Current sensor

Abstract

The invention provides a current sensor, and relates to the technical field of current detection devices, and the current sensor comprises a magnetic circuit core which forms a magnetic circuit with an opening and is used for concentrating magnetic flux generated by a primary side circuit; the compensation coil comprises a wire which is flatly wound on the magnetic circuit core; the Hall element is arranged at the opening of the compensation coil and the magnetic circuit core, the plane normal direction of the Hall element is the same as the magnetic field direction generated by the primary circuit, and the Hall element is used for sensing the magnetic field to obtain Hall potential and transmitting the Hall potential to the circuit board; and the circuit board is connected with the compensation coil and the Hall element and is at least used for acquiring Hall potential size data and adjusting the current direction and size of the compensation coil. According to the current sensor, the compensation coil adopts a flat winding mode, the winding difficulty of the compensation coil can be reduced, the manufacturing efficiency is improved, and the batch manufacturability is high. The Hall element is arranged at the opening of the compensation coil and the magnetic circuit core, no extra shielding measure is needed, and the magnetic field interference resistance is high.

Description

Technical Field

[0001] The invention relates to a current detection device, in particular to a current sensor. Background Art

[0002] In the field of power systems and industrial control, accurate current measurement is essential to ensure safe operation of equipment and improve production efficiency. As a device for measuring current, current sensors are mainly installed on the current conductor on the AC side of photovoltaic inverters or energy storage converters to provide real-time detection signals of current. As an advanced measurement device, closed-loop Hall current sensors are widely praised for their high precision and stability. The core working principle of closed-loop Hall current sensors is based on the magnetic balance Hall principle, that is, the closed-loop principle. When the current in the primary conductor generates magnetic flux, these magnetic fluxes are concentrated in the magnetic circuit through the magnetic circuit core to form magnetic lines of force with a magnetic field strength proportional to the current magnitude. These magnetic lines of force reach their maximum value at the air gap (magnetic circuit gap), thereby generating Hall potential in the normal direction of the Hall element plane. The magnitude of this potential is proportional to the magnitude of the primary current. In order to achieve accurate measurement, the closed-loop Hall current sensor uses a secondary compensation coil. The purpose of this design is to offset the magnetic flux generated by the primary current so that the magnetic flux in the air gap is always kept at zero. When the primary current changes, the compensation coil automatically adjusts the current direction and magnitude to maintain the magnetic balance state. This self-regulation mechanism ensures that the sensor output can output a current that accurately reflects the changes in the primary current.

[0003] As the power density of application systems continues to increase, the interference magnetic field generated by power devices to the outside world continues to increase. This magnetic field will affect the operation of current sensors, and current sensors usually work by detecting the magnetic field generated by the current. If the external magnetic field is too large or too complex, it will affect the current sensor's accurate detection of the current. For this problem, one possible solution is to improve the design and layout of the current sensor to make it more resistant to magnetic field interference. For example, you can choose a suitable installation location to avoid the current sensor directly facing the magnetic field generated by the photovoltaic inverter. Another solution is to choose a current sensor with high anti-interference ability. This type of sensor can still maintain high measurement accuracy under strong magnetic field interference.

[0004] In an application environment with strong external magnetic field interference, the traditional closed-loop Hall current sensor has the following main defects: 1. The traditional closed-loop Hall current sensor adopts a ring-shaped magnetic circuit core, and the compensation coil is wound on the surface of the magnetic circuit core in a circular manner. The winding process is complicated and the manufacturing process is difficult.

[0005] 2. Interphase magnetic field interference is prone to occur on the three-phase AC control side. Due to the limited volume of the three-phase AC control side, the device layout is relatively compact, and the spacing between the copper rods carrying current between phases is relatively close. The current sensor detects the current by sensing the magnetic field generated by the current on the perforated copper rods. The magnetic field coupling generated by the adjacent phase currents will cause measurement errors.

