JPH01113674A - Current detector - Google Patents

Abstract

PURPOSE:To enable the accurate compensation of temperature in a Hall element and to improve the precision of measurement of a current, by a method wherein the Hall element inserted into a gap of a ferromagnetic core forming a closed magnetic circuit is combined with a temperature sensor by a material having an excellent heat conductivity. CONSTITUTION:A minute gap is formed in a part of a ferromagnetic core FC being formed by winding around a conductor, through which a current to be measured flows, to form a closed magnetic circuit. The magnetic flux density of a magnetic field generated in the gap is detected by a Hall element HE inserted into this gaps, and a current in the proportional relationship with the magnetic flux density is measured therefrom. Since the Hall element HE is combined with a temperature sensor TS by a material TC having an excellent heat conductivity, the generation of a temperature difference can be prevented. Moreover, a driving circuit DU of a current detector, the Hall element HE including the ferromagnetic core FC, and a temperature sensor TS, are integrated with a base plate BP interposed, and therefore it is unnecessary to connect a number of leads with a cable wiring. According to this constitution, it is made possible to improve the accuracy and reliability of the current detector, resulting in the enhancement of miniaturization and quantity production thereof.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a current detector using a Hall element.

[Prior Art] FIG. 15 shows the basic configuration of a current detector using a Hall element. The principle of the current detector is that a gap 22 is formed in a part of a ferromagnetic core 21 that surrounds a conductor 11 through which current flows.
By detecting the magnetic flux density of the magnetic field generated by the Hall element 23, a current that is proportional to the magnetic flux density is measured. There are various types of Hall elements used in current detectors, such as a Hall element made of a compound semiconductor thin film containing 1nAsb, In, or 8S. Since the sensitivity of the Hall element is temperature dependent, the accuracy of the current detector deteriorates over a wide temperature range. Therefore, in high-precision current detectors, a temperature compensation circuit is generally used to avoid errors resulting from the temperature dependence of the sensitivity of the Hall element.

[Problems to be Solved by the Invention] In order for the temperature compensation circuit to accurately compensate for the temperature of the Hall element, it is necessary to detect the accurate temperature of the Hall element using a temperature sensor. However, in a structure in which the temperature sensor 26 is placed near the Hall element 23, as in the current detector illustrated in FIG. Figure (a) is a top view of the current detector, and figure (b) is a side view. On the substrate 25 are a ferromagnetic core 21 in which a Hall element 23 is inserted in the air gap 22, and a drive circuit 2.
4 and a temperature sensor 26 are provided. 29 is an external connection terminal.

To solve this problem, the temperature sensor may be brought into close contact with the Hall element, but this method has problems for the following reasons.

(A) The gap in the ferromagnetic core in which the Hall element is inserted is minute, and if the temperature sensor is placed in the gap with the Hall element, many leads will be used from the narrow space, making multi-wire connection with cable wiring. is required, and lacks long-term stability and reliability due to the risk of poor contact and disconnection.

(It) Inserting a temperature sensor into a minute gap not only reduces the functionality of the current detector, but also complicates the manufacturing process, making it difficult to make a high-performance current detector that can be mass-produced at low cost.

For this reason, when the temperature sensor and the Hall element are separated, a temperature difference occurs between the two, making it difficult to accurately detect the temperature of the Hall element, and causing a problem that temperature compensation does not function properly. This is due to the fact that conventional current detectors using Hall elements have poor current measurement accuracy, which is a major hindrance to industrial mass production.

[Means for Solving the Problems] The present invention has been made to solve the above-mentioned problems, and includes: a ferromagnetic core forming a closed magnetic path; In a current detector that has a structure in which a Hall element inserted into a minute gap and a drive circuit including a temperature compensation circuit are integrated, the temperature detection element and the Hall element are coupled via a thermal conductor. It is characterized by the presence of

That is, in the present invention, as in the main structure shown in FIG. 1, the temperature sensor TS and the Hall element HE are coupled with a material TC having good thermal conductivity, thereby preventing the generation of a temperature difference. Furthermore, the drive circuit DO of the current detector, the Hall element 11E including the ferromagnetic core FC, and the temperature sensor TS are integrated, so there is no need to connect many leads and cable wiring.

By these means, it is possible to improve the accuracy and reliability of the current detector, and also to reduce the size and improve mass productivity.

