Method and system for generating predetermined electromagnetic pulses

Abstract

A method of generating a predetermined electromagnetic pulse using a voltage source (32) comprising a chain of N switchable modules (12) is disclosed, the method comprising the steps of: determining a target voltage pulse waveform adapted to generate the predetermined electromagnetic pulse when applied to a load (33); determining, based on the target voltage pulse waveform, an individual starting module voltage for each of the N modules; charging an energy storage device (18) of each module (12) to reach the corresponding determined starting module voltage; and generating, at the voltage source, a time-varying output voltage approximating the target voltage pulse waveform by selectively switching the switchable modules (12).

Description

Technical Field

[0001] This application relates to a method and apparatus for generating predetermined electromagnetic pulses. More specifically, this application relates to a method and apparatus for generating stimulation pulses for inductive neuronal stimulation, particularly magnetic stimulation pulses for transcranial magnetic stimulation (TMS). Background Technology

[0002] Magnetic stimulation technology uses electromagnetic fields applied to the outside of human tissues to stimulate specific cells. It is currently the only technology that can stimulate neurons in the brain painlessly and non-invasively. Furthermore, this technology is increasingly being used in the field of peripheral nervous system rehabilitation.

[0003] Magnetic stimulation is typically based on the principle of electromagnetic induction. A conductive coil (the so-called treatment coil or stimulation coil) is placed near the patient, and a time-varying current is passed through the coil, generating a corresponding time-varying magnetic field. This magnetic field penetrates human tissue and induces a time-varying electric field within the tissue, which is then used to stimulate neurons. A major advantage of inductive magnetic stimulation is that it does not require physical contact with the coil; the magnetic field generated by the coil can cover human tissue at a certain distance from the coil. Furthermore, compared to electrical stimulation, this technique is almost completely painless, avoiding high current density in areas with high pain receptor distribution, such as the skin. Based on these advantages, this technique is also suitable for stimulating deep tissue structures such as the cerebral cortex through the skull, and can also achieve painless muscle stimulation.

[0004] The potential fluctuations required to stimulate a neuronal membrane are only on the order of millivolts, but conventional stimulation devices, mostly based on resonant circuit principles, generate pulse power in the megawatt range, sometimes resulting in waste heat losses of several kilowatts. The stimulation coils experience severe temperature rise, and the usable time for a single treatment session is often only a few minutes. Furthermore, the power requirements significantly limit the practical application of magnetic stimulation technology, primarily due to the capacity required by the power supply unit and the high pulse repetition frequency. Current neuromodulation protocols require up to four stimulators operating in parallel for a single patient. However, these devices are large, heavy, and cumbersome, making them practically unusable outside of large medical institutions.

[0005] Figure 1 A conventional circuit topology for generating controllable high-intensity monophasic magnetic pulses for transcranial magnetic stimulation is shown. This topology includes a resonant circuit consisting of a high-voltage capacitor C and a stimulation coil L, connected by a switch Q (e.g., a transistor). A charging circuit charges the capacitor C to several kilovolts, storing up to several hundred joules of energy. When switch Q is closed, current flows through coil L, generating a stimulation magnetic field, but most of the energy is lost as waste heat through resistor R.

[0006] Figure 2An improved circuit topology that reduces waste heat loss is schematically illustrated, as described in [the document / document / etc.]. AV Peterchev The article published by [names of authors] Repetitive Transcranial Magnetic Stimulator with Controllable Pulse Parameters (Repetitive Transcranial Magnetic Stimulation Device with Controllable Pulse Parameters) (《《 Journal of Neural Engineering (Journal of Neural Engineering), Vol. 8, No. 3, 2011, 036016). In this half-bridge configuration, the stimulation coil L is alternately connected to high-voltage capacitors Cp and Cm via switches Q1 and Q2. When switch Q1 is closed, energy taken from capacitor Cp but not converted into a magnetic pulse in coil L can be at least partially recharged to capacitor Cm. When switch Q2 is subsequently closed, capacitor Cm feeds capacitor Cp in the reverse direction. Figure 1 Compared to the switching configuration, this solution results in lower waste heat loss. Furthermore, the two independent capacitors, Cp and Cm, are each equipped with a charging circuit, improving the flexibility of pulse waveform generation.

[0007] Figure 3 Show Figure 2 The full-bridge circuit, a further improvement upon the half-bridge circuit, is detailed in [reference needed]. AV Peterchev Published Circuit Topology Comparison and Design Analysis for Controllable Pulse Parameter Transcranial Magnetic Stimulators (Comparison and Design Analysis of Circuit Topologies for Controllable Pulse Parameter Transcranial Magnetic Stimulation Devices) (Proceedings of the 5th IEEE International Conference on Neuroengineering, 2011, p. 646). With Figure 2 Depending on the configuration, the full-bridge circuit includes four switches Q1, Q2, Q3, and Q4, which can apply two different voltage levels to the stimulation coil L. If the charging voltage of capacitor Cp is denoted as V, the stimulation coil L can switch between voltages V, -V, and 0. If a second capacitor branch (charging voltage V′) is added to this circuit, a voltage difference VV′ can also be applied across the coil. The pulse waveforms achievable with this configuration are detailed in the specifications of US Patents US7753836B2 and US7946973B1.

[0008] Figure 2 and Figure 3 The circuit configuration improves the flexibility of magnetic pulse shaping while reducing heat loss. However, even with the above circuit, extremely high pulse power is still required to generate sufficient potential fluctuations in the neuronal membrane.

[0009] SMGötz The article published by [names of authors] Analysis and Optimization of Pulse Dynamics for Magnetic Stimulation(Magnetic Stimulation Pulse Dynamics Analysis and Optimization) (preprint arXiv: 1106.3452v1, June 17, 2011) demonstrates through complex simulations that a well-designed pulse waveform can significantly improve the energy efficiency of magnetic stimulation. Numerical optimization simulations targeting Aα fibers and upper motor neurons (pyramidal cells, a preferred target tissue for magnetic stimulation) revealed that setting a pre-edge pulse with relatively gentle dynamic changes and a current direction opposite to the main pulse exhibits excellent energy-saving effects. (Source: [Original Source Name]) Götz Literature published by [authors] Figure 4 The time-domain waveform corresponding to the coil current is schematically shown. Figure 4 The leading edge 10 is clearly visible. This leading edge 10 first causes the carrier to fall to a negative position, and then leads to the actual main pulse 12. The effect of the carrier falling to a negative position is that the leading pulse allows the subsequent main pulse to have a relatively longer rise edge, thereby obtaining a higher induced electric field intensity. At the same time, it limits the peak current (power loss is proportional to the square of the current). The maximum value of the voltage change rate (an indicator characterizing the dynamic characteristics) in the leading stage can be more than a hundred times lower than the gradient value in the main pulse stage. SMGötz Simulation calculations by researchers show that by using specially shaped pulses (especially with the addition of a leading edge), the energy loss in the magnetic pulse generation process can be reduced by several times compared to existing technologies. However, none of the aforementioned conventional magnetic stimulation devices can generate the pulse waveform that has been verified by simulation to have excellent performance.

[0010] To address the aforementioned deficiencies, the applicant's earlier application DE 10 2012 101 921 A1 discloses a device for generating stimulation pulses for inductive neuronal stimulation. This device includes at least one stimulation coil and at least one first half-bridge circuit, the output of which is electrically connected to the stimulation coil. The first half-bridge circuit is a multi-level half-bridge, possessing at least three different voltage levels. The applicant's earlier patent application has confirmed that this type of circuit topology is highly suitable for inductive magnetic stimulation, capable of generating both high-efficiency pulse waveforms and the flexible generation of various desired pulse waveforms.

