WO2013011859A1

WO2013011859A1 - Current sensor

Info

Publication number: WO2013011859A1
Application number: PCT/JP2012/067506
Authority: WO
Inventors: 雅俊野村
Original assignee: アルプス・グリーンデバイス株式会社
Priority date: 2011-07-21
Filing date: 2012-07-09
Publication date: 2013-01-24
Also published as: JPWO2013011859A1; JP5688572B2

Abstract

The purpose of the present invention is to provide a current sensor capable of preventing current measurement accuracy from decreasing due to the effect of the output offset of a magnetic sensor. The current sensor comprises: a plurality of current sensor units (1a, 1b) corresponding to a plurality of current lines, each current sensor unit comprising a set of magnetic sensors (11a to 11d) disposed so as to sandwich a current line (2a, 2b) and a substrate (12a, 12b) on which the respective set of magnetic sensors is disposed; and a calculation device for calculating the difference between the outputs of the respective set of magnetic sensors of each current sensor unit and, by removing the effects of the adjacent current line from the output of each current sensor unit, calculating the value of a current to be measured. In each set of magnetic sensors included in the current sensor units, the magnetic sensors are connected to each other so that the temperatures thereof become substantially equal to each other, said magnetic sensors being connected to each other by the ground terminals (11a_GND to 11d_GND) of the magnetic sensors and a ground electrode (12a_GND, 12b_GND) provided on the respective substrate.

Description

Current sensor

The present invention relates to a current sensor that measures current without contact.

In fields such as motor drive technology in electric vehicles and hybrid cars, a relatively large current is handled, so a current sensor capable of measuring a large current in a contactless manner is required. As such a current sensor, a system that detects a change in a magnetic field caused by a current to be measured by a magnetic sensor has been put into practical use. For example, Patent Document 1 discloses a current sensor using a magnetoresistive effect element as an element for a magnetic sensor.

In the above-described current sensor for detecting a change in magnetic field, when a current flows through a conductor arranged close to the conductor through which the current to be measured flows, the magnetic field generated by the current flowing through the conductor The current measurement accuracy may be affected. In order to solve this problem, a current sensor in which n + 1 magnetic sensors are arranged so that two magnetic sensors are adjacent to each of n conductors has been proposed (for example, see Patent Document 2). ). According to this configuration, it is possible to correct the influence of the adjacent current, and thus it is possible to prevent a decrease in current measurement accuracy.

JP 2002-156390 A JP-T-2004-507747

By the way, in the elements for magnetic sensors including the magnetoresistive effect element, there is a characteristic variation due to a process variation. For example, in a magnetic sensor that uses voltage drops of a plurality of magnetoresistive elements, the effect of variations in characteristics of each magnetoresistive element appears as a magnetic sensor output (hereinafter referred to as an offset) in a zero magnetic field. The offset varies depending on the temperature, but if the temperature of the magnetic sensor differs depending on the position of the magnetic sensor in the current sensor (for example, the inner side where heat is easily trapped and the outer side where it is easily affected by outside air temperature), the offset of each magnetic sensor Therefore, when such a magnetic sensor is used, the current measurement accuracy of the current sensor is lowered.

The present invention has been made in view of such a point, and an object thereof is to provide a current sensor capable of suppressing a decrease in current measurement accuracy due to an influence of an offset of a magnetic sensor output.

The current sensor of the present invention includes a plurality of current lines each including a set of magnetic sensors arranged so as to sandwich a target current line and a substrate on which the set of magnetic sensors is arranged. Calculate the difference between the output of each of the corresponding current sensor units and the set of magnetic sensors in each current sensor unit, and remove the influence of the adjacent current line from the output of each current sensor unit to measure the current of the current being measured. A pair of magnetic sensors included in the current sensor unit are connected to each other by a ground terminal of each magnetic sensor and a ground electrode provided on the substrate so that the temperatures thereof are substantially equal to each other. It is characterized by being.

According to this configuration, in the set of magnetic sensors arranged so as to sandwich the current line, the ground terminals are connected to each other, so that the temperatures of the magnetic sensors become substantially equal and vary depending on the temperature. The output offset is approximately equal. Since the offsets are almost equal, if the output difference between the two magnetic sensors is calculated, the offset is canceled out and its influence can be reduced. Moreover, since the output of the current sensor unit corresponding to a plurality of current lines is used, the influence of the current flowing through the current line other than the current line through which the current to be measured flows can be reduced.

In the current sensor of the present invention, it is particularly preferable that the pair of magnetic sensors included in the current sensor unit have the same temperature characteristics of the offset change. The magnitude of the offset can be considered by dividing it into a magnitude of the offset at a reference temperature (for example, 25 ° C.) and a change due to temperature. Even if the magnitude of the offset at the reference temperature is slightly different for a set of magnetic sensors, the influence can be removed by calculation. On the other hand, if the amount of change due to temperature differs for a set of magnetic sensors, the difference becomes an error and cannot be removed. Therefore, the error can be minimized by making the temperature characteristics of the offset change substantially equal.

In the current sensor of the present invention, the set of magnetic sensors included in the current sensor unit has a sensitivity axis so that the influence of the current flowing through the current line appears in the opposite polarity in the output of the set of magnetic sensors. It is preferable that they are arranged in the same direction. According to this configuration, the influence of the offset can be sufficiently reduced by taking the difference between the outputs of the magnetic sensors.

In the current sensor of the present invention, a first current sensor unit including a first magnetic sensor and a second magnetic sensor disposed so as to sandwich a first current line through which a current to be measured flows, and the measured current And a second current sensor unit including a third magnetic sensor and a fourth magnetic sensor arranged to sandwich a second current line through which a current different from the current flows.

