Wurth Electronics Midcom EMI
WURTH ELECTRONICS MIDCOM INC.
2012
Presentation
EMC, Inductors,
& filtering
Speaker: Douglas A. Toth, PE
doug.toth@we-online.com
Sept 2012
1
Agenda
• EMC- basics
• Magnetic field basics
• Filtering & Signals
• Insertion loss calculation
• Filter topologies
• Simulation
• Live measuring with spectrum analyzer
Sept 2012
2
EMC - requirement
Electromagnetic Compatibility
Emission
Conducted
Emission
Sept 2012
Immunity
Radiated
Emission
Conducted
Suscept.
Radiated
Suscept.
3
EMC - Affect
economical point of view:
• depends when you will start to design EMC conform
Cost
R
ew
o
rks
EM
Cinadvanceconsidered
Pre-design
Sept 2012
Prototype
Production
Time
4
Magnetic field
• Right-hand rule
current flowing
through wire
Magnetic field „B“
Current direction ”I”
Electro magnetic
(Lorentz) Force „F“
Sept 2012
5
Magnetic Field
Current conducted wires are generate
a magnetic field around them
Magnetic flux lines
Current I
Magnetic field H
Sept 2012
6
Magnetic Field
Ma
g
n
e
t
i
cf
l
uxl
i
n
es
Sept 2012
7
Magnetic Field – Term Used for Different Vector
Fields
N
O
R
T
H
S
O
U
T
H
Current I
Sept 2012
8
EMI: Conducted Emission Measurement
§
Power supply V 1.0
PCB
Buck Converter ST L4960/2.5A/fs 85-115KHz
Sept 2012
9
EMI: Conducted Emission Measurement
§
Power supply V 1.1
PCB
Schematic
Sept 2012
10
EMI: Be Aware:
§ Select the right parts for your
application
§ Do not always look on cost
Very easy solution with a
dramatic result!!!
or
Choke before
Sept 2012
Choke after
11
EMI: Shielded vs. Unshielded Power Inductor
unshielded
Sept 2012
shielded
12
EMI: Shielded vs. Unshielded Power Inductor
Sept 2012
13
EMI: Shielded vs. Unshielded Power Inductor
• Magnetic field
Sept 2012
shielded
unshielded
14
EMC - Coupling
…sometimes occurs as inter-system-influence
• a sufficient EMC-design can be done at noise source, coupling path or at coupled load
à Primary procedure
…low emission of noise at source
à Secondary procedure
… eliminate the noise by interrupting it from path of the coupling
à Tertiary procedure
… increase the noise immunity of load
Load
Noise source
Coupling Path
Sept 2012
15
EMC – Electromagnetic Wave
Sept 2012
16
EMC – Electromagnetic Wave
1 cycle = 0o to 360o
Period (S) = 0 seconds to 20uS
Frequency (F) = 1 / Period
= 1 / 20uS
= 50 kHz
0o
0S
360o
Wavelength (?) = Speed of Light (m/s) / Frequency
= 300x106 / 50000
= 6000 metres
Sept 2012
20uS
17
EMC – Electromagnetic Wave
Frequency = 50kHz
Wavelength (?) = 6000 metres
Sept 2012
Frequency (F) = 500MHz
Wavelength (?) = 0.6 metres
18
CISPR* 22
– Special International Committee on Radio Interference
– Non regulatory agency, but CISPR has adopted
• 150kHz to 30MHz
Conducted
• 30MHz to 1GHz
Radiated
FCC** 15
– Regulatory agency
• 450kHz to 30MHz
• 30MHz to 1GHz
Conducted
Radiated
*Special International Committee on Radio Interference, Pub .22
**Federal Communications Commission, Part 15
Sept 2012
19
Sept 2012
20
EMC - Norms
Since 1996 it is a must, that in EU all electronic devices are CE conform
according to 2004/108/EC
World wide:
IEC 61000-4-1
- Introduction, terms and conditions
IEC 61000-4-7
- Interharmonics
IEC 61000-4-2
- Electrostatic discharge requirements
IEC 61000- 4-8
- Magnetic Field Immunity
IEC 61000-4-3
- Radiated Immunity
IEC 61000-4-9
- Magnetic Field Immunity
IEC 61000-4-4
- Testing and measurement techniques
IEC 61000-4-10
- Magnetic Field Immunity
IEC 61000-4-5
- Installation and mitigation guidelines
IEC 61000-4-11
- Dips & Interrupts
IEC 61000-4-6
- Generic standards
IEC 61000-4-12
- Damped Oscillatory
European norms
Emission
Immunity
Information technology equipment
EN 55022 (P)
EN 55024 (P)
Industrial plant
EN 50081-2 (FG)
EN 50082-2 (FG)
Industrial, scientific and medical equipment RF equipment
EN 55011 (P)
EN 50082-2 (FG)
Signalling on low-voltage electrical installations
EN 50065 (P)
EN 50082-2 (FG)
Sound and television broadcast receivers
EN 55013 (P)
EN 55020 (P)
Requirements for household appliances, electric tools etc.
