CN116707494B - Multi-waveform magnetic field generating device and control method - Google Patents
Multi-waveform magnetic field generating device and control method Download PDFInfo
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- CN116707494B CN116707494B CN202310927715.0A CN202310927715A CN116707494B CN 116707494 B CN116707494 B CN 116707494B CN 202310927715 A CN202310927715 A CN 202310927715A CN 116707494 B CN116707494 B CN 116707494B
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Classifications
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- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K3/00—Circuits for generating electric pulses; Monostable, bistable or multistable circuits
- H03K3/02—Generators characterised by the type of circuit or by the means used for producing pulses
- H03K3/53—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback
- H03K3/57—Generators characterised by the type of circuit or by the means used for producing pulses by the use of an energy-accumulating element discharged through the load by a switching device controlled by an external signal and not incorporating positive feedback the switching device being a semiconductor device
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61N—ELECTROTHERAPY; MAGNETOTHERAPY; RADIATION THERAPY; ULTRASOUND THERAPY
- A61N2/00—Magnetotherapy
- A61N2/02—Magnetotherapy using magnetic fields produced by coils, including single turn loops or electromagnets
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0067—Converter structures employing plural converter units, other than for parallel operation of the units on a single load
- H02M1/007—Plural converter units in cascade
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/08—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters
- H02M1/088—Circuits specially adapted for the generation of control voltages for semiconductor devices incorporated in static converters for the simultaneous control of series or parallel connected semiconductor devices
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/02—Conversion of dc power input into dc power output without intermediate conversion into ac
- H02M3/04—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters
- H02M3/10—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M3/145—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M3/155—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/156—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators
- H02M3/158—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load
- H02M3/1588—Conversion of dc power input into dc power output without intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of output voltage or current, e.g. switching regulators including plural semiconductor devices as final control devices for a single load comprising at least one synchronous rectifier element
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
- H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
- H02M7/06—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes without control electrode or semiconductor devices without control electrode
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03K—PULSE TECHNIQUE
- H03K5/00—Manipulating of pulses not covered by one of the other main groups of this subclass
- H03K5/01—Shaping pulses
- H03K5/04—Shaping pulses by increasing duration; by decreasing duration
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Abstract
The invention discloses a multi-waveform magnetic field generating device and a control method, and belongs to the field of low-intensity pulse power. The invention adopts a mode of two-stage combined closed-loop regulation of the voltage regulating circuit and the bridge circuit to realize a magnetic field with adjustable multiple parameters, steep rising edge and high stability. Firstly, a voltage regulating circuit is utilized to realize controllable high voltage, so that the output voltage of the voltage regulating circuit synchronously changes according to different target magnetic field amplitudes, the rapid rise of a pulse magnetic field is ensured, the pressure difference required by a magnet in a rising stage and a flat-top stage is minimized, and the difficulty of closed-loop control is reduced; the flexibility of outputting magnetic field waveforms is achieved using bridge circuits. And secondly, a hybrid controller is adopted, the optimal transient characteristic of a hysteresis controller is utilized in the magnetic field rising stage, and the strong tracking capability of a PI controller is utilized in the flat-top stage, so that the stability of the magnetic field in the flat-top stage is ensured. Furthermore, the present invention eliminates the effect of parasitic capacitance of the magnet by providing a suitable freewheel loop.
Description
Technical Field
The invention belongs to the field of low-intensity pulse power, and particularly relates to a multi-waveform magnetic field generating device and a control method.
Background
Such medical means as electromagnetic fields are increasingly receiving attention. Several studies have shown that stimulation of electromagnetic fields not only can promote cell differentiation and regeneration, regulate cell metabolism, activate tissue repair capability; can also inhibit the survival of toxic cells such as cancer cells, and does not affect normal tissues. The use of pulsed magnetic field (Pulsed Magnetic Field, PMF) radiation as a medical condition for various medical conditions such as spinal cord injury, bone fracture, arthritis, osteoporosis, pain relief, breast cancer treatment, migraine and the like has therefore become increasingly appreciated by countries around the world. However, different combinations of frequencies, waveforms, amplitudes, durations, etc. set by the pulsed magnetic field device have different effects on biological cells, tissues, etc., and may excite different biological effects. Thus, studies of different cell stimuli require appropriate signals to generate PMFs.
In the investigation of biological effects, it is often necessary to generate a series of different pulsed magnetic field waveforms to determine the optimal cell stimulation conditions. Contrary to the conventional method of long-term and repeated exposure to low-frequency magnetic fields, researches by related scholars indicate that the periodic short-term, low-intensity (several mT) exposure is performed in a magnetic field environment of a short pulse square wave sequence for a certain time (several hundred mu s), thereby being more beneficial to regulating the paracrine function of mesenchymal stem cells and promoting cartilage regeneration. In addition, the similar pulse magnetic field sequence is used for inhibiting the activity of breast cancer cells, promoting the mitochondrial respiration and the like, and has better stimulation effect.
