CN116430100A

CN116430100A - Weak current sensor signal processing circuit based on TMR

Info

Publication number: CN116430100A
Application number: CN202310575131.1A
Authority: CN
Inventors: 张巨锋; 李伟; 陈忠斌; 刘鹏; 裴蕴智
Original assignee: Hylight Technology Co ltd; East China Jiaotong University
Current assignee: Hylight Technology Co ltd; East China Jiaotong University
Priority date: 2023-05-22
Filing date: 2023-05-22
Publication date: 2023-07-14

Abstract

The invention belongs to the field of current sensors, and particularly relates to a high-precision high-sensitivity TMR weak current sensor signal processing circuit. The signal processing circuit comprises a power circuit module, a TMR sensor chip, an instrument amplifying circuit, a filter circuit, a bias zero setting circuit, a power amplifying circuit, a feedback circuit, a sampling circuit and the like. The weak current to be measured generates a magnetic field, and under the action of an externally added magnetic focusing ring and a feedback coil, the closed loop structure type measurement is realized through the circuit processing part of the invention, and the accurate measurement of the current to be measured is realized through extracting, amplifying, filtering, sampling and the like of signals through a TMR sensor chip, an instrument amplifying circuit, a filtering circuit, a bias zero setting circuit, a power amplifying circuit, a feedback circuit, a sampling circuit and the like, meanwhile, the influence of external interference factors on the measurement is greatly reduced through the closed loop structure, and the high-precision and high-sensitivity measurement requirements of the sensor on the weak current measurement are realized.

Description

Weak current sensor signal processing circuit based on TMR

Technical Field

The invention belongs to the field of current sensors, and particularly relates to a weak current sensor signal processing circuit based on a tunneling magneto-resistance effect.

Background

Current sensors are an important branch of the modern sensor industry, and with the steady rapid development of science and technology, the acquisition of information data has very important significance in the internet informatization age nowadays. In particular, although the weak signal is acquired with great difficulty, the weak signal has great value in practical application. In recent years, detection of weak current is widely used in the fields of signal processing, measurement technology, communication technology, information technology and the like, and development of related fields is greatly promoted.

The study of the current sensor can be divided according to the measurement mode and the measurement principle, wherein the study can be divided into contact measurement and non-contact measurement according to the measurement mode; the principle of measurement can be divided into three main categories based on ohm's law, ampere loop law and other indirect measurement techniques. The current divider based on ohm's law is the only type of contact current sensor, and the other current sensors are all non-contact current sensors. The non-contact current sensor is divided according to the principle, wherein the current sensor based on ampere loop law is divided into two modes of directly measuring magnetic induction intensity B and Faraday electromagnetic induction law measurement. The current sensor for directly measuring the magnetic induction intensity B comprises a Hall current sensor, a fluxgate current sensor and a magnetoresistive current sensor; there are rogowski coils and current transformers applying faraday's law of electromagnetic induction. Other indirect measurement techniques current sensors mainly use magnetic fields in combination with other physical principles or effects for measurement. These current sensors all have their own most suitable application scenario.

The current divider based on ohm's law belongs to access type measurement, and has the advantages of low cost and convenient application; but it has thermal stability error, and the current loss is big when measuring, does not have electric insulation, has the safety problem and measurement accuracy is relatively low. The current transformer is divided into an ac current transformer and a dc current transformer. The alternating current transformer has the advantages of high stability and high breakdown voltage resistance, but is not suitable for measuring current with too high or too low frequency, and can generate large errors. The direct current transformer has the defects that the current to be measured cannot be too large, and the structure is inconvenient to install and detach. The current sensor of the Rogowski coil has no saturation characteristic of an iron core, has no hysteresis effect, has the advantages of high breakdown voltage, small volume, low price and easy installation, is particularly suitable for measuring high-frequency current, large current and transient current, but the current sensor of the Rogowski coil which is developed at present cannot drive some common follow-up equipment and is also easily influenced by external interference magnetic fields, thus definitely limiting the application of the sensor. The current precision level of the open loop structure of the Hall current sensor is 1.0 level, the closed loop structure has higher precision, and the precision level is 0.1 level or higher. The limitation is that it is not suitable for measuring too large or too small currents, the breakdown voltage is low, and the closed loop structure needs to improve the driving capability of the driving circuit when measuring large currents.

The current sensors are not suitable for weak current measurement study due to the limitation of the defects. The remaining classes of sensors are described below for weak current studies. Firstly, the application of the fluxgate current sensor is relatively mature, and the fluxgate current sensor is also widely applied to the weak current measurement. The fluxgate current sensor measures a magnetic field by utilizing nonlinear current of a magnetized iron body in a saturation region, and the structure of the fluxgate current sensor comprises a magnetic core, an exciting coil and an induction coil, and the structure of the fluxgate is various according to different requirements. The current measurement range is in the mA-A level, and the resolution is 10uA-100uA. Compared with the sensor mentioned before, the precision is improved, and the sensor has the advantages of low zero drift, high resolution and sensitivity, large bandwidth, high response speed and the like, but has high cost, is inconvenient to install and has complex manufacturing process.

Current sensors based on the magneto-resistive effect have also found wide application in conjunction with the discovery of the magneto-resistive effect, including anisotropic magneto-resistive current (AMR) based sensors, giant magneto-resistive current sensors (GMR) based, tunneling magneto-resistive effect based current sensors (TMR) based, three types. Compared with other sensors, the current sensor based on the magneto-resistance effect has the advantages of greatly improved performance, wider application, low nonlinearity, wide linear range, quick response and frequency range reaching DC-1000kHz, but has the limitations of temperature drift, zero drift, large power consumption and the like, and needs to be optimized and improved. Several types of elements, AMR, GMR and TMR are now in practical use, in particular in current sensors. Where the sensitivity of AMR, GMR, etc. elements is relatively high, but the linear range is not sufficient. The TMR current sensor has more obvious advantages in practical application, and has relatively higher sensitivity and relatively better linearity. However, how to use TMR current sensors to achieve high accuracy measurement of weak currents with reasonable circuit designs still faces challenges.

Disclosure of Invention

The invention aims to provide a TMR-based weak current sensor signal processing circuit with high precision and high sensitivity. The circuit comprises a power circuit module, a TMR current sensor chip, an instrument amplifying circuit, a filter circuit, a bias zero setting circuit, a power amplifying circuit, a feedback circuit, a sampling circuit and the like. The weak current to be measured generates a magnetic field, and under the action of the externally-added magnetic focusing ring and the feedback coil, closed-loop structure type measurement is realized through the circuit processing part, the signal is extracted, amplified, filtered, sampled and the like to realize accurate measurement of the current to be measured, and meanwhile, the closed-loop structure also greatly reduces the influence of external interference factors on measurement, so that the measurement requirements of the sensor on the high precision and the high sensitivity of the weak current measurement are realized.

In order to achieve the above object, the technical scheme of the present invention is as follows.

