A giant magneto-impedance device and a giant magneto-impedance device detection circuit

Abstract

A giant magneto-impedance device and a giant magneto-impedance device detection circuit, comprising a magnetic core, a first helical coil and a second helical coil. The first helical coil is wound around the magnetic core, and the second helical coil is wound outside the first helical coil, and the winding direction is opposite to that of the first helical coil. The giant magneto-impedance device GMI sensor of the present invention uses low-cost soft magnetic materials and enameled copper wires. Compared with GMI sensors that require complex processing techniques for preparation, this magnetic core winding coil process is relatively mature, has a simple structure, low cost, and is easy to mass-produce.

Description

Technical Field

[0001] The present invention belongs to the technical field of sensors, and particularly relates to a giant magneto-impedance device and a detection circuit for the giant magneto-impedance device. Background Art

[0002] In fields such as power systems, motor control, and energy management, the accurate measurement of current is crucial for ensuring the safe and efficient operation of the system. Traditional current sensors, such as electromagnetic and Hall effect sensors, although quite mature in industrial applications, tend to show certain limitations when faced with extreme environmental conditions, strong electromagnetic interference, or the need for long-term stable operation. In environments with high temperature, high humidity, or strong magnetic fields, the measurement accuracy of these sensors may be affected, resulting in data deviation, which in turn affects the control accuracy and reliability of the entire system. Summary of the Invention

[0003] The purpose of the present invention is to provide a giant magneto-impedance device and a detection circuit for the giant magneto-impedance device to solve the problem that the measurement accuracy of existing sensors may be affected, resulting in data deviation.

[0004] To achieve the above purpose, the present invention adopts the following technical solutions:

[0005] A giant magneto-impedance device includes a magnetic core, a first spiral coil, and a second spiral coil. The first spiral coil is wound around the magnetic core, and the second spiral coil is wound outside the first spiral coil with a winding direction opposite to that of the first spiral coil.

[0006] Further, the magnetic core material is selected as a soft magnetic material, the shape of the magnetic core is a cylinder with a diameter of 0.8 mm and a length of 3 - 10 mm.

[0007] Further, the first spiral coil is formed by evenly and overlappingly winding 500 - 1000 turns of enameled copper wire with a diameter of 0.025 mm in a single-wire one-way winding method.

[0008] Further, before winding the coil, epoxy resin is evenly coated on the surface of the magnetic core, and epoxy resin is coated again after the coil winding is completed.

[0009] Further, the second spiral coil is formed by evenly and overlappingly winding 200 - 500 turns of enameled copper wire with a diameter of 0.1 mm in the opposite direction of the first spiral coil in a single-wire one-way winding method.

[0010] A giant magneto-impedance device detection circuit, based on a giant magneto-impedance device, further includes an open-loop circuit and a closed-loop feedback circuit. The open-loop circuit is connected to the first spiral coil and the closed-loop feedback circuit. The open-loop circuit is used for zero adjustment and filter amplification of the voltage signal. After the demodulated voltage signal is subjected to zero adjustment, the voltage signal is transmitted to the feedback circuit. The feedback circuit is connected to the second spiral coil.

[0011] Further, the open-loop circuit includes a signal generator, a detector, and a zero-adjustment and filter amplifier. The signal generator generates signal S1. The output port of the first spiral coil of the giant magneto-impedance device is connected in series with a resistor R to form a voltage-dividing circuit. The detector, as a demodulation unit, performs amplitude demodulation on the amplitude change of signal S1 distributed to the resistor end. The filter amplifier is used for zero adjustment and filter amplification of the voltage signal. After the demodulated voltage signal is subjected to zero adjustment, the voltage signal is transmitted to the feedback circuit.

[0012] Further, the feedback circuit includes a signal amplifier, a power amplification unit, and a sampling resistor. The output voltage signal of the open-loop circuit is amplified by the signal amplifier and the power amplifier, and the current signal is input to the input port of the second spiral coil of the giant magneto-impedance device. The second spiral coil of the giant magneto-impedance device serves as a negative feedback coil. The output port of the second spiral coil is connected in series with a resistor to form a sampling circuit. The voltage signal of the sampling resistor is output through a voltage follower to obtain a voltage signal linearly related to the magnetic field.

