A unified approach to zero-crossing point detection of back EMF for brushless DC motor drives without current and hall sensors

The main theme of this paper is to present a unified approach to back electromotive force (EMF) detection of brushless dc motor (BLDCM) drives without using any current and Hall sensors. Pulsewidth modulation (PWM) techniques and theoretical analysis of back EMF detection are presented, and followed by the proposed unified back EMF detection method. It will be shown that the back EMF detection depends upon the PWM techniques and the method is required to be slightly modified as the PWM technique is changed. Experimental results derived from BLDCM drives without using any current and Hall sensors fully confirm the theoretical analysis.