JP3013596U - Overcurrent protection device and overcurrent protection circuit - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an inexpensive and small overcurrent protection device capable of easily identifying an abnormality in an electric circuit. [Structure] A PTC element 11 formed by mixing conductive particles in a crystalline polymer and a series circuit of light emitting diodes 12, 13 and a resistor 14 connected in parallel to the PTC element 11 are connected in parallel. Connect and store in housing 15. The housing 15 is provided with a light transmitting portion that transmits the light of the light emitting diodes 12 and 13. The overcurrent protection circuit 10 is connected in series to the load. When the current increases, P due to Joule heat
When the temperature of the TC element 11 rises and the resistance value increases, the current value is lowered, and the current is bypassed to the light emitting diodes 12, 13 to turn on the light emitting diodes 12, 13 to notify the abnormality.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to an overcurrent protection device and an overcurrent protection circuit that can be used repeatedly and continuously and that an increase in current value can be confirmed by a light emitting diode.

[0002]

[Prior art]

 Conventionally, when protecting an electric circuit from an overcurrent, a fuse using a metal wire is generally used as a protection element to interrupt a rapidly increasing current in the electric circuit.

However, since the metal wire itself of the fuse is broken by heat melting and interrupts the electric current, it is necessary to replace the fuse once it is broken and opened.

In addition, since the fuse uses a thin metal wire for the portion to be melted, it is not easy to visually confirm the disconnection. Furthermore, since it is necessary to replace the fuse of the same rating, the replacement work is also required. It is complicated.

As described above, in order to avoid the complexity of requiring replacement for each disconnection, an overcurrent protection device using a PTC element that can be repeatedly used has been used in recent years. That is, the PTC element itself generates heat due to Joule heat generation due to overcurrent by utilizing the characteristic that the electric resistance value significantly increases in a relatively narrow temperature range as the temperature of the PTC element increases. The resistance value sharply increases and the current decreases.

Further, since the PTC element can return to its low resistance value as the temperature decreases, it can be used semipermanently. That is, the PTC element has a low resistance value when the electric circuit is used in a normal state, whereas an abnormality such as a short circuit occurs in the electric circuit and a current larger than the normal state is applied to the PTC element. When it flows, the temperature of the PTC element rises to a certain temperature range due to Joule heat generation, and the resistance value suddenly increases, thereby lowering the current and protecting the electric circuit.

However, in the case of such a conventional PTC element, it is not possible to visually determine the state in which an abnormality has occurred in the electric circuit and the resistance value of the PTC element has increased.

In particular, when used in an electric device having an electric circuit having many functions, a plurality of PTC elements as overcurrent protection elements are arranged according to the electric circuit having each function, so Even if an abnormality occurs in the electric circuit and one of the PTC elements is stopped, the electric device cannot function as a whole. The operation until the abnormality of the electric circuit is confirmed is complicated and time-consuming, and the abnormal electric circuit cannot be easily identified.

On the other hand, a no-fuse breaker is also used as an overcurrent protection element. This NORFUSE breaker can easily confirm the abnormality of the electric circuit and does not need to be replaced each time after the current is cut off.

However, the large size and high price of the no-fuse breaker restricts its use in many electric devices.

[0011]

[Problems to be solved by the device]

 As described above, in the case of the PTC element, after the failure of the electric circuit is eliminated, the PTC element can return its resistance value to a low state as the temperature decreases. Is difficult to judge from the appearance of the PTC element.

On the other hand, since the no-fuse breaker has a large size and a high price, its use is limited in many electric devices.

The present invention has been made in view of such a problem, and there is no need to replace it after the current has dropped, and the state of the current drop can be easily identified on the appearance, and an inexpensive small overcurrent protection device is provided. Another object of the present invention is to provide an overcurrent protection circuit.

[0014]

[Means for Solving the Problems]

 The overcurrent protection device according to claim 1, comprising a PTC element, a light emitting diode connected in parallel to the PTC element, and a resistor connected in series to the light emitting diode. is there.

