An air flow regulating device includes a housing, an air supply unit and a circuit board which are arranged inside the housing. The air supply unit includes an impeller and a single-phase permanent magnet brushless motor configured to drive the impeller. The single-phase permanent magnet brushless motor includes a stator and a rotor which can rotate relative to the stator. The stator includes a stator core and a single-phase winding wound around the stator core. The rotor includes a shaft and a permanent magnet fixed to the shaft. Numbers of magnetic poles of the stator and the rotor are the same and not greater than six. An outer diameter of the stator core is less than 35 mm and/or an axial thickness of the stator core is between 10 mm and 20 mm.