A high-temperature-drift-resistant low-bias high-precision closed-loop hall current sensor

Abstract

The application discloses a high-temperature-drift-resistant low-bias high-precision closed-loop Hall current sensor, which comprises a magnetic core assembly, a Hall sensor module, a signal preprocessing module, a temperature-drift self-adaptive compensation module, a closed-loop feedback driving module, an output calibration module and a power management module. The high-temperature-drift-resistant low-bias high-precision closed-loop Hall current sensor disclosed by the application is based on the magnetic balance type Hall effect principle, and through double-Hall differential sensing, full-temperature-range self-adaptive temperature-drift compensation, dynamic bias elimination, complementary push-pull closed-loop driving and other core designs, temperature drift and bias errors are inhibited from the source, and the measurement sensitivity and precision of the sensor are greatly improved.

Description

Technical Field

[0001] This invention belongs to the field of Hall current sensor technology, specifically relating to a high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias. Background Technology

[0002] Hall effect current sensors achieve non-contact current measurement based on the Hall effect and are widely used in electric vehicle charging stations, photovoltaic inverters, industrial servo drives, and other fields. Existing sensors are divided into open-loop and closed-loop types. Open-loop sensors have low accuracy and large temperature drift; closed-loop sensors use the magnetic balance principle and theoretically have higher accuracy, but still have significant drawbacks. 1. Temperature drift is difficult to eliminate: Hall elements are made of semiconductor materials, and their sensitivity drifts with temperature changes (the thermal drift coefficient is usually several hundred to several thousand ppm / ℃). Existing technologies mainly use physical heat dissipation (such as adding heat sinks or semiconductor cooling chips) or simple thermistor compensation. The former is costly and bulky, while the latter can only compensate for the first term of temperature change, but introduces the second term error, and cannot fundamentally eliminate the impact of temperature drift on measurement accuracy.

[0003] 2. Bias voltage affects zero-position accuracy: Hall elements inherently possess an offset voltage, which varies with factors such as temperature and stress, causing the output to be non-zero at zero current, thus affecting the accuracy of small current measurements. Current technology lacks effective methods for dynamic bias elimination.

[0004] 3. Low core positioning accuracy: The arc-shaped core that makes up the magnetic ring is difficult to position accurately in the circumferential direction. It is easy to shift during assembly and use, which leads to changes in the air gap and affects the stability of the magnetic field and the measurement accuracy.

[0005] 4. Output parameters are not adjustable: The output sensitivity and static voltage of traditional sensors are fixed values, which cannot be flexibly adjusted according to different application scenarios, resulting in poor adaptability. Summary of the Invention

[0006] The main objective of this invention is to provide a high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias. Based on the principle of magnetic balance Hall effect, it suppresses temperature drift and bias error from the source through core designs such as dual Hall differential sensing, full-temperature-range adaptive temperature drift compensation, dynamic bias elimination, and complementary push-pull closed-loop drive, thereby significantly improving the sensor's measurement sensitivity and accuracy.

[0007] To achieve the above objectives, this invention provides a high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias, comprising a magnetic core assembly, a Hall sensing module, a signal preprocessing module, a temperature drift adaptive compensation module, a closed-loop feedback drive module, an output calibration module, and a power management module, wherein: The magnetic core assembly surrounds the primary conductor of the measured current. The Hall sensor module is located in the air gap of the magnetic core assembly, and its output is connected to the input of the signal preprocessing module. The output of the signal preprocessing module is connected to the inputs of the temperature drift adaptive compensation module and the closed-loop feedback drive module, respectively. The output of the temperature drift adaptive compensation module is connected to the control terminal of the closed-loop feedback drive module. The power output of the closed-loop feedback drive module is connected to the feedback winding of the magnetic core assembly, and its sampling output is connected to the input of the output calibration module. The power management module supplies power to each module.

[0008] As a further preferred embodiment of the above technical solution, the magnetic core assembly includes a split soft magnetic ring, a feedback winding, and a double-layer magnetic shielding shell, wherein: The split soft magnetic ring is formed by interlocking two semi-annular iron-based nanocrystalline magnetic cores of the same size and magnetic properties to form a complete circular magnetic ring. The center of the magnetic ring is a through hole for a primary conductor, and two symmetrically distributed air gaps are formed at the interlocking point. The feedback winding uses high-conductivity oxygen-free copper enameled wire, which is uniformly wound in the slot of the lower half magnetic ring. The number of turns of the winding is designed to match the rated range of the sensor. Its two ends are electrically connected to the power output terminal of the closed-loop feedback drive module to pass in compensation current and generate a reverse compensation magnetic field. The double-layer magnetic shielding shell has a double-layer nested structure, completely enclosing the outside of the magnetic ring and reserving only one conductor wire hole and pin outlet to isolate the external stray magnetic field from the interference of the magnetic circuit and Hall element.

