JP2019035634A - Current sensor with overcurrent detection function - Google Patents

Abstract

To provide a current sensor with an overcurrent detection function which allows quick detection of an overcurrent flowing in a measured current line.SOLUTION: A current sensor with an overcurrent detection function comprises: a magnetic detection circuit 10 detecting an induction field generated by a current flowing in a measured current line; a balance controlling amplifier 20 operating on the basis of output of the magnetic detection circuit 10; a feedback coil 30 generating a magnetic field that eliminates the induction field, on the basis of output of the balance controlling amplifier 20; a current detection part 40 outputting a signal according to a current flowing in the feedback coil 30; and a determination circuit part 50 determining an overcurrent on the basis of voltage generated in the feedback coil 30.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a current sensor, and more particularly to a current sensor with an overcurrent detection function capable of detecting that an overcurrent has flowed through a current line to be measured.

  Patent Document 1 describes a current sensor that is a magnetic balance type current sensor and uses a detection resistor and a differential amplifier that measures a voltage between both ends thereof. Since the magnetic balance type current sensor measures a current using a magnetic field region having good measurement accuracy in a magnetic detection circuit including a magnetoelectric conversion element such as a Hall element, high measurement accuracy can be realized. However, as shown in FIG. 1 of Patent Document 1, since the feedback coil is operated using a complicated circuit, it is not easy to follow a rapid change in the current (primary current) flowing through the current line to be measured. . As a specific example of the sudden change in the primary current, there is an overcurrent caused by a sudden operation of the regenerative brake. Such a delay in response of the current sensor to the overcurrent may cause damage to the current sensor or malfunction of a device that operates according to an output signal from the current sensor.

  Patent Document 2 describes a current sensor that determines an overcurrent without passing through an A / D converter from the output terminal of the sensor unit for the purpose of quickly detecting that an overcurrent has flowed through the current line to be measured. ing.

JP 2009-168644 A JP, 2006-217963, A

  However, even with the current sensor as described in Patent Document 2, when the degree of overcurrent is large, that is, when the amount of current flowing through the current line to be measured changes extremely rapidly, the determination of overcurrent is made. May have been delayed.

  In view of the present situation, an object of the present invention is to provide a current sensor with an overcurrent detection function that can quickly detect that an overcurrent has flowed through a current line to be measured.

  In order to solve the above problems, an aspect of the present invention provides a magnetic detection circuit that detects an induced magnetic field generated by a current flowing through a current line to be measured, and a balance control amplifier that operates based on an output of the magnetic detection circuit. A feedback coil that generates a magnetic field that cancels the induced magnetic field based on the output of the balance control amplifier, a current detector that outputs a signal corresponding to the current flowing in the feedback coil, and a voltage generated in the feedback coil. An overcurrent detection function-equipped current sensor comprising: a determination circuit unit that determines overcurrent based on the current detection circuit.

  When a current flows through the current line to be measured, an induced magnetic field of the current is applied to a magnetic detection element included in the magnetic detection circuit, and a signal corresponding to the magnetic field strength is output from the magnetic detection circuit. A magnetic field that cancels the induction magnetic field is generated from the feedback coil based on the output from the balance control amplifier that receives the output signal. Here, when an overcurrent flows through the current line to be measured, the magnetic field strength for canceling the induced magnetic field increases, and thus a large current flows from the balance control amplifier to the feedback coil. In order to solve this problem, the present inventors have applied the induced magnetic field of the primary current (current flowing through the current line to be measured) to the magnetic detection element, but also to the feedback coil. Pay attention. When an induced magnetic field of a primary current is applied to the feedback coil, an electromotive force based on a change in the applied induced magnetic field is generated at both ends of the feedback coil. For this reason, the voltage generated at both ends of the feedback coil corresponds to the change in the primary current earlier than the output of the current sensor. That is, even when the current increases so rapidly that the output of the current sensor cannot follow, an overcurrent can be detected quickly by examining the voltage across the feedback coil. As described above, the current sensor with an overcurrent detection function according to the present invention includes the determination circuit unit that determines the overcurrent based on the voltage generated in the feedback coil, so that the overcurrent can be detected quickly. .

  The current sensor with an overcurrent detection function may include a balance control stop unit that is controlled by the determination circuit unit and stops the flow of current from the balance control amplifier to the feedback coil. If it is determined by the determination circuit section that an overcurrent has flowed through the current line to be measured, the current sensor is protected from damage by stopping the current from flowing from the balance control amplifier to the feedback coil. Is possible.

