JP7193941B2 - SHUNT RESISTOR AND CURRENT DETECTION DEVICE USING THE SAME - Google Patents

Description

The present invention relates to shunt resistors and the like.

In recent years, the current used in electronic devices is increasing to about 1 kA, for example. In this case, it is necessary to control the short-circuit current in order to ensure safety when the circuit is short-circuited. When trying to achieve this kind of control with a shunt resistor, it is important to have a structure that can withstand a large current when the circuit is short-circuited. It is also important.

Therefore, shunt resistors used for such applications are required to have a low resistance value of, for example, 100 μΩ or less. In such a case, it is conceivable to eliminate the connection between the electrode of the shunt resistor and the resistor as much as possible, or to shorten the length of the resistor as much as possible. As a structure that eliminates the connecting portion between the electrode and the resistor, a structure in which the electrode and the resistor are made of the same material, such as manganin, is also conceivable (see, for example, Patent Document 1).

Japanese Patent Application Laid-Open No. 2001-116771

By the way, if the electrode of the shunt resistor and the resistor are made of the same material, such as copper, which has a low resistivity, the resistance becomes small, but there is a problem that the TCR becomes large.
On the other hand, if the electrodes of the shunt resistor and the resistor are made of the same material, such as manganin or geranin, which have a small TCR, the TCR can be reduced, but the excess resistance (the resistance value of the portion outside the voltage measurement terminal) becomes large, and there is a problem that the power consumption becomes large.

Moreover, forming the electrodes and the resistor from different materials also poses a problem that the mechanical strength of the joints (for example, welds) between the electrodes and the resistors is reduced.
SUMMARY OF THE INVENTION An object of the present invention is to achieve low resistance and low TCR in a shunt resistor in which a resistor and an electrode are made of the same material.

Another object of the present invention is to provide a current detection device suitable for detecting a large short-circuit current using the shunt resistor as described above.

According to one aspect of the present invention, there is provided a shunt resistor in which a Cu—Ni—Zn alloy containing copper as a main component and further containing nickel and zinc is used as a resistor material for a shunt resistor composed of a single resistor. be done.

The Cu—Ni—Zn alloy preferably contains 1.5 to 10 wt % Ni, 0.1 to 12 wt % Zn, and the balance Cu.
Furthermore, it preferably contains 0.3 to 0.9 wt % of Si. Furthermore, it is preferable to contain at least one metal of Sn and Mg in an amount of 0.1 to 1 wt %.

The Cu--Ni--Zn alloy may further contain 0.1 to 1 wt % of at least one of Si, Sn, Mg and Ti.

The present invention is the shunt resistor according to any one of the above, wherein the pair of voltage detection terminals may be formed by raising a part of the plate made of the single resistor.

The present invention includes the shunt resistor described above, and a current measurement circuit that measures current by signals from a pair of first and second voltage signal lines respectively connected to the pair of voltage detection terminals. It may also be a current measuring device.

According to the present invention, it is possible to achieve low resistance and low TCR in a shunt resistor in which a resistor and an electrode are made of the same material.

BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows one structural example of the shunt resistor by the 1st Embodiment of this invention. FIG. 10 is a perspective view showing a configuration example of a current detection device using a shunt resistor according to a second embodiment of the present invention, and is a perspective view showing a configuration example before mounting the shunt resistor on a circuit board; 1 is a perspective view showing one configuration example of a current detection device using a shunt resistor according to the present embodiment, and is a perspective view showing a configuration example after mounting a shunt resistor on a circuit board; FIG. FIG. 4 is a cross-sectional view along line IIIa-IIIb of FIG. 3, showing a configuration example after the shunt resistor is mounted on the circuit board; 1 is a circuit diagram (block diagram) showing one configuration example of a current detection device using a shunt resistor according to the present embodiment; FIG. FIG. 10 is a perspective view of a shunt resistor according to a third embodiment of the present invention, which uses a Cu--Ni--Zn alloy as a material of a plate (resistor);

DETAILED DESCRIPTION OF THE INVENTION A shunt resistor and a current detection device using the same according to embodiments of the present invention will be described in detail below with reference to the drawings.

(First embodiment)
First, a first embodiment of the present invention will be described. FIG. 1 is a perspective view showing a configuration example of a shunt resistor according to this embodiment.

As shown in FIG. 1, the shunt resistor A according to the present embodiment is a shunt resistor made up of a long flat plate 1 having a composition as described later, for example. In the shunt resistor A, a pair of voltage detection terminals 11a and 11b separated in the longitudinal direction of the plate 1 are formed on the plate 1 which is a single resistor. A pair of voltage detection terminals 11a and 11b is obtained by cutting out the other three sides of the plate 1, leaving two first sides facing each other, and raising the surface side with the two first sides as references. can be easily formed.

