JPH07209336A - Current sensor - Google Patents

Abstract

PURPOSE:To obtain a big dynamic range of input current and to simplify the structure, relating to a current sensor that detects magnetic field caused by electric current. CONSTITUTION:A conductor 5 makes measurement current flow, and a pair of magnetoresistance elements 6 for detecting a small current and a pair of magnetoresistance elements 7 for detecting a large current are provided at the positions, on a substrate 9, with different distance from the current sensor of the conduct 5, respectively. Magnets 8 are attached to the magnetoresistance elements 6 and 7, for optimum operation point.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus, such as an electric vehicle, which is partially provided with electric power equipment which consumes little electric power for a long time and large electric power for a short time without being constantly supplied with energy. The present invention relates to a current sensor for monitoring the power used.

[0002]

2. Description of the Related Art Conventionally, some current sensors of this type utilize a current transformer or a Hall element. These current sensors are of various types, from direct current to alternating current, and from small current to large current.

In recent years, a battery-operated power device has a large power operation inherent to the device and a low power operation only for a control computer, and a large dynamic range as a battery operating current. Therefore,
A wide dynamic range is also required for the current sensor necessary for controlling the electric power and electric energy. For example, in an electric vehicle, a large current during acceleration, a low current during normal traveling and a stop, and an ultra-low current for backing up equipment when not in use, such as a current signal of 60 dB to 70 dB.
A dynamic range is being demanded.

FIG. 12 shows a current sensor using a Hall element. In the figure, 1 is a current path to be measured, 2 is a magnetic flux generation core, 3 is a Hall element, and 4 is a drive / measurement circuit.

The operation of the above configuration will be described. When a current flows through the current path 1, a magnetic field is generated around it. This magnetic field produces a large magnetic flux at the core 2 and is input to the Hall element 3. The Hall element 3 generates a voltage proportional to the input magnetic flux under an appropriate bias circuit. By using this voltage as an output, it operates as a current sensor.

[0006]

However, in the above conventional configuration, the temperature characteristics of the magnetic sensor, the influence of the external magnetic field,
This is affected by the offset drift of the circuit, and in order to cover a wide dynamic range, it is necessary to spend a great deal of money on compensation and adjustment of temperature characteristics, or to combine two or more current sensors with different sensitivities. Therefore, two kinds of soft magnetic cores are prepared, which inevitably leads to an increase in cost and increases the size and shape.

[0007] Further, output fluctuation factors other than the disturbance, for example,
There is a problem in that the sensor itself can have a means for finding out problems such as aging and failure of the magnetic sensor.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a current sensor which can obtain a wide dynamic range of an input current at a low cost.

[0009]

In order to solve the above-mentioned conventional problems, the present invention provides, as a first problem solving means, a current sensor for detecting a magnetic field generated by an electric current,
A plurality of magnetoresistive elements are provided at positions different in distance from the current center. A second means for solving the problem is to provide a plurality of magnetoresistive elements at positions different in distance from the center of the current in a current sensor for supplying a compensation current so that the magnetic field generated by the current becomes zero. As a third means for solving the problem, means for switching the output of the magnetoresistive element group depending on the magnitude of the input current is provided. A fourth means for solving the problem is to provide a means for inspecting whether the magnetoresistive element groups output the input currents without any contradiction. Further, as a fifth means for solving the problem, means for separately detecting a portion due to the disturbance of the input current from the output of the magnetoresistive element group and removing the disturbance portion is provided.

[0010]

In the above structure, the operation of the first problem solving means is to dispose two current sensors having different sensitivities because a plurality of magnetoresistive elements are provided at positions where the distance from the current center is different. A wide dynamic range of the input current can be covered as a measurement area. The second
The action of the problem solving means is that the generated magnetic field can be canceled with a current smaller than the measured current by flowing the servo current in the vicinity of the magnetoresistive element. Further, as the operation of the third problem solving means, the large and small input current signals can be switched by providing the means for switching the output. In addition, the operation of the fourth problem solving means is that the self-diagnosis signal of abnormality can be output to the external circuit by providing the inspection means. Further, as a function of the fifth problem solving means, a true input signal can be obtained without being affected by the disturbance by providing a means for removing the disturbance portion.

