Current sensor

Abstract

The invention relates to a current sensor. The current sensor comprises a magnetism gathering ring, a first magnetic modulation chip, a second magnetic modulation chip, an output unit and a compensation coil. A coil to be measured is placed in the magnetism gathering ring, and current passes through the coil to be measured. The magnetism gathering ring is provided with a first end and a second end, the first end is provided with the first magnetic modulation chip, and the second end is provided with the second magnetic modulation chip; the first magnetic modulation chip outputs a first voltage and a second voltage, and the second magnetic modulation chip outputs a third voltage and a fourth voltage; the input end of the output unit is respectively connected with the output end of the first magnetic modulation chip and the output end of the second magnetic modulation chip, and the output unit is used for outputting a fifth voltage; the compensation coil is connected with the output end of the output unit and generates compensation current under the action of the fifth voltage, and the compensation current is used for enabling the magnetism gathering ring to keep zero magnetic flux. According to the current sensor, the measurement precision of the current sensor can be improved at low cost.

Description

Technical Field

[0001] The present application relates to the technical field of precision current sensing, and in particular to a current sensor. Background Art

[0002] Current sensors play an important role in smart grids, aerospace, precision instrument measurement and other fields. Common current sensors include Hall current sensors, shunts, current transformers, fluxgate current sensors, giant magnetoresistance current sensors, etc. Among them, magnetic modulation current sensors are superior to other sensors in terms of temperature stability, sensitivity, magnetic interference, volume, cost, etc. Therefore, current sensors based on magnetic modulation effect have been widely used at home and abroad.

[0003] In order to meet the increasingly high accuracy requirements, the current sensor based on the magnetic modulation effect currently reduces the influence of nearby wires and stray magnetic fields on the measurement accuracy of the current sensor by improving the magnetic shielding shell, so as to improve the accuracy of the current sensor. However, this method has high requirements on the material and structural design of the magnetic shielding shell, which brings high research costs.

[0004] Regarding the current sensor with magnetic modulation effect, how to improve the measurement accuracy of the current sensor at low cost is still an urgent issue to be considered. Summary of the invention

[0005] Based on this, it is necessary to provide a current sensor that can improve the measurement accuracy of the current sensor at a low cost.

[0006] In a first aspect, a current sensor is provided, comprising: a magnetic focusing ring, a first magnetic modulation chip, a second magnetic modulation chip, an output unit and a compensation coil;

[0007] The coil under test is placed in the magnetic focusing ring, and a current flows through the coil under test;

[0008] The magnetic focusing ring is provided with a first end and a second end, the first end and the second end are arranged opposite to each other to form an opening, the first end is provided with the first magnetic modulation chip, and the second end is provided with the second magnetic modulation chip;

[0009] The first magnetic modulation chip outputs a first voltage and a second voltage, and the second magnetic modulation chip outputs a third voltage and a fourth voltage;

[0010] The input end of the output unit is connected to the output end of the first magnetic modulation chip and the output end of the second magnetic modulation chip respectively, and the output unit is used to output a fifth voltage based on the first voltage, the second voltage, the third voltage and the fourth voltage;

[0011] The compensation coil is connected to the output end of the output unit, and generates a compensation current under the action of the fifth voltage, and the compensation current is used to keep the magnetic flux of the magnetic focusing ring zero.

[0012] In one embodiment, the first magnetic modulation chip includes: a resistor R1, a resistor R2, a resistor R3 and a resistor R4;

[0013] The first end of the resistor R1 is connected to the second end of the resistor R3, the first end of the resistor R3 is connected to the second end of the resistor R4, the first end of the resistor R4 is connected to the second end of the resistor R2, and the first end of the resistor R2 is connected to the second end of the resistor R1;

[0014] The connection point between the resistor R1 and the resistor R2 is used to output the first voltage, and the connection point between the resistor R3 and the resistor R4 is used to output the second voltage; the connection point between the resistor R1 and the resistor R3 is used to receive external power supply, and the connection point between the resistor R2 and the resistor R4 is grounded;

[0015] The resistor R2 and the resistor R3 are provided with a magnetic field shielding layer.

[0016] In one embodiment, the second magnetic modulation chip includes: a resistor R5, a resistor R6, a resistor R7 and a resistor R8;

[0017] The first end of the resistor R5 is connected to the second end of the resistor R7, the first end of the resistor R7 is connected to the second end of the resistor R8, the first end of the resistor R8 is connected to the second end of the resistor R6, and the first end of the resistor R6 is connected to the second end of the resistor R7;

[0018] The connection point between the resistor R5 and the resistor R6 is used to output the third voltage, and the connection point between the resistor R7 and the resistor R8 is used to output the fourth voltage; the connection point between the resistor R5 and the resistor R7 is used to receive external power supply, and the connection point between the resistor R6 and the resistor R8 is grounded;

[0019] The resistor R6 and the resistor R7 are provided with an electromagnetic shielding layer.

