JP2006003209A - Current detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a current detector utilizing a high precision and low cost Hall element in a current detector utilizing magneto-electric transducer such as a Hall element by improving an inhibiting factor in current measurement precision due to the temperature characteristic that the Hall element has, and by adding a temperature compensation circuit. <P>SOLUTION: A Hall current detector using magneto-electric transducer arranged in a magnetic path in a magnetic body comprises: a Hall element; temperature sensing element; a constant current generation circuit for driving the Hall element; a constant voltage generation circuit necessary for adjusting the temperature compensation signal and the offset voltage; a temperature compensation signal generation circuit consisting of an amplifier; a voltage amplifier circuit for amplifying the output voltage of the Hall element; and a temperature compensation circuit. The temperature compensation signal utilizing the characteristic of the temperature sensing element by the temperature compensation circuit is added on the way to the circuit for amplifying the output voltage out of the Hall element to compensate temperature, and a Hall current detector with very little temperature drift is obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a current detector, and more particularly to a temperature compensation circuit for a current detector using a magnetoelectric transducer such as a Hall element.

  As a current detection method of a conventional current detector, for example, a Hall current sensor, a current detector of a magnetic proportional method (Open-loop type) as shown in FIG. 2, that is, a current conductor to be detected in an open magnetic circuit magnetic body The magnetic flux generated by the current If flowing through the current conductor to be detected is converted into a voltage Vh by a magnetoelectric conversion element such as a Hall element and output through an amplifier. Detected in the current detector having the above-described configuration and the magnetic balance type (Closed-loop type) current detector as shown in FIG. 3, that is, in the open magnetic circuit magnetic body equipped with the secondary winding A current element is passed through a Hall element in the gap of the magnetic material, an amplifier is provided on the Hall element side, the output of this amplifier is connected to the secondary winding, and the current If flowing through the detected current conductor The generated magnetic flux is converted to voltage Vh by a magnetoelectric transducer such as a Hall element. In other words, there is a current detector configured to amplify a current through an amplifier and to flow in the secondary winding mounted in a direction to cancel the magnetic flux generated by the current If. The magnetic flux is extremely close to zero, and the current value Io is determined by the primary and secondary winding ratio.

Both of these types of current detectors are in practical use. To compare both types of current detectors, however, the configuration is magnetically proportional to the amount of secondary magnetic coil mounted on an open magnetic circuit magnetic body. Although the method is simpler, in any of the current detection methods shown in FIGS. 2 and 3, the temperature drift of the offset voltage is determined by the characteristics of the magnetoelectric conversion element itself such as the Hall element to be used. .
That is, in a current detector using a magnetoelectric conversion element such as a Hall element, it has been impeded to improve current measurement accuracy due to the temperature characteristics of the Hall element.

  Also, if Hall elements having temperature characteristics with respect to various temperatures are prepared, it is necessary to manufacture a large number of types of Hall elements having temperature characteristics corresponding to the respective temperatures, and the Hall element itself is difficult to be expensive. is there.

  The object of the present invention is to add a temperature compensation circuit to improve the current measurement accuracy obstructed due to the temperature characteristics of the Hall element in the current detector using a magnetoelectric conversion element such as a Hall element. By doing so, it is intended to provide a highly accurate current detector using an existing inexpensive Hall element.

The current detector of the present invention is a Hall current detector using a magnetoelectric conversion element arranged in a magnetic path of a magnetic material, and a Hall element, a temperature sensing element, a constant current generating circuit for driving the Hall element, A constant voltage generation circuit necessary for adjusting the temperature compensation signal and offset voltage, a temperature compensation signal generation circuit comprising an amplifier, and a voltage amplification circuit for amplifying the output voltage from the Hall element, and utilizing the characteristics of the temperature sensing element A temperature compensation circuit is used in which the temperature correction signal is added in the middle of the circuit for amplifying the output voltage from the Hall element.
The temperature compensation circuit adds a temperature correction voltage capable of canceling a difference between offset voltages at normal temperature and other temperatures to the amplifier circuit so as to cancel temperature drift caused by the Hall element itself.

  In order to improve this point, the present invention amplifies the output voltage from the Hall element in two stages, and adds the temperature correction signal to the amplifier by the signal obtained from the temperature sensing element after the first stage amplifier. As shown in the characteristics comparison table, we succeeded in obtaining a Hall current sensor with extremely high measurement accuracy. Moreover, the drift of the offset voltage in the actual operating temperature range (20 ° C to 60 ° C) was 0.0013% / ° C, 1 / 7.6 times that of the magnetic equilibrium type and 1/19 of the magnetic example type.

