Method and apparatus for bias current adjustment

Abstract

The application relates to the technical field of power supply conditioning circuits, and discloses a method and device for bias current adjustment, the method comprising the following steps: acquiring the magnetic field intensity in a magnetic shielding device, generating a pulse width modulation signal based on the magnetic field intensity, generating an alternating current based on the pulse width modulation signal, performing demagnetization operation on the magnetic shielding device based on the driving of the alternating current under the condition that the transmission of the alternating current is controlled based on the pulse width modulation signal, and acquiring the magnetic field intensity change amount in the magnetic shielding device under the condition that the transmission of the alternating current is stopped based on the pulse width modulation signal, readjusting the pulse width modulation signal and the alternating current based on the magnetic field intensity change amount and performing demagnetization operation until the magnetic field intensity change amount is zero. The zero-current bias recognition capability is improved; meanwhile, the whole process does not need manual intervention, can be automatically detected and iteratively adjusted, realizes closed-loop control of demagnetization, can reduce the workload, and improves the intelligentization and integration degree of the circuit.

Description

Technical Field

[0001] This invention relates to the field of power conditioning circuit technology, and more specifically to a method and apparatus for adjusting bias current. Background Technology

[0002] Magnetic field shielding technology refers to techniques that minimize the influence of external magnetic fields on the magnetic field within a specific area. In modern production and scientific research activities, various interference sources exist in the working environment, necessitating magnetic field shielding.

[0003] After passive magnetic shielding and active magnetic compensation, large magnetic shielding devices can significantly weaken the ambient magnetic field, achieving a near-zero magnetic environment. Zero-magnetic environments play a crucial role in various fields such as aerospace engineering, space science, life sciences, and fundamental physics, and a low-gradient and low-drift zero-magnetic-field environment is a prerequisite for achieving higher-precision measurements.

[0004] Common magnetic shielding devices must be demagnetized before use to reduce or eliminate residual magnetic fields within the material. Although Hall current sensors can currently achieve measurement accuracy of 1 ppm or even higher, the demagnetizing current typically needs to gradually decay from hundreds of amperes to zero, and current sensors with such a wide range of currents are very expensive and have low accuracy. Summary of the Invention

[0005] This invention provides a method and apparatus for adjusting bias current, in order to solve the problems of high cost and low accuracy in detecting demagnetizing current using current sensors with varying magnitudes.

[0006] In a first aspect, the present invention provides a method for adjusting a bias current, the method comprising: acquiring the magnetic field strength within a magnetic shielding device; generating a pulse width modulation signal based on the magnetic field strength; generating an alternating current based on the pulse width modulation signal; performing a demagnetizing operation on the magnetic shielding device based on the driving force of the alternating current while controlling the transmission of the alternating current based on the pulse width modulation signal; and acquiring the change in magnetic field strength within the magnetic shielding device while stopping the transmission of the alternating current based on the pulse width modulation signal; readjusting the pulse width modulation signal and the alternating current based on the change in magnetic field strength and performing the demagnetizing operation until the change in magnetic field strength is zero.

[0007] In one optional implementation, generating an alternating current based on the pulse width modulation signal includes: amplifying and power-converting the pulse width modulation signal to obtain a converted pulse width modulation signal; and generating the alternating current based on the converted pulse width modulation signal.

[0008] In an optional embodiment, the method further includes: if the change in magnetic field strength within the magnetic shielding device is not zero after the demagnetization operation, adjusting the pulse width modulation signal bit by bit; and performing the amplification and power conversion based on the adjusted pulse width modulation signal to obtain the converted pulse width modulation signal.

[0009] In one optional implementation, generating a pulse width modulation signal based on the magnetic field strength includes: sampling an analog quantity representing the magnetic field strength to obtain a digital signal; and processing the digital signal based on a preset digital signal processing algorithm to obtain the pulse width modulation signal.

[0010] Secondly, the present invention provides a device for adjusting bias current, the device comprising: a fluxgate sensor module for acquiring the magnetic field strength within a magnetic shielding device; a digital signal processing module connected to the fluxgate sensor module, the digital signal processing module being used to acquire the magnetic field strength and generate a pulse width modulation signal based on the magnetic field strength; a single-phase inverter circuit module connected to the digital signal processing module, the single-phase inverter circuit module being used to acquire the pulse width modulation signal and generate an alternating current based on the pulse width modulation signal; and a relay module connected to both the digital signal processing module and the single-phase inverter circuit module, the relay module being used to acquire the pulse width modulation signal and the alternating current, and to control the pulse width modulation signal. The system is configured to either turn on to transmit the alternating current or turn off under the control of the pulse width modulation signal to stop transmitting the alternating current; a demagnetizing coil load module is wound around the surface of the magnetic shielding device and is connected to the relay module. The demagnetizing coil load module is used to perform a demagnetizing operation on the magnetic shielding device under the drive of the alternating current; the fluxgate sensor module is also used to acquire the change in magnetic field strength within the magnetic shielding device after the demagnetizing operation is performed; the digital signal processing module, the single-phase inverter circuit module, the relay module, and the demagnetizing coil load module regenerate the pulse width modulation signal and the alternating current based on the change in magnetic field strength and perform the demagnetizing operation until the change in magnetic field strength is zero.

