Fluxgate current sensor

Abstract

The invention provides a fluxgate current sensor, and belongs to the technical field of current detection sensors. Comprising a front shell provided with a through first through hole; the rear shell is provided with a second through hole coaxial with the first through hole, and a hollow cavity is defined by the rear shell and the front shell; a connector male end is also arranged on one side, far away from the front shell, of the rear shell; the magnetic core unit is embedded in the cavity, surrounds the second through hole and is used for acquiring an excitation current signal of the current wire to be detected; the control circuit board is embedded in the cavity, is electrically connected with the magnetic core unit and is used for acquiring and outputting an excitation current signal of the magnetic core unit; wherein the first through hole or the second through hole is used for a to-be-detected current lead to radially pass through; the magnetic core unit only comprises one coil; the control circuit board further drives the magnetic core unit to generate an excitation magnetic field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of current detection sensors, in particular to a magnetic flux gate current sensor. BACKGROUND

[0002] With the increasing requirements of new energy vehicle electric control system on current detection accuracy, response speed and anti-electromagnetic interference ability, traditional Hall current sensor and shunt resistance sensor face limitations in high-precision application scenarios. Magnetic flux gate current sensor is concerned due to its high precision, low temperature drift and strong anti-interference ability.

[0003] However, the traditional magnetic flux gate sensor usually adopts a double-coil structure, with excitation and detection separated, resulting in large volume, high cost and complex circuit, which limits its wide application in the compact vehicle environment. In addition, the traditional magnetic flux gate technology is mostly based on the second harmonic detection method, and the signal processing circuit is complex and has low integration, which is not conducive to stable and reliable measurement in harsh vehicle environment.

[0004] Therefore, it is necessary to provide a magnetic flux gate current sensor, which improves the compactness and reliability of the current sensor by improving the device structure and layout method, using a single-winding structure. SUMMARY

[0005] Therefore, the present application provides a magnetic flux gate current sensor based on the H-bridge self-oscillation principle, which overcomes the defects of large volume, complex circuit and poor environmental adaptability of the traditional magnetic flux gate current sensor in the prior art, and provides a magnetic flux gate current sensor with single-winding integrated design and reverse self-triggering commutation mechanism.

[0006] The present application provides a magnetic flux gate current sensor, comprising: a front shell provided with a first through hole; a rear shell provided with a second through hole coaxial with the first through hole, the rear shell and the front shell forming a hollow cavity; a magnetic core unit embedded in the cavity and arranged around the second through hole, for obtaining a current signal of a current lead to be measured; a control circuit board embedded in the cavity and electrically connected to the magnetic core unit, for obtaining an excitation current signal of the magnetic core unit and outputting; wherein the first through hole or the second through hole is provided for the current lead to be measured to pass radially; the magnetic core unit only includes one coil; and the control circuit board further drives the magnetic core unit to generate an excitation magnetic field.

[0007] Based on the above technical solutions, preferably, the magnetic core unit includes a strip magnetic core, a protective shell, and a coil. The strip magnetic core is arranged around the second through hole, and the protective shell is sleeved on the outer surface of the strip magnetic core. The coil is wound on the outer surface of the protective shell to form a single winding structure, and the two ends of the coil extend out and are electrically connected to the control circuit board.

[0008] Preferably, the control circuit board includes an MCU, a power management sub-circuit, an H-bridge self-excitation sub-circuit, a three-stage amplifier sub-circuit, and a CAN communication sub-circuit. The power management sub-circuit is used to boost or buck the vehicle power supply for use by the MCU, the H-bridge self-excitation sub-circuit, the three-stage amplifier sub-circuit, and the CAN communication sub-circuit. The H-bridge self-excitation sub-circuit is electrically connected to both ends of the coil to drive the coil to generate alternating positive and negative saturated pulsed excitation current waveforms and form an excitation magnetic field. This excitation magnetic field is superimposed on the magnetic field generated by the current in the conductor under test to form a voltage signal ΔU corresponding to the difference in excitation current ΔI. The three-stage amplifier sub-circuit is used to acquire the voltage signal ΔU corresponding to the difference in excitation current ΔI and amplify it. The amplified voltage signal is sent to the MCU. The MCU performs analog-to-digital conversion on the input amplified excitation current difference to obtain the current value under test and sends it to the CAN communication sub-circuit. The CAN communication sub-circuit is used to output the current value under test via communication.

[0009] Further preferably, the pulsed excitation current waveform with alternating forward and reverse saturation includes a forward saturation segment, a forward unsaturation segment, a reverse saturation segment, and a reverse unsaturation segment within a single cycle; when there is no current in the current conductor under test, the durations of the forward saturation segment and the reverse saturation segment are equal, and the durations of the forward unsaturation segment and the reverse unsaturation segment are symmetrically equal; when there is current in the current conductor under test, the durations of the forward unsaturation segment and the reverse unsaturation segment are not equal, and the excitation current of the forward unsaturation segment and the reverse unsaturation segment generates a difference ΔI.

