A heavy frequency bipolar flat-top magnetic field topology circuit and a control method thereof

Abstract

The application discloses a kind of heavy frequency bipolar flat-top magnetic field circuit topology and control method, belong to the technical field of pulse power.Circuit includes: active power factor correction circuit, LLC resonant converter, charge-discharge switch, energy storage capacitor, full bridge, inductive load;When discharging, energy storage capacitor discharges inductive load through full bridge, load current rises, when inductive load current rises to reference current, charge-discharge switch interrupts the discharge of capacitor to inductive load, and LLC resonant converter is powered to inductive load, so as to maintain inductive load current to reach reference value, and the switch tube of full bridge is turned off to make inductive load current feedback back to energy storage capacitor;The application has the advantages that: circuit is simple and reliable, inductive load energy feedback can be realized, efficiency and power density are high, different positive and negative rising edge steepness can be realized, and the size and repetition frequency of load current in flat-top stage are wide-range adjustable.

Description

Technical Field

[0001] This invention belongs to the field of pulse power technology, and more specifically, relates to a high-repetition-rate bipolar flat-top magnetic field topology circuit and its control method. Background Technology

[0002] The magnetism of sintered NdFeB materials primarily stems from their easily magnetized crystal structure. Under the influence of a strong external magnetic field, they acquire extremely high magnetism, and this magnetism persists even after the external magnetic field is removed. Therefore, magnetization is a crucial step in achieving magnetism in sintered NdFeB materials. The purpose of magnetic field orientation is to align the easily magnetized directions of each powder particle in the same direction, creating anisotropic magnets. Thus, powder magnetic field orientation is one of the key process technologies for producing high-performance sintered NdFeB. Currently, most orientation methods are single-stage, meaning the direction of the applied orientation magnetic field remains constant during the orientation process. This method is easy to implement, but it can cause NdFeB powder agglomeration, leading to incomplete particle orientation.

[0003] To address the aforementioned issues, a combination of multi-pulse and bidirectional orientation methods is employed for magnetizing sintered NdFeB materials. However, existing orientation equipment still suffers from complex structures, high losses, and large size, necessitating optimized design. In principle, the orientation power supply is essentially a high-repetition-rate flat-top magnetic field power supply. Therefore, optimizing the orientation power supply can be categorized as optimizing the high-repetition-rate flat-top magnetic field power supply. However, existing high-repetition-rate flat-top magnetic field power supplies exhibit low flexibility and require further miniaturization and simplification for industrial applications. Specifically, for the orientation process of sintered NdFeB materials, current high-repetition-rate flat-top magnetic field power supplies lack bipolar flat-top functionality and struggle to precisely adjust the rise steepness of the positive and negative directions. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to propose a high-repetition-rate bipolar flat-top magnetic field topology circuit and its control method, which aims to solve the problems of low flexibility, low accuracy and low repeatability of traditional high-repetition-rate circuits under low output current.

[0005] To achieve the above objectives, this invention provides a high-repetition-rate bipolar flat-top magnetic field topology circuit, including an active power factor correction circuit, an LLC resonant converter, a charge / discharge switch, an energy storage capacitor, a full-bridge circuit, and an inductive load. The input terminal of the active power factor correction circuit is connected to the power grid, and the output terminal is connected to the LLC resonant converter. The active power factor correction circuit converts the AC power from the power grid into DC power for use by the subsequent LLC resonant converter and improves the power factor. The energy storage capacitor is connected to the output terminal of the LLC resonant converter via the charge / discharge switch. The full-bridge circuit is connected to the output terminal of the LLC resonant converter, and the inductive load is connected between the midpoints of the two arms of the full-bridge circuit. The voltage generated by the inductive load current ripple is higher than the energy storage capacitor voltage, causing the charge / discharge switch to conduct. During the flat-top period, the LLC resonant converter replenishes the energy storage capacitor without the need for additional charging equipment.

[0006] Furthermore, the charge / discharge switch includes two MOSFETs connected in reverse series.