[0011]

Example 1 Example 1 of the present invention will be described below with reference to FIG.
-It demonstrates, referring FIG.

In FIG. 1, 5 is a conductor for flowing a measurement current, 6 is a pair of magnetoresistive elements for detecting a small current, 7 is a pair of magnetoresistive elements for detecting a large current, and 8 is a magnetoresistive element 7.
Is a magnet for optimizing the operation point of, and 9 is a substrate for forming and holding the above components. In FIG. 2, 1
Reference numerals 0 and 11 denote bridge circuits for replacing the resistance value change due to the input of a small current and a large current magnetic field with a voltage change, respectively.
2 is a constant current source for the drive.

FIG. 3 shows a block diagram in this embodiment. Reference numeral 13 is a converter for converting the current to be measured into a magnetic field, which is substantially determined by the arrangement of the conductor 5, the substrate 9, the small current magnetic resistance element 6, the large current magnetic resistance element 7, and the like. 1
Reference numerals 4 and 15 are amplifiers for amplifying bridge outputs for small current and large current, respectively. Then, when there is a current input, a magnetic field is generated at the position of the magnetoresistive elements 6 and 7, whereby the resistance value of the magnetoresistive elements 6 and 7 forming the bridge circuits 10 and 11 changes, and a bridge voltage is generated. To do. The generated bridge voltage is amplified by the amplifiers 14 and 15 and becomes an output.

In FIG. 4, 16 is a differential amplifier for amplifying the bridge voltage of the large current magnetic resistance element 7, and 17 is a differential amplifier for amplifying the bridge voltage of the small current magnetic resistance element 6. FIG. 5 is a diagram in which a circuit 18 that outputs a high potential when a small current output is invalid is added to the above circuit.
Reference numeral a is a full-wave rectification circuit for outputting an absolute value, and reference numeral 18b is a comparator for comparison with the reference voltage Vsh.

With the above configuration, the output of the comparator 18b has a low potential when the input current is a small current, but when the input current reaches the overlap region for the small current and the large current, the output of the absolute value amplifier circuit is output. The voltage exceeds Vsh, and the comparator 18b outputs a high potential. In this way, the output of the comparator 18b can add and output a signal indicating which of the small current magnetic resistance element 6 and the large current magnetic resistance element 7 is effective.

The operation of the above configuration will be described. First, when an input current flows through the conductor 5, a magnetic field proportional to the input current is generated in each of the small current magnetic resistance element 6 and the large current magnetic resistance element 7. The proportional constant is smaller in the large-current magnetoresistive element 7 as the distance from the conductor 5 is longer.

When the same magnetoresistive element is used for both small current and large current, each magnetoresistive element bears the output voltage for the magnetic field input in the same range. This is because the small-current magnetoresistive element 6 having a short distance from the conductor 5 is in the small-current region, and the large-current magnetoresistive element 7 is far from the conductor 5.
Is responsible for the large current region. The distance from the conductor 5 of each magnetoresistive element is determined so that the area covered by both magnetoresistive elements overlaps with the intermediate area of small current and large current.

Further, in this embodiment, the conductor 5 is bent as shown in the figure and the magnetic field due to the reciprocating current is detected to weaken the input magnetic field to the large current magnetoresistive element 7. That is, the large current magnetoresistive element 7 is brought closer to the conductor 5 to secure a wide dynamic range. Further, the small-current magnetic resistance element 6 is separated from each other in a symmetrical position, and the large-current magnetic resistance element 7 is brought closer to each other in a symmetrical position, so that the magnetic field attenuation effect due to the distance from the conductor 5 can be further utilized. .

As described above, in this embodiment, the current detecting portion of the current sensor having a wide dynamic range can be constructed only by optimally designing the positions of the two sets of magnetoresistive elements with respect to the conductor 5.

FIG. 6 shows the input magnetic field and dynamic range of a current sensor using a magnetoresistive element alone, and the input magnetic field and dynamic range of each magnetoresistive element of the current sensor.

