JP5504483B2 - Current sensor - Google Patents

Description

  The present invention relates to a current sensor that measures the magnitude of a current, and more particularly, to a current sensor that detects a current flowing through a conductor via a magnetic detection element.

  In recent years, in the fields of electric vehicles and solar batteries, the current value handled has increased with the increase in output and performance of electric vehicles and solar battery devices. Sensors are widely used. As such a current sensor, a sensor having a magnetoelectric conversion element that detects a current flowing through a conductor to be detected through a change in a magnetic field around the conductor has been proposed.

  In addition, for the purpose of reducing the influence (disturbance) from the outside, a current for detecting the current flowing through the measured object based on the difference value of the magnetic vector in the opposite direction of the induced magnetic field generated by the measured current Sensors have been proposed (see, for example, Patent Document 1 and Patent Document 2).

Japanese Patent Application Laid-Open No. 08-293952 JP 2007-78418 A

  Thus, by arranging magnetic sensors on both sides of a conductor (also referred to as a “bus bar”) through which the current to be measured flows, the magnetic vectors in opposite directions are measured, and the difference between the output signals of the respective magnetic sensors is taken. This makes it possible to cancel the unnecessary magnetism due to disturbance and accurately measure the current to be measured.

  On the other hand, in the case where magnetic sensors are provided on both sides of a conductor (see, for example, Patent Document 2 (FIG. 15)), a structure in which a differential amplifier circuit is generally provided on the surface side on which one magnetic sensor is formed. It becomes. However, in the structure in which the differential amplifier circuit is provided on one side of the magnetic sensor arranged symmetrically with respect to the conductor, a wiring structure (length, shape, etc.) for connecting the differential amplifier circuit and each magnetic sensor is used. It will be different.

  Specifically, as shown in FIG. 4, the wiring A of the magnetic sensor A provided on the same surface side as the differential amplifier circuit is compared with the wiring B of the magnetic sensor B provided on the opposite surface side. Wiring is shortened. In this case, since the structures of the wiring A and the wiring B are different, it is difficult to remove noise applied from the outside such as a conductor to the two wirings in the differential amplifier circuit, and noise due to the difference in the wiring structure is newly generated. The problem is considered.

  In addition, since the substrate A on which the magnetic sensor A and the differential amplifier circuit are formed has a larger substrate size and circuit scale than the substrate B on which the magnetic sensor B is formed, capacitive coupling between the conductor and the substrate A is performed. There is also a difference between the noise due to the noise and the noise due to the capacitive coupling between the conductor and the substrate B, and there is a problem that affects current measurement.

  The present invention has been made in view of such points, and in a current sensor that detects a current based on a difference between magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a current to be measured, the effect of noise is effectively reduced. One of the purposes is to suppress it.

  One aspect of the current sensor of the present invention includes a first magnetic sensor and a second magnetic sensor that detect magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a current to be measured, and output an output signal. A differential amplifier circuit that outputs a difference between an output signal of the first magnetic sensor and an output signal of the second magnetic sensor; and an output terminal that electrically connects the output terminal of the first magnetic sensor and the input terminal of the differential amplifier circuit. 1 wiring, and a second wiring for electrically connecting the output terminal of the second magnetic sensor and the input terminal of the differential amplifier circuit, the first magnetic sensor, the second magnetic sensor, and the differential The amplifier circuit is provided over different substrates, and the wiring capacitances of the first wiring and the second wiring are approximately equal. According to this configuration, it is possible to effectively remove the noise applied to the first wiring and the second wiring due to the influence of the external magnetic field or the like by the differential amplifier circuit and measure the current value with high accuracy. .

  In the current sensor of the present invention, it is preferable that the first wiring and the second wiring have substantially the same length.

  In the current sensor of the present invention, it is preferable that the first wiring and the second wiring have substantially the same shape.

  In the current sensor of the present invention, the first magnetic sensor is provided on the first substrate facing the conductor through which the current to be measured flows, and the second magnetic sensor is opposed to the first substrate across the conductor. The differential amplifier circuit is preferably provided on a third substrate that is substantially orthogonal to the first substrate and the second substrate.

  In the current sensor of the present invention, it is preferable that the areas of the opposing surfaces of the first substrate and the second substrate are approximately equal.

  In the current sensor of the present invention, the main surface of the third substrate is provided in contact with the side surfaces of the first substrate and the second substrate, and the differential amplifier circuit is the first of the pair of main surfaces of the third substrate. It is preferable to be provided on the main surface facing the first magnetic sensor and the second magnetic sensor.