[0007] Furthermore, the LLC resonant converter includes a full-bridge inverter circuit, a resonant circuit, an isolation transformer, and a synchronous rectifier circuit; wherein, the full-bridge inverter circuit includes switches S1, S2, S3, and S4, one end of switch S1 is connected to one end of switch S3 and the positive terminal of the active power factor correction circuit, and one end of switch S2 is connected to one end of switch S4 and the negative terminal of the active power factor correction circuit; the resonant circuit includes a resonant inductor L r With resonant capacitor C r The synchronous rectifier circuit includes switches S5 and S6; the resonant circuit is connected in series with the primary side of the isolation transformer and connected to the midpoints A and B of the two arms of the full-bridge inverter circuit; the secondary side of the isolation transformer is connected to the synchronous rectifier circuit.

[0008] Furthermore, the full bridge includes switch S9 and switch S... 10 Switch S 11 Switch S 12 Inductor L1 and diode D1, one end of switch S9 is connected to switch S 10 Connect one end to the inductor L1, the cathode of diode D1, and the positive terminal of the LLC resonant converter output; switch S 11 One end of the switch is connected to switch S12, and the other end is connected to inductor L1 and the anode of diode D1; switch S 10 The other end and switch S 12 The other end shares a contact and is connected to the negative terminal of the LLC resonant converter output.

[0009] Beneficial effects: The repetition rate bipolar flat-top magnetic field topology described in this invention allows the inductive load current to flow back to the positive terminal of the energy storage capacitor through the full bridge, realizing energy feedback of the energy storage capacitor. At the same time, it reduces the number of switching devices and effectively simplifies the circuit topology.

[0010] The present invention also provides a control method for a repetitive frequency bipolar flat-top magnetic field topology circuit, comprising six stages: positive rising edge stage, positive flat-top stage, positive falling edge stage, negative rising edge stage, negative flat-top stage, and negative falling edge stage.

[0011] Furthermore, during the positive rising edge phase: S1 to S6 are all off, and S7, S8, S9, and S... 12 Connected. During this stage, the energy storage capacitor C... o Energy is released to the inductive load, and the voltage V of the energy storage capacitor increases. Co As the current decreases, the inductive load current increases, producing a steep rising edge. When the inductive load current reaches 0.98I... o1 * Then, proceed to the next stage.

[0012] Furthermore, the positive flat-top phases: S8, S9, and S... 12 S7 remains on while S7 is off. At this time, the energy storage capacitor C... o Discharge stops, and the LLC resonant converter starts operating to maintain the current in the inductive load. Simultaneously, the ripple voltage generated by the inductive load is higher than the energy storage capacitor voltage V. Co The voltage difference is high, therefore it will cause the anti-parallel diode of S7 to conduct. The LLC resonant converter supplies energy to the storage capacitor C through the anti-parallel diode of S7 and S8. o Charging. When the energy storage capacitor voltage V Co Reaching reference value V Co * When this happens, switch S8 is disconnected, and charging stops.

[0013] Furthermore, during the positive falling edge phase: all switches are off. At this time, L c r c S 11 D1, S7, S8, C O S 10 This forms a power feedback loop. Energy is fed back from the inductive load to C. o Therefore, the current in the inductive load decreases, and the energy storage capacitor C... o The voltage rises until the inductive load current is 0.

[0014] Furthermore, during the negative rising edge phase: S1 to S6 are all off, while S7, S8, and S... 10 and S 11 Connected. At this time, V CoS7, S8, L1, S 11 L c r c S 10 This forms a discharge circuit. Energy is transferred from C... o When the energy is released to the inductive load, the inductive load current rises, and the voltage of the energy storage capacitor drops. Unlike the positive rising edge, the inductor L1 is connected in series with the discharge circuit, increasing the inductance of the discharge circuit. Therefore, the negative rising edge is smoother than the positive rising edge.

[0015] Furthermore, the negative flat-top phase: S8 and S 11 Still on. S7 off. The LLC resonant converter starts working to maintain current in the inductive load.

[0016] Furthermore, during the negative falling edge phase: all switches are off. Energy is fed back from the inductive load to C. o Therefore, in inductive loads, L c The current decreases, and the energy storage capacitor C o The voltage rises.

[0017] Compared with the prior art, the above-described technical solutions conceived in this invention can achieve the following results.

