Circuit protection device

Abstract

A circuit protection device is disclosed, comprising: a housing; a first negative temperature coefficient thermistor, which is accommodated in the housing and comprises a first resistance heating element, a pair of electrodes installed on both sides of the first resistance heating element, and a first lead and a second lead respectively led out from the pair of electrodes; a thermal fuse, which is accommodated in the housing and comprises a thermal fuse body and a third lead and a fourth lead respectively connected to both ends of the thermal fuse body; and a second negative temperature coefficient thermistor, which is accommodated in the housing and comprises a second resistance heating element, a pair of electrodes installed on both sides of the second resistance heating element, and a fifth lead and a sixth lead respectively led out from the pair of electrodes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to and the benefit of Korean Patent Application No. 2019-0117006, filed on September 23, 2019, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] The present invention relates to a circuit protection device, and more particularly, to a circuit protection device configured to limit surge current when an electronic product is initially driven and prevent fire caused by an increase in internal temperature or overcurrent. Background Art

[0004] Typically, in the circuits of large electronic products such as air conditioners, washing machines, refrigerators, dryers, etc., a circuit protection device is provided at the power input terminal of the circuit, and protects the power circuit from malfunctions caused by surge currents, increases in internal temperature, continuous overcurrents, etc., which occur when the power is turned on.

[0005] Figure 1A and Figure 1B The components and operation of an existing circuit protection device are shown. The existing circuit protection device includes a fuse resistor RF, a first relay S1 connected in series with the fuse resistor RF, and a second relay S2 connected in parallel with the fuse resistor RF and the first relay S1. The fuse resistor RF includes a resistor R and a thermal fuse F, and the resistor R and the thermal fuse F are connected in series with each other.

[0006] In this circuit protection device, a state (a) in which the first relay S1 is closed and the second relay S2 is open during driving is converted to a state (b) in which the first relay S1 is open and the second relay S2 is closed after a certain time.

[0007] In state (a), the input current passes through the fuse resistor RF and the first relay S1 and is input to the circuit. Here, when the resistor R limits the surge current to a certain current and an overcurrent flows therein, the heat generated by the resistor R is conducted to the thermal fuse F, and the fusion body including the solid lead or polymer particles disposed inside the thermal fuse F is melted to short-circuit the circuit, thereby protecting the circuit of the household appliance. After the surge current disappears and the input current stabilizes for a certain time (e.g., about 0.5 seconds), the circuit protection device changes to state (b), so that a normal input current is input to the circuit via the second relay S2.

[0008] Since the circuit protection device includes three components, namely, the fuse resistor RF and the first relay S1 and the second relay S2, they have a relatively large volume, high cost and occupy a large space. In addition, the normal input current is in the range of 2A to 4A in the case of a washing machine, and is above 7A in the case of a dryer. Therefore, it is necessary to use a high-current relay for the first relay S1 and the second relay S2. Here, since the high-current relay is expensive and there are few domestically commercialized products, most of the high-current relays must be imported from Japan and the like.

[0009] In addition, since the operation of opening or closing the first relay S1 and the second relay S2 is repeatedly performed every time the electronic product is turned on or off, the durability of the electronic product decreases and failure occurs as the electronic product is used for a long time. The failure of the first relay S1 and the second relay S2 may cause the inflow of overcurrent or even cause a fire. Therefore, in the circuit protection device using relays, this risk is always inherent. Summary of the invention

[0010] An object of the present invention is to provide a circuit protection device that can replace a circuit protection device including a fuse resistor RF, a first relay S1, and a second relay S2, and can reduce costs and occupy less space without using relays.

[0011] Aspects of the present invention are not limited to the above-described aspects, and those skilled in the art will understand other undescribed aspects of the present invention from the following description.

