Portable multichannel time interference transcranial electrical stimulation system

Abstract

A portable multichannel time interference transcranial electrical stimulation system is characterized in that the portable multichannel time interference transcranial electrical stimulation system comprises an upper computer information management system and a portable multichannel time interference transcranial electrical stimulation device; the portable multichannel time interference transcranial electrical stimulation device comprises a single-chip microcomputer master control module, a power management system, a man-machine interaction module, a signal transmission module and a time interference electrical stimulation core unit. The modular design is adopted, and the number of the time interference core subunits can be increased to four through a board-to-board connector according to the requirements of users, so that four-channel time interference output with adjustable parameters is realized, the maximum output load is as high as 25 kilohms, and the driving capability of stimulation is improved. And the system has the advantages of high-precision current output, real-time monitoring and personalized management, provides convenience for data analysis and remote support for medical staff, and is beneficial to improving the treatment effect and the treatment experience of patients.

Description

[Technical field]

[0001] The present invention belongs to the field of transcranial electrical stimulation, and relates to a time-interference electrical stimulation technology, in particular to a portable multi-channel time-interference transcranial electrical stimulation system. [Background technology]

[0002] In recent years, the development of neuromodulation technology has provided new hope for the treatment of neurodegenerative diseases. Neuromodulation refers to the use of implantable or non-implantable technology to excite, inhibit or regulate the signal transmission of neurons or neural networks in adjacent or distant parts of the brain central, peripheral and autonomic nervous systems through electrical or chemical action, so as to improve the quality of life of patients or improve body function. Transcranial electrical stimulation, as the most common neuromodulation method, injects low-intensity current into specific brain areas through electrodes attached to the scalp or implanted in the skull to change the excitability of brain neurons or cortex, thereby regulating the brain's neural activity. In 2017, Grossman's team proposed a stimulation method called Temporal Interference Stimulation (TIS), which can generate a low-frequency envelope (10Hz) in the intersection area of ​​the two current fields by applying two high-frequency sinusoidal currents with slightly different frequencies (for example, 2000Hz and 2010Hz) outside the skull. Due to the low-pass filtering characteristics of the cell membrane itself, only neurons in the intersection area of ​​the two current fields will be activated, thereby achieving the purpose of accurately stimulating specific targets in the brain. Temporal interference has the advantages of both targeting and non-invasiveness, overcoming the problem that the two cannot coexist in transcranial electrical stimulation, and improving the spatial resolution and penetration of stimulation. This stimulation method does not require surgery, and only requires at least four electrodes attached to the scalp to achieve targeted stimulation of specific brain areas, avoiding the potential risk of infection and stroke during surgery.

[0003] At present, the academic community mainly uses simulation modeling methods to find the best electrode arrangement combination when studying time interference. This method includes increasing the number of output channels, changing the current ratio, optimizing the placement of electrodes, etc. Its purpose is to maximize the electric field envelope of the targeted brain area while minimizing the impact on the surrounding brain areas.

[0004] There are a series of problems with the electrical stimulation devices currently on the market and the equipment developed by the laboratory, including large size, low integration and modularization, limited number of output channels, poor load capacity, and low output current accuracy. In addition, since time interference requires the regulation of parameters such as amplitude, frequency, phase, transition time, and number of channels, the development of time interference electrical stimulation devices becomes difficult, and it is difficult to achieve high integration and portability. Limited by the area of ​​​​the circuit board and the difficulty of design, most time interference electrical stimulation devices only have a single output, and the adjustable parameters of the waveform are limited or unadjustable, which greatly limits the stimulation effect. In addition, the lack of a bioelectrical impedance measurement module and an actual current output measurement module results in an open-loop output for the entire output, which has a large error. Without a host computer and a patient information management system, medical staff cannot conveniently and uniformly manage patient files and monitor the changes in impedance parameters during treatment in real time, which may lead to inaccurate evaluation of treatment effects and difficulty in implementing personalized treatment.

[0005] Therefore, in order to solve the defects existing in the original technology, including large equipment size, limited number of output channels, poor load capacity, low output current accuracy, difficulty in achieving high integration and portability, few output channels and inability to expand, limited parameter adjustment, lack of bioimpedance measurement and actual current output measurement modules, and lack of a host computer management system that makes it difficult to uniformly manage patient files and monitor impedance parameter changes during treatment in real time, it is necessary to design a small and portable device that can provide multi-channel high-precision time interference electrical stimulation signal output, can accurately adjust various stimulation parameters, can accurately measure the bioimpedance and actual output current between the two electrodes, and is equipped with a host computer management system that can communicate wirelessly with it, so that medical staff can easily and uniformly manage patient files and monitor impedance parameter changes during treatment in real time, thereby achieving more accurate treatment effect evaluation and personalized treatment. [Summary of the invention]

[0006] The purpose of the present invention is to provide a portable multi-channel time-interference transcranial electrical stimulation system, which can overcome the shortcomings of the prior art and is a transcranial electrical stimulation system with a simple structure, easy implementation and portability.

[0007] The technical solution of the present invention: a portable multi-channel time-interference transcranial electrical stimulation system, characterized in that it includes two parts: a host computer information management system and a portable multi-channel time-interference transcranial electrical stimulation device; wherein the portable multi-channel time-interference transcranial electrical stimulation device specifically includes a single-chip microcomputer main control module, a power management system, a human-computer interaction module, a signal transmission module and a time-interference electrical stimulation core unit; the power management system is used to provide power to the single-chip microcomputer main control module, the signal transmission module and the time-interference electrical stimulation core unit; the single-chip microcomputer main control module is connected to the human-computer interaction module, the signal transmission module and the time-interference electrical stimulation core unit in a two-way data transmission manner; the host computer information management system and the portable multi-channel time-interference transcranial electrical stimulation device are connected in a two-way data transmission manner through the signal transmission module.

[0008] The single-chip main control module is composed of a STM32F103RCT6 single-chip microcomputer and its basic peripheral circuits; its connection is a conventional connection method; the CPU frequency of the single-chip microcomputer can reach up to 72MHz, with 256K bytes of flash memory and 48K bytes of RAM. It integrates 3 SPIs, 5 USARTs, 4 general timers, and 51 general IO ports and other peripherals.

[0009] The power management system is composed of a 1.25V reference voltage generation circuit, a ±15V voltage generation circuit, a 3.3V voltage generation circuit, and a 7.4V lithium battery; wherein the 7.4V lithium battery is composed of two 18650 lithium batteries connected in series, and its output voltage controls the on and off state of the total power supply of the portable multi-channel time-interference transcranial electrical stimulation device through a self-locking switch; the 3.3V voltage generation circuit is composed of an AMS1117 voltage regulator chip, and the input end of the AMS1117 is connected to the total power supply of the 7.4V lithium battery after passing through the self-locking switch, and the output obtains a 3.3V voltage output; the input and output ends of the AMS1117 voltage regulator chip are each connected in parallel with a 10uF tantalum capacitor for filtering the voltage. The ±15V voltage generating circuit is composed of an ADP5070 power management chip and its peripheral feedback loop; the input end of the ADP5070 power management chip is connected to the total power supply of a 7.4V lithium battery after passing through a self-locking switch, and a ±15V voltage output is obtained after passing through a DCDC voltage stabilizing circuit with a switching frequency of 1.2MHz; the 1.25V reference voltage generating circuit adopts a REF35125 reference voltage chip; the input end of the REF35125 reference voltage chip is connected to the 3.3V voltage output by the 3.3V voltage generating circuit, and its output end is connected in parallel with a 10uF ceramic capacitor to obtain a high-precision 1.25V reference voltage with a maximum error of only 0.05%.

[0010] The human-computer interaction module consists of 2 user buttons and a 1.69-inch LCD display screen. The user buttons are connected to the IO port of the single-chip main control module, and the button status is read through an external interrupt; the LCD display screen is powered by a 3.3V voltage generation circuit and is connected to the SPI3 interface of the single-chip main control module to achieve communication; when the user uses the device offline, the adjustable parameters of the device can be set through the user buttons, and the LCD display screen displays the current stimulation parameters and the actual output current and current size in real time.

[0011] The signal transmission module adopts a module with Bluetooth wireless transmission mode; the Bluetooth wireless transmission module adopts an HC-08 Bluetooth serial port communication module, which is powered by a 3.3V voltage generation circuit and is connected to the USART1 interface of the microcontroller main control module. It can convert the USART1 data of the microcontroller into Bluetooth signals and realize wireless communication with the host computer information management system.

[0012] The time interference electrical stimulation core unit is composed of no less than 1 and at most 4 time interference electrical stimulation core sub-units; each of the time interference electrical stimulation core sub-units is composed of a DDS (Direct Digital Synthesis) waveform generation circuit module, a Howland voltage-controlled current source module and a voltage and current measurement module; the DDS waveform generation circuit module and the Howland voltage-controlled current source module are connected in a unidirectional data transmission manner; the Howland voltage-controlled current source module and the voltage and current measurement module are connected in a unidirectional data transmission manner; the output end of the Howland voltage-controlled current source module is connected to the wire-to-board needle holder via the voltage and current measurement module, and the electrode is connected to the needle holder through a wire, so that the current can be transmitted to the human scalp through the electrode to achieve time interference electrical stimulation.

