier unit is used to remove common-mode interference from the lead-off voltage signal and then perform differential voltage amplification processing to obtain a differential amplified voltage signal; the comparison unit is used to compare the differential amplified voltage signal with the lead-off reference voltage and output a logic level signal.

[0010] Further, the power supply circuit includes an electrically connected voltage-stabilizing source unit, an operational amplifier, and an NPN transistor;

[0011] The anode of the voltage-stabilizing source unit is connected to one end of the resistor R5 and is grounded; the cathode of the voltage-stabilizing source unit is connected to the same-direction input pin of the operational amplifier, one end of the resistor R4 and one end of the resistor R2; the reference electrode of the voltage-stabilizing source unit is connected to the other end of the resistor R4 and the other end of the resistor R5, wherein: the reverse input pin of the operational amplifier is connected to the output pin of the operational amplifier and one end of the resistor R3; the fourth pin of the operational amplifier is grounded; the seventh pin of the operational amplifier is connected to the positive electrode of the external DC power supply, one end of the capacitor C1 and the other end of the resistor R2, and the other end of the capacitor C1 is grounded; the emitter of the NPN transistor is connected to the invasive sphygmomanometer lead, the base of the NPN transistor is connected to the other end of the resistor R3, the collector of the NPN transistor is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the positive electrode of the external DC power supply.

[0012] Furthermore, the instrument operational amplifier unit mainly includes a differential amplifier; the second pin and the third pin of the differential amplifier are respectively connected to the emitter and the base of the NPN transistor; the fourth pin of the differential amplifier is connected to one end of the capacitor C2 and the negative electrode of the external DC power supply, and the other end of the capacitor C2 is grounded; the fifth pin of the differential amplifier is grounded; and the sixth pin of the differential amplifier is connected to the comparison unit.

[0013] Further, the first pin of the differential amplifier is connected to one end of the resistor R10, and the other end of the resistor R10 is connected to the eighth pin of the differential amplifier.

[0014] Furthermore, the comparison unit mainly includes a comparator; the first input end of the comparator is connected to the sixth pin of the differential amplifier; the second input end of the comparator is connected to one end of the resistor R7 and one end of the resistor R11, the other end of the resistor R11 is grounded, and the other end of the resistor R7 is connected to the positive pole of the external DC power supply; the output end of the comparator is used to output a logic level signal.

[0015] Furthermore, the lead-off detection circuit also includes an optical coupling unit, which is used to perform photoelectric isolation on the logic level signal and output a detection current signal according to the received logic level signal.

[0016] Furthermore, the optocoupler unit mainly includes an optocoupler; a first input end of the optocoupler is connected to one end of a resistor R6, and the other end of the resistor R6 is connected to the positive electrode of an external DC power supply; a second input end of the optocoupler is connected to one end of a capacitor C4, one end of a resistor R8 and an output end of a comparator, the other end of the capacitor C4 is grounded, and the other end of the resistor R8 is connected to the positive electrode of the external DC power supply; a first output end of the optocoupler and a second output end of the optocoupler are used to output a detection current signal, the first output end of the optocoupler is connected to one end of a resistor R9, and the other end of the resistor R9 is grounded; and a second output end of the optocoupler is connected to an optocoupler drive power supply.

[0017] Furthermore, the invasive sphygmomanometer lead-off detection circuit provided in the embodiment of the present invention further includes an indication unit, which includes a display device and an audible and visual alarm; the indication unit is connected to the first output end of the optocoupler.

[0018] Furthermore, in an embodiment of the present invention, the voltage regulator unit is a precision voltage regulator TL43, the operational amplifier is an LF351 operational amplifier; the NPN transistor is an IBP RF transistor, the differential amplifier is an INA128 amplifier, the comparator is an LM339 comparator, and the optocoupler is a TLP521 coupler.

[0019] Furthermore, in the embodiment of the present invention, the resistance value of resistor R1 is 51Ω / 1W, the resistance value of resistor R2 is 1KΩ, the resistance value of resistor R3 is 1KΩ, the resistance value of resistor R4 is 20KΩ, the resistance value of resistor R5 is 9.1KΩ, the resistance value of resistor R6 is 3.6KΩ, the resistance value of resistor R7 is 5.9KΩ, the resistance value of resistor R8 is 300KΩ, the resistance value of resistor R9 is 10KΩ, the resistance value of resistor R10 is 5.9KΩ, and the resistance value of resistor R11 is 5.9KΩ; the capacitance of capacitor C1, capacitor C2, capacitor C3 and capacitor C4 are all 0.1μF.

