CN2605022Y - Nerve threshold stimulator - Google Patents

Abstract

The utility model relates to a nerve threshold stimulator which is composed by a microprocessor, a DDS signal generator, a low pass filter, an outgoing message photocoupler, a power amplifier and a stimulating current sample resistance, a feedback photocoupler and a stimulating current measurement circuit; the data bus, address bus and control bus of the DDS signal generator is connected with the corresponding bus of the microprocessor, the output of the DDS signal generator is connected with the input of the low pass filter, the output of the low pass filter is connected with the input end of the outgoing message photocoupler and the output end of the outgoing message photocoupler is connected with the input of the power amplifier, the output of the power amplifier is connected with the body electrode, the body electrode acts on the measuring brain nerves of the patient and the body of the patient connects the earth through the stimulating current sample resistance, the earth connection end and the power amplifier are on the earth at the same time, the unearth end of the sample resistance is simultaneously connected with the input end of the feedback photocoupler, the output end of the feedback photocoupler is connected with the input of the stimulating current measurement circuit while the output of the stimulating current measurement circuit is connected with the interruption input end of the microprocessor.

Description

Nerve threshold value stimulates instrument

Technical field

This utility model relates to a kind of human nerve unit cell of measuring stimulates instrument to the nerve threshold value that stimulating electrical signal reacts.

Background technology

Thereby in nerve-muscle illness process that the brain neuroblastoma lesion tissue that diagnoses and treatment is caused by a variety of causes causes, the medical personnel finds very early and can stimulate with the signal of telecommunication with certain intensity, frequency etc. the neuronal cell to difference in functionality by specific nerve fiber electrode, shrink (diastole) action so that the corresponding muscle of its domination produces, thereby reach the purpose of diagnoses and treatment illness.According to this principle, the someone has designed the practical instrument such as " cerebellum stimulators " that is similar to cardiac pacemaker, has also obtained certain effect clinically.But the sensitive level difference that different neuronal cells reacts to stimulating electrical signal, the signal of telecommunication of different nature stimulates the effect that is produced to neuronal cell, and also there were significant differences, this just makes the medical personnel can not select the electrical stimulation signal of same intensity for use when diagnosis and treatment nerve-muscle illness without exception, can not adopt unified electrical signal types without exception.In the selection for electrical stimulation signal type and intensity, clinical staff also is in the stage of groping by subjective experience at present.In order to open up a new road for diagnoses and treatment delayed ischemic neurological deficits disease, more its functional rehabilitation treatment provides quantitative criterion, need to measure obtains the quantitative criterion of the sensitive level that neuronal cell reacts to stimulating electrical signal, i.e. the nerve threshold value level.The stimulation and the therapeutic effect drafting pattern that is produced, i.e. nerve threshold value collection of illustrative plates that the threshold level and the same functional neurosurgery unit cell of the neuronal cell of difference in functionality are accepted again.Draw the nerve threshold value collection of illustrative plates and be applied to clinical, instruct clinical staff the patient to be carried out the diagnosis and the treatment of disease, clinical staff is come out of from the dark of groping by subjective experience, according to the nerve threshold value collection of illustrative plates, formulation science, reasonable, effective diagnosis and treatment scheme.

In the scientific research process of carrying out about " the nerve threshold value collection of illustrative plates is drawn and clinical application research ", needs according to research work, the applicant has designed the nerve threshold value stimulation instrument (see patent of invention " detection method of human nerve threshold value and detection system thereof ", number of patent application 02138352.9) of a cover based on the analog function signal generator.But find that in zoopery and clinical practice application process there is more shortcoming in this cover instrument, some shortcoming is quite big and be difficult to overcome to its performance impact, and it mainly shows: (1) is difficult to carry out exact figure control to the signal of output.The controlling elements of analog function signal generator almost all are analogue signals, the advanced line number mould of controlled quentity controlled variable must be changed the control of analog function signal generator by digital circuits such as processors, and the controlling elements of all analog forms very easily are subjected to various interference and tracking is got up pretty troublesome; (2) the low frequency signal instability of being exported, the distortion factor is big, and this is the unsurmountable shortcoming of simulative generator; (3) dispersion is big between the instrument individuality, and the signal conformance that different instrument is exported is poor, and the experimental result of scientific research is unreliable, poor repeatability.

