EMC Basics Speaker : lain Lafuente lain.lafuente@we-online.com
WHT IS EMC? 2
CE Marking With the formation of the single European market, standardization was required to remove technical barriers to trade. New pproach Directives were introduced to remove these barriers to trade 22 New pproach Directives Electro Magnetic Compatibility (EMC) Low Voltage Directive (LVD) Medical Devices Directive (MDD) 3
What s all the fuss about EMC? In Europe, we have a mechanism called CE Marking It is applicable to any electrical/electronic product EMC Directive, regulation to ensure that intentional RF transmission signals are not interfered with Ensures that Electrical/Electronic devices continue to operate as intended in a Electro Magnetic Environment Failure to comply with the law can be a offence, either criminal, civil or both 4
EMC Effect Economical point of view: dependent on when EMC conformity is considered in a design phase Cost Pre-design Prototype Production Time 5
EMC Basic Phenomena Electromagnetic Compatibility Emission Immunity Conducted Radiated Conducted Radiated 6 6
Filter and Signal Common Mode Filter differential mode common mode Source transmits noise in differential mode Differential mode noise is transmitted via conductive paths Transmitting paths are power supply or data lines earth is not affected by noise Load is disturbed by common mode noise Noise flow from source to load. The return path is over earth Transmitting paths are power supply or data lines earth is affected by noise 7
Common Mode Filter How it works It is a Bi-directional filter From device to outside environment From outside environment to inside device Intended Signal - Differential mode Interference Signal (noise) Common Mode Conclusion: almost no affect the signal - Differential mode high attenuation to the interference signal (noise) Common Mode 8 8
INSERTION LOSS 9
The problem Example, Radiated Emission plot 10
Insertion Loss Definition Z Z F U 0 U 1 U 2 Z B Source Coupling way Load System attenuation Impedance Z = 20 log + Z Z F + Z + Z Z 20 = F 10 B + ( Z + Z ) ( Z Z ) B B B in (db) in (Ω) 11
Insertion loss The real world equivalent circuit 12
System impedances Ω Ω Ω 13
The mathematical approach Z Z Z F F F = 10 = 10 20 20 20 = 180Ω ( Z + Z ) ( Z + Z ) ( 10 + 10 ) ( 10 + 10 ) B B B B = = = = 20 20 1. Require 20dB of attenuation at 200 MHz 2. Know that it is a power cable 3. Power port has 10 impedance 4. Result is a impedance of 180 20 log log log 20.00 db Z 10 10 Z + + 10 Z + F 180 + Z + F B 10 Z + B B 10 B 14
The practical approach 1. Require 20dB of attenuation at 200 MHz 2. Know that it is a power cable 3. Power port has 10 impedance 4. Result is a impedance of 180 180 15
Insertion loss Example WE-CBF 742 792 61 1000 CH1 Z CH2 XL CH3 R typischer Impedanzverlauf / typical Impedance curve 200 Impedanz / impedance [Ohm] 100 10 1 1 10 100 1000 Frequenz / frequency [MHz] 200MHz IF BW 10kHz POWER 0 dbm SWP134,5 msec STRT 1 MHz STOP 1,8 GHz Z XL R 16
Component selector 17
Component selector 18
Component selector 19
Component selector 20
Component selector 21
Component selector 22
Insertion loss - example pplication: sensor line, cable diameter 5mm 15dB @ 200 MHz 60 50 1 Ohm 10 Ohm 50 Ohm Insertion [db] 40 30 20 10 0 1 10 100 1000 Impedance of ferrite [] System impedance = 50 23
Star-Tec 24
Star-Tec 25
Star-Gap 26
Insertion loss Example Check the results Measuring the emission and compare the attenuation Level [dbμv/m] 60 50 40 30 20 10 0 30M 40M 50M 70M 100M 200M 300M 400M 600M 1G Frequency [Hz] 27
Insertion loss Example Choosing different system impedance Level [dbμv/m] 60 50 40 30 20 --- : With 10 system impedance it passes 10 0 30M 40M 50M 70M 100M 200M 300M 400M 600M 1G Frequency [Hz] 28
DESIGN GUIDES 29
Trilogy of Magnetics Now published as 4 th edition Three sections: Magnetic basics Components pplication notes Filtering DC/DC PSU design 30
THNK YOU ny Questions? 31