JP2021190543A - Shunt resistor - Google Patents

Abstract

To provide a shunt resistor that can reduce the error of detection voltage even when a high-frequency current is applied, thus enabling accurate current measurement.SOLUTION: A shunt resistor 1 includes a resistive body 3, first and second electrodes 5A, 5B connected to both sides of the resistive body 3, and first and second voltage detection terminals 6A, 6B electrically connected to the first and second electrodes 5A, 5B, respectively. Distances S from a centerline CL of the resistive element 3 to the first and second voltage detection terminals 6A, 6B are in the range of 21 to 29% of the width of the resistive element 3.SELECTED DRAWING: Figure 2

Description

The present invention relates to a shunt resistor for current detection, and more particularly to a voltage detection terminal of the shunt resistor.

Conventionally, shunt resistors have been widely used for high-current current detection applications such as monitoring the charging / discharging current of an in-vehicle battery. Such a shunt resistor comprises a resistor made of a low resistance material, electrodes connected to both ends of the resistor, and voltage detection terminals electrically connected to the electrodes (eg, patent literature). 1). The voltage detection terminal is connected to a voltmeter for measuring the voltage drop as the current flows through the resistor. By dividing the measured value of the voltmeter by the resistance value of the resistor, the current value flowing through the shunt resistance value can be found.

Japanese Unexamined Patent Publication No. 2017-009419

In a system that requires high-frequency current control using the high-frequency trans effect such as a non-contact charger, the high-frequency characteristics of current detection are a very important factor. With the increase in current, which is one of the market demands, resistors with a low resistance value of several hundred μΩ or less are used in order to reduce the power loss in the shunt resistor.

However, when a high-frequency alternating current is passed through a shunt resistor having such a resistor, the voltage detected through the shunt resistor deviates from the actual voltage. It is presumed that the reason for this is that the voltage drop due to the inductance of the shunt resistor itself is relatively large compared to the voltage drop due to the resistor. In particular, when an alternating current having a frequency of 10 kHz or higher is passed through the shunt resistor, the error between the actual voltage and the detected voltage is large. As a result, the current value calculated from the detected voltage contains a large error, and accurate current measurement cannot be achieved.

Therefore, the present invention provides a shunt resistor that can reduce the error of the detected voltage even when a high frequency alternating current is applied and enables accurate current measurement.

In one embodiment, the resistor, the first and second electrodes connected to both sides of the resistor, and the first voltage detection terminal and the first voltage detection terminal electrically connected to the first electrode and the second electrode, respectively. A shunt resistor having two voltage detection terminals, the distance from the center line of the resistor to the first voltage detection terminal and the second voltage detection terminal being within the range of 21 to 29% of the width of the resistor. A vessel is provided.

In one aspect, the distance is in the range of 23-27% of the width of the resistor.
In one aspect, the first voltage detection terminal and the second voltage detection terminal are made of a hardened fused material.
In one aspect, the fusing material comprises solder.
In one aspect, the shunt resistor is a shunt resistor for measuring alternating current.

According to the present invention, the position of the voltage detection terminal is within a range of 21 to 29% of the width of the resistor from the center line of the resistor. According to the AC current application simulation carried out by the inventor, a shunt resistor having a voltage detection terminal located within such a range has a detection voltage and an actual voltage when a high frequency AC current is passed through the resistor. It is known that the error with the voltage of can be reduced. Therefore, the shunt resistor according to the present invention can achieve high current detection accuracy.

It is a perspective view which shows one Embodiment of a shunt resistor. It is a top view of the shunt resistor shown in FIG. It is a graph which shows the result of the simulation which applies an alternating current to the shunt resistor shown in FIG. It is a perspective view which shows the other embodiment of a shunt resistor. FIG. 4 is a cross-sectional view taken along the line AA of FIG. It is sectional drawing which shows the shunt resistor before the fusion material melts.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a perspective view showing an embodiment of a shunt resistor, and FIG. 2 is a top view of the shunt resistor shown in FIG. The shunt resistor 1 is electrically connected to the resistor 3, the first electrode 5A and the second electrode 5B connected to both sides of the resistor 3, and the first electrode 5A and the second electrode 5B, respectively. It includes a voltage detection terminal 6A and a second voltage detection terminal 6B.