[0020] In one embodiment, the output unit includes: a first amplification unit, a feedback controller, and a second amplification unit;

[0021] The first amplifying unit has an input end connected to the output end of the first magnetic modulation chip and the output end of the second magnetic modulation chip, and an output end connected to the input end of the feedback controller;

[0022] The first amplifying unit is used for performing differential amplification processing on the first voltage, the second voltage, the third voltage and the fourth voltage to output a sixth voltage;

[0023] The feedback controller has an output end connected to the input end of the second amplifying unit, and the feedback controller is used to output a seventh voltage based on the sixth voltage; the feedback controller is also connected to the compensation coil, and is used to control the magnitude of the seventh voltage according to the compensation current;

[0024] The second amplifying unit has an output end connected to the compensation coil, and is used to amplify the seventh voltage and output it as the fifth voltage.

[0025] In one embodiment, the first amplification unit includes: a first operational amplifier, a second operational amplifier and a comparison amplifier;

[0026] The first input terminal of the first operational amplifier is connected to the output terminal of the first magnetic modulation chip for receiving the first voltage, and the second input terminal is connected to the output terminal of the first magnetic modulation chip for receiving the second voltage; the output terminal of the first operational amplifier outputs an eighth voltage;

[0027] The first input terminal of the second operational amplifier is connected to the output terminal of the second magnetic modulation chip for receiving the third voltage, and the second input terminal is connected to the output terminal of the second magnetic modulation chip for receiving the fourth voltage; the output terminal of the second operational amplifier outputs a ninth voltage;

[0028] The first input terminal of the comparison amplifier is connected to the output terminal of the first operational amplifier for receiving the eighth voltage, the second input terminal is connected to the output terminal of the second operational amplifier for receiving the ninth voltage, and the output terminal is used to output the sixth voltage.

[0029] In one embodiment, the first amplification unit includes:

[0030] A power amplifier circuit, wherein the input end of the power amplifier circuit is connected to the output end of the first amplifying unit, and the output end of the power amplifier circuit is connected to the input end of the feedback controller.

[0031] In one embodiment, the power amplifier circuit includes: a first diode, a second diode, a resistor R9, a resistor R10, a first transistor and a second transistor;

[0032] The cathode of the first diode and the anode of the second diode are both connected to the output end of the comparison amplifier;

[0033] The anode of the first diode is connected to the first end of the resistor R9 and is also connected to the control end of the first transistor; the second end of the resistor R9 is connected to the first end of the first transistor; the second end of the first transistor is connected to the input end of the feedback controller;

[0034] The cathode of the second diode is connected to the first end of the resistor R10 and is also connected to the control end of the second transistor; the second end of the resistor R10 is connected to the first end of the second transistor; the second end of the second transistor is connected to the input end of the feedback controller;

[0035] The first end of the first transistor also receives an external positive voltage, and the first end of the second transistor also receives an external negative voltage.

[0036] In one embodiment, it further includes: a resistor R11;

[0037] A first end of the resistor R11 is connected to the output end of the compensation coil, and a second end thereof is grounded;

[0038] The voltage across the resistor R11 is used to calculate the magnitude of the compensation current.

[0039] In one embodiment, the second amplifying unit includes at least one operational amplifier.

[0040] In one of the embodiments, a first magnetic shielding cover is disposed at the first end of the magnetic focusing ring, and a second magnetic shielding cover is disposed at the second end.

[0041] The above-mentioned current sensor is provided with a first magnetic modulation chip and a second magnetic modulation chip at the opening of the magnetic focusing ring. The first magnetic modulation chip and the second magnetic modulation chip are both connected to the output unit, and the output unit is connected to the compensation coil. The voltage output by the first magnetic modulation chip and the second magnetic modulation chip changes under the influence of the magnetic field generated by the measured coil (the magnetic field on the magnetic focusing ring), and the magnitude of the compensation current generated by the compensation coil is related to the magnitude of the voltage output by the first magnetic modulation chip and the second magnetic modulation chip. The compensation coil will generate a compensation current, which will generate a feedback current magnetic potential to keep zero magnetic flux on the magnetic focusing ring, and will also make the voltage output by the first magnetic modulation chip and the second magnetic modulation chip close to 0 volts, reducing the influence of nearby wires (i.e., the measured coil) on the measurement accuracy of the current sensor, so as to improve the accuracy of the current sensor. In addition, the first magnetic modulation chip and the second magnetic modulation chip may also be interfered by external factors such as external stray magnetic fields and temperature, thereby causing the output voltage to change. The current sensor provided in this embodiment can also reduce the interference of external factors such as stray magnetic fields or temperature on the current sensor through the compensation current. The current sensor provided in the embodiment of the present application has a simple structure and low manufacturing cost, and can improve the accuracy of the magnetic modulation effect current sensor at a low cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the conventional technology, the drawings required for use in the embodiments or the conventional technology descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] FIG1 is a current sensor according to an embodiment;