The weak current sensor signal processing circuit based on TMR comprises a power circuit module, a bias zero setting circuit, a TMR sensor chip, an instrument amplifying circuit, a filter circuit, a power amplifying circuit, a feedback circuit and a sampling circuit, wherein the power circuit module is respectively and electrically connected with the TMR sensor chip and the bias zero setting circuit, the TMR sensor chip and the bias zero setting circuit are both electrically connected with the instrument amplifying circuit, the instrument amplifying circuit is electrically connected with the filter circuit, the filter circuit is electrically connected with the power amplifying circuit, the power amplifying circuit is electrically connected with the feedback circuit, and the feedback circuit is respectively and electrically connected with the sampling circuit and the TMR sensor chip; the TMR sensor chip is used for collecting and converting magnetic field signals; the power circuit module can realize the conversion from unipolar voltage to bipolar voltage and meet the power supply stability; the bias zeroing circuit is used for zeroing a bias voltage signal generated by the TMR sensor chip; the instrument amplifying circuit is used for amplifying the output signal of the TMR current sensor chip; the filter circuit is used for carrying out filter processing on the signals and eliminating the interference of spurious signals; the power amplifying circuit is used for amplifying the power of the front-end signal so as to drive the feedback coil to operate; the feedback circuit is used for feeding back the formation of current; the sampling circuit is used for obtaining the voltage of the sampling resistor and indirectly knowing the magnitude of the feedback current.

Further, the power supply parts VCC and VEE of the circuit are provided by an external power supply, the 1 pin of the integrated chip U6 of the power supply circuit module is respectively connected with one end of an inductor L3 and one end of a capacitor C26, the other end of the inductor L3 is respectively connected with the positive voltage end VCC and one end of a capacitor C25, the other end of the capacitor C25 and the 2 pin of the integrated chip U6 are grounded, the other end of the capacitor C26 is connected with one end of a capacitor C27, and the other end of the capacitor C27 is grounded; the 6 pin of the integrated chip U6 is respectively connected with one end of an inductor L2 and one end of a capacitor C21, the other end of the capacitor C21 is grounded, the other end of the inductor L2 is respectively connected with a positive voltage end VCC and one end of a capacitor C22, and the other end of the capacitor C22 is grounded; the 4 pin of the integrated chip U6 is respectively connected with one end of an inductor L4 and one end of a capacitor C23, the other end of the capacitor C23 is grounded, the other end of the inductor L4 is respectively connected with a negative voltage end VEE and one end of a capacitor C24, and the other end of the capacitor C24 is grounded; the 5-pin five of the integrated chip U6 is grounded.

Further, the instrument amplifying circuit comprises a front end amplifying circuit and a secondary signal amplifying circuit; the filter circuit comprises a resistor R2, a capacitor C3, a capacitor C7, a resistor R12 and a capacitor C9 which are connected with the front-end amplifying circuit, and a resistor R19, a capacitor C11, a filter capacitor C13, a resistor R24 and a capacitor C15 which are connected with the secondary signal amplifying circuit.

Further, in the front-end amplifying circuit, the 3 pin of the operational amplifier U2A is connected to one end of the resistor R2, one end of the capacitor C3 and one end of the capacitor C7, the other end of the resistor R2 is connected to the SIGNAL input point SIGNAL1+, the other end of the capacitor C3 is grounded, and the other end of the capacitor C7 is connected to the 5 pin of the operational amplifier U2B; the pin 5 of the operational amplifier U2B is also connected with one end of a resistor R12 and one end of a capacitor C9 respectively, the other end of the capacitor C9 is grounded, and the other end of the resistor R12 is connected with a SIGNAL input point Signal 1-. The 2 pin of the operational amplifier U2A is respectively connected with one ends of a resistor R8 and a resistor R5, the other end of the resistor R5 is connected with a SIGNAL output point SIGNAL < 2+ >, and meanwhile, a capacitor C5 is connected in parallel on the resistor R5; the other end of the resistor R8 is respectively connected with one end of the resistor R9 and the 6 pin of the operational amplifier U2B, the other end of the resistor R9 is connected with the SIGNAL output point Signal2-, and meanwhile, a capacitor C8 is connected in parallel with the resistor R9. The 5-pin serial resistor R1 of the operational amplifier U2A is connected with the positive voltage end VCC, and the 1-pin of the operational amplifier U2A is connected with the SIGNAL output point SIGNAL < 2+ >; the 7 pin of the operational amplifier U2B is connected with the SIGNAL output point Signal 2-. The 3 pin of the follower U3A is respectively connected with one end of a resistor R4 and one end of a resistor R6, the other end of the resistor R4 is connected with a SIGNAL output point SIGNAL2+, and the other end of the resistor R6 is connected with the SIGNAL output point SIGNAL 2-; the 2 pin of the follower U3A is respectively connected with the 3 pin of the voltage stabilizing tube Q1, the 2 pin of the voltage stabilizing tube Q2 and the SIGNAL input point SIGNAL0, the 2 pin of the voltage stabilizing tube Q1 is connected with the capacitor C1 in series and then grounded, the 1 pin of the voltage stabilizing tube Q1 is respectively connected with one end of the resistor R3 and one end of the resistor R7, the other end of the resistor R3 is connected with one end of the 3 pin of the voltage stabilizing tube Q1 and one end of the resistor R10, the 3 pin of the voltage stabilizing tube Q1 is connected with the 2 pin of the voltage stabilizing tube Q2, the other end of the resistor R10 is respectively connected with one end of the resistor R11 and the 1 pin of the voltage stabilizing tube Q2, and the other end of the resistor R11 is respectively connected with the 3 pin of the voltage stabilizing tube Q2, one end of the capacitor C10, one end of the resistor R15 and the 4 pin of the operational amplifier U2A; the other end of the capacitor C10 is grounded, and the other end of the resistor R15 is connected to the negative voltage terminal VEE. The 1 pin of the follower U3A is connected with a SIGNAL input point SIGNAL 0; the 4 pin of the follower U3A is respectively connected with the negative voltage end VEE and one end of the capacitor C6, and the other end of the capacitor C6 is grounded; the 5 pin of the follower U3A is respectively connected with the positive voltage end VCC and one end of the capacitor C2, and the other end of the capacitor C2 is grounded; the 4 pin of the operational amplifier U2B is connected to the capacitor C10, and the 8 pin of the operational amplifier U2B is connected to the capacitor C1.

Further, in the secondary signal amplifying circuit, an adjustable resistor R17 is connected in parallel outside the 1 pin and the 8 pin of the integrated chip U4 and is used for setting the gain of the whole circuit; the 2 pin of the integrated chip U4 is respectively connected with one end of a capacitor C11, one end of a filter capacitor C13 and one end of a resistor R19, the other end of the resistor R19 is connected with a SIGNAL output point SIGNAL2-, and the other end of the filter capacitor C13 is grounded; the 3 pin of the integrated chip U4 is respectively connected with one end of a capacitor C15, the other end of a filter capacitor C13 and one end of a resistor R24, the other end of the resistor R24 is connected with a SIGNAL output point SIGNAL < 2+ >, and the other end of the capacitor C15 is grounded; the 4 pin of the integrated chip U4 is respectively connected with one end of a resistor R26 and one end of a capacitor C16, the other end of the resistor R26 is connected with a-5V power supply end, and the other end of the capacitor C16 is grounded; the 5 pin of the integrated chip U4 is used as a REF1 pin, and the REF1 pin is connected with a resistor R27 in series and then grounded; the pin 7 of the integrated chip U4 is respectively connected with one end of a resistor R22 and one end of a capacitor C14, the other end of the resistor R22 is connected with a +5V power supply end, and the other end of the capacitor C14 is grounded; the 6 pins of the integrated chip U4 are the outputs vout11.

