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safety for electronic systems
High-frequency Filtering of DC Power Lines
Technical, constructional and practical issues with filtering on dc power lines
Wolfgang L. KlampferManager Training Center
safety for electronic systems
Contents
EMC issues for base stations
Filtering at high frequencies
Contacting under high load
Conventional solutions
A new approach
safety for electronic systems
Basestations and EMC
Standard requirements in Europe
Noise sources and distribution
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Requirements for Base Stations
AC Mains
DC Supply
Antenna
Other lines
Radio Interface
Enclosure
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Requirements for Base Stations
Emission EN 55022
CISPR 16-1
Immunity EN 61000-4-4 EN 61000-4-6
AC Mains
DC Supply
Antenna
Other lines
Radio Interface
Enclosure
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Conducted Emission according to EN 55022, CISPR 16-1
EUT
Supply
PE
EMI Receiver
DC LISN
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Differential mode noise
R
LL
N
PE
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Parasitic components as cause for differential mode noise
ES
LE
SR
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Characteristics for differential mode noise
Current through ESL and ESR
“Lower” frequencies
Switching frequency and harmonics
Loop structures
ES
LE
SR
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Common mode noise
R
LL
N
PE
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Insulation as cause for common mode noise
~=
ICM
distance
AreaC
dt
dUCICM ~;
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Characteristics of common mode noise
Usually high frequency problems, e.g. switching/oscillating at higher frequencies
Affected by circuit layout, e.g. heat sinks
Cables
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Differential to common mode conversion
Perfectly balanced only differential mode no radiation
Slight unbalance differential to common mode
conversion conducted and radiated noise
at high frequencies
safety for electronic systems
Filtering at high frequencies
Problems with resonances and solutions
Special filter requirements for base stations
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Capacitors and chokes for noise suppression
Two metal plates, separated by insulation
Often realised by 2 metallized plastic foils
Wire wound to a coil
Usually winding is placed on magnetic material (core)
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Frequency response of capacitors and chokes
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Use of capacitors and chokes in circuits
CLoad~
AC mains path RF path
Load~
L
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Resonances of capacitors and chokes
Connection leads of capacitors work like small series inductances
Inductors can have significant capacitance between windings
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Frequency response of feedthrough capacitors
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Filters for Base Stations
Special Requirements: Customized power requirements Mixed AC and DC configurations Environmental stress High attenuation Special enclosure forms
AC Mains
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Power Layout
Filter Circuit
Line
Load
L1
L2
GND
L1L2GND
L1L2GND
L1L2GND
60A
60A
20A20A
20A20A
20A20A
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Environmental Requirements
Corrosion resistance
Thermal shock
Vibration
Impact resistance
Transportation shock and vibration
Earthquakes
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Attenuation Requirements
Insertion Loss, Line to GND, 50
1.0 MHz – 5.0 MHz 20 dB
5.0 MHz – 10.0 MHz 30 dB
10.0 MHz – 30.0 MHz 40 dB
30.0 MHz – 4.0 GHz 40 dB
safety for electronic systems
Contacting at high loads
Special issues and requirements for contacts
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Requirements for dc power connections
Reliable contact
Easy connect/disconnect
Low contact resistance
High number of connect-disconnect cycles
Hot-pluggable
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Potential threats and problems
Reliable contact Force of contacts over time
Easy connect/disconnect Installation/maintenance time
Low contact resistance Risk of overheating
High number of connect-disconnect cycles Wear-out of contact surface
Hot-pluggable Arcing between male and female
connector; destruction of contacts
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Specialties about a proper contact
Fixed beams Surround spring(Activates only cantilevered beams)
Cantilevered beams
Crimp barrel
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Function of the surround spring
assists cantilevered beams at operating temperatures > 80 °C provides high mechanical shock/vibration stability with no contact
bounce
Male pin engaging fixed beams – hot plug surface
Male pin engaging cantilevered beams
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Function of the beams
Fixed beams provide mechanical guidance thermal conductivity sacrificial hot plug / hot swap
location
Cantilevered beams low contact resistance low current density optimum insertion force
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Contact material selection for power connectors
High conductivity copper = low temperature rise
Good manufacturing process
Copper with good spring properties at contact interface = normal force
Copper with good formability for crimping to finely stranded copper conductors
safety for electronic systems
Conventional solution
Standard approach for dc filtering and connecting
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
DC Power to Filter
Filter to Bus Bar
Traditional installation until today
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Some considerations for the conventional solution
8 parts with 10 (!) connection points
Necessary extra provisions for capacitor grounding
Overall attenuation relies on quality of connection
Work- and cost-intensive installation
Many connections means many potential failure sources
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Relation between attenuation and earth resistance
0
10
20
30
40
50
60
70
80
90
0.01 0.1 1 10 100
0 Ohm 0.01 Ohm 0.1 Ohm 1 Ohm 3 Ohm
safety for electronic systems
A new approach
Advanced filtering and contacting solution
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Requirements for a contacting-filtering solution
Easy connect and disconnect under full-load
Easy and quick installation
Reduced number of connection points
Reliable filtering up to several GHz
Protection against reverse polarity
Protection against wrong connections in case of several power lines
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
The solution: ACARA
2 parts with 2 connection points
High-quality contacts for connection and disconnection under full-load
Time/cost/space saving solution
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Frequency response of ACARA
CH1 S 21 log MAG 10 dB/ REF 0 dB
START .010 000 MHz STOP 6 000.000 000 MHz
Avg 10 Smo
PRm
6 Jan 2003 16:43:35
1
2
3
4
1_:-36.83 dB 1.000 000 MHz
2_:-43.866 dB
21.786 MHz 3_:-57.211 dB
38.639 MHz 4_:-106.97 dB
6 GHz
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Reverse polarity protection and code keying
Protection against reverse polarity
Pins for keying of connector pairs 6 positions for keying pins
IEEE Dallas EMC Society January 20, 2004
safety for electronic systems
Thank you very much for your attention
Any questions?
