Stepping motors and drive circuits therefor.

摘要

In a stepping motor having phase windings A, B etc. the current through the phase windings is switched by a drive circuit including switching transistors T1A, Tie etc. in series with each individual phase winding. The transistors are controlled by a phase sequence logic circuit 14. A current flow characteristic is indicative of rotor position and is measured and used to operate the phase sequence logic circuit. The drive circuit may incorporate a chopper-type control operated through further transistors T2A, T28 etc. also in series with each phase winding. The current flow characteristic that is measured may be current rise time, current decay time or chopping frequency. The current characteristic being monitored may be the characteristic in an energised winding or else in an unenergised winding at low current level. The drive circuit may alternatively provide a constant voltage power supply to the phase windings in sequence with current being repeatedly switched at a low level to an unenergised winding to monitor rotor position.