[0006] Based on this, this application is filed. Summary of the invention

[0007] In order to solve the technical defects existing in the background technology, the present invention provides a current sensor with strong mass manufacturability and strong resistance to magnetic field interference.

[0008] As conceived above, the technical solution adopted by the present invention is as follows: A current sensor comprises: a magnetic circuit core, comprising a first magnetic circuit core and a second magnetic circuit core, forming a magnetic circuit with an opening, for concentrating the magnetic flux generated by a primary circuit; a compensation coil, comprising a flatly wound conductor, wrapped around the outer periphery of the magnetic circuit core; a Hall element, disposed at the opening, the plane normal direction of the Hall element being the same as the direction of the magnetic field generated by the primary circuit, for sensing the magnetic field, obtaining the Hall potential and transmitting it to a circuit board; a circuit board, connecting the compensation coil and the Hall element, for at least obtaining Hall potential magnitude data and adjusting the current direction and magnitude of the compensation coil.

[0009] As a preferred solution, the magnetic field sensing plane of the Hall element is as follows Figure 5 The xyz three-dimensional coordinate system shown is perpendicular to the x-axis.

[0010] As a preferred solution, the magnetic circuit core is formed by stacking two or more U-shaped magnetic materials arranged opposite to each other and then riveting them together to obtain the first magnetic circuit core and the second magnetic circuit core.

[0011] As a preferred solution, one end of one of the magnetic materials of the magnetic circuit core is led out to form a lead-out end, and the lead-out end is electrically connected to the low-voltage end of the circuit board.

[0012] As a preferred solution, the circuit board is provided with a dynamic chopping modulation module connected to the output end of the Hall element, and a demodulation filtering module connected to the output end of the dynamic chopping modulation module. The dynamic chopping modulation module and the demodulation filtering module are used to stimulate the Hall element to output a modulation signal, and decouple and filter the modulation signal.

[0013] In the above-mentioned current sensor, the compensation coil is wound flatly, which can reduce the difficulty of winding the compensation coil, improve manufacturing efficiency, reduce manufacturing costs, and has strong batch manufacturability. The Hall element is placed at the opening of the compensation coil and the magnetic circuit core, and the closed-loop Hall current sensor itself is designed using the compensation coil and magnetic circuit opening. The normal direction of the plane of the Hall element is the same as the direction of the magnetic field generated by the primary circuit. The magnetic field sensing plane of the Hall element is perpendicular to the x-axis in the xyz three-dimensional coordinate system, and the magnetic field interference on the left and right sides of the sensor through-hole position is achieved in a targeted manner. No additional shielding measures are required, and the ability to resist magnetic field interference is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the winding method of the magnetic circuit core compensation coil of the traditional closed-loop Hall current sensor ring structure; Figure 2 A schematic diagram of the structure of a current sensor provided by an embodiment of the present invention (explosion diagram); Figure 3 A schematic diagram of winding a compensation coil in a current sensor provided in one embodiment of the present invention; Figure 4 A schematic diagram of the position of a Hall element in a current sensor provided in one embodiment of the present invention; Figure 5 It is the layout diagram of the current sensor of the three-phase system; Figure 6 A schematic diagram of the structure of a magnetic circuit core in a current sensor provided in one embodiment of the present invention; Figure 7 A schematic diagram of the structure of a skeleton in a current sensor provided in one embodiment of the present invention; Figure 8 A schematic diagram of a structure in which a wire is wound around a frame in a current sensor provided by an embodiment of the present invention; Fig. 9 A schematic diagram of the connection between the circuit board, the Hall element, and the lead-out end of the magnetic circuit core in a current sensor provided in one embodiment of the present invention; Fig.10 A circuit principle block diagram of a current sensor provided in one embodiment of the present invention.

