Electricity: electrical systems and devices – Safety and protection of systems and devices – Circuit interruption by thermal sensing
Patent
1990-04-02
1992-06-02
Stephan, Steven L.
Electricity: electrical systems and devices
Safety and protection of systems and devices
Circuit interruption by thermal sensing
361 18, 323907, H02H 504
Patent
active
051192659
ABSTRACT:
FET protection circuit (10; 100) senses the temperature of a FET (11) and, via a control circuit (24), increases FET conduction in response to sensed FET temperature exceeding a high temperature threshold (160.degree. C.) close to the maximum rated junction temperature (175.degree. C.) of the FET. This allows the FET to survive excessive drain-to-source voltages which occur during load dump conditions even when load dump is sensed by a zener diode (26) which initially turns on the FET. During load dump after a zener diode (26) turns on the FET, in response to sensing excessive FET temperature the FET is turned in harder so as to reduce the drain-to-source voltage (V.sub.DS) and minimize power dissipation during load dump thereby protecting the FET. Normal overcurrent and maximum temperture turn off circuitry (44, 33, 60-63) is effectively overridden by high temperature threshold turn-on circuitry (50). Preferably, a majority of the control circuit (24) is provided on an integrated circuit, but an external resistor (31) allows effective adjustment of two temperature thresholds (150.degree. C., 160.degree. C.) above which control signals provided to the FET will be modified.
REFERENCES:
patent: 4516865 (1985-05-01), Hideo
patent: 4667516 (1987-05-01), Schulz
patent: 4896245 (1990-01-01), Qualich
patent: 4924194 (1990-05-01), Opas
patent: 4937697 (1990-06-01), Edwards et al.
"High Side Driver FET Load-Dump Protection", by John Qualich, Motorola Technical Developments vol. 9, Aug. 1989, pp. 62-63.
"Built-in Protection Makes TEMPFET Resistant to Catastrophic Failures" by Miro Glogolja, Power Conversion & Intelligent Motion, Mar. 1989 pp. 19-23.
"Self-Thermal Protection Power MOSFETS", by Tsazaki, Y.; Yamauka, M. and Kawamuto, K.; IEEE Power Electronic Specialists Conference, Paper No. 880411, pp. 41-45 or 87CH2459-6, pp. 31-36.
"Prior Low Side FET Switch",m (Sketch) Feb. 21, 1990.
Pigott John M.
Qualich John R.
Robb Stephen P.
Berhane Adolf D.
Melamed Phillip H.
Motorola Inc.
Stephan Steven L.
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