Motorola M68HC08 manual Running Commutation Time Calculation

Freescale Semiconductor, Inc.

Freescale Semiconductor, Inc.

BLDC Motor Control

COMMUTATION DONE
BEMF ZERO CROSSING	NO	CORRECTIVE CALCULATION 1.
DETECTED BETWEEN PREVIOUS
COMMUTATIONS?
YES
SERVICE OF COMMUTATION:
PRESET COMMUTATION
WAIT FOR PER_TOFF UNTIL PHASE
CURRENT DECAYS TO ZERO
	YES	BEMF ZERO CROSSING MISSED
BEMF ZERO CROSSING		CORRECTIVE CALCULATION 2
MISSED?		CORRECTED SETTING
		OF COMMUTATION TIME
NO
	YES	SERVICE OF RECEIVED BEMF
BEMF ZERO CROSSING		ZERO CROSSING:
		CORRECTED SETTING
DETECTED?
		OF COMMUTATION TIME
NO
NO
HAS COMMUTATION			NO
TIME EXPIRED?		HAS COMMUTATION
		TIME EXPIRED?
YES		YES
MAKE MOTOR COMMUTATION

Figure 3-16. BLDC Commutation with Back-EMF

Zero Crossing Sensing Flowchart

3.3.1.3 Running — Commutation Time Calculation

Commutation time calculation is shown in Figure 3-17.

Designer Reference Manual		DRM028 — Rev 0
42	BLDC Motor Control	MOTOROLA

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