Further, in the bias zeroing circuit, the 5 pin of the operational amplifier U5A is respectively connected with one end of a resistor R21 and one end of a capacitor C12, the other end of the capacitor C12 is grounded, the other end of the resistor R21 is connected with the adjusting end of an adjustable resistor R20, one end of the adjustable resistor R20 is connected with a resistor R16 in series and then connected with a positive voltage end VCC, and the other end of the adjustable resistor R20 is connected with a resistor R28 in series and then connected with a negative voltage end VEE; meanwhile, a resistor R18 and a resistor R25 which are connected in series are connected in parallel outside the adjustable resistor R20. The

pins

6 and 7 of the operational amplifier U5A are connected with the resistor R23 in series and then connected with the pin REF1 of the integrated chip U4. The 8 pin of the operational amplifier U5A is connected with a positive voltage end VCC; the 4 pin of the operational amplifier U5A is connected to the negative voltage terminal VEE.

Further, the power amplifying circuit is provided with an operational amplifier U6A, and the feedback circuit comprises a feedback coil J1 and a sampling resistor R32; the 3 pin of the operational amplifier U6A is respectively connected with one end of a resistor R29 and one end of a capacitor C29, the other end of the capacitor C29 is grounded, and the other end of the resistor R29 is connected with the output vout11 of the secondary signal amplifying circuit; the 1 foot and the 2 foot of operational amplifier U6A are connected with the one end of resistance R30, and the other end of resistance R30 is connected with feedback coil J1 one end, and feedback coil J1's the other end is connected with sampling resistance R32 one end, and sampling resistance R32 other end ground connection. The 8 pin of the operational amplifier U6A is respectively connected with one end of the capacitor C17 and the positive voltage end VCC, and the other end of the capacitor C17 is grounded; the 4 pin of the operational amplifier U6A is connected to one end of the capacitor C19 and the negative voltage terminal VEE, respectively, and the other end of the capacitor C19 is grounded.

Further, the sampling circuit is provided with an operational amplifier U7A, the 5 pin of the operational amplifier U7A is connected with one end of a capacitor C20, and the other end of the capacitor C20 is grounded; the pin 6 of the operational amplifier U7A is respectively connected with one ends of a resistor R33 and a resistor R34, the other end of the resistor R34 is grounded, the other end of the resistor R33 is connected with one end of a test port J2, the pin 7 of the operational amplifier U7A is also connected with one end of the test port J2, and the other end of the test port J2 is grounded. The 8 pin of the operational amplifier U7A is connected with the positive voltage end VCC; the 4 pin of the operational amplifier U7A is connected to the negative voltage terminal VEE.

The TMR weak current sensor circuit provided by the invention meets the functional requirements of each module to the greatest extent through the analysis of each module and the design of the circuit, and meets the functional requirements of each circuit module after connection. The weak current to be measured generates a magnetic field, and under the action of an externally added magnetic focusing ring and a feedback coil, closed-loop structure type measurement is realized through a circuit processing part, signals are extracted, amplified, filtered, sampled and the like to realize accurate measurement of the current to be measured, the influence of external interference factors on measurement is greatly reduced by a closed-loop structure, and the measurement requirements of a sensor on high precision and high sensitivity of weak current measurement are realized; the invention provides a solution for the circuit structure design of the TMR sensor in weak current measurement and how to realize the low-error and high-sensitivity TMR weak current sensor design through the circuit design.

The circuit part design scheme of the TMR weak current sensor provides reference for solving the problem that the TMR sensor is applied to weak current measurement, and the schematic block diagram of a sensor system of the TMR current sensor design aiming at a closed loop structure type meets the functional requirements of all modules to the greatest extent through the analysis of all modules and the design of circuits, and meets the functional requirements of all circuit modules after connection. The key of the invention is the application of isolating the power supply of the power supply module, the design of the circuit of the amplifying part of the instrument, and the design requirement of high sensitivity performance of the TMR weak current sensor can be met as far as possible through the design of the circuit and the chip selection.

Drawings

Fig. 1 is a schematic block diagram of a signal processing system of a closed loop structure type TMR weak current sensor of the invention.

Fig. 2 is a schematic diagram of a circuit for converting unipolar voltage into bipolar voltage in a power circuit module of the signal processing circuit of the present invention.

Fig. 3 is a schematic diagram of a front-end amplifying circuit of a TMR-based weak current sensor signal processing circuit of the present invention.

Fig. 4 is a schematic diagram of a secondary signal amplifying circuit of the TMR-based weak current sensor signal processing circuit of the present invention.

Fig. 5 is a schematic diagram of a bias zeroing circuit of the TMR-based weak current sensor signal processing circuit of the present invention.

Fig. 6 is a schematic diagram of an operational amplifier driving circuit and a feedback circuit of the TMR-based weak current sensor signal processing circuit of the present invention.

Fig. 7 is a schematic diagram of a sampling circuit of a TMR-based weak current sensor signal processing circuit of the present invention.

Detailed Description

In order that the above-recited objects, features and advantages of the present invention will be more clearly understood, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present invention, however, the present invention may be practiced in other ways than those described herein, and therefore the present invention is not limited to the specific embodiments disclosed below.

The invention provides a weak current sensor signal processing circuit based on TMR, which comprises a power supply circuit module, a TMR current sensor chip, an instrument amplifying circuit, a filter circuit, a bias zero setting circuit, a power amplifying circuit, a feedback circuit and a sampling circuit, as shown in figure 1. The power supply is an important part in the circuit, the normal work of the TMR chip is not powered off, the chips needed by other part processing circuits are not powered off, the high-precision measured chip has higher requirements on the stability of the power supply voltage, the performance of the whole circuit is directly influenced by the advantages and disadvantages of the power supply performance, the design of the power supply module needs to consider the stability of the power supply, and the interference problem of the power supply end on the subsequent processing circuits. The selection of the TMR current sensor chip needs to be considered in combination with the requirements of the designed sensor on the aspects of sensitivity, noise floor, sensitive axis and the like, and meanwhile, the size of the chip relates to the design of the gap size of the magnetic ring, and the sensitivity of the designed sensor is influenced, so that the TMR current sensor chip is also in the category of consideration.

