CN108107388B - Current synthesis circuit based on electric induction coil - Google Patents

Current synthesis circuit based on electric induction coil Download PDF

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CN108107388B
CN108107388B CN201711419324.9A CN201711419324A CN108107388B CN 108107388 B CN108107388 B CN 108107388B CN 201711419324 A CN201711419324 A CN 201711419324A CN 108107388 B CN108107388 B CN 108107388B
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current
electrically connected
power supply
compensation
bridge
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CN108107388A (en
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徐维正
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
    • G01R33/00—Arrangements or instruments for measuring magnetic variables
    • G01R33/20—Arrangements or instruments for measuring magnetic variables involving magnetic resonance
    • G01R33/28—Details of apparatus provided for in groups G01R33/44 - G01R33/64
    • G01R33/32—Excitation or detection systems, e.g. using radio frequency signals
    • G01R33/36—Electrical details, e.g. matching or coupling of the coil to the receiver

Abstract

The invention discloses a current synthesis circuit based on an electric induction coil, which comprises: the power supply isolator is used for carrying out interference isolation processing on an input alternating current power supply, rectifying and outputting a direct current power supply and providing energy to the current generation module; the main digital controller is used for outputting pulse information to a switching tube in the current generation module so as to control the switching tube to be switched on and off; the current generation module is used for performing power conversion on the input direct-current power supply and providing driving current for a gradient coil of the nuclear magnetic resonance imaging equipment to work; the main current sensor is used for detecting the real-time current value generated by the current generation module and sending the detected real-time current value to the main digital controller; the main digital controller compares the received real-time current value detected by the main current sensor with a preset current value and controls and outputs corresponding pulse information according to a comparison result; the current generation module comprises a plurality of H bridges composed of a plurality of switching tubes.

Description

Current synthesis circuit based on electric induction coil
Technical Field
The invention relates to the field of information control, in particular to a current synthesis circuit based on an electric induction coil.
Background
The gradient current generation module and the matched gradient coil in a Magnetic Resonance Imaging (MRI) are taken as an example for explanation: the industry generally calls for current waveforms to be fed to the gradient coils, as shown in FIG. 9: wherein, Amax is 600A, precision is 0.01%, d is 500uS, and T is 3000 uS; in recent years, to improve the technical performance and efficiency of MRI, if desired: the expected index Amax is above 850A, d is below 200 uS; t is 1200uS or less.
Displaying according to the data; obviously, the current peak value is improved by 42%; the detection rate (frequency) is improved by 150%; in order to meet the current index, the prior art generally adopts an H-type inverter bridge (H-bridge for short) circuit with a bus voltage as high as 800V, and directly outputs a current waveform shown in fig. 8 to feed into a gradient coil.
The main problems of the prior art in the application process are as follows:
Meeting the existing indexes is very laborious, can not meet the expected indexes at all, and can not generate any waveform. Since the IGBT of the H-bridge already operates around its limit values for switching frequency, voltage and current capability. The reason for adopting the modulation mode of phase-staggered frequency multiplication is that the limit switching frequency of the IGBT is 40KHz, which can not meet the requirements of the current indexes, and the frequency multiplication to 80KHz can only marginally meet the requirements of the current indexes.
The power conversion efficiency is very low because the group IGBTs in the H-bridge must use high frequency linear IGBTs and operate at the limit switching capability (40 KHz). The switching characteristic of the high-frequency linear IGBT is very poor, so that the conversion efficiency of the whole device is not enough even 50%; such low conversion efficiency brings additional trouble that the H-bridge must be water-cooled, thus resulting in high cost of cooling equipment and high running cost.
The 40KHz switching capability of the linear IGBT still can not meet the requirements of the current indexes, the PWM modulation technology of 'phase-staggered frequency multiplication to 80 KHz' has to be adopted, and the cost of the technology is that the inverter bridge generates a large amount of 'common mode current' pollution. This kind of electromagnetic pollution not only further reduces conversion efficiency, has still brought huge pollution abatement cost.
Based on the above technical problems, the present application provides a technical solution to solve the above technical problems.
Disclosure of Invention
The invention aims to provide a current synthesis circuit based on an electric induction coil, which is characterized in that a plurality of H bridges are decomposed and connected in parallel to form a plurality of topological structures, so that the working efficiency is improved, the product cost is reduced, and the electromagnetic energy-saving effect is achieved.
The technical scheme provided by the invention is as follows:
An electrical induction coil based current synthesizing circuit comprising: the system comprises a power supply isolator, a current generation module, a main digital controller and a main current sensor; the power supply isolator is used for carrying out interference isolation processing on an input alternating current power supply, rectifying and outputting a direct current power supply and providing energy to the current generation module; the main digital controller is used for outputting pulse information to a switching tube in the current generation module so as to control the switching tube to be switched on and off; the current generation module is used for performing power conversion on the input direct-current power supply and providing driving current for a gradient coil of the nuclear magnetic resonance imaging equipment to work; the main current sensor is used for detecting a real-time current value generated by the current generation module and sending the detected real-time current value to the main digital controller; the main digital controller compares the received real-time current value detected by the main current sensor with a preset current value and controls and outputs corresponding pulse information according to the comparison result; the current generation module comprises a plurality of H bridges formed by a plurality of switching tubes.
Preferably, the current generation module includes: the system comprises a plurality of current generation sub-modules and 1 current compensation module; acquiring the number of the current generation submodules according to preset current waveform parameters and performance parameters of a preset switching tube; each current generation submodule generates equivalent current; a plurality of the current generation submodules are electrically connected to the power isolator in parallel; the main current sensor monitors the current sum generated by the current generation submodules and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with preset current parameters, outputs equivalent pulse information corresponding to the number of the current generation submodules and compensation pulse information according to a comparison result, and correspondingly controls the current information generated by each current generation submodule and the waveform information output by the current compensation module respectively so that the generated current information meets the preset current waveform parameters for the gradient coil to work.
