Closed loop current sensor

Abstract

A closed-loop current sensor includes: a pair of openable iron cores, a secondary feedback coil wound outside the iron core, a magnetoresistance sensing unit and a signal processing circuit; the iron core is coated with a multiferroic material film, and the magnetoresistance sensing unit is arranged at the gap of the magnetic circuit formed by the iron core; the signal processing unit includes a signal acquisition circuit, a signal amplification circuit, a current feedback circuit, a voltage follower circuit and a voltage feedback circuit; the signal acquisition circuit is connected to the output end of the magnetoresistance sensing unit, and transmits the voltage signal to the signal amplification circuit, the signal amplification circuit has two outputs, one output to the current feedback circuit, and the other output to the voltage follower circuit; the output end of the current feedback current is connected to one end of the secondary feedback coil, and the other end of the secondary feedback coil is connected to the secondary resistor; the output end of the voltage follower circuit is connected to the voltage feedback circuit, and the output end of the voltage feedback circuit is connected to the multiferroic material film. The sensor of the present invention can achieve low power consumption.

Description

Technical Field

[0001] The invention belongs to the technical field of current measurement, and in particular relates to a closed-loop current sensor with an open-close structure. Background Art

[0002] Open-and-close zero-flux closed-loop current sensors are widely used in the field of current measurement due to their ease of installation, high measurement accuracy, and reliability. Traditional open-and-close zero-flux closed-loop current sensors are based on the zero-flux principle (mutual inductor principle). During measurement, the secondary current cancels the magnetic field generated by the primary current being measured according to the ampere-turn ratio formula of I1N1=I2N2, thereby generating a zero-flux state in the core. Since the closed-loop current sensor needs to provide current feedback to the secondary coil, and the power consumption = feedback current * power supply voltage, the larger the feedback current, the greater the power consumption. How to reduce the power consumption of the closed-loop current sensor is one of the problems that need to be solved in the industry. Summary of the invention

[0003] The object of the present invention is to provide a low-power closed-loop current sensor.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions:

[0005] A closed-loop current sensor comprises: a pair of openable iron cores, a secondary feedback coil wound outside the iron cores, a magnetoresistance sensing unit and a signal processing unit; the iron cores are coated with a multiferroic material film, and the magnetoresistance sensing unit is arranged at the air gap of the magnetic circuit formed by the iron cores; the signal processing unit comprises a signal acquisition circuit, a signal amplification circuit, a current feedback circuit, a voltage follower circuit and a voltage feedback circuit; wherein the signal acquisition circuit is connected to the output end of the magnetoresistance sensing unit and transmits the collected voltage signal to the signal amplification circuit, the output end of the signal amplification circuit has two outputs, one output to the current feedback circuit and the other output to the voltage follower circuit; the output end of the current feedback circuit is connected to one end of the secondary feedback coil, and the other end of the secondary feedback coil is connected to the secondary resistor; the output end of the voltage follower circuit is connected to the voltage feedback circuit, and the output end of the voltage feedback circuit is connected to the multiferroic material film.

[0006] More specifically, the magnetoresistive sensing unit is a TMR unit, a GMR unit, an AMR unit, or a Hall element.

[0007] More specifically, the multiferroic material film includes a ferromagnetic layer formed of a magnetic material and a piezoelectric layer formed of a piezoelectric material.

[0008] More specifically, the initial magnetic permeability of the magnetic material is greater than 1000 and the magnetostriction coefficient is greater than 10 ppm.

[0009] More specifically, the magnetic material is Ni or Fe or Co or an alloy thereof.

[0010] More specifically, the electrostriction coefficient of the piezoelectric material is greater than 500 ppm.

[0011] More specifically, the piezoelectric material is PZT or PZN-PT or PMN-PT or AlN or HfO2.

[0012] More specifically, the multiferroic material film includes: a substrate, a first conductive layer formed on the substrate, a piezoelectric layer and a ferromagnetic layer formed on the first conductive layer, an insulating layer formed on the ferromagnetic layer, and a second conductive layer formed on the insulating layer, wherein the first conductive layer and the second conductive layer are respectively formed with an upper electrode and a lower electrode connected to the voltage feedback circuit.

[0013] More specifically, the signal acquisition circuit includes a first amplifier, the inverting input terminal and the non-inverting input terminal of the first amplifier are respectively connected to the two output terminals of the magnetoresistive sensing unit via resistors, the inverting input terminal of the first amplifier is simultaneously connected to the output terminal of the first amplifier via a resistor, the non-inverting output terminal is simultaneously connected to the output terminal of the first amplifier via a resistor, the non-inverting output terminal is also grounded via a resistor, and the output terminal of the first amplifier is connected to the input terminal of the signal amplification circuit.

