阅读说明：本技术 一种融合经颅电刺激和迷走神经刺激的电刺激装置 (Electrical stimulation device fusing transcranial electrical stimulation and vagus nerve stimulation ) 是由 秦伟 杨群 郑斌 于 2019-08-22 设计创作，主要内容包括：本发明公开了一种融合经颅电刺激和迷走神经刺激的电刺激装置,由经颅电刺激模块和迷走神经电刺激模块组成,经颅电刺激模块由ARM控制单元、FPGA波形发生单元和模拟电路组成,ARM控制单元将控制命令波形参数信息通过FSMC发送给FPGA,FPGA波形产生单元产生四通道数字波形信号,首先通过数模转换电路转换为四通道模拟信号波形,然后通过初级放大电路进行放大,然后通过滤波电路滤除除了波形信号以外的干扰信号,再经过次级放大电路将波形放大到控制单元要求的波形幅值进行输出。非常高的安全性,其电流大小波形参数等要能够实时调节,确保不会危害人体安全,同时本模块既能输出恒流刺激,也能在经颅交流电刺激模式下,输出不同种类的波形。(The invention discloses an electrical stimulation device fusing transcranial electrical stimulation and vagus nerve stimulation, which consists of a transcranial electrical stimulation module and a vagus nerve electrical stimulation module, wherein the transcranial electrical stimulation module consists of an ARM control unit, an FPGA waveform generation unit and an analog circuit, the ARM control unit sends control command waveform parameter information to an FPGA through an FSMC, the FPGA waveform generation unit generates a four-channel digital waveform signal, the four-channel digital waveform signal is firstly converted into a four-channel analog signal waveform through a digital-to-analog conversion circuit, then the four-channel analog signal waveform is amplified through a primary amplification circuit, then interference signals except the waveform signal are filtered through a filter circuit, and the waveform is amplified to a waveform amplitude required by the control unit through a secondary amplification circuit and is output. The module has very high safety, the current size waveform parameters and the like can be adjusted in real time, the safety of a human body is ensured not to be damaged, and meanwhile, the module can output constant-current stimulation and can also output different types of waveforms in a transcranial alternating current stimulation mode.)

1. An electrical stimulation apparatus for fusing transcranial electrical stimulation and vagal electrical stimulation, characterized in that: consists of a transcranial electrical stimulation module and a vagus nerve electrical stimulation module.

2. The electrical stimulation apparatus as claimed in claim 1, wherein: the transcranial electrical stimulation module consists of an ARM control unit, an FPGA waveform generation unit and an analog circuit, wherein the ARM control unit sends control command waveform parameter information to the FPGA through an FSMC (frequency modulated controller), the FPGA waveform generation unit generates a four-channel digital waveform signal, the four-channel digital waveform signal is firstly converted into a four-channel analog signal waveform through a digital-to-analog conversion circuit, then the four-channel analog signal waveform is amplified through a primary amplification circuit, then interference signals except the waveform signal are filtered through a filter circuit, and the waveform is amplified to a waveform amplitude value required by the control unit through a secondary amplification circuit and then output;

The transcranial electrical stimulation module selects an iCore3ARM + FPGA double-core board, the ARM chip and the FPGA chip are integrated on a circuit board by the development board, the ARM chip adopts STM32F407IGT6 and carries a 168MHz dominant frequency Cortex-M4 kernel, the FPGA chip adopts 256-pin Cyclone fourth-generation EP4CE10F17C8N, the two chips are connected through a variable static storage controller, the ARM chip is connected with a DAP simulator through an SWD interface, and the FPGA chip is connected with a USBBlaser through a JTAG port.

3. The electrical stimulation apparatus as claimed in claim 1, wherein: the transcranial electrical stimulation module is provided with a current detection circuit to avoid overhigh output current, and the current detection circuit adopts an INA286 bidirectional shunt detector; in the output process of the signal, firstly, a 5-omega resistor is used for realizing differential mode sampling; the reference voltage is 2.5V, the difference is amplified by 100 times to obtain the measuring current between +/-2.5 mA, and then the conversion process from an analog signal to a digital signal is carried out by utilizing an analog-to-digital converter ADS 7814; the FPGA acquires digital signals and transmits the digital signals to the ARM, and the ARM calculates the digital signals to form feedback and output stable current.