EN 55014-1 (P)
EN 55104-2 (P)
Sept 2012
21
Interference - Transmitter / Receiver
Field
Load
BUS
I/O Signal
SYSTEM
Source
Power supply
Sept 2012
Ground
connections
22
EMC – Coupling Paths
1) Conductive
•
Coupling path between source and victim is formed by direct contact.
2) Capacitive
•
Electric field coupling
3) Inductive
•
Magnetic field coupling
4) Radiative
•
Sept 2012
Source is the “transmitter” and victim is the “receiver”
23
EMC and EMI
§
EMC
–
Electromagnetic compatibility
• The electro magnetic
compatibility is the ability of an
electrical device, unit or system
to function sufficiently well in its
electromagnetic environment
without generating unintentional
interference to the other
equipment in the system
§
EMI
–
Electromagnetic Interference
• Electromagnetic energy emanating
from one device which degrades or
obstructs the effective performance of
another device.
Sept 2012
24
EMC and EMI
§
§
§
§
§
Sept 2012
Stray capacitance is Undesirable capacitance between circuit wires, between wires and the
chassis, or between components and the chassis of electronic equipment.
Magnetic flux caused by common mode current is accumulated and high impedance is produced.
Magnetic flux caused by differential mode current cancels each other and impedance is not
produced.
Common mode choke coils are suited for noise suppression on lines with large current flows, such
as ac/dc power supply lines.
Common mode choke coils are suited for noise suppression on lines where signal waveform
distortion cause problem, such as video signal lines.
25
EMC – Coupling Paths (Capacitive Coupling)
• Capacitive coupling between conductors cause parasitic currents
• Noise voltage increases with frequency. Higher frequency means more high
frequency harmonics flow through the capacitor.
• Two wires with 2 mm diameter and spaced by 1 cm shows about 0.1pF of
parasitic capacitance.
26
Sept 2012
EMC - Coupling
Capacitive coupling
• effects are dominating, if the dimensions are smaller than 10% of wave length (l < /10)
-> Why 1/10 ?
- harmonics
-> reduction ?
- increase the distance
Sept 2012
Field model
Network model
27
EMC – Coupling Paths (Magnetic Coupling)
• Magnetic coupling between conductors causes parasitic induced voltages.
• Noise current increases with frequency.
• Two wires with 2mm diameter and spaced by 1cm, shows about 10nH/cm of
parasitic inductance.
Sept 2012
28
EMC - Coupling
Inductive coupling
• effects are dominating, if the PCB traces are smaller than 25% of noise wave length
(l < /4)
• antenna principle –> each piece of wire is an antenna
c=
à reduction?
Sept 2012
×f
- increase the distance (r³)
Field model
Network model
29
EMC – Coupling Paths
AC “noise” source may “couple” to a DC circuit through mutual inductance
(M stray) and capacitance (C stray) along the length of the conductors
Sept 2012
30
Interference Characteristics
Sy
mme
t
r
i
c
a
l
As
y
mmet
r
i
c
a
l
Fi
el
d
c
on
duc
t
e
d
n
oi
s
e
Powdero
rr
od
c
or
ech
o
k
e
s
Co
up
l
e
dno
i
s
e
r
a
d
i
a
t
edno
i
s
e
CM-c
hok
e
s
EMIf
er
r
i
t
es
,
s
h
i
el
d
i
ng
0,01
0,1
1
10
100
1000
Sept 2012
f
(MHz)
31
Comparison of Core Materials: Inductive behavior
Sept 2012
32
Comparison of Different Core Materials: losses behavior
=> It depends on frequency range to filter !
Sept 2012
33
What is the main different between a Inductor and
EMC-Ferrite?
