A transcranial micro-current stimulation device based on digital PI control

Abstract

The application discloses a transcranial micro-current stimulation device based on digital PI control, which comprises a feedback module, a power supply module, an interaction module, a current source module and a control module; the input end of the feedback module is connected with a load, the output end of the feedback module is connected with the control module, and the feedback module is used for converting output current flowing through the load into feedback voltage; the control module is connected with the control end of the current source module, and is used for adjusting the reference voltage of the current source module according to the feedback voltage output by the feedback module; the output end of the current source module is connected with the load, and is used for outputting stimulation current corresponding to the reference voltage to the load; the control module is connected with the interaction module, is used for detecting the triggering state of three function switches, is used for detecting the instruction of three knobs, and is used for display; the power supply module is connected with the interaction module, the control module, the feedback module and the current source module respectively, and is used for providing corresponding power supply voltage to each module; the control module is connected with a boost chip in the current source module power supply unit of the power supply module, and is used for closing the current source module power supply when the feedback voltage exceeds a preset safety threshold. The application can provide stable stimulation current to the load without pre-measuring the load impedance and without taking the load impedance as an input parameter of the digital PI control algorithm, and can reduce the influence of sampling noise on output control precision without setting an independent hardware noise reduction module.

Description

Technical Field

[0001] This invention relates to a transcranial microcurrent stimulation device based on digital PI control, belonging to the technical field of intelligent electrical stimulation devices, specifically a transcranial microcurrent stimulation device. Background Technology

[0002] Transcranial microcurrent stimulation (TCMS) devices modulate the excitability of brain nerves by applying weak electrical currents to the head. They are widely used to treat certain common mental disorders and neurological diseases, achieving some clinical efficacy. This non-invasive or minimally invasive treatment method reduces patient risks and discomfort. Furthermore, the intensity and duration of current stimulation can be adjusted according to the severity of the patient's condition; therefore, TMS devices are widely used in clinical research and experiments.

[0003] A search revealed Chinese patent application publication number CN118022173A, which discloses a transcranial microcurrent stimulation device and control method, comprising an impedance detection module, a current source, and a noise reduction module. The impedance detection module detects the bioimpedance of the human head, the control module adjusts the output voltage of the microcurrent stimulation device based on the device's operating parameters and the detection results, and the noise reduction module reduces current fluctuations caused by external noise.

[0004] However, the equivalent load impedance between the human head and the stimulation electrodes is easily affected by factors such as electrode fit, skin condition, and the stimulation process. When using impedance detection results in stimulation output control, a corresponding impedance detection circuit needs to be set up, and the load impedance needs to be measured or calculated; impedance measurement errors and impedance changes may further affect the output control quantity determined based on impedance. At the same time, setting up independent impedance detection and noise reduction modules will increase the number of functional modules, hardware complexity, and development costs of the device. Therefore, how to enable the device to provide a stable and accurate stimulation current to the load without using the pre-measured or calculated value of the load impedance as the basis for stimulation current control is a technical problem that needs to be solved in this field. Summary of the Invention

[0005] To address the problems of existing transcranial microcurrent stimulation (TCMS) devices requiring load impedance detection and incorporating the impedance detection results into stimulation output control, which leads to the control process being affected by impedance measurement errors and impedance variations, and the increased hardware complexity and development costs resulting from setting up independent impedance detection and noise reduction modules, this invention provides a TMS device based on digital PI control. This invention uses a feedback module to collect the output current flowing through the load in real time and convert it into a feedback voltage. The control module performs mean filtering on the feedback voltage, compares the filtered feedback voltage with the target feedback voltage corresponding to the target output current, and performs digital PI calculations based on the deviation between the two to adjust the reference voltage of the current source module in a closed loop. Therefore, it eliminates the need to pre-measure the load impedance or use the load impedance as an input parameter for the digital PI control algorithm, providing a stable stimulation current to the load and reducing the impact of sampling noise on output control accuracy without the need for an independent hardware noise reduction module.

