AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 7

• Manufacturer Part Number: AN1914
• Description: 3-Phase BLDC Motor Control with Sensorless Back EMF Zero Crossing Detection Using DSP56F80x
• Manufacturer: Freescale Semiconductor / Motorola

3.3 Why Sensorless Control?
3.4 Power Stage - Motor System Model
As explained in the previous section, the rotor position must be known in order to drive a Brushless
DC motor. If any sensors are used to detect rotor position, then sensed information must be transferred
to a control unit (see
may not be acceptable for some applications. There are at least two reasons why you might want to
eliminate the position sensors:
In order to explain and simulate the idea of Back-EMF sensing techniques a simplified mathematical
model based on the basic circuit topology (see
•
•
AC Line Voltage
Inability to make additional connections between position sensors and the control unit
Cost of the position sensors and wiring
Speed
Setting
DSP56F80x MC PWM Module in Motor Control Applications
Figure
Freescale Semiconductor, Inc.
Control Signals
~
For More Information On This Product,
=
3-4). Therefore additional connections to the motor are necessary. This
Figure 3-4. Classical System
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Control Unit
Power Stage
Figure
3-5) has been created.
Position
Feedback
M
Sensors
Position
Target Motor Theory
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