Method and device for controlling an electronically commutated polyphase d.c. motor

Abstract

A device and method for driving a polyphase DC motor, in which a phase selector circuit, in each case, selects only one phase, which is fed to a commutation detection circuit. After each commutation detected by a commutation detection circuit, as a result of a pulse of constant duration generated by a monoflop, the phase discriminator circuit and, as a consequence, the commutation logic are advanced in a fixed and preestablished sequence. This occurs irrespective of the rotation direction of the motor using the sequential logic device embodied by the commutation logic. When the motor rotates in the preferred direction, constant current-flow angles of 120° are achieved for each phase. When the motor rotates in the reverse direction, markedly varying current-flow angles of the individual phases are generated, and these varying current-flow angles, as a function of the course of the specifically corresponding voltages induced in the individual phases, result in a counter-torque. This counter-torque causes a braking of the motor to a standstill and a reliable startup in the preferred direction. The exemplary electronics, in this context, do not distinguish between the two rotation directions so that no additional electronics expense is required to reliably startup from a reverse rotation condition.