Peak-hold ac impedance measuring device and impedance measuring method using the same

Abstract

The present application relates to a peak hold type AC impedance measurement device and an impedance measurement method using the same. The peak hold type AC impedance measurement device comprises a digital sine wave generating circuit configured to generate a digital sine voltage signal with adjustable frequency; a digital-to-analog conversion circuit configured to convert the digital sine voltage signal into an analog sine voltage signal; a filter circuit configured to filter the analog sine voltage signal; a coupling capacitor configured to convert an output voltage signal of the filter circuit into a current signal; an amplification circuit configured to amplify the analog sine voltage signal across the impedance to be measured; a peak sampling and holding circuit configured to sample and hold the peak of the amplified analog sine voltage signal; and an analog-to-digital conversion circuit configured to convert the analog sine voltage signal output by the peak sampling and holding circuit into a digital signal, thereby obtaining a final voltage value of the impedance to be measured.

Description

Technical Field

[0001] This invention relates to the field of impedance measurement in implantable neurostimulators, and more particularly to a peak-hold AC impedance measurement device and an impedance measurement method using the device. Background Technology

[0002] In recent years, with the continuous advancement of science and technology, implantable neurostimulators, as a cutting-edge medical device, have received widespread attention and application in the fields of rehabilitation medicine and the diagnosis and treatment of neurological diseases. This device can effectively regulate neuronal activity by sending precise electrical signals to specific nerve fibers, providing a new technological approach for the diagnosis and treatment of related diseases.

[0003] In the structure of an implantable neurostimulator, the impedance measurement circuit plays a core role in acquiring impedance information between electrodes. Its working principle is as follows: after acquiring impedance data from both sides of the electrodes, it compares it with a preset impedance threshold; when the measured impedance value reaches the set standard, the neurostimulation module is triggered to output a constant current, initiating the neurostimulation process; if the measured impedance does not meet the standard, the electrode position or related parameters are automatically adjusted until the stimulation initiation requirements are met.

[0004] In existing technologies, impedance measurement mostly employs direct current (DC) measurement, but this method has significant drawbacks, including considerable damage to human tissue and insufficient measurement accuracy. To avoid excessive stimulation current damaging biological tissue, DC measurements typically use a blocking capacitor to achieve passive charge balance—that is, a large-capacity blocking capacitor is connected in series between the electrode-tissue interface and the stimulator output terminal to isolate the circuit, preventing the current output by the stimulator from directly acting on the electrode-tissue interface. In comparison, alternating current (AC) measurement offers greater safety advantages; furthermore, in AC measurement mode, the impedance of human skin decreases significantly, and its impact is negligible, thus significantly improving the accuracy of impedance measurement.

[0005] However, existing AC impedance measurement circuits still have many shortcomings, generally suffering from complex structures, high costs, and poor linearity. When measuring the AC impedance of blood, a sine wave is required as the excitation signal, necessitating the addition of a sine wave generator to the circuit. However, most existing sine wave generators are complex in structure and have high production costs, further contributing to the high cost of the entire AC impedance measurement circuit. For example, the sine wave generator circuit disclosed in utility model patent application number 201520179843.2, and the related patent technology based on a sine wave generator in application number 201720712565.1, both clearly demonstrate the aforementioned limitations.

[0006] Furthermore, invention patent application number 201610100889.X discloses an impedance measurement method. This method applies a sinusoidal excitation current to both ends of the impedance, converts the sinusoidal voltage across the impedance into a DC value through a shaping and filtering circuit, and then performs analog-to-digital conversion through an analog-to-digital converter circuit to finally obtain the impedance measurement result. This technology is based on a sinusoidal excitation current design of a specific frequency. When facing impedance measurement requirements with different properties and frequency characteristics, it is difficult to achieve flexible adaptation through simple parameter adjustments, thus limiting its applicability.

[0007] In summary, developing low-cost, high-performance AC impedance measurement devices and methods to address the core pain points of existing technologies is of great significance for promoting the large-scale and widespread application of implantable neurostimulators in the medical field.