[0010] More preferably, the H-bridge self-excited sub-circuit includes an upper bridge arm, a lower bridge arm, a MOSFET switching unit, a sampling resistor, and a comparator. The upper bridge arm is electrically connected to the output of the power management sub-circuit, and the common terminals of the upper and lower bridge arms are electrically connected to each other. The upper and lower bridge arms are respectively electrically connected to one end of a coil. The output terminal of the lower bridge arm is electrically connected to the drain of the MOSFET switching unit. The source of the MOSFET switching unit is electrically connected to one end of the sampling resistor and the inverting input terminal of the comparator. The other end of the sampling resistor is grounded. The gate of the MOSFET switching unit is electrically connected to the output terminal of the comparator. The non-inverting input terminal of the comparator is connected to a fixed reference voltage. When the H-bridge self-excited sub-circuit is powered on... When the sampled voltage obtained by the comparator from the sampling resistor is less than the fixed reference voltage, the comparator outputs a high level to turn on the MOSFET switching unit, and the excitation current flows through the coil to charge the long strip magnetic core. When the long strip magnetic core is saturated, the sampled voltage obtained by the comparator from the sampling resistor exceeds the fixed reference voltage, and the comparator outputs a low level to turn off the MOSFET switching unit. The coil switches to the discharge state and generates a reverse electromotive force to drive the upper and lower bridge arms to commutate. After the reverse electromotive force stabilizes, the comparator outputs a high level again to turn on the MOSFET switching unit, and the excitation current flows in reverse through the coil to achieve reverse charging. This cycle is repeated to achieve a pulsed excitation current waveform with alternating forward and reverse saturation and to form an excitation magnetic field.

[0011] In a further preferred embodiment, the upper bridge arm includes a first MOSFET Q1, a second MOSFET Q2, a third MOSFET Q3A, and a fourth MOSFET Q3B, and the lower bridge arm includes a fifth MOSFET Q4, a sixth MOSFET Q5, a seventh MOSFET Q6A, and an eighth MOSFET Q6B; the drains of the first MOSFET Q1 and the second MOSFET Q2 are both electrically connected to the output of the power management sub-circuit; the gate of the first MOSFET Q1 is electrically connected to the drain of the third MOSFET Q3A; the gate of the second MOSFET Q2 is electrically connected to the drain of the fourth MOSFET Q3B; the gates of the third MOSFET Q3A and the fourth MOSFET Q3B are both electrically connected to the absorption network; and the source of the first MOSFET Q1 is connected to the line... One end of the coil, the source of the fourth MOSFET Q3B, the source of the fifth MOSFET Q4, and the source of the seventh MOSFET Q6A are electrically connected. The source of the second MOSFET Q2 is electrically connected to one end of the coil, the source of the third MOSFET Q3A, the source of the sixth MOSFET Q5, and the source of the eighth MOSFET Q6B, respectively. The drain of the seventh MOSFET Q6A is electrically connected to the gate of the sixth MOSFET Q5. The drain of the eighth MOSFET Q6B is electrically connected to the gate of the fifth MOSFET Q4. The gates of the seventh MOSFET Q6A and the eighth MOSFET Q6B are both electrically connected to the absorption network. The drains of the fifth MOSFET Q4 and the sixth MOSFET Q5 are both electrically connected to the source of the MOSFET switching unit.

[0012] More preferably, the absorption network includes a first capacitor C1, a second capacitor C2, a first Zener diode D1, a second Zener diode D2, and a first resistor R1. The cathode of the first Zener diode D1 and one end of the first capacitor C1 are both electrically connected to the output of the power management sub-circuit. The anode of the first Zener diode D1 is electrically connected to the other end of the first capacitor C1, one end of the first resistor R1, the gate of the third MOSFET Q3A, and the gate of the fourth MOSFET Q3B, respectively. The cathode of the second Zener diode D2 and one end of the second capacitor C2 are both electrically connected to the other end of the first resistor R1, the gate of the seventh MOSFET Q6A, and the gate of the eighth MOSFET Q6B. The anode of the second Zener diode D2 and the other end of the second capacitor C2 are both grounded.

[0013] Preferably, the three-stage amplifier sub-circuit has three different amplification branches, the amplification factor of the first amplification branch is less than that of the second amplification branch, and the amplification factor of the second amplification branch is less than that of the third amplification branch; the corresponding amplification branch is selected for amplification processing according to the magnitude of the difference ΔI of the excitation current.

[0014] Preferably, the end face of the rear housing away from the front housing is also provided with a male connector terminal, and the CAN communication sub-circuit is embedded in the male connector terminal. The terminals of the CAN communication sub-circuit pass through the rear housing through the connector and communicate with the MCU.