In the current sensor of the present invention, the sensitivity coefficient X ₁₁ related to the current flowing through the first current line of the first current sensor unit, and the current flowing through the second current line of the second current sensor unit. Sensitivity coefficient X ₂₂ , sensitivity coefficient X ₁₂ related to the current flowing through the second current line of the first current sensor unit, sensitivity coefficient related to current flowing through the first current line of the second current sensor unit X ₂₁ , the difference ΔV ₁ between the output of the _first magnetic sensor and the output of the _second magnetic sensor, and the difference ΔV ₂ between the output of the third magnetic sensor and the output of the fourth magnetic sensor The current value I ₁ of the current to be measured that flows through the first current line can be calculated from the following expression (7) that is used.

In the current sensor of the present invention, a first current sensor unit including a first magnetic sensor and a second magnetic sensor disposed so as to sandwich a first current line through which a current to be measured flows, and the measured current A second current sensor unit including a third magnetic sensor and a fourth magnetic sensor disposed so as to sandwich a second current line through which a second current different from the current flows; A third current sensor unit including a fifth magnetic sensor and a sixth magnetic sensor disposed so as to sandwich a third current line through which a third current different from the second current flows. You may prepare.

In the current sensor of the present invention, the sensitivity coefficient X _mn relating to the current flowing through the n-th current line (n is a natural number of 1 to 3) of the m-th current sensor unit (m is a natural number of 1 to 3), The difference ΔV ₁ between the output of the first magnetic sensor and the output of the second magnetic sensor, the difference ΔV ₂ between the output of the third magnetic sensor and the output of the fourth magnetic sensor, and the fifth The current value I ₁ of the current to be measured flowing through the first current line is expressed by the following equation (18) expressed using the difference ΔV ₃ between the output of the magnetic sensor and the output of the sixth magnetic sensor. Can be calculated.

However, D satisfies the following formula (21).

According to the present invention, it is possible to provide a current sensor that can suppress a decrease in current measurement accuracy due to the influence of an offset of the magnetic sensor output.

4 is a schematic diagram illustrating a configuration example of a current sensor according to Embodiment 1. FIG. 2 is a block diagram showing a configuration of a current sensor according to Embodiment 1. FIG. 3 is a block diagram illustrating a configuration example of a current sensor unit according to Embodiment 1. FIG. 3 is a circuit diagram illustrating a configuration example of a magnetic sensor according to Embodiment 1. FIG. It is a block diagram which shows the modification of the current sensor unit which concerns on Embodiment 1. FIG. It is a characteristic view which shows a mode that the influence of offset is reduced. 6 is a schematic diagram illustrating a configuration example of a current sensor according to Embodiment 2. FIG. 6 is a block diagram illustrating a configuration of a current sensor according to Embodiment 2. FIG.

(Embodiment 1)
Hereinafter, the current sensor of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a schematic diagram illustrating a configuration example of a current sensor 1 according to the present embodiment. In the following, the direction corresponding to the lower left direction (Y + direction) of FIG. 1 is the front, the direction corresponding to the upper right direction (Y− direction) is the rear, the direction corresponding to the left direction (X− direction) is the left, the page The direction corresponding to the right direction (X + direction) is called right, the direction corresponding to the upward direction (Z + direction) on the page is called up, and the direction corresponding to the down direction (Z− direction) on the page is called down.

The current sensor 1 shown in FIG. 1 includes a first current sensor unit 1a disposed close to the first current line 2a through which the measured current Ia flows, and a second current line 2b through which the adjacent current Ib flows. And a second current sensor unit 1b arranged close to each other. The first current sensor unit 1a has a thin plate-like first substrate 12a partially cut away so that the first current line 2a can be arranged, and a substantially rectangular parallelepiped shape arranged on the main surface of the first substrate 12a. The first magnetic sensor 11a and the second magnetic sensor 11b are included. The second current sensor unit 1b has a thin plate-like second substrate 12b partially cut away so that the second current line 2b can be arranged, and a substantially rectangular parallelepiped shape arranged on the main surface of the second substrate 12b. A third magnetic sensor 11c and a fourth magnetic sensor 11d are included. In FIG. 1, the arrows attached to the magnetic sensors indicate the directions of the sensitivity axes, the arrows attached to the current lines indicate the directions of currents flowing through the current lines, The arrows arranged around the lines indicate the direction of the induced magnetic field due to the current flowing through each current line. In addition, here, in order to simplify the calculation formula, an example is shown in which sensor units are arranged symmetrically in the left-right direction in each current sensor unit, but the essence of calculation is the same even if the arrangement of sensor units is asymmetric in the left-right direction And the obtained effect is unchanged.

The first magnetic sensor 11a and the second magnetic sensor 11b are arranged on one main surface of the first substrate 12a so that the distance from the first current line 2a extending in the vertical direction is substantially equal. Further, the first magnetic sensor 11a and the second magnetic sensor 11b are arranged such that the sensitivity axes are directed in substantially the same direction. For this reason, the first magnetic sensor 11a and the second magnetic sensor 11b receive the induced magnetic field Ha caused by the current Ia to be measured and generate outputs having opposite polarities. By arranging the first magnetic sensor 11a and the second magnetic sensor 11b in this way, the influence of the external magnetic field can be reduced by taking the difference between the output of the first magnetic sensor 11a and the output of the second magnetic sensor 11b. . Further, the offset of the output of the first magnetic sensor 11a and the offset of the output of the second magnetic sensor 11b can be offset to reduce the influence of the offset.