  The current sensor with an overcurrent detection function may include an overcurrent output terminal that is connected to the determination circuit unit and outputs a signal indicating an overcurrent to the outside. When it is determined by the determination circuit section that an overcurrent has flowed through the current line to be measured, an output signal from the overcurrent output terminal is used to send an abnormal signal from the current sensor to the circuit connected to the current sensor. It becomes possible to protect the flowing in.

  In the current sensor with an overcurrent detection function, the determination circuit unit includes a feedback coil differential amplifier that outputs a potential difference between both ends of the feedback coil, and a potential difference output in advance from the feedback coil differential amplifier. You may provide the 1st comparator which compares the signal which shows the set reference potential difference, and the determination circuit which determines an overcurrent based on the output of the said 1st comparator. By measuring the electromotive force based on the change of the induced magnetic field as a potential difference between both ends of the feedback coil, it is possible to detect the occurrence of overcurrent more stably.

  The current sensor with an overcurrent detection function may include an overcurrent detected by the first comparator and a second comparator that detects an overcurrent in the reverse direction. By having the second comparator in this way, it is possible to more stably detect the occurrence of overcurrent or to obtain information on the direction of overcurrent flowing through the current line to be measured. .

  In the current sensor with an overcurrent detection function, the determination circuit unit includes: a first comparator that compares a potential at one end of the feedback coil with a first reference potential that is set in advance; And a determination circuit that determines overcurrent based on the output. With this configuration, it is possible to stably detect overcurrent. In this case, the determination circuit unit further includes a second comparator that compares a potential at the other end of the feedback coil with a preset second reference potential, and the determination circuit includes the first comparator. The overcurrent may be determined based on the output from the comparator or the output from the second comparator. By doing in this way, generation | occurrence | production of overcurrent can be detected more stably, or the information regarding the direction of the overcurrent which flows into a to-be-measured current line can be obtained.

  ADVANTAGE OF THE INVENTION According to this invention, the current sensor with an overcurrent detection function which can detect rapidly that overcurrent flowed into the to-be-measured current line is provided.

It is a figure which shows the current sensor with an overcurrent detection function which concerns on 1st Embodiment of this invention. It is a figure which shows the current sensor with an overcurrent detection function which concerns on 2nd Embodiment of this invention. It is a figure which shows the current sensor with an overcurrent detection function which concerns on the modification of 2nd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following description, the same members are denoted by the same reference numerals, and the description of the members once described is omitted as appropriate.

(First embodiment)
FIG. 1 is a diagram showing a current sensor with an overcurrent detection function according to the first embodiment of the present invention. As shown in FIG. 1, the current sensor 100 with an overcurrent detection function operates based on a magnetic detection circuit 10 that detects an induced magnetic field of a current flowing through a current line to be measured (not shown), and an output of the magnetic detection circuit 10. A balance control amplifier 20, a feedback coil 30 that generates a magnetic field that cancels the induced magnetic field based on the output of the balance control amplifier 20, a current detection unit 40 that outputs a signal corresponding to the current flowing through the feedback coil 30, Is provided.

  The magnetic detection circuit 10 is composed of, for example, a full bridge circuit including a plurality of magnetic detection elements such as a magnetoresistive effect element and a Hall element, and the midpoint potentials of the two half bridge circuits are output from the magnetic detection circuit 10. The

  The balance control amplifier 20 receives two midpoint potentials output from the magnetic detection circuit 10 as inputs. A specific example of the balance control amplifier 20 is a differential amplifier, and an output current is set based on a difference between two input midpoint potentials. The balance control amplifier 20 shown in FIG. 1 has two outputs, each of which is electrically connected to the feedback coil 30, and can pass a current in two directions through the feedback coil 30. Specifically, the current from one output of the balance control amplifier 20 to one end of the feedback coil 30 via the wiring E1 and the feedback coil 30 from the other output of the balance control amplifier 20 via the wiring E2 Current toward the other end. When the current flowing through the current line to be measured is unidirectional (ie, direct current), the balance control amplifier 20 may be replaced with a differential amplifier with one output. In this case, the output of the balance control amplifier 20 is electrically connected to one end of the feedback coil 30, and the other end of the feedback coil 30 is electrically connected to the ground.

