CN219223623U

CN219223623U - High-frequency electrotome negative plate contact area detection circuit

Info

Publication number: CN219223623U
Application number: CN202223361075.1U
Authority: CN
Inventors: 徐辉; 崔瑞; 毛海军; 曾凡宇; 王娟
Original assignee: Jiangxi Yuansai Medical Technology Co ltd
Current assignee: Jiangxi Yuansai Medical Technology Co ltd
Priority date: 2022-12-14
Filing date: 2022-12-14
Publication date: 2023-06-20
Anticipated expiration: 2032-12-14

Abstract

The utility model discloses a detection circuit for the contact area of a negative plate of a high-frequency electrotome, which comprises a Wheatstone bridge, a voltage acquisition circuit, a pre-signal processing circuit, a first isolation circuit, an operational amplification circuit, a controller and a follower circuit, wherein the Wheatstone bridge is connected with the voltage acquisition circuit; the input ends of the Wheatstone bridge are respectively and electrically connected with the split double-piece negative plate of the high-frequency electric knife; the output end of the Wheatstone bridge is electrically connected with the input end of the voltage acquisition circuit; the output end of the voltage acquisition circuit is electrically connected with the input end of the preposed signal processing circuit; the output end of the preamble signal processing circuit is electrically connected with the input end of the first isolation circuit; the output end of the first isolation circuit is electrically connected with the input end of the operational amplifier circuit; the output end of the operational amplifier circuit is electrically connected with the input end of the controller through the follower circuit. The utility model can accurately detect the contact area between the high-frequency electrotome negative plate and human tissues.

Description

High-frequency electrotome negative plate contact area detection circuit

Technical Field

The utility model relates to the technical field of medical equipment, in particular to a circuit for detecting the contact area of a negative plate of a high-frequency electrotome.

Background

The high-frequency electrotome is mainly divided into a monopole mode and a bipolar mode in clinical application; the circuit in the monopole mode mainly consists of a high-frequency generator, an electrode, a connecting wire, a negative plate and the like in an electrotome, and the negative plate is divided into a single-piece negative plate and a split negative plate. The high-frequency electric knife is an electrosurgical instrument, and compared with a traditional mechanical surgical knife, the high-frequency electric knife utilizes the electrode tip to generate high-frequency voltage and current, and after the high-frequency electric knife is contacted with a patient body, the high-frequency electric knife heats body tissues, so that the cutting and separation of the tissues are finished, coagulation of a cutting part is realized, and the surgical steps of tissue cutting, postoperative hemostasis and the like are finished. The negative plate is used as an important component of the high-frequency electrotome, is safe to use, can effectively ensure the treatment effect of the operation, can also ensure the safety of the operation, and avoids burning the patient. The disposable negative plate can only play a role of reducing current density by current diversion if stuck completely, and poor adhesion caused by any reason can cause burn of patients. The contact area between the negative plate and human tissues is monitored, and important guarantee is provided for the superiority of the high-frequency electrotome operation. The high-frequency electric knife is high-power high-frequency electric equipment, so that the requirement on the use safety is very strict, if problems occur in the operation, different degrees of burns can be caused to patients, even various potential risks, life hazards and the like can be caused, the safety application of the high-frequency electric knife in the operation is ensured, and the method has practical value in monitoring the contact area of the negative plate and the human body.

At present, in the application of the high-frequency electrotome, the contact area of the negative plate and human tissues is ensured to be as large as possible, and the adhesive type electrotome is selected to be used as much as possible so as to reduce the influence of return current on a machine body. The purpose of the neutral electrode (i.e. negative plate) safety management (Resistance Emergency Management, REM) is to avoid deleterious physical effects of equipment or artificially induced neutral electrode failure causing patient burns and the like. The detection specification prescribes that the alarm is given when the resistance value is larger than R_th-H. The detection item can be connected with an adjustable resistor box for testing. According to the international IEC standard related regulation, REM alarm is a range, and the resistance range is R_min-R_max. The smaller the interval is, the higher the safety coefficient of the detected equipment system is; conversely, the lower the requirement for the material of the corresponding negative plate and the adhesion level of the nursing staff is more strict. The IEC international standard requires that the alarm lower limit value is between R_th-L and R_min, and the alarm maximum value is between R_max and R_th. In actual detection, the measured value is between R_min and R_max, so that the normal operation can be ensured.

Based on the above-mentioned current situation, how to design a device for detecting the contact area between the negative plate of the high-frequency electrotome and human tissues (such as skin) is a problem to be solved.

Disclosure of Invention

The utility model provides a circuit for detecting the contact area of a high-frequency electrotome negative plate, which can accurately detect the contact area of the high-frequency electrotome negative plate and human tissues in order to solve the problem that the prior art cannot accurately detect the contact area of the high-frequency electrotome negative plate and the human tissues.

