JP2015184120A - current sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current sensor with improved response performance capable of acquiring current to be measured as a binary digit data.SOLUTION: The current sensor 8 includes: plural one bit sensors 5a-5h; and a detection section (calculation processing section 9). The one bit sensors 5a-5h outputs a value either one of 2 values. The detection section (calculation processing section 9) detects a current I to be measured based on the output from the plural one bit sensors 5a-5h. The detection section (calculation processing section 9) receives the output from the plural 1 bit sensors as a binary digit data to detect the current I to be measured.

Description

  The present invention relates to a current sensor, and more particularly, to a current sensor using a magnetoresistive element.

  In some current sensors, a voltage corresponding to a current to be measured (current to be measured) is acquired as an analog signal. Using the acquired analog voltage, the magnitude of the current to be measured is measured.

  For example, Japanese Unexamined Patent Application Publication No. 2008-164449 proposes a current sensor that compares an acquired analog signal with a triangular wave and converts the analog signal into a PWM (Pulse Width Modulation) signal. According to this current sensor, the analog signal is converted into pulse width information and transmitted digitally, so that, for example, the influence of noise can be suppressed.

JP 2008-164449 A

  According to the technique proposed in Japanese Patent Application Laid-Open No. 2008-164449, a triangular wave generator for generating a triangular wave and a comparator for comparing an analog signal with a triangular wave are required. For this reason, the number of parts increases, and for example, costs increase.

  Further, since an analog signal is converted into a PWM signal by comparison with a triangular wave, the conversion process requires a longer time than the period of the triangular wave. As a result, it is difficult to shorten the response time of the current sensor, that is, to improve the responsiveness of the current sensor.

  In addition, when it is desired to perform arithmetic processing in the current sensor, it is necessary to handle binary data. For this reason, a circuit for converting an analog signal or a PWM signal into binary data is required separately. The responsiveness of the current sensor is also impaired by the time required for such conversion processing.

  An object of the present invention is to provide a current sensor with improved response performance while acquiring a current to be measured as binary data.

  In one aspect, the present invention is a current sensor including a plurality of 1-bit sensors and a detection unit. The 1-bit sensor outputs one of two values. The detection unit detects the current to be measured based on the outputs of the plurality of 1-bit sensors. The 1-bit sensor includes a magnetoresistive element and a conversion unit. The resistance value of the magnetoresistive element is switched according to the magnetic field generated by the current to be measured. The conversion unit converts the two resistance values of the magnetoresistive element into binary values. The detection unit receives the outputs of the plurality of 1-bit sensors as binary data and detects the current to be measured.

  In the current sensor configured as described above, the resistance value of the magnetoresistive element of the 1-bit sensor is switched by the current to be measured. By appropriately arranging a plurality of 1-bit sensors with respect to the current to be measured, the magnetoresistive elements of some 1-bit sensors have a relatively large resistance value, for example, depending on, for example, the magnitude of the current to be measured. The other magnetoresistive elements of the 1-bit sensor are switched so as to have a relatively small resistance value, for example. For example, a relatively large resistance value is converted into one of two values by the conversion unit, and a relatively small resistance value is converted into the other value of the two values by the conversion unit. As a result, depending on the current to be measured, some 1-bit sensors output one value and the other 1-bit sensors output the other value. The output of these 1-bit sensors is handled as binary data by the detection unit, whereby the current to be measured is acquired as a binary number. That is, in the current sensor configured as described above, the current to be measured is directly converted into binary data and output by the 1-bit sensor.

  In another aspect, the present invention may include an output terminal instead of the detection unit. The output terminal is used to output the outputs of a plurality of 1-bit sensors as binary data to the outside of the current sensor. The binary data output from the output terminal can be used as data indicating the magnitude of the current to be measured, for example.

  According to the present invention, a current sensor having improved response performance while acquiring a current to be measured as binary data is provided.

It is a 1st figure for demonstrating the outline | summary of a current sensor. It is a 2nd figure for demonstrating the outline | summary of a current sensor. It is a figure for demonstrating schematic structure of a TMR element. It is the 1st figure for explaining composition and operation of a 1 bit sensor. It is a 2nd figure for demonstrating a structure and operation | movement of a 1 bit sensor. 4 is a diagram for explaining a schematic configuration of a current sensor according to Embodiment 1. FIG. It is a figure for demonstrating arrangement | positioning of the 1-bit sensors 1a-1h in FIG. It is a figure for demonstrating the measurement ready state of the current sensor. It is a figure for demonstrating the measurement state of the current sensor. 5 is a diagram for explaining a schematic configuration of a current sensor according to Embodiment 2. FIG. It is a figure for demonstrating arrangement | positioning of 1 bit sensor 1a-1p in FIG. It is a figure for demonstrating the measurement ready state of the current sensor. It is a 1st figure for demonstrating the measurement state of the current sensor. It is a 2nd figure for demonstrating the measurement state of the current sensor. 10 is a diagram for explaining a schematic configuration of a current sensor according to Embodiment 3. FIG. FIG. 10 is a diagram for explaining a schematic configuration of a current sensor according to a fourth embodiment.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Outline of current sensor]
FIG. 1 is a first diagram for explaining an outline of a current sensor. The current sensor 8A is used to measure a current I flowing through the conductive wire 10 (hereinafter also referred to as “measured current I”).

  Referring to FIG. 1, current sensor 8 </ b> A includes 1-bit sensors 5 a to 5 h, current source 6, and arithmetic processing unit 9.