[0014] More specifically, the signal amplification circuit includes a second amplifier, the in-phase input terminal of the second amplifier is connected to the output terminal of the signal acquisition circuit via a resistor, the inverting input terminal is grounded via a resistor and simultaneously connected to the output terminal of the second amplifier via a resistor, and the output terminal of the second amplifier is respectively connected to the current feedback circuit and the voltage follower circuit.

[0015] More specifically, the current feedback circuit includes a third amplifier, the non-inverting input terminal of the third amplifier is grounded via a resistor, the inverting input terminal is connected to the output terminal of the signal amplification circuit via a resistor, and is simultaneously connected to the output terminal of the third amplifier via a capacitor and a resistor, and the output terminal of the third amplifier is connected to the secondary feedback coil.

[0016] More specifically, the voltage follower circuit includes a fourth amplifier, the in-phase input terminal of the fourth amplifier is connected to the output terminal of the second amplifier, the inverting input terminal is connected to the output terminal of the fourth amplifier, and the output terminal of the fourth amplifier is connected to the input terminal of the voltage feedback circuit.

[0017] More specifically, the voltage feedback circuit includes a fifth amplifier, the in-phase input terminal of the fifth amplifier is connected to the output terminal of the voltage follower circuit through a resistor, the inverting input terminal is grounded through a resistor, the inverting input terminal is also connected to the output terminal of the fifth amplifier through a resistor, and the output terminal of the fifth amplifier is connected to the multiferroic material film.

[0018] Alternatively, the magnetoresistive sensing unit is replaced by an RC modulation circuit.

[0019] It can be seen from the above technical scheme that the present invention covers a layer of multiferroic material film on the outside of the iron core of the current sensor, utilizes the characteristics of the multiferroic material, isolates part of the voltage signal and loads it on the multiferroic material film, and changes the magnetic flux in the iron core by changing the magnetic permeability of the multiferroic material film, thereby reducing the power consumption of the zero flux sensor without affecting the accuracy of the sensor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0021] Figure 1 It is a structural schematic diagram of an embodiment of the present invention;

[0022] Figure 2 Schematic diagram of magnetoelectric effect of multiferroic materials;

[0023] Figures 3a to 3e Schematic diagram of the preparation process of the multiferroic material film according to an embodiment of the present invention;

[0024] Figure 4 It is the basic circuit diagram of the RC modulation circuit in the prior art. DETAILED DESCRIPTION

[0025] In order to make the above and other purposes, features and advantages of the present invention more obvious, embodiments of the present invention are specifically cited below and described in detail with reference to the accompanying drawings.

[0026] like Figure 1As shown, the current sensor of this embodiment includes a pair of openable iron cores 1, the two iron cores 1 are arranged oppositely to form a ring-shaped magnetic circuit, and the iron core 1 can be a magnetic core made of conventional magnetic materials such as silicon steel sheets, Permalloy, nanocrystals, etc. The iron core 1 is coated with a layer of multiferroic material film (not shown), and the multiferroic material film is made of multiferroic material. The iron core 1 coated with the multiferroic material film is arranged in an insulating sub-shell (not shown), and is wound with insulating enameled wire outside the insulating sub-shell to form a secondary feedback coil 2, one end of the secondary feedback coil 2 is connected to a secondary resistor R13, and the other end is connected to a rear-end signal processing unit (current feedback circuit C), and the other end of the secondary resistor R13 is grounded. A magnetoresistance sensor unit 3 is arranged in the air gap a of the magnetic circuit formed by the iron core 1. The magnetoresistance sensor unit 3 can be a TMR unit, a GMR unit, an AMR unit or a Hall element, etc. The magnetoresistance sensor unit of this embodiment is a TMR chip, and the output end of the magnetoresistance sensor unit 3 is connected to the signal processing unit. The magnetoresistive sensing unit 3 of this embodiment is a modulation and demodulation module of the current sensor, which is used to modulate and demodulate the primary measured current. In other embodiments, the modulation and demodulation circuit can also adopt an RC modulation circuit ( Figure 4 ) and other traditional magnetic modulation circuits, that is, they are not necessarily completed by the magnetoresistive sensing unit 3.