The relationship between the third magnetic sensor 11c and the fourth magnetic sensor 11d and the second current line 2b is the same. That is, the third magnetic sensor 11c and the fourth magnetic sensor 11d are arranged on one main surface of the second substrate 12b so that the distance from the second current line 2b extending in the vertical direction is substantially equal. Further, the third magnetic sensor 11c and the fourth magnetic sensor 11d are arranged so that the sensitivity axes are directed in substantially the same direction, so that outputs of opposite polarities are generated under the influence of the induced magnetic field Hb by the adjacent current Ib. It has become. Thereby, the influence of an external magnetic field can be reduced. Further, the influence of offset can be reduced.

As described above, the current sensor 1 according to the present embodiment is close to the second current line 2b in addition to the first current sensor unit 1a including the first magnetic sensor 11a and the second magnetic sensor 11b. And a second current sensor unit 1b including a third magnetic sensor 11c and a fourth magnetic sensor 11d. As a result, the correction can be made in consideration of the influence of the adjacent current Ib flowing through the second current line 2b, so that the measured current Ia can be calculated with high accuracy. A specific process related to the calculation of the current Ia to be measured will be described later.

Each of the magnetic sensors (11a to 11d) includes a plurality of terminals, and is connected to the first substrate 12a or the second substrate 12b via each terminal. At least one of the terminals included in each of the magnetic sensors (11a to 11d) is a ground terminal, and the ground terminal is connected to a ground electrode provided on the first substrate 12a or a ground electrode provided on the second substrate 12b. ing. Specifically, the ground terminal 11a_GND of the first magnetic sensor 11a is connected to the ground electrode 12a_GND provided on the first substrate 12a, and the ground terminal 11b_GND of the second magnetic sensor 11b is provided on the first substrate 12a. It is connected to the ground electrode 12a_GND. The ground terminal 11c_GND of the third magnetic sensor 11c is connected to the ground electrode 12b_GND provided on the second substrate 12b, and the ground terminal 11d_GND of the fourth magnetic sensor 11d is connected to the ground electrode 12b_GND provided on the second substrate 12b. It is connected to the. That is, the first magnetic sensor 11a and the second magnetic sensor 11b are connected via the ground terminal 11a_GND, the ground terminal 11b_GND, and the ground electrode 12a_GND, and the third magnetic sensor 11c and the fourth magnetic sensor 11d are connected to the ground terminal 11c_GND. Are connected via a ground terminal 11d_GND and a ground electrode 12b_GND.

The first substrate 12a and the second substrate 12b are substrates having a substantially U-shaped planar shape on which a wiring pattern is formed. In the first substrate 12a, a first current line 2a extending in a direction substantially orthogonal to the first main surface of the first substrate 12a is disposed in a space that forms a substantially U-shaped notch. . That is, the first substrate 12a is arranged in a plane substantially perpendicular to the direction of flow of the current Ia to be measured. In the second substrate 12b, a second current line 2b extending in a direction substantially orthogonal to the first main surface of the second substrate 12b is disposed in a space that forms a substantially U-shaped notch. Is done. That is, the second substrate 12b is disposed in a plane substantially perpendicular to the direction in which the adjacent current Ib flows.

As described above, the ground electrode 12a_GND is provided on the first main surface of the first substrate 12a. A ground electrode 12b_GND is provided on the first main surface of the second substrate 12b. The ground electrode 12a_GND and the ground electrode 12b_GND are connected to a ground GND (not shown). The ground electrode 12a_GND applies a ground voltage by the ground GND to the first magnetic sensor 11a connected via the ground terminal 11a_GND and the second magnetic sensor 11b connected via the ground terminal 11b_GND, and is connected to one side. The heat of one magnetic sensor can be transferred to the other magnetic sensor. The ground electrode 12b_GND applies a ground voltage by the ground GND to the third magnetic sensor 11c connected through the ground terminal 11c_GND and the fourth magnetic sensor 11d connected through the ground terminal 11d_GND, and is connected to the ground electrode 12b_GND. The heat of one magnetic sensor can be transferred to the other magnetic sensor. Thereby, the temperature of a set of magnetic sensors included in the same current sensor unit becomes substantially equal. The ground electrodes 12a_GND and 12b_GND are made of a material having high conductivity and thermal conductivity in order to apply a ground voltage to each magnetic sensor so that heat transfer between the magnetic sensors is performed appropriately. It is desirable that Examples of such a material include silver, copper, gold, and aluminum.

Further, the first substrate 12a and the second substrate 12b have wirings (not shown) for supplying a power supply voltage to the magnetic sensors (11a to 11d) and wirings for transmitting input / output signals of the magnetic sensors (11a to 11d). (Not shown) is provided. In addition to the magnetic sensors (11a to 11d) and the ground electrodes 12a_GND and 12b_GND, the first substrate 12a and the second substrate 12b may be provided with an arithmetic device (not shown).

FIG. 2 is a block diagram illustrating a configuration example of the current sensor 1 including the first current sensor unit 1a and the second current sensor unit 1b. As shown in FIG. 2, the current sensor 1 includes an arithmetic device 1d that calculates the current value of the current Ia to be measured from the output of the first current sensor unit 1a and the output of the second current sensor unit 1b. . As described above, the current sensor 1 includes the first current sensor unit 1a corresponding to the first current line 2a and the second current sensor unit 1b corresponding to the second current line 2b, and an operation for calculating these outputs. By providing the device 1d, the influence of the adjacent current Ib can be corrected and the current value of the measured current Ia can be calculated with high accuracy as will be described later. Note that the arithmetic device 1d may be provided outside the current sensor 1. That is, the current sensor 1 may be configured by a current measurement module that does not include the arithmetic device 1d. In this case, the current measurement module includes a first current sensor unit 1a and a second current sensor unit 1b.

