Kenneth L Cook

US Patent:

46985824, Oct 6, 1987

Filed:

Jul 23, 1986

Appl. No.:

6/889642

Inventors:

Jeffrey J. Braun - Chandler AZ
Kenneth M. Cook - Palatine IL

Assignee:

Motorola, Inc. - Schaumburg IL

International Classification:

G05F 1573

US Classification:

323285

Abstract:

A power driver having a power transistor (15) uses a disable unit (17) to disable the transistor (15) upon sensing a short circuit condition. No current sense resistors are used. The base-emitter voltage of the transistor (15) is compared by a comparator (14) with a reference signal provided by a reference signal unit (16) to determine the existence or absence of a short circuit condition. In the presence of a short circuit, the comparator (14) provides a fault detected signal to the disable unit (17). The disable unit functions to deny the control signal to the transistor (15) and to ground the base of the power transistor (15) to thereby doubly ensure disablement. In addition, the disable unit (17) has memory and will disable the transistor (15) until the control signal recycles.