[0011] Modular multilevel converters (MMCs) can further enhance the flexibility of waveform generation. The earliest record of modular multilevel converters is found in DE 102 17 889 A1, and related extended discussions can be found in... S. Allebrod, R. Hamerski,R. Marquardt 《 New transformerless, scalable modular multilevel converters for hvdc-transmission(Transformerless Scalable Modular Multilevel Converters for HVDC Transmission) (IEEE Power Electronics Experts Meeting, June 2008, pp. 174-179). Such MMCs include one or more converter arms, each consisting of multiple modules connected in series. Each module has a capacitor as an energy storage device, an input terminal, an output terminal, and multiple switches. These switches can selectively connect the capacitors of adjacent modules in series, or bypass or "disable" the capacitors. By selecting a portion of the module capacitors to connect in series at any given time, the target total voltage can be obtained across the converter arm.

[0012] In traditional MMCs, the capacitors in each module have uniform specifications, ensuring a consistent average voltage during operation. The applicant's recent patent publication, DE 10 2017 108 099 A1, discloses a novel modular multilevel converter, which can be named an "exponential modular multilevel converter (EMMC)." Compared to traditional MMCs, EMMCs reduce cost and circuit complexity. The core reason for the cost reduction is that EMMCs require fewer modules to provide the same output voltage with the same number of output voltage levels. For the working principle and detailed structure of EMMCs, please refer to DE 10 2017 108 099 A1, the full text of which is incorporated herein by reference and may also be consulted. M. Kuder, A. Kersten, L. Bergmann The article published by et al. in 2019 Exponential Modular Multilevel Converter for Low Voltage Applications (Exponential Modular Multilevel Converter for Low-Voltage Applications) (21st European Power Electronics and Applications Conference EPE 2019ECCE Europe, pp. 1-11, DOI: 10.23919 / EPE.2019.8915156).

[0013] Figure 5 An EMMC 10 is shown. Figure 5 The EMMC 10 shown includes four cascaded modules 12. Each module 12 has a first terminal, a second terminal, a capacitor 18, and multiple switches. In this embodiment, the switches form a complete H-bridge topology. The four modules 12 are cascaded to form a converter arm 22, which has a first end 24 and a second end 26.

[0014] For each pair of adjacent modules 12, the first terminal of one module 12 is connected to the second terminal of the other module 12. By controlling the on / off state of the switch, the capacitor 18 of each module 12 can be selectively connected in series with the capacitor 18 of the adjacent module 12 in either forward or reverse direction. The real-time voltages of the forward and reverse series capacitors are superimposed to form the total voltage between the first end 24 and the second end 26 of the converter arm 22. In addition, the switch can also put the module 12 into a "bypass" or "disabled" state. In this state, the capacitor 18 is bypassed and does not participate in the series / reverse series connection, thus not contributing to the total voltage across the converter arm 22.

[0015] Figure 5 In the EMMC shown, the capacitor 18 of the topmost module 12 (hereinafter referred to as the "main module") is continuously connected to the DC voltage U provided by the DC voltage source. o The capacitor voltages of the other three modules decrease in powers of 2 during operation, i.e., U... o / 2 n Where n=1, 2, 3, corresponding to voltage levels of 200V, 100V, and 50V respectively. The voltage of the additional module 12 decreases exponentially, hence the converter is named exponential MMC (EMMC).

[0016] Using the configuration shown in the diagram, the minimum voltage step amplitude of the output voltage curve for converter arm 22 is 50V. This minimum step amplitude is equal to the voltage of the "smallest" auxiliary module (i.e., module 12 with the lowest rated voltage for capacitor 18). This can be combined with... Figure 6 Intuitive understanding Figure 6 Only the series connection of each module 12 is shown (no reverse series connection). Figure 6 The table on the left lists the "on" status corresponding to each output voltage between 0V and 750V, which is the module 12 connected in series, marked with the symbol "×". The remaining modules are in bypass state. Figure 6 The curve on the right exemplarily shows the voltage waveform that can be output between the first end 24 and the second end 26 of the converter arm 22 after the module 12 is switched to the state corresponding to the table.

[0017] Depend on Figure 6 It is known that, in principle, the positive voltage can reach up to twice the main module voltage minus the minimum additional module voltage; in this embodiment, this value is 750V. If a negative voltage is required, then... Figure 5 The module runs in reverse, i.e., using -U o -U o / 2 equal voltage. By changing the voltage step amplitude, this system can highly flexibly approximate various output waveforms. An important application of EMMC is the generation of stepped approximate sine waveforms with virtually no frequency limitations, which can be used to drive loads such as motors. However, the core advantage of MMC (especially EMMC) lies in its ability to generate arbitrary time-varying output voltages, including target voltage pulse waveforms suitable for coil devices and capable of generating predetermined magnetic pulses. The applicant's earlier patent application DE 10 2017 108 084 A1 utilizes this characteristic, using EMMC as a voltage source to generate magnetic stimulation pulses, which is particularly suitable for TMS applications.

[0018] In the operating mode described above, all conducting modules 12 are connected with the same polarity (all positive or all reverse). This situation can usually only be maintained for a short time because the modules that contribute positively to the total voltage will be discharged by the load current. Existing MMC operating mechanisms all rely on a fixed, predetermined module voltage (i.e., the "set" voltage) to achieve multi-level output. In other words, maintaining the module energy storage device voltage stable at the predetermined "set" voltage is the core requirement for the operation of existing MMC and EMMC. For this reason, the module energy storage device will charge and discharge alternately during the operation of MMC and EMMC. That is, a single module connected to the total voltage across the converter arm 22 with reverse polarity will be charged. Therefore, connecting the selected module capacitor 18 in reverse series with most of the modules (voltage contribution level) can both charge the reverse series module capacitor 18 and expand the types of output voltages that can be achieved because the voltage of this module will be deducted from the total voltage.

[0019] Figure 7 This is explained below, where the curve on the right shows the waveform oscillating between 0V and 400V, and the table on the left summarizes the total voltage "U". A "The required output voltages for each of the 12 modules are as follows: the main module is labeled "HM", and the auxiliary modules are labeled "ZM1", "ZM2", and "ZM3" respectively. As shown in the table, except for 0V and 400V, the total voltage level U for each module..." A All of these can be achieved through two or more different switching states.

[0020] More specifically, Figure 7 Both tables correspond to the positive voltage rise and fall over time shown by the curve on the right. At the start of the first sequence summarized in the left table, all capacitors are fully charged (charge state "+"), while in the second sequence summarized in the right table, the capacitors of the auxiliary modules ZM2 (100V) and ZM3 (50V) are undercharged (charge state "-"), requiring reverse series connection upon initial use. The timing of each switch state shows that the auxiliary modules alternate between charging and discharging modes. The main module HM can be connected in the positive direction at any time as needed, for the following reasons... Figure 5As shown, the main module remains connected to a DC current source. The control logic for determining the next switching state follows this principle: intentionally creating a voltage deficit and allowing it to expand exponentially until it is eventually compensated and offset by the main module.

[0021] However, with Figure 6 Unlike the "all positive cases" scenario, it no longer always exceeds the 400V base module voltage as the maximum voltage. Instead, Figure 7 In the combined charging / discharging case, at least some of the capacitors 18 are connected in reverse series, therefore the selected capacitors 18 are connected with polarity opposite to the total voltage U. A Conversely, the maximum total voltage is limited to the main module voltage, which is 400V in this case.

[0022] The selected capacitor 12 can be reverse-connected for charging, significantly reducing the capacity requirement of capacitor 12. This is because multiple sets of different switching states can output the same total voltage U. A Therefore, it is possible to balance the charge and voltage of all module capacitors at any point in time.