The instrument amplifying circuit mainly plays a role in amplifying the output signal of the TMR current sensor chip. The filter circuit mainly filters signals to eliminate the interference of spurious signals and also determines the frequency range and the bandwidth of the sensor. Because the TMR chip adopts a bridge structure, the four initial values of the resistors in the TMR chip cannot be guaranteed to be completely consistent due to the limitation of the process, and meanwhile, the TMR chip is influenced by surrounding stray magnetic fields and the like, and the fixed output bias voltage can influence the output result, so that the bias zero setting circuit is designed to offset the inherent bias. The power amplification circuit mainly considers that the structure of the closed-loop TMR current sensor can relate to a feedback coil, an output signal of the front end is required to drive the coil, and meanwhile, the feedback circuit is mainly in a series connection and grounding mode of the feedback coil and a sampling resistor, and mainly relates to the number of turns of the coil and the selection of the resistance value of the sampling resistor.

Fig. 2 is a schematic diagram of a circuit for converting unipolar voltage of a power circuit module into bipolar voltage, wherein U6 is an integrated chip suitable for circuit design situations with relatively stable voltage of an input power supply, isolation between input and output, and low requirements on stability of output voltage and ripple noise. In the embodiment, the integrated chip U6 is of the type A2409S-2WR3, and is of a constant voltage input, isolating non-stabilized positive and negative double-circuit output, and has sustainable short circuit protection and high power density. In order to further reduce input and output ripples, the input and output ends of the integrated chip U6 are respectively connected with a proper capacitance filter network, so that the ripple interference is reduced by filtering, the transformation from unipolar voltage to bipolar voltage is realized, and the power supply stability is met.

As shown in fig. 2, the power supply portions VCC and VEE of the circuit are provided by an external power supply, the 1 pin of the integrated chip U6 of the power circuit module is connected with one end of the inductor L3 and one end of the capacitor C26 respectively, the other end of the inductor L3 is connected with the positive voltage end VCC and one end of the capacitor C25 respectively, the other end of the capacitor C25 and the 2 pin of the integrated chip U6 are grounded, the other end of the capacitor C26 is connected with one end of the capacitor C27, and the other end of the capacitor C27 is grounded; the 6 pin of the integrated chip U6 is respectively connected with one end of an inductor L2 and one end of a capacitor C21, the other end of the capacitor C21 is grounded, the other end of the inductor L2 is respectively connected with a positive voltage end VCC and one end of a capacitor C22, and the other end of the capacitor C22 is grounded; the 4 pin of the integrated chip U6 is respectively connected with one end of an inductor L4 and one end of a capacitor C23, the other end of the capacitor C23 is grounded, the other end of the inductor L4 is respectively connected with a negative voltage end VEE and one end of a capacitor C24, and the other end of the capacitor C24 is grounded; the 5 pin of the integrated chip U6 is grounded. The inductor L3 and the capacitor C25 at one side of the integrated chip U6 form a simple filter circuit, and a filter network is also arranged at the output end part of the integrated chip U6, so that ripple interference is reduced through common filtering, and power supply stability is improved.

In this embodiment, the meter amplification circuit includes a front-end amplification circuit and a secondary signal amplification circuit. The filter circuit comprises a resistor R2, a capacitor C3, a capacitor C7, a resistor R12 and a capacitor C9 which are connected with the front-end amplifying circuit, and a resistor R19, a capacitor C11, a filter capacitor C13, a resistor R24 and a capacitor C15 which are connected with the secondary signal amplifying circuit.

Fig. 3 is a schematic diagram of a front-end amplifying circuit, which includes an operational amplifier U2A, an operational amplifier U2B, and a follower U3A. The floating common mode bootstrap design is adopted, so that the common mode rejection ratio is improved. If the common reference point of the positive and negative power supplies of the operational amplifier U2A and the operational amplifier U2B is not grounded, but is connected to the common mode voltage equipotential point, the output common mode signal is zero for the operational amplifier U2A and the operational amplifier U2B, so that common mode interference is eliminated. According to this idea, in this embodiment, the SIGNALs SIGNAL1+ and SIGNAL 1-input from both ends are filtered by a simple filter circuit formed by a resistor R2 and a capacitor C3 and a simple filter circuit formed by a resistor R12 and a capacitor C9, and then amplified by operational amplifiers U2A and U2B, and on this basis, the power supplies of the operational amplifiers U2A and U2B are respectively supplied by a regulator Q1 and a regulator Q2, so that a common reference point is subjected to floating processing and connected to the output point of the follower U3A. The common-mode voltage generated by the input SIGNAL at the two points of SIGNAL1 and SIGNAL1 is connected to the center point of the floating power supply through the follower U3A, so that the power supply voltage is changed along with the common-mode voltage, the common-mode SIGNAL is counteracted, and the common-mode SIGNAL rejection ratio of the circuit is increased. Meanwhile, the Shield0 signal is used as a shielding layer of the input electrode wire, so that the purpose of common mode driving is achieved. The operational amplifier U2A, the operational amplifier U2B and the follower U3A all adopt TLC2272 chips.

As shown in fig. 3, in the front-end amplifying circuit, the 3 pin of the operational amplifier U2A is connected to one end of the resistor R2, one end of the capacitor C3 and one end of the capacitor C7, the other end of the resistor R2 is connected to the SIGNAL input point SIGNAL1+, the other end of the capacitor C3 is grounded, and the other end of the capacitor C7 is connected to the 5 pin of the operational amplifier U2B; the pin 5 of the operational amplifier U2B is also connected with one end of a resistor R12 and one end of a capacitor C9 respectively, the other end of the capacitor C9 is grounded, and the other end of the resistor R12 is connected with a SIGNAL input point Signal 1-. The 2 pin of the operational amplifier U2A is respectively connected with one ends of a resistor R8 and a resistor R5, the other end of the resistor R5 is connected with a SIGNAL output point SIGNAL < 2+ >, and meanwhile, a capacitor C5 is connected in parallel on the resistor R5; the other end of the resistor R8 is respectively connected with one end of the resistor R9 and the 6 pin of the operational amplifier U2B, the other end of the resistor R9 is connected with the SIGNAL output point Signal2-, and meanwhile, a capacitor C8 is connected in parallel with the resistor R9. The 5-pin serial resistor R1 of the operational amplifier U2A is connected with the positive voltage end VCC, and the 1-pin of the operational amplifier U2A is connected with the SIGNAL output point SIGNAL < 2+ >; the 7 pin of the operational amplifier U2B is connected with the SIGNAL output point Signal 2-. The 3 pin of the follower U3A is respectively connected with one end of a resistor R4 and one end of a resistor R6, the other end of the resistor R4 is connected with a SIGNAL output point SIGNAL2+, and the other end of the resistor R6 is connected with the SIGNAL output point SIGNAL 2-; the 2 pin of the follower U3A is respectively connected with the 3 pin of the voltage stabilizing tube Q1, the 2 pin of the voltage stabilizing tube Q2 and the SIGNAL input point SIGNAL0, the 2 pin of the voltage stabilizing tube Q1 is connected with the capacitor C1 in series and then grounded, the 1 pin of the voltage stabilizing tube Q1 is respectively connected with one end of the resistor R3 and one end of the resistor R7, the other end of the resistor R3 is connected with one end of the 3 pin of the voltage stabilizing tube Q1 and one end of the resistor R10, the 3 pin of the voltage stabilizing tube Q1 is connected with the 2 pin of the voltage stabilizing tube Q2, the other end of the resistor R10 is respectively connected with one end of the resistor R11 and the 1 pin of the voltage stabilizing tube Q2, and the other end of the resistor R11 is respectively connected with the 3 pin of the voltage stabilizing tube Q2, one end of the capacitor C10, one end of the resistor R15 and the 4 pin of the operational amplifier U2A; the other end of the capacitor C10 is grounded, and the other end of the resistor R15 is connected to the negative voltage terminal VEE. The 1 pin of the follower U3A is connected with a SIGNAL input point SIGNAL 0; the 4 pin of the follower U3A is respectively connected with the negative voltage end VEE and one end of the capacitor C6, and the other end of the capacitor C6 is grounded; the 5 feet of the follower U3A are respectively connected with the positive voltage end VCC and one end of the capacitor C2, and the other end of the capacitor C2 is grounded. The 4 pin of the operational amplifier U2B is connected to the capacitor C10, and the 8 pin of the operational amplifier U2B is connected to the capacitor C1. Wherein, SIGNAL1+ and SIGNAL 1-are all the access points outputting differential voltage SIGNALs with TMR sensor chip, SIGNAL0 is the access point connected with the shielding wire.

