JP2001194391A - Current measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To measure the measuring current flowing in a circuit without having any influence on the circuit system where the measuring current flows. SOLUTION: This current measuring device comprises a magnetic resistance element arranged in the vicinity of a signal line so that the magnetic field generated in the flowing of the measuring current to the signal line acts thereon, and a means for measuring the measuring current according to the change of the resistance of the magnetic resistance element according to the intensity of the working magnetic field.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current measuring device for measuring a current flowing through a signal line.

[0002]

2. Description of the Related Art Conventionally, for example, when a relatively large driving current (DC) flowing through a motor of an electric vehicle is measured and feedback control of the motor driving is performed, a resistor for directly measuring a current is provided in a motor driving circuit. Is provided to measure the current according to the voltage drop. However, the drive voltage of the motor is reduced, and the measurement resistor generates heat.

Conventionally, a measuring coil is directly provided in a motor circuit to measure a current by a magnetic field generated when a current flows through the coil. Has had a negative impact.

[0004]

The problem to be solved is that a relatively large driving current flowing through the motor of an electric vehicle is measured by directly providing a measuring resistor or coil in a circuit through which the current flows. In this case, the current may affect the circuit system through which the current flows, or generate heat.

[0005]

SUMMARY OF THE INVENTION A current measuring device according to the present invention, when measuring a relatively large driving current or the like flowing through a motor of an electric vehicle, affects a circuit system through which the current flows or generates heat. In order to prevent the occurrence of a magnetic field generated when a current to be measured flows through the signal line, a magnetoresistive element is provided near the signal line, and the magnetoresistive element according to the strength of the magnetic field acts on the signal line. Is measured by a measuring circuit.

In the current measuring apparatus according to the present invention, the current to be measured flows through the signal line so that the current flowing through the circuit can be indirectly measured without affecting the circuit system of the current to be measured. In addition to providing a magnetoresistive element so that a magnetic field generated when the current flows through the signal line, the magnetic field generated when the current to be measured flows through the signal line is generated in a direction opposite to the direction in which the magnetic field acts on the magnetoresistive element. A coil wound around the magnetoresistive element 5 is provided, and a current value is measured when a current that cancels a magnetic field generated when a measured current flows through a signal line is supplied to the coil. I am trying to do it.

[0007]

1 and 2 show a basic configuration of a current detecting section in a current measuring device according to the present invention.

Here, the insulating layer 4 extends over the signal line 1 through which the current to be measured I, which is wired on the semiconductor substrate 3, flows.
Element (MR element or GMR element) 5 via
Has been finely processed by IC manufacturing technology by forming a thin film. Lead wires 2 are connected to both ends of the magnetoresistive element 5. Reference numeral 6 denotes a protective film for the magnetoresistive element 5.

The magnetoresistive element 5 has such a characteristic that the resistance value is largely changed by slightly applying a magnetic field so that the lines of magnetic force act in the plane direction. FIG. 4 shows the characteristics of the rate of change in resistance of the magnetoresistive element 5 with respect to the applied magnetic field. The magnetoresistive element 5 is resistant to heat, and the characteristics of resistance change due to the applied magnetic field are stable without being affected by heat.

In the current detecting section having the above configuration, when the measured current I flows through the signal line 1, a magnetic field H is generated around the signal line 1 as shown in FIG. The intensity of the generated magnetic field H is proportional to the magnitude of the current I to be measured, and the resistance value is proportionally changed by the lines of magnetic force acting in the surface direction of the magnetoresistive element 5.

Therefore, the magnetoresistive element 5 according to the strength of the magnetic field acting when the current I flows through the signal line 1
By detecting the change in the resistance at the time, the current I to be measured can be indirectly measured.

At this time, the strength of the generated magnetic field H when the current to be measured I flows through the signal line 1 is inversely proportional to the distance from the signal line 1. The sensitivity of the magnetoelectric conversion can be sufficiently increased.

FIG. 5 shows a specific measuring circuit for measuring a current I to be measured by detecting a change in resistance in the magnetoresistive element 5.

Here, the magnetoresistive element 5 is connected to one branch.
However, the other three branches have reference resistances Rs1, Rs2, Rs
3 are provided, and the resistance I of the magnetoresistive element 5 is changed by the current I to be measured flowing through the signal line 1 by using the resistance bridge circuit 7 which is in an equilibrium state when no current flows through the signal line 1. The unbalanced output current Id of the resistive bridge circuit 7 at this time is amplified by the amplifier circuit 8, and the current is measured by the strength of the magnetic field generated when the amplified current flows through the measurement coil 9. Specifically, similarly to a general ammeter, the pointer of the meter may be swung by a magnetic field generated when the current flows through the measuring coil 9. At this time, the unbalanced output current I of the resistance bridge circuit 7
d may be passed through a resistor for current measurement, and the current may be measured based on the voltage drop.