[0008] The above description of the background technology is only for the purpose of facilitating a deeper understanding of the technical solution of the present invention (the technical means used, the technical problems solved, and the technical effects produced, etc.), and should not be regarded as an admission or in any form an implication that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] This invention aims to propose a peak-hold AC impedance measurement device for implantable neurostimulators and an impedance measurement method using the same device. This technical solution uses AC signals to measure impedance, effectively reducing the risk of damage to human tissues. By outputting a frequency-adjustable sine wave signal, the measurement accuracy and resistance measurement range can be flexibly adjusted, significantly improving measurement adaptability. Simultaneously, the use of digital circuits to generate the sine wave signal, and the signal processing and output using a peak sampling and holding circuit, greatly simplifies the circuit structure, combining ease of implementation and cost advantages, providing an efficient and practical solution for impedance measurement in implantable neurostimulators.

[0010] According to an embodiment of the present invention, a peak-hold AC impedance measuring device is provided, comprising: a digital sine wave generation circuit configured to generate a digital sine wave voltage signal with adjustable frequency; a digital-to-analog converter circuit, the input terminal of which is electrically connected to the output terminal of the digital sine wave generation circuit, the digital-to-analog converter circuit being configured to convert the digital sine wave voltage signal generated by the digital sine wave generation circuit into an analog sine wave voltage signal; a filter circuit, the input terminal of which is electrically connected to the output terminal of the digital-to-analog converter circuit, the filter circuit being configured to filter the analog sine wave voltage signal output by the digital-to-analog converter circuit to generate a filtered analog sine wave voltage signal impedance to be measured; and a coupling capacitor, the first terminal of which is electrically connected to the output terminal of the filter circuit, and the second terminal of which is electrically connected to the first terminal of the impedance to be measured, the coupling capacitor being configured to convert the filtered analog sine wave voltage signal into an analog sine wave voltage signal. A sinusoidal current signal is applied to both ends of the impedance under test; an amplifier circuit is configured to amplify the analog sinusoidal voltage signal across the impedance under test according to a preset amplification factor, and obtain an amplified analog sinusoidal voltage signal; a peak sampling and holding circuit is configured to sample and hold the peak value of the amplified analog sinusoidal voltage signal, with its input terminal electrically connected to the output terminal of the amplifier circuit; and an analog-to-digital converter circuit is configured to convert the analog sinusoidal voltage signal output by the peak sampling and holding circuit into a digital signal, thereby obtaining the final voltage value and impedance value of the impedance under test.

[0011] Preferably, the amplification circuit further includes: a first switch, a second switch, a first blocking capacitor, and a second blocking capacitor; a first terminal of the first switch is electrically connected to the non-inverting input terminal of the amplification circuit, and a second terminal of the first switch is electrically connected to the first terminal of the first blocking capacitor; a first terminal of the second switch is electrically connected to the inverting input terminal of the amplification circuit, and a second terminal of the second switch is electrically connected to the inverting input terminal of the amplification circuit; a second terminal of the first blocking capacitor is electrically connected to the first terminal of the impedance to be measured; and a first terminal of the second blocking capacitor is electrically connected to the second terminal of the impedance to be measured.

[0012] Preferably, the frequency of the digital sinusoidal current signal generated by the digital sine wave generating circuit is controlled by the frequency of the system clock.

[0013] Preferably, the preset amplification factor of the amplifier circuit is selected according to the range of the impedance to be measured.

[0014] According to an embodiment of the present invention, an impedance measurement method using a peak-hold AC impedance measuring device is provided. The peak-hold AC impedance measuring device is the peak-hold AC impedance measuring device according to an embodiment of the present invention. The impedance measurement method includes: turning off the digital sine wave generation circuit, opening the first switch and the second switch, and calculating the offset voltage value of the amplifier circuit using the output voltage of the peak sampling and holding circuit and the common-mode voltage of the amplifier circuit; turning on the digital sine wave generation circuit, closing the first switch and the second switch, and correcting the output value of the amplifier circuit using the offset voltage value of the amplifier circuit, thereby obtaining the final voltage value.

[0015] Preferably, the offset voltage value is obtained by subtracting the common-mode voltage from the output voltage of the peak sampling and holding circuit.