It can be seen that as research goes deep, the pulsed magnetic field has not been limited to low frequencies, and higher demands are placed on waveform flexibility. In order to more comprehensively explore the biological effect of a magnetic field on cells, a multi-waveform magnetic field device integrating a low-frequency pulse magnetic field and a medium-high frequency pulse magnetic field sequence is urgently needed to be developed so as to provide a more flexible magnetic field experimental environment. However, the increase in frequency requires steep pulsed magnetic field edges, the magnet is essentially a large inductive load, and the magnet voltage during the rising edge is several tens of times higher than the plateau. The large pressure difference at the magnet rising and plateau stage makes it difficult to achieve high di/dt of the magnet current rising edge and high precision adjustment during plateau at the same time.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a multi-waveform magnetic field generating device and a control method, and aims to solve the problem that the prior art is difficult to realize high di/dt of the rising edge of a magnet current and high-precision adjustment during the flat top.
To achieve the above object, in a first aspect, the present invention provides a multi-waveform magnetic field generation control method, including:
receiving specification of a target magnetic field waveform parameter;
acquiring output current of a magnetic field excitation coil, terminal voltage of an energy storage capacitor in a synchronous rectification Buck converter and temperature of the magnetic field excitation coil in real time;
according to the waveform parameters of the target magnetic field and the magnetic field excitation coil data acquired in real time, N paths of PWM control signals are formed and sent into a driving circuit to respectively control the on and off of N direct current control switches in the main circuit, so that the closed-loop regulation of the output current of the magnetic field excitation coil is realized;
wherein the main circuit includes: a cascaded voltage regulating circuit and a bridge chopper circuit; the voltage regulating circuit includes: full bridge rectifier and synchronous Buck converter; the input end of the full-bridge rectifier is used for being connected with 220V alternating current, and the output end of the full-bridge rectifier is connected with the filter capacitor in parallel and is connected to the input end of the synchronous Buck converter; the output end of the synchronous Buck converter is connected to the input end of the bridge chopper circuit; the middle points of the two half bridges of the bridge chopper circuit are used for connecting with a magnetic field excitation coil.
Preferably, the on and off of each dc control switch in the synchronous Buck converter is controlled by:
(1) Calculating the required output voltage of the synchronous Buck converter according to the rise time of the target magnetic field and the amplitude of the target magnetic fieldAnd magnetic field excitation coil output current +.>；
(2) And obtaining the PWM control signal duty ratio of each direct current control switch of the synchronous Buck converter according to the input-output relation of the voltage regulating circuit.
Preferably, the current ratio constant is based on the magnetic field of the coilAnd target magnetic field amplitudeBThe magnetic field excitation coil required for the inversion outputs current +.>；
According to the rise time of the target magnetic fieldThe desired synchronous Buck converter output voltage is inverted>：
S 1 AndS 2 a complementary control mode is adopted and,S 1 the duty cycle of (2) is:
S 2 the duty cycle of (2) is:
wherein ,L m the coil inductance is excited for the magnetic field,R m exciting a coil resistance for a magnetic field;u i is an effective value of 220V alternating current.
Preferably, the on and off of each dc control switch in the bridge chopper is controlled by:
1) Collecting output current of magnetic field exciting coilOutput current of the excitation coil corresponding to the required magnetic field>Comparing and setting the flag bit +.>、/> and />The method comprises the steps of carrying out a first treatment on the surface of the Marker bit->For determining the polarity of the target magnetic field,/-, for example>For no magnetic field output->Is a positive magnetic field>Is a reverse magnetic field; marker bit->For determining the working phase of the forward magnetic field and in +.>Every time +.>In the case of self-increase 1, in->When in use, setting zero; marker bit->For determining the working phase of the opposing magnetic field and is +.>Every time +.>In the case of self-increase 1, in->When in use, setting zero;
2) If it isAnd->Then it is determined that the output current of the magnetic field excitation coil is in a positive rising stage,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by adopting a hysteresis controllerS 3 So that the output current +.>Rapidly rising to a desired value, and realizing smooth transition from a rising edge to a flat top;
3) If it isAnd->Then the positive flat-top stage of the output current of the magnetic field exciting coil is judged,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by a PI controllerS 3 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value;
4) If it isAnd->Then, it is determined that the output current of the magnetic field excitation coil is in a reverse rising stage,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by adopting a hysteresis controllerS 5 So that the output current +.>Rapidly rising to a desired value, and realizing smooth transition from a rising edge to a flat top;
5) If it isAnd->Then the phase of the reverse flat-top of the output current of the magnetic field exciting coil is judged,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by a PI controllerS 5 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value;
6) If it isAnd->Not equal to 0, the output current of the magnetic field excitation coil is determined to be in a falling stage,S 3 、S 4 、S 5 、S 6 all turn off, the energy of the magnetic field exciting coil passes through when the target magnetic field is positiveS 5 AndS 6 internally integrated diodes or by the target magnetic field being reversedS 3 AndS 4 the internal integrated diode is fed back to the energy storage capacitor of the synchronous rectification Buck converter;
7) If it isAnd->When 0, it is determined that the output oscillation of the magnetic field excitation coil is eliminated, and the circuit is turned offS 3 AndS 5 turn onS 4 AndS 6 the magnetic field exciting coil outputs residual energy through a DC control switchS 4 A kind of electronic device with high-pressure air-conditioning systemS 6 Releasing;
wherein ,is the proportion coefficient of the width of the hysteresis loop,S 3 is an upper direct current control switch of the left bridge arm,S 4 is a lower direct current control switch of the right bridge arm,S 5 is an upper direct current control switch of the right bridge arm,S 6 is a lower direct current control switch of the left bridge arm.