An overcurrent protection device according to a second aspect is the overcurrent protection device according to the first aspect, further comprising a housing that houses the PTC element, the light emitting diode and the resistor, and the housing is configured to prevent the light of the light emitting diode from being emitted. It has a transparent portion that transmits light.

The overcurrent protection device according to claim 3 is the overcurrent protection device according to claim 1 or 2, wherein the PTC element is formed by mixing conductive particles in a crystalline polymer. is there.

According to a fourth aspect of the present invention, there is provided an overcurrent protection circuit in which the overcurrent protection device according to any one of the first to third aspects is connected in series to a load.

[0018]

[Action]

 In the overcurrent protection device according to claim 1, since the light emitting diode is connected in parallel to the PTC element, when an overcurrent flows through the PTC element, the temperature of the PTC element rises due to Joule heat generation, and the resistance value increases. The current can be decreased by increasing rapidly, and the voltage between both terminals of the PTC element is increased to increase the voltage between both terminals of the light emitting diode. The PTC element lowers the current and turns on the light emitting diode. It is displayed that the resistance value of the PTC element is increasing and the current is decreasing, and the current flowing in the light emitting diode can be suppressed by the current limiting action of the resistor.

The overcurrent protection device according to a second aspect is the overcurrent protection device according to the first aspect, in which the PTC element, the light emitting diode and the resistor are housed in the housing, so that they can be integrated and the light of the light emitting diode can be integrated. By providing a light-transmitting portion that transmits light, the light emission of the light emitting diode can be discriminated from the outside.

The overcurrent protection device according to claim 3 is the overcurrent protection device according to claim 1 or 2, wherein the PTC element is formed by mixing conductive particles in a crystalline polymer. The volume resistivity of the material itself becomes low, the resistance value at normal time can be suppressed to be low, and the voltage drop at normal time can be made small.

Since the overcurrent protection circuit according to claim 4 connects the overcurrent protection device according to any one of claims 1 to 3 in series with a load, when an overcurrent occurs in the load or the like, an overcurrent protection occurs. The PTC element of the current protection device protects the load by lowering the current, and by turning on the light emitting diode, the resistance value of the PTC element increases and the current is reduced. In addition, the current limiting action of the resistor can suppress the current flowing through the light emitting diode and protect the light emitting diode.

[0022]

【Example】

 A configuration of an embodiment of an overcurrent protection device and an overcurrent protection circuit of the present invention will be described below with reference to FIGS. 1 to 3.

As shown in FIG. 1, the overcurrent protection device 10 includes a PTC element 11 whose resistance value rapidly increases when the temperature exceeds a predetermined temperature, two light emitting diodes 12 and 13 arranged in antiparallel, and A series circuit of a resistor 14 that limits a current flowing through the light emitting diodes 12 and 13 is connected in parallel, and connection terminals 10a and 10b are formed at both ends thereof, as shown in FIG.

As shown in FIG. 2, the overcurrent protection device 10 has a housing 15 formed of a resin such as an epoxy resin, a phenol resin, or a silicone resin on the outside, and the housing 15 is provided in the housing 15. The PTC element 11, the light emitting diodes 12 and 13 and the resistor 14 are housed, and a part of the housing 15 faces the light emitting diodes 12 and 13 and transmits light signals of the light emitting diodes 12 and 13. The part 16 is formed. Furthermore, the connection terminals 10a and 10b are provided in a leg shape.

As shown in FIG. 3, in the PTC element 11, the PTC flat plate 21 is sandwiched between the electrode pieces 22 and 22 of nickel electrolytic foil, and the leg-shaped connecting terminals are connected to the electrode pieces 22 and 22 of the nickel electrolytic foil. 23, 23 are connected.