[0018] Beneficial effects:

[0019] 1. By combining energy storage capacitors with LLC resonant converters, this invention achieves a simple structure, stable control, high reliability, and a wide range of adjustable load current and repetition frequency during the flat-top phase.

[0020] 2. This invention employs a power supply circuit combining an energy storage capacitor and an LLC resonant converter. This not only generates steep rising and falling edges, but also, because the LLC resonant converter is a buck isolated DC-DC converter, its primary-side resonant current peak is much lower than its secondary-side output current. Therefore, controlling the inductive load current by adjusting the switching frequency and duty cycle of the LLC resonant converter results in lower switching losses compared to directly controlling the switching action of the full bridge.

[0021] 3. By introducing inductor L1 and diode D1, this invention can control the steepness of discharge in different directions. Simultaneously, it has no impact on the operation of the power supply during the flat-top process, greatly improving the power supply's flexibility.

[0022] 4. When the inductive load current is very small, the LLC resonant converter enters burst mode. In this mode, even with a very low output inductive load current, high accuracy can still be maintained. The combination of burst mode and duty cycle adjustment ensures a wide range of adjustable load current during the flat-top phase. Attached Figure Description

[0023] Figure 1 The present invention relates to a high-repetition-rate bipolar flat-top magnetic field circuit structure.

[0024] Figure 2 This is the repetition rate bipolar flat-top magnetic field circuit topology in this embodiment of the invention.

[0025] Figure 3 The control waveform diagram and current waveform diagram of the switching device are shown in the control strategy of the embodiments of the present invention. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0027] This invention provides a repetition rate bipolar flat-top magnetic field circuit topology, such as... Figure 1 As shown, the system includes: an active power factor correction circuit, an LLC resonant converter, a charge / discharge switch, an energy storage capacitor, a full-bridge circuit, and an inductive load. The input of the active power factor correction circuit is connected to the power grid, and its output is connected to the LLC resonant converter. This circuit converts AC power from the grid into DC power for the subsequent LLC resonant converter and improves the power factor. The energy storage capacitor is connected to the output of the LLC resonant converter via the charge / discharge switch. The full-bridge circuit is also connected to the output of the LLC resonant converter, and the inductive load is connected between the midpoints of the two arms of the full-bridge. The voltage generated by the inductive load current ripple is higher than the energy storage capacitor voltage, causing the charge / discharge switch to conduct. During the flat-top period, the LLC resonant converter replenishes the energy storage capacitor without requiring additional charging equipment.

[0028] Figure 2 This is the repetition rate bipolar flat-top magnetic field circuit topology in this embodiment of the invention.

[0029] Specifically, the charge / discharge switch includes two reverse-connected MOSFETs S7 and S8.

[0030] Specifically, the LLC resonant converter includes a full-bridge inverter circuit, a resonant circuit, an isolation transformer, and a synchronous rectifier circuit. The full-bridge inverter circuit includes switches S1, S2, S3, and S4. One end of switch S1 is connected to one end of switch S3 and the positive terminal of the active power factor correction circuit, and one end of switch S2 is connected to one end of switch S4 and the negative terminal of the active power factor correction circuit. The resonant circuit includes a resonant inductor L.r With resonant capacitor C r The synchronous rectifier circuit includes switches S5 and S6; the resonant circuit is connected in series with the primary side of the isolation transformer and connected to the midpoints A and B of the two arms of the full-bridge inverter circuit; the secondary side of the isolation transformer is connected to the synchronous rectifier circuit.

[0031] Specifically, the full bridge includes switch S9 and switch S... 10 Switch S 11 Switch S 12 Inductor L1 and diode D1, one end of switch S9 is connected to switch S 10 Connect one end to the inductor L1, the cathode of diode D1, and the positive terminal of the LLC resonant converter output; switch S 11 One end is connected to switch S 12 One end is connected to the inductor L1 and the anode of the diode D1; switch S 10 The other end and switch S 12 The other end shares a contact and is connected to the negative terminal of the LLC resonant converter output.

[0032] This invention also provides a control method for a high-repetition-rate bipolar flat-top magnetic field topology circuit, comprising six stages: a positive rising edge stage, a positive flat-top stage, a positive falling edge stage, a negative rising edge stage, a negative flat-top stage, and a negative falling edge stage. An inductive load is used as an example, represented by an electromagnetic coil.