=> Application Storage Choke: (Inductor)
Request: lowest possible losses at application frequency
high Q-factor
=> Application as absorber-filter: (EMC Ferrite)
Request: highest losses possible at application frequency range
low Q-factor
Sept 2012
34
Inductor vs. EMI-Ferrite:
Comparison Q-Factor: Ferrite vs. Inductor
Q=
XL
R
Q-Factor
Inductor
Losses
Ferrite
Frequency [MHz]
Sept 2012
35
Impedance increase vs. numbers of turns
increasesImpedance
2 turns
Sept 2012
Fres.-decrease
36
Ferrite Inductors WE-CBF
Sept 2012
37
Sept 2012
38
Why CMC‘s instead of Chip Beads
Impact of DC-bias (pre-magnetization (saturation)
800O@100MHZ (0ADC)
420O@100MHZ (1,7ADC)
230O@100MHZ (3ADC)
Sept 2012
742792514 (3A typ)
39
Impact of DC-Bias (pre-magnetization (saturation)
Sept 2012
40
Advantage of a Common Mode Choke
Filtering with Two Inductors or Chip beads
Signal before filtering
after filtering
ØRise-time of the signal is affected
which could cause problems for
fast data and signal lines
which occurs from the DC current the filtering
performance is shortened.
Øbecause of the pre-magnetization (saturation)
Sept 2012
41
Advantage of a Common Mode Choke
Filtering with a Common Mode Choke
Signal before filtering
after filtering
Ø no affect on the signal rise-time,
because of magnetic field compensation
Ø no influence of the wanted signal
(the two windings are ma
g
n
e
t
i
ca
l
l
y
coupled)
Ø no pre-magnetization (saturation) occurs from the DC current,
because of magnetic coupling
Ø much better performance vs. two separate inductors or ferrites
Sept 2012
42
How Much Inductance is Needed?
before
after
only changed one component
30mH!
Sept 2012
43
Replace a “Snap Ferrite“ by a common choke ?
We can replace ferrite by common mode choke
Both are common mode filters !
First check for the technology and look the impedance curve
Sept 2012
44
Common mode choke - construction
WE-split ferrite – Is it a CMC?
• Yes, CMC with one winding
e.g. 74271712
comparable with bifilar winding CMC
• both will absorb Common Mode interferences
Sept 2012
45
Differential Noise Example: Flyback Converter
Appearance of differential noises on the input line of a Flyback Converter
mostly high Caps >100uF; Xc=1/(? xC)
differential interference
L1
N
differential interference
Switch (e.g Transistor)
PE
Earth ground
differential interference occurs mainly at lower frequencies
Sept 2012
46
Common Mode Noise Example: Flyback Converter
Appearance of common mode noises on the input line of a Flyback Converter
mostly high Cap Values >100uF; Xc=1/(? xC)
common mode interference
L1
differential interference
N
common mode interference
Switch (e.g Transistor)
PE
Earth ground
parasitic capacities ; in the lower pF/nF (e.g: VCC layer to GND layer( coupling))
common mode interference occurs mainly at higher
frequencies
Sept 2012
47
Why Filter? – example: Fly back-Converter
Which filter do we need?
L1
N
P
E
àParasitic capacities
e.g.: collector to cooling element
Sept 2012
48
Filtering Noise Example: Flyback Converter
Filtering the mains power line for common mode and differential mode
WE-VD
L1 (+)
N (-)
PE (GND)
Sept 2012
Cx
C=0,1µF
WE-LF SMD
L= 2x2.2mH
2xCy
Cx
C=2,2nF C=1nF
2xWE-UKW
L= ca.5~10µH
L‘1
N‘
PE‘
49
Common Mode Choke
• comparison common mode chokes CMB – CMB NiZn
CMB
70
14 µH
CMB NiZn
30 µH
60
47 µH
100 µH
attenuation [dB]
50
1 mH
5 mH
40
10 mH
20 mH
39 mH
30
20
10
0
0,1
1
10
100
1000
frequency [MHz]
Sept 2012
50
Common Mode Choke Magnetic Field
Sept 2012
Sep-12
BW
51
Common mode / Differential mode
Interference source
interference sink
differential mode current
symmetrical interference voltage
~
~
~
Common mode current
Asymmetrical interference voltage
The DIFFERENTIAL Mode Signal creates a Flux in opposite directions – Thereby canceling
The COMMON MODE signal does not cancel and an Inductive Impedance is created thereby
acting as a filter
Sept 2012
52
operational current / wanted signal
(diff. mode)
N1
2
1
disturbance current
(common mode)
4
3
Loadly
5V AC/DC Converter
Source
e.g. 24AC Supply
Functionality of a common mode choke:
N2
The DIFFERENTIAL Mode Signal creates a Flux in opposite directions – Thereby canceling
The operational current (diff. mode) is routed by all relevant conductors through the core
(e.g. +/- or L/N). That´s why the magnetic fields of these two conductors compensate each
other to zero => no influence on the wanted signal
The COMMON MODE signal does not cancel and an Inductive Impedance is created thereby
acting as a filter
The disturbance current flows on both wires in the same direction and generates a magnetic
field in the toroidal core => the choke is able to filter unwanted noises.