Summary of the invention

The purpose of this utility model is exactly in order to address the above problem, and provides a kind of and can carry out exact figure control, and the low frequency signal of being exported nerve threshold value stable and high conformity stimulates instrument.

Technical solution of the present utility model:

A kind of nerve threshold value stimulates instrument, it is characterized in that it is by microprocessor, the DDS signal generator, low pass filter, the output signal photoelectrical coupler, power amplifier, the stimulating current sampling resistor, feedback photoelectric coupler, stimulating current is measured circuit and is formed, the data/address bus of DDS signal generator, address bus links to each other with the corresponding bus of microprocessor respectively with control bus, the output of DDS signal generator connects the low pass filter input, the output of low pass filter connects the input of output signal photoelectrical coupler, the input of the output termination power amplifier of output signal photoelectrical coupler, the output of power amplifier meets the body electrode, the body electrode acts on patient's tested cranial nerve, patient's human body is by stimulating current sampling resistor ground connection, this earth terminal simultaneously with power amplifier altogether, the non-earth terminal of sampling resistor links to each other with the input of feedback photoelectric coupler simultaneously, the output of feedback photoelectric coupler connects the input that stimulating current is measured circuit, and the output of stimulating current mensuration circuit connects the interrupting input end of microprocessor.

This utility model can carry out exact figure control to the signal of output, and what overcome the analog function signal generator very easily is subjected to various interference and the tracking pretty troublesome defective of getting up; The low frequency signal that this utility model is exported is stable, and is undistorted; The signal conformance that this utility model is exported is good, and the experimental result of scientific research is reliable, and repeatability is high.This utility model is simple in structure, and is easy to use, and effect is very good.

Description of drawings

Fig. 1 is a theory diagram of the present utility model.

Fig. 2 is a graph of a relation between DDS output signal and signal phase, the waveform address ram.

Fig. 3 is a DDS generator theory diagram.

Fig. 4 is the sketch map that concerns of variation of DDS waveform address ram and PIR.

Fig. 5 is the structured flowchart of DDS signal generator of the present utility model.

Fig. 6 is a current-voltage conversion circuit electrical schematic diagram of the present utility model.

Fig. 7 is the electrical schematic diagram of 9 rank Elliptical wave filter of the present utility model.

Fig. 8 is the electrical schematic diagram of 7 rank Bessel wave filter of the present utility model.

Fig. 9 is the amplitude-versus-frequency curve figure of this utility model 9 rank Elliptical wave filter.

Figure 10 is the amplitude-versus-frequency curve figure of this utility model 7 rank Bessel wave filter.

Figure 11 is a power amplifier electrical schematic diagram of the present utility model.

Figure 12 is a floating ground of the present utility model buffer circuit theory diagram.

Figure 13 is that stimulating current of the present utility model is measured the circuit electrical schematic diagram.

The specific embodiment

As Fig. 1, nerve threshold value of the present utility model stimulates instrument, it is by microprocessor, DDS (Direct Digital synthetic technology) signal generator, low pass filter, the output signal photoelectrical coupler, power amplifier, the stimulating current sampling resistor, feedback photoelectric coupler, stimulating current is measured circuit and is formed, the data/address bus of DDS signal generator, address bus links to each other with the corresponding bus of microprocessor respectively with control bus, the output of DDS signal generator connects the low pass filter input, the output of low pass filter connects the input of output signal photoelectrical coupler, the input of the output termination power amplifier of output signal photoelectrical coupler, the output of power amplifier meets the body electrode, the body electrode acts on patient's tested cranial nerve, patient's human body is by stimulating current sampling resistor ground connection, this earth terminal simultaneously with power amplifier altogether, the non-earth terminal of sampling resistor links to each other with the input of feedback photoelectric coupler simultaneously, the output of feedback photoelectric coupler connects the input that stimulating current is measured circuit, and the output of stimulating current mensuration circuit connects the interrupting input end of microprocessor.

The DDS signal generator is delivered to power amplifier at generation stimulation voltage signal under the control of microprocessor and is amplified after low pass filter filtering and the coupling of output signal photoelectrical coupler, stimulation voltage signal after the amplification acts on patient's cranial nerve through body electrode's (as metal hook), the patient is subjected to this stimulation voltage signal effect meeting to produce corresponding stimulating current, this stimulating current just is converted to the correspondent voltage signal by the stimulating current sampling resistor, after the feedback photoelectric coupler coupling, deliver to stimulating current and measure circuit, measure the intensity of stimulating current by it, after microprocessor output.

