JP2015034774A - Current detection system, current detection method, and charge control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the occurrence of variations in detected values against variations in spaces between magnetic sensors and conductive wires of current detection systems.SOLUTION: A current detection system according to the present invention comprises: two terminals E, F; a conductor 101 constituting a current path having no branch between the terminals E, F; and a magnetic sensor 102 for detecting an intensity of a magnetic field generated by a current flowing in the conductor 101. The conductor 101 includes a first and a second conductor portion, each corresponding to different sections included in the current path. The first and second conductor portions are provided adjacent to each other and substantially parallel to each other, and the first and second conductor portions are provided so that, when a current flows in the conductor 101, currents reverse in direction to each other flow in the first and second conductor portions. The magnetic sensor 102 is disposed between the first and second conductor portions of the conductor 101.

Description

  The present invention relates to a current detection system using a magnetic sensor, a current detection method, and a charge control device.

  A current detection system using a magnetic sensor is known. The magnetic sensor includes, for example, a Hall element and a magnetoresistive element (AMR (Anisotropic Magnetoresistance) element, GMR (Giant Magnetoresistance) element, TMR (Tunneling Magnetoresistance) element, etc.)). Such a current detection system is disposed in the vicinity of a conductive line through which a current to be measured flows, and detects the intensity of a magnetic field generated by the current flowing through the conductive line.

  As a current detection system using a magnetic sensor, for example, the inventions of Patent Documents 1 to 3 are known. For example, according to Patent Document 1, a Hall element is disposed in the vicinity of a conductive line, and a magnetic field is generated in a direction substantially aligned with the maximum response axis of the Hall element by a current flowing through the conductive line.

  However, conventionally, in a current detection system using a magnetic sensor, if the distance between the conductive wire and the magnetic sensor varies, the magnetic flux density of the magnetic field generated by the conductive wire and reaching the magnetic sensor also varies. As a result, the detection result of the current detection system is varied to deteriorate the accuracy. For this reason, in order to realize a highly accurate current detection system, an advanced manufacturing technique and manufacturing apparatus for manufacturing with a constant distance between the conductive wire and the magnetic sensor are required. If correction for ensuring accuracy is to be performed, it is necessary to add a correction function to the current detection system and to add a correction process to the manufacturing process, which increases costs.

  The objective of this invention is providing the electric current detection system which can suppress that the dispersion | variation in a detection value arises with respect to the dispersion | variation in the space | interval of a conductive wire and a magnetic sensor.

According to the current detection system of the aspect of the present invention,
Two terminals,
A conductor constituting a current path having no branch between the two terminals;
A current detection system comprising a magnetic sensor for detecting the intensity of a magnetic field generated by a current flowing through the conductor,
The conductor includes first and second conductor portions respectively corresponding to different sections included in the current path, wherein the first and second conductor portions are provided close to each other and substantially parallel to each other; The first and second conductor portions are provided such that when current flows through the conductor, currents in opposite directions flow through the first and second conductor portions,
The magnetic sensor is arranged between the first and second conductor portions.

  According to the current detection system of the present invention, it is possible to suppress the occurrence of variations in detection values with respect to variations in the distance between the conductive wire and the magnetic sensor.

1 is a perspective view showing a configuration of a current detection system according to a first embodiment of the present invention. It is an equivalent circuit diagram which shows the structure of the magnetic sensor comprised as a bridge circuit of a magnetoresistive element. It is a perspective view which shows the structure of the electric current detection system which concerns on the modification of the 1st Embodiment of this invention. FIG. 4 is a diagram for explaining magnetic flux generated when a current is passed through one conductive wire 1. It is a graph which shows the relationship of the magnetic flux density with respect to the distance from the conductive wire 1 of FIG. It is a figure explaining the case where the electric current which flows into the two conductive wires 2 and 3 is detected. It is a figure explaining the magnetic flux which generate | occur | produces when an electric current is sent through the conductive wires 2 and 3 of FIG. It is a graph which shows the relationship of the magnetic flux density with respect to the position between the conductive wires 2 and 3 of FIG. It is a block diagram which shows the structure of the charging system which concerns on the 2nd Embodiment of this invention.