[0006] The technical solution of this invention is:

[0007] A transcranial microcurrent stimulation device based on digital PI control includes: a feedback module, a power supply module, an interaction module, a current source module, and a control module;

[0008] The input terminal of the feedback module is connected to the load, and the output terminal of the feedback module is connected to the control module, which is used to convert the output current flowing through the load into a feedback voltage.

[0009] The control module is connected to the control terminal of the current source module and is used to adjust the reference voltage of the current source module according to the feedback voltage output by the feedback module; the output terminal of the current source module is connected to the load and is used to output a stimulation current corresponding to the reference voltage to the load.

[0010] The control module is connected to the interaction module and is used to detect the trigger status of the three function switches, detect the commands of the three knobs, and display them.

[0011] The power supply module is connected to the interaction module, control module, feedback module and current source module respectively, and is used to provide corresponding power supply voltage to each module; the control module is connected to the boost chip in the current source module power supply unit of the power supply module, and is used to shut off the power supply of the current source module when the feedback voltage exceeds a preset safety threshold.

[0012] Furthermore, the feedback module includes a sampling resistor and an instrumentation amplifier; the sampling resistor is connected in series at the low end of the load to convert the output current into a sampling voltage; the input terminal of the instrumentation amplifier is connected to the sampling resistor, and the output terminal of the instrumentation amplifier is connected to the feedback ADC terminal of the control module to amplify the sampling voltage to form a feedback voltage.

[0013] Furthermore, the interactive module includes an LCD screen, a Set function switch, a Start function switch, a Toggle function switch, and three knobs; the Set function switch, the Toggle function switch, and the three knobs are used in conjunction to adjust the first stimulation parameter and the second stimulation parameter; the LCD screen is connected to the control module via an SPI bus.

[0014] Furthermore, the Set function switch, Toggle function switch, and three knobs are used in conjunction to adjust the first stimulation parameter and the second stimulation parameter.

[0015] With the Start function switch released, press the Set function switch and use knobs 1, 2, and 3 to enter the first stimulation parameter adjustment mode: Knob 2 is used to coarsely adjust the stimulation current amplitude, with an adjustment range of 50μA to 1.65mA, and the step size is set to the first step; Knob 1 is used to finely adjust the stimulation current amplitude, with an adjustment range of 1μA to 50μA, and the step size is set to the second step, where the first step is larger than the second step; the stimulation current amplitude in the first stimulation parameter is set to the sum of the coarse and fine stimulation current amplitudes; Knob 3 is used to set the stimulation frequency in the first stimulation parameter, with an adjustment range of 10 Hz to 1kHz, and the step size is set to the third step.

[0016] With the Start function switch released, pressing the Toggle function switch will cause knobs 2 and 3 to enter the second stimulation parameter adjustment mode: knob 3 is used to adjust the total stimulation time, which is the second stimulation parameter; knob 2 is used to adjust the stimulation interval, which is adjusted from 10 min to 1 h, and the stimulation interval step size is set to the fourth step size.

[0017] Furthermore, the power supply module includes a power input unit, a control module power supply unit, a feedback module power supply unit, and a current source module power supply unit; the power input unit regulates VBAT to VCC5V; the control module power supply unit regulates VBAT to VCC3.3V to supply power to the control module and the interaction module; the feedback module power supply unit converts VBAT to VCC3.3V, and boosts VCC3.3V to VCC10V and VEE-10V to supply power to the feedback module; the current source module power supply unit boosts VCC5V to VCC15V, and after regulation, generates VCC12V, and VCC15V and VCC12V supply power to the current source module.

