JP2824366B2 - Current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a threshold value for an alternating current or a direct current in a current detector for detecting a magnetic flux generated at this time by flowing a current into a ferromagnetic core using a magneto-sensitive element. And a current detector for detecting the presence or absence of a current.

[0002]

2. Description of the Related Art Hitherto, many current detectors of this type which detect a current flowing in an electric circuit by a magnetic field have been devised so as to obtain a linear output proportional to a detected current. FIG. 4 is a diagram showing the configuration of this type of current detector, FIG. 5 is a diagram showing the operation of the magneto-sensitive element, and FIG. 6 is a diagram showing the conventional current detector disclosed in Japanese Utility Model Application Laid-Open No. 2-57069. It is an example of the internal circuit diagram of a container.

The operation of this type of current detector will be described with reference to FIGS. 4, 5 and 6. In FIG. 4, 1 is a magnetic sensing element, 19 is a ferromagnetic core, 20 is a primary conductor through which a current to be detected flows, 21 is a magnetic gap, and 22 is a magnetic flux.
Now, when the current I flows through the primary conductor 20, the magnetic gap 2
A magnetic flux having a strength proportional to the current I is generated in the magnetic sensor 1 and penetrates the magneto-sensitive element 1. As shown in FIG. 5, the magneto-sensitive element 1 is converted into a voltage V _H that is proportional to the strength of the magnetic flux passing through the element by passing a control current Ic.

Accordingly, a voltage having a magnitude proportional to the current I can be obtained from the magneto-sensitive element 1. Since this voltage is usually a very small voltage of several tens of mV, an amplifier circuit as shown in FIG. 6 is required. By amplifying by the amplifier 23 in FIG. 6 and outputting to the outside, a linear output proportional to the current I can be obtained as a result. Further, in this example, the internal circuit is constituted by a single power supply. However, there are many circuit constitutions which obtain a linear output with respect to an input current in both positive and negative directions, which is constituted by the dual power supply.

[0005]

As a recent trend, for example, a predetermined threshold value is used as a current detector used for detecting burnout of various lights, disconnection detection of a lamp of an automobile, or detection of AC / DC power supply interruption. The demand for a current detector capable of detecting the presence or absence of a current based on the comparison with the above has greatly increased.

[0006] As one application example of such a current detector, let us consider a case where an engine generator welder is to be used more efficiently. Now, when the engine is rotating and it is in the power generation state, and only when it is in contact with the metal to be welded (current is flowing), the engine rotates at a high speed,
If the engine is designed to reduce the rotation when it is not in contact (current is not flowing), it is considered that the rotation of the engine can be reduced when unnecessary and the fuel consumption can be reduced.

However, since welding is usually performed at several locations at a time, the current is turned on and off every time the welding location is changed, so that the rotation of the engine frequently fluctuates, thereby deteriorating the work efficiency. It is possible. Therefore, if the output of the current detector can be maintained as if the current is flowing for a certain period of time after the interruption of the current, the engine rotation does not decrease during that time, so that it is possible to work efficiently. Then, when welding is not resumed even after a certain period of time, the rotation of the engine is reduced, so that fuel efficiency can be improved.

The current detector configured as shown in FIG. 6 can detect a linear current, but cannot detect disconnection or energization that detects the presence or absence of a current by a certain threshold value. In order to perform detection using a threshold value using the above-described current detector, an external comparison circuit is required. However, the comparison circuit alone can detect DC current, but cannot detect AC current, and if AC current is to be detected in the same way, more parts are required, which increases the cost and the number of parts as a whole. There was the above problem.

Further, if the current detector having the delay function described above is to be realized by using a conventional current detector that obtains a linear output, a timer and a linear output for triggering the timer are converted into a square wave. A circuit for conversion is required.
As a result, not only the cost is increased, the number of components as a whole is increased, but also a large mounting space is required, which is contrary to the trend of the world where the miniaturization of the device is progressing, which is not preferable.

The present invention has been made in order to solve such a problem. The present invention is used for both AC and DC, and can detect the presence or absence of a current with a predetermined threshold value. An object of the present invention is to provide a current detector capable of holding an output at a small size and at a low price.

