Sensorless Control Based on Virtual Neutral Voltage for BLDC Motor Drive

Abstract

Based on the characteristics of the back electromotive force (back-EMF), the rotor position information would be detected. Hence, the main theme of this paper is to design a practical approach to detect the zero cross point (ZCP) of back-EMF through virtual neutral voltage for sensorless brushless direct current (BLDC) motor drives. In contrast to conventional methods, the real neutral voltage of motor is not needed. In order to compensate the phase delay of the back-EMF due to low-pass filter (LPF) under different speeds, a voltage-controlled phase shifter, consisted of hysteresis comparator and voltage-controlled resistor (VCR), is proposed in this paper. The detail circuit model is introduced and some experimental results obtained from a sensorless prototype are shown to confirm the practicality of proposed senosorless drive method.