JP2010122239A - Current measurement device and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve frequency property of a magnetic sensor to current in a current measurement device in which the magnetic sensor and a wide conductor to be measured are placed in proximity. <P>SOLUTION: By placing an adjacent magnetic sensor 10 at a position between the center and the end rather than the center in terms of the width direction of the conductor to be measured 1, the frequency property of the magnetic sensor 10 to current is changed, thereby the frequency property can be adjusted. By placing the magnetic sensor 10 at the best position within the range, the frequency property to current of the magnetic sensor 10 becomes nearly equivalent to the frequency property to magnetism inherent for the magnetic sensor 10, then the outputs become stable over a wide frequency band in comparison to the case of placing the sensor at the center, thereby the frequency property can be improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a current measuring device and a current measuring method for measuring the magnitude of a current flowing through a conductor to be measured using a magnetic sensor, and more particularly to a current measuring device in which a magnetic sensor is arranged in proximity to a flat conductor to be measured. And a current measuring method.

  Until now, a current measuring method using a magnetic sensor has been known as a technique for measuring the magnitude of a current flowing through a conductor (see, for example, Patent Document 1, Patent Document 2, and Patent Document 3). The magnetic sensor includes a magnetic detection element inside the sensor, and outputs a voltage proportional to the magnitude of the magnetic field input to the magnetic detection element. The measurement method is a method of measuring the magnitude of the current flowing through the conductor by disposing a magnetic sensor at a certain position around the conductor and detecting the induced magnetic field caused by the current flowing through the conductor with the magnetic sensor.

  Based on this method, there is a current measuring device that measures the magnitude of current by arranging a surface-mountable magnetic sensor on a substrate having a conductor to be measured. This is because the magnetic sensor can detect a magnetic field parallel to the mounting surface. By placing the magnetic sensor on the conductor to be measured, the magnetic sensor detects the magnetic field generated in the width direction of the conductor to be measured. Thus, the magnitude of the current flowing through the conductor to be measured can be measured.

JP-A-8-233865 JP-A-10-267965 US Pat. No. 5,942,895

  However, a magnetic sensor capable of detecting a magnetic field generated in the width direction of the conductor to be measured is disposed close to the conductor to be measured on a wide width of the conductor to be measured, at a center position with respect to the width direction of the conductor to be measured. At this time, the frequency characteristic band of the magnetic sensor with respect to the current flowing in the conductor to be measured, which is denoted as “0 mm” in FIG. I understood.

  Here, the frequency characteristic of the magnetic sensor with respect to the current means that when the current flowing through the conductor to be measured is constant and the frequency of the current is changed, the magnetic sensor detects the induced magnetic field generated by the current, and the magnetic sensor responds. It is the frequency characteristic of current sensitivity obtained from the output. In addition, the frequency characteristics of the magnetic sensor with respect to magnetism are the magnetic sensitivity obtained from the output of the magnetic sensor responding when the magnetic sensor detects the magnetic field when the magnetic field frequency is changed and the magnetic field frequency is changed. It is a frequency characteristic. The band is a frequency up to a point where the current sensitivity or magnetic sensitivity of DC is reduced by 3 dB.

In an application for measuring an alternating current from a direct current to a low frequency, as described above, the magnetic sensor may be arranged at a center position with respect to the width direction of the conductor to be measured. However, in applications that want to stably measure currents in a wide frequency band from DC to high frequencies, for example, in applications that measure motor control currents, currents that change instantaneously, such as periodic currents and startup Therefore, a decrease in frequency characteristics of the magnetic sensor with respect to the current becomes a problem.
The present invention clarifies the cause of the decrease in the frequency characteristics of the magnetic sensor with respect to the current, and improves the frequency characteristics of the magnetic sensor with respect to the current when the magnetic sensor and the wide conductor to be measured are arranged close to each other. An object of the present invention is to provide a current measuring device and a current measuring method capable of performing the above.

As a result of intensive studies to solve the above problems, the present inventor has found that the frequency characteristics of the magnetic sensor with respect to the current change depending on the position of the magnetic sensor and the wide conductor to be measured, and the physicality that causes the change. As a result, the present invention has been clarified.
A current measuring device according to claim 1 of the present invention includes a magnetic sensor having a pair of sensor elements for detecting a magnetic field generated by a current flowing through a flat conductor to be measured. The magnetic sensor is configured to measure the current based on the center of the pair of sensor elements from a center position in the width direction perpendicular to the current flow of the conductor to be measured. The magnetic field is provided at a position separated by a predetermined distance in the width direction, and the magnetic field is the magnetic field in the width direction.

