Method and apparatus for operating polyphase dc motors using a PWM chopping signal in zero crossing determination

摘要

A method and a circuit for operating a polyphase dc motor having a plurality of driving coils are presented. According to them, drive current supplied to the driving coils is chopped to control the maximum current delivered thereto by turning the drive current on and off. Zero crossings of a back emf voltage of the driving coils that are connected into a floating state are detected for producing a commutation signal, and the detection of zero crossings is inhibited for a predetermined time after the drive current is turned off during the chopping step to avoid detecting a false zero crossing. The chopping is performed as a part of a PWM operation.