[0044] FIG2 is a current sensor according to another embodiment;

[0045] FIG3 is a current sensor according to another embodiment;

[0046] Description of reference numerals:

[0047] 10. Current sensor; 11. Magnetic focusing ring; 12. First magnetic modulation chip; 13. Second magnetic modulation chip; 14. Output unit; 15. Compensation coil; 16. Magnetic field shielding layer; 20. Measured coil;

[0048] 110, a first magnetic shield; 120, a second magnetic shield;

[0049] 140. A first amplifying unit; 141. A feedback controller; 142. A second amplifying unit; 143. A first operational amplifier; 144. A second operational amplifier; 145. A comparison amplifier; 146. A power amplifier circuit; 147. A first diode; 148. A second diode; 149. A first transistor; 150. A second transistor; 151. An operational amplifier. DETAILED DESCRIPTION

[0050] In order to facilitate understanding of the present application, the present application will be described more fully below with reference to the relevant drawings. Embodiments of the present application are provided in the drawings. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present application more thorough and comprehensive.

[0051] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application.

[0052] It is understood that the terms "first", "second", etc. used in this application may be used herein to describe various elements, but these elements are not limited by these terms. These terms are only used to distinguish a first element from another element. For example, without departing from the scope of this application, a first resistor may be referred to as a second resistor, and similarly, a second resistor may be referred to as a first resistor. Both the first resistor and the second resistor are resistors, but they are not the same resistor.

[0053] It can be understood that the “connection” in the following embodiments should be understood as “electrical connection”, “communication connection”, etc. if the connected circuits, modules, units, etc. have electrical signals or data transmission between each other.

[0054] It can be understood that “at least one” means one or more, “plurality” means two or more, and “at least a portion of an element” means a part or all of an element.

[0055] When used herein, the singular forms "a", "an", and "said / the" may also include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "include / comprise" or "have" and the like specify the presence of stated features, wholes, steps, operations, components, parts, or combinations thereof, but do not exclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof. At the same time, the term "and / or" used in this specification includes any and all combinations of the relevant listed items.

[0056] Current sensors play an important role in smart grids, aerospace, precision instrument measurement and other fields. Common current sensors include Hall current sensors, shunts, current transformers, fluxgate current sensors, giant magnetoresistance current sensors, etc. Among them, magnetic modulation current sensors are superior to other sensors in terms of temperature stability, sensitivity, magnetic interference, volume, cost, etc. Therefore, current sensors based on magnetic modulation effect have been widely used at home and abroad.

[0057] In order to meet the increasingly high accuracy requirements, the current sensor based on the magnetic modulation effect currently reduces the influence of nearby wires and stray magnetic fields on the measurement accuracy of the current sensor by improving the magnetic shielding shell, so as to improve the accuracy of the current sensor. However, this method has high requirements on the material and structural design of the magnetic shielding shell, which brings high research costs.

[0058] As shown in FIG1 , a current sensor 10 according to an embodiment of the present invention includes a magnetic focusing ring 11 , a first magnetic modulation chip 12 , a second magnetic modulation chip 13 , an output unit 14 and a compensation coil 15 .

[0059] The coil 20 to be tested is placed in the magnetic field collecting ring 11, and current flows through the coil 20 to be tested. The coil 20 to be tested is a straight wire with current flowing through it, and the magnetic field collecting ring 11 is used to collect the magnetic field generated by the straight wire with current flowing through it. Current flows through the coil 20 to be tested, causing the magnetic field to be generated by the magnetic field collecting ring 11. The material of the magnetic field collecting ring 11 can be iron.

[0060] As shown in the figure, the magnetic focusing ring 11 is not a closed ring, and the magnetic focusing ring 11 is provided with a first end and a second end, and the first end and the second end are arranged opposite to each other to form an opening. The formed opening can also be understood as an air gap on the magnetic focusing ring 11.

[0061] The first end is provided with the first magnetic modulation chip 12, and the second end is provided with the second magnetic modulation chip 13. As shown in the figure, the first magnetic modulation chip 12 is provided at the first end, and outputs the first voltage and the second voltage under the influence of the magnetic field at the first end. As shown in the figure, the second magnetic modulation chip 13 is provided at the second end, and outputs the third voltage and the fourth voltage under the influence of the magnetic field at the second end. The magnitude of the first voltage and the second voltage output by the first magnetic modulation chip 12 depends on the degree to which the first magnetic modulation chip 12 is affected by the magnetic field. In other words, the stronger the magnetic field at the first end of the magnetic focusing ring 11, the greater the first voltage and the second voltage. The stronger the magnetic field at the second end of the magnetic focusing ring 11, the greater the third voltage and the fourth voltage.