According to a second aspect of the present invention, there is provided a current measuring apparatus including only one sensor element for detecting a magnetic field generated by a current flowing through a flat conductor to be measured, or a magnetic sensor comprising one sensor and an amplifier circuit. A current measuring device for measuring the current based on a magnetic field detected by the magnetic sensor, wherein the magnetic sensor has a magnetic sensitive surface of the sensor element perpendicular to a width direction of the conductor to be measured; and The sensor element is provided such that the center of the sensor element is located at a position separated by a predetermined distance in the width direction from the center position in the width direction perpendicular to the current flow of the conductor to be measured. The magnetic field is in the width direction.
In this way, by arranging the magnetic sensor closer to the conductor end than the center position rather than the center position with respect to the width direction of the conductor to be measured, the magnetic sensor is positioned at the center position in the width direction of the conductor to be measured. Compared with the arrangement, the frequency characteristic band of the magnetic sensor with respect to the current can be widened and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

The current measuring device according to claim 3 of the present invention is characterized in that, in claim 1 or 2, the magnetic sensor is arranged so as to be close to the conductor to be measured. By disposing the magnetic sensor close to the conductor to be measured, the magnetic sensor can detect the magnetic field generated by the current flowing through the conductor to be measured, and a high current sensitivity can be obtained.
The current measuring device according to claim 4 of the present invention is the current measuring device according to any one of claims 1 to 3, wherein the magnetic sensor detects the converged magnetic field and a magnetic converging plate that converges the magnetic field in the width direction. And a hall element as a sensor element. The magnetic converging plate makes it easy to converge the magnetic field, and the current can be measured by detecting the converged magnetic field with a Hall element.

The current measuring device according to claim 5 of the present invention is characterized in that, in claim 4, the width of the conductor to be measured is wider than the width of the magnetic converging plate. When the width of the conductor to be measured is wider than the width of the magnetic converging plate, a desired frequency characteristic can be obtained depending on the position where the magnetic sensor is disposed.
The current measuring device according to a sixth aspect of the present invention is the current measuring device according to any one of the first to fifth aspects, wherein the predetermined distance is (W / 2) × (1/16) with respect to the width W of the conductor to be measured. ) To (W / 2) × (16/16). By providing a magnetic sensor at a position away from the center of this range with respect to the width of the conductor to be measured, compared to the case where the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured, The band of the frequency characteristic of the sensor can be expanded and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  According to a seventh aspect of the present invention, in the current measurement device according to any one of the first to fifth aspects, the predetermined distance is (W / 2) × (10/16) with respect to the width W of the conductor to be measured. ) To (W / 2) × (14/16). Compared to the case where the magnetic sensor is disposed at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at a position where the distance of this range is away from the center with respect to the width of the conductor to be measured, the magnetic sensor for current Thus, the frequency characteristic of the magnetic sensor is substantially the same as the frequency characteristic of the magnetic sensor with respect to the original magnetism, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  The current measuring device according to claim 8 of the present invention is the current measuring device according to any one of claims 1 to 5, wherein the predetermined distance is (W / 2) × (20/15) with respect to the width W of the conductor to be measured. ) To (W / 2) × (24/15). Even when the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at the position outside the width of the conductor to be measured and at a position away from the center in this range. In comparison, the frequency characteristic of the magnetic sensor with respect to the current is close to the original frequency characteristic with respect to the magnetism of the magnetic sensor, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  According to a ninth aspect of the present invention, there is provided a current measuring method for measuring the current based on a magnetic field detected by a magnetic sensor having a pair of sensor elements for detecting a magnetic field generated by a current flowing through a flat conductor to be measured. The center between the pair of sensor elements is located at a position away from the central position in the width direction perpendicular to the current flow of the conductor to be measured by a predetermined distance in the width direction. The magnetic sensor is provided, and the magnetic field is a magnetic field in the width direction.

The current measuring method according to claim 10 of the present invention is detected by only one sensor element for detecting a magnetic field generated by a current flowing through a flat conductor to be measured or by a magnetic sensor comprising one sensor and an amplifier circuit. A current measuring method for measuring the current based on a measured magnetic field, wherein a magnetic sensitive surface of the sensor element is perpendicular to a width direction of the conductor to be measured, and a center of the sensor element is the measurement target. The magnetic sensor is provided so as to be located at a predetermined distance in the width direction from a center position in the width direction perpendicular to the current flow of the conductor, and the magnetic field is a magnetic field in the width direction. It is characterized by that.
Thus, by placing the magnetic sensor closer to the conductor end than the center with respect to the width direction of the conductor to be measured, compared to when the magnetic sensor is disposed at the center position in the width direction of the conductor to be measured, The band of the frequency characteristic of the magnetic sensor with respect to the current can be widened and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

The current measuring method according to an eleventh aspect of the present invention is characterized in that, in the ninth or tenth aspect, the magnetic sensor is disposed so as to be close to the conductor to be measured. By arranging the magnetic sensor close to the conductor to be measured, the magnetic sensor can detect the magnetic field generated by the current flowing through the conductor to be measured, so that high current sensitivity can be obtained.
The current measurement method according to a twelfth aspect of the present invention is the current measurement method according to any one of the ninth to eleventh aspects, wherein the magnetic sensor detects a magnetic converging plate that converges the magnetic field in the width direction and the converged magnetic field. And a hall element as a sensor element. The magnetic converging plate makes it easy to converge the magnetic field, and the current can be measured by detecting the converged magnetic field with a Hall element.