[0015] Figure numerals: shell 1, chamber 11, positioning column 12, shell cover 2, compensation coil 3, wire 31, skeleton 32, magnetic circuit core 4, first magnetic circuit core 41, second magnetic circuit core 42, lead end 43, circuit board 5, Hall element 6, dynamic chopping modulation module 71, demodulation filter module 72, push-pull and sampling module 73, amplification module 74. DETAILED DESCRIPTION

[0016] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only the parts related to the present invention are shown in the accompanying drawings, rather than all.

[0017] Please refer to Figure 1 The traditional closed-loop Hall current sensor has a ring-shaped magnetic circuit core, and the compensation coil is wound around the surface of the magnetic circuit core in a circular manner. The winding process is complicated and the process is difficult. Please refer to Figure 2 The current sensor in one embodiment of the present invention mainly includes a magnetic circuit core 4, a compensation coil 3, a circuit board 5 and a Hall element 6. The magnetic circuit core 4 has a first magnetic circuit core 41 and a second magnetic circuit core 42, forming a magnetic circuit with an opening for concentrating the magnetic flux generated by the primary circuit; the compensation coil 3 has a flatly wound conductor 31, which is wrapped around the outer periphery of the magnetic circuit core 4.

[0018] Please refer to Figure 3 In the current sensor of this embodiment, the compensation coil 3 is wound flat, which can reduce the difficulty of winding the compensation coil 3, improve manufacturing efficiency, and reduce manufacturing costs, that is, improve batch manufacturability, which is more conducive to realizing automated production. Among them, the Hall element 6 is placed at the opening of the magnetic circuit core 4, and the normal direction of its plane is the same as the direction of the magnetic field generated by the primary circuit. It is used to sense the magnetic field and transmit the Hall potential to the circuit board 5 after obtaining it. The Hall element is a magnetically sensitive element that can realize the conversion of magnetic-electric signals. Interphase magnetic field interference generally occurs in three-phase with limited volume (such as Figure 5 In the A phase, B phase, and C phase of the AC control side, due to the limited volume, the device layout is relatively compact, and the spacing between the copper bars passing through the phases is relatively close. Each current sensor (current sensor A, current sensor B, and current sensor C) senses the magnetic field generated by the current on the perforated copper bar (i.e., the primary current Ip) to detect the current. The magnetic field coupling generated by the adjacent phase currents will cause measurement errors. Please refer to Figure 4 In order to reduce the influence of external interference magnetic field on the Hall element, the Hall element 6 is placed at the opening overlap position of the compensation coil 3 and the magnetic circuit core 4, that is, the magnetic field sensing plane of the Hall element 6 is perpendicular to the xyz three-dimensional coordinate system. Figure 5 Considering that when the sensor detects one phase current, the interference magnetic field vectors generated by the other two phase currents are mostly parallel to the yz plane, then if the Hall element sensing plane is also parallel to the yz plane (that is, perpendicular to the x-axis, such as Figure 5), the effect of reducing magnetic field interference can be achieved. Specifically, the advantage of this embodiment is that the closed-loop Hall current sensor is designed by using the compensation coil and magnetic circuit opening of the closed-loop Hall current sensor itself to specifically achieve magnetic field interference on the left and right sides of the sensor through hole position, that is, Figure 5 As shown, the magnetic field interference of the adjacent phase current on the left and right sides of the sensor is eliminated without the need for additional shielding measures, and the anti-magnetic field interference capability is strong. The circuit board 5 connects the compensation coil 3 and the Hall element 6 to obtain the Hall potential size data and adjust the current direction and size of the compensation coil 3.

[0019] In one embodiment, please refer to Figure 6 The magnetic circuit core 4 is formed by stacking two or more U-shaped magnetic materials arranged opposite to each other and then riveting to obtain the first magnetic circuit core 41 and the second magnetic circuit core 42. The magnetic circuit core is formed by stacking multiple pieces of magnetic materials to increase the magnetic cross-sectional area and reduce the influence of the interfering magnetic field generated by the adjacent phase current.