[0012] According to one aspect of the present invention, a circuit protection device is provided, which includes: a housing; a first negative temperature coefficient thermistor, which is accommodated in the housing and includes a first resistance heating element, a pair of electrodes installed on both sides of the first resistance heating element, and a first lead and a second lead respectively led from the pair of electrodes; a thermal fuse, which is accommodated in the housing and includes a thermal fuse body and a third lead and a fourth lead respectively connected to both ends of the thermal fuse body; and a second negative temperature coefficient thermistor, which is accommodated in the housing and includes a second resistance heating element, a pair of electrodes installed on both sides of the second resistance heating element, and a fifth lead and a sixth lead respectively led from the pair of electrodes. Here, the second lead and the third lead are connected to each other in the housing, and the fourth lead and the fifth lead are connected to each other.

[0013] The circuit protection device may further include a first pin connected to the first lead and a second pin connected to the sixth lead. Here, a first guide groove and a second guide groove may be formed in the housing, the first guide groove being configured to guide the first pin to be led outward from the housing, and the second guide groove being configured to guide the second pin to be led outward from the housing.

[0014] The first pin may include a plate-shaped body having one side connected to the first lead, the second pin may include a plate-shaped body having one side connected to the sixth lead, and the first pin and the second pin each include at least one extension portion extending from the other side of the body and having a width smaller than a width of the body.

[0015] The body of the first pin may include a first portion connected to the first lead at one side and inserted into the first guide groove, the body of the second pin may include a first portion connected to the sixth lead at one side and inserted into the second guide groove, and the bodies of the first pin and the second pin respectively include a second portion extending from the other side of the first portion and having a width greater than that of the first portion and leading outward from the housing.

[0016] The housing may include a partition wall extending from an inner wall of the housing and disposed between the thermal fuse body, the first resistance heating element, and the second resistance heating element.

[0017] The circuit protection device may include a first cable and a second cable, one end of the first cable is connected to the first lead, and one end of the second cable is connected to the sixth lead. Here, a first guide groove and a second guide groove may be formed in the housing, the first guide groove is configured to guide the first cable to be led out of the housing, and the second guide groove is configured to guide the second cable to be led out of the housing. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The above and other objects, features and advantages of the present disclosure will become more apparent to those skilled in the art by describing in detail exemplary embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0019] Figure 1A and Figure 1B The components and operation of a conventional circuit protection device are shown;

[0020] Figure 2 is a perspective view of a circuit protection device according to a first embodiment of the present invention;

[0021] Figure 3A and Figure 3B2 is a cross-sectional view showing the first negative temperature coefficient thermistor 20 taken along lines AA and BB, respectively;

[0022] Figure 4A and Figure 4B 2 is a cross-sectional view showing the second negative temperature coefficient thermistor 40 taken along lines CC and DD, respectively;

[0023] Figure 5 The housing 10 is shown as receiving Figure 2 A perspective view of the negative temperature coefficient thermistor 20 and 40, the thermal fuse 30, etc., which are then filled with filler;

[0024] Figure 6 1. A circuit protection device according to a first embodiment of the present invention is shown as being mounted on a circuit board;

[0025] Figure 7 is a perspective view of a circuit protection device according to a second embodiment of the present invention;

[0026] Figure 8 The housing 10 is shown as receiving Figure 7 2 is a perspective view of a state where the negative temperature coefficient thermistors 20 and 40, the thermal fuse 30, etc. are then filled with a filler. DETAILED DESCRIPTION

[0027] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Hereinafter, throughout the specification and the accompanying drawings, substantially the same elements will be represented by the same reference numerals, and repeated descriptions thereof will be omitted. In addition, in the description of the embodiments of the present invention, when it is considered that a detailed description of a known function or component of the prior art will obscure the understanding of the embodiments of the present invention, such detailed description will be omitted.

[0028] Figures 2 to 5 1 is a view showing components of a circuit protection device according to a first embodiment of the present invention. Figure 2 is a perspective view of a circuit protection device according to a first embodiment. Figure 3A and Figure 3B 2 are cross-sectional views showing the first negative temperature coefficient thermistor 20 taken along lines AA and BB, respectively. Figure 4A and Figure 4B 2 are cross-sectional views showing the second negative temperature coefficient thermistor 40 taken along lines CC and DD, respectively. Figure 5 The housing 10 is shown as receiving Figure 2 2 is a perspective view of a state where the negative temperature coefficient thermistors 20 and 40, the thermal fuse 30, etc. are then filled with a filler.