The material with good thermal conductivity used to connect the temperature sensor and the Hall element is preferably non-magnetic metal, ceramics,
Examples include glass ceramics and highly thermally conductive resins. Among these, metals are more preferably aluminum or copper, ceramics are alumina or aluminum nitride, high-strength glass ceramics, and highly thermally conductive resins are epoxy resins, acrylic resins, etc. containing highly thermally conductive fillers, and materials with a thermal conductivity of 1 are more preferred. ．． It is more than OW/mK.

Next, the thermal conductor that connects the temperature sensor and the Hall element will be explained.

Thermal conductors have a wide variety of structures, and typical ones are illustrated below, but the present invention is not limited thereto.The structure of the thermal conductor will be explained with reference to the drawings.

Figure 2 shows a case where the thermal conductor has a plate-like structure, and in the same figure (al) and (a2), the thermal conductor TC is sandwiched between the pole element 11E and the ferromagnetic core FC. Top and side views of the structure coupled to the temperature sensor TS, the same figure (
bl) and (b2) are a top view and a side view of a structure in which a thermal conductor TC is brought into contact with the end surface of the Hall element 11E and coupled to the temperature sensor 1'S, respectively, and (cl) and (c
2) is a top view and a side view, respectively, of a structure in which the thermal conductor TC contacts the end face of the Hall element 11H from the planar direction of the ferromagnetic core FC and is coupled to the temperature sensor TS, using any of the materials mentioned above. be able to.

Next, Fig. 3 shows the case where the thermal conductor has a block-like structure.
A bulky thermal conductor TC surrounds the temperature sensor TS and the temperature sensor TS.
Top and side views of the structure forming and joining the
bl) and (b2) are a top view and a side view of a structure in which the entire ferromagnetic core FC, Hall element +1E, and temperature sensor TS are molded and combined, respectively, and the same figure (cl
) and (c2) are top and side views of a structure in which a lumpy thermal conductor TC is formed and bonded between the Hall element +1E and the temperature sensor TS, respectively. ing.

The above structure is a case where the thermal conductor TC is in direct contact with the Hall element HE, but FIG. 4 shows a structure in which the ferromagnetic core FC also serves as the thermal conductor TC.
(a2) is a top view and side view of the structure in which the thermal conductor TC is in contact with the outer periphery of the ferromagnetic core FC, and the same figure (bl)
, (b2) are a top view and a side view of a structure in which a temperature sensor TS is brought into close contact with a ferromagnetic core FC, respectively.

Next, the drive circuit Dll of the current detector, the ferromagnetic core FC
The structure, material, and mutual relationship of each component that integrates the Hall element +1E including the temperature sensor TS will be explained.

First, in the case of the structure shown in FIG. 1 in which a thermal conductor TC is formed to couple the Hall element 11E and the temperature sensor TS, the material of the substrate BP is preferably metal, ceramics, or reinforced resin. In the structure in which the ferromagnetic core FC also serves as the thermal conductor TC (later shown in FIGS. 12 and 14), 1. substrate[
The material of IP is preferably metal, ceramics, or reinforced resin, and the structure in which the substrate BP also serves as a thermal conductor TC (later the 9th
(shown in the figure), the material of the substrate 81' is preferably metal or ceramic.

Next, a structure in which the Hall element +1E and the temperature sensor TS are locally molded with a highly thermally conductive resin to form a thermal conductor TC as shown in FIGS. There is a structure as shown in FIGS. 3(bl) and (b2) in which the entire structure is molded and serves both as an integral fixing member and as a thermal conductor TC, both of which are excellent in mass production.

Furthermore, a structure in which other components are formed on the ferromagnetic core FC is to form a thermal conductor TC as shown in FIGS.
.

Structures that connect
) has a structure in which the ferromagnetic core FC also serves as the thermal conductor TC, which makes it possible to realize a current detector with a simple structure and has high practical value.

The temperature sensor used in the current detector may be any commonly used sensor as long as the thermal conductor is made of the material and structure described above, but an element with a large temperature coefficient is preferred. The temperature coefficient required here is the rate of change with respect to temperature of impedance such as resistance, capacitance, or actance, and contact potential or electromotive force such as Hall voltage.

Examples of such temperature sensors include metal or semiconductor thin film resistive elements, variable capacitance or variable inductive elements, thermocouples, Hall elements, and the like.

