Methods and apparatus for automatic lead angle adjustment using fly-back voltage for brushless DC control

摘要

A method includes: outputting high side driver gate signals to a plurality of high side driver devices and outputting low side driver gate signals to a plurality of low side driver devices configured to control current supplied to a motor having coils coupled to receive the current at a plurality of phase nodes; at a time approximately prior to an expected zero crossing of a voltage at a selected one of the plurality of phase nodes, disabling the high side driver gate signal and the low side driver gate signal; measuring a back electromotive force (BEMF) voltage and observing a zero crossing time; estimating a next zero crossing time; prior to the next zero crossing time, disabling the high side driver gate signal and the low side driver gate signal and observing the selected one of the phase nodes to form a first sample; and following the next zero crossing time, observing a second voltage at the selected one of the phase nodes to form a second sample.