[0029] The circuit protection device according to the first embodiment of the present invention includes a housing 10 , a first negative temperature coefficient thermistor 20 , a thermal fuse 30 , a second negative temperature coefficient thermistor 40 , a first pin 50_1 , and a second pin 50_2 .

[0030] The housing 10 includes, for example, a ceramic material, and includes a side wall 11 and a front wall 12, a rear wall 13, and a bottom wall 14, thereby forming a receiving groove with an open top, in which the first negative temperature coefficient thermistor 20, the thermal fuse 30, and the second negative temperature coefficient thermistor 40 are received. A first guide groove 15_1 and a second guide groove 15_2 are formed on the rear wall 13 to guide the first pin 50_1 and the second pin 50_2 to be led out of the housing 10, respectively.

[0031] like Figures 2 to 3B As shown in the figure, the first negative temperature coefficient thermistor 20 includes a first resistance heating element 21, a pair of electrodes 22 and 23 installed on both sides of the first resistance heating element 21, and a first lead 25 and a second lead 26 respectively led out from the pair of electrodes 22 and 23, both of which are coated with a coating material 24.

[0032] Thermistor is a resistor element with a thermal resistance value that changes sensitively, and in particular has a characteristic that the resistance value changes according to the change of its temperature or ambient temperature. Among such thermistors, thermistors with a negative temperature coefficient are called negative temperature coefficient thermistors. Negative temperature coefficient thermistors have a resistance value that decreases according to the increase of its temperature or ambient temperature.

[0033] The thermal fuse 30 includes a thermal fuse body 31 and a third lead 32 and a fourth lead 33 respectively connected to both ends of the thermal fuse body 31. Generally, the thermal fuse body 31 includes an insulating ceramic rod having a certain length and a fusion body, and the third lead 32 and the fourth lead 33 can be connected to conductive covers respectively installed at both ends of the ceramic rod.

[0034] like Figure 2 , Figure 4A and Figure 4B As shown in the figure, the second negative temperature coefficient thermistor 40 includes a second resistance heating element 41, a pair of electrodes 42 and 43 installed on both sides of the second resistance heating element 41, and a fifth lead 45 and a sixth lead 46 respectively led out from the pair of electrodes 42 and 43, all of which are coated with a coating material 44.

[0035] like Figure 2As shown in , the second lead 26 of the first negative temperature coefficient thermistor 20 and the third lead 32 of the thermal fuse body 30 are connected to each other. The second lead 26 can be bent and extended to be connectable to the third lead 32 of the thermal fuse 30. In addition, the fourth lead 33 of the thermal fuse 30 and the fifth lead 45 of the second negative temperature coefficient thermistor 40 are connected to each other. The fifth lead 45 can be bent and extended to be connectable to the fourth lead 33. The connection between the second lead 26 and the third lead 32 and the connection between the fourth lead 33 and the fifth lead 45 can also be performed by welding, arc welding, spot welding, laser welding, clamping, etc.

[0036] At the same time, a first pin 50_1 and a second pin 50_2 are provided as conductive materials and connected to the circuit board to perform electrical connection between the circuit and the circuit protection device. One end of the first pin 50_1 is connected to the first lead 25 of the first negative temperature coefficient thermistor 20 in the housing 10, and extends through the first guide groove 15_1 so that the other end thereof is led outward from the housing 10. One end of the second pin 50_2 is connected to the sixth lead 46 of the second negative temperature coefficient thermistor 40 in the housing 10, and extends through the second guide groove 15_2 so that the other end thereof is led outward from the housing 10.