[0018] Furthermore, the current source module includes an operational amplifier constant current circuit and a Wilson current mirror circuit. The operational amplifier constant current circuit includes an OPA type operational amplifier, an NPN type transistor, resistors, and potentiometers. The control terminal of the operational amplifier constant current circuit is connected to the DAC terminal of the control module to convert the DAC output reference voltage into a reference current. The Wilson current mirror circuit consists of two voltage divider resistors and three PNP type transistors. The input terminal of the Wilson current mirror circuit is connected to the output terminal of the operational amplifier constant current circuit, and the output terminal of the Wilson current mirror circuit is connected to the load to mirror the reference current into a stimulation current. The relationship between the relative error between the reference current and the stimulation current and the current amplification factor of the PNP type transistor in the Wilson current mirror circuit is as follows:

[0019] ;

[0020] In the formula, The relative error between the reference current and the stimulation current, This represents the current amplification factor of the PNP transistor in the current source module.

[0021] Furthermore, the control module includes an STM32 microcontroller, a reset circuit, and a clock circuit; the STM32 microcontroller detects the Set, Start, and Toggle function switches in the interactive module through three external interrupt input terminals, and collects the commands of the three knobs in the interactive module through three parameter ADC terminals to complete the adjustment of the first stimulation parameter and the second stimulation parameter.

[0022] Furthermore, the STM32 microcontroller acquires the feedback voltage output by the feedback module through the ADC terminal, and directly filters the feedback voltage using a mean filtering algorithm to obtain the filtered voltage.

[0023] The STM32 microcontroller compares the filtered voltage with the target feedback voltage corresponding to the target output current, and directly calculates the DAC output reference voltage through a digital PI control algorithm.

[0024] The beneficial effects of this invention are as follows: This invention generates a stimulation current through an operational amplifier constant current circuit and a Wilson current mirror, which can reduce the impact of load impedance changes and ambient temperature changes on the stimulation current within the allowable load range of the current source module. The feedback module collects the output current flowing through the load in real time and converts it into a feedback voltage. The control module performs mean filtering on the feedback voltage, compares the filtered feedback voltage with the target feedback voltage corresponding to the target output current, and performs digital PI calculation based on the deviation between the two to achieve closed-loop adjustment of the reference voltage of the current source module. Therefore, this invention eliminates the need to pre-measure the load impedance or use the load impedance as an input parameter for the digital PI control algorithm to perform closed-loop correction of the reference voltage, improving the stability and output accuracy of the stimulation current. Compared with schemes that require independent impedance detection modules and hardware noise reduction modules, this invention reduces the number of functional modules and components, simplifying the hardware structure and reducing equipment development costs. Furthermore, the current source module uses an independent power supply, and the control module can shut off the power supply to the current source module via the EN1 terminal when an abnormal feedback voltage is detected, thus terminating the stimulation current output in a timely manner and improving the safety of the equipment. Attached Figure Description

[0025] Figure 1 This is a structural block diagram of the transcranial microcurrent stimulation device of the present invention;

[0026] Figure 2 This is a circuit diagram of the power supply module in this invention;

[0027] Figure 3 This is a circuit diagram showing the connection of the control module, feedback module, current source module, and interaction module in this invention.

[0028] Figure 4 The results of the analysis on the impact of different loads and different ambient temperatures on the output of the current source module in the embodiment of the present invention;

[0029] Figure 5 The actual measurement results output by the device in this embodiment of the invention are shown. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of this application can be arbitrarily combined with each other.

[0031] Example 1: As Figures 1 to 5As shown, a transcranial microcurrent stimulation device based on digital PI control includes a feedback module, a power supply module, an interaction module, a current source module, and a control module.

[0032] The input terminal of the feedback module is connected to the load (human head) via a patch electrode, and the output terminal of the feedback module is connected to the feedback ADC terminal of the control module, which is used to convert the output current flowing through the load into a feedback voltage.

[0033] The DAC terminal of the control module is connected to the control terminal of the current source module and is used to adjust the reference voltage of the current source module according to the feedback voltage output by the feedback module; the output terminal of the current source module is connected to the load through a patch electrode and is used to output a stimulation current corresponding to the reference voltage to the load.