Sept 2012
53
Unbalanced Current
- the operating current on both conductors is almost the same. When the difference
between input and output current is too big, the common mode choke is no longer
compensated and starts saturating very fast !
Sept 2012
54
Common Mode Choke
sectional winding
bifilar winding
< advantage? >
Sept 2012
55
Stray inductance: Bifilar / Sectional
Sept 2012
Sectional
Bifilar
LS ~ 0.5 … 2.0% * L p
LS ~ 0.1 … 1.0 %O * Lp
56
Sectional winding:
For example: WE-SL2 744227S
Common Mode suppression
Differential Mode suppression
is high!
Sept 2012
57
Bifilar winding vs. Sectional winding
For example: WE-SL2 744227
Common Mode suppression
Differential Mode S-Type
Differential Mode suppression
is low!
Sept 2012
58
Common mode chokes for SMD:
Size [mm]
WE-CNSW
WE-SL
WE-SL 1
2.0 x 1.2 x 1.2
3.2 x 1.6 x 1.9
Impedance [O] Current [A] Application
130 – 910
60 – 400
0.28 – 0.4
0.20 – 0.37
USB 2.0
Firewire/ high speed dataline
ISDN
12.7 x 10.5 x 5,75
1100 – 14400
0.20 – 2.70
Telecom Applications
PCMCIA cards
6.5 x 3.6 x 1.65
300 – 2000
0.30
9.2 x 6.0 x 5.0
1000 – 20000
0.40 – 1.60
VCC Power & Datalines
9.2 x 6.6 x 2.5
1250 – 5000
0.50 – 0.70
VCC Power & Datalines
higher current ratings
0.35 – 2.50
VCC Power Lines
744212xxx
WE-SL 2
WE-SL 3
744252/253xxx
WE-SL 5
10.0 x 8.2 x 6.5
290 – 13000
744272xxx
Sept 2012
59
Common Mode Choke
• different designs
WE-SL2 744226S
sectional winding
10000
comm. bifilar
diff. bifilar
comm. sectional
diff. sectional
Impedance [Ohm]
1000
WE-SL2 7442276
bifilar winding
100
10
1
1
10
100
1000
Frequency [MHz]
Sept 2012
60
CMC - USB 2.0 Filtering for Common Mode Noise
Sept 2012
61
CMC- USB 2.0 Filtering with WE-CNSW
measurement point
EMI-filter
90 Ohm @ 100 MHz C.M.
20 Ohm @ 240 MHz D.M.
Sept 2012
TP2
EMI-filter
600 Ohm @ 100 MHz C.M
40 Ohm @ 240 MHz D.M.
WE-CBF
120 Ohm @ 100 MHz
Too much differential mode impedance distorts the USB 2.0 eye pattern
62
Conducted Emissions Example – Test and
Compare
§
§
§
§
Sept 2012
Differential Choke
Bifilar Wound Common Mode Choke
Sector Wound Common Mode Choke
Chip Bead
63
Conducted Emissions Example - Test Setup
a) no load
b) 1.5A load
300KHz fsw.
Sept 2012
64
Conducted Emissions Example - LISN
•Isolates DUT (device under
test) from Power Source
(typically mains) Noise
•Provide characteristic
Impedance to DUT (50ohms in
this case)
•Path for Conducted noise from
DUT to Spectrum Analyzer
Sept 2012
65
Conducted Emissions Example – Demo Board
FCC Class B limit
Sept 2012
66
Conducted Emissions Example – Electrical
Load
Sept 2012
67
Conducted Emissions Example – Test Board
- DC/DC Converter
- Input Voltage20V-25V
- Output Voltage12V/6.25A
- Fsw: 300KHz
Testcondition:
- no load
- max. load 1.5A
Sept 2012
68
Conducted Emissions Example – No Filter
FCC Class B limit
Sept 2012
69
Conducted Emissions Example – Chip Bead
Chip Bead 530? / 3A
Sept 2012
70
Conducted Emissions Example – Chip Bead Results
no load >
Chip Bead 530? / 3A
Sept 2012
load 1.5A>
71
Conducted Emissions Example – Chip Bead
Chip Bead 530? / 3A
Sept 2012
72
Conducted Emissions Example – Differential Choke
Differential Line Choke 220uH
Sept 2012
73
Conducted Emissions Example – Differential Choke Results
no load >
load 1.5A>
Sept 2012
74
Conducted Emissions Example – Bifilar CMC
CMC 4.7mH Bifilar Winding
Sept 2012
75
Conducted Emissions Example – Bifilar CMC
Warning: Don’t try this at home!