By doing so, the area inside the area (marked L1, L2) inside the first side of the plate 1 becomes the effective resistor 3 in current detection, and the area from the outside to both ends are the effective electrodes 5a and 5b.

As shown in FIG. 1, a voltage detection terminal is obtained by cutting out a plate 1 and bending it as it is to form a voltage detection terminal. can be done. Furthermore, the inductance value of the shunt resistor can be reduced.

In addition to the example shown in FIG. 1, the voltage detection terminal may be a separate pin-shaped terminal provided on the plate 1 . The pin-shaped terminals can be fixed to the plate 1 by welding the pin-shaped terminals to the surface of the plate 1 or by forming a hole in the plate 1 and inserting the pin-shaped terminal into the hole. There is a way.

In the shunt resistor shown in FIG. 1, a pair of holes 7a and 7b are formed at positions spaced apart in the longitudinal direction of the plate 1 so that they can be fixed to a bus bar or wiring board (not shown) using bolts or the like. is configured to
Next, the composition of the material forming the plate 1 made of a single resistor will be described.
If the material of the plate 1 is copper (100%) having a general composition, the specific resistance (μΩ/cm) is as low as about 1.72, but the TCR (ppm/°C) is about 3970. expensive.

On the other hand, if the material of the plate 1 is manganin (registered trademark), the TCR (ppm/°C) is as low as about ±50, but the specific resistance (μΩ/cm) is as high as about 44. In the case of geranin 30 (registered trademark), the TCR (ppm/°C) is as low as about 29, but the specific resistance value (μΩ/cm) is as high as about 29.

Therefore, in the present embodiment, materials for the plate 1 as shown in the table below were used. The plate according to this embodiment had a specific resistance of 4 to 5 and a TCR of 1,000 to 2,000. That is, compared to manganin, the specific resistance is about 1/10, and the TCR is 1000 to 2000, which is higher than manganin but lower than copper.

Table 1 is a table showing an example of the material of the plate 1 according to this embodiment. As shown in Table 1, the main component of the material (alloy material) forming the plate 1 composed of a single resistor is copper indicated by symbol D1, for example, 77 to 98.4 wt%. In addition to copper, which is the main component, in the present embodiment, zinc (Zn) denoted by symbol B1 and Ni denoted by symbol A1 are included. Furthermore, as indicated by symbol C1, at least one of Si, Sn, Mg, and Ti is contained in an amount of 0 to 1 wt%. The amount of zinc (Zn) is 0.1 to 12 wt% and the amount of Ni is 1.5 to 10 wt% (100 wt% in total). The alloy material according to the present invention may contain unavoidable impurities.

Considering that manganin also contains Ni, for example, about 2 wt %, it can be inferred that the reason why the specific resistance value was able to be lowered is due to the alloy containing Zn. According to the inventor's speculation, Zn is easily oxidized and forms an oxide film ZnO. By mixing a small amount of Zn in an alloy containing Cu as a main component, the ZnO oxide film on the surface of the alloy forming the plate 1 plays the role of a surface protective film for copper, which is a bulk low-resistance metal. In addition, the effect of reducing TCR can also be obtained by including Ni in the same manner as manganin or the like. Hereinafter, the plate alloy according to the present embodiment to which a predetermined amount of Zn is added is referred to as a Cu--Ni--Zn alloy.

At least one of Si, Sn, Mg and Ti may be added to the Cu--Ni--Zn alloy in an amount of 0 to 1 wt %. Such alloys are also referred to as Cu--Ni--Zn alloys.

The use of the Cu--Ni--Zn alloy according to the present embodiment provides good durability at high temperatures and stable characteristics. For example, when a high temperature storage test was conducted for 1000 hours at a high temperature of 175° C., the amount of change in the resistance value showed a small variation within ±0.5%.

Normally, copper and copper alloys different from the present embodiment have low stability at high temperatures, and their resistance changes due to oxidation show values greater than ±1%. It can be said that the Ni--Zn alloy has stable characteristics and excellent durability.

(Second embodiment)
Next, a second embodiment of the invention will be described. 2 and 3 are perspective views showing one configuration example of a current detection device using a shunt resistor according to the present embodiment, and FIG. 2 shows a configuration example before mounting a shunt resistor on a circuit board. It is a perspective view showing. FIG. 3 is a perspective view showing a configuration example after the shunt resistor is mounted on the circuit board. FIG. 4 is a cross-sectional view along line IIIa-IIIb of FIG. 3, showing a configuration example after the shunt resistor is mounted on the circuit board. FIG. 5 is a circuit diagram (block diagram) showing a configuration example of a current detection device using a shunt resistor according to this embodiment.