The current measuring method according to claim 13 of the present invention is characterized in that, in claim 12, the width of the conductor to be measured is wider than the width of the magnetic converging plate. When the width of the conductor to be measured is wider than the width of the magnetic converging plate, a desired frequency characteristic can be obtained depending on the position where the magnetic sensor is disposed.
A current measuring method according to a fourteenth aspect of the present invention is the current measuring method according to any one of the ninth to thirteenth aspects, wherein the predetermined distance is (W / 2) × (1/16) with respect to the width W of the conductor to be measured. ) To (W / 2) × (16/16). By providing a magnetic sensor at a position away from the center of this range with respect to the width of the conductor to be measured, compared to the case where the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured, The band of the frequency characteristic of the sensor can be expanded and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  The current measuring method according to claim 15 of the present invention is the current measuring method according to any one of claims 9 to 13, wherein the predetermined distance is (W / 2) × (10/16) with respect to the width W of the conductor to be measured. ) To (W / 2) × (14/16). Compared to the case where the magnetic sensor is disposed at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at a position where the distance of this range is away from the center with respect to the width of the conductor to be measured, the magnetic sensor for current The frequency characteristics of the magnetic sensor are substantially the same as the frequency characteristics of the magnetic sensor with respect to the original magnetism, and the frequency characteristics of the magnetic sensor with respect to the current can be improved.

  According to a sixteenth aspect of the present invention, in the current measurement method according to any one of the ninth to thirteenth aspects, the predetermined distance is (W / 2) × (20/15) with respect to the width W of the conductor to be measured. ) To (W / 2) × (24/15). Even when the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at the position outside the width of the conductor to be measured and at a position away from the center in this range. In comparison, the frequency characteristic of the magnetic sensor with respect to the current is close to the original frequency characteristic with respect to the magnetism of the magnetic sensor, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  The present invention relates to an apparatus for measuring the magnitude of a current flowing in a conductor to be measured using a magnetic sensor, and in particular, in a current measuring apparatus in which a magnetic sensor is disposed close to a wide conductor to be measured, the magnetic sensor is The magnetic sensor is arranged not in the center position with respect to the width direction of the conductor to be measured but at a position separated by a predetermined distance from the center position in the width direction, that is, close to the conductor end from the center position. Compared to the case where it is placed at the center position, the band of the frequency characteristic of the magnetic sensor with respect to the current can be widened and adjusted, and the frequency of the magnetic sensor with respect to the current can be adjusted by placing it at an optimum position within this range. As a characteristic, a characteristic equivalent to the frequency characteristic with respect to magnetism inherent in the magnetic sensor is obtained, and the frequency characteristic of the magnetic sensor with respect to current can be improved.

It is sectional drawing which shows the positional relationship of a magnetic sensor and a to-be-measured conductor. It is a top view which shows the positional relationship of a magnetic sensor and a to-be-measured conductor. It is a figure which shows the structure inside the package of a magnetic sensor. It is a figure which shows the current frequency characteristic by the position of a magnetic sensor and a to-be-measured conductor. It is a figure which shows the output waveform of a magnetic sensor by the position of a magnetic sensor and a to-be-measured conductor. It is a schematic diagram which shows the electric current and eddy current in a conductor when the frequency of an electric current is high. It is a figure which shows embodiment which arrange | positions a magnetic sensor to the back side of a to-be-measured conductor with respect to a printed circuit board. It is a figure which shows embodiment which uses a bus-bar for a to-be-measured conductor. It is a figure which shows embodiment which uses a Hall element for a magnetic sensor. It is a figure which shows embodiment which affixed two magnetic convergence boards and IC chip directly on the to-be-measured conductor. It is a schematic diagram which shows magnetic flux density intensity distribution which arises around a to-be-measured conductor. (A) is a figure which shows the bus bar which is an example of a to-be-measured conductor, (b) is a figure which shows the state which mounted the bus bar which is to-be-measured conductor on the printed circuit board, (c) is a top view of the state of (b). is there. It is a figure which shows the frequency characteristic of the current sensitivity in case the distance between a bus-bar and a magnetic sensor is 4 [mm]. It is a figure which shows the frequency characteristic of a current sensitivity in case the distance between a bus-bar and a magnetic sensor is 2 [mm]. It is a figure which shows the frequency characteristic of a current sensitivity in case the distance between a bus bar and a magnetic sensor is 0 [mm].

