WO2015124976A1

WO2015124976A1 - Electric current measurement device

Info

Publication number: WO2015124976A1
Application number: PCT/IB2015/000084
Authority: WO
Inventors: 吉田　博; 淳平遠藤; 雄介宮村; 明実塩川
Original assignee: パナソニックＩｐマネジメント株式会社
Priority date: 2014-02-24
Filing date: 2015-01-30
Publication date: 2015-08-27
Also published as: JP2015158392A; TW201546460A; JP6455812B2

Abstract

An electric current measurement device comprising: a circuit board; an electric current measurement coil that is formed on the circuit board; an integrated circuit that is mounted on the wiring board and has a plurality of legs that protrude to the exterior; two lead lines that are formed on the circuit board and lead from the electric current measurement coil; and connection parts that respectively connect the two lead lines to two legs among the plurality of legs. The electric current measurement device is characterized in that the connection parts are provided with conductive pattern structures that are affected by external magnetic fields in order to counteract the effects of the external magnetic fields on the portions surrounded by the two legs.

Description

Current measuring device

The present invention relates to a current measuring device used as a current measuring sensor in a distribution board or the like, and more particularly to a current measuring device in which an IC is mounted on a circuit board on which a current measuring coil is formed.

Rogowski coils are used as current measurement sensors in distribution boards, etc., but energy saving is progressing in LED bulbs and other electrical equipment, and high sensitivity is required so that less current can be detected. ing. By the way, since the Rogowski coil is coreless, it has the merits that it does not saturate magnetically and there is no heat generation or hysteresis error due to magnetic loss, but it has the demerit that the output voltage is low and the S / N decreases due to the influence of an external magnetic field. Have.

The influence of the external magnetic field will be described with reference to FIG. 8A shows a configuration of a general CT (current transformer) in which a toroidal coil is wound around a toroidal core made of a magnetic material, and FIG. 8B shows a configuration of a coreless Rogowski coil. Show. (C) shows an area surrounded by a general CT with respect to an external magnetic field in a direction perpendicular to the paper surface, and (d) shows an area surrounded by the Rogowski coil with respect to an external magnetic field in a direction perpendicular to the paper surface. .

As shown in FIG. 8 (a), in general CT, a conductor is spirally wound around a toroidal core and wound around the toroidal direction to finish winding, so a direction perpendicular to the toroidal direction (that is, paper surface) Is equivalent to a one-turn coil. Therefore, as shown in FIG. 8C, for the external magnetic field in the direction perpendicular to the toroidal direction, the cross section perpendicular to the toroidal direction of the toroidal coil is directly affected by the external magnetic field (left oblique hatching). Become. However, since a general CT has a magnetic core, the output S due to the magnetic field to be measured passing through the inside of the toroidal core is much larger than the noise N due to the external magnetic field. It doesn't matter. However, since the Rogowski coil is coreless, the output S due to the magnetic field to be measured is small and is easily affected by the external magnetic field, so that a decrease in S / N becomes a problem. Therefore, as shown in FIG. 8B, the conductor is spirally wound, and after making a round in the toroidal direction, the central portion of the toroidal coil is rewound by one turn in the reverse direction. Therefore, as shown in FIG. 8 (d), for an external magnetic field perpendicular to the toroidal direction, the cross section perpendicular to the toroidal direction of the toroidal coil in the winding advance direction is rewound for one turn in the unwinding direction. The area of the region (right oblique hatching) that is offset by the cross section of the coil and affected by the external magnetic field is small.

It is conceivable to increase the number of turns of the toroidal coil as a technique for increasing the S / N of the Rogowski coil. However, for example, a Rogowski coil of a type that forms a coil with conductive patterns and through holes (via holes) on both sides of a circuit board as described in Patent Document 1, the diameter of a processable through hole, the outer diameter of a land, and the like Due to this limitation, the number of turns of the coil is limited. Therefore, the Rogowski coil described in Patent Document 1 is further devised in the conductive pattern formed on the circuit board surface so as to cancel the influence of the external magnetic field.