[0020] An invasive blood pressure monitor lead-off detection circuit provided in an embodiment of the present invention improves the detection range of a wide voltage by setting up an invasive blood pressure monitor lead-off detection circuit composed of a power supply circuit and a lead-off detection circuit, and overcomes the shortcomings of the prior art such as complex circuits and high precision requirements due to the AC coupling method. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0022] Figure 1 A schematic diagram of a lead-off detection circuit structure of an invasive blood pressure monitor provided by an embodiment of the present invention;

[0023] Figure 2 A schematic diagram of a power supply circuit provided by an embodiment of the present invention;

[0024] Figure 3 A schematic diagram of a lead-off detection circuit for an invasive blood pressure monitor provided by an embodiment of the present invention;

[0025] Figure 4 A schematic diagram of a TL43 precision voltage regulator TL43 provided in an embodiment of the present invention;

[0026] Figure 5 A voltage distribution diagram of a TL43 precision voltage regulator provided in an embodiment of the present invention;

[0027] Figure 6 An internal structure diagram of an LF351 operational amplifier provided in an embodiment of the present invention;

[0028] Figure 7 An internal structure diagram of an INA128 amplifier provided in an embodiment of the present invention;

[0029] Figure 8 An internal structure diagram of an LM339 comparator provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0030] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0031] like Figure 1 As shown, an embodiment of the present invention provides a lead-off detection circuit for an invasive blood pressure monitor, including but not limited to: a power supply circuit and a lead-off detection circuit electrically connected to each other, wherein:

[0032] The power supply circuit is used to obtain the state of the invasive sphygmomanometer lead and convert the state into a lead-off voltage signal for transmission to the lead-off detection circuit; the lead-off detection circuit includes an instrument operational amplifier unit and a comparison unit electrically connected in sequence; the instrument operational amplifier unit is used to remove common-mode interference from the lead-off voltage signal and then perform differential voltage amplification processing to obtain a differential amplified voltage signal; the comparison unit is used to compare the differential amplified voltage signal with the lead-off reference voltage and output a logic level signal.

[0033] Among them, the invasive sphygmomanometer measuring device is used to directly measure the pressure in the blood vessel. Its measuring principle is: first, the measuring catheter is placed in the blood vessel of the measured part by puncture, and the outer end of the catheter is directly connected to the pressure sensor. Since the fluid has a pressure transmission function, the pressure in the blood vessel will be transmitted to the external pressure sensor through the liquid in the catheter, so that the dynamic waveform of the real-time pressure change in the blood vessel can be obtained. Through the corresponding calculation method, the systolic pressure, diastolic pressure and mean arterial pressure of the blood vessel at the measured part can be obtained. The non-invasive blood pressure measurement method is a method of indirectly measuring human blood pressure. The blood pressure measured by various non-invasive blood pressure measurement methods is different from the real blood pressure value of the human body. Since the invasive sphygmomanometer is generally used for continuous, reliable and accurate real-time monitoring of the blood pressure of patients with shock, some heart surgery or other major surgery patients. Therefore, it is necessary to monitor whether the lead of the invasive sphygmomanometer is detached. When the lead is detached, the staff can be reminded in time to handle it.

[0034] An invasive sphygmomanometer lead detachment provided in an embodiment of the present invention is mainly used to connect a pressure sensor of an invasive sphygmomanometer, and converts the pressure change detected by the pressure sensor into a corresponding current change, and then outputs it to a corresponding indication unit, so that the staff can read it directly. Specifically, when the lead of the invasive sphygmomanometer is detached or partially detached, it will cause a change in the varistor in the pressure sensor; and the varistor is connected in series to a set branch of the power supply circuit, so the resistance change of the branch can be converted into a voltage change signal, that is, a detachment voltage signal is generated.