(Frequency characteristics of magnetic sensor)
First, the reason why the frequency characteristics of the magnetic sensor with respect to the current are lower than the frequency characteristics with respect to the original magnetism of the magnetic sensor when the adjacent magnetic sensor is placed at the center position in the width direction of the conductor to be measured is explained. To do.
FIG. 1 shows that a magnetic field 20 generated in the width direction of a conductor to be measured 1 is detected on a copper foil conductor 1 having a thickness of 35 [μm] and a width of 16 [mm] formed on a printed board 11a. This is an example in which magnetic sensors 10 that can be arranged are arranged so as to be close to each other. The width of the conductor 1 to be measured is a surface that is perpendicular to the energizing direction and has a long side on a flat surface. Further, the short side is the thickness of the conductor 1 to be measured. For example, the measured conductor 1 is a printed wiring.
FIG. 2 is a diagram seen from the upper surface side of the conductor to be measured 1 of FIG. In FIG. 2, the printed board 11b is not shown. Here, the magnetic sensor 10 is made of a surface-mountable TSSOP (Thin Shrink Small Outline Package).

  FIG. 3 is a diagram showing a structure inside the package of the magnetic sensor 10. Two magnetic converging plates 45 are provided under the IC chip 43 incorporating the Hall element 44 and an amplifier circuit (not shown). The material of the magnetic flux concentrating plate 45 is a soft magnetic material having a small coercive force and a high magnetic permeability. In this example, the total length of the two magnetic converging plates 45 is 2.2 [mm], and the two magnetic converging plates 45 are arranged at a predetermined interval. By doing so, the magnetic field 46 in a direction parallel to the package surface is converged on the Hall element 44 in the IC chip 43. That is, the magnetic sensor 10 can detect a magnetic field 46 in a direction parallel to the package surface, and the magnetic sensor 10 can be positioned in the width direction of the measured conductor 1 by making the package surface and the surface of the measured conductor 1 face each other. The magnetic field 20 is detected. The band of the frequency characteristic with respect to magnetism of the magnetic sensor 10 is approximately 150 [KHz]. Here, the total length of the two magnetic converging plates 45 is the width of the magnetic sensor.

  4 shows that the center 3 of the magnetic sensor 10 is magnetized from 0 to 5 [mm], 6 [mm], and 8 [mm] from the center position 2 that is the center in the width direction of the conductor 1 to be measured. It is the result of investigating the frequency characteristic of the magnetic sensor 10 with respect to the electric current in each position when the sensor 10 is arranged. The horizontal axis in the figure is the frequency. Further, the vertical axis in the figure represents a current sensitivity obtained from the effective output of the magnetic sensor 10 at each frequency of the current of 100 [Hz] when an effective current of 4 [Arms] is passed through the conductor 1 to be measured. It is standardized by current sensitivity.

  From the results shown in FIG. 4, the frequency characteristic band when the magnetic sensor is provided at 0 [mm] from the central position 2 of the conductor 1 to be measured (that is, provided at the central position) is a broken line in FIG. It can be seen that the frequency characteristic is lower than the band of the frequency characteristic with respect to the original magnetism of the magnetic sensor 10 shown in FIG. On the other hand, the frequency characteristic when the magnetic sensor is provided at 8 [mm] from the center position 2 of the conductor 1 to be measured decreases from about 10 [KHz], with the current sensitivity rising from about 10 [KHz]. It shows a trend. In this way, as the magnetic sensor 10 is arranged close to the end of the conductor from the center position 2 of the conductor 1 to be measured, the frequency characteristic of the magnetic sensor 10 with respect to the current changes, and the frequency characteristic band tends to be widened. I understood that.

  FIG. 5 shows that when the magnetic sensor 10 is placed at 0 [mm] and 8 [mm] from the central position 2 with respect to the width direction of the conductor 1 to be measured, the central 3 of the magnetic sensor 10 is 100 [ It is the result of examining the output waveform of the magnetic sensor 10 at KHz]. At this time, an effective current of 4 [Arms] was passed through the conductor 1 to be measured. From this result, the output waveform of the magnetic sensor 10 when placed at 8 [mm] from the central position 2 of the conductor 1 to be measured is advanced by about 1 [μsec] from the output waveform when placed at 0 [mm]. I found out.

(Skin effect of conductor to be measured)
From the above results, the present inventor has found that when the frequency of the current is high, the current sensitivity decreases at the center of the conductor to be measured and the current sensitivity increases at the end portion. It was clarified that a phenomenon called The skin effect refers to a phenomenon in which, when the frequency of the current flowing through the measured conductor increases, the current concentrates on the end of the measured conductor due to electromagnetic induction. When the frequency of the current is high, the current density decreases at the center of the conductor to be measured, so the current sensitivity of the magnetic sensor placed in the center of the conductor decreases, while the current density increases near the end of the conductor to be measured. The current sensitivity of the magnetic sensor placed at the end of the conductor is considered to have increased.