[0011]

According to a first aspect of the present invention, there is provided a current detector, wherein a magneto-sensitive element is disposed in a magnetic gap provided in a part of an annular magnetic path of a ferromagnetic core, A current detector comprising a primary conductor penetrating through the ring of the magnetic path, wherein an alternating current or a direct current is passed through the primary conductor as a current to be detected, and the energized state is detected based on the output of the magnetic sensing element. A rectangular wave converting means for converting the output of the magnetic element into a rectangular wave, a monostable multivibrator which is torn by the rectangular wave and holds an output for a predetermined time, and alternately based on the output of the monostable multivibrator and the rectangular wave Two transistors wired or connected so as to be turned on and off, and connected to the magneto-sensitive element, the rectangular wave converter, the monostable multivibrator, and the two transistors It is obtained by a single power source.

According to a second aspect of the present invention, in the current detector, the magneto-sensitive element is disposed in a magnetic gap provided in a part of the annular magnetic path of the ferromagnetic core, and penetrates the annular magnetic path. A current detector that supplies an alternating current or a direct current as a current to be detected to the primary conductor and detects the energized state based on the output of the magneto-sensitive element. , A monostable multivibrator that is triggered by the rectangular wave and holds an output for a predetermined time, and a wired OR that is turned on and off alternately based on the output of the monostable multivibrator and the rectangular wave. Two connected transistors, the magneto-sensitive element, the rectangular wave converter, the monostable multivibrator, and a single power supply connected to the two transistors Together, which is constituted by the magnetic detection block that integrates with the sensing element and the rectangular wave conversion means.

Further, in the current detector according to a third aspect of the present invention, the magneto-sensitive element is disposed in a magnetic gap provided in a part of the annular magnetic path of the ferromagnetic core, and penetrates through the ring of the annular magnetic path. A current detector that supplies an alternating current or a direct current as a current to be detected to the primary conductor and detects the energized state based on the output of the magneto-sensitive element. Square wave conversion means for converting
A monostable multivibrator whose output holding time is adjustable while the output is held for a predetermined time while being toggled by the rectangular wave, and a wired such that the output is alternately turned on and off based on the output of the monostable multivibrator and the rectangular wave. It is provided with two OR-connected transistors, the magneto-sensitive element, the rectangular wave converting means, the monostable multivibrator, and a single power supply connected to the two transistors.

[0014]

According to the first aspect of the present invention, since the internal circuit is constituted by a single power supply, a unidirectional output can be obtained from the magneto-sensitive element even when an alternating current is input, and a rectangular wave can be easily obtained. The rectangular wave periodically triggers the monostable multivibrator, and the output of the monostable multivibrator and the rectangular wave alternately turn on and off the two transistors, thereby providing a quadrature threshold. Enables current detection by value.

According to the second aspect of the present invention, by forming a magnetic sensing block in which the magneto-sensitive element and the rectangular wave converting means are integrated, the detection value conversion factor is eliminated and the detection accuracy is improved.

Further, in the third aspect, the time for holding the output of the monostable multivibrator can be adjusted so that the output is held for an arbitrary time after the current is cut off.

[0017]

【Example】

Embodiment 1 FIG. Next, an embodiment of the present invention will be described with reference to the drawings. The configuration of the first embodiment is similar to that of FIG.
In this figure, 19 is a ferromagnetic core, 20 is a primary conductor through which a current to be detected flows, 21 is a magnetic gap, 22 is a magnetic flux,
1 is a magneto-sensitive element. Now, when the current I flows through the primary conductor 20, a magnetic flux having a strength proportional to the current I is generated in the magnetic gap 21 and penetrates the magneto-sensitive element 1. Magnetic sensing element 1
As shown in FIG. 5, it is converted into a voltage V _H which is proportional to the intensity of the magnetic flux passing through the element by'll flowing a control current Ic. Therefore, a voltage having a magnitude proportional to the current I can be obtained from the magneto-sensitive element 1.