[0009] As a further preferred embodiment of the above technical solution, the Hall sensor module adopts a dual Hall differential sensing structure, including a paired first Hall element, a second Hall element, and a constant current drive sub-circuit, wherein: The first Hall element and the second Hall element are produced in the same batch and on the same wafer, and are respectively installed at the two symmetrical air gap centers of the magnetic core assembly, with opposite sensitive axis directions; The constant current drive sub-circuit provides a series constant drive current for the two Hall elements, ensuring that the operating current of the two Hall elements is consistent; the signal output terminals of the first Hall element and the second Hall element form a differential output, and output a differential Hall voltage signal to the signal preprocessing module.

[0010] As a further preferred technical solution of the above technical solution, the signal preprocessing module is used to amplify, filter and offset the differential Hall signal, including an instrumentation amplifier, a second-order low-pass filter circuit and a two-stage dynamic offset offset elimination circuit; the two-stage dynamic offset offset elimination circuit consists of an offset sample-and-hold circuit, an error integrator and an analog adder, to realize real-time correction of offset error.

[0011] As a further preferred technical solution of the above technical solution, the temperature drift adaptive compensation module includes a high-precision temperature sensor, a non-volatile memory, a programmable gain adjustment circuit, and a constant current drive adjustment circuit; by calculating the gain compensation coefficient and the drive current compensation coefficient through piecewise linear interpolation, and by real-time temperature sampling and closed-loop adjustment, dual-parameter linkage compensation across the entire temperature range is achieved.

[0012] As a further preferred technical solution of the above technical solution, the closed-loop feedback drive module is used to generate bidirectional compensation current and realize zero flux closed-loop control, including an integrator, a complementary push-pull power amplifier circuit, and a high-precision sampling resistor; the complementary push-pull power amplifier circuit is composed of NPN and PNP paired power transistors, bias diodes and current limiting resistors, and a precise bias network is set between the output of the integrator and the base of the power transistor to eliminate crossover distortion.

[0013] As a further preferred technical solution of the above technical solution, the output calibration module is used to convert the voltage signal on the high-precision sampling resistor into a high-precision standard output. It adopts piecewise linear correction, adaptive zero-point tracking and digital filtering, and adopts a non-equidistant calibration point selection strategy during piecewise linear correction to densify calibration points in the low-current core area.

[0014] As a further preferred technical solution to the above technical solution, the working principle of the high-precision closed-loop Hall current sensor is as follows: Step S1: When the measured current Ip passes through the primary conductor, a ring-shaped induced magnetic field is generated in the split soft magnetic ring. The first Hall element and the second Hall element in the two symmetrical air gaps sense the change in the magnetic field and output a differential Hall voltage signal. The effective differential mode signal is doubled, and the common mode temperature drift and bias signal cancel each other out. Step S2: The differential Hall voltage signal is amplified and filtered by the signal preprocessing module, while the two-stage dynamic bias elimination circuit eliminates the bias error in the signal in real time; the temperature drift adaptive compensation module collects the working temperature in real time through the temperature sensor, calls the full temperature range correction coefficient, and dynamically adjusts the signal gain and Hall drive current to suppress temperature drift. Step S3: The processed error voltage signal is input to the integrator, which drives the complementary push-pull power amplifier circuit to output a bidirectional compensation current Is to the feedback winding. The compensation current generates a compensation magnetic field in the split soft magnetic ring that is equal in magnitude and opposite in direction to the original magnetic field, so that the total magnetic flux is always zero and the system reaches a magnetic balance state. Step S4: Under magnetic balance, the compensation current Is in the feedback winding is in strict linear proportion to the measured current Ip. The voltage signal of the compensation current is acquired through a high-precision sampling resistor. After linear correction and zero-point calibration by the output calibration module, a standardized analog / digital signal that accurately corresponds to the measured current is output, thus achieving high-precision and high-stability measurement of the measured current.

[0015] Beneficial effects of this invention: 1. High resistance to temperature drift across the entire temperature range; 2. Ultra-low bias; 3. Double-layer magnetic shielding provides strong anti-interference and overload resistance; 4. The complementary push-pull drive has no measurement dead zone, fast response, and wide measurement range. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the magnetic core assembly of the present invention.

[0017] Figure 2 This is a schematic diagram of the installation of the Hall element of the present invention.

[0018] Figure 3 This is a block diagram of the overall architecture of the present invention.

[0019] Figure 4 This is a comparison chart of the temperature drift compensation effect of the present invention.

[0020] Figure 5 This is the open-loop Bode diagram of the closed-loop feedback drive module of the present invention.

[0021] Figure 6 This is the closed-loop step response curve of the closed-loop feedback drive module of the present invention.

[0022] Figure 7 This is the circuit diagram of the complementary push-pull power amplifier of the present invention. Detailed Implementation

[0023] The following description is intended to disclose the present invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description can be applied to other embodiments, modifications, improvements, equivalents, and other technical solutions that do not depart from the spirit and scope of the invention.

[0024] In the preferred embodiments of the present invention, those skilled in the art should note that the primary conductors and the like involved in the present invention can be considered as prior art.

[0025] Preferred embodiment.

