JPS6028084Y2 - Current control element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current control element composed of a barium titanate semiconductor ceramic thermistor (hereinafter referred to as a positive temperature coefficient thermistor) having a positive temperature coefficient of resistance.

Positive characteristic thermistors exhibit positive resistance-temperature characteristics in which the electrical resistance increases rapidly when a certain temperature is reached, and have two functions: a self-temperature control function that automatically controls self-heating, and a current limit function that limits the current. Demonstrate function.

As a device focusing on the self-temperature control function, a positive temperature coefficient thermistor constant temperature heating element used as a heat source in various heat generating devices is well known; The present invention focuses on the current limiting function, and is useful for overcurrent protection circuits in electronic equipment, automobile-mounted equipment, etc., for example.

By the way, a positive temperature coefficient thermistor reaches thermal equilibrium at the point where the amount of heat dissipation increases or decreases, and the input energy also increases or decreases. Therefore, when using a positive coefficient thermistor as a constant temperature heating element, heat sinks etc. are installed on both sides of the positive coefficient thermistor. It is common practice to increase the amount of heat dissipation by bringing the materials into close contact with each other, thereby increasing the input energy, that is, the amount of heat generated.

However, when using it as a current limiting element, the most important issue is to minimize the residual current, so contrary to when using it as a constant temperature heating element, the amount of heat dissipated is small and the self It is necessary to maintain the heat generation temperature at a high value and operate in a high resistance region.

Therefore, the conventional current control element, as shown in Fig. 1,
Spring terminals 4 and 5 are connected in contact with the electrodes 2 and 3 provided on both sides of the PTC thermistor 1, or lead wires 6 and 7 are connected to the electrodes 2 and 3 of the PTC thermistor 1 as shown in FIG.
The structure was such that the parts were soldered at an angle of 8°9 to minimize the amount of heat dissipated.

However, such a point-contact structure has extremely poor heat dissipation, and moreover, current concentrates in the center of the PTC thermistor 1, where the spring terminals 4 and 5 and the lead wires 6 and 7 are connected. This has the disadvantage that it generates heat locally and is easily destroyed at low voltages.

In particular, when realizing current limiting elements for DC circuits of 12V power supplies and 24V power supplies that are often used in various electronic devices and automobile equipment, etc., in order to obtain the necessary current limiting characteristics,
Total surface area is 5cm or more and thickness is 10μm to 1000μ
It is necessary to use a thin plate-shaped positive temperature coefficient thermistor in the range of
It was considered difficult to put it into practical use because it was easily destroyed by low voltage.

This invention eliminates the above-mentioned conventional drawbacks, and has a breakdown voltage that is more than three times higher than the conventional one, and is sufficient for 12V and 24V power supply DC circuits, which are often used as power sources for various electronic devices and automotive equipment. The purpose of the present invention is to provide a current control element that can be used for a long time.

In order to achieve the above object, the current limiting element according to the present invention has a surface area of 5 cm or more and a thickness of 10 μm to 1000 μm.
The present invention is characterized in that it is configured to include a positive temperature coefficient thermistor in the range of m, and that a heat dissipation plate that also serves as an electrode plate is brought into surface contact with the entire surface of both surfaces of the positive temperature coefficient thermistor in the thickness direction.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The content of the present invention will be specifically described below with reference to the accompanying drawings, which are examples.

Figure 3A is a front view of the current control element according to the present invention;
Figure B is also a side view thereof.

In this example, the total surface area is 5C71! As described above, the configuration includes a disk-shaped positive temperature coefficient thermistor 1 having a thickness t in the range of 10 μm to 1000 μm, and the entire surface of the electrodes 2° 3 on both sides of the positive temperature coefficient thermistor 1 in the thickness direction is made of a metal plate. Heat dissipating plates 10 and 11, which also serve as electrode plates, are brought into close surface contact.