FIG. 9 shows a conventional Rogowski coil 201 described in Patent Document 1. In FIG. 9, in order to avoid the intersection of the lead wires, the reference numerals of the winding advance coil and the rewinding coil are shown at positions separated from each other.

On the surface of the circuit board 202, a conductive pattern 251 is formed that extends radially from the through hole 211 constituting the winding coil toward the outer periphery and is dog-legged to the right near the outer periphery. A through hole 221 is formed at the point where the conductive pattern 251 is doglegged to the right. On the back surface of the circuit board 202, a conductive pattern that extends radially from the through hole 212 adjacent to the right of the through hole 211 toward the outer periphery and left dog leg (right dog leg when viewed from the back side) in the vicinity of the outer periphery. 252 is formed and further connected to the through hole 221. In this way, the conductive pattern 251 on the front surface, the through hole 221, the conductive pattern 252 on the back surface, and the through hole 212 are wound to form one turn of the coil. Such conductive patterns and through holes are formed on the annular circuit board 202 so as to make a round in the toroidal direction, thereby forming a winding coil.

On the surface of the circuit board 202, a conductive pattern 261 extending linearly in the radial direction toward the outer peripheral portion is formed from the through hole 231 constituting the rewinding coil, and the through hole 241 is provided at the tip of the conductive pattern 261. Is formed. On the back surface of the circuit board 202, a short conductive pattern 262 is formed from the through hole 241, which is a left dog leg (right dog leg when viewed from the back side) toward the outside, and is connected to the through hole 242. On the surface of the circuit board 202, a short conductive pattern 263 that is dog-legged to the left is formed from the through hole 242 and connected to the through hole 243. On the back surface of the circuit board 202, a conductive pattern 264 extending linearly in the radial direction from the through hole 243 toward the inner periphery is formed and connected to the through hole 232. Thus, one turn of the rewinding coil is formed by the conductive pattern 261 on the front surface, the through hole 241, the conductive pattern 262 on the back surface, the through hole 242, the conductive pattern 263 on the front surface, the through hole 243, the conductive pattern 264 on the back surface, and the through hole 232. Is formed. Such conductive patterns and through-holes are formed on the annular circuit board 202 so as to make a round in the toroidal direction, thereby forming a rewinding coil.

In this Rogowski coil 201, a toroidal coil is continuously formed in double in the winding direction and the unwinding direction, and 1 in the winding coil as seen from the direction perpendicular to the circuit board 202 (direction in which the current to be measured flows). The conductive pattern is formed so that the area of the region S1 for the turn and the area of the region S2 for one turn of the rewinding coil are substantially equal. As a result, the influence of the winding coil from the external magnetic field is offset by the influence of the unwinding coil from the external magnetic field, and the S / N is further increased by reducing the noise component.

On the other hand, in Patent Document 2, an IC (Integrated Circuit) that performs A / D conversion of the current flowing through the Rogowski coil into a measurement value and outputs it as measurement data is mounted on the circuit board on which the Rogowski coil is formed. A current measuring device is disclosed. In this current measuring device, a shield portion of a nonmagnetic conductor is formed on the front and back surfaces of a circuit board to cover the Rogowski coil, thereby improving the effect of blocking an external magnetic field that causes noise.

The conventional current measuring coil and current measuring device disclosed in Patent Document 1 and Patent Document 2 are both devised to reduce the influence of an external magnetic field on the Rogowski coil itself. Thus, no contrivance has been made to reduce the influence of an external magnetic field on the lead-out line from the IC to the IC and the leg projecting outside from the IC. However, as a result of measurement by the present inventor, it has been found that even the legs protruding outward from the IC are affected by the external magnetic field, and the S / N is lowered.

