Page 1 ELMOS Semiconductor AG Application Note QM

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E910.40
SENSORLESS POSITION CONTROL OF DC-MOTORS, RIPPLE COUNTER IC
Scope
Features
This application note provides information about
Ripple Detection method, external part configuration and schematic examples in conjunction with the
E910.40 IC.
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General Description
The Ripple Counter IC E910.40 allows a µC to track
the position of a DC-motor by counting its current
ripples.
The ripple signal is available on an output pin to
connect to microcontrollers or dedicated logic.
With the bidirectional interface the actual position
can be read out and IC parameters are motor and
PWM to control high side drivers.
The IC can be adapted to different motor characteristics by changing a few external components.
Operating voltage range VDD 9V to 16V
Full motor control and diagnosis
Driving N-channel-power-MOSFET full bridge
8-bit PWM resolution for high-side drivers
Nominal PWM frequency of 23kHz
Smooth motor acceleration and deceleration
Active motor braking
-40°C to +125°C operating temperature
SO20w package
Applications
ÿ Seat adjustment
ÿ Steering column adjustment
ÿ Fuel pump
VBAT
VCC
VDD
RB
VSA
VGH 2
VDD Reg
AVDD
VREF
µC
VGH 1
BIAS
BSI
slewrate
controlled
VREF
RSR
FET
Driver
Control
TEMP
M
Short
Circuit
Detect
DATA
IMPOUT
Incr.
Detect
BRTH
VGL 1
VGL 2
SENSE 1
SENSE 2
Filter & Amplifier
S/H
ODIF
IDIF
OLP
VREF
ELMOS Semiconductor AG
Application Note
1/25
QM-No.: 03AN0401E.01
E910.40
Package Pin Out
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2
19
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Pin Description
1)
Pin-No.
Name
Typ 1)
Description
1
GND
S
2
VGH1
AO
Gate voltage for high side driver 1
3
VGH2
AO
Gate voltage for high side driver 2
4
VGL1
AO
Gate voltage for low side driver 1
5
VGL2
AO
Gate voltage for low side driver 2
6
VDD
S
Input supply voltage
7
BSI
AI
Input bootstrap voltage
8
SENSE1
AI
Voltage sense bridge 1
9
SENSE2
AI
Voltage sense bridge 2
10
RSR
AI
External resistor to adjust the slew rate
11
OLP
AO
Output low pass filter
12
IDIF
AI
Inverting input differentiating amplifier
13
ODIF
AO
Output differentiating amplifier
14
VSA
AI
Internal 9V analog supply
15
RB
AI
External bias resistor
16
VREF
AO
Internal 5V supply voltage
17
BRTH
AI
Input brake threshold
18
TEMP
AI
Input temperature monitor
19
IMP OUT
AO
Incremental output for counting pulses, open drain
20
DATA I/O
AO
Serial data I/O
Ground
D = digital, A = Analog, S = Supply, I = Input, O = Output, HV = High Voltage (max. 40V)
ELMOS Semiconductor AG
Application Note
2 /25
QM-No.: 03AN0401E.01
E910.40
SO20w Package Outline
2 1
E
Index
Area
H
3
N
D
h x 45˚
Seating
Plane
A
e
ELMOS Semiconductor AG
B
C
A1
phi
L
Application Note
3 /25
QM-No.: 03AN0401E.01
E910.40
1 Introduction to ripple detection
An applied voltage across the the DC-motor terminals causes a current flow which establishes a rotation of the
rotor. To keep the rotor turning the motor windings need to be activated at the right moment to create a torque
which is the cause of the mechanical rotation. The commutation (activating the windings at the right moment)
is done mechanically by the commutator.
Figure 1 shows a DC-motor with stator (2 permanent magnets), rotor with 3 windings, brushes and
the commutator.
Figure 1: Simple example of a DC motor
Electrically a DC motor can be viewed as a series RL network with a voltage generator V(ω). The generator represents the back electromotive force (BEMF) generated by the motor’s rotation and which opposes the electromotive force of the supply. The value of the BEMF is a function of the motor’s angular velocity. If the motor has no
external load and its velocity is not limited, it will accelerate up to the velocity which equals V(w) at the supply
voltage Vs. In our example the BEMF is a vector sum of the three winding voltages P1, P2 and P3 which is shown
below.
Figure 2: Electrical schematics of motor windings
ELMOS Semiconductor AG
Application Note
4 /25
QM-No.: 03AN0401E.01
E910.40
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Figure 3: Generation of Commutation
During rotor‘s movement the resistance measured at the motor terminals for a short period of time
(during the commutation) changes its value; here from R tot=R || 2 R=
2
R to
3
1
R tot=R || R= R
2
(excluding effects caused by switching of winding inductances).