[0013] Further, the output voltage of the closed-loop feedback circuit is expressed as:

[0014] Compared with the prior art, the present invention has the following technical effects:

[0015] The giant magneto-impedance device GMI sensor of the present invention uses low-cost soft magnetic materials and enameled copper wires. Compared with GMI sensors that require complex processing technologies, this magnetic core winding coil process is relatively mature, has a simple structure, low cost, and is easy to mass-produce. Using soft magnetic materials as the magnetic core material has a high magneto-impedance change rate. The designed sensor can detect very weak magnetic field changes, thereby realizing high-resolution current measurement. Since the diameter and length of the magnetic core can be optimized as needed, and the fine winding of the coil, the overall size of the sensor is designed to be compact, suitable for miniaturized and integrated applications. Compared with the traditional closed-loop feedback current sensor with a magnetic flux concentrating ring structure, the coil 2 wound in the reverse direction is used as the closed-loop feedback coil, and the number of turns wound is significantly reduced, the self-inductance effect of the coil is reduced, the response speed of the sensor is improved, the power of the feedback circuit is reduced, and at the same time, the overall energy consumption of the sensor is greatly reduced, prolonging the service life of the sensor and reducing energy consumption, which is particularly important for power monitoring and control systems that need to operate for a long time. Description of the Drawings

[0016] Figure 1 It is a schematic diagram of the GMI device structure.

[0017] Figure 2 It is the self-resonance curve of the GMI device and the curve of impedance varying with magnetic field. Figure 2 On the left is the self-resonance curve of the GMI device, Figure 2 on the right is the curve of impedance varying with magnetic field when different external magnetic fields are applied to the GMI device.

[0018] Figure 3 It is the curve of impedance varying with frequency and current when different intensities of DC current excitation are applied to the GMI device through coil 2.

[0019] Figure 4 It is the curve of self-resonance frequency varying with current when different intensities of DC current excitation are applied to the GMI device through the feedback coil, Figure 4 on the left is the curve of self-resonance frequency varying with current when different intensities of DC current excitation are applied to the GMI device through coil 2, Figure 4 on the right is the curve of self-resonance frequency varying with current when different intensities of DC current excitation are applied to the GMI device through the magnetic flux concentrating ring feedback coil.

[0020] Figure 5 It is the curve of the power of coil 2 and the magnetic flux concentrating ring feedback coil varying with frequency.

[0021] Figure 6 It is the schematic diagram of the hardware detection circuit of the GMI sensor.

[0022] In the figure: 1 - magnetic core, 2 - first helical coil, 3 - second helical coil, 4 - input port of the first helical coil, 5 - output port of the first helical coil, 6 - input port of the second helical coil, 7 - output port of the second helical coil. Specific embodiments

[0023] The present invention will be further described below with reference to the accompanying drawings:

[0024] Please refer to Figures 1 to 6 , a giant magneto-impedance device includes a magnetic core 1, a first helical coil 2 and a second helical coil 3. The input port 4 of the first helical coil, the output port 5 of the first helical coil, the input port 6 of the second helical coil, the output port 7 of the second helical coil. As Figure 1 shown.

[0025] The material of the magnetic core 1 is selected as a soft magnetic material, including amorphous magnetic alloys and soft ferrites, etc. The shape of the magnetic core is a cylinder with a diameter of 0.8 mm and a length of 3 - 10 mm.

[0026] The first spiral coil 2 is formed by evenly and overlappingly winding 500 - 1000 turns of enameled copper wire with a diameter of 0.025 mm in a single - wire unidirectional winding method. Since the diameter of the magnetic core is relatively thin, a layer of epoxy resin is evenly coated on the surface of the magnetic core before winding the coil to increase the adhesion. After the coil winding is completed, epoxy resin is coated again to seal and fix.

[0027] The second spiral coil 3 is formed by evenly and overlappingly winding 200 - 500 turns of enameled copper wire with a diameter of 0.1 mm in a single - wire unidirectional winding method in the opposite direction to that of coil 1.

[0028] Since the enameled copper wire winding of the magnetic - core winding inductance generates parasitic capacitance, the parasitic capacitance and the inductance are in a parallel - resonance state, and self - resonance will occur at a certain frequency. There are two coil windings in the present invention. The resonance frequency of the magnetic - core winding inductance is: and As Figure 2 shown, when different external magnetic fields are applied, the magnetic permeability of the magnetic core 1 will change, resulting in the change of the inductance resonance frequency.

