A multi-level back electromotive force suppression circuit of a large magnetic moment magnetic moment device

Abstract

This invention relates to a multi-level back electromotive force (EMF) suppression circuit for a large magnetic moment torque converter, comprising: an H-bridge drive circuit configured to drive a large magnetic moment torque converter load; an isolation diode, the anode of which is connected to a power supply terminal to which a supply voltage is applied, and the cathode of which is connected to the anode of the H-bridge drive circuit, forming a back EMF detection point; an energy discharge control circuit electrically connected to the detection point; a first-stage TVS suppression circuit, the cathode of which is connected to the power supply terminal, and the anode grounded; and a second-stage TVS suppression circuit connected to both ends of the large magnetic moment torque converter load. This invention, through the coordinated operation of multiple protection circuits, maximally suppresses and eliminates the back EMF generated from the load end.

Description

Technical Field

[0001] This invention relates to the field of spacecraft attitude control technology, and to a multi-level back EMF suppression circuit for a large magnetic moment torque generator, particularly to a multi-level back EMF suppression circuit for a large magnetic moment torque generator with simple structure and high reliability. Background Technology

[0002] Large magnetic moment torquers are key actuators in the attitude control systems of large spacecraft. They generate controllable magnetic moments that interact with the Earth's magnetic field to achieve precise attitude adjustments. These torquers typically exhibit high inductance (henry to tens of henry) and high current (ampere to ten ampere) characteristics, requiring bidirectional drive via an H-bridge circuit. During actual operation of the H-bridge drive circuit, switching between commutation and shutdown conditions causes sudden changes in current flowing through the torquer coil, resulting in extremely high back electromotive force (EMF) – sometimes 5 to 10 times the bus voltage. This transient high-voltage spike poses a serious threat to the H-bridge power transistors, drive circuit, and bus capacitors, potentially leading to device breakdown, degraded circuit performance, or reduced reliability.

[0003] To address the aforementioned issues, existing technologies have developed related energy discharge and back EMF protection solutions. Among them, Chinese patent CN103107718B proposes an energy discharge control circuit for a large magnetic moment torquer, specifically outlining an energy discharge scheme that transfers energy from the torquer body to the discharge resistor via a separate energy discharge circuit. However, this scheme has the following shortcomings: 1) Poor discharge control stability: The drive circuit design of the discharge tube is relatively simple, and under high current and wide temperature ranges, it is prone to underdrive or overdrive, leading to instability in the discharge process and even oscillation; 2) Lack of negative back EMF protection: The design only addresses positive overvoltage and does not consider potential negative voltage spikes, which can also damage the preceding control circuit; 3) Insufficient source suppression: Energy discharge is a "post-processing" measure, failing to suppress the generation of back EMF at its source, resulting in the discharge circuit itself bearing significant stress. Summary of the Invention

[0004] This invention provides a multi-level back EMF suppression circuit for a large magnetic moment torquer. Specifically, it provides a multi-level back EMF suppression circuit for a large magnetic moment torquer with a simple structure and high reliability, in order to solve the technical problems of unstable discharge control, lack of negative spike protection, and insufficient source suppression in the prior art.

[0005] The circuit of this invention includes an H-bridge drive circuit, an energy discharge control circuit, a first-stage TVS suppression circuit, and a second-stage TVS suppression circuit. The energy discharge control circuit employs a PNP type excitation transistor, an NPN type power discharge transistor, a base current-limiting resistor, a first discharge current-limiting resistor, a current-limiting and feedback resistor, and a second discharge current-limiting resistor. The current-limiting and feedback resistor and the second discharge current-limiting resistor form a voltage feedback network, automatically adjusting the base bias of the PNP type excitation transistor according to the collector voltage of the NPN type power discharge transistor, ensuring the NPN type power discharge transistor operates in the linear region and achieving stable energy discharge. The first-stage TVS suppression circuit is a unidirectional TVS transistor connected in reverse parallel between the positive terminal of the third freewheeling diode and ground, used to eliminate the negative back electromotive force. The second-stage TVS suppression circuit is a bidirectional TVS transistor connected in parallel across the load, used to suppress both positive and negative back electromotive forces at the source. This invention, through the coordinated operation of multi-level protection circuits, suppresses and eliminates back electromotive force generated from the load end to the greatest extent. It has the advantages of simple structure, high reliability, and bidirectional protection, and can be widely used in the drive control of spacecraft and other large inductive loads.