Brush
Winding
Resistance
R
R tot = R ll 2R = 2/3 R
R tot = R ll R = 1/2 R
Figure 4: Generation of Commutation Spikes
This causes a change of the current value seen as short commutation spikes, also called commutation ripple
which follows this equation:
Imot: Motor current
BEMF: Back ElectroMotive Force
ELMOS Semiconductor AG
I mot=
V BAT
BEMF
Rtot
Vbat
Rtot
Application Note
5 /25
: Battery voltage
: Total winding resistance
QM-No.: 03AN0401E.01
E910.40
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Figure 5: Motor resistance change with resulting current ripple (neglecting the armature inductance)
Additional inductance in the windings reduces the peak amplitude and creates an quasi-sinusoidal signal shape
of the current.
ELMOS Semiconductor AG
Application Note
6/25
QM-No.: 03AN0401E.01
E910.40
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Figure 6: Quasi-sinusoidal current shape
To improve the inductive coupling between the windings they can be wrapped around two armatures. In this
case the DC-motor can have unsymmetrical windings, the ripple current gets additional dynamic component as
a superpositioned sinusoidal wave with lower frequency which corresponds with the motor speed. This is caused
by different copper wire lengths of the different windings. Consequently the different winding resistance causes
fluctuating current flowing through the motor.
Figure 7: Unsymmetrical windings
ELMOS Semiconductor AG
Application Note
7 /25
QM-No.: 03AN0401E.01
E910.40
Figure 8: Low frequency signal superposition
Further parasitic effect on the ripple current is the magnetic flux weakening across the rotor and motor housing
caused by its geometry.
potentially
saturated
Figure 9: Stator field weakening
Another unwanted effect is the bending of the stator magnetic field caused by superposition of the rotor‘s
magnetic flux. This effect is strongly motor current and turning direction dependent and is intensified when the
motor current rises.
Figure 10: Stator field distortion
The result are double pulses which can be out of the commutation phase and must be recognized by the
ripple counter.
ELMOS Semiconductor AG
Application Note
8 /25
QM-No.: 03AN0401E.01
E910.40
Figure 11: Undefined Phase Relation due to Field Bending
2 Motor ripple signal processing with E910.40
The E910.40 measures the motor current fluctuation indirectly via the SENSE1/2 pins. The voltage drop across the
MOSFET‘s RDSON is measured and subsequently filtered. The filtered analog ripple signal is provided to a
min/max detection circuit which further generates a TTL compatible signal provided to the µC.
The SENSE1/2 input is internally connected to a 2nd order low-pass filter with an edge frequency of 2.5kHz to
surpress the PWM frequence
Following the low-pass filter a band pass filter using external components is implemented:
ÿ Pin 11 – OLP output internal 2nd order low pass filter,
ÿ Pin 12 – IDIF Inverting input differential amplifier,
ÿ Pin 13 – ODIF Output differential amplifier
Vbat
0
-
M
+
LOWPASS
SENSEx
OLP
C1
R1
Internal LP Filter
2,5kHz
4V
IDIF
+
ODIF
>> Ripple Detection Unit
(min/max)
-
R2
RDSon
C2
0
Figure 12: Filter schematics
ELMOS Semiconductor AG
Application Note
9 /25
QM-No.: 03AN0401E.01
E910.40
Mathematical description of the low pass filter followed by a band pass circuit:
2nd order Low Pass frequency response:
2
1
A 1=
1
j
0
with ω0 = 2πf0 ; f0 = 2.5kHz
Band pass frequency response:
1
j C1
X 1= R 1
X 2 =R2 ||
|A 2 |=
1
j
C2
X2
=
X1
R2
R1
1
R1
j
R2C 2
1
j
C2
=
1
1
j C1
1
R1
The expressions
R 2 ||
1
R2
j
R2
=
=
1
= R2
R2
R1
1
R2 C 2
R1 C 1
j
1
C1
R2C 2
R1C 1
j
R1 R2 C 2
1
R2C 2 R
1
1
j C1
R2 C 2
C1
1
j
1
R1 C 1
R2 C 2
the frequency independent amplification factor of the amplified voltage
across the motor and MOSFET voltage. The equation
1
1
R2 C 2
R1 C 1
can be simplified to
R2
R1
which is more suitable for further empiric component adjustment.
ELMOS Semiconductor AG
Application Note
10/25
QM-No.: 03AN0401E.01
E910.40
With ω = 2πƒ the expression
f 2=
2
1
R2 C 2
f 1=
2
1
R1 C 1
indicates the lower edge frequency of the band pass filter.
on the other hand is the higher band pass frequency of the band pass.