[0029] Using an impedance analyzer (TH2851) to test the curve of the impedance value of the second spiral coil 3 of the GMI device changing with frequency under the excitation of DC currents with different intensities. The test results are as Figure 3 shown. When the DC current applied to the second spiral coil 3 of the GMI device gradually increases, the second spiral coil 3 provides a bias magnetic field along the direction of the magnetic core, and the bias magnetic field also gradually increases. The resonance frequency of the inductance increases significantly, and the impedance value at the resonance point gradually decreases. When no current is applied to the second spiral coil 3 of the GMI device, the initial self - resonance frequency is about 2.4 MHz. By applying different levels of DC current to the second spiral coil 3 of the GMI device, the current range is 0 mA - 80 mA. From applying 15 mA current to 30 mA current to the second spiral coil 3, the change trend of the self - resonance frequency increases rapidly. As the applied current continues to increase, the change trend of the self - resonance frequency slows down and gradually approaches saturation. The self - resonance frequency in the saturation state is about 5.0 MHz. At the same time, a comparison is made with the way of providing a bias magnetic field by a traditional magnetic - concentrating ring feedback coil. Place the GMI device with no current in the second spiral coil 3 at the air gap of the magnetic - concentrating ring, and change the current of the feedback coil on the magnetic - concentrating ring to provide a changing bias magnetic field. By applying different intensities of DC current to the feedback coil of the magnetic - concentrating ring, the current range is 0 mA - 40 mA, as Figure 4 shown. As the current of the feedback coil increases, the self - resonance frequency of the GMI device shows an increasing trend and gradually approaches saturation. The self - resonance frequency in its saturation state is about 5.0 MHz.

[0030] In the present invention, the second spiral coil 3 of the GMI device is used as the feedback coil and compared with the traditional magnetic flux concentrating ring feedback coil. The impedance analyzer (TH2851) is used to measure the resistance values of the two coils. The resistance value of the second spiral coil of the GMI device is 10.14 Ω, and the resistance value of the magnetic flux concentrating ring feedback coil is 394.28 Ω. According to the power calculation formula: P = UI = I 2 ²R = U 2 ² / R, the powers of the two different feedback methods are calculated. As Figure 5 shown, it is the curve of the powers of the second spiral coil 3 and the magnetic flux concentrating ring feedback coil changing with the resonance frequency. When the diameter of the enameled copper wire used for winding the coil is the same, the number of turns and the length of the feedback coil of the magnetic flux concentrating ring winding are much larger than those of the second spiral coil 3 of the GMI device. When a direct current is applied to provide the same magnetic field, the power required by the magnetic flux concentrating ring feedback coil is greater. When the self-resonance frequency is 2.5 MHz, the power of the magnetic flux concentrating ring feedback coil is 7.81 mW, while the power of the second spiral coil 3 of the GMI device is 2.28 mW. The power of the magnetic flux concentrating ring feedback coil is 3.43 times that of the second spiral coil 3 of the GMI device. According to the test and analysis results, an obvious conclusion can be drawn that the four-port device based on the giant magneto-impedance effect proposed in the present invention as a closed-loop feedback current sensor is completely feasible, and its power consumption is lower than that of the traditional magnetic flux concentrating ring feedback coil.

[0031] As Figure 6 shown, the present invention provides a hardware detection circuit based on a giant magneto-impedance device, which includes two parts: an open-loop circuit and a closed-loop feedback circuit. The open-loop circuit consists of a signal generator, a detector, zero-point adjustment, and filter amplification. The signal generator is a MAX038 waveform generator chip, which generates a signal S1. The output port 5 of the first spiral coil of the GMI sensor is connected in series with a resistor R to form a voltage-dividing circuit. The detector selects an AD606 logarithmic detector as the demodulation unit, and the detector performs amplitude demodulation on the amplitude change of the excitation signal S1 distributed to the resistor end. The AD620 amplifier is selected for zero-point adjustment and filter amplification of the voltage signal. After the demodulated voltage signal is subjected to zero-point adjustment, the voltage signal Vref is transmitted to the feedback circuit.

