Controller for brushless DC motor without position sensor

A controller for a brushless DC motor without a position sensor including an inverter for driving the motor under chopper control and utilizing a counter electromotive force generated in stator coils of respective phases as a rotor is rotated in order to detect a position of the rotor and thereby to generate a commutation signal, said controller comprising

• a mode detector connected to the inverter for detecting
• a commutation timing signal detector connected to said mode detector to generate a commutation timing signal,
• an output pattern mode generator connected to said commutation timing signal detector to generate output patterns of several types with which said stator coils are excited,
• a pattern coincidence detector connected to said commutation timing signal detector and said output pattern mode generator to detect a coincidence that signals output from said commutation timing signal detector and said output pattern mode generator match each other and
• a starting controller connected to said pattern coincidence detector to stop a motor drive output once when no coincidence is detected by said pattern coincidence detector and to cause a restarting.