Novel Back-EMF Detection Technique of Brushless DC Motor Drives for Wide Range Control Without Using Current and Position Sensors

This paper presents a new back-electromotive force (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-EMF which is used for generating proper commutation control of inverter is calculated by sampling the voltage of floating phase. Therefore, no current and position sensors are required for the implementation. The presented method can be easily implemented using digital controller. An field programmable gate array-based BLDCM driver system is set up to demonstrate that the presented technique works well from standstill to rated speed.