The resistor R2 and the capacitor C3 and the resistor R12 and the capacitor C9 play a role of a simple filter small circuit, and perform primary filter treatment on signals; the capacitor C7 is mainly used for eliminating differential mode signal interference; the operational amplifier U2A and the operational amplifier U2B form an amplifying function for signals; the structure of the voltage stabilizing tube Q1, the voltage stabilizing tube Q2, the resistor R3, the resistor R7, the resistor R10 and the resistor R11 is mainly used for providing stable voltage input for two operational amplifiers U2A and U2B; the resistor R1 and the capacitor C1 and the resistor R15 and the capacitor C10 are used for filtering an external power supply; the follower U3A is externally added with a capacitor C2, and the capacitor C6 forms a voltage follower circuit for signal transmission.

Fig. 4 is a schematic diagram of a secondary signal amplifying circuit, and the signal amplification factor in the front-end amplifying circuit is not set to be too large, so that the signal needs to be amplified again. Wherein U4 is an integrated chip, and the REF1 pin is a reference pin, and is used for designing a reserved interface of the bias zeroing circuit. According to the principle of virtual break and virtual short of the operational amplifier, the gain G of the circuit is determined by two resistors R16 and R27 together, and the signal amplification factor can be adjusted according to actual needs. The resistor R19, the capacitor C11, the resistor R24 and the capacitor C15 in the front-end peripheral circuit are filter circuits for the interference of common-mode signals at the two ends, and the filter capacitor C13 can effectively inhibit the interference of differential-mode signals. The integrated chip U4 is an AD620AR integrated chip, the power supply voltage is set to be +/-5V, wherein a REF1 pin is a reference pin, and the access of the bias zero setting circuit is reserved. The circuit gain G is determined by the adjustable resistor R17, g=49.4K/r17+1, and the amplification factor is adjusted according to the requirement. The filter circuit formed by the resistor R19 and the capacitor C11 and the resistor R24 and the capacitor C15 in the front-end peripheral circuit can filter common-mode signal interference at two ends of the secondary signal amplifying circuit, and the filter capacitor C13 can effectively inhibit the interference of the differential-mode signal.

As shown in fig. 4, an adjustable resistor R17 is connected in parallel to the outside of the 1 pin and the 8 pin of the integrated chip U4 in the secondary signal amplifying circuit, for setting the gain of the whole circuit; the 2 pin of the integrated chip U4 is respectively connected with one end of a capacitor C11, one end of a filter capacitor C13 and one end of a resistor R19, the other end of the resistor R19 is connected with a SIGNAL output point SIGNAL 2-of the front-end amplifying circuit, and the other end of the filter capacitor C13 is grounded; the 3 pin of the integrated chip U4 is respectively connected with one end of a capacitor C15, the other end of a filter capacitor C13 and one end of a resistor R24, the other end of the resistor R24 is connected with a SIGNAL output point SIGNAL < 2+ > of a front-end amplifying circuit, and the other end of the capacitor C15 is grounded; the 4 pin of the integrated chip U4 is respectively connected with one end of a resistor R26 and one end of a capacitor C16, the other end of the resistor R26 is connected with a-5V power supply end, and the other end of the capacitor C16 is grounded; the 5 pin of the integrated chip U4 is used as a REF1 pin, and the REF1 pin is connected with a resistor R27 in series and then grounded; the pin 7 of the integrated chip U4 is respectively connected with one end of a resistor R22 and one end of a capacitor C14, the other end of the resistor R22 is connected with a +5V power supply end, and the other end of the capacitor C14 is grounded; the 6 pins of the integrated chip U4 are the outputs vout11. The resistor R19 and the capacitor C11, the resistor R24 and the capacitor C15 are filter circuits of signals at two ends and are used for eliminating common mode signal interference; the filter capacitor C13 is used for eliminating differential mode signal interference; the resistor R26 and the capacitor C16 play a role in filtering, and the resistor R22 and the capacitor C14 play a role in filtering; the REF1 pin is used as an additional pin for circuit zeroing.

Fig. 5 is a schematic diagram of a bias zeroing circuit, in which the source impedance on the REF1 reference pin of the integrated chip U4 in the secondary signal amplification circuit should be as low as possible to ensure optimal performance of the integrated chip. The voltage follower circuit has the advantages of high input impedance, low output impedance, front-back isolation, capability of improving load capacity and function of impedance transformation in the circuit, and therefore the requirement of small source impedance on the REF1 pin can be met. The voltage on the REF1 pin is adjustable, and the requirement of counteracting the bias voltage of the TMR sensor under different external environments can be met. Therefore, as shown in fig. 5, the bias zero setting circuit in this embodiment uses a chip with the model TLC2272 as an operational amplifier to build a voltage follower circuit, the 5 pin of the operational amplifier U5A is connected to one end of the resistor R21 and one end of the capacitor C12 respectively, the other end of the capacitor C12 is grounded, the other end of the resistor R21 is connected to the adjusting end of the adjustable resistor R20, one end of the adjustable resistor R20 is connected to the positive voltage end VCC after being connected in series with the resistor R16, and the other end of the adjustable resistor R20 is connected to the negative voltage end VEE after being connected in series with the resistor R28; meanwhile, a resistor R18 and a resistor R25 which are connected in series are connected in parallel outside the adjustable resistor R20. The

pins

6 and 7 of the operational amplifier U5A are connected with the resistor R23 in series and then connected with the pin REF1 of the integrated chip U4. The 8 pin of the operational amplifier U5A is connected with a positive voltage end VCC; the 4 pin of the operational amplifier U5A is connected to the negative voltage terminal VEE. The operational amplifier U5A, a filter circuit formed by the resistor R21 and the capacitor C12 and the resistor R23 form a voltage follower circuit for extracting and transmitting signals; the adjustable resistor R20, the resistor R16 and the resistor R28 are mainly used for distributing and acquiring voltages and are used for acquiring the voltages as inputs of a voltage follower circuit; resistor R18 and resistor R25 are also involved in voltage distribution, with REF1 pin serving as a reference pin for integrated chip U4.