[0013] The DDS waveform generating circuit module is composed of two DDS waveform generating circuits, each of which is a circuit structure composed of a 25MHz active crystal oscillator, an AD9834DDS chip and an AD8237 instrument amplifier; the DDS waveform generating circuit module is composed of resistor R37, resistor R38, resistor R39, resistor R40, resistor R41, resistor R42, resistor R43, resistor R44, resistor R45, resistor R46, resistor R47, resistor R48, resistor R49, resistor R50, capacitor C7, capacitor C8, capacitor C9, capacitor C10, capacitor C11, capacitor C12, capacitor C13, capacitor C14, capacitor C15, capacitor C16, capacitor C17, capacitor C18, capacitor C19, capacitor C20, capacitor C21, capacitor C22, capacitor C23, capacitor C24, capacitor C25, capacitor C26, active crystal oscillator XTAL1, active crystal oscillator XTAL2, AD9834 DDS chip I, AD9834 DDS chip II, AD8237 instrument amplifier I, instrument amplifier AD8237II; the resistors R37, R38, R39, R40, and R41 are composed of resistors R The resistor R41, the resistor R42, the resistor R43, the capacitor C7, the capacitor C8, the capacitor C9, the capacitor C10, the capacitor C11, the capacitor C12, the capacitor C13, the capacitor C14, the capacitor C15, the capacitor C16, the active crystal oscillator XTAL1, the AD9834DDS chip I, and the AD8237 instrument amplifier I together constitute the first DDS waveform generating circuit; the resistor R44, the resistor R45, the resistor R46, the resistor R47, the resistor R48, the resistor R49, the resistor R50, the capacitor C17, the capacitor C18, the capacitor C19, the capacitor C20, the capacitor C21, the capacitor C22, Capacitor C23, capacitor C24, capacitor C25, capacitor C26, active crystal oscillator XTAL2, AD9834DDS chip II, and AD8237 instrument amplifier II together constitute the second DDS waveform generating circuit; the power supply pins VDD and GND of the active crystal oscillator XTAL1 are respectively connected to the output end and ground of the 3.3V voltage generating circuit, the Tri-State pin is suspended, and the OUTPUT pin is connected to the MCLK pin of the AD9834DDS chip I; the resistor R37 is connected in parallel with the capacitor C8, and one end is connected to the DS of the AD9834DDS chip I ADJUST pin, and the other end is grounded; one end of the capacitor C9 is connected to the REFOUT pin of the AD9834DDS chip 1, and the other end is grounded; the capacitors C7, C11, C12, and C16 are connected in parallel, one end is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; one end of the capacitor C10 is connected to the COMP pin of the AD9834DDS chip 1, and the other end is connected to the 3.3V voltage generating circuit.3V voltage generating circuit is connected; one end of the capacitor C13 is connected to the CAP / 2.5V of the AD9834DDS chip I, and the other end is grounded; the resistor R38 is connected in parallel with the capacitor C14, one end is connected to the IOUT pin of the AD9834DDS chip I, and the other end is grounded; the resistor R39 and the capacitor C15 are connected in parallel, one end is connected to the IOUTB pin of the AD9834DDS chip I, and the other end is grounded; the FSELECT pin, PSELECT pin, SLEEP pin, and RESET pin of the AD9834DDS chip I are all connected to the ground, and the VIN pin, SIGN BIT The OUT pins are all suspended, the SCLK pin and the SDATA pin are connected to the SPI2 bus of the single-chip main control module, and the FSYNC pin is connected to the GPIO of the single-chip main control module; the resistor R40 is a 2kΩ potentiometer, one end of which is fixed and connected to the output end of the AD8237 instrument amplifier I, and the other end of which is suspended, and the sliding end is connected to one end of the resistor R42; the other end of the resistor R42 is connected to one end of the resistor R43 and the FB pin of the AD8237 instrument amplifier I; the other end of the resistor R43 is connected to one end of the resistor R41 The first end is connected to the output end of the 1.25V reference voltage generating circuit; the other end of the resistor R41 is connected to the REF pin of the AD8237 instrument amplifier I; the power supply pins +Vs and -Vs of the AD8237 instrument amplifier I are respectively connected to the output and ground of the 3.3V voltage generating circuit, the positive input terminal and the inverting input terminal are respectively connected to the IOUT pin and IOUTB pin of the AD9834DDS chip I, and the BW pin is connected to the ground; the wiring method of the second DDS waveform generating circuit is the same as that of the first DDS waveform generating circuit. .

[0014] The AD9834DDS chip I is controlled by the microcontroller master module through the SPI2 interface, and can generate two frequency-complementary, phase-adjustable sine waves on the IOUT and IOUTB pins, as shown in formulas (1) and (2), respectively, in units of V:

[0015]

[0016] Among them, f1, are the settable frequency and phase, and π is the pi.

[0017] The two sinusoidal signal outputs of the AD9834DDS chip I are connected to the positive input terminal and the negative input terminal of the AD8237 instrument amplifier I respectively, and the potentiometer resistor R40 is adjusted to meet the requirements. At this time, the resistor network gain of the AD8237 instrumentation amplifier I is 1.75 times, and there is a 1.25V voltage bias provided by the 1.25V reference voltage generation circuit. The output voltage waveform V1 at this time can be obtained in V, as shown in formula (3):

[0018]

[0019] Among them, the output voltage V1 is the voltage signal after being amplified by the AD8237 instrument amplifier I;

[0020] Similarly, the output voltage V2 of the second DDS waveform generating circuit is V, as shown in formula (4):

[0021]

[0022] Among them, f2, The frequency and phase set for the second DDS waveform generating circuit.

[0023] Each time interference electrical stimulation core subunit includes a DDS waveform generating circuit module, and each DDS waveform generating circuit module includes two DDS waveform generating circuits for generating two high-frequency sine waves with slight differences. The single-chip microcomputer communicates with a total of 8 DDS waveform generating circuits of up to 4 time interference electrical stimulation core subunits through the chip select pin and the SPI2 bus; in addition to the sine wave, the single-chip microcomputer can also control the module to generate square waves, triangle waves, and DC signals, so the system is compatible with other classic DC and AC electrical stimulation.

[0024] The Howland voltage-controlled current source module is composed of two current output channels, each of which is composed of a Howland enhanced differential complementary voltage-controlled current source and a dual-channel digital potentiometer; the Howland enhanced differential complementary voltage-controlled current source is a circuit structure composed of a pair of ADA4610 operational amplifiers and ADA4622 operational amplifiers; specifically, it is composed of resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and R11. , resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, wire-to-board pin header P2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier I, ADA4622 operational amplifier II, ADA4622 operational amplifier III, ADA4622 operational amplifier IV; the resistor R 1. Resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, capacitor C1, capacitor C2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4622 operational amplifier I, and ADA4622 operational amplifier II together constitute the Howland enhanced differential complementary voltage-controlled current source of the first current output channel; the resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R 17, resistor R18, resistor R19, resistor R20, capacitor C3, capacitor C4, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier III, ADA4622 operational amplifier IV constitute the Howland enhanced differential complementary voltage-controlled current source of the second current output channel; one end of the resistor R1 is connected to the output of the first DDS signal generating circuit, and the other end thereof is connected to the positive input end of the ADA4610 operational amplifier I; one end of the resistor R3 is connected to 1.The output end of the 25V reference voltage generating circuit is connected, and the other end is connected to the negative input end of the ADA4610 operational amplifier I; the output end of the ADA4610 operational amplifier I is connected to the digital potentiometer via the resistor R5; the resistor R4 is connected between the negative input end and the output end of the ADA4610 operational amplifier I; the positive input end of the ADA4622 operational amplifier I is connected to the digital potentiometer, and its negative input end is short-circuited with its output end; the ADA4610 operational amplifier I and the ADA4622 operational amplifier I are also connected to the output end of the ±15V voltage generating circuit, and the ±15V voltage generating circuit provides working power for both; one end of the resistor R2 is connected to the positive input end of the ADA4610 operational amplifier I, and the other end is connected to the output end of the ADA4622 operational amplifier I; the specific circuit connection mode of the Howland enhanced differential complementary voltage-controlled current source of the second current output channel is the same as that of the first current output channel. .

[0025] The dual-channel digital potentiometer adopts a dual-channel 2.5kΩ digital potentiometer chip AD5248 structure, specifically composed of 2.5kΩ digital potentiometer chips AD5248-I, AD5248-II, capacitor C1, capacitor C2, capacitor C3, and capacitor C4; the 2.5kΩ digital potentiometer chip AD5248-I, capacitor C1, and capacitor C2 together constitute a dual-channel digital potentiometer for the first current output channel; the 2.5kΩ digital potentiometer chip AD5248-II, capacitor C3, and capacitor C4 together constitute a dual-channel digital potentiometer for the second current output channel; wherein the VDD terminal of the 2.5kΩ digital potentiometer chip AD5248-I is connected to the 3.3V voltage The output end of the voltage generating circuit is connected, the B1 terminal and the B2 terminal are respectively connected to one end of the resistor R5 and one end of the resistor R10 of the two current output channels of the Howland enhanced differential complementary voltage-controlled current source, the W1 terminal and the W2 terminal are respectively connected to the positive input end of the ADA4622 operational amplifier I and the positive input end of the ADA4622 operational amplifier II in the first current output channel of the Howland enhanced differential complementary voltage-controlled current source; the capacitor C1 and the capacitor C2 are connected in parallel, one end of which is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; the specific circuit connection method of the dual-channel digital potentiometer of the second current output channel is the same as that of the first current output channel.

