JP2019074341A - Current detector - Google Patents

Abstract

To provide a current detector capable of increasing a magnetic flux density passing a magnetic material core and optimizing probe coil arrangement according to a structure of the magnetic material core.SOLUTION: A current sensor 10 comprises: a plurality of magnetic material core members 22 and 23 laminated in a state in which plate-like long leg parts 22b and 23b overlap with each other in a position along one long side in a thickness direction and plate-like upper short leg parts 22c and 23c and lower short leg parts 22d and 23d are abutted on each other with gaps in a position along the other long side; a probe coil unit 50 arranged in a position along the other long side on a magnetic circuit; secondary windings 60a and 70a which generate, in the magnetic circuit, a magnetic field reverse to the magnetic field generated by a detected current; a detection circuit which outputs a detection signal according to the detected current on the basis of the secondary current required to causing dissipation of an output current of the probe coil; and a first conductor 30 which forms a conduction path surrounding the outside of the probe coil and extending through the inside of the magnetic circuit.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a flux gate type current detector.

  With regard to this type of current detector, conventionally, the magnetic core constituting the magnetic circuit is formed of two plate-like members formed by bending a core, and two bent portions are disposed facing each other from both sides across an air gap. The prior art of the current sensor is known (for example, refer patent document 1). The two plate-like members are a pair of substantially three-letter shapes in which two plate shapes bent into a substantially U-shape are integrally connected, and the portions where the substantially U-shape bends are connected The above-mentioned bending part is formed.

Patent No. 5926911

The above-described prior art is useful in that the magnetic core can be formed of only two plate members, so that the structure is simple and the manufacturing cost can be reduced.
However, since the current sensor of the prior art is formed by bending the magnetic core in the thickness direction, the cross-sectional area in the passing direction of the magnetic flux is small, and the magnetic flux density can not be made very large.
Also, the current sensor of the prior art has a structure in which the probe coil is disposed on the side opposite to the mounting surface (upper side when the lower surface is the mounting surface), but the arrangement is optimal when the structure of the magnetic core is changed. Is unknown.

  Therefore, the present invention provides a technology for increasing the magnetic flux density passing through the magnetic core and optimizing the arrangement of the probe coils in accordance with the structure of the magnetic core.

  In order to solve the above-mentioned subject, the present invention adopts the following solution means.

  The present invention provides a current detector. The current detector of the present invention adopts a structure in which a plurality of plate-like magnetic core members are stacked in the conduction direction of the current to be detected. Also, the current detector of the present invention adopts a primary conductor in the form of extending through the inside of the magnetic circuit and surrounding the outside of the probe coil.

  The magnetic core member constitutes a rectangular magnetic circuit that converges the magnetic field generated by the conduction of the current to be detected. At this time, in the magnetic core members, the plate-like long legs extending opposite to each other overlap in the thickness direction at a position along one long side of the magnetic circuit, and extend opposite to each other at a position along the other long side. The plate-like short legs are stacked in the conduction direction of the current to be detected (the transverse direction of the magnetic circuit) in a state in which a gap is opened between the tips and the butt is formed. Thus, in the state in which the plurality of magnetic core members are stacked, the cross-sectional area in the transverse direction of the magnetic circuit can be increased according to the number of stacked layers, so that the magnetic flux density to be passed can be increased. Further, the arrangement is such that the primary conductor surrounds the outside of the probe coil, and the arrangement can be optimized for the structure in which a plurality of magnetic core members are stacked.

  Preferably, the magnetic core member opens the probe coil without shielding between the primary conductor and the probe coil around the probe coil except inside the magnetic circuit. Thereby, optimization of arrangement to a structure in which a plurality of magnetic core members are stacked can be further improved.

  According to the present invention, the magnetic flux density passing through the magnetic core can be increased, and the arrangement of the probe coils can be optimized according to the structure of the magnetic core.

FIG. 1 is a perspective view schematically showing a configuration of a current sensor of an embodiment. It is a front view which shows roughly the structure of the current sensor of one Embodiment. It is a disassembled perspective view which shows the structure of a magnetic body core. It is a longitudinal cross-sectional view (sectional view in alignment with the IV-IV line | wire in FIG. 2) of a current sensor. It is a perspective view of the magnetic body core shown by FIG. It is a block diagram which shows the circuit structure of a current sensor roughly. It is a perspective view showing roughly the composition of the current sensor used as a comparative example. It is a wave form diagram showing the response characteristic of the output voltage obtained when detected current changes in the shape of a step with the current sensor of this embodiment. It is a wave form diagram showing the response characteristic of the output voltage obtained when detected current changes in the shape of a step by the current sensor of a comparative example.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiment, although a fluxgate type current sensor is mentioned as an example of a current detector, the present invention is not limited to this.