(A) shows the state of the magnetic field generated by each current at the position A of the magnetoresistive element located at the position I from the center of the current due to the reciprocating current I, and the H direction input to the magnetoresistive element. A simple theoretical formula of the magnetic field component of is shown.

In (b), when the current a distance between currents of 100 amperes is 5 mm, the magnetic resistance element at the point A when I and the distance d between the magnetoresistance elements shown in (a) are variously changed. The input magnetic field of is shown. Here, if the position of the small current magnetic resistance element 6 is set to I = 4 mm and d = 5 mm, and the position of the large current magnetic resistance element 7 is set to I = 18 mm and d = 2 mm (a)
As shown in, the input magnetic field for small current is about 26000A.
/ M, the input magnetic field for large current is 260 A / m, and 1
It turns out that it will be 00 times.

(C) shows how the input magnetic field changes depending on the input current when the magnetoresistive element is placed at the above position. Here, if a magnetic resistance element having an input magnetic field dynamic range of 10 to 1100 A / m is used, a dynamic range of 40 mA to 60 A for a small current and 40 A to 600 A for a large current can be obtained, both of which are 83.5 dB. A vast dynamic range can be obtained.

On the other hand, when the same magnetoresistive element is used alone, only a single dynamic range of 427 dB can be obtained.

As described above, according to the present embodiment, the small-current magnetoresistive element 6 and the large-current magnetoresistive element 7 are arranged at positions different in distance from the conductor 5, so that it is easy and inexpensive. A wide dynamic range current sensor can be obtained.

(Embodiment 2) FIGS. 7 and 8 show a second embodiment of the present invention. In each of the drawings, the same parts as those in the first embodiment are designated by the same reference numerals, and their description will be omitted. Omit it.

The characteristic configuration of the present embodiment relates to a so-called servo type current sensor in which a current for canceling the magnetic field generated by the current to be measured and making it zero is passed through a separately provided current path. In the figure, 19 is a small current servo circuit, 20 is a large current servo circuit, 21 is a small current servo current generation circuit, 22 is a large current servo current generation circuit, and 23 and 24 are small current and large current, respectively. Is a conductor for the servo current path, and is arranged in the vicinity of the magnetoresistive elements 6 and 7 as compared with the conductor 5 of the current to be measured.

According to the above configuration, each servo circuit 19, 2
0 outputs a voltage to the servo current generating circuits 21 and 22 of the next stage so that the change of the output of the amplifier of the previous stage due to the combined magnetic field of the measured current and the servo current becomes zero, and the voltage proportional to the output is output to the sensor. There is a place to do. Further, by causing the servo current to flow in the immediate vicinity of the magnetoresistive elements 6 and 7, it is possible to cancel the magnetic field generated by the measured current with a current much smaller than the measured current.

According to the above construction, a servo type current sensor using a magnetoresistive element is provided with a small current magnetoresistive element and a large current magnetoresistive element, and by adopting a servo configuration for each, a wider dynamic range is obtained. be able to.

(Third Embodiment) FIG. 9 shows a third embodiment of the present invention. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted. The characteristic configuration of the present embodiment is that the output of the magnetoresistive element group is switched depending on the magnitude of the input current. That is, 25 is a transistor that opens and closes by the output of the comparator 18b, and 26 is a relay that switches the output by opening and closing the transistor 25.

With the above configuration, the transistor 25 receiving the signal is turned on and off, and the relay 26 switches the signal for the small current and the signal for the large current.

The above circuit can be applied to the servo type current sensor of the second embodiment.

(Fourth Embodiment) FIG. 10 shows a fourth embodiment of the present invention. In the figure, the same parts as those in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.
The characteristic configuration of the present embodiment is to inspect whether or not outputs which are consistent with each other with respect to the input current of the magnetoresistive element group.

That is, 27 is a small-current magnetic resistance element 6
Attenuator for matching the level of the output with the output of the large-current magnetic resistance element 7, 28 is a differential amplifier that takes the difference between the outputs, 29 is a full-wave rectifier that takes the absolute value of the difference, and 30 is the difference between the two. Is a comparator that outputs a high potential when V exceeds Vsh.