For Demonstration Purposes Only!
Load is 1.5A
And…..
CMC 4.7mH Bifilar Winding
Sept 2012
CMC
76
Conducted Emissions Example – Bifilar CMC Results
no load >
CMC 4.7mH Bifilar Winding load 1.5A>
Sept 2012
77
Conducted Emissions Example – Sectional CMC
CMC 47mH sectional winding
Sept 2012
78
Conducted Emissions Example – Sectional
CMC
CMC 47mH Sectional Winding
Leakage Inductance Ls~ 250uH (5% of L)
Sept 2012
79
Conducted Emissions Example – Sector CMC Results
no load >
CMC 47mH sectional winding
Sept 2012
load 1.5A>
80
Conducted Emissions Example - Conclusions
§ High Frequency Noise Appears Under Load
§ Noise is Differential Mode
§ Differential Choke
– Attenuates low frequency noise because of SRF
§ Bifilar CMC
– Does not attenuate because of very low leakage inductance.
§ Sector CMC
– Attenuates both high and low because of leakage inductance with
high SRF.
§ Chip Bead
– Without a load there is some affect at high frequencies, but with a load
the bead pre-magnetizes and there is no affect at all.
Sept 2012
81
Transformers for EMC – Power Supply
Current Compensated
Snubber
Choke WE-FC
Y-Cap
Transformer
Output Filter
WE-TI
Switch IC
Sept 2012
82
Transformers for EMC – Schematic
Current Compensated
Choke WE-FC
Sept 2012
Switch IC
Snubber Transformer
Y-Cap
Output Filter
WE-TI
83
Transformers for EMC – Example 1
•Without Current
Compensated Choke
•With Adjusted Snubber
•Without Adjusted Y-Cap
Peak
Avg.
Peak
Avg.
EMC- Test Failed
Sept 2012
84
Transformers for EMC – Example 2
•With Current
Compensated Choke
•With Adjusted Snubber
•Without Adjusted Y-Cap
Peak
Avg.
Peak
Avg.
EMC- Test Failed
Sept 2012
85
Transformers for EMC – Example 3
•With Current
Compensated Choke
•With Adjusted Snubber
•With Adjusted Y-Cap
Peak
Avg.
Peak
Avg.
EMC- Passed
Sept 2012
86
Transformers for EMC – Example 4
•With Current
Compensated Choke
•Without Adjusted
Snubber
•With Adjusted Y-Cap
Peak
Avg.
Peak
Avg.
EMC- Passed
Sept 2012
87
Transformer for EMC – Conclusion for this
Supply
§ Necessary to Pass
– Current Compensated Choke
– Y-Caps
§ Not Necessary to Pass
– Optimized Snubber
Sept 2012
88
Switching Regulator Topologies
Switch Mode Power Supply
Non-Isolated
Step-down
converter
Step-up
converter
WE-PD
WE-PD
Isolated
SEPIC
2 xWE-PD
or 1x WE-DD
Flyback
converter
Forward
converter
Push-Pull
converter
WE-FLEX
with airgap
WE-FLEX
FlexÜT o.
w/o
airgap
Luftspalt
+ WE-PD
+ PD
WE-FLEX
w/o airgap
+ WE-PD
WE-PoE
Insulation Voltage
WE-PoE
è 0-100V ------------ -------è 0-500V --------------------- è >=1500V
Sept 2012
89
Topologies
Buck
Sept 2012
Boost
Buck Boost
Sepic
Fly-back
Forward
2 Switch Active Clamp
Half Bridge
Forward
Forward
Push Pull
Full Bridge
Phase
Shift ZVT
90
Toplogies for Lighting Applications
Topology Comparison
Operational
Concept
FLYBACK
Parallel
Resonnant
PUSH-PULL
Parallel
Resonnant,
Current Fed
HALF BRIDGE
Parallel
Resonnant,
Voltage Fed
Sept 2012
Complexity
High
Medium
Low
Cost
Medium
Medium
Low
Dimming
Feature
Advantage
Possible
Cost effective
Multiple O/P
Regulation
Difficult
Simplicity & ability
to upscale power
Easy
Low output Ripple &
Noise
91
Topologies
Sept 2012
92
Half Bridge Converter
Advantages of half bridge converters are:
Small magnetic cores.