[0026] The ADA4610 operational amplifier I and the ADA4622 operational amplifier I are powered by a ±15V voltage generated by a ±15V voltage generating circuit; When the resistance values ​​of B1 and W1, B2 and W2 of the dual-channel digital potentiometer are R BW1_1 and R BW1_2When the current I 1_P , unit A, as shown in formula (5):

[0027]

[0028] Where V in1_1+ is the voltage at the left end of resistor R1, V in1_1- is the voltage at the left end of resistor R3;

[0029] when When the current I 1_P , unit A, as shown in formula (6):

[0030]

[0031] Similarly, the current I output from the CH1_N terminal at the positive input of the ADA4622 operational amplifier II is 1_N , unit A, as shown in formula (7):

[0032]

[0033] Where V in1_2+ is the voltage at the left end of resistor R6, V in1_2- is the voltage at the left end of resistor R8;

[0034] V in1_1+ and V in1_2- Connected to the first output V1 of the DDS waveform generation circuit, V in1_1- and V in1_2+ connected to the output terminal of the 1.25V reference voltage generating circuit; and the resistance value R BW1_1 , the resistance value R between B2 and W2 BW1_2 Same and both are R BW1 When , a pair of complementary differential current sources from CH1_P terminal to CH1_N terminal can be obtained. If the direction of the current from CH1_P terminal to CH1_N terminal is positive, the differential current I flowing through the load between CH1_P terminal and CH1_N terminal is L1 , unit A, as shown in formula (8):

[0035]

[0036] Similarly, the second current output channel outputs the current I flowing through the load. L2 , unit A, as shown in formula (9):

[0037]

[0038] Since the two resistance values ​​of the dual-channel digital potentiometer can be independently adjusted in the range of 320-2810Ω, two differential complementary sinusoidal current outputs with maximum values ​​independently adjustable in the range of 0.5mA-1.5mA can be achieved. This small current is applied to the appropriate position of the patient's scalp through the electrode through the connector to achieve single-channel time interference electrical stimulation; since each time interference core subunit contains one Howland voltage-controlled current source module, four-channel time interference electrical stimulation output can be achieved by stacking four time interference core subunits.

[0039] The voltage and current measurement module is composed of two measurement channels, each of which is composed of a current measurement circuit and a differential voltage measurement circuit; the current measurement circuit is a circuit structure composed of an INA198 shunt detection chip; specifically, it is composed of a resistor R21, a resistor R29, a capacitor C5, a capacitor C6, an INA198 shunt detection chip I, and an INA198 shunt detection chip II; the resistor R21, the capacitor C5, and the INA198 shunt detection chip I together constitute the current measurement circuit of the first measurement channel; the resistor R29, the capacitor C6, and the INA198 shunt detection chip II together constitute the current measurement circuit of the second measurement channel The current measurement circuit of the measurement channel; one end of the resistor R21 is connected to the CH1_P terminal at the positive input end of the ADA4622 operational amplifier I, and the other end thereof is connected to the wire-to-board needle seat; one end of the capacitor C5 is connected to the output end of the 3.3V voltage generation circuit, and the other end is grounded; the V+ terminal of the INA198 shunt detection chip I is connected to the output end of the 3.3V voltage generation circuit, the VIN+ terminal and the VIN- terminal are respectively connected to the two ends of the resistor R29, and the OUT terminal is connected to the ADC channel of the single-chip microcomputer; the specific circuit connection method of the current detection circuit of the second measurement channel is the same as that of the first measurement channel;

[0040] When the differential complementary current between CH1_P and CH1_N is I L1 When the resistance value of resistor R29 is 20Ω, the output voltage ADC_I1 of the OUT terminal of the INA198 shunt detection chip I of the first measurement channel is in mV, as shown in formula (10):

[0041]

[0042] Similarly, the output voltage ADC_I2 of the OUT terminal of the second measurement channel INA198 shunt detection chip I is in mV, as shown in formula (11).

[0043]

[0044] The differential voltage measurement circuit is a composite differential amplifier circuit composed of ADA4622, which is used to measure the differential voltage of the output channel. Specifically, it is composed of resistor R22, resistor R23, resistor R24, resistor R25, resistor R26, resistor R27, resistor R28, resistor R30, resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier V, ADA4622 operational amplifier VI, ADA4622 operational amplifier VII, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, and ADA4622 operational amplifier X; the resistor R22, resistor R23, resistor R24 , resistor R25, resistor R26, resistor R27, resistor R28, ADA4622 operational amplifier V, ADA4622 operational amplifier VI, ADA4622 operational amplifier VII together constitute the differential voltage measurement circuit of the first measurement channel; the resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, ADA4622 operational amplifier X together constitute the differential voltage measurement circuit of the second measurement channel; the differential voltage measurement circuit is specifically a three-stage circuit composed of a voltage follower, a differential proportional amplifier circuit, and a waveform clamping circuit; wherein the voltage follower The device is the first stage, which is composed of a resistor R22 and an ADA4622 operational amplifier V; the differential proportional amplifier circuit is the second stage, which is composed of a resistor R23, a resistor R24, a resistor R25, a resistor R26, and an ADA4622 operational amplifier VI; the waveform clamp circuit is the third stage, which is composed of a resistor R27, a resistor R28, and an operational amplifier VII; the positive input end of the ADA4622 operational amplifier V is connected to one end of the resistor R21, and its inverting input end is connected to the output end through the resistor R22; one end of the resistor R23 is connected to the output end of the first stage voltage follower, and the other end is connected to the positive input end of the ADA4622 operational amplifier VI; one end of the resistor R24 ​​is connected to one end of the resistor R23 The resistor R25 is connected to the CH1_N terminal of the first current output channel of the Howland voltage-controlled current source module, and the other end is connected to the inverting input end of the ADA4622 operational amplifier VI; the inverting input end of the ADA4622 operational amplifier VI is connected to the output end through the resistor R26; one end of the resistor R27 is connected to the output end of the second-stage differential proportional amplifier circuit, and the other end is connected to the positive input end of the ADA4622 operational amplifier VII; the inverting input end of the ADA4622 operational amplifier VII is connected to the output end through the resistor R28, and the output end is connected to the ADC channel of the single-chip microcomputer; the differential voltage measurement circuit of the second measurement channel is the same as that of the first channel;Then the output ADC_V1 of the third-stage waveform clamp circuit, in mV, is as shown in formula (12):

[0045]

[0046] Where V o1+ is the voltage at the positive input terminal of the ADA4622 operational amplifier V, V o1- is the voltage at one end of resistor R25;

[0047] Similarly, the output ADC_V2 of the third-stage waveform clamp circuit of the differential voltage measurement circuit of the second measurement channel is as shown in formula (13) (unit: mV):

[0048]

[0049] Where V o2+ is the voltage at the positive input terminal of ADA4622 operational amplifier VIII, V o2- is the voltage at one end of resistor R33.

[0050] The voltage and current measurement module of each time-interference electrical stimulation core subunit includes two current measurement circuits and two differential voltage measurement circuits. The entire device has a total of 16 feedback channels, all of which are connected to the ADC input channel of the single-chip microcomputer.

[0051] Working principle of the present invention: The portable multi-channel time interference transcranial electrical stimulation device is specifically divided into two parts: a driving unit (single-chip microcomputer main control module, power management system, human-computer interaction module, signal transmission module) and a time interference core unit (consisting of a DDS waveform generation circuit module, a Howland voltage-controlled current source module, and a voltage and current measurement module), and the two are integrated on different circuit boards. The driving unit is responsible for the power supply, coordination, control, and communication of the entire device; the time interference core unit is responsible for receiving instructions and generating different stimulation waveforms according to user needs. The driving unit and the time interference core unit are integrated on different circuit boards, and the time interference core unit can be installed on the driving unit through a board-to-board connector. Each time interference core subunit can provide a 1-channel time interference electrical stimulation output, and the time interference core subunits can be superimposed to 4 to achieve 4-channel time interference output. The driver board and the core board are connected by 35 lines, including 16 voltage and current measurement paths connected to the ADC channel of the microcontroller; the MOSI and SCK pins of the SPI2 of the microcontroller and 8 GPIOs, which are used to control the AD9834 chip of 8 DDS waveform generating circuits; the SCL and SDA pins of the I2C1 and I2C2 channels of the microcontroller, which are used to control the 8 digital potentiometers of the Howland current source; and the power supply and voltage references 3.3V, ±15V, 1.25V, and GND.