[0023] Figure 8 Detailed Figure 7 The waveform examples for the first two voltage levels (50V and 100V) include four different switching states for each level. In each switching state, the discharge of the forward-connected capacitor and the charging of the reverse-connected capacitor both cause a continuous voltage drop; the voltage tolerance of a single capacitor can be set, for example, to ±1V. The number of achievable intermediate voltage levels is limited only by a reasonable upper limit on the switching frequency.

[0024] As described in DE 10 2017 108 084 A1, from multiple perspectives, EMMC can serve as an ideal voltage source for generating stimulation pulses (especially TMS magnetic stimulation pulses). One advantage is that, relying on the operating logic described above, the energy storage device voltage can be easily maintained at the set value, eliminating the need for large-capacity capacitors as energy storage elements. Further analysis reveals that even if the module voltage control accuracy is lower than the standard described above, the module voltage exhibits a "self-stabilizing" effect when the EMMC is connected to an inductive load (such as a stimulation coil). This is because the EMMC switching control logic always operates according to the module's set voltage. If the actual voltage of a module temporarily exceeds the set voltage, the discharge level will be automatically increased during operation. If the module has a voltage deficit (but the control logic still operates according to the set voltage), the inductive load will charge the module. In other words, as long as the module switches frequently, the module voltage will achieve automatic stabilization.

[0025] Compared to a traditional MMC with equal voltage levels across all modules, another advantage of the EMC is that it can provide a significantly higher number of output voltage levels for a given number of modules. In other words, a traditional MMC with N equal voltage modules can only output 2... N +1 output voltage level (N positive voltage levels, N negative voltage levels, and zero level), while the EMMC of N modules can output 2 N +1 output voltage level. In this output voltage level count, the highest output voltage is not the sum of all module voltages, but rather the voltage of the module with the highest output voltage (i.e., the main module mentioned earlier). Setting this voltage upper limit ensures that the module's energy storage device can complete charging during operation. Although this statistical method does not include all the theoretically output voltage levels of the EMMC, for a given number of modules, the number of EMMC output voltage levels is still significantly higher than that of a traditional MMC, and the difference becomes more pronounced as the number of modules N increases. This means that the step amplitude between consecutive output voltage levels of the EMMC can be much smaller than that of a traditional MMC, allowing for a more accurate approximation of the target voltage pulse.

[0026] DE 10 2017 108 084 A1 highlights the advantage of EMMC in having a large number of output voltage levels, making it suitable for stimulus pulse generation scenarios. However, EMMC output is still limited by discrete output voltages and cannot generate continuous, smooth output voltage waveforms. DE 10 2017 108 084 A1 proposes two solutions to this deficiency: adding a filter circuit to smooth the stepped voltage levels, or adding a simulation module in the series connection of modules to output continuous voltages and achieve interpolation compensation between the stepped voltages. Summary of the Invention

[0027] The technical problem to be solved by this application is to provide a method and apparatus for generating a predetermined electromagnetic pulse using a voltage source and a load connected thereto, which can approximate the target voltage pulse waveform with high accuracy using only a simple structure.

[0028] This application solves the above-mentioned technical problems through the method of claim 1 and the system of claim 13. Preferred embodiments are described in the dependent claims.

[0029] According to a first aspect of this application, a method is provided for generating a predetermined electromagnetic pulse using a voltage source and a load connected thereto. In this method, the predetermined electromagnetic pulse may be a magnetic stimulation pulse, and the load may be a stimulation coil device.

[0030] The voltage source comprises a chain of modules, with N modules connected in series, where N ≥ 3, and wherein the voltage across the chain of modules represents the output voltage to be applied to the load by the voltage source. Each module includes an energy storage device (with a module voltage) and multiple switching devices configured to selectively switch to at least three operating states: - In a series connection configuration, the energy storage devices are connected in a positive polarity manner, introducing the module voltage of the energy storage device into the voltage path along the chain of modules, thereby making a positive contribution to the output voltage of the voltage source. - In a reverse series connection, the energy storage devices are connected with opposite polarity, introducing the module voltage of the energy storage device into the voltage path along the chain of modules, thereby making a negative contribution to the output voltage of the voltage source. - Bypass mode: In bypass mode, the module provides a conduction path through the module, and the energy storage device does not contribute to the output voltage of the voltage source. Note that the terms "positive" polarity and "reverse" polarity are used only to distinguish the two polarization directions in which the energy storage devices of a module can be connected in a module chain.

[0031] The method includes the following steps: - Determine the target voltage pulse waveform, which is suitable for generating a predetermined electromagnetic pulse when applied to the load. - Based on the target voltage pulse waveform, determine the independent starting module voltage for each of the N modules. - Charge the energy storage device of each module to bring it up to the corresponding predetermined initial module voltage. - By selectively switching the switching devices of each of the modules over time to enter one of at least three operating states, a time-varying output voltage approximating the target voltage pulse waveform is generated at the voltage source and applied to the load.

[0032] In this document, "time-varying switching" refers to the fact that the operating state of each module can change over time (usually in real time), thereby generating an output voltage that also changes over time. As described above, an electromagnetic pulse can be, for example, a magnetic pulse generated by a voltage source supplying power to a coil device. Knowing the impedance of the coil device ("load"), a set of voltage pulse waveforms can be deduced. When this waveform is applied to the coil device, it generates an adaptive current to produce a predetermined magnetic pulse. This voltage pulse waveform is referred to herein as the "target voltage pulse waveform," and the objective of this application is to reproduce this waveform as accurately as possible using a voltage source.

[0033] Finally, the step of determining the independent starting module voltage for each of the N modules includes an optimization process in which the starting module voltage is determined to reduce the deviation between the generated time-varying output voltage and the target voltage pulse waveform.

[0034] Therefore, unlike the EMMC used as a voltage source in DE 10 2017 108 084 A1 (where the module voltage always has a fixed value and remains so during operation), in this application, the starting module voltage is determined individually based on the target voltage pulse waveform and is "optimized" to reduce the deviation between the time-varying output voltage obtained when using these starting voltages and the target voltage pulse waveform.

[0035] Note that the core objective of the term "optimization" is to determine the individual starting module voltages so that the deviation (hereinafter referred to as deviation) between the time-varying output voltage generated by the voltage source and the target voltage pulse waveform is minimized. However, this term does not mean that the final set of starting module voltages is necessarily the theoretically optimal solution. In fact, there is no algorithm that can directly determine and ensure the absolute minimum deviation of the starting module voltages. The "optimization process" described in this paper can refer to any type of process: for a given target voltage pulse waveform, the deviation of the starting module voltage group output by this process is less than the deviation that can be achieved by an EMMC voltage source with the same number of modules. In other words, the optimization process satisfies the following conditions: after using the starting module voltages output by the process, one or both of the maximum deviation and average deviation between the time-varying output voltage and the target voltage pulse waveform are less than the maximum deviation and average deviation that can be achieved by the voltage source (32), preferably less than 75% of the maximum deviation or average deviation that can be achieved by the voltage source, more preferably less than 50% of the maximum deviation or average deviation that can be achieved by the voltage source, and the voltage source is in -V pulse,max with +V pulse,max There are 2 between them N +1 uniformly distributed voltage states, where V pulse,max It represents the maximum absolute value of the target voltage pulse waveform.

[0036] In this paper, "maximum deviation" refers to the maximum absolute value of the voltage difference between the time-varying output voltage and the target voltage waveform during the entire voltage pulse duration, and "average deviation" refers to the arithmetic mean of the absolute values ​​of the voltage difference between the time-varying output voltage and the target voltage waveform over several discrete time steps (which can correspond to the switching frequency of the switching device).

[0037] Note that the term "module" is a broad concept, primarily referring to a unit in a voltage source that can perform the above functions and has at least three operating states. In some implementations, the module is an independent component that can be manufactured separately and then assembled in series to form a voltage source. However, a module can also be composed of "virtual" segmented regions within a larger circuit, as long as it possesses the aforementioned structure and functions.

