3-Phase BLDC Motor Sensorless Control Using MC56F8013

System ConceptStarting — Calculation of Commutation TimesDuring starting, next commutation time is calculated in three different way, according to zero crossingdetection, after regular operations during start.• Normal operation — During start, zero crossing is detected and the next commutation time iscalculated.2 FastCommutatio1 2 3Z E R OC R O S S1, 2 & 3 are fixed durations without calculation;1 : PER_START_PROCCMT_US2 : PER_TOFF_START_US3 : PER_CMT_START_USZero Cross detected and next commutation time is calculated.• No zero crossing detected — During startup, no zero crossing is detected and corrective action 1is performed.2 FastCommu123Z E R OC R O S S1, 2 & 3 are fixed durations without calculation;1 : PER_START_PROCCMT_US2 : PER_TOFF_START_US3 : PER_CMT_START_USNo Zero Cross detected and Corrective Action 1 is performed atnext commutation time.3-Phase BLDC Motor Sensorless Control using MC56F8013, Rev. 038 Freescale Semiconductor