Preferably, the current generation submodule includes: 1 said H-bridge, sub-digital controller, sub-current sensor; the H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the H bridge is electrically connected with the positive end of the power supply of the sub-current sensor; the negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the sub current sensor is correspondingly and electrically connected with the data control port of the sub digital controller, and the common connecting end of the sub current sensor is correspondingly and electrically connected with the data control port of the main digital controller.
Preferably, the current compensation module; the current compensation module is provided with: 1 information compensation H bridge, compensation digital controller, compensation current sensor; the information compensation H bridge consists of 4 switching tubes and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the information compensation H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the information compensation H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the information compensation H bridge is electrically connected with the positive end of the power supply of the compensation current sensor; the negative power supply end of the compensating current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the compensation current sensor is correspondingly and electrically connected with the data control port of the compensation digital controller, and the common connecting end of the compensation current sensor is electrically connected with the data compensation control port of the main digital controller.
Preferably, the current generation sub-module and the current compensation module further include: a step-up transformer and a filter; judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform; the positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
Preferably, the current synthesizing circuit based on the inductive coil further includes: the positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
Preferably, the current generation module further includes: a plurality of topologies of different frequencies and 1 current compensation module; the topological structures with different frequencies are electrically connected to an alternating current power supply end in parallel through the corresponding power supply isolators; according to a first preset current waveform parameter output by the current generation module, acquiring a plurality of second preset current waveform parameters with different frequencies by using a mathematical model of a preset second algorithm; establishing the topological structure of corresponding frequency according to the second preset current waveform parameters of different frequencies; the main current sensor detects the current sum generated by a plurality of topological structures and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with a first preset current waveform parameter, outputs pulse information corresponding to the topological structures with different frequencies and compensation pulse information according to the comparison result, and correspondingly controls the current information generated by each topological structure and the waveform information output by the current compensation module respectively so that the current information generated by the topological structures meets the preset current waveform parameter for the gradient coil to work.
Preferably, the topology of the same frequency includes: the system comprises a plurality of current generation submodules, 1 auxiliary digital controller and 1 auxiliary current sensor; the information output ends of the current generation sub-modules are respectively and correspondingly electrically connected with the digital control ports of the auxiliary digital controller; the positive output ends of the current generation submodules are electrically connected with the positive end of the power supply of the auxiliary current sensor; the negative output ends of the current generation sub-modules are respectively and electrically connected with the positive output end of the current compensation module and the positive power supply end of the main current sensor; the negative end of the power supply of the main current sensor is electrically connected with one end of the gradient coil; the other end of the gradient coil is electrically connected with the positive electrode output end of the current compensation module and the power supply negative electrode end of the auxiliary current sensor in the current generation submodule respectively; the information output end of the main current sensor is correspondingly and electrically connected with the data control port of the main digital controller; the signal control end of the current compensation module is correspondingly and electrically connected with the data control port of the main digital controller; and the auxiliary data control ports of the auxiliary digital controller are electrically connected with the data control ports of the main digital controller in a one-to-one correspondence manner.
Preferably, the current generation submodule includes: 1H bridge, 1 sub digital controller and 1 sub current sensor; the H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the H bridge is electrically connected to the positive end of the power supply of the sub-current sensor in parallel; the signal control end of the H bridge is electrically connected with the data control ports of the sub-digital controllers in a one-to-one correspondence manner; the negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel; the information output ends of the sub current sensors are electrically connected with the data control ports of the sub digital controllers in a one-to-one corresponding mode, and the public connecting ends of the sub current sensors are electrically connected with the data control ports of the main digital controller in a one-to-one corresponding mode.
Preferably, the current compensation module includes: 1 information compensation H bridge, compensation digital controller and compensation current sensor; the information compensation H bridge consists of 4 switching tubes and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the information compensation H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the information compensation H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the information compensation H bridge is electrically connected with the positive end of the power supply of the compensation current sensor; the negative power supply end of the compensating current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the compensation current sensor is correspondingly and electrically connected with the data control port of the compensation digital controller, and the common connecting end of the compensation current sensor is electrically connected with the data compensation control port of the main digital controller.
Preferably, the current generation sub-module and the current compensation module further include: a step-up transformer and a filter; judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform; the positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
Preferably, the method further comprises the following steps: the positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
The invention provides a current synthesis circuit based on an electric induction coil, which can bring at least one of the following beneficial effects:
1. In the invention, based on inductive load, the gradient coil is preferably applied to an MRI system, and can also be an electron accelerator in nuclear physics experiments, a pulse hardening device for processing the strength of metal materials, an electromagnetic gun in military, an ejector and the like, namely, in the occasion of needing to use high-strength Lorentz force in various forms, the application field is wider, the cost is low, and the control implementation method is flexible.
2. In the invention, the MOS tube is used for replacing the IGBT in the prior art, so that the problem that the conversion efficiency of the whole device is lower than 50 percent due to the extremely poor switching characteristic of the high-frequency linear IGBT in the prior art because of the limitation of the working frequency of the IGBT is solved; the problem of very low electric energy conversion efficiency is solved, and the working efficiency is improved; in the second aspect, the conversion efficiency is low, the power consumption is high, the working system is easy to heat, and the H bridge is required to be cooled by water, so that the problem of high cost is solved.