[0038] In a preferred embodiment, during the step of generating the time-varying output voltage, the energy storage device may experience voltage changes due to energy transfer to the load and energy transfer between modules, and these voltage changes are taken into account in the step of determining the set of initial module voltages.

[0039] It can be seen that although the hardware used in this method is the same as that of MMC / EMMC, their operation is fundamentally different. In MMC, the starting point is a predetermined set of module voltages (traditional MMC is usually uniformly distributed, while EMMC is exponentially distributed), and these module voltages remain constant during operation through voltage equalization or the inherent voltage stabilization mechanism of EMMC. In the operation of traditional MMC / EMMC, these predetermined and usually fixed module voltages are then combined by selecting one of the three operating states (series state, anti-series state, and bypass state) to generate an output voltage at both ends of the module chain that is closest to the target output voltage.

[0040] In contrast, according to this application, a suitable starting module voltage is determined separately for each target voltage pulse waveform to be simulated by the voltage source. Therefore, these individual starting module voltages do not follow any regular pattern and are typically different for each target voltage pulse waveform to be simulated. Importantly, the selection of the starting module voltages should minimize deviations (e.g., the aforementioned maximum or average deviations) occurring throughout the time-varying output voltage generated as a result (i.e., during the entire "voltage pulse"), even taking into account the variations in the individual module voltages during the voltage pulse. This is conceptually quite different from the operation of conventional MMC / EMMC.

[0041] In a preferred embodiment, the optimized process includes the following steps: Step a) Simulate the time-varying output voltage, which can be obtained from a given set of initial module voltages. Step b) Determine the deviation index, which indicates the deviation between the simulated time-varying output voltage and the target voltage pulse waveform, and Step c) Based on the determined deviation index, correct at least one, some or all of the starting module voltages.

[0042] In this text, the "deviation index" could be, for example, the aforementioned "maximum deviation." The "deviation index" should be an indicator that guides the correction of the starting module voltage in step c), so that a smaller deviation can be expected when using the corrected starting module voltage. "Maximum deviation" is a good choice of this type of index because it does provide guidance for correcting all or part of the starting module voltage, thereby at least reducing the maximum deviation. However, other deviation indices can also be used, as long as they provide appropriate guidance for improving the starting module voltage.

[0043] In the simulation of step a), the target voltage pulse waveform is discretized into a finite number of time steps. For each time step, an appropriate operating state (series connection, reverse series connection, bypass) is selected for each module to make the total output voltage as close as possible to the target voltage pulse waveform at that time point. Clearly, the available module voltage at each time step depends not only on the selected initial module voltage group but also on the fluctuations in the module voltage that have occurred before reaching that time step. This is because, unlike traditional MMCs and EMMCs, this application allows the module voltage to change during operation due to energy transfer to the load and energy transfer between modules.

[0044] In a preferred embodiment, the simulation of step a) includes: estimating the time-varying current flowing into the load and taking into account the changes in module voltage associated with the time-varying current.

[0045] In a preferred embodiment, steps a) to c) are performed iteratively until a stopping criterion is met. The stopping criterion may be a convergence criterion, particularly the following criterion: the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is below a threshold, or stops decreasing within a given number of consecutive iterations.

[0046] To ensure the convergence of the initial voltage iterative optimization process, when correcting part or all of the initial module voltages in step c), the following must be followed: the overall deviation between the corrected initial voltage group and the time-varying output voltage of the entire process and the target waveform should be smaller. According to one implementation, in step b), the error voltage is determined. V E Error voltage V E Corresponding to the maximum deviation between the simulated time-varying output voltage and the target voltage pulse waveform, and in step c), the starting module voltage is corrected by subtracting different voltage values ​​from all or at least a portion of the starting module voltage, the sum of which is at least approximately equal to the error voltage. V E Note the error voltage. V E The maximum deviation, as defined earlier, refers to the maximum absolute value of the voltage difference between the time-varying output voltage and the target voltage pulse waveform throughout the entire voltage pulse duration, regardless of whether the deviation is positive or negative. V E It is always a positive value.

[0047] Assuming the output voltage is higher than the target voltage at the time step corresponding to the maximum deviation (output "too high"), correcting the starting voltage according to this rule can significantly reduce this deviation. However, if the output voltage is lower than the target voltage (output "too low"), this correction rule also applies. The principle is that the corrected module voltage can be compensated by connecting them in reverse series. For example, if the starting voltage of all four modules is 50V and the target voltage is 90V, the closest achievable output is 100V, hence "too high". After reducing the voltage of the first module by 10V to 40V, connecting the first and second modules in forward series and bypassing the third and fourth modules will accurately output 90V. However, if the target voltage is 110V, the closest basic output is still 100V, but it will be "too low". In this case, the first module can be reduced to 40V and connected in reverse series, while the second to fourth modules are connected in forward series, and the summed outputs will be 110V.

[0048] The key point is that this implementation requires subtracting different voltage values ​​from the initial voltage of all or at least some of the modules to adjust the relative voltages between the modules. The sum of all subtracted voltage values ​​is approximately equal to the error voltage. V E There are several different ways to distribute the error voltage. V E The subtracted portion, these methods can all lead to convergence. In a preferred embodiment, in step c), the initial module voltage of the nth module is subtracted... V E / （2·n） ,in, n = 1, …, N. This starting voltage correction rule can quickly and stably converge the time-varying output voltage to the target voltage pulse waveform.

[0049] A key advantage of this application is that even with a small number of modules N, the generated time-varying output voltage can still approximate the target voltage pulse waveform with high accuracy (i.e., the average and maximum deviations are extremely small). In a preferred embodiment, 10 ≥ N ≥ 3, and more preferably, 8 ≥ N ≥ 4.

[0050] In a preferred embodiment, the switching device includes a transistor switching device, particularly a MOSFET switching device or an IGBT switching device.

[0051] According to a second aspect of this application, a system for generating predetermined electromagnetic pulses is provided. The system includes a voltage source and a load connected thereto. The voltage source includes a control device and a chain of modules, in which N modules are connected in series, wherein N ≥ 3, and wherein the voltage across the chain of modules represents the output voltage to be applied by the voltage source to the load. Each module includes an energy storage device and a plurality of switching devices. The energy storage device has a module voltage, wherein, under the control of the control device... The control device is further configured to: receive information representing a target voltage pulse waveform, or determine such a target voltage pulse waveform, the target voltage pulse waveform being suitable for generating a predetermined electromagnetic pulse when applied to a load, wherein the control device is further configured to: - Based on the target voltage pulse waveform, determine the independent starting module voltage for each of the N modules. - Control the charging of the energy storage device in each module so that the energy storage device reaches the corresponding predetermined starting module voltage. - Control the switching elements to selectively switch the switching devices of each in the module over time to enter one of at least three operating states, thereby generating a time-varying output voltage at the voltage source that approximates the target voltage pulse waveform.

[0052] In this paper, the control device is configured to use an optimization process to determine an independent starting module voltage for each of the N modules. In the optimization process, the starting module voltage is determined to reduce the deviation between the generated time-varying output voltage and the target voltage pulse waveform.

[0053] In a preferred embodiment of the system, the predetermined electromagnetic pulse is a magnetic stimulation pulse, and the load is a stimulation coil device.

[0054] In a preferred embodiment of the system, the optimization process satisfies the following: when using the determined starting module voltage, one or both of the maximum and average deviations between the time-varying output voltage and the target voltage pulse waveform are less than the maximum and average deviations achievable by the voltage source (32), preferably less than 75% of the maximum or average deviations achievable by the voltage source (32), more preferably less than 50% of the maximum or average deviations achievable by the voltage source (32), and the voltage source (32) is at -V pulse,max with +V pulse,max There are 2 between them N +1 uniformly distributed voltage states, where V pulse,max It represents the maximum absolute value of the target voltage pulse waveform.

