Patent ID: 6876164

Claim:
A complementary fan rotational speed control apparatus for simultaneously monitoring the rotation speeds of two or more fans, comprising: a control unit for outputting pulse width modulation control power supply; a first fan connected to the control unit, the first fan receiving the pulse width modulation control power supply from the control unit, having a first rotation speed when activated and outputting a first rotation pulse signal to the control unit; and a second fan connected to the control unit, the second fan receiving the pulse width modulation control power supply from the control unit, having at a second rotation speed when activated and outputting a second rotation pulse signal to the control unit; the control unit detecting an actual rotation speed of the first fan based on the first rotation pulse signal and an actual rotation speed of the second fan based on the second rotation pulse signal, the control unit comparing the actual rotation speed of the first fan with the first rotation speed and comparing the actual rotation speed of the second fan with the second rotation speed, when the actual rotation speed of the first fan is lower than the first rotation speed, the control unit increasing the actual rotation speed of the second fan and issuing a warning signal to alert malfunction of the first fan.