Patent ID: 6481974
Filing Date: 2002-11-19
Classification: F04D,Y02B

Abstract:
A fan motor with constant speed control by a microprocessor system, the fan motor comprising:a fan outputting a speed signal; a microprocessor system mounted between a power source and the fan, the microprocessor system controlling output of a drive voltage to the fan; a register for actual fan speed, the register receiving the detected speed signal from the fan for retrieval by the microprocessor system, the register for actual fan speed being connected to the microprocessor system via a bus control logic; a register for fan state connected to the microprocessor system via the bus control logic for storing data for output; a register for speed set-up connected to the microprocessor system via the bus control logic for storing data for output; a braking/running enabling control logic for controlling a fan state and the drive voltage to be outputted to the fan, the braking/running enabling control logic receiving fan state data stored in the register for fan state after processing by the microprocessor system and receiving speed data stored in the register for speed set-up after processing by the microprocessor system; and a linear variable voltage circuit control logic connected between the register for actual speed and the fan, the linear variable voltage circuit control logic being connected between the braking/running enabling control logic and the register for speed set-up, a set-up speed in the register for speed set-up forming a linearly varying drive voltage outputted to the braking/running enabling control logic for controlling output to the fan, the drive voltage being outputted to the fan via the linear variable voltage circuit control logic to maintain continuous linear fluctuation, thereby forming a smooth waveform; wherein the microprocessor system is arranged to retrieve and process data of the detected speed signal in the register for actual fan speed and then to store the fan state data in the register for fan state and to store data for altering speed/drive voltage in the register for speed set-up; and wherein during retrieval and processing of data of the detected speed signal in the register for actual fan speed by the microprocessor system, when the fan speed is lower than a predetermined value, said drive voltage is outputted to keep the fan running at a constant speed.