JPS5927083B2 - barista - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a varistor that absorbs surge voltages and noise voltages, and provides a varistor that has high protection characteristics with a significantly reduced limiting voltage.

Figure 1 shows the structure of a conventional varistor.

In the figure, 1 is a disk-shaped varistor element, 2 and 2
' (z is not shown) is an electrode baked (or metallized) on both the front and back sides of element 1, 3 and 3' are electrodes 2, and lead wires electrically connected by soldering, etc. It is.

FIG. 2 shows a circuit when the conventional varistor shown in FIG. 1 is connected to, for example, a power supply line 4.

5 is a varistor element, 6 and 61 are the above lead wires 3, 3.
′ is the stray inductance of .

Now, when a surge noise voltage is applied between power line 4,
Current flows in the direction of the arrow.

At this time, the voltage drop V due to the floating inductance 6.6'
Knee Ld i/a t occurs.

Here, L is the lead stray inductance, and dL/at is the rate of change of current.

Therefore, lead wire 3. If the current is long, or if the current contains high-degree C. and frequency components, the voltage drop will be large, and the voltage limit of the varistor element 5 will become high, reducing the protective effect.

The voltage-current characteristics shown in FIG. 3 show this situation.

In FIG. 3, curve A is the limiting voltage characteristic of only the varistor element 5,
Curve B is the limiting voltage characteristic in which the voltage drop occurring in the stray inductance 6, C is superimposed on the limiting voltage characteristic of the varistor element 5, and the varistor shown in Fig. 1 is used in the power supply line 4, etc. as shown in Fig. 2. The limiting voltage characteristic at this time is curve B.

As described above, in conventional varistors, the limiting voltage increases significantly against surge noise voltages including high frequencies, and the protection characteristics thereof are not sufficient.

The present invention has been made to solve the above-mentioned conventional problems, and aims to provide a varistor with excellent characteristics.

An embodiment of the present invention will be described below with reference to FIG.

In FIG. 4, 7 is a disk-shaped varistor element mainly made of metal oxide such as ZnO, and 8 and 8'(8' is not shown) are electrodes provided on both the front and back surfaces of the varistor element γ.

9 and G are each one lead wire, and a rectangular coil portion 10, 1α (1σ is not shown) is constructed in the middle of each lead wire, and a coil portion 10, 10', respectively.
One outer surface of the electrode 8. It is electrically connected to &′ by soldering, etc.

Both ends of the lead wires 9, 9' serve as electrical terminals, resulting in a four-terminal structure in this example.

The operating principle of the varistor shown in FIG. 4 will be explained using FIG. 5.

FIG. 5 shows an equal circuit in which the varistor is connected between the power supply lines 11, and 12 and 12' are inductances formed by the coil portions 10 and 1α, and 13
is an equivalent varistor when the varistor element 7 is viewed from a distributed circuit constant perspective.

Now, when a surge noise voltage is applied between the lines on the power supply side A, a surge current flows in the direction of the arrow, but the current density and current increase rate d i /at become lower as it gets closer to the load side B. .

This is because the inductance seen from the power supply side A increases as it approaches the load side B.

Lower current density and di//dt mean lower limiting voltage, making it possible to obtain excellent protection properties.

In addition, since the inductance 12.12' is connected in series with the load circuit (not shown), it has the characteristic of blocking abnormal voltage with high frequency components, and reduces the abnormal voltage towards the load side B. - is prevented and provides effective protection properties.

Furthermore, since the varistor of the present invention has four terminals,
The influence of stray inductance of the lead wires, which has been a problem in the conventional example, can also be prevented.

Furthermore, by covering the varistor element 7 and the coil portions 10 and 10' of the lead wires 9 and 9' with an insulating material, the influence of the environment on the electrical characteristics is reduced, and the mechanical strength is also increased. occurs.

Next, an example of the specific characteristics of the limiting voltage in the varistor will be described.

Use a varistor with a voltage of 200V and a noise pulse of 60
0V (output impedance 50Ω, rise time In5)
When a voltage of 436 is applied to a conventional product, the limiting voltage is 436
v, the product of the present invention showed a reduction effect of about 10 factors, which was 395V.

FIG. 6 shows a modification of the shape of the coil portion of the lead wire, and the shape of the coil portion is circular with respect to the four corners of FIG.

Moreover, other shapes such as an ellipse or a semicircle may be used as the shape of the coil portion.

Here, in the above embodiment, a case was explained in which a coil portion was provided on two lead wires, but the effect is slightly reduced even if a coil portion is provided on only one lead wire, but the conventional example It shows more effective characteristics.

At this time, the electrode on the other side may be made into a normal circular shape, and a U-shaped lead wire may be connected to it.

The varistor of the present invention is constructed as described above, and the connecting portion of the lead wire to the electrode is formed into a coil shape.
By having a distributed circuit constant equivalent circuit, a lower limit voltage can be obtained, and by using a four-terminal structure, it is also possible to prevent the influence of conventional lead inductance.

By covering the varistor element and the connection portion of the lead wire to the electrode with an insulating material, it is less susceptible to environmental influences (and can have sufficient mechanical strength against external forces).

[Brief explanation of the drawing]

Fig. 1 is a front view of a conventional varistor, Fig. 2 is an equivalent circuit diagram showing an application example of the varistor, Fig. 3 is a voltage-current characteristic diagram of the varistor, and Fig. 4 is a diagram of the varistor according to the present invention. FIG. 5 is an equivalent circuit diagram showing an application example of the varistor, and FIG. 6 is a perspective view showing a modification of the coil portion of the lead wire constituting the varistor. 7... Varistor element, 8, 8'... Electrode, 91g... Lead wire, 10, 10'...
,...Coil part.

Claims (1)

[Scope of Claims] Electrodes are provided on both the front and back surfaces of a varistor element mainly made of metal oxide such as I ZnO, and at least one of the lead wires electrically connected to each electrode is connected to the electrode. A varistor characterized in that a coil portion is used, and both ends of the lead wire are electrical terminals. 2. The varistor according to claim 1, wherein the varistor element and the connection portion of the lead wire to the electrode are coated with an insulating material.