4. The electrical stimulation apparatus as claimed in claim 1, wherein: the digital-to-analog conversion circuit adopts a high-performance digital-to-analog conversion chip TLV5614 of TI company, which is a four-channel DAC with 12-bit precision and serial input digital-to-analog conversion chip, pins 2 to 7 of the chip are input control pins, firstly, a pin CS of a pin 6 is set to be low, then, a falling edge of a pin FS of the 7 starts to move waveform data to an internal register of a falling edge of a clock signal of a pin SCLK of a pin 5 bit by bit, when 16-bit data or a rising edge of a signal of the pin FS are transmitted, data of the register is moved to an internal latch of the digital-to-analog conversion chip TLV5614, so that data transmission is completed sequentially, pins 10 and 15 are reference power supply input pins, and pins 11 to 14 are analog signal output pins, and the waveform analog signals after digital-to-analog conversion are output to a next processing circuit.

5. the electrical stimulation apparatus as claimed in claim 1, wherein: the amplifying and filtering circuit comprises a primary amplifying filter and a secondary amplifying filter, two inverse proportion amplifiers are selected to amplify the analog signals output by the DAC, the sampling frequency of the DAC is 1kHz, the signals output by the DAC have 2.5V direct-current voltage, half of the DAC input voltage is added to the positive input end of the operational amplifier, and the direct-current part is subtracted through a subtracter; the amplifier part of the later stage is an inverse proportional amplifier with variable gain, and the gain is adjusted by a slide rheostat and is in the range of-10 to 0 times.

6. The electrical stimulation apparatus as claimed in claim 1, wherein: the topological structure of the two serially connected second-order low-pass filters is a Sallen-key active low-pass filter; the filter cut-off frequency is 500Hz, the channel gain is 1 and the stop band gain is-40 dB.

7. The electrical stimulation apparatus as claimed in claim 1, wherein: the power supply of the analog circuit system is positive and negative 12V voltage, 2.5V voltage is generated by an lm385-2.5 voltage stabilizing diode, stable voltage is output through a follower formed by an operational amplifier, and reference voltage of-2.5V is generated through a 1: 1 inverse proportional amplifier.

8. the electrical stimulation apparatus as claimed in claim 1, wherein: the vagus nerve stimulation module comprises a signal transmission unit, a waveform generation and current control unit and a power management unit; the signal transmission unit comprises a control key used for setting the pulse width and frequency parameters of stimulation; the waveform generation and current control unit generates a needed voltage-controlled bidirectional microampere-level pulse stimulation current waveform and is controlled by two paths of PWM waveforms; the power management module comprises an isolation power supply and a DC-DC boosting module, and the adjustable resistor is used for dividing voltage and adjusting output voltage.

9. the electrical stimulation apparatus of claim 8, wherein: the circuit framework of the vagus nerve stimulation module comprises a power supply protection circuit, an isolation power supply circuit, an MCU master control module, a DC-DC booster circuit and an output circuit; the MCU main control module generates a needed voltage-controlled bidirectional microampere-level pulse stimulation current waveform, and is controlled by two paths of pulse width modulation waveforms, and the output circuit divides the voltage by an adjustable resistor and adjusts the output voltage; the vagus nerve stimulation module is powered by a 5V direct current stabilized power supply, and a patch self-recovery fuse SMD1812P050TF is adopted to ensure the safety of power supply input.

10. the electrical stimulation apparatus of claim 8, wherein: the vagus nerve stimulation module is provided with a stable power supply device for carrying out a stable power supply process, 5V direct current stabilized power supply is used for supplying power, the realization of 3.3V voltage is reduced by depending on a power management chip MP2451 and the power supply for a main control chip is realized, and the two power supply voltages are completed by depending on an isolation power supply circuit; the vagus nerve stimulation circuit is set to be constant current, the size of a stimulation gear is represented by different voltages, the adjustable resistor is used for dividing the voltage, the output voltage is adjusted, and the voltage of the output gear is adjustable between 9V and 30V, so that the voltage of a 5V power supply is increased to 9V through the DC-DC booster circuit and then is increased to the maximum 30V through the transformer; constant current output is ensured through a current control circuit, the constant current source circuit consists of two operational amplifiers, and the MCU controls two paths of PWM signals to generate pulse waveforms required by stimulation.

The technical field is as follows:

The invention belongs to the technical field of medical instruments, and particularly relates to an electrical stimulation device fusing transcranial electrical stimulation and vagus nerve stimulation.