FIG. 3 is a block diagram showing a specific configuration example of the first current sensor unit 1a. FIG. 4 is a circuit diagram showing a configuration example of the first magnetic sensor 11a and the second magnetic sensor 11b.

As shown in FIG. 3, the first current sensor unit 1a includes a magnetic balance type first magnetic sensor 11a and a second magnetic sensor 11b, and a first control circuit that controls the first magnetic sensor 11a and the second magnetic sensor 11b. 13a and a second control circuit 13b, and an arithmetic device 14a that calculates a voltage difference between the output on the first magnetic sensor 11a side and the output on the second magnetic sensor 11b side.

The first magnetic sensor 11a and the second magnetic sensor 11b include

feedback coils

111a and 111b arranged to generate a magnetic field in a direction that cancels the induced magnetic field Ha generated by the current Ia to be measured, and four magnetoresistive elements M1. To

bridge circuits

112a and 112b configured by M4. The first magnetic sensor 11a and the second magnetic sensor 11b may be magnetic proportional magnetic sensors that do not include the feedback coils 111a and 111b. Further, the number of magnetoresistive elements constituting the

bridge circuits

112a and 112b is not limited to four. The

bridge circuits

112a and 112b may be configured by combining any number of magnetoresistance effect elements and fixed resistance elements.

As the first magnetic sensor 11a and the second magnetic sensor 11b, magnetic sensors having substantially equal temperature characteristics of output offset change are used. This is to sufficiently suppress the influence of offset in the magnetic sensor output. Specifically, for example, a magnetic sensor with small variations in element characteristics may be used, such as a magnetic sensor manufactured using the same substrate or a magnetic sensor manufactured using the same lot. As described above, when the temperature characteristics of the offset change are substantially equal in a pair of magnetic sensors included in the same current sensor unit, the influence of the offset of the magnetic sensor can be offset by simple correction using only this pair. .

The first control circuit 13a and the second control circuit 13b amplify the differential outputs of the

bridge circuits

112a and 112b, and control the feedback currents of the feedback coils 111a and 111b. I /

V amplifiers

132a and 132b for converting to voltage. The first control circuit 13a and the second control circuit 13b have a function of correcting the absolute value of the offset voltage. Thereby, the influence of the offset in the 1st magnetic sensor 11a and the 2nd magnetic sensor 11b can fully be reduced. The offset correction is performed, for example, by increasing or decreasing the voltage value of each output so that the absolute value of the offset at a predetermined reference temperature (for example, 25 ° C.) becomes substantially equal. The function for correcting the absolute value of the offset voltage may be included in the arithmetic device 14a or the arithmetic device 1d.

The computing device 14a is configured to be able to output the difference between the output voltages from the

control circuits

13a and 13b (that is, the output voltages of the I /

V amplifiers

132a and 132b). The arithmetic device 14a is composed of, for example, a differential amplifier. The influence of an external magnetic field such as geomagnetism can be canceled by the arithmetic processing in the arithmetic device 14a. Further, the offset of the output on the first magnetic sensor 11a side and the offset of the output on the second magnetic sensor 11b side can be offset. Thereby, the current value can be measured with high accuracy.

As shown in FIG. 4, the feedback coils 111a and 111b are arranged in the vicinity of the magnetoresistive elements M1 to M4 constituting the

bridge circuits

112a and 112b, and cancel the induced magnetic field Ha generated by the current Ia to be measured. Generates a canceling magnetic field. As the magnetoresistive elements M1 to M4 of the

bridge circuits

112a and 112b, GMR (Giant Magneto Resistance) elements, TMR (Tunnel Magneto Resistance) elements, or the like are used. The magnetoresistive element has a characteristic that the resistance value is changed by an induced magnetic field from the current to be measured. By configuring the

bridge circuits

112a and 112b using magnetoresistive elements having such characteristics, a highly sensitive current sensor 1 can be realized.

One power supply terminal a of the

bridge circuits

112a and 112b is connected to the power supply Vdd, and the other power supply terminal b is connected to the ground GND. The power supply terminal b corresponds to the ground terminal 11a_GND and the ground terminal 11b_GND shown in FIG. The outputs from the two output terminals c and d of the

bridge circuits

112a and 112b are differentially amplified by the differential /

current amplifiers

131a and 131b, respectively. The feedback coils 111a and 111b receive the feedback current through the terminals e and f. Flowing. When the feedback current flows through the feedback coils 111a and 111b, a cancellation magnetic field that cancels the induced magnetic field Ha is generated by the feedback current. Then, the currents flowing through the feedback coils 111a and 111b when the induced magnetic field Ha and the canceling magnetic field are balanced are converted into voltages by the I /

V amplifiers

132a and 132b, respectively, and the first magnetic sensor 11a. Side output and output on the second magnetic sensor 11b side.

In addition, in FIG. 3, although the 1st current sensor unit 1a including the arithmetic unit 14a was illustrated, the structure of a current sensor unit is not limited to this. For example, as shown in FIG. 5, it is good also as a structure which does not include the arithmetic unit 14a. In this case, the arithmetic device 1d shown in FIG. 2 may have the function of the arithmetic device 14a. Each magnetic sensor is not limited to a magnetic sensor using a magnetoresistive element. For example, a magnetic sensor using a Hall element may be applied.