[0035] Furthermore, the power supply circuit is electrically connected to the lead-off detection circuit to transmit the lead-off voltage signal to the lead-off detection circuit. Since normal blood pressure is generally 90-140 mmHg (systolic pressure), and the change in the resistance of the pressure sensor caused by the change in blood pressure is very limited, the resulting lead-off voltage signal is also weak and difficult to be directly read and processed. In an embodiment of the present invention, at least one instrument operational amplifier unit is provided in the lead-off detection circuit to facilitate amplification of the lead-off voltage signal for subsequent circuit processing.

[0036] Furthermore, a comparison unit is provided in the lead-off detection circuit of the invasive sphygmomanometer provided in the present embodiment, which is used to determine whether the voltmeter lead is off according to the differential amplified voltage signal generated after amplification output by the instrument operational amplifier unit. Specifically, the differential amplified voltage signal and the off-state voltage signal can be respectively connected to the two input ends of the comparison unit, and at this time, it can be determined whether the voltmeter lead is off according to the logic level signal output by the comparison unit. The logic level signal can be a high level signal or a low level signal.

[0037] The invasive blood pressure meter lead-off detection circuit provided in the embodiment of the present invention improves the detection range of wide voltage by setting up the invasive blood pressure meter lead-off detection circuit composed of a power supply circuit and a lead-off detection circuit, and overcomes the shortcomings of the prior art such as complex circuits and high precision requirements due to the AC coupling method.

[0038] Based on the content of the above embodiment, as an optional embodiment, Figure 2 As shown, the power supply circuit comprises an electrically connected voltage-stabilizing source unit, an operational amplifier and an NPN transistor, wherein the anode (2) of the voltage-stabilizing source unit is connected to one end of the resistor R5 and is grounded; the cathode (3) of the voltage-stabilizing source unit is connected to the same-direction input pin (3) of the operational amplifier, one end of the resistor R4 and one end of the resistor R2; and the reference electrode (1) of the voltage-stabilizing source unit is connected to the other end of the resistor R4 and the other end of the resistor R5.

[0039] The reverse input pin (2) of the operational amplifier is connected to the output pin (6) of the operational amplifier and one end of the resistor R3; the fourth pin of the operational amplifier is grounded (4); the seventh pin (7) of the operational amplifier is connected to the positive electrode of an external DC power supply (such as +12VS), one end of a capacitor C1 and the other end of the resistor R2, and the other end of the capacitor C1 is grounded.

[0040] The emitter (2) of the NPN transistor is connected to the lead of the invasive blood pressure meter, the base (1) of the NPN transistor is connected to the other end of the resistor R3, the collector (3) of the NPN transistor is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the positive electrode of the external DC power supply.

[0041] Among them, a suitable external DC power supply can be selected according to actual needs, which can be 9V, 12V, 36V, etc., and this embodiment does not make any specific limitation on this. The grounding mentioned here refers to the working grounding.

[0042] In the embodiment of the present invention, there is no specific limitation on the selection of the voltage stabilizing source unit Q2, the operational amplifier U1 and the NPN transistor Q1.

[0043] The emitter of the NPN transistor Q1 is connected to the sensor BP-DR of the invasive blood pressure monitor. The working principle of the power supply circuit provided by the embodiment of the present invention may be that since the sensor BP-DR exhibits resistance characteristics, the magnitude of the resistance changes with the change of pressure.

[0044] When the lead of the invasive blood pressure monitor is not detached, the emitter of the NPN transistor is connected to the invasive blood pressure sensor. At this time, current flows through the NPN transistor, and there is a potential difference between the base and the emitter. Once the lead of the invasive blood pressure monitor is detached, the emitter of the NPN transistor is suspended, no current flows through the NPN transistor, and the base and emitter potentials are equal. At this time, the changes in the base and emitter potentials can be converted into corresponding detachment voltage signals, and the signal is transmitted to the lead detachment detection circuit.

[0045] The power supply circuit provided in the embodiment of the present invention realizes the generation of the dropout voltage signal by setting a reference voltage regulator, an operational amplifier and an NPN transistor, without introducing power frequency interference, and has a simple and stable circuit structure and is less affected by the environment.

[0046] Based on the contents of the above embodiments, Figure 3 As shown, as an optional embodiment, the instrument operational amplifier unit mainly includes a differential amplifier U4; the second pin (2) and the third pin (3) of the differential amplifier U4 are respectively connected to the emitter (2) and the base (3) of the NPN transistor Q1; the fourth pin (4) of the differential amplifier is connected to one end of the capacitor C2 and the negative electrode of the external DC power supply, and the other end of the capacitor C2 is grounded; the fifth pin (5) of the differential amplifier is grounded; and the sixth pin (6) of the differential amplifier is connected to the comparison unit.

