Back-EMF detection technique of brushless DC motor drives for Wide range control

This paper presents a new back-EMF detection technique which provides wide range control for Brushless DC Motor (BLDCM) drives. As compared with previous techniques which can be used either for low duty-ratio control or for high duty-ratio control only, the proposed technique deals with the above-mentioned problem to give both low and high duty-ratio control while not invoking any position and current sensors. The zero crossing point of back-EMT which is used for generating proper commutation control of inverter is calculated by sampling the voltage of floating phase. The presented method can be easily implemented using digital controller. An FPGA-based BLDCM driver system is set up to demonstrate that the presented technique works well from standstill to rated speed.