Background art:

Chinese patent (application number: 201810910152.3 application date: 2018-08-10) discloses a non-invasive closed-loop transcranial electrical stimulation device, which comprises an electrode cap, a preamplifier, a host and an upper computer; the electrode cap is worn on the head of a user and comprises a plurality of disc-shaped electrodes for acquiring electroencephalogram signals and applying electrostimulation; the preamplifier is connected with the electrode cap through a cable, comprises a plurality of selection switches and a plurality of amplifiers and is used for switching the acquisition and stimulation functions of each electrode and pre-amplifying electroencephalogram signals; the host is connected with the preamplifier through a cable and is used for collecting, real-time calculating and transmitting electroencephalogram signals and generating transcranial electrical stimulation signals; the upper computer is in wireless connection with the host and is used for receiving the multichannel electroencephalogram signals recorded by the host and displaying and recording the signals; or download the real-time signal analysis algorithm and closed-loop control strategy to the host computer. The patent lacks the adjusting device of current size wave form parameter, has certain insecurity.

Chinese patent (application number: 201810104245.7 application date: 2018-02-02) discloses a multichannel transcranial electrical stimulation device and a method thereof, wherein the multichannel transcranial electrical stimulation device comprises an upper computer module, an ARM control module, an FPGA waveform generation module and an analog circuit module; the ARM control module is mainly responsible for control data sent by the upper computer module and transmits the control data to an RAM storage unit of the FPGA waveform generation module through the variable static storage controller; the FPGA waveform generation module comprises a plurality of mutually independent channels, each channel is provided with a waveform generation module and can independently generate waveforms, and the control data obtained by the RAM storage unit can control the generation of the waveforms of each channel.

Transcranial direct current stimulation (tDCS) is a non-invasive technique for regulating brain cortical neuronal activity using a constant, low-intensity direct current (1-2 mA). The brain stimulator is divided into an anode electrode and a cathode electrode, wherein weak current released by the electrodes can penetrate through the skull to directly stimulate the cerebral cortex, change the state of shallow resting membrane potential, change the excitability of neurons, improve the excitability of nerves by anode stimulation, and reduce the excitability of nerves by cathode stimulation. The vagus nerve is a peripheral nervous system which is widely distributed in vivo, ear branches of the vagus nerve are the only branches of the vagus nerve on the body surface, and the nerve fiber membrane potential is changed by directly stimulating vagus nerve fibers in a mode of ear percutaneous vagal nerve electrical stimulation (tVNS), so that the effect of activating brain stem nuclei such as solitary fasciculation nucleus, locus coeruleus, trigeminal nucleus and the like is generated. In order to achieve the above-mentioned purpose, the transcranial direct current stimulation directly changes the excitability of cerebral cortex and other modes, thereby affecting the behaviors and cognition of human and animals, and being an up-to-down nerve regulation means; transcutaneous vagal nerve stimulation is a down-to-up neuromodulation means that affects human behavior and cognition by activating the excitability of nerve fibers in the peripheral nervous system, which is transmitted along the nerve fibers to higher order nerve centers, altering the excitability of higher order centers. For both of these neuromodulation approaches, the direction of their modulation is exactly opposite, however, they each have their own unique effects. The two regulation and control means are interested to be applied cooperatively, and whether the 'super-sum' effect similar to '1 +1> 2' is generated or not is judged, so that a more meaningful nerve regulation and control value is obtained, and the research and clinical work are greatly promoted; there is no device in the prior art which combines the two.

The invention content is as follows:

The invention aims to overcome the defects of the prior art and provide an electrical stimulation device fusing transcranial electrical stimulation and vagus nerve stimulation, which has very high safety, and the current waveform parameters and the like of the electrical stimulation device can be adjusted in real time to ensure that the safety of a human body is not damaged.

The purpose of the invention is solved by the following technical scheme:

an electrical stimulation device fusing transcranial electrical stimulation and vagus nerve stimulation is composed of a transcranial electrical stimulation module and a vagus nerve electrical stimulation module.

