Magnetic Sensing Chip, Closed-Loop Feedback Current Sensor and Preparation Method Thereof

Abstract

Magnetic sensing chip, closed-loop feedback current sensor and its manufacturing method. The closed-loop feedback current sensor includes: a housing; a magnetic sensing chip and a signal processing circuit disposed within the housing. The magnetic sensing chip includes a magnetic sensing unit composed of magnetoresistive elements and a feedback coil disposed above the magnetic sensing unit. The feedback coil is a planar spiral structure etched from a conductive material, and the plane of the spiral is perpendicular to the sensitive direction of the magnetic sensing unit. The signal processing circuit includes a magnetic balance circuit and a current sampling circuit. The magnetic sensing chip is connected to a power supply through an input terminal and is connected to the magnetic balance circuit through an output terminal. The magnetic balance circuit is connected to the feedback coil to supply current to the feedback coil to generate a feedback magnetic field. The current sampling circuit is connected to the feedback coil to collect the current signal of the feedback coil and output it. The present invention integrates magnetoresistive elements and a feedback coil within the magnetic sensing chip, reducing the volume and weight of the closed-loop feedback current sensor.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensing measurement, and particularly relates to a magnetic sensing chip and a closed-loop feedback current sensor. Background Art

[0002] Current sensors are divided into two major types: open-loop sensors and closed-loop sensors. Open-loop current sensors use magnetic sensitive elements to generate an analog signal proportional to the measured current to achieve the purpose of measuring current. Open-loop current sensors have a simple structure and strong overload capacity, but the open-loop method results in poor linearity, which affects the measurement accuracy of the current sensor.

[0003] Compared with open-loop current sensors, closed-loop feedback current sensors have higher sensitivity and a wider measurement range. Closed-loop feedback current sensors include closed-loop feedback current sensors based on magnetic modulation and closed-loop feedback current sensors based on magnetic sensors.

[0004] For the closed-loop feedback current sensor based on magnetic modulation, its principle is to first carry the magnetic field signal of the measured current onto the self-excited generated fundamental wave through a modulation circuit, and then remove the carried fundamental wave by a demodulation circuit, leaving the magnetic field signal of the measured current; the signal processing circuit controls the magnitude of the magnetic field generated by the feedback coil winding by judging the magnetic field signal of the measured current to achieve the magnetic balance state of the current sensor; when the current sensor is in the magnetic balance state, the magnitude of the measured current can be calculated by measuring the current in the feedback coil winding. However, the closed-loop feedback current sensor based on magnetic modulation is usually only used to measure small DC signals, and its application scenarios are limited.

[0005] The closed-loop feedback current sensor based on magnetic sensors uses magnetic sensors to detect the magnetic field, and the signal processing circuit adjusts the current of the feedback coil winding according to the magnetic field detected by the magnetic sensors, so that the feedback magnetic field is equal in magnitude and opposite in direction to the magnetic field of the measured current, and the magnetic field near the magnetic sensors reaches the balance state; when the current sensor is in the magnetic balance state, the magnitude of the measured current can be calculated by measuring the current in the feedback coil winding. The closed-loop feedback current sensor based on magnetic sensors can measure AC and DC signals, has a wider application scenario, and its circuit structure is relatively simpler than that in the closed-loop feedback current sensor based on magnetic modulation. However, for this type of current sensor, a feedback coil winding needs to be wound outside the magnetic ring, and winding the feedback coil winding increases the volume and weight of the current sensor, and cannot meet the application requirements of miniaturization. Summary of the Invention

[0006] The purpose of the present invention is to provide a magnetic sensing chip with a small volume and light weight.

[0007] Another purpose of the present invention is to provide a closed-loop feedback current sensor with an even smaller volume and lighter weight.

[0008] To achieve the above first object, the present invention adopts the following technical solutions:

[0009] A magnetic sensing chip, comprising: a magnetic sensing unit composed of magnetoresistive elements, and a feedback coil disposed above the magnetic sensing unit, the feedback coil being a planar spiral structure etched from a conductive material, and a spiral plane of the feedback coil being perpendicular to a sensitive direction of the magnetic sensing unit.