[0033] (1) Positive rising edge phase: S1 to S6 are all closed, S7, S8, S9 and S 12 Connected. At this moment, C o S7, S8, S9, L c r c S 12 To form a discharge circuit, the energy storage capacitor C o Energy is released into the electromagnetic coil, causing the voltage of the energy storage capacitor to drop and the coil current to rise, resulting in a steep rising edge. When the coil current reaches 0.98I... o1 * Then, proceed to the next stage.

[0034] (2) Positive flat-top phase: S8, S9 and S 12 S7 remains on while S7 is off. At this time, the energy storage capacitor C... o Discharge stops, and the LLC resonant converter starts working to maintain the current in the magnetic coil. Simultaneously, due to the ripple voltage generated by the coil being greater than V... Co The voltage difference is high, therefore it will cause the anti-parallel diode of S7 to conduct. The LLC resonant converter supplies energy to the storage capacitor C through the anti-parallel diode of S7 and S8. o Charging. To ensure the energy storage capacitor C... oWhen the voltage is within the rated range, and the energy storage capacitor voltage V Co Reaching reference value V Co * When the time reaches the set value t2-t1, switch S8 is opened, and charging stops. When the positive flat-top time continues to reach the set value t2-t1, the next stage begins.

[0035] (3) Positive falling edge phase: All switches are off. At this time, L c r c S 11 D1, S7, S8, C o S 10 This forms a coil power supply circuit. Energy is fed back from the electromagnetic coil to C. o Therefore, the current in the coil decreases, and the energy storage capacitor C... o The voltage rises until the coil current is 0.

[0036] (4) Negative rising edge phase: S1 to S6 are all closed, S7, S8, S 10 and S 11 Connected. At this time, V Co S7, S8, L1, S 11 L c r c S 10 This forms a discharge circuit. Unlike the positive rising edge, the inductor L1 is connected in series with the discharge circuit, increasing the inductance of the discharge circuit. Therefore, the negative rising edge is smoother than the positive rising edge.

[0037] (5) Negative flat-top phase: S8 and S 11 S7 remains on. S7 is off. The LLC resonant converter begins operation to maintain the current in the magnetic coil. When the positive flat-top time reaches the set value t5-t4, it enters the next stage.

[0038] (6) Negative falling edge stage: All switches are off. Energy is fed back from the electromagnetic coil to C. o Therefore, coil L c The current decreases, and the energy storage capacitor C o The voltage rises.

[0039] (1)-(6) can form a complete bipolar flat-top magnetic field waveform, by setting the current reference value I o1 * I o2 * and the rated voltage V of the energy storage capacitor Co1 * V Co2 * The duration of the flat-top phase can generate different repetition-frequency bipolar flat-top magnetic fields. Figure 3The diagram shows the control waveforms and current waveforms of the switching devices under the control strategy in this embodiment of the invention. This invention is applicable to generating repetitive frequency flat-top magnetic fields commonly used in most industrial production processes, and has certain universality and broad application prospects.

[0040] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-repetition-rate bipolar flat-top magnetic field topology circuit, characterized in that, include: The system comprises an active power factor correction circuit, an LLC resonant converter, a charge / discharge switch, an energy storage capacitor, a full-bridge circuit, and an inductive load. The input of the active power factor correction circuit is connected to the power grid, and its output is connected to the LLC resonant converter. The active power factor correction circuit converts AC power from the power grid into DC power for use by the subsequent LLC resonant converter. The energy storage capacitor is connected to the output of the LLC resonant converter via the charge / discharge switch. The full-bridge circuit is connected to the output of the LLC resonant converter, and the inductive load is connected between the midpoints of the two arms of the full-bridge circuit. When the voltage generated by the inductive load current ripple is higher than the voltage of the energy storage capacitor, the charge / discharge switch is activated, and during the flat-top period, the LLC resonant converter replenishes the energy storage capacitor.

2. The high-repetition-rate bipolar flat-top magnetic field topology circuit according to claim 1, characterized in that, The charge / discharge switch includes two reverse-connected MOSFETs, S7 and S8.

