Repetitive-frequency bipolar flat-top magnetic field topology circuit and control method thereof

Abstract

The invention discloses a repetition-frequency bipolar flat-topped magnetic field circuit topology and a control method, and belongs to the technical field of pulse power. The circuit comprises an active power factor correction circuit, an LLC resonant converter, a charging and discharging switch, an energy storage capacitor, a full bridge and an inductive load. During discharging, the energy storage capacitor discharges the inductive load through the full bridge, the load current rises, when the inductive load current rises to the reference current, the charging and discharging switch interrupts the discharging of the inductive load by the capacitor, and the LLC resonant converter supplies power to the inductive load, so that the inductive load current is maintained to reach the reference value. The current of the inductive load is fed back to the energy storage capacitor by turning off a full-bridge switching tube; the circuit has the advantages that the circuit is simple and reliable, inductive load energy feedback can be achieved, efficiency and power density are high, different rising edge gradients in the positive direction and the negative direction can be achieved, and the average width range of the load current and the repetition frequency in the flat top stage can be adjusted.

Description

Technical Field

[0001] The invention belongs to the technical field of pulse power, and more specifically, relates to a repetition-frequency bipolar flat-top magnetic field topology circuit and a control method thereof. Background Art

[0002] The magnetism of sintered NdFeB materials mainly comes from its easily magnetized crystal structure. It can obtain extremely high magnetism under the action of a strong external magnetic field, and its magnetism will not disappear after the external magnetic field disappears. Therefore, magnetization is a key step in obtaining magnetism in sintered NdFeB materials. The purpose of magnetic field orientation is to make the easy magnetization direction of each powder particle oriented in the same direction to make anisotropic magnets. Therefore, powder magnetic field orientation is one of the key process technologies for producing high-performance sintered NdFeB. At present, most of the orientation methods are one-time orientation, that is, the direction of the orientation magnetic field applied during the orientation process remains unchanged. This method is easy to implement, but it will cause NdFeB powder to aggregate, resulting in incomplete orientation of powder particles.

[0003] In order to solve the above problems, a method combining multi-pulse orientation and bidirectional orientation is now used to magnetize sintered NdFeB materials. However, the existing orientation equipment still has problems such as complex structure, high loss, and large size, and it is in urgent need of optimized design. In principle, the essence of the orientation power supply is the heavy-frequency flat-top magnetic field power supply. Therefore, the optimization design of the orientation power supply can be attributed to the optimization design of the heavy-frequency flat-top magnetic field power supply. However, the existing heavy-frequency flat-top magnetic field power supply has low flexibility and needs to be further miniaturized and simplified for industrial applications. Specifically, for the orientation process of sintered NdFeB materials, the current heavy-frequency flat-top magnetic field power supply lacks a bipolar flat-top function, and it is difficult to accurately adjust the steepness of the rising edge in the positive and negative directions. Summary of the invention

[0004] In view of the defects of the prior art, the purpose of the present invention is to propose a repetition rate bipolar flat-top magnetic field topology circuit and a control method thereof, aiming to solve the problems of low flexibility, low accuracy at low output current and low repeatability of traditional repetition rate circuits.

[0005] To achieve the above-mentioned purpose, the present invention provides a repetitive 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, and an inductive load. The input end of the active power factor correction circuit is connected to the power grid, and the output end is connected to the LLC resonant converter. The active power factor correction circuit is used to convert the AC power of the power grid into DC power for use by the subsequent LLC resonant converter, and can improve the power factor; the energy storage capacitor is connected to the output end of the LLC resonant converter through the charge-discharge switch, the full bridge is connected to the output end of the LLC resonant converter, and the inductive load is connected between the midpoints of the two bridge arms of the full bridge. The voltage generated by the inductive load current ripple is higher than the voltage of the energy storage capacitor, so that the charge-discharge switch is turned on, and the LLC resonant converter replenishes the energy of the energy storage capacitor during the flat-top period without the need for additional charging equipment.