[0010] Further, the magnetoresistive element is a TMR unit or a GMR unit or an AMR unit.

[0011] Further, a thermistor is further included, the thermistor being located on an electrode layer of the magnetoresistive element, the electrode layer being a ruthenium metal layer or having ruthenium metal in the electrode layer, the thermistor being a ruthenium resistor; the magnetoresistive element being a TMR unit or a GMR unit.

[0012] Further, the magnetoresistive elements are connected in a bridge to form a magnetic sensing unit of a full-bridge structure.

[0013] To achieve the above second object, the present invention adopts the following technical solutions:

[0014] A closed-loop feedback current sensor, comprising: a housing; a magnetic sensing chip disposed within the housing, the magnetic sensing chip being the aforementioned magnetic sensing chip; a signal processing circuit disposed within the housing, the signal processing circuit including a magnetic balance circuit and a current sampling circuit, the magnetic sensing chip being connected to a power supply through an input terminal and connected to the magnetic balance circuit through an output terminal; the magnetic balance circuit being connected to the feedback coil to supply a current to the feedback coil to generate a feedback magnetic field; the current sampling circuit being connected to the feedback coil to collect a current signal of the feedback coil and output it.

[0015] Further, the signal processing circuit further includes a first analog-to-digital converter, a digital-to-analog converter, a second analog-to-digital converter, and a micro-control processor; the micro-control processor is connected to the magnetic sensing unit through the first analog-to-digital converter, connected to the magnetic balance circuit through the digital-to-analog converter, and connected to the current sampling circuit through the second analog-to-digital converter.

[0016] Further, a temperature compensation circuit connected to the thermistor is further included; the feedback coil is connected to the temperature compensation circuit to output a current signal to the temperature compensation circuit, and the temperature compensation circuit is configured to compensate a detection result according to signals output by the thermistor and the feedback coil and then output it.

[0017] Further, it further includes a temperature compensation circuit connected to the thermistor; the feedback coil is connected to the temperature compensation circuit and outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is configured to compensate the detection result according to the signals output by the thermistor and the feedback coil and then output; the magnetic balance circuit includes a differential voltage sampling circuit and a push-pull emitter follower connected in sequence, the differential voltage sampling circuit is connected to the magnetic sensing unit, and the push-pull emitter follower is connected to the feedback coil; the temperature compensation circuit includes a temperature sampling circuit and an addition ratio circuit connected in sequence, the temperature sampling circuit is connected to the thermistor, and the addition ratio circuit is connected to the output end of the temperature sampling circuit and the output end of the current sampling circuit and outputs a measurement result.

[0018] Further, it further includes a temperature compensation circuit connected to the thermistor; the feedback coil is connected to the temperature compensation circuit and outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is configured to compensate the detection result according to the signals output by the thermistor and the feedback coil and then output; the magnetic balance circuit includes a push-pull emitter follower connected to the feedback coil; the temperature compensation circuit includes a temperature sampling circuit connected to the thermistor, and the micro control processor is connected to the push-pull emitter follower through the digital-to-analog converter and is connected to the temperature sampling circuit through the third analog-to-digital converter.

[0019] The present invention also provides a method for preparing a magnetic sensing chip, including the following steps:

[0020] Provide a substrate;

[0021] Deposit a lower electrode layer, a pinned layer, a non-magnetic layer, and a free layer on the substrate;

[0022] Etch out the magnetoresistive element region according to the layout;

[0023] Deposit an upper electrode layer, prepare an electrical connection structure, and electrically connect it to the magnetoresistive element;

[0024] Deposit a feedback coil layer, etch out the feedback coil with a planar spiral structure, and electrically connect the feedback coil;

[0025] Package the chip.

[0026] Further, when depositing the lower electrode layer, the lower electrode layer is prepared from ruthenium material;

[0027] According to the layout, etch out the magnetoresistive element region and the thermistor region;

[0028] After depositing the upper electrode layer, prepare an electrical connection structure and electrically connect it to the magnetoresistive element and the thermistor.

