Impedance measuring circuit and measuring method

Abstract

The invention relates to an impedance measurement circuit and method, and belongs to the field of impedance measurement, the impedance measurement circuit comprises a plurality of stimulation electrodes, a voltage measurement circuit and a controller, the stimulation electrodes are in contact with nervous tissue, each stimulation electrode is connected in series with a blocking capacitor and a single-pole double-throw switch, one end of the single-pole double-throw switch is connected with a stimulation input end, and the other end of the single-pole double-throw switch is connected with a voltage measurement circuit. The other end of the single-pole double-throw switch is connected with the stimulation output end; the voltage measuring circuit is connected with the stimulation input end and the stimulator output end and used for measuring stimulation voltage between the stimulation input end and the stimulation output end. The controller is connected with the voltage measuring circuit and used for obtaining a target impedance value according to the stimulation voltage and the stimulation current flowing into the stimulation input end or flowing out of the stimulation output end. The method has the effect of improving the impedance measurement precision.

Description

Technical Field

[0001] This application relates to the technical field of impedance measurement, and in particular, to an impedance measurement circuit and a measurement method. Background Art

[0002] In the field of nerve therapy, an implantable nerve stimulation system is used to treat patients. The implantable nerve stimulation system includes a nerve stimulator and an external controller. The nerve stimulator is implanted into the patient's body, and the external controller and the nerve stimulator use wireless communication. The user adjusts the stimulation parameters of the external controller and sends the stimulation parameters to the nerve stimulator through wireless communication to control the working state of the nerve stimulator.

[0003] Before that, it is necessary to measure the impedance of the stimulation point and give appropriate electrical stimulation according to the measured impedance.

[0004] Currently, a blocking capacitor is generally used to measure the impedance. However, due to the charging and discharging of the blocking capacitor and its inherent characteristic that the voltage cannot change suddenly, the voltages of the two electrodes of the electrical stimulation cannot directly reflect the DC impedance of the human body. It is necessary to give a square wave voltage through the stimulation electrodes and measure the step response of the voltages of the two electrodes connected to the capacitor or measure the average value of the voltages of the two electrodes connected to the capacitor. It is also possible to directly measure the voltages of the two electrodes through a digital-to-analog converter. These methods have problems such as limited measurement accuracy, the need for multiple measurements, and high device cost. Summary of the Invention

[0005] In order to improve the measurement accuracy of the impedance, this application provides an impedance measurement circuit and a measurement method.

[0006] In the first aspect of this application, an impedance measurement circuit is provided. The circuit includes a plurality of stimulation electrodes, a voltage measurement circuit, and a controller. The stimulation electrodes are in contact with nerve tissue. Each stimulation electrode is connected in series with a blocking capacitor and a single-pole double-throw switch. One end of the single-pole double-throw switch is connected to the stimulation input terminal, and the other end of the single-pole double-throw switch is connected to the stimulation output terminal. The voltage measurement circuit is respectively connected to the stimulation input terminal and the stimulator output terminal for measuring the stimulation voltage between the stimulation input terminal and the stimulation output terminal. The controller is connected to the voltage measurement circuit for obtaining a target impedance value according to the stimulation voltage and the stimulation current flowing into the stimulation input terminal or flowing out of the stimulation output terminal.

[0007] It can be seen from the above technical solutions that the stimulation voltage between the stimulation input terminal and the stimulation output terminal can be directly obtained by using the voltage measurement circuit, reducing the device cost for measuring the stimulation voltage, and thus reducing the cumulative error that occurs during the voltage measurement, and achieving the effect of improving the measurement accuracy of the stimulation voltage and the target impedance value.

[0008] In a possible implementation, the voltage measurement circuit includes a current mirror, a voltage measurement resistor, and a resistor array; The first input terminal of the current mirror is connected to the stimulation input terminal through the voltage measurement resistor, the second input terminal of the current mirror is connected to the stimulation output terminal, and the output terminal of the current mirror is connected to the power supply voltage through the resistor array.

[0009] As can be seen from the above technical solution, by using a current mirror to copy the stimulation current into the voltage measurement circuit and then adjusting the resistor array to make the current mirror operate in the transistor saturation region, the stimulation voltage can be obtained from the resistance value of the resistor array and the stimulation current.