[0034] The control module is connected to the interaction module. It detects the trigger status of the three function switches through three external interrupt input terminals, detects the commands of the three knobs through three parameter ADC terminals, and is connected to the LCD screen of the interaction module through the SPI bus. The three function switches are Set function switch, Start function switch, and Toggle function switch.

[0035] The power supply module is connected to the interaction module, control module, feedback module and current source module respectively, and is used to provide corresponding power supply voltage to each module; the EN1 terminal of the control module is connected to the EN terminal of the boost chip in the power supply unit of the current source module of the power supply module, and is used to shut off the power supply of the current source module when the feedback voltage exceeds a preset safety threshold.

[0036] Furthermore, the feedback module includes a sampling resistor and an instrumentation amplifier; the sampling resistor is connected in series at the low end of the load to convert the output current into a sampling voltage; the input terminal of the instrumentation amplifier is connected to the sampling resistor, and the output terminal of the instrumentation amplifier is connected to the feedback ADC terminal of the control module to amplify the sampling voltage to form a feedback voltage.

[0037] Furthermore, the interactive module includes an LCD screen, a Set function switch, a Start function switch, a Toggle function switch, and three knobs. The Set function switch, Toggle function switch, and three knobs are used in conjunction to adjust the first stimulation parameter and the second stimulation parameter. The LCD screen is connected to the control module via an SPI bus and is used to display the stimulation current amplitude, stimulation frequency, total stimulation time, and device operating status. In the above, the first stimulation parameter can be the stimulation current amplitude or stimulation frequency, and the second stimulation parameter is the total stimulation time.

[0038] Furthermore, the Set function switch, Toggle function switch, and three knobs are used in conjunction to adjust the first stimulation parameter and the second stimulation parameter.

[0039] With the Start function switch released, press the Set function switch and use knobs 1, 2, and 3 to enter the first stimulation parameter adjustment mode: Knob 2 is used to coarsely adjust the stimulation current amplitude, with an adjustment range of 50μA to 1.65 mA, and the step size is set to the first step; Knob 1 is used to finely adjust the stimulation current amplitude, with an adjustment range of 1μA to 50μA, and the step size is set to the second step, where the first step is larger than the second step; the stimulation current amplitude in the first stimulation parameter is set to the sum of the coarse-adjusted stimulation current amplitude and the fine-adjusted stimulation current amplitude; Knob 3 is used to set the stimulation frequency in the first stimulation parameter, with an adjustment range of 10 Hz to 1kHz, and the step size is set to the third step.

[0040] With the Start function switch released, pressing the Toggle function switch will cause knobs 2 and 3 to enter the second stimulation parameter adjustment mode: knob 3 is used to adjust the total stimulation time, which is the second stimulation parameter; knob 2 is used to adjust the stimulation interval, which is adjusted from 10 min to 1 h, and the stimulation interval step size is set to the fourth step size.

[0041] Furthermore, the power supply module includes a power input unit, a control module power supply unit, a feedback module power supply unit, and a current source module power supply unit; the power input unit regulates VBAT to VCC5V; the control module power supply unit regulates VBAT to VCC3.3V to supply power to the control module and the interaction module; the feedback module power supply unit converts VBAT to VCC3.3V, and boosts VCC3.3V to VCC10V and VEE-10V to supply power to the feedback module; the current source module power supply unit boosts VCC5V to VCC15V, and after regulation, generates VCC12V, which supplies power to the current source module; F1 is a self-resetting fuse connected in series between VBAT and the control module power supply unit for overcurrent protection and is not used as an operating switch for the equipment.