[0026] like Figure 3 As shown, this invention discloses a high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias, comprising a magnetic core assembly, a Hall sensing module, a signal preprocessing module, a temperature drift adaptive compensation module, a closed-loop feedback drive module, an output calibration module, and a power management module, wherein: The magnetic core assembly surrounds the primary conductor of the measured current. The Hall sensor module is located in the air gap of the magnetic core assembly, and the output terminal of the Hall sensor module is connected to the input terminal of the signal preprocessing module. The output terminal of the signal preprocessing module is connected to the input terminals of the temperature drift adaptive compensation module and the closed-loop feedback drive module, respectively. The output terminal of the temperature drift adaptive compensation module is connected to the control terminal of the closed-loop feedback drive module. The power output terminal of the closed-loop feedback drive module is connected to the feedback winding of the magnetic core assembly, and the sampling output terminal is connected to the input terminal of the output calibration module. The power management module supplies power to each module (providing stable isolated power).

[0027] Specifically, such as Figure 1 As shown, the magnetic core assembly includes a split soft magnetic ring, a feedback winding, and a double-layer magnetic shielding shell, wherein: The split-type soft magnetic ring is formed by interlocking two semi-annular iron-based nanocrystalline magnetic cores of the same size and magnetic properties to form a complete circular magnetic ring (divided into an upper half and a lower half). The center of the magnetic ring is a through hole for a primary conductor, and two symmetrically distributed air gaps are formed at the interlocking point (the size and spacing of the two air gaps are exactly the same to ensure the symmetry of the magnetic circuit). The feedback winding uses high-conductivity oxygen-free copper enameled wire, which is uniformly wound in the slot of the lower half magnetic ring. The number of turns of the winding is designed to match the rated range of the sensor. Its two ends are electrically connected to the power output terminal of the closed-loop feedback drive module to pass in compensation current and generate a reverse compensation magnetic field. The double-layer magnetic shielding shell is a double-layer nested structure (permalloy), which completely wraps the outside of the magnetic ring and only reserves one conductor wire hole and pin outlet to isolate the interference of external stray magnetic field on the magnetic circuit and Hall element; It is worth mentioning that the magnetic core assembly is the core carrier for achieving magnetic field coupling and magnetic balance. The magnetic ring has an inner diameter of 20 mm and an outer diameter of 40 mm, with two symmetrical air gaps, each 1.5 mm wide and spaced 180° apart. The iron-based nanocrystalline magnetic core has a saturation magnetic flux density ≥1.2 T and an initial permeability ≥80000.

[0028] Two symmetrical air gaps (180° apart) make the magnetic circuit of the core centrally symmetrical. The magnetic field strength deviation of the annular magnetic field generated by the measured current at the two air gaps is ≤±1%, which is far better than the magnetic field uniformity of a single-air-gap magnetic core. The air gap width of 1.5mm is selected based on the following: if the air gap width is <1mm, the installation process of the Hall element will be significantly more difficult, and the bias voltage will easily drift due to stress; if the air gap width is >2mm, the magnetic reluctance of the magnetic core will increase significantly, the magnetic field will be significantly attenuated, and the sensitivity of the Hall sensor will decrease. 1.5mm is the optimal balance between installation process and magnetic field sensitivity, while ensuring that the saturation magnetic flux density of the iron-based nanocrystalline magnetic core is ≥1.2T to avoid magnetic saturation.

[0029] More specifically, such as Figure 2 As shown, the Hall sensor module adopts a dual Hall differential sensing structure, including a paired first Hall element, a second Hall element, and a constant current drive sub-circuit, wherein: The first Hall element and the second Hall element are produced from the same batch and wafer (such as the SS495A1 type, with consistent Hall coefficients, unequal potentials, and temperature characteristics). They are respectively installed at the two symmetrical air gap centers of the magnetic core assembly, with opposite sensitive axis directions. The Hall elements are fixed to the air gap center by a ceramic base. The thermal expansion coefficient of the ceramic base matches that of the iron-based nanocrystalline magnetic core (≤±5ppm / ℃) to avoid stress bias caused by temperature changes and further ensure stability.

[0030] The constant current drive sub-circuit provides a series constant drive current for the two Hall elements, ensuring that the operating current of the two Hall elements is consistent; the signal output terminals of the first Hall element and the second Hall element form a differential output, outputting a differential Hall voltage signal to the signal preprocessing module (working principle: the magnetic field generated by the measured current in the two symmetrical air gaps is equal in magnitude and in the same direction, and the sensitive axes of the two Hall elements are opposite, so the output signal amplitude of the effective magnetic field is equal and the polarity is opposite, and the sensitivity is doubled after the differential signal is superimposed; while the unequal potential of the Hall element, the common mode noise caused by temperature drift, and the bias voltage cancel each other out during differential output, suppressing bias and temperature drift errors from the source).

