Abstract: A control circuit for a collectorless d.c. motor, without a commutation sensor, and comprising a stator with a multiphase system and a permanent-magnet rotor. The commutation state of the motor depends on the voltages induced in the stator windings. A comparison signal is generated which indicates whether the sign of that winding voltage which is not connected to a direct current source by means of the circuit electronic switching elements is in conformity with a predetermined sign which depends on the instantaneous commutation state. This comparison signal is inhibited during those time intervals in which transient effects which may cause spurious zero crossings occur in the windings as a result of the electronic switching elements being turned off. The switching elements are always switched one commutation step further if the comparison signal does not have the appropriate sign.

Abstract: A DC motor is commutated by magnetically controllable electronic switches in the form of integrated semiconductor circuits. Each switch comprises a first switching path between a first input terminal and an output terminal and a second switching path between a second input terminal and the output terminal. The two switching paths are controlled by the magnetic field of the rotor such that either the one or the other switching path is closed and that both switching paths are open in positions intermediate between these two positions.

Abstract: A magnetically controllable electronic switch in the form of an integrated semiconductor circuit comprises a first switching path between a first input terminal and an output terminal and a second switching path between a second input terminal and the output terminal. The two switching paths are controllable by a magnetic field in such a way that either the one or the other switching path is closed and the two switching paths are open in the transition range between these two modes. Such a switch is particularly suitable for use as an electronic commutator for small electric motors.