Although not particularly shown, a voltage drop in the magnetoresistive element 5 when a steady current flows through a measuring circuit in which the magnetoresistive elements 5 are connected in series is detected without using a resistance bridge circuit. By doing so, it is possible to indirectly measure the measured current I.

FIG. 6 shows another example of the configuration of the current detector in the current measuring device according to the present invention.

Here, in particular, the current I to be measured is applied to the signal line 1.
The magnetic flux of the magnetic field H generated when
The magnetic member 10 having high magnetic permeability to be concentrated on the portion is provided.

The magnetic member 10 is formed in a loop shape in which both ends are brought into contact with each other via a gap G having a predetermined distance L.
Are magnetically coupled to form a magnetically closed circuit. Then, the magnetic member 10 is disposed so that the signal line 1 passes through the loop.

FIG. 7 shows the details of the coupling state of the magnetoresistive element 5 in the gap G portion of the magnetic member 10. Here, a small gap (for example, about 0.1 μm) between SiO2 and the like is provided between the magnetoresistive element 5 and the magnetic member 10 so that only the resistance change of the magnetoresistive element 5 can be electrically extracted. An insulating layer 11 is provided. In order to minimize the magnetic resistance in the portion of the insulating layer 11, the creeping length l of the magnetoresistive element 5 with respect to the magnetic member 10 is increased so that a sufficient magnetic flux passes between them.

Therefore, according to such a configuration, the magnetic flux of the magnetic field H generated when the measured current I flows through the signal line 1 by the magnetic member 10 is concentrated on the portion of the magnetoresistive element 5 and Consumption of the magnetomotive force in portions other than the element 5 is effectively suppressed, and a highly sensitive response to a change in the measured current I flowing through the signal line 1 can be achieved.

When the magneto-resistive element 5 is magnetically coupled to the gap G of the magnetic member 10, a plurality of magneto-resistive elements 5 are provided as shown in FIG. It is made to meander repeatedly. In this case, the width W1 of the portion of the magnetoresistive element 5 that straddles the gap G is the width W2 of the portion of the magnetoresistive element 5 that rises over the magnetic member 10 (the creepage length 1 with respect to the magnetic member 10)
In this case, the magnetic resistance is increased so as to be larger than the gap G where the magnetic flux is concentrated.

FIG. 9 shows another embodiment of the current measuring device according to the present invention.

Here, the magnetoresistive element 5 is generated such that a magnetic field H generated when the measured current I flows through the signal line 1 is generated in a direction opposite to the direction in which the magnetic field H acts on the magnetoresistive element 5. A coil 12 wound around the coil 12 is provided as a center, and a current value when a current Is is applied to the coil 12 to cancel a generated magnetic field H when the measured current I flows through the signal line 1 is measured. Thus, the measured current I is obtained.

More specifically, for example, as shown in FIG. 10, a magnetoresistive element 5 is provided in one branch, and reference resistances Rs1, Rs2, Rs3 are provided in the other three branches, respectively. 1 so that the unbalanced current of the resistance bridge circuit 7 when the measured current I flows through the signal line 1 becomes zero by using the resistance bridge circuit 7 that is in a balanced state when the measured current I does not flow through the signal line 1. That is, the current Is is caused to flow through the coil 12 so that the pointer of the galvanometer 13 becomes zero.

In this case, similarly to the case of FIG. 6, the magnetic flux of the magnetic field H generated when the current to be measured I flows through the signal line 1 is concentrated on the portion of the magnetoresistive element 5 and has a high magnetic permeability. After the member 10 is provided, the coil 12 is disposed so as to wind around one side of the gap G where the magnetoresistive element 5 is magnetically coupled.

Thus, the signal line 1 is arranged so as to pass through the inside of the loop-shaped magnetic member 10, and the one side where the magnetoresistive element 5 is magnetically coupled is wound around the gap G. By arranging the coil 12, it is possible to concentrate magnetic flux due to each generated magnetic field when the measured current I flows through the signal line 1 and when the current flows through the coil 12, at the portion of the magnetoresistive element 5. The measurement of the measured current I can be performed with high accuracy.

FIGS. 11 and 12 show specific examples of the current measuring device shown in FIG. 9 when it is finely processed using a plurality of semiconductor substrates 3.

