Patent ID: 8724320

Claim:
A fan system comprising: a pulse signal generation portion; and a plurality of fans; wherein each of the plurality of fans includes: a motor portion; an impeller arranged to be rotated by the motor portion; a drive circuit arranged to drive the motor portion; a rotation detection portion arranged to detect rotation of the motor portion; and a rotation rate control circuit arranged to, based on a reference pulse signal supplied from the pulse signal generation portion and an actual rotation pulse signal supplied from the rotation detection portion, perform feedback control on a rotation rate of the motor portion in accordance with a period of the reference pulse signal; the rotation rate control circuits perform the feedback control on the rotation rates of the motor portions based on a time difference between rising edges of the reference pulse signal and rising edges of the actual rotation pulse signal; and the pulse signal generation portion is arranged to change the period of the reference pulse signal and arranged to transmit the reference pulse signal to each of the plurality of fans in order to change the rotation rates of the motor portions.