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I've currently developed a BLDC motor controller and it generally works fine. During some events however the microcontroller locks up (e.g. stopping the motor or fast changes of duty cycle). Because of this, I want to isolate the microcontroller from the power side (i.e. isolated supply and optocoupled signals) the issue however is I'm using sensorless control and am wondering what the best way of relaying the phase values back to the microcontroller would be?

I currently detect the zero crossing in software and use this to commutate my phases (as per the Microchip AN970 amongst others). I'd rather not use comparators on the power side and optocouplers to send back a digitized version of the phase voltages as I want to have the ability to change the trigger point.

I've looked at isolation amplifiers but they seem pretty expensive and I was wondering if there were any potentially cheaper solutions.

Thanks

Pyrohaz
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Maybe have a look at this document: https://www.silabs.com/documents/public/application-notes/AN614.pdf. We use this design, but in a total different application. I dont' really know much about BLDC motors but maybe it helps.

kind regards

Mike
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