Abstract: A method of controlling a sensorless motor (32). The method contains the steps of determining a current speed of the motor (32); selectively using a first method, a second method, or a third method to determine a position of a rotor of the motor (32), depending on the current speed of the motor (32); and transmitting a drive signal to the motor (32) based on the determined position of the rotor. A sensorless motor assembly is also disclosed. According to the method, multiple rotor position detection methods are provided to the sensorless motor (32) which cover a full speed range of the motor (32).

Abstract: A computer system including a chassis, a plurality of motherboards, a fan control module and a plurality of fans is provided. A plurality of motherboard position signal generating units is disposed in the chassis. Each of the motherboards includes a signal generating circuit and a board management controller. The signal generating circuit coordinates with one of the motherboard position signal generating units to generate a motherboard position signal. The board management controller receives the motherboard position signal and a motherboard working temperature signal to output a motherboard working state signal. The fan control module coupled to the board management controller of each of the motherboards receives the motherboard working state signals and generates a plurality of fan control signals accordingly. The fans coupled to the fan control module determine operation according the fan control signals.