Examples of the material of the resistor 3 include a nickel-chromium alloy, a copper nickel alloy, a copper manganese alloy, and a copper-manganese-nickel alloy, and the material of the resistor 3 can achieve the intended purpose. As long as it is a thing, it is not particularly limited. Copper (Cu) is mentioned as an example of the material of the first electrode 5A and the second electrode 5B, but the material of the first electrode 5A and the second electrode 5B can also achieve the intended purpose as long as it can achieve the intended purpose. Not particularly limited. The first electrode 5A and the second electrode 5B each have bolt holes 9A and 9B for fixing the overall position of the shunt resistor 1.

The first voltage detection terminal 6A and the second voltage detection terminal 6B are made of a conductive material. As shown in FIG. 1, the first voltage detection terminal 6A and the second voltage detection terminal 6B project from the surfaces of the first electrode 5A and the second electrode 5B, respectively. In the present embodiment, the first voltage detection terminal 6A and the second voltage detection terminal 6B are composed of conductive pins, but the specific configuration of the first voltage detection terminal 6A and the second voltage detection terminal 6B is Not particularly limited.

As shown in FIG. 2, the first voltage detection terminal 6A and the second voltage detection terminal 6B are located outside the center line CL of the resistor 3. The center line CL is an imaginary line extending in the longitudinal direction of the shunt resistor 1. The distance S from the center line CL to the first voltage detection terminal 6A and the second voltage detection terminal 6B is S = W × 25% ± 4%, that is, the width of the resistor 3, assuming that the width of the resistor 3 is W. It is in the range of 21 to 29% of W. According to the AC current application simulation carried out by the inventor, it was found that the shunt resistor 1 provided with the voltage detection terminals 6A and 6B located within such a range can reduce the error between the detected voltage and the actual voltage. ing.

FIG. 3 is a graph showing the results of an alternating current application simulation. The horizontal axis of FIG. 3 represents the frequency of the AC current applied to the shunt resistor 1, and the vertical axis of FIG. 3 is the detection voltage (voltage drop) at the first voltage detection terminal 6A and the second voltage detection terminal 6B. , Represents the error between the applied AC current and the theoretical voltage (voltage drop) calculated from the resistance value of the resistor 3. The simulation conditions were that the width W of the resistor 3 was 10 mm, the thickness of the resistor 3 was 1 mm, and the alternating current applied to the resistor 3 was 100 A.

As can be seen from the simulation results of FIG. 3, when the frequency of the alternating current is 1 kHz or less, the voltage error is almost 0, but when it exceeds 10 kHz, the voltage error becomes large. In particular, when the frequency of the alternating current is 50 kHz or more, the voltage error appears remarkably. However, when the distance S from the center line CL of the resistor 3 to the voltage detection terminals 6A and 6B is within the range of 21 to 29% of the width W of the resistor 3, the frequency of the alternating current is 50 kHz or more. However, the voltage error is small. For example, when the distance S is 26% of the width W of the resistor 3, the voltage error at a frequency of 100 kHz is close to 0%, whereas when the distance S is 0 (that is, the voltage detection terminals 6A and 6B). Is on the center line CL of the resistor 3), the voltage error is about -30%.

The relationship between the voltage error and the frequency of the alternating current may vary slightly depending on the thickness and width of the resistor 3, but if the distance S is within the range of 21-29% of the width W of the resistor 3, the high frequency It was found from the simulation results that the voltage error when the AC current in the band was applied was small.

As shown in FIG. 3, in the high frequency band, the voltage error increases with the frequency of the applied alternating current. Therefore, from the viewpoint of reducing the voltage error in the high frequency band (for example, 50 kHz or more), in one embodiment, the distance S may be in the range of 22 to 28% of the width W of the resistor 3. Further, in one embodiment, the distance S may be in the range of 23 to 27% of the width W of the resistor 3. When the distance S is 20% or less or 30% or more of the width W of the resistor 3, the voltage error becomes large in the high frequency band (for example, 50 kHz or more).

As described above, according to the simulation results, if the voltage detection terminals 6A and 6B are arranged at positions away from the center line CL of the resistor 3, the voltage error can be reduced. It is presumed that the reason is that the voltage drop due to the inductance of the shunt resistor 1 itself when the alternating current flows through the shunt resistor 1 is reduced.

The shunt resistor 1 of the present embodiment can reduce the error between the detected voltage and the actual voltage when a high frequency alternating current is passed through the resistor 3. Therefore, the shunt resistor 1 according to the present embodiment can achieve high current detection accuracy.

FIG. 4 is a perspective view showing another embodiment of the shunt resistor, and FIG. 5 is a sectional view taken along line AA of FIG. Since the configuration of the present embodiment, which is not particularly described, is the same as that of the embodiments described with reference to FIGS. 1 to 3, the duplicate description thereof will be omitted.