  Current sensor 8A is fixed to conductive wire 10 by clamp 60, for example. Thereby, the positional relationship between the measured current I and the current sensor 8A is fixed. Means other than the clamp 60 may be used to fix the positional relationship. The current sensor 8A is connected to a device outside the current sensor 8A, for example, an oscilloscope, for example, by a cable 70.

  Each of the 1-bit sensors 5a to 5h outputs one of two values (for example, two voltage values). The outputs of the 1-bit sensors 5a to 5h are output to the output terminals 4a to 4h, respectively. The output terminals 4 a to 4 h are connected to the arithmetic processing unit 9. Outputs of the 1-bit sensors 5 a to 5 h are input to the arithmetic processing unit 9.

  The current source 6 is used for initialization (described later) of the outputs of the 1-bit sensors 5a to 5h, for example.

  The arithmetic processing unit 9 detects the current to be measured based on the outputs of the 1-bit sensors 5a to 5h. The arithmetic processing unit 9 receives the output of the 1-bit sensors 5a to 5h as binary data as a whole. The arithmetic processing unit 9 detects the measured current I based on the binary data. Thereby, the current sensor 8A measures the current I to be measured.

  FIG. 2 is a second diagram for explaining the outline of the current sensor. The current sensor 8B is also used to measure the current I to be measured, similarly to the current sensor 8A shown in FIG.

  The current sensor 8B shown in FIG. 2 differs from the current sensor 8A shown in FIG. 1 in that the arithmetic processing unit 9 is not included and the output connector 80 is included.

  In FIG. 2, the outputs from the output terminals 4a to 4h are shown as bit data Sa to Sh, respectively. Each of the bit data Sa to Sh is transmitted to the output connector 80 via a wiring or the like (not shown). The output connector 80 is used to output the outputs of the 1-bit sensors 5a to 5h as binary data as a whole to the outside of the current sensor 8B. The binary number data output from the output connector 80 is sent to an external device, for example, and used as data indicating the magnitude of the current I to be measured. The external device is configured to include a function similar to that of the arithmetic processing unit 9 illustrated in FIG. 1, for example.

  The 1-bit sensor (such as the 1-bit sensors 5a to 5h in FIG. 1) includes a magnetoresistive element and a conversion unit, as will be described with reference to FIGS.

[Example of magnetoresistive element]
As an example, a tunneling magnetoresistive (TMR) element is employed as the magnetoresistive element.

  FIG. 3 is a diagram for explaining a schematic configuration of the TMR element. As shown in FIG. 3, the TMR element 1 includes a fixed layer PL (Pinned Layer), a free layer FL (Free Layer), and an insulating film DB (Dielectric Barrier).

  The free layer FL is made of a ferromagnetic material and is magnetized. The arrows shown in FIG. 3 conceptually indicate the direction of magnetization. The magnetization of the free layer FL changes (inverts) by an external magnetic field, for example, a magnetic field generated by the current I to be measured shown in FIG. The fixed layer PL is made of a ferromagnetic material and is magnetized. The magnetization of the fixed layer PL is not changed (fixed) by the external magnetic field. The insulating film DB insulates the fixed layer PL and the free layer FL.

  The TMR element 1 has a resistance value. When the magnetization direction of the free layer FL is parallel and the same as the magnetization direction of the fixed layer PL, the resistance value is minimized. When the magnetization direction of the free layer FL is parallel and opposite to the magnetization direction of the fixed layer PL, the resistance value is maximized. The magnetization direction of the free layer FL depends on the magnetic field in which the TMR element 1 is placed. For example, the magnetization direction of the free layer FL is determined according to the magnetic field generated by the measured current I shown in FIG. 1, and the resistance value of the TMR element 1 is switched.

  Although the case where a TMR element is used as the magnetoresistive element has been described above, an element having the same characteristics as the TMR element can be used as a magnetoresistive element, even if it is not a TMR element.

[Configuration example of 1-bit sensor]
FIG. 4 is a diagram for explaining the configuration and operation of the 1-bit sensor. The 1-bit sensor 5 includes a TMR element 1, a resistor 2, a comparator 3, and an output terminal 4. The resistor 2 and the comparator 3 constitute a conversion unit that converts the resistance value of the TMR element 1 into one of two values.

  One end (for example, the fixed layer PL side) of the TMR element 1 is connected to the ground (GND). The other end of TMR element 1 (for example, the free layer FL side) is connected to node 15.

  One end of the resistor 2 is connected to the node 15. The other end of the resistor 2 is connected to the power supply terminal T.

  One input terminal of the comparator 3 is connected to the node 15. A reference potential Vref is applied to the other input terminal of the comparator 3. The output terminal of the comparator 3 is connected to the output terminal 4. Another circuit (such as a filter) may be provided between the output terminal of the comparator 3 and the output terminal 4.

  A power supply voltage is applied to the power supply terminal T. A voltage (node voltage) divided by the TMR element 1 and the resistor 2 is generated at the node 15. When the resistance value of the TMR element 1 is small, the node voltage is small. When the resistance of the TMR element 1 is large, the node voltage increases. The node voltage is compared with the reference potential Vref by the comparator 3. For example, when the node voltage is equal to or higher than the reference potential Vref, the comparator 3 outputs a low voltage, and when the node voltage is lower than the reference potential Vref, the comparator 3 outputs a high voltage. Alternatively, when the node voltage is equal to or higher than the reference potential Vref, the comparator 3 may output a high voltage, and when the node voltage is lower than the reference potential Vref, the comparator 3 may output a low voltage. The low voltage is set to, for example, a ground (GND) potential or a potential close thereto. The high voltage is higher than the low voltage. The high voltage and the low voltage need only be different from each other, for example, by the arithmetic processing unit 9 shown in FIG. The high voltage and the low voltage correspond to bit data of “0” and “1”. For example, the high voltage corresponds to the bit data “1”, and the low voltage corresponds to the bit data “0”.