Fig. 6 is a schematic diagram of a power amplifying circuit (i.e. an operational amplifier driving circuit) and a feedback circuit, and since weak current sensor research is studied, in theory, the differential voltage output by a chip can drive the operation of a coil after passing through the amplifying circuit, and therefore, only a simple operational amplifier is used for driving the feedback coil for the design of the power amplifying part. The J1 module is a feedback coil, the R32 is a sampling resistor, the feedback coil and the sampling resistor are connected in series to the front-end circuit and then grounded, and the current in the current-carrying wire can be indirectly reflected by measuring the voltage on the sampling resistor R32. As shown in fig. 6, the operational amplifier driving circuit is provided with an operational amplifier U6A, the model is TLC2272, and the feedback circuit includes a feedback coil J1 and a sampling resistor R32; the 3 pin of the operational amplifier U6A is respectively connected with one end of a resistor R29 and one end of a capacitor C29, the other end of the capacitor C29 is grounded, and the other end of the resistor R29 is connected with the output vout11 of the secondary signal amplifying circuit; the 1 foot and the 2 foot of operational amplifier U6A are connected with the one end of resistance R30, and the other end of resistance R30 is connected with feedback coil J1 one end, and feedback coil J1's the other end is connected with sampling resistance R32 one end, and sampling resistance R32 other end ground connection. The 8 pin of the operational amplifier U6A is respectively connected with one end of the capacitor C17 and the positive voltage end VCC, and the other end of the capacitor C17 is grounded; the 4 pin of the operational amplifier U6A is connected to one end of the capacitor C19 and the negative voltage terminal VEE, respectively, and the other end of the capacitor C19 is grounded. The resistor R29 and the capacitor C29 form a filtering effect, the capacitor C17 and the capacitor C19 also form a filtering effect, and the resistor R30 shares a voltage effect; the J1 is used for connecting two ends of the feedback coil; the sampling resistor R32 is used for realizing voltage acquisition in cooperation with a sampling circuit.

Fig. 7 is a schematic diagram of a sampling circuit, and the voltage on the sampling resistor R32 is simply extracted by using an operational amplifier. As shown in fig. 7, the sampling circuit is provided with an operational amplifier U7A, the model is TLC2272, the 5 pin of the operational amplifier U7A is connected to one end of a capacitor C20, and the other end of the capacitor C20 is grounded; the pin 6 of the operational amplifier U7A is respectively connected with one ends of a resistor R33 and a resistor R34, the other end of the resistor R34 is grounded, the other end of the resistor R33 is connected with one end of a test port J2, the pin 7 of the operational amplifier U7A is also connected with one end of the test port J2, and the other end of the test port J2 is grounded. The 8 pin of the operational amplifier U7A is connected with the positive voltage end VCC; the 4 pin of the operational amplifier U7A is connected to the negative voltage terminal VEE. The capacitor C20 plays a role of a filter circuit, the resistor R34 plays a role of buffering, and the resistor R33 is used for an input and output signal transmission channel of the operational amplifier; and J2 is a reserved test port used for acquiring a voltage value. And J2 is an external universal meter or other testing instrument, and is used for obtaining a voltage value through reserved testing.

The working principle of the signal processing circuit of the weak current sensor based on TMR of the invention is as follows:

after the working power supply is switched on, the power supply related in the signal processing circuit is powered by an external power supply, and the power supply circuit module in fig. 2 firstly completes conversion and voltage stabilizing treatment on the external power supply. The magnetic field intensity SIGNAL generated by the current to be measured is converted into a differential voltage output SIGNAL through a TMR chip, the differential voltage output SIGNAL is input through a SIGNAL input point SIGNAL & lt1+ & gt and a SIGNAL input point SIGNALL & lt- & gt in the figure 3, then the differential voltage output SIGNAL is amplified through an operational amplifier U2A and an operational amplifier U2B, and the differential voltage output SIGNAL is output through a SIGNAL output point SIGNAL & lt2+ & gt and two ends. And the common mode signal interference at two ends is filtered by a filter circuit consisting of a front-end peripheral circuit resistor R19 and a capacitor C11, a resistor R24 and a capacitor C15 in fig. 4, and the filter capacitor C13 effectively inhibits the interference of differential mode signals. The rear signal enters an integrated chip U4, the size of an adjustable resistor R17 is adjusted, the signal is amplified, an output voltage signal is output through a vout11, a REF1 pin is connected with a five-bias zero-setting circuit, and the input voltage of the REF1 pin can be changed by adjusting the size of the adjustable resistor R20, so that the output of the vout11 is adjusted. The vout11 is connected to the feedback coil J1 after passing through the operational amplifier driving circuit of fig. 6, and then connected to the sampling resistor R32 in series, and then grounded. The sampling circuit of figure 7 is connected to the sampling resistor to obtain the voltages at two ends of the sampling resistor, and the feedback current I is obtained through the ratio of the voltages to the resistor _s The magnitude and the secondary side ampere-turns relation when the system reaches balanceRatio N ₁ I _p ＝N ₂ I _s Indirectly obtain primary side current I _p The magnitude of the current to be detected is detected.

The design scheme of the TMR weak current sensor circuit part comprises the following steps:

(1) According to the size and the range of the current to be measured, the size of a magnetic field is generated through simulation, and then a proper TMR sensor chip is selected; and selecting proper/chip packaging by combining the size of the magnetic ring gap at the front end and considering the sensitive axis direction of the sensor chip, so that the model and packaging of the sensor chip are determined.

(2) According to the determined power supply conditions of the sensor design, a power supply circuit module is designed, wherein the conversion of positive and negative voltages and the design of a voltage stabilizing part are involved, and the power supply voltage of a sensor chip and the power supply voltage of a subsequent operational amplifier are required to be considered.

(3) According to the sensitivity of the sensor chip and the magnitude of a magnetic field signal generated by simulating current to be measured, the output differential voltage signal of the TMR sensor chip is roughly calculated, and is taken as a reference of the gain of the amplifying circuit part; the magnetic field intensity of the corresponding air gap part is calculated by the com simulation software, for example, the corresponding value is 2oe, the sensitivity of the chip is assumed to be 5mV/V/oe, wherein under the magnetic field intensity of 1oe, the corresponding output of each 1V power supply voltage is 5mV, and therefore, when the power supply voltage of the chip is 1V, the chip output differential voltage value is 10mV through simple calculation. And meanwhile, a proper filter circuit is designed according to the frequency range or bandwidth requirement of the designed sensor.