(Eddy current in the conductor under measurement)
Furthermore, the present inventor has found that eddy currents exist in the measured conductor from experimental evidence that a time difference occurs in the output waveform of the magnetic sensor in the same measured conductor when the frequency of the current is high. Revealed. FIG. 6 is a diagram schematically showing the state of the current 30 and the eddy current 31 in the conductor 1 to be measured when the frequency of the current is high.
In the figure, the phase relationship between the current 30 and the eddy current 31 flowing through the conductor 1 to be measured is such that the eddy current 31 flows 90 [°] ahead of the current 30 in the direction shown in the figure by electromagnetic induction. Therefore, since the current 30 and the eddy current 31 advanced by 90 [°] are combined with each other, the current flowing through the end of the conductor 1 to be measured is combined with the magnetic sensor 10 as seen in the result shown in FIG. It is considered that the output waveform of the magnetic sensor 10 when the signal is disposed at the end of the conductor 1 to be measured is output with a phase advance than when the signal is disposed at the center position 2.
As described above, the reason why the frequency characteristic of the magnetic sensor with respect to the current is lower than the original frequency characteristic with respect to the magnetism of the magnetic sensor is that when the frequency of the current is increased, electromagnetic induction occurs in the measured conductor, and the skin effect This is because eddy currents appear.

Next, the present invention will be described with reference to FIGS. 1 to 4 while solving the physical phenomenon that occurs in the conductor to be measured.
As shown in FIGS. 1 and 2, when the magnetic sensor 10 is disposed not in the center position 2 but in the width direction of the conductor 1 to be measured but between the center position 2 and the end of the conductor 1 to be measured, FIG. As a result, the frequency characteristic of the magnetic sensor 10 with respect to the current changes, and the band can be widened and the frequency characteristic can be adjusted. In this range, when the magnetic sensor 10 is arranged at 6 [mm] from the central position 2 of the conductor 1 to be measured 1 in the center 3 of the magnetic sensor 10, the frequency characteristics of the magnetic sensor 10 with respect to the current are the inherent magnetic properties of the magnetic sensor 10. As compared with the case where the magnetic sensor is arranged at the central position 2 of the conductor 1 to be measured, the current sensitivity is stable over a wide frequency band, and the frequency characteristic can be improved.

(Positional relationship between magnetic sensor and measured conductor)
As described above, the embodiment of the present invention has been described. However, as illustrated in FIG. 7, the present invention provides the magnetic sensor 10 on the back surface of the printed board 11 a on which the conductor 1 to be measured is mounted. Even in the case of mounting, the same effect as in the embodiment of FIG. 1 can be obtained. Further, as shown in FIG. 8, the present invention can be applied to the case of the embodiment of FIG. 1 even when a thin bus bar 51 having a flat shape provided independently from a printed circuit board is used as a conductor to be measured. The same effect can be obtained.

  FIG. 9 shows an example in which a magnetic sensor 52 having only a Hall element or a Hall element and an amplifier circuit (not shown) is arranged so as to be close to the wide conductor 1 to be measured. In this example, the magnetic sensor 52 is provided on the printed circuit board 11b. Also in this case, since the magnetic sensitive surface of the Hall element of the magnetic sensor 52 is placed perpendicular to the width direction of the conductor 1 to be measured, the magnetic field 20 generated in the width direction of the conductor 1 to be measured can be detected. The same effect as that of the embodiment of FIG. 1 can be obtained.

Further, according to the present invention, as shown in FIG. 10, an IC chip 43 including two magnetic converging plates 45, a Hall element 44, and an amplifier circuit (not shown) is attached to the conductor 1 to be measured. The effect similar to that of the embodiment shown in FIG.
As described with reference to FIGS. 7 to 10, the magnetic sensor 10 is not provided at the center position in the width direction of the conductor 1 to be measured, but at a position between the center position and the conductor end. In other words, the type of package of the magnetic sensor 10, the presence or absence of the package, and direct or indirect bonding of the IC chip 43 and the conductor 1 to be measured are not essential matters.

  When a conductor having a low resistivity is used as the material of the conductor 1 to be measured, a skin effect or eddy current is likely to occur due to electromagnetic induction. As described above, according to the present invention, the frequency characteristic of the magnetic sensor 10 with respect to the current can be equivalent to the frequency characteristic with respect to the original magnetism of the magnetic sensor 10. For this reason, it is appropriate to select a metal having a low resistivity such as copper or aluminum or an alloy thereof in order to reduce the voltage drop and heat generation due to the resistance of the conductor as the material of the conductor 1 to be measured.

(Magnetic flux density distribution)
In FIG. 11, a current of a predetermined magnitude is passed through the conductor 1 to be measured, and the magnetic flux density intensity distribution of the component in the width direction of the conductor 1 to be measured generated around the conductor 1 is taken into account with the effect of electromagnetic induction. Results obtained by numerical magnetic field analysis are shown. Here, the material of the conductor to be measured 1 was copper, the width W of the conductor to be measured 1 was 9 [mm], and the thickness t was 35 [μm]. The figure shows a schematic diagram of the cross-sectional shape of the conductor to be measured 1 superimposed on the magnetic flux density intensity distribution.