[0029] As can be seen from the above technical solutions, the present invention integrates a magnetoresistive element and a feedback coil into a magnetic sensing chip. Moreover, the feedback coil is a planar spiral structure arranged above the magnetic sensing unit, and the magnetic sensing unit is located on the axis of the feedback coil winding. The feedback coil winding can generate a stronger magnetic field at the magnetic sensing unit. At the same time, the feedback coil winding is a planar spiral structure, which is also beneficial to reducing the volume of the chip and the processing difficulty. The magnetoresistive element, feedback coil of the present invention and the magnetic balance link in the signal processing circuit outside the chip together constitute a closed-loop feedback current sensor. Since the feedback coil is integrated inside the sensor chip, it not only reduces the volume and weight of the closed-loop feedback current sensor.

[0030] In a preferred technical solution, a thermistor is integrated inside the magnetic sensing chip. The thermistor element is connected to the temperature compensation link outside the chip to form a temperature drift compensation circuit. Since the area where the thermistor collects temperature is closer to the area where the magnetic field is detected, the temperature information fed back by the thermistor element is more accurate, and it can more precisely reflect the temperature information of the detection area, thereby making a more accurate temperature drift compensation for the current sensor. Moreover, a ruthenium resistor is used as the thermistor element. Since the ruthenium element itself is used to prepare the tunnel junction magnetoresistive element, only a temperature detection area needs to be divided in the magnetic sensing chip and connected to the temperature compensation circuit. The original preparation process of the magnetic sensing chip remains basically unchanged, and no other equipment needs to be added, which is beneficial to controlling the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] In order to more clearly illustrate the embodiments of the present invention, the following will briefly introduce the drawings required for use in the embodiments or the description of the prior art. Obviously, the following drawings are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0032] Figure 1 It is a schematic structural diagram of Embodiment 1 of the present invention;

[0033] Figure 2 It is a circuit block diagram of Embodiment 1 of the present invention;

[0034] Figure 3 It is a schematic structural diagram of the magnetic sensing chip of Embodiment 1 of the present invention;

[0035] Figure 4 The circuit block diagram of Embodiment 2 of the present invention;

[0036] Figure 5 It is a circuit block diagram when the thermistor element and the temperature compensation circuit are not provided in Embodiment 1 of the present invention;

[0037] Figure 6This is the circuit block diagram when the thermal component and the temperature compensation circuit are not provided in Embodiment 2 of the present invention. Detailed implementation manners

[0038] To make the above and other objects, features, and advantages of the present invention more obvious, the embodiments of the present invention are hereinafter specifically exemplified and described in detail in conjunction with the accompanying drawings as follows.

[0039] Embodiment 1

[0040] Referring to Figure 1 and Figure 2 , the closed-loop feedback current sensor of this embodiment includes a housing 10 and a magnetic sensing chip 1 and a signal processing circuit 20 disposed in the housing 10. Among them, the signal processing circuit includes a magnetic balance circuit 2, a temperature compensation circuit 3, and a current sampling circuit 4. This embodiment has a circular opening at the center of the housing 10, and the conductor 21 to be measured can pass through the opening. The magnetic sensing chip 1 and the signal processing circuit 20 are respectively disposed on a circuit board. The magnetic sensing direction of the magnetic sensing chip 1 (magnetic sensing unit) is perpendicular to the conductor 21 to be measured, and the signal processing circuit 20 is electrically connected to the magnetic sensing chip 1 through pins or wires. In other embodiments, the housing may not be provided with an opening. The opening is provided at the center of the housing in this embodiment for convenient installation and fixation.

[0041] In this embodiment, a feedback coil and a thermistor are integrated in the magnetic sensing chip 1. The magnetic sensing chip 1 includes a magnetic sensing unit 1-1 composed of magnetic resistance elements, a feedback coil 1-2, and a thermistor 1-3. The magnetic sensing unit 1-1 is used to measure the magnetic field; the feedback coil 1-2 is used to generate a feedback magnetic field to cooperate with the magnetic sensing unit 1-1 to make the current sensor reach a magnetic balance state; the thermistor 1-3 is used to measure the temperature and collect temperature information for the temperature compensation circuit. The magnetic resistance element of this embodiment is a TMR unit. In addition to being a TMR unit, it can also be a GMR or AMR, etc.