The configuration of the second current sensor unit 1b is the same as that of the first current sensor unit 1a. That is, the second current sensor unit 1b includes a third magnetic sensor 11c and a fourth magnetic sensor 11d, a third control circuit 13c and a fourth control circuit 13d that control the third magnetic sensor 11c and the fourth magnetic sensor 11d, An arithmetic device 14b that calculates a voltage difference between the output on the third magnetic sensor 11c side and the output on the fourth magnetic sensor 11d side is provided. The configurations of the third magnetic sensor 11c and the fourth magnetic sensor 11d are the same as the configurations of the first magnetic sensor 11a and the second magnetic sensor 11b, and the configurations of the third control circuit 13c and the fourth control circuit 13d are the same. The same as the first control circuit 13a and the second control circuit 13b. That is, the third magnetic sensor 11c and the fourth magnetic sensor 11d include the feedback coils 111c and 111d arranged to generate a magnetic field in a direction that cancels the induction magnetic field Hb generated by the adjacent current Ib, and four magnetoresistive elements. And

bridge circuits

112c and 112d composed of M1 to M4. The third control circuit 13c and the fourth control circuit 13d amplify the differential outputs of the

bridge circuits

112c and 112d, and control the feedback currents of the feedback coils 111c and 111d. I /

V amplifiers

132c and 132d for converting a current into a voltage. The third control circuit 13c and the fourth control circuit 13d have a function of correcting the absolute value of the offset voltage in the same manner as the first control circuit 13a and the second control circuit 13b.

In the current sensor 1 described above, there is usually an offset in the output of each magnetic sensor (11a to 11d). This offset varies depending on the temperature. If the offset is constant regardless of the temperature, the effect of the offset can be reduced sufficiently by simply taking the difference in sensor output. However, if the offset has temperature characteristics in this way, the difference is simply taken. It is not possible to sufficiently reduce the influence of offset. This is because the offset value varies depending on the temperature of each magnetic sensor. Therefore, in the current sensor 1 according to the present embodiment, a set of magnetic sensors included in the same current sensor unit are connected by a ground terminal and a ground electrode so that their temperatures are approximately equal to each other. Try to take the difference in output. Thereby, the influence of the offset which fluctuates depending on the temperature can be reduced.

Before calculating the difference between the sensor outputs, the first control circuit 13a, the second control circuit 13b, the calculation device 14a, the calculation device 1d, etc. determine the absolute value of the offset at a predetermined reference temperature (for example, 25 ° C.). Correction is performed so as to be substantially equal. Thereby, the influence of offset can be reduced sufficiently. Further, in the current sensor 1 according to the present embodiment, the temperature characteristics of the output offset change are substantially equal in a set of magnetic sensors included in the same current sensor unit. Thereby, by combining with the above correction, the offset of a set of magnetic sensors included in the same current sensor unit can be made substantially equal regardless of the temperature of the magnetic sensors. Therefore, by taking the difference between the sensor outputs, it is possible to sufficiently reduce the influence of the offset that varies depending on the temperature.

FIG. 6 is a characteristic diagram showing how the influence of offset is reduced. FIG. 6A shows the temperature characteristics of the offset voltage in the first magnetic sensor 11a and the second magnetic sensor 11b. As shown in FIG. 6A, in the first magnetic sensor 11a and the second magnetic sensor 11b, the values of the offset voltage at the same temperature are different, but the slopes of the curves indicating the temperature characteristics are substantially equal. That is, the temperature characteristics of the offset change are substantially equal. FIG. 6B shows the temperature characteristics of the offset voltage after correction and the difference therebetween. As shown in FIG. 6B, when the slopes of the temperature characteristics are equal, the offset voltages of the two magnetic sensors are corrected by correcting the output of the magnetic sensors so that the offset voltages are substantially equal under a certain temperature condition (for example, 25 ° C.). The curves indicating the temperature characteristics can be made substantially coincident. In this case, the difference between the offset of the first magnetic sensor 11a and the offset of the second magnetic sensor 11b can be made substantially zero by making the temperatures of the first magnetic sensor 11a and the second magnetic sensor 11b substantially equal.

Next, calculation processing performed to calculate the measured current Ia in the

calculation devices

14a and 14b and the calculation device 1d of the current sensor 1 according to the present embodiment will be described.

First, arithmetic processing in the arithmetic device 14a on the first current sensor unit 1a side will be described. When the output from the first magnetic sensor 11a and the first control circuit 13a and the output from the second magnetic sensor 11b and the second control circuit 13b are input to the arithmetic device 14a, the arithmetic device 14a is set to a predetermined temperature ( For example, a correction value that makes the offset voltages of the two outputs substantially equal at 25 ° C. is added to the output, and the corrected output (V _1A ) on the first magnetic sensor 11a side and the corrected second magnetic sensor The output (V _1B ) on the 11b side is obtained. Then, the arithmetic device 14a calculates the difference between the output (V _1A ) and the output (V _1B ) to obtain the output (ΔV ₁ ) of the first current sensor unit 1a.

Here, the corrected output (voltage) V _1A on the first magnetic sensor 11a side passes the current value of the measured current Ia flowing through the first current line 2a through I ₁ and the second current line 2b. The current value of the adjacent current Ib is I ₂ , the sensitivity coefficient relating to the current flowing through the first current line 2a of the first current sensor unit 1a is X ₁₁ , and the second current line 2b of the first current sensor unit 1a is passed through. The sensitivity coefficient relating to the flowing current is represented by the equation (1), where X _{12 is} the corrected offset voltage and V _O1 is the corrected offset voltage.

Further, the output (voltage) V _1B on the second magnetic sensor 11b side is similarly expressed by Expression (2).

The sensitivity coefficient is a coefficient indicating the relationship between the current flowing through a certain current line and each sensor output. For example, “the sensitivity coefficient related to the current flowing through the first current line 2a of the first current sensor unit 1a” is the current value flowing through the first current line 2a and the sensor output (or the first magnetic sensor 11a side). The relationship with the sensor output on the second magnetic sensor 11b side) is shown. Specifically, the sensitivity coefficient corresponds to a value obtained by dividing the sensor output by the current value flowing through the current line. Thus, for example, when the sensitivity coefficient for current second flowing through the current line 2b of the first current sensor unit 1a is X _12, the current value of the adjacent current Ib flowing through the second current line 2b If I ₂ , the sensor output on the first magnetic sensor 11a side (or the sensor output on the second magnetic sensor 11b side) is represented by X ₁₂ I ₂ .