[0055] In a preferred embodiment of the system, the control device is configured to control a switch such that during the step of generating a time-varying output voltage, the energy storage device's voltage is allowed to change due to energy transfer to the load and energy transfer between modules, wherein the control device is configured to consider the voltage change in the step of determining the set of independent starting module voltages.

[0056] In a preferred embodiment of the system, the optimization process includes the following steps: Step a) Simulate the time-varying output voltage, which can be obtained from a given set of initial module voltages. Step b) Determine the deviation index, which indicates the deviation between the simulated time-varying output voltage and the target voltage pulse waveform, and Step c) Based on the determined deviation index, correct part or all of the initial module voltage.

[0057] In the relevant implementation, the simulation of step a) includes: estimating the time-varying current flowing into the load and taking into account the changes in module voltage associated with the time-varying current.

[0058] In relevant embodiments, the control device is configured to iteratively execute steps a) to c) until a stopping criterion is met. Preferably, the stopping criterion is a convergence criterion, particularly the following criterion: in which the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is below a threshold, or stops decreasing within a given number of consecutive iterations.

[0059] In a preferred embodiment of the system, the control device is configured to: determine the error voltage in step b). V E Error voltage V E The maximum deviation corresponds to the maximum absolute value of the voltage difference between the time-varying output voltage and the target voltage pulse waveform during the entire duration of the voltage pulse, and in step c), the starting module voltage is corrected by subtracting different voltage values ​​from all or at least a portion of the starting module voltage, the sum of which is at least approximately equal to the error voltage. V E .

[0060] In a relevant implementation, the control device is configured to: in step c), subtract the starting module voltage of the nth module from... V E / （2·n） ,in, n = 1, …, N .

[0061] In the preferred embodiment of the system, 10≥N≥3, and more preferably 8≥N≥4.

[0062] In a preferred embodiment of the system, the energy storage device is a capacitor.

[0063] In a preferred embodiment of the system, the switching device includes a transistor switching device, particularly a MOSFET switching device (16) or an IGBT switching device (16). Attached Figure Description

[0064] Figure 1 A conventional resonant circuit for generating magnetic stimulation pulses is shown.

[0065] Figure 2 A conventional dual-level half-bridge circuit for generating magnetic stimulation pulses is shown.

[0066] Figure 3 It is a full-bridge circuit used in the prior art to generate TMS pulses.

[0067] Figure 4 The diagram illustrates the current waveform of a magnetic stimulation coil with excellent energy efficiency, including the pre-pulse and the main pulse.

[0068] Figure 5 This is a schematic diagram of an exponential modular multilevel converter (EMMC).

[0069] Figure 6 Show Figure 5 The table below shows the EMMC output voltage waveform and the corresponding module switch status.

[0070] Figure 7 Show Figure 5 The table shows another output voltage waveform of the EMMC and the switching status of the two associated modules.

[0071] Figure 8 Show Figure 7 The waveform shown includes detailed examples of the first two voltage levels, including four different module switching states.

[0072] Figure 9 This is a schematic diagram of a system according to an embodiment of this application.

[0073] Figure 10 This is a schematic diagram of a system according to another embodiment of this application.

[0074] Figure 11 An exemplary target voltage pulse waveform (damped cosine) and a similar time-varying output voltage are shown, which is generated using a voltage source with four modules and the method of this application.

[0075] Figure 12 Showing with Figure 11 The same target voltage pulse waveform and a similar time-varying output voltage are generated using a conventional EMMC with four modules.

[0076] Figure 13 Showing with Figure 11 The same target voltage pulse waveform and a similar time-varying output voltage are generated using a voltage source with three modules and the method of this application.

[0077] Figure 14 Showing with Figure 11The same target voltage pulse waveform and a similar time-varying output voltage are generated using a conventional EMMC with three modules.

[0078] Figure 15 An exemplary target voltage pulse waveform (undamped cosine) and a similar time-varying output voltage are shown, which is generated using a voltage source with four modules and the method of this application.

[0079] Figure 16 Showing with Figure 15 The same target voltage pulse waveform and a similar time-varying output voltage are generated using a conventional EMMC with four modules.

[0080] Figure 17 Showing with Figure 15 The same target voltage pulse waveform and a similar time-varying output voltage are generated using a voltage source with three modules and the method of this application.

[0081] Figure 18 Showing with Figure 15 The same target voltage pulse waveform and a similar time-varying output voltage are generated using a conventional EMMC with three modules. Detailed Implementation

[0082] It should be understood that the above general description and the following description of embodiments are exemplary and explanatory only, and are not intended to limit the methods and systems described herein. Singular nouns in this application may encompass plural meanings unless expressly defined herein. Where applicable, “or” means “and / or” unless otherwise stated herein. Those skilled in the art will recognize that the following description is merely illustrative and has no limiting effect. Other embodiments will be readily apparent to those skilled in the art who benefit from this disclosure. Various implementations of the exemplary embodiments shown in the accompanying drawings will now be described in detail. In the drawings and the following description, the same reference numerals will be used as far as possible to refer to the same or similar items.

[0083] Figure 9 A schematic diagram of a system 30 for generating a predetermined electromagnetic pulse is shown. System 30 includes a voltage source 32 and a stimulation coil device 33. Figure 9 As shown, the voltage source 32 includes a module chain and a control device 34. Each module 12 includes a capacitor 18 (an example forming the aforementioned energy storage device) and four switches 16. Figure 9The diagram only shows one of the switches. The capacitors 18 within each module 12 are interconnected to form the output voltage of the voltage source 32, which is applied to the stimulation coil device 33. In other words, the "output voltage" is the voltage across the chain of module 12 in a given switching state.

[0084] Under the control of the control device 34, the switch 16 can be operated to cause each module 12 to enter one of the following at least three operating states: - In a series connection state, given that capacitor 18 of module 12 is connected in a positive polarity configuration, the module voltage of capacitor 18 is introduced into the voltage path along the chain of module 12, thereby making a positive contribution to the output voltage of the voltage source. - In the reverse series connection state, given that capacitor 18 of module 12 is connected in reverse polarity, the module voltage of capacitor 18 is introduced into the voltage path along the chain of module 12, thereby making a negative contribution to the output voltage of the voltage source, and - Bypass mode: In bypass mode, the module provides a conduction path through the module, and capacitor 18 does not contribute to the output voltage of the voltage source.

[0085] These operating states can be selected so that the target output voltage of voltage source 32 can be obtained at any given time point.

[0086] Furthermore, each module 12 is connected to a charging voltage source 36, which in this embodiment is a controllable DC / DC converter. Under the control of the control device 34, the charging voltage source 36 allows each capacitor 18 to be charged to reach the corresponding "starting voltage" as determined in detail below.

[0087] The "control device" 34 described herein can be any control device suitable for controlling the switch 16 and the charging voltage source 36. Specifically, the control device 34 may include one or more microprocessors. Alternatively, the control device 34 may be hardwired logic circuitry or an FPGA programmed to perform the control functions described herein. Furthermore, the control device 34 may include multiple distributed interconnected control units, such as dedicated module control units (not shown), each associated with a corresponding unit in module 12, and each dedicated module control unit is uniformly controlled by a main control unit or a central control unit (not shown). In some embodiments, the control device 34 communicates via signal lines ( Figure 9 (Not shown in the accompanying drawings for simplicity) The control device 34 communicates with the switch 16 and the charging voltage source 36, while in other embodiments, the control device 34 communicates wirelessly with the switch 16 and the charging voltage source 36.