Further, the PTC element 11 was obtained by using 200 g of thermal black (trade name: Thermax N-990 Ultra Pure, manufactured by Cancarb Co., Ltd.) as conductive particles, and 100 g of high-density and low-pressure polyethylene (commercial polymer) as a crystalline polymer. Name: Mitsui Petrochemical Co., Ltd. Hi-Zex3000B) and 2.5-dimethyl-2.5- (t-butylperoxy) h exyne-3 (trade name: as an organic peroxide of 1.25 g). Perhexin 25B-40 manufactured by Nippon Oil & Fats Co., Ltd. is kneaded on a roll mill heated to 160 ° C., and after cooling, the kneaded PTC material is pulverized into granules.

Further, a nickel electrolytic foil having a thickness of 25 μm manufactured by Fukuda Metal Foil & Powder Co., Ltd. is sandwiched between the electrode pieces 22 and 22 and a PTC material granulated by crushing is sandwiched and pressed in a mold. While being heated and cooled while being molded, it is processed into a thin piece having a thickness of about 0.5 mm. Then, the flaky PTC material is cross-linked by irradiating γ-rays with 10 Mrad to form a PTC flat plate 21, and then cut into a size of 15 mm × 13 mm, and solder-plated copper wires are attached to the two electrode pieces 22 and 22. The PTC element 11 is obtained by mounting with solder dip and using it as a connection terminal. When the ambient temperature of the PTC element 11 is changed from 20 ° C to 150 ° C, there is almost no change in the resistance value up to a temperature of about 130 ° C, the normal resistance value is about 25 mΩ, and the temperature is 130 ° C. ℃ exceeds the resistance increases at elevated ratio of 1 0 ^6.

Then, the light emitting diodes 12, 13 and the resistor 14 are connected to the front surface of the printed circuit board having a size smaller than the PTC element 11, for example, 15 mm × 10 mm, and the back surface of the printed board is connected to one side of the PTC element 11. Attach it to the electrode piece 22. Further, the PTC element 11, the light emitting diodes 12, 13 and the resistor 14 are housed in a housing 15 and arranged so that the light of the light emitting diodes 12, 13 is emitted from the light transmitting portion 16.

Next, the operation of the above embodiment will be described.

The operating current of the light emitting diodes 12 and 13 is 3 mA, and the resistance value of the resistor 14 is 4. The resistance value of the PTC element 11 is as described above, and a resistance of 8Ω is connected to the load.

First, when the electric circuit is normal, when a load and the overcurrent protection device 10 are connected in series and a cross current of 24 V is applied, a current of about 3 A flows, and the resistance of the PTC element 11 of the overcurrent protection device 10 increases. Since the value is as low as 25 mΩ, most of the current flows in the PTC element 11, so the current flowing in each of the light emitting diodes 12 and 13 is 0.02 mA or less, and the light emitting operation of the light emitting diodes 12 and 13 is stopped. The PTC element 11 does not cause a large loss with respect to the current flowing through the load.

On the other hand, when a load is short-circuited in the electric circuit and the resistance value of the load is set to 1Ω, a current of about 24 A flows, the PTC element 11 generates heat due to Joule heat, and the temperature of the PTC element 11 rises. When the temperature exceeds 130 ° C, the resistance value rises to about 400Ω, the circuit current can be reduced from 24A to 0.06A, and the load can be protected from overcurrent. At this time, since a current of about 5 mA flows through the light emitting diodes 12 and 13, the light emitting diodes 12 and 13 having an operating current of 3 mA emit light, so that light is emitted from the light emitting unit 16 of the overcurrent protection device 10. A circuit abnormality can be easily determined at a glance from the appearance of the overcurrent protection device 10. Further, since the resistor 14 is connected in series to the light emitting diodes 12 and 13, the resistor 14 serves as a current limiting element and no inrush current flows to the light emitting diodes 12 and 13, so the light emitting diodes 12 and 13 are protected. it can.