Preferably, the open loop transfer function of the main circuit is deduced from the circuit model：
And further obtaining PI coefficients of the PI controller under different target magnetic fields according to the following equation set：
wherein ,exciting the coil inductance for the magnetic field, ">Exciting coil resistance for magnetic field, < >>Differential operator for Laplace transformation, +.>Is->Phase angle of>Is->Amplitude of>Is->Phase angle margin of (2), in (2)>Is thatIs a cross-over frequency of (c).
Preferably, the method further comprises:
comparing and judging the acquired end voltage of the energy storage capacitor, the current of the magnetic field excitation coil or the temperature of the magnetic field excitation coil with the fault threshold value of the magnetic field excitation coil, if the threshold value is exceeded, controlling PWM to enable all the direct current control switches in the bridge chopper circuit to be turned off, and releasing magnetic field energy by the magnetic field excitation coil through diodes integrated in all the direct current control switches until the current of the magnetic field excitation coil is reduced to zero.
In order to achieve the above object, in a second aspect, the present invention provides a multi-waveform magnetic field generating apparatus comprising: the sensor comprises a main circuit, a sensor, a driving circuit, a controller and a magnetic field excitation coil;
the sensor is used for collecting output current of the magnetic field excitation coil, terminal voltage of the energy storage capacitor in the synchronous rectification Buck converter and temperature of the magnetic field excitation coil in real time and transmitting the output current and the terminal voltage and the temperature of the magnetic field excitation coil to the controller;
the driving circuit is used for isolating and amplifying the control signal and can drive the on and off of the direct current control switch;
the controller for performing the method according to the first aspect;
the magnetic field exciting coil is used for generating a multi-waveform magnetic field with adjustable multiple parameters and high stability under the power supply of the circuit topology.
Preferably, the frequency range of the multi-waveform magnetic field covers 1Hz-5kHz, the pulse edge is less than 50 mu s, the waveform parameters are flexibly configured and output, the peak intensity is as high as 10mT, and the output waveform is a unipolar pulse or a bipolar pulse.
Preferably, the waveform parameter flexible configuration means that the amplitude, frequency, duty cycle, stimulation interval time and total duration of the magnetic field are all adjustable.
Preferably, the multi-waveform magnetic field generating device is applied to cell activity research.
In general, the above technical solutions conceived by the present invention have the following beneficial effects compared with the prior art:
the invention provides a multi-waveform magnetic field generating device and a control method, which adopt a mode of two-stage joint closed-loop regulation of a voltage regulating circuit and a bridge circuit to realize a magnetic field with adjustable multi-parameter (adjustable magnetic field polarity, amplitude, frequency, duty ratio, stimulation interval time and total duration), steep rising edge and high stability. Firstly, a voltage regulating circuit is utilized to realize controllable high voltage, so that the output voltage of the voltage regulating circuit synchronously changes according to different target magnetic field amplitudes and rising time, the rapid rising of a pulse magnetic field is ensured, the pressure difference required by a magnet in a rising stage and a flat-top stage is minimized, and the difficulty of closed-loop control is reduced; the flexibility of outputting magnetic field waveforms is achieved using bridge circuits. Secondly, in order to prevent the integral saturation of the controller, the transition stage of the pulse from rising to flat top is more stable, a hybrid controller is adopted, the optimal transient characteristic of the hysteresis controller is utilized in the magnetic field rising stage, the strong tracking capability of the PI controller is utilized in the flat top stage, and the stability during the flat top period of the magnetic field is ensured. In addition, the invention takes voltage oscillation caused by parasitic capacitance of the magnet at high frequency into consideration, and eliminates the influence of the parasitic capacitance by providing a proper freewheel loop. Compared with the prior art, the flexibility and stability of the pulse magnetic field are improved, so that optimal stimulation conditions for researching the cell activity by using the multi-dimensional pulse magnetic field waveforms are provided.
Drawings
FIG. 1 is a diagram of a multi-waveform magnetic field generating device according to the present invention.
Fig. 2 is a schematic diagram of a pulse magnetic field waveform according to an embodiment of the present invention.
Fig. 3 is a waveform diagram of current and voltage of a unipolar pulse magnet according to an embodiment of the present invention.
FIG. 4 shows a DC control switch with unipolar pulses having one current period according to an embodiment of the present inventionS 3 、S 4 Is a waveform diagram of (a).
Fig. 5 is a diagram showing current and voltage waveforms of a bipolar pulse magnet according to an embodiment of the present invention.
