JPH0385460A - Current detector - Google Patents

Abstract

PURPOSE:To detect a current with high accuracy by supplying the AC control signal modulated by a current to be detected to a Hall element. CONSTITUTION:An electric wire 1 pierces a ferromagnetic body 2 and the ferro magnetic body 2 is formed by providing a magnetic gap G to a part of a revolution-shaped magnetic path and arranging a Hall element 3 therein. When a current I to be detected containing an AC component flows through the elec tric wire 1, a magnetic field B is generated in the ferromagnetic body 2 and, when a control apparatus 5 supplies the control current ia modulated by the current I to the element 3, and output signal Va is generated in the element 3. When the signal Va is inputted to a demodulator 7, the demodulator 7 removes an AC control signal component containing unbalanced voltage and obtains only the component of the current to be detected. Therefore, it is unnec essary to control the error difference due to the unbalanced voltage at each time of measurement and a current can be detected with high accuracy.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an IT current detector using a Hall element.
This relates to a current detector with high accuracy.

[Conventional technology]

Generally, a non-contacted carp type current detector measures the value of the current to be detected by measuring the magnetic flux density generated by the current to be measured using a sensor or the like. An example of such a conventional electric i detector is shown in Figure 2 (Sensor Technology, November 1982).
(See monthly issue). In the figure, (1) is an electric wire through which the current to be detected flows, and (2) is a circular ferromagnetic core surrounding a part of this electric wire (11).

This is the magnetic conduction path for the magnetic field B generated by the current being detected. (3) is a hole and an element disposed in the magnetic gap (air gap) G between the end faces (2a) and (2b) of the ferromagnetic core (2), and (4) is the Hall element (3). ) control@ff style input lead, (5) is the drive circuit for the Hall element (3), and the Hall element (3) is connected via the input lead (4).
Supplies control current to (6) is an output lead for taking out the output voltage of the Hall element (3). Figure 3 is the Matsushita Electronics Industry Catalog (publicity material serial number D-077/1■
In this circuit, the Hall element (3) is connected to the control power supply v0°, vll through the resistors R1, 12 as the input lead (4a) of the control current.

(4b) are connected by. Hall element (3
) Regulations eIJ Electric i1. (Usually, a DC current of sma is applied to l. The output voltage V of the Hall element (3) is normally in phase with the differential amplifier circuit (8) consisting of the resistor Ft3.R4゜R5, R6 and the operational amplifier OP. After removing the voltage and amplifying it, it is output as an output (lout).The variable resistor TR connects the Hall element (3) and the differential amplifier circuit (8).
Adjust the offset voltage of

Next, the operation of this device will be explained. Drive circuit (5)
A control current 1d is supplied to the Hall element (3) in advance. When the current to be detected flows through the electric wire 11).

The magnetic field B proportional to the current to be detected is the ferromagnetic core +2
Occurs through 1. This magnetic field BK generates a magnetic field B and a control current 1 (1
A voltage proportional to the product of , that is, an output voltage V proportional to the product of the detected current and the control current 1d is generated.

Connect this output voltage V to the output lead (6m) * (6b
) can be taken out. From what I said above.

The output voltage V of the Hall element +3).

V = 1, id - engineering -...+
11 However, xl: constant of proportionality.

It is expressed as oe13. However, due to the unbalanced voltage vEIO proportional to the static suppression 11cl of the Hall element (3), the output/voltage V of the Hall element (3) becomes =2・1d R2: expressed as a proportionality constant, and the unbalanced voltage vEIO of the Hall element (3) will be output with an error of i [Problem to be solved by the invention] The conventional current detector is as follows. It is configured as follows,
The unbalanced voltage VFIO of the Hall element (3) is
Since it is added to the output voltage V of step 3) and an error occurs in the detection in step 11, it is necessary to adjust the error to zero each time the measurement is made. However, there were problems such as the need for a device for adjustment.

This invention was made to solve the above problems, and it is not necessary to adjust the error due to unbalanced voltage to zero each time a measurement is made, and it is possible to perform current detection with high accuracy. The purpose is to obtain a vessel.

[Means to solve the problem]

A current detector according to the present invention includes a ferromagnetic material having a Km gap in a part of a circular magnetic path forming a hole through which a current to be detected containing an alternating current component flows through a conductor; a control circuit that supplies the Hall element with an AC control signal modulated by the detected current; and a control circuit that supplies the Hall element with an AC control signal modulated by the current to be detected, and a signal corresponding to the ejected 'fIl flow from the modulation signal outputted by the Hall element. It is equipped with a demodulator that outputs waves.