[0016] Preferably, the output value of the amplifier circuit is the value obtained by multiplying the voltage across the impedance to be measured by the amplification factor of the amplifier circuit and then adding it to the common-mode voltage; the voltage across the impedance to be measured is determined based on the filtered analog sinusoidal voltage signal, the frequency of the filtered analog sinusoidal voltage signal, and the capacitance value of the coupling capacitor.

[0017] Preferably, the final voltage value is obtained by sampling the output value of the amplifier circuit through a peak sampling and holding circuit; the corrected final voltage value is obtained by subtracting the offset voltage value from the final voltage value.

[0018] Preferably, the resistance value of the impedance to be measured is obtained using the following formula: V FINAL = V sin × 2πC0f × R0× A V + V CM - V OFFSET , Among them, V FINAL The final corrected voltage value, V sin The signal is a filtered analog sinusoidal voltage signal, f is the frequency of the filtered analog sinusoidal voltage signal, C0 is the capacitance of the coupling capacitor, R0 is the resistance of the impedance to be measured, and A V V is the amplification factor of the amplifier circuit. CM For common-mode voltage, V OFFSET This represents the offset voltage value of the amplifier circuit.

[0019] The present invention adopts the above technical solution, which has the following beneficial effects: The circuit architecture constructed in this invention is simple and compact, which can significantly reduce production costs while ensuring high measurement accuracy and high safety in use. Specifically, by using AC signals for impedance measurement, potential damage to human tissue can be greatly reduced, providing a solid and reliable safety guarantee for medical applications. The peak sampling and holding circuit can accurately acquire the peak value of the sine wave, enabling convenient and efficient acquisition of impedance measurement information and effectively avoiding measurement errors caused by complex signal processing procedures. The application of adjustable frequency sine wave signals allows for flexible adjustment of the measured resistance range, significantly improving measurement accuracy and circuit linearity, and fully meeting the diverse impedance measurement needs in different medical scenarios.

[0020] Furthermore, the peak-hold AC impedance measurement device for implantable neurostimulators provided in this invention, and the impedance measurement method based on this device, have undergone comprehensive pre- and post-simulation verification using EDA software, and have successfully completed tape-out and chip testing. Test data shows that the measured impedance value and the output result exhibit a good linear relationship, and the measurement range and accuracy can be flexibly adjusted by adjusting the sine wave frequency. This result fully demonstrates that the peak-hold AC impedance measurement device for implantable neurostimulators provided in this invention not only possesses good feasibility in impedance measurement but also stably outputs accurate and reliable measurement results, providing stable, efficient, and low-cost technical support for impedance measurement of implantable neurostimulators. Attached Figure Description

[0021] The exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. For clarity, the same components in different drawings are shown with the same reference numerals. It should be noted that the drawings are for illustrative purposes only and are not necessarily drawn to scale. In these drawings: Figure 1 A block diagram illustrating a peak-holding AC impedance measuring device according to an embodiment of the present invention.

[0022] Figure 2 A circuit diagram illustrating a peak-hold AC impedance measuring device according to an embodiment of the present invention is provided.

[0023] Figure 3 The diagram illustrates the measurement results of an impedance measurement method using a peak-hold AC impedance measuring device according to an embodiment of the present invention. Detailed Implementation

[0024] The following provides a detailed description of the embodiments of the present invention. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0025] In the following, embodiments of the invention will be described in detail with reference to the accompanying drawings.

[0026] Figure 1 A block diagram illustrating a peak-hold AC impedance measuring device according to an embodiment of the present invention. See also... Figure 1 According to an embodiment of the present invention, the peak-hold AC impedance measuring device may include a digital sine wave generating circuit 110, a digital-to-analog conversion circuit 120, a filtering circuit 130, a coupling capacitor 140, an amplifier circuit 150, a peak sampling and holding circuit 160, and an analog-to-digital conversion circuit 170.

[0027] The digital sine wave generation circuit 110 can generate a digital sine voltage signal with an adjustable frequency, that is, input the code value of the sine wave to the digital-to-analog converter circuit 120 according to different time intervals.