[0011] In some optional embodiments, the device further includes: a drive module, the input terminal of which is connected to the digital signal processing module, and the output terminal of which is connected to the single-phase inverter circuit module; the drive module is used to acquire the pulse width modulation signal, amplify and convert the pulse width modulation signal to obtain a converted pulse width modulation signal, and transmit the converted pulse width modulation signal to the single-phase inverter circuit module.

[0012] In some optional implementations, the single-phase inverter circuit module includes: an H-bridge inverter unit and a filter unit; the H-bridge inverter unit is used to generate pulsed alternating current based on the control of the pulse width modulation signal; the filter unit is used to filter and modulate the pulsed alternating current to generate the alternating current.

[0013] In some optional embodiments, the device further includes: an analog-to-digital converter (ADC) module and a digital-to-analog converter (DAC) module; the input terminal of the ADC module is connected to the fluxgate sensor module, and the output terminal of the ADC module is connected to the digital signal processing module; the ADC module is used to convert the magnetic field strength or the change in magnetic field strength into a digital signal and transmit the digital signal to the digital signal processing module; the input terminal of the DAC module is connected to the digital signal processing module, and the output terminal of the DAC module is connected to the drive module; the DAC module is used to convert the pulse width modulation signal into an analog signal and transmit the analog signal to the drive module.

[0014] In some optional implementations, the output of the analog-to-digital converter module is connected to the digital signal processing module, including: the analog-to-digital converter module and the digital signal processing module transmit the digital signal through a parallel interface.

[0015] In some alternative implementations, the fluxgate sensor module includes a triaxial orthogonal sensor.

[0016] Thirdly, the present invention provides an electronic device, comprising: a memory and a processor, the memory and the processor being communicatively connected to each other, the memory storing computer instructions, and the processor executing the computer instructions to perform the method for bias current adjustment described in the first aspect or any corresponding embodiment thereof.

[0017] Fourthly, the present invention provides a computer-readable storage medium storing computer instructions for causing a computer to perform the method for bias current adjustment described in the first aspect or any corresponding embodiment thereof.

[0018] Fifthly, the present invention provides a computer program product, including computer instructions for causing a computer to execute the method for bias current adjustment described in the first aspect or any corresponding embodiment thereof.

[0019] The method and apparatus for bias current adjustment provided in this embodiment use the magnetic field strength within the magnetic shielding device to characterize the change in bias current. By converting the analog quantity characterizing the magnetic field strength into a PWM signal, and then using the PWM signal to generate and control the on / off state of the AC current, the magnetic field within the magnetic shielding device is adjusted, so that the inside of the magnetic shielding device is in a zero-bias state, thus improving the zero-current bias identification capability. At the same time, the entire process does not require manual intervention and can achieve demagnetization closed-loop control through automatic detection and iterative adjustment. This simplifies engineering practice steps, reduces workload, improves operational efficiency, and enhances the intelligence and integration of the circuit. Attached Figure Description

[0020] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0021] Figure 1 A flowchart of a method for adjusting bias current according to an embodiment of this application is shown;

[0022] Figure 2 A schematic diagram of the structure of the device for bias current adjustment provided in an embodiment of this application is shown;

[0023] Figure 3 Another schematic diagram of the device structure for bias current adjustment provided in an embodiment of this application is shown;

[0024] Figure 4 This illustration shows yet another schematic diagram of the device structure for bias current adjustment provided in an embodiment of this application;

[0025] Figure 5 This illustration shows another structural schematic diagram of the device for bias current adjustment provided in an embodiment of this application;

[0026] Figure 6 This is a schematic diagram of the hardware structure of an electronic device according to an embodiment of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] It is understood that before using the technical solutions disclosed in the various embodiments of the present invention, users should be informed of the types, scope of use, and usage scenarios of the personal information involved in the present invention and their authorization should be obtained in accordance with relevant laws and regulations through appropriate means.

[0029] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0030] The demagnetization method used in related technologies is the AC dynamic demagnetization method. If the demagnetizing AC current has zero bias, that is, there is a deviation between the actual position of the zero potential and the ideal zero potential, it will cause the material to undergo hysteresis magnetization, resulting in an unsatisfactory demagnetization result, or even causing the residual magnetism level inside the material to be higher than before demagnetization, thereby affecting the passive shielding performance of the magnetic shielding device. Therefore, zeroing the output current bias of the demagnetizing power supply is a very important step.

[0031] According to an embodiment of the present invention, a method embodiment for bias current adjustment is provided. It should be noted that the steps shown in the flowchart in the accompanying drawings can be executed in a computer system such as a set of computer-executable instructions. Furthermore, although a logical order is shown in the flowchart, in some cases the steps shown or described may be executed in a different order than that shown here.

[0032] This embodiment provides a method for adjusting bias current, which can be used in magnetic shielding devices, such as a programmable demagnetization system for standard magnetic shielding rooms, mini magnetic shielding chambers, magnetic shielding boxes, magnetic shielding barrels, and other magnetic shielding devices. Figure 1 A flowchart of a method for bias current adjustment according to an embodiment of this application is shown, such as... Figure 1 As shown, the process includes the following steps:

[0033] Step S101: Obtain the magnetic field strength inside the magnetic shielding device, generate a pulse width modulation signal based on the magnetic field strength, and generate an alternating current based on the pulse width modulation signal.