  In the drawing, the width (W / 2) × (16/16) from the center position 2 to the end of the conductor to be measured 1 is shown together with the total width W of the conductor to be measured 1. Further, in the figure, the magnetic flux density intensity distribution of the component in the width direction of the conductor 1 to be measured generated around the conductor 1 to be measured is divided by a threshold value of a certain magnetic flux density intensity, and the distribution is emphasized. The side closer to the conductor to be measured 1 than the threshold line of the magnetic flux density intensity distribution indicates a region having a high magnetic flux density strength, and the side far from the conductor to be measured 1 indicates a region having a low magnetic flux density strength.

When the current flowing through the measured conductor 1 is a direct current, referring to the magnetic flux density intensity distribution 61 generated around the measured conductor 1 in FIG. 11, the magnetic flux density near the center position 2 with respect to the width direction of the measured conductor 1. It can be seen that the strength is strong.
When the frequency of the current flowing through the conductor 1 to be measured is 100 [KHz], referring to the magnetic flux density intensity distribution 62 generated around the conductor 1 to be measured in FIG. It can be seen that the magnetic flux density strength in the vicinity of 2 is weakened, and the region where the magnetic flux density strength is strong spreads in the end direction with respect to the width direction.

When the frequency of the current flowing through the conductor to be measured 1 is 300 [KHz], referring to the magnetic flux density intensity distribution 63 generated around the conductor to be measured 1 in FIG. It can be seen that the magnetic flux density strength at the position of 2 is clearly weakened, and the region where the magnetic flux density strength is strong further expands toward the end with respect to the width direction.
From the analysis result of FIG. 11, when the current frequency is increased, the magnetic flux density strength of the width direction component generated around the conductor 1 to be measured is gradually weakened in the center of the conductor 1 to be measured due to the effect of electromagnetic induction. It can be visually seen that it becomes stronger at the end of 1. Here, when the magnetic sensor 10 is arranged at the central position 2 with respect to the width direction of the conductor 1 to be measured, the frequency characteristic of the magnetic sensor 10 with respect to the current is the magnetic flux at the center of the conductor 1 to be measured when the current frequency is high. It shows that the density strength decreases due to weakening.

  On the other hand, as shown in FIG. 11, (W / 2) × (1/16) ≦ X ≦ (W / 2) × (16/16) with respect to the width direction W of the conductor 1 to be measured. When the magnetic sensor is arranged in the range, the magnetic flux density intensity does not change or is small with respect to the current frequency in this range. For this reason, the frequency characteristic of the magnetic sensor with respect to the current can be adjusted with a tendency to widen the band as compared with the case where the magnetic sensor is arranged at the center position 2 with respect to the width direction of the conductor 1 to be measured. A current measuring device with improved frequency characteristics can be realized.

Further, when the magnetic sensor is arranged in a range of (W / 2) × (10/16) ≦ X ≦ (W / 2) × (14/16) with respect to the width direction of the conductor 1 to be measured, There is almost no change in magnetic flux density with respect to the frequency of the current. For this reason, the frequency characteristic of the magnetic sensor with respect to the current is substantially the same as the frequency characteristic of the magnetic sensor with respect to the current inherent to the magnetic sensor, and a current measuring device with improved frequency characteristics can be realized.
This range is the result of FIG. 4 described above, and the center of the magnetic sensor is 6 [mm] (= (W / 2) × (12/16): W = 16) from the center position of the conductor 1 to be measured. It can be seen that when the magnetic sensor is arranged, the frequency characteristic of the magnetic sensor with respect to the current coincides with the result that the frequency characteristic with respect to the original magnetism of the magnetic sensor is substantially equal to the result, which is a reasonable range.

(Measurement of current flowing through the bus bar)
The inventor, for a conductor made of aluminum (Al) or copper (Cu) and having a thickness of several millimeters (hereinafter referred to as a bus bar), a central position in the width direction perpendicular to the current flow through the conductor. A magnetic sensor was provided at a position separated by a predetermined distance in the width direction, and the current was measured. At this time, the predetermined distance is from (W / 2) × (1/16) to (W / 2) × (16/16) with respect to the width W of the conductor to be measured as described in claim 6 of the present application. In the case of any distance, as described in claim 7 of the present application, the distance is also any distance from (W / 2) × (10/16) to (W / 2) × (14/16). The current measurement performance was confirmed for the case. As a result, it was confirmed that the frequency characteristic of the current sensitivity was greatly improved as compared with the case where the bus bar was arranged at the center position in the width direction (L = 0 [mm]).

  As an example, it was confirmed that the frequency characteristic of the current sensitivity was improved when the current flowing through the aluminum (Al) bus bar was measured using a magnetic sensor. As shown in FIG. 12A, the bus bar 1a used as the conductor 1 to be measured has a width BW of 30 [mm], a thickness BT of 1 [mm], and a length BL of 120 [mm]. It is a flat shape. In addition, the arrow Y in the same figure is the direction through which an electric current flows.

