CONTROLLER/DRIVER FOR SENSORLESS DC BRUSHLESS MOTOR

摘要

PURPOSE: To operate a sensorless DC brushless motor constantly in the vicinity of maximum efficiency through an inexpensive constitution by providing a control section with a conduction delay angle for switching the conduction pattern while delaying until a rotor advances by a predetermined angle after variation of a third signal. CONSTITUTION: A comparison circuit 11 compares a signal from an integration circuit 10 with a synthesized signal of different phases to produce a digital signal. A third signal is further advanced with respect to a first signal and a counter electromotive force by setting the resistance and delayed by 50 deg. when the phase difference from the counter electromotive force is zero. The third signal from the comparison circuit 11 is fed to the external interruption terminal of a control section 12 and the conduction pattern is switched by providing a conduction delay angle being determined according to the load and r.p.m. using the state change of the signal as a trigger. Consequently, the motor can be rotated constantly in the vicinity of maximum efficiency even if the phase is shifted due to the load or the r.p.m. by regulating the conduction delay angle.