[0031] Furthermore, the signal preprocessing module is used to amplify, filter, and eliminate bias in the differential Hall signal, including an instrumentation amplifier, a second-order low-pass filter circuit, and a two-stage dynamic bias elimination circuit. The two-stage dynamic bias elimination circuit consists of a bias sample-and-hold circuit, an error integrator, and an analog adder, achieving real-time correction of bias error. Specifically, the implementation is as follows: 1. Instrumentation amplifier differential amplification: Let the dual Hall differential output signal be: ; ; in Hall sensitivity, , This is the bias voltage. For common-mode noise, the differential output is: ; when When, it is simplified to: ; The instrumentation amplifier uses an instrumentation amplifier chip with high input impedance and high common-mode rejection ratio (≥120dB), such as the AD8422, with an adjustable gain G1 of 10~100, to perform primary amplification of differential signals. .

[0032] 2. Second-order low-pass filter circuit: Using a Butterworth low-pass filter topology, the transfer function is: ; Cutoff frequency The bandwidth is set according to the measured current, with a typical value of [value missing]. It is used to filter out high-frequency switching noise and electromagnetic interference, while retaining the effective current signal.

[0033] 3. Two-stage dynamic bias elimination circuit: The two-stage dynamic bias elimination circuit consists of a bias sample-and-hold circuit, an error integrator, and an analog adder.

[0034] Level 1: During system reset or periodic idle periods (e.g., executed once every 100ms, each lasting 1ms), the signal link is output. Compared with the benchmark reference source The difference is sampled and held to obtain the static bias error. The sampling switch is controlled by the MCU.

[0035] Second stage: The bias error is integrated in reverse by an error integrator to generate a continuous correction voltage. : ; in , For integrating resistors and capacitors, typical values =10kΩ, =0.1μF, integration time constant 1ms.

[0036] The analog adder superimposes the correction voltage onto the signal link in real time: ; This structure enables continuous, stepless bias elimination, in steady state. = The bias error is suppressed to the μV level.

[0037] Furthermore, the temperature drift adaptive compensation module includes a high-precision temperature sensor, a non-volatile memory, a programmable gain adjustment circuit, and a constant current drive adjustment circuit. It calculates the gain compensation coefficient and the drive current compensation coefficient through piecewise linear interpolation, and achieves full-temperature-range dual-parameter linkage compensation through real-time temperature sampling and closed-loop adjustment. Specifically, the core of the temperature drift adaptive compensation module lies in establishing a high-precision mathematical model between the Hall element sensitivity and temperature, and achieving full-temperature-range dynamic compensation through real-time temperature sampling and closed-loop adjustment.

[0038] The compensation system employs piecewise linear interpolation. During the calibration phase, the sensor is calibrated at at least eight temperature points: -40℃, -20℃, 0℃, 25℃, 50℃, 85℃, 125℃, and 150℃. The calibration procedure is as follows: Place the sensor in a temperature chamber and set the temperature T = -40℃. After the temperature stabilizes, apply the rated primary current, adjust the programmable gain adjustment circuit and constant current source until the output reaches the standard value, and record the result. and Raise the temperature to the next calibration point, repeating the steps until 150°C; at each temperature point Below, record the gain compensation coefficient that keeps the output sensitivity constant. and drive current compensation coefficient These coefficients are stored in non-volatile memory. During operation, a high-precision temperature sensor (e.g., model TMP117) is mounted close to the Hall element to acquire the temperature T in real time. The MCU determines the temperature range within which T falls. , The current compensation coefficient is calculated using the piecewise linear interpolation formula: ; ; Programmable gain adjustment circuit according to Dynamically adjust signal link gain : ; Meanwhile, the constant current drive sub-circuit according to Adjusting the Hall drive current, Hall constant current drive current Adjusted to: ; Through the above-mentioned gain and excitation dual-parameter linkage compensation, the overall output sensitivity is improved. Maintaining a constant temperature across the entire range, the sensitivity temperature drift is ≤±30ppm / ℃, and the zero-point temperature drift is ≤±0.02%FS / ℃, both exceeding those of traditional closed-loop Hall sensors by more than an order of magnitude. To verify the compensation effect, simulation tests were conducted on the sensor across the entire temperature range of -40℃ to 150℃. Figure 4 As shown, the horizontal axis represents temperature (°C), and the vertical axis represents the output relative error (%). Without compensation (solid line), the relative error of the Hall element output is approximately -4.5% to -9.5%. After employing the piecewise linear interpolation and dual-parameter linkage compensation of this invention (dashed line), the comprehensive error across the entire temperature range (including residual temperature drift, nonlinearity, noise, etc.) is suppressed to within ±0.08%FS. The black dots in the figure correspond to the factory calibration temperature points (-40°C, -20°C, 0°C, 25°C, 50°C, 85°C, 125°C, 150°C). The compensation curves precisely pass through each calibration point, verifying the accuracy of piecewise linear interpolation and the effectiveness of dual-parameter linkage compensation.

[0039] Preferably, the closed-loop feedback drive module is used to generate bidirectional compensation current and realize zero-flux closed-loop control, including an integrator, a complementary push-pull power amplifier circuit, and a high-precision sampling resistor; the complementary push-pull power amplifier circuit consists of paired NPN and PNP power transistors, a bias diode, and a current-limiting resistor, and a precise bias network is set between the output of the integrator and the base of the power transistor to eliminate crossover distortion, specifically implemented as follows: The closed-loop feedback drive module is the core of the magnetic balance closed-loop system. It generates bidirectional compensation current to achieve zero-flux closed-loop control and includes an integrator, a complementary push-pull power amplifier circuit, and a high-precision sampling resistor. Its dynamic behavior can be modeled as a typical second-order system, ensuring fast response and steady-state accuracy.

