BLDC Motor Control
Used Control Technique
DRM028 — Rev 0
Designer Reference Manual
MOTOROLA
BLDC Motor Control
39
position is known, and can be used to calculate the speed and
processing of the commutation in the running state.
Figure 3-14. Commutation Control Stages
3.3.1.1 Alignment
Be
fore the motor starts, there is a short time (depending on the motor’s
electrical time constant) when the rotor position is stabilized by applying
PWM signals to only two motor phases (no commutation). The current
controller keeps current within predefined limits. This state is necessary
in order to create a high start-up torque. When the preset time-out
expires then this state is finished.
ALIGNMENT
STARTING
(BACK-EMF ACQUISITION)
RUNNING
ALIGNMENT TIME
EXPIRED?
START MOTOR
MINIMAL CORRECT
COMMUTATIONS DONE?
NO
YES
YES
NO
F
re
e
sc
a
le
S
e
m
ic
o
n
d
u
c
to
r,
I
Freescale Semiconductor, Inc.
For More Information On This Product,
Go to: www.freescale.com
n
c
.
..