[0028]

As described above, in the current measuring device according to the present invention,
A magnetoresistive element is provided near the signal line so that the magnetic field generated when the measured current flows through the signal line, and the change in the resistance of the magnetoresistive element according to the strength of the acting magnetic field is measured by a measuring circuit. The measurement is performed, and has an advantage that the measured current flowing through the circuit can be measured indirectly without affecting the circuit system through which the measured current flows.

Further, the current measuring device according to the present invention is provided with a magnetoresistive element so that a magnetic field generated when the current to be measured flows through the signal line acts on the signal line. A coil wound around the magnetoresistive element 5 is provided around the magnetoresistive element 5 so as to generate a magnetic field in a direction opposite to the direction in which the generated magnetic field acts on the magnetoresistive element. The current to be measured is obtained by measuring the current value when a current is applied that cancels out the generated magnetic field when the current flows,
This has the advantage that the measured current flowing in the circuit can be measured indirectly without affecting the circuit system through which the measured current flows.

[Brief description of the drawings]

FIG. 1 is a front sectional view showing a basic configuration of a current detector in a current measuring device according to the present invention.

FIG. 2 is a plan view of a current detector in the basic configuration.

FIG. 3 is a front cross-sectional view showing a state in which a magnetic field line acts in a plane direction of a magnetoresistive element by a magnetic field generated when a measured current flows through a signal line in the basic configuration.

FIG. 4 is a diagram illustrating characteristics of a rate of change in resistance with respect to an applied magnetic field of a magnetoresistive element.

FIG. 5 is an electric circuit diagram showing a configuration example of a measuring circuit for measuring a current to be measured by detecting a change in resistance in the magnetoresistive element.

FIG. 6 is a front view showing another example of the configuration of the current detector in the electricity measuring device according to the present invention.

FIG. 7 is a partial front view showing details of a coupling state of a magnetoresistive element in a gap portion of a magnetic member in another configuration example.

FIG. 8 is a partial plan view showing one mode of a magnetoresistive element coupled to a gap portion of a magnetic member in another configuration example.

FIG. 9 is a perspective view showing another embodiment of the current measuring device according to the present invention.

FIG. 10 is an electric circuit diagram showing a circuit configuration example for flowing a current for canceling a generated magnetic field when a measured current flows through a signal line to a coil in another embodiment.

11 is a plan view showing a specific configuration example when the current measuring device shown in FIG. 9 is finely processed using a plurality of semiconductor substrates.

FIG. 12 is a front cross-sectional view of the configuration example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Signal line 5 Magnetoresistive element 10 Magnetic member 12 Coil

Claims (7)

[Claims] A magnetoresistive element is provided so that a magnetic field generated when a current to be measured flows through a signal line is provided, and a change in the resistance of the magnetoresistive element according to the strength of the applied magnetic field is measured by a measuring circuit. A current measuring device characterized in that the current is measured. 2. The current measurement according to claim 1, wherein the current is measured by a voltage drop in the magnetoresistive element when a steady current flows through a measuring circuit in which the magnetoresistive elements are connected in series. Current measuring device. 3. A magnetoresistive element is provided in one branch,
Using a resistive bridge circuit that is in a balanced state when the measured current does not flow through the signal line, the current is measured by the unbalanced output current of the resistive bridge circuit when the measured current flows through the signal line. The current measuring device according to claim 1, wherein: 4. The current measuring device according to claim 1, further comprising a magnetic member for concentrating a magnetic flux generated when a current to be measured flows through the signal line to a portion of the magnetoresistive element. 5. A magnetoresistive element is provided so that a magnetic field generated when a measured current flows through a signal line, and a magnetic field generated when a measured current flows through the signal line acts on the magnetoresistive element. A coil wound around the magnetoresistive element 5 so as to generate a magnetic field in a direction opposite to the direction in which the current to be measured flows through a signal line through the coil. A current measuring device for measuring a current value when a current for canceling the current is applied. 6. A magnetoresistive element is provided in one branch,
Using a resistive bridge circuit that is in a balanced state when the measured current does not flow through the signal line, the current is applied to the coil so that the unbalanced current of the resistive bridge circuit when the measured current flows through the signal line becomes zero. The current measuring device according to claim 5, wherein a current is supplied. 7. A current according to claim 5, wherein a magnetic member is provided for concentrating a magnetic flux generated when a current to be measured flows through the signal line and a magnetic flux generated by the coil in a portion of the magnetoresistive element. measuring device.