[0027] The signal processing unit of this embodiment includes a signal acquisition circuit A, a signal amplification circuit B, a current feedback circuit C, a voltage follower circuit D and a voltage feedback circuit E. Among them, the signal acquisition circuit A is connected to the magnetoresistive sensing unit 3, and is used to collect the voltage signal output by the magnetoresistive sensing unit 3. The signal acquisition circuit of this embodiment includes a first amplifier U1A, which is a differential amplifier, and its inverting input terminal is connected to one output terminal of the magnetoresistive sensing unit 3 through a resistor R1, and its in-phase input terminal is connected to the other output terminal of the magnetoresistive sensing unit 3 through a resistor R3. The inverting input terminal of the first amplifier U1A is simultaneously connected to the output terminal of the first amplifier U1A through a resistor R2, and the in-phase output terminal is simultaneously connected to the output terminal of the first amplifier U1A through a resistor R4, and the in-phase output terminal is also grounded through a resistor R5. The output terminal of the first amplifier U1A (signal acquisition circuit) is connected to the input terminal of the signal amplification circuit B.

[0028] The signal amplification circuit B includes a second amplifier U1B, which is used to amplify the collected voltage signal. The in-phase input terminal of the second amplifier U1B is connected to the output terminal of the signal collection circuit (first amplifier) ​​via a resistor R7, the inverting input terminal is grounded via a resistor R8, and the inverting input terminal is simultaneously connected to the output terminal of the second amplifier U1B via a resistor R9. The output terminal of the second amplifier U1B, i.e., the output terminal of the signal amplification circuit B, has two outputs, one output to the current feedback circuit C, and the other output to the voltage follower circuit D.

[0029] The current feedback circuit C includes a third amplifier U1C, the inverting input terminal of the third amplifier U1C is connected to the output terminal of the signal amplifier circuit B (second amplifier) ​​via a resistor R10, and is simultaneously connected to the output terminal of the third amplifier U1C via a capacitor C3 and a resistor R12, the in-phase input terminal of the third amplifier U1C is grounded via a resistor R11, and the output terminal of the third amplifier U1C is connected to one end of the secondary feedback coil 2. The current feedback circuit C is used to perform negative feedback on the residual magnetic flux of the core, so that a zero magnetic flux state is generated inside the core.

[0030] The voltage follower circuit D includes a fourth amplifier U2C, the in-phase input terminal of the fourth amplifier U2C is connected to the output terminal of the second amplifier U1B, the inverting input terminal is connected to the output terminal of the fourth amplifier U2C, and the output terminal of the fourth amplifier U2C is connected to the input terminal of the voltage feedback circuit E. The voltage follower circuit D isolates and extracts the amplified voltage signal while providing current feedback.

[0031] The voltage feedback circuit E includes a fifth amplifier U2A, the in-phase input terminal of the fifth amplifier U2A is connected to the output terminal of the voltage follower circuit D (fourth amplifier) ​​through a resistor R14, the inverting input terminal is grounded through a resistor R16, and the inverting input terminal is simultaneously connected to the output terminal of the fifth amplifier U2A through a resistor R15, and the output terminal of the fifth amplifier U2A is connected to the multiferroic material film. The voltage feedback circuit E and the voltage follower circuit D feed back the voltage signal to the multiferroic material film to form a voltage loop, and the voltage follower circuit D, the voltage feedback circuit E and the multiferroic material film complete the voltage feedback together.

[0032] like Figure 2 As shown, multiferroic material is a material with ferroelectric (PE) characteristics and magnetoelectric (MH) characteristics, and there is a magneto-electric cross-regulation effect, that is, the electric polarization (P) can be regulated by the magnetic field (H), or the magnetization (M) can be regulated by the electric field (E). Under the action of electric field polarization, the magnetic domain angle can be caused to change, that is, the saturation magnetic field size and magnetic permeability of the multiferroic material itself can be changed by applying voltage to the multiferroic material. The multiferroic material film of this embodiment mainly includes a ferromagnetic layer and a piezoelectric layer. The ferromagnetic layer is formed by magnetic materials such as metals such as Ni, Fe, Co or their alloys. The initial magnetic permeability of the magnetic material is greater than 1000 and the magnetostriction coefficient is greater than 10ppm; the piezoelectric layer is formed by piezoelectric materials such as PZT or PZN-PT or PMN-PT or AlN or HfO2, and the electrostriction coefficient of the piezoelectric material is greater than 500ppm. When voltage is loaded on the piezoelectric layer, based on the characteristics of piezoelectric materials, the piezoelectric layer will deform under the action of voltage, and the deformation will be further transmitted to the ferromagnetic layer, causing the magnetic permeability of the ferromagnetic layer to change accordingly due to its own deformation (under the action of large voltage, the magnetic permeability of the ferromagnetic layer will increase), thereby affecting the distribution of the external magnetic field.

