Current Limiter for NMOS H Bridge

One side of the H Bridge and it's gate drive circuit, with a comparator attached to pull the top gate down and limit the current through the MOSFETs to 4A. Set the input low to turn the bridge on. Current limit is controlled by the reference voltage, currently set to 400mV. increase the power of the globe to 55W to see it kick in. I was trying to set the comparator to hard off the gates and override the input signal, but the hysteresis effect causes it to oscillate and drain the gate voltage slowly until the top gate starts to turn of enough to bring the current down. which is a cool effect, but a half-on MOSFET will overheat and die; 6V drop at 4A makes the top side fet into a 24W soldering iron. need a fix for this.

published 11 years ago