AN1627 Freescale Semiconductor / Motorola, AN1627 Datasheet - Page 14

• Manufacturer Part Number: AN1627
• Description: Low Cost High Efficiency Sensorless Drive for Brushless dc Motor Using MC68HC (7)05MC4
• Manufacturer: Freescale Semiconductor / Motorola

5.2.2
This routine performs the start algorithm and consists of the parts mentioned in the Control Algorithm
Section.
5.2.2.1
The required value of the current is set. The Current Controller keeps the current at the required value.
The Current Controller subroutine is called every 512
been obtained. The PWM signals are applied onto only two motor phases (no commutation). The motor
current and rotor position is stabilized.
5.2.2.2
The commutation period is decreased in order to reach the maximal speed within 5 seconds (see Figure
5-4.).
The following subroutines are called: Current Controller (512
voltage sensing, Commutation and Ramp.
When finished ramping-up (the motor is running at the required speed), the program flow continues.
5.2.2.3
Here, the motor speed is stabilized before the PLL Acquisition takes place. The motor is running with
constant speed. After a certain time (which depends on the application), the program flow continues to
the next stage.
The Current Controller (512
the Commutation subroutines are called from this part.
5.2.2.4
The current peak during one commutation is detected, if it is higher than the preset limit (2.5A), then the
PWM duty cycle is decreased. The Timer Input Capture interrupt is enabled ~20
MOTOROLA
14
START
Alignment
Ramp-up
Stabilizing
PLL Acquisition
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s period), the Speed Setting & DC-Bus voltage sensing and
Figure 5-2.
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PLL Acquisition
s after new value of the DC-Bus current have
s period), Speed Setting & DC-Bus
REV 0.2
AN1627
s after