[0033] When there is a measured current in the measured conductor, part of the voltage of the magnetoresistive sensing unit is fed back to the multiferroic material film through the voltage follower circuit and the voltage feedback circuit. The magnetic permeability of the ferromagnetic layer in the multiferroic material film will change under the action of voltage, causing the magnetic permeability of the multiferroic material film (ferromagnetic layer) to increase, making it easier for the magnetic field to flow through the multiferroic material film, thereby reducing the magnetic field flowing through the iron core, thereby changing the magnetic flux inside the iron core. When the magnetic flux inside the iron core decreases, the required feedback current also decreases accordingly, thereby achieving the purpose of reducing power consumption.

[0034] The following is a further description of the method for preparing the multiferroic material thin film of the present invention using a specific embodiment:

[0035] like Figure 3a As shown, a substrate 21 is provided, the surface of the substrate 1 is flat and has good insulation performance, and the substrate 1 is pretreated, and the pretreatment steps include: using acetone, alcohol and deionized water to ultrasonically clean the substrate 21 for 5 minutes, then blowing it dry with N2, and keeping it in an oven at 115°C for 20 minutes; the substrate of this embodiment is a Si substrate;

[0036] A first predefined pattern is formed on the substrate 21 by using photolithography technology, and a first conductive layer 22 corresponding to the shape of the first predefined pattern is deposited on the substrate 1 by using magnetron sputtering thin film growth technology. The first conductive layer 22 can be formed of conductive non-magnetic materials such as Cu and Au. The thickness of the first conductive layer 22 is about 10nm to 50nm. The first conductive layer 22 is used to form a lower electrode. After removing the photoresist with acetone, a lower electrode is formed on the substrate 21. Figure 3b As shown;

[0037] A second predefined pattern is formed on the first conductive layer 22 by photolithography technology, and a magnetoelectric composite layer 23 composed of a piezoelectric layer and a ferromagnetic layer is deposited on the first conductive layer 22 by using piezoelectric material and ferromagnetic material in sequence. Figure 3c As shown, a multilayer structure of substrate-lower electrode-piezoelectric layer-ferromagnetic layer is formed; the thickness of the magnetoelectric composite layer 23 is related to the size of the actual device and can be 500nm to 5000nm;

[0038] Using acetone to remove the photoresist, and forming a third predefined pattern on the magneto-electric composite layer 23 by photolithography;

[0039] like Figure 3d As shown, an insulating layer 24 is grown on the magneto-electric composite layer 23. The thickness of the insulating layer 24 is thicker than that of the magneto-electric composite layer 23. Generally, the thickness of the insulating layer 24 can be about 50 nm thicker than that of the magneto-electric composite layer 23. The insulating layer 24 can be formed of insulating materials such as SiO2 and Al2O3.

[0040] removing the photoresist with acetone, and forming a fourth predefined pattern on the insulating layer 24 by photolithography;

[0041] like Figure 3e As shown, a second conductive layer 25 is grown on the insulating layer 24, and the second conductive layer 25 is used to form an upper electrode. The material of the second conductive layer 25 is the same as that of the first conductive layer 22; the upper electrode and the lower electrode are used to connect a voltage feedback circuit;

[0042] The photoresist is removed by cleaning with acetone to obtain a multiferroic material film.

[0043] In the above steps, the method for forming the predefined pattern is as follows: after adding photoresist to the substrate, the substrate is first rotated at 600 rpm for 10 seconds on a coating machine so that the photoresist covers the Si wafer, and then rotated at 4000 rpm for 40 seconds to make the thickness of the photoresist uniform; the Si substrate with the spin-coated photoresist is placed in an oven and heated at 115°C for 20 minutes to completely cure the photoresist; the photoresist layer is exposed to ultraviolet light through a mask of a predefined pattern; and the excess photoresist is developed to remove the excess photoresist, leaving a predefined pattern on the Si substrate.