  In the current sensor of the present invention, the main surface of the third substrate is provided in contact with the side surfaces of the first substrate and the second substrate, and the differential amplifier circuit is a conductor of the pair of main surfaces of the third substrate. It is preferable that it is provided on the main surface opposite to the main surface opposite to.

  In the current sensor of the present invention, it is preferable that a conductive film functioning as a ground is provided on a main surface facing the conductor of the pair of main surfaces of the third substrate.

  In the current sensor of the present invention, it is preferable to have a shield cover that covers the first magnetic sensor and the second magnetic sensor.

  In the current sensor of the present invention, it is preferable that the first magnetic sensor and the second magnetic sensor are formed of GMR elements.

  According to one aspect of the present invention, the influence of noise can be effectively suppressed in a current sensor that detects current based on the difference between magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a measurement current. .

It is a figure showing an example of a block diagram and a circuit diagram of a current sensor concerning an embodiment of the invention. It is a figure which shows the structural example of the current sensor which concerns on embodiment of this invention. It is a figure which shows an example of a structure of a magnetic sensor and a differential amplifier circuit in the current sensor which concerns on embodiment of this invention. It is a figure which shows the outline | summary and circuit diagram of the current sensor which detects an electric current based on the difference of the conventional magnetic vector. It is a figure which shows the output waveform of the current sensor which concerns on the Example and comparative example of this invention.

  The present inventor has provided a current sensor that detects a current based on a difference between magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a current to be measured, and is provided symmetrically across a conductor through which the current to be measured flows. The influence of the external magnetic field applied to the wiring between each magnetic sensor and the differential amplifier circuit differs depending on the arrangement relationship between the magnetic sensor and the differential amplifier circuit, and noise is mixed in the signal output from the differential amplifier circuit. I found out. Therefore, in order to solve this problem, the present inventors independently control the arrangement relationship between the magnetic sensor provided symmetrically with the conductor interposed therebetween and the differential amplifier circuit, so that the wiring capacities of the two wirings become equal. The present invention has been completed with the idea that the influence of noise caused by the wiring capacitance can be effectively suppressed by using the structure.

  In addition, in the current sensor, how to suppress radiation noise that jumps in from the outside in addition to noise caused by wiring capacitance is a problem. Therefore, the inventor of the present application has an effect of radiating noise generated from a conductor or the like by adjusting the arrangement of the magnetic sensor and the differential amplifier circuit when each magnetic sensor and the differential amplifier circuit are provided on different substrates. It was found that it can be suppressed.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. First, the outline of the current sensor according to the present embodiment will be described with reference to FIG. 1A shows a block diagram of the current sensor, and FIG. 1B shows an example of a circuit diagram of the current sensor.

  The current sensor according to the present embodiment includes a first magnetic sensor 101 and a second magnetic sensor 102 that detect magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a current to be measured and output an output signal. A differential amplifier circuit 103 for outputting a difference between an output signal of the first magnetic sensor 101 and an output signal of the second magnetic sensor 102; an output terminal of the first magnetic sensor 101; and an input terminal of the differential amplifier circuit 103 A first wiring 104 electrically connecting the output terminal of the second magnetic sensor 102 and a second wiring 105 electrically connecting the input terminal of the differential amplifier circuit 103. The first magnetic sensor 101, the second magnetic sensor 102, and the differential amplifier circuit 103 are arranged so that the wiring capacitances of the wiring 104 and the second wiring 105 are substantially equal.

  The wiring capacity means a capacity accompanying the wiring such as a capacity between the wiring and the substrate and a capacity between adjacent wirings. In addition, the wiring capacity of the first wiring 104 and the second wiring 105 is equal to the capacitance formed between the first wiring 104 and the substrate or another wiring, and the second wiring 105 and the substrate or other wiring. It means that the capacitance formed between the wirings is equal. For example, when the peripheral structure of the first wiring 104 and the second wiring 105 is the same, the first wiring 104 and the second wiring 105 have the same wiring structure, so that the first wiring 104 and the second wiring 105 have the same structure. The wiring capacity of the second wiring 105 is the same. Note that the peripheral structure of the first wiring 104 and the second wiring 105 is the same as that of the first wiring 104 and the second wiring 105 and a substrate that forms a capacitor having a magnitude that affects current measurement. Even when there is no wiring or when there is a substrate or wiring that forms capacitance with the first wiring 104 and the second wiring 105, the wiring is formed around the first wiring 104 and the second wiring 105. The case where the arrangement | positioning of a board | substrate and another wiring is the same.

