A driver circuit is coupled to the stator windings of a brushless three phase DC motor which is responsive to the open circuit back EMF voltage induced in the next stator winding to be energized as a permanent magnet rotor of the motor is caused to be rotated for producing phase current drive to the stator winding in synchronous with the operation of the motor. The driver circuit includes an increment drive circuit for supplying periodic switching command signals in succession to a switching circuit to produce phase current drive in each stator. The increment drive circuit increments a switch command signal to cause phase current through the next phase stator winding in reference to the magnitude of the EMF voltage induced across said phase stator winding falling below a reference level. A feature of the invention is that the frequency of the periodic switch command signals is varied during starting of the motor dependent on the magnitude of starting potential supplied to the driver circuit to prevent the motor from "locking" which would otherwise inhibit start thereof.