JP 2007-155427 A JP 2009-85620 A

The present invention has been made in order to solve the above-described problem of the conventional example, and a current measuring device that can improve the S / N by reducing the influence of an external magnetic field on a leg protruding outward from an IC. provide.
Means for solving the problem

A current measurement device according to an aspect of the present invention includes a circuit board, a current measurement coil formed on the circuit board, an IC mounted on the circuit board and including a plurality of legs protruding to the outside, and the circuit Two lead wire portions formed on the substrate and drawn from the current measuring coil, and connection portions for connecting the two lead wire portions to two legs of the plurality of legs, respectively. In the current measuring apparatus, the connection portion includes a conductive pattern structure that is affected by the external magnetic field in order to cancel the influence of the portion surrounded by the two legs from the external magnetic field.

The connecting portion has a pattern portion having an area substantially the same as the area surrounded by the two legs, and the pattern portion is configured such that a current flows in a direction opposite to a current flowing through the two legs. Preferably it is formed.

It is preferable that the connection portion further includes an additional pattern intersecting in an X shape when viewed from the thickness direction of the circuit board.

The circuit board has a plurality of conductive layers and a plurality of insulating layers alternately stacked, and an opening that penetrates a conductor through which a current to be measured flows, and the current measurement coil is formed to surround the opening. It is preferable.

Each of the plurality of conductive layers includes a conductive pattern, and the circuit board further includes a plurality of through holes that electrically connect the conductive patterns of the plurality of conductive layers, and the two lead lines and the connection portion Each of which is composed of the conductive pattern and the plurality of through holes, and the additional pattern portion is formed by three-dimensionally intersecting conductive patterns formed in different conductive layers among the plurality of conductive layers. It may be formed.

The pattern portion is formed on the same surface as the surface of the circuit board on which the IC is mounted, and is parallel to the two legs from below the IC opposite to the protruding direction of the two legs. Further, it can be formed so as to pass under the IC and protrude from the two legs.

The additional pattern portion is preferably wire bonding that crosses three-dimensionally.
The invention's effect

According to the present invention, the influence of the external magnetic field on the portion enclosed between the two legs protruding outward from the IC is affected by the two lead wires and the two legs protruding outward from the IC. Since the structure provided in the connecting portion cancels out due to the influence from the external magnetic field, the S / N can be prevented from decreasing. In addition, such a structure affected by an external magnetic field can be formed at the same time when the circuit board is manufactured, and does not increase the cost of the current measuring device.

1 is a plan view showing a current measurement device according to an embodiment of the present invention, that is, a circuit board on which a current measurement coil is formed and an IC is mounted. The top view which shows the 1st conductive pattern formed in the 1st conductive layer of the circuit board in the said embodiment. The top view which shows the 2nd conductive pattern formed in the 2nd conductive layer of the circuit board in the said embodiment. The top view which shows the 3rd conductive pattern formed in the 3rd conductive layer of the circuit board in the said embodiment. The top view which shows the 4th conductive pattern formed in the 4th conductive layer of the circuit board in the said embodiment. The elements on larger scale of FIG. The figure which shows the other structural example of the electric current measurement apparatus which concerns on one Embodiment of this invention. Comparison explanatory drawing of the influence by the external magnetic field of general CT and Rogowski coil. The top view which shows the conventional Rogowski coil.

A current measuring device according to an embodiment of the present invention will be described. As shown in FIG. 1, a current measuring device 100 according to the present embodiment is formed on a circuit board 2, that is, a current measuring coil 1, an IC mounted on the circuit board 2, and a current measuring coil 1. It consists of a plurality of conductive patterns and a plurality of through holes that electrically connect the circuit board 2. In FIG. 1, only the conductive patterns of the first conductive layer (solid line) and the third conductive layer (broken line) are shown for easy understanding.