  Specifically, the current sensor according to the present embodiment includes the first magnetic sensor 101, the second magnetic sensor 102, and the differential amplifier circuit 103 on different substrates (first substrate 111 to third substrate 113). Each substrate is arranged so that the wiring capacity of the first wiring 104 and the second wiring 105 is equal. For example, in a state where the peripheral structures of the first wiring 104 and the second wiring 105 are the same, the substrates are arranged so that the wiring structures (length and shape) of the first wiring 104 and the second wiring 105 are equal. Deploy.

  Unlike the conventional configuration, the differential amplifier circuit is not provided on the same substrate as one of the two magnetic sensors (the first magnetic sensor 101 or the second magnetic sensor 102), but the first magnetic sensor 101, By providing the second magnetic sensor 102 and the differential amplifier circuit 103 independently on different substrates, the wiring structure of the first wiring 104 and the second wiring 105 is detailed while considering the positional relationship with other circuits. Can be set to For example, the first magnetic sensor 101, the second magnetic sensor 102, and the differential amplifier circuit 103 can be provided so that the wiring structures (length and shape) of the first wiring 104 and the second wiring 105 are equal. It becomes.

  The first magnetic sensor 101 and the second magnetic sensor 102 are magnetic detection elements whose characteristics are changed by an induced magnetic field from a current to be measured flowing through a conductor, and are respectively formed on the first substrate 111 and the second substrate 112. Is formed. The first magnetic sensor 101 and the second magnetic sensor 102 are a feedback coil that generates a magnetic field in a direction that cancels an induced magnetic field from the current to be measured (hereinafter referred to as a “cancel magnetic field”), and a magnetic detection element. It can be constituted by a magnetic balance type sensor provided with a bridge circuit composed of two magnetoresistive effect elements and two fixed resistance elements. As the magnetoresistive effect element of the bridge circuit, a GMR (Giant Magneto Resistance) element, a TMR (Tunnel Magneto Resistance) element, or the like can be used.

  The differential amplifier circuit 103 processes the differential value between the output signal of the first magnetic sensor 101 and the output signal of the second magnetic sensor 102 as a sensor output. By performing such processing, output signals due to induction magnetic fields acting on the first magnetic sensor 101 and the second magnetic sensor 102 are added, and noise caused by the influence of the external magnetic field is removed (cancelled). Therefore, the current can be measured with high accuracy.

  The first wiring 104 and the second wiring 105 are provided so that their wiring capacities are approximately equal. For example, the first wiring 104 and the second wiring 105 are formed to have substantially the same length. As a result, even if the signal output from the first wiring 104 and the second wiring 105 includes noise or the like due to the influence of an external magnetic field or the like, the differential amplifier circuit 103 cancels the influence of the noise. Can do. From the viewpoint of more effectively reducing the influence of noise, it is preferable that the materials, shapes, and the like forming the first wiring 104 and the second wiring 105 are substantially the same. The term “substantially the same” as used herein includes a certain range in consideration of the influence of variations caused by devices and the like in the manufacturing process in addition to the case where they are completely the same.

  In FIG. 2, a first substrate 111 provided with a first magnetic sensor 101, a second substrate 112 provided with a second magnetic sensor 102, and a third substrate 113 provided with a differential amplifier circuit 103 are shown. The schematic diagram of is shown. 2A shows the first substrate 111, FIG. 2B shows the second substrate 112, and FIG. 2C shows the third substrate 113.

  A first magnetic sensor 101 including a sensor unit 101 a and an operational amplifier 101 b is provided on the main surface of the first substrate 111, and the result detected by the first magnetic sensor 101 is output from the first wiring 104. Output as.

  A second magnetic sensor 102 including a sensor unit 102 a and an operational amplifier 102 b is provided on the main surface of the second substrate 112, and a result detected by the second magnetic sensor 102 is output from the second wiring 105. Output as. The structure of the second magnetic sensor 102 can be the same as that of the first magnetic sensor 101. Similarly, the first wiring 104 formed over the first substrate 111 and the second wiring 105 formed over the second substrate 112 are preferably formed with the same length and shape.

  Further, in the current sensor according to the present embodiment, the first substrate 111 and the second substrate 112 have the same configuration and the same size (area) of the first substrate 111 and the second substrate 112. Is preferably provided symmetrically with respect to the conductor through which the current to be measured flows. As a result, it is possible for the differential amplifier circuit 103 to effectively cancel the influence of noise caused by capacitive coupling between the conductor and the substrate 111 and noise caused by capacitive coupling between the conductor and the substrate 112.

  A differential amplifier circuit 103 is provided on the main surface of the third substrate 113, and the first wiring 104 and the second wiring 105 are electrically connected. Further, the output signal of the first magnetic sensor 101 is supplied to the differential amplifier circuit 103 via the first wiring 104, and the output signal of the second magnetic sensor 102 is supplied via the second wiring 105. Supplied. In addition, the first wiring 104 and the second wiring 105 formed over the third substrate 113 are preferably formed with the same length and shape.