[0042] Furthermore, the current source module includes an operational amplifier constant current circuit and a Wilson current mirror circuit. The operational amplifier constant current circuit includes an OPA type operational amplifier, an NPN type transistor, resistors, and potentiometers. The control terminal of the operational amplifier constant current circuit is connected to the DAC terminal of the control module to convert the DAC output reference voltage into a reference current. The Wilson current mirror circuit consists of two voltage divider resistors and three PNP type transistors. The input terminal of the Wilson current mirror circuit is connected to the output terminal of the operational amplifier constant current circuit, and the output terminal of the Wilson current mirror circuit is connected to the load to mirror the reference current into a stimulation current. The relationship between the relative error between the reference current and the stimulation current and the current amplification factor of the PNP type transistor in the Wilson current mirror circuit is as follows:

[0043] ;

[0044] In the formula, The relative error between the reference current and the stimulation current, This represents the current amplification factor of the PNP transistor in the current source module. From this relationship, it can be seen that selecting a PNP transistor with a larger current amplification factor can reduce current image error and improve the accuracy of the output current.

[0045] Furthermore, the control module includes an STM32 microcontroller, a reset circuit, and a clock circuit; the STM32 microcontroller detects the Set, Start, and Toggle function switches through three external interrupt input terminals, and collects the commands of the three knobs through three parameter ADC terminals to complete the setting of the stimulation current amplitude, stimulation frequency, and total stimulation time parameters.

[0046] Furthermore, the STM32 microcontroller acquires the feedback voltage output by the feedback module through the ADC terminal, and directly filters the feedback voltage using a mean filtering algorithm, as follows:

[0047] ;

[0048] In the formula, For the first The filtered voltage obtained from the calculation. This represents the number of sampling points within the mean filtering window. To find the summation index, For the first The feedback voltage obtained from the first acquisition.

[0049] The control module compares the filtered voltage with the target feedback voltage corresponding to the target output current, and directly calculates the DAC output reference voltage using a digital PI control algorithm, as follows:

[0050] ;

[0051] In the formula, For the first The integral term obtained from this calculation The integral coefficient is... For the first During the secondary control calculation, the target feedback voltage corresponding to the target output current is calculated, and , This represents the amplification factor of the operational amplifier in the current source module. The resistance value of the sampling resistor in the feedback module. To set the current flowing through the sampling resistor (i.e., the target output current), The sampling time interval between two adjacent control calculations. For the first The reference voltage output from the DAC terminal obtained from this calculation. This is the proportionality coefficient.

[0052] The control module is also used to monitor whether the output current is abnormal. When the feedback voltage collected by the feedback ADC exceeds the preset safety threshold, the control module immediately sets the EN1 terminal to a low level, causing the boost chip in the current source module power supply unit to stop working, thereby terminating the output current.

[0053] As can be seen from the above technical solution, the operator inputs stimulation parameters through the interactive module, and the control module generates a reference voltage accordingly; the DAC terminal of the control module outputs the reference voltage to the current source module, and the current source module outputs stimulation current to the load; the feedback module collects the output current flowing through the load, converts it into a feedback voltage, and sends it to the feedback ADC terminal of the control module; the control module updates the DAC output after performing mean filtering and digital PI calculation on the feedback voltage in the voltage domain, and then... The linear relationship forms an equivalent closed-loop control of the output current. The control module sends the stimulation current amplitude, stimulation frequency, total stimulation time, and device operating status to the LCD screen via the SPI bus. The power supply module supplies power to each module separately, with the current source module using an independent power supply unit. The control module can quickly shut down this power supply unit in case of an abnormality via the EN1 pin. The specific circuit is as follows: Figure 2 As shown.

[0054] In a specific embodiment, the interactive module's LCD screen uses a 12864 LCD, and all three knobs are potentiometers; the control module uses an STM32F103RCT6 microcontroller. The LCD screen is connected to the control module via an SPI bus; the Set, Start, and Toggle function switches are connected to three external interrupt inputs respectively; the three potentiometers are connected to three parameter ADCs respectively; the feedback module output is connected to the feedback ADC; the control module's DAC is connected to the current source module control; and the control module's EN1 is connected to the EN terminal of the boost chip in the current source module's power supply unit.