[0042] As Figure 3As shown, in this embodiment, four groups of magnetoresistive elements (5, 6, 7, 8) are deposited on the substrate of the magnetic sensor chip 1 by magnetron sputtering technology, and four connecting terminals (12, 13, 15, 16) are provided. The structure of each group of magnetoresistive elements is the same, and they all include at least an upper electrode layer, a lower electrode layer, a pinned layer, a free layer and a non-magnetic layer. The non-magnetic layer is located between the pinned layer and the free layer. The upper electrode layer and the lower electrode layer are the two outermost layers of the magnetoresistive element. The magnetization direction of the pinned layer in the magnetoresistive element does not change with the change of the external magnetic field, and the magnetization direction of the free layer changes with the change of the external magnetic field. The resistance value of the magnetoresistive element changes with the change of the angle between the magnetization direction of the free layer and the magnetization direction of the pinned layer, thereby realizing the detection of the magnetic field. The magnetoresistive elements are bridge-connected to form a magnetic sensor unit 1-1 of a full-bridge structure, and a differential voltage signal is outputted to the outside. The magnetoresistive element is located on the bridge arm of the full-bridge structure. Each connecting terminal is connected to two adjacent bridge arms respectively. Among the four connection terminals, one pair of connection terminals (13, 15) are input terminals, and an external power supply provides a voltage drop for the magnetic sensor chip 1 through the input terminals, so that the full-bridge circuit is in a working state; the other pair of connection terminals (12, 16) are output terminals, and the magnetic sensor chip 1 outputs a differential voltage signal related to the magnetic field through the output terminals.

[0043] The thermistor of this embodiment is a ruthenium resistor 4 integrated on the substrate of the magnetic sensor chip 1. The ruthenium resistor 4 is used to collect temperature information of the magnetic field detection area. The ruthenium resistor 4 is connected to the temperature compensation circuit 3 through the connection terminals (10, 14). The ruthenium resistor 4 and the magnetic resistance element are deposited on the same substrate, but are respectively located in two independent areas on the substrate (magnetic sensor chip). Ruthenium is one of the materials for preparing the electrode layer and pinning layer of the tunnel junction magnetoresistance element (TMR). Since the pinning layer is thin, it is not suitable for preparing thermistors. Therefore, it is preferred to set the ruthenium resistor in the electrode layer. Compared with conventional thermistors made of platinum, copper, nickel and other materials, the thermistor is formed by the electrode layer, so that the thermistor is integrated into the magnetic sensor chip. On the one hand, the temperature collection area is closer to the magnetic field detection area, so that the temperature information fed back by the thermistor is more accurate, and the temperature information of the detection area can be more accurately reflected, so that the temperature compensation of the current sensor is more accurate; on the other hand, since the ruthenium element itself is used to prepare the tunnel junction magnetoresistance element, it is only necessary to divide an independent temperature detection area in the magnetic sensor chip and connect it to the temperature compensation circuit. The original preparation process of the magnetic sensor chip remains basically unchanged, and no other equipment needs to be added, which is conducive to controlling production costs and realizing miniaturized design. When the magnetoresistance element is a GMR, ruthenium material can also be added to the preparation material to integrate the thermistor into the chip.

[0044] The feedback coil 1-2 is a uniform planar spiral structure fabricated using the MEMS process (Microfabrication Process), and the feedback coil 1-2 is etched from a conductive material. The feedback coil 1-2 of the present invention has a planar structure, and compared with the existing feedback coil winding wound around a magnetic ring, the volume of the feedback coil is reduced. The feedback coil 1-2 is disposed (vertically) above the full-bridge structure (magnetic sensing unit 1-1) formed by the magnetoresistive element. The spiral plane of the feedback coil 1-2 is perpendicular to the sensitive direction of the magnetic sensing unit 1-1 (the sensitive direction of the magnetic sensing unit can be changed by changing the material or structure of the TMR). The two ends of the feedback coil 1-2 are connected to the magnetic balance circuit 2 and the temperature compensation circuit 3 through connection terminals (11, 17). The feedback current output by the magnetic balance circuit 1-2 flows through the connection terminals to the feedback coil 1-2, causing the feedback coil 1-2 to be in an operating state and generating a uniform magnetic field inside the coil. The feedback coil 1-2 outputs a current signal to the temperature compensation circuit 3.