[0015] Based on the above technical solutions, preferably, the front outer shell is provided with a plurality of buckles and plates, all of which extend radially along the first through hole, and the thickness of the end of the plate away from the front outer shell is greater than the thickness of the other end; the rear outer shell edge is provided with a plurality of bosses and flange plates, which extend radially along the rear outer shell; the buckles are provided with through slots, and the bosses pass through the slots; the flange plates are provided with through stepped holes, and the plates pass through the stepped holes and abut against the end face of the stepped holes.

[0016] The fluxgate current sensor provided by this invention has the following advantages compared to the prior art: 1. By using a single-winding integrated design, the excitation and sensing dual-winding structure commonly found in traditional fluxgate sensors is replaced. The H-bridge self-excitation sub-circuit is combined with a reverse self-triggering commutation mechanism, which achieves a high degree of circuit integration and reduces the number of external components and circuit complexity. Overall, this makes the sensor structure compact and small in size, making it easy to use in space-constrained applications, such as vehicle environments.

[0017] 2. The front and rear shells are combined to form a cavity, which encapsulates the magnetic core unit and control circuit board, providing good physical protection and electromagnetic shielding, and enhancing the sensor's tolerance to harsh industrial or automotive environments; the CAN communication sub-circuit is used for data output, which meets the high requirements of automotive electronics and industrial automation for communication reliability and anti-interference.

[0018] 3. The H-bridge self-excited sub-circuit generates alternating forward and reverse saturated pulsed excitation current waveforms, which can sensitively detect magnetic field changes caused by the measured current. By comparing the duration difference between the forward and reverse unsaturated segments, it accurately reflects the magnitude of the measured current. Based on the different excitation current differences ΔI, it automatically selects branches with different amplification factors, effectively extending the sensor's measurement range. The self-excited oscillation mechanism enables the circuit to quickly respond to changes in the magnetic core state, achieving rapid magnetic field switching and signal generation. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a three-dimensional view of the exploded state of a fluxgate current sensor according to the present invention; Figure 2 This is a three-dimensional view of the combined state of a fluxgate current sensor according to the present invention; Figure 3 This is a perspective view of the combined state of the magnetic core and the magnetic core protective shell of a fluxgate current sensor according to the present invention. Figure 4 This is a circuit structure block diagram of the control circuit board for a fluxgate current sensor according to the present invention. Figure 5 This is a circuit diagram of an H-bridge self-excited sub-circuit of a fluxgate current sensor according to the present invention. Figure 6 This is a waveform of the excitation current of a fluxgate current sensor of the present invention, characterized by alternating positive and negative saturation.

[0021] Reference numerals: 101, Front housing; 102, Rear housing; 10, First through hole; 200, Second through hole; 2, Magnetic core unit; 3, Coil; 4, Control circuit board; 103, Snap-fit; 104, Boss; 105, Stepped hole; 106, Flange plate; 108, Mounting hole; 109, Connector male terminal; 201, Protective shell; 202, Long strip magnetic core; 401, MCU; 402, Power management sub-circuit; 403, H-bridge self-excitation sub-circuit; 404, Three-stage amplifier sub-circuit; 405, CAN communication sub-circuit; 501, Upper bridge arm; 502, Lower bridge arm; 503, MOSFET switching unit; 504, Sampling resistor; 505, Comparator; 506, Absorption network; 601, Forward saturation section; 602, Reverse saturation section; 603, Forward unsaturated section; 604, Reverse unsaturated section. Detailed Implementation

[0022] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] Traditional fluxgate sensors typically employ a dual-coil structure, separating excitation and detection. This results in larger size, higher cost, and more complex circuitry, limiting their widespread application in compact automotive environments. Furthermore, traditional fluxgate technology is largely based on second harmonic detection, leading to complex signal processing circuits and low integration, which is detrimental to achieving stable and reliable measurements in harsh automotive environments. Therefore, if... Figure 1 and Figure 2 As shown, the present invention provides a fluxgate current sensor, comprising:

[0024] The front housing 101 is provided with a through hole 100; The rear outer shell 102 is provided with a second through hole 200 coaxial with the first through hole 100. The rear outer shell 102 and the front outer shell 101 together form a hollow cavity; the first through hole 100 or the second through hole 200 allows the wire of the current to be measured to pass through radially. The magnetic core unit 2 is embedded in the cavity and arranged around the second through hole 200 to acquire the current signal of the current conductor to be measured. The control circuit board 4 is embedded in the cavity and electrically connected to the magnetic core unit 2. It is used to acquire and output the excitation current signal of the magnetic core unit 2. The magnetic core unit 2 consists of only one coil 3; the control circuit board 4 also drives the magnetic core unit 2 to generate an excitation magnetic field. This single-winding integrated design replaces the common dual-winding structure for excitation and induction found in traditional fluxgate sensors, simplifying the sensor's electrical structure and facilitating integration and miniaturization.

