AN2357 Freescale Semiconductor / Motorola, AN2357 Datasheet - Page 12

• Manufacturer Part Number: AN2357
• Description: Sine Voltage Powered 3-Phase Permanent Magnet Motor with Hall Sensor
• Manufacturer: Freescale Semiconductor / Motorola

AN2357/D
Period Calculation
Phase-Locked Loop
12
Sine Voltage Powered 3-Phase Permanent Magnet Motor with Hall Sensor
To eliminate the difference between the rotor poles, the edges from same poles
are used for period calculation. The motor used has three pole pairs. The
principle of period calculation is shown in
each signal edge, but the time from same edge and same pole is used for the
period calculation in the current time.
The PLL provides synchronization of generated sine voltage with Hall sensor
signal, and maintains sine wave frequency according to the Hall sensor signal.
The frequency of the sine wave is given by “phase_increment”. The actual
angle of sine wave is increased by this increment at each PWM reload. The
new “phase_increment” is counted, from the difference between the Hall
sensor signal and the sine wave period. See
The phase increment difference ∆α is calculated as:
where:
Freescale Semiconductor, Inc.
•
•
•
For More Information On This Product,
∆T — Position difference [sec]
α
T
— Phase increment [deg]
— Phase period (T = 256
∆α
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=
Figure 9. Calculation of Hall Sensor Period
pole I pole II pole III pole I pole II pole III
∆T
⋅
2 α
---------- -
T
⋅
2
period_hall_sensor
)
Figure
Figure
9. The period is calculated on
10.
MOTOROLA
Equation 4