This utility model is based on Direct Digital synthetic (Direct Digital Synthesis, DDS) technical nerve threshold value stimulation instrument.Stimulate instrument to comprise that mainly signal generator, power amplifier, stimulating current based on the DDS technology measure circuit, floating ground buffer circuit, power supply etc. and other auxiliary circuit based on the nerve threshold value of DDS technology.Signal generator is mainly realized the parameter setting of output signal and synthesizing of output signal, power amplifier is finished the power amplification of output signal, stimulating current is measured circuit and is mainly measured the intensity that output signal acts on the stimulating current that produces behind the human body, floating ground buffer circuit is realized the conversion of floating ground, isolation and the transmission of signal, and power circuit provides stable, low noise power supply for system.

Direct Digital synthetic technology (DDS) is to utilize a kind of new frequency synthesis technique of the directly synthetic required waveform of digital technology from the phase place notion.In the DDS system, the range value of a complete cycle of the synthetic signal of desire sequentially leaves in the wave storage (RAM), under the driving of system clock, phase accumulator produces desires a series of phase value of composite signal in one-period, and these values can be mapped in the address field of waveform RAM one by one; When thereby the variation of desire composite signal phase place makes with it the address ram of mapping variation one by one, digital to analog converter converts the signal amplitude value on the appropriate address among the waveform RAM to analog voltage signal, and the frequency of the synthetic signal of this Direct Digital is directly proportional (as shown in Figure 2) with the speed that signal phase changes in other words with address ram.

In the DDS system, complete DDS generator generally include a N position full adder (N bits FullAdder, FA), a N _LPosition phase increment depositor (N _LBits Phase Increment register, PIR), N position phase register (N bits Phase Register, PR), the digital to analog converter (DAC) of a M position and waveform RAM (Wave RAM, WRAM) and part such as controller, as shown in Figure 3.In each system clock cycle, the phase increment that is stored in the phase increment depositor (PIR) all adds up in full adder with the phase value that is stored in the phase register (PR), its result still latchs in phase register (PR), the most significant end N of phase register (PR) _AThe position is used for determining the address (N of waveform RAM _AGet the figure place that is the waveform address ram, the capacity of waveform RAM should be

).When phase register (PR) when overflowing, the DDS generator is finished the scanning to whole waveform RAM, the signal waveform of a complete cycle of digital to analog converter (DAC) output simultaneously.The value that changes phase increment depositor (PIR) just changes the rate of change of waveform address ram to change the changing value of phase register (PR) in each clock cycle, thereby changes the output frequency of waveform, as shown in Figure 4.

In the DDS system, according to the principle of Direct Digital synthetic technology, the common and system clock frequency F of output signal frequency F _Clk, the figure place N of phase register (PR), the value PIR of phase increment depositor (PIR) have following relation: $F=\frac{\mathrm{PIR}\·F_{\mathrm{clk}}}{2^N}.$ The minimum frequency F of output signal _MinShould be: $F_{\min }=\frac{F_{\mathrm{clk}}}{2^N}$ The value PIR=1 of phase increment depositor this moment (PIR) is according to Nyquist (Nyquist) theorem, output signal frequency maximum F _MaxShould be: $F_{\max }=\frac{F_{\mathrm{clk}}}{2}$ The value PIR=2 of phase increment depositor this moment (PIR) ^N-1When requiring the signal precision to export each data among the waveform RAM just all to be range value in one-period of output signal, the peak frequency F of output signal _MaxWith system clock frequency F _Clk, the waveform address ram figure place N _AFollowing relation is arranged: $F_{\max }=\frac{F_{\mathrm{clk}}}{2^{N_A}}---\left(1\right)$ The value of phase increment depositor this moment (PIR) $\mathrm{PIR}=2^{{N-N}_A},$ The minimum frequency F of output signal _MinWith system clock frequency F _Clk, phase register (PR) figure place N following relation is arranged: $F_{\min }=\frac{F_{\mathrm{clk}}}{2^N}---\left(2\right)$ The value PIR=1 of phase increment depositor this moment (PIR), the minimum change of output signal frequency F: $\mathrm{\Δ}{F}_{\min }=\frac{F_{\mathrm{clk}}}{2^N}---\left(3\right)$ The value of phase increment depositor this moment (PIR) $1\≤\mathrm{PIR}\≤2^{{N-N}_A}.$