The shunt resistor 1 has a first voltage detection terminal 6A and a second voltage detection terminal 6B made of a conductive fusion material, and a first electrode 5A and a second voltage detection terminal 6B by a first voltage detection terminal 6A and a second voltage detection terminal 6B. A substrate 10 electrically connected to the two electrodes 5B is provided. Also in this embodiment, the distance from the center line CL to the first voltage detection terminal 6A and the second voltage detection terminal 6B is within the range of 21 to 29% of the width W of the resistor 3.

In this embodiment, solder is used as a conductive fusion material. However, a material other than solder may be used as the welding material as long as it has the intended properties (conductivity, etc.).

As shown in FIG. 5, the first voltage detection terminal 6A is arranged in the first through hole 7A formed in the substrate 10. The first voltage detection terminal 6A made of the fusion material is in a cured state after the fusion material is heated and melted, and the end portion of the first voltage detection terminal 6A is in contact with the first electrode 5A. The second voltage detection terminal 6B is arranged in the second through hole 7B formed in the substrate 10. Similarly to the first voltage detection terminal 6A, the second voltage detection terminal 6B made of the fused material is also in a state of being cured after the fused material is heated and melted. The end of the second voltage detection terminal 6B is in contact with the second electrode 5B.

The substrate 10 used in this embodiment is a wiring board (or printed circuit board) on which wiring is printed. The substrate 10 has a base plate 12 and an insulating layer 14 that covers the upper and lower surfaces of the base plate 12. Examples of the material of the base plate 12 include resins such as glass epoxy, ceramics, metals such as aluminum, and combinations thereof. The upper and lower surfaces of the substrate 10 are formed of an insulating layer 14, and the insulating layer 14 forming the lower surface of the substrate 10 is in contact with the first electrode 5A, the second electrode 5B, and the resistor 3. Although not shown, the substrate 10 may further include an amplifier, an A / D converter, a temperature sensor, and the like. The substrate 10 shown in FIGS. 4 and 5 is an example, and the configuration of the substrate 10 is the implementation shown in FIGS. 4 and 5 as long as the base plate 12, the first through hole 7A, and the second through hole 7B are provided. It is not limited to the form.

The first through hole 7A faces the first electrode 5A, and the second through hole 7B faces the second electrode 5B. The substrate 10 is formed on the first conductive layer 15A constituting the inner wall of the first through hole 7A, the second conductive layer 15B constituting the inner wall of the second through hole 7B, and the first conductive layer 15A and the second conductive layer 15B. Further, the first wiring 17A and the second wiring 17B, which are electrically connected to each other, are further provided. Examples of the first conductive layer 15A and the second conductive layer 15B include conductive materials such as copper foil, gold leaf, and silver foil. The copper foil, gold leaf, and silver foil can be formed on the base plate 12 by plating. The first voltage detection terminal 6A and the second voltage detection terminal 6B are electrically connected to the first wiring 17A and the second wiring 17B arranged on the back surface of the base plate 12. In the present embodiment, the first wiring 17A and the second wiring 17B are printed wirings.

The horizontal cross-sectional shape of the first through hole 7A and the second through hole 7B is not particularly limited, and examples of the horizontal cross-sectional shape include a circle and a semicircle. In the case of a circular shape, the diameters of the first through hole 7A and the second through hole 7B are 10 mm or less.

The first voltage detection terminal 6A is in contact with the first conductive layer 15A and the first electrode 5A constituting the inner wall of the first through hole 7A. Therefore, the first voltage detection terminal 6A establishes an electrical connection between the first conductive layer 15A and the first electrode 5A. Similarly, the second voltage detection terminal 6B is in contact with the second conductive layer 15B and the second electrode 5B constituting the inner wall of the second through hole 7B. Therefore, the second voltage detection terminal 6B establishes an electrical connection between the second conductive layer 15B and the second electrode 5B. In addition, in order to mechanically connect the substrate 10 to the first electrode 5A and the second electrode 5B, mechanical connecting elements such as screws, bolts, and resin materials may be further provided.

The first voltage detection terminal 6A and the second voltage detection terminal 6B shown in FIG. 5 are in a state of being cured after the fused material made of solder is heated and melted. FIG. 6 is a cross-sectional view showing the shunt resistor 1 before the welding material melts. As shown in FIG. 6, the fused materials 6A'and 6B' made of solder are arranged (filled) in the first through hole 7A and the second through hole 7B.