[0006] Furthermore, the charge and discharge switch includes two MOS tubes 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 the switch S1 is connected to one end of the switch S3 and the positive electrode of the active power factor correction circuit, and one end of the switch S2 is connected to one end of the switch S4 and the negative electrode of the active power factor correction circuit; the resonant circuit includes a resonant inductor L r With the resonant capacitor C r The synchronous rectification 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 bridge arms of the full-bridge inverter circuit; the secondary side of the isolation transformer is connected to the synchronous rectification circuit.

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

[0009] Beneficial effect: In the repetitive bipolar flat-top magnetic field topology described in the present invention, the inductive load current flows back to the positive electrode of the energy storage capacitor through the full bridge, thereby realizing energy feedback of the energy storage capacitor, while reducing switching devices and effectively simplifying the circuit topology.

[0010] The present invention also provides a control method for a repetitive bipolar flat-top magnetic field topology circuit, which includes 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.

[0011] Furthermore, in the positive rising edge stage: S1 to S6 are all closed, S7, S8, S9 and S 12 At this stage, the energy storage capacitor C o Release the energy to the inductive load, the energy storage capacitor voltage V Co The inductive load current increases, producing a steep rising edge. When the inductive load current reaches 0.98I o1 * , enter the next stage.

[0012] Furthermore, the forward flat top stage: S8, S9 and S 12 Still remains on, S7 is closed. At this time, the energy storage capacitor C o Stop discharging, and the LLC resonant converter starts to work to maintain the current in the inductive load. At the same time, the ripple voltage generated by the inductive load is greater than the energy storage capacitor voltage V Co The voltage difference will make the anti-parallel body diode of S7 conduct, and the LLC resonant converter supplies the energy storage capacitor C through the anti-parallel body diode of S7 and S8. o Charging. When the energy storage capacitor voltage V Co Reach reference value V Co * When , switch S8 is disconnected and charging stops.

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

[0014] Furthermore, in the negative rising edge stage: S1 to S6 are all closed, S7, S8, S 10 and S 11 At this time, V Co, S7, S8, L1, S 11 , L c 、r c , S 10 The energy from C o When released to the inductive load, the inductive load current increases and the energy storage capacitor voltage decreases. Unlike the positive rising edge, the inductor L1 is connected in series with the discharge circuit, increasing the inductance of the discharge circuit, so the negative rising edge is smoother than the positive rising edge.

[0015] Furthermore, the negative plateau stage: S8 and S 11 Still open. S7 closes. The LLC resonant converter starts operating to maintain the current in the inductive load.

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

[0017] Compared with the prior art, the above technical solutions conceived by the present invention can achieve the following

[0018] Beneficial effects:

[0019] 1. The present invention adopts a combination of energy storage capacitor and LLC resonant converter, which can achieve simple structure, stable control, high reliability, and wide adjustable range of load current size and repetition frequency in the flat-top stage.

[0020] 2. The present invention adopts a power supply circuit combining a storage capacitor and an LLC resonant converter, which can not only generate steep rising and falling edges, but also the LLC resonant converter is a step-down isolated DC-DC converter, and its primary side resonant current peak is much lower than the secondary side output current. Therefore, by adjusting the switching frequency and duty cycle of the LLC resonant converter to control the current of the inductive load, there is less switching loss than directly controlling the switching action of the full bridge.

[0021] 3. The present invention can control the steepness of discharge in different directions by introducing the inductor L1 and the diode D1. At the same time, it has no effect on the operation of the power supply in the flat-top process, which greatly improves the flexibility of the power supply.

[0022] 4. When the inductive load current is very small, the LLC resonant converter enters the burst mode. In this mode, even if the output inductive load current is very low, it can still maintain high accuracy. The combination of the burst mode and the duty cycle adjustment ensures that the load current in the flat-top stage can be adjusted over a wide range. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is the repetitive frequency bipolar flat-top magnetic field circuit structure of the present invention.

[0024] Figure 2 This is the topology of the repetitive-frequency bipolar flat-top magnetic field circuit in the embodiment of the present invention.

