文档介绍：AVR440: Sensorless Control of Two-Phase
Brushless DC Motor
8-bit
Features Microcontrollers
• Sensorless Control of Two-phase Motor typically used in Fans
• Adjustable speed with according to external speed reference
• PWM-based speed control with closed loop speed control
• Motor stall detection and automatic restart after short delay Application Note
• Configurable start-up speed ramp to match motor characteristics
• Low cost implementation with few and ponents
• Firmware written in C
• In Circuit Debugging through debugWIRE interface
• Firmware modification and adaptation to specific motor easy
• Optional tacho output signal
1 Introduction
Two-phase brushless DC motors (BLDC) are widely used in fans for ventilating and
cooling CPUs, graphics processors, power supplies and many other applications.
The advantage of the BLDC motors is that they, compared to brushed DC motors
are lighter, accelerate faster, produce little electrical and acoustic noise, and that
they require no maintenance (no brush wearing). The requirements for cooling fans
are continuously increasing as the use of powerful heat-producing electronics is
increasing. As more fans are installed in more products, the need for low cost fan
solutions is evident to keep the overall cost of end-products low. Further, as the
number of fans in homes and offices are increased, the need to keep these fans as
quiet and efficient as possible is also getting more pronounced. The characteristics
of BLDC motors match the requirements of fans very well.
This application note describes how to implement the electronics and
microcontroller firmware to control a two-phase BLDC motor using an 8-bit AVR
microcontroller. The implementation is based on the small and low cost ATtiny13.
The built-in ADC and PWM are used in a way so that Hall-sensors are not required
(Patent Filed); it uses the EMF voltage over the passive coil to determine when to
perform mutation