A protective circuit (1A) is provided with: a protective element (10A): a plurality or secondary battery cells (20), (20), . . . ; an external positive electrode terminal (30a) and an external negative electrode terminal (30b); an auxiliary power supply (40); a first controlling dev ice (50): and a switch (60). The protective element (10A) includes: a first fusible conductor (15) of which the two ends are connected to a first terminal (11) and a second terminal (12): and a heat generating body (16) disposed in a first energizing path (P1.sub.A) between a third terminal (13) and a fourth terminal (14). The auxiliary power supply (40) is provided electrically independently of the plurality of secondary battery cells (20), (20), . . . . In this protective circuit (1A), a signal from the first controlling device (50) causes the switch (60) to switch in such a way as to conduct electricity, thus causing the heat generating body (16) of the protective element (10A) to generate heat which fuses the first fusible conductor (15), thereby isolating the plurality of secondary battery cells (20), (20), . . . from the external negative electrode terminal (30b).

It is an object of the invention to provide an electric wire having an excellent electrical conductivity in use of the high melting point metal and being able to surely cut off by fusing the conductive material itself at a temperature lower than the melting point of the high melting point metal, even where heat is generated from flowing overcurrent in the electrical circuit. The electric wire of the invention has a feature including a conductive material formed of a first conductive member made of a low melting point metal, and a second conductive member made of a high melting point metal, which are provided adjacent to each other, wherein the conductive material is fused by erosion of the high melting point metal according to melting of the low melting point metal.

A fuse device and a fuse element having excellent rapid blowout properties and excellent insulation properties after blowout even in a size-reduced fuse device are provided. A fuse element constitutes a current path of a fuse device and blows out due to self-generated heat when a rating-exceeding current flows, a length W in a width direction perpendicular to a conduction direction being greater than a total length L in the conduction direction in the fuse element. In particular, the fuse element includes a low melting point metal layer and a high melting point metal layer, the low melting point metal layer eroding the high melting point metal layer when current flows to cause blowout.

A fuse element (10) includes a low-melting-point metal layer (11), a high-melting-point metal layer (12) laminated on at least one surface of the low-melting-point metal layer (11), and an intermediate layer (13) disposed between the low-melting-point metal layer (11) and the high-melting-point metal layer (12), in which the high-melting-point metal layer (12) and the intermediate layer (13) are layers formed of a metal which is melted by a molten material of the low-melting-point metal layer (11), and the intermediate layer (13) has a higher ionization tendency than an ionization tendency of the high-melting-point metal layer (12).

A protection device comprises a substrate, a fusible element and a heating element. The substrate comprises a first electrode and a second electrode on its surface. The fusible element is disposed on the substrate and connects to the first electrode and the second electrode at two ends. The fusible element comprises a first metal layer and a second metal layer disposed on the first metal layer. The second metal layer has a lower melting point than that of the first metal layer. The heating element is disposed on the substrate. In the event of over-voltage or over-temperature, the heating element heats up to melt and blow the fusible element. The second metal layer is 40-95% of the fusible element in thickness.

An electronic assembly, has at least one circuit board with conductor tracks, at least one current-limiting arrangement in the form of a thermal predetermined breaking point in at least one of the conductor tracks, and a fire-containment device in the region of the current-limiting arrangement.

A fuse including an electrically insulating, tubular fuse body, electrically conductive first and second endcaps disposed over opposing ends of the fuse body, a fusible element extending through the fuse body and connecting the first endcap to the second endcap, the fusible element having a central portion adapted to melt and separate upon an overcurrent condition in the fuse, and first and second arc barriers disposed on the fusible element on opposing sides of the central portion, the first and second arc barriers formed of a silicone composition that includes an arc quenching filler suspended in a silicone resin.

Some embodiments include a fuse having a tungsten-containing structure directly contacting an electrically conductive structure. The electrically conductive structure may be a titanium-containing structure. An interface between the tungsten-containing structure and the electrically conductive structure is configured to rupture when current through the interface exceeds a predetermined level. Some embodiments include a method of forming and using a fuse. The fuse is formed to have a tungsten-containing structure directly contacting an electrically conductive structure. An interface between the tungsten-containing structure and the electrically conductive structure is configured to rupture when current through the interface exceeds a predetermined level. Current exceeding the predetermined level is passed through the interface to rupture the interface.

Some embodiments include a fuse having a tungsten-containing structure directly contacting an electrically conductive structure. The electrically conductive structure may be a titanium-containing structure. An interface between the tungsten-containing structure and the electrically conductive structure is configured to rupture when current through the interface exceeds a predetermined level. Some embodiments include a method of forming and using a fuse. The fuse is formed to have a tungsten-containing structure directly contacting an electrically conductive structure. An interface between the tungsten-containing structure and the electrically conductive structure is configured to rupture when current through the interface exceeds a predetermined level. Current exceeding the predetermined level is passed through the interface to rupture the interface.

A protective element (30) includes an insulating substrate (33), a plurality of electrodes (34) provided on the insulating substrate (33), a fuse element (35) electrically connected to any electrode (34) of the plurality of electrodes (34), and a heat generation element (38) provided on the insulating substrate (33) for heating and fusing the fuse element (35). The fuse element (35) contains a composite metal material in which a first fusible metal (31) and a second fusible metal (32) are stacked, some of a component of the first fusible metal (31) being dissolved at a joint working temperature, the second fusible metal (32) being lower in melt temperature than the first fusible metal (31), at least some of a component of the second fusible metal (32) being molten at the joint working temperature.