Stimulate in the instrument development work at actual nerve threshold value, according to the requirement of research work, determine that the signal generator running parameter is as follows: the peak frequency F of output signal _Max=100Hz, minimum frequency F _Min=0.01Hz, frequency variation is Δ F=0.01Hz when F＜1.0Hz, is Δ F=0.1Hz when frequency 1≤F＜10Hz, is Δ F=1Hz when frequency 10≤F≤100Hz.For considerations such as output waveform precision and design are convenient, the figure place of getting digital to analog converter DAC among the DDS is 14, and the capacity of getting waveform RAM is 16KB, i.e. M=14bits, N _A=14bits.Determine DDS system clock F by above-mentioned formula (1) _ClkMinima is, $F_{\mathrm{clk},\min }=F_{\max }\·2^{N_A},$

So, F _{Clk, min}=100 * 2 ¹⁴,

That is F, _{Clk, min}≈ 1.6MHz;

Determine that by formula (3) the figure place N minima of phase register (PR) is again, $2^N=\frac{F_{\mathrm{clk},\min }}{\mathrm{\Δ}{F}_{\min }},$

So, $N_{\min }={\log }_2^{\frac{F_{\mathrm{clk},\min }}{\mathrm{\Δ}{F}_{\min }}},$

That is, $N_{\min }={\log }_2^{\frac{1.6\mathrm{MHz}}{0.01}}\≈27;$ Convenient and take into account output signal accuracy and consider based on design, in actual design, N generally gets 8,16,32 ... equivalence, get 32 here, determine DDS system clock F by formula (2) again _ClkMaximum is,

F _{Clk, max}=Fmin2 ^N=0.01 * 2 ³²≈ 42.9MHz takes all factors into consideration factors such as PIR value, the selection of circuit elements device and software programming, gets F _Clk=14.318MHz.Like this, determine that each parameter is as follows among the DDS:

N＝32bits，

N _A＝14bits，

M＝14bits，

F _Clk=14.318MHz when PIR=2.999697 ≈ 3, can get output signal F _Min=0.01Hz when PIR=29996.9779 ≈ 30000, can get output signal F _Max=100Hz when Δ PIR=2.999697 ≈ 3, can get output signal Δ F=0.01Hz.

Principle according to the DDS technology, based on the signal generator of DDS technology mainly by the DDS controller, high speed static RAM, high-speed A/D converter, low pass filter, reset circuit, digital power, analog powers etc. are partly formed, wherein the DDS controller is used for finishing and MPI, waveform RAM refreshes, the scanning of waveform RAM is read, refreshing and function such as control of high-speed A/D converter data, high speed static RAM is used for depositing Wave data, the waveform that high-speed A/D converter is finished under DDS controller control digital form carries out simulated conversion output, and low pass filter is attached to high-frequency digital spurious signal on the low frequency signals in order to filtering.

Since the DDS technology have other frequency synthesis technique incomparable advantage, so it has obtained using widely at numerous areas.Also its extensive use just, impelled numerous semiconductor device supplier unexpectedly mutually research and development released DDS special IC (ASIC) with different characteristics, more famous DDS special IC has AD985X series of series such as Q2220, Q2230, Q2334, Q2240, the Q2368 of Qualcomm company and U.S. ADI company or the like, in addition, PLD supplier has also released the IP kernel based on the DDS of own CPLD, FPGA one after another, therefore, design the DDS controller now relatively simply, easily.Take all factors into consideration the factors such as requirement, design difficulty, design complexity and design cost of system to the DDS controller, stimulate in the instrument design at nerve threshold value, this utility model has adopted the EPM7128AETC144-10 PLD of ALTERA company to design the DDS controller.