A current measuring coil (Rogowski coil) 1 according to the present embodiment is formed on a circuit board 2 formed by alternately laminating four conductive layers and three insulating layers, as shown in FIG. A circular opening 3 is formed in the center of the circuit board 2 for passing through the conductor through which the current to be measured flows. Further, along the circular opening 3, through holes 61..., 81. Further, on the outer peripheral portion of the circuit board 2, through holes 51,... 71,. Each through hole is formed so as to penetrate through four conductive layers and three insulating layers. Further, a first lead wire portion 4 and a second lead wire portion 5 for taking out a signal are led out from the current measuring coil 1, and two pieces projecting outside from the IC 7 mounted on the circuit board 2. Are connected to the

legs

7a and 7b. For example, the IC 7 A / D converts the current flowing through the current measuring coil 1 into a measured value and outputs it as measurement data.

The winding and rewinding coils that make up the Rogowski coil are each formed as a toroidal coil. The winding coil mainly has a diameter of the second conductive pattern 20 of the second conductive layer, the fourth conductive pattern 40 of the fourth conductive layer, the outer peripheral side through hole 51, and the inner peripheral side through hole. It is composed of through holes 61 formed on a small concentric circle. The rewinding coil mainly includes the first conductive pattern 10 of the first conductive layer, the third conductive pattern 30 of the third conductive layer, the outer peripheral side through hole 71, and the inner peripheral side through hole. It is composed of through holes 81 formed on a concentric circumference having a large diameter.

The first lead wire portion 4 for taking out the signal is connected to the through hole 51 of the first conductive layer which is the starting point portion of the winding coil shown in FIG. The through hole 51 is connected to the conductive pattern formed in the fourth conductive layer 40 shown in FIG. 5, and the conductive pattern 41 of the fourth conductive layer 40 is connected to the through hole 61. The through hole 61 is connected to the conductive pattern formed in the second conductive layer 20 shown in FIG. 3, and the conductive pattern 21 of the second conductive layer 20 is connected to the through hole 52. The through hole 52 is connected to the through hole 62 by the conductive pattern 41 shown in FIG. Thereafter, such a loop goes around the opening 3 clockwise to form a winding coil. The last through hole 6 x of the winding advance coil is connected to a linear conductive pattern 11 x formed in the first conductive layer 10 shown in FIG. 2, and the conductive pattern 11 x is connected to the through hole 71.

The through hole 71 is connected to the through hole 81 by the conductive pattern 31 formed in the third conductive layer 30 shown in FIG. The through hole 81 is connected to the conductive pattern formed in the first conductive layer 10 shown in FIG. 2 and is connected to the through hole 72 by the conductive pattern 11 of the first conductive layer 10. The through hole 72 is connected to the through hole 82 by the conductive pattern 31 shown in FIG. Thereafter, such a loop is made around the opening 3 counterclockwise to form a rewinding coil. The last through-hole 8x of the rewinding coil is connected to the linear conductive pattern 2x of the second conductive layer 20 shown in FIG. 3, and the conductive pattern 2x which is the end point of the rewinding coil is a second for extracting a signal. The lead wire part 5 is connected.

As can be seen by comparing FIG. 2 and FIG. 3, the first lead line portion 4 and the second lead line portion 5 are formed in the first conductive layer 10 and the second conductive layer 20, respectively. The conductive pattern of the first conductive layer 10 and the conductive pattern of the second conductive layer 20 are electrically connected via each other. In the conductive pattern constituting the first lead wire portion 4 and the conductive pattern constituting the second lead wire portion 5, currents flow in opposite directions and are seen through from the stacking direction of the conductive layer 2 (hereinafter abbreviated as a plan view). It is formed in an X-shaped intersection pattern (see FIG. 1) that partially overlaps.

