KR20060093628A - Ptc device having varistor therin - Google Patents

Abstract

Varistor integrated PTC device according to the present invention, the PTC portion having a PTC characteristic; A first electrode electrically connected to one surface of the PTC unit; A second electrode electrically connected to the other surface of the PTC unit; And a varistor part electrically connecting the first electrode and the second electrode; and an insulating part interposed between the PTC part and the varistor part. The first electrode-varistor part when an overvoltage is applied to both ends of the PTC part. The varistor part is arranged in parallel with the PTC part so that an electric conduction through which current flows to the second electrode is formed.

 According to the present invention, the PTC device and the varistor device are implemented as one device so that the circuit can be protected by using one device even when overvoltage and overcurrent occur.

Description

Varistor integrated PTC device {PTC device having varistor therin}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to

1 and 2 are circuit configuration diagrams using a PTC device and a varistor according to the prior art.

3 is a cross-sectional configuration diagram of a conventional varistor integrated PTC device.

4 is a cross-sectional configuration diagram of a varistor integrated PTC device according to an embodiment of the present invention.

5 is a cross-sectional configuration diagram of a varistor integrated PTC device according to another embodiment of the present invention.

6 to 8 are views for explaining the operation of the varistor integrated PTC device according to a preferred embodiment of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit protection device, and more particularly, to a varistor integrated PTC (Positive Temperature Coefficient) device which protects a circuit when an overcurrent flows or an overvoltage is applied to an electric circuit.

The PTC device is a device that protects the circuit from overcurrent by breaking the electrically connected circuit by increasing the temperature when the overcurrent of the allowable current is increased, thereby increasing the resistance of the device.

In other words, the PTC element is a constant current element through which a constant current flows during normal operation, but functions as a constant voltage element that cuts off the circuit when a current exceeding the allowable current flows. However, when a voltage exceeding the allowable voltage is applied to the PTC device, the PTC device is destroyed or damaged. To prevent this, a varistor having a characteristic that a current does not flow below a predetermined voltage and allows a current to flow through an overvoltage state is prevented. Techniques for protecting circuits in conjunction with

Examples of protection circuits in which varistors and PTC devices are used together are disclosed in US Pat. Nos. 5,737,160, 5,745,322, and 5,313,184.

1 is a circuit diagram illustrating a PTC device and a varistor disclosed in US Pat. No. 5,737,160. Referring to FIG. 1, the varistor 3 connected to the PTC element 2 in parallel bypasses the current according to the abnormal voltage when an abnormal voltage equal to or higher than the allowable voltage is applied to the PTC element 2. Damage to the PTC element 2 is prevented.

2 is a circuit diagram of a PTC device and a varistor disclosed in US Pat. No. 5,745,322 used together. Referring to FIG. 2, the bimetal switch 4 is connected in parallel to a circuit in which the PTC element 2 and the varistor 3 are connected in parallel. The bimetal switch 4 is attached to two metal elements in a normal condition, but when overheated due to an abnormal current, the two metals connected to each other fall and cut off the current to protect the circuit. Thus, the bimetal switch 4 is similar in function to the PTC element 2 to assist in blocking overcurrent that is not blocked by the PTC element 2.

However, the conventional overcurrent protection circuits have a problem in that PTC components, varistors, bimetals, and the like must be separately configured.

Therefore, in order to solve such a problem, a device in which a PTC device and a varistor of US Patent No. 5,313,184 are integrally implemented has been proposed, and the device is shown in FIG. 3. The device is a device integrating the PTC device 2 and the varistor 3, and is connected to a circuit to be protected through the electrodes 6 provided at both ends of the device.

However, the device has a problem in that the PTC device 2 is exposed to the outside, causing flashover phenomenon (a phenomenon in which a high voltage is applied between the electrodes, which causes arc discharge through air), resulting in breakdown of the insulation. 2) and the varistor (3) is electrically connected there is a problem causing mutual interference.

In addition, since the PTC element 2 and the varistor 3 are in contact with each other, and an overcurrent flows into the PTC element 2, the volume of the PTC element 2 expands and mechanical stress is applied to the varistor 3 to make the ceramic material. There is a problem of damaging or damaging the varistor 3.

The present invention has been made to solve the above problems, by implementing a PTC device and varistor as a single compact device to protect the circuit in the event of overcurrent and overvoltage, to prevent the flashover phenomenon generated in the PTC device and the It is an object of the present invention to provide a varistor integrated PTC device capable of preventing damage to the varistor due to thermal expansion.

Varistor integrated PTC device according to the present invention for achieving the above technical problem, PTC unit having a PTC characteristic; A first electrode electrically connected to one surface of the PTC unit; a second electrode electrically connected to the other surface of the PTC unit; And a varistor part electrically connecting the first electrode and the second electrode; and an insulating part interposed between the PTC part and the varistor part. The first electrode-varistor part when an overvoltage is applied to both ends of the PTC part. The varistor part is arranged in parallel with the PTC part so that an electric conduction through which current flows to the second electrode is formed.