The equation for both filters in series:
R2
|A|= A1 A2 =
R1
2
1
1
j
1
0
R2 C 2
R1 C 1
1
j
R2 C 2
1
R1C 1
3 Adjusting the parameters C1, C2, R1, R2 of the band pass filter
First the amplification factor
R2 must be adjusted to the expected voltage drop across the switching MOSFET.
R1
The voltage range at the SENSE1/2 pin is -1.5V..2V. The internal OPA‘s supply voltage is 9V and the working voltage
was set to 4V.
Later on the edge frequencies f 1 and f2 are adjusted to the expected frequency range of the motor current
ripple. These steps are done by empirical measuring and analyzing of the signal quality at OLP/IDIF/ODIF pins.
Examining several automotive DC-motors allowed to extract following suitable start parameters for further
“fine-tuning” approach:
ÿ
ÿ
ÿ
ÿ
R1 = 10kΩ
R2 = 330kΩ
C1 = 1µF
C2 = 470pF
ÿ f1 = 16Hz
ÿ f2 = 1026Hz
ELMOS Semiconductor AG
Application Note
11 /25
QM-No.: 03AN0401E.01
E910.40
Frequency response of the band pass filter with listed parameters above (including the internal
E910.40 2nd-order low pass filter):
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Figure 13: Proposed filter frequency response
4 Dynamic ripple amplification gain adjustment
Because the analog ripple counting signal processing bases on a standard OPA circuit it can be modified to your
application needs.
Depending on the ripple counter application, a possible modification of the described band pass filter is the
dynamic amplification gain adjustment of the OPA to prevent the OPA from overdrive.
Circuit which decreases the amplification factor of the OPA during high motor current ripple.
ELMOS Semiconductor AG
Application Note
12/25
QM-No.: 03AN0401E.01
E910.40
0
0
+
IN
V1 =
V2 =
TD =
TR =
TF =
PW =
PER =
-1
1
1ms
1ms
1ms
2ms
4ms
+
C5
R2
+
5
IN_OP
6
4
V+
+
V2
9V
OUT
7
V11
-
10k
1µF
V4
-
V1
4V
R3
-
330k
C2
0
470p
R1
D3
D4
33k
R6
10k
C1
100nF
0
Figure 14: Dynamic gain reduction (schematics)
Measured signal at IN_OP and digital ripple counter output:
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Figure 15: Dynamic gain reduction (simulation)
ELMOS Semiconductor AG
Application Note
13/25
QM-No.: 03AN0401E.01
E910.40
Figure 16: Dynamic gain reduction (measured)
Circuit which increases the amplification factor of the OPA during high motor current ripple.
0
0
+
IN
V1 =
V2 =
TD =
TR =
TF =
PW =
PER =
-1
1
1ms
1ms
1ms
2ms
4ms
+
V4
C1
1µF
R2
-
V1
4V
+
5
IN_OP
6
10k
+
-
4
V+
V2
9V
OUT
7
V11
R3
-
330k
C2
0
470p
R1
D3
D4
33k
R6
10k
C1
100nF
0
Figure 17: Dynamic gain amplification (schematics)
ELMOS Semiconductor AG
Application Note
14/25
QM-No.: 03AN0401E.01
E910.40
Measured signal at IN_OP and digital ripple counter output:
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Figure 18: Dynamic gain amplification (simulation)
Figure 19: Dynamic gain amplification (measured)
ELMOS Semiconductor AG
Application Note
15/25
QM-No.: 03AN0401E.01
E910.40
Example of misconfigured filter parameters
The following oscilloscope screenshot shows a misconfigured bandpass filter. The ripple frequency signal is
suppressed. Some of the ripple counter pulses are lost.
Figure 20: Example of misconfigured bandpass filter
Example of well configured filter parameters
The following screenshot shows well configured filter parameters. No pulses are lost.
Figure 21: Example of well configured bandpass filter
ELMOS Semiconductor AG
Application Note
16/25
QM-No.: 03AN0401E.01
E910.40
5 Temperature supervision
The E910.40 provides temperature supervision of any connected application device.
Two possible temperature sensitive devices or a digital information circuit can be used:
ÿ 1.
ÿ 2.
ÿ 3.
NTC device
PTC device
external digital signal source
1.
2.
Vref (PIN 16)
3.