In order to achieve the above purpose of the present utility model, the following technical scheme is adopted:

the circuit comprises a Wheatstone bridge for converting the contact area of human tissue and a negative plate into a corresponding contact resistance size relation, a voltage acquisition circuit for acquiring a first voltage signal output by the Wheatstone bridge, a pre-signal processing circuit for receiving and processing the first voltage signal and outputting a second voltage signal, a first isolation circuit for receiving and processing the second voltage signal and outputting a third voltage signal, an operational amplification circuit for receiving and amplifying the third voltage signal and outputting a fourth voltage signal, a follower circuit for receiving and processing the fourth voltage signal and outputting a fifth voltage signal, and a controller for receiving the fifth voltage signal and identifying the contact area size according to the fifth voltage signal;

The input ends of the Wheatstone bridge are respectively and electrically connected with the split double-piece negative plate of the high-frequency electric knife; the output end of the Wheatstone bridge is electrically connected with the input end of the voltage acquisition circuit;

the output end of the voltage acquisition circuit is electrically connected with the input end of the preposed signal processing circuit;

the output end of the preamble signal processing circuit is electrically connected with the input end of the first isolation circuit;

the output end of the first isolation circuit is electrically connected with the input end of the operational amplifier circuit;

the output end of the operational amplifier circuit is electrically connected with the input end of the controller through the follower circuit.

Preferably, the voltage acquisition circuit comprises a resistor R3, a sampling resistor RS and a resistor R4;

one end of the resistor R3 is used as a first input end and is electrically connected with a first output end of the Wheatstone bridge and used for receiving a positive signal of a first voltage signal output by the Wheatstone bridge;

the other end of the resistor R3 is electrically connected with one end of the resistor R4 through a sampling resistor RS;

the other end of the resistor R4 is used as a second input end and is electrically connected with a second output end of the Wheatstone bridge and used for receiving a negative signal of the first voltage signal output by the Wheatstone bridge;

One end of the resistor R3, which is commonly connected with the sampling resistor RS, is used as a first output end of the voltage acquisition circuit, is used for outputting a positive signal of a first voltage signal output by the Wheatstone bridge, and is electrically connected with a first input end of the level shifting circuit;

one end of the sampling resistor RS, which is commonly connected with the resistor R4, is used as a second output end of the voltage acquisition circuit and is used for outputting a negative signal of a first voltage signal output by the Wheatstone bridge and is grounded.

Preferably, the pre-signal processing circuit comprises a reference voltage source circuit for providing a constant reference voltage and a level shifting circuit for processing the first voltage signal acquired by the voltage acquisition circuit and outputting a second voltage signal;

the first input end of the level shifting circuit is electrically connected with the first output end of the voltage acquisition circuit and is used for receiving a positive signal of a first voltage signal output by the voltage acquisition circuit;

the input end of the reference voltage source circuit is used for externally connecting a power supply VCC;

the second input end of the level shifting circuit is electrically connected with the output end of the reference voltage source circuit and is used for receiving constant reference voltage output by the reference voltage source circuit;

The output end of the level shifting circuit is electrically connected with the input end of the first isolation circuit and is used for outputting a second voltage signal.

Further, the reference voltage source circuit comprises a resistor R11, a voltage stabilizing chip U2, a resistor R6 and a resistor R5;

one end of the resistor R11 is used as an input end of the reference voltage source circuit and is used for externally connecting a power supply VCC;

the other end of the resistor R11 is respectively and electrically connected with the 3 pin of the voltage stabilizing chip U2 and one end of the resistor R5;

the pin 2 of the voltage stabilizing chip U2 is electrically connected with one end of the resistor R6; one end of the pin 2 of the voltage stabilizing chip U2, which is commonly connected with the resistor R6, is grounded;

the pin 1 of the voltage stabilizing chip U2 is respectively and electrically connected with the other end of the resistor R6 and the other end of the resistor R5;

one end of the resistor R5 is used as an output end of the reference voltage source circuit, is used for outputting constant reference voltage, and is electrically connected with a second input end of the level shifting circuit.

Further, the level shifting circuit comprises a differential amplifier sub-circuit and a voltage follower sub-circuit;

the first input end of the differential amplifying sub-circuit is electrically connected with the first output end of the voltage acquisition circuit and is used for receiving a positive signal of a first voltage signal;

The second input end of the differential amplifying sub-circuit is electrically connected with the output end of the reference voltage source circuit and is used for receiving constant reference voltage;

the output end of the differential amplifying sub-circuit is electrically connected with the input end of the voltage follower sub-circuit;

the output end of the voltage follower sub-circuit is electrically connected with the input end of the first isolation circuit and is used for outputting a second voltage.

Still further, the differential amplifying sub-circuit includes a resistor R9, a resistor R7, a resistor R10, a resistor R8, a first operational amplifier U1A, and a capacitor C5;

one end of the resistor R9 is used as a first input end of the level shifting circuit, is electrically connected with a first output end of the voltage acquisition circuit and is used for receiving a positive signal of a first voltage signal;

the other end of the resistor R9 is electrically connected with the inverting input end of the first operational amplifier U1A;

one end of the resistor R7 is used as a second input end of the level shifting circuit, is electrically connected with the output end of the reference voltage source circuit and is used for receiving constant reference voltage;

the other end of the resistor R7 is electrically connected with the non-inverting input end of the first operational amplifier U1A;

one end of the resistor R10 is connected between the resistor R9 and the inverting input end of the first operational amplifier U1A;

The other end of the resistor R10 is electrically connected with the output end of the first operational amplifier U1A;

the positive power supply of the first operational amplifier U1A is connected with a power supply VCC; while being grounded through a capacitor C5.