[0047] The invasive blood pressure monitor lead-off detection circuit provided in the embodiment of the present invention provides an instrument operational amplifier unit for amplifying the received lead-off voltage signal while effectively removing common-mode interference, and the component can effectively provide a wide voltage detection range.

[0048] Based on the content of the above embodiment, as an optional embodiment, the first pin (1) of the above differential amplifier is connected to one end of the resistor R10, and the other end of the resistor R10 is connected to the eighth pin (8) of the differential amplifier.

[0049] In this embodiment, the resistor 10 can be configured as a sliding resistor, and by adjusting different resistance values, the differential gain of the differential amplifier U4 can be effectively adjusted.

[0050] Based on the contents of the above embodiments, Figure 3 As shown, as an optional embodiment, the comparison unit mainly includes a comparator U3; the first input terminal (4) of the comparator is connected to the sixth pin (6) of the differential amplifier U4; the second input terminal (5) of the comparator U3 is connected to one end of the resistor R7 and one end of the resistor R11, the other end of the resistor R11 is grounded, and the other end of the resistor R7 is connected to the positive electrode of the external DC power supply; the output terminal (2) of the comparator U3 is used to output the logic level signal.

[0051] As another embodiment, the connection relationship between the first input terminal (4) and the second output terminal (5) is interchangeable.

[0052] Furthermore, the dropout reference voltage connected to the second input terminal of the comparator can be set by adjusting the resistances of R7 and R11.

[0053] Since the comparators are all open-drain outputs, a pull-up resistor R8 is added to the output end of the comparator in this embodiment to strengthen the transmitted logic level signal.

[0054] The embodiment of the present invention provides a comparison unit to convert the irregular amplified dropout voltage signal into a logic level signal, which is convenient for intuitive display and reading.

[0055] Based on the contents of the above embodiments, Figure 3 As shown, an invasive blood pressure monitor lead-off detection circuit provided in an embodiment of the present invention also includes an optical coupling unit, which is used to perform photoelectric isolation on the logic level signal and output a detection current signal according to the received logic level signal.

[0056] Since the invasive sphygmomanometer lead-off detection circuit provided in this embodiment is used as a device for monitoring the invasive sphygmomanometer, its external application device part for further processing and analyzing the logic level signal may be connected to the mains, posing a hidden danger to the safety of the monitored person. In order to ensure the safety of the monitored person, effective human-electrical isolation is required. In this embodiment, the logic level signal output by the comparator U3 is connected to the optical coupling unit to achieve photoelectric isolation of the application device part.

[0057] Furthermore, if Figure 3 As shown, the above-mentioned optical coupling unit mainly includes an optical coupler U2; the first input end (1) of the optical coupler U2 is connected to one end of a resistor R6, and the other end of the resistor R6 is connected to the positive electrode of an external DC power supply; the second input end (2) of the optical coupler is connected to one end of a capacitor C4, one end of a resistor R8 and an output end (2) of a comparator U3, the other end of the capacitor C4 is grounded, and the other end of the resistor R8 is connected to the positive electrode of the external DC power supply; the first output end (15) of the optical coupler and the second output end (16) of the optical coupler are used to output a detection current signal, the first output end (15) of the optical coupler is connected to one end of a resistor R9, and the other end of the resistor R9 is grounded; the second output end (16) of the optical coupler is connected to an optical coupler driving power supply.

[0058] Wherein, under the action of the optocoupler, the logic level signal received at its input end is converted into a corresponding detection current signal and outputted via the first output end (15).

[0059] Based on the contents of the above embodiments, Figure 3 As shown, in the invasive blood pressure monitor lead-off detection circuit provided in the embodiment of the present invention, an indication unit is also included, and the indication unit includes a display device and an audible and visual alarm; the indication unit is connected to the first output end of the optocoupler.

[0060] Furthermore, the voltage regulator unit in the above embodiment can be selected as a precision voltage regulator TL43, the operational amplifier can be selected as an LF351 operational amplifier; the NPN transistor can be selected as an IBP RF transistor, the differential amplifier can be selected as an INA128 amplifier, the comparator can be selected as an LM339 comparator, and the optical coupler can be selected as a TLP521 coupler.