[0028] According to an embodiment of the present invention, the operating frequency of the digital sine wave generation circuit 110 (i.e., the time interval for generating digital code values ​​of the sine wave) can be controlled by the frequency of the system clock (i.e., the time interval for outputting sine wave code values ​​is different at different system clock frequencies). By adjusting the operating frequency of the digital sine wave generation circuit 110, the frequency of the generated sine wave voltage signal can be changed, thereby obtaining measurement ranges with different accuracies.

[0029] The input terminal of the digital-to-analog converter (DAC) circuit 120 can be electrically connected to the output terminal of the digital sine wave generator circuit 110. The DAC circuit 120 can convert the digital sine wave voltage signal output by the digital sine wave generator circuit 110 into an analog sine wave voltage signal.

[0030] The input terminal of the filter circuit 130 can be electrically connected to the output terminal of the digital-to-analog converter circuit 120. The filter circuit 130 can filter the analog sinusoidal voltage signal output by the digital-to-analog converter circuit 120. Since the output of the digital-to-analog converter circuit 120 is not a smooth sinusoidal signal, it is filtered by the filter circuit 130 to generate a smooth analog sinusoidal voltage signal.

[0031] The first terminal of the coupling capacitor 140 can be electrically connected to the output terminal of the filter circuit 130, and the second terminal of the coupling capacitor 140 can be electrically connected to the first terminal of the impedance to be measured. The coupling capacitor 140 can convert the filtered analog sinusoidal voltage signal into an analog sinusoidal current signal, and apply the analog sinusoidal current signal to both ends of the impedance to be measured (i.e., the two acquisition electrodes of the implanted neurostimulator) to obtain a voltage signal proportional to the impedance to be measured.

[0032] The amplifier circuit 150 can be electrically connected to both ends of the impedance to be measured. The amplifier circuit 150 can amplify the analog sinusoidal voltage signal across the impedance to be measured and obtain the amplified analog sinusoidal voltage signal for subsequent circuits to acquire.

[0033] According to an embodiment of the present invention, the amplification circuit 150 can be configured with different amplification factors, which can be selected according to the range of the measured impedance. Different parts of the human body have significantly different impedances, while the amplitude of the simulated sinusoidal current signal generated in this invention remains consistent. Based on this premise, when measuring parts of the human body with low impedance (such as superficial nerves or small tissue areas), the voltage signal amplitude is low due to the small impedance value. To ensure that the signal strength meets the requirements of subsequent measurements and improves measurement accuracy, a large amplification factor can be used to amplify the signal. When measuring parts of the human body with high impedance (such as deep tissues or large body areas), the voltage signal amplitude is higher due to the larger impedance value. If a large amplification factor is still used, it will cause signal saturation in the back-end circuit, affecting the measurement accuracy. Therefore, the amplification factor needs to be reduced accordingly to ensure that the amplified signal is within the effective processing range of the back-end circuit, thereby achieving accurate amplification and stable measurement.

[0034] The input terminal of the peak sampling and holding circuit 160 can be electrically connected to the output terminal of the amplifier circuit 150. The peak sampling and holding circuit 160 can sample and hold the peak value of the analog sine wave signal amplified by the amplifier circuit 150. The peak value of the sine wave contains information about the measured impedance.

[0035] The input of the analog-to-digital converter (ADC) circuit 170 can be electrically connected to the output of the peak sampling and holding circuit 160. The ADC circuit 170 can convert the analog sine wave signal output by the peak sampling and holding circuit 160 into a digital signal, thereby obtaining the impedance measurement result.

[0036] According to an embodiment of the present invention, a peak-hold AC impedance measuring device generates a frequency-adjustable sinusoidal AC excitation signal through a digital sine wave generation circuit, which is applied to the acquisition electrodes. Since the system formed by the electrodes and surrounding tissue has certain impedance characteristics, a corresponding current response is generated between the electrodes when the AC signal passes through. By measuring the peak value of this response signal, the impedance between the electrodes can be calculated. The peak-hold AC impedance measuring device according to an embodiment of the present invention can perform measurements over a wide frequency range, obtaining more information about the electrode-tissue interface.

[0037] The following describes in detail the circuit diagram of the peak-holding AC impedance measuring device according to an embodiment of the present invention. Figure 2 A circuit diagram illustrating a peak-hold AC impedance measuring device according to an embodiment of the present invention is provided.

