Apparatus and method for eliminating false current limit triggering in a grounded source/emitter power switching circuit

A current sense/limit circuit utilizable in power processing circuits, such as switching voltage regulators, containing controlled power switches, diodes, inductors and/or transformers and capacitors. The current sense/limit circuit senses the power switch's current and turns off the switch when its peak current surpasses a preprogrammed value. In order to prevent the circuit from reacting to the leading edge switch current spike, which is the result of the reverse recovery of the clamp or free-wheeling diode that is part of most power processing circuits, the current sense/limit circuit monitors the voltage on the power switch and disables the current sense circuitry as long as this voltage does not drop below a predetermined threshold value. This threshold is higher than the worst case voltage on the switch during its on-time under normal operating conditions, and much lower than the switch voltage during off-time. Because the voltage on the switch is lower than its off-time value during most of the diode's recovery time, this method adaptively blocks the current sense mechanism during most of the reverse recovery current spike period. The circuit also includes a timer that turns the switch off if the current sense circuit remains disabled longer than a predetermined time after turn-on. This prevents switch damage in case of a short circuit of a switch's drain-collector to the supply voltage.