Zipper fuse

Abstract

This invention includes a current limiting circuit comprised of an array of switch-fuse pairs. Switches are coupled in series with fuses to form fuse-switch pairs. The fuse switch pairs are coupled in parallel forming an equivalent fuse. A current censing circuit senses the current flowing in the equivalent fuse. When the current exceeds a predetermined threshold, the current sense circuit actuates a control circuit that clears the fuses by opening all the transistors save one. This forces the entire current through a single fuse, causing it to clear. Each fuse is cleared in similar fashion in much the same way that a zipper is opened one tooth at a time. In other words, under normal conditions, all switches are on and each fuse carries Ta/n amps, where Ta is the current rating of the fuse and n is the number of fuses. If all but one transistor is turned off, then Ta amps would flow through a single fuse. If the fuse were rated for 2Ta/n, the fuse would clear.

Dependencies are inferred from the claim text.