[0045] As Figure 2 shown, the magnetic sensing unit 1-1 in the magnetic sensing chip 1 is connected to the magnetic balance circuit 2 through the output terminal. The magnetic balance circuit 2 of this embodiment includes a differential voltage sampling circuit 2-1 and a push-pull emitter follower 2-2 connected in sequence. The differential voltage sampling circuit 2-1 is used to collect the differential voltage signal V M . The push-pull emitter follower 2-2 is connected to the feedback coil 1-2, and it provides current for the feedback coil 1-2 to generate a feedback magnetic field H, so that the current sensor reaches a magnetic balance state. The push-pull emitter follower 2-2 generates a current I s output to the feedback coil 1-2 according to the differential voltage signal. The feedback coil 1-2 is connected to the temperature compensation circuit 3 through the current sampling circuit 4 and outputs a current signal to the temperature compensation circuit 3.

[0046] The temperature compensation circuit 3 of this embodiment includes a temperature sampling circuit 3-1 and an addition proportional circuit 3-2 connected in sequence. Among them, the temperature sampling circuit 3-1 is connected to the thermistor 1-3 (ruthenium resistor) and outputs a voltage signal V T proportional to the temperature information. The current sampling circuit 4 is connected to the feedback coil 1-2 to collect the current signal I S of the feedback coil 1-2, and converts the current signal I S in the feedback coil 1-2 into a voltage signal V S and outputs it to the temperature compensation circuit 3. The addition proportional circuit 3-2 is connected to the output terminal of the temperature sampling circuit 3-1 and the output terminal of the current sampling circuit 4, and adds and amplifies the voltage signal V T of the temperature sampling and the voltage signal V S of the current sampling to obtain the output signal V of the current sensor after temperature compensationo 。

[0047] The working principle of this embodiment will be described below in conjunction with Figure 1 :

[0048] In conjunction with Figure 1 As shown, when the current sensor measures, the conductor 21 to be measured passes through the opening on the housing 10. When there is current passing through the conductor 21 to be measured, a magnetic field H is generated around the conductor 21 to be measured P ; the magnetic sensing chip 1 detects the magnitude of the magnetic field at its location and outputs a differential voltage signal V M ; the magnetic balance circuit 2 collects the differential voltage signal V output by the magnetic sensing chip 1 M and adjusts the input current I of the feedback coil 1-2 S ; under the action of the current I S of the feedback coil 1-2, a feedback magnetic field is generated inside the coil; when the differential voltage signal V M is zero, the magnetic field generated by the conductor 21 to be measured is equal in magnitude and opposite in direction to the magnetic field generated by the feedback coil winding, that is, the internal magnetic flux of the feedback coil winding is zero.

[0049] The preparation method of the sensor chip of this embodiment is as follows:

[0050] Provide a substrate;

[0051] Deposit a lower electrode layer, a pinned layer, a non-magnetic layer and a free layer on the substrate. The lower electrode layer is prepared with ruthenium material;

[0052] According to the layout, etch out the magnetoresistive element area and the thermistor area;

[0053] Deposit an upper electrode layer and prepare an electrical connection structure, including connection terminals and wiring terminals connected to the magnetoresistive element, the thermistor and the feedback coil, and electrically interconnect the magnetoresistive element and the thermistor;

[0054] Deposit a feedback coil layer, etch out a feedback coil with a planar spiral structure, and connect the feedback coil to the wiring terminal;

[0055] Package the chip.