[0055] Figure 3In the current source module, the control and interaction modules are powered by VCC 3.3V; the VSS of the OPA277UA in the current source module is connected to GND, and the VDD is connected to VCC 15V; the upper common power supply node of the PNP transistor in the Wilson current mirror circuit is connected to VCC 12V; the VDD of the INA129U in the feedback module is connected to VCC 10V, and the VSS is connected to VEE-10V. In the current source module, the resistance of potentiometer R11 is 20kΩ, the resistance of resistor R2 is 10kΩ, the resistance of resistor R3 is 2kΩ, and the NPN transistor Q1 is BC846C; the resistance of voltage divider resistors R4 and R5 is 1kΩ each, and the PNP transistors Q2, Q3, and Q4 are all BC857C, with the collector of Q4 connected to the load. In the feedback module, the gain setting resistor R7 of INA129U is 2.6 kΩ, the gain G of the operational amplifier INA129U is 20, and the sampling resistor Rs is 100Ω; the upper end of Rs is connected to the load, and the lower end is grounded, forming a low-end sampling circuit.

[0056] The specific operation method of the transcranial microcurrent stimulation device in this embodiment is as follows:

[0057] First, the external DC power supply is connected to the power supply module through DC1 to form VBAT; after VBAT generates various power supply voltages through the F1 self-resetting fuse and each voltage regulator and boost unit, the equipment is powered on and started. Figure 2 The circuit shown does not have a separate power button; F1 is used for overcurrent protection. After the device is started, the LCD screen of the interactive module displays the current stimulation current amplitude, stimulation frequency, total stimulation time, and device operating status.

[0058] With the Start function switch released, press the Set function switch and use knobs 1, 2, and 3 to enter the first stimulation parameter adjustment mode: Knob 2 is used to coarsely adjust the stimulation current amplitude, with an adjustment range of 50μA to 1.65 mA and a step size of 50μA; Knob 1 is used to finely adjust the stimulation current amplitude, with an adjustment range of 1μA to 50μA and a step size of 1μA; the stimulation current amplitude in the first stimulation parameter is set to be the sum of the coarse-adjusted stimulation current amplitude and the fine-adjusted stimulation current amplitude; Knob 3 is used to set the stimulation frequency in the first stimulation parameter, with an adjustment range of 10 Hz to 1kHz and a step size of 10Hz.

[0059] With the Start function switch released, pressing the Toggle function switch will activate knobs 2 and 3 to enter the second stimulation parameter adjustment mode: knob 3 is used to adjust the total stimulation time, which is the second stimulation parameter; knob 2 is used to adjust the stimulation interval, which ranges from 10 min to 1 h, with a step size of 5 min.

[0060] After setting the parameters for the first and second stimulation parameter adjustment modes, press the Start function switch to activate the stimulation current output. At this time, the interactive module exits the parameter setting mode, and the three knobs are locked. The parameters can be reset by releasing the Start function switch and then pressing the Set function switch. During stimulation, the LCD screen displays the first and second stimulation parameters and the device operating status in real time (for example, the device operating status can be the device start / stop status; pressing the Start function switch displays "start," and releasing the Start function switch displays "stop").