[0025] In one embodiment, the front housing 101 is provided with a plurality of buckles 103 and a retaining plate, all of which extend radially along the first through hole 100. The thickness of the retaining plate at one end away from the front housing is greater than the thickness at the other end. The rear housing 102 is provided with a plurality of bosses 104 and a flange plate 106 at its edge, and the bosses 104 and the flange plate 106 extend radially along the rear housing. The buckles 103 are provided with through slots, and the bosses 104 pass through the slots. The flange plate 106 is provided with through stepped holes 105, and the retaining plate passes through the stepped holes 105 and abuts against the end face of the stepped holes 105.

[0026] like Figure 3 As shown, the magnetic core unit 2 includes a strip magnetic core 202, a protective shell 201, and a coil 3. The strip magnetic core 202 is arranged around the second through hole 200, and the protective shell 201 is sleeved on the outer surface of the strip magnetic core 202. The coil 3 is wound on the outer surface of the protective shell 201 to form a single winding structure, and the two ends of the coil 3 are respectively led out and electrically connected to the control circuit board 4.

[0027] The assembly process of the above components is as follows: First, the long strip magnetic core 202 is bent and placed in the protective shell 201. Then, a 1500-turn coil 3 is wound on the protective shell 201 to form a single-winding magnetic core unit 2. The magnetic core unit 2 is embedded in the cavity and surrounds the second through hole. The control circuit board 4 is fixedly installed in the cavity to input positive and negative alternating saturation excitation current to the coil 3. The front shell 101 is equipped with three spaced-apart buckles 103 and at least one pair of retaining plates. The rear shell 102 is equipped with several bosses 104 and flange plates 106. The bosses and buckles 103 achieve precise assembly. Combined with the stepped holes 105 on the structure of at least one pair of retaining plates and flange plates 106, the position of the front shell is better locked. The mounting holes 108 on the flange plate 106 are used to fix the rear shell 102. The first through hole 100 or the second through hole 200 cooperates with the magnetic core unit 2 to obtain the current signal of the current conductor to be measured.

[0028] like Figure 4As shown, the control circuit board 4 includes an MCU 401, a power management sub-circuit 402, an H-bridge self-excitation sub-circuit 403, a three-stage amplifier sub-circuit 404, and a CAN communication sub-circuit 405. The power management sub-circuit 402 is used to boost or buck the vehicle power supply for use by the MCU 401, H-bridge self-excitation sub-circuit 403, three-stage amplifier sub-circuit 404, and CAN communication sub-circuit 405. The H-bridge self-excitation sub-circuit 403 is electrically connected to the two ends of the coil 3 to drive the coil 3 to generate alternating positive and negative saturated pulse excitation current waveforms. An excitation magnetic field is formed and superimposed with the magnetic field generated by the current in the conductor under test, forming a voltage signal ΔU corresponding to the difference in excitation current ΔI. The three-stage amplification sub-circuit 404 is used to acquire the voltage signal ΔU corresponding to the difference in excitation current ΔI and amplify it. The amplified voltage signal is sent to the MCU 401. The MCU 401 performs analog-to-digital conversion on the input amplified excitation current difference, converts it into the current value under test, and sends it to the CAN communication sub-circuit 405. The CAN communication sub-circuit 405 is used to output the current value under test through communication.

[0029] The control circuit board 4 is used to boost the vehicle's 12V power supply to obtain high-voltage DC, such as 40V, specifically for high-voltage applications, via a BOOST boost circuit, or to convert it to low-voltage DC, such as 5V or 3.3V, via an LDO step-down converter. This provides operating power to the MCU 401, the H-bridge self-excitation sub-circuit 403, the three-stage amplifier sub-circuit 404, and the CAN communication sub-circuit 405. The BOOST boost circuit and LDO step-down converter used in the power management sub-circuit 402 are conventional techniques in this field and will not be described in detail here. The H-bridge self-excitation sub-circuit 403 connects to both ends of the coil 3 and is used to input alternating positive and negative saturated pulsed excitation current waveforms into the coil 3 to establish stable self-excited oscillation.

[0030] In one embodiment, a male connector terminal 109 is provided on the end face of the rear housing 102 away from the front housing 101. A CAN communication sub-circuit 405 is embedded in the male connector terminal 109. The terminals of the CAN communication sub-circuit 405 pass through the rear housing 102 via the connector and communicate with the MCU 401. The CAN communication sub-circuit 405 has a reserved communication interface, which allows the MCU to periodically output the measured current value, the overall operating status of the fluxgate current sensor, and CAN frames containing fault indicators in real time. This enables the host computer to acquire and monitor the power supply voltage, oscillation status, and signal chain integrity in real time. When the power supply voltage of the fluxgate current sensor is abnormal or the oscillation fails, the fault information is reported through the CAN communication sub-circuit 405, notifying maintenance personnel to take appropriate protective measures.