In addition, in the current sensor 1 according to the present embodiment, the temperature characteristics of the offset change of a pair of magnetic sensors (here, the first magnetic sensor 11a and the second magnetic sensor 11b) existing in the same current sensor unit. Since they are substantially equal, the offset voltage after correction in the sensor output on the first magnetic sensor 11a side and the sensor output on the second magnetic sensor 11b side are expressed as expressed by the above formulas (1) and (2). The corrected offset voltage is substantially equal even at a temperature other than the predetermined temperature.

The arithmetic device 14a calculates the difference between the output (V _1A ) represented by the above formula ( ₁ ) and the output (V _1B ) represented by the above formula (2). Thereby, the output (ΔV ₁ ) of the first current sensor unit 1a represented by the expression (3) is obtained. As shown in Expression (3), the offset voltage term is canceled in the output (ΔV ₁ ) of the first current sensor unit 1a. Thus, by calculating the difference between the output (V _1A ) and the output (V _1B ), it is possible to sufficiently remove the influence of the offset and increase the current measurement accuracy.

Similarly, the output from the third magnetic sensor 11c and the third control circuit 13c and the output from the fourth magnetic sensor 11d and the fourth control circuit 13d are input to the arithmetic device 14b on the second current sensor unit 1b side. Then, the arithmetic device 14b adds a correction value so that the offset voltages of the two outputs become substantially equal at a predetermined temperature (for example, 25 ° C.), and outputs the corrected output on the third magnetic sensor 11c side ( V _2A ) and the corrected output (V _2B ) on the fourth magnetic sensor 11d side are obtained. Then, the arithmetic device 14a calculates the difference between the output (V _2A ) and the output (V _2B ) to obtain the output (ΔV ₂ ) of the second current sensor unit 1b.

The output of the third magnetic sensor 11c side _{(voltage) V 2A,} the current values of the adjacent current Ib the current value of the measured current Ia flowing through the first current line 2a _{to I 1,} flowing through the second current line 2b I ₂ , the sensitivity coefficient related to the current flowing through the first current line 2a of the second current sensor unit 1b is X ₂₁ , and the sensitivity coefficient related to the current flowing through the second current line 2b of the second current sensor unit 1b _Is represented by Equation (4) where X ₂₂ is X ₂₂ and the corrected offset voltage is V _O2 .

Similarly, the output (voltage) V _2B on the fourth magnetic sensor 11d side is expressed by the equation (5).

The calculation device 14b calculates the difference between the output (V _2A ) expressed by the above formula (4) and the output (V _2B ) expressed by the above formula (5), and is expressed by the formula (6). The output (ΔV ₂ ) of the second current sensor unit 1b is obtained.

The arithmetic device 14a outputs the output (ΔV ₁ ) of the first current sensor unit 1a obtained by the arithmetic processing described above to the arithmetic device 1d. The computing device 14b outputs the output (ΔV ₂ ) of the second current sensor unit 1b to the computing device 1d. The current value I _{1 of} the current Ia to be measured and the current value I ₂ of the adjacent current Ib are expressed as in Expressions (7) and (8) using ΔV ₁ and ΔV ₂ . Therefore, the arithmetic unit 1d, the output of the first current sensor unit 1a ([Delta] V _1), and with output ([Delta] V ₂₎ of the second current sensor unit 1b, and calculates a current value _{I 1} of the current to be measured Ia be able to.

Computing device 1d, when calculating the current value I ₁ to be measured current Ia based on the equation (7), and outputs the calculation result to the outside. The arithmetic unit 1d, based on the equation (8) is calculated current value I ₂ of the adjacent current Ib, may be output to the outside together with the calculation result of the current value I ₁ of the current to be measured Ia.

As described above, the current sensor 1 according to the present embodiment is configured so that the temperatures of the pair of magnetic sensors arranged so as to sandwich the current line are substantially equal, and thus varies depending on the temperature. The influence of the offset of the magnetic sensor output can be appropriately removed. Further, since the output of the current sensor unit corresponding to each of the plurality of current lines is used, the influence of the current flowing through the current line other than the current line through which the current to be measured flows can be eliminated. As a result, it is possible to suppress a decrease in current measurement accuracy.

(Embodiment 2)
In the present embodiment, a modification of the current sensor 1 shown in FIG. 1 will be described. In the following description, description of parts common to the first embodiment is omitted.

FIG. 7 is a schematic diagram showing a configuration example of the current sensor 1 ′ according to the present embodiment. As shown in FIG. 7, the current sensor 1 ′ includes a first current sensor unit 1 a disposed close to the first current line 2 a through which the measurement current Ia flows, and a second current through which the adjacent current Ib flows. A second current sensor unit 1b arranged close to the line 2b; and a third current sensor unit 1c arranged close to the third current line 2c through which the adjacent current Ic flows. The configuration of each current sensor unit (1a to 1c) is the same as the configuration of each current sensor unit (1a, 1b) in the first embodiment.

FIG. 8 is a block diagram illustrating a configuration example of a current sensor 1 ′ including a first current sensor unit 1a, a second current sensor unit 1b, and a third current sensor unit 1c. As shown in FIG. 8, the current sensor 1 ′ has a current Ia to be measured from the output of the first current sensor unit 1a, the output of the second current sensor unit 1b, and the output of the third current sensor unit 1c. An arithmetic device 1d for calculating a value is provided. Note that the arithmetic device 1d may be provided outside the current sensor 1 ′. In other words, the current sensor 1 ′ may not include the arithmetic device 1d.