[0010] In a possible implementation, the voltage measurement circuit includes a current mirror, a voltage measurement resistor, and a resistor array; the first input terminal of the current mirror is connected to the stimulation output terminal through the voltage measurement resistor, the second input terminal of the current mirror is connected to the stimulation input terminal, and the output terminal of the current mirror is connected to the ground through the resistor array.

[0011] In a possible implementation, the resistor array includes a plurality of resistors connected in series, and the common connection terminal of the plurality of resistors is respectively connected to the output terminal of the current mirror, the power supply voltage, or the ground through a resistor switch.

[0012] In a possible implementation, the resistor array includes a plurality of resistor units connected in parallel. Each resistor unit includes a resistor and a resistor switch connected in series. One common terminal of the resistor unit is connected to the output terminal of the current mirror, and the other common terminal of the resistor unit is connected to the power supply voltage or the ground.

[0013] In a possible implementation, the voltage measurement circuit includes a first current mirror, a second current mirror, a voltage measurement resistor, and a resistor array; The first input terminal of the first current mirror is connected to the stimulation input terminal through the voltage measurement resistor, the second input terminal of the first current mirror is connected to the stimulation output terminal, the output terminal of the first current mirror is connected to the first input terminal of the second current mirror, the second input terminal of the second current mirror is connected to the power supply voltage, and the output terminal of the second current mirror is connected to the ground through the resistor array.

[0014] In a possible implementation, the voltage measurement circuit includes a first current mirror, a second current mirror, a voltage measurement resistor, and a resistor array; The first input terminal of the first current mirror is connected to the stimulation output terminal through the voltage measurement resistor, the second input terminal of the first current mirror is connected to the stimulation input terminal, the output terminal of the first current mirror is connected to the first input terminal of the second current mirror, the second input terminal of the second current mirror is connected to the stimulation output terminal, and the output terminal of the second current mirror is connected to the power supply voltage through the resistor array.

[0015] In a second aspect of the present application, an impedance measurement method is provided. The method includes: Closing any two single-pole double-throw switches to form a first loop between the stimulation input terminal and the stimulation output terminal; Switching the two single-pole double-throw switches to form a second loop between the stimulation input terminal and the stimulation output terminal, and the current direction in the second loop is opposite to that in the first loop; Obtaining the voltage change waveform diagrams of the first loop and the second loop; Determining the target impedance value according to the voltage change waveform diagrams.

[0016] In a possible implementation, determining the target impedance value according to the voltage change waveform diagrams includes: Obtaining a first voltage value at a first moment and a second voltage value at a second moment during the voltage rising process in the voltage change waveform diagram, where the first moment refers to the moment when the step occurs; Obtaining the voltage rising rate according to the first voltage value at the first moment and the second voltage value at the second moment; Determining the target impedance value according to the voltage rising rate and the capacitance values of the DC-blocking capacitors corresponding to the two single-pole double-throw switches.

[0017] In a possible implementation, determining the target impedance value according to the voltage rising rate and the capacitance values of the DC-blocking capacitors corresponding to the two single-pole double-throw switches includes: Wherein, t a represents the first moment, t b represents the second moment, V a represents the first voltage value at the first moment, V b represents the second voltage value at the second moment, I represents the stimulation current in the first loop or the second loop, C1 and C2 represent the capacitance values of the DC-blocking capacitors corresponding to the two single-pole double-throw switches, and R represents the target impedance value.

[0018] In summary, the present application includes at least one beneficial technical effect: By using the stimulation voltage that can be directly obtained by the voltage measurement circuit between the stimulation input terminal and the stimulation output terminal, the equipment cost for measuring the stimulation voltage is reduced, and thus the cumulative error occurring during the voltage measurement is reduced, and the effect of improving the measurement accuracy of the stimulation voltage and the target impedance value can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is a schematic structural diagram of the impedance measurement circuit provided by an embodiment of the present application.

[0020] Figure 2It is a schematic circuit diagram of the voltage measurement circuit in the impedance measurement circuit provided by an embodiment of the present application.

[0021] Figure 3 It is a schematic circuit diagram of the voltage measurement circuit in the impedance measurement circuit provided by an embodiment of the present application.

[0022] Figure 4 It is a schematic diagram of the structure of the resistor array in the impedance measurement circuit provided by an embodiment of the present application.