Still further, the voltage follower sub-circuit includes a second operational amplifier U1B, a resistor R12;

the non-inverting input end of the second operational amplifier U1B is electrically connected with the output end of the first operational amplifier U1A;

one end of the resistor R12 is electrically connected with the inverting input end of the second operational amplifier U1B;

the other end of the resistor R12 is electrically connected with the output end of the second operational amplifier U1B;

the output end of the second operational amplifier U1B is used as the output end of the level shifting circuit, is used for outputting a second voltage signal and is electrically connected with the input end of the first isolation circuit.

Preferably, the first isolation circuit includes a two-channel nonlinear optocoupler OP, a third operational amplifier U1C, a fourth operational amplifier U3A, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a capacitor C6, and a capacitor C7;

the inverting input end of the third operational amplifier U1C is used as the input end of the first isolation circuit and is electrically connected with the output end of the level shifting circuit and used for receiving the second voltage signal;

The non-inverting input end of the third operational amplifier U1C is respectively and electrically connected with one end of the resistor R14, one end of the capacitor C6 and the 5 pins of the two-channel nonlinear optocoupler OP;

one end of the resistor R13 is electrically connected with the inverting input end of the third operational amplifier U1C;

the other end of the resistor R13 and the other end of the resistor R14 are grounded;

the output end of the third operational amplifier U1C is electrically connected with the 4 pin of the double-channel nonlinear optical coupler OP through a resistor R15;

the other end of the capacitor C6 is connected between the output end of the third operational amplifier U1C and the resistor R15;

the 2 pins and the 3 pins of the two-channel nonlinear optical coupler OP are connected with each other; the 1 pin of the two-channel nonlinear optical coupler OP is connected with a power supply VCC;

the 8 pins of the two-channel nonlinear optical coupler OP are connected with a power supply VDD;

the 7 pin of the two-channel nonlinear optical coupler OP is electrically connected with the non-inverting input end of the fourth operational amplifier;

the 6 pins of the two-channel nonlinear optical coupler OP are connected with a power supply VCC;

one end of the resistor R16 is connected between the 7 pin of the two-channel nonlinear optical coupler OP and the non-inverting input end of the fourth operational amplifier U3A;

the positive power supply of the fourth operational amplifier U3A is connected with the power supply VDD and grounded through a capacitor C7;

The inverting input end of the fourth operational amplifier U3A is connected with the output end of the fourth operational amplifier U3A;

the output end of the fourth operational amplifier U3A is used as the output end of the first isolation circuit, is electrically connected with the input end of the operational amplifier circuit and is used for outputting a third voltage signal.

Preferably, the operational amplifier circuit includes a fifth operational amplifier U3C, a resistor R18, a resistor R19, and a resistor R17;

one end of the resistor R19 is used as an input end of the operational amplifier circuit, is electrically connected with an output end of the first isolation circuit and is used for receiving a third voltage signal;

the non-inverting input end of the fifth operational amplifier U3C is electrically connected with the other end of the resistor R19;

the inverting input end of the fifth operational amplifier U3C is respectively and electrically connected with one end of the resistor R18 and one end of the resistor R17;

the other end of the resistor R18 is grounded;

the other end of the resistor R17 is connected with the output end of the fifth operational amplifier U3C;

the output end of the fifth operational amplifier U3C is used as the output end of the operational amplifying circuit and is used for outputting a fourth voltage signal.

Preferably, the follower circuit comprises a sixth operational amplifier U3B and a resistor R20;

The non-inverting input end of the sixth operational amplifier U3B is used as the input end of the follower circuit, is electrically connected with the output end of the operational amplifier circuit and is used for receiving a fourth voltage signal;

the inverting input end of the sixth operational amplifier U3B is electrically connected with the output end of the sixth operational amplifier U3B through a resistor R20;

the output end of the sixth operational amplifier U3B is used as the output end of the follower circuit, is electrically connected with the input end of the controller and is used for outputting a fifth voltage signal.

The beneficial effects of the utility model are as follows:

according to the utility model, the contact area between the human tissue and the negative plate is converted into the corresponding contact resistance according to the Wheatstone bridge, so that the contact area between the human tissue and the negative plate is indirectly judged through the first voltage signal output by the Wheatstone bridge, the first voltage signal is acquired through the voltage acquisition circuit, and the first voltage signal is sequentially processed through the preposed signal processing circuit, the first isolation circuit, the operational amplification circuit and the follower circuit, and then a fifth voltage signal is output to the controller to identify the contact area, so that the contact area between the human tissue and the negative plate is monitored in real time.