[0062] Optionally, the first magnetic modulation chip 12 and the second magnetic modulation chip 13 have the same structure and model. Both the first magnetic modulation chip 12 and the second magnetic modulation chip 13 can be a shielded bridge structure, the first magnetic modulation chip 12 can be composed of four magnetic sensitive elements, and the second magnetic modulation chip 13 can be composed of four magnetic sensitive elements. The resistance of the magnetic sensitive element will change with the external magnetic field, so the internal resistance of the first magnetic modulation chip 12 will change with the magnetic field of the first end of the magnetic focusing ring 11, and the internal resistance of the second magnetic modulation chip 13 will change with the magnetic field of the second end of the magnetic focusing ring 11. The smaller the magnetic field of the magnetic focusing ring 11, the smaller the internal resistance of the first magnetic modulation chip 12, and the smaller the output first voltage. The smaller the magnetic field of the magnetic focusing ring 11, the smaller the internal resistance of the second magnetic modulation chip 13, and the smaller the output second voltage.

[0063] The input end of the output unit 14 is connected to the output end of the first magnetic modulation chip 12 to receive the first voltage and the second voltage. The input end of the output unit 14 is also connected to the output end of the second magnetic modulation chip 13 to receive the third voltage and the fourth voltage.

[0064] The output unit 14 is used to output a fifth voltage based on the first voltage, the second voltage, the third voltage and the fourth voltage. Optionally, the output unit 14 can perform differential amplification processing on the first voltage and the second voltage, and can also perform differential amplification processing on the third voltage and the fourth voltage. The output unit 14 can also perform multiple amplification processing on the voltage after differential amplification processing.

[0065] The compensation coil 15 is connected to the output end of the output unit 14, and generates a compensation current under the action of the fifth voltage, and the compensation current is used to keep the magnetic flux of the magnetic focusing ring 11 zero. The compensation coil 15 is a winding coil, and the number of turns can be selected according to actual needs. The compensation coil 15 generates a feedback current magnetic potential on the magnetic focusing ring 11 with an air gap, so that the magnetic flux on the magnetic focusing ring 11 is maintained zero. Specifically, the compensation current of the compensation coil 15 will generate a feedback current magnetic potential opposite to the magnetic field generated by the current of the measured coil 20 (that is, the primary side current), thereby reducing the magnetic field on the magnetic focusing ring 11. Since the magnitude of the output voltage of the first magnetic modulation chip 12 and the second magnetic modulation chip 13 is affected by the magnetic field on the magnetic focusing ring 11, the smaller the magnetic field on the magnetic focusing ring 11, the smaller the output voltage of the first magnetic modulation chip 12 and the second magnetic modulation chip 13. When there is zero magnetic flux on the magnetic focusing ring 11, the output voltage of the first magnetic modulation chip 12 and the second magnetic modulation chip 13 is close to 0 volts.

[0066] When the magnetic flux of the magnetic focusing ring 11 is zero, ,in, represents the current of the coil 20 under test, represents the number of turns of the coil 20 under test, represents the current of the compensation coil 15, represents the number of turns of the compensation coil 15.

[0067] The current sensor 10 provided in this embodiment has a first magnetic modulation chip 12 and a second magnetic modulation chip 13 disposed at the opening of the magnetic focusing ring 11. The first magnetic modulation chip 12 and the second magnetic modulation chip 13 are both connected to the output unit 14, and the output unit 14 is connected to the compensation coil 15. The voltage output by the first magnetic modulation chip 12 and the second magnetic modulation chip 13 changes under the influence of the magnetic field generated by the measured coil 20 (the magnetic field on the magnetic focusing ring 11), and the magnitude of the compensation current generated by the compensation coil 15 is related to the magnitude of the voltage output by the first magnetic modulation chip 12 and the second magnetic modulation chip 13. The compensation coil 15 generates a compensation current, which generates a feedback current magnetic potential, so that the magnetic flux on the magnetic focusing ring 11 is kept zero, and the voltage output by the first magnetic modulation chip 12 and the second magnetic modulation chip 13 is close to 0 volts, reducing the influence of the nearby wires (i.e., the measured coil 20) on the measurement accuracy of the current sensor 10, so as to improve the accuracy of the current sensor 10. In addition, the first magnetic modulation chip 12 and the second magnetic modulation chip 13 may also be interfered by external factors such as external stray magnetic fields and temperature, thereby causing the output voltage to change. The current sensor 10 provided in this embodiment can also reduce the interference of external factors such as stray magnetic fields or temperature on the current sensor 10 through the compensation current. The current sensor 10 provided in this embodiment has a simple structure and low manufacturing cost, and can improve the accuracy of the magnetic modulation effect current sensor 10 at a low cost.

[0068] In one embodiment, referring to FIG. 2 , the first magnetic modulation chip 12 includes: a resistor R1 , a resistor R2 , a resistor R3 , and a resistor R4 .