[0023] Figure 5 It is a schematic diagram of the structure of the resistor array in the impedance measurement circuit provided by an embodiment of the present application.

[0024] Figure 6 It is a schematic flowchart of the impedance measurement method provided by an embodiment of the present application.

[0025] Figure 7 It is a schematic diagram of the switch closing structure in the impedance measurement method provided by an embodiment of the present application.

[0026] Figure 8 It is a waveform diagram of the voltage change in the impedance measurement method provided by an embodiment of the present application.

[0027] In the figure, 1 is the controller; 2 is the voltage measurement circuit; 21 is the current mirror; 22 is the voltage measurement resistor; 23 is the resistor array; 24 is the first current mirror; 25 is the second current mirror; 26 is the resistor unit; 27 is the resistor switch; 3 is the single-pole double-throw switch; 4 is the DC-blocking capacitor. Detailed implementation manners

[0028] To make the objectives, technical solutions, and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Apparently, the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present application without creative efforts shall fall within the protection scope of the present application.

[0029] In addition, the term "and / or" in this document is merely a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. In addition, the character " / " in this document generally represents an "or" relationship between the associated objects before and after unless otherwise specified.

[0030] Before using a stimulator to treat a patient, it is necessary to determine the impedance of the part of the patient to be stimulated. Different impedances will affect the stimulation intensity during the treatment of the patient. It is necessary to determine an appropriate stimulation voltage or stimulation current according to the different impedances. Therefore, it is necessary to measure the impedance of the patient.

[0031] The methods for measuring impedance are mainly divided into two categories. One is the direct measurement method without using the blocking capacitor 4, and the other is the measurement method using the blocking capacitor 4.

[0032] For the measurement method without using the blocking capacitor 4, the voltage difference between the positive and negative stimulation electrodes connected to the patient's nerve tissue and the current flowing through the two electrodes are directly measured, and the two are divided to obtain the DC impedance of the human body. Although this method can accurately and directly obtain the impedance, it will cause a certain degree of adverse effects on the human body. First, the stimulation electrodes will continuously stimulate a specific position of the human body (the nerve tissue in contact with the human body by the stimulation electrodes) in the form of leakage. This kind of stimulation will cause more abnormal tissues to be generated at this position. Second, the stimulation electrodes are in contact with the nerve tissue of the human body in a long-term leakage state, and ionization will occur between the stimulation electrodes and the tissue fluid of the nerve tissue. This ionization phenomenon is essentially a kind of corrosion of the stimulation electrodes. When the corrosion reaches a certain degree, problems such as poor contact or detachment of the stimulation electrodes will occur. When problems such as poor contact or detachment occur, doctors need to surgically remove or replace them.

[0033] In the field of bioelectrical nerve stimulation, in order to maintain the positive and negative charge balance of the stimulation electrodes within a period of time, it is necessary to use the blocking capacitor 4 to isolate the DC component in the stimulation output current.

[0034] When measuring impedance using the DC-blocking capacitor 4, due to the charging and discharging of the DC-blocking capacitor 4 and the characteristic that its inherent voltage cannot change suddenly, the voltage across the two stimulating electrodes of the electrical stimulation cannot directly reflect the DC impedance of the human body. Therefore, the first method can be used, applying a square wave voltage to the stimulating electrodes and measuring the step response of the voltage of the two stimulating electrodes connected to the DC-blocking capacitor 4. However, this method requires multiple measurements to obtain the step response curve and fit to obtain the human DC impedance. At the same time, the measurement accuracy of this method will be limited by the measurement method, resulting in a relatively low accuracy of the measured impedance. The second method can also be used, giving a sine wave through the stimulating electrodes and measuring the average value of the voltage of the two stimulating electrodes connected to the DC-blocking capacitor 4. This method requires a sine wave generator and an envelope detector, with many measurement devices and a complex measurement principle. The measurement passes through multiple signal link links, resulting in a large cumulative error. The third method can also be used. For the differential signal of the stimulating electrodes, directly use an analog-to-digital converter for measurement. The above differential signal may directly exceed the measurement range of the analog-to-digital converter, resulting in problems such as inability to measure or damage to the analog-to-digital converter. For the third method, the differential signal of the stimulating electrodes can also be obtained for threshold detection. If it exceeds the measurement range of the analog-to-digital converter, the above differential signal is divided by voltage and then measured using the analog-to-digital converter. If the above differential signal is small, it can be amplified by an operational amplifier first and then measured using the analog-to-digital converter. However, in this way, on the one hand, the measurement process is complex, and on the other hand, devices such as voltage division and signal amplification are used, resulting in more power consumption and device costs.

