Importance

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Abstract

A current sense/limit circuit senses a current of a power switch and turns off the switch when a peak current of the power switch surpasses a preprogrammed value. To prevent the circuit from reacting to a leading edge current spike resulting from the reverse recovery of a clamp or diode which is a 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. The predetermined threshold value is higher than the worst case voltage on the power switch during its on-time under normal operating conditions, and much lower than the switch voltage during off-time. As a result, 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/limit circuit remains disabled longer than a predetermined time to prevent switch damage resulting from a short circuit of the switch's drain-collector to the supply voltage.

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First Claim