  Embodiments of the present invention will be described below with reference to the drawings.

First embodiment.
FIG. 1 is a perspective view showing the configuration of the current detection system according to the first embodiment of the present invention. The current detection system includes a conductor 101 that forms a current path having no branch between terminals E and F, and a magnetic sensor 102 that detects the intensity of a magnetic field generated by the current flowing through the conductor 101. The conductor 101 includes first and second conductor portions that respectively correspond to different sections included in the current path. The first and second conductor portions are provided in close proximity to each other and substantially parallel to each other, and the first and second conductor portions are connected to the first and second conductor portions when current flows through the conductor 101. It is provided so that a reverse current flows. For example, as shown in FIG. 1, the conductor 101 is formed by forming a strip-shaped conductor plate in a U shape. The magnetic sensor 102 is disposed between the first and second conductor portions of the conductor 101. The magnetic sensor 102 includes, for example, a Hall element or a magnetoresistive element such as an AMR element, a GMR element, or a TMR element. When a current is passed from the terminal E to the terminal F of the conductor 101, the lines of magnetic force generated by the current are in the same direction between the first and second conductor portions of the conductor 101 (position where the magnetic sensor 102 is provided). Therefore, the magnetic fields generated by the two conductor portions are added together. The magnetic sensor 102 detects the magnetic flux density of the added magnetic field. The magnetic sensor 102 is connected to an external signal processing circuit (not shown) via signal lines 103 and 104. When the magnetic sensor 102 is a magnetoresistive element, when the strength of the magnetic field generated by the current flowing through the conductor 101 changes, the resistance value of the magnetoresistive element changes. The external signal processing circuit detects a change in the resistance value of the magnetoresistive element as a change in voltage or current via the signal lines 103 and 104, and calculates the magnitude of the current flowing through the conductor 101 based on the detection result. To do.

  Next, the operation principle of the current detection system of FIG. 1 will be described with reference to FIGS.

  FIG. 4 is a diagram for explaining the magnetic flux generated when a current is passed through one conductive wire 1. FIG. 4 shows that when a current is passed through a conductive wire (wiring made of a conductor; an electric wire, a conductive wire, a conductor pattern of a printed circuit board, etc.) 1, it is generated on a plane perpendicular to the longitudinal direction of the conductive wire 1. Represents the state of magnetic flux. When a current is passed through the conductive wire 1, a magnetic field is generated around the conductive wire 1 according to Ampere's right-hand screw law. A central rectangle is a cross section of the conductive wire 1, and current flows in a direction perpendicular thereto. A plurality of concentric lines drawn so as to surround the conductive line 1 represent a magnetic field, and the interval between the lines represents a magnetic flux density. That is, when the line interval is narrow, the magnetic flux density is large, and when the line interval is wide, the magnetic flux density is small. When a current is passed through one conductive wire 1, the magnetic field strength (synonymous with magnetic flux density) is inversely proportional to the square of the distance from the conductive wire 1.

  FIG. 5 is a graph showing the relationship of the magnetic flux density with respect to the distance from the conductive wire 1 in FIG. The graph of FIG. 5 shows the magnetic field strength up to a position (point D) that is 4 mm away from the conductive line 1 with the surface (point C) of the conductive line 1 of FIG. As can be seen from FIG. 5, the magnetic flux density rapidly decreases as the distance from the conductive wire 1 increases.

FIG. 6 is a diagram for explaining a case where a current flowing through two conductive lines 2 and 3 is detected.
The conductive lines 2 and 3 are provided close to each other and substantially parallel to each other, and currents I1 and I2 in opposite directions flow through the conductive lines 2 and 3, respectively. The magnitudes of the currents I1 and I2 are the same.

