Patent ID: 7684682
Filing Date: 2010-03-23
Classification: H02P,H05K

Abstract:
1. A fan speed control circuit for receiving a pulse width modulation (PWM) signal from a system to control a rotation speed of a fan, comprising: a programmable control unit receiving the PWM signal and connected to a Hall element for receiving a voltage signal from the Hall element, the Hall element detecting the rotation speed of the fan, and providing a control signal; and a current control unit taking the control signal of the programmable control unit and controlling current flowing through a stator coil unit of the fan so as to control the rotation speed of the fan; wherein the programmable control unit has a program written for the PWM signal, and when the fan speed control circuit is used in another system with a different PWM signal, the programmable control unit can be given a new program for the different PWM signal for controlling the rotation speed of the fan; wherein the current control unit comprises a first MOSFET and a second MOSFET; and wherein the first MOSFET and the second MOSFET are p-channel depletion MOSFETs.