  In the example shown in FIG. 4, the magnetization direction of the free layer FL is parallel to and the same direction as the magnetization direction of the fixed layer PL. Therefore, the resistance value of the TMR element 1 is small, and the 1-bit sensor outputs “1”.

  On the other hand, in the example shown in FIG. 5, the magnetization direction of the free layer FL is parallel to and opposite to the magnetization direction of the fixed layer PL. Therefore, the resistance value of the TMR element is large and the 1-bit sensor outputs “0”.

[Embodiment 1]
FIG. 6 is a diagram for explaining a schematic configuration of the current sensor according to the first embodiment.

  Referring to FIG. 6, current sensor 8 includes 1-bit sensors 5 a to 5 h, current source 6, and current line 7. Each of 1-bit sensors 5a to 5h includes TMR elements 1a to 1h and output terminals 4a to 4h.

  A current I to be measured flows through the conductive wire 10. The 1-bit sensors 5a to 5h are arranged along a direction away from the measured current I (that is, the conductive wire 10).

  The current source 6 supplies an initial state current to the current line 7. The initial state current sets (initializes) the resistance values of the TMR elements 1a to 1h to the initial state. Specifically, the magnetization of the free layer included in the TMR elements 1a to 1h is aligned in a certain direction by the magnetic field generated by the initial state current. The current line 7 is appropriately arranged so that the TMR elements 1a to 1h are appropriately initialized by the magnetic field generated by the initial state current.

  The output terminals 4a to 4h output binary data 11 as a whole. The binary number data 11 is input to the arithmetic processing unit 9. The arithmetic processing unit 9 performs various calculations for detecting the measured current I based on the binary data 11. The arithmetic processing unit 9 includes various logic circuits capable of digital signal processing. For example, the arithmetic processing unit 9 may include a logic circuit realized using an FPGA (Field Programmable Gate Array), or may include a microcomputer and an application specific integrated circuit (ASIC). It may be constituted by.

  In the example shown in FIG. 6, the number of 1-bit sensors is 8 (5a to 5h), but the number of 1-bit sensors is not limited to this.

  FIG. 7 is a diagram for explaining the arrangement of TMR elements 1a to 1h in FIG. 6 (that is, the arrangement of each 1-bit sensor). In FIG. 7, the cross section of the conductive wire 10 is illustrated in front of the drawing. As shown in FIG. 7, the TMR elements 1 a to 1 h are arranged in this order along the direction away from the current I to be measured.

  The current sensor 8 is set in the “measurement ready state” as preparation for measuring the current I to be measured. FIG. 8 is a diagram for explaining the measurement ready state of the current sensor 8. In the measurement ready state, the current I to be measured does not flow (I = 0).

As shown in FIG. 8, an initial state current I _INI is supplied from the current source 6 to the current line 7. The direction of the initial state current I _INI is indicated by an arrow in the current source 6 in the figure. When the initial state current I _INI flows through the current line 7, a magnetic field is generated around the initial state current I _INI . For example, when the initial state current I _INI flows through the upper current line 7 in the figure, the magnetic field H100 is generated, and when the initial state current I _INI flows through the lower current line 7 in the figure, the magnetic field H101 is generated. The magnetic field H100 and the magnetic field H101 have the same magnitude and different directions. These are explained, for example, by Ampere's law.

  Each of TMR elements 1a to 1h is arranged at an equal distance from current line 7, for example. Further, the TMR elements 1a to 1h are arranged closer to the upper current line 7 in the drawing than the lower current line 7 in the drawing. Thereby, each TMR element 1a-1h is set | placed on the magnetic field H100 of the same magnitude | size. The free layers of the TMR elements 1a to 1h are magnetized in the same direction by the magnetic field H100.

  For example, the free layers of the TMR elements 1a to 1h are all magnetized in parallel and in the same direction as the magnetization direction of the fixed layer. In that case, the TMR elements 1a to 1h are switched so as to have the same resistance value (minimum resistance value). As a result, the outputs of the 1-bit sensors 5a to 5h are all “1”. As a result, the binary data 11 is “11111111”. The binary number data “11111111” is detected by the arithmetic processing unit 9 as a measured current I = 0 (A).

That is, it can be said that the “measurement ready state” is a state in which the resistance values of the TMR elements 1 a to 1 h and the outputs of the 1-bit sensors 5 a to 5 h are initialized by the initial state current I _INI . After being set in the measurement ready state, the current sensor 8 is set in the “measurement state” and measures the current I to be measured.

FIG. 9 is a diagram for explaining the measurement state of the current sensor 8. In the measurement state, the current I to be measured flows through the conductive wire 10 (I ≠ 0). An initial state current I _INI flows through the current line 7.

  As shown in FIG. 9, when the current I to be measured flows through the conductive wire 10, a magnetic field H is generated around the current I to be measured. For convenience of explanation, the magnetic field H at each position is illustrated as, for example, a magnetic field H110 to a magnetic field H114. The magnetic field H becomes weaker away from the current I to be measured. Comparing the strengths of the magnetic fields H110 to H114, the magnetic field H110 is the strongest and the magnetic field H114 is the weakest.

On the other hand, the magnetic field H100 and magnetic field H101 occurs around the initial current _{I INI.} For example, the magnetic field H100 is generated so as to cancel the magnetic field H in each of the TMR elements 1a to 1h. When the initial state current I _INI having an appropriate magnitude and direction is supplied to the current line 7 or the current line 7 is appropriately disposed, the magnetic field H100 can be generated so as to cancel the magnetic field H.

