Introduction

This application note describes a sensorless Brushless Direct Current (BLDC) motor control method using a Plug-In Module (PIM) based on the AVR128DA48 or AVR128DB48 microcontrollers from the AVR® DA and AVR DB families.

The first part of the document focuses on the motor control theory from which the software implementation is derived. It describes the sensored and sensorless control methods, details about trapezoidal commutation, and other important information about how to drive the motor.

The second part is dedicated to the software and hardware implementation of the system.

The example application uses the AVR128DA48 or the AVR128DB48-based PIM connected to a dsPICDEM™ MCLV-2 Development Board (Motor Control Low-Voltage) (MCLV-2). The MCLV-2 board offers a potentiometer for adjusting the speed of rotation, while the input protection and Back Electromotive Force (BEMF) circuitry are found on the PIM.

The system is capable of regenerative braking, which is inherent to the driving method used.

The driving waveforms for the motor are generated independently from the core, using the hardware capabilities of the microcontroller’s peripherals.

Additionally, the application employs several protection mechanisms such as stall detection, false input detection, and overcurrent protection in both directions.

The system can drive a wide range of BLDC motors with an adequate tuning of the firmware. Guidelines for tuning the parameters needed for different types of motors are outlined at the end of the document.

BLDC motors are used in a wide range of applications such as cordless power tools, computers, hard drives, multimedia equipment, cooling fans in small electronic equipment, electric vehicles and are a growing market for the electric future. The presented solution creates a cost-effective motor driver by using an 8-bit microcontroller when traditionally, only 16-bit microcontrollers or more were used in creating this device.