[0040] Define error voltage The difference between the signal preprocessing module output and the compensation reference value: ; The integrator transfer function is: ; in This is the integration time constant. The operational amplifier selected is the ADA4522-1 (low offset, low noise). =1kΩ (0.1%, 25ppm / ℃), =1nF (COG, ±5%).

[0041] The electromagnetic system consisting of the feedback winding and the magnetic core can be modeled as an inductor-resistor series model: ; sampling resistor Compensation current Converted to feedback voltage: The open-loop transfer function of the entire closed-loop system is: ; The total gain K is: ; In the formula: Hall element differential sensitivity (V / T), typical value 12V / T; Total voltage gain of the signal preprocessing module (instrumentation amplifier + bias cancellation), typically 10~100; The equivalent transconductance (A / V) of a complementary push-pull power amplifier stage is determined by the bias circuit and power transistor parameters, with a typical value of 0.2~1A / V. Sampling resistor (Ω), typical value 0.1~1Ω.

[0042] By selection , and Matching is performed to ensure a system phase margin PM ≥ 60°, guaranteeing a magnetic balance response without overshoot or oscillation. In practical design, to ensure a system phase margin PM ≥ 60°, the crossover angular frequency is... Should meet: Take the design value Solving for the required total gain: .

[0043] The feedback winding uses 0.5mm diameter oxygen-free copper enameled wire, evenly wound 200 turns in the lower half-ring of the magnetic core. The measured inductance L=2μH, resistance R=10Ω, and the selected integration time constant τ=1μs, the calculation results are as follows: ; ; Select =12V / T, =10, =0.5A / V, =0.5Ω, then K=12×10×0.5×0.5=30, which is slightly greater than 25.42. It can be fine-tuned. Or fine-tuning Exact match. Figure 5 The diagram is an open-loop Bode plot. The actual crossover frequency is 367kHz, and the phase margin is 65.2°. Figure 6 The closed-loop step response curve shows a rise time (10%~90%) of 0.59μs and a settling time (2% error band) of 0.88μs, indicating that the system response time is ≤1μs, which fully meets the requirements for high-frequency dynamic current measurement.

[0044] A complementary push-pull structure enables bidirectional current output: The circuit diagram of a complementary push-pull power amplifier is shown below. Figure 7 As shown. When When the current is greater than 0, NPN transistor Q1 is turned on, PNP transistor Q2 is turned off, and the compensation current flows forward; when... When the voltage is less than 0, PNP transistor Q2 is turned on, NPN transistor Q1 is turned off, and the compensation current flows in reverse. To eliminate crossover distortion, a precise bias network is set between the integrator output and the base of the power transistor. This bias network consists of two diodes D1 and D2 connected in series in the same direction, a current-limiting resistor R1, and bias resistors R2 and R3. The anode of D1 is connected to the positive bias voltage +Vcc through R2, and the cathode of D2 is grounded (for single power supply) or negatively biased by -Vcc through R3. The integrator output is connected to the midpoint of the series connection of D1 and D2 through R1. This limits the integrator output current, protecting the diodes and power transistor; it also superimposes the integrator output drive voltage onto the bias network, achieving dynamic control of the conduction state of Q1 and Q2. Typical values ​​are R1 = 1kΩ, R2 = R3 = 10kΩ. A feedback winding is connected in series at the power output. With high-precision sampling resistor Output bidirectional compensation current Simultaneously, the voltage across the sampling resistor serves as both the closed-loop feedback signal and the measurement output signal. Bias diodes D1 and D2 are both 1N4148 silicon-based diodes. The forward voltage drop temperature coefficient of the 1N4148 silicon-based diode is approximately -2mV / ℃, which highly matches the temperature coefficient of the emitter junction of the 2SC5200 / 2SA1943 power transistor (approximately -1.8~-2.1mV / ℃). This creates a complementary temperature characteristic: as the temperature increases, the decrease in diode voltage drop is essentially the same as the decrease in the forward voltage drop of the power transistor's emitter junction. This ensures that the base-emitter bias voltage of Q1 and Q2 varies by ≤±50mV across the entire temperature range of -40℃ to 150℃, guaranteeing the temperature stability of the bias voltage and thus ensuring that the linearity near zero current is unaffected by temperature. This structure provides a static bias voltage of approximately 1.2V~1.4V for Q1 and Q2, keeping both transistors in a slightly conducting state when there is no input signal, thereby eliminating crossover distortion and ensuring linearity near zero current. The NPN transistor is selected as 2SC5200, and the PNP transistor is selected as 2SA1943. They are used in pairs to ensure the temperature stability of the bias voltage.

[0045] Preferably, the present invention can flexibly expand the measurement range by adjusting the number of turns N of the feedback winding, the air gap width of the magnetic core, and the corresponding closed-loop parameters according to different rated current measurement requirements. The parameter configuration method is illustrated below using rated currents of 200A, 500A, and 1000A as examples.