[0044] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may 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. Closed-loop current sensor, including: A pair of openable iron cores, a secondary feedback coil wound outside the iron cores, a magnetic resistance sensor unit and a signal processing unit; Features: The iron core is coated with a multiferroic material film, and the magnetic resistance sensor unit is arranged at the air gap of the magnetic circuit formed by the iron core; The signal processing unit includes a signal acquisition circuit, a signal amplification circuit, a current feedback circuit, a voltage follower circuit and a voltage feedback circuit; wherein the signal acquisition circuit is connected to the output end of the magnetoresistive sensing unit, and transmits the collected voltage signal to the signal amplification circuit, the output end of the signal amplification circuit has two outputs, one output to the current feedback circuit, and the other output to the voltage follower circuit; the output end of the current feedback circuit is connected to one end of the secondary feedback coil, and the other end of the secondary feedback coil is connected to the secondary resistor; the output end of the voltage follower circuit is connected to the voltage feedback circuit, and the output end of the voltage feedback circuit is connected to the multiferroic material film; The multiferroic material film comprises: a substrate, a first conductive layer formed on the substrate, a piezoelectric layer and a ferromagnetic layer formed on the first conductive layer, an insulating layer formed on the ferromagnetic layer, and a second conductive layer formed on the insulating layer, wherein the first conductive layer and the second conductive layer are respectively formed with an upper electrode and a lower electrode connected to the voltage feedback circuit; wherein the ferromagnetic layer is formed of a magnetic material, and the piezoelectric layer is formed of a piezoelectric material; When there is a measured current in the measured conductor, part of the voltage of the magnetoresistive sensing unit is fed back to the multiferroic material film through the voltage follower circuit and the voltage feedback circuit, and the magnetic permeability of the ferromagnetic layer changes under the action of the voltage, causing the magnetic flux inside the iron core to decrease.

2. The closed-loop current sensor according to claim 1, characterized in that: The magnetoresistive sensing unit is a TMR unit, a GMR unit, or an AMR unit, or the magnetoresistive sensing unit is replaced by a Hall element.

3. The closed-loop current sensor according to claim 1, wherein: The initial magnetic permeability of the magnetic material is greater than 1000 and the magnetostriction coefficient is greater than 10 ppm.

4. The closed-loop current sensor according to claim 1 or 3, characterized in that: The magnetic material is Ni, Fe, Co or an alloy thereof.

5. The closed-loop current sensor according to claim 1, wherein: The electrostriction coefficient of the piezoelectric material is greater than 500 ppm.

6. The closed-loop current sensor according to claim 1 or 5, characterized in that: The piezoelectric material is PZT or PZN-PT or PMN-PT or AlN or HfO2.

7. The closed-loop current sensor according to claim 1, characterized in that: The signal acquisition circuit includes a first amplifier, wherein an inverting input terminal and a non-inverting input terminal of the first amplifier are respectively connected to two output terminals of the magnetoresistive sensing unit via resistors, an inverting input terminal of the first amplifier is simultaneously connected to the output terminal of the first amplifier via a resistor, a non-inverting output terminal of the first amplifier is simultaneously connected to the output terminal of the first amplifier via a resistor, the non-inverting output terminal of the first amplifier is also grounded via a resistor, and the output terminal of the first amplifier is connected to the input terminal of the signal amplification circuit.

8. The closed-loop current sensor according to claim 1, wherein: The signal amplification circuit includes a second amplifier, the in-phase input terminal of the second amplifier is connected to the output terminal of the signal acquisition circuit via a resistor, the inverting input terminal of the second amplifier is grounded via a resistor and is simultaneously connected to the output terminal of the second amplifier via a resistor, and the output terminal of the second amplifier is respectively connected to the current feedback circuit and the voltage follower circuit.

9. The closed-loop current sensor according to claim 1, characterized in that: The current feedback circuit includes a third amplifier, a non-inverting input terminal of the third amplifier is grounded via a resistor, an inverting input terminal of the third amplifier is connected to the output terminal of the signal amplification circuit via a resistor, and is simultaneously connected to the output terminal of the third amplifier via a capacitor and a resistor, and the output terminal of the third amplifier is connected to the secondary feedback coil.

10. The closed-loop current sensor according to claim 1, characterized in that: The voltage follower circuit includes a fourth amplifier, the in-phase input terminal of the fourth amplifier is connected to the output terminal of the signal amplification circuit, the inverting input terminal of the fourth amplifier is connected to the output terminal of the fourth amplifier, and the output terminal of the fourth amplifier is connected to the input terminal of the voltage feedback circuit.

11. The closed-loop current sensor according to claim 1, wherein: The voltage feedback circuit includes a fifth amplifier, the in-phase input terminal of the fifth amplifier is connected to the output terminal of the voltage follower circuit through a resistor, the inverting input terminal of the fifth amplifier is grounded through a resistor, the inverting input terminal of the fifth amplifier is simultaneously connected to the output terminal of the fifth amplifier through a resistor, and the output terminal of the fifth amplifier is connected to the multiferroic material film.

12. The closed-loop current sensor according to claim 1, wherein: The magnetoresistive sensing unit is replaced by an RC modulation circuit.

Images