  Next, a specific configuration example of the current sensor according to the present embodiment will be described with reference to FIG.

  As shown in FIG. 3, in the current sensor according to the present embodiment, the first substrate 111 and the second substrate 112 are arranged to face each other with the conductor through which the current to be measured flows, and the third substrate 113. Are provided so as to be substantially orthogonal to the main surfaces (surfaces on which magnetic sensors are formed) of the first substrate 111 and the second substrate.

  In this case, as shown in FIG. 3A, the main surface of the third substrate 113 is provided so as to be in contact with the side surfaces (surfaces other than the pair of main surfaces) of the first substrate 111 and the second substrate 112. The first magnetic sensor 101 is provided on the main surface of the first substrate 111 facing the conductor, and the second magnetic sensor 102 is provided on the main surface of the second substrate 112 facing the conductor. The dynamic amplifier circuit 103 can be provided on the main surface of the third substrate 113 on the side facing the first magnetic sensor 101 and the second magnetic sensor 102.

  Thus, even when the first magnetic sensor 101, the second magnetic sensor 102, and the differential amplifier circuit 103 are provided on different substrates, the first magnetic sensor 101, the second magnetic sensor 102, The lengths of the first wiring 104 and the second wiring 105 in which the differential amplifier circuit 103 can be arranged close to each other can be shortened. As a result, the routing of the first wiring 104 and the second wiring 105 can be simplified and the influence of the external magnetic field can be reduced.

  Further, from the viewpoint of reducing radiation noise that jumps in from the outside, in the configuration shown in FIG. 3A, the differential amplifier circuit 103 is replaced with the first magnetic sensor 101 and the second magnetic sensor on the third substrate 113. A structure provided on a surface opposite to the main surface on the side facing the sensor 102 can be employed (see FIG. 3B). In this case, a conductive film 106 is formed on the main surface of the third substrate 113 on the side facing the first magnetic sensor 101 and the second magnetic sensor 102. Note that the conductive film 106 preferably functions as the ground of the third substrate 113. In this way, by forming the grounded conductive film 106 on the surface opposite to the surface on which the differential amplifier circuit 103 of the third substrate 113 is provided (the surface facing the conductor), the first wiring is formed. In addition to being able to shorten the lengths of the 104 and the second wiring 105, it is possible to suppress the influence of radiation noise generated from a conductor or the like on the differential amplifier circuit 103.

  In order to reduce radiation noise to the first magnetic sensor 101 and the second magnetic sensor 102, shield covers 107 and 108 are provided so as to cover the first magnetic sensor 101 and the second magnetic sensor 102, respectively. A configuration may be employed (see FIG. 3C). The shield covers 107 and 108 can be formed using a metal material. The shield covers 107 and 108 are made of a nonmagnetic material so that the first magnetic sensor 101 and the second magnetic sensor 102 detect a change in the magnetic field generated when a current flows through the conductor. For example, the shield covers 107 and 108 are preferably formed using aluminum, copper, silver, or the like. As a result, it is possible to effectively suppress the influence of noise caused by the wiring capacitance and the influence caused by radiation noise, and improve the measurement accuracy of the current value.

  In the present embodiment, a magnetic balance type sensor is used as the first magnetic sensor and the second magnetic sensor. However, the present invention is not limited to this configuration. Any magnetic sensor may be used as long as it outputs output signals from each other by an induced magnetic field from a current to be measured passing through a current line. For example, a magnetic proportional sensor, a Hall element, or other magnetic detection element may be used. . By using a magnetic proportional sensor, it is possible to reduce power consumption as compared with a configuration using a magnetic balance sensor.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

  As shown in FIG. 1, the current sensor of this embodiment is configured so that the first magnetic sensor 101, the second magnetic sensor 102, and the differential amplifier circuit 103 are different from each other (first substrate 111 to third substrate). 113) and the substrates are arranged so that the wiring capacity of the first wiring 104 and the second wiring 105 is equal. Specifically, the wiring structures (length and shape) of the first wiring 104 and the second wiring 105 are equal in a state where the peripheral structures of the first wiring 104 and the second wiring 105 are the same. Each substrate was arranged as shown in FIG. The conditions of each component were as follows.