[0035] Therefore, the embodiment of the present application proposes an impedance measurement circuit, which simplifies the measurement principle, reduces the hardware required for measurement, reduces the cumulative error caused by too many signal links, and realizes accurate measurement of impedance.

[0036] The following further describes the embodiment of the present application in detail with reference to the accompanying drawings of the specification.

[0037] The embodiment of the present application provides an impedance measurement circuit. Referring to Figure 1 , the impedance measurement circuit includes multiple stimulating electrodes, a voltage measurement circuit 2, and a controller 1. The above stimulating electrodes are in contact with nerve tissue. Each of the above stimulating electrodes is connected in series with a DC-blocking capacitor 4 and a single-pole double-throw switch 3. One end of the above single-pole double-throw switch 3 is connected to the stimulation input end, and the other end of the above single-pole double-throw switch 3 is connected to the stimulation output end. By switching the above single-pole double-throw switch 3, it can be selected to connect to the stimulation input end or to the stimulation output end.

[0038] The above-mentioned voltage measurement circuit 2 is respectively connected to the above-mentioned stimulation input end and the above-mentioned stimulator output end, and is used to measure the stimulation voltage between the above-mentioned stimulation input end and the above-mentioned stimulation output end. The above-mentioned controller 1 is connected to the above-mentioned voltage measurement circuit 2, and is used to obtain a target impedance value according to the above-mentioned stimulation voltage and the stimulation current flowing into the above-mentioned stimulation input end or flowing out of the above-mentioned stimulation output end.

[0039] Those skilled in the art can clearly understand that for the convenience and simplicity of description, the specific working processes of the described voltage measurement circuit 2 and controller 1 can refer to the corresponding processes in the impedance measurement method embodiments described later, and will not be elaborated here.

[0040] It can be understood that the stimulation electrode is in contact with or connected to the nerve tissue, and the impedance corresponding to the stimulation electrode can reflect the contact condition between the stimulation electrode and the nerve tissue. The better the contact condition of the stimulation electrode, the larger the impedance value; on the contrary, the worse the contact condition of the stimulation electrode, the smaller the impedance value. In Figure 1 , the resistance generated by the stimulation electrode due to contact with the nerve tissue is equivalent to the contact resistance R1 - Rn, where n is a positive integer. Where P1 represents the contact point between the stimulation electrode and the nerve tissue, and the contact resistance R1 is the resistance generated at point P1. Similarly, Pn represents the contact point between the stimulation electrode and the nerve tissue, and the contact resistance Rn represents the contact resistance generated at point Pn.

[0041] In the first embodiment, the above-mentioned voltage measurement circuit 2 includes a current mirror 21, a voltage measurement resistor 22, and a resistor array 23; the first input end of the above-mentioned current mirror 21 is connected to the above-mentioned stimulation input end through the above-mentioned voltage measurement resistor 22, the second input end of the above-mentioned current mirror 21 is connected to the above-mentioned stimulation output end, and the output end of the above-mentioned current mirror 21 is connected to the power supply voltage through the above-mentioned resistor array 23. Refer to Figure 2 (a), O1 represents the stimulation input end, that is, the stimulation current flows into the voltage measurement circuit 2 through O1, and O2 represents the stimulation output end, that is, the stimulation current flows out of the voltage measurement circuit 2 through O2. The stimulation current will flow from O1 through the voltage measurement resistor 22R0 into the current mirror 21, and then through the current mirror 21 into the resistor matrix R1, and the other end of R1 is connected to the power supply voltage. Figure 2 The voltage at the end of the resistor array 23R1 far from the power supply voltage is denoted as Vmeasure, and Vmeasure is the voltage between O1 and O2. Among them, Vmeasure = VDD - IR1, VDD is the above-mentioned power supply voltage, and I represents the stimulation current.