[0031] like Figure 4 Combination Figure 5As shown, the H-bridge self-excited sub-circuit 403 includes an upper bridge arm 501, a lower bridge arm 502, a MOSFET switching unit 503, a sampling resistor 504, and a comparator 505. The upper bridge arm 501 is electrically connected to the output of the power management sub-circuit 402, and the common terminals of the upper bridge arm 501 and the lower bridge arm 502 are electrically connected to each other. The upper bridge arm 501 and the lower bridge arm 502 are respectively electrically connected to one end of the coil 3. The output terminal of the lower bridge arm 502 is electrically connected to the drain of the MOSFET switching unit 503. The source of the MOSFET switching unit 503 is electrically connected to one end of the sampling resistor 504 and the inverting input terminal of the comparator 505. The other end of the sampling resistor 504 is grounded. The sampling resistor 504 is... Figure 5 The resistor R38 in the circuit is used to electrically connect the gate of the MOSFET switching unit 503 to the output of the comparator 505. The non-inverting input of the comparator 505 is connected to a fixed reference voltage. When the H-bridge self-excited sub-circuit 403 is powered on, the sampling voltage obtained by the comparator 505 from the sampling resistor 504 is less than the fixed reference voltage VREF. The comparator 505 outputs a high level to turn on the MOSFET switching unit 503, and the excitation current flows through the coil 3 to charge the long strip magnetic core. When the long strip magnetic core is saturated, the sampling voltage obtained by the comparator 505 from the sampling resistor 504 exceeds the fixed reference voltage VREF. The comparator 505 outputs a low level to turn off the MOSFET switching unit 503. The coil 3 switches to the discharge state and generates a reverse electromotive force to drive the upper bridge arm 501 and the lower bridge arm 502 to commutate. After the reverse electromotive force stabilizes, the comparator 505 outputs a high level again to turn on the MOSFET switching unit 503, and the excitation current flows in reverse through the coil 3 to achieve reverse charging. This cycle is repeated to achieve a pulsed excitation current waveform with alternating forward and reverse saturation and to form an excitation magnetic field.

[0032] Specifically, such as Figure 5As shown, the upper bridge arm 501 includes a first MOSFET Q1, a second MOSFET Q2, a third MOSFET Q3A, and a fourth MOSFET Q3B; the lower bridge arm 502 includes a fifth MOSFET Q4, a sixth MOSFET Q5, a seventh MOSFET Q6A, and an eighth MOSFET Q6B. The drains of the first MOSFET Q1 and the second MOSFET Q2 are both electrically connected to the output of the power management sub-circuit 402. The gate of the first MOSFET Q1 is electrically connected to the drain of the third MOSFET Q3A, and the gate of the second MOSFET Q2 is electrically connected to the drain of the fourth MOSFET Q3B. The gates of the third MOSFET Q3A and the fourth MOSFET Q3B are both electrically connected to the absorption network 506. The source of the first MOSFET Q1 is connected to the coil... One end of coil 3, the source of the fourth MOSFET Q3B, the source of the fifth MOSFET Q4, and the source of the seventh MOSFET Q6A are electrically connected. The source of the second MOSFET Q2 is electrically connected to one end of coil 3, the source of the third MOSFET Q3A, the source of the sixth MOSFET Q5, and the source of the eighth MOSFET Q6B, respectively. The drain of the seventh MOSFET Q6A is electrically connected to the gate of the sixth MOSFET Q5. The drain of the eighth MOSFET Q6B is electrically connected to the gate of the fifth MOSFET Q4. The gates of the seventh MOSFET Q6A and the eighth MOSFET Q6B are both electrically connected to the absorption network 506. The drains of the fifth MOSFET Q4 and the sixth MOSFET Q5 are both electrically connected to the source of the MOSFET switching unit 503.

[0033] The absorption network 506 includes a first capacitor C1, a second capacitor C2, a first Zener diode D1, a second Zener diode D2, and a first resistor R1. The cathode of the first Zener diode D1 and one end of the first capacitor C1 are both electrically connected to the output of the power management sub-circuit 402. The anode of the first Zener diode D1 is electrically connected to the other end of the first capacitor C1, one end of the first resistor R1, the gate of the third MOSFET Q3A, and the gate of the fourth MOSFET Q3B, respectively. The cathode of the second Zener diode D2 and one end of the second capacitor C2 are both electrically connected to the other end of the first resistor R1, the gate of the seventh MOSFET Q6A, and the gate of the eighth MOSFET Q6B. The anode of the second Zener diode D2 and the other end of the second capacitor C2 are both grounded.

[0034] As shown in the attached diagram, all MOS transistors in the upper bridge arm 501 are PMOS transistors, and all MOS transistors in the lower bridge arm 502 are NMOS transistors.