[0006] This invention provides a multi-level back electromotive force suppression circuit for a large magnetic moment torquer, comprising: An H-bridge drive circuit is configured to drive a large magnetic moment torque generator load; the H-bridge drive circuit is connected to the large magnetic moment torque generator load and realizes its bidirectional drive. An isolation diode, with its anode connected to the power supply terminal to which the supply voltage is applied, and its cathode connected to the anode of the H-bridge drive circuit, forms a back EMF detection point to receive the voltage feedback from the back EMF of the magnetic torquer. The isolation diode is configured to achieve unidirectional power supply isolation, blocking the back EMF generated by the large magnetic torquer from flowing back to the front stage (the power supply terminal to which the supply voltage is applied), and forming a back EMF detection point. The power supply terminal to which the supply voltage is applied supplies power to the H-bridge drive circuit via the isolation diode. An energy discharge control circuit is electrically connected to the detection point to form a dual-path discharge dissipative magnetic torque storage device, and avoids discharge oscillation through a voltage feedback network; The first-stage TVS suppression circuit has its cathode connected to the power supply terminal and its anode grounded. This first-stage TVS suppression circuit is configured to clamp negative back EMF spikes, protecting the preceding low-voltage devices (power supply circuit devices and low-voltage active devices in the energy discharge control circuit). The second-stage TVS suppression circuit is connected to both ends of the large magnetic moment torquer load and is configured to clamp the positive and negative back electromotive force from the source, reducing the electrical stress of the subsequent circuit.

[0007] Furthermore, the H-bridge drive circuit includes: Four power switches, including a first power switch, a second power switch, a third power switch, and a fourth power switch; and Four freewheeling diodes, including a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, and a fourth freewheeling diode, correspond to the first power switch, the second power switch, the third power switch, and the fourth power switch, and are configured to provide an initial freewheeling and energy feedback path for the inductor current of the large magnetic moment torquer when the H-bridge drive circuit is commutated or turned off.

[0008] Furthermore, the drain of the first power switch and the drain of the third power switch are connected together to the detection point; the source of the second power switch and the source of the fourth power switch are connected together to the circuit ground; the cathode of the first freewheeling diode is connected to the drain of the first power switch, and the anode of the first freewheeling diode is connected to the source of the first power switch; the cathode of the second freewheeling diode is connected to the drain of the second power switch, and the anode of the second freewheeling diode is connected to the source of the second power switch; the cathode of the third freewheeling diode is connected to the drain of the third power switch, and the anode of the third freewheeling diode is connected to the source of the third power switch; the cathode of the fourth freewheeling diode is connected to the drain of the fourth power switch, and the anode of the fourth freewheeling diode is connected to the source of the fourth power switch. That is, the first freewheeling diode is connected in reverse parallel between the drain and source of the first power switch, the second freewheeling diode is connected in reverse parallel between the drain and source of the second power switch, the third freewheeling diode is connected in reverse parallel between the drain and source of the third power switch, and the fourth freewheeling diode is connected in reverse parallel between the drain and source of the fourth power switch.

[0009] Furthermore, the source of the third power switch is connected to the drain of the fourth power switch to form a second output terminal; the first output terminal and the second output terminal are used to connect the large magnetic moment torque generator load.