[0020] In one embodiment, please refer to Figure 7 and Figure 8 The compensation coil 3 also includes a skeleton 32 sleeved outside the magnetic circuit core 4, and the wire is flatly wound on the skeleton 32. The skeleton 32 adopts a cavity plastic skeleton, and the first magnetic circuit core 41 and the second magnetic circuit core 42 can be inserted into the cavity of the skeleton 32. The compensation coil 3 adopts copper wire (conductor 31) flatly wound on the skeleton 32. The magnetic circuit core 4 and the compensation coil 3 are separated. The cavity skeleton is used as a winding bracket, which can realize the rotation and translation of the skeleton, and the copper wire is evenly wound on the skeleton. This method is called a flat winding process. This process scheme can realize the simultaneous winding of multiple skeletons on a single machine, which can further reduce the difficulty of coil winding, improve the winding efficiency, and increase the cross-sectional area of ​​the magnetic circuit, and further adapt to the application environment with strong external magnetic field interference.

[0021] In one embodiment, please refer to Figure 1 The current sensor is also provided with a shell 1 and a shell cover 2. The shell 1 has a chamber 11. The shell cover 2 covers the shell 1 and is fixed to the shell 1. The magnetic circuit core 4 and the circuit board 5 are installed in the chamber 11 of the shell 1. The circuit board 5 is installed between the shell cover 2 and the compensation coil 3. The shell 1 and the shell cover 2 are used to protect the compensation coil 3 and the circuit board 5 in the current sensor, and isolate them from the outside world, and are waterproof and insulated. Preferably, a positioning column 12 is provided in the shell 1, and the compensation coil 3 is surrounded by the periphery of the positioning column 12, which can facilitate the installation and fixation of the compensation coil 3.

[0022] In one embodiment, please refer to Figure 6 and Fig. 9, one end of one of the magnetic materials of the magnetic circuit core 4 is led out to form a lead-out terminal 43, and the lead-out terminal 43 is electrically connected to the low-voltage end of the circuit board 5. In the field of power systems and industrial control, there is a certain impulse voltage on the conductor. If the magnetic circuit core is not grounded, a certain voltage difference will be induced on the magnetic circuit core, and a withstand voltage breakdown phenomenon is likely to occur between the magnetic circuit core and the Hall element due to the close electrical gap. In order to solve this problem, in a preferred embodiment of the present invention, one end of one of the magnetic materials is led out when the magnetic circuit core 4 is formed, and the lead-out terminal 43 is electrically connected to the low-voltage end of the circuit board 5 (the sensor power supply 0V end), and the potential of the magnetic circuit core 4 is fixed to the low-voltage end of the circuit board 5, reducing the voltage difference between the magnetic circuit core 4 and the Hall element 6, making it less likely to have a withstand voltage breakdown problem with the Hall element 6, and more suitable for application scenarios with large impulse voltage interference.

[0023] In one embodiment, please refer to Fig.10 , a dynamic chopping modulation module 71 connected to the output end of the Hall element 6 and a demodulation filter module 72 connected to the output end of the dynamic chopping modulation module 71 are provided on the circuit board 5, which are used to excite the Hall element 6 to output a modulation signal, and filter out the modulation signal after decoupling. Since the Hall element 6 of the closed-loop Hall current sensor has a certain unequal potential and its temperature drift, it is easy to cause the zero-point output error and zero-point temperature drift of the sensor to be large, affecting the current detection accuracy. The traditional closed-loop Hall sensor adopts the method of adding a temperature compensation circuit and a zero adjustment circuit, which not only increases the cost, but also brings about a manual zero adjustment process, which is not conducive to batch automated production. In order to solve this problem, in the embodiment of the present invention, the Hall element is stimulated to output a modulation signal by a dynamic chopping method, and the modulation signal is filtered out after decoupling, which can effectively eliminate the offset and temperature drift caused by the unequal potential of the Hall element, save the manual zero adjustment process, and adapt to the possibility of mass production of closed-loop Hall circuit sensors.