The utility model enables the controller to monitor the contact area of the negative plate in real time, thereby ensuring the safety of patients during operation in time by adjusting the energy output condition of the output plate. During operation, the contact area between human tissue and the negative plate is easily interfered by external factors, and has a very important factor for operation safety, so that the high-frequency electrotome has a function of detecting the contact area of the negative plate.

Drawings

Fig. 1 is a schematic block diagram of a detecting circuit for the contact area of a negative plate of a high-frequency electrotome according to the utility model.

Fig. 2 is a basic circuit diagram of the high-frequency electric knife.

Fig. 3 is a circuit diagram of a wheatstone bridge according to the present utility model.

Fig. 4 is a schematic illustration of the connection of human tissue to a split negative plate.

Fig. 5 is a circuit diagram of a voltage acquisition circuit according to the present utility model.

Fig. 6 is a circuit diagram of a reference voltage source circuit according to the present utility model.

Fig. 7 is a circuit diagram of a level shifting circuit according to the present utility model.

Fig. 8 is a circuit diagram of a first isolation circuit according to the present utility model.

Fig. 9 is a circuit diagram of an operational amplifier circuit according to the present utility model.

Fig. 10 is a circuit diagram of a follower circuit according to the present utility model.

Detailed Description

The utility model is described in detail below with reference to the drawings and the detailed description.

Example 1

As shown in fig. 1, the circuit comprises a wheatstone bridge for converting the contact area between human tissue and a negative plate into a corresponding contact resistance, a voltage acquisition circuit for acquiring a first voltage signal output by the wheatstone bridge, a pre-signal processing circuit for receiving and processing the first voltage signal and outputting a second voltage signal, a first isolation circuit for receiving and processing the second voltage signal and outputting a third voltage signal, an operational amplification circuit for receiving and amplifying the third voltage signal and outputting a fourth voltage signal, a follower circuit for receiving and processing the fourth voltage signal and outputting a fifth voltage signal, and a controller for receiving the fifth voltage signal and identifying the contact area according to the fifth voltage signal;

In this embodiment, the first voltage signal is a voltage difference between the first output end and the second output end of the wheatstone bridge, and the voltage values of the second voltage signal, the third voltage signal, the fourth voltage signal and the fifth voltage signal are all the same.

In this embodiment, the basic circuit of the high-frequency electric knife is shown in fig. 2, and the basic circuit includes an output board, a first optocoupler isolation circuit, a first isolation power supply, a second isolation power supply, and a main power supply, and the specific connection relationship is shown in fig. 2. The basic circuit of the high-frequency electric knife is prior art, and the present embodiment does not improve it, so a detailed description will not be given here. The high-frequency electrotome of this embodiment is configured as a split double-piece negative plate.

As shown in fig. 3 and 4, the wheatstone bridge includes a capacitor C1, a capacitor C2, a resistor R1 and a resistor R2, and the connection relationship is shown in fig. 3.

Because the high-frequency electrotome is provided with the split double-piece negative plate, in the monopolar mode, the energy output of the pencil is divided into two parallel paths through human tissues, namely a path 1 and a path 2, wherein the path 1 is a left single-piece negative plate, and the path 2 is a right single-piece negative plate. The wheatstone bridge of the present embodiment is shown in fig. 3, wherein the capacitance value c1=c2; path 1 corresponds to resistor R1 and path 2 corresponds to resistor R2; the resistor R1 and the resistor R2 are resistors formed by the positive electrode E+ of the knife pen energy output end after flowing through two single-piece negative plates of the negative plate separated by human tissues and summarizing the negative electrode E-of the knife pen energy output end. The resistor R1 is composed of three parts, namely human tissue resistor, resistor of the single negative plate (left single plate) and contact resistor between human tissue and the single negative plate (left single plate), wherein the resistor of the single negative plate (left single plate) is negligible and is zero. The resistor R2 is composed of three parts, namely human tissue resistor, resistor of the single negative plate (right single plate) and contact resistor between human tissue and the single negative plate (right single plate), wherein the resistor of the single negative plate (right single plate) is negligible and is zero. The energy emitted by the output plate is transmitted to network marks E+ and E-of the Wheatstone bridge, if the resistance value difference between the resistor R1 and the resistor R2 is larger, the larger the voltage difference of the output first voltage signal of the Wheatstone bridge is, namely, the larger the absolute value of Vi= ((Vi+) - (Vi-)) is, the human tissue resistances of the path 1 and the path 2 paths are basically equal, and the difference value R1-R2 of the resistors is the difference value of contact resistances between human tissue and two single-piece negative plates. Therefore, the absolute value of vi= ((vi+) - (Vi-)) can reflect the relationship between the contact area of the human tissue and the negative plate, and the larger the contact area is, the smaller the contact resistance is, and the smaller the absolute value of the difference vi= ((vi+) - (Vi-)). And (5) carrying out similar analysis: the smaller the contact area between the human tissue and the negative plate is, the larger the contact resistance is, and the larger the absolute value of the difference vi= ((vi+) - (Vi-)).