Vref (PIN 16)
Vref (PIN 16)
TEMP (PIN 18)
TEMP (PIN 18)
NTC
TEMP (PIN 18)
PTC
Figure 22: Temperate supervision circuits
As soon as the voltage at the pin TEMP (pin 18) reaches the threshold of
0.5±0.1 V ref
the OVERLOAD bit will be set to ‚1‘.
The following formula is used for estimation of V TEMP at pin 18.
Using an NTC:
V TEMP=V ref
Using a PTC:
V TEMP=V ref
R
=V ref
R R NTC
R PTC
=V ref
R R PTC
1
1
1
R NTC
R
where
R NTC = f T
1
where
R PTC= f T
R
R PTC
Using a digital signal source:
V TEMP high
V TEMP low
ÿ OVERLOAD bit ‚1‘
ÿ OVERLOAD bit ‚0‘
ELMOS Semiconductor AG
Application Note
17/25
QM-No.: 03AN0401E.01
E910.40
6 Adjusting the slew rate of Power MOSFET gate signals
The E910.40 provides an EMI conform switching behavior of the Power MOSFETs by reducing the gate signal‘s
slew rate. The resistor RSR connected to pin 10 of the E910.40 is responsible for the slew rate adjustment which
can reach values from 2 to 15 V/µs.
Note: The slew rate adjustment strongly depends on the gate capacitance of the Power MOSFET.
Note: RSR = 47kΩ @ CGS = 1.5nF provides a good EMI performance of the circuit.
7 Adjusting the motor braking ripple threshold
After a stop or direction change command during motor run it will be smoothly stopped by increasing/decreasing of the switching PWM duty cycle. In addition the ripple signal is evaluated again and the braking PWM
change actively adjusted.
Figure 23: Smooth PWM duty cycle change from 100% to 0%
The threshold of the succeeding ripple signal can be adjusted by an external voltage (i.e. Voltage divider) at the
pin BRTH. The equation for the braking threshold:
V BRTH brake threshold
=
5V
50 mV
brake threshold =
V BRTH 50 mV
5V
A use of a voltage divider of 2x10kΩ:
brake threshold =
ELMOS Semiconductor AG
2.5 V 50 mV
=25 mV
5V
Application Note
18/25
QM-No.: 03AN0401E.01
Application Note
19/25
MOTOR 2
MOTOR 1
GND
220p
C27
GND
NO REVERSE POLARITY PROTECTION !!!!
RIPPLE COUNTER UNIT
X5
X4
GND
VS
100nF
50V
GND
22
R4
8
7
6
5
4
3
1k
NC
SI
SO
GND
47µF
35V
C5
E910.18
TXD
RXD
BUS
TEST
GND3
RESET
VTR
GND2
EN
GND1
VDD
SENSE
VS
IC2
100nF
50V
C2
9
100nF
50V
C3
10
11
12
13
14
15
16
VSUP
GND
R2
100k
R3
100k
T3
FQB30N06
T1
FQB30N06
GND
1µF
C1
GND
GND
GND
100nF
16V
C14
10
9
8
7
6
5
4
3
2
1
T4
FQB30N06
T2
FQB30N06
GND
R1
100k
GND
1µF
C15
IDIF
OLP
SENSE2
RSR
E910.40
ODIF
SENSE1
VGL2
RB
VREF
VGL1
VSA
BRTH
VGH2
BSI
TEMP
VGH1
VDD
DATA_I/0
IMP_OUT
GND
IC1
VCC
11
12
13
14
15
16
17
18
19
20
1µF
C11
10k
R13
33k
R12
10k
R11
R10
330k
D2
470p
C10
100nF
100nF
BAV99
GND
C8
C9
R14
4,7k
100nF
16V
C7
100nF
C12
GND
GND
R9
330k
GND
R8
10k
R7
10k
GND
1k
R6
R15
4,7k
GND
T7
BC847BSMD
R16
4,7k
To µC
Dokument-No.: 03SP0275E.xx
X3
X2
100µF
35V
GND
2
1
D3
R17
BAW56
C13
D1
ELMOS Semiconductor AG
C4
BAW56
(LIN TRANSC.USED AS LEVEL SHIFTER + VOLT.REG.)
ELMOS RELIN
VCC POWER SUPPLY + LEVEL SHIFTER
E910.40
8 E910.40 DATA I/O protocol
For detailed information and examples please refer to the E910.40 datasheet.
Specification E910.40
9 Typical E910.40 Application
Figure 24: E910.40 Typical application
QM-No.: 03AN0401E.01
E910.40
10 E910.40 Evaluation Kit
For evaluation of the E910.40 ELMOS Semiconductor AG provides an E910.40 Evaluation Kit which can be
ordered at [email protected].