  Depending on the strength relationship between the magnetic field H (the magnetic field H110 to the magnetic field H114, etc.) and the magnetic field H100, the resistance values of the TMR elements 1a to 1h, that is, the outputs of the 1-bit sensors 5a to 5h can change. For example, when the magnetic field H is larger than the magnetic field H100, some (or all) of the 1-bit sensors 5a to 5h are strongly influenced by the magnetic field H, and the magnetization direction of the free layer FL is in the direction along the magnetic field H. It changes (inverts), and the output changes from “1” to “0”. In the example shown in FIG. 9, the magnetization direction of the free layer FL of the 1-bit sensors 5 a to 5 e is reversed in the direction along the magnetic field H. Therefore, the outputs of the 1-bit sensors 5a to 5e are set to “0” and are output from the output terminals 4a to 4e. On the other hand, the magnetization direction of the free layer FL of the 1-bit sensors 5f to 5h is not reversed. Therefore, the outputs of the 1-bit sensors 5f to 5h remain “1” and are output from the output terminals 4f to 4h. That is, the binary number data 11 is “00000111”.

  The arithmetic processing unit 9 receives the binary data 11 and executes predetermined arithmetic processing. The predetermined calculation process includes a process for calculating the magnitude of the measured current I based on the binary number data 11. Thereby, the current sensor 8 can measure the current I to be measured.

  The binary data 11 shows different values depending on the magnitude of the current I to be measured. If the measured current I decreases, for example, the outputs of the 1-bit sensors 5a to 5d can be set to “0”, and the outputs of the 1-bit sensors 5e to 5h can be set to “1”. As a result, the binary number data 11 becomes “00001111”. Conversely, when the measured current I increases, for example, the outputs of the 1-bit sensors 5a to 5f can be set to “0” and the outputs of the 1-bit sensors 5g to 5h can be set to “1”. As a result, the binary data 11 is “00000011”.

  According to the first embodiment, in the current sensor, the magnitude of the current to be measured is acquired as binary data directly (directly) without performing analog / digital conversion processing. Therefore, the response time of the current sensor is shortened, and the response performance of the current sensor is improved.

[Embodiment 2]
Next, a configuration in which the current sensor further detects the direction of the measured current I in addition to the magnitude of the measured current I will be described as a second embodiment.

FIG. 10 is a diagram for explaining a schematic configuration of the current sensor according to the second embodiment.
Referring to FIG. 10, current sensor 16 includes 1-bit sensors 5a-5p, current source 6, current line 7, logic circuits 120a-120h, and output terminals 121a-121h. Each of 1-bit sensors 5a-5p includes output terminals 4a-4p.

  The 1-bit sensors 5a to 5p are arranged in two rows along the direction away from the measured current I. In the example shown in FIG. 10, 1-bit sensors 5a to 5h are arranged in one of the two columns. 1-bit sensors 5i to 5p are arranged in the other of the two columns.

  Outputs of the 1-bit sensors 5a to 5p are input to the logic circuits 120a to 120h via the output terminals 4a to 4p. Specifically, the outputs of the 1-bit sensors 5a and 5i are input to the logic circuit 120a. Outputs of the 1-bit sensors 5b and 5j are input to the logic circuit 120b. The outputs of the 1-bit sensors 5c and 5k are input to the logic circuit 120c. The outputs of the 1-bit sensors 5d and 5l are input to the logic circuit 120d. The outputs of the 1-bit sensors 5e and 5m are input to the logic circuit 120e. The outputs of the 1-bit sensors 5f and 5n are input to the logic circuit 120f. The outputs of the 1-bit sensors 5g and 5o are input to the logic circuit 120g. The outputs of the 1-bit sensors 5h and 5p are input to the logic circuit 120h.

  The logic circuits 120a to 120h output an exclusive OR (XOR) of the two input signals. Outputs of the logic circuits 120a to 120h are output to the output terminals 121a to 121h.

  The output terminals 121a to 121h output the binary number data 13 as a whole. The binary number data 13 is input to the arithmetic processing unit 9A. The arithmetic processing unit 9 </ b> A performs various calculations for detecting the measured current I based on the binary data 13. Similar to the arithmetic processing unit 9 described above with reference to FIG. 6, the arithmetic processing unit 9A includes various logic circuits capable of digital signal circuits.

  The output of the 1-bit sensor 5i is also output to the output terminal 4i ′. The 1-bit sensor 5i is a 1-bit sensor arranged closest to the current I to be measured. The output of the 1-bit sensor 5i is input as bit data 12 to the arithmetic processing unit 9A.

  When the 1-bit sensor 5a is arranged closest to the current I to be measured instead of the 1-bit sensor 5i, the output of the 1-bit sensor 5a, not the output of the 1-bit sensor 5i, is used as the bit data 12. It may be input to the arithmetic processing unit 9A. When both the 1-bit sensor 5a and the 1-bit sensor 5i are arranged closest to the current I to be measured, the output of one of the 1-bit sensors is input as the bit data 12 to the arithmetic processing unit 9A. It is good to do so. The bit data 12 is used to detect the direction of the current I to be measured, as will be described later.

  In the example shown in FIG. 10, the number of 1-bit sensors is 16 (5a to 5p), but the number of 1-bit sensors is not limited to this.

  FIG. 11 is a diagram for explaining the arrangement of TMR elements 1a to 1p in FIG. 10 (that is, the arrangement of each 1-bit sensor). In FIG. 11, the cross section of the conductive wire 10 is shown in front of the drawing.