[0025] Figure 3 The control waveform diagram of the switch device and its current waveform diagram under the control strategy in the embodiment of the present invention are shown. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0027] The present invention provides a repetitive frequency bipolar flat-top magnetic field circuit topology, such as Figure 1 As shown, it includes: an active power factor correction circuit, an LLC resonant converter, a charge and discharge switch, an energy storage capacitor, a full bridge, and an inductive load. The input end of the active power factor correction circuit is connected to the power grid, and the output end is connected to the LLC resonant converter. The active power factor correction circuit is used to convert the AC power of the power grid into DC power for use by the subsequent LLC resonant converter, and can improve the power factor; the energy storage capacitor is connected to the output end of the LLC resonant converter through the charge and discharge switch, the full bridge is connected to the output end of the LLC resonant converter, and the inductive load is connected between the midpoints of the two bridge arms of the full bridge. The voltage generated by the inductive load current ripple is higher than the energy storage capacitor voltage, so that the charge and discharge switch is turned on, and the LLC resonant converter replenishes the energy of the energy storage capacitor during the flat-top period without the need for additional charging equipment.

[0028] Figure 2 This is the topology of the repetitive-frequency bipolar flat-top magnetic field circuit in the embodiment of the present invention.

[0029] Specifically, the charge and discharge switch includes two MOS tubes S7 and S8 connected in reverse series.

[0030] Specifically, 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 the switch S1 is connected to one end of the switch S3 and the positive electrode of the active power factor correction circuit, and one end of the switch S2 is connected to one end of the switch S4 and the negative electrode of the active power factor correction circuit; the resonant circuit includes a resonant inductor Lr With the resonant capacitor C r The synchronous rectification 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 bridge arms of the full-bridge inverter circuit; the secondary side of the isolation transformer is connected to the synchronous rectification circuit.

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

[0032] The present invention also provides a control method for a repetitive bipolar flat-top magnetic field topology circuit, which includes 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. Take the inductive load as an electromagnetic coil as an example.

[0033] (1) Positive rising edge stage: S1 to S6 are all closed, S7, S8, S9 and S 12 At this time, C o , S7, S8, S9, L c 、r c , S 12 The discharge circuit is composed of energy storage capacitor C o The energy is released to the electromagnetic coil, the voltage of the energy storage capacitor drops, and the coil current rises, resulting in a steep rising edge. When the coil current reaches 0.98I o1 * , enter the next stage.

[0034] (2) Positive flat top stage: S8, S9 and S 12 Still remains on, S7 is closed. At this time, the energy storage capacitor C o Stop discharging, and the LLC resonant converter starts to work to maintain the current in the magnetic coil. At the same time, since the ripple voltage generated by the coil is higher than V Co The voltage difference will make the anti-parallel body diode of S7 conduct, and the LLC resonant converter supplies the energy storage capacitor C through the anti-parallel body diode of S7 and S8. o In order to ensure that the energy storage capacitor C oThe voltage of the energy storage capacitor is within the rated range. Co Reach reference value V Co * When the positive plateau time reaches the set value t2-t1, the next stage is entered.

[0035] (3) Positive falling edge stage: All switches are turned off. At this time, L c 、r c , S 11 , D1, S7, S8, C o , S 10 The energy is fed back from the electromagnetic coil to C o Therefore, the coil current decreases and the energy storage capacitor C o The voltage increases until the coil current reaches 0.

[0036] (4) Negative rising edge stage: S1 to S6 are all closed, S7, S8, S 10 and S 11 At this time, V Co , S7, S8, L1, S 11 , L c 、r c , S 10 Different from the positive rising edge, the inductor L1 is connected in series with the discharge circuit, which increases the inductance of the discharge circuit. Therefore, the negative rising edge is smoother than the positive rising edge.

[0037] (5) Negative flat top stage: S8 and S 11 Still open. S7 is closed. LLC resonant converter starts to work to maintain the current in the magnetic coil. When the forward flat top time reaches the set value t5-t4, it enters the next stage.

[0038] (6) Negative falling edge stage: All switches are closed. Energy is fed back from the electromagnetic coil to C o Therefore, the coil L c The current drops, 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 energy storage capacitor voltage rating V Co1 * 、V Co2 * and the duration of the flat-top stage, so as to generate bipolar flat-top magnetic fields with different repetition rates. Figure 3The control waveform of the switch device and its current waveform under the control strategy in the embodiment of the present invention are shown in FIG. The present invention is suitable for generating a heavy-frequency flat-top magnetic field commonly used in most industrial productions, and has certain universality and broad application prospects.