[0037] In this embodiment of the present invention, when the circuit protection device is mounted on a circuit board, the first pin 50_1 and the second pin 50_2 perform the functions of making an electrical connection between the circuit and the circuit protection device, dissipating the heat generated by the circuit protection device, and separating the housing 10 from the circuit board by a certain interval.

[0038] The first pin 50_1 and the second pin 50_2 may include plate-shaped bodies 51_1 and 51_2 and extensions 52_1 and 52_2 extending from the bodies 51_1 and 51_2 and having a width smaller than that of the bodies 51_1 and 51_2. Generally, the extensions 52_1 and 52_2 are portions that are inserted into holes of a circuit board and are soldered to perform electrical connection, and the bodies 51_1 and 51_2 are portions that are configured to dissipate heat and space the housing 10 from the circuit board at a certain interval.

[0039] In detail, the first pin 50_1 may include a body 51_1 and an extension 52_1, one side of the body 51_1 is connected to the first lead 25, and the extension 52_1 extends from the other side of the body 51_1, and the width is smaller than the width of the body 51_1. The second pin 50_2 may include a body 51_2 and an extension 52_2, one side of the body 51_2 is connected to the sixth lead 46, and the extension 52_2 extends from the other side of the body 51_2, and the width is smaller than the width of the body 51_2. The first lead 25, the sixth lead 46, and the bodies 51_1 and 51_2 may be connected by welding, arc welding, spot welding, laser welding, clamping, etc.

[0040] Moreover, the main bodies 51_1 and 51_2 may include first portions 51a_1 and 51a_2 having relatively small widths and second portions 51b_1 and 51b_2 having relatively large widths. Typically, the first portions 51a_1 and 51a_2 are portions connected to the leads 25 and 46 and inserted into the guide grooves 15_1 and 15_2, while the second portions 51b_1 and 51b_2 are portions that are led outward from the housing 10 to space the housing 10 from the circuit board by a certain interval. In addition, the second portions 51b_1 and 51b_2 may each include one or more protrusions 51c that improve heat dissipation performance.

[0041] Specifically, the body 51_1 of the first pin 50_1 includes a first portion 51a_1 and a second portion 51b_1, one side of the first portion 51a_1 is connected to the first lead 25 and inserted into the first guide groove 15_1, and the second portion 51b_1 extends from the other side of the first portion 51a_1, has a width greater than the width of the first portion 52a_1, and is led outward from the housing 10. The body 51_2 of the second pin 50_2 includes a first portion 51a_2 and a second portion 51b_2, one side of the first portion 51a_2 is connected to the sixth lead 46 and inserted into the second guide groove 15_2, and the second portion 51b_2 extends from the other side of the first portion 51a_2, has a width greater than the width of the first portion 51a_2, and is led outward from the housing 10.

[0042] Meanwhile, since the negative temperature coefficient thermistors 20 and 40 and the thermal fuse 30 are arranged adjacent to each other in the sealed space inside the housing 10, so that the temperature of the circuit protection device or its ambient temperature increases, the thermal fuse 30 that should not be short-circuited may be short-circuited due to the heating of the negative temperature coefficient thermistors 20 and 40. Therefore, a partition wall 16 may be installed between the thermal fuse body 31 and the resistance heating elements 21 and 41 of the negative temperature coefficient thermistors 20 and 40, so as to maintain a certain interval or more between the thermal fuse body 31 and the resistance heating elements 21 and 41. The partition wall 16 may extend from the inner wall (e.g., the rear wall 13) of the housing 10. The partition wall 16 is installed so as not to completely separate the space accommodating the resistance heating elements 21 and 41 from the space accommodating the thermal fuse body 31, thereby forming a path through which the second lead 26 and the third lead 32 extend, and forming a path through which the fourth lead 33 and the fifth lead 45 extend. In one embodiment, the partition wall 16 may include a first partition wall 16 a extending from the rear wall 13 and a second partition wall 16 b extending in both directions from one end of the first partition wall 16 a , the width of the second partition wall 16 b substantially corresponding to the length of the thermal fuse body 31 .