In a current detector using a magnetoelectric conversion element such as a Hall element (referred to as a Hall current detector, Hall current sensor, HCT, etc., hereinafter referred to as a Hall current sensor), the output voltage magnetoelectrically converted by the Hall element is The value is as small as mV, and it is necessary to amplify it with an electronic amplifier in order to use it practically.
As shown in FIG. 1, the current detector of the present invention uses a magnetic proportional type current detector having a simple configuration, and employs a temperature compensation circuit according to the present invention to achieve high performance using an inexpensive Hall element. Configure an accurate current detector.
A current detector having a conventional configuration as shown in FIG. 2, that is, a detected current conductor is passed through an open magnetic circuit magnetic body, a Hall element is interposed in the gap of the magnetic body, and the detected current conductor flows. The magnetic flux generated by the current If is converted into a voltage Vh by a magnetoelectric conversion element such as a Hall element, and a current detector that outputs the converted voltage Vh through an amplifier Amp1 is connected to an amplifier Amp2. The temperature sensing element for this Hall element, the offset temperature correction signal generation circuit that compensates for the offset voltage temperature drift, and the output voltage temperature correction signal generation circuit are connected as shown in the figure. Thus, the temperature compensation circuit of the current detector according to the present invention is configured.

FIG. 4 is a block diagram of a circuit for implementing the temperature compensation circuit of the current detector of the present invention. In FIG. 4, a circuit block A comprising an amplifier OP1 such as an operational amplifier is a constant current generating circuit for driving the Hall element H1 installed in the magnetic path of the magnetic material shown in FIG. 1, and a circuit block comprising an amplifier OP2. B is a constant voltage generation circuit necessary for adjusting the temperature compensation signal and offset voltage, a circuit block C comprising amplifiers OP3 and OP4 is a circuit for generating a temperature compensation signal, and a circuit block D comprising amplifiers OP5 and OP6 is a Hall element. It is a circuit which amplifies the output voltage of. VR1, VR2, VR3, and VR4 are semi-fixed variable resistors for adjusting circuit constants, H1 is a Hall element, and TR1 and TR2 are temperature sensing elements whose resistance values change with temperature.
These circuit elements are connected and arranged as shown in FIG. 4 to constitute a temperature compensation circuit of the current detector of the present invention.

  By adjusting the constant of the above circuit according to the procedure shown below, a Hall current detector having a very small temperature drift can be obtained.

1) Adjustment at room temperature After adjusting the variable resistor VR4 so that the P1 point in the circuit block of FIG. The variable part is set at a substantially midpoint so that adjustment is easy. Further, the variable resistor VR2 is adjusted at the output terminal 3 so that the output voltage at zero current of the current detector, that is, the offset voltage becomes zero, and the sensitivity as the current detector is adjusted and fixed by the variable resistor VR1. In the embodiment of the present invention, the output voltage at 100 A was adjusted to 4 V, and the offset voltage was adjusted to about 0.002 V.

2) Adjustment at high temperature The current detector was adjusted at normal temperature or any temperature other than 25 ° C., or at 80 ° C. in the case of implementation of the present invention. That is, the variable resistor VR3 is adjusted and fixed so that the final output terminal 3 becomes zero at 80 ° C.

An explanation of the operation of temperature compensation according to the above procedure is as follows.
In FIG. 4, the variable resistor VR2 is used for normal offset adjustment without temperature compensation, and this offset voltage changes depending on the temperature variation of the Hall element itself. The voltage fluctuation difference is defined as ΔV here. (It changes at 0.025% / ° C when temperature compensation is not performed due to temperature drift of so-called offset voltage.)

  On the other hand, the voltage at the point P1 composed of the temperature sensing elements TR1, VR4 and other fixed resistors changes with the temperature change due to the characteristics of the temperature sensing element. At this time, the constant ratio for combining the temperature sensing elements TR1, VR4 and other fixed resistors is determined in advance so as to correspond to the temperature change rate ΔVo of the offset voltage by the Hall element.

  The voltage at the point P1, which is a signal voltage for temperature correction, passes through the variable resistor VR3 of the circuit block C composed of the amplifiers OP3 and OP4, and the amplifier OP6 so as to cancel the offset voltage at the output terminal 3 adjusted by the variable resistor VR2. Is added as a bias.

  For the variable resistor VR3, depending on the Hall element, the offset temperature drift changes in the positive or negative direction with respect to the ambient temperature, but the voltage and polarity that can cancel the ΔVo by the variable resistor VR3 are selected. Can be adjusted.