[0042] In the second embodiment, the voltage measurement circuit 2 includes a current mirror 21, a voltage measurement resistor 22, and a resistor array 23. The first input terminal of the current mirror 21 is connected to the stimulation output terminal through the voltage measurement resistor 22. The second input terminal of the current mirror 21 is connected to the stimulation input terminal. The output terminal of the current mirror 21 is grounded through the resistor array 23. Refer to Figure 2 (b), O1 represents the stimulation input terminal, that is, the stimulation current flows into the voltage measurement circuit 2 through O1. O2 represents the stimulation output terminal, that is, the stimulation current flows out of the voltage measurement circuit 2 through O2. The stimulation current will flow from O1 through the current mirror 21 into the voltage measurement resistor R0 and the resistor array R1, and the other end of R1 is grounded. Figure 2 (b) Denote the voltage at the common terminal of the resistor array R1 and the current mirror 21 as Vmeasure, and Vmeasure is the voltage between O1 and O2. Among them, Vmeasure = IR1, and I represents the stimulation current.

[0043] In the above voltage measurement circuit 2, using one current mirror 21 can achieve the measurement of the voltage between O1 and O2. However, in some cases, the voltages on O1 and O2 may far exceed the power supply voltage VDD. At this time, two current mirrors 21 are needed, and the drains in the two current mirrors 21 are used to bear the relatively high voltage.

[0044] In the third embodiment, the voltage measurement circuit 2 includes a first current mirror 24, a second current mirror 25, a voltage measurement resistor 22, and a resistor array 23. The first input terminal of the first current mirror 24 is connected to the stimulation input terminal through the voltage measurement resistor 22. The second input terminal of the first current mirror 24 is connected to the stimulation output terminal. The output terminal of the first current mirror 24 is connected to the first input terminal of the second current mirror 25. The second input terminal of the second current mirror 25 is connected to the power supply voltage. The output terminal of the second current mirror 25 is grounded through the resistor array 23. Refer to Figure 3 (a), O1 represents the stimulation input terminal, and O2 represents the stimulation output terminal. The stimulation current will flow from O1 through the voltage measurement resistor 22R0 into the first current mirror 24, and then the stimulation current is copied to the second current mirror 25 through the first current mirror 24, and flows into the resistor matrix R1 through the second current mirror 25. The other end of the resistor matrix R1 is grounded. Denote the voltage at the common terminal of the resistor array R1 and the second current mirror 25 as Vmeasure, and Vmeasure is the voltage between O1 and O2. Among them, Vmeasure = IR1, and I represents the stimulation current.

[0045] In the fourth embodiment, the voltage measurement circuit 2 includes a first current mirror 24, a second current mirror 25, a voltage measurement resistor 22, and a resistor array 23. The first input terminal of the first current mirror 24 is connected to the stimulation output terminal through the voltage measurement resistor 22. The second input terminal of the first current mirror 24 is connected to the stimulation input terminal. The output terminal of the first current mirror 24 is connected to the first input terminal of the second current mirror 25. The second input terminal of the second current mirror 25 is connected to the stimulation output terminal. The output terminal of the second current mirror 25 is connected to the power supply voltage through the resistor array 23. Refer to Figure 3 (b), O1 represents the stimulation input terminal, and O2 represents the stimulation output terminal. The stimulation current will flow from O1 through the replication of the first current mirror 24 into the voltage measurement resistor R0, and then through the replication of the second current mirror 25 into the resistor matrix R1. The other end of the resistor matrix R1 is connected to the power supply voltage. Denote the voltage at the common terminal of the resistor array R1 and the second current mirror 25 as Vmeasure, and Vmeasure is the voltage between O1 and O2. Among them, Vmeasure = VDD - IR1, VDD is the above-mentioned power supply voltage, and I represents the stimulation current.

[0046] In a specific embodiment, refer to Figure 4 , the resistor array 23 includes a plurality of resistor units 26. The plurality of resistor units 26 are connected in parallel. The resistor unit 26 includes a resistor and a resistor switch 27. The resistor and the resistor switch 27 are connected in series. In the first and second embodiments, one common terminal of the resistor unit 26 is connected to the output terminal of the current mirror 21, and the other common terminal of the resistor unit 26 is connected to the power supply voltage or grounded. In the third and fourth embodiments, one common terminal of the resistor unit 26 is connected to the output terminal of the second current mirror 25, and the other common terminal of the resistor unit 26 is connected to the power supply voltage or grounded.