[0046] 200A range example (basic example): The feedback winding has N=200 turns and is uniformly wound on the lower half of the magnetic ring using 0.5mm diameter oxygen-free copper enameled wire. The measured coil inductance L=2μH and resistance R=10Ω. The integration time constant τ=1μs, the total gain K=25.42, the system phase margin 65.2°, and the response time 0.59μs. This configuration is suitable for 200A-class current measurement scenarios such as electric vehicle charging piles.

[0047] Example of 500A range measurement: To measure a rated current of 500A, based on the magnetic balance relationship... When the compensation current capability is limited (usually For a current ≤0.5A, the number of turns N in the feedback winding needs to be increased. Let N=500, using a finer wire diameter (0.3mm) for uniform winding. Due to the increased number of turns, the coil inductance L increases to approximately 12.5μH (proportional to the square of the number of turns), and the resistance R increases to approximately 25Ω. To maintain a system phase margin ≥60°, the integration time constant τ and the total gain K need to be redesigned. Choosing τ=2.5μs, then ; Adjusting the instrumentation amplifier gain to K=30.2 yields a phase margin of 63.5° and a response time of approximately 0.8μs.

[0048] Example of 1000A range measurement: Given N=1000, wire diameter 0.2mm, inductance L=50μH, and resistance R=100Ω, calculate... =9.23×10 5 rad / s (147kHz). Taking τ = 5μs, then K≈48.5. The compensation current at this time... = =1A, requires selection A high-power sampling resistor of 0.1Ω (20W alloy resistor) is used, with power transistors connected in parallel. The phase margin is 64.2°, and the response time is approximately 1.0μs.

[0049] Preferably, the output calibration module is used to convert the voltage signal on the high-precision sampling resistor into a high-precision standard output, employing piecewise linear correction, adaptive zero-point tracking, and digital filtering. Furthermore, during piecewise linear correction, a non-equidistant calibration point selection strategy is used to densify calibration points in the low-current core area. Specifically, the implementation is as follows: The output calibration module is responsible for converting the voltage signal on the sampling resistor into a high-precision standard output, which mainly includes linear correction, zero-point calibration and digital filtering.

[0050] Let the voltage across the sampling resistor be... Theoretical output current It should be consistent with the current being measured. satisfy: ; Where N is the number of turns in the feedback winding (in this embodiment, N=200); However, due to factors such as core hysteresis, amplifier nonlinearity, and PCB trace resistance, nonlinear errors actually exist. A piecewise linear correction method is adopted: during calibration, a standard current source is applied to the sensor, and 16 calibration points are selected within the range of 0~1000A. , A non-equidistant calibration point selection strategy is adopted. In the 0-5% rated current (low-current core region), the number of calibration points is increased to 8, and in the 5%-100% rated current region, 8 calibration points are selected in 10% increments. This increased density in the low-current region improves the fitting accuracy of the calibration curve by more than double in the low-current range, ensuring that the measurement error under 1% rated low-current conditions is ≤0.2%FS, matching the sensor's low-current measurement performance. During operation, the measurement value is... Locate the interval, interpolate to obtain the corrected output: ; Adaptive zero-point tracking: When the system is powered on or during periodic idle periods, the MCU detects the output value when there is no primary current. ;like Deviation from zero reference voltage Then update the zero-point compensation amount: ; In the formula, μ is the update step size, ranging from 0.001 to 0.01, and the update frequency is 1Hz. Simultaneously, restrictions need to be placed on... The range of variation (e.g., ±10mV) is used to prevent abnormal jumps.

[0051] ADC sampling frequency Set to 10kHz, using a first-order IIR low-pass filter: ; in , The filtering time constant is typically 1~10ms and can be configured according to response speed requirements. The final output is converted into a 0-5V / 0-10V / 4-20mA standard signal through an analog output circuit (16-bit DAC), or output as a digital signal through an RS485 / CAN interface.

[0052] Preferably, the power management module is used to provide a stable and isolated power supply for the entire system, including a safety protection circuit, a first voltage regulator, a second voltage regulator, and an isolated DC / DC circuit.

[0053] The safety protection circuit consists of a varistor, a transient suppression diode, and a common-mode inductor, and is connected to the power input terminal. It is used to suppress power surges, spikes, and common-mode interference, thereby improving the electromagnetic compatibility performance of the sensor. The isolated DC / DC circuit is used to achieve electrical isolation between the primary and secondary sides, with an isolation voltage ≥2500VAC, ensuring the electrical safety of current measurement.

[0054] The first voltage regulator is a low-dropout linear regulator that outputs a low-temperature drift reference voltage and a supply voltage to power the Hall sensor module, the signal preprocessing module, and the temperature drift adaptive compensation module. The second voltage regulator provides independent isolated power supplies for the MCU and the output calibration module to avoid mutual interference between digital and analog circuits.

[0055] This module supports a single power supply of 3.3V-5V, while also being compatible with dual power supplies of ±12V / ±15V, adapting to different industrial application scenarios.