[0061] To verify the effectiveness of the current source module proposed in this invention, the output of the current source module in the above embodiments can be scanned with a load resistance of 100Ω-20KΩ and a temperature of 0-100℃ using simulation software (e.g., PSpice). Figure 4 The top left figure shows the scan results of the actual output with load resistance changes when the target output current is 50μA. It can be seen that the current source module output value only produces a small error during external load changes, with the maximum output error at 20KΩ being only -0.3285μA (relative error approximately 0.657%). The bottom left figure shows the scan results of the actual output with temperature changes when the target output current is 50μA. It can be seen that the maximum output error caused by ambient temperature changes within 0℃-100℃ is only -0.34μA (relative error approximately 0.68%). The top right figure shows the scan results of the actual output with load resistance changes when the target output current is 1.65mA. It can be seen that the circuit scheme in the above embodiment can drive a maximum load resistance of approximately 6.1K ohms, after which the output will rapidly decrease. However, research shows that the equivalent impedance of the human brain is within 5KΩ, which is consistent with practical application ranges. The lower right figure shows the actual output variation with temperature at a target output current of 1.65mA. It can be observed that the maximum error is only 0.925μA (relative error of approximately 0.058%). These simulation results demonstrate that the current source module involved in this invention can meet application requirements.

[0062] Furthermore, an actual transcranial microcurrent stimulation device was constructed according to the component parameters in the embodiment, and the input and output of pulsed stimulation signals were tested at room temperature. The test results are shown in [the table / document / etc.]. Figure 5 In the test, the input signal test point is the DAC point of the current source module, and the output test point is the ADC point of the feedback module. The figure above shows the open-loop test results with a load resistance of 5KΩ, a target output current amplitude of 50μA, and a stimulation frequency of 1KHz. =20 * 100Ω * 50μA = 100mV. The maximum voltage after filtering is 106mV. It can be seen that the environmental electromagnetic interference has the greatest impact, causing a 6mV error, corresponding to a 3μA output current error. The figure below shows the open-loop test results with a load resistance of 5KΩ, a target output current amplitude of 1.65mA, and a stimulation frequency of 5Hz. =20 * 100Ω * 1.65mA = 3.3V. The maximum voltage after filtering is 3.36V. It can be seen that the environmental electromagnetic interference has the greatest impact, causing an error of 0.06V, corresponding to an output current error of 30μA. This shows that the output error can be reduced by adjusting the PI algorithm in the control module. Furthermore, the circuit performance can be further optimized by improving the PCB layout or adding an electromagnetic interference shielding layer to ensure the final output accuracy.

[0063] The specific embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A transcranial microcurrent stimulation device based on digital PI control, characterized in that, It includes a feedback module, a power supply module, an interaction module, a current source module, and a control module; The input terminal of the feedback module is connected to the load, and the output terminal of the feedback module is connected to the control module, which is used to convert the output current flowing through the load into a feedback voltage. The control module is connected to the control terminal of the current source module and is used to adjust the reference voltage of the current source module according to the feedback voltage output by the feedback module; the output terminal of the current source module is connected to the load and is used to output a stimulation current corresponding to the reference voltage to the load. The control module is connected to the interaction module and is used to detect the trigger status of the function switch, detect the command of the knob, and display the information. The power supply module is connected to the interaction module, control module, feedback module and current source module respectively, and is used to provide corresponding power supply voltage to each module; the control module is connected to the boost chip in the current source module power supply unit of the power supply module, and is used to shut off the power supply of the current source module when the feedback voltage exceeds a preset safety threshold.

2. The transcranial microcurrent stimulation device based on digital PI control according to claim 1, characterized in that, The feedback module includes a sampling resistor and an instrumentation amplifier; the sampling resistor is connected in series with the low end of the load to convert the output current into a sampling voltage; the input terminal of the instrumentation amplifier is connected to the sampling resistor, and the output terminal of the instrumentation amplifier is connected to the feedback ADC terminal of the control module to amplify the sampling voltage to form a feedback voltage.

3. The transcranial microcurrent stimulation device based on digital PI control according to claim 1, characterized in that, The interactive module includes an LCD screen, a Set function switch, a Start function switch, a Toggle function switch, and three knobs; the Set function switch, Toggle function switch, and three knobs are used in conjunction to adjust the first stimulation parameter and the second stimulation parameter; the LCD screen is connected to the control module via an SPI bus.