(4) According to the current measurement principle of the TMR current sensor with the closed loop structure, namely the ampere-turns relation ratio, the proper number of turns of the coil is determined by combining the measurement range of the current sensor, and the magnitude of the current in the feedback circuit when the magnetic balance is realized is approximately calculated; the formula is N ₁ I _p ＝N ₂ I _s ，I _p For primary side current to be measured, the current-carrying conductor is regarded as a coil with 1 turns, i.e. the primary coil has N turns ₁ 1 is shown in the specification; i _s For feeding back current, N ₂ For feedback coil J1Turns of turns; and then the gain of the amplifying circuit part and the size of the sampling resistor are comprehensively considered and determined, and finally the simple design of the sampling circuit for extracting the voltage signal of the sampling resistor is carried out.

The following is one embodiment of the present invention:

the design of the TMR current sensor circuit is developed by taking weak current of 0-10mA as a detection object. And selecting a TMR2901 chip according to the model of the TMR sensor chip in the measuring range, wherein the sensitive axis is the y axis, and the power supply voltage is set to be 5V. The chip U6 used in the isolating power supply schematic diagram designed in FIG. 2 is an integrated chip with the model of A2409S-2WR3, the chip is A2W constant voltage input, isolating non-stabilized positive and negative double-circuit output, the chip has sustainable short-circuit protection, high power density, no-load input current as low as 8mA, working temperature range of-40 ℃ to-105 ℃ and efficiency as high as 86%, and a peripheral circuit as shown in the figure is additionally arranged, so that the conversion from 24V voltage to positive and negative 9V voltage is realized. In fig. 3, the two-channel operational amplifier TLC2272 is selected for each of the types of the operational amplifier U2A, the operational amplifier U2B, and the follower U3A, and the total circuit gain is set to 2 times. The dual channel op-amp supports all amplifiers with the same bias circuit, thereby reducing complexity, chip area and cost. Since the amplifiers are co-located on the same chip, they have very high consistency and also reduce sensor errors.

In fig. 4, the chip U4 of the secondary signal amplifying circuit is an AD620AR integrated chip, the supply voltage is set to ±5v, and the ref1 pin is used as a reference pin for designing the bias zeroing circuit. The gain G of the circuit is determined by a resistor R16 and a resistor R27 together, G=49.4K/Rg+1, and the signal amplification factor is adjusted according to actual needs. In the bias zeroing circuit in fig. 5, a voltage follower circuit is built by using an op-amp TLC2272, so that voltage on a REF pin can be adjusted. In fig. 6, the J1 module is a feedback coil, R32 is a sampling resistor, in practical design, the feedback coil J1 is made of enameled wires, and is uniformly wound on the magnetic flux collecting ring, and the number of turns of the feedback coil is set to be 100 without being excessively large. By measuring the voltage across resistor R32, the current inside the current carrying wire can be reflected indirectly. It should be ensured that the sampling resistor R32 is large enough to obtain a good output voltage resolution, which is roughly calculated to be a precision resistor of 750 Ω with a gain of 10 for the secondary amplifying circuit.

Claims

1. The weak current sensor signal processing circuit based on TMR is characterized by comprising a power circuit module, a bias zero setting circuit, a TMR sensor chip, an instrument amplifying circuit, a filter circuit, a power amplifying circuit, a feedback circuit and a sampling circuit, wherein the power circuit module is respectively and electrically connected with the TMR sensor chip and the bias zero setting circuit, the TMR sensor chip and the bias zero setting circuit are both electrically connected with the instrument amplifying circuit, the instrument amplifying circuit is electrically connected with the filter circuit, the filter circuit is electrically connected with the power amplifying circuit, the power amplifying circuit is electrically connected with the feedback circuit, and the feedback circuit is respectively and electrically connected with the sampling circuit and the TMR sensor chip; the TMR sensor chip is used for collecting and converting magnetic field signals; the power circuit module can realize the conversion from unipolar voltage to bipolar voltage and meet the power supply stability; the bias zeroing circuit is used for zeroing a bias voltage signal generated by the TMR sensor chip; the instrument amplifying circuit is used for amplifying the output signal of the TMR current sensor chip; the filter circuit is used for carrying out filter processing on the signals and eliminating the interference of spurious signals; the power amplifying circuit is used for amplifying the power of the front-end signal so as to drive the feedback coil in the feedback circuit to operate; the feedback circuit is used for feeding back the formation of current; the sampling circuit is used for obtaining the voltage on the sampling resistor in the feedback circuit, and indirectly knowing the magnitude of the feedback current.

2. The TMR-based weak current sensor signal processing circuit according to claim 1, wherein the positive voltage terminal VCC and the negative voltage terminal VEE of the power supply part of the signal processing circuit are provided by an external power supply, the power supply circuit module is provided with an integrated chip U6, the 1 pin of the integrated chip U6 is respectively connected with one end of an inductor L3 and one end of a capacitor C26, the other end of the inductor L3 is respectively connected with the positive voltage terminal VCC and one end of a capacitor C25, the other end of the capacitor C25 and the 2 pin of the integrated chip U6 are grounded, the other end of the capacitor C26 is connected with one end of a capacitor C27, and the other end of the capacitor C27 is grounded; the 6 pin of the integrated chip U6 is respectively connected with one end of an inductor L2 and one end of a capacitor C21, the other end of the capacitor C21 is grounded, the other end of the inductor L2 is respectively connected with a positive voltage end VCC and one end of a capacitor C22, and the other end of the capacitor C22 is grounded; the 4 pin of the integrated chip U6 is respectively connected with one end of an inductor L4 and one end of a capacitor C23, the other end of the capacitor C23 is grounded, the other end of the inductor L4 is respectively connected with a negative voltage end VEE and one end of a capacitor C24, and the other end of the capacitor C24 is grounded; the 5 pin of the integrated chip U6 is grounded.