[0038] See Figure 2 R0 is the impedance to be measured; C1 and C2 are blocking capacitors, preventing the current output by the stimulator from directly reaching the electrode-tissue interface; S0 and S1 are switching devices, which can be composed of MOS switches; V CM Vp and Vn are the common-mode voltage; Vp and Vn are the non-inverting and inverting input terminals of the amplifier circuit, respectively.

[0039] The circuit is described below from several aspects, including the generation of sinusoidal current, the selection of measurement path, the amplification of impedance information, the sampling of impedance information, and the acquisition of operational amplifier offset voltage.

[0040] 1. Generation of sinusoidal current The analog sinusoidal current can be generated by a digital sine wave generator circuit, a DAC circuit, a filter, and a coupling capacitor C0. The digital sine wave generator circuit, DAC circuit, filter, and coupling capacitor C0 are electrically connected in sequence. The digital sine wave generator circuit inputs the generated sinusoidal voltage signal to the DAC circuit at different time intervals, the time intervals of which can be controlled by the system clock frequency. After the generated sinusoidal voltage signal is input to the DAC circuit, it is converted into an analog sinusoidal voltage signal, which is then input to the filter (e.g., a low-pass filter), thereby outputting a smooth sinusoidal voltage signal. The analog sinusoidal voltage signal is converted into an analog sinusoidal current signal through the coupling capacitor C0, and the frequency of the current is the same as the frequency of the voltage.

[0041] A digital sine wave generation circuit can generate an analog sine wave voltage signal by inputting the digital code value corresponding to the sine wave into a DAC circuit in each clock cycle. By changing the clock cycle of the digital sine wave generation circuit (i.e., the time interval between outputting the sine wave code value is different at different system clock frequencies), the frequency of the sine wave can be changed, thereby changing the frequency of the sine wave voltage signal and obtaining measurement ranges with different accuracies. This digital sine wave generation circuit also features a simpler circuit and lower cost.

[0042] 2. Selection of Measurement Path The measurement path can be selected using a first switch S0 and a second switch S1. The first terminal of the first switch S0 can be electrically connected to the non-inverting input Vp of the amplifier circuit, and the second terminal of the first switch S0 can be electrically connected to the first terminal of the first blocking capacitor C1. The first terminal of the second switch S1 can be electrically connected to the second terminal of the second blocking capacitor C2, and the second terminal of the second switch S1 can be electrically connected to the inverting input of the amplifier circuit. The second terminal of the first blocking capacitor C1 is electrically connected to the first terminal of the impedance to be measured R0. The first terminal of the second blocking capacitor C2 is also electrically connected to the second terminal of the impedance to be measured R0.

[0043] According to an embodiment of the present invention, the opening or closing of the first switch S0 and the second switch S1 can be controlled by a control signal (not shown). When both the first switch S0 and the second switch S1 are closed, it indicates that the impedance is being tested, a sinusoidal current signal is simulating flowing through the path, and a sinusoidal voltage signal is generated across the impedance to be tested.

[0044] 3. Amplification of impedance information The non-inverting input terminal Vp of the amplifier circuit can be electrically connected to the second terminal of the coupling capacitor C0 and the first terminal of the first switch S0. The inverting input terminal Vn of the amplifier circuit can be connected to the second terminal of the second switch S1 and the common-mode voltage Vn. CM Electrical connection.

[0045] In a closed-loop feedback system composed of an amplifier circuit, based on the "virtual short" principle, the voltage Vp at the non-inverting input terminal of the amplifier circuit is approximately equal to the voltage Vn at the inverting input terminal. However, since the sinusoidal current signal output through the coupling capacitor C0 flows through the impedance under test and generates a sinusoidal voltage signal across the impedance under test, there is a voltage difference between the voltage Vp at the non-inverting input terminal and the voltage Vn at the inverting input terminal (i.e., the sinusoidal voltage signal generated by the sinusoidal current signal flowing across the impedance under test). This voltage difference is amplified by the amplifier circuit, and the amplified sinusoidal voltage signal contains information about the impedance under test.