[0069] The first end of the resistor R1 is connected to the second end of the resistor R3 , the first end of the resistor R3 is connected to the second end of the resistor R4 , the first end of the resistor R4 is connected to the second end of the resistor R2 , and the first end of the resistor R2 is connected to the second end of the resistor R1 .

[0070] The connection point of the resistor R1 and the resistor R2 is used to output the first voltage, and the connection point of the resistor R3 and the resistor R4 is used to output the second voltage. The connection point of the resistor R1 and the resistor R3 is connected to the external power supply terminal for receiving external power supply. The voltage of the external power supply is VCC (Volt Current Condenser) as shown in the figure, and the connection point of the resistor R2 and the resistor R4 is grounded. The connection point of the resistor R2 and the resistor R3 may also not be grounded, but connected to a power supply terminal with a lower voltage.

[0071] The resistor R2 and the resistor R3 are provided with a magnetic field shielding layer 16. The magnetic field shielding layer 16 shields the external magnetic field, so the resistance of the resistor R2 and the resistor R3 will not change with the external magnetic field. However, the resistor R1 and the resistor R4 are not provided with a magnetic field shielding layer 16, so the resistance of the resistor R1 and the resistor R4 will change with the external magnetic field. The material of the magnetic field shielding layer 16 can be selected according to actual needs, and this embodiment does not limit it.

[0072] The initial resistance values ​​of resistors R1, R2, R3 and R4 are The resistance values ​​of resistors R1 and R4 will change with the external magnetic field. When there is no external magnetic field, the resistance values ​​of resistors R1, R2, R3 and R4 are , the output voltage of the first magnetic modulation chip 12 is 0 volts. At this time, the output voltage of the first magnetic modulation chip 12 is , where represents the resistance value of resistor R1, represents the resistance value of resistor R2, represents the resistance value of resistor R3, represents the resistance value of resistor R4, represents the first voltage, represents the second voltage, Represents the reference voltage.

[0073] When the current sensor 10 is disturbed by an external magnetic field, the resistance values ​​of the resistors R1 and R4 will change by , and this change It is linearly related to the magnitude of the magnetic field. The resistance values ​​of resistors R2 and R3 are still At this time, the output voltage of the first magnetic modulation chip 12 is , where Represents the resistance change, represents the first voltage, represents the second voltage, Represents the reference voltage.

[0074] Please refer to FIG. 2 . Similarly, the second magnetic modulation chip 13 includes a resistor R5 , a resistor R6 , a resistor R7 and a resistor R8 .

[0075] The first end of the resistor R5 is connected to the second end of the resistor R7, the first end of the resistor R7 is connected to the second end of the resistor R8, the first end of the resistor R8 is connected to the second end of the resistor R6, and the first end of the resistor R6 is connected to the second end of the resistor R7.

[0076] The connection point of the resistor R5 and the resistor R6 is used to output the third voltage, and the connection point of the resistor R7 and the resistor R8 is used to output the fourth voltage. The connection point of the resistor R5 and the resistor R7 is used to receive external power supply, and the connection point of the resistor R6 and the resistor R8 is grounded. The voltage of the external power supply is VCC (full name Volt Current Condenser) as shown in the figure, and the connection point of the resistor R6 and the resistor R8 is grounded. The connection point of the resistor R6 and the resistor R8 may not be grounded, but connected to a power supply terminal with a lower voltage.

[0077] Resistors R6 and R7 are provided with electromagnetic shielding layers. The magnetic field shielding layer 16 shields the external magnetic field, so the resistance values ​​of resistors R6 and R7 will not change with the external magnetic field. Resistors R5 and R8 are not provided with magnetic field shielding layer 16, so the resistance values ​​of resistors R5 and R8 will change with the external magnetic field. The material of the magnetic field shielding layer 16 can be selected according to actual needs, and this embodiment does not limit it.

[0078] The initial resistance values ​​of resistors R5, R6, R7 and R8 are The resistance values ​​of resistors R5 and R8 will change with the change of external magnetic field. When there is no external magnetic field, the resistance values ​​of resistors R5, R6, R7 and R8 are , the output voltage of the first magnetic modulation chip 12 is 0 volts. At this time, the output voltage of the first magnetic modulation chip 12 is , where represents the resistance value of resistor R5, represents the resistance value of resistor R6, represents the resistance value of resistor R7, represents the resistance value of resistor R8, represents the third voltage, represents the fourth voltage, Represents the reference voltage.

[0079] When the current sensor 10 is disturbed by an external magnetic field, the resistance values ​​of the resistors R5 and R8 will change by , and this change It is linearly related to the magnitude of the magnetic field. The resistance values ​​of resistors R6 and R7 are still At this time, the output voltage of the first magnetic modulation chip 12 is , where Represents the resistance change, represents the third voltage, represents the fourth voltage, Represents the reference voltage.