[0056] Preferably, the working principle of the high-precision closed-loop Hall current sensor is as follows: Step S1: When the measured current Ip passes through the primary conductor, a ring-shaped induced magnetic field is generated in the split soft magnetic ring. The first Hall element and the second Hall element in the two symmetrical air gaps sense the change in the magnetic field and output a differential Hall voltage signal. The effective differential mode signal is doubled, and the common mode temperature drift and bias signal cancel each other out. Step S2: The differential Hall voltage signal is amplified and filtered by the signal preprocessing module, while the two-stage dynamic bias elimination circuit eliminates the bias error in the signal in real time; the temperature drift adaptive compensation module collects the working temperature in real time through the temperature sensor, calls the full temperature range correction coefficient, and dynamically adjusts the signal gain and Hall drive current to suppress temperature drift. Step S3: The processed error voltage signal is input to the integrator, which drives the complementary push-pull power amplifier circuit to output a bidirectional compensation current Is to the feedback winding. The compensation current generates a compensation magnetic field in the split soft magnetic ring that is equal in magnitude and opposite in direction to the original magnetic field, so that the total magnetic flux is always zero and the system reaches a magnetic balance state. Step S4: Under magnetic balance, the compensation current Is in the feedback winding is in strict linear proportion to the measured current Ip (Ip=Is×N, where N is the number of turns in the feedback winding). The voltage signal of the compensation current is acquired through a high-precision sampling resistor. After linear correction and zero-point calibration by the output calibration module, a standardized analog / digital signal that accurately corresponds to the measured current is output, thus achieving high-precision and high-stability measurement of the measured current.

[0057] Compared with existing closed-loop Hall current sensors, the present invention has the following significant technical advantages and beneficial effects: 1. High resistance to temperature drift across the entire temperature range and extremely strong temperature stability: Through a triple approach of dual Hall differential common-mode cancellation (suppressing the temperature drift common-mode noise of the Hall element itself at the source), full-temperature adaptive dynamic compensation (modeling based on the temperature characteristics of the Hall coefficient, and canceling sensitivity temperature drift through dual-parameter linkage), and low-temperature drift device selection (complementary temperature characteristics of diodes and power transistors to ensure bias temperature drift suppression), temperature drift suppression is achieved across the entire chain from signal acquisition, signal correction, and power drive. This completely solves the industry pain point of decreased measurement accuracy due to temperature changes, achieving sensitivity temperature drift ≤ ±30ppm / ℃, zero-point temperature drift ≤ ±0.02%FS / ℃, and overall error ≤ ±0.08%FS across the entire temperature range of -40℃ to 150℃.

[0058] 2. Ultra-low bias and offset errors, outstanding small current measurement capability: The differential detection structure suppresses common-mode bias at the source, and the two-stage dynamic bias elimination circuit combined with closed-loop negative feedback realizes real-time dynamic bias correction. The sensor zero-point bias is ≤±0.1mV, and the static offset error is ≤±0.02%FS / ℃. It can still maintain a measurement accuracy of 0.2 class under 1% rated low current conditions, which solves the problem of inaccuracy in small current measurement of traditional sensors.

[0059] 3. Strong anti-interference capability and wide environmental adaptability: The permalloy double-layer magnetic shielding structure combined with the high common-mode rejection ratio differential amplifier circuit can effectively suppress external stray magnetic fields, power supply noise, and electromagnetic interference. It can still maintain stable measurement performance in complex industrial environments with strong electromagnetic interference, such as frequency converters and inverter cabinets. The iron-based nanocrystalline magnetic core has high saturation magnetic flux density and low hysteresis characteristics. Its overload resistance can reach 5 times the rated current, making it suitable for a wide range of current measurements.

[0060] 4. Excellent driving performance with no measurement dead zone: The complementary push-pull power drive structure enables bidirectional linear current measurement under single power supply, completely eliminating the measurement dead zone of traditional single power supply solutions; at the same time, it has strong current driving capability, which can be adapted to the closed-loop measurement requirements of a wide range of 5A-1000A, and the closed-loop response time is ≤1μs, which can meet the measurement requirements of high-frequency dynamic current.

[0061] It is worth mentioning that the technical features such as the primary conductor involved in this patent application should be regarded as prior art. The specific structure, working principle, and possible control methods and spatial arrangement of these technical features can be adopted using conventional choices in the field, and should not be regarded as the inventive point of this patent. This patent will not be further elaborated in detail.

[0062] For those skilled in the art, modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

Claims

1. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias, characterized in that, It includes a magnetic core assembly, a Hall sensor module, a signal preprocessing module, a temperature drift adaptive compensation module, a closed-loop feedback drive module, an output calibration module, and a power management module, among which: The magnetic core assembly surrounds the primary conductor of the measured current. The Hall sensor module is located in the air gap of the magnetic core assembly, and its output is connected to the input of the signal preprocessing module. The output of the signal preprocessing module is connected to the inputs of the temperature drift adaptive compensation module and the closed-loop feedback drive module, respectively. The output of the temperature drift adaptive compensation module is connected to the control terminal of the closed-loop feedback drive module. The power output of the closed-loop feedback drive module is connected to the feedback winding of the magnetic core assembly, and its sampling output is connected to the input of the output calibration module. The power management module supplies power to each module.