FIG. 6 shows a bipolar pulse DC control switch with one current period according to an embodiment of the present inventionS 3 、S 4 、S 5 、S 6 Is a waveform diagram of (a).
Detailed Description
The present invention will be described in further detail with reference to the drawings and examples, in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
As shown in fig. 1, the present invention provides a multi-waveform magnetic field generating apparatus, which mainly includes: self-restoring fuseFThe method comprises the steps of carrying out a first treatment on the surface of the Rectifying bridgeD 1 、D 2 、D 3 、D 4 Wherein the input end of the rectifier bridge is connected withD 1 Positive electrodeD 2 The negative electrode is connected to one end, the other end is connected toD 3 Positive electrodeD 4 The negative electrode is connected to oneA dot); filtering capacitorC 1 The method comprises the steps of carrying out a first treatment on the surface of the Energy storage capacitorC 2 The method comprises the steps of carrying out a first treatment on the surface of the Filtering inductanceL 1 The method comprises the steps of carrying out a first treatment on the surface of the DC control switchS 1 、S 2 、S 3 、S 4 、S 5 、S 6 The method comprises the steps of carrying out a first treatment on the surface of the Magnet [ ]R m For the resistance of the magnet,L m for the magnet to be inductive,C m is the parasitic capacitance of the magnet); a current sensor CT; a voltage sensor VT; a temperature sensor TP; bidirectional transient suppression diodeD 8 The method comprises the steps of carrying out a first treatment on the surface of the A controller; and a PC.
As shown in fig. 1, the connection relationships of the components are as follows: the commercial power (220V alternating current) is connected to the input end of the rectifier bridge through the self-recovery fuse, and the rectifier bridge outputs a parallel filter capacitorC 1 Connected to the synchronous Buck converter input; DC control switchS 1 S pole, DC control switchS 2 D pole of (D) and filter inductanceL 1 Is connected to a point (node c), filter inductanceL 1 Is connected to the energy storage capacitor at the other endC 2 Together forming a synchronous Buck converter; energy storage capacitorC 2 And bidirectional transient suppression diodeD 8 Parallel connection; the output of the synchronous Buck converter is connected to the input end of the H bridge; DC control switch for left bridge arm of H bridgeS 3 AndS 6 series connection, right bridge arm is by direct current control switchS 4 AndS 5 series connection, DC control switchS 3 S pole and DC control switch of (C)S 5 S pole connection, DC control switchS 4 D pole and DC control switch of (C)S 6 D pole connections of (c); the middle points of the two bridge arms are connected through a magnet, and one end of the magnet is connected with a direct current control switchS 3 D pole, DC control switch of (C)S 6 Is connected to a point (node a); the other end of the magnet and the DC control switchS 4 S pole, DC control switchS 5 Is connected to a point (node b).
The current sensor CT, the voltage sensor VT and the temperature sensor TP are respectively acquired in real timeMagnet currenti m CapacitorC 2 Terminal voltage of (2)u c Magnet temperatureT m Transmitting to a controller, outputting 6 paths of PWM control signals by the controller, sending the signals to a driving circuit, and respectively controlling a DC control switchS 1 、S 2 、S 3 、S 4 、S 5 、S 6 G pole of (c).
The whole device is divided into a main circuit, a detection circuit and a control circuit, and the working principle and the control method of each part are as follows.
The main circuit is composed of a voltage regulating circuit and a bridge type chopping two-stage topology.
The first stage topology is input from the mains supply, sent into the synchronous Buck converter after passing through the rectifier bridge, and is controlled by the direct currentS 1 、S 2 Adopts complementary control to PWM control signal of capacitorC 2 Charging and energy storage are realized by changing a direct current control switchS 1 、S 2 The PWM control signal duty cycle of (2) provides for providing proper voltage for target magnetic fields with different magnitudes, and the bidirectional transient suppression diodeD 8 Protective capacitorC 2 And the voltage prevents the magnet from being damaged by the overhigh voltage.
The second level topology is an H-bridge. The stage topology is controlled in stages by setting a state zone bit, and a target magnetic field is divided into a unipolar pulse magnetic field and a bipolar pulse magnetic field. In the working mode of a unipolar pulse magnetic field, the working process is divided into a magnet current positive rising stage, a magnet current positive flat-top stage, a magnet current falling stage and a magnet oscillation elimination stage; in the working mode of bipolar pulse magnetic field, the working process is divided into a magnet current forward rising stage, a magnet current forward flat-top stage, a magnet current reverse rising stage, a magnet current reverse flat-top stage, a magnet current falling stage and a magnet oscillation eliminating stage. Wherein, in bipolar mode, the magnet current is in positive rising stage, magnet current is in positive flat top stage, magnet current is in negative falling stage and magnet oscillation eliminating stage, and the switch is controlled by DCS 3 、S 4 、S 5 、S 6 The switch state of the magnetic field is consistent with that of the unipolar pulse magnetic field.