In this embodiment, the voltage difference of the first voltage signal output by the wheatstone bridge is an ac voltage value, and the difference between vi+ and Vi "is positive or negative, i.e., vrs+ represents the positive signal of the first voltage signal output, and VRS" represents the negative signal of the first voltage signal output.

In this embodiment, two capacitors are used as two bridge arms of the wheatstone bridge to match the human body resistor to form a signal acquisition mode of the bridge, and in another specific embodiment, inductors may be used for the two bridge arms of the wheatstone bridge instead of the capacitors.

The working principle of this embodiment is as follows: according to the Wheatstone bridge, the contact area of the human tissue and the negative plate is converted into the corresponding contact resistance, the smaller the voltage difference is, the smaller the contact resistance is, and the larger the contact area is, so that the contact area of the human tissue and the negative plate can be indirectly judged through the absolute value of the voltage difference output by the Wheatstone bridge. The voltage acquisition circuit is used for acquiring a first voltage signal output by the Wheatstone bridge, namely a voltage difference, the prepositive processing circuit is used for carrying out prepositive processing on the first voltage signal acquired by the voltage acquisition circuit, the first isolation circuit is used for carrying out isolation protection processing on the second voltage signal, the operational amplification circuit is used for carrying out operational amplification processing on the third voltage signal, the following circuit is used for carrying out signal isolation processing on the fourth voltage signal, transmitting voltage in the forward direction and the like, and then outputting a fifth voltage signal to the controller for processing, and the contact area size is identified according to the fifth voltage signal, so that the contact area size of human tissues and a negative plate is monitored in real time. The follower circuit plays an isolating role and transmits voltage in the forward direction, but the input part is isolated from the output part and cannot affect each other.

Example 2

Based on the detection circuit of the contact area of the negative plate of the high-frequency electrotome in the embodiment 1, more specifically, the embodiment provides a specific circuit of the voltage acquisition circuit, as shown in fig. 5, the voltage acquisition circuit comprises a resistor R3, a sampling resistor RS and a resistor R4;

one end of the resistor R3 is used as a first input end and is electrically connected with a first output end of the Wheatstone bridge; a positive signal for receiving a first voltage signal output by the wheatstone bridge;

In this embodiment, the voltage vi= ((vi+) - (Vi-)) generated by the wheatstone bridge is serially divided to obtain the voltage difference vrs= ((vrs+) - (VRS-)) of the collected voltage, and since the first voltage signal output by the wheatstone bridge is an ac voltage, the voltage difference VRS of the collected voltage is also an ac voltage. The peak voltage of the VRS can reflect the contact area of human tissues and the negative plate, and the larger the peak voltage of the VRS is, the smaller the contact area is; the smaller the peak voltage of the VRS, the larger the contact area.

In the embodiment, the voltage acquisition circuit adopts a manner of acquiring the output voltage of the wheatstone bridge in a form of series connection of resistors, and in another specific embodiment, an isolation transformer can also be adopted to replace the output voltage of the wheatstone bridge acquired in a form of series connection of resistors.

Example 3

Based on the detection circuit of the contact area of the negative plate of the high-frequency electric knife in embodiment 1 or embodiment 2, more specifically, the embodiment provides a specific circuit of the pre-signal processing circuit, wherein the pre-signal processing circuit comprises a reference voltage source circuit for providing a constant reference voltage, and a level shifting circuit for processing the first voltage signal acquired by the voltage acquisition circuit and outputting a second voltage signal; the level shifting circuit is used for biasing the positive signal of the first voltage signal acquired by the voltage acquisition circuit to the positive voltage direction.

The first input end of the level shifting circuit is electrically connected with the first output end of the voltage acquisition circuit; a positive signal for receiving the first voltage signal output by the voltage acquisition circuit;

In a specific embodiment, as shown in fig. 6, the reference voltage source circuit includes a resistor R11, a voltage stabilizing chip U2, a resistor R6, and a resistor R5;

One end of the resistor R5 is used as an output end of the reference voltage source circuit and is used for outputting constant reference voltage, namely a VZ signal, and is electrically connected with a second input end of the level shifting circuit.

In this embodiment, after the power VCC is divided by the resistor R11, the voltage input to the 3 pin of the voltage stabilizing chip U2 triggers the pin 1 of the U2 to serve as the output terminal of the reference voltage source circuit to output the reference voltage VREF, which is determined by the characteristics of the U2 chip itself, and VREF is a constant voltage.

As shown in fig. 6, the voltage of pin 1 of the voltage stabilizing chip U2 is a reference voltage VREF, which is a constant value, determined by the characteristics of the chip. After the constant reference voltage VZ is divided by the series connection of the resistor R5 and the resistor R6, the voltage on the resistor R6 is the reference voltage VREF, and the constant reference voltage vz= ((R5/R6) +1) VREF is easily obtained by simple calculation, and the constant reference voltage VZ is the voltage shifted upwards by the level shifting circuit. When the circuit parameters are configured, the constant reference voltage VZ is greater than the peak voltage of the sampling voltage VRS, so that the ac voltage VRS can be converted into the dc voltage.

