JPH0628702Y2 - Current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention is an electric and electronic device that increases sensitivity by using a plurality of magnetic sensitive elements such as Hall elements or magnetoresistive elements inserted in a magnetic gap of a ferromagnetic magnetic core. The present invention relates to a current detector used in devices and the like.

[Conventional technology]

Generally, in order to measure a current to be measured, as shown in FIG. 3, a winding 2 is provided on a magnetic core 1 made of a ferromagnetic material in which a magnetic gap 3 is provided in a part of a circumference, and a Hall element or A magnetic sensing element 4 such as a magnetoresistive element is provided. The magnitude of the magnetic flux generated in the magnetic core 1 when a current to be measured is passed through the winding 2 is converted into an electric output by the magnetic sensitive element 4, an exciting current is passed through the constant current circuit 6, amplified by the operational amplifier 5, and amplified from the output. The measured current value is detected. In other words, a magnetic field proportional to the measured current flowing in the winding 2 is generated in the magnetic gap 3, and the magnetic sensitive element 4 provides an output voltage proportional to the strength of the magnetic field. Further, FIG. 4 shows an example of an electronic circuit with an increased number of magnetic sensitive elements.

“Problems to be solved by the device” However, in the conventional current detector of this type, the magnetic sensing element 4 is used.
Since the output from is small, the amplification degree of the operational amplifier 5 must be increased in order to improve the sensitivity, and therefore the temperature drift increases and the response characteristic deteriorates. Therefore, a circuit synthesized by using two Hall elements as shown in FIG. 4 is used. Each Hall element has a positive side output terminal and a negative side output terminal, and the output of the Hall element is originally obtained as a differential signal before a predetermined output is obtained. However, in this circuit, one of the positive and negative output terminals of the two magnetic sensitive elements 4 is grounded, and the positive and negative output terminals of the two magnetic sensitive elements 4 are grounded. Only the signal of the other output terminal of is connected to one of the non-inverting and inverting input terminals of the operational amplifier 5, and the signal of one of the plus side and minus side output terminals of the two magnetic sensitive elements 4 is connected. Since only the output is taken out (that is, the operational amplifier 5 is made to act as an inverting amplifier), the output of the magnetic sensitive element 4 becomes 1/2, and even if the outputs are combined, only 1 time is obtained and sufficient sensitivity cannot be obtained. There are drawbacks.

[Means for solving problems]

Except for such drawbacks of the prior art, the present invention has a magnetic gap 3 provided in a part of the circumference of a ring-shaped magnetic core 1 made of a ferromagnetic material around which a winding 2 through which a measured current flows is wound. It is a current detector comprising an operational amplifier which combines and combines the outputs of a plurality of inserted magneto-sensitive elements as inputs.

That is, according to the present invention, a magnetic gap 3 is provided in a part of a ring-shaped ferromagnetic core 1 and a plurality of magnetic sensitive elements 4 and 4'each having a positive side output terminal and a negative side output terminal are provided. The magnitude of the current is detected by the plurality of magnetic sensitive elements, which are arranged in the magnetic gap 3 and sense the magnitude of the magnetic field generated by the current flowing through the winding 2 wound around the ferromagnetic core 1. In a current detector for detecting the height, a non-inverting input terminal connected to the positive side terminals of the plurality of magnetic sensing elements and an inverting input terminal connected to the negative side terminals of the plurality of magnetic sensing elements And a differential amplifier for amplifying the outputs of the plurality of magnetic sensitive elements, and an operational amplifier 5 for outputting a combined value proportional to the sum of the outputs, and a current detector characterized by the above. .

[Action]

Without increasing the amplification degree of the operational amplifier 5 more than necessary by increasing the number of the magnetic sensitive elements 4, the temperature drift is small and the response characteristic is high sensitivity even within a certain range.

〔Example〕

An embodiment of the current detector according to the present invention is shown in FIG.
In the example in which one magnetic pole is used, a magnetic gap 1 is provided in a part of the circumference of a magnetic core 1 made of a ferromagnetic material around which a winding 2 through which a current to be measured flows is wound, and two magnetic sensitive elements are provided therein. 4,
Insert 4 '.

A constant current circuit 6 for flowing a constant current is connected to the two magnetic sensitive elements 4 and 4 '. Of the four outputs of the respective magnetic sensitive elements 4 and 4 ', one plus side terminal is coupled to the non-inverting input side of the operational amplifier 5, and the other minus side terminal is coupled and synthesized to the inverting input side of the operational amplifier 5. Connected to form a current detector.

When a current to be measured is passed through the winding 2, a magnetic flux corresponding to the current is generated in the magnetic core 2 and the outputs generated by the magnetic sensitive element 4 in the magnetic gap 3 are combined by the operational amplifier 5.

That is, the positive side output terminals of the two magnetic sensitive elements 4 and 4'are connected to the non-inverting input terminal of the operational amplifier 5, and the negative side output terminals of the two magnetic sensitive elements 4 and 4'are connected to the operational amplifier 5. By connecting to the inverting input terminal, the output voltages of the two magnetic sensitive elements are differentially amplified by the operational amplifier 5 and the output voltage proportional to the sum of the outputs of the two magnetic sensitive elements 4 and 4'is operational amplifier. It is obtained as a composite value by 5.

Further, as shown in FIG. 2, the magnetic sensing elements 4, 4 ', 4 ", 4
The sensitivity can be easily increased simply by increasing the input resistance 7 of the operational amplifier 6.

[Effect of device]

As described above, according to the present invention, the number of the magnetic sensitive elements 4 is increased to increase the sensitivity multiple times. Therefore, the amplification degree of the operational amplifier 5 is set to a certain range or less, the overall sensitivity is increased, and the temperature draft is small. A highly accurate current detector with good characteristics can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram of a magnetic sensing element part and an electronic circuit of an embodiment of a current detector of the present invention, FIG. 2 is a block diagram of an electronic circuit of another embodiment in which a temperature sensing element is increased, and FIG. FIG. 4 is a block diagram of a magnetic sensing element portion and an electronic circuit of an example of a conventional current detector, and FIG. 4 is a block diagram of an electronic circuit of an example using a plurality of conventional magnetic sensing elements. 1 ... magnetic core, 2 ... winding, 3 ... magnetic gap,
4, 4 ', 4 ", 4 ... Magnetic sensitive element, 5 ... Operational amplifier, 6 ... Constant current circuit, 7 ... Input resistance.

Claims (1)

[Scope of utility model registration request] 1. A magnetic gap 3 is provided in a part of a ring-shaped ferromagnetic core 1, and a plurality of magnetic sensitive elements 4, 4'each having a positive side output terminal and a negative side output terminal are provided in the magnetic gap 3. Detecting the magnitude of the current by sensing the magnitude of the magnetic field generated by the current flowing through the winding 2 wound around the ferromagnetic core 1 inside the plurality of magnetic sensitive elements. In the current detector, a non-inverting input terminal connected to the positive side terminal of the plurality of magnetic sensing elements, and an inverting input terminal connected to the negative side terminal of the plurality of magnetic sensing elements, A current detector comprising: an operational amplifier 5 that differentially amplifies the outputs of the plurality of magneto-sensitive elements and outputs a combined value proportional to the sum of both outputs.