3. The high-repetition-rate bipolar flat-top magnetic field topology circuit according to claim 2, characterized in that, The LLC resonant converter includes a full-bridge inverter circuit, a resonant circuit, an isolation transformer, and a synchronous rectifier circuit. The full-bridge inverter circuit includes switches S1, S2, S3, and S4. One end of switch S1 is connected to one end of switch S3 and the positive terminal of the active power factor correction circuit, and one end of switch S2 is connected to one end of switch S4 and the negative terminal of the active power factor correction circuit. The resonant circuit includes a resonant inductor L. r With resonant capacitor C r The synchronous rectifier circuit includes switches S5 and S6; the resonant circuit is connected in series with the primary side of the isolation transformer and connected to the midpoint of the two bridge arms of the full-bridge inverter circuit; the secondary side of the isolation transformer is connected to the synchronous rectifier circuit.

4. The high-repetition-rate bipolar flat-top magnetic field topology circuit according to claim 3, characterized in that, The full bridge includes switch S9 and switch S1. 10 Switch S 11 Switch S 12 Inductor L1 and diode D1, one end of switch S9 is connected to switch S 10 Connect one end to the inductor L1, the cathode of diode D1, and the positive terminal of the LLC resonant converter output; switch S 11 One end is connected to switch S 12 One end is connected, and the other end is connected to the anode of inductor L1 and diode D1; switch S 10 The other end and switch S 12 The other end shares a contact and is connected to the negative terminal of the LLC resonant converter output.

5. A control method for a high-repetition-rate bipolar flat-top magnetic field topology circuit as described in claim 4, characterized in that, It includes six phases: positive rising edge phase, positive flat top phase, positive falling edge phase, negative rising edge phase, negative flat top phase, and negative falling edge phase; The positive rising edge phase: S1 to S6 are all off, S7, S8, S9 and S 12 Connect; Energy storage capacitor C o Energy is released to the inductive load, and the voltage V of the energy storage capacitor increases. Co As the current decreases, the inductive load current increases; when the inductive load current reaches 0.98I... o1 * At that time, it enters the positive flat-top stage; among them, I o1 * This is the reference current for the positive flat-top phase. The positive flat-top phase: S8, S9, and S 12 S7 remains on, S7 is off; energy storage capacitor C o When the discharge stops, the LLC resonant converter starts working to maintain the current in the inductive load; the ripple voltage generated by the inductive load and the energy storage capacitor voltage V Co The voltage difference causes the anti-parallel diode of S7 to conduct, and the LLC resonant converter supplies energy to the storage capacitor C through the anti-parallel diode of S7 and S8. o Charging; when the energy storage capacitor voltage V Co Reaching reference value V Co * When this happens, switch S8 is disconnected, and charging stops; During the positive falling edge phase: all switches are off; L c r c S 11 D1, S7, S8, C O S 10 This forms a power feedback loop, where energy is fed back from the inductive load to C. o As the current of the inductive load decreases, the energy storage capacitor C... o The voltage rises until the inductive load current is 0; During the negative rising edge phase: S1 to S6 are all off, S7, S8, and S... 10 and S 11 Conductive; C o S7, S8, L1, S 11 L c r c S 10 Forming a discharge circuit, energy flows from C o When the energy is released to the inductive load, the inductive load current increases, and the voltage of the energy storage capacitor decreases. The negative flat-top phase: S8 and S 11 S7 remains on while S7 is off; the LLC resonant converter starts operating to maintain current in the inductive load. During the negative falling edge phase: all switches are off, and energy is fed back from the inductive load to C. o In inductive loads, L c The current decreases, and the energy storage capacitor C o The voltage rises.

6. An electronic device, characterized in that, include: Computer-readable storage media and processors; The computer-readable storage medium is used to store executable instructions; The processor is configured to read executable instructions stored in the computer-readable storage medium and execute the method as described in claim 5.

7. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores computer instructions for causing a processor to perform the method as described in claim 5.

8. A computer program product, comprising a computer program or instructions, characterized in that, When the computer program or instructions are executed by the processor, they implement the method as described in claim 5.

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