A transcranial electrical stimulation module comprises an ARM control unit, an FPGA waveform generation unit and an analog circuit, wherein the ARM control unit sends control command waveform parameter information to an FPGA through an FSMC, the FPGA waveform generation unit generates a four-channel digital waveform signal, the four-channel digital waveform signal is firstly converted into a four-channel analog signal waveform through a digital-to-analog conversion circuit, then the four-channel analog signal waveform is amplified through a primary amplification circuit, then interference signals except the waveform signal are filtered through a filter circuit, and the waveform is amplified to a waveform amplitude required by the control unit through a secondary amplification circuit and then output.

The transcranial electrical stimulation module selects an iCore3ARM + FPGA dual core board, the ARM chip and the FPGA chip are integrated on a circuit board by the development board, the ARM chip adopts STM32F407IGT6 and carries a 168MHz dominant frequency Cortex-M4 kernel, the FPGA chip adopts 256-pin Cyclone four-generation EP4CE10F17C8N, the two chips are connected through a variable static storage controller, the ARM chip is connected with a DAP simulator through an SWD interface, and the FPGA chip is connected with a USBBlaser through a JTAG port.

The transcranial electrical stimulation module is provided with a current detection circuit to avoid overhigh output current, and the current detection circuit adopts an INA286 bidirectional shunt detector; in the output process of the signal, firstly, a 5-omega resistor is used for realizing differential mode sampling; the reference voltage is 2.5V, the difference is amplified by 100 times to obtain the measuring current between +/-2.5 mA, and then the conversion process from an analog signal to a digital signal is carried out by utilizing an analog-to-digital converter ADS 7814; the FPGA acquires digital signals and transmits the digital signals to the ARM, and the ARM calculates the digital signals to form feedback and output stable current.

The digital-to-analog conversion circuit adopts a high-performance digital-to-analog conversion chip TLV5614 of TI company, which is a four-channel DAC with 12-bit precision and serial input digital-to-analog conversion chip, pins 2 to 7 of the chip are input control pins, firstly, a pin CS of a pin 6 is set to be low, then, a falling edge of a pin FS of the 7 starts to move waveform data to an internal register of a falling edge of a clock signal of a pin SCLK of a pin 5 bit by bit, when a signal of 16-bit data or the signal of the pin FS is transmitted, the data of the register is moved to an internal latch of the digital-to-analog conversion chip TLV5614, so that the data transmission is sequentially completed, pins 10 and 15 are reference power supply input pins, pins 11 to 14 are analog signal output pins, and the waveform analog signal after digital-to-analog conversion is output to a next processing circuit.

The amplifying and filtering circuit comprises a primary amplifying filter and a secondary amplifying filter, two inverse proportion amplifiers are selected to amplify the analog signals output by the DAC, the sampling frequency of the DAC is 1kHz, the signals output by the DAC have 2.5V direct-current voltage, one half of the DAC input voltage is added to the positive input end of the operational amplifier, and the direct-current part is subtracted through a subtracter; the amplifier part of the later stage is an inverse proportional amplifier with variable gain, and the gain is adjusted by a slide rheostat and is in the range of-10 to 0 times.

the topological structure of the two serially connected second-order low-pass filters is a Sallen-key active low-pass filter; the filter cut-off frequency is 500Hz, the channel gain is 1 and the stop band gain is-40 dB.

The power supply of the analog circuit system is positive and negative 12V voltage, 2.5V voltage is generated by an lm385-2.5 voltage stabilizing diode, the stabilized voltage is output through a follower formed by an operational amplifier, and then-2.5V reference voltage is generated through a 1: 1 inverse proportional amplifier.

The vagus nerve stimulation module comprises a signal transmission unit, a waveform generation and current control unit and a power management unit; the signal transmission unit comprises a control key used for setting the pulse width and frequency parameters of stimulation; the waveform generation and current control unit generates a needed voltage-controlled bidirectional microampere level pulse stimulation current waveform and is controlled by two paths of PWM waveforms; the power management module comprises an isolation power supply and a DC-DC boosting module, and the adjustable resistor is used for dividing voltage and adjusting output voltage.

The circuit framework of the vagus nerve stimulation module comprises a power supply protection circuit, an isolation power supply circuit, an MCU master control module, a DC-DC booster circuit and an output circuit; the MCU main control module generates a needed voltage-controlled bidirectional microampere-level pulse stimulation current waveform, and is controlled by two paths of pulse width modulation waveforms, and the output circuit divides the voltage by an adjustable resistor and adjusts the output voltage; the vagus nerve stimulation module is powered by a 5V direct-current stabilized power supply, and a patch self-recovery fuse SMD1812P050TF is adopted to ensure the safety of power supply input.