FIG. 1 is a block diagram showing the configuration of the internal circuit of this embodiment. In this example, as a means for converting the output of the magneto-sensitive element 1 into a square wave, the output is amplified and then a square wave is generated using a Schmitt trigger circuit. And then output with a transistor. FIG. 2 is a waveform at each point when an AC current is input, and FIG. 3 is a waveform at each point when a DC current is input.

In FIG. 1, 1 is a magnetic sensing element, 2 is an amplifier, 3 is a Schmitt trigger circuit, 4, 10, and 11 are transistors, 5, 12 are pull-up resistors, 6 is an inverting circuit,
8 is a monostable multivibrator, and 9 is a delay time adjusting circuit.

In the above configuration, the output of the magneto-sensitive element 1 is amplified by the amplifier 2 and input to the Schmitt trigger circuit 3. In the Schmitt trigger circuit 3, this input is compared with a certain threshold value and the result is output. The output of the Schmitt trigger circuit 3 is input to the base of the transistor 4, and the transistor 4 turns on and off. The transistor 4 is pulled up by a resistor 5.

The inverting circuit 6 is a circuit for inverting the on / off state of the transistor 4. The inverting circuit 6 may be an inverter or a transistor. The monostable multivibrator 8 includes the transistor 4
To generate a delay time t determined by the delay time adjustment circuit 9 and hold the output for that time.
This delay time adjusting circuit 9 is composed of a resistor and a capacitor.

The output of the monostable multivibrator 8 and the output of the inverting circuit 6 are input to the bases of the transistors 10 and 11, respectively, whereby the transistors 10 and 11 are turned on and off. Transistor 10 and transistor 11 are wired-OR connected, open collector,
Pulled up by 2.

Next, the operation will be described with reference to FIGS. Since the above-mentioned circuit is constituted by a single power supply, the magneto-sensitive element 1 reacts only when a current is input in a single direction and outputs a minute voltage. Now, when an alternating current as shown in FIG. 2A is input as the current to be detected, the magneto-sensitive element 1 outputs a half-wave rectified minute voltage.

After this output is amplified and passed through the Schmitt trigger circuit 3 and input to the base of the transistor 4, a square wave as shown in FIG. Since the output is inverted by the inverting circuit 6, the output of the inverting circuit 6 outputs a waveform as shown in FIG.

Then, the output of the transistor 4 is input to the trigger terminal and the reset terminal of the monostable multivibrator 8, and the monostable operation starts at the negative edge. However, as long as the reset terminal is at "L", the output is held at "L", the reset is released at the positive edge of the reset terminal, and after holding the output at "H" for a time t, the output is kept at "L".
become. The output waveform of the monostable multivibrator 8 is shown in FIG.

The time t for holding the output of the monostable multivibrator 8 at "H" is determined by the delay time adjusting circuit 9. Since the transistors 10 and 11 are turned on and off by the outputs of the monostable multivibrator 8 and the inverting circuit 6, a current flows through the wired-OR connected collector pulled up by the resistor 12, as shown in FIG. During this time, the output is always "L", and when the current is cut off, the output is maintained at "L" for a certain time and then becomes "H".

When a DC current as shown in FIG. 4 is input as the detected current, the operation is basically the same as that described above. While the DC current is flowing, “H” is output from the inverting circuit 6. Then, when the current is cut off, the monostable multivibrator 8 starts operating, and keeps the output at “H” for a time t and then goes to “L”.

The output of the inverting circuit 6 and the output of the monostable multivibrator 8, the transistor 10 and the transistor 1
As in the case of inputting the AC current, the collector 1 always outputs "L" while the current is flowing, and outputs "H" after maintaining the output at "L" for a certain time when the current is cut off. be able to.

Embodiment 2 FIG. In another embodiment of the present invention, in the circuit shown in FIG.
, An amplifier 2, a Schmitt trigger circuit 3, and an output transistor 4 are integrated as a detection block. In the configuration diagram of FIG. By inserting the detection block (commonly referred to as a Hall IC) 7 into the magnetic gap 21, it is possible to eliminate the cause of the fluctuation of the detection value and improve the detection accuracy.

