Intelligent Thermal Management Using Brushless DC Fans
Microchip Technology Inc.
The brushless DC fan (BDC Fan) has become the air mover of choice in computing equipment, office automation products, home entertainment systems, and the like. Unlike conventional DC fans, the BDC fan is mechanically robust because it contains no rotating commutator/brush assembly to shed dust particles, wear out, or act as an ignition source. In addition, its magnetic coils are stationary and are usually mounted within a rigid frame for superior structural integrity and thermal dissipation. BDC fans are electrically quiet: they lack the rotating magnetic fields of AC motors and the arcing of conventional DC motors that broadcast electronic noise. Although BDC fans are superior to conventional fans, they are still a less than optimum thermal management solution. Because they are electromechanical devices, BDC fans do not achieve the same level of reliability as
the system electronics they protect. BDC fan failure commonly results from wear-out mechanisms (primarily fan bearing failures), physical damage, blockage by foreign objects, or electrical failure. Like all air moving devices, BDC fans generate acoustic noise, a growing concern given the number of electronic systems introduced to the home and workplace. These issues can be minimized by adding BDC fan management circuitry to operate the fan only as necessary to maintain system temperature within limits.
TB064, Thermal Management, Brushless DC Fan, Smart Fans, BDC