Figure 25: E910.40 Evaluation Board
Figure 26: E910.40 Evaluation Board Control
ELMOS Semiconductor AG
Application Note
20/25
QM-No.: 03AN0401E.01
E910.40
Features:
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
ÿ
Designed for 12V automotive applications,
Driving motor with a blocking current up to 30A,
Based on an easy to use ATMEGA32L™ * µC,
C-sources available,
Basic functions like:
ÿ speed up motor,
ÿ slow down motor,
ÿ motor position counter reset,
are accessed by integrated on-board switches,
Processing of 2 end position switches,
Feedback and diagnosis available via RS232,
PC connection via parallel port,
PC based LabVIEW GUI, allows operations like:
ÿ cyclic motor speed ramp generation,
ÿ cyclic direction change,
ÿ watchdog function,
ÿ graphical motor position tracking,
ÿ processing of end switches,
Easy accessible test points to adjust the filter components,
External ripple filter components designed to be in SMD and through hole technology
* ATMEGA32L is a Trade Mark of Atmel Corparation
ELMOS Semiconductor AG
Application Note
21/25
QM-No.: 03AN0401E.01
E910.40
11 Record of Revisions
Chapter
1
Rev.
Change and Reason for Change
Date
1
Initial Revision
18.01.2006
2
New Figure 7
18.05.2006
ELMOS Semiconductor AG
Application Note
22/25
Released
ZOE/EM
QM-No.: 03AN0401E.01
E910.40
Contents
Package Pin Out.......................................................................................................................................................................................
Pin Description.........................................................................................................................................................................................
SO20w Package Outline........................................................................................................................................................................
1 Introduction to ripple detection ....................................................................................................................................................
2 Motor ripple signal processing with E910.40 ............................................................................................................................
3 Adjusting the parameters C1, C2, R1, R2 of the band pass filter .............................................................................................
4 Dynamic ripple amplification gain adjustment .......................................................................................................................
5 Temperature supervision .................................................................................................................................................................
6 Adjusting the slew rate of Power MOSFET gate signals ........................................................................................................
7 Adjusting the motor braking ripple threshold ..........................................................................................................................
8 E910.40 DATA I/O protocol ..............................................................................................................................................................
9 Typical E910.40 Application ............................................................................................................................................................
10 E910.40 Evaluation Kit.....................................................................................................................................................................
11 Record of Revisions............................................................................................................................................................................
2
2
3
4
9
10
12
17
18
18
19
19
20
22
List of Figures
Figure 1: Simple example of a DC motor .......................................................................................................................................... 4
Figure 2: Electrical schematics of motor windings ....................................................................................................................... 4
Figure 3: Generation of Commutation Ripple ................................................................................................................................ 5
Figure 4: Generation of Commutation Spikes ................................................................................................................................ 5
Figure 5: Motor resistance change with resulting current ripple (neglecting the armature inductance) .................. 6
Figure 6: Quasi-sinusoidal current shape......................................................................................................................................... 7
Figure 7: Unsymmetrical windings..................................................................................................................................................... 7
Figure 8: Low frequency signal superposition ................................................................................................................................ 8
Figure 9: Stator field weakening ......................................................................................................................................................... 8
Figure 10: Stator field distortion ......................................................................................................................................................... 8
Figure 11: Undefined Phase Relation due to Field Bending ......................................................................................................... 9
Figure 12: Filter schematics ................................................................................................................................................................... 9
Figure 13: Proposed filter frequency response ................................................................................................................................ 12
Figure 14: Dynamic gain reduction (schematics) ........................................................................................................................... 13
Figure 15: Dynamic gain reduction (simulation) ............................................................................................................................ 13
Figure 16: Dynamic gain reduction (measured) ............................................................................................................................. 14
Figure 17: Dynamic gain amplification (schematics) .................................................................................................................... 14
Figure 18: Dynamic gain amplification (simulation) ..................................................................................................................... 15
Figure 19: Dynamic gain amplification (measured) ...................................................................................................................... 15
Figure 20: Example of misconfigured bandpass filter ................................................................................................................. 16
Figure 21: Example of well configured bandpass filter ................................................................................................................ 16
Figure 22: Temperate supervision circuits ....................................................................................................................................... 17
Figure 23: Smooth PWM duty cycle change from 100% to 0% ................................................................................................. 18
Figure 24: E910.40 Typical application .............................................................................................................................................. 19
Figure 25: E910.40 Evaluation Board .................................................................................................................................................. 20
Figure 26: E910.40 Evaluation Board Control ................................................................................................................................. 20
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Application Note
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QM-No.: 03AN0401E.01
E910.40
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