[0035] Upon initial power-up, the fixed reference voltage input to the non-inverting input of comparator 505 is greater than the sampling voltage across sampling resistor 504. Comparator 505 outputs a high level, and MOSFET switching unit 503 is turned on, causing lower bridge arm 502 to turn on. Assuming the current path at this time is power supply - first MOSFET Q1 - coil 3 - sixth MOSFET Q5 - sampling resistor 504 - ground, the current in coil 3 increases linearly, and the long strip magnetic core 202 gradually enters the magnetization state.

[0036] As the current in coil 3 gradually increases, the strip magnetic core 202 reaches saturation, the inductance drops sharply, and the sampling voltage at sampling resistor 504 also increases until the sampling voltage is greater than the fixed reference voltage. The comparator 505 outputs a low level, which turns off the MOS transistor switching unit 503.

[0037] When MOSFET switching unit 503 is turned off, the current path of the lower bridge arm is cut off, and the first MOSFET Q1 and the sixth MOSFET Q5 are turned off. Coil 3 generates a reverse electromotive force, that is, the polarity of the induced voltage reverses. This reverse electromotive force conducts through the second MOSFET Q2 of the upper bridge arm and the fifth MOSFET Q4 of the lower bridge arm. This commutation process is jointly realized by the third MOSFET Q3A, the fourth MOSFET Q3B, the seventh MOSFET Q6A, the eighth MOSFET Q6B and the snubber network 506. After the commutation conduction, the output of comparator 505 will become high again after the reverse electromotive force stabilizes, and MOSFET switching unit 503 will conduct again. The current path becomes power supply - second MOSFET Q2 - coil 3 - fifth MOSFET Q4 - sampling resistor 504 - ground. At this time, the coil current increases in the reverse direction, and the strip magnetic core 202 is reverse magnetized until reverse saturation is reached. After reverse saturation, the voltage across sampling resistor 504 exceeds the fixed reference voltage, causing comparator 505 to output a low level, turning off MOSFET switching unit 503 again. This cycle repeats, creating alternating forward and reverse saturation magnetization in the strip core 202. Because the magnetization reverses immediately after each saturation cycle, the coil current waveform is as follows: Figure 6 The spike pulse waveform shown.

[0038] In the absorption network 506, the first Zener diode D1 and the second Zener diode D2 serve as freewheeling and clamping. When a reverse electromotive force (EMF) is generated, to suppress the EMF spike and prevent it from striking the MOSFET in the upper or lower bridge arm current loop, the first Zener diode D1 and the second Zener diode D2 provide a low-impedance high-voltage discharge path, thereby clamping the voltage across the MOSFET in the upper or lower bridge arm current loop to a safe level. The first capacitor C1 and the second capacitor C2 are connected in parallel with the first Zener diode D1 and the second Zener diode D2 respectively, used to charge and absorb the energy of the reverse EMF spike. The stored energy is then released as heat through the first resistor R1. The first resistor R1 also limits the charging current of the first capacitor C1 and the second capacitor C2; a large resistor, such as 100kΩ, is selected.

[0039] Reference Figure 4 As shown, the three-stage amplifier sub-circuit 404 has three different amplification branches. The amplification factor of the first amplification branch is less than that of the second amplification branch, and the amplification factor of the second amplification branch is less than that of the third amplification branch. The corresponding amplification branch is selected for amplification based on the magnitude of the excitation current difference ΔI. The three-stage amplifier sub-circuit 404 selectively amplifies the voltage signal ΔU corresponding to the current signal on coil 3 independently and sends them to the independent ADC channels of the MCU. Specifically, I_A_OUT1 serves as the first-stage amplification output with a lower amplification factor, used for amplifying larger current differences ΔI; I_A_OUT2 serves as the second-stage amplification output with a moderate amplification factor, used for amplifying smaller current differences ΔI; and I_A_OUT3 serves as the third-stage amplification output with a higher amplification factor, used for amplifying minute current differences ΔI. The MCU 401 automatically selects the appropriate ADC channel for sampling based on the range of the current to be measured, calculating the average value and then obtaining the difference within the positive and negative non-saturation time periods of the excitation current. The difference is proportional to the current to be measured. After conversion with the corresponding calibration coefficient and the number of coil turns, an accurate current measurement value is obtained.

[0040] like Figure 6 As shown, the pulsed excitation current waveform with alternating forward and reverse saturation includes a forward saturation segment 601, a forward unsaturated segment 603, a reverse saturation segment 602, and a reverse unsaturated segment 604 within a single cycle. When there is no current in the conductor under test, the durations of the forward saturation segment 601 and the reverse saturation segment 602 are equal, and the durations of the forward unsaturation segment 603 and the reverse unsaturation segment 604 are symmetrically equal. When there is current in the conductor under test, the durations of the forward unsaturation segment 603 and the reverse unsaturation segment 604 are not equal, and the excitation currents of the forward unsaturation segment 603 and the reverse unsaturation segment 604 generate a difference ΔI.