The total surface area of positive temperature coefficient thermistor 1 is 5c7I! As above,
The reason why the thickness was set in the range of 10 μm to 1000 μm was because
This is because current limiting characteristics suitable for overcurrent protection in a DC circuit of a 12V power supply or a 24V power supply can be obtained.

Furthermore, the positive characteristic thermistor 1 has a specific resistance of 10Ω- at room temperature.
Use one that is smaller than cm.

In other words, when a positive temperature coefficient thermistor with the above shape and dimensions is used in an automobile, a positive temperature coefficient thermistor of 12V
It has been found that in order to operate a positive temperature coefficient thermistor stably when it is driven by applying a DC voltage, its resistance value needs to be 0.2Ω or less.

The positive temperature coefficient thermistor according to the present invention has a surface area of 5 crl!
As mentioned above, since the thickness is in the range of 10 μm to 1000 μm, in order to suppress the resistance value to 0.2Ω or less, the resistance to resistance needs to be 10−00 or less.

With the above structure, the breakdown voltage is reduced to about 3.3V compared to the conventional breakdown voltage of 15V due to the heat dissipation by the heat sinks 10 and 11 and the current spreading effect of the heat sinks 10 and 11 as electrode plates.
It was found that the voltage rose to 50V, which is twice as high.

Therefore, according to the present invention, it is possible to provide a current control element that can be satisfactorily used in a DC power supply circuit using a 24V power supply.

Next, the effects of the present invention will be explained in more detail with reference to the measured data shown in FIG.

Figure 4 shows a voltage-current characteristic diagram, where the horizontal axis shows the applied voltage (DC
V) and the current A is plotted on the vertical axis.

The scale is a logarithmic scale.

Curve A4 is the voltage-current characteristic of the conventional current-limiting element (spring terminal structure) shown in Figure 1, and curve A4 is the voltage-current characteristic of the conventional current-limiting element (lead soldering structure) shown in Figure 2. The characteristics and curves respectively show the voltage-current characteristics of the current limiting element according to the present invention.

For positive characteristic thermistors, curves A□ and A2? ! 's
In both cases, specific resistance at room temperature ρ9=10Ω−o1 resistance at room temperature R
20 = 0.2Ω, thickness t = 0.1Ω, diameter D = 2.
A thin disc-shaped one measuring 52 cm was used.

Curve A1. As is clear from A2, the current limiting element of the conventional structure shown in FIGS. 1 and 2 has a breakdown voltage of 15V.
However, as is clear from the curve, the current limiting element according to the present invention has a breakdown voltage of 50V, which indicates that the breakdown voltage has been improved by more than 3.3@ compared to the conventional device. Recognize.

As mentioned above, the current limiting element according to the present invention has a total surface area of 55C71! Above, the thickness is 10 μm to 100 μm
It is configured with a positive temperature coefficient thermistor in the range of 0 μm, and is characterized in that a heat dissipation plate that also serves as an electrode plate is brought into surface contact with both surfaces of the positive temperature coefficient thermistor in the thickness direction. When used in a power supply circuit, we have developed a current-limiting element that exhibits suitable current-limiting characteristics, has a breakdown voltage of as much as 50V, and can withstand use as overcurrent protection for a DC power supply circuit of a 24V power supply. can be provided.

[Brief explanation of drawings]

FIG. 1 is a front view of a conventional current limiting element, FIG. 2 is a front view of another example, FIG. 3A is a front view of a current limiting element according to the present invention, and FIG. 3B is a front view of the same. The side view and FIG. 4 are voltage-current characteristic diagrams. 1...Positive characteristic thermistor, 2, 3...
Electrode, 10.11... Heat sink.

Claims (1)

[Scope of utility model registration request] The surface area is 5al! Above, the thickness is 10p, m to ioo
opm range and has a specific resistance of 10 Ω-α or less, the positive temperature coefficient thermistor is configured with a heat dissipation plate that also serves as an electrode plate in surface contact with the entire surface of both sides in the thickness direction of the positive temperature coefficient thermistor. Characteristic current control element.