COMPANY CONFIDENTIAL 1
eBike Sensorless Motor Control
Alex Lollio, Global Rotation Engineer
Automotive Products Business UnitProvence Design Centre, France
May, 2013 - Jul, 2013
Project Manager : Andre MourrierProgram Mentor : Massimo Grasso
COMPANY CONFIDENTIAL
e-Bike Overview
Market Info:
• $8.4 billion in 2013*
• 90% of e-Bike sales in China*
General Specifications:
•Battery 40-48V (10AH)
•Power 150W - 500W
•Input Current 10-15ARMS
•BLDC Motor
48V Lit Battery
Control Board BLDC Motor
*http://www.navigantresearch.com/research/electric-bicycles
IR Interests:
• 6 Power MOSFETS (IRFB3607)
• IC Controller and Gate Driver (IR3230)
COMPANY CONFIDENTIAL
BLCD Motor Working Principle: 2 Pole
COMPANY CONFIDENTIAL
IR Controller for e-Bike: IR3230
Main Features:•Brushless DC Motor Sensor Decoder & HVIC MOSFET Driver•Charge pump operation (No bootstrap capacitor)•Up to 30Khz PWM switching capability (on the low switches)
•Programmable over current and over temperature protections
Green = sensor2
Green = Ph2
Yellow = Ph3
Battery power supply -Battery power supply +
Blue = Ph1
Blue = sensor1
Yellow = sensor3
+5V
GNDIR32
30
+5V
GND
COMPANY CONFIDENTIAL
Project Goal: Sensorless Implementation
Power FETs: 0.2$ x 6 ≈ 1.2$
Discrete Components ≈ 0.5$
Microcontroller ≈ 0.6$
Hall Sensors: 0.4$ x 3 ≈ 1.2$
Electronic Board BLDC Motor
Goal of the Project:
• Adapt IR3230 Controller & HVIC driver for a Sensorless implementation
Sensorless Cost Saving
Costumer Request:
• Sensorless driving strategy: reducing costs, simplify motor assembly and reducing failure (most failure = Hall sensors)
Sensors(0.15$)+Assembly(0.15$)+Cabling(0.1$)
COMPANY CONFIDENTIAL
IR3230 Typical Schematic
Basic Idea: replacing the Hall Sensor with a Micro which senses the generated BEMF
+5v
Gnd_p
+V b a t
G ro u n d
I / O
5.6V
Power _mosf et
Vb
att
ery
Gn
d
P h 1
P h 2
P h 3
G h s 1
S k _ p h 1
G ls 1
G h s 2
S k _ p h 2
G ls 2
G h s 3
S k _ p h 3
G ls 3
Cpump
CTN Rshunt
IR3230
Gn
d
V s s
V s 1
V s 2
V s 3F lt _ rs t
M o t / R e g e n
F lt
1 2 0 / 6 0
R e v / F wd G n d p wr
S h t p
O u t _ S u p p ly
Vc
c
P wm
E nS e n s 1
H o 1
S e n s 2
H o 2
Tp
S e n s 3
H o 3
L o 1
L o 2
S h t m
Pm
p
L o 3
+5v
Di gi t al
Cd
Gnd
R d ig _ in
+ +
M 1
P h 1
P h 2
P h 3
S e n s 1S e n s 2S e n s 3
+5 v
G n d
R d ig _ in 1
R d ig _ in 2
R d ig _ in 3
R d ig _ in 4
R d ig _ in 5
R d ig _ in 6
Gnd_p
Gnd
Gnd
+5v
SOIC28
TºC
Mea
sure
men
t
5V Power Supply
Charge pumpShunt
Sensors interface
Diagnostic and Reset
Order input and Selection
Power Mosfet
BLDC Motor
IR3230
COMPANY CONFIDENTIAL
What is Back Electromagnetic Force?
turning rotor
GND
Floating
Example: Trapezoidal Motor Driving
Faraday Law:
The induced Electromagnetic Force (EMF) is the voltage produced by changing magnetic flux into the windings
A
B
C
Floating phase, C, can be used to measure the Back EMF generated by the turning rotor.Generated Back EMF is proportional to angular rotation speed
A
B
C BEMF+-
VCC
COMPANY CONFIDENTIAL
Back EMF when duty cycle is 100%
BEMF crosses VDD/2 in the middle of the switching period
Switching Period
VDD/2
VDD
Low Side ON
High Side ON
Z 0 Z1 1PHA
High Side ON
Inductive transient
Inductive transient
Step 1
0Step 2 3 4 5 6 1
Trapezoidal Driving6 Step Sequence
A A
A A
A A
C C
B
B
B
B
B
C C
C B C
PHAStep 2
Step 3 Step 4
Step 5 Step 6
THIS GRAPH SHOWS THE VOLTAGE OF NODE PHA
COMPANY CONFIDENTIAL
Back EMF @Duty=20% (low side modulation)
Switching Period
VDD/2
Low Side PWM
High Side ON
Z PWM Z1 1PHA
High Side ON
Step 1
PWMStep 2 3 4 5 6 1
Trapezoidal Driving6 Step Sequence
A A
A A
A A
C C
B
B
B
B
B
C C
C B C
PHAStep 2
Step 3 Step 4
Step 5 Step 6
THIS GRAPH SHOWS THE VOLTAGE OF NODE PHA
COMPANY CONFIDENTIAL
BEMF in Trapezoidal Motor Driving
PH1-A
PH2-B
PH3-C
Sens1
Sens2
Sens3
1 2 3 4 5
0
1
1
0
0
1
1
0
1
1
0
0
1
1
0
0
1
0
1
Z
0
Z
1
0
0
1
Z
0
Z
1
Z
0
1
1
0
Z
66 STEPS
Algorithm Strategy: VDD/2 crossing point in the middle of the switching cycle
VDD/2
VDD
T/2 T
COMPANY CONFIDENTIAL
TSBEMF
Voltage
TS/2
time
VREF
Basic Idea: Circuital Implementation
zero-cross
POWER MOSFET
A
B
C
RA1RB1 RB3
SNS1SNS2SNS3
PWM
RE0RE1RE2
RD5
MOTORWINDINGSPICF1937 IR3230
RA3
VSUP
VREF
• Microcontroller compares the BEMF voltages to the reference voltage VREF
• When BEMF<VREF the internal comparator generates an interrupt (let’s call this event “zero-cross”)
COMPANY CONFIDENTIAL
Basic Idea: Algorithm working principle
Time
FFFFh
0000h
-N
-N/2
error
errorPerfect zero-cross
Late zero-cross
-N’ = -(N+error)
-N’/2
Perfect zero-cross
Commutation periods
Full commutation preset
Half commutation preset
TIMER1
Timer1 overflow
The Back EMF tracking Algorithm works like a PLL: adjusting the commutation period in order to keep zero-cross in the middle
COMPANY CONFIDENTIAL
Demoboard Image
BEMF Voltage Divider
BEMF Voltage Divider are tested for input supply voltage into the range 12-48V
PWM Trimmer
Connector to ICD3 programmer
PHA
PHB
PHC
IR3230
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