ORIGINAL: danvel
However I still have doubts regarding your advance. Based on Quax posts it seems that 7,5º is a suitable advance (being 30º=half cyle). That means one should conmutate 22,5º after BEMF zero cross has been detected.I think you don't have a tight control over this delay and that's why I would like to see a couple (30%,60%) scope figures of your BEMF and some efficiency comparation between your driver and a commercial one (if you have it).
Hi danvel,
You could be right. I did not compare efficiency with commercial controllers. My assumption has been that I was doing ok since the FETs stay cool. It does work great from very low rpm all the way to full rpm.? I will try to capture the waveforms when I get a chance. I would like to learn more about this myself. Have a great holiday. Look forward to hearing about your progress with the changes to backemf circuit.
tve