3 phase bldc driver, no hall?

[vlad777]

I keep seeing these motors used in rc planes , and they are connected to driver
with only three wires ,so if they are 3 phase, hall sensors are not used.

So is there a three phase BLDC motor driver chip that doesn't use
hall position sensors?


Many thanks.

 

[dknguyen]

Yes there are. Allegro Microsystems has some I believe. But they are *very* limited since you are limited to the MOSFETs and/or drivers used in the chips. You can do the same thing yourself with some analog circuitry and programming a microcontroller.

Google around "sensorless BLDC" and you will find various app notes that cover different areas and methods. Here is one example. Make sure to look for others. Each has explains certain things better and other things worse.
https://www.st.com/stonline/books/pdf/docs/10401.pdf

You can also google "DIY Brushless ESC" to find example circuits of other brushless motor drivers people have built themselves for RC and see how the sensorless BEMF detection circuit works.