AN1914 Freescale Semiconductor / Motorola, AN1914 Datasheet - Page 16

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

Control Technique
5.
5.1 Control Technique - General Overview
5.2 PWM voltage Generation for BLDC
16
POWER
SOURCE
DC VOLTAGE
the switching of the IGBTs (MOSFETs). This signal is transferred to the DSP Encoder Input which is
also used as a digital filter. The SW selects one of the phase comparator outputs which corresponds to
the current commutation step.
The general overview of used control technique is shown in
following subsections:
The implementation of the control technique with all the SW processes is shown in Flow Chart, State
diagrams and Data Flow (see
As was already explained, the three phase voltage system shown in
run the BLDC motor. It is provided by 3-phase power stage with 6 IGBTs (MOSFET) controlled by
the on-chip PWM module (see
Figure 5-2
Figure 5-2
This is needed for any effective control of Brushless DC motor with trapezoidal BEMF.
•
•
•
Control Technique
PWM voltage generation for BLDC
Sensorless Commutation Control
Speed Control
and
shows that both Bottom and Top power switches of the “free“ phase must be switched off.
PWM1
Figure
3-PHASE POWER STAGE
DSP56F80x MC PWM Module in Motor Control Applications
PWM1
PWM2
S
S
PULSE WIDTH MODULATOR
(PWM) MODULE
AT
5-3.
AB
Figure 5-1. PWM with BLDC Power Stage
Freescale Semiconductor, Inc.
PWM2 PWM3
For More Information On This Product,
Figure 7-2
MOSFET/IGBT DRIVERS
Figure
Go to: www.freescale.com
PWM3
PWM4
S
S
BT
BT
PWM4 PWM5
through
5-1). The PWM signals with state currents are shown in
Figure
PWM5
PWM6
S
S
CT
CT
PWM6
7-8).
Figure
DSP56F80X
Figure 3-2
4-9. It will be described in
3-PHASE BLDC MOT
A
needs to be created to
B
C