Brush motor amplifier with overspeed protection

Claim 1

An amplifier control system for controlling the armature current of a DC brush motor comprising: a supply of DC operating voltage; a first pair of current switching deivces connecting to said voltage supply and said DC brush motor for driving said motor in a first direction; a second pair of current switching devices connecting to said voltage supply and said DC brush motor for driving said motor in a second direction; a plurality of driver circuits connected to each of said current switching devices in said first and second pairs; a gate circuit operative upon the driver circuits to provide switching signals for operation of said first and second pairs of current switching devices; speed sensing means for sensing the speed of the armature rotation of said DC brush motor, said speed sensing means including an encoder coupled to said brush motor for producing an output signal indicative of the motor speed and comparison means comparing said encoder signal to a predetermined maximum motor speed for establishing a reference voltage corresponding to a predetermined maximum motor speed threshold; and shut off means, coupled to said comparison means, operative upon said gate circuit to interrupt said first and second current switching devices in the event the motor speed exceeds said predetermined maximum motor speed threshold, said gate circuit including a plurality of gates each having one input commonly connected to said shut-off means.