"220V Cooling Fan" chip is the use of a single-phase brush less DC fan motor drive circuit PWM variable speed control, in addition to changing the VTH terminal voltage directly to the governor, but also an external thermistor to control "220V Cooling Fan" Speed , when the system temperature is high, the fan speed quickly, the temperature is low, slow speed, to meet the system cooling requirements while saving system power, reduce system noise, mainly used in the CPU "220V Cooling Fan" on, to meet the PC, cooling requirements workstations, telecom and LAN servers, and industrial control and instrumentation systems.