Patent ID: 6054824
Filing Date: 2000-04-25
Classification: H02H,H02P

Abstract:
A drive circuit for a DC brushless fan motor comprising:a Hall effect sensor for detecting the magnetic polarity of a rotor in said fan motor;a first transistor having a collector connected to a fan motor power input through a first magnetic coil, an emitter connected to a grounding line, and a base connected to an output terminal of said IIal effect sensor;a second transistor having a collector connected to said fan motor power input through a second magnetic coil, an emitter connected to said grounding line, and a base connected to the collector of said first transistor, wherein the improvement comprises;a first capacitor for connection at a first electrode to the collector of said second transistor and a second electrode connected to said grounding line through a resistor;a field effect transistor having a gate connected to the second electrode of said capacitor, a drain connected to said grounding line, and a source connected to an external power source through a pull-up resistor, said external power source being different from said fan motor power input, the source of said field effect transistor being provided for signal detection;a diode for connection at the anode to the second electrode of said first capacitor and at the cathode to the gate of said field effect transistor; anda second capacitor connected between the cathode of said diode and said grounding line.