No magnetic path gap therefore low stray magnetic field.
Frequency seen by secondary circuits is double the basic switching frequency - small filter components (L
and C) in secondary circuits.
Low output ripple and noise.
Multiple output configurations easily implemented.
Relatively low radiated noise, especially if the secondary inductors are toroidal cores.
Disadvantage:
A disadvantage is because they are working at half the supply voltage the switching transistors are
working at twice the collector current compared with the basic push pull circuit.
Sept 2012
93
Toroidal Inductor Choice
Characteristics:
WE-FI offers you perfect filtering for interference
frequencies up to 10 MHz.
Current loading up to 5 A
High storage capacity
Iron powder cores with low losses
Low magnetically leakage field
Applications:
Voltage transformers and power supplies
For interference frequencies up to 10 MHz
Switching regulator up to 150 kHz switching
frequency
Perfect for filtering of symmetric interferences
Sept 2012
94
Additional Inductor Choices
Choices:
WE-FI offers Custom build transformers
EP10, EP13, ETD15, ETD20, ETD25, ER11, ER14
(various other sizes)
SMD Topologies
High storage capacity
Mn-Zn Ferrite Material
Applications:
Custom power supplies
Switching regulator up to 150 kHz switching
frequency
Sept 2012
95
High Current WE-HC
Type
A
(mm)
B
(mm)
C
(mm)
D
(mm)
E
(mm)
744312X
6.6
7.3
3.4
2.5
4.3
744310X
7.0
6.9
3.0
1.2
3.8
744311X
7.0
6.9
4.0
1.2
3.4
744324X
10.5
10.0
3.9
2.4
5.6
744313X
12.9
12.8
3.5
2.4
6.0
744315X
14.0
12.8
4.8
2.3
7.6
744318X
14.0
12.8
5.3
2.3
7.6
Applications:
Characteristics:
Lower losses and no thermal aging because of
the new advanced core material Superflux 200.
Flat wire coil for lower losses at high frequency ranges
Low leakage field
Extremely low profile design
Current capability up to 40 A
Operating temperature: -40°C to +150°C
Sept 2012
Graphic cards
Laptops
Industrial computers
Motherboards
High current switching regulators
High temperature electronics
Polyphase-switching regulators
96
Switching Power Supply
High Current Switch Mode Power Supply
Various magnetic components
for various circuit operations
Sept 2012
97
Identifying Magnetics on Circuit Board
Which Magnetics are on the board?
Common Mode Filter
Power Transformer
Sept 2012
98
Lighting Circuit Board
Lighting Product
Power transformer
Flyback transformer – increase frequency
Output inductor
Maintain lamp output current
Sept 2012
99
Controller Circuit Board
Frequency Conversion Board Controller
Filter Inductors
Power Transformer
Sept 2012
100
Operation of Switching Power Supply
Power Supplies have 3 functional stages for magnetics
1) Input stage
Initial stage where common mode inductors are located for lowering distortion
2) Transformer stage
Section where input voltage is either increased or decreased for proper operational voltage
3) Output Stage
Section which uses power inductors to maintain operational current levels
There can be a 4th stage that is added
4) Current sensing
Optional section that is used to regulate the power supply is working properly
Sept 2012
101
Switching Power Supply
Power Supply Magnetic Components
Common Mode Inductor
used on the input side of device
filters input line lowering distortions
Power Filter Inductor
used on the output of the device
keeps output current at same level
Power Transformer
used in central part of device
used to increase or decrease output voltage
Sept 2012
102
Switching Power Supplies
Switching Supplies have Magnetic products in different locations
Input Filter Transformer
Power transformer
Sept 2012
103
Power Supply Circuit Board
Computer Power Supply has several magnetic components
Common Mode Filter
Power Current Inductor
Step Down Transformer
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Topics
§
§
§
WE-LT – Gasket
WE-LS – Conductive Foam
Stampings of WE-LT / WE-LS
§
WE-CF / WE-TS – Conductive Foils / Conductive
Tape
§
§
WE-FAS – Flexible Absorber Sheet
WE-FAS RFID – Flexible Absober Sheet for RFID
Applications
WE-FAS EMI – Flexible Absorber Sheet for lower
frequency
§
§
Other Shielding Products of WE eiSos
§
IP Classes
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Faraday’s Law / Lenz’s Rule
FL: If the Magnetic Flux changes with time, a voltage
will be induced.