[0046] The amplification factor of the amplifier circuit can be configured using digital signals, allowing for the selection of an appropriate amplification factor based on the range of the impedance to be measured. According to an embodiment of the present invention, to adapt to impedances of different magnitudes, the amplification factor of the amplifier circuit can be flexibly configured using digital signals. Multiple amplification gain levels can be preset, allowing the user to dynamically select the matching amplification factor based on the estimated range of the impedance to be measured. This adaptive adjustment mechanism not only effectively avoids signal saturation distortion caused by excessive amplification but also prevents signal overload caused by insufficient amplification, significantly improving the dynamic range and detection accuracy of the measurement system.

[0047] 4. Sampling of impedance information The peak sampling and holding circuit can be electrically connected to the output of the amplifier circuit and the input of the ADC respectively. It samples and holds the peak value of the voltage across the amplified impedance and then inputs it to the input of the ADC.

[0048] Since the generated sinusoidal current is constant, the larger the impedance value to be measured, the larger the peak value of the sinusoidal voltage generated across the resistor. Therefore, the output of the peak sampling and holding circuit is positively correlated with the impedance to be measured.

[0049] The peak sampling and holding circuit samples the peak value of the sinusoidal voltage of the impedance to be measured after amplification by the amplifier circuit, thus obtaining the sampled voltage. The peak value of the sinusoidal voltage signal contains the impedance information of the impedance to be measured. The sampled voltage is input to the input terminal of the ADC circuit for analog-to-digital conversion, thereby obtaining the voltage value corresponding to the impedance to be measured and the impedance measurement value of the impedance to be measured.

[0050] 5. Acquisition of offset voltage value of amplifier circuit Because the amplifier circuit has an offset voltage, which will cause a certain deviation in the output result, it is necessary to collect the offset voltage value and then subtract the offset voltage value from the impedance measurement result to obtain a more accurate impedance measurement result.

[0051] According to an embodiment of the present invention, the operational amplifier offset voltage value can be acquired as follows: The first switch S0 and the second switch S1 are opened, and the digital sine wave generation circuit is turned off. At this time, the output voltage of the DAC circuit is 0. While the voltages at the two input terminals of the amplifier circuit (non-inverting input Vp and inverting input Vn) should theoretically be equal (virtual short), the actual output may not be zero. Therefore, a small voltage difference (i.e., the offset voltage value V) needs to be applied to the input terminals. OFFSET Only then can the output be zero.

[0052] Because the amplifier circuit has an offset voltage, the non-inverting input Vp is equal to the sum of the inverting input Vn and the offset voltage (Vp = Vn + V). OFFSET At this time, the output voltage V1 is the common-mode voltage V. CM With offset voltage value V OFFSET The sum (V1 = V) CM + V OFFSET According to an embodiment of the present invention, the common-mode voltage V can be subtracted from the output V1 of the peak sampling and holding circuit. CM To obtain the offset voltage value V OFFSET .

[0053] The operation of the peak-hold AC impedance measuring device according to an embodiment of the present invention is described in detail below.

[0054] First, the digital sine wave generation circuit is turned off, and the first switch S0 and the second switch S1 are opened to measure the offset voltage value of the amplifier circuit. At this time, the output after the peak sampling and holding circuit and the analog-to-digital conversion circuit is: V1 = V CM +V OFFSET Thus, the offset voltage value V of the amplifier circuit is obtained. OFFSET .

[0055] Secondly, the digital sine wave generation circuit is turned on, and the first switch S0 and the second switch S1 are connected. The current through the impedance to be measured is: I R = V sin × 2πC0f, where V sin is the filtered analog sinusoidal voltage signal, and f is the frequency of the filtered analog sinusoidal voltage signal.

[0056] The voltage across the impedance to be measured can be expressed as: V R = I R × R0 = V sin × 2πC0f × R0, where R0 is the resistance value of the impedance to be measured.

[0057] The amplifier circuit converts the voltage V across the impedance to be measured. R Amplification: The output of the amplifier circuit is: V O = V R × A V + V CM = V sin × 2πC0f × R0× A V + V CM , where A V V is the amplification factor of the amplifier circuit. CM This is the common-mode voltage.