Embodiment 3 FIG. In another embodiment of the present invention, the resistance or the capacitor of the delay time adjusting circuit 9 in the circuit of FIG. 1 is made variable so that the delay time t can be adjusted.
The output can be held for an arbitrary time after the current is cut off. Further, the corresponding terminal may be provided outside for external adjustment.

[0031]

As described above, according to the first aspect of the present invention, the internal circuit is constituted by a single power supply, the means for converting the output of the magneto-sensitive element into a square wave, the transistor, the inverting circuit, By combining a stable multivibrator, it is possible to provide a small-sized and inexpensive current detector based on a threshold value for dual use.

According to the second aspect of the present invention, by forming the magneto-sensitive element and the rectangular wave conversion means as a single detection block, it is possible to improve the detection accuracy by eliminating the cause of the fluctuation of the detection value.

According to the third aspect of the present invention, the delay time of the monostable multivibrator can be adjusted.
After the current is cut off, the output can be held for an arbitrary time.

[Brief description of the drawings]

FIG. 1 is a block diagram of an internal circuit configuration according to an embodiment of the present invention.

FIG. 2 is a waveform diagram at each point when an alternating current is input.

FIG. 3 is a waveform diagram at each point when a DC current is input.

FIG. 4 is a diagram illustrating the operation of the current detector.

FIG. 5 is a diagram illustrating the operation of the magneto-sensitive element.

FIG. 6 is an internal circuit diagram of a conventional current detector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Magnetic sensing element 2 Amplifier 3 Schmitt trigger circuit 4 Transistor 7 Detection block 8 Monostable multivibrator 19 Ferromagnetic core 20 Primary conductor 21 Magnetic gap

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01R 15/00-15/12 G01R 19/00-19/32

Claims (3)

(57) [Claims] A magnetic sensing element is arranged in a magnetic gap provided in a part of an annular magnetic path of a ferromagnetic core, and a primary conductor penetrating through the annular magnetic path is provided. In a current detector that supplies an AC or DC current as a current to be detected and detects an energized state based on an output of the magneto-sensitive element, a rectangular wave converting means for converting an output of the magneto-sensitive element into a rectangular wave; A monostable multivibrator which is held by a rectangular wave and maintains an output for a predetermined time; and a wired-OR connection 2 which is turned on and off alternately based on the output of the monostable multivibrator and the rectangular wave
A current detector comprising: one transistor; a magneto-sensitive element; the rectangular wave converter; the monostable multivibrator; and a single power supply connected to the two transistors. 2. A magnetic sensing element is arranged in a magnetic gap provided in a part of an annular magnetic path of a ferromagnetic core, and a primary conductor penetrating through the ring of the annular magnetic path is provided. In a current detector that supplies an AC or DC current as a current to be detected and detects an energized state based on an output of the magneto-sensitive element, a rectangular wave converting means for converting an output of the magneto-sensitive element into a rectangular wave; A monostable multivibrator which is held by a rectangular wave and maintains an output for a predetermined time; and a wired-OR connection 2 which is turned on and off alternately based on the output of the monostable multivibrator and the rectangular wave
One transistor connected to the magneto-sensitive element, the rectangular wave converting means, the monostable multivibrator, and the single power supply connected to the two transistors, and the magneto-sensitive element and the rectangular wave converting means are integrated. A current detector comprising a magnetic detection block formed as described above. 3. A magnetic sensing element is disposed in a magnetic gap provided in a part of an annular magnetic path of a ferromagnetic core, and a primary conductor penetrating through the ring of the annular magnetic path is provided. In a current detector that supplies an AC or DC current as a current to be detected and detects an energized state based on an output of the magneto-sensitive element, a rectangular wave converting means for converting an output of the magneto-sensitive element into a rectangular wave; A monostable multivibrator capable of holding an output for a predetermined time while being held down by a rectangular wave and having an adjustable output holding time, and a wired OR such that the monostable multivibrator is turned on and off alternately based on the output of the monostable multivibrator and the rectangular wave. Two connected transistors, the magneto-sensitive element, the rectangular wave conversion means, the monostable multivibrator, and a single power supply connected to the two transistors. A current detector, characterized in that: