JPH0650321B2 - Current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a magnetic field of the above-mentioned ferromagnetic core which is changed by passing a detected DC current through a conductor wound around or penetrating the ferromagnetic core. And a current detector for detecting a direct current.

[Conventional technology]

A conventional current detector of this type is shown in FIG. In the figure, 1 is an annular ferromagnetic core, and a magnetic gap 2 is provided in a part of a magnetic path having a circular shape. In the magnetic gap 2, a magnetic sensing element 3 such as a Hall element is fixedly provided with resin 4. A conducting wire 5 through which a current to be detected flows is wound around the magnetic path of the ferromagnetic core 1. The magnetic sensing element 3 is connected to the connector 7 by a lead wire 6.
Although not shown, the connector 7 is connected to a circuit board on which components of a signal processing circuit such as an amplifier are mounted. An external terminal fitted to the connector 7 and a variable resistor for adjusting the output signal are attached to the circuit board. Such a current detector is disclosed, for example, in Japanese Utility Model Laid-Open No. 57-7.
It is disclosed in Japanese Patent No. 3664.

In the above configuration, when a current to be detected flows through the conductor 5, a magnetic field having a magnitude proportional to the current value is generated in the magnetic gap 2, and the magnetic sensitive element 3 generates a detection signal (electrical signal) proportional to the generated magnetic field. It is output through the lead wire 6 and the connector 7. This detection signal is amplified by an amplifier (not shown) on the circuit board and then output as a detection signal of the detected current. On the other hand, the variable resistor attached to the circuit board adjusts the amplification amount of the signal from the magnetic sensing element 3. This is adjusted so that a desired current can be obtained by applying a test current to the lead wire 5 after incorporating the current detector into the device to be measured whose current value is to be detected.

[Problems to be solved by the invention]

As described above, in the conventional current detector, the magnetic sensing element 3 and the circuit board on which the signal processing circuit component is mounted are separate bodies.
For this reason, the magnetic sensing element 3 and the circuit board must be connected by the twisted lead wires 6 for preventing noise, and the number of parts increases and the mounting work and management thereof are required. there were.

The present invention has been made in order to solve such problems, and an object thereof is to obtain a current detector having a small number of parts and requiring no connecting lead wire.

Another object of the present invention is to obtain a current detector in which the fluctuation of the output signal is small with respect to the change of the environment and the final adjustment is not required after the assembly.

[Means for solving problems]

A current detector according to the present invention comprises a ferromagnetic core having a magnetic gap provided in a part of a magnetic path, a magnetic sensing element, and an amplifier for amplifying a detection signal from the magnetic sensing element. The element is mounted on a circuit board on which a signal processing circuit is configured and disposed in the magnetic gap, and an output signal output port of the amplifier and a reference voltage for comparison with the output voltage of the amplifier are provided on the circuit board. And an adjusting resistor for trimming for adjusting the reference voltage value are provided on the circuit board.

[Action]

Since the magnetic sensing element is mounted on a circuit board having an amplifier for processing the output signal of the magnetic sensing element, a lead wire for connecting the magnetic sensing element and the circuit board is unnecessary. Also, on the circuit board,
An output signal proportional to the output of the amplifier, that is, an output signal outlet proportional to the current to be detected, an output voltage of the amplifier and a reference voltage outlet for comparison, and a trimming resistor for adjusting the reference voltage value. Is provided, the fluctuation of the output signal is small even with changes in mechanical vibration, humidity, power supply voltage, etc., the noise resistance level is high, and the reliability is improved.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

1 (a), (b) and (c) are views showing the structure of an embodiment of the present invention, and the same reference numerals as in FIG. 4 indicate the same or corresponding parts. The magnetic sensing element 3 including a Hall element or a magnetoresistive element is integrally mounted on a circuit board 8 on which a circuit having a signal processing function from the magnetic sensing element 3 is mounted together with other components. The mounting surface of the magnetic sensitive element 3 on the circuit board 8 is interposed in the gap 2 of the ferromagnetic core 1 substantially parallel to the gap forming surface. The magnetic field generated in the magnetic gap 2 is converted into an electric signal by the magnetic sensing element 3, processed by the circuit on the circuit board 8, and output as a detection signal from the external terminal 9 as an outlet. . The external terminal 9 also includes an input terminal for power supply. The ferromagnetic core 1 and the circuit board 8 are housed and fixed in an insulating case 10. The case 10 is an accommodating portion 100 having an annular recess for accommodating the ferromagnetic core 1.
1 and a housing portion 100-2 for the circuit board 8. The housing portion of the ferromagnetic core 1 of the case 10 is closed by the lid 101 at the upper portion thereof.

The conductor wire 5 is wound or penetrated from the outside of the case 10 around the ferromagnetic core 1, and both ends 5-1 and 5-2 of the conductor wire 5 are mechanically stopped at the hooking portion 102 provided in the case 10. Has been. The upper portion of the circuit board 8 is exposed to the outside of the case 10 as shown in FIG. 3C, and trimming-adjustable resistor 13 is formed on this exposed portion. After adjusting the resistance value by trimming, a cover 11 is attached to the case 10 on the side where the circuit board 8 is housed.

