Brushless D.C. motor driving system

Claim 1

In a brushlesss direct current motor including a permanent magnet rotor having a plurality of poles, an electromagnet stator having a plurality of poles unequal to the number of rotor poles, and a plurality of angular rotor position sensing means spaced around the periphery of the stator and producing overlapping, phase displaced, rectangular waveforms, and reciprocal waveforms thereof, each waveform having an on-time duration or flow angle of 180 electrical ° with respect to the rotor, an improved stator winding drive circuit comprising: (a) a resistive addition network responsive to the sensing means waveforms for producing a plurality of staircase signals, the upper portions of which have sequential, consecutive, non-overlapping flow angles, (b) a plurality of stator windings, and (c) a threshold switching circuit responsive to the staircase signals and conductive only during the upper portions thereof for supplying the stator windings with sequential, consecutive, non-overlapping drive currents, whereby the motor efficiency is improved and torque ripple is reduced, wherein the addition network comprises a plurality of series connected, equal valued resistor pairs, two sensing means waveforms are coupled to the ends of each pair, and a staircase signal is taken from the junction of each pair.