[0034] In this step, the magnetic shielding device is used to characterize a device or structure that blocks or weakens the interference of external magnetic fields on internal components, or prevents the internal magnetic field from spreading outward. Magnetic field strength is a physical quantity describing the strength and direction of a magnetic field, and its effectiveness can be judged based on the magnetic field strength. Pulse Width Modulation (PWM) is a high-frequency square wave pulse signal used to characterize a digital signal that controls the amplitude of the output signal by adjusting the duty cycle of the high-level time of the pulse, i.e., the ratio of the high-level time to the period. PWM can equivalently change the average value of the output voltage or current. Alternating current, used to characterize a current whose direction and magnitude change periodically with time, can be used in step S101 to generate a changing magnetic field to achieve demagnetization.

[0035] Specifically, the current magnetic field strength inside the magnetic shielding device can be detected, and based on this, a PWM signal can be generated. The PWM signal can then be converted into an alternating current so that the current parameters match the magnetic field strength.

[0036] Step S102: Under the condition of controlling the transmission of AC current based on the pulse width modulation signal, the magnetic shielding device is demagnetized based on the drive of AC current.

[0037] In this step, the demagnetization operation is used to characterize the process of eliminating residual magnetism inside the magnetic shielding device by applying a specific changing magnetic field, thereby restoring its magnetic field strength to an ideal state.

[0038] Specifically, PWM signals can be used to control the on / off state and amplitude changes of AC current. By transmitting the changing magnetic field generated by the AC current, the magnetic shielding device can be demagnetized to reduce the residual magnetism inside the magnetic shielding device.

[0039] Step S103: When the AC current transmission is stopped based on the pulse width modulation signal, the change in magnetic field strength inside the magnetic shielding device is obtained. Based on the change in magnetic field strength, the pulse width modulation signal and AC current are readjusted and a demagnetization operation is performed until the change in magnetic field strength is zero.

[0040] In this step, under the control of the pulse width modulation signal without AC current transmission, that is, after the demagnetization operation, the magnetic field strength inside the magnetic shielding device is detected again, the difference between the magnetic field strength and that before demagnetization is calculated, and the change in magnetic field strength is obtained. The change in magnetic field strength is used as a feedback quantity to regenerate the PWM signal and AC current, and the demagnetization operation is repeated until the change in magnetic field strength is zero before and after the AC current is switched on and off.

[0041] In this embodiment, a preliminary control link is formed by detecting the magnetic field, generating a drive signal, and performing demagnetization, which can ensure that the demagnetization operation is targeted. At the same time, by detecting the change in the residual magnetic field inside the magnetic shielding device, the change in magnetic field strength is introduced as an iterative judgment condition. If the change in magnetic field strength is not zero, it indicates that the demagnetization is incomplete. The demagnetization effect can be continuously optimized by readjusting the PWM signal and AC current. This process is repeated until the change in magnetic field strength before and after the AC current is switched on and off is zero, that is, the residual magnetic field inside the magnetic shielding device does not change.

[0042] The method for adjusting bias current provided in this embodiment uses the magnetic field strength within the magnetic shielding device to characterize the change in bias current. By converting the analog quantity characterizing the magnetic field strength into a PWM signal, and then using the PWM signal to generate and control the on / off state of the AC current, the magnetic field within the magnetic shielding device is adjusted, so that the inside of the magnetic shielding device is in a zero-bias state, thus improving the zero-current bias identification capability. At the same time, the entire process does not require manual intervention and can achieve demagnetization closed-loop control through automatic detection and iterative adjustment. This simplifies engineering practice steps, reduces workload, improves operational efficiency, and enhances the intelligence and integration of the circuit.

[0043] In some alternative implementations, generating an alternating current based on a pulse width modulation (PWM) signal includes: amplifying and power-converting the PWM signal to obtain a converted PWM signal; and generating an alternating current based on the converted PWM signal.

[0044] In this embodiment, amplification refers to enhancing the current or voltage amplitude of the PWM signal through an amplification circuit, enabling the PWM signal to drive subsequent power conversion circuits. Power conversion refers to transforming the energy form of the amplified PWM signal, such as DC-AC conversion or voltage level adjustment, so that the transformed pulse width modulation signal meets the power requirements for generating the target AC current.

[0045] Specifically, the initial PWM signal generated based on the analog quantity characterizing the magnetic field strength cannot directly drive the demagnetizing coil acting on the magnetic shielding device. The driving capability of the PWM signal can be improved by amplification, and then the amplified PWM signal can be converted into a power level that meets the load requirements through power conversion to obtain the converted PWM signal. The duty cycle information of the initial PWM signal is retained and transmitted to the AC current generation stage, which can realize the control of AC current amplitude and frequency.

[0046] In this way, the duty cycle of the PWM signal can be precisely adjusted through digital circuits. After amplification and power conversion, the amplitude and frequency of the generated AC current can be changed based on control commands to meet the fine control requirements of magnetic field strength during demagnetization. At the same time, by adjusting the duty cycle and frequency of the PWM signal, AC currents with different waveforms and parameters can be flexibly generated, which is suitable for the demagnetization requirements of magnetic shielding devices with different materials and different initial magnetic field states. In addition, by controlling the high voltage with low voltage, precise, efficient and flexible control of AC current is achieved, providing a reliable energy drive basis for the closed-loop demagnetization operation of the magnetic shielding device.