DC control switch for 6 working stagesS 3 、S 4 、S 5 、S 6 The switch states of (a) are as follows:
(1) Magnet current rising stage, DC control switchS 4 The electric conduction is carried out,S 5 、S 6 turn off, magnet currenti m Is the state feedback quantity (detected by the current sensor CT),S 3 by using hysteresis control mode, the capacitorC 2 Discharge to supply power for magnet, DC control switchS 5 、S 6 Internal anti-parallel diode is subjected to back-voltage cutoff and uses a capacitorC 2 The optimal transient characteristic of the hysteresis controller is utilized to enable the current of the magnet to rise rapidly;
(2) Magnet current flat-top stage, DC control switchS 4 The electric conduction is carried out,S 5 、S 6 turn off to store energy in capacitorC 2 Terminal voltageu c (detected by a voltage sensor VT) is a control quantity, and the magnet currenti m The PI controller with strong tracking ability is used for controlling the switch by changing the direct Current (CT) as the state feedback quantityS 3 The PWM control signal duty ratio of (2) carries out negative feedback control on the magnet current, and keeps the average voltage of the magnet asR m i m ；
(3) DC control switch for magnet current reverse rising stageS 6 The electric conduction is carried out,S 3 、S 4 the switch-off is performed and the switch-off is performed,S 5 capacitor using hysteresis controlC 2 Discharge to supply power for magnet, DC control switchS 3 、S 4 Internal anti-parallel diode is subjected to back-voltage cutoff and uses a capacitorC 2 The optimal transient characteristic of the hysteresis controller is utilized to enable the current of the magnet to rise rapidly;
(4) Magnet current reverse flat top stepSegment, DC control switchS 6 The electric conduction is carried out,S 3 、S 4 turn off to store energy in capacitorC 2 Terminal voltageu c (detected by a voltage sensor VT) is a control quantity, and the magnet currenti m The PI controller with strong tracking ability is used for controlling the switch by changing the direct Current (CT) as the state feedback quantityS 5 The PWM control signal duty ratio of (2) is used for carrying out negative feedback control on the magnet current, and keeping the average voltage of the magnet at-R m i m ；
(5) Magnet current falling stage, DC control switchS 3 、S 4 、S 5 、S 6 Cut-off, magnet energy passes through the direct current control switchS 5 、S 6 Internal anti-parallel diodes (with the target field being forward) orS 3 、S 4 An internal anti-parallel diode (the target magnetic field is reversed) is fed back to the capacitorC 2 Charging, realizing energy recovery, at which time the magnet voltage is-u c . Parasitic capacitance due to magnetsC m After the phase of causing the magnet current to drop, the magnet currenti m High frequency resonance occurs, resulting in current still existing inside the magnet;
(6) Magnet oscillation eliminating stage, turn-off DC control switchS 3 、S 5 On DC control switchS 4 、S 6 Magnet surplus energy passing DC control switchS 4 DC control switchS 6 Releasing.
Further, the magnet parasitic capacitance value may be expressed using a conventional coil parasitic capacitance estimation expression, or alternatively, by the magnet currenti m The oscillation frequency is obtained by using a conventional oscillation circuit calculation method of RL series connection and C parallel connection.
The detection circuit is used for collecting the energy storage capacitorC 2 Terminal voltageu c (detected by voltage sensor VT), magnet currenti m (sensed by current)CT detector) and magnet temperatureT m (detected by the temperature sensor TP) and fed back to the control circuit.
The control circuit is composed of a controller and a PC, and is used for setting parameters of a target magnetic field waveform, closed-loop adjustment of output current, and monitoring and judging abnormal conditions of magnet overcurrent, overvoltage and overtemperature. Specifically, the PC sets the target waveform parameters (magnetic field amplitude, frequency, duty cycle, stimulation interval time, total duration) and the magnet fault threshold (overpressure point, overflow point, over-temperature point), and sends them to the controller, which generates the reference waveform of the target waveform.
First, a required pre-stage output voltage is calculated according to a set magnetic field amplitudeu c Magnet currenti m And corresponding PI coefficient, and regulate and control the direct-current control switchS 1 、S 2 Is provided.
According to the magnetic field current ratio constant of the coilAnd target magnetic field amplitude +.>The magnetic field excitation coil required for the inversion outputs current +.>；
According to the rise time of the target magnetic fieldThe desired synchronous Buck converter output voltage is inverted>：
S 1 AndS 2 a complementary control mode is adopted and,S 1 the duty cycle of (2) is:
S 2 the duty cycle of (2) is:
wherein ,exciting the coil inductance for the magnetic field, ">Exciting a coil resistance for a magnetic field; />Is an effective value of 220V alternating current.
Preferably, the open loop transfer function of the main circuit is deduced from the circuit model：
And further obtaining PI coefficients of the PI controller under different target magnetic fields according to the following equation set：
wherein ,exciting the coil inductance for the magnetic field, ">Exciting coil resistance for magnetic field, < >>Differential operator for Laplace transformation, +.>Is->Phase angle of>Is->Amplitude of>Is->Phase angle margin of (2), in (2)>Is thatIs a cross-over frequency of (c).
