Fan speed controlling system

摘要

A fan speed controlling system for a power supply comprises a fan having two pins and a voltage comparator connected to the fan. The voltage comparator comprises a first input terminal for receiving a first reference voltage controlled by an external temperature of the power supply and a second input terminal for receiving a second reference voltage controlled by an interior temperature of the power supply. The voltage comparator outputs a higher voltage of the first and second reference voltage to the fan via the two pins.