Novel Back-EMF Detection Technique of Brushless DC Motor Drives for Whole Duty-Ratio Range Control

The main theme of this paper is to present a novel back-EMF detection technique which provides whole duty-ratio range control for Brushless DC Motor (BLDCM) drives. The problems for previous back-EMF detection techniques [7-11] are clearly explained first It will be shown that these techniques can be used either for low duty-ratio control [7-10] or for high duty-ratio control [11] only. The proposed technique deals with the above-mentioned problem to give a whole duty-ratio control while not invoking any position and current sensors. Experimental results derived from an FPGA-based BLDCM for air-conditioner applications demonstrate that the presented technique works well from standstill to closed-loop operation, extreme low duty ratio, e. g. 1%, and extreme high duty ratio control, e. g. 100%.