Secondly, the on and off of each direct current control switch in the synchronous Buck converter is controlled by the following modes:
1) Collecting output current of magnetic field exciting coilOutput current of the excitation coil corresponding to the required magnetic field>Comparing and setting the flag bit +.>、/> and />The method comprises the steps of carrying out a first treatment on the surface of the Marker bit->For determining the polarity of the target magnetic field,/-, for example>For no magnetic field output->Is a positive magnetic field>Is a reverse magnetic field; marker bit->For determining the working phase of the forward magnetic field and in +.>Every time +.>In the case of self-increase 1, in->When in use, setting zero; marker bit->For determining the working phase of the opposing magnetic field and is +.>Every time +.>In the case of self-increase 1, in->And (3) setting zero.
2) If it isAnd->Then it is determined that the output current of the magnetic field excitation coil is in a positive rising stage,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by adopting a hysteresis controllerS 3 So that the output current +.>Rapidly rises to a desired value and achieves a smooth transition from rising edge to flat top.
3) If it isAnd->Then the positive flat-top stage of the output current of the magnetic field exciting coil is judged,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by a PI controllerS 3 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value.
4) If it isAnd->Then, it is determined that the output current of the magnetic field excitation coil is in a reverse rising stage,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by adopting a hysteresis controllerS 5 So that the output current +.>Rapidly rises to a desired value and achieves a smooth transition from rising edge to flat top.
5）If it isAnd->Then the phase of the reverse flat-top of the output current of the magnetic field exciting coil is judged,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by a PI controllerS 5 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value.
6) If it isAnd->Not equal to 0, the output current of the magnetic field excitation coil is determined to be in a falling stage,S 3 、S 4 、S 5 、S 6 all turn off, the energy of the magnetic field exciting coil passes through when the target magnetic field is positiveS 5 AndS 6 internally integrated diodes or by the target magnetic field being reversedS 3 AndS 4 the internally integrated diode is fed back to the storage capacitor of the synchronous rectification Buck converter.
7) If it isAnd->When 0, it is determined that the output oscillation of the magnetic field excitation coil is eliminated, and the circuit is turned offS 3 AndS 5 turn onS 4 AndS 6 the magnetic field exciting coil outputs residual energy through a DC control switchS 4 A kind of electronic device with high-pressure air-conditioning systemS 6 Releasing.
wherein ,is the proportion coefficient of the width of the hysteresis loop,S 3 is an upper direct current control switch of the left bridge arm,S 4 is a lower direct current control switch of the right bridge arm,S 5 is an upper direct current control switch of the right bridge arm,S 6 is a lower direct current control switch of the left bridge arm.
In addition, the collected energy storage capacitorC 2 Terminal voltageu c Magnet currenti m And magnet temperatureT m Respectively comparing and judging with the magnet fault threshold value, and if the threshold value is exceeded, controlling PWM to enableS 3 、S 4 、S 5 、S 6 The magnet is turned off, and the anti-parallel diode inside the direct current control switch releases magnetic field energy until the magnet current is reduced to zero.
Examples
DC control switch selected in this embodimentS 1 、S 2 IPA60R360P7S, drain-source voltage 600V, continuous drain current 9A, on-resistance 360mΩ, uniform model, and voltage withstanding>400V, continuous drain current>9A, the on-resistance is low, other models can be adopted, and no fixing requirement exists.
DC control switchS 3 、S 4 、S 5 、S 6 The IRF520NPBF has a drain-source voltage of 100V, a continuous drain current of 9.7A, an on-resistance of 200mΩ, and a consistent model, and meets the withstand voltage>80V, continuous drain current>7A, the on-resistance is low, other models can be adopted, and no fixing requirement exists.
Filtering capacitorC 1 The capacitor is an in-line aluminum electrolytic capacitor (the nominal parameter is 450V/100 mu F, and the model is EWH2WM101M30 OT); energy storage capacitorC 2 3 direct-insert aluminum electrolytic capacitors are connected in parallel (nominal parameter 100V/1000 mu F, model NXA100VB1000M 18)40 LO）。
The rectifier bridge is KBPC2510W, and the bidirectional transient suppression diodeD 8 For SMBJ51CA, filter inductanceL 1 The inductance of the 27mm iron-silicon-aluminum magnetic ring is 220 mu H.
The self-restoring fuse F functions to protect the entire current from accidents. The model of the self-recovery fuse selected in this embodiment is TRF250-2000, which has a withstand voltage of 250V, a holding current of 2A, and a maximum current of 4A.
The magnet is used to convert the circuit current into a magnetic field. The electrical parameters of the magnet selected in this embodiment are: the inductance value 353 [ mu ] H and the resistance value at 25 ℃ are 388mΩ. The coil field current specific constant is 2mT/A, i.e. 2mT field is generated per 1A current. The magnet parameters have no fixed requirements, and the requirements can be met through simulation and experiments.