[0058] The peak sampling and holding circuit outputs a sinusoidal voltage signal V to the amplifier circuit. O If the peak value is sampled, the output result V of the peak sampling and holding circuit will be obtained. O_MAX The sinusoidal voltage signal V O The peak value of V can be seen from this. O_MAX It is directly proportional to the resistance value R0 of the impedance to be measured.

[0059] By V O_MAX With offset voltage value V OFFSET Subtraction is used to correct the error in the amplifier circuit. The final corrected voltage value is: V FINAL = V O_MAX - V OFFSET = V sin × 2πC0f × R0× A V + V CM - V OFFSET .

[0060] Finally, the corrected final voltage value V FINAL The signal is converted into a digital voltage signal by an ADC circuit.

[0061] After measuring VFINAL Then, substituting this into the formula above, we can obtain the resistance value of the impedance to be measured, R0.

[0062] The peak-hold AC impedance measurement device and method according to the embodiments of the present invention underwent comprehensive pre-simulation and post-simulation verification using EDA software, and fabrication and chip testing were completed. Test data show that the impedance under test exhibits a good linear relationship with the output result, and the measurement range and accuracy can be flexibly adjusted by adjusting the sine wave frequency.

[0063] Figure 3 The diagram illustrates the measurement results of an impedance measurement method using a peak-hold AC impedance measuring device according to an embodiment of the present invention.

[0064] See Figure 3 This diagram illustrates the test results under different excitation frequencies. Three different frequencies were selected for testing: f1 = 10kHz (measurement results are marked with diamonds), f2 = 8kHz (measurement results are marked with squares), and f3 = 15kHz (measurement results are marked with triangles). The resistance value of the impedance under test is plotted on the x-axis, and the corresponding output result (e.g., the output code value of the ADC) is plotted on the y-axis.

[0065] The test conditions were set to an 8V DC power supply. Resistors of varying resistance values ​​were inserted between the electrodes to measure linearity, and the frequency was changed to test the differences at different frequencies. Each value was measured twice and the average value was taken. Figure 3 It can be seen that under the excitation of sinusoidal waves of different frequencies, the output signal and the impedance value are linearly related, thus verifying the measurement accuracy of the measuring device.

[0066] The above results fully demonstrate that the peak-hold AC impedance measurement device and method according to the embodiments of the present invention have good feasibility in impedance measurement, can output accurate and reliable measurement results, and provide stable and efficient technical support for impedance measurement of implantable neurostimulators.

[0067] The various embodiments of the present invention are not an exhaustive list of all possible combinations, but are intended to describe representative aspects of the invention, and the contents described in the various embodiments can be applied independently or in two or more combinations.

[0068] The description of the exemplary embodiments presented above is merely illustrative of the technical solutions of the present invention and is not intended to be exhaustive, nor is it intended to limit the invention to the precise forms described. Obviously, those skilled in the art can make many changes and variations based on the above teachings. The exemplary embodiments were chosen and described to explain the specific principles of the invention and its practical application, thereby enabling others skilled in the art to understand, implement, and utilize the various exemplary embodiments of the invention and their various alternatives and modifications. The scope of protection of the present invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A peak-hold AC impedance measuring device, comprising: A digital sine wave generating circuit is configured to generate a digital sine voltage signal with an adjustable frequency; A digital-to-analog converter circuit, the input terminal of which is electrically connected to the output terminal of a digital sine wave generating circuit, the digital-to-analog converter circuit being configured to convert the digital sine wave voltage signal generated by the digital sine wave generating circuit into an analog sine wave voltage signal; A filtering circuit, the input of which is electrically connected to the output of a digital-to-analog converter circuit, is configured to filter the analog sinusoidal voltage signal output by the digital-to-analog converter circuit to generate a filtered analog sinusoidal voltage signal impedance to be measured. A coupling capacitor, the first end of which is electrically connected to the output terminal of the filter circuit, and the second end of which is electrically connected to the first terminal of the impedance to be measured, is configured to convert the filtered analog sinusoidal voltage signal into an analog sinusoidal current signal and apply the analog sinusoidal current signal to both ends of the impedance to be measured. An amplifier circuit is provided, wherein its non-inverting input terminal is electrically connected to the first terminal of the impedance to be measured, and its inverting input terminal is electrically connected to the second terminal of the impedance to be measured. The amplifier circuit is configured to amplify the analog sinusoidal voltage signals at both ends of the impedance to be measured according to a preset amplification factor, and obtain the amplified analog sinusoidal voltage signals. The peak sampling and holding circuit has its input terminal electrically connected to the output terminal of the amplifier circuit. The peak sampling and holding circuit is configured to sample and hold the peak value of the amplified analog sinusoidal voltage signal. An analog-to-digital converter circuit is electrically connected to the output of a peak sampling and holding circuit. The analog-to-digital converter circuit is configured to convert the analog sinusoidal voltage signal output by the peak sampling and holding circuit into a digital signal, thereby obtaining the final voltage value and impedance value of the impedance to be measured.