By heating the fused materials 6A'and 6B', the fused materials 6A'and 6B' are melted. As a result, as shown in FIG. 5, the fused materials 6A'and 6B' melt in the first through hole 7A and the second through hole 7B and come into contact with the first electrode 5A and the second electrode 5B, respectively. The heating temperature is equal to or higher than the melting point of the fused materials 6A'and 6B'. The heating of the fused materials 6A', 6B' may heat the entire shunt resistor 1 including the fused materials 6A', 6B' and the substrate 10, or the fused materials 6A', 6B' may be locally heated. May be heated. For example, the heating of the welding materials 6A'and 6B' can be carried out by using a reflow device, a laser heater, or the like.

After melting the fused materials 6A'and 6B', as the temperature of the fused materials 6A' and 6B' decreases, the fused materials 6A' and 6B' are cured, and the first voltage detection terminals 6A and the second are used. The voltage detection terminal 6B is formed. The first voltage detection terminal 6A made of the cured fusion splicer 6A'is bonded to both the first electrode 5A and the first conductive layer 15A forming the inner wall of the first through hole 7A, and the cured fusion splicer 6B is formed. The second voltage detection terminal 6B made of ′ is bonded to both the second electrode 5B and the second conductive layer 15B forming the inner wall of the second through hole 7B. In this way, the substrate 10 is electrically connected to the first electrode 5A and the second electrode 5B through the first voltage detection terminal 6A and the second voltage detection terminal 6B.

In this embodiment, elements such as pins, bonding wires, and screws for fixing the first voltage detection terminal 6A and the second voltage detection terminal 6B are unnecessary, and the current detection accuracy due to improper installation of these elements or the like is not required. Does not decrease. Therefore, the shunt resistor 1 of the present embodiment can achieve high current detection accuracy. Further, according to the present embodiment, since it is not necessary to form a through hole or a screw hole in the first electrode 5A and the second electrode 5B, it is possible to prevent a decrease in the current detection accuracy due to the hole processing accuracy. Can be done.

Examples of the solder as the fusing materials 6A'and 6B' forming the first voltage detection terminal 6A and the second voltage detection terminal 6B include solder paste and thread solder. The fused materials 6A'and 6B' may be materials other than solder as long as they are conductive and have an adhesive function. For example, a copper paste or a conductive adhesive may be used.

In the above-described embodiment, a single substrate 10 having both the first through-hole 7A and the second through-hole 7B is used, but the present invention is not limited to the above-mentioned embodiment. In one embodiment, the substrate 10 may include a first substrate having a first through hole 7A and a second substrate having a second through hole 7B. Also in this configuration, the first substrate is connected to the first electrode 5A by the first voltage detection terminal 6A arranged in the first through hole 7A, and by the second voltage detection terminal 6B arranged in the second through hole 7B. The second substrate is connected to the second electrode 5B.

The shunt resistor 1 of each of the above-described embodiments can be applied to current measurement such as 4-terminal measurement. If the shunt resistor 1 according to the above embodiment is used, highly accurate current detection can be achieved.

The above-described embodiments have been described for the purpose of allowing a person having ordinary knowledge in the technical field to which the present invention belongs to carry out the present invention. Various modifications of the above embodiment can be naturally made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the invention is not limited to the described embodiments, but is to be construed in the broadest range in accordance with the technical ideas defined by the claims.

1 Shunt resistor 3 Resistor 5A 1st electrode 5B 2nd electrode 6A 1st voltage detection terminal 6B 2nd voltage detection terminal 7A 1st through hole 7B 2nd through hole 9A, 9B Bolt hole 10 Board 12 Base plate 14 Insulation Layer 15A First conductive layer 15B Second conductive layer 17A First wiring 17B Second wiring

Claims (5)

With a resistor,
The first and second electrodes connected to both sides of the resistor,
A first voltage detection terminal and a second voltage detection terminal electrically connected to the first electrode and the second electrode, respectively, are provided.
A shunt resistor in which the distance from the center line of the resistor to the first voltage detection terminal and the second voltage detection terminal is within the range of 21 to 29% of the width of the resistor. The shunt resistor according to claim 1, wherein the distance is in the range of 23 to 27% of the width of the resistor. The shunt resistor according to claim 1 or 2, wherein the first voltage detection terminal and the second voltage detection terminal are made of a cured fusion material. The shunt resistor according to claim 3, wherein the welding material contains solder. The shunt resistor according to any one of claims 1 to 4, wherein the shunt resistor is a shunt resistor for measuring an alternating current.

Images