[0040] It will be easily understood by those skilled in the art that the above description is only 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 in the protection scope of the present invention.

Claims

1. A repetition rate bipolar flat-top magnetic field topology circuit, characterized in that: include: An active power factor correction circuit, an LLC resonant converter, a charge and discharge switch, an energy storage capacitor, a full bridge, and an inductive load; the input end of the active power factor correction circuit is connected to a power grid, and the output end is connected to the LLC resonant converter, and the active power factor correction circuit is used to convert the alternating current of the power grid into direct current for use by a subsequent LLC resonant converter; the energy storage capacitor is connected to the output end of the LLC resonant converter through the charge and discharge switch, the full bridge is connected to the output end of the LLC resonant converter, and the inductive load is connected between the midpoints of the two bridge arms of the full bridge; when the voltage generated by the current ripple of the inductive load is higher than the voltage of the energy storage capacitor, the charge and discharge switch is turned on, and the LLC resonant converter replenishes energy for the energy storage capacitor during the flat-top period.

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

3. The repetition rate bipolar flat-top magnetic field topology circuit according to claim 1, characterized in that: 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 the switch S1 is connected to one end of the switch S3 and the positive electrode of the active power factor correction circuit, and one end of the switch S2 is connected to one end of the switch S4 and the negative electrode of the active power factor correction circuit; the resonant circuit includes a resonant inductor L r With the resonant capacitor C r The synchronous rectification 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 of the two bridge arms of the full-bridge inverter circuit, and the secondary side of the isolation transformer is connected to the synchronous rectification circuit.

4. The repetition rate bipolar flat-top magnetic field topology circuit according to claim 1, characterized in that: The full bridge includes a switch S9, a switch S 10 , switch S 11 , switch S 12 , inductor L1 and diode D1, one end of the switch S9 is connected to the switch S 10 The other end is connected to the inductor L1, the cathode of the diode D1, and the positive electrode of the LLC resonant converter output; the switch S 11 One end of the switch S 12 One end of the switch S is connected to the inductor L1 and the anode of the diode D1. 10 The other end and switch S 12 The other end shares a contact and is connected to the negative electrode of the LLC resonant converter output.

5. A control method for a repetition rate bipolar flat-top magnetic field topology circuit according to any one of claims 1 to 4, characterized in that: It includes 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; In the positive rising edge stage: S1 to S6 are all closed, S7, S8, S9 and S 12 Connect; energy storage capacitor C o Release the energy to the inductive load, the energy storage capacitor voltage V Co The inductive load current increases, and when the inductive load current reaches 0.98I o1 * When , it enters the positive flat top stage; among them, I o1 * is the reference current of the forward flat-top stage; The positive flat top stage: S8, S9 and S 12 Still remains on, S7 is closed; the energy storage capacitor C o Stop discharging, LLC resonant converter starts to work 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 makes the anti-parallel body diode of S7 conduct, and the LLC resonant converter supplies the energy storage capacitor C through the anti-parallel body diode of S7 and S8. o Charging; when the energy storage capacitor voltage V Co Reach reference value V Co * When , switch S8 is disconnected and charging stops; In the positive falling edge stage: all switches are turned off; L c 、r c , S 11 , D1, S7, S8, C O , S 10 The energy is fed back from the inductive load to C o , the current of the inductive load decreases, the energy storage capacitor C o The voltage rises until the inductive load current is 0; In the negative rising edge stage: S1 to S6 are all closed, S7, S8, S 10 and S 11 Conductivity; C o , S7, S8, L1, S 11 , L c 、r c , S 10 The discharge circuit is formed, and the energy is transferred from C o When released to the inductive load, the inductive load current increases and the energy storage capacitor voltage decreases; The negative flat top stage: S8 and S 11 Still remains on, S7 is closed; the LLC resonant converter starts working to maintain the current in the inductive load; During the negative falling edge phase: All switches are turned off, and energy is fed back from the inductive load to C o ; Inductive load L c The current drops, the energy storage capacitor C o The voltage rises.

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

7. A computer-readable storage medium, characterized in that: The computer-readable storage medium stores computer instructions, and the computer instructions are used to cause a processor to execute the method according to claim 5.

8. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the method according to claim 5 is implemented.

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