The vagus nerve stimulation module is provided with a stable power supply device for carrying out a stable power supply process, 5V direct current stabilized power supply is used for supplying power, the realization of 3.3V voltage depends on a power supply management chip MP2451 for reducing voltage and realizing the power supply for a main control chip, and the two power supply voltages are completed by an isolation power supply circuit; the vagus nerve stimulation circuit is set to be constant current, the size of a stimulation gear is represented by different voltages, the adjustable resistor is used for dividing the voltage, the output voltage is adjusted, the voltage of the output gear is adjustable between 9V and 30V, so that the voltage of a 5V power supply is increased to 9V through the DC-DC booster circuit and then is increased to the maximum 30V through the transformer; constant current output is ensured through a current control circuit, the constant current source circuit consists of two operational amplifiers, and the MCU controls two paths of PWM signals to generate pulse waveforms required by stimulation.

The invention has the beneficial effects that:

The module combines transcranial direct current stimulation and transcranial alternating current stimulation together, outputs constant current stimulation in a transcranial direct current stimulation mode, and outputs different types of waveforms in a transcranial alternating current stimulation mode.

Description of the drawings:

FIG. 1 is a schematic structural diagram of a transcranial electrical stimulation module;

FIG. 2 is an analog circuit diagram;

FIG. 3 is a TLV5614 digital-to-analog conversion circuit diagram;

FIG. 4 is an enlarged filter circuit diagram;

FIG. 5 is a circuit diagram of current detection;

FIG. 6 is a schematic diagram of analog circuitry;

Fig. 7 is a circuit block diagram of a vagal nerve stimulation module;

FIG. 8 is a schematic diagram of a power input protection circuit;

FIG. 9 is a schematic diagram of an isolated power supply circuit;

FIG. 10 is a schematic diagram of a DC-DC boost circuit;

FIG. 11 is a schematic diagram of a current control circuit;

FIG. 12 is a Block design;

FIG. 13 is a graph of activation intensity for four experimental groups in five brain regions; FIG. 13-1 is a graph of right lateral cingulate gyrocembrial region activation intensity; FIG. 13-2 is a left thalamic region activation intensity graph; FIG. 13-3 is a graph of left pallidose brain region activation intensity; FIGS. 13-4 are graphs of right thalamic region activation intensity; FIGS. 13-5 are graphs of right putamen region activation intensity;

Wherein the ordinate is the activation intensity, and the abscissa is the corresponding group: tDCS + tVNS, tDCS + tVNS pseudo stimulation, tDCS pseudo stimulation + tVNS pseudo stimulation. Values in the graph are mean ± standard deviation. The english abbreviations in the figures correspond to: PGR: right lateral cingulum, LTL: left thalamus, LPaL: left pallor, RTR: right thalamus, RPuR: right putamen.

The specific implementation mode is as follows:

the invention is described in further detail below with reference to the accompanying drawings:

as shown in fig. 1 and 2, the transcranial electrical stimulation module applies direct current or alternating current to the head of a human body, and changes the activity of cerebral neurons through current so as to regulate the process of body pathology, so that the module firstly requires very high safety, and the current size and waveform parameters and the like of the module can be regulated in real time so as to ensure that the safety of the human body is not damaged; meanwhile, the module combines transcranial direct current stimulation and transcranial alternating current stimulation together, constant current stimulation is required to be output in a transcranial direct current stimulation mode, different types of waveforms are required to be output in a transcranial alternating current stimulation mode, the waveforms are sine waves, square waves, triangular waves and random noise waveforms respectively, the frequency and amplitude of the sine waves, the square waves and the triangular waves can be adjusted in real time by an upper computer, and conditions are provided for different output requirements; finally, the module is designed to generate four-channel transcranial electrical stimulation, parameters such as output waveforms, amplitudes and the like of all channels are the same, and specific technical index parameters are as follows: the number of channels is 4, the current is less than or equal to 2mA, the types of waveforms are 5, the amplitude of the waveform is 0-12V, and the frequency is 1-100 Hz.