[0032] The feedback circuit consists of a signal amplifier, a power amplification unit, and a sampling resistor. The signal amplifier selects an AD620. The power amplification is composed of two triodes, and the emitter of the triode can provide a maximum current output Is of 120 mA. The output voltage signal Vref of the open-loop circuit undergoes signal amplification and power amplification, and the current signal Is is input into the input port 6 of the second spiral coil of the GMI sensor. Through the second spiral coil 3 of the GMI sensor as the negative feedback coil, the output port 7 of the second spiral coil is connected in series with a resistor Rm to form a sampling circuit. The voltage signal Vm of the sampling resistor is output through a voltage follower to obtain a voltage signal Vout that is linear with the magnetic field.

[0033] The output voltage Vout of the circuit reflects the amplitude Is of the current in the feedback coil. The feedback magnetic field generated in the feedback coil is Bs. The closed-loop negative feedback of this design is a differential regulation system, that is, the magnetic field generated by the feedback coil is opposite to the direction of the external magnetic field and the intensity is approximate, but there is always an error ε. The output voltage of the closed-loop feedback circuit can be expressed as:

[0034] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the above embodiments, those of ordinary skill in the art should understand that: modifications or equivalent replacements can still be made to the specific implementation manners of the present invention, and any modifications or equivalent replacements that do not depart from the spirit and scope of the present invention shall be covered by the protection scope of the claims of the present invention.

Claims

1. A detection circuit for a giant magneto-impedance device, characterized in that, Based on a giant magneto-impedance device, the giant magneto-impedance device includes: a magnetic core (1), a first spiral coil (2) and a second spiral coil (3). The first spiral coil (2) is wound around the magnetic core (1), and the second spiral coil (3) is wound outside the first spiral coil (2) with a winding direction opposite to that of the first spiral coil (2). It further includes an open-loop circuit and a closed-loop feedback circuit. The open-loop circuit is connected to the first spiral coil (2) and the closed-loop feedback circuit, and the feedback circuit is connected to the second spiral coil (3). The second spiral coil (3) serves as a negative feedback coil. The open-loop circuit includes a signal generator, a detector, zero-point adjustment and a filter amplifier. The signal generator generates a signal S1. The output port of the first spiral coil (2) of the giant magneto-impedance device is connected in series with a resistor Rm to form a voltage-dividing circuit. The detector serves as a demodulation unit to perform amplitude demodulation on the amplitude change of the signal S1 distributed to the resistor end. The filter amplifier serves as zero-point adjustment and filtering amplification of the voltage signal. After the demodulated voltage signal is subjected to zero-adjustment processing, the voltage signal is transmitted to the feedback circuit.

2. The detection circuit of a giant magneto-impedance device according to claim 1, wherein The feedback circuit includes a signal amplifier, a power amplification unit and a sampling resistor. The output voltage signal of the zero-point adjustment is amplified in signal and power, and the current signal is input into the input port of the second spiral coil (3) of the giant magneto-impedance device. The second spiral coil (3) of the giant magneto-impedance device serves as a negative feedback coil. The output port of the second spiral coil (3) is connected in series with a resistor to form a sampling circuit, and the voltage signal of the sampling resistor is output to the input end of the filter amplification through a voltage follower.

3. The giant magneto-impedance device detection circuit according to claim 1, wherein The output voltage of the closed-loop feedback circuit is expressed as: .

4. A giant magneto-impedance device detection circuit according to claim 1, characterized in that The magnetic core material is selected as a soft magnetic material. The shape of the magnetic core is a cylinder with a diameter of 0.8 mm and a length of 3 - 10 mm.

5. The detection circuit of a giant magneto-impedance device according to claim 1, characterized in that The first spiral coil (2) is a coil formed by uniformly and overlappingly winding 500 - 1000 turns of enameled copper wire with a diameter of 0.025 mm by the single-wire unidirectional close-winding method.

6. The giant magneto-impedance device detection circuit according to claim 5, characterized in that, Before winding the coil, epoxy resin is uniformly coated on the surface of the magnetic core, and epoxy resin is coated again after the coil winding is completed.

7. The detection circuit of a giant magneto-impedance device according to claim 1, characterized in that The second spiral coil (3) is a coil formed by uniformly and overlappingly winding 200 - 500 turns of enameled copper wire with a diameter of 0.1 mm in the direction opposite to that of the first spiral coil (2) by the single-wire unidirectional close-winding method.

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