3. In the invention, the problems that the switching capacity of the linear IGBT in the prior art cannot meet the requirements of the current indexes and the PWM modulation technology of 'phase-staggered frequency multiplication' has to be adopted, so that a large amount of 'common mode current' is generated by an H bridge, great electromagnetic pollution is caused, and later-stage pollution is caused and the cost is controlled are solved through the selected components.
4. In the invention, multiple tests are carried out according to the circuit design and the implementation of the scheme, and the actual conversion efficiency of the electric energy can be measured to be over 95 percent, so that only an air-cooled H bridge is needed. Compared with the prior art, the conversion efficiency is lower than 50%, a huge water cooling system needs to be maintained to operate, a huge and expensive common mode rejection measure needs to be adopted, and the economic effect is not improved by many times.
5. In the invention, the method of decomposing the H bridge and the preset parameters and then outputting the H bridge and the preset parameters in parallel is undoubtedly the mode with the lowest material cost and the fastest development speed for various requirements of large and small product coverage markets.
Drawings
The above features, technical features, advantages and implementation of a current combining circuit based on an inductive coil will be further explained in a clearly understandable way in the following description of preferred embodiments in conjunction with the accompanying drawings.
FIG. 1 is one embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 2 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 3 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 4 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 5 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 6 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 7 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
FIG. 8 is another embodiment of a current synthesizing circuit based on an inductive coil of the present invention;
Fig. 9 is another embodiment of a current synthesizing circuit based on an inductive coil according to the present invention.
Detailed Description
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following description will be made with reference to the accompanying drawings. It is obvious that the drawings in the following description are only some examples of the invention, and that for a person skilled in the art, other drawings and embodiments can be derived from them without inventive effort.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "one" means not only "only one" but also a case of "more than one".
An electrical induction coil based current synthesizing circuit comprising: the system comprises a power supply isolator, a current generation module, a main digital controller and a main current sensor; the power supply isolator is used for carrying out isolation processing on safety and electromagnetic interference on an input alternating current power supply, rectifying and outputting a direct current power supply, and providing energy to the current generation module; the main digital controller is used for outputting pulse information to a switching tube in the current generation module so as to control the switching tube to be switched on and off; the current generation module is used for performing power conversion on the input direct-current power supply and providing driving current for a gradient coil of the nuclear magnetic resonance imaging equipment to work; the main current sensor is used for detecting a real-time current value generated by the current generation module and sending the detected real-time current value to the main digital controller; the main digital controller compares the received real-time current value detected by the main current sensor with a preset current value and controls and outputs corresponding pulse information according to the comparison result; the current generation module comprises a plurality of H bridges formed by a plurality of switching tubes.
Specifically, in the present embodiment, refer to fig. 1; the current synthesis circuit of the electric induction coil is used for generating current values with different waveforms and different intensities, so that the requirement of the load is met, and the load can normally run; the current parameters for normal operation of the load are generally the waveforms shown with reference to fig. 5, in this application supplying AC, and in this application also providing an AC to DC converter, i.e. conversion between AC/DC; after passing through the isolation processor, the interference of electromagnetic noise is removed, and the direct current power supply subjected to isolation and denoising processing is loaded at two ends of the current generation module to provide energy for the current generation module; according to different use environments and load parameters, the current generation module generates currents with corresponding parameters, the current sensor is used for detecting the magnitude of the current value generated by the current generation module in real time, and the current generation module is composed of an H bridge constructed by a plurality of switch tubes; the on-off of the H bridge is determined by generating different PWM waveforms in a digital controller, and the magnitude of the generated current is further adjusted by the duty ratio of the PWM waveforms.
On the basis of the above embodiment, the present invention provides yet another embodiment; as shown with reference to fig. 2 and 5; the current generation module includes: the system comprises a plurality of current generation sub-modules and 1 current compensation module; acquiring the number of the current generation submodules according to preset current waveform parameters and performance parameters of a preset switching tube; each current generation submodule generates equivalent current; the current generation submodules are electrically connected to an alternating current power supply end in parallel through the corresponding power supply isolators; the main current sensor monitors the current sum generated by the current generation submodules and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with preset current parameters, outputs equivalent pulse information corresponding to the number of the current generation submodules and compensation pulse information according to a comparison result, and correspondingly controls the current information generated by each current generation submodule and the waveform information output by the current compensation module respectively so that the generated current information meets the preset current waveform parameters for the gradient coil to work.
Specifically, in this embodiment, when the current synthesizing circuit is applied in different environments, the frequency f of the current waveform required by the current synthesizing circuit is different from 1/T; peak value A of the current maxThe current is different, namely the effective value of the current is different, and the rising time d when the current reaches the peak value is also different; when the frequency f of the current waveform is 1/T relatively low, the peak rising time d is relatively low; in this embodiment According to the working frequency of the load and the rated current value; and according to the parameters of the components meeting the requirements of the working environment; carrying out equivalent decomposition on the load rated current value; the method is characterized in that an H bridge in the prior art is subjected to equivalent decomposition, the H bridge is decomposed into a plurality of H bridges generating small currents, then the outputs of the plurality of H bridges generating small currents are connected in parallel, and the sum of the generated equivalent small currents is loaded in a main current sensor and a load coil; the main current sensor is used for detecting the sum of equivalent small currents in the embodiment; when the sum of the small currents does not meet the preset rated current value of the load operation of the application, a current compensation module is connected in parallel to the plurality of equivalent H bridges of the embodiment and is used for compensating and adjusting the sum of the small currents not to meet the preset rated current value of the load operation; when the embodiment of the present application is applied to an MRI system (the magnetic resonance imaging apparatus is mainly composed of four parts, namely, a magnet system, a gradient magnetic field system, a radio frequency system, a computer, and an image processing system), the following will be further described by taking fig. 2 as an example: in the H-bridge in the prior art, N high-precision, medium/small arbitrary current waveforms of the H-bridge, Unit1 and Unit2 … Unitn (hereinafter referred to as U1 and U2 … Un) are equivalently decomposed. U1, U2.. Un, Un +1 each Un can work independently, outputting trapezoidal current wave with high precision and small/medium intensity. The electrical schematic topology of Un is shown in fig. 6, and the outputs of U1, U2... Un are directly fed into the load (gradient coil) in parallel, so that high-precision, high-intensity and trapezoidal current waves can be synthesized and generated in the load (gradient coil). The control circuit monitors and compares the difference between the current waveform synthesized in the load and the current waveform required to be output in real time, and takes the difference as the reference input of Un +1 in real time, and the corresponding output of the difference is simultaneously connected with the outputs of U1, U2.
