AN1913 Motorola / Freescale Semiconductor, AN1913 Datasheet - Page 6

• Manufacturer Part Number: AN1913
• Description: AN1913 3-phase BLDC Motor Control with Sensorless Back-EMF ADC Zero Crossing Detection using DSP 56F80x
• Manufacturer: Motorola / Freescale Semiconductor

Target Motor Theory
3.2 3-Phase BLDC Power Stage
3.3 Why Sensorless Control?
6
The voltage for a 3-phase BLDC motor is provided by a 3-phase power stage. The 3-phase power stage
is controlled by the DSP on-chip PWM module; which creates the desired switch control signals. A
DSP with a BLDC motor and power stage is shown in
As explained in the previous section, the rotor position must be known in order to energize the phase
pair and control phase voltage of a BLDC motor. If any sensors are used to detect rotor position, then
sensed information must be transferred to a control unit (see
Therefore, additional connections to the motor are necessary. This may not be acceptable for some
kind of applications. There are at least two reasons why you might want to eliminate the position
sensors: impossibility to make additional connections between position sensors and the control unit
cost of the position sensors and wiring.
The first reason might be solved by integration of the driver within the motor body. However, a
significant number of applications requiring a sensorless solution still remain.
For additional BLDC control information, refer to
AC Line Voltage
Speed
Setting
BLDC control with BEMF Zero Crossing using ADC
Control Signals
~
=
Figure 3-4. Classical System
Control Unit
Power Stage
Section 5
Figure
Figure
and AN1627
Position
Feedback
5-1.
M
3-4).
Sensors
Position
(Section
11.2).
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