[0052] The upper computer software consists of a patient information management system and a graphical user control interface: ① The patient information management system can create a patient profile to save the patient's personal information, medical history, diagnosis results, etc. Save the patient's personalized treatment plan, including the setting of stimulation parameters, treatment plan and real-time progress tracking. Save the data during the treatment process, including stimulation parameters, impedance changes and other information. Before and after each treatment, a paradigm for testing cognition, movement, working memory and other functions can be generated according to the different conditions of each patient to evaluate the effect of treatment and rehabilitation. ② The graphical user interface is wirelessly connected to the lower computer, and the stimulation parameters can be remotely controlled, including stimulation waveform, frequency, phase, current size, duration, rise time, etc., and the parameters of different channels can be adjusted independently, or the stimulation parameters can be automatically generated according to the patient's treatment plan. During the stimulation process, the voltage and current feedback information sent by the lower computer can be received in real time, and the impedance can be calculated and displayed in real time.

[0053] Advantages of the present invention: The present invention adopts a modular design, which is divided into a driving unit and a time interference core unit. The time interference core subunit can be increased to 4 according to user needs through a board-to-board connector, thereby realizing 4-channel time interference output with adjustable parameters, and the maximum load of each output is up to 25kΩ, which improves the driving ability of stimulation. Each output has a current detection and voltage detection module, and is read through the ADC channel of the single-chip microcomputer, so that the system can adjust the output and achieve high-precision current output. Equipped with a host computer system, users can use the host computer to monitor and personalize the treatment process in real time, which provides medical staff with the convenience of data analysis and remote support, and helps to improve the treatment effect and the patient's treatment experience.

Brief Description of the Drawings

[0054] Figure 1 The present invention is a schematic diagram of the overall structure of a portable multi-channel time-interference transcranial electrical stimulation system.

[0055] Figure 2 The present invention is a schematic diagram of the circuit structure of a DDS waveform generating circuit module in a portable multi-channel time-interference transcranial electrical stimulation system.

[0056] Figure 3 The present invention is a schematic diagram of the circuit structure of a Howland voltage-controlled current source module in a portable multi-channel time-interference transcranial electrical stimulation system.

[0057] Figure 4 The present invention is a schematic diagram of the circuit structure of a differential voltage detection module in a portable multi-channel time-interference transcranial electrical stimulation system.

[0058] Figure 5 This is a schematic diagram of time-interference electrical stimulation of a portable multi-channel time-interference transcranial electrical stimulation system involved in the present invention. [Specific implementation method]

[0059] Embodiment: A portable multi-channel time-interference transcranial electrical stimulation system, such as Figure 1 As shown, it is characterized in that it includes two parts: a host computer information management system and a portable multi-channel time-interference transcranial electrical stimulation device; wherein the portable multi-channel time-interference transcranial electrical stimulation device specifically includes a single-chip microcomputer main control module, a power management system, a human-computer interaction module, a signal transmission module and a time-interference electrical stimulation core unit; the power management system is used to provide power to the single-chip microcomputer main control module, the signal transmission module and the time-interference electrical stimulation core unit; the single-chip microcomputer main control module is connected to the human-computer interaction module, the signal transmission module and the time-interference electrical stimulation core unit in a two-way data transmission manner; the host computer information management system and the portable multi-channel time-interference transcranial electrical stimulation device are connected in a two-way data transmission manner through the signal transmission module.

[0060] The single-chip main control module is composed of a STM32F103RCT6 single-chip microcomputer and its basic peripheral circuits; its connection is a conventional connection method; the CPU frequency of the single-chip microcomputer can reach up to 72MHz, with 256K bytes of flash memory and 48K bytes of RAM. It integrates 3 SPIs, 5 USARTs, 4 general timers, and 51 general IO ports and other peripherals.

[0061] The power management system is composed of a 1.25V reference voltage generation circuit, a ±15V voltage generation circuit, a 3.3V voltage generation circuit, and a 7.4V lithium battery; wherein the 7.4V lithium battery is composed of two 18650 lithium batteries connected in series, and its output voltage controls the on and off state of the total power supply of the portable multi-channel time-interference transcranial electrical stimulation device through a self-locking switch; the 3.3V voltage generation circuit is composed of an AMS1117 voltage regulator chip, and the input end of the AMS1117 is connected to the total power supply of the 7.4V lithium battery after passing through the self-locking switch, and the output obtains a 3.3V voltage output; the input and output ends of the AMS1117 voltage regulator chip are each connected in parallel with a 10uF tantalum capacitor for filtering the voltage. The ±15V voltage generating circuit is composed of an ADP5070 power management chip and its peripheral feedback loop; the input end of the ADP5070 power management chip is connected to the total power supply of a 7.4V lithium battery after passing through a self-locking switch, and a ±15V voltage output is obtained after passing through a DCDC voltage stabilizing circuit with a switching frequency of 1.2MHz; the 1.25V reference voltage generating circuit adopts a REF35125 reference voltage chip; the input end of the REF35125 reference voltage chip is connected to the 3.3V voltage output by the 3.3V voltage generating circuit, and its output end is connected in parallel with a 10uF ceramic capacitor to obtain a high-precision 1.25V reference voltage with a maximum error of only 0.05%.

[0062] The human-computer interaction module consists of 2 user buttons and a 1.69-inch LCD display screen. The user buttons are connected to the IO port of the single-chip main control module, and the button status is read through an external interrupt; the LCD display screen is powered by a 3.3V voltage generation circuit and is connected to the SPI3 interface of the single-chip main control module to achieve communication; when the user uses the device offline, the adjustable parameters of the device can be set through the user buttons, and the LCD display screen displays the current stimulation parameters and the actual output current and current size in real time.

[0063] The signal transmission module adopts a module with Bluetooth wireless transmission mode; the Bluetooth wireless transmission module adopts an HC-08 Bluetooth serial port communication module, which is powered by a 3.3V voltage generation circuit and is connected to the USART1 interface of the microcontroller main control module. It can convert the USART1 data of the microcontroller into Bluetooth signals and realize wireless communication with the host computer information management system.

[0064] The time interference electrical stimulation core unit is composed of no less than 1 and no more than 4 time interference electrical stimulation core subunits, such as Figure 1As shown, each of the time interference electrical stimulation core subunits is composed of a DDS (Direct Digital Synthesis) waveform generation circuit module, a Howland voltage-controlled current source module and a voltage and current measurement module; the DDS waveform generation circuit module and the Howland voltage-controlled current source module are connected in a unidirectional data transmission manner; the Howland voltage-controlled current source module and the voltage and current measurement module are connected in a unidirectional data transmission manner; the output end of the Howland voltage-controlled current source module is connected to the wire-to-board needle holder via the voltage and current measurement module, and the electrode is connected to the needle holder through the wire, so that the current can be transmitted to the human scalp through the electrode to achieve time interference electrical stimulation.

[0065] The DDS waveform generating circuit module is composed of two DDS waveform generating circuits, each of which is a circuit structure composed of a 25MHz active crystal oscillator, an AD9834DDS chip and an AD8237 instrument amplifier. Figure 2As shown; the DDS waveform generating circuit module is composed of a resistor R37, a resistor R38, a resistor R39, a resistor R40, a resistor R41, a resistor R42, a resistor R43, a resistor R44, a resistor R45, a resistor R46, a resistor R47, a resistor R48, a resistor R49, a resistor R50, a capacitor C7, a capacitor C8, a capacitor C9, a capacitor C10, a capacitor C11, a capacitor C12, a capacitor C13, a capacitor C14, a capacitor C15, a capacitor C16, a capacitor C17, a capacitor C18, a capacitor C19, a capacitor C20, The capacitor C21, the capacitor C22, the capacitor C23, the capacitor C24, the capacitor C25, the capacitor C26, the active crystal oscillator XTAL1, the active crystal oscillator XTAL2, the AD9834DDS chip I, the AD9834DDS chip II, the AD8237 instrument amplifier I, the instrument amplifier AD8237II; the resistor R37, the resistor R38, the resistor R39, the resistor R40, the resistor R41, the resistor R42, the resistor R43, the capacitor C7, the capacitor C8, the capacitor C9, the capacitor C10, the capacitor C11, the resistor Capacitor C12, capacitor C13, capacitor C14, capacitor C15, capacitor C16, active crystal oscillator XTAL1, AD9834DDS chip I, and AD8237 instrument amplifier I together constitute the first DDS waveform generating circuit; the resistor R44, resistor R45, resistor R46, resistor R47, resistor R48, resistor R49, resistor R50, capacitor C17, capacitor C18, capacitor C19, capacitor C20, capacitor C21, capacitor C22, capacitor C23, capacitor C24, capacitor C25, capacitor C26 6. The active crystal oscillator XTAL2, AD9834DDS chip II, and AD8237 instrument amplifier II together constitute the second DDS waveform generating circuit; the power supply pins VDD and GND of the active crystal oscillator XTAL1 are respectively connected to the output end and ground of the 3.3V voltage generating circuit, the Tri-State pin is suspended, and the OUTPUT pin is connected to the MCLK pin of the AD9834DDS chip I; the resistor R37 is connected in parallel with the capacitor C8, and one end is connected to the DS of the AD9834DDS chip I ADJUST pin, and the other end is grounded; one end of the capacitor C9 is connected to the REFOUT pin of the AD9834DDS chip 1, and the other end is grounded; the capacitors C7, C11, C12, and C16 are connected in parallel, one end is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; one end of the capacitor C10 is connected to the COMP pin of the AD9834DDS chip 1, and the other end is connected to the output end of the 3.3V voltage generating circuit; one end of the capacitor C13 is connected to the CAP / 2.5V, and the other end is grounded; the resistor R38 and the capacitor C14 are connected in parallel, one end is connected to the IOUT pin of the AD9834DDS chip I, and the other end is grounded; the resistor R39 and the capacitor C15 are connected in parallel, one end is connected to the IOUTB pin of the AD9834DDS chip I, and the other end is grounded; the FSELECT pin, PSELECT pin, SLEEP pin, and RESET pin of the AD9834DDS chip I are all connected to the ground, and the VIN pin, SIGN BIT The OUT pins are all suspended, the SCLK pin and the SDATA pin are connected to the SPI2 bus of the single-chip main control module, and the FSYNC pin is connected to the GPIO of the single-chip main control module; the resistor R40 is a 2kΩ potentiometer, one end of which is fixed and connected to the output end of the AD8237 instrument amplifier I, and the other end of which is suspended, and the sliding end is connected to one end of the resistor R42; the other end of the resistor R42 is connected to one end of the resistor R43 and the FB pin of the AD8237 instrument amplifier I; the other end of the resistor R43 is connected to one end of the resistor R41 and the output end of the 1.25V reference voltage generating circuit; the other end of the resistor R41 is connected to the REF pin of the AD8237 instrument amplifier I; the power supply pins +Vs and -Vs of the AD8237 instrument amplifier I are respectively connected to the output and ground of the 3.3V voltage generating circuit, the positive input terminal and the inverting input terminal are respectively connected to the IOUT pin and IOUTB pin of the AD9834DDS chip I, and the BW pin is connected to the ground; the wiring method of the second DDS waveform generating circuit is the same as that of the first DDS waveform generating circuit, such as. Figure 2 shown.

