A sensorless drive system for brushless DC motors using a digital phase-locked loop

This paper proposes a sensorless drive system for Brushless DC (BLDC) motors using a Digital Phase-Locked Loop (DPLL). The Back Electromotive Force (BEMF) voltage is measured from the motor winding to determine the permanent magnet rotor position using the DPLL, and Pulse Width Modulation (PWM) limits the motor current to control the speed of BLDC motors. The proposed method can drive BLDC motors using an open-loop control without stepping out. Also, the proposed method is compared experimentally with a control method that uses Hall sensors. Experimental results for the BLDC motor show the effectiveness of the proposed method. (C) 2002 Wiley Periodicals, Inc.