Patent Application
20140211355
The present invention relates to a surge protector, more particularly to a surge protector applicable to a power supply circuit of an electronic device and having a dielectric material in contact with two conductive plates by two corresponding side surfaces thereof respectively, which not only allows a shock current to pass through the dielectric material evenly for effectively reducing the damage that the shock current may cause to the dielectric material, but also can dissipates heat from the dielectric material both rapidly and evenly through the two conductive plates for significantly slowing the rise of temperature. In addition, the surge protector further includes a temperature-actuated metal plate having a temperature-actuated portion which lies against one of the two conductive plates when in a low-temperature state and will curve toward the spare space when in a high-temperature state and separate from the conductive plate, such that the tripping of the temperature-actuated portion effectively controls the temperature of the surge protector by opening the circuit through the surge protector under high heat. Consequently, the dielectric material is kept from rapid aging which may otherwise result from heat accumulation.
With the advanced development of microelectronic technology, electronic devices have been more and more sophisticated in design. To ensure normal operation of such electronic devices, the industry has endeavored to prevent damages attributable to surges flowing through the circuits of these devices.
Surges, also known as voltage (or current) spikes, can be generally divided by source into those generated outside a circuit and those generated within a circuit. The former is mostly the result of lightning taking place around or directly striking a circuit and is hence called lightning surges. The latter often accompanies the switching of an electronic switch in a circuit and is therefore also referred to as switching surges.
If an electronic device is provided with a control element such as a relay, a switch, or a solenoid, the control element is very likely to be turned on and off a great number of times during operation of the device, thereby generating a lot of surges, which may have undesirable effects on the circuits of the electronic device and give rise to false actions. One conventional solution is to install a surge protector in the power supply circuit of the electronic device, wherein the surge protector forms a discharge path upon occurrence of a surge and can guide the surge to a grounding end of the circuit, thus protecting the electronic device from damage which may otherwise result from the surge.
Metal oxide varistors (MOVs) are dielectric elements traditionally used in surge protectors. The most common MOVs are polycrystalline semiconductor ceramic elements made by sintering zinc oxide grains with a small amount of other metal oxides or polymers. Within such an MOV, the boundaries between the zinc oxide grains and the other metal oxides adjacent to the zinc oxide grains form boundary layers where diode effects occur. As an MOV contains a vast amount of disorderly zinc oxide grains, the entire MOV is equivalent to an aggregate of a large number of diodes connected back to back. When the MOV is subjected to a low voltage, only a small reverse leak current flows through the MOV, but when a high voltage is applied to the MOV, the punch-through effect takes place, causing the large current of the high voltage to pass through the MOV. The reason why MOVs are extensively used in making surge protectors lies in their non-linear current-voltage characteristic curves, in which electrical resistance is high under a low voltage and low under a high voltage.
While surge discharge can be achieved using surge protectors made of MOVs, thanks to the non-linear current-voltage characteristic attributable to the boundary layers of the zinc oxide grains, a long-term observation by the inventor of the present invention, however, reveals the various design drawbacks of the conventional surge protectors. First of all, as the wires and MOVs of a conventional surge protector are connected via “line contact”, the limited areas at the fixed connection regions between the MOVs and the wires result in an extremely high voltage and current per unit area, which tends to cause breakage of the physical connections. Moreover, due to the extremely high voltage and current that the MOVs have to withstand per unit area, a strong transient overvoltage may pass through the MOVs and form through holes in the resistors such that an even larger current runs through the resistors in an instant, causing high heat or fire, the phenomenon being known as “transient overvoltage damage”. Apart from that, research results show that an MOV which has undergone the impact of large currents many times tends to age prematurely even if no transient breakup or fire occurs, and premature aging will eventually lead to linearization of the low resistance range and formation of weak points. Once a large leak current flows to the weak points in a concentrated manner, the weak points may melt and become short-circuit holes. Should a large current gush into the short-circuit holes, high heat and consequently fire will occur.
According to the above description, the conventional surge protectors are so designed that, after multiple instances of passing relatively high-voltage currents (e.g., switching surges) or extremely high-voltage currents (e.g., lightning surges), their wires or MOV plates may be irrevocably damaged. Not only may the MOVs themselves age rapidly during use, but also the fixed connection regions between the MOVs and the wires may break such that the surge discharge function is totally lost.
As far as ordinary consumers are concerned, the more sophisticated and expensive an electronic device is, the more emphasis tends to be placed on its surge protection function, with the purpose of preventing losses associated with any damage of the electronic device. Most consumers believe that the surge protector in an electronic device can provide complete protection for the device; however, the aforesaid drawbacks of the conventional surge protectors make long-term overvoltage protection impossible. When the MOVs become aged or when the fixed connections between the MOVs and the wires are broken, the surge protector fails to discharge surges. If another surge strikes now, the sophisticated and expensive electronic device to be protected by the surge protector will be severely damaged, causing a huge property loss. Furthermore, as the design of the conventional surge protectors cannot protect the MOVs from high heat, the MOVs may burn under high heat, increasing the risk of fire.
Hence, the issue to be addressed by the present invention is to design a surge protector capable of discharging surges repeatedly so that the surge protector will not fail as would the conventional ones with broken or burned MOVs. Thus, an electronic device equipped with the surge protector will be effectively kept from damage resulting from surges.
In view of the aforesaid shortcomings of the conventional surge protectors, the inventor of the present invention incorporated years of practical experience in the related industry into designing and repeated experiments and finally succeeded in developing a surge protector as disclosed herein. The present invention is intended to substantially increase the durability of a surge protector and thereby effectively enhance the safety of electronic devices during use.
It is an object of the present invention to provide a surge protector which includes an insulating base, a dielectric material, a first conductive plate, a second conductive plate, and a temperature-actuated metal plate. The insulating base defines therein a receiving space and a spare space. The dielectric material is a polycrystalline semiconductor ceramic element containing zinc oxide and is provided in the receiving space. The first conductive plate is enclosed in the insulating base and is attached to one side of the dielectric material by surface contact. The portion of the first conductive plate that extends out of the insulating base forms a first pin. The second conductive plate is also enclosed in the insulating base and has a first side attached to the other side of the dielectric material by surface contact. The temperature-actuated metal plate is enclosed in the insulating base, too, and the portion of the temperature-actuated metal plate that extends out of the insulating base forms a second pin. The temperature-actuated metal plate has a first side corresponding in position to the other side (hereinafter the second side) of the second conductive plate, and a second side of the temperature-actuated metal plate corresponds in position to the spare space in the insulating base. The temperature-actuated metal plate has a temperature-actuated portion which lies against the second side of the second conductive plate when in a low-temperature state. When in a high-temperature state, however, the temperature-actuated portion curves toward the spare space and thus separates from the second conductive plate. As the first conductive plate and the second conductive plate are respectively attached to the two corresponding sides of the dielectric material by surface contact, the surge protector not only allows a shock current flowing therethrough to pass through the dielectric material evenly for effectively reducing the damage that the shock current may cause to the dielectric material, but also can dissipate heat from the dielectric material both rapidly and evenly through the first conductive plate and the second conductive plate for significantly slowing the rise of temperature. Besides, the tripping of the temperature-actuated portion effectively controls the temperature of the surge protector by opening the circuit through the surge protector under high heat. Consequently, the dielectric material is kept from rapid aging which may otherwise result from heat accumulation.
The structure as well as further objects and advantages of the present invention will be best understood by referring to the following detailed description of some illustrative embodiments in conjunction with the accompanying drawings, in which:
The present invention discloses a surge protector applicable to the power supply circuit of an electronic device. Referring to
The first conductive plate 13 is enclosed in the insulating base 11. In this preferred embodiment, the first conductive plate 13 is located between the first housing A and the inner frame C and is attached to one side of the dielectric material 12 (hereinafter referred to as the first side of the dielectric material 12) by surface contact. The first conductive plate 13 has a portion which extends out of the insulating base 11 to form a first pin 131, allowing the surge protector 1 to electrically connect with a circuit. The second conductive plate 14 is also enclosed in the insulating base 11 and has one side (hereinafter referred to as the first side of the second conductive plate 14) attached to the other side of the dielectric material 12 (hereinafter referred to as the second side of the dielectric material 12) by surface contact. In the first preferred embodiment, both the second conductive plate 14 and the dielectric material 12 are provided in the receiving space 111, and the inner frame C has an inner periphery which corresponds in position to the receiving space 111 and whose one side is adjacent to the second housing B and protrudingly provided with a flange C1. Once the second conductive plate 14 and the dielectric material 12 are sequentially disposed in the receiving space 111, the other side of the second conductive plate 14 (hereinafter referred to as the second side of the second conductive plate 14) is pressed against the flange C1 and is restricted in the receiving space 111 by the flange C1. Meanwhile, the dielectric material 12 is pressed against the first side of the second conductive plate 14 and is restricted in the receiving space 111 by the second conductive plate 14. The foregoing is merely one preferred embodiment of the present invention. In particular, although the flange C1 in the first preferred embodiment is provided continuously along and around the inner periphery of the inner frame C and corresponds in position to the receiving space 111, the present invention is not limited to such a configuration. For example, the flange C1 may be designed as a plurality of spaced-apart projections instead, and these projections as a whole serve as the flange C1. In addition, the arrangement of the second conductive plate 14 may be changed such that the second conductive plate 14 is directly embedded in the inner frame C by insert molding. All equivalent alterations or modifications which are based on the disclosure of the present invention and readily conceivable by a person skilled in the art should fall within the scope of the present invention.
Referring to
In the first preferred embodiment, the two corresponding sides of the dielectric material 12 are respectively attached to the first conducive plate 13 and the second conductive plate 14 by surface contact. Hence, heat can be rapidly and evenly guided away from the dielectric material 12 through the first conductive plate 13 and the second conductive plate 14 to achieve optimal heat dissipation. However, the present invention is not limited to the foregoing design. For instance, the surge protector 1 may be so designed as to dispense with the second conductive plate 14. In that case, the spacing between the temperature-actuated metal plate 15 and the dielectric material 12 should be adjusted as appropriate, allowing the temperature-actuated portion 152 to lie against the second side of the dielectric material 12 in a low-temperature (i.e., lower than the threshold temperature) state and to separate from the dielectric material 12 in a high-temperature (i.e., higher than the threshold temperature) state. While the omission of the second conductive plate 14 compromises heat dissipation efficiency of the surge protector 1, structural complexity is effectively reduced, and material and assembly costs can be lowered. As the temperature-actuated metal plate 15 can still automatically cut off the current path through the surge protector 1 when the temperature of the surge protector 1 becomes too high, the intended effect of preventing heat accumulation is retained.
It can be known from the above that the surface-contact attachment of the first conductive plate 13 and the second conductive plate 14 to the two corresponding sides of the dielectric material 12 not only allows a current through the surge protector 1 to be evenly distributed over the dielectric material 12, but also keeps the dielectric material 12 from passing a shock current through a single point. Moreover, the first conductive plate 13 and the second conductive plate 14 can rapidly dissipate heat from the dielectric material 12, and the tripping of the temperature-actuated portion 152 can effectively control the temperature of the surge protector 1 by opening the circuit of the surge protector 1 in a high-temperature state, thus avoiding heat accumulation and hence premature aging of the dielectric material 12. In other word, the surge protector 1 of the present invention solves the aforementioned problems of the conventional surge protectors, which mainly include failure to discharge surges because the MOVs are broken or burned. As stated previously, such failure may cause damage to the electronic devices being protected, and the burning of the MOVs may cause fire. The surge protector 1 of the present invention, on the other hand, features a long service life and is greatly enhanced in safety.
Please refer to
With continued reference to
When the surge protector 2 of the second preferred embodiment is applied to the power supply circuit of an electronic device, the pins of the first temperature-actuated metal plate 241 and second temperature-actuated metal plate 242 are respectively connected to a grounding circuit, and the first conductive plate 23a and the second conductive plate 23b are respectively connected to the live line and the zero line (also known as the neutral line) of the power supply circuit. Thus, when a surge occurs, the shock current of the surge will flow through the first temperature-actuated metal plate 241 or the second temperature-actuated metal plate 242 of the surge protector 2 and be guided to the grounding circuit to protect the electronic device from damage by the surge. In the second preferred embodiment, when one of the first dielectric material 22a and the second dielectric material 22b has a higher temperature than the other such that the temperature of the first temperature-actuated metal plate 241 or the second temperature-actuated metal plate 242 exceeds the threshold temperature, the corresponding first temperature-actuated portion 24a or second temperature-actuated portion 24b will trip and therefore no more press against the first dielectric material 22a or the second dielectric material 22b. Meanwhile, however, the surge in the circuit can still be discharged to the grounding circuit via the first temperature-actuated metal plate 241 or the second temperature-actuated metal plate 242 that has not tripped. In other words, the surge protector 2 of the second preferred embodiment is so designed that, while the first temperature-actuated metal plate 241 and the second temperature-actuated metal plate 242 protect the first dielectric material 22a and the second dielectric material 22b from damage, the electronic device intended to be protected is also under protection because the surge discharge function will not be temporarily lost during the time when the temperature of the first temperature-actuated metal plate 241 or the second temperature-actuated metal plate 242 has yet to fall below the threshold temperature.
Referring to
While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope of the invention set forth in the claims
| Number | Date | Country | Kind |
|---|---|---|---|
| 102103470 | Jan 2013 | TW | national |