[0080] When external factors (such as temperature) change, the output voltage of the magnetic modulation chip will also change. The output voltage of the magnetic modulation chip can be expressed as .in The voltage offset caused by the external stray magnetic field, is the voltage offset caused by temperature, is the sensitivity of the magnetic modulation chip. The magnetic modulation chip here represents the first magnetic modulation chip 12 and also represents the second magnetic modulation chip 13.

[0081] In one embodiment, referring to FIG. 3 , the output unit 14 includes a first amplifying unit 140 , a feedback controller 141 and a second amplifying unit 142 .

[0082] The first amplifying unit 140 has an input end connected to the output end of the first magnetic modulation chip 12 and the output end of the second magnetic modulation chip 13, and an output end connected to the input end of the feedback controller 141. The first amplifying unit 140 is used to perform differential amplification processing on the first voltage, the second voltage, the third voltage and the fourth voltage to output a sixth voltage.

[0083] The first amplifier unit 140 is used to differentially amplify the first voltage and the second voltage to output an eighth voltage, and differentially amplify the third voltage and the fourth voltage to output a ninth voltage. The eighth voltage and the ninth voltage are differentially amplified and then output as a sixth voltage.

[0084] Optionally, the first operational amplification unit may include a first operational amplifier 143 , a second operational amplifier 144 and a comparison amplifier 145 .

[0085] The first input terminal of the first operational amplifier 143 is connected to the output terminal of the first magnetic modulation chip 12 for receiving the first voltage. The second input terminal of the first operational amplifier 143 is connected to the output terminal of the first magnetic modulation chip 12 for receiving the second voltage. The output terminal of the first operational amplifier 143 outputs an eighth voltage. As shown in the figure, the first input terminal of the first operational amplifier 143 is a negative phase input terminal, and the second input terminal is a positive phase input terminal. The first operational amplifier 143 is used to perform differential amplification on the first voltage and the second voltage and output them as an eighth voltage.

[0086] The first input terminal of the second operational amplifier 144 is connected to the output terminal of the second magnetic modulation chip 13 for receiving the third voltage, and the second input terminal is connected to the output terminal of the second magnetic modulation chip 13 for receiving the fourth voltage. The output terminal of the second operational amplifier 144 outputs a ninth voltage. As shown in the figure, the first input terminal of the second operational amplifier 144 is a negative phase input terminal, and the second input terminal is a positive phase input terminal. The second operational amplifier 144 is used to perform differential amplification on the third voltage and the fourth voltage and output them as a ninth voltage.

[0087] The first input terminal of the comparison amplifier 145 is connected to the output terminal of the first operational amplifier 143, and is used to receive the eighth voltage. The second input terminal of the comparison amplifier 145 is connected to the output terminal of the second operational amplifier 144, and is used to receive the ninth voltage. The output terminal of the comparison amplifier 145 is used to output the sixth voltage. As shown in the figure, the first input terminal of the comparison amplifier 145 is a positive phase input terminal, and the second input terminal of the comparison amplifier 145 is a negative phase input terminal. The comparison amplifier 145 is used to perform differential amplification on the eighth voltage and the ninth voltage and output them as the sixth voltage.

[0088] Since the first magnetic modulation chip 12 and the second magnetic modulation chip 13 are bipolar giant magnetoresistive chips of the same model and the same type stacked together, the voltage output by the first magnetic modulation chip 12 is converted into a single-ended output by the first operational amplifier 143, and the output voltage of the second magnetic modulation chip 13 is converted into a single-ended output by the second operational amplifier 144, and the output voltage of the first operational amplifier 143 and the output voltage of the second operational amplifier 144 are then output by the comparison amplifier 145. Therefore, the first magnetic modulation chip 12, the second magnetic modulation chip 13, the first operational amplifier 143, the second operational amplifier 144 and the comparison amplifier 145 constitute a differential component based on the magnetic modulation effect. The sixth voltage output by the differential component is: , where represents the eighth voltage, represents the ninth voltage, represents the sensitivity of the magnetic modulation chips (the first magnetic modulation chip 12 and the second magnetic modulation chip 13 ).

[0089] The feedback controller 141 has an output end connected to an input end of the second amplifying unit 142, and the feedback controller 141 is used to output a seventh voltage based on the sixth voltage. The feedback controller 141 is also connected to the compensation coil 15 (not shown in the connection diagram), and is used to control the magnitude of the seventh voltage according to the compensation current. Specifically, the feedback controller 141 determines whether the magnetic flux of the magnetic focusing ring 11 is zero according to the compensation current. If it is not zero, the magnitude of the seventh voltage is controlled to maintain zero magnetic flux on the magnetic focusing ring 11.

[0090] The output end of the second amplifying unit 142 is connected to the compensation coil 15, and is used to amplify the seventh voltage and output it as the fifth voltage. The second amplifying unit 142 may include at least one operational amplifier 151, and the operational amplifier 151 further amplifies the seventh voltage and outputs it as the fifth voltage.