On the basis of the above embodiment, the present invention provides yet another embodiment; as shown with reference to FIG. 3; the current generation submodule includes: 1 said H-bridge, sub-digital controller, sub-current sensor; the H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the H bridge is electrically connected with the positive end of the power supply of the sub-current sensor; the negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the sub current sensor is correspondingly and electrically connected with the data control port of the sub digital controller, and the common connecting end of the sub current sensor is correspondingly and electrically connected with the data control port of the main digital controller. The current compensation module is provided with: 1 information compensation H bridge, compensation digital controller, compensation current sensor; the information compensation H bridge consists of 4 switching tubes and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the information compensation H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the information compensation H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the information compensation H bridge is electrically connected with the positive end of the power supply of the compensation current sensor; the negative power supply end of the compensating current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the compensation current sensor is correspondingly and electrically connected with the data control port of the compensation digital controller, and the common connecting end of the compensation current sensor is electrically connected with the data compensation control port of the main digital controller.
Specifically, in the present embodiment, since one large-current H-bridge is split into multiple small-current H-bridges, the current generation submodules are referred to as current generation submodules in the present application, and each current generation submodule includes 1H-bridge constructed by a switch tube and 1 sub-current sensor; the sub-current sensor is used for detecting the current value of the current generation sub-module, and the magnitude of the current is controlled by the PWM waveform generated by the sub-digital controller; as shown with reference to FIG. 2; u1, U2, U3, … Un represent each current generation submodule; un +1 represents a current compensation module; the current value generated by the current generation submodule and the current compensation module is generated by an H bridge built by an MOS tube in the current generation submodule and the current compensation module, the positive end out + of the current value is completely loaded at one end of a load, and the negative end out-of the current value is loaded at the positive input end of the main current sensor; the reference current of each current submodule comes from a main digital controller, and as can be seen from the figure, the main controller outputs U1Ref, U2Ref, U3Ref and … Unref to be sent to an information control end Ref in each current output submodule; forming a feedback information flow in each current generation submodule again, and comparing all output currents with the real-time current value of the pin end detected by the main current sensor by the main digital control to form a current difference delta I; the current difference value delta I is compensated through the information compensation current submodule; this compensation is typically achieved by PID control; as can be seen from the figures; a digital electronic control is also included in each current generating submodule for adjusting the value of the current in each module; therefore, each submodule can be ensured to output equivalent and accurate current information.
On the basis of the above embodiment, the present invention provides yet another embodiment; the current generation sub-module and the current compensation module further comprise: a step-up transformer and a filter; judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform; the positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
On the basis of the above embodiment, the present invention provides yet another embodiment; as shown with reference to FIG. 3; further comprising: the positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
Specifically, in this embodiment, when the current synthesizing circuit is applied in different environments, the frequency f of the current waveform required by the current synthesizing circuit is different from 1/T; peak value A of the current maxThe current is different, namely the effective value of the current is different, and the rising time d when the current reaches the peak value is also different; when the frequency f of the current waveform is 1/T relatively low, the peak rising time d is relatively low; the step-up transformer is used for solving the problem of rise time; more preferably, the method is suitable for the conditions that the frequency f is higher, the current peak value Amax is larger, the rising time d is shorter, namely the rising time is faster, and a step-up transformer is added to realize the higher, larger and faster conditions according to the formula
Figure GDA0002471257090000131
it can be seen that the current value reaches the set peak value A even within the set time Deltat maxThe load parameters are not constant, the only variable load parameters are the power supply voltage, and the input voltage loaded in the whole circuit is constant, so that the problems are solved and the input voltage can be changed only through a step-up transformer; judging whether the rising time meets the requirement when the peak current is increased under the condition of no voltage increase, and if not, realizing the judgment through a step-up transformer; according to the transformation ratio formula U1/U2 ═ n2/n 1; calculating the phase strain A booster of the ratio parameter; and the boosted voltage is subjected to interference filtering processing through a filter and loaded at two ends of a load.
On the basis of the above embodiment, the present invention provides yet another embodiment; wherein the current generation module further comprises: a plurality of topologies of different frequencies and 1 current compensation module; the topological structures with different frequencies are electrically connected to an alternating current power supply end in parallel through the corresponding power supply isolators; according to a first preset current waveform parameter output by the current generation module, acquiring a plurality of second preset current waveform parameters with different frequencies by using a mathematical model of a preset second algorithm; the Fourier series establishes the topological structure of the corresponding frequency according to the second preset current waveform parameters of different frequencies; the current values in each topology are different; the main current sensor detects the current sum generated by a plurality of topological structures and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with a first preset current waveform parameter, outputs pulse information corresponding to the topological structures with different frequencies and compensation pulse information according to the comparison result, and correspondingly controls the current information generated by each topological structure and the waveform information output by the current compensation module respectively so that the generated sum current information meets the preset current waveform parameter for the gradient coil to work.