[0061] Specifically, Figure 4 A schematic diagram of a TL43 precision voltage regulator TL43 provided in an embodiment of the present invention, wherein the first figure is an external shape structure diagram, including a voltage regulator body and three pins, namely: reference pole R, anode A and cathode K. The middle figure is an electrical component diagram, and the last figure is a pin diagram.

[0062] Figure 5 A voltage distribution diagram of a TL43 precision voltage regulator provided in an embodiment of the present invention; Figure 5 The current flow and voltage distribution in the TL43 precision voltage regulator can be shown in Figure 1, which can be adjusted by setting the size of R1 and R2 and according to the input voltage (input or V KA ) to provide accurate output voltage (V ref ) and output current (I ref ).

[0063] Figure 6 An internal structure diagram of an LF351 operational amplifier provided in an embodiment of the present invention; Figure 6 As shown, the VCC terminal is used to receive the trigger voltage, which can amplify the input voltage (-VEE) and output the voltage VO.

[0064] Figure 7 An internal structure diagram of an INA128 amplifier provided in an embodiment of the present invention; Figure 7 As shown, the magnification G can be obtained by setting R G to set the size.

[0065] Figure 8 An internal structure diagram of an LM339 comparator provided by an embodiment of the present invention is shown in FIG. Figure 8As shown, the comparator provided in this embodiment can be used to compare the voltages of two input terminals (IN+, IN-) to determine whether a corresponding level signal is output at the output terminal (OUT).

[0066] Based on the content of the above embodiment, as an optional embodiment, combined with Figure 1 as well as Figure 2 As shown, the resistance value of resistor R1 is 51Ω / 1W, the resistance value of resistor R2 is 1KΩ, the resistance value of resistor R3 is 1KΩ, the resistance value of resistor R4 is 20KΩ, the resistance value of resistor R5 is 9.1KΩ, the resistance value of resistor R6 is 3.6KΩ, the resistance value of resistor R7 is 5.9KΩ, the resistance value of resistor R8 is 300KΩ, the resistance value of resistor R9 is 10KΩ, the resistance value of resistor R10 is 5.9KΩ, and the resistance value of resistor R11 is 5.9KΩ; the capacitance of capacitors C1, C2, C3 and C4 are all 0.1μF.

[0067] Through the above reasonable selection of all resistors and capacitors, a wide voltage detection range can be achieved while effectively detecting lead shedding, and the reference voltage can be adjusted. In addition, the voltage across the transistor is amplified by the instrument amplifier and compared with the resistance value in the designed voltage divider circuit, which facilitates accurate measurement; at the same time, the op amp components are used to provide a stable power supply voltage, and the transistor components are used to increase the current output capacity of the power supply end, without the introduction of power frequency interference, the circuit structure is simple and stable, and is less affected by the environment.

[0068] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated. Some or all of the modules may be selected according to actual needs to achieve the purpose of the present embodiment. Those of ordinary skill in the art may understand and implement the present invention without creative effort.