  FIG. 7 is a diagram for explaining the magnetic flux generated when a current is passed through the conductive wires 2 and 3 in FIG. FIG. 7 shows the state of magnetic flux generated in the WXYZ plane of FIG. 6 when a current is passed through the conductive wires 2 and 3. When a current is passed through the conductive lines 2 and 3, a magnetic field is generated around the conductive lines 2 and 3 in accordance with Ampere's right-hand rule. Since the currents I1 and I2 flow in opposite directions, the directions of the magnetic flux between the conductive lines 2 and 3 match. Therefore, the magnetic flux generated by the current flowing through the conductive wire 2 and the magnetic flux generated by the current flowing through the conductive wire 3 are added to each other, and the magnetic flux density is larger than when the current flows through one conductive wire 1 (FIG. 4). It has become.

  FIG. 8 is a graph showing the relationship of the magnetic flux density with respect to the position between the conductive lines 2 and 3 in FIG. When the surface (point A) of the conductive line 2 is 0 mm among the surfaces where the conductive lines 2 and 3 of FIG. 7 face each other, the surface (point B) of the conductive line 3 is 4 mm from the surface of the conductive line 2. Suppose you are at a distance. As can be seen from FIG. 8, the magnetic flux density is lowest at a position between the point A and the point B (distance 2 mm), and the magnetic flux density increases as the conductive wire 2 or 3 is approached from this position. Although not shown in FIG. 8 because it is out of range, the magnetic flux density is maximized in the vicinity of the surface of the conductive wire 2 (point A) and the surface of the conductive wire 3 (point B).

  Hereinafter, when a current is passed through one conductive line 1 (FIG. 5), and when currents flowing in opposite directions are passed through two conductive lines 2 and 3 provided in close proximity to each other and substantially parallel to each other (FIG. 8). ), That is, the case of the current detection system of FIG.

  When a current is passed through one conductive wire 1, the magnetic flux density decreases in inverse proportion to the square of the distance from the conductive wire 1 as described above. Here, for example, a current detection system in which a magnetic sensor is arranged at a position 2 mm from the surface of the conductive wire 1 is assumed. This corresponds to the current detection system of Patent Document 1. In this case, according to FIG. 5, the magnetic sensor is in a magnetic field of about 1.25 μT (at a distance of 2 mm). By the way, when the current detection system is actually mass-produced, it is impossible to dispose the magnetic sensor at an accurate position of 2 mm from the surface of the conductive wire 1, and a predetermined manufacturing variation always occurs. For example, assuming that the variation in the distance from the surface of the conductive wire 1 to the magnetic sensor is 1.5 mm to 2.5 mm (2.0 mm ± 0.5), the magnetic flux density has a maximum value of 2 when the distance is 1.5 mm. When the distance is 2.5 mm, the magnetic flux density has a minimum value of 0.8 μT. Therefore, compared with the ideal value of magnetic flux density of 1.25 μT (at a distance of 2 mm), the magnetic flux density changes by + 76% at the maximum value and by −36% at the minimum value. The maximum value of the magnetic flux density is 2.75 times the minimum value of the magnetic flux density.

  On the other hand, when currents flowing in opposite directions are passed through two conductive wires 2 and 3 provided in close proximity to each other and substantially parallel to each other, as described above, the magnetic flux density is intermediate between the conductive wires 2 and 3. At the position of According to FIG. 8, the magnetic sensor is in a magnetic field of about 2.5 μT at an intermediate position between the conductive wires 2 and 3 (at a distance of 2 mm). For example, it is assumed that the variation in the position of the magnetic sensor between the conductive wires 2 and 3 is a distance of 1.5 mm to 2.5 mm (2.0 mm ± 0.5). In this case, when the distance is 1.5 mm and 2.5 mm, the magnetic flux density has a maximum value of 3.0 μT, and when the distance is 2.0 mm, the magnetic flux density has a minimum value of 2.5 μT. Therefore, compared with the ideal value 2.5 μT of the magnetic flux density (when the distance is 2 mm), the magnetic flux density changes by + 20% at the maximum value and changes by 0% at the minimum value. These rates of change are significantly less than when current is passed through one conductive line 1 (+ 76% and −36%). The maximum value of the magnetic flux density is 1.2 times the minimum value of the magnetic flux density. Accordingly, the range in which the magnetic flux density fluctuates due to the variation in the position of the magnetic sensor between the conductive wires 2 and 3 is also applied when current flows through one conductive wire 1 (the maximum value of the magnetic flux density is 2. 75 times). In order to correct this variation in magnetic flux density, when a current is passed through one conductive line 1, it must be correctable over the range of −36% to + 76% of the ideal value, whereas the current in FIG. In the case of a detection system, it is sufficient if correction is possible over 0% to + 20%. Therefore, according to the current detection system of FIG. 1, there is an advantage that the scale of the correction circuit can be reduced, the correction accuracy can be improved, and the manufacturing cost can be reduced.