[0043] Reference Figure 5 , the housing 10 is filled with a filler 80 while accommodating the negative temperature coefficient thermistors 20 and 40, the thermal fuse 30, etc. The filler 80 not only supports the negative temperature coefficient thermistors 20 and 40 and the thermal fuse 30 in the accommodating groove, but also enables heat to be effectively dissipated from the negative temperature coefficient thermistors 20 and 40 and the thermal fuse 30. Therefore, the filler 80 may include a material having high heat dissipation properties.

[0044] Figure 6 A state in which the circuit protection device according to the first embodiment of the present invention is mounted on a circuit board P is shown.

[0045] Reference Figure 6 , the extension 52 of the pin 50 of the circuit protection device is inserted to pass through the hole H formed in the circuit board P and is soldered, so that the circuit protection device is fixed to the circuit board P and electrically connected to the circuit on the circuit board P. Therefore, the length d2 of the extension 52 is formed to be greater than the thickness dP of the circuit board P.

[0046] Meanwhile, in the case of an electronic product such as a washing machine or a dryer to which water is supplied or from which water is generated, the circuit board P includes a molded portion M having a waterproof material such as polyurethane to protect the circuit board P from water. Since the molded portion M is relatively heat-resistant, when the heat generated from the circuit protection device is directly transferred to the molded portion M, the molded portion M may melt and its waterproof performance may deteriorate. Therefore, it is necessary to install the housing 10 of the circuit protection device to be separated from the circuit board P or the molded portion M by a certain interval. In the pin 50, the second part 51b of the main body 51 led outward from the housing 10 of the circuit protection device is installed so that the housing 10 is separated from the circuit board P or the molded portion M by a certain interval. The housing 10 is separated from the circuit board P by a height d1 of the second part 51b. When the thickness of the molded portion M is expressed as dM, the housing 10 and the molded portion M are separated by an interval of d1-dM. Therefore, d1 may be greater than dM. In addition, the molded portion M diffuses the heat from the circuit protection device to assist in heat dissipation.

[0047] Figure 7 and Figure 8 2 is a view showing components of a circuit protection device according to a second embodiment of the present invention. Figure 7 is a perspective view of a circuit protection device according to a second embodiment. Figure 8 The housing 10 is shown as receiving Figure 7 2 is a perspective view of a state where the negative temperature coefficient thermistors 20 and 40, the thermal fuse 30, etc. are then filled with a filler.

[0048] In the second embodiment, compared with the first embodiment, the first pin 50_1 and the second pin 50_2 are replaced by the first cable 60_1 and the second cable 60_2, respectively. That is, in the second embodiment, the circuit protection device is implemented not to be directly mounted on the circuit board, but to be mounted separately from the circuit board, and connected to the corresponding terminals of the circuit board using the first cable 60_1 and the second cable 60_2. For convenience, in the second embodiment, redundant descriptions overlapping with the first embodiment will be omitted.

[0049] The first cable 60_1 and the second cable 60_2 include wires 61_1 and 61_2 and coatings 62_1 and 62_2 covering the wires 61_1 and 61_2, respectively. The first cable 60_1 and the second cable 60_2 may be harness cables.

[0050] One end of the wire 61_1 of the first cable 60_1 is connected to the first lead 25 of the first negative temperature coefficient thermistor 20 in the housing 10, and extends through the first guide slot 15_1, so that the other end thereof is led outward from the housing 10. One end of the wire 61_2 of the second cable 60_2 is connected to the sixth lead 46 of the second negative temperature coefficient thermistor 40 in the housing 10, and extends through the second guide slot 15_2, so that the other end thereof is led outward from the housing 10.

[0051] Since the circuit protection device according to the second embodiment is mounted separately from the circuit board, there is an advantage that heat generated at the circuit protection device is not transferred to the circuit board.