DDS signal generator of the present utility model as shown in Figure 5, it is by 16 phase increment depositor PIR, 32 full adder ACC, 32 phase register PR, systematic clock generator F _Clk, Wave data ram memory (model can be CY7C199) and 14 high-speed A/D converter DAC (model can be MAX7535) form, the data input pin of increment register PIR links to each other with the data/address bus of microprocessor CPU (model can be DS87C520), the output of the output of PIR and phase register PR all links to each other with the input of full adder ACC, systematic clock generator F _ClkOutput connect the clock end of ACC, the output of ACC connects the input of PR, promptly at F _ClkDriving under ACC the value of PIR and PR is carried out addition, addition result is delivered to PR latchs.High 14 outputs of PR are by the address bus of waveform address ram logical block welding wave data memory RAM, another input of waveform address ram logical block links to each other with the address bus of microprocessor CPU, the data/address bus of Wave data ram memory links to each other with the data/address bus of microprocessor CPU by Wave data logical block one tunnel, another road connects the data input pin of high-speed AD converter DAC, the read-write control end of RAM by waveform RAM read-write logical block respectively with systematic clock generator F _ClkLink to each other with the control bus of microprocessor CPU, the control bus of CPU links to each other with the control input end of high-speed AD converter DAC by DAC control logic unit simultaneously, and the output of DAC connects power amplifier by low pass filter and output signal photoelectrical coupler.

In the DDS signal generator, 16 phase increment depositor PIR, 32 full adder ACC, 32 phase register PR, waveform RAM data logical block, waveform RAM read-write logical block, Wave data logical block and DAC control logic unit all can write in the PLD (CPLD) (model can be EPM7128AETC144-10), are finished by device of this CPLD.

DDS controller based on PLD EPM7128AETC144-10 design can be divided into unit such as 16-bits phase increment depositor (16-bits PIR), 32-bits full adder, 32-bits phase register (32-bitsPR), waveform address ram logic, Wave data logic, waveform RAM read-write logic, DAC control logic, in normal operation, each unit is driven by system clock, under the state of quitting work, each unit is subjected to microprocessor (CPU) to drive system works/stop to be subjected to microprocessor to control.

The DDS controller is before entering operate as normal, and microprocessor must be provided with the value (3≤PIR≤30000) of PIR, makes the DDS controller enter normal operating conditions then.In normal operation, be subjected to the driving of system clock, the 32-bits full adder is with 16-bits phase increment depositor (16-bits PIR) and 32-bits phase register (32-bits PR) addition, the result still latchs in PR, its high 14-bits outputs to waveform address ram logic simultaneously, and waveform address ram logic will output on the address foot (A13-A0) of two waveform RAM (MSB+LSB) when DDS controller operate as normal from the address of the high 14-bits of PR; Simultaneously, be subjected to the driving of system clock, waveform RAM read-write logic produces corresponding chip selection signal and read signal, this signal outputs to respectively on the chip select pin (CE) and output enable (OE) of two waveform RAM (MSB+LSB), so the data among two waveform RAM just are read out and are input to the Wave data logic.Equally, be subjected to the driving of system clock, the DAC control logic is according to the chip selection signal of waveform RAM read-write logic generation and the sequential of read signal, control digital to analog converter (DAC) is accepted the Wave data from two waveform RAM of Wave data logic output, and Wave data is converted to analogue signal output.When microprocessor quits work the DDS system, waveform address ram logic, Wave data logic, waveform RAM read-write logic, DAC control logic switch to the control bus of address, data, read-write control bus and the DAC of waveform RAM respectively on the address, data, read-write control bus of microprocessor (CPU), microprocessor make waveform RAM and DAC accept the control of microprocessor, so that can refresh, change the data among the waveform RAM and make DAC be in certain mode of operation.

Signal generator based on the DDS technology must be converted to analogue signal output with its digital signal by digital to analog converter (DAC).Stimulate the instrument system designing requirement according to nerve threshold value, this utility model has been selected the MAX7535 of the U.S. U.S. letter (MAXIM) company for use.MAX7535 is the high-speed A/D converter of 14 digit current output types, and the difference configuration for the MAX7535 output signal can be configured to its output signal one pole negative output and bipolar output, as shown in Figure 6.This utility model is connected to current-voltage conversion circuit in the output of high-speed A/D converter DAC, this change-over circuit is by amplifier A1, A2 and resistance R 1-R4 constitute, the inverting input of A1 links to each other with the current output terminal Iout of DAC, the in-phase input end of A1 links to each other with the analogue ground of DAC, and with connecing simulation simultaneously, the output of A1 links to each other with the reference feedback end RFB of DAC, it can be used as the output Voutl of negative-going signal, the output of A1 connects the inverting input of A2 simultaneously by R2, the inverting input of A2 connects the outfan of reference voltage Vref and A2 again simultaneously respectively by R1 and R4, the output of A2 is just as two-way signaling output Vout2.