  The inventor mounted such a flat bus bar 1a on the printed circuit board 11a as shown in FIG. In this example, since a current flows from the near side to the far side in the figure, the magnetic field 20 is generated. FIG. 2C is a plan view showing the mounting state. In this state, the frequency characteristic of the current sensitivity when the distance Gap between the bus bar 1a and the magnetic sensor 10 was changed and the distance L from the center position 2 in the width direction of the bus bar 1a was changed was examined. The results are shown in FIGS. In these drawings, the distance L is 0 [mm], 10 [mm], 10.5 [mm], 11 [mm], 16 [mm], 18 [mm], 20 [mm], 22 [mm]. ], 24 [mm].

  The data shown in FIG. 13 has a distance Gap of 4 [mm], the data shown in FIG. 14 has a distance Gap of 2 [mm], and the data shown in FIG. 15 has a distance Gap of 0 [mm]. The frequency characteristics of sensitivity. 13 to 15, L = 10 to 11 [mm] indicated by a broken line is described in the claims of the present application as an optimum position, and the frequency characteristics are improved in any case and condition. I understand that.

As a result of the measurement, it was found that there is a mounting position with good frequency characteristics of current sensitivity other than the range of the distance L described above. That is, the magnetic sensor 10 is mounted in a range of L = (BW / 2) × (20/15) to (BW / 2) × (24/15), which is an outside position that protrudes from the width of the bus bar 1a. In this case, it was found that the frequency characteristic of the current sensitivity is improved although the sensitivity is lowered. Actually referring to the above data 1 and data 2, in the range of L = 20 to 24 [mm], the change of current sensitivity is within the range of change of about ± 1.5 [dB].
By the way, since the direction of the magnetic field generated by the current changes along the surface of the bus bar 1a, the direction of the magnetic focusing plate may be adjusted according to the direction. The adjustment method includes, for example, a method of mounting the mold package obliquely with respect to the printed circuit board, or inclining the magnetic flux converging plate inside the mold package in advance. By adjusting the orientation of the magnetic flux converging plate in this way, the current sensitivity can be increased and the frequency characteristics can be improved.

(Current measurement method)
According to the current measuring apparatus described above, the following current measuring method is realized. That is, a current measurement method for measuring the current based on a magnetic field detected by a magnetic sensor that detects a magnetic field generated by a current flowing through a flat conductor to be measured, with respect to the current flow of the conductor to be measured. Thus, a current measuring method is realized in which the magnetic sensor is provided at a position separated by a predetermined distance in the width direction from the center position in the vertical direction. Thus, by placing the magnetic sensor closer to the conductor end than the center with respect to the width direction of the conductor to be measured, compared to when the magnetic sensor is disposed at the center position in the width direction of the conductor to be measured, The band of the frequency characteristic of the magnetic sensor with respect to the current can be widened and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

The magnetic sensor is preferably arranged so as to be close to the conductor to be measured. By arranging the magnetic sensor close to the conductor to be measured, the magnetic sensor can detect the magnetic field generated by the current flowing through the conductor to be measured, so that high current sensitivity can be obtained.
Further, the magnetic field in the width direction generated by the current flowing through the conductor to be measured is detected by the magnetic sensor. By detecting the magnetic field in the width direction, the current flowing through the conductor to be measured can be measured.

  Furthermore, the magnetic sensor includes a magnetic converging plate that converges the magnetic field in the width direction, and a Hall element that detects the converged magnetic field. The magnetic converging plate makes it easy to converge the magnetic field, and the current can be measured by detecting the converged magnetic field with a Hall element. In this case, the width of the conductor to be measured may be wider than the width of the magnetic convergence plate. When the width of the conductor to be measured is wider than the width of the magnetic converging plate, a desired frequency characteristic can be obtained depending on the position where the magnetic sensor is disposed.

  The predetermined distance is any distance from W / 32 to W / 2 with respect to the width W of the conductor to be measured. By providing a magnetic sensor at a position away from the center of this range with respect to the width of the conductor to be measured, compared to the case where the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured, The band of the frequency characteristic of the sensor can be expanded and adjusted, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  Furthermore, the predetermined distance is any distance from (W / 2) × (10/16) to (W / 2) × (14/16) with respect to the width W of the conductor to be measured. Compared to the case where the magnetic sensor is disposed at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at a position where the distance of this range is away from the center with respect to the width of the conductor to be measured, the magnetic sensor for current The frequency characteristics of the magnetic sensor are substantially the same as the frequency characteristics of the magnetic sensor with respect to the original magnetism, and the frequency characteristics of the magnetic sensor with respect to the current can be improved.

  The predetermined distance may be any distance from (W / 2) × (20/15) to (W / 2) × (24/15) with respect to the width W of the conductor to be measured. . Even when the magnetic sensor is arranged at the center position in the width direction of the conductor to be measured by providing the magnetic sensor at the position outside the width of the conductor to be measured and at a position away from the center in this range. In comparison, the frequency characteristic of the magnetic sensor with respect to the current is close to the original frequency characteristic with respect to the magnetism of the magnetic sensor, and the frequency characteristic of the magnetic sensor with respect to the current can be improved.