[0047] In another specific embodiment, refer to Figure 5 , the resistor array 23 includes a plurality of resistors. The plurality of resistors are connected in series. In the first and second embodiments, one end of the series-connected resistors is connected to the current mirror 21, and the other end is connected to the power supply voltage or grounded. And the common connection terminal of the plurality of resistors is respectively connected to the output terminal of the current mirror 21 or to the power supply voltage or grounded through the resistor switch 27. In the third and fourth embodiments, one end of the series-connected resistors is connected to the second current mirror 25, and the other end is connected to the power supply voltage or grounded. And the common connection terminal of the plurality of resistors is respectively connected to the output terminal of the second current mirror 25 or to the power supply voltage or grounded through the resistor switch 27.

[0048] It can be understood that during actual use, the stimulation current will change according to actual needs, so the current flowing into the voltage measurement circuit 2 will also change. Then, the current mirrors 21, the first current mirror 24, and the second current mirror 25 in the voltage measurement circuit 2 may not operate in the transistor saturation region. It is necessary to adjust the resistance of the access circuit in the resistance array 23 to enable the current mirrors 21, the first current mirror 24, and the second current mirror 25 in the voltage measurement circuit 2 to operate in the transistor saturation region.

[0049] In a specific example, the relationship between the voltage measurement resistor R0 and the resistance array R1 satisfies R1 = nR0 or nR1 = R0, where n is a positive integer. For example, the resistance value of each resistor in the resistance array 23 is the same as the resistance value of the voltage measurement resistor 22. In other embodiments, resistors with other resistance values can also be used to form the resistance array 23 to achieve the operation of the current mirror 21 in the transistor saturation region by adjusting the resistance array 23.

[0050] The embodiment of the present application provides an impedance measurement method, and the main process of the above method is described as follows.

[0051] As Figure 6 shown: Step S101: Close the single-pole double-throw switch 3 to form a first loop and a second loop.

[0052] Specifically, close any two single-pole double-throw switches 3 to form a first loop between the stimulation input end and the stimulation output end; switch the above two single-pole double-throw switches 3 to form a second loop between the stimulation input end and the stimulation output end, and the current direction in the second loop is opposite to the current direction in the first loop.

[0053] In a specific example, referring to Figure 7(a), taking the closed single-pole double-throw switches 3S1 and S2 as an example, Out1 represents the input terminal of the stimulation current passing through the voltage measurement circuit 2, and Out2 represents the output terminal of the stimulation current passing through the voltage measurement circuit 2. That is, the stimulation current flows from O1 through the voltage measurement circuit 2 to Out1, and Out1 flows through the above-mentioned single-pole double-throw switch 3, the DC-blocking capacitor 4, and the stimulation electrode and flows out from Out2, and then flows out from O2 through the voltage measurement circuit 2. First, at time t0, switch S1 is switched to terminal a to connect to the stimulation input terminal, and switch S2 is switched to terminal b to connect to the stimulation output terminal. At this time, the stimulation current sequentially flows through S1, DC-blocking capacitor C1, contact resistance R1, contact resistance R2, DC-blocking capacitor C2 and flows out from switch S2. Then at time t1, switch S1 is switched to terminal b to connect to the stimulation output terminal, and switch S2 is switched to terminal a to connect to the stimulation input terminal. At this time, the stimulation current sequentially flows through S2, DC-blocking capacitor C2, contact resistance R2, contact resistance R1, DC-blocking capacitor C1 and flows out from switch S1. Finally, at time t2, the output of the stimulation current is stopped, switch S1 is restored to terminal a, and switch S2 is restored to terminal b.

[0054] Through the above process, the switching of the current direction of the stimulation current flowing through the DC-blocking capacitor C1, contact resistance R1, contact resistance R2, and DC-blocking capacitor C2 can be completed.

[0055] Step S102: Obtain the voltage change waveform diagrams of the first loop and the second loop.

[0056] Step S103: Determine the target impedance value according to the voltage change waveform diagram.