[0088] Figure 10 Another embodiment of system 30 is shown. In this embodiment, Figure 9 Switch 16, represented only by general symbols, is specifically shown as a semiconductor switch with a parallel freewheeling diode. An alternative embodiment of the charging voltage source 36 is also shown.

[0089] The function of voltage source 32 is to output time-varying voltage to coil device 33, thereby generating a predetermined magnetic pulse (e.g., in TMS application scenarios). Based on the impedance of coil device 33, an adaptation voltage curve can be determined. When this adaptation voltage curve is applied to coil device 33, it can generate a target magnetic pulse. This adaptation voltage curve is referred to in this paper as the "target voltage pulse waveform".

[0090] The conventional operating logic of MMC and EMMC is as follows: at each time point, a suitable subset of capacitors 18 are selected and connected in series in both forward and reverse directions, and all capacitors 18 maintain a predetermined fixed voltage. However, in this embodiment, the control device 34 executes differentiated control logic, abandoning the design concept of "fixed module voltage". Instead, the control device determines an "optimized" set of starting voltages for each module capacitor, and during pulse generation, controls the switch based on the optimized starting voltage to approximate the target voltage pulse waveform as closely as possible, and no longer forcibly maintains the voltage of each module at the corresponding starting voltage value during operation.

[0091] In a preferred exemplary embodiment, the iterative process described below determines the starting voltage: For simplicity, assume there are only three modules, with corresponding capacitor voltages U1, U2, and U3. The maximum module voltage is set to 10V. The initial configuration condition for the iterative process is: all module voltages (voltage at capacitor 18) are set to the maximum value of 10V.

[0092] Each of the three modules has three possible running states, therefore there are a total of 3 3 =27 switching states, all of which can be summarized into matrix S: .

[0093] In this matrix, the first, second, and third columns correspond to the selectable switch states of the first, second, and third modules, respectively. "1" represents a series connection state, "-1" represents a reverse series connection state, and "0" represents a bypass state.

[0094] The voltages of the first, second, and third modules 12 are combined into a voltage vector. , .

[0095] By combining the above matrix S with the voltage vector Multiplying them together yields the possible output voltages. ,Right now, .

[0096] Starting voltage is At that time, the possible output voltages are as follows: .

[0097] Using the maximum voltage of 10V for U1, U2, and U3 as the initial starting voltage, the target voltage pulse waveform can be approximated through simulation. During the simulation, a time step is selected... The adaptive component in the simulation is typically selected as the component with the smallest deviation from the target voltage pulse waveform at that time point. The time step can be consistent with the switching frequency of the switch, for example, corresponding to 1 microsecond. Thus, the output voltage change curve is obtained through simulation. This simulation process considers the voltage changes of each capacitor 18 caused by the inflow or outflow of charging and discharging current, i.e. The components do not remain constant at their initial values, but rather change over time.

[0098] The simulated output waveform is compared with the target voltage pulse waveform to determine the error voltage. V E Error voltage V E The maximum deviation corresponds to the maximum absolute value of the voltage difference between the simulated time-varying output voltage and the target voltage pulse waveform throughout the entire duration of the voltage pulse. When using an "unoptimized" starting voltage, the deviation will be quite large. V E The voltage will be significantly higher. To reduce the deviation, an improved starting voltage is selected by correcting the starting module voltage of the previous iteration step. In this embodiment, the starting module voltage is iteratively corrected by subtracting different voltage values ​​from all the starting module voltages, and the sum of these subtracted different voltage values ​​is at least approximately equal to the error voltage. V E In a specific implementation, the initial module voltage of the nth module is subtracted by... V E / （2·n） ,in, n = 1, …, N .

[0099] Assuming the initial voltage of each module is 10V, calculate the error voltage. V E = 3V, and the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is 0.6V. Therefore, the voltage values ​​to be subtracted from the starting voltage of each module are calculated as follows: Module 1: 3V / (2×1) = 1.5V, rounded down to 1.5V; Module 2: 3V / (2×2) = 0.75V, rounded down to 0.8V; Module 3: 3V / (2×3) = 0.5V, rounded down to 0.5V.

[0100] Therefore, the total correction error is 2.8V. In other words, the voltage after subtraction is approximately equal to the error voltage. V E Then, the corrected starting voltage is obtained as follows: .

[0101] Using these corrected voltages, the possible output voltages can again be obtained by multiplying the voltage vector by the matrix S, i.e.: .

[0102] After using the new starting voltage, in the next step of the iteration, the approximate target voltage pulse waveform is attempted again. Assume that in the second round, the error voltage... V E The measured value was 1.2V, with an average deviation of 0.1V. Therefore, the voltage value that each module needs to subtract from the starting voltage is determined as follows: Module 1: 1.2V / (2 × 1) = 0.6V, rounded down to 0.6V; Module 2: 1.2V / (2 × 2) = 0.3V, rounded down to 0.3V; Module 3: 1.2V / (2×3) = 0.2V, rounded down to 0.2V.

[0103] Therefore, the total correction error is (0.6 + 0.3 + 0.2) = 1.1V. In other words, the sum of the subtracted voltages is approximately equal to the error voltage. V E .

[0104] Repeat the above process until some termination criteria are met. For example, the iteration can be terminated when the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is lower than a threshold. Alternatively, the optimization process can be stopped if the average deviation no longer decreases within a given number of consecutive iterations.

[0105] Studies have shown that, compared to MMC or EMMC using traditional control methods, this process can significantly reduce the deviation between the output voltage and the target voltage pulse waveform. This effect will be further explained in the following description. Figures 11 to 18 Please provide an explanation.

[0106] Figure 11The damped cosine wave, shown as an example of the target voltage pulse waveform, is illustrated by dashed lines and serves as a reference. The undamped cosine wave has an amplitude of 100V, corresponding to the aforementioned maximum pulse voltage V. pulse,max This refers to the maximum absolute value of the target voltage pulse waveform. Note that in this disclosure, "pulse" is a broad concept, also encompassing signals with multiple peaks and / or oscillating characteristics, such as... Figure 11 The waveform shown contains six positive peaks and six negative peaks. Damped oscillatory pulses are actually quite common in existing devices. However, using the method of this application, almost any form of pulse waveform can be generated, for example... Figure 4 The various waveforms shown are illustrated. The horizontal axis in the figure represents the "time step," which is equal to the reciprocal of the switching frequency and can be on the order of approximately 1 microsecond. The solid line in the figure also shows the time-varying output voltage fitted to the target waveform, which is generated by the method according to the embodiments of this application using a voltage source containing four modules.

[0107] When generating the time-varying output voltage, the initial voltage of each module is determined through the iterative optimization process described above. The final initial voltages obtained are 58.62V, 59.32V, 86.2V, and 89.66V. Using these initial voltages, the time-varying output voltage can achieve a very high degree of fit with the target voltage pulse waveform, with an average absolute error of only 1.06V. In this paper, "average deviation" refers to "average absolute error," which is the arithmetic mean of the absolute values ​​of the differences between the time-varying output voltage and the target voltage waveform over several discrete time steps (e.g., the time step for executing the module switching action). This is precisely the time step example "corresponding to the switching frequency of the switching device" described earlier, where the duration of the time step is essentially equal to the reciprocal of the switching frequency.