[0056] Embodiment 2

[0057] The differences between this embodiment and Embodiment 1 are as follows: In this embodiment, the circuit with an integration link in the signal processing circuit is replaced by digital signal processing to reduce the temperature drift caused by the integration circuit. The signal processing circuit 20 of this embodiment includes a first analog-to-digital converter 2-1, a push-pull emitter follower 2-2, a digital-to-analog converter 2-3, a current sampling circuit 4, a second analog-to-digital converter 2-5, a temperature sampling circuit 2-6, a third analog-to-digital converter 2-7, and a microcontroller processor 2-8. Among them, the push-pull emitter follower 2-2 constitutes a magnetic balance circuit, and the temperature sampling circuit 2-6 constitutes a temperature compensation circuit. The first analog-to-digital converter 2-1 is connected to the magnetic sensing unit 1-1 to collect the voltage signal V M , and convert the collected voltage signal into a digital signal and send it to the microcontroller processor 2-8. After processing the voltage signal V M , the microcontroller processor 2-8 outputs an instruction to the push-pull emitter follower 2-2 through the digital-to-analog converter 2-3 connected to the push-pull emitter follower 2-2. The push-pull emitter follower 2-2 is connected to the feedback coil winding 1-2 and provides current for the feedback coil winding 1-2 to generate a feedback magnetic field, so that the current sensor reaches a magnetic balance state. The feedback coil 1-2 is connected to the current sampling circuit 4, and the current sampling circuit 4 converts the current signal I S collected from the feedback coil 1-2 into a voltage signal V S , and converts the voltage signal V S into a digital signal through the second analog-to-digital converter 2-5 and transmits it to the microcontroller processor 2-8. The temperature sampling circuit 2-6 is connected to the thermistor 1-3, and the temperature sampling circuit 2-6 converts the collected voltage signal V T into a digital signal through the third analog-to-digital converter 2-7 and sends it to the microcontroller processor 2-8. The microcontroller processor 2-8 processes the voltage signal of temperature sampling and the voltage signal V S of current sampling to obtain the output signal D of the current sensor after temperature compensation.

[0058] The magnetic balance circuit and temperature compensation circuit of the present invention are the same as those in the current sensor using an ordinary thermistor for temperature compensation, which are not the invention points of the present invention and will not be elaborated here.

[0059] Setting a thermosensitive element and a temperature compensation circuit in the sensor can improve the measurement accuracy of the sensor, but the thermosensitive element and the corresponding temperature compensation circuit are not necessary. As Figure 5 shown, Figure 5 is the circuit block diagram when the thermosensitive element and the temperature compensation circuit are not set in Embodiment 1 of the present invention. Figure 6This is the circuit block diagram when the thermal element and temperature compensation circuit are not provided in Embodiment 2 of the present invention. In the absence of the thermal element and temperature compensation circuit, the magnetic sensing unit and the feedback coil form a closed-loop feedback inside the chip, and the detection of the current of the conductor to be measured can also be achieved.

[0060] When no thermistor is integrated in the sensor chip, the preparation method of the sensor chip is as follows:

[0061] Provide a substrate;

[0062] Deposit a lower electrode layer, a pinned layer, a non-magnetic layer, and a free layer on the substrate;

[0063] Etch out the magnetoresistive element region according to the layout;

[0064] Deposit an upper electrode layer, and prepare an electrical connection structure, including connection terminals and wiring terminals connected to the magnetoresistive element and the feedback coil, so that the magnetoresistive element is electrically interconnected;

[0065] Deposit a feedback coil layer, etch out the feedback coil with a planar spiral structure, and connect the feedback coil to the wiring terminal;

[0066] Package the chip.

[0067] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A magnetic sensing chip, characterized in that, Comprising: A magnetic sensing unit composed of magnetoresistive elements, and a feedback coil disposed above the magnetic sensing unit. The feedback coil is a planar spiral structure etched from a conductive material, and the plane of the spiral of the feedback coil is perpendicular to the sensitive direction of the magnetic sensing unit; The magnetic sensing chip includes a substrate, on which a lower electrode layer, a pinned layer, a non-magnetic layer, and a free layer are deposited, and a magnetoresistive element region and a thermistor region are etched. The thermistor region is located in the lower electrode layer. The lower electrode layer is a ruthenium metal layer or contains ruthenium metal in the electrode layer. The thermistor region forms a thermistor, and the thermistor is a ruthenium resistor.