4. The transcranial microcurrent stimulation device based on digital PI control according to claim 3, characterized in that, The Set and Toggle function switches, along with the three knobs, are used to adjust the first and second stimulation parameters. With the Start function switch released, press the Set function switch and enter the first stimulation parameter adjustment mode according to knobs 1, 2 and 3: knob 2 is used to coarsely adjust the stimulation current amplitude, the coarse adjustment stimulation current amplitude adjustment range is 50μA~1.65mA, and the coarse adjustment stimulation current amplitude step size is set to the first step size; Knob 1 is used to fine-tune the amplitude of the stimulation current. The adjustment range of the amplitude of the stimulation current is 1μA to 50μA. The step size of the amplitude of the stimulation current is set to the second step size, and the first step size is greater than the second step size. The amplitude of the stimulation current in the first stimulation parameter is set to be the sum of the amplitude of the coarse stimulation current and the amplitude of the fine stimulation current. Knob 3 is used to set the stimulation frequency in the first stimulation parameter. The adjustment range of the stimulation frequency is 10 Hz to 1kHz. The step size of the stimulation frequency is set to the third step size. With the Start function switch released, pressing the Toggle function switch will cause knobs 2 and 3 to enter the second stimulation parameter adjustment mode: knob 3 is used to adjust the total stimulation time, which is the second stimulation parameter; knob 2 is used to adjust the stimulation interval, which is adjusted from 10 min to 1 h, and the stimulation interval step size is set to the fourth step size.

5. The transcranial microcurrent stimulation device based on digital PI control according to claim 1, characterized in that, The power supply module includes a power input unit, a control module power supply unit, a feedback module power supply unit, and a current source module power supply unit. The power input unit regulates VBAT to VCC5V. The control module power supply unit regulates VBAT to VCC3.3V to supply power to the control module and the interaction module. The feedback module power supply unit converts VBAT to VCC3.3V, and boosts VCC3.3V to VCC10V and VEE-10V to supply power to the feedback module. The current source module power supply unit boosts VCC5V to VCC15V, and after regulation, generates VCC12V. VCC15V and VCC12V supply power to the current source module.

6. The transcranial microcurrent stimulation device based on digital PI control according to claim 1, characterized in that, The current source module includes an operational amplifier constant current circuit and a Wilson current mirror circuit. The operational amplifier constant current circuit includes an OPA type operational amplifier, an NPN type transistor, resistors, and potentiometers. The control terminal of the operational amplifier constant current circuit is connected to the DAC terminal of the control module to convert the DAC output reference voltage into a reference current. The Wilson current mirror circuit consists of two voltage divider resistors and three PNP type transistors. The input terminal of the Wilson current mirror circuit is connected to the output terminal of the operational amplifier constant current circuit, and the output terminal of the Wilson current mirror circuit is connected to the load to mirror the reference current into a stimulation current. The relationship between the relative error between the reference current and the stimulation current and the current amplification factor of the PNP type transistor in the Wilson current mirror circuit is as follows: ； In the formula, The relative error between the reference current and the stimulation current, This represents the current amplification factor of the PNP transistor in the current source module.

7. The transcranial microcurrent stimulation device based on digital PI control according to claim 1, characterized in that, The control module includes an STM32 microcontroller, a reset circuit, and a clock circuit. The STM32 microcontroller detects the Set, Start, and Toggle function switches in the interactive module through three external interrupt input terminals, and collects the commands of the three knobs in the interactive module through three parameter ADC terminals to complete the adjustment of the first stimulation parameter and the second stimulation parameter.

8. The transcranial microcurrent stimulation device based on digital PI control according to claim 7, characterized in that, The STM32 microcontroller acquires the feedback voltage output by the feedback module through the ADC terminal, and directly filters the feedback voltage using a mean filtering algorithm to obtain the filtered voltage. The STM32 microcontroller compares the filtered voltage with the target feedback voltage corresponding to the target output current, and directly calculates the DAC output reference voltage through a digital PI control algorithm.

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