The present application relates to a protection device. More specifically, it relates to a protection device capable of preventing over-voltage, over-current and/or over-temperature.
Fuses containing low-melting metals, e.g., lead, tin or antimony, are well-known protection devices to cut off currents. To prevent over-current and over-voltage, various protection devices are continuously developed. For example, a device containing a substrate on which a heating layer and a low-melting metal layer are stacked in sequence. The heating layer heats up in the event of over-voltage, and then the heat is transferred upwards to the low-melting metal layer. As a result, the low-melting metal layer is melted and blown to sever currents flowing therethrough, so as to protect circuits or electronic apparatuses.
Recently, mobile apparatuses such as cellular phones and laptop computers are widely used, and people increasingly rely on such products over time. However, burnout or explosion of batteries of cellular phones or portable products during charging or discharging is often seen. Therefore, the manufacturers continuously improve the designs of over-current and over-voltage protection devices to prevent the batteries from being blown due to over-current or over-voltage during charging or discharging.
In a known protection device, the low-melting metal layer is in series connection to a power line of a battery, and the low-melting metal layer and a heating layer are electrically coupled to a switch and an integrated circuit (IC) device. When the IC device detects an over-voltage event, the IC device enables the switch to “on”. As a result, current flows through the heating layer to generate heat to melt and blow the low-melting metal layer, so as to sever the power line to the battery for over-voltage protection. Moreover, it can be easily understood that the low-melting metal layer, e.g., fuses, can be heated and blown by a large amount of current in the event of over-current, and therefore over-current protection can be achieved also.
To obtain a short blowing time of the low-melting metal layer 140 of the protection device 100, the heating element 120 may use a large heating power and have a low resistance to acquire a large current. However, the heating element 120 of a certain resistance has a corresponding adequate endurable voltage. The heating element 120 of a low resistance has a low endurable voltage and may be blown if undergoing a high voltage. It is desirable to increase voltage endurance and enlarge voltage application range of the protection device.
The present application provides a protection device for over-current, over-voltage and/or over-temperature protection. The protection device comprises at least two heating elements of different resistances. To adapt to an applying voltage, either one of the heating elements can be automatically activated to heat the fusible element, thereby increasing the voltage endurance and enlarging voltage application range.
In accordance with an embodiment of the present application, a protection device comprises a first planar substrate, a second planar substrate, a heater and a fusible element. The first planar substrate comprises a first surface, and the second planar substrate comprises a second surface facing the first surface. The heater comprises a first heating element and a second heating element connected in parallel. The first heating element is disposed on the first surface. The fusible element is disposed on the first surface and is adjacent to the first heating element and the second heating element to absorb the heat generated by at least one of the first and second heating elements and thereby be melted. The resistance of the second heating element is at least twice that of the first heating element.
In an embodiment, the first heating element is blown and a current flowing therethrough is cut off when a voltage applied to the protection device exceeds a predetermined voltage.
In an embodiment, when the voltage is smaller than the predetermined voltage, the first heating element heats up to heat the fusible element. When the voltage is larger than the predetermined voltage, the second heating element heats up to heat the fusible element.
In an embodiment, the second heating element is disposed on the second surface and the fusible element is disposed between the first heating element and the second heating element.
In an embodiment, the fusible element has two ends connecting to a first electrode and a second electrode. The first heating element has two ends connecting to a third electrode and a fourth electrode. The second heating element has two ends connecting to a fifth electrode and a six electrode.
In an embodiment, the third electrode and the fifth electrode are electrically coupled through conductive posts, and the fourth electrode and the sixth electrode are electrically coupled through other conductive posts.
In an embodiment, the fusible element has two ends connecting to a first terminal and a second terminal, and the middle of the fusible element connects to a central electrode. The heater has two ends connecting to the central electrode and a third terminal.
In an embodiment, an absorbent element is disposed above the middle of the fusible element to absorb molten fusible element.
In an embodiment, the first heating element is printed on the first surface, and the second heating element is printed on the second surface.
In an embodiment, the protection device further comprises a third heating element in parallel connection to the first and second heating elements.
In an embodiment, the third heating element and the first heating element are formed on a same plane.
In an embodiment, the resistance of the second heating element does not exceed 12 times the resistance of the first heating element.
In the protection device of the present application, the resistance of the second heating element is at least twice that of the first heating element. For a low voltage, most of current flows through the first heating element of a low resistance and the first heating element heats up to heat the fusible element. When the voltage exceeds a predetermined voltage, the first heating element cannot withstand it and therefore is blown to cut off the current flowing therethrough. The current is switched to the second heating element in parallel connection with the first heating element, and then the second heating element heats up to blow the fusible element. The second heating element of a larger resistance can withstand a higher voltage in comparison with the first heating element. According to different applying voltages, the protection device can automatically select the first or second heating element to heat and blow the fusible element. It is advantageous to increase voltage endurance and enlarge voltage application range of the protection device.
The present application will be described according to the appended drawings in which:
The making and using of the presently preferred illustrative embodiments are discussed in detail below. It should be appreciated, however, that the present application provides many applicable inventive concepts that can be embodied in a wide variety of specific contexts. The specific illustrative embodiments discussed are merely illustrative of specific ways to make and use the invention, and do not limit the scope of the invention.
In the above embodiment, the first heating element 33 and the second heating element 25 connect to electrodes at elongated ends. However, electrodes may connect to lateral sides of the first heating element 33 and the second heating element 25 to obtain different resistances of the heating elements 33 and 25 if needed.
In an embodiment, the components such as the first heating element 33 and the fusible element 29 are sequentially formed on the first surface 38 of the first planar substrate 36 (base substrate), whereas other components such as the second heating element 25 are sequentially formed on the second surface 39 of the second planar substrate 23 (upper substrate). When components are individually fabricated on the first planar substrate 36 and the second planar substrate 23 as bases, the first surface 38 and the second surface 39 face upward to allow the first heating element 33 and the second heating element 25 to be printed thereon. Accordingly, the first heating element 33 is a printing member on the first surface 38, and the second heating element 25 is a printing member on the second surface 39.
Afterwards, the second planar substrate 23 is turned over to combine with the first planar surface 36 to form the protection device 20. The first planar substrate 36 and the second planar substrate 23 serve as bases, allowing primary components to be made by printing. As a result, the thicknesses of the heating elements and electrodes can be decreased for miniaturization. A cap of a traditional protection device is not a planar substrate, and therefore it does not allow the components to be printed thereon. Therefore, the manufacturing efficiency is not good, and the protection device is not easily miniaturized. Moreover, the manufacturing is conducted on the base substrate and the upper substrate individually and can be conducted simultaneously to increase throughput. If defective semi-manufactured products are found before combination, they can be screened out to increase production yield.
In an embodiment, the first planar substrate 36 and the second planar substrate 23 may be a rectangular insulating substrate including aluminum oxide, aluminum nitride, zirconium oxide and/or heat-resistant glass. The first electrode 35, the second electrode 45, the third electrode 34, the fourth electrode 44, the fifth electrode 24 and/or the sixth electrode 47 may comprise silver, gold, copper, tin, nickel or other conductive metals, and the thickness is approximately 0.005-1 mm. In addition to making the electrodes by printing, they may be alternatively made of metal sheets for high-voltage applications. The fusible element 29 may comprise low-melting metal or its alloy, e.g., Sn—Pb—Ag, Sn—Ag, Sn—Sb, Sn—Zn, Zn—Al, Sn—Ag—Cu, Sn. The length and width of the fusible element 29 vary according to the designated current flowing therethrough, but they should not exceed the lengths and widths of the first planar substrate 36 and the second planar substrate 23. The thickness of the fusible element 29 is 0.005-1 mm, preferably 0.01-0.5 mm. A thicker fusible element 29 can be used for the applications of a large current such as 30-100A. The first and second heating elements 33 and 25 may comprise ruthenium oxide (RuO2) with additives of silver (Ag), palladium (Pd), and/or platinum (Pt). The insulating layers 32 and 26 between the first and second heating elements 33, 25 and the fusible element 29 may contain glass, epoxy, aluminum oxide, silicone or glaze. The absorbent element 48 may be made by printing or electroplating. The composition of the absorbent element 48 may comprise silver, gold, copper, nickel, tin, lead, antimony, or alloy thereof, and may be in the form of a single layer or multiple layers.
An equivalent circuit diagram of the protection device 20 of this embodiment is depicted in
Table 1 shows embodiments E1-E4 in which the protection device 20 includes the first and second heating elements 33 and 25 with different resistances. In each of E1-E4, the resistance of the first heating element 33 is 0.95Ω, and the resistance of the second heating element 25 is at least twice that of the first heating element 33. The resistances of the second heating elements 25 in E1-E4 are 3.7Ω, 6.5Ω, 8.5Ω and 11.5Ω, respectively. The protection devices 20 are of a form factor 3820. Because the first heating element 33 and the second heating element 25 are in parallel connection, the resistances of the heaters 50 in E1-E4 are 0.77Ω, 0.82Ω, 0.85Ω and 0.87Ω, respectively, upon calculation.
The protection devices of E1-E4 are subjected to 5V, 10V, 15V and 21V testing according to the circuit shown in
In E1-E4, when the voltage exceeds a predetermined voltage, e.g., 12V, the current goes through the first heating element 33 first and then switches to the second heating element 25 after the first heating element 33 is blown. The relationship of the current vs. time is shown in
The melting times of E1-E4 are listed in Table 2, and the melting time vs. voltage diagram is shown in
Table 3 shows the protection devices 20 including the first and second heating elements 33 and 25 with different resistances in accordance with the embodiments E5-E8 in which the resistances of the first heating elements 33 are 1.05Ω, 1.4Ω, 1.4Ω and 1.8Ω, and the resistances of the second heating elements 25 have higher resistances of 4.4Ω, 5.8Ω, 7.5Ω and 15.5Ω, respectively. The devices of E5-E8 are of a form factor 2213 which is smaller than that of E1-E4. Because the first and second heating elements 33 and 25 are in parallel connection, the resistances of the heaters 50 of E5-E8 are calculated to be 0.85Ω, 1.11Ω, 1.22Ω and 1.64Ω, respectively.
The protection devices of E5-E8 are subjected to 5V, 10V and 15V testing according to the circuit in
In the embodiments shown in
The third heating element 63 in
In sum, the protection device of the present application uses at least two heating elements in parallel connection to generate heat to blow the fusible element in the event of over-voltage. The resistances of the two heating elements differ by at least two times. Accordingly, the heating element of a low resistance serves as a heat source to blow the fusible element at low voltages. When the voltage exceeds a predetermined value, the heating element of a low resistance cannot withstand the corresponding power and therefore is blown. Current is switched to the heating element of a high resistance which replaces the one of low of resistance as a heat source to blow the fusible element. In other words, the low-resistance heating element serves as the source to heat and blow the fusible element when the voltage is below the predetermined value, e.g., at low voltages. The high-resistance heating element is automatically switched to be the heat source to blow the fusible element when the voltage exceeds the predetermined value, i.e., at high voltages. As such, the voltage endurance is improved, and the voltage application range is enlarged.
The above-described embodiments of the present invention are intended to be illustrative only. Numerous alternative embodiments may be devised by persons skilled in the art without departing from the scope of the following claims.
Number | Date | Country | Kind |
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107126571 A | Jul 2018 | TW | national |
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