  The feedback coil 30 is disposed in the vicinity of the magnetic detection element of the magnetic detection circuit 10 and generates a cancel magnetic field that cancels the induced magnetic field generated by the current to be measured. The output current from the balance control amplifier 20 is controlled so that the two midpoint potentials input to the balance control amplifier 20 are equal (that is, the difference between the two midpoint potentials is 0V). At this time, the current flowing through the feedback coil 30 is measured by the current detector 40. In the current sensor 100 with the overcurrent detection function, the current detection unit 40 is located in the path of the wiring E2 that connects the output of the balance control amplifier 20 and the other end of the feedback coil 30, and is connected to the shunt resistor Rs and both ends thereof. The I / V amplifier 41 is connected. A potential signal related to the current measured in the current detection unit 40 is output from the current sensor output terminal 60 connected to the output of the I / V amplifier 41 as one of the output signals of the current sensor 100 with an overcurrent detection function. .

  The above configuration is common to the current sensor according to the related art. The current sensor 100 with an overcurrent detection function according to the first embodiment of the present invention includes a determination circuit unit 50 that determines whether or not an overcurrent has flowed through the current line to be measured based on a voltage generated in the feedback coil 30. When the potential at both ends of the feedback coil 30 is input to the determination circuit unit 50 and it is determined that an overcurrent flows through the current line to be measured, an OFF signal is output.

  The OFF signal is input to a switch 70 provided in the middle of the wiring E1 that connects the output of the balance control amplifier 20 and one end of the feedback coil 30. The switch 70 stops the current from the balance control amplifier 20 to the feedback coil 30 by disconnecting the wiring E1. That is, the switch 70 is a specific example of a balanced control stop unit that operates in response to an OFF signal. The balance control stop unit may stop the current from flowing from the balance control amplifier 20 to the feedback coil 30 by stopping the operation of the balance control amplifier 20.

  When the current stops flowing through the feedback coil 30 due to the operation of the balance control stop unit, the output signal from the current sensor output terminal 60 becomes LOW (0 V) or HIGH (operating voltage such as 5 V). By setting to, an overcurrent can be detected from the output signal from the current sensor output terminal 60. By doing so, when an overcurrent flows through the current line to be measured, the absolute value of the current flowing through the feedback coil 30 increases in accordance with the overcurrent, and as a result, the current sensor output terminal 60 An electric signal based on the overcurrent can be output from the current sensor output terminal 60 in a time shorter than the time required for the output signal to actually become LOW (0 V) or HIGH (an operating voltage such as 5 V). If you have a circuit that reduces the amount of current that flows through the current to be measured using this electrical signal as an input, the device with the current wire to be measured can operate normally due to the overcurrent flowing through the current to be measured. Problems that disappear are less likely to occur.

  Further, by operating the balance control stop unit, it is possible to prevent a large current generated based on the overcurrent from flowing to the feedback coil 30. Although this large current may cause the feedback coil 30 to burn out, the current sensor 100 with an overcurrent detection function having a configuration in which the balance control stop unit is operated by an OFF signal from the determination circuit unit 50 causes an excessive current to be measured. Even if an electric current flows, it is hard to be destroyed and it is excellent in operational stability than the current sensor according to the prior art.

  The OFF signal output from the determination circuit unit 50 is output from the overcurrent output terminal 80 as another one of the output signals of the current sensor 100 with an overcurrent detection function. The output signal from the overcurrent output terminal 80 is also based on the fact that the amount of current flowing through the feedback coil 30 actually increases in response to the overcurrent and the overcurrent flows from the current sensor output terminal 60 as described above. An electric signal indicating that an overcurrent has flowed through the current line to be measured can be output from the current sensor 100 with an overcurrent detection function in a shorter time than the output of the electric signal. If you have a circuit that reduces the amount of current that flows through the current to be measured using this electrical signal as an input, the device with the current wire to be measured can operate normally due to the overcurrent flowing through the current to be measured. Problems that disappear are less likely to occur.

  The determination circuit unit 50 of the current sensor 100 with an overcurrent detection function according to the first embodiment includes a first comparator 51, a second comparator 52, and a determination circuit 53.

  The first comparator 51 inputs a potential Vc1 at one end of the feedback coil 30 and a first reference potential Vs1 set in advance, compares these values, and a first determination signal Sj1 including a comparison result. Is output. The first reference potential Vs1 is stored in the first internal memory 51M. The determination circuit 53 receives the first determination signal Sj1 and outputs an OFF signal on condition that the first determination signal Sj1 is a signal indicating that the potential Vc1 is equal to or higher than the first reference potential Vs1. .

  The second comparator 52 inputs the potential Vc2 at the other end of the feedback coil 30 and a preset second reference potential Vs2, compares these values, and a second determination signal including the comparison result. Sj2 is output. The second reference potential Vs2 is stored in the second internal memory 52M. The determination circuit 53 receives the second determination signal Sj2 and outputs an OFF signal on condition that the second determination signal Sj2 is a signal indicating that the potential Vc2 is equal to or higher than the second reference potential Vs2. To do. The second reference potential Vs2 is different from the first reference potential Vs1 because the shunt resistor Rs is connected to the other end side of the feedback coil 30.