  As shown in FIG. 11, the TMR elements 1a to 1p are arranged in two rows along the direction away from the current I to be measured. In addition, the TMR elements 1a to 1h are arranged in this order in one of the two columns, and the TMR elements 1i to 1p are arranged in this order in the other two columns. The TMR elements 1a and 1i are arranged to face each other. The same applies to the TMR elements 1b and 1j, 1c and 1k, 1d and 1l, 1e and 1m, 1f and 1n, 1g and 1o, 1h and 1p.

  The TMR element 1a and / or the TMR element 1i are arranged closest to the current I to be measured.

FIG. 12 is a diagram for explaining a measurement ready state of the current sensor 16. As shown in FIG. 12, the initial state current I _INI generates a magnetic field H100 and a magnetic field H101. For example, the magnetic field H100 and the magnetic field H101 have the same size and different directions.

  By appropriately arranging the current line 7, for example, the magnetic field H100 causes the TMR elements 1a to 1h to switch so as to have a first resistance value (for example, the minimum resistance value). The TMR elements 1i to 1p are switched by the magnetic field H101 so as to have the second resistance value (for example, the maximum resistance value). Thereby, the outputs of the bit sensors 5a to 5h are set to “1”. The outputs of the bit sensors 5i to 5p are set to “0”. Therefore, “1” and “0” are input to each of the logic circuits 120a to 120h. As a result, all of the logic circuits 120a to 120h output “1”.

  That is, in the measurement ready state, the binary data 13 is “11111111”. The binary number data “11111111” is detected by the arithmetic processing unit 9A as the measured current I = 0 (A). In the measurement ready state, the bit data 12 is “0”. Arithmetic processor 9A receives bit “0”.

  FIG. 13 is a diagram for explaining the measurement state of the current sensor 16. In the figure, “D1” and “D2” indicate the directions of the current I to be measured. In the example shown in FIG. 13, the measured current I flows in the direction D2.

  As shown in FIG. 13, when the current I to be measured flows, a magnetic field H is generated around the current I to be measured. For convenience of explanation, the magnetic field H at each position is illustrated as H140 to H144. The magnetic field H becomes weaker away from the current I to be measured. Comparing the strengths of H140 to H144, H140 is the strongest and H144 is the weakest.

On the other hand, by flowing the initial state current _{I INI,} magnetic H100 and magnetic field H101 occurs around the current line 7.

  Depending on the strength relationship between the magnetic field H (such as the magnetic field H140) and the magnetic field 100, for example, the resistance values of the TMR elements 1a to 1h, that is, the outputs of the 1-bit sensors 5a to 5h may change. For example, when the magnetic field H is larger than the magnetic field H100, some (or all) of the 1-bit sensors 5a to 5h are strongly influenced by the magnetic field H, and the output changes from “1” to “0” in the measurement ready state. Change. In the example illustrated in FIG. 13, the outputs of the 1-bit sensors 5a to 5d are “0”. On the other hand, the outputs of the 1-bit sensors 5e to 5h are set to “1”. The outputs of the 1-bit sensors 5i to 5p are set to “0”. As a result, the binary number data 13 is “00001111”. The arithmetic processing unit 9A receives the binary data 13 and detects the magnitude of the current I to be measured. Thereby, the current sensor 16 measures the current I to be measured.

  The output “0” of the 1-bit sensor 5i is output to the output terminal 4i. As a result, the bit data 12 becomes “0”.

  Since the bit data 12 is “0”, the arithmetic processing unit 9A determines that the direction of the measured current I is D2. Thereby, the direction of the current I to be measured is detected. If the bit data 12 is “1”, the arithmetic processing unit 9A determines that the direction of the current to be measured is D1.

  FIG. 14 is a second diagram for explaining the measurement state of the current sensor 16. In the example shown in FIG. 14, the direction of the measured current I is D1.

  As shown in FIG. 14, when the current I to be measured flows, a magnetic field H is generated around the current I to be measured. For convenience of explanation, the magnetic field H at each position is illustrated as, for example, a magnetic field H130 to a magnetic field H134. The magnetic field H decreases as the distance from the measured current I increases. Comparing the magnitudes of the magnetic fields H130 to H134, the magnetic field H130 is the largest and the magnetic field H134 is the smallest.

  Depending on the magnitude relationship between the magnetic field H (such as the magnetic field H130) and the magnetic field H101, the resistance values of the TMR elements 1i to 1p, that is, the outputs of the 1-bit sensors 5i to 5p may change. For example, when the magnetic field H is larger than the magnetic field H101, some (or all) of the 1-bit sensors 5i to 5p are strongly influenced by the magnetic field H, and the output is “1” from “0” in the measurement ready state. To change. In the example illustrated in FIG. 14, the outputs of the 1-bit sensors 5i to 5m are “1”. On the other hand, the outputs of the 1-bit sensors 5n to 5p are set to “0”. The outputs of the 1-bit sensors 5a to 5h are “1”. As a result, the binary number data 13 is “00000111”. The arithmetic processing unit 9A receives the binary data 13 and detects the magnitude of the current I to be measured. Thereby, the current sensor 16 measures the current I to be measured.

  The output “1” of the 1-bit sensor 5i is output to the output terminal 4i. As a result, the bit data 12 becomes “1”. Since the bit data 12 is “1”, the arithmetic processing unit 9A determines that the direction of the measured current I is D1. Thereby, the direction of the current I to be measured is detected.

  As described above, by arranging the 1-bit sensors in two rows, the current sensor can measure not only the magnitude of the current to be measured but also the direction of the current to be measured.

