Brushless DC fan is a type of DC motor that does not have a mechanical commutator or electric brush. It uses an electronic commutation device to overcome the weaknesses of general DC motors, such as commutation sparks, poor reliability, high noise, and radio interference. It has both the mechanical characteristics and adjustability of general DC motors, as well as the advantages of wide speed range, small size, fast starting, reliable operation, high efficiency, and long service life. Currently widely used in the small household appliance fan industry, with a general power of less than 100W. Topology structures include P+N, N+N, and 3 phases.