The analogue signal of digital to analog converter (DAC) output must be attached to high-frequency digital spurious signal on the low frequency signals with filtering through low pass filter.Consider different output signal types, this utility model has designed two kinds of different low pass filters: the bandwidth that is used to handle sinusoidal wave and square-wave signal is that the 9 rank Elliptical wave filter of 10MHz are 7 rank Bessel (Bezier) wave filter of 5MHz with the bandwidth that is used to handle other type signal, shown in Fig. 7,8.When nerve threshold value stimulated instrument need produce different signals, microprocessor was selected corresponding low pass filter automatically, so that nerve threshold value stimulates instrument to obtain best analogue signal output.The amplitude-frequency characteristic of two kinds of wave filter is seen shown in Fig. 9,10.

(0.01～100Hz), so power amplifier must adopt the push-pull type amplifying circuit of direct-current coupling, as shown in figure 11, power tube adopts three audions that model is TIP41C among the figure because this utility model instrument output signal frequency is lower.This amplifying circuit has simple in structure, and noise is little, and the distortion factor is low, and plurality of advantages such as dependable performance are more a kind of in numerous direct current power amplifiers.This power amplifier can be by transistor Q1-Q3, resistance R 5-R7 constitutes, wherein the base input end of Q1 and Q3 meets the signal output Vi of output signal photoelectrical coupler respectively by R6, R7, the equal ground connection of their emitter-base bandgap grading, the colelctor electrode of Q1 connects power supply with the base stage of Q2 by R5, the colelctor electrode of Q2 directly links to each other with power supply, and the emitter-base bandgap grading of Q2 is exported Vout with the colelctor electrode of Q3 as the signal of power amplifier and met the body electrode.

Because nerve threshold value stimulates the signal of instrument output to directly act on human body, so its electrical security seems still for important; Add as Medical Instruments, it must reach the concerned countries standard of Medical Instruments electrical safety, and for this reason, this utility model has adopted floating ground isolation technology to guarantee that nerve threshold value stimulates the safety of instrument.

It is the photoelectric coupled device of HCNR200A that output signal photoelectrical coupler of the present utility model and feedback photoelectric coupler should adopt model, and it can realize the effect of floating ground and buffer circuit well.According to the structure of nerve threshold value stimulation instrument, this utility model has mainly adopted floating ground isolation technology in signalling channel and power pack, as shown in figure 12.On signalling channel, after level is adjusted, be carried in the input of output signal photoelectrical coupler based on the signal of the signal generator of DDS technology output, signal carries out power amplification from its outfan output after buffering, after electrode output; Through amplifying, be carried in after the buffering input of feedback photoelectric coupler, signal is input to stimulating current peak-to-peak value measuring circuit from its outfan output after buffering carries out current peak and measures from the signal that stimulates the current sampling resistor feedback.Provide the power supply of power to adopt isolation type switching power supply to power amplifier, isolate fully between its switch transformer primary and secondary.Between the input/output terminal of photoelectrical coupler HCNR200A, withstand voltage between the switch transformer primary and secondary of isolation type switching power supply can be up to 4500V, like this, nerve threshold value stimulates the output of instrument just to isolate with the other parts of instrument, satisfies the electrical safety requirement fully.

Stimulating current of the present utility model is measured circuit as shown in figure 13, it is by serial digital to analog converter Ud (model can be TLC5615), comparator A3, amplifier A4, A5 and phase inverter U constitute, the serial data input port DIN of Ud, serial clock input SCLK and sheet choosing end CS respectively with the serial data outfan RXD0 of microprocessor CPU, serial clock outfan TXD0 links to each other with signal output part P2.3, the output of Ud links to each other with the in-phase input end of comparator A3, the inverting input of A3 links to each other with the output of amplifier A5, the input of A5 links to each other with the output of amplifier A4, A4 self constitutes voltage follower, the in-phase input end of A4 links to each other with the stimulating current sampling resistor by feedback photoelectric coupler, and the output of comparator A3 meets the interrupting input end INT2 of microprocessor CPU by phase inverter U.