Specifically, in the above embodiment, the equivalent decomposition H bridge is set forth and then connected in parallel; as shown in connection with fig. 3 and 4; in this embodiment, the first preset current waveform parameter refers to an ideal current waveform, and is a theoretical value; decomposing the H bridge non-equivalence; in the above equivalent solutions, lower f and smaller A can be satisfied maxThe requirement of slower d; but does not satisfy the requirements of higher f, larger A maxFaster d requirements; in the embodiment, the set parameters are decomposed into current generation sub-modules with a plurality of frequencies according to Fourier series expansion, namely a second preset algorithm; the decomposition principle is as follows: by expanding Fourier series, a plurality of sine waves with different frequencies and different peak values can be obtained The flow waveform can meet the requirements of high frequency and low frequency in the practical application process; the working efficiency of the system is further improved. The peak value of each grade corresponds to a corresponding frequency and reaches the rise time d of the peak value, then a corresponding topological structure is established according to the peak value of the same grade, the corresponding frequency and the rise time, then equivalence decomposition is carried out in each topological structure according to the size of the peak value to form a plurality of current generation sub-modules, similarly, a main current sensor detects the sum of the currents in the whole synthesis circuit, the generated current sum is compared with a current parameter set at a preset pin end, a control algorithm program in a main digital controller according to the comparison result comprises a PID control algorithm to realize real-time control of the current difference value to meet the set requirement, the current difference value compensation parameter needs to give a corresponding reference value through a corresponding data control port of the main digital controller, a reference value current compensation module carries out compensation, and the balance of the current synthesis circuit is realized through the reference value and the PID control algorithm, and simultaneously, the working requirement of the load coil is met.
On the basis of the above embodiment, the present invention provides yet another embodiment; the topology of the same frequency includes: the system comprises a plurality of current generation submodules, 1 auxiliary digital controller and 1 auxiliary current sensor; the information output ends of the current generation sub-modules are respectively and correspondingly electrically connected with the digital control ports of the auxiliary digital controller; the positive output ends of the current generation submodules are electrically connected with the positive end of the power supply of the auxiliary current sensor; the negative output ends of the current generation sub-modules are respectively and electrically connected with the positive output end of the current compensation module and the positive power supply end of the main current sensor; the negative end of the power supply of the main current sensor is electrically connected with one end of the gradient coil; the other end of the gradient coil is electrically connected with the positive electrode output end of the current compensation module and the power supply negative electrode end of the auxiliary current sensor in the current generation submodule respectively; the information output end of the main current sensor is correspondingly and electrically connected with the data control port of the main digital controller; the signal control end of the current compensation module is correspondingly and electrically connected with the data control port of the main digital controller; and the auxiliary data control ports of the auxiliary digital controller are electrically connected with the data control ports of the main digital controller in a one-to-one correspondence manner.
Specifically, the description is given by specific parameters; assume that the desired waveform is a trapezoidal wave as shown in fig. 5: parameter A thereof max850A; the precision is 0.02%; t is 1ms, i.e., f is 1000 Hz; d is 120 us; expansion by fourier series:
Figure GDA0002471257090000151
Figure GDA0002471257090000152
k is an odd number; after corresponding expansion, the frequency domain parameters shown in the following table 1 are obtained:
Table 1:
Peak value of fundamental wave Peak value of 3 th harmonic Peak value of 5 th harmonic 7 th harmonic peak Peak value of 9 th harmonic 11 th harmonic peak
1012.438 182.018 0.000182828 -33.432 -12.503 8.367
In the desired trapezoidal wave of fig. 5, the main frequency components are the fundamental wave and the 3 rd harmonic, and the effective values and peak values of the harmonics of 5 th order and 13 th order or more have no influence on the output accuracy and can be ignored. 7. The harmonics of 9 and 11 are not negligible, but the effective value of the current peak value of the three and the higher order composite accounts for the proportion of the fundamental current, which is less than 5%. According to the idea, the main current module shown in fig. 1 is decomposed into three sub-current modules of Ua, Ub and Uc: referring to fig. 4, Ua is exclusively responsible for outputting the fundamental wave (rms 715.9a f1 Hz sine wave); ub is exclusively responsible for outputting 3 harmonics (rms 128.71a at f2 at 3000Hz sine wave); uc is exclusively responsible for outputting the remaining harmonics. (including higher harmonics of 7, 9, 11, etc.). The output of Ua and Ub is f1 and f2 for single frequency, although the current intensity is high, the difficulty and cost of circuit design can be greatly reduced. The output component of the Uc is relatively complex, but the rms content is less than 5%, so the difficulty of designing the Uc can be greatly reduced. Since the desired waveform of fig. 5 can be decomposed into the frequency components shown in table 1, the three outputs of Ua, Ub and Uc responsible for outputting the frequency components are directly connected in parallel based on kirchhoff's current law, and fed into the load (gradient coil), so that the current waveform meeting the desired specification of fig. 5 can be synthesized in the load (gradient coil).
1. The expression of Ua output current, Iua (t) 1012.438 sin (2 pi 1000Hz t), with peak value 1012.438a, rms 715.9 a; sine wave current with frequency of 1000 Hz.
2. Ub output current expression: iub (t) ═ 182.018 × sin (2 × pi × 3000Hz × t), with a peak value of 182.018a, rms ═ 128.71 a; a sine wave current with a frequency of 3000 Hz.