  As described above, the determination circuit 53 outputs an OFF signal when the potential Vc1 satisfies at least one of the first reference potential Vs1 and the potential Vc2 being the second reference potential Vs2.

  The determination circuit unit 50 of the current sensor 100 with an overcurrent detection function according to the first embodiment described above includes the first comparator 51 and the second comparator 52, but only one of them. May be. In this case, the potential input to the determination circuit unit 50 may be only one potential of one end and the other end of the feedback coil 30.

(Second Embodiment)
FIG. 2 is a diagram showing a current sensor with an overcurrent detection function according to the second embodiment of the present invention. The current sensor 200 with an overcurrent detection function according to the second embodiment is the first configuration in that the basic configuration as a current sensor and the determination circuit unit 50 capable of outputting an OFF signal with the potentials at both ends of the feedback coil 30 as inputs are provided. It is common with the current sensor 100 with an overcurrent detection function according to one embodiment. The difference between the current sensor 200 with an overcurrent detection function according to the second embodiment and the current sensor 100 with an overcurrent detection function according to the first embodiment is the internal configuration of the determination circuit unit 50.

  The determination circuit unit 50 of the current sensor 200 with an overcurrent detection function according to the second embodiment includes a feedback coil differential amplifier 54 that receives the potentials at both ends of the feedback coil 30 as inputs. The feedback coil differential amplifier 54 comprises a differential amplifier and outputs a difference value (potential difference) ΔV0 between these inputs. This difference value (potential difference) ΔV 0 is input to each of the first comparator 51 and the second comparator 52.

  The first comparator 51 also receives the first reference potential difference Vd1 stored in the first internal memory 51M, compares the difference value (potential difference) ΔV0 with the first reference potential difference Vd1, and includes a comparison result. The first determination signal Sd1 is output. The determination circuit 53 receives the first determination signal Sd1, and the first determination signal Sd1 is OFF as a condition that the first reference potential difference Vd1 is a signal indicating that the first reference potential difference Vd1 is greater than or equal to a difference value (potential difference) ΔV0. Output a signal.

  The second reference potential difference Vd2 stored in the second internal memory 52M is also input to the second comparator 52, the difference value (potential difference) ΔV0 is compared with the second reference potential difference Vd2, and the comparison result is included. The second determination signal Sd2 is output. The determination circuit 53 receives the second determination signal Sd2, and the second determination signal Sd2 is OFF as a condition that the second reference potential difference Vd2 is a signal indicating that the second reference potential difference Vd2 is equal to or less than a difference value (potential difference) ΔV0. Output a signal.

  By having such a configuration, when the difference value (potential difference) ΔV0 is a positive value and the absolute value thereof is excessive, the determination is made based on the first determination signal Sd1 from the first comparator 51. An OFF signal is output from the circuit 53. On the other hand, when the difference value (potential difference) ΔV0 is a negative value and its absolute value is excessive, an OFF signal is output from the determination circuit 53 based on the second determination signal Sd2 from the second comparator 52. Is done. When the OFF signal is output, it is confirmed whether the determination circuit 53 outputs based on the first determination signal Sd1 or based on the second determination signal Sd2, so that the overcurrent is covered. It is possible to determine the direction of flowing through the measurement current line. That is, when output based on the first determination signal Sd1, it is determined that an overcurrent has flowed in a predetermined direction, and when output based on the second determination signal Sd2, an overcurrent is generated in a direction opposite to that direction. What is necessary is just to determine that has flowed.

  FIG. 3 is a diagram showing a current sensor with an overcurrent detection function according to a modification of the second embodiment of the present invention. The difference between the current sensor 300 with an overcurrent detection function and the current sensor 200 with an overcurrent detection function according to the second embodiment is that the current sensor 200 with an overcurrent detection function is for a feedback coil including a single output type differential amplifier. In contrast to having the differential amplifier 54, the current sensor 300 with an overcurrent detection function has a feedback coil differential amplifier 55 composed of a two-output type differential amplifier, and each output is input to a different comparator. is there. Specifically, the feedback coil differential amplifier 55 outputs a difference value (potential difference) ΔV1 (= Vc1−Vc2) of the potential Vc1 at one end of the feedback coil 30 with respect to the potential Vc2 at the other end. The difference value (potential difference) ΔV2 (= Vc2−Vc1) of the potential Vc2 at the other end of the feedback coil 30 with respect to the potential Vc1 at one end is output.