[0069] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. An invasive blood pressure monitor lead-off detection circuit, characterized in that: include: A power supply circuit and a lead-off detection circuit electrically connected to each other; The power supply circuit is used to obtain the state of the lead of the invasive blood pressure monitor, and convert the state into a lead-off voltage signal to be transmitted to the lead-off detection circuit; The lead-off detection circuit comprises an instrument operational amplifier unit and a comparison unit electrically connected in sequence; The instrument operational amplifier unit is used to remove common mode interference from the dropout voltage signal and then perform differential voltage amplification processing to obtain a differential amplified voltage signal; The comparison unit is used to output a logic level signal after comparing the differential amplified voltage signal with the shedding reference voltage; The power supply circuit includes an electrically connected voltage-stabilizing source unit, an operational amplifier and an NPN transistor; The anode of the voltage-stabilizing source unit is connected to one end of the resistor R5 and is grounded; the cathode of the voltage-stabilizing source unit is connected to the same-direction input pin of the operational amplifier, one end of the resistor R4 and one end of the resistor R2; the reference electrode of the voltage-stabilizing source unit is connected to the other end of the resistor R4 and the other end of the resistor R5; The reverse input pin of the operational amplifier is connected to the output pin of the operational amplifier and one end of the resistor R3; the fourth pin of the operational amplifier is grounded; the seventh pin of the operational amplifier is connected to the positive electrode of the external DC power supply, one end of the capacitor C1 and the other end of the resistor R2, and the other end of the capacitor C1 is grounded; The emitter of the NPN transistor is connected to the invasive blood pressure monitor lead, the base of the NPN transistor is connected to the other end of the resistor R3, the collector of the NPN transistor is connected to one end of the resistor R1, and the other end of the resistor R1 is connected to the positive electrode of the external DC power supply; The instrument operational amplifier unit includes a differential amplifier; The second pin and the third pin of the differential amplifier are connected to the emitter of the NPN transistor and the base of the NPN transistor respectively; The fourth pin of the differential amplifier is connected to one end of the capacitor C2 and the negative electrode of the external DC power supply, and the other end of the capacitor C2 is grounded; The fifth pin of the differential amplifier is grounded; The sixth pin of the differential amplifier is connected to the comparison unit; The first pin of the differential amplifier is connected to one end of the resistor R10, and the other end of the resistor R10 is connected to the eighth pin of the differential amplifier; The resistor R10 is a sliding rheostat; Another pin of the differential amplifier is connected to one end of the capacitor C3 and the positive electrode of the external DC power supply, and the other end of the capacitor C3 is grounded.

2. The invasive sphygmomanometer lead-off detection circuit according to claim 1, characterized in that: The comparison unit includes a comparator; The first input terminal of the comparator is connected to the sixth pin of the differential amplifier; The second input end of the comparator is connected to one end of the resistor R7 and one end of the resistor R11, the other end of the resistor R11 is grounded, and the other end of the resistor R7 is connected to the positive electrode of the external DC power supply; The output terminal of the comparator is used to output the logic level signal.

3. The invasive sphygmomanometer lead-off detection circuit according to claim 2, characterized in that: The lead-off detection circuit further includes an optical coupling unit, which is used to perform photoelectric isolation on the logic level signal and output a detection current signal according to the logic level signal.

4. The invasive sphygmomanometer lead-off detection circuit according to claim 3, characterized in that: The optical coupling unit includes an optical coupler; The first input end of the optocoupler is connected to one end of the resistor R6, and the other end of the resistor R6 is connected to the positive electrode of the external DC power supply; The second input end of the optocoupler is connected to one end of the capacitor C4, one end of the resistor R8 and the output end of the comparator, the other end of the capacitor C4 is grounded, and the other end of the resistor R8 is connected to the positive electrode of the external DC power supply; The first output end of the optocoupler and the second output end of the optocoupler are used to output the detection current signal, the first output end of the optocoupler is connected to one end of the resistor R9, and the other end of the resistor R9 is grounded; The second output end of the optocoupler is connected to an optocoupler driving power supply.

5. The invasive sphygmomanometer lead-off detection circuit according to claim 4, characterized in that: It also includes an indication unit, which includes a display device and an audible and visual alarm; The indicating unit is connected to the first output terminal of the optocoupler.

6. The invasive sphygmomanometer lead-off detection circuit according to claim 5, characterized in that: The voltage stabilizing source unit is a precision voltage stabilizing source TL43, the operational amplifier is an LF351 operational amplifier; the NPN transistor is an IBP RF transistor, the differential amplifier is an INA128 amplifier, the comparator is an LM339 comparator, and the optical coupler is a TLP521 coupler.

7. The invasive sphygmomanometer lead-off detection circuit according to claim 6, characterized in that: The resistance value of the resistor R1 is 51Ω / 1W, the resistance value of the resistor R2 is 1KΩ, the resistance value of the resistor R3 is 1KΩ, the resistance value of the resistor R4 is 20KΩ, the resistance value of the resistor R5 is 9.1KΩ, the resistance value of the resistor R6 is 3.6KΩ, the resistance value of the resistor R7 is 5.9KΩ, the resistance value of the resistor R8 is 300KΩ, the resistance value of the resistor R9 is 10KΩ, the resistance value of the resistor R10 is 5.9KΩ, and the resistance value of the resistor R11 is 5.9KΩ; the capacitance of the capacitor C1, the capacitor C2, the capacitor C3 and the capacitor C4 are all 0.1μF.

Images