A new sensorless drive scheme for a BLDC motor based on the terminal voltage difference

This paper presents a new sensorless drive scheme for a brushless DC (BLDC) motor based on the terminal voltage difference. Unlike the zero crossing point (ZCP) of the phase back electro-motive force (BEMF) which has been used in the conventional sensorless drive schemes, the ZCP of the BEMF difference between two phases corresponds to the commutation point of a BLDC motor accurately. So as to detect the ZCP and adopt it to the BLDC motor commutation, a circuit which constitutes of a differential amplifier and a comparator is designed. Some experimental results show that the output of the suggested circuit is analogous to the hall sensor signal and it can be used for BLDC motor sensorless drive.