[0091] The first amplifying unit 140 , the feedback controller 141 and the second amplifying unit 142 have simple structures, which reduces the manufacturing cost of the current amplifier.

[0092] In one embodiment, as shown in FIG3 , the first amplifying unit 140 further includes a power amplifying circuit 146 . The input end of the power amplifying circuit 146 is connected to the output end of the first amplifying unit 140 . The output end of the power amplifying circuit 146 is connected to the input end of the feedback controller 141 .

[0093] The power amplifier circuit 146 may include a plurality of transistors to amplify the voltage power.

[0094] For example, the power amplifier circuit 146 includes a first diode 147 , a second diode 148 , a resistor R9 , a resistor R10 , a first transistor 149 , and a second transistor 150 as shown in the figure.

[0095] The cathode of the first diode 147 and the anode of the second diode 148 are both connected to the output terminal of the comparison amplifier 145. The cathode of the first diode 147 is connected to the anode of the second diode 148.

[0096] The anode of the first diode 147 is connected to the first end of the resistor R9. The anode of the first diode 147 is also connected to the control end of the first triode 149. The second end of the resistor R9 is connected to the first end of the first triode 149. The second end of the first triode 149 is connected to the input end of the feedback controller 141.

[0097] The cathode of the second diode 148 is connected to the first end of the resistor R10. The cathode of the second diode 148 is also connected to the control end of the second triode 150. The second end of the resistor R10 is connected to the first end of the second triode 150. The second end of the second triode 150 is connected to the input end of the feedback controller 141.

[0098] The first end of the first transistor 149 also receives an external positive voltage, and the first end of the second transistor 150 also receives an external negative voltage.

[0099] As shown in the figure, the first triode 149 and the second triode 150 are triodes of different types. The first end of the first triode 149 is a collector, and the second end is an emitter. The first end of the second triode 150 is a collector, and the second end is an emitter. The collector of the first triode 149 and the collector of the second triode 150 are both connected to the input end of the feedback controller 141.

[0100] The first diode 147 , the second diode 148 , the first transistor 149 , the second transistor 150 , the resistor R9 and the resistor R10 form a class AB complementary symmetrical power amplifier circuit for driving the compensation coil 15 to generate a compensation current.

[0101] The power amplifier circuit 146 has a simple structure, which reduces the manufacturing cost of the current sensor 10 .

[0102] In some embodiments, the current sensor 10 further includes a resistor R11. A first end of the resistor R11 is connected to the output end of the compensation coil 15, and a second end of the resistor R11 is grounded. The voltage across the resistor R11 is used to calculate the magnitude of the compensation current. Specifically, as shown in the figure, the compensation current Through the resistor R11, the voltage across the resistor R11 can be measured as The feedback controller 141 is implemented by It can be determined As described above, when The magnetic flux can be kept zero only when the magnetic flux collecting ring 11 is Cannot satisfy When the seventh voltage is adjusted, the The size of satisfy .

[0103] Therefore, the measurement accuracy of the current sensor 10 can be further improved by providing the feedback controller 141 .

[0104] In some embodiments, see FIG3 , the first end of the magnetic focusing ring 11 is provided with a first magnetic shield 110, and the second end is provided with a second magnetic shield 120. The first magnetic shield 110 and the second magnetic shield 120 can shield other magnetic interferences, thereby improving the measurement accuracy of the current sensor 10. Other magnetic interferences refer to magnetic interferences not generated by the measured coil 20.

[0105] In the description of this specification, the description with reference to the terms "some embodiments", "other embodiments", etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In this specification, the schematic description of the above terms does not necessarily refer to the same embodiment or example.

[0106] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0107] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the present application. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A current sensor, characterized in that: include: A magnetic focusing ring, a first magnetic modulation chip, a second magnetic modulation chip, an output unit and a compensation coil; The coil under test is placed in the magnetic focusing ring, and a current flows through the coil under test; The magnetic focusing ring is provided with a first end and a second end, the first end and the second end are arranged opposite to each other to form an opening, the first end is provided with the first magnetic modulation chip, and the second end is provided with the second magnetic modulation chip; The first magnetic modulation chip outputs a first voltage and a second voltage, and the second magnetic modulation chip outputs a third voltage and a fourth voltage; The input end of the output unit is connected to the output end of the first magnetic modulation chip and the output end of the second magnetic modulation chip respectively, and the output unit is used to output a fifth voltage based on the first voltage, the second voltage, the third voltage and the fourth voltage; The compensation coil is connected to the output end of the output unit, and generates a compensation current under the action of the fifth voltage, and the compensation current is used to keep the magnetic flux of the magnetic focusing ring zero.