  FIG. 1 is a perspective view schematically showing the configuration of a current sensor 10 according to an embodiment. FIG. 2 is a front view schematically showing the configuration of the current sensor 10 according to one embodiment.

[Magnetic circuit]
The current sensor 10 includes a magnetic core 20. The magnetic core 20 constitutes a rectangular magnetic circuit extending in a direction perpendicular to the penetration direction (horizontal direction in FIG. 1) of the current to be detected. The magnetic core 20 is configured by overlapping a plurality of plate-shaped magnetic core members 22 and 23 (stacking in the penetrating direction of the detection current), and the magnetic core members 22 and 23 mutually It has a shape that is symmetrical in pairs. The magnetic core members 22 and 23 will be described later with reference to further drawings.

[Secondary winding]
The current sensor 10 includes two bobbin units 60 and 70. Each bobbin unit 60 and 70 accommodates the magnetic core 20 (magnetic core members 22 and 23) inside and a secondary winding outside The lines 60a and 70a are held. In the state shown in FIGS. 1 and 2, one bobbin unit 60 is located at the upper side, and the other bobbin unit 70 is located at the lower side. Although not shown, each bobbin unit 60, 70 may have a plurality of lead terminals in addition to the secondary windings 30a, 40a described above. The current sensor 10 can be mounted on a circuit board or connected to another electronic device via the lead terminals. In addition to the bobbin units 60 and 70, a bobbin unit (not shown) may be arranged.

[Probe coil (field probe)]
As shown in FIG. 2 (not shown in FIG. 1), the current sensor 10 includes a probe coil unit 50, and the probe coil unit 50 is accommodated inside the lower bobbin unit 70. More specifically, the two magnetic core members 22 and 23 form a housing (without the reference numeral) inside the bobbin unit 70, and the probe coil unit 50 is disposed in the housing, and the bobbin unit 70 is It is housed inside. Further, the probe coil unit 50 has a probe coil (field probe) not shown, and in the assembled state of the current sensor 10, the probe coil is disposed on the magnetic circuit (within the air gap of the magnetic core 20). ing. The probe coil unit 50 can also have a plurality of lead terminals (not shown), and can be connected to the probe coil through these lead terminals.

  The current sensor 10 includes, for example, a casing 40 made of resin, and the magnetic core 20, the bobbin units 60 and 70, the probe coil unit 50, and the like described above are accommodated inside the casing 40. Further, the housing 40 has a through passage (or a through hole) (not shown) inside the magnetic circuit (inner periphery of the magnetic core 20), and the detection current can penetrate through the through passage.

[Primary conductor]
The current sensor 10 includes, for example, two primary conductors 30. The primary conductors 30 are disposed to penetrate the inside of the magnetic circuit, and when the current sensor 10 is used, the detected current conducts the two primary conductors 30. In the state shown in FIGS. 1 and 2, the two primary conductors 30 pass through the inside of the magnetic circuit in the horizontal direction because the magnetic circuit is in the upright posture. In addition, these primary conductors 30 are bent in one direction (downward in FIGS. 1 and 2) on both sides of the magnetic circuit, and both ends extend in the same direction to form an inverted U shape as a whole. There is no. Such a primary conductor 30 forms a conduction path extending around the outside of the probe coil unit 50 while penetrating the inside of the magnetic circuit when conducting the detected current. The two primary conductors 30 are disposed inside the magnetic circuit in a state of being supported by the housing 40, and the housing 40 is formed with a holding groove communicating with the above-mentioned through passage. Both bent ends 30 are held in the holding groove. Further, the number of primary conductors 30 is not limited to two, and may be one or three or more.

[Detection circuit]
A circuit board (not shown) is connected to the probe coil unit 50, and a signal output IC (also not shown) is mounted on the circuit board. When the current sensor 10 is used, if a magnetic field is generated around the primary conductor 30 (magnetic circuit) due to the conduction of the detected current, the signal output IC outputs a secondary current (feedback current) to the secondary windings 60a and 70a. Then, control is performed to generate a magnetic field in the reverse direction and to dissipate the output current of the probe coil. At this time, the signal output IC converts the secondary current into a voltage signal with a shunt resistor, and outputs it as a detection signal according to the detected current.

