Electricity: electrical systems and devices – Safety and protection of systems and devices – With specific current responsive fault sensor
Patent
1995-07-28
1998-05-05
Leja, Ronald W.
Electricity: electrical systems and devices
Safety and protection of systems and devices
With specific current responsive fault sensor
361 59, 315307, H02H 300
Patent
active
057484287
ABSTRACT:
A pulse width modulation circuit includes a transistor pass element alternately switched on and off by an oscillator and connecting a power source to a load. Current through the transistor pass element is compared to a reference signal by a comparator. If the current through the transistor pass element exceeds the reference signal, the comparator generates a fault signal, and the transistor pass element is switched off for the remainder of the cycle. After a predetermined number of faults, the transistor pass element is switched off for a plurality of cycles. The pulse width modulation circuit prevents damage to the transistor pass element caused by the low initial resistance of the load and supplies sufficient current to slowly heat the load to steady state operation. This also allows for downsizing of the pass element for steady state conditions thereby saving product cost.
REFERENCES:
patent: 4477748 (1984-10-01), Grubbs
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patent: 4739226 (1988-04-01), Murata
patent: 4761702 (1988-08-01), Pinard
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patent: 4994934 (1991-02-01), Bouhenguel
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Article: EDN Sense-cell MOSEFET eliminates losses in source circuit, Jun. 1986.
Kelley Jeffrey T.
Wrenbeck Bruce
Leja Ronald W.
United Technologies Automotive Inc.
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