[0047] In some optional embodiments, the aforementioned method for adjusting the bias current further includes: if the change in magnetic field strength within the magnetic shielding device is not zero after the demagnetization operation, adjusting the pulse width modulation signal bit by bit; and amplifying and converting the adjusted pulse width modulation signal to obtain the converted pulse width modulation signal.

[0048] In this embodiment, after the demagnetization operation, if the change in magnetic field strength within the magnetic shielding device is not zero, indicating that the demagnetization target has not been achieved and the residual magnetic field still fluctuates, it means that the AC current parameters corresponding to the current PWM signal do not match the actual demagnetization requirements, and the PWM signal can be adjusted. The adjustment direction of each bit can be determined based on the direction of the change in magnetic field strength. For example, if the change in magnetic field strength is positive, it indicates that the residual magnetic field still needs further demagnetization; if the change in magnetic field strength is negative, it indicates that demagnetization is excessive.

[0049] Specifically, if the demagnetization corresponding to the current PWM duty cycle is insufficient, the highest bit can be set from 0 to 1 to increase the duty cycle, and the change can be observed to see if it decreases. If the change is still not zero, the second highest bit can be adjusted to gradually reduce the deviation. By adjusting bit by bit, the adjustment amplitude of the PWM signal can be controlled to achieve gradual correction from coarse to fine adjustment, avoiding excessive magnetic field fluctuations caused by a large adjustment at once.

[0050] In this way, bit-by-bit adjustment, by controlling the increase or decrease of binary bits, achieves a gradual change in the PWM duty cycle, which can accurately match the minute changes in magnetic field strength and avoid over- or under-demagnetization caused by a large adjustment at once, thus significantly improving the final accuracy of demagnetization. At the same time, for scenarios where the magnetic field distribution inside the magnetic shielding device is uneven and the initial residual magnetic field fluctuation is large, the gradual nature of bit-by-bit adjustment can avoid the interference of violent magnetic field fluctuations on sensitive components inside the device. Through closed-loop feedback and real-time correction, it can be ensured that the device can stably converge to the target state under different operating conditions.

[0051] In some optional implementations, generating a pulse width modulation signal based on the magnetic field strength includes: sampling an analog quantity representing the magnetic field strength to obtain a digital signal; and processing the digital signal based on a preset digital signal processing algorithm to obtain the pulse width modulation signal.

[0052] In this embodiment, the magnetic field strength can be detected by a magnetic field sensor. The magnetic field sensor outputs an analog quantity, which can be sampled by an analog-to-digital converter (ADC). The analog voltage or current output by the magnetic field sensor can be read at a fixed frequency and converted into a binary digital signal. The sampled digital signal is then analyzed and calculated based on a preset digital signal processing algorithm to obtain a PWM signal.

[0053] The preset digital signal processing algorithm includes filtering, amplitude extraction, error calculation, and a control law. The filtering algorithm in the preset digital signal processing algorithm can perform noise suppression and smoothing on the sampled magnetic field strength digital signal to remove interference components. The amplitude extraction algorithm in the preset digital signal processing algorithm can extract the amplitude that characterizes the strength of the magnetic field from the filtered magnetic field strength signal. The error calculation algorithm in the preset digital signal processing algorithm can compare the extracted magnetic field strength amplitude with the target magnetic field strength and calculate the difference between the two. The control law algorithm in the preset digital signal processing algorithm can determine a specific adjustment strategy based on the error calculation result, i.e., generate the parameters of the PWM signal to achieve closed-loop control of the magnetic field strength. The control law can be one or more of proportional control, proportional-integral control, and proportional-integral-derivative control.

[0054] In this way, the analog quantity representing the magnetic field strength is converted into a digital signal by the ADC, which avoids the drift and noise interference problems common in analog circuits. At the same time, the digital signal processing algorithm can further suppress noise, ensuring that the magnetic field strength data input to the algorithm is closer to the real value, providing a reliable basis for the accurate generation of PWM signals.

[0055] This embodiment also provides a device for adjusting bias current, which is used to implement the above embodiments and preferred embodiments; details already described will not be repeated. As used below, the term "module" can refer to a combination of software and / or hardware that implements a predetermined function. Although the device described in the following embodiments is preferably implemented in software, hardware implementation, or a combination of software and hardware, is also possible and contemplated.

[0056] This embodiment provides a device for adjusting bias current. Figure 2 A schematic diagram of the structure of the device for bias current adjustment provided in an embodiment of this application is shown, as follows: Figure 2 As shown, it includes:

[0057] A fluxgate sensor module 21 is used to acquire the magnetic field strength within the magnetic shielding device. A digital signal processing module 201, connected to the fluxgate sensor module 21, is used to acquire the magnetic field strength and generate a pulse-width modulation (PWM) signal based on it. A single-phase inverter circuit module 202, connected to the digital signal processing module 201, is used to acquire the PWM signal and generate an alternating current based on it. A relay module 203, connected to both the digital signal processing module 201 and the single-phase inverter circuit module 202, is used to acquire both the PWM signal and the alternating current, and is activated under the control of the PWM signal. The system transmits alternating current, or, under the control of a pulse width modulation signal, shuts off and stops transmitting alternating current; a demagnetizing coil load module 22 is wound around the surface of the magnetic shielding device, and the demagnetizing coil load module 22 is connected to the relay module 203. The demagnetizing coil load module 22 is used to perform demagnetization operation on the magnetic shielding device under the drive of alternating current; the fluxgate sensor module 21 is also used to acquire the change in magnetic field strength in the magnetic shielding device after the demagnetization operation is performed; the digital signal processing module 201, the single-phase inverter circuit module 202, the relay module 203, and the demagnetizing coil load module 22, based on the change in magnetic field strength, regenerate the pulse width modulation signal and alternating current and perform the demagnetization operation until the change in magnetic field strength is zero.