First substrate: 0.8 mm thick glass epoxy substrate Second substrate: 0.8 mm thick glass epoxy substrate Third substrate: 0.8 mm thick glass epoxy substrate First wiring: length 14 .9mm
Second wiring: length 14.8mm

(Comparative example)
As shown in FIG. 4 above, the current sensor of the comparative example is provided with the magnetic sensor A and the magnetic sensor B on different substrates (substrate A and substrate B), and the differential amplifier circuit is provided on one of the magnetic sensors (here, Provided on a substrate provided with a magnetic sensor A). That is, in the configuration of the comparative example, the wiring A of the magnetic sensor A provided on the same surface side as the differential amplifier circuit is shorter than the wiring B of the magnetic sensor B provided on the opposite surface side. The wiring capacities of the wiring A and the wiring B are different. The conditions of each component were as follows.

Substrate A: 0.8 mm thick glass epoxy substrate Substrate B: 0.8 mm thick glass epoxy substrate Wiring A: 10.5 mm length
Wiring B: Length 16.7mm

(Evaluation)
Next, in the current sensors of the example and the comparative example, when current was passed through the conductor (bus bar), the waveform of the output voltage of the current sensor was measured when rectangular wave noise was applied to the conductor. The measurement results are shown in FIG.

  From FIG. 5, it can be seen that the influence of noise appears in the output waveform in the current sensor of the comparative example (see FIG. 5B), but the influence of noise is greatly reduced in the current sensor of the embodiment. It was confirmed that it was made (see FIG. 5A). This is considered to be because the influence of noise can be effectively canceled in the differential amplifier circuit 103 by making the wiring capacitances of the first wiring 104 and the second wiring 105 equal.

  The present invention is not limited to the above embodiment, and can be implemented with various modifications. In addition, the material, the arrangement position of the current sensor, the thickness, the size, the manufacturing method, and the like in the above embodiment can be changed as appropriate. In addition, the present invention can be implemented with appropriate modifications without departing from the scope of the present invention.

  The present invention can be applied to a current sensor that detects the magnitude of current in an electric vehicle or the like.

DESCRIPTION OF SYMBOLS 101 1st magnetic sensor 101a sensor part 101b operational amplifier 102 2nd magnetic sensor 102a sensor part 102b operational amplifier 103 differential amplifier circuit 104 1st wiring 105 2nd wiring 106 electrically conductive film 107,108 shield cover 111 1st board | substrate 112 Second substrate 113 Third substrate

Claims (10)

A first magnetic sensor and a second magnetic sensor for detecting magnetic vectors in directions opposite to each other with respect to an induced magnetic field from a current to be measured and outputting an output signal; an output signal of the first magnetic sensor; and A differential amplifier circuit that outputs a difference between output signals of the second magnetic sensor; a first wiring that electrically connects an output terminal of the first magnetic sensor and an input terminal of the differential amplifier circuit; A second wiring for electrically connecting the output terminal of the second magnetic sensor and the input terminal of the differential amplifier circuit;
The first magnetic sensor, the second magnetic sensor, and the differential amplifier circuit are provided on different substrates, and a wiring capacity of the first wiring and the second wiring is approximately equal. Sensor.   The current sensor according to claim 1, wherein the lengths of the first wiring and the second wiring are substantially the same.   The current sensor according to claim 1, wherein the first wiring and the second wiring have substantially the same shape.   The first magnetic sensor is provided on a first substrate facing a conductor through which the current to be measured flows, and the second magnetic sensor is disposed facing the first substrate across the conductor. The differential amplifier circuit is provided on a second substrate, and the differential amplifier circuit is provided on a third substrate that is substantially orthogonal to the first substrate and the second substrate. The current sensor according to claim 3.   The current sensor according to claim 4, wherein areas of the opposing surfaces of the first substrate and the second substrate are approximately equal.   The main surface of the third substrate is provided in contact with the side surfaces of the first substrate and the second substrate, and the differential amplifier circuit includes the first surface of the pair of main surfaces of the third substrate. 6. The current sensor according to claim 4, wherein the current sensor is provided on a main surface facing the magnetic sensor and the second magnetic sensor.   The main surface of the third substrate is provided in contact with the side surfaces of the first substrate and the second substrate, and the differential amplifier circuit includes the conductor of the pair of main surfaces of the third substrate. 6. The current sensor according to claim 4, wherein the current sensor is provided on a main surface opposite to the opposing main surface.   8. The current sensor according to claim 7, wherein a conductive film functioning as a ground is provided on a main surface facing the conductor of the pair of main surfaces of the third substrate. 9.   The current sensor according to claim 1, further comprising a shield cover that covers the first magnetic sensor and the second magnetic sensor.   The current sensor according to any one of claims 1 to 9, wherein the first magnetic sensor and the second magnetic sensor are formed of GMR elements.

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