Patent ID: 8558495

Claim:
A method of detecting back electromotive force (BEMF) for controlling a brushless DC (BLDC) motor, the method comprising: measuring, by a microcontroller coupled to a BLDC motor, BEMF voltages during a start period of the BLDC motor; determining, by the microcontroller, an average BEMF voltage value from the measured BEMF voltages by calculating averages based on an order of a commutation switching sequence for driving the BLDC motor, wherein calculating the averages includes: calculating a first average value for odd steps of the commutation switching sequence, and calculating a second average value for even steps of the commutation switching sequence; determining, by the microcontroller, an instantaneous BEMF voltage; and comparing, by the microcontroller, the average BEMF voltage with the instantaneous BEMF voltage to detect a crossover time, which converges to zero crossing of the BEMF voltage.