[0058] like Figure 2 As shown, in this embodiment, the fluxgate sensor module 21 can be located at the center point inside the magnetic shielding device, replacing a conventional current sensor as the sensing element. The fluxgate sensor is a weak magnetic field measuring device based on the nonlinear magnetization characteristics of a high-permeability iron core in an alternating magnetic field. Its core structure includes a magnetic core made of a high-permeability soft magnetic material (such as permalloy), an excitation coil, and an induction coil. It can measure the magnetic field by detecting the second harmonic signal generated by the iron core under alternating saturation excitation.

[0059] The demagnetizing power supply 20 includes a digital signal processing module 201, a single-phase inverter circuit module 202, and a relay module 203. A fluxgate sensor module 21 can be used as a sensor to detect changes in the output current of the demagnetizing power supply 20. Before and after the demagnetizing power supply 20 is turned on, the fluxgate sensor module 21 detects the magnetic field strength inside the magnetic shielding device to determine whether the current output is zero. The change in magnetic field strength output by the fluxgate sensor module 21 is used as feedback to adjust the control quantity of the demagnetizing power supply 20 until the change in magnetic field strength inside the magnetic shielding device is zero before and after the demagnetizing power supply 20 is turned on.

[0060] The PWM signal output by the DSP module can be used as the control signal for the single-phase inverter circuit module. Based on the switching control of the PWM signal, the single-phase inverter circuit module switches the DC power to an AC voltage waveform. After filtering and modulation, a controllable AC voltage or current with adjustable frequency and amplitude can be obtained at the output of the single-phase inverter circuit module.

[0061] The fluxgate sensor module 21 senses the change in magnetic field strength inside the magnetic shielding device to indirectly determine the output state of the demagnetizing power supply 20. Before and after the demagnetizing power supply 20 is turned on, the opening or closing of the current will cause transient changes in the residual magnetic field inside the magnetic shielding device. The fluxgate sensor module 21 detects the magnetic field jump and uses this jump as a feedback signal to adjust the bias of the demagnetizing power supply 20 until the magnetic field no longer jumps before and after the turn-on, which means that the output current of the demagnetizing power supply 20 has truly reached zero.

[0062] In this way, by replacing the current sensor with a fluxgate sensor, which is an essential sensor for evaluating the demagnetization results, the resolution of the bias conditioning process and the accuracy of the conditioning results can be improved without adding additional components. At the same time, by replacing the current sensor with a fluxgate sensor, the change in magnetic field strength within the magnetic shielding device can be used to characterize the power supply output bias, reducing the accuracy requirements of a wide-range current sensor and lowering circuit costs.

[0063] Figure 3 Another schematic diagram of the device structure for bias current adjustment provided in an embodiment of this application is shown. For example... Figure 3 As shown, in some optional embodiments, the aforementioned device for adjusting the bias current further includes:

[0064] The driver module 204 has its input terminal connected to the digital signal processing module 201 and its output terminal connected to the single-phase inverter circuit module 202. The driver module 204 is used to acquire the pulse width modulation signal, amplify and convert the pulse width modulation signal to obtain the converted pulse width modulation signal, and transmit the converted pulse width modulation signal to the single-phase inverter circuit module 202.

[0065] In some alternative implementations, the single-phase inverter circuit module includes: an H-bridge inverter unit and a filter unit; the H-bridge inverter unit is used to generate pulsed alternating current based on the control of the pulse width modulation signal; the filter unit is used to filter and modulate the pulsed alternating current to generate alternating current.

[0066] In this embodiment, the single-phase inverter circuit module can adopt a full-bridge or half-bridge IGBT / MOSFET H structure, specifically an H full-bridge structure, and the switching device is a silicon carbide MOSFET device. The silicon carbide MOSFET device can be driven by the transformed PWM signal output from the drive module, and the voltage of the transformed PWM signal output from the drive module is -8V to +15V.

[0067] Figure 4 This illustration shows yet another schematic diagram of the device structure for bias current adjustment provided in an embodiment of this application. For example... Figure 4 As shown, in some optional embodiments, the aforementioned device for bias current adjustment further includes: an analog-to-digital converter module 205 and a digital-to-analog converter module 206; the input terminal of the analog-to-digital converter module 205 is connected to the fluxgate sensor module 21, and the output terminal of the analog-to-digital converter module 205 is connected to the digital signal processing module 201; the analog-to-digital converter module 205 is used to convert the magnetic field strength or the change in magnetic field strength into a digital signal and transmit the digital signal to the digital signal processing module 201; the input terminal of the digital-to-analog converter module 206 is connected to the digital signal processing module 201, and the output terminal of the digital-to-analog converter module 206 is connected to the drive module 204; the digital-to-analog converter module 206 is used to convert the pulse width modulation signal into an analog signal and transmit the analog signal to the drive module 204.