[0066] The AD9834DDS chip I is controlled by the microcontroller master module through the SPI2 interface, and can generate two frequency-complementary, phase-adjustable sine waves on the IOUT and IOUTB pins, as shown in formulas (1) and (2), respectively, in units of V:

[0067]

[0068] Among them, f1, are the settable frequency and phase, and π is the pi.

[0069] The two sinusoidal signal outputs of the AD9834DDS chip I are connected to the positive input terminal and the negative input terminal of the AD8237 instrument amplifier I respectively, and the potentiometer resistor R40 is adjusted to meet the requirements. At this time, the resistor network gain of the AD8237 instrumentation amplifier I is 1.75 times, and there is a 1.25V voltage bias provided by the 1.25V reference voltage generation circuit. The output voltage waveform V1 at this time can be obtained in V, as shown in formula (3):

[0070]

[0071] Among them, the output voltage V1 is the voltage signal after being amplified by the AD8237 instrument amplifier I;

[0072] Similarly, the output voltage V2 of the second DDS waveform generating circuit is V, as shown in formula (4):

[0073]

[0074] Among them, f2, The frequency and phase set for the second DDS waveform generating circuit.

[0075] Each time interference electrical stimulation core subunit includes a DDS waveform generating circuit module, and each DDS waveform generating circuit module includes two DDS waveform generating circuits for generating two high-frequency sine waves with slight differences. The single-chip microcomputer communicates with a total of 8 DDS waveform generating circuits of up to 4 time interference electrical stimulation core subunits through the chip select pin and the SPI2 bus; in addition to the sine wave, the single-chip microcomputer can also control the module to generate square waves, triangle waves, and DC signals, so the system is compatible with other classic DC and AC electrical stimulation.

[0076] The Howland voltage-controlled current source module is composed of two current output channels, each of which is composed of a Howland enhanced differential complementary voltage-controlled current source and a dual-channel digital potentiometer. Figure 3As shown; the Howland enhanced differential complementary voltage-controlled current source is a circuit structure consisting of a pair of ADA4610 operational amplifiers and ADA4622 operational amplifiers; specifically, it is composed of resistors R1, resistors R2, resistors R3, resistors R4, resistors R5, resistors R6, resistors R7, resistors R8, resistors R9, resistors R10, resistors R11, resistors R12, resistors R13, resistors R14, resistors R15, resistors R16, resistors R17, resistors R18, resistors R19, resistors R20, wire-to-board pin header P2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier I, ADA4622 operational amplifier II, ADA4622 operational amplifier III, and ADA4622 operational amplifier IV; the resistors R1, resistors R2, resistors R3, resistors R4, resistors R5, resistors R6, resistors R7, resistors R8, resistor R9, resistor R10, capacitor C1, capacitor C2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4622 operational amplifier I, ADA4622 operational amplifier II together constitute the Howland enhanced differential complementary voltage-controlled current source of the first current output channel; the resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, capacitor C3, capacitor C4, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier III, ADA4622 operational amplifier IV constitute the Howland enhanced differential complementary voltage-controlled current source of the second current output channel; one end of the resistor R1 is connected to the output of the first DDS signal generating circuit, and the other end thereof is connected to the positive input end of the ADA4610 operational amplifier I; one end of the resistor R3 is connected to 1.The output end of the 25V reference voltage generating circuit is connected, and the other end is connected to the negative input end of the ADA4610 operational amplifier I; the output end of the ADA4610 operational amplifier I is connected to the digital potentiometer via the resistor R5; the resistor R4 is connected between the negative input end and the output end of the ADA4610 operational amplifier I; the positive input end of the ADA4622 operational amplifier I is connected to the digital potentiometer, and its negative input end is short-circuited with its output end; the ADA4610 operational amplifier I and the ADA4622 operational amplifier I are also connected to the output end of the ±15V voltage generating circuit, and the ±15V voltage generating circuit provides working power for both; one end of the resistor R2 is connected to the positive input end of the ADA4610 operational amplifier I, and the other end is connected to the output end of the ADA4622 operational amplifier I; the specific circuit connection mode of the Howland enhanced differential complementary voltage-controlled current source of the second current output channel is the same as that of the first current output channel, such as. Figure 3 shown.

[0077] The dual-channel digital potentiometer adopts a dual-channel 2.5kΩ digital potentiometer chip AD5248 structure, specifically composed of 2.5kΩ digital potentiometer chips AD5248-I, AD5248-II, capacitor C1, capacitor C2, capacitor C3, and capacitor C4; the 2.5kΩ digital potentiometer chip AD5248-I, capacitor C1, and capacitor C2 together constitute a dual-channel digital potentiometer for the first current output channel; the 2.5kΩ digital potentiometer chip AD5248-II, capacitor C3, and capacitor C4 together constitute a dual-channel digital potentiometer for the second current output channel; wherein the VDD terminal of the 2.5kΩ digital potentiometer chip AD5248-I is connected to the 3.3V voltage The output end of the voltage generating circuit is connected, the B1 terminal and the B2 terminal are respectively connected to one end of the resistor R5 and one end of the resistor R10 of the two current output channels of the Howland enhanced differential complementary voltage-controlled current source, the W1 terminal and the W2 terminal are respectively connected to the positive input end of the ADA4622 operational amplifier I and the positive input end of the ADA4622 operational amplifier II in the first current output channel of the Howland enhanced differential complementary voltage-controlled current source; the capacitor C1 and the capacitor C2 are connected in parallel, one end of which is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; the specific circuit connection method of the dual-channel digital potentiometer of the second current output channel is the same as that of the first current output channel, such as Figure 3 shown.

[0078] The ADA4610 operational amplifier I and the ADA4622 operational amplifier I are powered by a ±15V voltage generated by a ±15V voltage generating circuit; When the resistance values ​​of B1 and W1, B2 and W2 of the dual-channel digital potentiometer are RBW1_1 and R BW1_2 When the current I 1_P , unit A, as shown in formula (5):

[0079]

[0080] Where V in1_1+ is the voltage at the left end of resistor R1, V in1_1- is the voltage at the left end of resistor R3;

[0081] when When the current I 1_P , unit A, as shown in formula (6):

[0082]

[0083] Similarly, the current I output from the CH1_N terminal at the positive input of the ADA4622 operational amplifier II is 1N , unit A, as shown in formula (7):

[0084]

[0085] Where V in1_2+ is the voltage at the left end of resistor R6, V in1_2- is the voltage at the left end of resistor R8;

[0086] V in1_1+ and V in1_2- Connected to the first output V1 of the DDS waveform generation circuit, V in1_1- and V in1_2+ connected to the output terminal of the 1.25V reference voltage generating circuit; and the resistance value R BW1_1 , the resistance value R between B2 and W2 BW1_2 Same and both are R BW1 When , a pair of complementary differential current sources from CH1_P terminal to CH1_N terminal can be obtained. If the direction of the current from CH1_P terminal to CH1_N terminal is positive, the differential current I flowing through the load between CH1_P terminal and CH1_N terminal is L1 , unit A, as shown in formula (8):

[0087]

[0088] Similarly, the second current output channel outputs the current I flowing through the load. L2 , unit A, as shown in formula (9):

[0089]

[0090] Since the two resistance values ​​of the dual-channel digital potentiometer can be independently adjusted in the range of 320-2810Ω, two differential complementary sinusoidal current outputs with maximum values ​​independently adjustable in the range of 0.5mA-1.5mA can be achieved. This small current is applied to the appropriate position of the patient's scalp through the electrode through the connector to achieve single-channel time interference electrical stimulation; since each time interference core subunit contains one Howland voltage-controlled current source module, four-channel time interference electrical stimulation output can be achieved by stacking four time interference core subunits.

