FAST ACTING OVER CURRENT POWER CIRCUIT PROTECTION SCHEME

摘要

A power circuit protection scheme is presented which utilizes a fast acting, digital output,Hall effect based over current detector. The scheme combines a pulse by pulse currentlimit with a pulse count shutdown. The pulse by pulse current limit provides a fastacting shutdown. The pulse count shutdown acts to distinguish a normal over currentevent from a hard failure, and latch off the circuit in the case of a hard failure. Theeffectiveness of the scheme is demonstrated by application to a low inductance powerMOSFET circuit. In this demonstration circuit, a MOSFET is connected directly acrossa DC power source. A very fast rising, high current (comparable to a shoot throughcurrent on a bridge circuit) is generated when the MOSFET is turned on. Waveforms arepresented showing the current, detector output, gate drive, and MOSFET switchingwaveforms.