[Embodiment 3]
In Embodiment 1 and Embodiment 2 described above, the upper limit and lower limit (measurement range) of the magnitude of the current to be measured that can be measured by the current sensor are constant. In the third embodiment, a configuration in which the measurement range can be made variable will be described.

  As shown in FIG. 9 described above, the measurement range of the current sensor 8 is limited as follows. That is, in the case of the current sensor 8, the magnetization direction of the TMR elements 1a to 1h, that is, the output of the 1-bit sensors 5a to 5h is determined by a magnetic field (referred to as “synthetic magnetic field”) obtained by combining the magnetic field H and the magnetic field H100. Is done. When the magnetic field H100 is generated so as to cancel the magnetic field H, the magnitude of the synthesized magnetic field is simply expressed as, for example, synthesized magnetic field = magnetic field H−magnetic field H100. Since the magnitude of the magnetic field H is proportional to the magnitude of the measured current I, the magnitude of the synthesized magnetic field is also proportional to the magnitude of the measured current I.

  In the measurement ready state, the outputs of the 1-bit sensors 5a to 5h are all “1”, but in the measurement state, some outputs of the 1-bit sensors 5a to 5h are “0” due to the influence of the combined magnetic field. . Thereby, the magnitude of the current I to be measured is measured.

  When the measured current I increases and the combined magnetic field increases, all the outputs of the 1-bit sensors 5a to 5h become “0” and become saturated. The magnitude of the current I to be measured at this time becomes an upper limit current value (upper limit value) that can be measured by the current sensor 8, and a current larger than that cannot be measured.

Here, the upper limit value depends on the magnitude of the combined magnetic field. The magnitude of the synthesized magnetic field depends on the magnitude of the magnetic field H100. The magnitude of the magnetic field H100 depends on the initial state current _IINI . Therefore, the upper limit value can be adjusted by changing the magnitude of the initial state current I _INI . For example, when the initial state current I _INI is increased, the magnetic field H100 is also increased. Therefore, the combined magnetic field (magnetic field H−magnetic field H100) becomes small. Therefore, the current sensor 8 can measure a larger current value of the current I to be measured.

  When the measured current I decreases and the combined magnetic field decreases, all outputs of the 1-bit sensors 5a to 5h become “1”. The magnitude of the measured electricity at this time is the lower limit current value (lower limit value) that can be measured by the current sensor 8, and currents smaller than that cannot be measured.

Here, the lower limit value also depends on the magnitude of the synthetic magnetic field, as with the upper limit value. That is, the lower limit value can be adjusted by changing the magnitude of the initial state current _IINI . For example, when the initial state current I _INI is reduced, the magnetic field H100 is also reduced. Therefore, a synthetic magnetic field (magnetic field H-magnetic field H100) becomes large. Therefore, the current sensor 8 can measure the current value of the smaller current I to be measured.

  FIG. 15 is a diagram for explaining a schematic configuration of the current sensor according to the third embodiment. Referring to FIG. 15, current sensor 17 includes 1-bit sensors 5a to 5h, current source 6A, current line 7, terminals 25 and 26, and selectors 27 and 28. Each of TMR elements 1a-1h and output terminals 4a-4h is included in 1-bit sensors 5a-5h, respectively.

  In FIG. 15, the cross section of the conductive wire 20 is shown to be the front of the drawing. A current to be measured I (not shown) flows through the conductive wire 20. The cross-sectional shape of the conductive wire through which the current to be measured I flows is not limited. For example, in the example shown in FIG. 15, the cross section of the conductive wire 20 is substantially square, and in the example shown in FIG. 7 and the like, the cross section of the conductive wire 10 is substantially circular.

  The current source 6A includes a low-range current source (L current source) 21, a middle-range current source (M current source) 22, a high-range current source (H current source) 23, a selector 27, and a selector 28. Including.

L current source 21 via the selector 27, and supplies the measurement range adjustment current _{I L} to the current line 7. The M current source 22 supplies the measurement range adjustment current I _M to the current line 7 via the selectors 27 and 28. The H current source 23 supplies the measurement range adjustment current I _H to the current line 7 via the selectors 27 and 28.

The measurement range adjustment currents I _L , I _M and I _H play the same role as the initial state current _INI in the first and second embodiments. That is, the measurement range adjustment current _I L, by _{I M} and _{I H,} the resistance value of the TMR element 1a~1h is initialized. Further, a magnetic field is generated by the measurement range adjustment currents I _L , I _M and I _H so as to cancel the magnetic field generated by the current to be measured.

When the magnitudes of the measurement range adjustment currents I _L , I _M and I _H are compared, I _L is the smallest and I _H is the largest.

  In the example shown in FIG. 15, the selector 27 switches the connection between the current line 7 and the terminals on the high potential side (+ side) of the L current source 21, the M current source 22, and the H current source 23. The selector 28 switches the connection between the current line 7 and the terminals on the low potential side (− side) of the L current source 21, the M current source 22, and the H current source 23. Specifically, when the high potential side terminal of the L current source 21 is connected to the current line 7 by the selector 27, the low potential side terminal of the L current source 21 is connected to the current line 7 by the selector 28. When the high potential side terminal of the M current source 22 is connected to the current line 7 by the selector 27, the low potential side terminal of the M current source 22 is connected to the current line 7 by the selector 28. When the high potential side terminal of the H current source 23 is connected to the current line 7 by the selector 27, the low potential side terminal of the H current source 23 is connected to the current line 7 by the selector 28.