[0052] According to an embodiment of the present invention, since the resistance value of the negative temperature coefficient thermistors 20 and 40 is large at room temperature or a relatively low temperature, and decreases as its temperature or ambient temperature increases, a large resistance value is used to limit the surge current to a certain current when driving, and a resistance value that decreases due to temperature increase is used to maintain a normal input current after a certain time. At the same time, when the negative temperature coefficient thermistors 20 and 40 are overheated due to an abnormal phenomenon in the circuit or an abnormal increase in ambient temperature, the thermal fuse 30 short-circuits and cuts off the inflow of current to prevent fire. Therefore, the circuit protection device according to the embodiment can replace Figure 1A and Figure 1B In addition, since the negative temperature coefficient thermistors 20 and 40 have a relatively small volume and are relatively cheap compared to large current relays, the cost of the circuit protection device can be reduced and the space occupied can be reduced. Moreover, since no relay is used, the risk factor caused by the failure of the relay can be fundamentally eliminated.

[0053] The circuit protection device according to the present invention can replace the circuit protection device including the fuse resistor RF, the first relay S1 and the second relay S2. Since the circuit protection device includes the negative temperature coefficient thermistor and the thermal fuse, which are relatively low in price, the cost can be reduced. Compared with the relay, the negative temperature coefficient thermistor and the thermal fuse have a small volume and occupy less space. In addition, since the relay is not used, the risk of overcurrent or fire caused by the failure of the relay can be fundamentally eliminated.

[0054] Exemplary embodiments of the present invention have been described above. It will be appreciated by those skilled in the art that the present invention may be implemented in a modified form without departing from the basic features of the present invention. Therefore, the disclosed embodiments should not be considered restrictive, but descriptive. The scope of the present invention will be shown in the claims rather than in the above description, and all differences within the equivalent scope of the claims should be interpreted as included in the present invention.

Claims

1. A circuit protection device, comprising: case; a first negative temperature coefficient thermistor accommodated in the housing and comprising a first resistance heating element, a pair of electrodes mounted on both sides of the first resistance heating element, and a first lead and a second lead respectively led from the pair of electrodes; a thermal fuse accommodated in the housing and including a thermal fuse body and third and fourth leads respectively connected to both ends of the thermal fuse body; and a second negative temperature coefficient thermistor housed in the housing and comprising a second resistance heating element, a pair of electrodes mounted on both sides of the second resistance heating element, and a fifth lead and a sixth lead respectively led from the pair of electrodes, wherein the second lead and the third lead are connected to each other, and the fourth lead and the fifth lead are connected to each other in the housing, wherein the housing includes a partition wall extending from an inner wall of the housing and disposed between the thermal fuse body, the first resistance heating element, and the second resistance heating element, and The partition wall includes a first partition wall extending from a rear wall of the housing, and a second partition wall extending from one end of the first partition wall in two directions and having a width corresponding to a length of the thermal fuse body.

2. The circuit protection device according to claim 1, further comprising: a first pin connected to the first lead; as well as The second pin is connected to the sixth lead, A first guide groove and a second guide groove are formed in the housing, wherein the first guide groove is configured to guide the first pin to be led out of the housing, and the second guide groove is configured to guide the second pin to be led out of the housing.

3. The circuit protection device according to claim 2, wherein the first pin includes a plate-shaped body connected to the first lead on one side, the second pin includes a plate-shaped body connected to the sixth lead on one side, and the first pin and the second pin each include at least one extension portion extending from the other side of the body and having a width less than the width of the body.

4. A circuit protection device according to claim 3, wherein the body of the first pin includes a first part connected to the first lead on one side and inserted into the first guide groove, the body of the second pin includes a first part connected to the sixth lead on one side and inserted into the second guide groove, and the bodies of the first pin and the second pin respectively include a second part extending from the other side of the first part and having a width greater than the width of the first part and leading outward from the housing.

5. The circuit protection device according to claim 1, further comprising: a first cable having one end connected to the first lead; as well as a second cable, one end of which is connected to the sixth lead, A first guide groove and a second guide groove are formed in the housing, wherein the first guide groove is configured to guide the first cable to be led out of the housing, and the second guide groove is configured to guide the second cable to be led out of the housing.

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