3. As can be seen from table 1, the Uc output current mainly has a sinusoidal waveform with frequency components of 7000Hz,9000Hz, and 11000Hz, and has a very low intensity component, and the Uc can be regarded as an output of a small current multi-harmonic waveform, and a digital controller of a gradient amplifier subtracts Ia + Ib output of Ua + Ub from a preset total current I1 in real time, and a difference Δ I thereof is a reference input Ic of the Uc, that is, an output Ic of referrence c, Uc, and is added to the output of Ua + Ub in parallel in real time, and a load (a gradient coil) can synthesize a current waveform which is expected according to fig. 1.
In the present embodiment, each Ua has a topology corresponding to 1 auxiliary current sensor and 1 auxiliary digital controller; meanwhile, the reference current comes from a port which is configured in a main digital controller and corresponds to the port; taking the reference current received by the main digital controller as a preset current value of the topological structure; then configuring the information control end of each sub-module of the auxiliary digital controller through the auxiliary digital controller; the real-time current value output by each current generation submodule is loaded on an auxiliary current sensor in the topological structure; the auxiliary current sensor sends the sum of the current values to the main current sensor and an auxiliary digital controller of the topological structure; therefore, each topological structure can be independently regulated and controlled, the work of other topological structures is not influenced, and the topological structures are finally sent to the main current controller and the main current sensor, so that unified management and regulation are realized.
On the basis of the above embodiment, the present invention provides yet another embodiment; refer to fig. 3 and 4; the current generation submodule includes: 1H bridge, 1 sub digital controller and 1 sub current sensor; the H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the H bridge is electrically connected to the positive end of the power supply of the sub-current sensor in parallel; the signal control end of the H bridge is electrically connected with the data control ports of the sub-digital controllers in a one-to-one correspondence manner; the negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel; the information output ends of the sub current sensors are electrically connected with the data control ports of the sub digital controllers in a one-to-one corresponding mode, and the public connecting ends of the sub current sensors are electrically connected with the data control ports of the main digital controller in a one-to-one corresponding mode.
On the basis of the above embodiment, the present invention provides yet another embodiment; the current compensation module includes: 1 information compensation H bridge, compensation digital controller and compensation current sensor; the information compensation H bridge consists of 4 switching tubes and is provided with an energy input end, a signal control end and an energy output end; the energy input end of the information compensation H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator; the positive end of the energy output end of the information compensation H bridge is electrically connected to one end of the gradient coil in parallel; the negative end of the energy output end of the information compensation H bridge is electrically connected with the positive end of the power supply of the compensation current sensor; the negative power supply end of the compensating current sensor is electrically connected with the other end of the gradient coil in parallel; the information output end of the compensation current sensor is correspondingly and electrically connected with the data control port of the compensation digital controller, and the common connecting end of the compensation current sensor is electrically connected with the data compensation control port of the main digital controller.
On the basis of the above embodiment, the present invention provides yet another embodiment; the current generation sub-module and the current compensation module further comprise: a step-up transformer and a filter; judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform; the positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
On the basis of the above embodiment, the present invention provides yet another embodiment; further comprising: the positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge; the negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge; the positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter; the negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor; the other end of the capacitor in the filter is electrically connected with the gradient coil.
In particular, reference is made to fig. 3 and 4; the connection relationship and the trend of the control signal of this embodiment are completely consistent with those of the equivalent embodiment, and are not described herein again. The design in the topology of different frequencies is further explained
Following the above-described embodiments
Design of Ua:
assuming that the Ua peak current output capability is required to reach more than 1000A, Ua must be processed according to the equivalent decomposition scheme, wherein the Ua is equivalently decomposed into 10H bridges Ua1, Ua2, Ua 10. each Uan has the output capability of 120A 1000Hz sine wave current, the map after Uan decomposition refers to the topology circuit in fig. 3. Uan outputs 1000Hz sine wave current, the PWM frequency of H bridge is 100 Hz 1000Hz 100HKz, the bus voltage is 800V, the H bridge is 1200V NMosfet, bipolar modulation, and common mode noise is greatly avoided.
Designing Ub: the Ub is required to output sine waves with peak current of 185A or more and frequency of 3000Hz, and the PWM frequency of the H bridge is required to be: 100 x 3KHz 300 KHz. To handle this frequency, NMosfet is already quite laborious and so SiC Mosfet should be chosen. The mature technical scheme is that the output peak current capacity of an H bridge composed of SiC mosfets is less than 75A, so that Ub is equally divided into 3H bridges which are Ub1, Ub2 and Ub3 respectively, and the peak current capacity of parallel output reaches 195A. The decomposition method of Ub, also based on engineering practice, is a result of a reasonable balance of cost and performance. Ubn also employ the electrical schematic topology of fig. 5. Ubn bus voltage is 800V, 1200V SiC Mosfet is selected for an H bridge, bipolar modulation is achieved, and common mode noise is greatly avoided. The step-up transformer N is 2.
Design of Uc: the frequency content of the output current of Uc is high, and the PWM frequency of the H-bridge is at least: 100 × 11000Hz ═ 1.1 mHz. SiC mosfets cannot reach such high frequencies, and DaN mosfets, i.e. gallium nitride mosfets, must be selected for bipolar modulation, using the electrical schematic topology of fig. 5. The voltage of the 400V bus is boosted to 1600V, and the transformation ratio N of the transformer is 4. The electrical schematic topology of the ean, Ubn, Uc is shown in figure 3,
Based on the embodiments provided by the invention, the following technical effects can be obtained by designing and calculating: refer to fig. 6 and 7; in the present invention, the circuit topology and design methodology provide a more cost effective and reasonable way to achieve the desired current waveform in an inductive load by practical engineering means.
In the invention, based on inductive load, the gradient coil is preferably applied to an MRI system, and can also be an electron accelerator in nuclear physics experiments, a pulse hardening device for strengthening treatment of metal materials, an electromagnetic gun in military, an ejector and the like, namely, wherever high-strength Lorentz force of various forms is needed, the application field is wider, the cost is low, and the control implementation method is flexible.
In the invention, the MOS tube is used for replacing the IGBT in the prior art, so that the problem that the conversion efficiency of the whole device is lower than 50 percent due to the extremely poor switching characteristic of the high-frequency linear IGBT in the prior art because of the limitation of the working frequency of the IGBT is solved; the problem of very low electric energy conversion efficiency is solved, and the working efficiency is improved; in the second aspect, the conversion efficiency is low, the power consumption is high, the working system is easy to heat, and the H bridge is required to be cooled by water, so that the problem of high cost is solved.
In the invention, the problems that the switching capacity of the linear IGBT in the prior art cannot meet the requirements of the current indexes and the PWM modulation technology of 'phase-staggered frequency multiplication' has to be adopted, so that a large amount of 'common mode current' is generated by an H bridge, great electromagnetic pollution is caused, and later-stage pollution is caused and the cost is controlled are solved through the selected components.
As can be seen by comparing fig. 7 and 8; the output current curve expressed in the upper half part is a current waveform synthesized by ' fundamental wave +3 times +7 times ', and can be used in the occasions of ' emphasizing fast and not emphasizing precision too, so that the cost can be reduced, the speed is faster, and the waveform is accelerated by 10% compared with the expected waveform of FIG. 8; the lower curve of fig. 7 is the output current curve for 100% implementation of the solution of fig. 4. It can be seen that the current waveform expected in fig. 1 is met regardless of the accuracy and speed of the output current, and compared with the expected curve in fig. 1, the arc of the corner at the top and bottom of the trapezoid is transited. Has no influence in practical application.
In the invention, according to the implementation of the circuit design and the scheme, the actual conversion efficiency of the electric energy can be measured to be as high as 95 percent by carrying out a plurality of tests, so that the air cooling is only needed. Compared with the prior art, the conversion efficiency is lower than 50%, a huge water cooling system needs to be maintained to operate, a huge and expensive common mode rejection measure needs to be adopted, and the economic effect is not improved by many times.
In addition, Uan, Ubn, Un, Uc and the like described in the patent can be applied to the situation of outputting small current (below peak current 120A) alone or 2-9 parallel circuits to the situation of medium current. In such an application, the step-up transformer in fig. 3 may even be unnecessary, and after the bus voltage Vbus is reasonably selected, the H-bridge may directly output current through the filter, which is beneficial to reducing the cost.
In the invention, the method of decomposing the H bridge and the expected current waveform, expecting the current value and then outputting the current value in parallel is undoubtedly the mode with the lowest material cost and the fastest development speed for covering various demands of the market by products.
In the present invention, if implemented in the form of software functional units and sold or used as a separate product, it may be stored in a computer-readable storage medium. Based on such understanding, the technical solution of the present application may be substantially implemented or a portion of the technical solution or all or part of the technical solution may be embodied in the form of a software product stored in a storage medium, and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) or a processor to execute all or part of the steps of the method according to the embodiments of the present application. The storage value packet data server, the cloud server, the Read-Only Memory (ROM), the Random Access Memory (RAM), the mobile communication device, or various media capable of storing codes, such as an optical disc or a usb disk.
It should be noted that the above embodiments can be freely combined as necessary. The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.

Claims (10)

1. A current combining circuit based on an inductive coil, comprising: the system comprises a power supply isolator, a current generation module, a main digital controller and a main current sensor;
The power supply isolator is used for carrying out interference isolation processing on an input alternating current power supply, rectifying and outputting a direct current power supply and providing energy to the current generation module;
The main digital controller is used for outputting pulse information to a switching tube in the current generation module so as to control the switching tube to be switched on and off;
The current generation module is used for performing power conversion on the input direct-current power supply and providing driving current for a gradient coil of the nuclear magnetic resonance imaging equipment to work;
The main current sensor is used for detecting a real-time current value generated by the current generation module and sending the detected real-time current value to the main digital controller;
The main digital controller compares the received real-time current value detected by the main current sensor with a preset current value and controls and outputs corresponding pulse information according to the comparison result;
The current generation module consists of a plurality of H bridges consisting of a plurality of switching tubes;
The current generation module comprises 1 current compensation module;
The current compensation module is provided with: 1 information compensation H bridge, compensation digital controller, compensation current sensor;
The information compensation H bridge consists of 4 switching tubes and is provided with an energy input end, a signal control end and an energy output end;
The energy input end of the information compensation H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator;
The positive end of the energy output end of the information compensation H bridge is electrically connected to one end of the gradient coil in parallel;
The negative end of the energy output end of the information compensation H bridge is electrically connected with the positive end of the power supply of the compensation current sensor;
The negative power supply end of the compensating current sensor is electrically connected with the other end of the gradient coil in parallel;
The information output end of the compensation current sensor is correspondingly and electrically connected with the data control port of the compensation digital controller, and the common connecting end of the compensation current sensor is electrically connected with the data compensation control port of the main digital controller.
2. The inductive coil based current synthesizing circuit of claim 1 wherein said current generating module comprises: a plurality of current generation sub-modules;
Acquiring the number of the current generation submodules according to preset current waveform parameters and performance parameters of a preset switching tube; each current generation submodule generates equivalent current; the current generation submodules are electrically connected to an alternating current power supply end in parallel through the corresponding power supply isolators;
The main current sensor monitors the current sum generated by the current generation submodules and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with preset current parameters, outputs equivalent pulse information corresponding to the number of the current generation submodules and compensation pulse information according to a comparison result, and correspondingly controls the current information generated by each current generation submodule and the waveform information output by the current compensation module respectively so that the generated current information meets the preset current waveform parameters for the gradient coil to work.
3. The electric current synthesizing circuit based on the inductive coil as claimed in claim 2, wherein the current generating submodule comprises: 1 said H-bridge, sub-digital controller, sub-current sensor;
The H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end;
The energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator;
The positive end of the energy output end of the H bridge is electrically connected to one end of the gradient coil in parallel;
The negative end of the energy output end of the H bridge is electrically connected with the positive end of the power supply of the sub-current sensor;
The negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel;
The information output end of the sub current sensor is correspondingly and electrically connected with the data control port of the sub digital controller, and the common connecting end of the sub current sensor is correspondingly and electrically connected with the data control port of the main digital controller.
4. The inductive coil based current synthesizing circuit of claim 3 wherein said current generating sub-module and said current compensation module further comprise: a step-up transformer and a filter;
Judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform;
The positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge;
The negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge;
The positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter;
The negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor;
The other end of the capacitor in the filter is electrically connected with the gradient coil.
5. The inductive coil based current synthesizing circuit of claim 4 further comprising:
The positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge;
The negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge;
The positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter;
The negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor;
The other end of the capacitor in the filter is electrically connected with the gradient coil.
6. The inductive coil based current synthesizing circuit of claim 1 wherein said current generating module further comprises: a plurality of different frequency topologies;
The topological structures with different frequencies are electrically connected to an alternating current power supply end in parallel through the corresponding power supply isolators;
According to a first preset current waveform parameter output by the current generation module, acquiring a plurality of second preset current waveform parameters with different frequencies by using a mathematical model of a preset second algorithm;
Establishing the topological structure of corresponding frequency according to the second preset current waveform parameters of different frequencies;
The main current sensor detects the current sum generated by a plurality of topological structures and the current compensation module in real time and sends the current sum to the main digital controller, the main digital controller compares the current sum with a first preset current waveform parameter, outputs pulse information corresponding to the topological structures with different frequencies and compensation pulse information according to the comparison result, and correspondingly controls the current information generated by each topological structure and the waveform information output by the current compensation module respectively so that the current information generated by the topological structures meets the preset current waveform parameter for the gradient coil to work.
7. The inductive coil based current synthesizing circuit according to claim 6 wherein said topology of the same frequency comprises: the system comprises a plurality of current generation submodules, 1 auxiliary digital controller and 1 auxiliary current sensor;
The information output ends of the current generation sub-modules are respectively and correspondingly electrically connected with the digital control ports of the auxiliary digital controller;
The positive output ends of the current generation submodules are electrically connected with the positive end of the power supply of the auxiliary current sensor;
The negative output ends of the current generation sub-modules are respectively and electrically connected with the positive output end of the current compensation module and the positive power supply end of the main current sensor;
The negative end of the power supply of the main current sensor is electrically connected with one end of the gradient coil;
The other end of the gradient coil is electrically connected with the positive electrode output end of the current compensation module and the power supply negative electrode end of the auxiliary current sensor in the current generation submodule respectively;
The information output end of the main current sensor is correspondingly and electrically connected with the data control port of the main digital controller;
The signal control end of the current compensation module is correspondingly and electrically connected with the data control port of the main digital controller;
And the auxiliary data control ports of the auxiliary digital controller are electrically connected with the data control ports of the main digital controller in a one-to-one correspondence manner.
8. The electrical induction coil-based current synthesizing circuit according to claim 7 wherein the current generating submodule comprises: 1H bridge, 1 sub digital controller and 1 sub current sensor;
The H bridge consists of 4 switching tubes, and is provided with an energy input end, a signal control end and an energy output end;
The energy input end of the H bridge is electrically connected to the alternating current power supply end in parallel through the power supply isolator;
The positive end of the energy output end of the H bridge is electrically connected to the positive end of the power supply of the sub-current sensor in parallel;
The signal control end of the H bridge is electrically connected with the data control ports of the sub-digital controllers in a one-to-one correspondence manner;
The negative power supply end of the sub-current sensor is electrically connected with the other end of the gradient coil in parallel;
The information output ends of the sub current sensors are electrically connected with the data control ports of the sub digital controllers in a one-to-one corresponding mode, and the public connecting ends of the sub current sensors are electrically connected with the data control ports of the main digital controller in a one-to-one corresponding mode.
9. The inductive coil based current synthesizing circuit of claim 8 wherein said current generating sub-module and said current compensation module further comprise: a step-up transformer and a filter;
Judging whether the rise time of a current waveform formed by the current sum reaching a peak value meets a preset rise time or not, if not, acquiring the parameters of the step-up transformer by using a first preset algorithm according to the current sum, the preset rise time and the parameter information of the gradient coil, and enabling the adjusted parameters of the step-up transformer to meet the preset rise time of the current waveform;
The positive electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge;
The negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the H bridge;
The positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter;
The negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor;
The other end of the capacitor in the filter is electrically connected with the gradient coil.
10. The electrical induction coil-based current synthesizing circuit according to claim 9 further comprising:
The positive input end of the primary coil of the boosting transformer is electrically connected with the positive end of the energy output end of the information compensation H bridge;
The negative electrode input end of the primary coil of the boosting transformer is electrically connected with the positive electrode end of the energy output end of the information compensation H bridge;
The positive output end of the secondary coil of the boosting transformer is electrically connected with the gradient coil through an inductor in the filter;
The negative output end of the secondary coil of the boosting transformer is electrically connected with one end of a capacitor in the filter and then is electrically connected with the sub-current sensor or the positive power supply end of the compensation current sensor;
The other end of the capacitor in the filter is electrically connected with the gradient coil.
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