A novel direct back EMF detection for sensorless brushless DC (BLDC) motor drives

A novel back EMF detection method for sensorless BLDC motor drives without the motor neutral point voltage information is presented in this paper. The true phase back EMF signal can be directly obtained from the motor terminal voltage by properly choosing the PWM and sensing strategy. As a result, the method proposed is not sensitive to switching noise, no filtering is required, and good motor performance is achieved over a wide speed range. The detailed circuit model is analyzed and experimental results verify the analysis and demonstrate advantages of the new technique.