As shown in FIGS. 2 and 3, the shunt resistor A using the Cu—Ni—Zn alloy according to the first embodiment as the material of the plate (resistor) 1 is used in a current measurement circuit, for example, an amplifier circuit B. to form a current measuring device X. The amplifier circuit B is a circuit for amplifying the output signal from the shunt resistor A. FIG.

The connection between the shunt resistor A and the amplifier circuit B is established by connecting the voltage detection terminals 11a, 11a provided upright on the shunt resistor A to through holes 23a, 23b formed in the circuit board 21 of the amplifier circuit B. insert. A circuit board 21 such as a printed circuit board on which the amplifier circuit B is formed is provided with an amplifier circuit (board) for amplifying the output signal from the shunt resistor A. FIG. Reference numeral 35 denotes a terminal portion for outputting a signal from the amplifier circuit B to other control equipment or the like.

By soldering and connecting the voltage detection terminals 11a and 11b using the through holes 23a and 23b of the circuit board 21, the distance between the circuit parts such as the amplifier on the circuit board 21 and the shunt resistor A is brought closer. can be connected.

Further, according to the cross-sectional view of the current detection circuit shown in FIG. 4, the plate 1 of the shunt resistor A is cut out, bent and erected as it is to form the voltage detection terminals 11a and 11b. Terminals 11a and 11b can be formed with short intervals and short lengths. Furthermore, the inductance value of the shunt can be reduced, and durability can be ensured.

As shown in FIG. 5, the amplifier circuit B includes a delta-sigma conversion analog isolation amplifier 25 that includes, for example, a photocoupler, an electrostatic coupling capacitor C, or the like. An A/D converter 27 is provided on the output side of the delta-sigma conversion analog isolation amplifier 25 via a line L13. A first signal output terminal 11a and a second signal output terminal 11b of the shunt resistor A are connected to two input terminals of the amplifier circuit by wirings L11 and L12, respectively.

The amplifier circuit B has input terminals, which are connected to the ΔΣ conversion analog isolation amplifier 25 via resistors or the like. A capacitor C is provided between the wirings L11 and L12 from the input terminals. As a result, entry of normal mode noise into the ΔΣ conversion analog isolation amplifier 25 can be suppressed. A positive power supply terminal of the delta-sigma conversion analog isolation amplifier 25 is connected to Vcc, and a negative power supply terminal is connected to GND31.

The input side and the output side can be electrically isolated by using the delta-sigma conversion analog isolation amplifier 25 using a photocoupler, an electrostatic coupling capacitor, or the like. Therefore, it is possible to reduce the influence of noise on the pair of voltage signal lines (wirings L11 and L12) connected to the amplifier circuit provided in the current measuring device X for amplifying the signal.

Incidentally, according to this embodiment, the output signal can be a digital output. Due to the TCR characteristics of the shunt resistor A, it is not suitable for applications that require highly accurate current detection, so it is preferable to reduce the processing load on the control device side by making the output signal a digital signal as well.

A high level is output when the current value exceeds a specified value, and a low level is output when the current value is within the specified value. The digital circuit used can be a simple circuit using a comparator or the like. The circuit insulation function can be realized by a simple component such as the photocoupler as described above.

In addition, the current detection circuit according to this embodiment can be added to other detection circuits. For example, it can be used for voltage detection by providing a voltage detection circuit or the like.

(Third Embodiment)
Next, a third embodiment of the invention will be described. This embodiment includes another form of shunt resistor. FIG. 6 is a perspective view of a shunt resistor according to the present embodiment, in which a Cu--Ni--Zn alloy is used as the material of the plate body (resistor) 1. FIG.

The shunt resistor D according to the present embodiment uses a Cu--Ni--Zn alloy as the long plate body 1 in the same manner as in the first embodiment. It has a lifting structure that lifts the body 3 area upward. Other structures are the same as in FIG. A shunt resistor D having such a bent structure can be surface-mounted on a circuit for use.
According to this embodiment, the shunt resistor can be further miniaturized as compared with the first embodiment.

(Fourth embodiment)
Next, a shunt resistor according to a fourth embodiment of the invention will be described. The basic structure of the shunt resistor may be the same as in any one of the first to third embodiments.
Table 2 shows a more specific example of the composition ratio of each metal material shown in Table 1.

In the example shown in Example 1-1 among the Cu-Ni-Zn alloys shown in Table 2, for example, Ni is 1.5 to 4.0 wt%, Zn is 0.1 to 0.5 wt%, and Si is 0 .3 to 0.9 wt%, at least one of Sn and Mg is 0.1 to 1 wt%, and the balance is Cu (93.6 to 98 wt%) (100 wt% in total).
In this example, the specific resistance value is 4-5 μΩ·cm and the TCR is about 1000-2000.