2. The current sensor according to claim 1, characterized in that: The first magnetic modulation chip includes: a resistor R1, a resistor R2, a resistor R3 and a resistor R4; The first end of the resistor R1 is connected to the second end of the resistor R3, the first end of the resistor R3 is connected to the second end of the resistor R4, the first end of the resistor R4 is connected to the second end of the resistor R2, and the first end of the resistor R2 is connected to the second end of the resistor R1; The connection point between the resistor R1 and the resistor R2 is used to output the first voltage, and the connection point between the resistor R3 and the resistor R4 is used to output the second voltage; the connection point between the resistor R1 and the resistor R3 is used to receive external power supply, and the connection point between the resistor R2 and the resistor R4 is grounded; The resistor R2 and the resistor R3 are provided with a magnetic field shielding layer.

3. The current sensor according to claim 1, characterized in that: The second magnetic modulation chip includes: a resistor R5, a resistor R6, a resistor R7 and a resistor R8; The first end of the resistor R5 is connected to the second end of the resistor R7, the first end of the resistor R7 is connected to the second end of the resistor R8, the first end of the resistor R8 is connected to the second end of the resistor R6, and the first end of the resistor R6 is connected to the second end of the resistor R7; The connection point between the resistor R5 and the resistor R6 is used to output the third voltage, and the connection point between the resistor R7 and the resistor R8 is used to output the fourth voltage; the connection point between the resistor R5 and the resistor R7 is used to receive external power supply, and the connection point between the resistor R6 and the resistor R8 is grounded; The resistor R6 and the resistor R7 are provided with an electromagnetic shielding layer.

4. The current sensor according to any one of claims 1 to 3, characterized in that: The output unit includes: a first amplifying unit, a feedback controller and a second amplifying unit; The first amplifying unit has an input end connected to the output end of the first magnetic modulation chip and the output end of the second magnetic modulation chip, and an output end connected to the input end of the feedback controller; The first amplifying unit is used for performing differential amplification processing on the first voltage, the second voltage, the third voltage and the fourth voltage to output a sixth voltage; The feedback controller has an output end connected to the input end of the second amplifying unit, and the feedback controller is used to output a seventh voltage based on the sixth voltage; the feedback controller is also connected to the compensation coil, and is used to control the magnitude of the seventh voltage according to the compensation current; The second amplifying unit has an output end connected to the compensation coil, and is used to amplify the seventh voltage and output it as the fifth voltage.

5. The current sensor according to claim 4, characterized in that: The first amplification unit includes: a first operational amplifier, a second operational amplifier and a comparison amplifier; The first input terminal of the first operational amplifier is connected to the output terminal of the first magnetic modulation chip for receiving the first voltage, and the second input terminal is connected to the output terminal of the first magnetic modulation chip for receiving the second voltage; the output terminal of the first operational amplifier outputs an eighth voltage; The first input terminal of the second operational amplifier is connected to the output terminal of the second magnetic modulation chip for receiving the third voltage, and the second input terminal is connected to the output terminal of the second magnetic modulation chip for receiving the fourth voltage; the output terminal of the second operational amplifier outputs a ninth voltage; The first input terminal of the comparison amplifier is connected to the output terminal of the first operational amplifier for receiving the eighth voltage, the second input terminal is connected to the output terminal of the second operational amplifier for receiving the ninth voltage, and the output terminal is used to output the sixth voltage.

6. The current sensor according to claim 5, characterized in that: The first amplification unit comprises: A power amplifier circuit, wherein the input end of the power amplifier circuit is connected to the output end of the first amplifying unit, and the output end of the power amplifier circuit is connected to the input end of the feedback controller.

7. The current sensor according to claim 6, characterized in that: The power amplifier circuit includes: a first diode, a second diode, a resistor R9, a resistor R10, a first transistor and a second transistor; The cathode of the first diode and the anode of the second diode are both connected to the output end of the comparison amplifier; The anode of the first diode is connected to the first end of the resistor R9 and is also connected to the control end of the first transistor; the second end of the resistor R9 is connected to the first end of the first transistor; the second end of the first transistor is connected to the input end of the feedback controller; The cathode of the second diode is connected to the first end of the resistor R10 and is also connected to the control end of the second transistor; the second end of the resistor R10 is connected to the first end of the second transistor; the second end of the second transistor is connected to the input end of the feedback controller; The first end of the first transistor also receives an external positive voltage, and the first end of the second transistor also receives an external negative voltage.

8. The current sensor according to claim 4, characterized in that: Also includes: Resistor R11; A first end of the resistor R11 is connected to the output end of the compensation coil, and a second end thereof is grounded; The voltage across the resistor R11 is used to calculate the magnitude of the compensation current.

9. The current sensor according to claim 4, characterized in that: The second amplifying unit includes at least one operational amplifier.

10. The current sensor according to any one of claims 1 to 3, characterized in that: A first magnetic shielding cover is arranged at the first end of the magnetic focusing ring, and a second magnetic shielding cover is arranged at the second end.

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