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 are clearly explained first. It will be shown that these techniques 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 a whale duty-ratio control while nor 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%.