Among these, InSb thin film resistors, thermistors, etc. are particularly preferred. Also, thin film type! The NSB Hall element is the most preferable example because it has a large temperature coefficient of input resistance.

[Function] The current detector of the present invention has a structure in which the temperature sensor and the Hall element are coupled via a thermal conductor, and each element of the current detector is integrated.The effects thereof will be explained below. do.

First, with reference to FIGS. 5 and 6, the effect of coupling the temperature sensor and the Hall element through the thermal conductor will be explained.

The temperatures of the Hall element, temperature sensor, and ferromagnetic core are denoted as T, Ts, and T2, respectively. At time t0, the environmental temperature TA of the current detector changes stepwise from To to T, and at time t, it changes from T1 to T in four columns. When the temperature changes to , the respective temperatures become as shown in FIG. 5 when there is no heat conductor, and as shown in FIG. 6 when they are connected by a heat conductor. That is, in the case of the conventional structure without a thermal conductor, the temperature Ts of the temperature sensor changes following the environmental temperature TA, so the temperature difference Δ between the temperature rs of the temperature sensor and the temperature T of the Hall element is
T increases transiently, and the time required for both to reach temperature equilibrium within a certain error range is extremely long. On the other hand, in the case of the present invention in which both are coupled via a thermal conductor, the temperature TS of the temperature sensor changes to follow the temperature TH of the Hall element, so ΔT does not increase transiently, and both The time required for temperature equilibrium to be reached within a certain error range is short. Therefore, even if the environmental temperature changes, the temperature compensation of the TL flow detector always functions correctly, allowing accurate current measurement.

Next, with reference to FIGS. 7 and 8, the effects of having a structure in which each element of the current detector is integrated will be explained. In Figure 7, the current detector CS is not integrated.
Since the drive circuit Du is separated, the multi-core cable ll1c
This shows that the number of core wires increases significantly. FIG. 8 shows that in the case of the integrated structure of the present invention, the number of core wires of the multicore cable mc is reduced to less than half. That is, usually
There are at least 6 lead wires for the Hall element HE and temperature sensor 'TS, but the output of the drive circuit is 3 or 2 wires.
When using a large number of current detectors CS, the effect of reducing the number of core wires by integrating the drive circuit DO into the current detector C5 becomes very large, which reduces contact failure, disconnection, and wire breakage, which can be problems when connecting multiple wires. Alternatively, the risk of interference can be avoided, and long-term stability and reliability are greatly improved when viewed as a current measurement system.

[Example] FIG. 1 shows the main structure of a current detector of the present invention. That is,
A ferromagnetic core FC that goes around a conductor through which a current to be measured forms a closed magnetic path, a Hall element +12 inserted into a gap formed in a part of the ferromagnetic core FC, and a temperature compensation circuit Te.
In the current detector integrated with the drive circuit [11 including mp], the temperature detection element TS and the Hall element 11E
are coupled via a thermal conductor TC. The drive circuit DI includes a control power supply Vc, an amplifier mp, and a temperature compensation circuit Temp.

FIG. 9 shows a first embodiment of the present invention; FIG. 9(a) is a top view and FIG. 9(b) is a side view. In this embodiment, the ferromagnetic core 21 surrounding the conductor 11 through which the current to be measured flows has a relative magnetic permeability ur = 4000. Outer diameter 20n+m, inner diameter 10
It consists of a ferrite core with a thickness of 5 mm and a spacing of 1
A thin film type 1n8s Hall element 23 is inserted into a gap 22 with a thickness of 1 m and a drive circuit 24 including a temperature compensation circuit.
It is arranged on and integrated with a substrate 25 made of glass fiber reinforced epoxy resin.

A temperature sensor 26 consisting of a thin film type 1nSb Hall element is fixed using an epoxy adhesive to a 200 μm thick copper plate 27 which is sandwiched and fixed between the ferrite core 21 and the substrate 25.

Next, the temperature compensation results according to the first example will be explained. The current detector of Example 1 and the reference product shown in FIG. 16, which does not have a thermal conductor, are placed together in a constant temperature oven and left until the temperature of each current detector stabilizes at 25°C. The temperature change of the temperature sensor and Hall element was measured when a stepwise change of 10° C. was applied. In the conventional method without a thermal conductor, such as the current detector shown in Fig. 16, the temperature difference ΔT between the temperature sensor and the Hall element is 7°C at its maximum value, as shown in Fig. 1θ, and it is necessary for temperature equilibrium to occur. Time L2 is 20a+
In an environment where changes occur continuously, the temperature compensation of the current detector hardly functions normally.

