Electronic damper motor control

Abstract

There is disclosed a motor control circuit that is particularly useful for the control of a damper motor in a heating and ventilating system. The control circuit comprises a bridge circuit having a pair of operational amplifiers with cross connected input terminals. An input signal is provided by input signal circuit means to one of the cross-connecting conductors and a reference signal is provided to the other of the conductors by a reference signal circuit means. The operational amplifiers are provided with feedback circuit means between their output and noninverting terminals to drive the amplifiers into an unstable condition where they function as on and off switches. Dead band means in the form of a load dropping resistor is provided between the input signal circuit and the noninverting terminal of one of the amplifiers. The reference voltage signal supplied to the amplifiers is derived from a voltage divider circuit which is responsive to the motor position, thereby effecting proportional control of the motor. The feedback to the noninverting terminal of the amplifiers effects a latch-on condition whereby the circuit is held in the middle of the dead band, effecting a stepping action of the motor in response to an error signal, thereby eliminating hunting or oscillating of the motor and minimizing the frequency of making and breaking the switch contacts.

Dependencies are inferred from the claim text.