Myers Bigel Sibley & Sajovec
Three-phase brushless DC motor driving circuits and methods using one hall signal
 A three-phase brushless dc motor driving circuit can use only one Hall signal. The magnitude and phase of the Hall signal is used for commutation in order to perform soft switching, and an index marker circuit can determine the starting point of motor rotation. A clock signal is output at extreme points of the Hall signal generated by the Hall sensor. Based on the clock signal, three step voltage signals are generated, each step voltage signal having three voltage levels, signal periods three times that of the Hall signal and 120 and 240 degree phase differences with the other two step voltage signals. The direction of current flow in each stator coil is controlled based on the voltage difference each of the step voltage signals and the Hall signal. Index marker detection is performed by demagnetizing a portion of a magnet in a rotor of the motor and using an additional extreme point resulting in the Hall signal to output an index marker. 
Samsung Electronics Co., Ltd.
H H
H02K H02P
inventional inventional
Yun-Kee Shi-Hong
Lee Park