Abstract
A motor speed controlling driver and its drive method used to control running speed of a fan, an AC chopper is used to change the working cycle as a stepless speed regulation function of motor for a fan system. The invention comprises a high-frequency AC chopper, connected to a induction coil of a inductive motor; an AC source, connected to the high-frequency AC chopper; a controller, connected to the high-frequency AC chopper for outputting switching signals to the high-frequency AC chopper. By clipping of the AC source, the high-frequency AC chopper will output a drive voltage to change the rotational speed of inductive motor.