In a specific embodiment, as shown in fig. 7, the level shifting circuit includes a differential amplifier sub-circuit and a voltage follower sub-circuit;

the second input end of the differential amplifying sub-circuit is electrically connected with the output end of the reference voltage source circuit and is used for receiving constant reference voltage VZ;

The differential amplifying sub-circuit described in this embodiment includes a resistor R9, a resistor R7, a resistor R10, a resistor R8, a first operational amplifier U1A, and a capacitor C5;

one end of the resistor R7 is used as a second input end of the level shifting circuit, is electrically connected with the output end of the reference voltage source circuit and is used for receiving constant reference voltage VZ;

The other end of the resistor R7 is electrically connected with the non-inverting input end of the first operational amplifier U1A and is used for receiving constant reference voltage VZ;

The voltage follower sub-circuit described in this embodiment includes a second operational amplifier U1B, a resistor R12;

As shown in fig. 7, the level shifting circuit includes a first operational amplifier U1A and a second operational amplifier U1B, which are universal operational amplifier chips U1A, U B. For convenience of debugging, the resistor resistance value r7=r9, r8=r10 is configured, and the amplification factor of the differential amplifying sub-circuit is as follows: the input voltage of the differential amplifying sub-circuit is the voltage vrs= ((vrs+) - (VRS-)) on the sampling resistor and the output constant reference voltage VZ of the reference power supply, so that the output voltage of the differential amplifying sub-circuit:

V01=(R10/R9)*(VZ-VRS)=（R10/R9）*VZ+（R10/R9）*（-VRS）(1)

Equation (1) consists of two parts:

1) The first part is a level shifted voltage bias value (R10/R9) vZ, which is a fixed forward voltage;

2) The second part is the reverse voltage amplification value (R10/R9) of the voltage acquisition circuit (-VRS), and the change trend of the contact area of the acquired voltage value and human tissues is opposite, and the output voltage V01 of the differential amplification sub-circuit has the same change trend with the contact area because the voltage of the second part is reversely amplified: i.e. the larger V01, the larger the contact area; the smaller V01, the smaller the contact area.

The second operational amplifier chip U1B, the resistor R12, and the like form a voltage follower sub-circuit, and the voltage follower sub-circuit transmits the second voltage signal output by the differential amplifier circuit to the first isolation circuit, and the voltage follower sub-circuit outputs the second voltage signal v02=v01.

In this embodiment, a level shifting circuit and a reference voltage source circuit are adopted to form a preposed signal processing circuit for processing the ac acquisition voltage by single power supply, and in another specific embodiment, positive and negative power supplies can be adopted to process the preposed signal of the voltage acquisition circuit, that is, two input ends of the level shifting circuit can be connected with a reference voltage source.

Example 4

Based on the detection circuit of the contact area of the negative plate of the high-frequency electric knife according to embodiment 1, embodiment 2, or embodiment 3, more specifically, the embodiment provides a specific circuit of the first isolation circuit, as shown in fig. 8, the first isolation circuit includes a two-channel nonlinear optocoupler OP, a third operational amplifier U1C, a fourth operational amplifier U3A, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a capacitor C6, and a capacitor C7;

the 7 pin of the two-channel nonlinear optical coupler OP is electrically connected with the non-inverting input end of the fourth operational amplifier U3A;

the inverting input end of the fourth operational amplifier U3A is connected with the output end of the fourth operational amplifier;

As shown in fig. 8, the third operational amplifier U1C, the resistor R13, the resistor R14, the resistor R15, the capacitor C6 and the dual-channel nonlinear optocoupler OP form an input loop in the first isolation circuit; the fourth operational amplifier U3A, the resistor R16, the capacitor C7 and the dual-channel nonlinear optocoupler OP form an output loop in the first isolation circuit.

Input loop: the second voltage signal V02 of the level shifting circuit is connected to the inverting input DM-U1C of the third operational amplifier U1C, which is easily known according to the characteristics of "virtual short" and "virtual off" of the ideal operational amplifier: the voltage of the inverting input end of the operational amplifier U1C is equal to the voltage of the non-inverting input end; the input currents of the inverting input terminal and the non-inverting input terminal of the third operational amplifier U1C are both zero. So that the voltage values across the resistor R13 and the resistor R14 are equal, i.e

V_DP-U1C=V_DM-U1C=V02=V01=（R10/R9）*VZ+（R10/R9）*（-VRS） (2)

Current flowing through resistor R14:

I_R14=V_DP-U1C/R14=(（R10/R9）*VZ+（R10/R9）*（-VRS）)/R14(3)

as shown in fig. 8, two input emitting diodes of the two-channel nonlinear optical coupler OP (1-pin, 2-pin, 3-pin, and 4-pin of the two-channel nonlinear optical coupler OP); the output of the two-channel nonlinear optical coupler OP receives 6 pins and 5 pins of the two-channel nonlinear optical coupler OP, a negative feedback circuit is formed by a third operational amplifier U1C, a resistor R14 and a resistor R15 to realize the function of stably transmitting a second voltage signal, and the principle analysis is as follows:

when the current of the output transistors of the two-channel nonlinear optocoupler OP (6 pins and 5 pins of the two-channel nonlinear optocoupler OP) is increased due to certain accidental factors, the current of the resistor R14 and the current of the output transistors of the two-channel nonlinear optocoupler OP (6 pins and 5 pins of the two-channel nonlinear optocoupler OP) are in series connection, the currents of the resistor R14 are equal, so that the voltage values at two ends of the resistor R14 are increased, namely the voltage v_dp-U1C at the positive phase input end of the third operational amplifier U1C is increased, the voltage at the opposite phase input end of the third operational amplifier U1C is unchanged due to the fact that the second voltage signal is constant, the voltage at the output end of the third operational amplifier U1C is increased, the current flowing through the emitting diode of the two-channel nonlinear optocoupler OP is reduced through the current limiting of the resistor R15, and finally the current of the receiving transistor of the two-channel nonlinear optocoupler OP is also reduced, the negative feedback automatic regulation process is performed after a period of time, and the negative feedback circuit prevents the voltage value at two-channel nonlinear optocoupler OP (6 pins and 5 pins of the two-channel nonlinear optocoupler OP) from being increased, so that the current at the output end of the two-channel nonlinear optocoupler OP is stable, and the current at the output end of the two-channel nonlinear optocoupler OP 6C is stable; and (5) carrying out similar analysis: when the current of the output transistor of the dual-channel nonlinear optical coupler OP (6 pins, 5 pins of the dual-channel nonlinear optical coupler OP) is reduced due to some accidental factors, the negative feedback circuit prevents the current of the output transistor of the dual-channel nonlinear optical coupler OP (6 pins, 5 pins of the dual-channel nonlinear optical coupler OP) from being reduced, and finally the current of the output transistor of the dual-channel nonlinear optical coupler (6 pins, 5 pins of the dual-channel nonlinear optical coupler OP) is stabilized to be a certain value; the calculation formula is as follows:

I_OP-Pin5_Pin6=I_R14=V_DM-U1C/R14=(（R10/R9）*VZ+（R10/R9）*（-VRS）)/R14(4)

Because the emitting diodes of the two channels are in series connection, the emitting current values of the emitting diodes of the two channels in the two-channel nonlinear optical coupler OP are the same, the photoelectric transmission parameters of the optical couplers of the two channels in the same chip are basically consistent, the induction currents of the receiving transistors of the two channels of the two-channel nonlinear optical coupler OP are the same, and the resistor R16 is in series connection with the receiving transistor of the two-channel nonlinear optical coupler OP

I_R16=I_OP-Pin8_Pin7=I_OP-Pin5_Pin6=I_R14=V_DM-U1C/R14=(（R10/R9）*VZ+（R10/R9）*（-VRS）)/R14（5）

The output loop of the first isolation circuit consists of a voltage follower sub-circuit composed of a fourth operational amplifier U3A and a resistor R16, namely

V04=V_DM-U3A=V_R16=V_DP-U3A=I_R16*R16=(（R10/R9）*VZ(R16/R14)+（R10/R9）*（-VRS）)*(R16/R14)（6）

From the analysis of the negative feedback and the equation (6), the third voltage signal V04 is independent of the actual parameter of the two-channel nonlinear optocoupler. The method has a great relationship with the parameter consistency and the difference of two channels of the two-channel nonlinear optocoupler, and the parameter consistency of the two-channel nonlinear optocoupler of different channels in the same chip is good under normal conditions, and the output loop realizes the linear transmission of the third voltage signal V04.

In order to improve the precision, the resistor R9 and the resistor R10 in the level shifting circuit can select the patch resistor with high precision, the patch resistor can ensure that the parameter consistency of the two resistors is high, meanwhile, the two resistors belong to an input loop, the electrical interval requirement is low, and the resistor can meet the requirement. The resistor R16 and the resistor R14 can be chip resistors with high selection precision and cannot be selected for discharging, because the R16 belongs to an output loop and the R14 belongs to an input loop, the input loop and the output loop need to keep a certain electrical interval (the energy output of the high-frequency electric knife is high-voltage high-frequency energy), and the small-package chip resistor cannot meet the electrical isolation distance requirement required by the electric knife.

In this embodiment, a working mode of performing isolation transmission of the second voltage signal by using the two-channel nonlinear optocoupler, and in a specific embodiment, a transformer may also be used to perform isolation transmission of the second voltage signal.

In the embodiment, the first isolation circuit adopts a two-channel nonlinear optocoupler to realize the transmission mode of the linear second voltage signal, and in a specific embodiment, the two-channel nonlinear optocoupler can be replaced by the linear optocoupler.

