Speed control for brushless DC motor-driven fan - adjusts stator power supply in response to operational amplifier switching by variable resistance in air stream

摘要

The delta-connected stator winding (L1-L3) of the motor is fed from a commutation circuit (1) supplied from the emitter (E) of a semiconductor device (6), esp. a Darlington transistor, whose base (B) is driven by an operational amplifier (12) via a Zener diode (11). - A temp. -dependent resistance (15) in the air stream influences the switching state of the op.amp. (12) and thereby the amplitude of the commutation circuit's input voltage and current.