[0068] In this embodiment, the analog-to-digital converter module and the digital-to-analog converter module (DAC) are set up separately. In other embodiments, the analog-to-digital converter module and the digital-to-analog converter module can also be integrated into the digital signal processing module.

[0069] The analog-to-digital converter module can use an ADC chip with an input voltage range of ±10V and a resolution of 16 bits, and transmit data with the DSP core control circuit through a parallel interface.

[0070] In some optional implementations, the output of the analog-to-digital converter module is connected to the digital signal processing module, including: the analog-to-digital converter module and the digital signal processing module transmit digital signals through a parallel interface.

[0071] In this embodiment, the analog signal representing the change in magnetic field strength acquired by the fluxgate sensor is converted into a digital signal by the analog-to-digital converter module. The digital signal is then input to the DSP module, which generates a PWM signal based on the digital signal. The PWM signal is then input to the drive module, whose output is connected to the single-phase inverter circuit module. The output of the single-phase inverter circuit module is connected to the input of the relay module, the output of the DSP module is connected to the control terminal of the single-phase inverter circuit module, and the output of the relay module is connected to the demagnetizing coil load module.

[0072] Specifically, the digital signal obtained by sampling the analog signal representing the change in magnetic field strength output by the fluxgate sensor module is input into the DSP module. The DSP module determines the current magnetic field state and whether the demagnetizing current has reached the target value based on the preset digital signal processing algorithm. Based on the results output by the preset digital signal processing algorithm, the PWM duty cycle or frequency is calculated and the PWM signal is input into the drive module, thereby controlling the single-phase inverter circuit module to output AC current to the demagnetizing coil load module.

[0073] The single-phase inverter circuit module amplifies and converts the PWM signal output by the DSP into an AC current that can directly drive the demagnetizing coil after being amplified and power converted by the drive circuit.

[0074] In some optional implementations, the fluxgate sensor module includes a triaxial orthogonal sensor, such as the Bartington Mag13 series triaxial fluxgate sensor. It can measure ±100 microtesla, outputting a voltage signal of ±10V, and has an electronic resolution of 0.1mV for measuring the magnetic field, corresponding to a magnetic field of 0.01nT. In this embodiment, when a 1mA current is applied to the demagnetizing coil load module, a unidirectional magnetic field change of approximately 1nT can be generated inside the magnetic shielding device. Therefore, this triaxial fluxgate can effectively resolve magnetic field changes caused by a current close to 0.01mA.

[0075] In this embodiment, the analog signal output by the three-axis fluxgate sensor is converted into a digital signal by the ADC. The digital signal is processed by the DSP module and a closed-loop control strategy is adopted. The DAC outputs a control signal to the drive module to generate a PWM signal, which causes the H-bridge inverter to output AC current.

[0076] The PWM signal output by the DSP is not directly supplied to the degaussing coil load module, but is used to drive the power switching devices (MOSFET / IGBT) in the H-bridge inverter. The PWM signal output by the DSP is amplified and isolated by the drive module to ensure safe driving of the power switches in the H-bridge. The H-bridge includes four power switches, which can switch between forward, reverse, or zero voltage under different PWM signals. When the two diagonal switches are alternately turned on, the DC power supply is switched to a bidirectional square wave voltage. The PWM duty cycle controls the effective value of the square wave, i.e., the average voltage, thereby controlling the amplitude of the output current.

[0077] The PWM signal determines the on / off timing of the switching transistors in the H-bridge, thus determining the output waveform. The DSP can precisely control the magnitude and direction of the current by adjusting the PWM duty cycle and phase. Since the H-bridge directly outputs a high-frequency PWM square wave, it is not suitable for direct application to the degaussing coil load module. A filtering unit, such as an LC filter, can smooth the PWM square wave, filtering out high-frequency components and outputting a near-ideal continuous sine wave or DC current. Ultimately, the degaussing coil load module receives an AC current with controllable amplitude, controllable direction, and a smooth waveform.

[0078] Figure 5 This diagram illustrates yet another structural schematic of the device for bias current adjustment provided in an embodiment of this application. Figure 5 As shown, a demagnetizing coil load 503 is arranged on the surface of the magnetic shielding device 502. The fluxgate sensor 501 can be set at the center point inside the magnetic shielding device 502. The magnetic shielding device 502 can be a small magnetic shielding box. Based on the change in magnetic field strength inside the magnetic shielding device 502 obtained by the fluxgate sensor 501, the demagnetizing switching power supply is input. The change in magnetic field strength is converted into a digital signal by the DAC. The digital signal is processed by the DSP to obtain a PWM signal. After the PWM signal is amplified, inverted and filtered, an alternating current is generated. The generated alternating current is transmitted to the relay. At the same time, the relay is turned on by the PWM signal. Then, based on the alternating current, the demagnetizing coil load 503 is driven to demagnetize the inside of the magnetic shielding device 502. The change in magnetic field strength inside the magnetic shielding device 502 after the demagnetizing operation is obtained. It is determined whether the change in magnetic field strength is zero. If the magnetic field strength is not zero, the above process is repeated until the change in magnetic field strength is zero, then the adjustment is completed.