By changing the amplification factor of the amplifier OP6 using the temperature sensing element TR2, it is possible to improve the output temperature characteristic of the Hall current detector.
In this embodiment, since the output voltage of the Hall element decreases linearly as the ambient temperature increases, the amplification factor of the amplification circuit is adjusted by adjusting the temperature sensing element TR2 and the fixed resistor so that the amplification factor increases as the temperature increases. Use as a resistor.

  As a result of experiments using the above-described temperature compensation circuit of the current detector of the present invention, a temperature characteristic of an offset voltage as shown in FIG. 5 and an output voltage temperature characteristic as shown in FIG. 6 were obtained.

ホール電流検出器の特性上、最も重要なオフセット電圧の温度ドリフトは、−20℃から＋80℃の範囲で0.0075 %/℃と良好な結果が得られた。更に図５から使用温度範囲が、本発明電流検出器で最も良く使用される20℃から60℃の範囲では0.0013 %/℃となった。

Due to the characteristics of the Hall current detector, the most important offset voltage temperature drift was 0.0075% / ° C in the range of -20 ° C to + 80 ° C. Further, from FIG. 5, the operating temperature range was 0.0013% / ° C. in the range of 20 ° C. to 60 ° C. that is most often used in the current detector of the present invention.

  This value is about 1 / 7.6 of the best magnetic equilibrium type in the past when the ambient temperature is in the range of 20 ° C to 60 ° C, and 1 / 1.3 in the range of -20 ° C to + 80 ° C. Also, the temperature characteristic of the output is as small as 1/10 compared to the magnetic proportional type, and the temperature compensated magnetic proportional type, in which the temperature compensation is applied to the magnetic proportional type by adopting the circuit of the present invention, is equivalent to or higher than the magnetic balanced type. A current detector could be obtained.

The current detector according to this method does not have the secondary coil for current feedback found in the magnetic balance type, so it is light in weight and has a simple structure, and the larger the detected current, the better the cost merit. By the way, with a current detection of 1000A or more, the manufacturing cost can be reduced to about 1/10 compared with the magnetic balance type.
Furthermore, it is not necessary to manufacture an expensive Hall element having a desired temperature characteristic, and an existing inexpensive Hall element can be used.

  The current detector of the present invention includes control devices for railway vehicles, elevators, etc., rotary device control devices such as AC / DC servos / large inverters, charge / discharge current detectors for fuel cells / solar power generators, welding machines, industrial robots, etc. There are applications in various fields such as FA equipment such as air conditioners, plating devices, switchboards, CPUs, etc. Especially, a large current device exceeding 500 A can provide a great advantage in terms of small size and light weight and cost.

FIG. 1 is a block diagram showing an outline of a temperature-compensated magnetic proportional current detector according to the present invention. FIG. 2 is a block diagram showing an outline of a current detector based on a conventional magnetic proportional method. FIG. 3 is a block diagram showing an outline of a current detector using a conventional magnetic balance method. FIG. 4 is a circuit block diagram showing a temperature compensation circuit of the current detector of the present invention. FIG. 5 is an explanatory diagram showing the offset voltage temperature characteristics of the current detector of the present invention, FIG. 6 is an explanatory diagram showing the temperature characteristics of the output voltage by the current detector of the present invention.

Explanation of symbols

3 Output terminals
If Detected current
Vh Hall element output voltage A Constant current generator B Constant voltage generator C Temperature compensation signal generator D Voltage amplifier
H1 Hall element
TR1, TR2 Temperature sensing element
VR1, VR2, VR3, VR4 Semi-fixed variable resistors

Claims (2)

  In a Hall current detector using a magnetoelectric conversion element arranged in a magnetic path of a magnetic body, a Hall element, a temperature sensing element, a constant current generation circuit for driving the Hall element, a temperature compensation signal and an offset voltage adjustment A constant voltage generation circuit necessary for the above, a temperature compensation signal generation circuit including an amplifier, and a voltage amplification circuit that amplifies the output voltage from the Hall element, and a temperature correction signal using the characteristics of the temperature sensing element, A current detector using a temperature compensation circuit which adds an output voltage from a Hall element in the middle of a circuit for amplifying.   The temperature compensation circuit adds a temperature correction voltage capable of canceling a difference between an offset voltage at a normal temperature and a temperature other than the normal temperature to the amplifier circuit to cancel a temperature drift caused by the Hall element itself. The hall current detector according to claim 1, wherein

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