Apparatus and method for eliminating false current limit trigger

Details Apparatus and method for eliminating false current limit trigger Apparatus and method for eliminating false current limit trigger

1992-10-05

1993-07-20

Beha, Jr., William H.

Electricity: power supply or regulation systems

In shunt with source or load

Using choke and switch across source

361 18, 363 56, G05F 1569, H02H 712, H02M 3156

Patent

active

052297071

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.

REFERENCES:
patent: 4674020 (1987-06-01), Hill
patent: 4750079 (1988-06-01), Fay et al.
patent: 4837495 (1989-06-01), Zansky
patent: 4937697 (1990-06-01), Edwards et al.
patent: 5028861 (1991-07-01), Pace et al.
patent: 5138516 (1992-08-01), Chapman

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