The outer radial portions 11a of the respective

conductive patterns

11x, 11 ... of the first conductive layer 10 shown in FIG. 2 and the radial portions of the outer

conductive patterns

31x, 31 ... of the third conductive layer 30 shown in FIG. 31a overlaps each other in a plan view. Further, the radial portions 21a outside the respective

conductive patterns

21x, 21... Of the second conductive layer 20 shown in FIG. 3 and the outer sides of the respective

conductive patterns

41x, 41. The radial portions 41a overlap each other in plan view. On the other hand, each of the outer

radial portions

11a and 31a of the

conductive patterns

11x, 11... 31x, 31..., The second conductive layer 20 and the fourth conductive layer 40 of the first conductive layer 10 and the third conductive layer 30. The outer

radial portions

21a and 41a of the

conductive patterns

21x, 21 ..., 41x, 41 ... do not overlap with each other in plan view and are adjacent to each other.

Further, a circumferential portion 11b of each conductive pattern 11 ... of the first conductive layer 10 shown in FIG. 2 and a circumferential portion of each conductive pattern 21 ... of the second conductive layer 20 shown in FIG. 21b overlaps each other in plan view. Similarly, a circumferential portion 31b of each conductive pattern 31 of the third conductive layer 30 shown in FIG. 4 and a circumferential direction of each conductive pattern 41 of the fourth conductive layer 40 shown in FIG. The portions 41b overlap each other in plan view. Furthermore, the radial portion 11c inside each conductive pattern 11 ... of the first conductive layer 10 shown in FIG. 2 and the radial portion 31c inside each conductive pattern 31 ... of the third conductive layer 30 shown in FIG. , They overlap each other in plan view. Similarly, the radial part 21c inside each conductive pattern 21 ... of the second conductive layer 20 shown in FIG. 3 and the radial part 41c inside each conductive pattern 41 ... of the fourth conductive layer 40 shown in FIG. Are overlapped with each other in plan view.

Thus, the circuit board 2 has four conductive layers on which conductive patterns are formed, and the conductive patterns forming the winding advance coil and the rewinding coil overlap each other as seen through from the stacking direction of the conductive layers. ing. Therefore, compared to the conventional example shown in FIG. 9, the total number of turns of the Rogowski coil 1 can be increased, the voltage of the output signal can be increased, and the S / N can be increased. In addition, since the conductive pattern of the winding advance coil and the conductive pattern of the rewinding coil are formed in different conductive layers, an extra through hole is provided to overcome the conductive pattern of the winding advance coil and the conductive pattern of the rewinding coil. This is not necessary, and the total number of through holes in the circuit board 2 does not increase, and it is possible to prevent a decrease in yield. Furthermore, the area surrounded by the winding coil and the area surrounded by the rewinding coil are almost equal to the magnetic field parallel to the stacking direction of the conductive layer, so it is offset by the influence from the external magnetic field, and the noise component is reduced. Thus, the S / N can be further increased.

On the other hand, the area surrounded by one turn in the poloidal direction of the toroidal coil is affected by the external magnetic field orthogonal to the stacking direction of the conductive layers. However, the Rogowski coil 1 is formed on the circuit board 2 in which a plurality of conductive layers and a plurality of insulating layers are laminated, and as described above, the conductive patterns of overlapping winding coils overlap each other. The conductive patterns of the rewinding coil, and the overlapping conductive patterns of the rewinding coil and the rewinding coil are arranged so that current flows in opposite directions. More specifically, as shown in FIG. 6, the radial portion 11a of the conductive pattern 11 and the radial portion 31a of the conductive pattern 31 connected via the through hole 71 overlap each other in a plan view, Even under the influence of the external magnetic field, the direction of the current flowing in the radial portion 11a of the conductive pattern 11 and the direction of the current flowing in the radial portion 31a of the conductive pattern 31 are reversed and cancel each other. The same applies to the radial portion 21 a of the conductive pattern 21 and the radial portion 41 a of the conductive pattern 41 connected through the through hole 52.