  The current detection system of FIG. 1 is characterized in that a magnetic sensor 102 is disposed between two conductor portions in which a current in the conductor 101 reciprocates. If the magnetic sensor 102 is arranged in the middle of two conductor portions in which current flows in opposite directions, an error in magnetic flux density caused by an error in the position of the magnetic sensor 102 can be reduced. Thereby, even if the space | interval of the conductor 101 and the magnetic sensor 102 varies, the electric current detection system which cannot produce the dispersion | variation in a detection result is realizable.

  In the current detection system of FIG. 1, the magnetic sensor 102 may be fixed between the first and second conductor portions of the conductor 101 by resin or plastic. This makes it easier to handle the current detection system as a single component.

  In the current detection system of FIG. 1, the two conductor portions of the conductor 101 provided with the magnetic sensor 102 do not have to be completely parallel. Even if the two conductor parts are provided with an angle of, for example, 10 ° with respect to each other, the characteristic of FIG. 8 is not significantly affected, so that the angle between the two conductor parts is not affected by calibration of the current detection system. Can be removed.

  FIG. 2 is an equivalent circuit diagram showing a configuration of a magnetic sensor configured as a bridge circuit of a magnetoresistive element. The magnetic sensor may be configured as a bridge circuit of magnetoresistive elements. 2 is configured as a bridge circuit of magnetoresistive elements R1 to R4, and is connected to an external signal processing circuit (not shown) via signal lines 113 to 116. The magnetoresistive elements R1 to R4 are, for example, AMR elements, GMR elements, or TMR elements. Each of the magnetoresistive elements R1 to R4 has a resistance value that increases or decreases according to the strength of the magnetic field in the direction of the arrow. Therefore, for example, when the rightward magnetic field in FIG. 2 increases, the resistance values of the magnetoresistive elements R1 and R3 increase, and the resistance values of the magnetoresistive elements R2 and R4 decrease. Therefore, when a voltage is applied via the signal lines 114 and 116, the voltage on the signal lines 113 and 115 changes sensitively according to a change in the strength of the magnetic field. Further, the voltages on the signal lines 113 and 115 are oppositely changed. Therefore, by calculating the voltage difference between the signal lines 113 and 115, a change in magnetic field strength can be detected with high sensitivity.

  FIG. 3 is a perspective view showing a configuration of a current detection system according to a modification of the first embodiment of the present invention. The current detection system includes a conductor 111 that forms a current path that does not have a branch between terminals C1 and C2, and a magnetic sensor 112 that detects the intensity of a magnetic field generated by the current flowing through the conductor 111. The conductor 111 includes conductors 111a and 111b. The conductor 111a is formed, for example, as a conductor plate that is etched or punched. The conductor 111b is formed to have a predetermined three-dimensional shape so that a part of the conductor 111b is provided in proximity to and substantially parallel to the conductor 111a. A terminal C2 is provided at one end of the conductor 111a, a terminal C1 is provided at one end of the conductor 111b, and the other ends of the conductors 111a and 111b are electrically connected to each other. A part of the conductor 111a and a part of the conductor 111b correspond to different sections included in the current path of the conductor 111, respectively. A part of the conductor 111a and a part of the conductor 111b are provided close to each other and substantially parallel to each other, and the conductors 111a and 111b are a part of the conductor 111a and a part of the conductor 111b when a current flows through the conductor 111. Are provided such that currents in opposite directions flow through each other. The magnetic sensor 112 is disposed between the conductors 111a and 111b, for example, disposed on the conductor 111a. The magnetic sensor 112 is, for example, the magnetic sensor 112 of FIG. 2 and is connected to the terminals S1 to S4 via the signal lines 113 to 116. The signal lines 113 to 116 are, for example, conductive wires that connect terminals (not shown) of the magnetic sensor 112 and the terminals S1 to S4 by bonding. The terminals S1 to S4 are formed as, for example, etched or punched conductor plates. Terminals S1-S4 are connected to an external signal processing circuit (not shown). The external signal processing circuit detects a change in the strength of the magnetic field generated by the current flowing through the conductor 111, and calculates the magnitude of the current flowing through the conductor 111 based on the detection result.