- As shown in Figure 11, when using the thermal conductor invented by Riki, the maximum value of ΔT is 0.3°C, the relative error is about 0.1% near room temperature, and the overall Current detectors with measurement accuracy within 1% are possible.

FIGS. 12(a) and 12(b) show a top view and a side view of a second embodiment of the present invention. Here, ferrite core 2
1. The pole element 23, the substrate 25, the drive circuit 24, etc. are the same as in the first embodiment described above, so their explanation will be omitted. In this embodiment, the ferrite core 21 and the temperature sensor 26 are locally bonded using a resin 28 having good thermal conductivity. The resin is a two-component high thermal conductive epoxy resin manufactured by Dalais.
Stycast 285 OKT type (base resin) and Catalyst type 9 (curing agent) are used. The thermal conductivity of this resin is 4.31 W/+n. The resin 28 is the drive circuit 2
It may be in contact with 4 or may be apart.

FIGS. 13(a) and 13(b) show a top view and a side view of a third embodiment of the present invention. Here, ferrite core 2
1. The Hall element 23, the substrate 25, the drive circuit 24, etc. are the first
Since this is the same as the embodiment, the explanation will be omitted. In this embodiment, the entire current detector is molded with a resin 28 having good thermal conductivity. The resin 28 is the same as in the second embodiment described above, and is molded by a casting method using a separately manufactured mold.

FIGS. 14(a) and 14(b) show a top view and a side view of a fourth embodiment of the wooden invention. Here, the ferrite core 21, Hall element 23, substrate 25, drive circuit 24, etc. are the same as in the first embodiment, so their explanation will be omitted. In this embodiment, the temperature sensor 26 is directly attached to the ferrite core 21 using an adhesive.

The current detector with the conventional structure shown in Fig. 16 is a reference product manufactured for comparison when evaluating the effect of improving performance by the present invention, and the specifications and dimensions of the parts used are is the same as in Examples 1 to 4 above. [Effects of the Invention] As explained above, according to the invention, the current detector can be used over a wide temperature range, has high measurement accuracy even when rapid temperature changes occur, and is free from poor connections in cable connections. Disconnection,
It is possible to realize a current detector that has low risk of interference, high long-term stability and eccentricity, and is inexpensive and easy to mass-produce.

In addition, the model and shape of the temperature sensor are free.
There are also effects of cost reduction and downsizing due to suspension.

Furthermore, as in the third embodiment, the resin forming the heat conductor forms a protective layer, thereby improving environmental resistance.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the main structure of the present invention. Figures 2, 3 and 4 are diagrams explaining the structure of the thermal conductor. Figure 5 is a diagram showing the temperature change of a conventional current detector. Figure 6 is a diagram showing the temperature change of the current detector of the invention; Figure 7 is a diagram explaining the cable connection of the conventional current detector; Figure 8 is the cable connection of the current detector of the present invention. FIGS. 9, 12, 13 and 14 are diagrams each showing an embodiment of the tree invention, and FIGS. 10 and 11 are diagrams showing a conventional structure and a prototype current detection according to the present invention, respectively. Figure 15 is a diagram showing the basic configuration of the current detector, Figure 16 is a diagram showing the results of temperature changes in each part of the
The figure shows a current detector with a conventional structure. DESCRIPTION OF SYMBOLS 11... Conductor, 21, FC... Ferromagnetic core, 22... Air gap, 23, IIE... Hall element, 24, Dtl... Drive circuit, 25, BP... Substrate, 2B , TS...Temperature sensor, 27...Copper plate, 28...Resin, 29...External connection terminal. FC Zanbo's company has been suspended and this is the main reason for the current crisis (Fig. in rice, FuTfzuse (I large, Ki 1
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Claims (1)

[Claims] A ferromagnetic core that circles a conductor through which a current to be measured flows to form a closed magnetic path, a Hall element inserted into a gap formed in a part of the ferromagnetic core, and a drive circuit including a temperature compensation circuit. What is claimed is: 1. An integrated current detector, characterized in that a temperature detection element and a Hall element are coupled via a thermal conductor.