  The current measuring device and the current measuring method according to the present invention can be suitably used in the field of current sensors having a device for arranging a magnetic sensor close to a wide conductor to be measured.

DESCRIPTION OF SYMBOLS 1 Conductor to be measured 1a Bus bar 2 Center position 3 Center 10, 52 Magnetic sensor 11a, 11b Printed circuit board 20, 46 Magnetic field 30 Current 31 Eddy current 41 Mold package 42a Lead frame 42b Lead pin 43 IC chip 44 Hall element 45 Magnetic convergence plate 51 Bus bar 61, 62, 63 Magnetic flux density intensity distribution

Claims (16)

A current measuring device that includes a magnetic sensor having a pair of sensor elements for detecting a magnetic field generated by a current flowing through a flat conductor to be measured, and that measures the current based on the magnetic field detected by the magnetic sensor. And
The magnetic sensor is positioned such that the center between the pair of sensor elements is located at a predetermined distance in the width direction from the center position in the width direction perpendicular to the current flow of the conductor to be measured. A current measuring device provided, wherein the magnetic field is a magnetic field in the width direction. A magnetic sensor including only one sensor element or one sensor and an amplifier circuit for detecting a magnetic field generated by a current flowing through a flat conductor to be measured, and based on the magnetic field detected by the magnetic sensor A current measuring device for measuring current,
In the magnetic sensor, the magnetic sensitive surface of the sensor element is perpendicular to the width direction of the conductor to be measured, and the center of the sensor element is perpendicular to the current flow of the conductor to be measured. The current measuring device is provided so as to be located at a position away from a center position in the width direction by a predetermined distance in the width direction, and the magnetic field is a magnetic field in the width direction. The current measuring device according to claim 1 or 2,
The magnetic sensor is disposed so as to be close to the conductor to be measured. The current measuring device according to any one of claims 1 to 3,
The current sensor includes a magnetic converging plate that converges the magnetic field in the width direction, and a Hall element as the sensor element that detects the converged magnetic field. The current measuring device according to claim 4,
The current measuring device is characterized in that a width of the conductor to be measured is wider than a width of the magnetic converging plate. The current measuring device according to any one of claims 1 to 5,
The predetermined distance is any distance from (W / 2) × (1/16) to (W / 2) × (16/16) with respect to the width W of the conductor to be measured. A current measuring device. The current measuring device according to any one of claims 1 to 5,
The predetermined distance is any distance from (W / 2) × (10/16) to (W / 2) × (14/16) with respect to the width W of the conductor to be measured. A current measuring device. The current measuring device according to any one of claims 1 to 5,
The predetermined distance is any distance from (W / 2) × (20/15) to (W / 2) × (24/15) with respect to the width W of the conductor to be measured. A current measuring device. A current measurement method for measuring the current based on a magnetic field detected by a magnetic sensor having a pair of sensor elements for detecting a magnetic field generated by a current flowing through a flat conductor to be measured,
The magnetic sensor is arranged such that the center between the pair of sensor elements is located at a position separated by a predetermined distance in the width direction from the center position in the width direction perpendicular to the current flow of the conductor to be measured. The current measuring method is characterized in that the magnetic field is a magnetic field in the width direction. Current measurement for measuring the current based on a magnetic field detected by a magnetic sensor composed of only one sensor element or one sensor and an amplifier circuit for detecting a magnetic field generated by a current flowing through a flat conductor to be measured. A method,
The magnetic sensing surface of the sensor element is perpendicular to the width direction of the conductor to be measured, and the center of the sensor element is from the center position in the width direction perpendicular to the current flow of the conductor to be measured. A method for measuring current, wherein the magnetic sensor is provided so as to be positioned at a predetermined distance in the width direction, and the magnetic field is a magnetic field in the width direction. The current measuring method according to claim 9 or 10,
A method for measuring current, wherein the magnetic sensor is arranged so as to be close to the conductor to be measured. The current measuring method according to any one of claims 9 to 11,
The magnetic sensor includes a magnetic converging plate that converges the magnetic field in the width direction, and a Hall element as the sensor element that detects the converged magnetic field. A current measuring method according to claim 12, comprising:
A method for measuring current, wherein the width of the conductor to be measured is wider than the width of the magnetic converging plate. The current measuring method according to any one of claims 9 to 13,
The predetermined distance is any distance from (W / 2) × (1/16) to (W / 2) × (16/16) with respect to the width W of the conductor to be measured. Current measurement method. The current measuring method according to any one of claims 9 to 13,
The predetermined distance is any distance from (W / 2) × (10/16) to (W / 2) × (14/16) with respect to the width W of the conductor to be measured. Current measurement method. The current measuring method according to any one of claims 9 to 13,
The predetermined distance is any distance from (W / 2) × (20/15) to (W / 2) × (24/15) with respect to the width W of the conductor to be measured. Current measurement method.

Images