AN1913D Freescale Semiconductor / Motorola, AN1913D Datasheet - Page 26

• Manufacturer Part Number: AN1913D
• Description: 3-phase BLDC Motor Control with Sensorless Back-EMF ADC Zero Crossing Detection using DSP 56F80x
• Manufacturer: Freescale Semiconductor / Motorola

Control Technique
26
Figure 5-10
according to the rotor speed. During the Starting (Back-EMF Acquisition) state the commutation is
done in advance. In the Running state the commutation is done at the right moments.
Phase Back-EMF’s
Back-EMF Zero Crossings
Ideal Commutation Pattern when position is known
Real Commutation Pattern when position is estimated
Align
C
C
B
B
BOT
BOT
TOP
TOP
1’
st
demonstrates the Back-EMF during the start-up. The amplitude of the Back-EMF varies
2’
nd
BLDC control with BEMF Zero Crossing using ADC
A
C
A
Freescale Semiconductor, Inc.
Starting (Back-EMF Acquisition)
TOP
BOT
BOT
For More Information On This Product,
Figure 5-10. Back-EMF at Start-Up
Go to: www.freescale.com
C
TOP
Phase C
3’
rd
B
4’
BOT
Phase B
rd
B
BOT
Phase A
A
.................
TOP
A
TOP
C
C
BOT
BOT
B
Running
B
TOP
TOP
A
A
BOT
BOT
C
C
TOP
TOP