Further, since the resistance value of the PTC element 11 can be returned to the low state as the temperature of the PTC element 11 is lowered by stopping the power supply, it is necessary to replace the overcurrent protection device 10 every time. It is possible to obtain an inexpensive overcurrent protection device 10 that can be used many times without using the device. Then, after the abnormality is eliminated, it can be easily judged from the appearance of the overcurrent protection device 10 that the original normal state is restored.

Further, even when the power is turned on again in the normal state, the light emitting diodes 12 and 13 do not emit light, and when the temperature of the PTC element 11 rises due to the increase of the current value, the resistance value increases and the current decreases. , The light emitting diodes 12 and 13 emit light.

In the above examples, since the conductive particles are dispersed in the crystalline polymer, it is possible to reduce the normal resistance value as compared with the ceramic type having a high volume resistivity. In addition, the ceramic type has a problem that the resistance value sharply decreases due to the varistor effect when a high voltage is applied, and the resistance value increases when the temperature is lowered in a region where PTC does not appear, Such a problem can be reliably prevented.

When the overcurrent protection device 10 is connected to a series circuit and used, the same effect can be obtained by using one light emitting diode in the forward voltage direction.

Furthermore, since the housing 15 itself is transparent or semi-transparent, it is not necessary to separately form a light transmitting portion.

[0038]

[Effect of device]

 According to the overcurrent protection device of claim 1, since the light emitting diode is connected in parallel to the PTC element, when an overcurrent flows through the PTC element, the temperature of the PTC element rises due to Joule heat generation. The current value can be decreased by increasing the resistance value suddenly, and the voltage between the terminals of the PTC element is increased to increase the voltage between both terminals of the light emitting diode, and the PTC element decreases the current. Is displayed to indicate that the resistance value of the PTC element is increasing and the current is decreasing, and the current flowing in the light emitting diode can be suppressed by the current limiting action of the resistor.

According to the overcurrent protection device of the second aspect, in addition to the overcurrent protection device of the first aspect, since the PTC element, the light emitting diode and the resistor are housed in the housing, they can be integrated, and By providing the light transmitting portion that transmits the light of the light emitting diode, the light emission of the light emitting diode can be discriminated from the outside.

According to the overcurrent protection device of claim 3, in addition to the overcurrent protection device of claim 1 or 2, the PTC element is formed by mixing conductive particles in a crystalline polymer. In addition, the volume resistivity of the material itself becomes low, the resistance value under normal conditions can be suppressed low, and the voltage drop under normal conditions can be reduced.

According to the overcurrent protection circuit of the fourth aspect, the overcurrent protection device according to any one of the first to third aspects is connected in series to the load. Therefore, when an overcurrent occurs in the load, The PTC element of the current protector reduces the current to protect the load, etc., and lights up the light emitting diode to indicate that there is an abnormality in the electric circuit, and the current limiting function of the resistor. Thus, the current flowing through the light emitting diode can be suppressed and the light emitting diode can be protected.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of an overcurrent protection device of the present invention.

FIG. 2 is a perspective view showing an overcurrent protection circuit of the same.

FIG. 3 is a perspective view showing the same PTC element.

[Explanation of symbols]

 10 Overcurrent protection device 11 PTC element 12, 13 Light emitting diode 14 Resistor 15 Housing 16 Translucent part

Claims (4)

[Scope of utility model registration request] 1. An overcurrent protection device comprising: a PTC element; a light emitting diode connected in parallel to the PTC element; and a resistor connected in series to the light emitting diode. . 2. An overcurrent protection device according to claim 1, further comprising a housing for accommodating the PTC element, the light emitting diode and the resistor, the housing having a light transmitting portion for transmitting the light of the light emitting diode. apparatus. 3. The overcurrent protection device according to claim 1, wherein the PTC element is formed by mixing conductive particles in a crystalline polymer. 4. An overcurrent protection circuit in which the overcurrent protection device according to claim 1 is connected in series to a load.