Back EMF based sensorless BLDC drive using filtered line voltage difference

In this paper, a position sensorless brushless direct current (BLDC) drive operation is described. Detection of back EMF zero crossing from line voltage difference is employed here for the sensorless drive operation. The line voltage difference gives an amplified version of back EMF which makes the sensorless operation possible. Low pass filters are used for eliminating the spikes in the wave form and to provide the necessary delay required for the proper commutation of switches. Neutral potential is not needed for obtaining the commutation pulses. Sample and hold circuit is also not needed since the use of filter eliminates the spikes. Proposed sensorless drive is simulated using MATLAB/ SIMULINK and effectiveness of the method is verified.