[0041] The conversion of the current difference ΔI is achieved by sampling resistor 504, which collects the current change in coil 3 in real time, converts the current signal into a voltage signal ΔV, and transmits it to the three-stage amplifier circuit. The three-stage amplifier circuit selects an appropriate amplification factor based on the approximate range of the current to be measured. In this embodiment, the three-stage amplifier sub-circuit 404 has three different amplification branches: the first amplification branch has an amplification factor of 10, the second amplification branch has an amplification factor of 50, and the third amplification branch has an amplification factor of 200. Based on the acquired amplified voltage signal, MCU 401 can deduce the excitation current difference ΔI between the forward and reverse unsaturated sections using Ohm's law.

[0042] The MCU401 samples the amplified unsaturated voltage signal through its integrated ADC module. The sampling interval is strictly limited to the middle region between the forward unsaturated segment 603 and the reverse unsaturated segment 604 to avoid signal abrupt interference at the edges of the two segments and ensure sampling accuracy. 80-100 sampling points are collected for each unsaturated segment. The MCU401 filters the collected sampling points to remove abnormal fluctuation data and ensures that stable average values ​​of the forward and reverse unsaturated voltages are obtained.

[0043] This invention achieves high-precision measurement of current over a wide range through a multi-stage amplification channel design and an automatic range selection mechanism. At the same time, through optimized mechanical structure and simplified circuit design, it ensures the stable and reliable operation of the fluxgate current sensor in high-temperature and high-interference environments in vehicles.

[0044] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A fluxgate current sensor, characterized in that, include: The front casing has a through-hole. The rear outer shell is provided with a second through hole coaxial with the first through hole, and the rear outer shell and the front outer shell together form a hollow cavity; The magnetic core unit is embedded in the cavity and arranged around the second through hole to acquire the current signal of the current conductor under test. The control circuit board, embedded in the cavity, is electrically connected to the magnetic core unit and is used to acquire and output the excitation current signal of the magnetic core unit. The first or second through hole allows the conductor carrying the current to be measured to pass through radially; the magnetic core unit includes only one coil; the control circuit board also drives the magnetic core unit to generate an excitation magnetic field.

2. A fluxgate current sensor according to claim 1, characterized in that, The magnetic core unit includes a strip magnetic core, a protective shell, and a coil. The strip magnetic core is arranged around the second through hole, and the protective shell is fitted on the outer surface of the strip magnetic core. The coil is wound on the outer surface of the protective shell to form a single winding structure, and the two ends of the coil extend out and are electrically connected to the control circuit board.

3. A fluxgate current sensor according to claim 2, characterized in that, The control circuit board includes an MCU, a power management sub-circuit, an H-bridge self-excitation sub-circuit, a three-stage amplifier sub-circuit, and a CAN communication sub-circuit. The power management sub-circuit is used to boost or buck the vehicle power supply for the MCU, H-bridge self-excitation sub-circuit, three-stage amplifier sub-circuit, and CAN communication sub-circuit. The H-bridge self-excitation sub-circuit is electrically connected to both ends of the coil to drive the coil to generate alternating positive and negative saturated pulsed excitation current waveforms and form an excitation magnetic field. This excitation magnetic field is superimposed on the magnetic field generated by the current in the conductor under test to form a voltage signal ΔU corresponding to the difference in excitation current ΔI. The three-stage amplifier sub-circuit is used to acquire the voltage signal ΔU corresponding to the difference in excitation current ΔI and amplify it. The amplified voltage signal is sent to the MCU. The MCU performs analog-to-digital conversion on the input amplified excitation current difference to obtain the current value under test, and sends it to the CAN communication sub-circuit. The CAN communication sub-circuit is used to output the current value under test via communication.

4. A fluxgate current sensor according to claim 3, characterized in that, The pulsed excitation current waveform with alternating forward and reverse saturation includes a forward saturation segment, a forward unsaturation segment, a reverse saturation segment, and a reverse unsaturation segment within a single cycle. When there is no current in the conductor under test, the durations of the forward saturation segment and the reverse saturation segment are equal, and the durations of the forward unsaturation segment and the reverse unsaturation segment are symmetrically equal. When there is current in the conductor under test, the durations of the forward unsaturation segment and the reverse unsaturation segment are not equal, and the excitation current of the forward unsaturation segment and the reverse unsaturation segment generates a difference ΔI.

