Microchip Technology AN970
This application note describes BLDC motor speed control without the use of sensors.| Part No. | AN970 |
|---|---|
| Datasheet | AN970 Download |
| Manufacturer |  Microchip Technology |
| Description | Using the PIC18F2431 for Sensorless BLDC Motor Control |
| Buy | Stock & Price |
APPLICATIONS
like the compressor control in a refrigerator or in HVAC systems, which generates heat and an elevated temperature, may accelerate Hall sensor failures. Using sensorless control improves the reliability of total system. There are two disadvantages to sensorless control:● The motor must be moving at a minimum rate to generate sufficient BEMF to be sensed.
● Abrupt changes to the motor load can cause the BEMF drive loop to go out of lock. As the BEMF signal is proportional to the speed of rotation at standstill and at low speeds, the amplitude of the BEMF poses a challenge to determine the zero crossover point. In order to overcome this problem, the motor is normally run in open loop during starting and is accelerated to a speed where the BEMF has sufficient amplitude to detect and then synchronize with the zero crossing point. Running the motor in open loop makes it difficult to know the rotor position, when starting from standstill. So, the rotor can rotate in either direction when energized.