As described above, the winding advance coil and the rewinding coil are connected to each other, and the winding direction of the coil is reversed. Therefore, when affected by the external magnetic field in the direction of arrow B, the circumferential portion 11b of the conductive pattern 11 and the circumferential portion 21b of the conductive pattern 21 overlap each other in front view. The directions of the currents flowing in the circumferential portion 11b and the circumferential portion 21b of the conductive pattern 21 are reversed and cancel each other. The same applies to the circumferential portion 31b of the conductive pattern 31 and the circumferential portion 41b of the conductive patterns 41. Further, the radial portion 11 c inside the conductive pattern 11 and the inner radial portion 31 c next to the conductive pattern 31, and the radial portion 21 c inside the conductive pattern 21 and the inner radial portion 41 c next to the conductive pattern 41 are used. Is the same.

In this way, the current flowing through the conductive pattern formed in one conductive layer is offset by the current flowing through the conductive pattern formed in the conductive layer adjacent to the external magnetic field orthogonal to the stacking direction of the circuit board 2. Thus, the S / N can be further increased by reducing noise components. In particular, an external magnetic field generated by a current other than the current to be measured has a greater influence as it is closer to the current, and therefore, it is preferable to cancel the currents flowing in the conductive pattern formed in the closer conductive layer.

As can be seen from FIG. 1 to FIG. 3 and FIG. 6, the first lead line part 4 and the second lead line part 5, and the first lead line part 4 and the second lead line part 5 and the two

legs

7 a and 7 b of the IC 7. The connection portions 8 respectively penetrate the first conductive pattern 10 of the first conductive layer, the second conductive pattern 20 of the second conductive layer, and the circuit board 2 in the thickness direction, and the first conductive pattern 10 and the second conductive pattern 8 are connected to each other. It is composed of a plurality of through holes 6 that electrically connect the pattern 20. The conductive pattern constituting the first lead wire portion 4 and the conductive pattern constituting the lead wire portion 5 are partially overlapped so that currents flow in opposite directions, and the cross pattern is X-shaped in front view. Is formed. Therefore, the current flowing through the first lead line portion 4 and the current flowing through the second lead line portion 5 cancel each other against the influence of the external magnetic field, so the first lead line portion 4 and the second lead line portion 5 It is possible to prevent the S / N from being lowered.

Further, unlike the conductive patterns of the first lead wire portion 4 and the second lead wire portion 5, the connection portion 8 has a structure that is intentionally influenced by an external magnetic field and is parallel to each other in plan view. It has

portions

8a and 8b. Further, an intersection pattern 8e is formed between the

lands

8c and 8d to which the

parallel portions

8a and 8b and the two

legs

7a and 7b of the IC 7 are connected has an X shape when viewed from the front. Here, the area of the portion surrounded by the two

legs

7a and 7b (and the intersecting pattern 8e) protruding outward from the IC 7 and the

portions

8a and 8b (and the intersecting pattern) parallel to each other in the connecting portion 8 are described. The lengths and intervals of the

parallel portions

8a and 8b are set so that the area of the portion surrounded by 8e) is substantially equal.

When the two

legs

7a and 7b (and the cross pattern 8e) projecting outward from the IC 7 are regarded as one coil, the

portions

8a and 8b (and the cross pattern 8e) of the connecting portion 8 that are parallel to each other are also the same. It can be seen as one coil, and by interposing the cross pattern 8e as described above, when the influence of the external magnetic field is exerted, the directions of current flow are reversed to cancel the current generated by the external magnetic field. can do. Further, as described above, the area of the portion surrounded by the two

legs

7a and 7b (and the cross pattern 8e) projecting outward from the IC 7 and the

parallel portions

8a and 8b of the connecting portion 8 are also provided. (And the cross pattern 8e) are substantially equal in area to the portion surrounded by the same, and therefore the generated current value is substantially the same, so that the current value generated by the external magnetic field can be made substantially zero. .

FIG. 7 shows another configuration example of the current measuring device according to the present embodiment. In the configuration example shown in FIG. 7, the connection portion 8 is formed below the main body of the IC 7, that is, in a portion where the legs are not formed. As a structure that is affected by an external magnetic field, a conductive pattern formed on a surface (that is, the surface) of the circuit board 2 on which the IC 7 is mounted, and two legs 7a that protrude outward from the IC 7 and From the opposite side of the protruding direction of 7b,

conductive patterns

8f and 8g that pass under the IC 7 in parallel with the two

legs

7a and 7b and reach the outside of the IC 7 and below the two legs are formed. The

conductive patterns

8f and 8g function as parallel portions and lands of the connection portion 8. As is well known, the legs projecting outward from the IC 7 are formed three-dimensionally and have a portion floating in the air with respect to the mounting surface of the circuit board 2. Therefore, according to the configuration shown in FIG. 7, the direction of the current flowing through the conductive pattern 8f and the direction of the current flowing through the floating portion of the leg 7a projecting outward from the IC 7 are reversed. Moreover, it was enclosed between the area of the part enclosed between the two

legs

7a and 7b which protrude outside from IC7, and the

conductive patterns

8f and 8g which are mutually parallel parts among the connection parts 8. FIG. Since the area of the portion is substantially equal, the generated current value is also substantially the same, so that the current value generated by the external magnetic field can be made substantially zero.

In addition, this invention is not limited to description of the said embodiment, A various deformation | transformation is possible. First, the current measuring coil is not limited to a toroidal coil, and may be a general CT using a core. Further, the configuration of the circuit board is not necessarily the other board having a plurality of conductive layers, and the circuit board may be a single-layer circuit board. In that case, wire bonding is crossed three-dimensionally as a structure that is affected by the external magnetic field at the connection between the two lead wire portions drawn from the current measuring coil and the two legs projecting outward from the IC. And may be crossed in an X shape in plan view.
The preferred embodiments of the present invention have been described above, but the present invention is not limited to these specific embodiments, and various modifications and variations that do not depart from the scope of the claims are possible. It belongs to the category of the present invention.

Claims

A circuit board;
A current measuring coil formed on the circuit board;
An IC provided with a plurality of legs mounted on the circuit board and projecting to the outside;
Two lead wire portions formed on the circuit board and drawn from the current measuring coil;
A connecting portion for connecting the two lead wire portions to two of the plurality of legs,
Including
The current measuring device, wherein the connecting portion includes a conductive pattern structure that is affected by the external magnetic field in order to cancel the influence of the portion surrounded by the two legs from the external magnetic field.
The connecting portion has a pattern portion having substantially the same area as the area of the portion surrounded by the two legs,
The current measuring device according to claim 1, wherein the pattern portion is formed so that a current flows in a direction opposite to a current flowing through the two legs.
3. The current measuring device according to claim 1, wherein the connecting portion further includes an additional pattern intersecting in an X shape when viewed from the thickness direction of the circuit board.
The circuit board has a plurality of conductive layers and a plurality of insulating layers alternately stacked, and an opening that penetrates a conductor through which a current to be measured flows.
The current measuring device according to claim 3, wherein the current measuring coil is formed so as to surround the opening.
Each of the plurality of conductive layers includes a conductive pattern,
The circuit board further includes a plurality of through holes that electrically connect the conductive patterns of the plurality of conductive layers,
Each of the two lead lines and the connection portion includes the conductive pattern and the plurality of through holes,
The current measuring device according to claim 4, wherein the additional pattern portion is formed by three-dimensionally intersecting conductive patterns formed in different conductive layers among the plurality of conductive layers.
The pattern portion is formed on the same surface as the surface of the circuit board on which the IC is mounted, and is parallel to the two legs from below the IC opposite to the protruding direction of the two legs. 5. The current measuring device according to claim 2, wherein the current measuring device is formed so as to pass below the IC and protrude from the two legs.
4. The current measuring device according to claim 3, wherein the additional pattern portion is wire bonding intersecting three-dimensionally.