[0091] The voltage and current measurement module is composed of two measurement channels, each of which is composed of a current measurement circuit and a differential voltage measurement circuit. Figure 4 As shown; the current measurement circuit is a circuit structure composed of an INA198 shunt detection chip; specifically, it is composed of a resistor R21, a resistor R29, a capacitor C5, a capacitor C6, an INA198 shunt detection chip I, and an INA198 shunt detection chip II; the resistor R21, the capacitor C5, and the INA198 shunt detection chip I together constitute the current measurement circuit of the first measurement channel; the resistor R29, the capacitor C6, and the INA198 shunt detection chip II together constitute the current measurement circuit of the second measurement channel; one end of the resistor R21 is connected to A The CH1_P terminal at the positive input end of the DA4622 operational amplifier I is connected, and the other end is connected to the wire-to-board pin header; one end of the capacitor C5 is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; the V+ terminal of the INA198 shunt detection chip I is connected to the output end of the 3.3V voltage generating circuit, the VIN+ terminal and the VIN- terminal are respectively connected to the two ends of the resistor R29, and the OUT terminal is connected to the ADC channel of the single-chip microcomputer; the specific circuit connection method of the current detection circuit of the second measurement channel is the same as that of the first measurement channel, such as Figure 4 As shown;

[0092] When the differential complementary current between CH1_P and CH1_N is I L1 When the resistance value of resistor R29 is 20Ω, the output voltage ADC_I1 of the OUT terminal of the INA198 shunt detection chip I of the first measurement channel is in mV, as shown in formula (10):

[0093]

[0094] Similarly, the output voltage ADC_I2 of the OUT terminal of the second measurement channel INA198 shunt detection chip I is in mV, as shown in formula (11).

[0095]

[0096] The differential voltage measurement circuit is a composite differential amplifier circuit composed of ADA4622, which is used to measure the differential voltage of the output channel. Figure 4As shown; specifically, it is composed of resistor R22, resistor R23, resistor R24, resistor R25, resistor R26, resistor R27, resistor R28, resistor R30, resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier V, ADA4622 operational amplifier VI, ADA4622 operational amplifier VII, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, and ADA4622 operational amplifier X; the resistor R22, resistor R23, resistor R24, resistor R25, resistor R26, resistor R27, resistor R28, ADA4622 Operational amplifier V, ADA4622 operational amplifier VI, and ADA4622 operational amplifier VII together constitute a differential voltage measurement circuit for the first measurement channel; the resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, and ADA4622 operational amplifier X together constitute a differential voltage measurement circuit for the second measurement channel; the differential voltage measurement circuit is specifically a three-stage circuit consisting of a voltage follower, a differential proportional amplifier circuit, and a waveform clamp circuit; wherein the voltage follower is the first stage, and is composed of resistors R22, ADA4622 operational amplifier IX, and waveform clamp circuit. The differential proportional amplifier circuit is the second stage, which is composed of resistors R23, R24, R25, R26, and ADA4622 operational amplifier VI; the waveform clamp circuit is the third stage, which is composed of resistors R27, R28, and operational amplifier VII; the positive input end of the ADA4622 operational amplifier V is connected to one end of the resistor R21, and its inverting input end is connected to the output end through the resistor R22; one end of the resistor R23 is connected to the output end of the first-stage voltage follower, and the other end is connected to the positive input end of the ADA4622 operational amplifier VI; one end of the resistor R24 ​​is connected to one end of the resistor R23, and the other end is grounded; Resistor R25 is connected to the CH1_N terminal of the first current output channel of the Howland voltage-controlled current source module, and the other end is connected to the inverting input end of the ADA4622 operational amplifier VI; the inverting input end of the ADA4622 operational amplifier VI is connected to the output end through resistor R26; one end of the resistor R27 is connected to the output end of the second-stage differential proportional amplifier circuit, and the other end is connected to the positive input end of the ADA4622 operational amplifier VII; the inverting input end of the ADA4622 operational amplifier VII is connected to the output end through resistor R28, and the output end is connected to the ADC channel of the single-chip microcomputer; the differential voltage measurement circuit of the second measurement channel is the same as that of the first channel, such as Figure 4 As shown; then the output ADC_V1 of the third-stage waveform clamp circuit, in mV, is as shown in formula (12):

[0097]

[0098] Where V o1+ is the voltage at the positive input terminal of the ADA4622 operational amplifier V, V o1- is the voltage at one end of resistor R25;

[0099] Similarly, the output ADC_V2 of the third-stage waveform clamp circuit of the differential voltage measurement circuit of the second measurement channel is as shown in formula (13) (unit: mV):

[0100]

[0101] Where V o2+ is the voltage at the positive input terminal of ADA4622 operational amplifier VIII, V o2- is the voltage at one end of resistor R33.

[0102] The voltage and current measurement module of each time-interference electrical stimulation core subunit includes two current measurement circuits and two differential voltage measurement circuits. The entire device has a total of 16 feedback channels, all of which are connected to the ADC input channel of the single-chip microcomputer.

[0103] Taking the simplest mode of time interference electrical stimulation as an example, only 1 channel of time interference output is needed at this time, so only 1 time interference core subunit is needed to realize the simplest function, and users can expand to up to 4 channels of output according to their own needs. First, the user can view the patient's case and treatment plan on the host computer, and evaluate the patient's recovery after confirmation. After that, the stimulation parameters can be set directly by operating the host computer or through the buttons of the slave computer, including waveform, frequency, phase, current size, transition time and duration. After receiving the instruction, the single-chip microcomputer will parse it, and the waveform, frequency and phase are realized by operating different DDS waveform generating circuits through the SPI interface and chip select pins; the current size and transition time are realized by changing the resistance value of the digital potentiometer in the Howland current source circuit through the I2C pin; the duration is realized by the timer function of the single-chip microcomputer. Such as Figure 5 The electrodes are arranged as shown, E1 and E2 are a pair of differential complementary current sources, connected to the first current output channel of the Howland voltage-controlled current source;

[0104] E3 and E4 are a pair of differential complementary current sources, connected to the second current output channel of the Howland voltage-controlled current source, with an angle of 90° between them. Assuming that the stimulation set by the user is 1mA time interference electrical stimulation with a carrier frequency of 2000Hz and a difference frequency of 10Hz, and other parameters are not required, the current between E1 and E2 is (in mA):

[0105] I1=Sin(2Π·2000·t)

[0106] Then the current between E3 and E4 is (in mA):

[0107] I2=Sin(2Π·2010·t)

[0108] At this time, the focal center of the stimulation is at the center of the plane, and a time interference current waveform with an envelope frequency of 10 Hz can be obtained.

Claims

1. A portable multi-channel time-interference transcranial electrical stimulation system, characterized in that It includes two parts: a host computer information management system and a portable multi-channel time-interference transcranial electrical stimulation device; wherein, the portable multi-channel time-interference transcranial electrical stimulation device specifically includes a single-chip main control module, a power management system, a human-computer interaction module, a signal transmission module and a time-interference electrical stimulation core unit; the power management system is used to provide power to the single-chip main control module, the signal transmission module and the time-interference electrical stimulation core unit; the single-chip main control module is connected to the human-computer interaction module, the signal transmission module and the time-interference electrical stimulation core unit in a two-way data transmission manner; the host computer information management system and the portable multi-channel time-interference transcranial electrical stimulation device are connected in a two-way data transmission manner through the signal transmission module.

2. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 1, characterized in that The power management system is composed of a 1.25V reference voltage generation circuit, a ±15V voltage generation circuit, a 3.3V voltage generation circuit, and a 7.4V lithium battery; wherein the 7.4V lithium battery is composed of two 18650 lithium batteries connected in series, and its output voltage controls the on and off state of the total power supply of the portable multi-channel time-interference transcranial electrical stimulation device through a self-locking switch; the 3.3V voltage generation circuit is composed of an AMS1117 voltage regulator chip, and the input end of the AMS1117 is connected to the total power supply of the 7.4V lithium battery after passing through the self-locking switch, and the output obtains a 3.3V voltage output; the input and output ends of the AMS1117 voltage regulator chip are each connected in parallel with a 10uF tantalum capacitor for filtering the voltage. The ±15V voltage generation circuit is composed of an ADP5070 power management chip and its peripheral feedback loop; the input end of the ADP5070 power management chip is connected to the total power supply of a 7.4V lithium battery after a self-locking switch, and a ±15V voltage output is obtained after a DCDC voltage regulator circuit with a switching frequency of 1.2MHz; the 1.25V reference voltage generation circuit adopts a REF35125 reference voltage chip; the input end of the REF35125 reference voltage chip is connected to the 3.3V voltage output by the 3.3V voltage generation circuit, and its output end is connected in parallel with a 10uF ceramic capacitor to obtain a high-precision 1.25V reference voltage with a maximum error of only 0.05%; The human-computer interaction module is composed of two user buttons and a 1.69-inch LCD display screen. The user buttons are connected to the IO port of the single-chip main control module, and the button status is read through an external interrupt; the LCD display screen is powered by a 3.3V voltage generation circuit and connected to the SPI3 interface of the single-chip main control module to achieve communication; when the user uses the device offline, the adjustable parameters of the device can be set through the user buttons, and the LCD display screen displays the current stimulation parameters and the actual output current and current size in real time; The signal transmission module adopts a module with Bluetooth wireless transmission mode; the Bluetooth wireless transmission module adopts an HC-08 Bluetooth serial port communication module, which is powered by a 3.3V voltage generation circuit and is connected to the USART1 interface of the microcontroller main control module. It can convert the USART1 data of the microcontroller into Bluetooth signals and realize wireless communication with the host computer information management system.

3. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 2, characterized in that The time interference electrical stimulation core unit is composed of no less than 1 and at most 4 time interference electrical stimulation core sub-units; each of the time interference electrical stimulation core sub-units is composed of a DDS waveform generating circuit module, a Howland voltage-controlled current source module and a voltage and current measuring module; there is a unidirectional data transmission connection between the DDS waveform generating circuit module and the Howland voltage-controlled current source module; there is a unidirectional data transmission connection between the Howland voltage-controlled current source module and the voltage and current measuring module; the output end of the Howland voltage-controlled current source module is connected to the wire-to-board needle holder via the voltage and current measuring module, and the electrode is connected to the needle holder through the wire, so that the current can be transmitted to the human scalp through the electrode to realize time interference electrical stimulation.

4. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 3, characterized in that The DDS waveform generating circuit module is composed of two DDS waveform generating circuits, each of which is a circuit structure composed of a 25MHz active crystal oscillator, an AD9834DDS chip and an AD8237 instrument amplifier; the DDS waveform generating circuit module is composed of resistor R37, resistor R38, resistor R39, resistor R40, resistor R41, resistor R42, resistor R43, resistor R44, resistor R45, resistor R46, resistor R47, resistor R48, resistor R49, resistor R50, capacitor C7, capacitor C8, capacitor C9, capacitor C10, capacitor C11, capacitor C12, capacitor C13, capacitor C14, capacitor C15, capacitor C16, capacitor C17, capacitor C18, capacitor C19, capacitor C20, capacitor C21, capacitor C22, capacitor C23, capacitor C24, capacitor C25, capacitor C26, active crystal oscillator XTAL1, active crystal oscillator XTAL2, AD9834 DDS chip I, AD9834 DDS chip II, AD8237 instrument amplifier I, instrument amplifier AD8237II; the resistors R37, R38, R39, R40, and R41 are composed of resistors R The resistor R41, the resistor R42, the resistor R43, the capacitor C7, the capacitor C8, the capacitor C9, the capacitor C10, the capacitor C11, the capacitor C12, the capacitor C13, the capacitor C14, the capacitor C15, the capacitor C16, the active crystal oscillator XTAL1, the AD9834DDS chip I, and the AD8237 instrument amplifier I together constitute the first DDS waveform generating circuit; the resistor R44, the resistor R45, the resistor R46, the resistor R47, the resistor R48, the resistor R49, the resistor R50, the capacitor C17, the capacitor C18, the capacitor C19, the capacitor C20, the capacitor C21, the capacitor C22, Capacitor C23, capacitor C24, capacitor C25, capacitor C26, active crystal oscillator XTAL2, AD9834DDS chip II, and AD8237 instrument amplifier II together constitute the second DDS waveform generating circuit; the power supply pins VDD and GND of the active crystal oscillator XTAL1 are respectively connected to the output end and ground of the 3.3V voltage generating circuit, the Tri-State pin is suspended, and the OUTPUT pin is connected to the MCLK pin of the AD9834DDS chip I; the resistor R37 is connected in parallel with the capacitor C8, and one end is connected to the DS of the AD9834DDS chip I ADJUST pin, and the other end is grounded; one end of the capacitor C9 is connected to the REFOUT pin of the AD9834DDS chip 1, and the other end is grounded; the capacitors C7, C11, C12, and C16 are connected in parallel, one end is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; one end of the capacitor C10 is connected to the COMP pin of the AD9834DDS chip 1, and the other end is connected to the 3.3V voltage generating circuit.3V voltage generating circuit is connected; one end of the capacitor C13 is connected to the CAP / 2.5V of the AD9834DDS chip I, and the other end is grounded; the resistor R38 is connected in parallel with the capacitor C14, one end is connected to the IOUT pin of the AD9834DDS chip I, and the other end is grounded; the resistor R39 and the capacitor C15 are connected in parallel, one end is connected to the IOUTB pin of the AD9834DDS chip I, and the other end is grounded; the FSELECT pin, PSELECT pin, SLEEP pin, and RESET pin of the AD9834DDS chip I are all connected to the ground, and the VIN pin, SIGN BIT The OUT pins are all suspended, the SCLK pin and the SDATA pin are connected to the SPI2 bus of the single-chip main control module, and the FSYNC pin is connected to the GPIO of the single-chip main control module; the resistor R40 is a 2kΩ potentiometer, one end of which is fixed and connected to the output end of the AD8237 instrument amplifier I, and the other end of which is suspended, and the sliding end is connected to one end of the resistor R42; the other end of the resistor R42 is connected to one end of the resistor R43 and the FB pin of the AD8237 instrument amplifier I; the other end of the resistor R43 is connected to one end of the resistor R41 The first end is connected to the output end of the 1.25V reference voltage generating circuit; the other end of the resistor R41 is connected to the REF pin of the AD8237 instrument amplifier I; the power supply pins +Vs and -Vs of the AD8237 instrument amplifier I are respectively connected to the output and ground of the 3.3V voltage generating circuit, the positive input terminal and the inverting input terminal are respectively connected to the IOUT pin and IOUTB pin of the AD9834DDS chip I, and the BW pin is connected to the ground; the wiring method of the second DDS waveform generating circuit is the same as that of the first DDS waveform generating circuit. .

5. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 4, characterized in that The AD9834DDS chip I is controlled by the microcontroller master module through the SPI2 interface, and can generate two frequency-complementary, phase-adjustable sine waves on the IOUT and IOUTB pins, as shown in formulas (1) and (2), respectively, in units of V: in, are the frequency and phase that can be set, and Π is the circumference of a circle; The two sinusoidal signal outputs of the AD9834DDS chip I are connected to the positive input terminal and the negative input terminal of the AD8237 instrument amplifier I respectively, and the potentiometer resistor R40 is adjusted to meet the requirements. At this time, the resistor network gain of the AD8237 instrumentation amplifier I is 1.75 times, and there is a 1.25V voltage bias provided by the 1.25V reference voltage generation circuit. The output voltage waveform V1 at this time can be obtained in V, as shown in formula (3): Among them, the output voltage V1 is the voltage signal after being amplified by the AD8237 instrument amplifier I; Similarly, the output voltage V2 of the second DDS waveform generating circuit is V, as shown in formula (4): in, The frequency and phase set for the second DDS waveform generating circuit.

6. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 3, characterized in that The Howland voltage-controlled current source module is composed of two current output channels, each of which is composed of a Howland enhanced differential complementary voltage-controlled current source and a dual-channel digital potentiometer; the Howland enhanced differential complementary voltage-controlled current source is a circuit structure composed of a pair of ADA4610 operational amplifiers and ADA4622 operational amplifiers; specifically, it is composed of resistors R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, and R11. , resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R17, resistor R18, resistor R19, resistor R20, wire-to-board pin header P2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier I, ADA4622 operational amplifier II, ADA4622 operational amplifier III, ADA4622 operational amplifier IV; the resistor R 1. Resistor R2, resistor R3, resistor R4, resistor R5, resistor R6, resistor R7, resistor R8, resistor R9, resistor R10, capacitor C1, capacitor C2, ADA4610 operational amplifier I, ADA4610 operational amplifier II, ADA4622 operational amplifier I, and ADA4622 operational amplifier II together constitute the Howland enhanced differential complementary voltage-controlled current source of the first current output channel; the resistor R11, resistor R12, resistor R13, resistor R14, resistor R15, resistor R16, resistor R 17, resistor R18, resistor R19, resistor R20, capacitor C3, capacitor C4, ADA4610 operational amplifier III, ADA4610 operational amplifier IV, ADA4622 operational amplifier III, ADA4622 operational amplifier IV constitute the Howland enhanced differential complementary voltage-controlled current source of the second current output channel; one end of the resistor R1 is connected to the output of the first DDS signal generating circuit, and the other end thereof is connected to the positive input end of the ADA4610 operational amplifier I; one end of the resistor R3 is connected to 1.The output end of the 25V reference voltage generating circuit is connected, and the other end is connected to the negative input end of the ADA4610 operational amplifier I; the output end of the ADA4610 operational amplifier I is connected to the digital potentiometer via the resistor R5; the resistor R4 is connected between the negative input end and the output end of the ADA4610 operational amplifier I; the positive input end of the ADA4622 operational amplifier I is connected to the digital potentiometer, and its negative input end is short-circuited with its output end; the ADA4610 operational amplifier I and the ADA4622 operational amplifier I are also connected to the output end of the ±15V voltage generating circuit, and the ±15V voltage generating circuit provides working power for both; one end of the resistor R2 is connected to the positive input end of the ADA4610 operational amplifier I, and the other end is connected to the output end of the ADA4622 operational amplifier I; the specific circuit connection mode of the Howland enhanced differential complementary voltage-controlled current source of the second current output channel is the same as that of the first current output channel. .

7. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 6, characterized in that The dual-channel digital potentiometer adopts the dual-channel digital potentiometer chip AD5248 structure, specifically composed of a 2.5kΩ digital potentiometer chip AD5248-I, a 2.5kΩ digital potentiometer chip AD5248-II, a capacitor C1, a capacitor C2, a capacitor C3, and a capacitor C4; the 2.5kΩ digital potentiometer chip AD5248-I, the capacitor C1, and the capacitor C2 together constitute the dual-channel digital potentiometer of the first current output channel; the 2.5kΩ digital potentiometer chip AD5248-II, the capacitor C3, and the capacitor C4 together constitute the dual-channel digital potentiometer of the second current output channel; wherein the VDD terminal of the 2.5kΩ digital potentiometer chip AD5248-I is connected to the 3 .3V voltage generating circuit, B1 terminal and B2 terminal are respectively connected to one end of resistor R5 and one end of resistor R10 of two current output channels of Howland enhanced differential complementary voltage-controlled current source, W1 terminal and W2 terminal are respectively connected to the positive input end of ADA4622 operational amplifier I and the positive input end of ADA4622 operational amplifier II in the first current output channel of Howland enhanced differential complementary voltage-controlled current source; the capacitor C1 and the capacitor C2 are connected in parallel, one end is connected to the output end of the 3.3V voltage generating circuit, and the other end is grounded; the specific circuit connection method of the dual-channel digital potentiometer of the second current output channel is the same as that of the first current output channel.

8. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 6, characterized in that The ADA4610 operational amplifier I and the ADA4622 operational amplifier I are powered by a ±15V voltage generated by a ±15V voltage generating circuit; When the resistance values ​​of B1 and W1, B2 and W2 of the dual-channel digital potentiometer are R BW1_1 and R BW1_2 When the current I 1_P , unit A, as shown in formula (5): Where V in1_1+ is the voltage at the left end of resistor R1, V in1_1- is the voltage at the left end of resistor R3; when When R5 = 200Ω, the current I output from the CH1_N terminal at the positive input of the ADA4622 operational amplifier I 1_P , unit A, as shown in formula (6): Similarly, the current I output from the CH1_N terminal at the positive input of the ADA4622 operational amplifier II is 1_N , unit A, as shown in formula (7): Where V in1_2+ is the voltage at the left end of resistor R6, V in1_2- is the voltage at the left end of resistor R8; V in1_1+ and V in1_2- Connected to the first output V1 of the DDS waveform generation circuit, V in1_1- and V in1_2+ connected to the output terminal of the 1.25V reference voltage generating circuit; and the resistance value R BW1_1 , the resistance value R between B2 and W2 BW1_2 Same and both are R BW1 When , a pair of complementary differential current sources from CH1_P terminal to CH1_N terminal can be obtained. If the direction of the current from CH1_P terminal to CH1_N terminal is positive, the differential current I flowing through the load between CH1_P terminal and CH1_N terminal is L1 , unit A, as shown in formula (8): Similarly, the second current output channel outputs the current I flowing through the load. L2 , unit A, as shown in formula (9).

9. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 3, characterized in that The voltage and current measurement module is composed of two measurement channels, each of which is composed of a current measurement circuit and a differential voltage measurement circuit; the current measurement circuit is a circuit structure composed of an INA198 shunt detection chip, specifically composed of a resistor R21, a resistor R29, a capacitor C5, a capacitor C6, an INA198 shunt detection chip I, and an INA198 shunt detection chip II; the resistor R21, the capacitor C5, and the INA198 shunt detection chip I together constitute the current measurement circuit of the first measurement channel; the resistor R29, the capacitor C6, and the INA198 shunt detection chip II together constitute the current measurement circuit of the second measurement channel The current measurement circuit of the measurement channel; one end of the resistor R21 is connected to the CH1_P terminal at the positive input end of the ADA4622 operational amplifier I, and the other end thereof is connected to the wire-to-board needle seat; one end of the capacitor C5 is connected to the output end of the 3.3V voltage generation circuit, and the other end is grounded; the V+ terminal of the INA198 shunt detection chip I is connected to the output end of the 3.3V voltage generation circuit, the VIN+ terminal and the VIN- terminal are respectively connected to the two ends of the resistor R29, and the OUT terminal is connected to the ADC channel of the single-chip microcomputer; the specific circuit connection method of the current detection circuit of the second measurement channel is the same as that of the first measurement channel; When the differential complementary current between CH1_P and CH1_N is I L1 When the resistance value of resistor R29 is 20Ω, the output voltage ADC_I1 of the OUT terminal of the INA198 shunt detection chip I of the first measurement channel is in mV, as shown in formula (10): Similarly, the output voltage ADC_I2 of the OUT terminal of the second measurement channel INA198 shunt detection chip I is in mV, as shown in formula (11).

10. A portable multi-channel time-interference transcranial electrical stimulation system according to claim 9, characterized in that The differential voltage measurement circuit is a composite differential amplifier circuit composed of ADA4622, which is used to measure the differential voltage of the output channel. Specifically, it is composed of resistor R22, resistor R23, resistor R24, resistor R25, resistor R26, resistor R27, resistor R28, resistor R30, resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier V, ADA4622 operational amplifier VI, ADA4622 operational amplifier VII, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, and ADA4622 operational amplifier X; the resistor R22, resistor R23, resistor R24 , resistor R25, resistor R26, resistor R27, resistor R28, ADA4622 operational amplifier V, ADA4622 operational amplifier VI, ADA4622 operational amplifier VII together constitute the differential voltage measurement circuit of the first measurement channel; the resistor R31, resistor R32, resistor R33, resistor R34, resistor R35, resistor R36, ADA4622 operational amplifier VIII, ADA4622 operational amplifier IX, ADA4622 operational amplifier X together constitute the differential voltage measurement circuit of the second measurement channel; the differential voltage measurement circuit is specifically a three-stage circuit composed of a voltage follower, a differential proportional amplifier circuit, and a waveform clamping circuit; wherein the voltage follower The device is the first stage, which is composed of a resistor R22 and an ADA4622 operational amplifier V; the differential proportional amplifier circuit is the second stage, which is composed of a resistor R23, a resistor R24, a resistor R25, a resistor R26, and an ADA4622 operational amplifier VI; the waveform clamp circuit is the third stage, which is composed of a resistor R27, a resistor R28, and an operational amplifier VII; the positive input end of the ADA4622 operational amplifier V is connected to one end of the resistor R21, and its inverting input end is connected to the output end through the resistor R22; one end of the resistor R23 is connected to the output end of the first stage voltage follower, and the other end is connected to the positive input end of the ADA4622 operational amplifier VI; one end of the resistor R24 ​​is connected to one end of the resistor R23 The resistor R25 is connected to the CH1_N terminal of the first current output channel of the Howland voltage-controlled current source module, and the other end is connected to the inverting input end of the ADA4622 operational amplifier VI; the inverting input end of the ADA4622 operational amplifier VI is connected to the output end through the resistor R26; one end of the resistor R27 is connected to the output end of the second-stage differential proportional amplifier circuit, and the other end is connected to the positive input end of the ADA4622 operational amplifier VII; the inverting input end of the ADA4622 operational amplifier VII is connected to the output end through the resistor R28, and the output end is connected to the ADC channel of the single-chip microcomputer; the differential voltage measurement circuit of the second measurement channel is the same as that of the first channel;Then the output ADC_V1 of the third-stage waveform clamp circuit, in mV, is as shown in formula (12): Where V o1+ is the voltage at the positive input terminal of the ADA4622 operational amplifier V, V o1- is the voltage at one end of resistor R25; Similarly, the output ADC_V2 of the third-stage waveform clamp circuit of the differential voltage measurement circuit of the second measurement channel is as shown in formula (13) (unit: mV): Where V o2+ is the voltage at the positive input terminal of ADA4622 operational amplifier VIII, V o2- is the voltage at one end of resistor R33; The voltage and current measurement module of each time-interference electrical stimulation core subunit includes two current measurement circuits and two differential voltage measurement circuits. The entire device has a total of 16 feedback channels, all of which are connected to the ADC input channel of the single-chip microcomputer.

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