In the varistor integrated PTC device according to the present invention, the PTC unit is

PTC material layer made of a PTC material; and a metal thin film electrode bonded to opposite surfaces of the PTC material layer and connected to the first electrode and the second electrode.

In the varistor integrated PTC device according to the present invention, the insulating layer is preferably a thermoplastic polymer material or a thermosetting polymer material.

In the varistor integrated PTC device according to the present invention, it is preferable that the insulating layer has an electrical insulating property of 1 to 100 kV / mm.

In the varistor integrated PTC device according to the present invention, it is preferable that the insulating layer has a tensile strength of 50 to 1000 Kg / cm 2.

In the varistor integrated PTC device according to the present invention, the PTC material is preferably made of a mixture of a polymer resin and a conductive material.

In the varistor integrated PTC device according to the present invention, the composition of the polymer resin is preferably 30 to 70 wt% of the total PTC material.

In the varistor integrated PTC device according to the present invention, the PTC portion preferably has a specific resistance of 0.01 to 10? / Cm at room temperature.

In the varistor integrated PTC device according to the present invention, it is preferable that the PTC part has a melting point of 60 to 180 ° C.

In the varistor integrated PTC device according to the present invention, the polymer resin preferably has a heat of fusion of at least 30 J / g or more.

In the varistor integrated PTC device according to the present invention, the varistor portion has a composition of zinc oxide or silicon carbide having a composition of at least 80 wt% or more; and manganese (Mn) oxide, chromium (Cr) oxide, cobalt (Co) oxide, bismuth (Bi) And one or more additives selected from the group consisting of oxides, antimony (Sb) oxides, and mixtures thereof.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

4 is a cross-sectional configuration diagram of a varistor integrated PTC device according to an embodiment of the present invention, and is a cross-sectional configuration diagram of a varistor integrated PTC device having a disk shape.

Referring to FIG. 4, the varistor integrated PTC device according to the present invention is interposed between the PTC unit 10, the varistor unit 12, the PTC unit 10, and the varistor unit 12 to surround the PTC unit 10. An insulating layer 13 and a first electrode 14 and a second electrode 15 provided at both ends of the device to be connected to the circuit to be protected.

The PTC unit 10 is bonded to both surfaces of the PTC material layer 11 and the PTC material layer 11 to be connected to the first electrode 14 and the second electrode 15, respectively. ). The PTC material constituting the PTC material layer 11 has a low resistance value of 0.01 to 10Ω-cm at room temperature, but when connected to a circuit and a current of a predetermined size or more flows, the temperature rises to be several hundred times higher than the initial resistance. As a result, the resistance rises. A substance exhibiting such characteristics is a mixture of a polymer resin such as a thermoplastic resin and a thermosetting resin and a conductive material such as carbon. Preferably, the polymer resin accounts for 30 to 70 wt% of the total PTC material. The polymer resin preferably has a heat of fusion of at least 30 J / g or more, a melting point of 60 ° C. to 180 ° C., and a conductive material of carbon. In addition, the metal thin film electrode 16 is bonded to the PTC material layer 11 to lower the resistance of the PTC material layer 11, and is made of a conductive metal such as copper, lead, gold, or silver.

The varistor material constituting the varistor part 12 is a material whose resistance changes according to an applied voltage, and includes zinc oxide or silicon carbide having a composition of at least 80 wt%, manganese (Mn) oxide, chromium (Cr) oxide, and cobalt. (Co) oxide, bismuth (Bi) oxide, antimony (Sb) oxide and a mixture of any one selected from the group consisting of these. The first electrode 14 and the second electrode 15 are respectively joined to opposing surfaces of the varistor part 12. Therefore, the PTC section 10 and the varistor section 12 are connected in parallel in a circuit.

The insulating layer 13 is interposed between the PTC section 10 and the varistor section 12 to electrically insulate the PTC section 10 and the varistor section 12 and surround the sidewalls of the PTC section 10. Flashover is prevented from occurring between the first electrode 14 and the second electrode 15. The insulating layer 13 is a thermoplastic polymer material or a thermosetting polymer material, and the electrical insulating property is preferably 1 to 100 kV / mm. On the other hand, the PTC unit 10 is expanded when an overcurrent is applied, if the varistor portion 12 of a ceramic material of high hardness wraps around the PTC unit 10 without interposing the insulating layer 13, The varistor part 12 may be broken. Therefore, the material of the insulating layer 13 is an elastic material is used, the tensile strength is preferably 50 ~ 1000Kg / ㎠.

When an overcurrent is applied between the first electrode 14 and the second electrode 15 of the device configured as described above, the circuit is tripped by the resistance increase of the PTC unit 10. When the allowable voltage or more is applied to the PTC unit 11, the varistor 12 connected in parallel with the PTC unit 10 operates to bypass the current, thereby preventing the PTC unit 10 from being damaged by the overvoltage. Detailed operation of the device will be described later.

5 is a cross-sectional configuration diagram of a varistor integrated PTC device according to another embodiment of the present invention, and is a cross-sectional configuration diagram of a varistor integrated PTC device having a disk shape.