  FIG. 3 is an exploded perspective view showing the configuration of the magnetic core 20. As shown in FIG. As described above, the magnetic core 20 is configured by overlapping a plurality of plate-shaped magnetic core members 22 and 23. In this example, the magnetic core members 22 and 23 are alternately stacked in a predetermined number (for example, six).

  The magnetic core members 22 and 23 are made of, for example, a high magnetic permeability material such as permalloy. The magnetic core members 22 and 23 have a symmetrical shape in the center line viewed in the longitudinal direction of the rectangular magnetic circuit, and the magnetic core members 22 and 23 are located along the short sides of both sides of the magnetic circuit. Respectively have short side portions 22a and 23a. The magnetic core members 22 and 23 have long legs 22b and 23b at positions along one long side (here, upper side) of the magnetic circuit, and the long legs 22b and 23b have short sides. It mutually mutually extends in the longitudinal direction from the upper end of part 22a, 23a, and is mutually arrange | positioned alternately over substantially the whole longitudinal direction. The magnetic core member 22 has upper short legs 22c and 23c and lower short legs 22d and 23d at positions along the other (here, lower) long side of the magnetic circuit, among which the lower short legs The portions 22d and 23d extend from the lower ends of the short sides 22a and 23a in the longitudinal direction so as to be opposed to each other. The upper short legs 22c and 23c extend in the longitudinal direction from the short sides 22a and 23a at positions spaced upward from the lower short legs 22d and 23d.

  Here, the upper short legs 22c and 23c and the lower short legs 22d and 23d are not alternately stacked, but are disposed facing each other in the longitudinal direction. Therefore, in the combined state of the magnetic core 20, the upper short legs 22c and 23c and the lower short legs 22d and 23d are connected to face each other on the magnetic circuit. At this time, upper contact parts 22e and 23e are formed on the upper short leg parts 22c and 23c respectively, and lower contact parts 22f and 23f (see FIG. 4) are formed on the lower short leg parts 22d and 23d, respectively. ing. The upper contact portions 22e and 23e and the lower contact portions 22f and 23f contact each other in a combined state, or approach each other with a slight gap (for example, about 0.1 mm). Thus, while providing a gap (air gap) between the upper short legs 22c and 23c and the lower short legs 22d and 23d, the magnetic flux density in the upper contact portions 22e and 23e and the lower contact portions 22f and 23f is increased. be able to.

  FIG. 4 is a longitudinal cross-sectional view (a cross-sectional view taken along the line IV-IV in FIG. 2) of the current sensor 10. 5 is a perspective view of the magnetic core 22 shown in FIG. As described above, in the combined state of the magnetic cores 20, the long legs 22b and 23b of the magnetic core members 22 and 23 overlap each other at a position along the upper long side of the magnetic circuit, so that the magnetic circuit Constitute a relatively large cross-sectional area. The upper short legs 22c, 23c and the lower short legs 22d, 23d are butted together at a position along the lower long side of the magnetic circuit, but the upper contact 22e, 23e and the lower contact 22f , And 23f, it is not in contact and forms an air gap. The probe coil unit 50 is disposed between the upper contact portions 22 e and 23 e and the lower contact portions 22 f and 23 f, so that the magnetic flux leaked into the air gap passes through the probe coil unit 50.

  As apparent from FIG. 4, the primary conductor 30 penetrates the inside of the magnetic circuit and forms a conduction path extending around the outside of the probe coil unit 50 as described above. The magnetic core members 22 and 23 do not surround the probe coil unit 50 except for the upper short legs 22c and 23c and the lower short legs 22d and 23d, and do not shield the space between the primary conductor 30 and the magnetic core members 22 and 23 Is open. Thereby, the arrangement of the probe coil unit 50 with respect to the magnetic core members 22 and 23 can be optimized.

[Circuit configuration of current sensor]
FIG. 6 is a block diagram schematically showing a circuit configuration of current sensor 10. Referring to FIG. The probe coil 50a is connected to a signal output IC 80, and the signal output IC 80 incorporates a pulse power supply circuit (not shown). The probe coil 50a is wound around the flux gate core 50c, and when a high frequency rectangular wave current is supplied from the pulse power supply circuit to the probe coil 50a, the magnetic flux density in the flux gate core 50c is periodically saturated. Therefore, if a magnetic field is generated in the magnetic circuit (magnetic core 20) by the detected current Ip flowing through the primary conductor 30, the waveform of the voltage applied to the probe coil 50a is distorted by the magnetic field generated in the magnetic circuit. It will occur.

