Overview

This application note presents the motor control theory needed to drive a BLDC motor and contains a comparison between the sensored and sensorless motor control, a typical implementation of a power stage, modulation techniques as well as a detailed description of the custom PIM.

Moreover, the document covers a detailed presentation of bipolar switching, which is the focus of this example.

To obtain the position of the rotor, the zero-cross point detection method is covered, using a comparator with a variable voltage reference consisting of a virtual neutral of the motor.

The motor starts at an initial position after an alignment routine. This is done so that at start-up the motor follows the generated open-loop waveform.

At compile-time, the user can select the mode the motor must run in, open- or closed-loop.

A potentiometer on the MCLV-2 board provides a value read by the ADC that is used to compute a duty reference for the waveform timer, and this reading, along with the current, is done asynchronously from the motor logic drive of the software. This part runs in the main loop, while the motor control runs on interrupts to get the best response time possible.

At the end of this document, the user can find a brief introduction to tuning the parameters of the firmware to obtain the desired results.

This application example uses the following peripherals:

• Analog Comparator (AC)
• Analog-to-Digital Converter (ADC)
• I/O Pin Controller (PORT)
• Timer/Counter Type A (TCA)
• Timer/Counter Type B (TCB)
• Timer/Counter Type D (TCD)
• Custom Configurable Logic (CCL)
• Voltage Reference (V_REF)
• Universal Synchronous Asynchronous Receiver Transmitter (USART)