BEMF sense

[amirkargar110]

hello
I want to design a brushless sensorless BLDC speed controller.
I put a voltage divider and a low pass filter for sensing BEMF Zero cross sense. and then I connect its output to 3 channels of ADC.
do you think that is enough and effective?
my micro is STM32F030K6T6  and it does not have analoge comprator.
do you think adc speed is enough for this work or I put a zero cross circuit like the figure and connect it to a timer input?

[ali_asadzadeh]

Welcome to the forum,
why do you need a zero cross circuit? besides that I think you should use a current sense circuit with X amplification and using a compactor, or you can use the ADC reading the Back-emf, there is a feature  inside the MCU that's called analog watchdog! so you will set it's limit to the desired voltage and if the adc readings pass the certain window level it would generate an interrupt, but the problem with this approach is that there would be a lot of adc samples that you are in the zero crossing section, so maybe with some software trick you could disable the analog watch dog and re-enable it after the PWM pulse!

these are just plain Ideas.-