The measurement ranges adjustment currents I _L , I _M and I _H are selectively supplied from the L current source 21, the M current source 22 and the H current source 23 to the current line 7 by the selectors 27 and 28. Thereby, when the current I to be measured is measured by the current sensor 17, the current source 6 </ b> A is configured so that the current supplied from the current source 6 </ b> A to the current line 7 can be adjusted. The measurement range of the current sensor 17 is adjusted by adjusting the magnitude of the current.

For example, when the current sensor 17 is in a measurement state, the measurement range adjustment current _IL is supplied to the current line 7 and the magnitude of the current I to be measured is measured. At that time, if some outputs of the 1-bit sensors 5a to 5h are set to “0” and the remaining outputs are set to “1”, the magnitude of the current I to be measured is appropriately detected.

On the other hand, when the output of the 1-bit sensors 5a to 5h is all “0” and is saturated when the measurement range adjustment current _IL is supplied to the current line 7, the magnitude of the current I to be measured is appropriate. Not detected. In this case, the measurement range adjustment current I _M is supplied to the current line 7 by switching to the M current source 22.

When the measurement range adjustment current I _M is supplied to the current line 7 and the magnitude of the current I to be measured is measured, some outputs of the 1-bit sensors 5a to 5h are set to “0”, and the remaining outputs are When “1” is set, the magnitude of the current I to be measured is appropriately detected.

On the other hand, when the output of the 1-bit sensors 5a to 5h is all “0” and is saturated when the measurement range adjustment current _IM is supplied to the current line 7, the magnitude of the current I to be measured is appropriate. Not detected. Therefore, the measurement range adjustment current _IH is supplied to the current line 7 by switching to the H current source 23 next.

When the measurement range adjustment current I _H is supplied to the current line 7 and the magnitude of the current I to be measured is measured, some outputs of the 1-bit sensors 5a to 5h are set to “0”, and the remaining outputs are When “1” is set, the magnitude of the current I to be measured is appropriately detected.

  Thus, in the current sensor 17, the measurement range can be adjusted by adjusting the magnitude of the current supplied to the current line 7. The adjustment of the measurement range may be performed by a user operation or may be automatically performed by the current sensor 17.

  The current sensor 17 may be used with the external current source 24. The external current source 24 is used connected to the terminals 25 and 26. The high potential side (+ side) terminal of the external current source 24 is connected to the current line 7 via the terminal 25 and the selector 27. The terminal on the low potential side (− side) of the external current source 24 is connected to the current line 7 via the terminal 26 and the selector 28. That is, a current is supplied from the external current source 24 to the current line 7, and the measurement range of the current sensor 17 is adjusted. The user can use a current source capable of supplying a desired magnitude of current as the external current source 24.

Instead of the selector 27 and the selector 28, another selector may be employed. For example, in the other selector, in addition to the functions of the selector 27 and the selector 28 described above, the direction of the current supplied from the measurement range adjustment currents I _L , I _M, I _H and the external current source 24 to the current line 7 is changed. It may be configured to be switched. Thereby, the freedom degree of adjustment of a measurement range increases.

  The current sensor according to the third embodiment may be used in combination with the configuration of the current sensor according to the second embodiment. By doing so, the current sensor can measure the magnitude and direction of the current to be measured and adjust the measurement range.

[Embodiment 4]
Since the strength of the magnetic field H depends on the distance from the current to be measured, the resolution of the current sensor is determined (limited) by the interval at which the 1-bit sensor (TMR element) is arranged. When the resolution is limited, the measurement accuracy is also limited. In order to improve measurement accuracy, it is necessary to densely arrange 1-bit sensors in a direction away from the current I to be measured.

  In the current sensor 8 having the configuration shown in FIG. 9, the measurement accuracy is limited by the interval between the 1-bit sensors 5a to 5h arranged in one row. Specifically, the measurement accuracy is limited by the arrangement interval of the TMR elements 1a to 1h. The number that can be arranged in one column is limited by the size of each 1-bit sensor.

  Therefore, in the fourth embodiment, a description will be given of a configuration in which the limitation due to the arrangement interval of the TMR elements is eliminated and the measurement accuracy of the current sensor is improved by arranging the 1-bit sensors arranged in a plurality of columns so as to be shifted from each other. To do.

  FIG. 16 is a diagram for explaining a schematic configuration of the current sensor according to the fourth embodiment. Referring to FIG. 16, current sensor 18 includes 1-bit sensors 5a to 5h, 51a to 51h, and 52a to 52h, current source 6, and current line 7A. Each of TMR elements 1a-1h, 11a-11h, 12a-12h and output terminals 4a-4h, 41a-41h, 42a-42h are included in 1-bit sensors 5a-5h, 51a-51h, 52a-52h, respectively.

  In the current sensor 18, each 1-bit sensor is arranged in a plurality of rows along the direction away from the current I to be measured. In the example illustrated in FIG. 16, the plurality of columns include a first column in which 1-bit sensors 5a to 5h are disposed, a second column in which 1-bit sensors 51a to 51h are disposed, and 1-bit sensors 52a to 52h. And a third column in which are arranged. In each row, each 1-bit sensor is arranged with a predetermined arrangement interval. The current line 7A is arranged so that each 1-bit sensor is placed in the magnetic field H100.

  The 1-bit sensors 51a to 51h arranged in the second row are away from the measured current I by an interval of one third of the arrangement interval from the 1-bit sensors 5a to 5h arranged in the first row. They are shifted.

  The 1-bit sensors 52a to 52h arranged in the third column are away from the measured current I by an interval of one third of the arrangement interval from the 1-bit sensors 51a to 51h arranged in the second column. They are shifted.