The current sensor CT is a closed loop Hall current sensor with the measuring range of +/-19.2A and the rated measuring current of +/-6A, and the model is LTS 6 -NP, acquisition of magnet current signals; the voltage sensor VT adopts sampling resistor voltage division and isolation amplification, the isolation amplification chip adopts AMC1301, and the end voltage of the energy storage capacitor is collected; the temperature sensor TP is a high-precision temperature sensor, the model is selected as SI7051-A20-IMR, the resolution is 0.1 ℃ at the maximum, and a magnet temperature signal is acquired; and the collected current, voltage and temperature values are sent to a controller for real-time control.
The controller has the functions of: the flexible configuration of the related parameters of the magnetic field waveform is realized; control DC switchS 1 、S 2 、S 3 、S 4 、S 5 、S 6 Is turned on and off; collecting signals of a current sensor CT, a voltage sensor VT and a temperature sensor TP, performing closed-loop control according to the collected signals, and outputting PWM control signals to control the output of the synchronous Buck converter and the H bridge; the fault judgment of the system is realized, and the safe and reliable operation of the system is ensured. The controller in this embodiment employs a TMS 3 20F28379D control chip.
With the above configuration parameters, a magnet field waveform can be obtained as shown in FIG. 2, wherein the waveform can be configured in a unipolar and bipolar mode, peak (B m ) The adjustable precision is 0.1 mT, the frequency (1/T) range is 1Hz-5kHz, and the magnetic field duty ratio (D) is continuously adjustable.The total duration of the pulsed magnetic field application and the inter-stimulus time (ISI) of the pulse groups are adjustable. Setting the output waveform of the magnet to be single polarity, and outputting current by the required magnetic field excitation coilThe corresponding pulse magnetic field is 5×2mt=10mt, the magnetic field frequency is 3 kHz, the duty ratio d=50%, 20 pulse magnetic field periods are continuously applied, and the application is stopped for 30 ms. The resulting magnet unipolar pulse current and voltage waveforms are shown in fig. 3. Correspondingly, one current periodS 3 、S 4 As shown in fig. 4, consistent with the above-described operation mode.
Setting the output waveform of the magnet to be bipolar, and outputting current by the required magnetic field exciting coilThe corresponding pulse magnetic field is 5×2mt=10mt, the magnetic field frequency is 1 kHz, the duty ratio d=50%, 6 pulse magnetic field periods are continuously applied, and the application is stopped for 30 ms. The resulting bipolar pulse current and voltage waveforms for the magnet are shown in fig. 5. Correspondingly, one current periodS 3 、S 4 、S 5 、S 6 As shown in fig. 6, consistent with the above-described operation mode.
Therefore, the invention can realize multi-waveform magnetic fields with wide frequency range (1 Hz-5 kHz), steep pulse edge (< 50 mu s), flexible waveform configuration output and peak intensity up to 10 mT.
It will be readily appreciated by those skilled in the art that the foregoing description is merely a preferred embodiment of the invention and is not intended to limit the invention, but any modifications, equivalents, improvements or alternatives falling within the spirit and principles of the invention are intended to be included within the scope of the invention.
Claims (7)
1. A multi-waveform magnetic field generation control method, characterized by comprising:
receiving specification of a target magnetic field waveform parameter;
acquiring output current of a magnetic field excitation coil, terminal voltage of an energy storage capacitor in a synchronous rectification Buck converter and temperature of the magnetic field excitation coil in real time;
forming 6 paths of PWM control signals according to the target magnetic field waveform parameters and the magnetic field excitation coil data acquired in real time, and sending the signals into a driving circuit for respectively controlling the on and off of 6 direct current control switches in a main circuit to realize closed-loop regulation of the output current of the magnetic field excitation coil;
wherein the main circuit includes: a cascaded voltage regulating circuit and a bridge chopper circuit; the voltage regulating circuit includes: full bridge rectifier and synchronous Buck converter; the input end of the full-bridge rectifier is used for being connected with 220V alternating current, and the output end of the full-bridge rectifier is connected with the filter capacitor in parallel and is connected to the input end of the synchronous Buck converter; the output end of the synchronous Buck converter is connected to the input end of the bridge chopper circuit; the middle points of the two half bridges of the bridge chopper circuit are used for connecting a magnetic field excitation coil;
control of the DC control switches in a synchronous Buck converter byS 1 、S 2 Is turned on and off:
according to the magnetic field current ratio constant of the coilAnd target magnetic field amplitude +.>The magnetic field exciting coil required by the inversion outputs current：
According to the rise time of the target magnetic fieldThe desired synchronous Buck converter output voltage is inverted>：
S 1 AndS 2 a complementary control mode is adopted and,S 1 the PWM control signal duty cycle of (2) is:
S 2 the PWM control signal duty cycle of (2) is:
wherein ,exciting the coil inductance for the magnetic field, ">Exciting a coil resistance for a magnetic field; />Is the effective value of 220V alternating current;
the DC control switches in the bridge chopper circuit are controlled byS 3 、S 4 、S 5 、S 6 Is turned on and off:
