Matching Conducted EMI to International Standards

1
Matching Conducted EMI to International Standards

• Presenter Fernando Soares dos Reis
• Pontifical Catholic University of the Rio Grande
  do Sul
• Brazil

2
Table of Contents

• INTRODUCTION
• OBJECTIVES
• TERMS AND DEFINITIONS - EMC, EMI
• PFCs
• CONDUCTED EMI
• SIMULATION
• FILTER DESIGN
• CONCLUSIONS

3
INTRODUCTION

• Some examples of problems caused by EMI
• Pistol Drill may Interfere on TV
• Electronic Ballast's may change the TV channel
• Switching Inductive Load may generate noise in
  Radios
• Necessity of accordance with Standards...

4
OBJECTIVES

• To easily determine the EMI levels on basic PFC
  and to design the EMI input filter in the design
  step facing the following points
• Main Standards
• Simulation of the Conducted EMI
• EMI Minimization Techniques

5
TERMS AND DEFINITIONS

• Electromagnetic Compatibility - EMC
• Its the characteristic presented by an
  equipment, or system, working satisfactorily, in
  an electromagnetic environment without causing or
  suffering unacceptable degradation in its
  individually designed function.

6
INDUSTRIAL ENVIRONMENT

• EMI

• EMC

7
TERMS AND DEFINITIONS

• Electromagnetic Interference EMI
• Any electromagnetic disturbance that interrupts,
  obstructs, or otherwise degrades or limits the
  effective performance of electronics/electrical
  equipment. It can be induced intentionally, as in
  some forms of electronic warfare, or
  unintentionally, as a result of spurious
  emissions and responses, intermodulation
  products, and the like. Also called radio
  frequency interference RFI.

8
COMMUNICATION ENVIRONMENT

• EMC

• EMI

9
By Globalizations Highway...International
Rules...
10
GLOBALIZATIONS

• IEC - International Electrotechnical Commission
  
• CISPR - International Special Committee on Radio
  Interference
• CENELEC - Committee for Electrotechnical
  Standardization
• These organizations prepares and
  publishes international standards for
  all electrical, electronic and related
  technologies

11
CONSUMERS REQUIREMENTS
ELECTRONICS LOADS

• IN THE LAST YEARS THE ELECTRONIC LOADS GROW UP
  OVER THE WORLD
• BRAZIL WAS NOT AN EXEPTION AT THIS PROCESS

• EMC

• ELECTRONICS LOADS

12
CONVENTIONAL INPUT RECTIFIER

• LOW POWER FACTOR

INPUT POWER LINE
CAPACITORS VOLTAGE
CC
DIODES INPUT CURRENT
POWER LINE CURRENT

• HIGH THD

• ELECTRONICS LOADS

13
To solve those problems it was created the PFPs
PFPs

• Power Factor Pre-Regulators
• Power Factor Correctors
• Input Pre-Regulators
• Power Factor Rectifiers
• Resistance Emulators

• ELECTRONICS LOADS

14
EMI
Power Factor Pre-Regulators
High Frequency Switching Noise Degrades the
Power Quality.
Input Voltage
Input Current

• REMEMBER, PFP ARE GRID CONNECTED

15
CISPR 11
LIMIT STANDARDS
FCC 15
Class A. A device that is marketed for use in a
commercial, industrial or business environment
Class B A device that is marketed for use in a
residential environment notwithstanding use in
commercial, business and industrial environments
16
CONDUCTED EMI

• It is the part of the electromagnetic
  interference
• that flows by power cords.
• This kind of interference can be propagated in
• Differential Mode (DM) or in
• Common Mode (CM)

17
CONDUCTED EMI in DIFERENTIAL MODE
Phase
Z
i
LISN
CDM
Equipment
Neutral
18
CONDUCTED EMI IN COMMON MODE
Phase
Z
i
LISN
CCM
Equipment
Neutral
Ground - Common
Parasitic Capacitors
19
LABORATORY TESTS
Equipment Under Test (EUT) and
Measurements Apparatus
Conductive Surface Connected to Gnd
EMI Receiver
Equipment Under Test
40
cm
LISN
80

• CISPR 16

80 cm
cm
Layout for conducted emissions tests
20
Difficulties for realization of the tests
Conducted EMI test

• Few test Facilities (in Brazil and South
  America)
• Test apparatus are very expensive
• Technical Capacity
• Standards Interpretation

21
If your equipment did not attend the standard
limits...What can you do?
AFTER LAB TESTS
22
HOW TO MINIMIZE THE EMI?

• Preventives Actions
• Using Specific Control Methods
• Choosing the Best Topology
• Using Assembling Techniques

23
For example, you can use a Variable Switching
Frequency to Reduce de EMI
HOW TO MINIMIZE THE EMI?
INPUT CURRENT FM
10
1000 kHz
SWITCHING FREQUENCY (Hz)
24
PWM Input Current Harmonic Spectrum
HOW TO MINIMIZE THE EMI?
INPUT CURRENT PWM
In PWM the Power Interference is Concentrated
25
FM versus PWM
HOW TO MINIMIZE THE EMI?
For the some output power

• EMI TESTS results

26
HOW TO MINIMIZE THE EMI?
Choosing a Topology with an inductor in series
with the bridge rectifier.
Because the EMI is a function of the input
current ripple.
27
HOW TO MINIMIZE THE EMI?