Example 5

Based on the detection circuit of the contact area of the negative plate of the high-frequency electric knife according to embodiment 1, embodiment 2, embodiment 3, or embodiment 4, more specifically, the present embodiment provides a specific circuit of the operational amplifier circuit, as shown in fig. 9, the operational amplifier circuit includes a fifth operational amplifier U3C, a resistor R18, a resistor R19, and a resistor R17;

the non-inverting input end of the fifth operational amplifier U3C is used for receiving a third voltage signal and is electrically connected with the other end of the resistor R19;

The other end of the resistor R18 is grounded;

The operational amplifier circuit is shown in fig. 9, and is composed of a fifth operational amplifier U3C, a resistor R17, a resistor R18, a resistor R19, and the like, wherein the circuit is an in-phase amplifying circuit, the amplification factor is r17/r18+1, and in order to reduce the influence of the bias current of the actual operational amplifier, the configuration parameter r19=r17// r18 is provided. The output fourth voltage signal v05=v04.

Example 6

Based on the detection circuit of the contact area of the negative plate of the high-frequency electrotome described in embodiment 1, embodiment 2, embodiment 3, embodiment 4, or embodiment 5, more specifically, the present embodiment provides a specific circuit of the follower circuit, as shown in fig. 10, the follower circuit includes a sixth operational amplifier U3B and a resistor R20;

As shown in fig. 10, the follower circuit is composed of a sixth operational amplifier U3B, a resistor R20, and the like, and the follower circuit can reduce interference between the front stage circuit and the rear stage circuit, and output a fifth voltage signal v06=v05, and the fifth voltage signal V06 of the sixth operational amplifier is input to the controller for AD conversion, converted into a digital signal, and stored in the controller. The controller can recognize the contact area according to the digital signal, and the controller needs to calibrate the contact area of the negative plate before the controller.

It is to be understood that the above examples of the present utility model are provided by way of illustration only and not by way of limitation of the embodiments of the present utility model. Any modification, equivalent replacement, improvement, etc. which come within the spirit and principles of the utility model are desired to be protected by the following claims.

Claims

1. A high-frequency electrotome negative plate contact area detection circuit is characterized in that: the circuit comprises a Wheatstone bridge for converting the contact area of human tissue and a negative plate into a corresponding contact resistance size relation, a voltage acquisition circuit for acquiring a first voltage signal output by the Wheatstone bridge, a pre-signal processing circuit for receiving and processing the first voltage signal and outputting a second voltage signal, a first isolation circuit for receiving and processing the second voltage signal and outputting a third voltage signal, an operational amplification circuit for receiving and amplifying the third voltage signal and outputting a fourth voltage signal, a follower circuit for receiving and processing the fourth voltage signal and outputting a fifth voltage signal, and a controller for receiving the fifth voltage signal and identifying the contact area size according to the fifth voltage signal;

2. The high-frequency electrotome negative plate contact area detection circuit of claim 1, wherein: the voltage acquisition circuit comprises a resistor R3, a sampling resistor RS and a resistor R4;

One end of the resistor R3, which is commonly connected with the sampling resistor RS, is used as a first output end of the voltage acquisition circuit, is used for outputting a positive signal of a first voltage signal output by the Wheatstone bridge, and is electrically connected with a first input end of the preposed signal processing circuit;

3. The high-frequency electrotome negative plate contact area detection circuit of claim 1, wherein: the pre-signal processing circuit comprises a reference voltage source circuit for providing a constant reference voltage and a level shifting circuit for processing a first voltage signal acquired by the voltage acquisition circuit and outputting a second voltage signal;

4. The high-frequency electrotome negative plate contact area detection circuit of claim 3, wherein: the reference voltage source circuit comprises a resistor R11, a voltage stabilizing chip U2, a resistor R6 and a resistor R5;

5. The high-frequency electrotome negative plate contact area detection circuit of claim 3, wherein: the level shifting circuit comprises a differential amplifier sub-circuit and a voltage follower sub-circuit;

6. The high-frequency electrotome negative plate contact area detection circuit of claim 5, wherein: the differential amplifying sub-circuit comprises a resistor R9, a resistor R7, a resistor R10, a resistor R8, a first operational amplifier U1A and a capacitor C5;

7. The high-frequency electrotome negative plate contact area detection circuit of claim 6, wherein: the voltage follower sub-circuit comprises a second operational amplifier U1B and a resistor R12;

8. The high-frequency electrotome negative plate contact area detection circuit of claim 3, wherein: the first isolation circuit comprises a double-channel nonlinear optocoupler OP, a third operational amplifier U1C, a fourth operational amplifier U3A, a resistor R13, a resistor R14, a resistor R15, a resistor R16, a capacitor C6 and a capacitor C7;

9. The high-frequency electrotome negative plate contact area detection circuit of claim 1, wherein: the operational amplifier circuit comprises a fifth operational amplifier U3C, a resistor R18, a resistor R19 and a resistor R17;

the other end of the resistor R18 is grounded;

10. The high-frequency electrotome negative plate contact area detection circuit of claim 1, wherein: the follower circuit comprises a sixth operational amplifier U3B and a resistor R20;