3. The TMR-based weak current sensor signal processing circuit according to claim 1, wherein the meter amplification circuit comprises a front-end amplification circuit, and the filter circuit comprises a resistor R2, a capacitor C3, a capacitor C7, a resistor R12 and a capacitor C9 connected with the front-end amplification circuit; the front end amplifying circuit is internally provided with an operational amplifier U2A, a 3 pin of the operational amplifier U2A is respectively connected with one end of a resistor R2, one end of a capacitor C3 and one end of a capacitor C7, the other end of the resistor R2 is connected with a SIGNAL input point SIGNAL1 < + >, the other end of the capacitor C3 is grounded, and the other end of the capacitor C7 is connected with a 5 pin of the operational amplifier U2B; the pin 5 of the operational amplifier U2B is also connected with one end of a resistor R12 and one end of a capacitor C9 respectively, the other end of the capacitor C9 is grounded, and the other end of the resistor R12 is connected with a SIGNAL input point Signal 1-; the 2 pin of the operational amplifier U2A is respectively connected with one ends of a resistor R8 and a resistor R5, the other end of the resistor R5 is connected with a SIGNAL output point SIGNAL < 2+ >, and meanwhile, a capacitor C5 is connected in parallel on the resistor R5; the other end of the resistor R8 is respectively connected with one end of the resistor R9 and the 6 pin of the operational amplifier U2B, the other end of the resistor R9 is connected with the SIGNAL output point Signal2-, and meanwhile, the resistor R9 is connected with a capacitor C8 in parallel; the 5-pin serial resistor R1 of the operational amplifier U2A is connected with the positive voltage end VCC, and the 1-pin of the operational amplifier U2A is connected with the SIGNAL output point SIGNAL < 2+ >; the pin 7 of the operational amplifier U2B is connected with the SIGNAL output point SIGNAL 2-; the 3 pin of the follower U3A is respectively connected with one end of a resistor R4 and one end of a resistor R6, the other end of the resistor R4 is connected with a SIGNAL output point SIGNAL2+, and the other end of the resistor R6 is connected with the SIGNAL output point SIGNAL 2-; the 2 pin of the follower U3A is respectively connected with the 3 pin of the voltage stabilizing tube Q1, the 2 pin of the voltage stabilizing tube Q2 and the SIGNAL input point SIGNAL0, the 2 pin of the voltage stabilizing tube Q1 is connected with the capacitor C1 in series and then grounded, the 1 pin of the voltage stabilizing tube Q1 is respectively connected with one end of the resistor R3 and one end of the resistor R7, the other end of the resistor R3 is connected with one end of the 3 pin of the voltage stabilizing tube Q1 and one end of the resistor R10, the 3 pin of the voltage stabilizing tube Q1 is connected with the 2 pin of the voltage stabilizing tube Q2, the other end of the resistor R10 is respectively connected with one end of the resistor R11 and the 1 pin of the voltage stabilizing tube Q2, and the other end of the resistor R11 is respectively connected with the 3 pin of the voltage stabilizing tube Q2, one end of the capacitor C10, one end of the resistor R15 and the 4 pin of the operational amplifier U2A; the other end of the capacitor C10 is grounded, and the other end of the resistor R15 is connected with the negative voltage end VEE; the 1 pin of the follower U3A is connected with a SIGNAL input point SIGNAL 0; the 4 pin of the follower U3A is respectively connected with the negative voltage end VEE and one end of the capacitor C6, and the other end of the capacitor C6 is grounded; the 5 pin of the follower U3A is respectively connected with the positive voltage end VCC and one end of the capacitor C2, and the other end of the capacitor C2 is grounded; the 4 pin of the operational amplifier U2B is connected to the capacitor C10, and the 8 pin of the operational amplifier U2B is connected to the capacitor C1.

4. The TMR-based weak current sensor signal processing circuit according to claim 3, wherein the meter amplification circuit further comprises a secondary signal amplification circuit, the filter circuit further comprising a resistor R19, a capacitor C11, a filter capacitor C13, a resistor R24 and a capacitor C15 connected to the secondary signal amplification circuit; an integrated chip U4 is arranged in the secondary signal amplifying circuit, and an adjustable resistor R17 is connected in parallel outside a pin 1 and a pin 8 of the integrated chip U4 and is used for setting the gain of the whole circuit; the 2 pin of the integrated chip U4 is respectively connected with one end of a capacitor C11, one end of a filter capacitor C13 and one end of a resistor R19, the other end of the resistor R19 is connected with a SIGNAL output point SIGNAL 2-of the front-end amplifying circuit, and the other end of the filter capacitor C13 is grounded; the 3 pin of the integrated chip U4 is respectively connected with one end of a capacitor C15, the other end of a filter capacitor C13 and one end of a resistor R24, the other end of the resistor R24 is connected with a SIGNAL output point SIGNAL < 2+ > of a front-end amplifying circuit, and the other end of the capacitor C15 is grounded; the 4 pin of the integrated chip U4 is respectively connected with one end of a resistor R26 and one end of a capacitor C16, the other end of the resistor R26 is connected with a-5V power supply end, and the other end of the capacitor C16 is grounded; the 5 pin of the integrated chip U4 is used as a REF1 pin, and the REF1 pin is connected with a resistor R27 in series and then grounded; the pin 7 of the integrated chip U4 is respectively connected with one end of a resistor R22 and one end of a capacitor C14, the other end of the resistor R22 is connected with a +5V power supply end, and the other end of the capacitor C14 is grounded; the 6 pins of the integrated chip U4 are the outputs vout11.

5. The TMR-based weak current sensor signal processing circuit according to claim 4, characterized in that an operational amplifier U5A is arranged in the bias zeroing circuit, the 5 pin of the operational amplifier U5A is respectively connected with one end of a resistor R21 and one end of a capacitor C12, the other end of the capacitor C12 is grounded, the other end of the resistor R21 is connected with the regulating end of an adjustable resistor R20, one end of the adjustable resistor R20 is connected with a positive voltage end VCC after being connected with a resistor R16 in series, and the other end of the adjustable resistor R20 is connected with a negative voltage end VEE after being connected with a resistor R28 in series; meanwhile, a resistor R18 and a resistor R25 which are connected in series are connected in parallel outside the adjustable resistor R20; the 6 pin and the 7 pin of the operational amplifier U5A are connected with a resistor R23 in series and then connected with the REF1 pin of the integrated chip U4; the 8 pin of the operational amplifier U5A is connected with a positive voltage end VCC; the 4 pin of the operational amplifier U5A is connected to the negative voltage terminal VEE.

6. The TMR-based weak current sensor signal processing circuit according to claim 4, wherein the power amplifying circuit is provided with an operational amplifier, and the feedback circuit comprises a feedback coil J1 and a sampling resistor R32; the 3 pin of the operational amplifier U6A is respectively connected with one end of a resistor R29 and one end of a capacitor C29, the other end of the capacitor C29 is grounded, and the other end of the resistor R29 is connected with the output vout11 of the secondary signal amplifying circuit; the 1 pin and the 2 pin of the operational amplifier U6A are connected with one end of a resistor R30, the other end of the resistor R30 is connected with one end of a feedback coil J1, the other end of the feedback coil J1 is connected with one end of a sampling resistor R32, and the other end of the sampling resistor R32 is grounded; the 8 pin of the operational amplifier U6A is respectively connected with one end of the capacitor C17 and the positive voltage end VCC, and the other end of the capacitor C17 is grounded; the 4 pin of the operational amplifier U6A is connected to one end of the capacitor C19 and the negative voltage terminal VEE, respectively, and the other end of the capacitor C19 is grounded.

7. The TMR-based weak current sensor signal processing circuit according to claim 1, wherein the sampling circuit is provided with an operational amplifier U7A, the 5 pin of the operational amplifier U7A is connected with one end of a capacitor C20, and the other end of the capacitor C20 is grounded; the pin 6 of the operational amplifier U7A is respectively connected with one ends of a resistor R33 and a resistor R34, the other end of the resistor R34 is grounded, the other end of the resistor R33 is connected with one end of a test port J2, the pin 7 of the operational amplifier U7A is also connected with one end of the test port J2, and the other end of the test port J2 is grounded; the 8 pin of the operational amplifier U7A is connected with the positive voltage end VCC; the 4 pin of the operational amplifier U7A is connected to the negative voltage terminal VEE.