[0024] In one embodiment, the circuit board 5 is also provided with a push-pull and sampling module 73 connected to the output end of the demodulation filter module 72, and the output end of the push-pull and sampling module 73 is connected to one end of the compensation coil 3, and the other end of the compensation coil 3 is connected to the Hall element 6. The circuit board 5 is also provided with an amplifier module 74 connected to the push-pull and sampling module 73, which is used to amplify the signal and output it. The push-pull and sampling module 73 drives the compensation coil 3 to output the compensation current, and converts the current signal into a voltage signal through sampling. Through the feedback mode of the compensation coil 3, the magnetic flux generated by the input current and the magnetic flux generated by the current of the compensation coil 3 offset each other to achieve a magnetic balance state.

[0025] In summary of the above embodiments, the closed-loop Hall current sensor of the present invention has the advantages of low cost, integration, high reliability, strong batch manufacturability, and strong ability to resist magnetic field interference.

[0026] 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.

[0027] The above-mentioned embodiments only express several implementation methods of the present invention, and the description thereof is relatively specific and detailed, but it cannot be understood as limiting the protection scope of the present invention. It should be pointed out that for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention.

Claims

1. A current sensor, characterized in that: include: A magnetic circuit core (4) having a first magnetic circuit core (41) and a second magnetic circuit core (42), forming a magnetic circuit with an opening, and used for concentrating the magnetic flux generated by the primary circuit; A compensation coil (3) comprising a flatly wound conductor (31) wrapped around the outer periphery of the magnetic circuit core (4); A Hall element (6) is placed at the opening, the plane normal direction of the Hall element (6) being the same as the direction of the magnetic field generated by the primary circuit, and is used to sense the magnetic field and obtain the Hall potential before transmitting it to the circuit board (5); The circuit board (5) is connected to the compensation coil (3) and the Hall element (6) and is used at least to obtain Hall potential magnitude data and adjust the current direction and magnitude of the compensation coil (3).

2. The current sensor according to claim 1, characterized in that: The magnetic circuit core (4) is formed by stacking two or more U-shaped magnetic materials arranged opposite to each other and then riveting them together to obtain the first magnetic circuit core (41) and the second magnetic circuit core (42).

3. The current sensor according to claim 1, characterized in that: The compensation coil (3) further comprises a frame (32) sleeved outside the magnetic circuit core (4), and the conductive wire is flatly wound on the frame (32).

4. The current sensor according to claim 1, characterized in that: Also includes: A shell (1) having a chamber (11) and a shell cover (2) covering the shell (1) and fixed to the shell (1); the magnetic circuit core (4) and the circuit board (5) are installed in the chamber (11) of the shell (1).

5. The current sensor according to claim 4, characterized in that: A positioning column (12) is provided in the housing (1), and the compensation coil (3) surrounds the periphery of the positioning column (12).

6. The current sensor according to claim 2, characterized in that: One end of one of the magnetic materials of the magnetic circuit core (4) is led out to form a lead-out end (43), and the lead-out end (43) is electrically connected to the low-voltage end of the circuit board (5).

7. The current sensor according to any one of claims 1 to 6, characterized in that: The circuit board (5) is provided with a dynamic chopping modulation module (71) connected to the output end of the Hall element (6), and a demodulation filter module (72) connected to the output end of the dynamic chopping modulation module (71). The dynamic chopping modulation module (71) and the demodulation filter module (72) are used to stimulate the Hall element (6) to output a modulation signal, and to decouple and filter the modulation signal.

8. The current sensor according to claim 7, characterized in that: The circuit board (5) is also provided with a push-pull sampling module (73) connected to the output end of the demodulation filter module (72); the output end of the push-pull sampling module (73) is connected to one end of the compensation coil (3); and the other end of the compensation coil (3) is connected to the Hall element (6).

9. The current sensor according to claim 8, characterized in that: The circuit board (5) is also provided with an amplification module (74) connected to the push-pull and sampling module (73) for amplifying the signal and outputting it.

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