2. The magnetic sensing chip according to claim 1, wherein: The magnetoresistive element is a TMR unit or a GMR unit or an AMR unit.

3. The magnetic sensing chip according to claim 1, wherein: The magnetoresistive elements are connected in a bridge to form a magnetic sensing unit with a full-bridge structure.

4. A closed-loop feedback current sensor, characterized in that, Comprising: A housing; A magnetic sensing chip disposed in the housing, and the magnetic sensing chip is the magnetic sensing chip according to any one of claims 1 to 3; A signal processing circuit disposed in the housing. The signal processing circuit includes a magnetic balance circuit and a current sampling circuit. The magnetic sensing chip is connected to a power supply through an input terminal and is connected to the magnetic balance circuit through an output terminal. The magnetic balance circuit is connected to the feedback coil to provide a current to the feedback coil to generate a feedback magnetic field. The current sampling circuit is connected to the feedback coil to collect the current signal of the feedback coil and output it.

5. The closed-loop feedback current sensor according to claim 4, wherein: The signal processing circuit further includes a first analog-to-digital converter, a digital-to-analog converter, a second analog-to-digital converter, and a microcontroller processor. The microcontroller processor is connected to the magnetic sensing unit through the first analog-to-digital converter, is connected to the magnetic balance circuit through the digital-to-analog converter, and is connected to the current sampling circuit through the second analog-to-digital converter.

6. The closed-loop feedback current sensor according to claim 4 or 5, characterized in that: It further includes a temperature compensation circuit connected to the thermistor. The feedback coil is connected to the temperature compensation circuit to output a current signal to the temperature compensation circuit. The temperature compensation circuit is used to compensate the detection result according to the signals output by the thermistor and the feedback coil and then output.

7. The closed-loop feedback current sensor according to claim 4, wherein: It further includes a temperature compensation circuit connected to the thermistor. The feedback coil is connected to the temperature compensation circuit to output a current signal to the temperature compensation circuit. The temperature compensation circuit is used to compensate the detection result according to the signals output by the thermistor and the feedback coil and then output; The magnetic balance circuit includes a differential voltage sampling circuit and a push-pull emitter follower connected in sequence. The differential voltage sampling circuit is connected to the magnetic sensing unit, and the push-pull emitter follower is connected to the feedback coil; The temperature compensation circuit includes a temperature sampling circuit and an addition proportional circuit connected in sequence. The temperature sampling circuit is connected to the thermistor, and the addition proportional circuit is connected to the output end of the temperature sampling circuit and the output end of the current sampling circuit and outputs a measurement result.

8. The closed-loop feedback current sensor according to claim 5, characterized in that: It further includes a temperature compensation circuit connected to the thermistor; the feedback coil is connected to the temperature compensation circuit and outputs a current signal to the temperature compensation circuit, and the temperature compensation circuit is configured to output the detection result after compensation according to the signals output by the thermistor and the feedback coil; The magnetic balance circuit includes a push-pull emitter follower connected to the feedback coil; the temperature compensation circuit includes a temperature sampling circuit connected to the thermistor, and the micro control processor is connected to the push-pull emitter follower through the digital-to-analog converter and is connected to the temperature sampling circuit through the third analog-to-digital converter.

9. The method for preparing a magnetic sensing chip according to any one of claims 1 to 3, characterized in that It includes the following steps: Provide a substrate; Deposit a lower electrode layer, a pinned layer, a non-magnetic layer and a free layer on the substrate; Etch out the magnetoresistive element region and the thermistor region according to the layout; Deposit an upper electrode layer, prepare an electrical connection structure, and electrically connect to the magnetoresistive element and the thermistor; Deposit a feedback coil layer, etch out the feedback coil with a planar spiral structure, and make electrical connection to the feedback coil; Package the chip.

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