Referring to FIG. 5, unlike the embodiment of FIG. 4, the first electrode 14 and the second electrode 15 are joined to only part of opposing surfaces of the PTC unit 10. The insulating layer 13 and the sidewall of the PTC unit 10 and the sidewalls of the first electrode 14 and the second electrode 15 except for both ends of the first electrode 14 and the second electrode 15 are formed. The varistor portions 12 are sequentially surrounded.

Referring to the operation of the varistor integrated PTC device according to an embodiment of the present invention configured as described above are as follows.

Referring to FIG. 6, when a voltage below the operation of the varistor part 12 is applied to the circuit, the varistor part 12 does not allow a current to pass through, and the PTC unit 10 has a small resistance and operates normally so that the current in the circuit is reduced. It flows only through the PTC unit 10.

Referring to FIG. 7, when an abnormality occurs in the circuit and an abnormal overcurrent flows into the PTC unit 10, the resistance of the PTC unit 10 rises and the circuit trips. At this time, since a voltage enough to drive the varistor part 12 is not applied to both ends of the varistor part 12, current does not flow not only in the PTC part 10 but also in the varistor part 12.

Referring to FIG. 8, when the temperature of the PTC unit 10 decreases after the overcurrent is applied and the circuit is cut off, the PTC unit 10 operates normally and a constant current flows into the PTC unit 10. At this time, a high inductance is generated and an overvoltage is applied between the first electrode 14 and the second electrode 15.

Here, the inductance is a factor that changes the voltage according to the current change, and increases or decreases the voltage when the current value changes. Therefore, as shown in FIG. 8, when the interrupted current flows suddenly, an ideal voltage rise is expected by the inductance.

The abnormal overvoltage generated by the sudden inductance protects the PTC unit 10 by driving the varistor unit 12 to pass a current through the varistor unit 12. Although the output terminals of the varistor part 12 and the PTC part 10 are shown in the same figure, it is preferable to ground the varistor part 12 so that a current passing through the varistor part 12 flows to the ground.

After the current flows into the varistor part 12 due to the abnormal overvoltage, when the voltage between the first electrode 14 and the second electrode 15 becomes low and the normal voltage is applied, the varistor part 12 is not driven and the PTC is not driven. Only the unit 10 is operated so that the current of the circuit flows back only to the PTC unit 10.

The technical problem of the present invention is achieved by the above technical configuration, and although the present invention has been described by the limited embodiments and the drawings, the present invention is not limited by this and the general knowledge in the technical field to which the present invention belongs. It is apparent that various modifications and variations can be made by those skilled in the art within the scope of the technical spirit of the present invention and the claims to be described below.

According to the present invention, the PTC device and the varistor device are implemented as one device so that the circuit can be protected by using one device even when overvoltage and overcurrent occur.

According to another aspect of the present invention, by preventing the flashover phenomenon of the PTC device, the PTC device can operate in a stable environment, through the insulating layer between the PTC device and the varistor device connected in parallel to prevent electrical interference, Damage to the varistor due to thermal expansion of the PTC device can be prevented when an overcurrent flows into the PTC device.

Claims (11)

A PTC unit having a PTC characteristic; A first electrode electrically connected to one surface of the PTC unit; A second electrode electrically connected to the other surface of the PTC unit; A varistor unit electrically connecting the first electrode and the second electrode; and And an insulation part interposed between the PTC part and the varistor part. When the overvoltage is applied to both ends of the PTC unit, the varistor unit PTC element is disposed in parallel with the PTC unit such that an electrical conduction current flows to the first electrode, the varistor unit, and the second electrode. . The method of claim 1, The PTC unit, A PTC material layer made of a PTC material; and And a metal thin film electrode bonded to opposite surfaces of the PTC material layer and connected to the first electrode and the second electrode. The method of claim 1, The insulating layer is a varistor integrated PTC device, characterized in that the thermoplastic polymer material or thermosetting polymer material. The method of claim 1, The insulation layer has a varistor integrated PTC device, characterized in that the electrical insulation properties 1 ~ 100kV / mm. The method of claim 1, Varistor integrated PTC device, characterized in that the insulating layer has a tensile strength of 50 ~ 1000Kg / ㎠. The method of claim 2, The PTC material is a varistor integrated PTC device, characterized in that made of a mixture of a polymer resin and a conductive material. The method of claim 6, The composition of the polymer resin is varistor integrated PTC device, characterized in that 30 to 70wt% of the total PTC material. The method of claim 1, The PTC unit has a varistor integrated PTC device, characterized in that the specific resistance is 0.01 ~ 10Ω / cm at room temperature. The method of claim 1, Varistor integrated PTC device, characterized in that the melting point of the PTC portion 60 ~ 180 ℃. The method of claim 6, The polymer resin has a varistor integrated PTC device, characterized in that the value of the heat of fusion is at least 30 J / g or more. The method of claim 1, The varistor unit, Zinc oxide or silicon carbide having a composition of at least 80 wt% or more; and And an additive material selected from the group consisting of manganese (Mn) oxide, chromium (Cr) oxide, cobalt (Co) oxide, bismuth (Bi) oxide, antimony (Sb) oxide, and mixtures thereof. Varistor integrated PTC element.

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