1. Field of the Invention
The present application relates to an over-current protection device, and more particularly to an over-current protection device having positive temperature coefficient (PTC) characteristic. The novel over-current protection device is configured to replace a traditional circuit breaker.
2. Description of Related Art Including Information Disclosed Under 37 CFR 197 and 137 CFR 1.98
In recent years, super-thin portable electronic apparatuses have been increasingly developed, resulting in the demand of lightweight, thin and large capacity batteries. To meet the demand of high voltage and large capacity, a battery may use a large capacity cell or a plurality of cells in parallel and/or series connection. In over-current and over-heat protection to batteries, circuit breakers in response to temperature are usually employed nowadays.
An over-current breaker usually uses bi-metal plates, and the bi-metal plates constitute a normally closed micro-switch. When the breaker has current flowing therein, the bi-metal plates are heated and bent and the bi-metal plates bent more intensively as current increases. If over-current occurs, extremely large current induces over-bending of the bi-metal plates, the micro-switch changes to and sustain in an open state to sever the current. As a result, the breaker prevents the circuit from damage which may be caused by over-current. When the over-current or over-temperature event has gone, the bi-metal plates cool down and return to be of original shapes to rebuild a conductive path.
FIG. 1 shows an appearance of a bi-metal breaker 5. The first metal plate 6 and the second metal plate 7 extend outwardly from the insulating body 8. The first metal plate 6 and the second metal plate 7 in the insulating layer 8 form a normally closed micro-switch, whereas the first metal plate 6 and the second metal plate 7 out of the insulating layer 8 serve as soldering, or welding interfaces.
Although the bi-metal design has been widely used in breakers, the bi-metal plates have to be made by precision machinery and need precision manufacturing techniques. As a result, the bi-metal breakers are usually costly. Therefore, it is highly demanded to generate a breaker with high reliability and stability for safety, and consider how to simplify manufacturing process and obtain low cost.