In the current sensor 1 ′, the measured current Ia is calculated by the following arithmetic processing.

If the output from the first magnetic sensor 11a and the first control circuit 13a and the output from the second magnetic sensor 11b and the second control circuit 13b are input to the calculation device 14a of the first current sensor unit 1a, the calculation is performed. The device 14a corrects the offset voltages of the two outputs to be substantially equal at a predetermined temperature (for example, 25 ° C.), and corrects the output (V _1A ) on the first magnetic sensor 11a side and the corrected first voltage. 2 The output (V _1B ) on the magnetic sensor 11b side is obtained. Then, the arithmetic device 14a calculates the difference between the output (V _1A ) and the output (V _1B ) to obtain the output (ΔV ₁ ) of the first current sensor unit 1a.

Here, the corrected output (voltage) V _1A on the first magnetic sensor 11a side passes the current value of the measured current Ia flowing through the first current line 2a through I ₁ and the second current line 2b. The current value of the adjacent current Ib is I ₂ , the current value of the adjacent current Ic flowing through the third current line 2c is I ₃ , and the sensitivity coefficient regarding the current flowing through the first current line 2a of the first current sensor unit 1a is X _{11 is} a sensitivity coefficient related to a current flowing through the second current line 2b of the first current sensor unit 1a, and X _{12 is} a sensitivity coefficient related to a current flowing through the third current line 2c of the first current sensor unit 1a. The coefficient is represented by X ₁₃ , and the offset voltage after correction is represented by V _O1 .

Similarly, the output (voltage) V _1B on the second magnetic sensor 11b side is expressed by Expression (10).

Next, the computing device 14a computes the difference between the output (V _1A ) represented by the above formula (9) and the output (V _1B ) represented by the above formula (10). Thereby, the output (ΔV ₁ ) of the first current sensor unit 1a represented by the equation (11) is obtained.

Similarly, the output from the third magnetic sensor 11c and the third control circuit 13c and the output from the fourth magnetic sensor 11d and the fourth control circuit 13d are input to the arithmetic device 14b of the second current sensor unit 1b. Then, the arithmetic device 14b corrects the offset voltages of the two outputs to be substantially equal at a predetermined temperature (for example, 25 ° C.), and corrects the corrected output (V _2A ) on the third magnetic sensor 11c side. The output (V _2B ) on the subsequent fourth magnetic sensor 11d side is obtained. Then, the arithmetic device 14a calculates the difference between the output (V _2A ) and the output (V _2B ) to obtain the output (ΔV ₂ ) of the second current sensor unit 1b.

The output of the third magnetic sensor 11c side _{(voltage) V 2A,} the current values of the adjacent current Ib the current value of the measured current Ia flowing through the first current line 2a _{to I 1,} flowing through the second current line 2b I ₂ , the current value of the adjacent current Ic flowing through the third current line 2 c is I ₃ , the sensitivity coefficient regarding the current flowing through the first current line 2 a of the second current sensor unit 1 b is X ₂₁ , the second The sensitivity coefficient related to the current flowing through the second current line 2b of the current sensor unit 1b is X ₂₂ and the sensitivity coefficient related to the current flowing through the third current line 2c of the second current sensor unit 1b is corrected to X ₂₃ . The later offset voltage is expressed by Expression (12) as V _O2 .

Similarly, the output (voltage) V _2B on the fourth magnetic sensor 11d side is expressed by Expression (13).

The arithmetic device 14b calculates the difference between the output (V _2A ) expressed by the above formula (12) and the output (V _2B ) expressed by the above formula (13), and is expressed by the formula (14). The output (ΔV ₂ ) of the second current sensor unit 1b is obtained.

Similarly, the arithmetic unit (not shown) of the third current sensor unit 1c includes the outputs from the fifth magnetic sensor 11e and the fifth control circuit (not shown), the sixth magnetic sensor 11f and the sixth control circuit (not shown). ), The arithmetic unit of the third current sensor unit 1c corrects the offset voltages of the two outputs to be substantially equal at a predetermined temperature (for example, 25 ° C.), and after correction The output (V _3A ) on the fifth magnetic sensor 11e side and the output (V _3B ) on the sixth magnetic sensor 11f side after correction are obtained. Then, the arithmetic device calculates the difference between the output (V _3A ) and the output (V _3B ) to obtain the output (ΔV ₃ ) of the third current sensor unit 1c.

The output of the fifth magnetic sensor 11e side _{(voltage) V 3A,} the current value of the adjacent current Ib the current value of the measured current Ia flowing through the first current line 2a _{to I 1,} flowing through the second current line 2b I ₂ , the current value of the adjacent current Ic flowing through the third current line 2 c is I ₃ , the sensitivity coefficient regarding the current flowing through the first current line 2 a of the third current sensor unit 1 c is X ₃₁ , the third The sensitivity coefficient related to the current flowing through the second current line 2b of the current sensor unit 1c is X ₃₂ , and the sensitivity coefficient related to the current flowing through the third current line 2c of the third current sensor unit 1c is corrected to X ₃₃ . The later offset voltage is expressed by Expression (15) as V _O3 .

The output of the sixth magnetic sensor 11f side _{(voltage) V 3B} is similarly represented by the formula (16).

The arithmetic unit of the third current sensor unit 1c calculates the difference between the output (V _3A ) expressed by the above formula (15) and the output (V _3B ) expressed by the above formula (16), The output (ΔV ₃ ) of the third current sensor unit 1c represented by (17) is obtained.