  According to the current detection system of FIG. 3, as in the current detection system of FIG. 1, it is possible to realize a current detection system in which detection results are less likely to vary even when the distance between the conductor 111 and the magnetic sensor 112 varies.

  In the current detection system of FIG. 3, the magnetic sensor 112 may be filled with a resin or the like, or may be subjected to a molding process, as in the case of widely used integrated circuit packages. This makes it easier to handle the current detection system as a single component. The conductor 111a and the terminals S1 to S4 are the same as the lead frame of the semiconductor package.

  In the current detection system of FIG. 3, the current sensor 102 having the two signal lines 103 and 104 of FIG. 1 may be used instead of the current sensor 112 having the four signal lines 113 to 116.

Second embodiment.
FIG. 9 is a block diagram showing a configuration of a charging system according to the second embodiment of the present invention. The charging system in FIG. 9 includes a power supply device 201, a charging control device 202, and a battery 203. The charging control device 202 receives power supplied from the power supply device 201 and charges the battery 203. The charging control device 202 includes a current detection system including the conductor 101 and the magnetic sensor 102 and detects a current Idet flowing through the battery 203. Further, the charging control device 202 detects a voltage Vdet applied to the battery 203. The charging control device 202 determines an appropriate current and voltage to be output to the battery 203 based on the detected current Idet and voltage Vdet. The charge control device 202 can accurately detect the current Idet flowing through the battery 203 and the amount of electric power charged in the battery 203 by using a current detection system configured similarly to the current detection system of FIG.

  A current detection system, a current detection method, and a charge control device according to an aspect of the present invention include the following configuration.

According to the current detection system of the first aspect of the present invention,
Two terminals,
A conductor constituting a current path having no branch between the two terminals;
A current detection system comprising a magnetic sensor for detecting the intensity of a magnetic field generated by a current flowing through the conductor,
The conductor includes first and second conductor portions respectively corresponding to different sections included in the current path, wherein the first and second conductor portions are provided close to each other and substantially parallel to each other; The first and second conductor portions are provided such that when current flows through the conductor, currents in opposite directions flow through the first and second conductor portions,
The magnetic sensor is arranged between the first and second conductor portions.

According to the current detection system according to the second aspect of the present invention, in the current detection system according to the first aspect,
The magnetic sensor includes a magnetoresistive element.

According to the current detection system according to the third aspect of the present invention, in the current detection system according to the second aspect,
The magnetoresistive element is an AMR (Anisotropic Magnetoresistance) element, a GMR (Giant Magnetoresistance) element, or a TMR (Tunneling Magnetoresistance) element.

According to the current detection system according to the fourth aspect of the present invention, in the current detection system according to any one of the first to third aspects,
The magnetic sensor is configured as a bridge circuit.

According to the charge control device of the fifth aspect of the present invention,
In the charge control device that receives power supply from the power supply device and charges the battery, the charge control device includes:
A conductor including a first section constituting a current path having no branch between the power supply device and the battery;
A current detection system comprising a magnetic sensor for detecting the intensity of a magnetic field generated by a current flowing through the first section of the conductor,
The first section of the conductor includes first and second conductor portions that respectively correspond to different partial sections included in the first section, and the first and second conductor portions are adjacent to each other. The first and second conductor portions are provided substantially in parallel so that when current flows through the first section of the conductor, currents in opposite directions flow through the first and second conductor portions. Provided in
The magnetic sensor is disposed between the first and second conductor portions;
The magnitude of the current flowing through the battery is calculated based on the strength of the magnetic field.