  That is, in the current sensor 18, among the plurality of columns in which the 1-bit sensor is arranged, in the adjacent column, the 1-bit sensor in one column and the 1-bit sensor in the other column are separated from the current I to be measured. They are offset from each other in the direction.

  By arranging the 1-bit sensors 5a to 5h, 51a to 51h, and 52a to 52h in this way, each 1-bit sensor is arranged at an interval of one third of the arrangement interval along the direction away from the measured current I. (That is, each TMR element) is arranged.

  For example, consider a case where the output of the 1-bit sensor 5b is “0” and the output of the 1-bit sensor 5c is “1” in the measurement state. At that time, as an example, the output of each 1-bit sensor is as shown in Table 1 below.

  The output of each 1-bit sensor is input to the arithmetic processing unit 9B as binary data 14 via the output terminals 4a to 4h, 41a to 41h, and 42a to 42h. The arithmetic processing unit 9B receives the binary number data 14 and performs various calculations for detecting the measured current I. Similar to the arithmetic processing unit 9 described above with reference to FIG. 6, the arithmetic processing unit 9B includes various logic circuits capable of digital signal circuits.

  If the 1-bit sensors 51a to 51h and 52a to 52h are not provided and only 5a to 5h are provided, the binary data 14 is “00111111”. That is, the measurement accuracy of the current sensor 18 is 8 digits in binary. On the other hand, the binary data 14 is “00000111111111111111111111” due to the presence of the 1-bit sensors 51a to 51h and 52a to 52h. That is, the measurement accuracy of the current sensor 18 is 24 digits in binary. In other words, the presence of 51a to 51h and 52a to 52h improves the resolution three times as compared with the case where there is no 51a to 51h and 52a to 52h.

  As described above, according to Embodiment 4, the measurement accuracy (resolution) of the current sensor is improved by disposing the 1-bit sensors arranged in a plurality of rows from each other. In FIG. 16, when each 1-bit sensor is arranged in N columns (N is a natural number of 2 or more), each 1-bit sensor is preferably arranged at an interval of 1 / N of the arrangement interval. .

  The current sensor according to the fourth embodiment may be used in combination with the configuration of the current sensor according to the second and third embodiments. By doing so, the current sensor can measure the magnitude and direction of the current to be measured, adjust the measurement range, and realize higher measurement accuracy.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiment but by the scope of the claims, and is intended to include all modifications within the meaning and scope equivalent to the scope of the claims.

  1, 1a to 1h, 11a to 11h, 12a to 12h TMR element, 5, 5a to 5h, 51a to 51h, 52a to 52h Bit sensor, 2 resistor, 3 comparator, 4, 4a to 4p, 121a to 121h output terminal, 6, 6A current source, 21 L current source, 22 M current source, 23 L current source, 7, 7A current line, 8, 8A, 8B, 16, 17, 18 current sensor, 9, 9A arithmetic processing unit, 10, 20 conductive lines, 11, 13, 14 binary data, 12 bit data, 15 nodes, 24 external current source, 25, 26 terminals, 27, 28 selector, 60 clamp, 70 cable, 80 output connector, H100, H101, H110 -H114, H130-H134, H140-H144 magnetic field, 120a-120h logic circuit, DB insulating film, FL free Layer, I Current to be measured, PL fixed layer, T Power supply terminal.

Claims (9)

A current sensor for measuring a current to be measured,
A plurality of 1-bit sensors that output one of two values;
A detection unit that detects the measured current based on outputs of the plurality of 1-bit sensors,
The 1-bit sensor
A magnetoresistive element whose resistance value is switched according to a magnetic field generated by the current to be measured;
A conversion unit that converts the resistance value into one of the two values,
The detection unit is a current sensor that receives the outputs of the plurality of 1-bit sensors as binary data and detects the current to be measured. The magnetoresistive element is
A fixed layer with a fixed magnetization direction;
A free layer whose magnetization direction changes with a magnetic field;
The current sensor according to claim 1, comprising an insulating film that insulates the fixed layer and the free layer.   The current sensor according to claim 1, wherein the plurality of 1-bit sensors are arranged along a direction away from the current to be measured.   The current sensor according to claim 1, further comprising a current source that supplies a current for initializing the resistance value of the magnetoresistive element. The plurality of 1-bit sensors are arranged in two rows along a direction away from the current to be measured,
The magnetoresistive elements of the 1-bit sensor arranged in one of the two columns are switched to have a first resistance value according to the current supplied by the current source,
The magnetoresistive element of the 1-bit sensor arranged in the other of the two columns is switched to have a second resistance value according to the current supplied by the current source. Current sensor.   6. The detection unit according to claim 1, wherein the detection unit receives an output of a 1-bit sensor arranged closest to the current to be measured among the plurality of 1-bit sensors and detects a direction of the current to be measured. The current sensor according to item 1.   The current sensor according to claim 4 or 5, wherein the current source is configured such that the magnitude of the current supplied by the current source can be adjusted when the measured current is measured by the current sensor. The plurality of 1-bit sensors are arranged in a plurality of rows along a direction away from the current to be measured.
5. In the adjacent columns of the plurality of columns, the 1-bit sensor in one column and the 1-bit sensor in the other column are arranged so as to be shifted from each other in the direction away from the current to be measured. The current sensor according to any one of the above. A current sensor for measuring a current to be measured,
A plurality of 1-bit sensors that output one of two values;
An output connector for outputting the outputs of the plurality of 1-bit sensors as binary data to the outside of the current sensor;
The 1-bit sensor
A magnetoresistive element whose resistance value is switched according to a magnetic field generated by the current to be measured;
A current sensor including a conversion unit that converts the resistance value into one of the two values.

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