Intrinsic element sensing integrated SOA protection for power MO

Details Intrinsic element sensing integrated SOA protection for power MO Intrinsic element sensing integrated SOA protection for power MO

1996-02-28

1998-04-07

Gaffin, Jeffrey A.

Electricity: electrical systems and devices

Safety and protection of systems and devices

With specific current responsive fault sensor

361 18, 361 86, 361 87, H02H 300

Patent

active

057371695

ABSTRACT:
A protective circuit for a power field effect transistor, e.g., a power MOSFET, employs a diode-switched pickup circuit, a threshold detector, and a timer. The pickup circuit includes a resistor and diode in series, with the diode connected with the MOSFET drain electrode and the resistor connected with the gate driver for the MOSFET gate electrode. A pickup voltage V.sub.1 appears at the junction of the diode and resistor. When the MOSFET is conducting the pickup voltage is the sum of the channel voltage V.sub.ds-on and the diode forward voltage V.sub.f. When the MOSFET is biased OFF, the pickup voltage is zero. The threshold detector compares the pickup voltage with a reference voltage that is offset some predetermined amount from the source electrode voltage. When threshold circuit goes high, the timer circuit provides a time-out or inhibit signal to an inhibit input of the gate driver circuit. Under high load current or high temperature conditions, the drain-source voltage V.sub.ds-on rises, and if the threshold is exceeded, the gate signal is cut off. This holds the transistor OFF for the timer period. This arrangement uses the MOSFET channel resistance R.sub.ds as the current sense resistor. The protective circuit can be integrated, and can be combined with the MOSFET in a single package.

REFERENCES:
patent: 4525765 (1985-06-01), Brajder
patent: 4703390 (1987-10-01), Fay et al.
patent: 4809122 (1989-02-01), Fitzner
patent: 5257155 (1993-10-01), Robb et al.
patent: 5465188 (1995-11-01), Pryor et al.

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