According to the charge control device of the sixth aspect of the present invention,
A voltage detecting device for detecting a voltage applied to the battery is further provided.

According to the current detection method of the seventh aspect of the present invention,
In a current detection method for detecting the magnitude of a current flowing in a conductor between two terminals in a current detection system,
The current detection system is
A conductor constituting a current path having no branch between the two terminals;
A magnetic sensor for detecting the strength of the magnetic field generated by the current flowing through the conductor,
The conductor includes first and second conductor portions respectively corresponding to different sections included in the current path, wherein the first and second conductor portions are provided close to each other and substantially parallel to each other; The first and second conductor portions are provided such that when current flows through the conductor, currents in opposite directions flow through the first and second conductor portions,
The magnetic sensor is disposed between the first and second conductor portions;
The current detection method is
Detecting the intensity of the magnetic field generated by the current flowing in the conductor between the two terminals by the current detection system;
Calculating the magnitude of the current flowing through the conductor based on the strength of the magnetic field.

101, 111, 111a, 111b ... conductors,
102, 112 ... Magnetic sensor,
103, 104, 113 to 116 ... signal lines,
201 ... power supply,
202 ... charge control device,
203 ... Battery,
C1, C2, S1 to S4 ... terminals,
R1 to R4: magnetoresistive elements.

JP 2011-069837 A Japanese Patent No. 4579538 JP 2003-329749 A

Claims (7)

Two terminals,
A conductor constituting a current path having no branch between the two terminals;
A current detection system comprising a magnetic sensor for detecting the intensity of a magnetic field generated by a current flowing through the conductor,
The conductor includes first and second conductor portions respectively corresponding to different sections included in the current path, wherein the first and second conductor portions are provided close to each other and substantially parallel to each other; The first and second conductor portions are provided such that when current flows through the conductor, currents in opposite directions flow through the first and second conductor portions,
The current detection system, wherein the magnetic sensor is disposed between the first and second conductor portions.   The current detection system according to claim 1, wherein the magnetic sensor includes a magnetoresistive element.   3. The current detection system according to claim 2, wherein the magnetoresistive element is an AMR (Anisotropic Magnetoresistance) element, a GMR (Giant Magnetoresistance) element, or a TMR (Tunneling Magnetoresistance) element.   The current detection system according to claim 1, wherein the magnetic sensor is configured as a bridge circuit. In the charge control device that receives power supply from the power supply device and charges the battery, the charge control device includes:
A conductor including a first section constituting a current path having no branch between the power supply device and the battery;
A current detection system comprising a magnetic sensor for detecting the intensity of a magnetic field generated by a current flowing through the first section of the conductor,
The first section of the conductor includes first and second conductor portions that respectively correspond to different partial sections included in the first section, and the first and second conductor portions are adjacent to each other. The first and second conductor portions are provided substantially in parallel so that when current flows through the first section of the conductor, currents in opposite directions flow through the first and second conductor portions. Provided in
The magnetic sensor is disposed between the first and second conductor portions;
A charge control device that calculates the magnitude of a current flowing through the battery based on the strength of the magnetic field.   6. The charge control device according to claim 5, further comprising a voltage detection device for detecting a voltage applied to the battery. In a current detection method for detecting the magnitude of a current flowing in a conductor between two terminals in a current detection system,
The current detection system is
A conductor constituting a current path having no branch between the two terminals;
A magnetic sensor for detecting the strength of the magnetic field generated by the current flowing through the conductor,
The conductor includes first and second conductor portions respectively corresponding to different sections included in the current path, wherein the first and second conductor portions are provided close to each other and substantially parallel to each other; The first and second conductor portions are provided such that when current flows through the conductor, currents in opposite directions flow through the first and second conductor portions,
The magnetic sensor is disposed between the first and second conductor portions;
The current detection method is
Detecting the intensity of the magnetic field generated by the current flowing in the conductor between the two terminals by the current detection system;
Calculating the magnitude of the current flowing through the conductor based on the strength of the magnetic field.

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