On the other hand, in the example shown in Example 1-2, for example, Ni is 1.6 wt%, Zn is 0.4 wt%, Si is 0.4 wt%, Sn is 0.5 wt%, and the balance is Cu (about 97.0 wt%). 1 wt%).
In this example, the specific resistance value is 4.3 μΩ·cm and the TCR is about 1500.

That is, since it corresponds to the case where the Cu ratio in Table 1 is high, the specific resistance value is lower than manganin and geranin 30, while the TCR is higher than manganin and geranin 30. Therefore, it is effective when it is highly necessary to reduce the specific resistance value.

(Fifth embodiment)
Next, a shunt resistor according to a fifth embodiment of the invention will be described. The basic structure of the shunt resistor may be the same as in the first embodiment.
Table 3 is a diagram showing a more specific example of the composition ratio of each metal material shown in Table 1.

Among the Cu—Ni—Zn alloys shown in Table 3, in the example shown in Example 2-1, for example, Ni is 5 to 10 wt%, Zn is 5 to 12 wt%, Si and/or Ti is 0 to 1 wt%, The balance is Cu (approximately 77-90 wt %).
In this example, the specific resistance value is 10-15 μΩ·cm and the TCR is about 200-1000.

On the other hand, in the example shown in Example 2-2, Ni is 6 wt %, Zn is 11 wt %, and the balance is Cu (approximately 83 wt %).
In this example, the specific resistance value is 11.5 μΩ·cm and the TCR is about 600.

That is, since it corresponds to the case in which the proportion of Cu in Table 1 is low, the specific resistance value is lower than that of manganin and geranin 30 but higher than that of Table 2, while the TCR is higher than that of manganin and geranin 30, but shows a lower value than the case of Therefore, it is effective when the resistance value is lowered but the TCR is not desired to be increased too much.

As described above, by including Zn, which is not included in manganin or geranin 30, in the alloy, it is possible to lower the resistance and lower the TCR.

According to the fourth and fifth embodiments, a shunt resistor having a TCR lower than that of copper and a resistance lower than that of manganin can be realized.
Therefore, according to the present embodiment, in the shunt resistor in which the resistor and the electrodes are made of the same material, it is possible to realize low resistance and obtain good TCR characteristics.

Also, by adjusting the ratio of the elements to be added, as can be seen from a comparison of Tables 2 and 3, it is possible to manufacture a shunt resistor having desired characteristic values to some extent.

Moreover, according to the present embodiment, such a material composition can be determined to provide an optimal shunt structure for detecting short-circuit current.
In addition, by connecting a current detection unit, a system capable of detecting a short circuit current can be realized.

In the above-described embodiments, the illustrated configurations and the like are not limited to these, and can be changed as appropriate within the scope of exhibiting the effects of the present invention. In addition, it is possible to carry out by appropriately modifying the present invention as long as it does not deviate from the scope of the purpose of the present invention.
In addition, each component of the present invention can be selected arbitrarily, and the present invention includes an invention having a selected configuration.

INDUSTRIAL APPLICABILITY The present invention is applicable to shunt resistors.

A Shunt resistor B Amplifier circuit X Current measuring device 1 Plate 3 Resistor 5a, 5b Electrode 11a, 11b Voltage detection terminal 21 Circuit board 23a, 23b Through hole (through hole)
25 ΔΣ conversion analog isolation amplifier 27 A/D converter

Claims (6)

A Cu—Ni—Zn alloy containing copper as a main component and further containing nickel and zinc is used as a resistor material for a shunt resistor composed of a single resistor ,
The Cu—Ni—Zn alloy has a Ni content of 1.5 to 10 wt%, a Zn content of 0.1 to 12 wt%, and the balance being Cu.
A shunt resistor characterized by: 2. The shunt resistor according to claim 1, further comprising 0.3 to 0.9 wt % of Si. moreover,
3. The shunt resistor according to claim 1, containing 0.1 to 1 wt % of at least one of Sn and Mg. In the Cu-Ni-Zn alloy,
2. The shunt resistor according to claim 1, further comprising 0.1 to 1 wt % of at least one metal selected from Si, Sn, Mg and Ti. A shunt resistor according to any one of claims 1 to 4 ,
A shunt resistor in which a pair of voltage detection terminals are formed by raising a part of the plate made of the single resistor. A shunt resistor according to claim 5 ;
and a current measuring circuit for measuring a current by a signal from a pair of first and second voltage signal lines respectively connected to the pair of voltage detection terminals.

Images