[Effect]

Since the control circuit in this invention supplies an AC control signal modulated by the detected IE flow to the Hall element, the AC control signal component is removed by demodulating the modulation signal output from the Hall element. Only the detected current component is obtained.

[Embodiments of the invention]

Hereinafter, an example of the current detector according to the present invention will be explained based on FIG.

In the figure, (1) is the electric wire as a conductor through which the current to be detected flows, and (2) is this electric wire a-! ! - A ferromagnetic material in which a magnetic gap G is provided in a part of a circumferential magnetic path forming a hole to be penetrated, and serves as a conductive path for the magnetic field B generated by the electrician to be detected. (3) is an enlarged view of the Hall element disposed within the magnetic gear G between the end face portions (2a) and (2b) of the ferromagnetic material (2). 14) is the two input leads of the Hall element (3), and (5) is a control signal which is an AC control signal modulated by the detected electrician to the Hall element (3) via these input leads 14). 'l
E style 1a style 1% supply control circuit, (6) is Hall element (3
) are two output leads for taking out the output voltage V as a modulation signal outputted by the motor.

(7) receives and receives the modulated signal from these output leads (6), demodulates it, removes the component of the control signal 1a, and outputs a signal wave corresponding to the detected R flow. ll
It is a vessel.

Next, the operation of this device will be explained. '1lEil
! When the detected current I flows through fl), a magnetic field B proportional to the detected current is generated in the ferromagnetic material (2). Therefore, the Hall element +31 VC arranged in the magnetic gear G is '7. == K2S tz m engineering + vHOa
--fa) However, +vHOa is the control current 1alc
The unbalanced voltage of the Hall element (〉7H□, oe 1
＠Therefore, vFioa = K5 '''& 3: An output voltage V expressed by a proportionality constant is generated.As can be seen from equation (3), the Hall element (3) K has a multiplication effect of 1 & and As shown in the signal waveforms in each part of Figure 3, (c) the waveform of the Hall element output signal is the result of multiplying (a) the waveform of the current to be detected and (b) the waveform of the control current. , control@1! indicates that the detected current is amplitude modulated by the current. 5 Next, the output signal of this Hall element (3) is inputted to the demodulator (7) K, and this demodulator (7) The current is rectified and the negative component is cut, and the high-frequency suppressing current component is removed by a ninth-order low-pass filter (not shown) K, leaving only the component of the current to be detected as the output of the demodulator (7). Of course, the signal waveforms of each part in Fig. 3 are (a) the waveform after rectification, and (e) the return F!Ili output signal.Among the signal waveforms of each part described above, (c) The waveforms of (a) and (e) are 2 of (a) and Cb), respectively.
Although the species is revealed, (a) vF1 of equation (3)! O
The waveform is shown assuming that a is not a brass instrument.

(b> indicates the actual waveform of equation (3) including vHOa.

fa), (tz) Comparing both waveforms * vHOa
The center level of the envelope is shifted by an amount of , indicating that a measurement offset is being applied. However, since this offset of vHOa is removed by the low-pass filter, the demodulator output signal (e) becomes (&
) * (1)) Both have the same waveform.

〔Effect of the invention〕

As described above, according to the present invention, since the AC control signal modulated by the current to be detected is configured to be supplied to the Hall element, the unbalanced voltage is included by demodulating the modulation signal output from the Hall element. A current detector that removes the AC control signal component and obtains only the current component to be detected, eliminates the need to adjust the error due to unbalanced voltage to zero each time a measurement is made, and can perform current detection with high accuracy. There are benefits to be gained.

[Brief explanation of drawings]

FIG. 1 shows a lightning detector according to an embodiment of the present invention.
Figure II and Figure 2 are diagonal diagrams showing a conventional current detector, and Figure 3 is a circuit diagram of its control circuit. In the figure, fl) is an 11i wire (conductor), and +21 is a ferromagnetic material. (3) is a Hall element, (5) is a control] □□□ path, (7)
is a 41A1 funeral. In addition, in Figure 1, ``Sasa No. 1'' indicates the same or equivalent part.

Claims (1)

[Claims] A ferromagnetic material in which a magnetic gap is provided in a part of a circular magnetic path that forms a hole through which a current to be detected containing an alternating current component flows through a conductor, a Hall element disposed within the magnetic gap, and this hole. A current detector comprising: a control circuit that supplies an AC control signal modulated by the current to be detected to an element; and a demodulator that outputs a signal wave corresponding to the current to be detected from a modulation signal output by the Hall element.