[0108] In contrast. Figure 12 The diagram illustrates the time-varying output voltage obtained when fitting the same damped cosine target voltage pulse waveform using a conventional EMMC consisting of four modules. As described above, this four-module EMMC can generate 2 4 +1 = 17 equally spaced voltage levels. In this scheme, the voltage of the highest voltage module is set to match the maximum pulse voltage V. pulse,max = 100 V corresponds to (the voltages of the other modules are 50V, 25V, and 12.5V respectively), therefore all 17 voltage levels can be effectively utilized. If the V of the target voltage pulse waveform pulse,maxWith only 50V, at most half of the available voltage levels can be used. In other words, in this comparative example, the EMMC module voltage is optimally matched to the target voltage pulse waveform. However, in real-world scenarios where the EMMC generates diverse or arbitrary pulses, this optimal condition is often difficult to achieve. Nevertheless, it can still be seen from the figure that, limited by the number of voltage levels, the deviation between the time-varying output voltage and the target voltage pulse waveform is significantly greater than... Figure 11 The output deviation of the method according to the embodiment of this application is shown. This difference is not only visually apparent, but also intuitively reflected in the mean absolute error value: the mean absolute error of this comparative example is 2.55V. That is to say, using the method according to the embodiment of this application, with the same number of modules, the "mean deviation" can be reduced to 1.06:2.55 = 42% of the original level.

[0109] Figure 13 and Figure 14 The dashed line in the image represents the target voltage pulse waveform, and... Figure 11 and Figure 12 The target waveform is consistent. Among them, Figure 13 The solid lines represent the corresponding time-varying output voltages generated by the three-module voltage source using the method according to the embodiment of this application. In the optimization process described above, the initial voltages of each module are 10.76V, 51.26V, and 67.5V, respectively. Figure 14 To generate the corresponding time-varying output voltage using a conventional EMMC with three identical modules, the module fixed voltages are 100V, 50V, and 25V respectively. It can also be intuitively seen that when using the method according to the embodiment of this application, the "average deviation" between the generated time-varying output voltage and the target voltage pulse waveform is... Figure 14 The traditional EMMC solution's 4.31V has been reduced to... Figure 13 The 1.74V of this application corresponds to a deviation that is reduced to 1.74:4.31 = 40% of the original level.

[0110] Figures 15 to 18 Comparison architecture and Figures 11 to 14 The two schemes are consistent, except that in this scheme, a cosine wave is used as an example of the target voltage pulse waveform.

[0111] Figure 15 and Figure 16 The corresponding time-varying output voltages are shown below: Figure 15 It is generated using the method according to the embodiments of this application. Figure 16 EMMC generation was performed using the conventional operating mode, with both schemes employing a four-module structure. Consistent with the aforementioned schemes, the starting voltage was obtained through the optimization process described above. The determined starting voltage, the fixed module voltage of the EMMC, and the corresponding mean absolute error are all marked in the attached figures. As can be seen from the figures, Figure 15The optimized starting voltages (28.16V, 64.04V, 76.04V, 82.08V) and... Figure 11 The significant differences in the starting voltage indicate that the starting voltage must be adapted for each given target voltage pulse waveform. Data shows that the "average deviation" between the generated time-varying output voltage and the target voltage pulse waveform ranges from... Figure 16 The traditional EMMC solution's 2.90V has been reduced to... Figure 15 The 1.16V of the implementation method of this application corresponds to a deviation reduced to the original level of 1.16 : 2.90 = 40%.

[0112] Figure 17 and Figure 18 and Figure 15 and Figure 16 The architecture is consistent with the comparison, the difference being that the voltage source / EMMC in this solution only adopts a three-module structure. Figure 18 Compared to the 5.62V mean absolute error (i.e., "mean deviation") obtained by the traditional EMMC scheme, the implementation method of this application ( Figure 17 The mean absolute error decreased to 2.77V, corresponding to a deviation of 49% from the original level of 2.77:5.62 = 49%.

[0113] Therefore, with the same number of modules, compared with the EMMC scheme, the method of this application can output a smoother voltage curve, and the generated time-varying output voltage has a better fit with the target voltage pulse waveform. In fact, the mean absolute error of this application using only three modules is still lower than the error level of the four-module EMMC structure. This performance advantage stems from the fact that, by flexibly selecting the starting voltage, the system and method of this application can theoretically achieve 3 N Different voltage levels can be obtained. Furthermore, the resulting voltage levels do not need to be uniformly distributed. Instead, dense voltage level ranges can be configured in the sections of the target voltage pulse waveform where high-precision fitting is truly required, typically regions with a smaller slope in the target waveform.

[0114] Although the present invention has been described in conjunction with specific embodiments, those skilled in the art can make various changes and modifications within the scope of the present application, and all such changes and modifications should be covered within the protection scope of this application. Accordingly, the protection scope of this application should be determined solely by the claims.

[0115] List of reference numerals

[0116] 10-pulse leading edge

[0117] 12 modules

[0118] 14 terminals

[0119] 16 Switching devices

[0120] 18 Capacitors

[0121] 22 Converter Arms

[0122] 24 Converter arm 22 First end

[0123] 26 Converter arm 22 Second end

[0124] 30 Systems for generating predetermined electromagnetic pulses

[0125] 32 Voltage Source

[0126] 33 Stimulation coil device

[0127] 34 Control device

[0128] 36. Charging voltage source.

Claims

1. A method for generating a predetermined electromagnetic pulse using a voltage source (32) and a load (33) connected to said voltage source (32), in, The voltage source (32) includes a chain of modules (12), in which N modules are connected in series, where N ≥ 3, and where the voltage across the chain of modules (12) represents the output voltage that the voltage source (32) applies to the load (33). Each of the modules (12) includes an energy storage device (18) and a plurality of switching devices (16), the energy storage device (18) having a module voltage, wherein the switching devices (16) are configured to allow selective establishment of at least three of the following operating states: - In a series connection state, the energy storage device (18) is connected in a positive polarity to introduce the module voltage of the energy storage device (18) into the voltage path along the chain of the module (12), thereby making a positive contribution to the output voltage of the voltage source (32). - In a reverse series connection state, the energy storage device (18) is connected in reverse polarity to introduce the module voltage of the energy storage device (18) into the voltage path along the chain of the module (12), thereby making a negative contribution to the output voltage of the voltage source (32), and - Bypass state, in which the module (12) provides a conduction path through the module (12), and the energy storage device (18) does not contribute to the output voltage of the voltage source (32). The method includes the following steps: - Determine a target voltage pulse waveform, said target voltage pulse waveform being adapted to generate the predetermined electromagnetic pulse when applied to the load (33). - Based on the target voltage pulse waveform, determine the independent starting module voltage for each of the N modules. - Charge the energy storage device (18) of each module (12) to bring the energy storage device (18) to the corresponding determined starting module voltage. - By selectively switching the switching device (16) of each of the modules (12) over time to enter one of the at least three operating states, a time-varying output voltage approximating the target voltage pulse waveform is generated at the voltage source and the time-varying output voltage is applied to the load (33). The step of determining an independent starting module voltage for each of the N modules includes an optimization process in which the starting module voltage is determined to reduce the deviation between the generated time-varying output voltage and the target voltage pulse waveform.

2. The method according to claim 1, wherein, The predetermined electromagnetic pulse is a magnetic stimulation pulse, and the load (33) is a stimulation coil device (33).

3. The method according to claim 1 or 2, wherein, The optimization process satisfies the following condition: when using the determined starting module voltage, one or both of the maximum deviation and average deviation between the time-varying output voltage and the target voltage pulse waveform are less than -V. pulse,max with +V pulse,max There are 2 between them N The maximum and average deviation achievable by a voltage source (32) with a uniformly distributed voltage state are preferably less than those at -V. pulse,max with +V pulse,max There are 2 between them N +1 The maximum deviation or average deviation achievable by a voltage source (32) with a uniformly distributed voltage state is 75%, more preferably less than 75% of the maximum deviation or average deviation achievable at -V pulse,max with +V pulse,max There are 2 between them N +1 The maximum deviation or average deviation that a voltage source (32) with a uniformly distributed voltage state can achieve is 50%, where V pulse,max It is the maximum absolute value of the target voltage pulse waveform.

4. The method according to any one of the preceding claims, wherein, During the step of generating the time-varying output voltage, the energy storage device (18) is allowed to change its voltage due to energy transfer to the load (33) and energy transfer between modules, and this voltage change is taken into account in the step of determining the set of independent starting module voltages.

5. The method according to any one of the preceding claims, wherein, The optimization process includes the following steps: Step a) Simulate the time-varying output voltage, which can be obtained from a given set of initial module voltages. Step b) Determine the deviation index, which indicates the deviation between the simulated time-varying output voltage and the target voltage pulse waveform, and Step c) Based on the determined deviation index, correct at least one, part or all of the starting module voltages.

6. The method according to claim 5, wherein, The simulation in step a) includes estimating the time-varying current flowing into the load (33) and taking into account the changes in the module voltage in relation to the time-varying current.

7. The method according to claim 5 or 6, wherein, The steps a) through c) are executed iteratively until a stopping criterion is met, wherein preferably, the stopping criterion is a convergence criterion, particularly the following criterion: in the criterion, the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is below a threshold, or stops decreasing within a given number of consecutive iterations.

8. The method according to any one of claims 5 to 7, wherein, In step b), the error voltage is determined. V E The error voltage V E The maximum deviation between the simulated time-varying output voltage and the target voltage pulse waveform corresponds to the maximum absolute value of the voltage difference between the time-varying output voltage and the target voltage waveform occurring throughout the entire duration of the voltage pulse, and in step c), the starting module voltage is corrected by subtracting different voltage values ​​from all or at least a portion of the starting module voltage, the sum of which is at least approximately equal to the error voltage. V E .

9. The method according to claim 8, wherein, In step c), the initial module voltage of the nth module is subtracted. V E / （2·n） ,in, n = 1, …, N .

10. The method according to any one of the preceding claims, wherein, 10≥N≥3, with 8≥N≥4 being the preferred value.

11. The method according to any one of the preceding claims, wherein, The energy storage device (18) is a capacitor (18).

12. The method according to any one of the preceding claims, wherein, The switching device (16) includes a transistor switching device (16), particularly a MOSFET switching device (16) or an IGBT switching device (16).

13. A system (30) for generating a predetermined electromagnetic pulse, the system (30) comprising a voltage source (32) and a load (33) connected to the voltage source (32). in, The voltage source (32) includes: Control device (34), and A chain of modules (12), in which N modules are connected in series, where N≥3, and where the voltage across the chain of modules (12) represents the output voltage that the voltage source (32) applies to the load (33). Each of the modules (12) includes an energy storage device (18) and a plurality of switching devices (16), the energy storage device (18) having a module voltage, wherein, under the control of the control device (34), the switching devices (16) are configured to allow selective establishment of at least three of the following operating states: - In a series connection state, the energy storage device (18) is connected in a positive polarity to introduce the module voltage of the energy storage device (18) into the voltage path along the chain of the module (12), thereby making a positive contribution to the output voltage of the voltage source (32). - In a reverse series connection state, the energy storage device (18) is connected in reverse polarity to introduce the module voltage of the energy storage device (18) into the voltage path along the chain of the module (12), thereby making a negative contribution to the output voltage of the voltage source (32), and - Bypass state, in which the module (12) provides a conduction path through the module (12), and the energy storage device (18) does not contribute to the output voltage of the voltage source (32). The control device (34) is further configured to: receive information representing a target voltage pulse waveform, or determine such a target voltage pulse waveform, the target voltage pulse waveform being adapted to generate the predetermined electromagnetic pulse when applied to the load (33), wherein the control device (34) is further configured to: - Based on the target voltage pulse waveform, determine the independent starting module voltage for each of the N modules. - Control the charging of the energy storage device (18) of each module (12) so that the energy storage device (18) reaches the corresponding determined starting module voltage. - Control the switching element to selectively switch the switching device (16) of each of the modules (12) over time to enter one of the at least three operating states, thereby generating a time-varying output voltage at the voltage source that approximates the target voltage pulse waveform. The control device (34) is configured to: use an optimization process to determine an independent starting module voltage for each of the N modules, wherein the starting module voltage is determined in the optimization process to reduce the deviation between the generated time-varying output voltage and the target voltage pulse waveform.

14. The system (30) according to claim 13, wherein, The predetermined electromagnetic pulse is a magnetic stimulation pulse, and the load (33) is a stimulation coil device (33).

15. The system (30) according to claim 13 or 14, wherein, The optimization process satisfies the following condition: when using the determined starting module voltage, one or both of the maximum deviation and average deviation between the time-varying output voltage and the target voltage pulse waveform are less than -V. pulse,max with +V pulse,max There are 2 between them N The maximum and average deviation achievable by a voltage source (32) with a uniformly distributed voltage state are preferably less than those at -V. pulse,max with +V pulse,max There are 2 between them N +1 The maximum deviation or average deviation achievable by a voltage source (32) with a uniformly distributed voltage state is 75%, more preferably less than 75% of the maximum deviation or average deviation achievable at -V pulse,max with +V pulse,max There are 2 between them N +1 The maximum deviation or average deviation that a voltage source (32) with a uniformly distributed voltage state can achieve is 50%, where V pulse,max It is the maximum absolute value of the target voltage pulse waveform.

16. The system (30) according to any one of claims 13 to 15, wherein, The control device (34) is configured to control the switch such that during the step of generating the time-varying output voltage, the energy storage device (18) is allowed to change its voltage due to energy transfer to the load (33) and inter-module energy transfer, wherein the control device (34) is configured to take into account the voltage change in the step of determining the set of independent starting module voltages.

17. The system (30) according to any one of claims 13 to 16, wherein, The optimization process includes the following steps: Step a) Simulate the time-varying output voltage, which can be obtained from a given set of initial module voltages. Step b) Determine the deviation index, which indicates the deviation between the simulated time-varying output voltage and the target voltage pulse waveform, and Step c) Based on the determined deviation index, correct part or all of the starting module voltage.

18. The system (30) according to claim 17, wherein, The simulation in step a) includes estimating the time-varying current flowing into the load (33) and taking into account the changes in the module voltage in relation to the time-varying current.

19. The system (30) according to claim 17 or 18, wherein, The control device (34) is configured to iteratively execute steps a) to c) until a stopping criterion is met, wherein preferably, the stopping criterion is a convergence criterion, particularly the following criterion: in the criterion, the average deviation between the simulated time-varying output voltage and the target voltage pulse waveform is below a threshold, or stops decreasing within a given number of consecutive iterations.

20. The system (30) according to any one of claims 17 to 19, wherein, The control device (34) is configured to: determine the error voltage in step b). V E The error voltage V E The maximum deviation between the simulated time-varying output voltage and the target voltage pulse waveform corresponds to the maximum absolute value of the voltage difference between the time-varying output voltage and the target voltage waveform occurring throughout the entire duration of the voltage pulse, and in step c), the starting module voltage is corrected by subtracting different voltage values ​​from all or at least a portion of the starting module voltage, the sum of which is at least approximately equal to the error voltage. V E .

21. The system (30) according to claim 20, wherein, The control device (34) is configured to: in step c), subtract the starting module voltage of the nth module from... V E / （2·n） ,in, n = 1, …, N .

22. The system (30) according to any one of claims 13 to 21, wherein, 10≥N≥3, with 8≥N≥4 being the preferred value.

23. The system (30) according to any one of claims 13 to 22, wherein, The energy storage device (18) is a capacitor (18).

24. The system (30) according to any one of claims 13 to 23, wherein, The switching device (16) includes a transistor switching device (16), particularly a MOSFET switching device (16) or an IGBT switching device (16).

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