The transcranial electrical stimulation module consists of an ARM control unit, an FPGA waveform generating unit and an analog circuit, as the adoption of the ARM development board and the FPGA development board causes overlarge volume and inconvenient debugging operation, the module adopts an iCore3ARM + FPGA dual core board, the development board integrates an ARM chip and an FPGA chip on one circuit board, the ARM chip adopts STM32F407IGT6, the FPGA chip is loaded with a 168MHz dominant frequency Cortex-M4 kernel, has excellent performance, meets the performance requirement of the module, adopts 256-pin Cyclone four-generation EP4CE10F17C8N, the module is low in power consumption and high in performance, meets the requirements of waveform generation of the module, the two chips are connected through a Flexible Static Memory Controller (FSMC) to perform data transmission, command sending and other operations, the highest transmission speed can reach 40M/s, the ARM chip is connected with the DAP simulator through an SWD interface to perform program downloading, and the FPGA chip is connected with the USBBlaser through a JTAG port to perform program downloading.

The analog circuit comprises the following circuit modules: a digital-to-analog conversion circuit, an amplifying circuit, a filter circuit, a current detection circuit and a power supply circuit, as shown in fig. 2.

The digital-to-analog conversion circuit selects a high-performance digital-to-analog conversion chip TLV5614 of TI company, which is a four-channel DAC with 12-bit precision and serial input digital-to-analog conversion chip, pins 2 to 7 of the chip are input control pins, firstly, pin 6 CS is set to be low, then the falling edge of pin 7 FS starts to move waveform data bit by bit to an internal register of the falling edge of a 5 th pin SCLK clock signal, when 16-bit data or the rising edge of an FS pin signal is transmitted, the data of the register is moved to an internal latch of the digital-to-analog conversion chip TLV5614, so that the data transmission is completed sequentially, pins 10 and 15 are reference power supply input pins, and pins 11 to 14 are analog signal output pins, and the waveform analog signal after digital-to-analog conversion is output to a next processing circuit. TLV5614 digital-to-analog conversion circuit is shown in fig. 3.

The amplifying and filtering circuit comprises a primary amplifying filter and a secondary amplifying filter, because the reference voltage of the DAC module of the previous stage is 2.5V, the output voltage range of the DAC module is 0-5V, and the signal amplitude is small, the DAC module is amplified by one time, then a 4-order low-pass filter is connected in series to remove high-frequency noise, and finally the signal is amplified to the required amplitude through an inverse proportion amplifier. The module adopts two inverse proportion amplifiers to amplify the analog signal output by the DAC, and because the signal output by the DAC has 2.5V direct current voltage, half of the DAC input voltage needs to be added at the positive input end of the operational amplifier, and the direct current part is subtracted by a subtracter. The amplifier part of the later stage is an inverse proportional amplifier with variable gain, and the gain is adjusted by a slide rheostat and is in the range of-10 to 0 times. The filter selected by the module is two second-order low-pass filters connected in series, and the topological structure of the filter is a Sallen-key active low-pass filter. As the DAC sampling frequency is 1kHz, the cut-off frequency of the filter is designed to be 500Hz, the channel gain is designed to be 1, and the stop band gain is designed to be-40 dB. The amplifying and filtering circuit is shown in fig. 4.

because this module direct action is at human head, need output stabilization current at 1 ~ 2mA, but what FPGA exported for voltage signal can not direct control current, need gather signal current and constitute the feedback and carry out current regulation and guarantee the stability of electric current.

The current detection chip mainly completes the conversion between current and voltage, and in order to realize the function, the INA286 bidirectional shunt detector is used in the patent. In the output process of the signal, a 5 Ω resistor is used to implement differential mode sampling. The reference voltage is 2.5V, the difference is amplified by 100 times, in this way, the measuring current between +/-2.5 mA can be obtained, and then, the conversion process from an analog signal to a digital signal is carried out by utilizing an analog-to-digital converter ADS 7814. The FPGA acquires digital signals and transmits the digital signals to the ARM, and the ARM calculates the digital signals to form feedback and output stable current. The current sensing circuit is shown in fig. 5.

The analog circuit system supplies power to positive and negative 12V voltage and is provided by a student power supply. Because the digital-to-analog conversion circuit needs stable reference voltage, for example, the DAC needs 2.5V reference voltage, and the voltage of-2.5V needs to remove the DC voltage brought by the DAC for the operational amplifier.