[0057] Specifically, obtain the first voltage value at the first moment and the second voltage value at the second moment during the voltage rising process in the above voltage change waveform diagram; obtain the voltage rising rate according to the first voltage value at the first moment and the second voltage value at the second moment, and the first moment refers to the moment when the step occurs; determine the target impedance value according to the voltage rising rate and the capacitance values of the DC-blocking capacitors 4 corresponding to the two single-pole double-throw switches 3.

[0058] Furthermore, where t a represents the above-mentioned first moment, t b represents the above-mentioned second moment, V a represents the first voltage value at the first moment, V b represents the second voltage value at the second moment, I represents the stimulation current in the first loop or the second loop, C1 and C2 represent the capacitance values of the DC-blocking capacitors 4 corresponding to the two single-pole double-throw switches 3, and R represents the above-mentioned target impedance value.

[0059] In a specific example, referring to Figure 8 ,Figure 8 (a) is a waveform diagram of the voltage difference between the positive electrodes of capacitor C1 and C2. Figure 8 (b) is a periodic square-wave current pulse generated by the current source that outputs the stimulating current. At time t0, the current source starts to output the stimulating current, and a voltage difference of V0 = I * R0 and the voltage of the resistor array 23R1 will be generated across the voltage measurement resistor R0. At time t1, the current direction switches, and the voltage difference between the positive electrodes of capacitor C1 and C2 will cause a voltage drop process of 2 * I * R0. During the period from t1 to t2, the voltage difference between the positive electrodes of capacitor C1 and C2 will gradually return to the voltage value of -IR0 as the capacitor discharges. At this time, the net charge flowing through C1 and C2 is 0, forming the effect of charge balance.

[0060] For example, at time t0, the voltage difference between the positive electrodes of capacitor C1 and C2 is V0, and at time tx, the voltage difference between the positive electrodes of capacitor C1 and C2 is Vx. During the period from t0 to t1, the rising rate of the voltage difference between the positive electrodes of capacitor C1 and C2 is Then Vx = V0 + I × (C1 ∥ C2) × (tx - t0). The target impedance value can be obtained from the above formula In the embodiment provided in this application, time t0 is selected as the above-mentioned first moment, and time tx is selected as the above-mentioned second moment. In other embodiments, the first moment is t0, and the second moment is any moment between t0 and t1. The voltage at time t0 is affected by various interference factors and is extremely difficult to measure accurately. However, the voltage at time tx has already been in a stable state of linearly increasing with the input current. The voltage measured at time tx can better represent the resistance value of the resistor to be measured than the voltage obtained at time t0. The above-mentioned first moment and second moment can be any moment between t0 and t1, but the first moment and the second moment are not the same moment. According to the first voltage value corresponding to the first moment and the second voltage value corresponding to the second moment, the target impedance value can be calculated. Among them, the DC-blocking capacitors C1, C2, and the stimulating current I are all values that can be detected or directly obtained.

[0061] The above description is only a preferred embodiment of this application and an explanation of the applied technical principles. Those skilled in the art should understand that the scope of the application involved in this application is not limited to the technical solution formed by the specific combination of the above technical features, and should also cover other technical solutions formed by any combination of the above technical features or their equivalent features without departing from the foregoing application concept. For example, the technical solutions formed by mutually replacing the above features with the (but not limited to) technical features with similar functions applied in this application.

Claims

1. An impedance measurement circuit, characterized in that, Comprising a plurality of stimulating electrodes, a voltage measurement circuit (2) and a controller (1), the stimulating electrodes are in contact with nerve tissue, each of the stimulating electrodes is connected in series with a DC blocking capacitor (4) and a single-pole double-throw switch (3), one end of the single-pole double-throw switch (3) is connected to a stimulation input terminal, and the other end of the single-pole double-throw switch (3) is connected to a stimulation output terminal; The voltage measurement circuit (2) is respectively connected to the stimulation input terminal and the stimulator output terminal for measuring the stimulation voltage between the stimulation input terminal and the stimulation output terminal; The controller (1) is connected to the voltage measurement circuit (2) for obtaining a target impedance value according to the stimulation voltage and the stimulation current flowing into the stimulation input terminal or flowing out of the stimulation output terminal.

2. The impedance measurement circuit according to claim 1, wherein The voltage measurement circuit (2) includes a current mirror (21), a voltage measurement resistor (22) and a resistor array (23); A first input terminal of the current mirror (21) is connected to the stimulation input terminal through the voltage measurement resistor (22), a second input terminal of the current mirror (21) is connected to the stimulation output terminal, and an output terminal of the current mirror (21) is connected to a power supply voltage through the resistor array (23).