[0079] Specifically, such as Figure 4 As shown, the demagnetizing switching power supply 20 also includes a current sensor 207. The current sensor 207 can be a LEM LT-108ST, with a measurement range of ±150A and a measurement accuracy of 0.9A. Its sensitivity is much lower than that of the fluxgate sensor in response to current changes, which can greatly reduce the zero bias of the output current of the demagnetizing switching power supply 20.

[0080] like Figure 5 As shown, the probe of the fluxgate sensor 501 is placed at the center point inside the magnetic shielding device 502. At this time, the fluxgate sensor 501 uses the analog signal characterizing the magnetic field strength as the input signal of the demagnetizing switching power supply 20, denoted as... Meanwhile, the current sensor 207 detects zero bias and, through closed-loop control, roughly controls the output current to around 0A. It then controls the relay module to conduct and records the magnetic field strength after conduction. Based on the formula Calculate the change in magnetic field strength By adjusting the digital input to the digital-to-analog converter module via the DSP, the current output of the demagnetizing switching power supply 20 is slightly altered. The magnetic field strength after the control relay module is turned on is then sampled and repeated until... A value of zero indicates the end of the zero-bias conditioning process.

[0081] The device for adjusting bias current provided in this application embodiment sends the analog signal acquired by the fluxgate sensor to the DSP module through the analog-to-digital converter module, and then adjusts the PWM signal bit by bit until the measured value acquired by the fluxgate sensor module does not change after the relay module is repeatedly switched on and off, at which point it is considered that there is no bias in the output.

[0082] Specifically, the DSP module controls the relay module to repeatedly open and close. Each time the relay module closes, the output current of the single-phase inverter circuit module is applied to the demagnetizing coil load module; when the relay module opens, the AC current is cut off. This repeated switching on and off detects the change in magnetic field strength caused by the bias current of the demagnetizing switching power supply. Before and after each relay module operation, the fluxgate sensor module acquires the changes in the magnetic field within the magnetic shielding device.

[0083] Through the conversion of analog signals from the analog-to-digital converter module to the DSP module, the DSP obtains digital feedback on whether the magnetic field inside the magnetic shielding device changes before and after the current is turned on or off. Based on the feedback from the fluxgate sensor module, the DSP determines whether the current PWM duty cycle, i.e., the magnitude and direction of the current in the coil, is appropriate. If there are still magnetic field changes before and after the relay module operates, it indicates the presence of bias current. The DSP fine-tunes the PWM output bit by bit, gradually adjusting the output current amplitude or zero point, continuously approaching the true zero point. When a certain state is reached, repeated switching of the relay module does not change the output value of the fluxgate sensor module, and no further magnetic field changes occur. This indicates that turning the power on or off no longer introduces additional current bias, meaning the device for adjusting bias current is considered to be in a zero-bias state.

[0084] In this way, by automatically reading the change in magnetic field strength obtained by the fluxgate sensor module and adjusting the PWM signal bit by bit, the tediousness of manual adjustment and the error caused by visual observation of the signal are eliminated, the zero-point accuracy, the integration and intelligence of the circuit are improved, and the workload is reduced.

[0085] The device for adjusting bias current provided in this embodiment of the invention can execute the method for adjusting bias current provided in any embodiment of the invention, and has the corresponding functional modules and beneficial effects for executing the method. Further functional descriptions of the various modules and units described above are the same as in the corresponding embodiments described above, and will not be repeated here.

[0086] Figure 6 This is a schematic diagram of the structure of an electronic device provided in an embodiment of the present invention.

[0087] The following is a detailed reference. Figure 6 This diagram illustrates a suitable structural design for implementing an electronic device according to embodiments of the present invention. The electronic device may include a processor (e.g., a central processing unit, graphics processor, etc.) 601, which can perform various appropriate actions and processes based on a program stored in read-only memory (ROM) 602 or a program loaded from memory 608 into random access memory (RAM) 603. RAM 603 also stores various programs and data required for the operation of the electronic device. The processor 601, ROM 602, and RAM 603 are interconnected via a bus 604. An input / output (I / O) interface 605 is also connected to the bus 604.

[0088] Typically, the following devices can be connected to I / O interface 605: input devices 606 including, for example, touchscreens, touchpads, keyboards, mice, cameras, microphones, accelerometers, gyroscopes, etc.; output devices 607 including, for example, liquid crystal displays (LCDs), speakers, vibrators, etc.; memory devices 608 including, for example, magnetic tapes, hard disks, etc.; and communication devices 609. Communication device 609 allows electronic devices to communicate wirelessly or wiredly with other devices to exchange data. Although Figure 6 Electronic devices with various devices are shown, but it should be understood that it is not required to implement or have all of the devices shown, and more or fewer devices may be implemented or have instead.

[0089] In particular, according to embodiments of the present invention, the processes described above with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a non-transitory computer-readable medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via a communication device 609, or installed from a memory 608, or installed from a ROM 602. When the computer program is executed by the processor 601, it performs the functions defined in the method for bias current adjustment according to embodiments of the present invention.

[0090] Figure 6 The electronic device shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.