The arithmetic device 14a outputs the output (ΔV ₁ ) of the first current sensor unit 1a obtained by the arithmetic processing described above to the arithmetic device 1d. The computing device 14b outputs the output (ΔV ₂ ) of the second current sensor unit 1b to the computing device 1d. The arithmetic device of the third current sensor unit 1c outputs the output (ΔV ₃ ) of the third current sensor unit 1c to the arithmetic device 1d. Current value _{I 1} of the measured currents Ia, a current value _{I 2} of the adjacent current Ib, and the current value _{I 3} of the adjacent current Ic, using [Delta] V _1, [Delta] V _2, and [Delta] V ₃ (18), (19) , (20). Arithmetic unit 1d, the output of the first current sensor unit 1a ([Delta] V _1), the output of the second current sensor unit 1b ([Delta] V _2), and with outputs ([Delta] V ₃₎ of the third current sensor unit 1c, to be measured it can be calculated current value I ₁ of the current Ia.

In Expressions (18), (19), and (20), D satisfies Expression (21).

Arithmetic unit 1d, the above equation (18), calculating the current value _{I 1} of the measured current Ia based on the (21), and outputs the calculation result to the outside. The arithmetic unit 1d, the above equation (19), to calculate a current value _{I 2} of the adjacent current Ib based on the (21), the equation (20), the current value I of the adjacent currents Ic based on the (21) ₃ is calculated, it may be output to the outside together with the calculation result of the current value I ₁ of the current to be measured Ia.

Note that the present invention is not limited to the above embodiment, and can be implemented with various modifications. For example, the number of current sensor units included in the current sensor may be four or more. In this case, the current value of the current to be measured can be accurately calculated by using the outputs of all the current sensor units. Further, the arrangement of each current sensor unit included in the current sensor is not limited to the arrangement of the above embodiment. As long as at least the influence (sensitivity coefficient) of the current flowing through each current line is known for each current sensor unit, the arrangement of each current sensor unit may be arbitrary.

In the above-described embodiment, the temperature characteristics of the offset change of the outputs of a pair of magnetic sensors included in the same current sensor unit are substantially equal. However, these characteristics are not necessarily substantially equal. As long as the required current measurement accuracy can be obtained in the required temperature range, the temperature characteristics of the offset may be slightly different.

The current sensor of the present invention can be used, for example, to detect the magnitude of a current for driving a motor of an electric vehicle or a hybrid car.

This application is based on Japanese Patent Application No. 2011-159812 filed on July 21, 2011. All this content is included here.

Claims

A plurality of current sensor units corresponding to a plurality of current lines each including a set of magnetic sensors arranged so as to sandwich the target current line and a substrate on which the set of magnetic sensors is arranged When,
An arithmetic unit that calculates a difference between outputs of the pair of magnetic sensors in each current sensor unit, and calculates a current value of a current to be measured by removing an influence of an adjacent current line from the output of each current sensor unit; Prepared,
A pair of magnetic sensors included in the current sensor unit are connected to each other by a ground terminal of each magnetic sensor and a ground electrode provided on the substrate so that the temperatures thereof are substantially equal.
The current sensor according to claim 1, wherein the set of magnetic sensors included in the current sensor unit have the same temperature characteristics of offset change.
The pair of magnetic sensors included in the current sensor unit are arranged with the sensitivity axes in the same direction so that the influence of the current flowing through the current line appears in the opposite polarity in the output of the pair of magnetic sensors. The current sensor according to claim 1, wherein the current sensor is a current sensor.
A first current sensor unit including a first magnetic sensor and a second magnetic sensor disposed so as to sandwich a first current line through which a current to be measured flows, and a current different from the current to be measured are passed. 3. A second current sensor unit including a third magnetic sensor and a fourth magnetic sensor arranged so as to sandwich a second current line flowing therethrough. 5. The current sensor according to any one of the above.
Sensitivity coefficient X 11 related to the current flowing through the first current line of the first current sensor unit, sensitivity coefficient X 22 related to the current flowing through the second current line of the second current sensor unit, first A sensitivity coefficient X 12 related to a current flowing through the second current line of the current sensor unit, a sensitivity coefficient X 21 related to a current flowing through the first current line of the second current sensor unit, and the first the difference [Delta] V 1 of the output of the magnetic sensor and the output of the second magnetic sensor, and the third formula represented using the difference [Delta] V 2 of the output of the magnetic sensor and the output of the fourth magnetic sensor of 5. The current sensor according to claim 4, wherein a current value I 1 of the measured current flowing through the first current line is calculated from (7).
A first current sensor unit including a first magnetic sensor and a second magnetic sensor arranged so as to sandwich a first current line through which a current to be measured flows, and a second current different from the current to be measured What is the second current sensor unit including the third magnetic sensor and the fourth magnetic sensor disposed so as to sandwich the second current line through which the current flows, and the current to be measured and the second current? And a third current sensor unit including a fifth magnetic sensor and a sixth magnetic sensor arranged so as to sandwich a third current line through which a different third current flows. The current sensor according to claim 1.
A sensitivity coefficient X mn relating to a current flowing through the n-th current line (n is a natural number of 1 to 3) of the m-th current sensor unit (m is a natural number of 1 to 3), and the output of the first magnetic sensor wherein the difference [Delta] V 1 of the output of the second magnetic sensor, the difference [Delta] V 2 of the output of the third the output of the magnetic sensor of the fourth magnetic sensor, and the output of the fifth magnetic sensor between the first The current value I 1 of the current to be measured flowing through the first current line is calculated from the following equation (18) expressed using the difference ΔV 3 with respect to the output of the magnetic sensor 6. The current sensor according to claim 6.

However, D satisfies the following formula (21).