3.22EjemploDRM007 Co..

Software Design Considerations
5.5 Commutation Algorithm
The commutation algorithm provides the generation of a rotational field
according to rotor position. This algorithm uses the Hall sensors to
obtain the rotor position. Outputs from the Hall sensors are connected to
three independent input-capture channels through an analog filter. The
timers are set to catch each input signal edge and call an interrupt
routine, which provides the commutation algorithm.
The Hall sensor consists of three sensors (sensor A, sensor B, and
sensor C). These sensors comprise six states (001, 010, 011, 100, 101,
and 110). Each state determines which motor phase the 3-phase
inverter should power. The interrupt routine reads the state of the Hall
sensors from the MCU port. This value is used as pointer to the
commutation table (see Table 5-1 and Table 5-2), which includes
information about the power MOSFETs gating. Figure 5-4 shows the
resultant voltage which is applied to a BLDC motor per one electrical
revolution.
Table 5-1. Commutation Sequence for Clockwise Rotation
Hall Sensor Inputs Two MOSFET Scheme Three MOSFET Scheme
Hall
Sensor A
Hall
Sensor B
Hall
Sensor C
Phase A Phase B Phase C Phase A Phase B Phase C
1 1 0 +Vdc NC –Vdc +Vdc –Vdc –Vdc
1 0 0 +Vdc –Vdc NC +Vdc –Vdc +Vdc
1 0 1 NC –Vdc +Vdc –Vdc –Vdc +Vdc
0 0 1 –Vdc NC +Vdc –Vdc +Vdc +Vdc
0 1 1 –Vdc +Vdc NC –Vdc +Vdc –Vdc
0 1 0 NC +Vdc –Vdc +Vdc +Vdc –Vdc
DRM007
BLDC Motor Control Board for Industrial and Appliance Applications
80 Software Design Considerations MOTOROLA