[0091] This invention also provides a computer-readable storage medium. The methods described above according to embodiments of the invention can be implemented in hardware or firmware, or implemented as recordable on a storage medium, or implemented as computer code originally stored on a remote storage medium or a non-transitory machine-readable storage medium and subsequently stored on a local storage medium after being downloaded via a network. Thus, the methods described herein can be processed by software stored on a storage medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware. The storage medium can be a magnetic disk, optical disk, read-only memory, random access memory, flash memory, hard disk, or solid-state drive, etc.; further, the storage medium can also include combinations of the above types of memory. It is understood that computers, processors, microprocessor controllers, or programmable hardware include storage components capable of storing or receiving software or computer code. When the software or computer code is accessed and executed by the computer, processor, or hardware, the method for bias current adjustment shown in the above embodiments is implemented.

[0092] A portion of this invention can be applied as a computer program product, such as computer program instructions, which, when executed by a computer, can invoke or provide the methods and / or technical solutions according to the invention through the operation of the computer. Those skilled in the art will understand that the forms in which computer program instructions exist in a computer-readable medium include, but are not limited to, source files, executable files, installation package files, etc. Correspondingly, the ways in which computer program instructions are executed by a computer include, but are not limited to: the computer directly executing the instructions, or the computer compiling the instructions and then executing the corresponding compiled program, or the computer reading and executing the instructions, or the computer reading and installing the instructions and then executing the corresponding installed program. Here, the computer-readable medium can be any available computer-readable storage medium or communication medium accessible to a computer.

[0093] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A method for adjusting bias current, characterized in that, The method includes: The magnetic field strength inside the magnetic shielding device is obtained, and a pulse width modulation signal is generated based on the magnetic field strength; the pulse width modulation signal is amplified and its power is converted to obtain a converted pulse width modulation signal; an alternating current is generated based on the converted pulse width modulation signal. When the AC current transmission is controlled based on the pulse width modulation signal, the magnetic shielding device is demagnetized based on the drive of the AC current. When the alternating current transmission is stopped based on the pulse width modulation signal, the change in magnetic field strength within the magnetic shielding device is obtained. If the change in magnetic field strength within the magnetic shielding device is not zero after the demagnetization operation, the pulse width modulation signal is adjusted bit by bit. Based on the adjusted pulse width modulation signal, the amplification and power conversion are performed to obtain the converted pulse width modulation signal. The alternating current is regenerated and the demagnetization operation is performed until the change in magnetic field strength is zero.

2. The method according to claim 1, characterized in that, The generation of a pulse width modulation signal based on the magnetic field strength includes: The analog quantity representing the magnetic field strength is sampled to obtain a digital signal; The digital signal is processed based on a preset digital signal processing algorithm to obtain the pulse width modulation signal.

3. A device for adjusting bias current, characterized in that, The device includes: The fluxgate sensor module is used to obtain the magnetic field strength inside the magnetic shielding device; A digital signal processing module is used to generate a pulse width modulation signal based on the magnetic field strength; The drive module is used to acquire the pulse width modulation signal, amplify and convert the pulse width modulation signal to obtain the converted pulse width modulation signal, and transmit the converted pulse width modulation signal to the single-phase inverter circuit module. A single-phase inverter circuit module is used to generate alternating current based on the transformed pulse width modulation signal; The relay module is used to turn on or off under the control of the pulse width modulation signal; A demagnetizing coil load module is used to perform demagnetizing operation on the magnetic shielding device based on the AC current when the relay module is turned on. The fluxgate sensor module is further configured to acquire the change in magnetic field strength within the magnetic shielding device after the demagnetization operation is performed; wherein, if the change in magnetic field strength is not zero after the demagnetization operation, the digital signal processing module is configured to adjust the pulse width modulation signal bit by bit; the driving module is configured to perform the amplification and power conversion based on the adjusted pulse width modulation signal to obtain the converted pulse width modulation signal, so as to regenerate the alternating current and perform the demagnetization operation until the change in magnetic field strength is zero.

4. The apparatus according to claim 3, characterized in that, The single-phase inverter circuit module includes: an H-bridge inverter unit and a filter unit; The H-bridge inverter unit is used to generate pulsed alternating current based on the control of the pulse width modulation signal; The filtering unit is used to filter and modulate the pulsed alternating current to generate the alternating current.

5. The apparatus according to claim 3, characterized in that, The device further includes: an analog-to-digital converter module and a digital-to-analog converter module; The input terminal of the analog-to-digital converter module is connected to the fluxgate sensor module, and the output terminal of the analog-to-digital converter module is connected to the digital signal processing module. The analog-to-digital converter module is used to convert the magnetic field strength or the change in magnetic field strength into a digital signal and transmit the digital signal to the digital signal processing module. The input terminal of the digital-to-analog converter module is connected to the digital signal processing module, and the output terminal of the digital-to-analog converter module is connected to the driving module. The digital-to-analog converter module is used to convert the pulse width modulation signal into an analog signal and transmit the analog signal to the driving module.

6. The apparatus according to claim 5, characterized in that, The output terminal of the analog-to-digital converter module is connected to the digital signal processing module, including: The analog-to-digital converter module and the digital signal processing module transmit the digital signal through a parallel interface.

7. The apparatus according to claim 3, characterized in that, The fluxgate sensor module includes a triaxial orthogonal sensor.

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