1) Collecting output current of magnetic field exciting coilOutput current of the excitation coil corresponding to the required magnetic field>Comparing and setting the flag bit +.>、/> and />The method comprises the steps of carrying out a first treatment on the surface of the Marker bit->For determining the polarity of the target magnetic field,/-, for example>For no magnetic field output->Is a positive magnetic field>Is a reverse magnetic field; marker bit->For determining the working phase of the forward magnetic field and in +.>Every time +.>In the case of self-increase 1, in->When in use, setting zero; marker bit->For determining the working phase of the opposing magnetic field and is +.>Every time +.>In the case of self-increase 1, in->When in use, setting zero;
2) If it isAnd->Then it is determined that the output current of the magnetic field excitation coil is in a positive rising stage,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by adopting a hysteresis controllerS 3 So that the output current +.>Rapidly rising to a desired value, and realizing smooth transition from a rising edge to a flat top;
3) If it isAnd->Then the positive flat-top stage of the output current of the magnetic field exciting coil is judged,S 5 andS 6 the switch-off is performed and the switch-off is performed,S 4 conduction is controlled by a PI controllerS 3 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value;
4) If it isAnd->Then, it is determined that the output current of the magnetic field excitation coil is in a reverse rising stage,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by adopting a hysteresis controllerS 5 So that the output current +.>Rapidly rising to a desired value, and realizing smooth transition from a rising edge to a flat top;
5) If it isAnd->Then the phase of the reverse flat-top of the output current of the magnetic field exciting coil is judged,S 3 andS 4 the switch-off is performed and the switch-off is performed,S 6 conduction is controlled by a PI controllerS 5 So that the magnetic field excitation coil outputs current +.>Stabilize at the desired value;
6) If it isAnd->Not equal to 0, the output current of the magnetic field excitation coil is determined to be in a falling stage,S 3 、S 4 、S 5 、S 6 all turn off, the energy of the magnetic field exciting coil passes through when the target magnetic field is positiveS 5 AndS 6 internally integrated diodes or by the target magnetic field being reversedS 3 AndS 4 the internal integrated diode is fed back to the energy storage capacitor of the synchronous rectification Buck converter;
7) If it isAnd->When 0, it is determined that the output oscillation of the magnetic field excitation coil is eliminated, and the circuit is turned offS 3 AndS 5 turn onS 4 AndS 6 the magnetic field exciting coil outputs residual energy through a DC control switchS 4 A kind of electronic device with high-pressure air-conditioning systemS 6 Releasing;
wherein ,is the proportion coefficient of the width of the hysteresis loop,S 3 is an upper direct current control switch of the left bridge arm,S 4 is a lower direct current control switch of the right bridge arm,S 5 is an upper direct current control switch of the right bridge arm,S 6 is a lower direct current control switch of the left bridge arm.
2. The method of claim 1, wherein the open loop transfer function of the main circuit is deduced from a circuit model：
And further obtaining PI coefficients of the PI controller under different target magnetic fields according to the following equation set：
wherein ,exciting the coil inductance for the magnetic field, ">Exciting coil resistance for magnetic field, < >>Differential operator for Laplace transformation, +.>Is->Phase angle of>Is->Amplitude of>Is->Phase angle margin of (2), in (2)>Is->Is a cross-over frequency of (c).
3. The method of claim 1 or 2, further comprising:
comparing and judging the acquired end voltage of the energy storage capacitor, the current of the magnetic field excitation coil or the temperature of the magnetic field excitation coil with the fault threshold value of the magnetic field excitation coil, if the threshold value is exceeded, controlling PWM to enable all the direct current control switches in the bridge chopper circuit to be turned off, and releasing magnetic field energy by the magnetic field excitation coil through diodes integrated in all the direct current control switches until the current of the magnetic field excitation coil is reduced to zero.
4. A multi-waveform magnetic field generating apparatus, comprising: the sensor comprises a main circuit, a sensor, a driving circuit, a controller and a magnetic field excitation coil;
the sensor is used for collecting output current of the magnetic field excitation coil, terminal voltage of the energy storage capacitor in the synchronous rectification Buck converter and temperature of the magnetic field excitation coil in real time and transmitting the output current and the terminal voltage and the temperature of the magnetic field excitation coil to the controller;
the driving circuit is used for isolating and amplifying the control signal and can drive the on and off of the direct current control switch;
the controller for performing the method of any one of claims 1 to 3;
the magnetic field exciting coil is used for generating a multi-waveform magnetic field with adjustable multiple parameters and high stability under the power supply of the circuit topology.
5. The apparatus of claim 4, wherein the multi-waveform magnetic field has a frequency range covering 1Hz-5kHz, pulse edges <50 μs, waveform parameters flexibly configured output, peak intensities up to 10mT, and output waveforms that are unipolar or bipolar pulses.
6. The apparatus of claim 5, wherein the flexible configuration of waveform parameters means that magnetic field amplitude, frequency, duty cycle, stimulation interval time, and total duration are all adjustable.
7. The device of any one of claims 4 to 6, wherein the multi-waveform magnetic field generating device is applied in cell activity studies.
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