[0010] Furthermore, the energy discharge control circuit includes a PNP type excitation transistor, an NPN type power discharge transistor, a base current-limiting resistor, a first discharge current-limiting resistor, a current-limiting and feedback resistor, and a second discharge current-limiting resistor. One end of the base current-limiting resistor is connected to the supply voltage, and the other end is connected to the base of the PNP type excitation transistor. The emitter of the PNP type excitation transistor is connected to the detection point (H-bridge power supply), and the collector is connected to one end of both the first discharge current-limiting resistor and the current-limiting and feedback resistor. The other end of the first discharge current-limiting resistor is grounded, and the other end of the current-limiting and feedback resistor is connected to the base of the NPN type power discharge transistor. The current-limiting and feedback resistor limits the current at the base of the NPN type power discharge transistor. The emitter of the NPN type power discharge transistor is grounded, and the collector is connected to one end of the second discharge current-limiting resistor. The other end of the second discharge current-limiting resistor is connected to the detection point, which is used to dissipate the energy storage of the load and achieve stable discharge.

[0011] Furthermore, the current limiting and feedback resistor and the second leakage current limiting resistor constitute the voltage feedback network (voltage feedback base current control network), which is used to automatically adjust the base bias of the PNP excitation tube according to the change of the collector voltage of the NPN power discharge tube, thereby controlling the conduction degree of the NPN power discharge tube and making the NPN power discharge tube work in the linear amplification region.

[0012] Furthermore, when the voltage at the detection point is 0.7V or higher than the supply voltage, the PNP type excitation transistor is forward biased and turned on, driving the NPN type power discharge transistor to turn on, forming the dual-path discharge path, which includes: The main discharge path, which is the detection point connected sequentially through the second discharge path current-limiting resistor, the NPN power discharge tube, and then grounded; and The auxiliary discharge path is a detection point that passes through the PNP type excitation tube and the first discharge path current-limiting resistor in sequence before being grounded.

[0013] Furthermore, the first-stage TVS suppression circuit is a unidirectional TVS diode, the cathode of which is connected to the positive terminal of the isolation diode, and the anode is grounded, that is, the unidirectional TVS diode is connected in reverse parallel between the positive terminal of the isolation diode and ground in the circuit.

[0014] Furthermore, the second-stage TVS suppression circuit is a bidirectional TVS diode, which is connected in parallel across the two ends of the large magnetic moment torquer load.

[0015] Furthermore, the breakdown voltage of the bidirectional TVS diode is greater than the maximum bus voltage of the H-bridge drive circuit, but less than the withstand voltage of the H-bridge power switch; and / or The peak pulse power of the bidirectional TVS diode is determined based on the inductance L of the magnetic torque load and the maximum operating current, satisfying PPP≥0.5LIm² / td, where Im is the maximum operating current of the load and td is the back EMF pulse width. Furthermore, the power supply terminal to which the supply voltage is applied is a low-voltage power supply independent of the bus voltage, and its voltage value is lower than the bus voltage of the H-bridge drive circuit.

[0016] Furthermore, the multi-level back EMF suppression circuit is suitable for driving large magnetic moment torquers in spacecraft attitude control systems.

[0017] The working principle of this invention is as follows: When the H-bridge drive circuit commutates, the magnetic torque load generates a high-amplitude back electromotive force. This electromotive force is fed back to the detection point through the freewheeling diode inside the H-bridge, causing the voltage at point V+ to rise.

[0018] Second-stage source suppression: The bidirectional TVS diode is directly connected in parallel across the load. Regardless of whether the back electromotive force is positive or negative, once it exceeds its breakdown voltage, it will immediately conduct and clamp, suppressing the spike amplitude at the source and reducing the pressure on the subsequent circuit.

[0019] Energy Discharge Control: When the V+ point voltage exceeds the supply voltage Vcc by more than 0.7V, the emitter junction (Vcc-V+) of the PNP type exciter is forward biased, and the PNP type exciter conducts. Its collector current is injected into the base of the NPN type power discharge transistor, driving the NPN type power discharge transistor into amplification or saturation state. After the NPN type power discharge transistor is turned on, a discharge path is formed: first output terminal (or second output terminal) of the magnetic torquer body → first freewheeling diode (or third freewheeling diode) → V+ point → second discharge path current limiting resistor → collector-emitter of NPN type power discharge transistor → ground → fourth freewheeling diode (or second freewheeling diode) → second output terminal (or first output terminal) of the magnetic torquer body. This path discharges the energy stored in the magnetic torquer, causing the V+ point voltage to decrease.

[0020] There is another discharge path: first output terminal (or second output terminal) of the magnetic torquer body → first freewheeling diode (or third freewheeling diode) → V+ point → PNP type excitation tube emitter - first discharge path current limiting resistor → ground → fourth freewheeling diode (or second freewheeling diode) → second output terminal (or first output terminal) of the magnetic torquer body.

[0021] The reverse electromotive force is discharged through the unidirectional TVS diode and the diode in the H-bridge.

[0022] Stable control: The current limiting resistor and the feedback resistor together with the current limiting resistor of the second leakage current path form a voltage feedback base current control network. According to the change of the collector voltage of the NPN power discharge tube, the base bias of the PNP excitation tube is automatically adjusted, thereby controlling the conduction degree of the NPN power discharge tube, so that the NPN power discharge tube always works in the linear amplification region and realizes automatic stabilization of the discharge current.

[0023] Negative spike elimination: If a negative spike (negative relative to ground) is generated during energy discharge due to the oscillation of circuit parasitic parameters, the first-stage TVS diode unidirectional TVS diode will quickly conduct, clamping the negative electromotive force to ground potential and protecting the preceding control circuit. This invention has at least the following beneficial effects: 1) This invention combines the high-efficiency protection characteristics of TVS diodes with optimized energy discharge control to achieve comprehensive protection from the source to the end, providing multi-level protection: from the load source (bidirectional TVS), the main discharge channel (optimized energy discharge circuit) to negative peak elimination (unidirectional TVS), a comprehensive protection system is constructed, with a back EMF peak suppression rate ≥90%; 2) This invention has high discharge control stability: through the voltage feedback network composed of current limiting and feedback resistors and the second discharge current-limiting resistor, the NPN power discharge tube operates in the linear region, avoiding... 1) It avoids underdrive or overdrive, ensuring the discharge process remains stable within the temperature range of -55℃ to +125℃ without oscillation; 2) It has bidirectional protection capability: simultaneously suppressing back electromotive force in both positive and negative directions, adapting to the actual needs of bidirectional operation of the magnetic torquer; 3) It requires minimal modification to existing circuits, few new components, is easy to implement in engineering, and has low cost; 4) It is not only applicable to large magnetic moment magnetic torquers for spacecraft, but can also be extended to other H-bridge drive applications with large inductive loads, such as motor drives, electromagnet control, switched reluctance motors, etc., and has wide industrial applicability. Attached Figure Description

[0024] To further illustrate the above and other advantages and features of the various embodiments of the present invention, a more specific description of the embodiments of the invention will be presented with reference to the accompanying drawings. It is to be understood that these drawings depict only typical embodiments of the invention and are therefore not intended to limit its scope. In the drawings, identical or corresponding parts will be indicated by identical or similar reference numerals for clarity.

[0025] Figure 1 A block diagram illustrating the principle of a multi-level back EMF suppression circuit for a large magnetic moment torquer in some embodiments of the present invention is shown. Figure 2 A schematic diagram of an energy discharge control circuit is shown in some embodiments of the present invention. Detailed Implementation

[0026] It should be noted that the components in the accompanying drawings may be shown exaggerated for illustrative purposes and may not be to scale.

[0027] In this invention, the various embodiments are merely intended to illustrate the solutions of the invention and should not be construed as limiting.

[0028] In this invention, unless otherwise specified, the quantifiers “a” and “one” do not exclude scenarios involving multiple elements.

[0029] It should also be noted that, in the embodiments of the present invention, only a portion of the parts or components may be shown for clarity and simplicity. However, those skilled in the art will understand that, under the teachings of the present invention, the required parts or components can be added as needed for specific scenarios.

[0030] It should also be noted that within the scope of this invention, the terms "same", "equal", and "equal to" do not mean that the two values ​​are absolutely equal, but allow for a certain reasonable error. In other words, the terms also cover "substantially the same", "substantially equal", and "substantially equal to".

[0031] It should also be noted that the terms "first" and "second" in the description of this invention are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0032] Furthermore, the embodiments of the present invention describe the process steps in a specific order. However, this is only for the convenience of distinguishing each step, and is not a limitation on the order of each step. In different embodiments of the present invention, the order of each step can be adjusted according to the process.

[0033] I. The following embodiment provides a multi-level back EMF suppression circuit for a large magnetic moment torque generator. Figure 1 A block diagram of a multi-level back EMF suppression circuit for a large magnetic moment torque generator is shown. The circuit includes: Magnetic torquer load L1; An H-bridge drive circuit is configured to drive a large magnetic moment torque generator load L1; the H-bridge drive circuit is connected to the large magnetic moment torque generator load L1 and realizes its bidirectional drive; the H-bridge drive circuit includes: Four power switches, including a first power switch Q3, a second power switch Q4, a third power switch Q5, and a fourth power switch Q6; and Four freewheeling diodes, including a first freewheeling diode D3, a second freewheeling diode D4, a third freewheeling diode D5, and a fourth freewheeling diode D6, correspond to the first power switch Q3, the second power switch Q4, the third power switch Q5, and the fourth power switch Q6, and are configured to provide an initial freewheeling and energy feedback path for the inductor current of the large magnetic moment torquer when the H-bridge drive circuit is commutated or turned off; the drain of the first power switch Q3 and the drain of the third power switch Q5 are connected to the detection point V+; the source of the second power switch Q4 and the source of the fourth power switch Q6 are connected to the circuit common ground; the cathode of the first freewheeling diode D3 is connected to the drain of the first power switch Q3, and the anode of the first freewheeling diode D3 is connected to the source of the first power switch Q3; the second freewheeling diode... The cathode of diode D4 is connected to the drain of the second power switch Q4, and the anode of the second freewheeling diode D4 is connected to the source of the second power switch Q4; the cathode of the third freewheeling diode D5 is connected to the drain of the third power switch Q5, and the anode of the third freewheeling diode D5 is connected to the source of the third power switch Q5; the cathode of the fourth freewheeling diode D6 is connected to the drain of the fourth power switch Q6, and the anode of the fourth freewheeling diode D6 is connected to the source of the fourth power switch Q6; the source of the first power switch Q3 is connected to the drain of the second power switch Q4, forming the first output terminal OUT1; the source of the third power switch Q5 is connected to the drain of the fourth power switch Q6, forming the second output terminal OUT2; the first output terminal OUT1 and the second output terminal OUT2 are used to connect the large magnetic moment torque generator load L1; Isolation diode D1 is configured to achieve unidirectional power supply isolation, blocking the back electromotive force generated by the large magnetic moment torque generator from flowing back to the front stage (the power supply terminal with applied supply voltage Vcc). The positive terminal of isolation diode D1 is connected to the power supply terminal, and the negative terminal is connected to the positive terminal of the H-bridge drive circuit, forming a back electromotive force detection point V+ to receive the voltage feedback from the back electromotive force of the torque generator. The power supply terminal with applied supply voltage Vcc supplies power to the H-bridge drive circuit through isolation diode D1. The power supply terminal with applied supply voltage Vcc is a low-voltage power supply independent of the bus voltage, and its voltage value is lower than the bus voltage of the H-bridge drive circuit. The energy discharge control circuit is electrically connected to the detection point V+ to form a dual discharge path for the dissipative magnetic torque to store energy, and avoids discharge oscillation through a voltage feedback network. Figure 2The connection relationship of the energy discharge control circuit is shown. The energy discharge control circuit includes a PNP type excitation transistor Q1, an NPN type power discharge transistor Q2, a base current limiting resistor R1, a first discharge current limiting resistor R2, a current limiting and feedback resistor R3, and a second discharge current limiting resistor R4. One end of the base current limiting resistor R1 is connected to the supply voltage Vcc, and the other end is connected to the base of the PNP type excitation transistor Q1. The emitter of the PNP type excitation transistor Q1 is connected to the detection point V+, and the collector is connected to one end of both the first discharge current limiting resistor R2 and the current limiting and feedback resistor R3. The other end of the first discharge current limiting resistor R2 is grounded, and the other end of the current limiting and feedback resistor R3 is connected to the NPN type power discharge transistor Q2. The base of the NPN power bleeder Q2 is connected to the current-limiting and feedback resistor R3, which limits the current at the base of the NPN power bleeder Q2. The emitter of the NPN power bleeder Q2 is grounded, and the collector is connected to one end of the second bleeder current-limiting resistor R4. The other end of the second bleeder current-limiting resistor R4 is connected to the detection point V+, which is used to dissipate the energy stored in the load L1 and achieve stable discharge. When the voltage at the detection point V+ is higher than the supply voltage Vcc by more than 0.7V, the PNP excitation transistor Q1 is forward biased and conducts, driving the NPN power bleeder Q2 to conduct, forming a dual-path discharge path. The dual-path discharge path includes: The main discharge path consists of the detection point V+, which passes sequentially through the second discharge path current-limiting resistor R4, the NPN power discharge transistor Q2, and then to ground; and The auxiliary discharge path is the detection point V+ connected to ground via PNP type excitation tube Q1 and first discharge path current limiting resistor R2. The first-stage TVS suppression circuit has its cathode connected to the power supply terminal and its anode grounded. It is configured to clamp negative back EMF spikes, protecting the preceding low-voltage devices (power supply circuit devices for supply voltage Vcc and low-voltage active devices in the energy discharge control circuit). The first-stage TVS suppression circuit is a unidirectional TVS diode D7, which is connected in reverse parallel between the positive terminal of the isolation diode D1 and ground. The unidirectional TVS diode D7 is connected to the positive terminal of the isolation diode D1, with its anode grounded. The second-stage TVS suppression circuit is connected across the large magnetic moment torquer load and configured to clamp the positive and negative back EMFs from the source, reducing the electrical stress on subsequent circuits. The second-stage TVS suppression circuit is a bidirectional TVS diode D8, which is connected in parallel across the large magnetic moment torquer load L1. The breakdown voltage of the bidirectional TVS diode D8 is greater than the maximum bus voltage of the H-bridge drive circuit and less than the withstand voltage of the H-bridge power switch. The peak pulse power of the bidirectional TVS diode D8 is determined based on the inductance L and the maximum operating current Im of the torquer load L1, satisfying PPP≥0.5LIm² / td, where Im is the maximum operating current of load L1 and td is the back EMF pulse width.

[0034] The current limiting and feedback resistor R3 and the second leakage current limiting resistor R4 constitute a voltage feedback network (voltage feedback base current control network), which is used to automatically adjust the base bias of the PNP excitation transistor Q1 according to the change of the collector voltage of the NPN power discharge transistor Q2, thereby controlling the conduction degree of the NPN power discharge transistor Q2 and making the NPN power discharge transistor Q2 work in the linear amplification region.

[0035] II. Selection Principles for Key Components The selection of bidirectional TVS diode D8 must meet the following conditions: Breakdown voltage VBR: should be greater than 1.2 times the maximum bus voltage Vbus_max of the H-bridge drive circuit and less than 0.8 times the withstand voltage of the H-bridge power switch tube, to ensure that it is in the off state and does not operate during normal operation, with minimal leakage current, reliable conduction during overvoltage, and to provide protection; Peak pulse power PPP: Based on the load inductance L and the maximum operating current Im, the inductance energy storage E = 0.5L1Im² is calculated. PPP ≥ E / td is selected, where td is the pulse width (usually tens of microseconds). This ensures that the bidirectional TVS diode D8 can withstand all the inductance energy stored during the turn-off / commutation of the magnetic torque converter, avoiding overheating and damage, and stably achieving back EMF clamping.

[0036] The selection of unidirectional TVS diode D7 must meet the following conditions: Breakdown voltage VBR: should be greater than 1.5 times the bus voltage Vbus_max, and the response time should be ≤1ns to ensure rapid suppression of spikes.

[0037] R1, R3, R4 parameter design: R1 is the base current limiting resistor for Q1, and its value is generally 1kΩ~10kΩ to ensure that the base current of Q1 does not exceed the allowable value; R3 is the feedback resistor and the base current limiting resistor. Together with R1, they determine the feedback depth. The value is generally 1kΩ~10kΩ. The circuit needs to be stabilized in the linear region through simulation or experimental debugging.

[0038] R4 is the current-limiting resistor for the discharge path. Its value is designed according to the discharge current and is usually a few ohms to tens of ohms. The power must meet the discharge energy requirements.

[0039] III. Collaborative Work Process Taking the H-bridge switching from forward conduction to shutdown as an example: 1. At time t0, Q1 and Q4 are turned off, the current of the magnetic torquer load L1 changes abruptly, generating a positive back electromotive force, which is fed back to point V+ through D1; 2. t0+Δt1 (nanosecond level), D8 operates to clamp the voltage across the load at the VBR level, suppressing peak amplitude; 3. t0 + Δt2 (microseconds), the voltage at point V+ rises rapidly. When V+ > Vcc + 0.7V, the emitter junction of Q1 is forward biased, Q1 is turned on, and its collector current is injected into the base of Q2. 4. Q2 conducts, and the discharge path is established: L1 (OUT1 terminal) → D1 → V+ → R3 → Q2 collector-emitter → ground → D4 → L1 (b terminal) (b terminal is OUT2 terminal). The energy stored in the magnetic torque is discharged through this path, and the voltage at point V+ begins to drop. 5. During the discharge process, R4 introduces feedback: if the discharge current is too large, causing the collector voltage of Q2 to rise (due to the increased voltage drop of R3), then the base voltage of Q1 is raised through R4, reducing the conduction degree of Q1, thereby reducing the base drive of Q2 and limiting the discharge current; if the discharge current is too small, the collector voltage of Q2 decreases, the feedback effect strengthens the drive, and maintains the discharge. This feedback automatically stabilizes the discharge current at an appropriate level. 6. If a negative spike is generated due to circuit oscillation during the discharge process (e.g., the voltage across L1 is reversed), D7 will quickly conduct to clamp the negative voltage to ground potential, protecting low-voltage devices such as Q1. 7. When the voltage at point V+ drops below Vcc+0.7V, Q1 is cut off, Q2 is turned off, and the discharge ends.

[0040] IV. Comparison of Experimental Data Comparative tests were conducted on a certain type of large magnetic moment torque generator (L=20H, Im=10A, Vbus=28V): No protection circuit: Back EMF peak value reaches 656V; Using only the CN103107718B scheme: the peak back EMF is reduced to 65V, but there are oscillations and spikes, and there is no negative protection; Using the scheme in this embodiment: the peak value of the back electromotive force is reduced to below 28V (bus voltage level), the waveform is smooth and there are no negative spikes, and the discharge process is stable and oscillating.

[0041] While some embodiments of the present invention have been described in this application, those skilled in the art will understand that these embodiments are merely illustrative. Numerous variations, alternatives, and improvements will arise in those skilled in the art under the teachings of this invention without departing from its scope. The appended claims are intended to define the scope of the invention and thereby cover methods and structures within the scope of the claims themselves and their equivalents.