FIG. 2 shows an example of a signal processing circuit formed on the circuit board 8 of FIG. In the figure, V _r is the output voltage of the constant voltage source 15 composed of a Zener diode or the like, and e _i is the output voltage of the magnetic sensing element 3, which is applied to the differential amplifier 14. 18 is a resistor connected to the inverting input terminal of the differential amplifier 14, 13-2
Is an adjusting resistor for setting a reference voltage, which is connected between the non-inverting input terminal of the differential amplifier 14 and the ground. V _o is connected to the external terminal 9 in the output voltage of the differential amplifier 14.
Reference numerals 16 and 13-3 respectively denote a fixed resistor and an adjusting resistor connected in series between the constant voltage source 15 and the ground, and the intersections thereof form the reference voltage V _s and are connected to the external terminal 9. The adjusting resistor 13-1 is connected between the output terminal and the inverting input terminal of the differential amplifier for feedback. In addition, the adjustment resistors 13-1, 13-2, 1
3-3 is provided for trimming, and FIG.
In (c), the resistors 13 for adjustment are collectively shown.

Next, the operation will be described.

Magnetic properties of the ferromagnetic core 1, the size of the magnetic gap 2 (gap), there is variation in the characteristics of the magnetic sensing element 3 and the differential amplifier 14 and the like, the output voltage V _o by the variation has a variation. Therefore, in order to keep this variation within a desired error, adjusting resistors 13-1, 13-2, (13-3) are provided in a part of the signal processing circuit on the circuit board 8, and the conducting wire 5 is used. adjusting resistors 13-1 and 13-2 while observing the output voltage _{V o} by applying a constant test current to, (13
-3) is trimmed and its resistance value is changed to reduce the above variation. In other words, the output voltage _{V o} is (R _f and R _i are the resistance values of the resistors 13-1 and 15 respectively), and the output can be adjusted by changing the resistance value of the adjustment resistor 13-1. Similarly, a desired reference voltage output _VST can be produced by trimming the adjustment resistor 13-3 to change the resistance value. For this trimming, there are a method of spraying abrasive powder, a method of using a laser beam, etc.
The reliability can be improved by coating the cover 11 or a resin on.

In this way, the magnetic sensing element 3 is mounted on the circuit board 8, and the output signal output port having a proportional relationship with the current to be measured and the reference voltage output signal output from the same constant voltage power source are output to the circuit substrate 8. Since it has a mouth, it has the following advantages. That is, a lead wire for connecting the magnetic sensing element 3 and the signal processing circuit is not required, which reduces the number of parts and facilitates the mounting work and management.

Stable output is obtained even when the environment changes.

Output from the external terminal 9 voltage _{V o} and the reference voltage signal _{V ST}
The reference voltage value V
An output inverted from the output signal V _o above and below _ST can be obtained from the comparator, and the output voltage V _o and the reference voltage signal V _o can be obtained.
_ST is because it is made of the same constant voltage source 15, even if vary the input voltage V _cc is large constant voltage output V _r is slightly varied, as shown in FIG. 3, the output voltage V _o Since the reference voltage signal V _ST changes at substantially the same rate, it is possible to make a current detector that is less affected by fluctuations in the power supply voltage. It is also possible to create a plurality of reference voltage signals having different values.

〔The invention's effect〕

As described above, according to the present invention, the magnetic sensitive element disposed in the magnetic gap of the ferromagnetic core is mounted on the circuit board of the signal processing circuit, and the output signal proportional to the detection signal is mounted on the circuit board. Since the reference voltage output signal output terminal divided from the same constant voltage source is provided, it is not necessary to attach and manage the connection lead wire. In addition, the output adjustment is easy and the fluctuation of the output signal is small even when the environment changes.
This has the effect of eliminating the need for final adjustment after assembly, and has the effect of inexpensively obtaining a device with a highly accurate control and protection output signal outlet.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention. FIG. 1A is a partially cutaway side view, FIG. 1B is a partially cutaway plan view, FIG. 1C is a side view, and FIG. FIG. 3 is a circuit diagram showing an example of a signal processing circuit configured on the circuit board shown in FIG. 3, FIG. 3 is a characteristic diagram showing one of its operating characteristics, and FIG. 4 is a configuration diagram of a conventional current detector. 1 ... Ferromagnetic core, 2 ... Magnetic gap, 3 ... Magnetic sensitive element, 5 ... Conductive wire, 8 ... Circuit board, 13-1, 13-
2, 13-3 ... adjusting resistor, 14 ... differential amplifier,
15: constant voltage source.

Front page continuation (72) Inventor Hiroshi Numakura 2-14-40 Ofuna, Kamakura City, Kanagawa Mitsubishi Electric Corporation Product Research Laboratory (72) Inventor Taido Sakamoto 3-18-1 Oka, Shizuoka-shi, Shizuoka Prefecture Mitsubishi Electric Kizu Co., Ltd. (56) References JP-A-59-151064 (JP, A) JP-A-63-18273 (JP, A) Practical application Sho-62-37781 (JP, U)

Claims (1)

[Claims] 1. A current comprising a ferromagnetic core having a magnetic gap provided in a part of a closed magnetic path, a magnetic sensitive element, and a signal processing circuit including an amplifier for amplifying a detection signal from the magnetic sensitive element. In the detector, the signal processing circuit has a reference voltage generation circuit for supplying a reference voltage to a circuit to be connected to the latter stage of the amplifier, and supplies a constant voltage to the magnetic sensing element and the reference voltage generation circuit. A constant voltage source for supplying the magnetic sensitive element is mounted on a circuit board on which the signal processing circuit is mounted and disposed in the magnetic gap, and the output of the amplifier is provided on the circuit board. A signal output port and a reference voltage output port from the reference voltage generation circuit are provided, and the reference voltage of the reference voltage generation circuit and the reference voltage for the amplifier are respectively provided for trimming mounted on the circuit board. Key Current detector, characterized in that the adjustable by resistors.