Patent ID: 6396231
Filing Date: 2002-05-28
Classification: F04D,Y02B

Abstract:
A fan motor having two-step speed control, the fan motor comprising:a fan (120); a buffer circuit (100) mounted between a voltage source and a source terminal of the fan, the buffer circuit (100) comprising a resistor (101) and a transistor (102); and a control voltage terminal (110) connected to a base of the transistor (102); wherein when the voltage of the voltage source (Vcc) equals to a control voltage (Vctrl) of the control voltage terminal (110), the transistor (102) of the buffer circuit (100) is open such that electric current cannot pass, the resistor (101) divides the voltage and lowers a fan-driving voltage (Vf) at the source terminal of the fan (120), and the fan (120) operates at the low-speed operation mode by a low voltage; and wherein when the control voltage (Vctrl) is zero, the transistor (102) of the buffer circuit (100) is closed such that the fan-driving voltage Vf equals to the voltage of the voltage source (Vcc), and the fan (120) is driven by full voltage of the voltage source and thus operates at the high-speed operation mode.