  The difference value (potential difference) ΔV1 is input to the first comparator 51, and the first comparator 51 compares the difference value (potential difference) ΔV1 with the first reference potential difference Vd1 stored in the first internal memory 51M. Then, the first determination signal Sd1 including the comparison result is output. The determination circuit 53 receives the first determination signal Sd1, and the first determination signal Sd1 is OFF as a condition that the difference value (potential difference) ΔV1 is a signal indicating that the difference is greater than or equal to the first reference potential difference Vd1. Output a signal.

  The difference value (potential difference) ΔV2 is input to the second comparator 52, and the second comparator 52 compares the difference value (potential difference) ΔV2 with the second reference potential difference Vd2 stored in the second internal memory 52M. The second determination signal Sd2 including the comparison result is output. The determination circuit 53 receives the second determination signal Sd2, and the second determination signal Sd2 is OFF as a condition that the difference value (potential difference) ΔV2 is a signal indicating that the difference is equal to or greater than the second reference potential difference Vd2. Output a signal.

  With such a configuration, an OFF signal is output from the determination circuit 53 when an overcurrent flows regardless of the direction in which the overcurrent flows through the current line to be measured. At this time, by checking whether the determination circuit 53 outputs based on the first determination signal Sd1 or based on the second determination signal Sd2, the direction in which the overcurrent flows through the current line to be measured is determined. It is possible to determine.

  Although the present embodiment has been described above, the present invention is not limited to these examples. For example, those in which the person skilled in the art appropriately added, deleted, and changed the design of each of the above-described embodiments, and combinations of the features of each embodiment as appropriate, also have the gist of the present invention. As long as they are within the scope of the present invention.

100, 200, 300: Current sensor with overcurrent detection function 10: Magnetic detection circuit 20: Balance control amplifier 30: Feedback coil 40: Current detection unit 41: I / V amplifier Rs: Shunt resistor 50: Determination circuit unit 51: First comparator 51M: first internal memory 52: second comparator 52M: second internal memory 53: determination circuit 54: feedback coil differential amplifier 55: feedback coil differential amplifier 60: current sensor output terminal 70: switch 80: overcurrent output terminal E1: wiring E2: wiring Vc1: potential Vc2 at one end of the feedback coil: potential Vs1 at the other end of the feedback coil: first reference potential Vs2: second reference potential Vd1: first Reference potential difference Vd2: second reference potential difference Sd1: first determination signal Sd : Second determination signal Sj1: first determination signal Sj2: second determination signal

Claims (7)

A magnetic detection circuit for detecting an induced magnetic field generated by a current flowing through the current line to be measured;
A balance control amplifier that operates based on the output of the magnetic detection circuit;
A feedback coil that generates a magnetic field that cancels the induced magnetic field based on the output of the balance control amplifier;
A current detector that outputs a signal corresponding to the current flowing through the feedback coil;
A determination circuit unit for determining an overcurrent based on a voltage generated in the feedback coil;
A current sensor with an overcurrent detection function.   2. The current with an overcurrent detection function according to claim 1, further comprising a balance control stop unit that is controlled by the determination circuit unit to stop a current from flowing from the balance control amplifier to the feedback coil. Sensor.   The current sensor with an overcurrent detection function according to claim 1, further comprising an overcurrent output terminal that is connected to the determination circuit unit and outputs a signal indicating an overcurrent to the outside.   The determination circuit unit compares a differential amplifier for a feedback coil that outputs a potential difference between both ends of the feedback coil, and a signal indicating a preset reference potential difference with the potential difference output from the differential amplifier for the feedback coil. 4. The overcurrent according to claim 1, further comprising: a first comparator configured to determine an overcurrent based on an output of the first comparator. 5. Current sensor with detection function.   The current sensor with an overcurrent detection function according to claim 4, further comprising an overcurrent detected by the first comparator and a second comparator that detects an overcurrent in the reverse direction.   The determination circuit unit includes a first comparator that compares a potential at one end of the feedback coil with a first reference potential that is set in advance, and a determination circuit that determines an overcurrent based on the output of the first comparator. The current sensor with an overcurrent detection function according to claim 1, wherein the current sensor has an overcurrent detection function. The determination circuit unit further includes a second comparator that compares a potential at the other end of the feedback coil with a second reference potential set in advance.
The current sensor with an overcurrent detection function according to claim 6, wherein the determination circuit determines an overcurrent based on an output from the first comparator or an output from the second comparator.