At first make impedance matching from the signal that stimulates the current sampling resistor feedback, to reduce of the influence of follow-up measuring circuit to stimulating current through voltage follower A4; Signal is isolated, is amplified through photoelectricity again, is amplified to certain magnitude of voltage, is added in the inverting input of comparator A3.The in-phase input end of comparator A3 is accepted from the voltage signal of serial digital to analog converter Ud output, and the signal of the output of comparator A3 is through level conversion, is converted to+is input to after the logic level of 5V the interruption input pin of microprocessor.When measuring the peak-to-peak value of stimulating current, at first send maximum digital signal to digital to analog converter Ud by microprocessor, make Ud output maximum voltage value, at this moment comparator A3 output low level signal always.Microprocessor reduces to be sent to the digital signal of Ud gradually then, the output voltage of Ud also reduces gradually, when the output voltage of Ud just has been less than or equal to the stimulating current feedback signal that is added in comparator A3 end of oppisite phase, comparator A3 exports a direct impulse, this pulse triggers microprocessor through level conversion and produces interruption, at this moment record is sent to the digital signal value of digital to analog converter Ud in interrupt service routine, and this value is the peak-to-peak value of stimulating current.

In order to reduce the influence of power pack as much as possible to the quality of instrument output signal, improve the energy conversion efficiency of power pack, and provide insulating power supply to power amplifier, and further enlarging the scope of complete machine input supply voltage, this utility model has adopted the power supply Design Mode of dual power supply module, Switching Power Supply-linear voltage stabilization.In the amplifier power supply module, adopt isolated switch transformer, withstand voltage between its primary and secondary can be up to 4500V, realize that complete electrical equipment isolates; In the system power supply module, input at power supply, we at first application switch power module generation+5V, ± three road voltages such as 15V, wherein+5V directly provides power supply for digital circuit, ± 15V voltage obtains behind linear manostat voltage regulation filtering ± and 12V voltage provides power supply for high-speed A/D converter MAX7535 and partial buffer operational amplifier, and the supply pin of the components and parts that each is important is all used ceramic disc capacitor filtering, the decoupling of electrochemical capacitor and the 0.1 μ F of 10F.

Synthesized to come through Direct Digital by the wave-shape amplitude data that are stored among the waveform RAM owing to the nerve threshold value based on the DDS technology stimulates its signal of instrument, this just provides possibility for the synthetic random waveform of numeral.Stimulate in the instrument at nerve threshold value, this utility model has designed the data communication circuit, passes through the self-defined random waveform of personal computer for user.

The data communication part mainly is made up of the serial communication electrical level transferring chip MAX202 of the U.S. U.S. letter (MAXIM) company and the asynchronous serial port of microprocessor.The TTL signal of 0～5V level of microprocessor serial port TXD foot is converted into+8V～-serial signal of the RS232 level of 8V and be output to the RXD foot of personal computer RS232 communication port, simultaneously, personal computer RS232 communication port TXD foot+8V～-serial signal of the RS232 level of 8V is converted into the TTL signal of 0～5V level and is output to microprocessor serial port RXD foot.In the practical application, selected identical baud rate, serial data format etc. when personal computer and nerve threshold value stimulate instrument, both sides can carry out duplex signaling, and the user can download any self-defined Wave data from personal computer by special-purpose software.The Wave data of downloading is stored in nerve threshold value to stimulate in the non-volatile memory (NVRAM) of instrument.

This utility model nerve threshold value stimulates instrument output signal parameter as follows:

Output signal frequency F:0.01～100Hz

Output signal dutycycle D:10%～90%

Amplitude output signal A:0%～100% or 0V～12V

Output signal type W: square wave, sawtooth waveforms, triangular wave, sine wave and User Defined ripple (downloading from personal computer) by communication port.