• Correctives Actions
• Using Filter
• Applying Shielding

28
Making the Conducted EMI Generated by Power
Factor Pre-Regulators Compatible with the
International Standards at the Design Time
29
FIRST OF ALL

• Input Current
• LISN
• EMI Receiver

30
SIMULATION OF THE LISN CHARACTERISTICS
CISPR 16
LISN
EMI Receptor
40
cm
80
80 cm
cm
31
Model for the measuring system
SIMULATION OF THE COMPLETE MEASURING SYSTEM
32
EMI SIMULATION RESULT

• EMI SIMULATION EXAMPLE

33
GENERATED ABACUS

• Using the proposed abacus we can determine the
  amplitude of the EMI (first harmonic) in dB/mV in
  accordance with the CISPR 16 standard, without
  simulation, for the following converters

• Boost
• Buck-Boost
• Zeta
• Sepic
• Cuk
• Buck

• Abacus

34
GENERATED ABACUS

• The EMI design curves (ABACUS) were built for an
  specific case (Reference Converter).
• How to correlate the results from the abacus
  with a real case?

35
U (dB/?V) 20 log P V
U (dB/?V)
GAIN EQUATIONS
USING THE GAIN EQUATIONS!
ref
g ref
nom
nom
P V
g nom
ref

• Abacus

36
U (dB/?V) 20 log P V
U (dB/?V)
GAIN EQUATIONS
g ref
ref
nom
nom
P V
g nom
ref

• Abacus

SWITCHING FREQUENCY (MHz)
37
EXPERIMENTAL RESULTS FM BOOST
Boost Converter in FM
dB
µV

• Abacus x Experimental Results

Experimental Result
SWITCHING FREQUENCY (MHz)
38
EMI FILTER

• EMI FILTER

39
EMI design curve for the Boost converter
102 dB
M ____V output____ n V input

• Abacus

150 kHz
40
CISPR 11
EMI FILTER DESIGN
Necessary AttenuationA1 102 - 66 36 dB
100
90
Limit Value
79
80
Quasi-peak (class A)

• Abacus

73
70
66
dB
56
60
60
µV
dB
50
M 1,23
µV
Quasi-peak (class B)
102
M 1,62
40
M 2,01
M 2,39
30
M 2,78
30
5
0.15
0.5
MHz
10
0.9
M 3,16
150 kHz
41
EMI FILTER EQUATIONS
fc is the cut-off frequency fx is the frequency
in which the required attenuation (A1) is
determined A2 is the filter characteristic
attenuation C1C2 value is 2.2 ?F For a proper
damping effect, C210C1
42
DESIGN EXAMPLE
40 dB
Line side
Converter side
322 mH
2 mF
USING C2 2?F
38 W
220 nF
0 dB
At 150 kHz, Attenuation is -36 dB
- 36 dB
- 80 dB
1 kHz 10 kHz
150 kHz 1
MHz
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CONCLUSIONS

• The proposed method for determination and
  reduction of PFC conducted EMI DM presented here
  can be an useful tool to help SMPS designers.
  This tool allows us to easily predict the
  amplitude of the first harmonic in dB/mV in
  accordance with the CISPR 16 and to design the
  EMI filter. In this way we can design the filters
  without needing to make a prototype or make
  complex simulations. This method could be a
  contribution to the reduction of the product
  development time.

44
CONCLUSIONS

• The analysis that we have developed in this
  paper is not a full description of the harmonics.
  But this simplification does not represent a big
  problem, because the design of the filter is
  generally made for the first harmonic. In the
  majority of cases the filter that eliminates the
  harmonics of low order (Fs) also eliminates the
  harmonics of high order.

45
CONCLUSIONS

• From the analysis we can conclude that the FM
  operation mode is an interesting solution in
  order to reduce the conducted EMI with simple
  control circuits. Unfortunately this solution is
  not effective for switching frequencies in the
  proximity and higher than 150 kHz.
• We must avoid design the converters in FM mode
  at Fs min around 150 kHz. Minimal SF around 100
  kHz are preferred.

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CONCLUSIONS

• The curves presented here are similar to those
  presented by Albach 4, but in this paper we
  present the curves as a function of normalised
  parameters M and d. These curves associated with
  the gain equations permit us to obtain the
  conducted EMI DM (first harmonic) for a large
  range of converter specifications.

47
INDEX

• Objective
• Motivation
• Main Terms and Definitions
• Main Regulations about EMC
• EMC Limits
• Conducted EMI
• Conducted EMI Tests
• Techniques to Reduce EMI
• Conclusions

48
OBJECTIVES

• Quantify EMI ( abacuses ).
• Minimize EMI ( FM and filter).

49
COMERCIAL LISN
E U T
50 µH
250 µH
Phase
.22 µF
Red
7.5 µF
W
39 k
2 µF
1 k
W
W
5
Receptor EMI
GND
W
5
1 k
W
50
W
39 k
W
2 µF
7.5 µF
250 µH
50 µH
Neutral
.22 µF
E U T
50
TIPICAL EMI REPRESENTATION
dB
µV
SWITCHING FREQUENCY (MHz)
51
EMI FILTER EFFECT
dB
µV
SWITCHING FREQUENCY (MHz)
52
Why you can use those equations
GAIN EQUATIONS
LISN
PFP
P nom. P ref
53
Why the Variable Frequency Techniques reduce EMI?
54
PROTOTYPES