Motorola M68HC08 Reference Manual page 9

Designer Reference Manual — Sensorless BLDC Motor Control
DRM028 — Rev 0
MOTOROLA
Freescale Semiconductor, Inc.
Figure
2-1 System Concept . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
3-1 BLDC Motor Cross Section. . . . . . . . . . . . . . . . . . . . . . . . . . . .24
3-2 3-Phase Voltage System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
3-3 BLDC Motor Back EMF and Magnetic Flux . . . . . . . . . . . . . . . 26
3-4 Classical System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
3-5 Power Stage — Motor Topology. . . . . . . . . . . . . . . . . . . . . . . . 28
3-6 Phase Voltage Waveform . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31
3-7 Mutual Inductance Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32
3-8 Detail of Mutual Inductance Effect . . . . . . . . . . . . . . . . . . . . . . 33
3-9 Mutual Capacitance Model . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
3-10 Distributed Back-EMF by Unbalanced
Capacity Coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .35
3-11 Balanced Capacity Coupling. . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3-12 Back-EMF Sensing Circuit Diagram . . . . . . . . . . . . . . . . . . . . .37
3-13 The Zero Crossing Detection . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3-14 Commutation Control Stages . . . . . . . . . . . . . . . . . . . . . . . . . . 39
3-15 Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3-16 BLDC Commutation with Back-EMF
Zero Crossing Sensing Flowchart. . . . . . . . . . . . . . . . . . . . . . . 42
3-17 BLDC Commutation Time with Zero Crossing Sensing . . . . . . 43
3-18 Vectors of Magnetic Fields . . . . . . . . . . . . . . . . . . . . . . . . . . . .47
3-19 Back-EMF at Start Up. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3-20 Calculation of the Commutation Times During the Starting
(Back-EMF Acquisition) State. . . . . . . . . . . . . . . . . . . . . . . . . . 49
4-1 High-Voltage Hardware System Configuration . . . . . . . . . . . . . 59
4-2 Low-Voltage Evaluation Motor Hardware
System Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
4-3 Low-Voltage Hardware System Configuration . . . . . . . . . . . . . 63
4-4 MC68HC908MR32 Control Board . . . . . . . . . . . . . . . . . . . . . . 65
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List of Figures
Title
Designer Reference Manual
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9