LR: The polarity of the voltage is such that a current
is generated in a closed circuit whose induced
magnetic field opposes the original magnetic flux.
Reduces the magnetic field.
µPC unit
Mains power
RAM/ROM
Clock
Air flow / cooling
Connection ports
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What is EMI shielding?
Used to protect an electronic product inside to outside
of your custom enclosures from electromagnetic
interference (EMI). You will need an electromagnetic
or electrostatic shielding called EMI shielding.
Faraday cage
Power supply
USB port
LAN port
µPC unit
WLAN
module
RAM/ROM
Clock
Bluetooth
module
Display / Touch panels
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Why is shielding requested?
Most of the times, the casing itself is not part of the electronics
development but is developed by the construction department
(Mechanical guys). They make sure that the openings in the casing,
e.g. for cable inlets and outlets, ventilation slots, operating buttons,
speakers, transducers or displays cause a massive reduction of the
shielding action.
GROUNDING!!
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Why are shielding requested ?
But even if the desired openings in the casing were not existent, no
complete overlap and hence no RF-density is attainable for
contiguous metal surfaces
Top
Slots/openings caused by uneven metal surfaces
Bottom
If you look at an even metal surface microscopically, you will not see this
ideal state. You will rather find that the material is uneven, with asperities on
the surface and therefore there is no continuous connection between these
two surfaces. Consequently, the shielding is disrupted by slots and if you
look at the bonding from a RF-technical point of view, it is “highly impedant”.
The slots and “eyes”, which were formed due to the asperities, are an open
gate for radio frequency interference, in both directions inó out
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How to build shielding ?
The solution to the problem lies in the bridging and sealing of these
asperities.
For that purpose, our conductive textile gaskets WE-LT are very well
suited
Per Faradays Law, Voltage will be induced into the WE-LT
Ohms Law?
WE-LT
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WE-LT gaskets – Best Compression Rate
Sept 2012
§
Measurement setup for
compression
§
Best results are at 50%
compression
§
Measurement result after 40
days
§
Stabilization after one
month
111
How to build shielding ?
The textile gasket requirements are always very different
and depend on the purpose for which it is used.
-Flammability: UL94-V0 approved material combinations
(always necessary if the end product is for the US market)
-Protection against rough environmental conditions (dust
& humidity) IP 54
-Good surface conductivity to obtain a low-impedance
connection
-Double-sided adhesive tape as fixation and mounting aid
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WE-LT Materials
PU sponge (thermo plastic rubber) enclosed in an electro conductive fabric weaved
from nickel copper polyester.
50% compression will give the optimum Z. If steady at 50%, it will keep the transitional
resistance over a long period of time, slow and steady.
Surface resistance typically lower that 8 mOhm. Achieved shielding is approx 80dB at
100Mhz and 75dB at 1Ghz. (Mil 285 STD)
IP54: International Protection
5: Complete protection, dust protected. 6 is dust proof
4: Spray protected, splashing. 9 is submersion proof.
Tape: Conductive or non-conductive. Ours is non-conductive. We can have
conductive but not as strong.
Custom lengths
Profiles and uses (D type, JDSU, etc…)
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IP Classes
Examples:
§
industrial applications IP54
§
switch cabinets IP20
§
automotive devices IP65
§
military technology IP67
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WE-LT gaskets – Technical Information
Sept 2012
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Applications
DC/DC
converter
Oscillator
Filtered con
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Applications
Displays
Metal Housings
Switching cabinets
For plastic housing, recommend the WE-LS (Foam) or flexible
absorber sheets.
WE-LS good to 1Ghz
Flex absorber good to 3Ghz (5Ghz coming)
2 new versions for RFID available
Custom stampings available.
