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US 4,360,852 AGranted
Overcurrent and overtemperature protective circuit for power transistor system
AssigneeAllis-Chalmers Corporation
InventorThomas P. Gilmore
Life of this patent
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AssigneeAllis-Chalmers Corporation
InventorThomas P. Gilmore
Estimating the term…
A power transistor switch is protected against thermal destruction that might be caused by accidental short circuiting of the load being switched by a protective circuit having a base-drive-removing transistor in shunt to the base-emitter junction of the power transistor; an RC circuit including a capacitor in series with a resistor connected across the power transistor with the capacitor coupled across the base-emitter junction of the base-drive-removing transistor; a forward-biased shunting transistor connected across the capacitor; a shunt-removing transistor connected across the base-emitter junction of the shunting transistor; and a turn-on transistor triggerable to the conductive state by a turn-on signal for applying base drive to the power transistor and for forward biasing the shunt removing transistor to thereby turn off the shunting transistor and permit the capacitor to charge. Excessive current flow through the power switch causing it to desaturate results in charging the capacitor and consequent turning on the base-drive-removing transistor to thereby remove base current from the power transistor and turn it off.
A protective circuit for a power transistor (Q1) adapted to switch a load (SOL) comprising, in combination,
A protective circuit for a power transistor (Q1) adapted to switch a load (SOL) comprising, in combination,
An overcurrent and overtemperature protective circuit for a power transistor (Q1) adapted to switch a load (SOL) comprising, in combination,
Dependencies are inferred from the claim text.