First, a digital voltage of 5V can be generated by an lm7805 linear regulator block, and the circuit principle is shown in fig. 6. The 2.5V voltage is generated by the lm385-2.5 voltage stabilizing diode, the stabilized voltage is output through a follower formed by an operational amplifier, and then the-2.5V reference voltage is generated through a 1: 1 inverse proportion amplifier, and the circuit principle is shown in figure 6.

the vagus nerve stimulation module comprises a signal transmission unit, a waveform generation and current control unit and a power management unit. The signal transmission unit comprises a control key and is mainly used for setting the pulse width and frequency parameters of stimulation; the waveform generation and current control unit generates a needed voltage-controlled bidirectional microampere level pulse stimulation current waveform and is mainly controlled by two paths of PWM waveforms; the power management module comprises an isolation power supply and a DC-DC boosting module, and the adjustable resistor is used for dividing voltage and adjusting output voltage.

(I) Circuit frame

the circuit framework of the vagus nerve stimulation module comprises a power supply protection circuit, an isolation power supply circuit, an MCU main control module, a DC-DC booster circuit and an output circuit. The MCU main control module generates a needed voltage-controlled bidirectional microampere-level pulse stimulation current waveform and is mainly controlled by two paths of pulse width modulation waveforms, and the output circuit divides the voltage by an adjustable resistor and adjusts the output voltage. The design scheme is shown in figure 7 below.

(II) power supply protection circuit

This patent vagus nerve stimulation module adopts 5V's direct current constant voltage power supply to supply power, adopts paster self-recovery fuse SMD1812P050TF to guarantee the safety of power input, and power input protection circuit schematic diagram is as follows shown in FIG. 8.

(III) isolation power supply circuit

the vagus nerve stimulation module needs to have a stable power supply device to perform a stable power supply process, according to output voltages (5V, 3.3V, 9V and 30V) required in system design, in order to prevent interference, a power supply isolation measure is a basic requirement for ensuring the stability of an output signal, the vagus nerve stimulation module of the patent supplies power by using a 5V direct current stabilized power supply, and the realization of the 3.3V voltage depends on a power management chip MP2451 to perform voltage reduction and realize the power supply to a main control chip. These two supply voltages are accomplished by means of an isolated power supply circuit. The isolated power supply circuit design is shown in fig. 9 below.

(IV) DC-DC booster circuit

The stimulation circuit is set to be constant current, the size of a stimulation gear is represented by different voltages, the adjustable resistor is used for dividing the voltage, the output voltage is adjusted, and the voltage of the output gear is adjustable between 9V and 30V, so that the voltage of a 5V power supply is increased to 9V through the DC-DC booster circuit and then is increased to 30V at most through the transformer. The DC-DC boost circuit principle is as in fig. 10.

(V) Current control Circuit

the stimulation part of the module is the vagus nerve of the ear and neck, the magnitude of the output current needs to be strictly controlled to ensure safety, so that the module designs a current control circuit to ensure constant current output, a constant current source circuit consists of two operational amplifiers, an MCU controls two paths of PWM signals to generate pulse waveforms required by stimulation, and a circuit schematic diagram is shown in FIG. 11.

We designed four control trials: the method comprises a tDCS (distributed control System) pseudo stimulation + tVNS (stimulated virtual Circuit system) pseudo stimulation group, a tDCS pseudo stimulation + tVNS group, a tDCS + tVNS pseudo stimulation group and a tDCS + tVNS group. the anode of the tDCS electrode is positioned at F3, and the cathode is positioned on the forehead on the right eye socket; the tVNS stimulation electrode is located at the ear. We collected these four groups of functional mri data in real time under electrical stimulation, and we selected the classic Block design for the experimental design of the electrical stimulation task, i.e. assuming that the electrical stimulation state is ON and the resting state is OFF, we used 66s OFF followed by 66s ON, and repeat this 3 times, and finally add a 66s OFF, totaling 462s for each group of mri scan, and the Block design is as shown in fig. 12.

by comparing different experimental design stimulation states through statistical analysis, a result that the activation effect of the tDCS + tVNS group existing in a plurality of brain areas such as the right lateral cingulate gyrus, the left thalamus, the left pallor matter, the right thalamus, the right putamen and the like is obviously higher than the sum of the activation effects of the tDCS + tVNS pseudo-stimulation group and the tDCS pseudo-stimulation + tVNS can be obtained (as shown in figure 13), namely, the generation of the 'super-sum' effect similar to '1 +1> 2' is verified.