Microcontroller for Variable Speed BLDC Fan （单片机对变速刷粉丝）.pdfVIP

Microcontroller for Variable Speed BLDC Fan Control System T.C. Lun System Engineer, Freescale Semiconductor, Inc. 1 Introduction Portable, feature rich, high-performance and compact in size are typical trends of most electronic products. The amount of heat generated by such electronic products, such as notebook computers, is a growing problem. Use of cooling fan remains the most common and efficient way of preventing electronics equipment from overheating. Microcontroller (MCU) based, intelligent, variable-speed control, brushless DC (BLDC) fans are needed in order to fulfill the rapidly changing electronics products specification. Variable speed control, low acoustic noise, reliability, long lifetime, low power consumption, protection features, easy to maintain/upgrade and communication interface capability are the characteristics of flash MCU based BLDC. This article describes variable speed control algorithms of BLDC fan, which include methods for acoustic noise reduction, power consumption consideration, lock detection and automatic restart, thermal shunt down and communication interface. Different between DC Fan and BLDC fan The physical appearance of conventional and BLDC fans are basically the same. Both of these fans operate on the same principle to convert the electrical energy to the mechanical motion. The fan is rotated when a dc voltage is applied to its terminals. The speed of the fan depends on the applied voltage across the terminals. The significant difference between the conventional and BLDC fans is in their internal construction. Both fan systems require the commutation that allows the direction of current flowing through the fan windings to reverse every 180o of rotation. In the conventional DC fan system, the stator of the permanent