  Further, an interface circuit 84 is built in the signal output IC 80, and the interface circuit 84 converts the voltage between the probe coils 50a into a PWM signal. The PWM signal output from the interface circuit 84 is a pulse signal of a predetermined duty ratio (for example, 50%) in the state where the magnetic field is not generated in the flux gate core 50 c (non-conductive state of the detection current Ip). The duty ratio of the PWM signal changes in accordance with the magnetic field strength applied to the flux gate core 50c.

  The signal output IC 80 incorporates a filter 86 and a driver circuit 88. The filter 86 converts the PWM signal from the interface circuit 84 into an analog signal and outputs the converted output voltage to the driver circuit 88. The secondary winding 60a, 70a is connected to the driver circuit 88 through two terminals Ic1, Ic2. The driver circuit 88 detects the difference between the output voltage from the filter 86 and the predetermined reference voltage Vref, and outputs a secondary current having a magnitude based on the difference to the secondary windings 60a and 70a. The generation of the feedback magnetic field by the secondary current cancels the magnetic field in the magnetic circuit induced by the detected current Ip conducted through the primary conductor 30, and control is performed to dissipate the output current of the probe coil 50a.

  The current sensor 10 outputs a detection signal corresponding to the detected current Ip by extracting the output voltage Vout obtained by detecting the secondary current with the shunt resistor Rs. Although the secondary current flowing through the secondary windings 60a and 70a periodically changes due to the above negative feedback, the signal processing using the differential amplifier circuit 89 in the signal output IC 80 causes the waveform of the output voltage Vout to be Since the waveform matches the waveform of the detected current Ip, the value substantially correlates with the magnitude of the detected current Ip.

[Verification of superiority]
The superiority of the current sensor 10 of the present embodiment as described above is verified in comparison with a comparative example.

Comparative Example
FIG. 7 is a perspective view schematically showing the configuration of a current sensor 200 as a comparative example. The current sensor 200 of the comparative example is characterized in that the primary conductor 30 is bent in the direction opposite to the probe coil unit 50, in other words, the current sensor 10 shown in FIG. This embodiment differs from the present embodiment in that it is in a positional relationship in which it is rotated by half in the circumferential direction of the magnetic circuit. The other configuration is the same as that of the present embodiment, and the same reference numeral including the illustration is attached to such a common configuration, and the duplicate description is omitted.

[Step response characteristic]
FIG. 8 is a waveform diagram showing the response characteristic of the output voltage Vout obtained when the current to be detected Ip changes stepwise in the current sensor 10 of the present embodiment. On the other hand, FIG. 9 is a waveform diagram showing the response characteristic of the output voltage Vout obtained when the detected current Ip is similarly changed stepwise in the current sensor 200 of the comparative example. Hereinafter, the superiority of the embodiment of the present invention will be specifically described in comparison with a comparative example.

This Embodiment
(A) in FIG. 8: At a certain time t1, the waveform of the detected current Ip changes (rises) stepwise. Such a step-like waveform change may occur, for example, when the target current to which the current sensor 10 is applied starts up (or outputs a PWM current) and the detected current Ip sharply rises. It can happen.
Comparative Example
In FIG. 9A (A): also in the comparative example, the waveform of the detected current Ip changes stepwise in the same conditions as the present embodiment.

This Embodiment
In FIG. 8 (B): In the case of the present embodiment, the waveform of the output voltage Vout of the current sensor 10 also responds in a step-like manner from time t1. It should be noted that immediately after time t1, although there is a temporary rise and fall in the response waveform, it can be confirmed that a generally stable step response waveform appears.
Comparative Example
In FIG. 9 (B), in the case of the comparative example, although the waveform of the output voltage Vout changes from time t1, the step-like response characteristic as in the present embodiment is not shown, and the waveform of the sharply rising waveform is A disturbance has appeared.

[Observation of voltage between Ic1-Ic2 terminals]
In the circuit configuration shown in FIG. 6, the inventor of the present invention has carried out the following verification, focusing on the fact that the change in voltage between the Ic1-Ic2 terminals is related to the change in the output voltage Vout.

This Embodiment
(C) in FIG. 8: That is, in the present embodiment, when the current to be detected Ip changes stepwise at time t1, the waveform of the voltage across terminals Ic1-Ic2 rises in a short time following this, and the time continues thereafter The Ic1-Ic2 terminal voltage is maintained for a long period Tf until t2. The change in the voltage between the Ic1 and Ic2 terminals is gradual also after time t2.
Comparative Example
(C) in FIG. 9: In the case of the comparative example, the voltage across the terminals Ic1-Ic2 temporarily turns downward while the current to be detected Ip is rising at time t1, and then rises over time from that point However, it can be seen that the period Tf in which the Ic1-Ic2 terminal voltage can be maintained at a high level is extremely shorter than in this embodiment. Further, even after time t2, the change in the voltage between the Ic1 and Ic2 terminals is more rapid as compared with the present embodiment.

This Embodiment
(A) and (B) in FIG. 8: As a result, in the present embodiment, the output voltage Vout exhibits a generally good step response characteristic over the entire period in which the detected current Ip changes stepwise. I understand that.
Comparative Example
(A) and (B) in FIG. 9: In the comparative example for this, the waveform of the output voltage Vout is violently disturbed immediately after the detected current Ip changes stepwise, and the overall undesirable step response characteristic is It is understood that it shows.

As described above, according to the present embodiment, the following advantages can be obtained.
(1) Since the magnetic core 20 is formed by laminating a plurality of plate-like magnetic core members 22 and 23, it is possible to increase the cross-sectional area and increase the magnetic flux density as compared with the bent plate material. it can.
(2) Further, since the primary conductor 30 is arranged to wind the probe coil unit 50, the arrangement of the probe coil unit 50 is optimized with respect to the structure in which a plurality of plate-shaped magnetic core members 22 and 23 are stacked, and the output voltage Vout Response characteristics can be improved.
(3) In addition, since the magnetic core members 22 and 23 are opened without shielding between the probe coil unit 50 and the primary conductor 30 in regions other than the inner side of the magnetic circuit, the magnetic core member 22, It is possible to further improve the optimization of the arrangement of the probe coil 50a with respect to 23 and further improve the response characteristic of the output voltage Vout.
(4) In particular, even in the case where the detection current Ip changes stepwise, it is possible to obtain a good and stable response characteristic of the output voltage Vout.

  The present invention is not limited to the above-described embodiment, and can be variously modified and implemented. For example, although the magnetic core members 22 and 23 have a shape forming a rectangular magnetic circuit, the magnetic core members 22 and 23 may have a shape forming a magnetic circuit with another shape.

  The current sensor 10 may be applied not only to a flux gate type current detector but also to a magnetic balance type current detector using a Hall element.

  In addition, the structures listed together with the drawings in the embodiments are merely preferable examples, and it is possible to preferably implement the present invention even if various elements are added to or a part of the basic structure is added. Nor.

DESCRIPTION OF REFERENCE NUMERALS 10 current sensor 20 magnetic core 22, 23 magnetic core member 22 b, 23 b long leg 22 c, 23 c upper short leg 22 d, 23 d lower short leg 30 primary conductor 40 housing 50 probe coil unit 50 a probe coil 60, 70 Bobbin unit 60a, 70a secondary winding

Claims (2)

A rectangular magnetic circuit is formed to converge the magnetic field generated by conduction of the current to be detected, and the long legs facing each other overlap in the thickness direction at a position along one of the long sides of the magnetic circuit. At the position along the other long side, a plurality of plate-like magnetic bodies stacked in the conduction direction of the detected current in a state in which the plate-like short legs extending opposite to each other open a gap between the tips and become butted. Core member,
A probe coil disposed at a position along the other long side on the magnetic circuit;
A secondary winding that causes the magnetic circuit to generate a magnetic field opposite to a magnetic field generated by conduction of a detected current;
A detection circuit that outputs a detection signal according to a detected current based on a secondary current of the secondary winding necessary to dissipate the output current of the probe coil;
A current detector comprising: a primary conductor which forms a conduction path extending around the outside of the probe coil while penetrating the inside of the magnetic circuit when conducting a current to be detected. In the current detector according to claim 1,
The magnetic core member is
A current detector characterized in that the probe coil is opened around the probe coil except the inside of the magnetic circuit without shielding between the primary conductor and the probe coil.

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