Claims (7)

1, a kind of nerve threshold value stimulates instrument, it is characterized in that it is by microprocessor, the DDS signal generator, low pass filter, the output signal photoelectrical coupler, power amplifier, the stimulating current sampling resistor, feedback photoelectric coupler, stimulating current is measured circuit and is formed, the data/address bus of DDS signal generator, address bus links to each other with the corresponding bus of microprocessor respectively with control bus, the output of DDS signal generator connects the low pass filter input, the output of low pass filter connects the input of output signal photoelectrical coupler, the input of the output termination power amplifier of output signal photoelectrical coupler, the output of power amplifier meets the body electrode, the body electrode acts on patient's tested cranial nerve, patient's human body is by stimulating current sampling resistor ground connection, this earth terminal simultaneously with power amplifier altogether, the non-earth terminal of sampling resistor links to each other with the input of feedback photoelectric coupler simultaneously, the output of feedback photoelectric coupler connects the input that stimulating current is measured circuit, and the output of stimulating current mensuration circuit connects the interrupting input end of microprocessor.

2, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that described DDS signal generator is by 16 phase increment depositor PIR, 32 full adder ACC, 32 phase register PR, systematic clock generator F _Clk, Wave data ram memory and 14 high-speed A/D converter DAC form, the data input pin of increment register PIR links to each other with the data/address bus of microprocessor CPU, the output of the output of PIR and phase register PR all links to each other with the input of full adder ACC, systematic clock generator F _ClkOutput connect the clock end of ACC, the output of ACC connects the input of PR, high 14 outputs of PR are by the address bus of waveform address ram logical block welding wave data memory RAM, another input of waveform address ram logical block links to each other with the address bus of microprocessor CPU, the data/address bus of Wave data ram memory links to each other with the data/address bus of microprocessor CPU by Wave data logical block one tunnel, another road connects the data input pin of high-speed AD converter DAC, the read-write control end of RAM by waveform RAM read-write logical block respectively with systematic clock generator F _ClkLink to each other with the sky system bus of microprocessor CPU, the control bus of CPU links to each other with the control input end of high-speed AD converter DAC by DAC control logic unit simultaneously, and the output of DAC connects power amplifier by low pass filter and output signal photoelectrical coupler.

3, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that being connected to current-voltage conversion circuit in the output of high-speed A/D converter DAC, this change-over circuit is by amplifier A1, A2 and resistance R 1-R4 constitute, the inverting input of A1 links to each other with the current output terminal Iout of DAC, the in-phase input end of A1 links to each other with the analogue ground of DAC, and with connecing simulation simultaneously, the output of A1 links to each other with the reference feedback end RFB of DAC, it is as the output Voutl of negative-going signal, the output of A1 connects the inverting input of A2 simultaneously by R2, the inverting input of A2 connects the outfan of reference voltage Vref and A2 again simultaneously respectively by R1 and R4, the output of A2 is exported Vout2 as two-way signaling.

4, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that described low pass filter adopts 9 rank Elliptical wave filter and 7 rank Bessel wave filter.

5, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that described power amplifier is by transistor Q1-Q3, resistance R 5-R7 constitutes, wherein the base input end of Q1 and Q3 meets the signal output Vi of output signal photoelectrical coupler respectively by R6, R7, the equal ground connection of their emitter-base bandgap grading, the colelctor electrode of Q1 connects power supply with the base stage of Q2 by R5, and the colelctor electrode of Q2 directly links to each other with power supply, and the emitter-base bandgap grading of Q2 is exported Vout with the colelctor electrode of Q3 as the signal of power amplifier and met the body electrode.

6, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that it is the photoelectric coupled device of HCNR200A that described output signal photoelectrical coupler and feedback photoelectric coupler should adopt model.

7, stimulate instrument by the described nerve threshold value of claim 1, it is characterized in that described stimulating current mensuration circuit is by serial digital to analog converter Ud, comparator A3, amplifier A4, A5 and phase inverter U constitute, the serial data input port DIN of Ud, serial clock input SCLK and sheet choosing end CS respectively with the serial data outfan RXD0 of microprocessor CPU, serial clock outfan TXD0 links to each other with signal output part P2.3, the output of Ud links to each other with the in-phase input end of comparator A3, the inverting input of A3 links to each other with the output of amplifier A5, the input of A5 links to each other with the output of amplifier A4, A4 self constitutes voltage follower, the in-phase input end of A4 links to each other with the stimulating current sampling resistor by feedback photoelectric coupler, and the output of comparator A3 meets the interrupting input end INT2 of microprocessor CPU by phase inverter U.

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