Claims

1. A multi-level back EMF suppression circuit for a large magnetic moment torque generator, characterized in that, include: The H-bridge drive circuit is configured to drive a large magnetic moment torquer load. An isolation diode, with its anode connected to the power supply terminal to which the supply voltage is applied, and its cathode connected to the anode of the H-bridge drive circuit, forms a detection point for back electromotive force. An energy discharge control circuit is electrically connected to the detection point; The first-stage TVS suppression circuit has its cathode connected to the power supply terminal and its anode grounded; and The second-stage TVS suppression circuit is connected to both ends of the large magnetic moment torquer load.

2. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 1, characterized in that, The H-bridge drive circuit includes: Four power switches, including a first power switch, a second power switch, a third power switch, and a fourth power switch; and Four freewheeling diodes, including a first freewheeling diode, a second freewheeling diode, a third freewheeling diode, and a fourth freewheeling diode, correspond to the first power switch, the second power switch, the third power switch, and the fourth power switch, and are configured to provide an initial freewheeling and energy feedback path for the inductor current of the large magnetic moment torquer when the H-bridge drive circuit is commutated or turned off.

3. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 2, characterized in that, The source of the first power switch is connected to the drain of the second power switch to form a first output terminal; the source of the third power switch is connected to the drain of the fourth power switch to form a second output terminal; the first output terminal and the second output terminal are used to connect the large magnetic moment torque generator load.

4. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 3, characterized in that, The energy discharge control circuit includes a PNP type excitation transistor, an NPN type power discharge transistor, a base current-limiting resistor, a first discharge current-limiting resistor, a current-limiting and feedback resistor, and a second discharge current-limiting resistor. One end of the base current-limiting resistor is connected to the supply voltage, and the other end is connected to the base of the PNP type excitation transistor. The emitter of the PNP type excitation transistor is connected to the detection point, and the collector is connected to one end of both the first discharge current-limiting resistor and the current-limiting and feedback resistor. The other end of the first discharge current-limiting resistor is grounded. The other end of the current-limiting and feedback resistor is connected to the base of the NPN type power discharge transistor, and the current-limiting and feedback resistor limits the current at the base of the NPN type power discharge transistor. The emitter of the NPN type power discharge transistor is grounded, and the collector is connected to one end of the second discharge current-limiting resistor, and the other end of the second discharge current-limiting resistor is connected to the detection point.

5. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 4, characterized in that, The current limiting and feedback resistor and the second leakage current limiting resistor constitute the voltage feedback network, which is used to automatically adjust the base bias of the PNP excitation tube according to the change of the collector voltage of the NPN power discharge tube, thereby controlling the conduction degree of the NPN power discharge tube and making the NPN power discharge tube work in the linear amplification region.

6. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 4, characterized in that, When the voltage at the detection point is 0.7V or higher than the supply voltage, the PNP excitation transistor is forward biased and turned on, driving the NPN power discharge transistor to turn on, forming the dual-path discharge path. The dual-path discharge path includes: The main discharge path, which is the detection point connected sequentially through the second discharge path current-limiting resistor, the NPN power discharge tube, and then grounded; and The auxiliary discharge path is a detection point that passes through the PNP type excitation tube and the first discharge path current-limiting resistor in sequence before being grounded.

7. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 4, characterized in that, The first-stage TVS suppression circuit is a unidirectional TVS diode, with the cathode of the unidirectional TVS diode connected to the positive terminal of the isolation diode and the anode grounded.

8. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 1, characterized in that, The second-stage TVS suppression circuit is a bidirectional TVS diode, which is connected in parallel across the load of the large magnetic moment magnetic torque generator.

9. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 8, characterized in that, The breakdown voltage of the bidirectional TVS diode is greater than the maximum bus voltage of the H-bridge drive circuit, but less than the withstand voltage of the H-bridge power switch; and / or The peak pulse power of the bidirectional TVS diode is determined based on the inductance of the magnetic torquer load and the maximum operating current.

10. The multi-level back EMF suppression circuit for the large magnetic moment torque generator according to claim 1, characterized in that, The power supply terminal to which the supply voltage is applied is a low-voltage power supply independent of the bus voltage, and its voltage value is lower than the bus voltage of the H-bridge drive circuit.

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