2. The high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 1, characterized in that, The magnetic core assembly includes a split soft magnetic ring, a feedback winding, and a double-layer magnetic shielding shell, wherein: The split soft magnetic ring is formed by interlocking two semi-annular iron-based nanocrystalline magnetic cores of the same size and magnetic properties to form a complete circular magnetic ring. The center of the magnetic ring is a through hole for a primary conductor, and two symmetrically distributed air gaps are formed at the interlocking point. The feedback winding uses high-conductivity oxygen-free copper enameled wire, which is uniformly wound in the slot of the lower half magnetic ring. The number of turns of the winding is designed to match the rated range of the sensor. Its two ends are electrically connected to the power output terminal of the closed-loop feedback drive module to pass in compensation current and generate a reverse compensation magnetic field. The double-layer magnetic shielding shell has a double-layer nested structure, completely enclosing the outside of the magnetic ring and reserving only one conductor wire hole and pin outlet to isolate the external stray magnetic field from the interference of the magnetic circuit and Hall element.

3. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 2, characterized in that, The Hall sensor module adopts a dual Hall differential sensing structure, including a paired first Hall element, a second Hall element, and a constant current drive sub-circuit, wherein: The first Hall element and the second Hall element are produced in the same batch and on the same wafer, and are respectively installed at the two symmetrical air gap centers of the magnetic core assembly, with opposite sensitive axis directions; The constant current drive sub-circuit provides a series constant drive current for the two Hall elements, ensuring that the operating current of the two Hall elements is consistent; the signal output terminals of the first Hall element and the second Hall element form a differential output, and output a differential Hall voltage signal to the signal preprocessing module.

4. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 3, characterized in that, The signal preprocessing module is used to amplify, filter, and eliminate bias in the differential Hall signal. It includes an instrumentation amplifier, a second-order low-pass filter circuit, and a two-stage dynamic bias elimination circuit. The two-stage dynamic bias elimination circuit consists of a bias sample-and-hold circuit, an error integrator, and an analog adder to achieve real-time correction of bias error.

5. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 4, characterized in that, The temperature drift adaptive compensation module includes a high-precision temperature sensor, a non-volatile memory, a programmable gain adjustment circuit, and a constant current drive adjustment circuit. Gain compensation coefficient and drive current compensation coefficient are calculated by piecewise linear interpolation, and dual-parameter linkage compensation across the entire temperature range is achieved through real-time temperature sampling and closed-loop adjustment.

6. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 5, characterized in that, The closed-loop feedback drive module is used to generate bidirectional compensation current and realize zero-flux closed-loop control. It includes an integrator, a complementary push-pull power amplifier circuit, and a high-precision sampling resistor. The complementary push-pull power amplifier circuit consists of NPN and PNP paired power transistors, bias diodes, and current-limiting resistors. A precise bias network is set between the output of the integrator and the base of the power transistors to eliminate crossover distortion.

7. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 6, characterized in that, The output calibration module is used to convert the voltage signal on the high-precision sampling resistor into a high-precision standard output. It adopts piecewise linear correction, adaptive zero-point tracking and digital filtering. In the piecewise linear correction, a non-equal spacing calibration point selection strategy is adopted to densify the calibration points in the low current core area.

8. A high-precision closed-loop Hall current sensor with high resistance to temperature drift and low bias according to claim 7, characterized in that, The working principle of a high-precision closed-loop Hall current sensor is as follows: Step S1: When the measured current Ip passes through the primary conductor, a ring-shaped induced magnetic field is generated in the split soft magnetic ring. The first Hall element and the second Hall element in the two symmetrical air gaps sense the change in the magnetic field and output a differential Hall voltage signal. The effective differential mode signal is doubled, and the common mode temperature drift and bias signal cancel each other out. Step S2: The differential Hall voltage signal is amplified and filtered by the signal preprocessing module, while the two-stage dynamic bias elimination circuit eliminates the bias error in the signal in real time; the temperature drift adaptive compensation module collects the working temperature in real time through the temperature sensor, calls the full temperature range correction coefficient, and dynamically adjusts the signal gain and Hall drive current to suppress temperature drift. Step S3: The processed error voltage signal is input to the integrator, which drives the complementary push-pull power amplifier circuit to output a bidirectional compensation current Is to the feedback winding. The compensation current generates a compensation magnetic field in the split soft magnetic ring that is equal in magnitude and opposite in direction to the original magnetic field, so that the total magnetic flux is always zero and the system reaches a magnetic balance state. Step S4: Under magnetic balance, the compensation current Is in the feedback winding is in strict linear proportion to the measured current Ip. The voltage signal of the compensation current is acquired through a high-precision sampling resistor. After linear correction and zero-point calibration by the output calibration module, a standardized analog / digital signal that accurately corresponds to the measured current is output, thus achieving high-precision and high-stability measurement of the measured current.

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