2. The peak-hold AC impedance measuring device according to claim 1, wherein, The amplifier circuit further includes: a first switch, a second switch, a first blocking capacitor, and a second blocking capacitor. The first terminal of the first switch is electrically connected to the non-inverting input terminal of the amplifier circuit, and the second terminal of the first switch is electrically connected to the first terminal of the first blocking capacitor. The first terminal of the second switch is electrically connected, and the second terminal of the second switch is electrically connected to the inverting input terminal of the amplifier circuit; The second terminal of the first blocking capacitor is electrically connected to the first terminal of the impedance to be measured. The first terminal of the second blocking capacitor is electrically connected to the second terminal of the impedance to be measured.

3. The peak-hold AC impedance measuring device according to claim 1, wherein, The frequency of the digital sinusoidal current signal generated by the digital sine wave generation circuit is controlled by the frequency of the system clock.

4. The peak-hold AC impedance measuring device according to claim 1, wherein, The preset amplification factor of the amplifier circuit is selected according to the range of the impedance to be measured.

5. An impedance measurement method using a peak-hold AC impedance measuring device, wherein the peak-hold AC impedance measuring device is the peak-hold AC impedance measuring device according to any one of claims 1 to 4, and the impedance measurement method comprises: The digital sine wave generation circuit is turned off, the first and second switches are opened, and the offset voltage of the amplifier circuit is calculated using the output voltage of the peak sampling and holding circuit and the common-mode voltage of the amplifier circuit. Turn on the digital sine wave generating circuit, connect the first and second switches, and use the offset voltage value of the amplifier circuit to correct the output value of the amplifier circuit, thereby obtaining the final voltage value.

6. The impedance measurement method using a peak-hold AC impedance measuring device according to claim 5, wherein, The offset voltage value is obtained by subtracting the common-mode voltage from the output voltage of the peak sampling and holding circuit.

7. The impedance measurement method using a peak-hold AC impedance measuring device according to claim 6, wherein, The output value of the amplifier circuit is obtained by multiplying the voltage across the impedance to be measured by the amplification factor of the amplifier circuit and then adding it to the common-mode voltage. The voltage across the impedance to be measured is determined based on the filtered analog sinusoidal voltage signal, the frequency of the filtered analog sinusoidal voltage signal, and the capacitance value of the coupling capacitor.

8. The impedance measurement method using a peak-hold AC impedance measuring device according to claim 7, wherein, The final voltage value is obtained by sampling the output value of the amplifier circuit through a peak sampling and holding circuit; The corrected final voltage value is obtained by subtracting the offset voltage value from the final voltage value.

9. The impedance measurement method using a peak-hold AC impedance measuring device according to claim 8, wherein, The resistance value of the impedance to be measured can be obtained using the following formula: V FINAL = V sin × 2πC0f × R0× A V + V CM - V OFFSET , Among them, V FINAL The final corrected voltage value, V sin The signal is a filtered analog sinusoidal voltage signal, f is the frequency of the filtered analog sinusoidal voltage signal, C0 is the capacitance of the coupling capacitor, R0 is the resistance of the impedance to be measured, and A V V is the amplification factor of the amplifier circuit. CM For common-mode voltage, V OFFSET This represents the offset voltage value of the amplifier circuit.

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