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WE-LT gaskets – Applications
–
–
–
–
Sept 2012
metal housing
switch cabinets
displays
transmit – and pick up module
118
WE – FAS RFID – Technical Information
§
Temperature range - 20°C to + 85°C
§
Fits for RFID Applications
§
Breaking strength 6 MPa (60 bar)
§
Improved fire resistance
§
Stamping parts are possible
§
Flexible material
§
Absorbtion of EMI – radiation like a ferrite
§
UL 94-V0 material
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WE – FAS EMI – Technical Information
§
Temperature range - 20°C to + 85°C
§
Breaking strength 6 MPa (60 bar)
§
increased fire resistance
§
Stamping parts are possible
§
Flexible material
§
Absorbtion of EMI – like a ferrite core
§
UL 94-V0 material
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WE - FAS – Technical Information
§
Frequency range 10 MHz ~ 3 GHz
§
Surface resistance 2 x 1010 ?
§
Isolation resistance 0,01 x 1010 ?
§
Breaking strength 47 MPa (470 bar)
§
UL 94-V0 material
§
Stamping parts are possible
§
Flexible material
§
Absorption of EMI – radiation like a
ferrite
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WE - FAS – Technical Information
§
It is a metal powder with special fire
retardant rubber and not silicone.
§
No silicone means they won’t need a
silicone primer which is hazardous
materials
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WE-FAS / FAS RFID / FAS EMI – Sales
Information
Applications:
§ LCD & LED displays
§ Housing
§ Between PCB boards
§ Processor and controller
§ Flat conductor
§ Notebooks
§ CD- / DVD – Player
§ digital camera and camcorder
§ PDA‘s and Mobile phone
§ GPS – receiver
Sept 2012
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et
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ect
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WE-LS – Conductive Foam – Technical
Information
§
Polyolefin foam with NiCu plating
§
High damping features on frequency domain
§
Excellent conductibility
§
High flexibility and consistency
§
Applications are
– LCD – displays
– HF – Module shielding
– metal housing
– transmit – and pick up module
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WE-CF / WE-TS – Conductive Foils /
Conductive Tape
§
§
§
§
§
§
§
WE-CF: Al or Cu lamination
Self – adhesive
UL – material
High shielding effectiveness
Surface resistance
Cu: 0,002 ? /cm², Al: 1,00 ? /cm²
EMI – protection for housing
Flexible material
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WE-CF / WE - TS - Sales Information
§
Applications
– Displays
– LCD
– Medicine
– Mobile Phone
§
Stamping parts are
possible
§
Different width possible
§
WE-TS can replace WECF
§
Lower price for WE-TS
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EMC Shielding Cabinet WE-SHC
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127
EMC Shielding Cabinet WE-SHC
Two-piece Shielding Cabinet WE-SHC
§
Consisting of top-cover
&
§
Frame in SMD version
or
§
Sept 2012
Frame in THT version
128
EMC Shielding Cabinet WE-SHC
Standard articles of WE-SHC
§ Selection procedures with the help of the size 30x30 (mm)
Ÿ Top-cover 30x30 (mm)
&
Ÿ SMD-Frame 30x30 (mm)
or
Ÿ THT-Frame 30x30 (mm)
§
Attention: dimension A ~ C refer to the inside mass
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EMC Shielding Cabinet WE-SHC
Shielding effectiveness WE-SHC
§
Shielding effectiveness measured after the principle of the Faraday Cage
Ÿ è MIL-STD-285 / IEEE-299
§
Shielding effectiveness
up to 60 dB @ 500 MHz ~ 3000 MHz
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EMC Shielding Cabinet WE-SHC
Sales information of WE-SHC
§
WE-SHC has a better quality opposite to the competitor!!
Ÿ Clip connections are more sure & more stable
Ÿ Low air gap
cl
i
pcon
ne
ct
i
on
s
§
Applications are:
Ÿ Oscillators
Ÿ RF output stages
Ÿ RF input & amplifier stages
Ÿ EMC sensitive parts in plastic cases
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What more do you need?
Look at our Book:
Chap.1: Basics
keep it simple, stupid
Chap.2: Components
Descriptions, Applications, Simulation
Models and many more
Chap.3: Filter-Circuits
Design, Grounding, Layout, Tips
Chap.4: Applications
Circuit, suggested parts, Layout
Chap.5: Appendices
from A to Z
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Online:
Sept 2012
www.we-online.com
133
Online:
Sept 2012
www.we-online.com
134
Inductor Selector Tool
Sept 2012
135
Wurth Electronics Midcom Inc. Brasil
Fabio Costa
Soraia Garcia
Bruno Cipriano
Sept 2012
136
Questions?
Sept 2012
137
Thank you!!!
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138