With the above configuration, when one of the magnetoresistive elements does not operate normally due to some abnormality, the output in the overlap region increases, and when the judgment reference Vsh is exceeded, an abnormal self-diagnosis signal is sent to the external circuit. Output.

The above circuit can be applied to the servo type current sensor of the second embodiment.

(Embodiment 5) FIG. 11 shows a fifth embodiment of the present invention. In the drawing, the same parts as those in the first embodiment are designated by the same reference numerals. In the figure, 31 is an attenuator for attenuating the output of the small-current magnetic resistance element 6 to match the level with the output of the large-current magnetic resistance element 7, and 32 is a difference for taking out the difference between both outputs and extracting a common disturbance component. A dynamic amplifier 33 is an amplifier for returning the level of the disturbance component to the output of the small current magnetic resistance element 6, and 34 and 35 are subtracters for removing a common disturbance component from the small current and large current signals. is there.

In the above structure, when common disturbances such as temperature fluctuation, external magnetic field, and change of bias magnet with time occur in the current detectors for small current and large current, the current detectors have different current sensitivities. Regardless, the disturbance sensitivities are the same, and Vs and Vb include disturbance component voltages of the same level. When the component due to the input current is Vis as the bridge output component of the small current magnetoresistive element 6 and Vib as the bridge output component of the large current magnetoresistive element 7, both have a constant current sensitivity Vs = A.Vb. I have a relationship. If the same disturbance Vn is output from both magnetoresistive elements, the output of the magnetoresistive element 6 for a small current is eventually Vs.
= A · Vb + Vn, the output of the large current magnetoresistive element 7 is V
b = Vib + Vn, and the current becomes (1 / A + 1) · Vn to Vn if the difference between 1 / A of the output of the small-current magnetic resistance element 6 and the output of the large-current magnetic resistance element 7 is obtained, You get a level. Vn is subtracted from the high current signal,
A true input current signal can be obtained by subtracting Vn / A from the small current signal.

The above circuit can be applied to the servo type current sensor of the second embodiment.

[0040]

As is apparent from the above-described embodiments, the current sensor of the present invention is provided with a plurality of magnetoresistive elements at different distances from the current center. Since a wide dynamic range can be obtained and the structure is simple, it can be manufactured at low cost.

[Brief description of drawings]

1A is a front view of a current sensor according to a first embodiment of the present invention, FIG. 1B is a plan view of the current sensor, and FIG. 1C is a side view of the current sensor.

FIG. 2 is a circuit diagram of a detection unit of the same current sensor.

FIG. 3 is a block diagram of the current sensor.

FIG. 4 is a signal processing circuit diagram of the current sensor.

FIG. 5 is a signal processing circuit diagram of the current sensor.

FIG. 6 is a diagram for explaining the operation of the current sensor.

FIG. 7 is a perspective view of a current sensor according to a second embodiment of the present invention.

FIG. 8 is a block diagram of the current sensor.

FIG. 9 is a signal processing circuit diagram of a current sensor according to a third embodiment of the present invention.

FIG. 10 is a signal processing circuit diagram of a current sensor according to a fourth embodiment of the present invention.

FIG. 11 is a signal processing circuit diagram of a current sensor according to a fifth embodiment of the present invention.

12A is a front view of a conventional current sensor, and FIG. 12B is a plan view of the current sensor.

[Explanation of symbols]

 6,7 Magnetoresistive element

Claims (5)

[Claims] 1. A current sensor for detecting a magnetic field generated by a current, wherein a plurality of magnetoresistive elements are provided at positions different in distance from a current center. 2. A current sensor in which a compensating current is passed so that a magnetic field generated by the current is zero, wherein a plurality of magnetoresistive elements are provided at positions different in distance from the current center. 3. The current sensor according to claim 1, further comprising means for switching the output of the magnetoresistive element group depending on the magnitude of the input current. 4. The current sensor according to claim 1 or 2, further comprising means for inspecting whether the magnetoresistive element groups output outputs which are consistent with each other with respect to an input current. 5. The current sensor according to claim 1, further comprising means for separately detecting a portion of the input current caused by disturbance from the output of the magnetoresistive element group and removing the disturbance portion.