3. The impedance measurement circuit according to claim 1, wherein The voltage measurement circuit (2) includes a current mirror (21), a voltage measurement resistor (22) and a resistor array (23); A first input terminal of the current mirror (21) is connected to the stimulation output terminal through the voltage measurement resistor (22), a second input terminal of the current mirror (21) is connected to the stimulation input terminal, and an output terminal of the current mirror (21) is grounded through the resistor array (23).

4. The impedance measurement circuit according to claim 2 or 3, characterized in that, The resistor array (23) includes a plurality of resistors, the plurality of resistors are connected in series, and a common connection end of the plurality of resistors is respectively connected to the output terminal of the current mirror (21) or to the power supply voltage or grounded through a resistor switch (27).

5. The impedance measurement circuit according to claim 2 or 3, characterized in that, The resistor array (23) includes a plurality of resistor units (26), the plurality of resistor units (26) are connected in parallel, the resistor unit (26) includes a resistor and a resistor switch (27), the resistor and the resistor switch (27) are connected in series, one common end of the resistor unit (26) is connected to the output terminal of the current mirror (21), and the other common end of the resistor unit (26) is connected to the power supply voltage or grounded.

6. The impedance measurement circuit according to claim 1, wherein, The voltage measurement circuit (2) includes a first current mirror (24), a second current mirror (25), a voltage measurement resistor (22) and a resistor array (23); A first input terminal of the first current mirror (24) is connected to the stimulation input terminal through the voltage measurement resistor (22), a second input terminal of the first current mirror (24) is connected to the stimulation output terminal, an output terminal of the first current mirror (24) is connected to a first input terminal of the second current mirror (25), a second input terminal of the second current mirror (25) is connected to a power supply voltage, and an output terminal of the second current mirror (25) is grounded through the resistor array (23).

7. The impedance measurement circuit according to claim 1, wherein The voltage measurement circuit (2) includes a first current mirror (24), a second current mirror (25), a voltage measurement resistor (22), and a resistor array (23); A first input terminal of the first current mirror (24) is connected to the stimulation output terminal through the voltage measurement resistor (22), a second input terminal of the first current mirror (24) is connected to the stimulation input terminal, an output terminal of the first current mirror (24) is connected to a first input terminal of the second current mirror (25), a second input terminal of the second current mirror (25) is connected to the stimulation output terminal, and an output terminal of the second current mirror (25) is connected to the power supply voltage through the resistor array (23).

8. An impedance measurement method, characterized in that, Applied to the impedance measurement circuit according to any one of claims 1-7, comprising: Closing any two single-pole double-throw switches (3) to form a first loop between the stimulation input terminal and the stimulation output terminal; Switching the two single-pole double-throw switches (3) to form a second loop between the stimulation input terminal and the stimulation output terminal, and the current direction in the second loop is opposite to the current direction in the first loop; Obtaining the voltage change waveform diagrams of the first loop and the second loop; Determining the target impedance value according to the voltage change waveform diagrams.

9. The impedance measurement method according to claim 8, wherein The determining the target impedance value according to the voltage change waveform diagrams includes: Obtaining a first voltage value at a first moment and a second voltage value at a second moment during the voltage rising process in the voltage change waveform diagrams, and the first moment refers to the moment when the step occurs; Obtaining the voltage rising rate according to the first voltage value at the first moment and the second voltage value at the second moment; Determining the target impedance value according to the voltage rising rate and the capacitance value of the DC-blocking capacitor (4) corresponding to the two single-pole double-throw switches (3).

10. The impedance measurement method according to claim 9, wherein, The determining the target impedance value according to the voltage rising rate and the capacitance value of the DC-blocking capacitor (4) corresponding to the two single-pole double-throw switches (3) includes: where t a represents the first moment, t b represents the second moment, V a represents the first voltage value at the first moment, V b represents the second voltage value at the second moment, I represents the stimulation current in the first loop or the second loop, C1 and C2 represent the capacitance values of the DC-blocking capacitors (4) corresponding to the two single-pole double-throw switches (3), and R represents the target impedance value.

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