5. A fluxgate current sensor according to claim 4, characterized in that, The H-bridge self-excited sub-circuit includes an upper bridge arm, a lower bridge arm, a MOSFET switching unit, a sampling resistor, and a comparator. The upper bridge arm is electrically connected to the output of the power management sub-circuit, and the common terminals of the upper and lower bridge arms are electrically connected to each other. The upper and lower bridge arms are each electrically connected to one end of a coil. The output terminal of the lower bridge arm is electrically connected to the drain of the MOSFET switching unit. The source of the MOSFET switching unit is electrically connected to one end of the sampling resistor and the inverting input terminal of the comparator. The other end of the sampling resistor is grounded. The gate of the MOSFET switching unit is electrically connected to the output terminal of the comparator. A fixed reference voltage is connected to the non-inverting input terminal of the comparator. When the H-bridge self-excited sub-circuit is powered on, the comparator... When the sampled voltage obtained from the sampling resistor is less than the fixed reference voltage, the comparator outputs a high level to turn on the MOSFET switching unit, and the excitation current flows through the coil to charge the long strip magnetic core. When the long strip magnetic core is saturated, the sampled voltage obtained from the sampling resistor by the comparator exceeds the fixed reference voltage, and the comparator outputs a low level to turn off the MOSFET switching unit. The coil switches to the discharge state and generates a reverse electromotive force to drive the upper and lower bridge arms to commutate. After the reverse electromotive force stabilizes, the comparator outputs a high level again to turn on the MOSFET switching unit, and the excitation current flows in the reverse direction through the coil to achieve reverse charging. This cycle is repeated to achieve a pulsed excitation current waveform with alternating forward and reverse saturation and to form an excitation magnetic field.

6. A fluxgate current sensor according to claim 5, characterized in that, The upper bridge arm includes a first MOSFET Q1, a second MOSFET Q2, a third MOSFET Q3A, and a fourth MOSFET Q3B; the lower bridge arm includes a fifth MOSFET Q4, a sixth MOSFET Q5, a seventh MOSFET Q6A, and an eighth MOSFET Q6B. The drains of the first MOSFET Q1 and the second MOSFET Q2 are both electrically connected to the output of the power management sub-circuit. The gate of the first MOSFET Q1 is electrically connected to the drain of the third MOSFET Q3A, and the gate of the second MOSFET Q2 is electrically connected to the drain of the fourth MOSFET Q3B. The gates of the third MOSFET Q3A and the fourth MOSFET Q3B are both electrically connected to the absorption network. The source of the first MOSFET Q1 is connected to one end of the coil. The sources of the fourth MOSFET Q3B, the fifth MOSFET Q4, and the seventh MOSFET Q6A are electrically connected. The source of the second MOSFET Q2 is electrically connected to one end of the coil, the source of the third MOSFET Q3A, the source of the sixth MOSFET Q5, and the source of the eighth MOSFET Q6B. The drain of the seventh MOSFET Q6A is electrically connected to the gate of the sixth MOSFET Q5. The drain of the eighth MOSFET Q6B is electrically connected to the gate of the fifth MOSFET Q4. The gates of the seventh MOSFET Q6A and the eighth MOSFET Q6B are both electrically connected to the absorption network. The drains of the fifth MOSFET Q4 and the sixth MOSFET Q5 are both electrically connected to the source of the MOSFET switching unit.

7. A fluxgate current sensor according to claim 6, characterized in that, The absorption network includes a first capacitor C1, a second capacitor C2, a first Zener diode D1, a second Zener diode D2, and a first resistor R1. The cathode of the first Zener diode D1 and one end of the first capacitor C1 are electrically connected to the output of the power management sub-circuit. The anode of the first Zener diode D1 is electrically connected to the other end of the first capacitor C1, one end of the first resistor R1, the gate of the third MOSFET Q3A, and the gate of the fourth MOSFET Q3B, respectively. The cathode of the second Zener diode D2 and one end of the second capacitor C2 are both electrically connected to the other end of the first resistor R1, the gate of the seventh MOSFET Q6A, and the gate of the eighth MOSFET Q6B. The anode of the second Zener diode D2 and the other end of the second capacitor C2 are both grounded.

8. A fluxgate current sensor according to claim 4, characterized in that, The three-stage amplifier sub-circuit has three different amplification branches. The amplification factor of the first amplification branch is less than that of the second amplification branch, and the amplification factor of the second amplification branch is less than that of the third amplification branch. The corresponding amplification branch is selected for amplification based on the magnitude of the difference in excitation current ΔI.

9. A fluxgate current sensor according to claim 3, characterized in that, The rear housing is provided with a male connector terminal on the end face away from the front housing. The CAN communication sub-circuit is embedded in the male connector terminal. The terminals of the CAN communication sub-circuit pass through the rear housing through the connector and communicate with the MCU.

10. A fluxgate current sensor according to claim 1, characterized in that, The front housing is provided with several buckles and plates, all of which extend radially along the first through hole. The thickness of the plate at the end furthest from the front housing is greater than the thickness at the other end. The rear housing edge is provided with several bosses and flanges, which extend radially along the rear housing. The buckles are provided with through slots, and the bosses pass through the slots. The flanges are provided with through stepped holes, and the plates pass through the stepped holes and abut against the end face of the stepped holes.

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